bi-monthly interface with the construction industry in ethiopia
Stone
humble yet endowed with magnificence
8
2007
www.constructionahead.com
Stone in Ethiopian architecture • What really is stone? • Deterioration of thin marble cladding
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From the editor The irreplaceable building material It is probably the first hard thing to result as the earth transformed from the gaseous to the solid state 3.4 billion years ago. That must be why it is omnipresent and easily found everywhere around the globe. Thanks to its relative and perceived indestructibility as its inherent characteristic, it is undoubtedly the repository and archive of humanity’s exercises of development and self expression: from Africa’s rock art going back to 50 000 years, the ziggurat of the Mayans, the Pyramids of Egypt, Petra in Jordan and Ellora in India to our own Lalibela churches. But all that is somewhat beside the point: stone has a special place and a way for it to take center stage, particularly in Ethiopia. In the traditional context, there exists no field of craftsmanship, specially in construction, that parallels what we have in stone. No wonder then that stone work is accepted as the most distinct and accomplished achievement of Ethiopian architecture; and we need not look beyond the world’s oldest (2.6 million years) material culture in the form of the stone tools from Afar, the temple ruin of Yeha, Axum’s stelae, the churches of Lalibela and the fascinating anthropomorphic stone statues of the south to ascertain this fact. Wondrous as these masterpieces of stonework are, that is not what we are inviting you to focus on here. The daunting task of dealing with Ethiopia’s stone architecture has to wait for another issue for sure. No. Rather we are inviting you here to ponder about and celebrate with us this - the most commonplace, humblest and cheapest of all building materials in and of itself. Stone. And, of course, the equally age-old art of masonry – represented with master craftsmen through all the ages of Ethiopian construction – that endows this ordinary substance with extraordinary magnificence. In function and purpose, it fits all requirements placed on it by the builder. The stone masons of Lalibela stopped carving down when they reached the basalt stone, letting it be the foundation. Stone figures as the main structural material, as flooring, as roofing and veneer, as exterior and interior for aesthetic dressing of buildings. But what exactly is this substance that we commonly and broadly call stone? What are the irreducible elements and constituents that it is made of? What are the characteristics of its many natural forms and varieties? And how about the particular Ethiopian legacy of working stone? Is it an innate knack one is born with? Or do the artisans acquire it through training and apprenticeship. You will find the answers to all this and a lot more in this issue dedicated to what is, after all, the irreplaceable building material.
Construction Ahead, nov-apr 2007
Bi-monthly interface with the Construction Industry Tel 515 24 77, 515 24 47 P.O.Box 81062 Addis Abeba, Ethiopia mail@constructionahead.com www.constructionahead.com
Published and distributed by
Mina Building 8th floor, Office No 802/4 Wollo Sefer, Addis Abeba, Ethiopia Editor in chief
Benedino Ferraresi
Deputy editor
Tigist Woldemikael
Research team Contributors Layout Design Printing Advertising design
Selamawit Berhe Yared Tezera Fasil Ghiorgis Yves Stranger Digital Impressions Plc. United Printers Plc., Ethiopia Digital Impressions Plc.
Suggestions and contributions are most welcome and can be mailed to : Construction ahead P.O.Box 81062 Addis Ababa, Ethiopia or posted using: www.constructionahead.com or e-mailed to: mail@constructionahead.com No part of this magazine may be reproduced or duplicated in any form without the written permission of the publisher. All rights reserved. Articles, Photos and Drawings sent by customers, are not returnable even if not published.
Views expressed in Opinions Column belong to authors and do not represent the views of the publisher.
Corrective apology These two photographs appeared in the last issue (No. 7) of Construction Ahead without the appropriate credit being given to their owners. We, hereby sincerely apologize for this unfortunate mishap as we thank once again Dr. Asfawossen Asrat for allowing us to use them. Corrigendum Some corrections are needed on our sixth issue’s news article concerning a new hydropower project. The name of the project is Gibe III (with no ‘Gilgel’ as a prefix) and the consultant is a joint venture of ELC- Electro Consult (ELC) of Italy and Coyne et Bellier (COB) of France. The height of the dam is 240m and the capacity of the related transmission line is 400Kv. We sincerely apologize for the mistakes. New dateline Try as we have been, it has proven impossible to bring the magazine up to date with respect to keeping its dateline. So, to avoid any confusion or undue misgiving arising from this impropriety, we have decided to do away with it, once and for all, by giving issue Number 8 the dateline: November 2006 – April 2007. Please note, this does not mean anything or affect any other aspect of the magazine other than the dateline.
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2007
W
hat our descendants may not have much chance to wonder about is our buildings - our architectural masterpieces of steel and glass, which, perishable as they are, won’t make it thousands of years from now. In this respect, at least, we have been outdone by our ancestors who have left us their legacy in stone.
ever wonder what our descendants would think of us, say, thousands of D oyearsyoufrom now? It is not hard to imagine they would be amazed at us much like
we are at our ancestors. They may wonder about how we led our lives, how we dressed and functioned and they may even dare to think of us as barbarians. They may find it hard to understand how our mechanical contraptions, which by that time are likely to be rusty scraps of metal (if at all) - could serve any desired purpose. What they may not have much chance to wonder about is our buildings - our architectural masterpieces of steel and glass, which, perishable as they are, won’t make it thousands of years from now. In this respect, at least, we have been outdone by our ancestors who have left us their legacy in stone.
20 22
Departments
Issue No. 8
COVER STORY
Construction Ahead, nov-dec 2006
As our descendants may wonder about us and our works down the distant future, we ponder about the megaliths of Tiya from the distant past. The question of who built them and the symbolism of the image carved on them remain still a mystery.
Construction Ahead, nov-dec 2006
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Features
4 from the editor
32
8 news 12 world news
But what really is stone?
Regulars 40 interview
Ato Beyene Egigu The definite and tangible, the concrete and solid, the natural and simple are an anathema to academicians, expert consultants. Not so with crafts-people. It is the contrary with them since they are short of words and every bit full of deeds.
Stone is that solid, dense and massive substance we use in all types of construction, consolidated enough to be cut, shaped or split into blocks or slabs for use in the construction of buildings and other infrastructure works.
58 opinion
A chip of the old block by Yves Stranger
Deterioration of thin Marble Cladding
62 product advertising Monolithic wells and accessories
64 technology 66 what’s new
Reviews 68 software review
Aftermarket Solutions for CAD Third-party programs increase AEC productivity.
72 books 74 snapshot
14 Stone in ethiopian architecture
52
a major international study This intriguing article reveals that problems can and do occur, even with materials like Carrara marbles that have been used extensively for many years.
Design competition awarded
news
First geothermal conference in Ethiopia
T
he first international conference on geothermal energy in the East African region took place from November 24-29, 2006 at the United Nations Conference Center in Addis Ababa. The conference with the theme ‘Geothermal Energy: an indigenous environmentally benign and renewable geothermal energy resource’ addressed the technical issues related to the resource from initial exploration to development and utilization. Relevant environmental, socioeconomic, and legal issues were also addressed, at times supplemented by case histories in different countries. The conference brought together specialists of various nationalities engaged in the exploration and production of geothermal energy. Eighty technical papers were presented of which 30 were authored by Ethiopian professionals. The event was applauded for presenting an unprecedented opportunity to communicate to a wider public research findings and developments in geothermal energy use in East
Africa and all over the world. Today, geothermal energy resources have been identified in more than 90 countries in the world and are being exploited in 71 of them. The Aluto Langano Geothermal Project, which was visited by conference participants, is the only one of its kind in our country. A paper presented during the conference by Professor W. Wolde Ghiorgis indicated that total proven geothermal resources could generate 7002000 MW MW electric power. The Danakil Depression, in the central Afar region, Tendaho and the Lakes Region, of the Ethiopian section of the African Rift Valley, are identified as having immense potential. Based on such potential of geothermal resources, Professor W. Wolde Ghiorgis said, a generating capacity of 60-120 MW is feasible for development within the next decade. This corresponds to a 2% - 3% geothermal power out of a total generating capacity of up to 4000 MW.
The winners of the architectural design competition on innovative rural housing were announced on an awarding ceremony held on February 10, 2006 at Addis Ababa University’s Technology North Campus. The competition, which was opened to all registered architects, engineers, town planners, design offices, and students of architecture in October, entertained a total of 46 entries, fewer than initial expectations. An exhibition showcasing all the submitted entries followed the award ceremony and was open to the public for two weeks. The competition entries were divided among two groups, professional entries, on one hand, and those made by students on the other, which were then evaluated in two stages for technical compliance and content by a jury comprising of renowned professionals. The Jury evaluated and ranked the entries based on their merit and responsiveness to the requirements stipulated in the competition brief. The award identified top three entries in both groups and awarded a total of ETB 240 000 to winners. Bet consulting architects and architect Tibebu Daniel won the first price in the professionals’ category, followed by architect Tilahun Bekele who took the third prize. Students from Arba Minch University took the two top prices while another student from Addis Ababa University’s technology South Faculty went home with the third prize. Entries submitted by students were commended for their superior creativity compared to those submitted by professionals. The jury, saying that the appraisal system adapted for the competition is in keeping with international standards and is unique for our country, suggested this method be further refined and adopted by AEA for fair and effective evolution in the future. The competition, the first of its kind in Ethiopia, envisaged to preserve the positive features of traditional housing while introducing modern amenities that would complement indigenous methods already in practice. All the winning entries based their works on case studies of existing vernacular homes in all corners of the country.
Construction Ahead, nov-apr 2007
E
thiopia’s grade one-construction contractors split from the Ethiopian Construction Contractors Association (ECCA) and founded the Ethiopian Grade One Contractors Association (EGOCA). Lack of appropriate and diligent representation is given as the reason. The EGOCA has received certification from the Ministry of Justice in October 2006. Its registered 41 members are all former members of ECCA. Ato. Fanuel, CEO of ECCA, however, claims that there are still grade one members serving on the executive board of his association and says that the EGOCA accounts for a small number of grade one contractors. Ato. Fanuel told CA, “The move to the split does not reflect the majority of members of the association and represents rather the view of only about 10 to 20 grade one contractors.” Out of the 2,000 contractors that are registered under the Ministry of Works and Urban Development, there are only 44 grade one-construction companies while 700 of the total construction companies are listed as ECCA members. Ato. Fanuel said, “The existence of two associations for the same purpose only creates problems for the development of the industry as seen both in undertaking certain activities and in the relations of the industry with the government.” Hence, the ECCA executive board has appointed a committee to investigate what led to the dissatisfaction and consequently to the split. He said, “If there is a leadership problem or lack of enough representation, this could be resolved by dissolving the present executive body and forming a new one that is to every one’s satisfaction.” However EGOCA has expressed disinterest in such discussions.
was rejected, “but we are still working on this and we need the collaboration of all contractors since this concern us all.” Another source of discontent from the part of contractors is the issue of Value Added Tax (VAT). Ato Fanuel said that some contractors are made to pay VAT on contracts signed before VAT was declared in the country and this is creating a huge problem among contractors. According to him this problem too has been presented by ECCA to the pertinent authority and is waiting for reply. Our effort to get the opinion of the executive members of the new association was not successful.
3rd Ethio-Con Exhibition
T
he Third International Construction Exhibition (Ethio-Con 2006) organized by the Ethiopian Construction Contractors Association (ECCA) and Century Promotion Services was held here in Addis from November 30 to December 6, 2006. About 150 construction companies, importers and producers of construction materials, consultants and others working in the construction sector participated in the exhibition. A symposium was also held on the concluding day of the exhibition bringing together construction professionals both from the private and public sector; papers were presented and discussed. Presenters from the public sector included Ministry of Works and Urban Development (MoWUD), Ministry of Capacity of Building (MCB), Ethiopian Chamber of Commerce (ECC) and the Ethiopian Roads Authority (ERA).
One of the bases for the split, as sources at EGOCA disclosed, is the lack of any solution to the issue of constant price escalation of construction items such as cement, fuel and steel prices that is forcing number of contractors to long delays of projects resulting in huge losses. The ECCA was expected to negotiate about the price escalation issues with public bodies to win compensation provisions for its members. Unfortunately it was unable to do that. Concerning this matter, Ato Fanuel said that his association had presented the compensation request to the prime minister’s office but that it Construction Ahead, nov-apr 2007
in
brief
ERA awards Indian company ETB 110 million road project SMS Infrastructure, an Indian firm has won its first bid to construct an 80 km gravel road in the southern part of the country at a cost of over ETB 110 million. The project will link the two towns - Key Afer and Permi – logistically important for tourist traffic visiting the traditional people of the area like the Bengi and Hamer. Meanwhile the authority has secured loan funds for four projects as part of the third phase of its Adaptable Program Lending (APL III). These road projects are: Aposto-Wendo-Negelle (268 km), Gedo- Nekempte (134 km), Gonder-Debark (103 km) and Yalo-Dalol (138 km). Road maintenance of ETB 756 million to be executed in budget year The Federal Road Fund Administration has announced that it will provide over ETB 756 million for maintenance and road safety works in the current Ethiopian budget year. Regional and city road authorities will also benefit from an additional ETB 10 million fund of which half is earmarked for Addis Ababa. The allotted fund is to be collected from various sources within the same budget year. Nile basin initiative conference The Nile Basin Development Forum (NBDF) 2006 international conference on the role of the River Nile on poverty reduction and economic development was held in Addis Ababa (November 20 - December 6 2006). The forum was held at a time when the Nile riparian nations are nearing an agreement that will allow them to jointly manage the waters of the contentious river. More cement factories on the pipeline Two new companies, East Cement Private Limited, a Chinese-Ethiopian joint venture, and Hilmat, a local company, are to set up cement factories with over ETB 555 million capital. Both factories are expected to near completion in the coming ten months and make use of raw materials from reserves nearby. EEPCo to study Gilgel Gibe IV The Ethiopian Electric Power Corporation (EEPCo) is expected to launch a feasibility study on the fourth phase of the Gilgel Gibe project proposed by Salini Construttori. The corporation has recently signed contract on Gilgel Gibe III project, the third cascade power plant on the Omo-Gibe River.
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Construction Ahead, nov-apr 2007
Workshop on nine years performance
A
pproaching the start of its third Road Sector Development Program (RSDP III), the Ethiopian Roads Authority (ERA) assessed its accomplishments during the past nine years in a one-day workshop on 30th November 2006 at the Sheraton Addis. According to the authority, the workshop was intended to assist key stakeholders and donors to take stock of progress achieved so far, exchange ideas on lessons learned and redirect efforts to a more efficient implementation of the program Ato Zaid Wolde Gebriel, Director General of the authority, said that considerable improvement has been made in the past nine years in improving the accessibility of regions all over the country and reopening of all main roads that had previously been closed to traffic because of deterioration. The percentage of roads that are now in good conditions has also increased from 35% in 2002 to 60% in 2006. A report distributed to participants during the conference shows that 89% of the intended rehabilitation of trunk roads at federal level was accomplished by June 2006, and a 98% rate of success was registered on upgrading of trunk roads. Construction and upgrading link roads recorded 96% and
63% success, respectively, while periodic maintenance was carried out significantly more than intended, thereby showing 158% success rate. The report shows a better rate of achievement in regional and community roads in terms of total physical and financial performance. Key policy changes have also taken place within the past nine years in the authority. The Road Fund is now fully functional although more needs to be done to widen its financial base. Many of the commercialization and decentralization efforts have taken fruit: according to ERA, the private sector has been awarded more tenders floated for construction and maintenance of roads, consultancy services and equipment lease. Of the total value of works awarded between 1997 and 2006, amounting to more than ETB 15.5 billion, local contractors were awarded close to ETB 5.2 billion. During the workshop, it was announced that RSDP III, scheduled to start in July 2007, is at ‘an advanced stage of preparation and expected implementation.’ The targets of the third phase are to reduce the inhabited land area further than 5 km from a road to 65 % and increase both road density and the percentage of acceptable roads throughout the country.
University Days celebrated
A
ddis Ababa University’s, Technology Faculty, hosted four University Days (November 15-18, 2006) showcasing the reforms carried out on its study programs. The event, supported by the Engineering Capacity Building Program (ECBP), started off with a panel discussion in the new library auditorium of the Technology, North Faculty. Professor Andreas Eshete, president of the university, opened the discussion by saying that the reform within the technology faculty must ensure its role in technological inventiveness. He also applauded the ECBP program, which he termed a ‘midwifery work in reform’ for extending the reach of the university. Ato Fikru Desalegn, State Minister of Capacity Building, was next to point out that a demand-oriented higher education will actively contribute to Ethiopia’s effort for development. High caliber graduates, he said, will be coming out of the ECBP reform program, which he regarded as comprehensive and ambitious. A presentation by Professor Mathias Wessler from the University of Kassel in Germany set off the panel discussion highlighting learning matrices, which indicate that much of the learning process within universities takes place unintentionally in informal
settings. The reform, he asserted, should take account of these processes if it is to become effective. He concluded his presentation saying that the university needs leadership that is ‘painfully humble as well as iron willed’ and ‘the consent of the professors’ if the reforms are to be implemented. The panel discussion continued with more presentations by representatives of the university like Ato Mohammed Nursenay, representing Manufacturing Industries Association, Mr Martin Mueller and Mr Werner Wasmuth, representing GTZ, and Dr. Abiy Tassie, Associate Vice President for International Relations in the university. An art exhibition of paintings, photographs and sculptures by eleven artists with the theme of Engineering Tomorrow was opened following the panel discussion. The University days that followed were enlivened by presentations of 13 workshops and the discussions that ensued. A ‘public day’ at the end of these events welcomed the public into the compounds of the North and South faculties of the Technology Faculty, where students and staff represented their departments.
Construction Ahead, nov-apr 2007
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world news
Record-breaking wind farm approved
WORLD OF CITIES
S
taking its reputation around an ethical debate, Venice, Italy’s 10th Biennale Architecture Show presents the successes and challenges of 16 of the world’s cities and asks: “can architects make a difference?” The “Cities, Architecture, and Society” exhibit curated by David Burdett, architect and professor at the London School of Economics, stops short of providing solutions, but states, “how we shape cities will determine the future of our planet.”
C
onstruction of the world’s largest wind farm off the Kent, UK coast has been approved by the UK government. Planning permission for the wind farm, located 20 km offshore in the outer Thames Estuary, has now been granted but, construction can not start until the scheme gains consent for an onshore substation. Developer London Array – formed by a joint venture of Shell WindEnergy, E.ON UK Renewables and CORE - plans to erect 271 turbines over a four year period to generate more than 1 GW of electricity. Once complete the wind farm could generate enough electricity to power more than 750000 homes in the south east of the UK. According to London Array director Andrew Murfin, the development will help the UK government meet 10% of its target for renewable energy production by 2010. A statement from London Array also said that the wind farm will prevent the emission of 1,9 million tonnes of carbon dioxide each year, compared to a fossil fuel power station generating the same amount of electricity. Source: Construction Europe
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Construction Ahead, nov-apr 2007
Final deck lifts for Tacoma Bridge
Libya to spend USD 40 billion on infrastructure
T
he Libyan Government has announced ambitious plans to spend USD 40 billion on a country-wide infrastructure and housing construction program. Unveiling the program at the Project Libya: Libya International Infrastructure and Construction Exhibition and Conference in Tripoli, Abuzeid Dorda, Secretary of Housing Projects, Infrastructure, and Public Utlilities, said the program will see the Government allocate about USD 13 billion to housing construction, USD 10.5 billion to infrastructure – road, rail, airports construction, and USD 4 billion to small, local infrastructure projects throughout the country. The program is designed to “revamp” the country’s decaying public infrastructure following years of international sanctions and under-investment by Colonel Gaddafi’s military dictatorship. Commenting on the program, Ryad Sunusi, president & CEO of the Phoenicia Group, a US-Libyan business consultancy that advises foreign companies on working in Libya, said it is “a subtle green light to US and international engineering and
T
he final 15 sections of bridge deck for the new Tacoma Narrows Bridge in Washington, US were delivered to the site earlier this month by ship from South Korea. The delivery takes the Washington State Department of Transport’s (WSDOT) USD 849 million project a step closer to its planned spring 2007 opening. The Tacoma Narrows Constructors – a joint venture of Bechtel and Kiewit – are now winching the final sections of deck for the new suspension bridge into position and expect to complete the work by the end of 2006. Once the deck sections are in place, the contractor will start work on welding and bolting them together and this phase is scheduled to be completed by March 2007. Construction of the 1.6 km suspension bridge is being
construction companies to establish a stake in the construction boom set to explode in the coming years.” In recent months, said Mr Sunusi, Libya has been holding auctions of its mineral and oil exploration rights. The monies generated from these auctions, which total several billions of US dollars, will be used to boost Government investment in the country’s infrastructure. “All public buildings and infrastructure will be renovated and large-scale civil projects - housing, tourism infrastructure, rail, roads, and airports – will be built. This is an exciting time for the construction sector in Libya and we welcome US and international companies for partnerships in the sector,” said Mr. Sunusi. Foreign engineering and construction companies wishing to do business in Libya must do so through joint ventures with a Libyan partner. On the 14 November the General People’s Committee, Libya’s executive decisionmaking body, passed GPC Decision 443/2006, which now makes this mandatory for any company wishing to work in the country. Source: International Construction
carried out parallel to the existing suspension bridge that was built in 1950 to replace the first bridge, Galloping Girtie, which collapsed in high winds in 1940. The 1950 suspension bridge is also being refurbished as part of the overall project and is expected to be completed by early 2008. Once both structures are complete, the new bridge will carry eastbound traffic into the city of Tacoma, while the older bridge will take the westbound traffic. According to WSDOT, the 1950 bridge currently carries 90000 vehicles per day – 30000 more than it was designed for. The new structure will enable the Tacoma crossings to meet future traffic growth, which is predicted to reach 120,000 by 2020. Source: International Construction
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Stone By Fasil Ghiorgis, Architect
B
eing one of the earliest settlements of the human race, Ethiopia does present us with the use of stone since prehistoric times. Pre-historic cave dwellers, for example, used stone tools and weapons for hunting and domestic purposes. The “obsidian”, a precious stone tool which can be compared with today’s knives and razor blades, was used up to the Axumite period and later for cutting and cleaning. The use of iron, an innovation which was probably brought over from across the Red Sea, enabled the Sabeans to quarry and cut stone for construction. The earliest form of stone construction in this country is probably the Cyclopean walls made by placing rough stones on top of one another (as in dry-wall masonry of today). After the arrival of the Sabeans during pre-Axumite times, dressed stone construction was introduced in the northern part of Ethiopia. The Sabeans used stone and wood roof lintels. As in most ancient civilizations, dressed stone blocks were fitted together with great skill and accuracy. The temple of Yeha, probably the oldest standing built up structure in sub-Saharan Africa, was built with this technique.
A tentative reconstruction of Grat Ba’al Gibri in Yeha, often considered to be a temple, but believed by others to have been a palace. The archeological site where the ruins of this structure lie is closed off to visitors.
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Construction Ahead, nov-apr 2007
in Eth archite
hiopian ecture
Construction Ahead, nov-apr 2007
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The building material used to construct the walls were micritic limestone blocks. These were carved with sizes of 25 cm height, from 80 up to more than 200 cm length and 38 cm deep. No mortar was used in the construction of the walls. Overlaying these blocks of stone makes walls with an average thickness of 1.23 meters. The walls are constructed with a double wall construction system laying two rows of parallel stone blocks. Alternating these rows are stone blocks laid perpendicular for the practical reason of interlocking them for additional strength and stability of the walls. The floor is made of dressed stone blocks with an average size of 50 cm x 75 cm and 20 cm thick. The Sabeans used stone and wood roof lintels. Being heavy, resistant to easy weathering and perceptibility and indestructible, stone was erected to commemorate the dead, and express the belief that powerful personalities live on. Carving stone to make monolithic stelae became an important activity for Axumite monarchs. It has been proven by archeological research that preparation for the afterlife was part of the religious customs of different societies around the Red Sea. Roughly cut stone slabs were brought from a quarry site known as Gobedra, some four and half kilometers away to the southwest of Aksum. According to oral tradition, the massive synite (a type of granite stone) slabs were pulled with the help of elephants. Reconstruction of Stela 4 by the Littman expedition. This is one of the most ornate stelae in Axum. It has a total of six storeys and, apart from the head, it is also carved on its back. The stelae has fallen backwards and now lies as it fell in several pieces.
Once the roughly cut monolith is brought to the royal burial ground, the carving work started. It is still a mystery as to how the Axumite craftsmen carved the synite, which is very hard to handle. There are church manuscripts which mention a certain technique or tool known as Ebena Admas. This tool was so powerful that it could cut or shape the synite to the desired form. It is evident that the Axumite monarchs had large numbers of slaves and others artisans working for them. The presence of elephants is also supported by travelers’ accounts and recent archeological finds. The Axumite civilization’s use of stone was not limited to the carving of commemorative monoliths. They also built large elite structures and religious buildings. Their built-up structures, which followed strict typologies, used basaltic stone (rubble) joined with clay mortar. The walls were strengthened with horizontal wooden braces, which protrude from the wall and are commonly known as monkey heads, and were finally plastered with lime. These braces are made to alternatively recess and protrude for better structural strength.
The monkey head is a typical feature of Axumite architecture in which timber ‘heads’ emerge from the stone walls in intermittent intervals.
A staggering section of a group of churches in Lalibela. Note the huge difference in plinth level and continuity of the escarpment. After Bianchi Barriviera.
After the decline of Axum starting around the 7th century, we see a new development in the eastern part of Tigray where rock-hewn churches were excavated between the 7th and 11th centuries. Going from monumental architecture stone cutting was further developed
to create rock churches. These rock churches clearly imitated built up prototypes complete with their wooden elements. The area has an abundance of large sandstone formations, which enabled workers to hew these unique churches. Due to their indestructible nature, rock churches survived in greater numbers than the built up models. Prior to the hewing of the Roha (Lalibela) rock churches, Lasta witnessed small churches built within caves. Unlike the built -up outdoor prototypes, these churches were protected from rain and excessive weather conditions. Imrahana-Kirstos and NaKuto Le’ab, both found in Lasta, are cave churches that followed Axumite construction techniques. Rock church excavation and carving reached its highest level in Roha, later known as Lalibela, taking the name of the king who was responsible for their realization. The rock churches of Lalibela differ from their earlier Tigrean prototypes in two ways. The main difference is that the churches of Lalibela are decorated both inside and outside while the Tigrean ones appear simple and undecorated externally and reserve all the wonder indoors. The majority of the Lalibela rock hewn churches are mainly free standing while most of the Tigrean rock churches are attached to the mountainside. Rock church hewing starts with the excavation of a big trench or freeing a huge block from the rocky mountainside. Once this part is isolated from the living rock mass to its plinth or floor level, work continues on carving the western entrance to hollow out the inner space. Controlling the thickness of the walls and hewing out enough interior space are among the most astonishing feats of this architecture.
The interior of the Lalibela churches are as remarkably carved as their outer façade. In the Church of Bethe Medhanealem, arched ribs connect columns that have pseudo-capitals composed of corbels.
The craftsmen involved particularly in rock hewing were probably divided into two groups. The first group, numerous in number, would do the bulk excavation work to isolate the required mass of rock, which will be further refined and elaborated by the second group. The more skilled craftsmen, who must have been less in number, would then do the elaborate details and final touches. In the late 16th and early 17th centuries, there was a renaissance of stone architecture around the Lake Tana area. This development culminated in the establishment of Gonder, as the capital of Ethiopia in 1632. The construction of the four-storey palace of Emperor Fasiledes took more than 6000 cubic meters of basaltic stone, lime and sand mortar. The thickness of the wall at the base reaches more than 1 m. Arched window and door openings were built of reddish volcanic tuff, which was cut and brought from quarries some 5 km away from the construction site. Stone was also used for the construction of ordinary houses in Gonder.
Arches characterize the masonry construction of the Gondarian period. Aside from their structural relevance, to span the space between walls, they enabled the masons of the day to open up larger windows and doors.
Construction Ahead, nov-apr 2007
17
Stone Art
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n the mid 19th century, Addis Ababa was a long way from being a ‘conglomeration of hamlets and huts’ but still not quite a city of high-rises and landmarks we know it to be today. The prominence enjoyed by wood and chika had given way to stone masonry, at least in public buildings, which was itself being gradually replaced by concrete. Then again, on one fateful occasion, stone was revived and made to take on a new challenge in construction, this time as the material for a sculpture of national prominence. In 1955, there was a frenzy of construction going on in the city in celebration of the emperor’s 25th coronation anniversary. Pavilions were built to house exhibitions, parades proceeded under newly constructed arches and a new opera house was built midway through Churchill road for the occasion. Most of these structures have since succumbed to the changes of time and disappeared from the face of the city. The emperor’s lion statue, north of the National theatre, however, stands in defiance having met the challenge and won. Of special interest is the lion; a dazzling assembly of ignimbrite masonry, which was designed by Henri
Chommet, a French architect. The Sculptor was another Frenchman, Maurice Calka, who gained worldwide fame for his work on the lion. The statue itself is famous on its own as a symbol of Africa’s entry into the modern era. An old joke has it that when the statue was inaugurated by the emperor in November 1955, the nobility present at the ceremony were not convinced that it actually resembled a lion and related this sentiment to the emperor. The emperor then replied, ‘the money spent on it will make it a lion.’
There is growing evidence about the role of Indians in the construction of the first palace of Fasiledes but it would have been impossible for them to accomplish such a monumental task without the involvement of skilled Ethiopian masons. Sometime later, a master builder by the name of Walde Giorghis was leading the construction of the Emperor Yohannes Library. The foundation of Gonder as a capital helped reestablish dying construction methods this time strengthened with foreign influences. It combined the skills of Indian craftsmen, and Ethiopian masons. James Bruce a century after the construction of the first palaces in Gondar wrote that ’The palace was built by masons from India and such Abyssinians as had been instructed in architecture by the Jesuits without embracing their religion’. Through the use of stone, Gonderian architecture introduced barrel vaults, wide arches, domes and circular corner towers to Ethiopia. Roughly cut stone joined with lime mortar was used for the construction. The use of stone in construction was not limited to the high architecture of the religious or the nobility. Societies in different corners of the country used it to solve basic problems- to define property, pave roads and build their homes- as much as they used it to honor gods or build impressive palaces. The traditional houses in Tigray, Lasta, Gondar, northern Shoa, Argoba, Harer and Konso use stone 18
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according to their local know-how and way of life. In Tigray, there are the circular type, found mainly in the western part and the rectangular Hudmo houses which are predominantly found in the east. The Lasta, Gonder and Sekota round houses are rather similar to those of Axum and Adowa of western Tigray. In these circular houses, stone is used in every part of the structures except the roof. The foundation is made of basalt, which is found easily in abundance. Softer stones such as trachyte or sandstone are used in the walls of ashlar masonry joined by chika (wattle and daub) mortar. The Hudmo type are flat roofed houses whose stone masonry is closely linked to the Axum tradition of large dressed stones at the corners and smaller undressed stones elsewhere. The selection and collection of stones for Hudmo houses goes on for years before actual construction begins. The Konso people of Southwest Ethiopia also present us a classic showcase in the profound appreciation and use of the widely available stone, making it the architectonic center piece of a whole land management and resource conservation system. The network of stone walls and fences making up the catacomb plans of their unique villages (called urban clusters by anthropologists) and their more than 500 year old stone terracing covering the entire Konso
country (and as such the only tradition of its kind in the African continent) have now been nominated as Ethiopia’s 8th UNESCO World Heritage. Harar, a walled Muslim town in the southeastern part of Ethiopia, is soon to become the 9th heritage thanks to its defensive walls built of stone in the 16th century to protect the town from invasion. Stone is also used in the traditional architecture of the Harari, who use light lava tuff and clay mortar to build their flat roofed rectangular houses. The use of stone, which has always been widely present as a traditional building material in Ethiopia, started to evolve again in the first two decades of the twentieth century. Stone went from its traditional building material functions to become the leading material used in public buildings in the then new Addis Ababa. European and Indian architectural influences revitalized cut and dressed stones that were used to construct structural walls or to finish surfaces. Exposed dressed stone was used for public buildings as a finishing material and arches, corners and entrances were built of stone by carefully carving each piece and pointing the joints. The Bank of Abyssinia, a neoclassical building entirely made of stone, the Arada Post Office, the Leul Genet Palace and the Qidus Giorghis Church, among others, all stand testimony
to the predominance enjoyed by stone in that era. Stone use, however, was not limited to public buildings. The nobility and wealthy continued to construct their homes up to two-stories high using stone masonry for the lower level walls in order to support the upper floor. The upper level was then completed with clay plastered wooden frame walls. A typical characteristic of these buildings, also evident in their public counterparts, is the decorative use of excellently dressed quoins at corners and all sides of main windows. Even during the Italian occupation, buildings continued to be made of stone. The distinguishing characteristics of this colonial structure typology are rough stone masonry with dressed corners and doorposts. The stone arcades and covered walkways that still lend character to our main streets are also remnants of that age. In the late 20th century, the relative monopoly enjoyed by stone was gradually replaced by cheaper and easier to use materials, such as brick and concrete. Stone then became a status symbol of the few, wealthy enough to build with it, and was eventually relegated to being used as a cladding material only. Most of the stone used in construction today goes into rough foundation walls and fences.
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by Selam Berhe
ever wonder what our descendants would think of us, say, thousands of D oyearsyoufrom now? It is not hard to imagine they would be amazed at us much like
we are at our ancestors. They may wonder about how we led our lives, how we dressed and functioned and they may even dare to think of us as barbarians. They may find it hard to understand how our mechanical contraptions, which by that time are likely to be rusty scraps of metal (if at all) - could serve any desired purpose. What they may not have much chance to wonder about is our buildings - our architectural masterpieces of steel and glass, which, perishable as they are, won’t make it thousands of years from now. In this respect, at least, we have been outdone by our ancestors who have left us their legacy in stone.
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photo by Antonio Fiorente
As our descendants may wonder about us and our works down the distant future, we ponder about the megaliths of Tiya from the distant past. The question of who built them and the symbolism of the image carved on them remain still a mystery.
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tarting from the earliest of times, one of the things that differentiated human beings from the other critters on earth was probably their need to settle down and build worthy shelters. This they did by gathering fieldstones, stacking them upon one another and, thereby building the very first structures. The earliest of such buildings must have been simple round huts, with no sharp corners to negotiate with and made of flat stones that needed no mortar to stay put. Whenever the necessary slate could be found nearby, men replaced their leaking thatched roofs with flat, slit or slate stones.
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Early builders were geographically limited to indigenous resources when it came to the type of stone they had to build with. Buildings of those by-gone times were thus harmonized with their environment since the very material they were built from consisted of stone from the surrounding. The need to trade called for transportation and consequently roads which were made by covering surfaces with crushed rock or cobblestones.
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Through the millennia, building shelters, paving pathways or defining property with stone fences proved no longer adequate. Visions of grandeur had to be simulated in concrete forms, gods had to be monumentalized and thus edifices had to be erected- all in stone. Early man, who from the dawn of civilization knew about the durability and permanence of stone, etched with it his beliefs and aspirations thereby leaving behind wondrous masterpieces in stone that puzzle us to this day. That is when stone started its evolution into a symbol of affluence, strength and status. When the masses turned to other materials such as wood that proved less toilsome, the high priests and political leaders embraced stone as their own. Enigmatic ways were found of quarrying and transporting large rocks, which were turned into even more mysterious megaliths.
1. The best-known pyramids, masterpieces in stone, are in Giza, Egypt. 2. The Mayas built their temples out of beautifully carved stones on top of stepped bases.
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In Egypt, where the earliest and most credited structures of the earth lie, stone was reserved for the mystical- the afterlife and the deities. While the gigantic pyramids were being built for the dead pharaohs, the living kins lived in brick palaces and the masses dwelt in buildings made of Nile mud. There
exists a staggering amount of speculation about the pyramids, ranging from mere hypothesis on how massive stones were transported to build them to the most recent claims publicized last December, that they were built with concrete. It seems the more information we get about them, the more confusing the story of pyramids becomes. A less known and publicized fact is that the Egyptian pyramids are rivaled in size and grandeur by similar feats of other civilizations far away from the Nile. The Mayans had an advanced stone architecture characterized by an exquisite sense of proportion and form. Their stepped pyramids or ziggurats - the most famous of the ceremonial monuments constructed by the Mayans - are outstanding examples of bold architectural endeavors. In Asia, a unique style of building was developed by Khmer architecture after it broke free from Indian influences in the 7th to 8th centuries AD. This architectural tradition is indebted to the megalomania of kings as it developed through their incessant attempt to outdo their predecessors with ever greater masterpieces. In stone. Luckily, the kings were not short of capable artisans who carved stone like they did wood. And when brick gave way to stone as a major construction material some centuries later, sandstone and porous laterite ensured the evolution of the architectural tradition that produced some of the greatest religious monuments the world has ever known.
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Khmer architects, nonetheless, didn’t find it easy to build with stone. They allowed vertical joints to run on top of one another making the walls very unstable since they also didn’t use any mortar. Khmers also never learned how to use an arch which made their stone edifices more liable to destruction. The Inca, half way around the world, had no such problems. This maybe was because they held precision in higher regard than they did flaunting their stone carving skills even though they are reputed to be the world’s greatest stonecutters. They could cut limestone and granite into any shape they wanted and built these so that the proverbial needle cannot pass between the stones in their walls. Even during strong earthquakes, the stones in the Inca’s incredible masonry ‘danced’ in their position to later returnto their designated niches never damaged or misplaced. Although chronologically one of the more recent of the “ancient civilizations”, the achievements of
3. The walls in Khmer temples, Angkor, Cambodia, are made of laterite, a porous stone, while sandstone is used in decorated. 4. The Incas built simple rectangular structures characterized by cyclopean stonework.
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5. Ruins of Greek Architecture 6. The Colosseum in Rome is a freestanding structure of stone and concrete
the Incas in moving and raising heavy stones are still astounding. Rewind time to a thousand years before Christ and we see that the Myceneans were not to be outdone by anyone and were themselves doing a great job of building walls and tombs from colossal blocks. The Greeks, awed by the enormity of the stones the Myceneans used, surmised that the blocks must have been raised by the one-eyed giants, the Cyclopes. It however took the Greeks, who used to build mainly with wood, mud brick or clay, some five centuries to give stone due recognition in their architecture. By the 6th century BC, however, the wooden columns of Greek temples were being replaced with stone and from this period onwards Greek architecture was dominated by stone, especially by limestone and marble, which were used to build walls, columns and other parts of religious and public buildings. The grandest testimony to this is the most famous of all Greek stone edifices, the Parthenon, which is entirely made of marble. The Romans, with their eclectic blend of architecture surpassed the limitations of building with heavy stone by creating concrete that used a dry mix of cement with rubble stone aggregate. Taking what they had learnt from the Greeks and incorporating them with certain elements from other cultures and civilizations, 24
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the Romans continued to experiment with their building techniques and finally came up with the idea of using stone as a cladding or surface dressing material as seen in the Coliseum of Rome. The holes that run along the entire surface of the Colesium are known to be anchors that used to hold marble veneer panels to the wall. Much as the Greeks influenced the Romans, immigrants from South Arabia influenced the architecture in their newfound home in what we now know as Ethiopia. Sergew Hableselassie in his book Ancient and Medieval Ethiopian History to 1270 tells us that even though wood was available in their new country, the South Arabians continued to build their rectangular homes in stone as they had done back home to exclude the heat of the Arabian desert. ‘Likewise’, he says, ’the temples they built [on this side of the Red Sea] did not differ essentially from those of South Arabia.’ Arguably, this is when and how stone masonry was introduced to Ethiopia. The Yeha temple of sandstone, which is dated at the 6th century BC, is an amazing feat of construction since no mortar was used to build the 15.2m high dead walls, which on the east side run for up to fifty-two courses. The Axumites, who followed suite, achieved no less than other ancient civilizations when it came
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to quarrying, transporting and erecting large stone blocks. Whereas the ancient cities of wood and possibly metal have disappeared falling victim to the ravages of time, the monolithic stelae of Axum stand erect in testimony to mankind’s persistent urge to reach for the sky. The stelae, built, we are told, in preparation for the afterlife, may well be among the tallest such structures ever erected by man.
circular markings where once wedges were stuck to splinter them. Curiously enough, a fierce looking lioness is carved in relief on one of the rocks, guarding it seems, this serene landscape of imposing stone. How quarrymen managed to cut the rock and, better yet, how they brought these large blocks to their site kilometers away is still a subject of debate.
The stelae are not the only tourist attractions of this realm. If you leave Axum on the grumpy road to Shire, you come to Gobdera about four kilometers from the town. This is an ancient quarry as well as one of Axum’s numerous historical sites that a billboard advertises as an ‘open museum’. What distinguishes the place more than the misdirected signboard is the imposing vertical column of rock that has been weathered through centuries and exploited by Axum’s early builders.
It appears that fate had designed other Middle Eastern forces, namely the rise of the Muslim Arabs that should cut Axum’s commercial ties and bring about its decline as a distinct civilization and imperial power. An isolated Christian kingdom thus had to protect its heritage by resorting to hollowing rock to tuck in their shrines into the rugged terrain of the land. The more than 150 or so churches of Tigray, carved from massive rocks, are thus as much a product and continuation of the architectural tradition of building as they are expressions of zeal and religious piety.
Archeological excavations in the 1970s revealed that late Stone Age industries thrived here along the steep crags of eroded phonolite rocks. It nonetheless takes dogged determination and an inquisitive eye, if not accompanied by local guides, to locate the blocks which were excavated and left behind showing
Piety is rewarded, or at least that was the reigning assumption of the time. It is no wonder to Ethiopians that Lalibela, a great king and master mason, was contracted by God in his dreams to build the eleven churches that bear his name. His crew, it is said, comprised of angels who expedited the construction
7. The largest monolithic stone mankind ever attempted to erect, Stelea One in Axum, is almost 33m tall and weighs 520 tonnes.
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8. The temple of Yeha, the earliest surviving edifice in Ethiopia, has mortar-less walls built with great precision. Deteriorated walls betray that the façade stones were dressed to perfection while the stones sandwiched within walls were only roughly chiseled. 9. The Nabateans, Arabs of South- West Jordan carved their city, Petra, into rock.
The masons of the rock hewn churches of Tigray and Lalibela cannot, however, take all admiration and credit for amazing feat of carved stonework. That would amount to forgetting the ‘cave’ architecture of Ellora in India and the massive, and media savvy, architecture of Petra in Jordan.
process and completed it in a record 27 years. So much for the European gothic churches of the time that took five times as long to be completed. Geologically speaking, Lalibela could not have chosen a better site for his project. As Building Stones of Ethiopia, a book by Haileyesus Walle and Tom Heldal has it; the red ignimbrites from which he hewed the churches with heavy axes and pick hammers are soft, porous rocks and easy to carve. The floor of the churches is a much harder and less workable black rock and best fit for foundation. So, Lalibeal’s stone masons stopped carving when they reached the basalt. What is more, the loose character of this type of rock meant that natural fractures would be almost absent. Had there bee any such fracture, the churches would have collapsed before completion. 28
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The overwhelming Petra, famously described as a ‘rose-red city half as old as time’, is a city carved in yellowish orange rock around the 10th century BC. These stone structures apparently served as tombs and temples having elaborate exteriors but at times perfunctory interiors. The monastery, which is an unfinished tomb façade, is probably the best known monument in Petra along with the city theater, built in Roman style with seats carved out of the rock. Buddhist monks of India continued this tradition of stone architecture when they carved multi-storied monasteries into mountain faces between the 3rd and the 2nd centuries BC. By the 7th century AD, the Ellora caves had come into prominence as magnificent temples of elaborate facades and interior walls, all cut from basalt cliffs. These stone structures had taken generations of planning and coordination to complete and there are no records of divine intervention in the case of Ellora.
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10. Beta Giyorgis, perhaps the best known of the churches in Lalibela, is a testament to the mason’s ingenuity. 11. Gondar’s palatial construction was a renaissance of stone masonry in Ethiopia. 12. The epitome of Indian architecture- there are about 35 such structures carved from the face of vertical cliffs in Ellora, India. 11
Centuries after angels stopped being commissioned as masons in Ethiopia, chiseling out shrines and marvelous from stone was superceded in favor of more prosaic methods of building on ground. Be it in the stone houses of the humble or the great imperial palaces of Gondar, stone work was mastered in Ethiopia - this time using mortar. The quadrangular castles of Gondar were made of irregular fieldstones of basalt that were cemented with lime mortar. Ignimbrites, quite similar to the ones in Lalibela were used in arches with striking resemblance 30
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to modern day brick blocks. The use of mortar- proverbially said to be concocted from Nug (nigger seed) oil, blood, eggs and what not- also gave us the stone bridges of the Gonder period. Always attributed to the Portuguese in their style of stone architecture, these undertaking of Emperor Fasil are the first real projects of infrastructure development with far reaching economic, communication and social impact. Worldwide, the use of stone has been dictated by its very natureprimarily its weightiness. Until
the 19th century, it fulfilled all requirements as a predominant structural material, exterior and interior finish, and was often used as flooring and roofing material. But when real estate demands changed at the beginning of the 20th century, the huge slabs had to be sidelined for what were becoming trendier construction materials. The limitation of the massive load bearing masonry units- less usable area at the base to accommodate growing heights, thicker walls, and small and sparse openings for windows and doors could no longer be tolerated. The stone trade, on its part, evolved too slowly to catch up with the emerging skycrapers. In many countries, the use of stone had to be limited to government buildings and residences of the high lofty since the labor-intensive techniques, unchanged through the centuries, proved too expensive. However, as it was being supplanted by better options in the West, stone work continued its momentum and developed further in Ethiopia as evident from the walls of Harer to the turn-of-the-century buildings in Addis. That is why taking a stroll along any street in Addis is a treat of stone work exhibition. From the high rise buildings that seem burdened by the weight of the marble they have to carry to the walled fences that are as high as the buildings they circumscribe, stone has found its way and become embedded into the city architecture. The ignimbrites, trachytes or basalts quarried from Addis Ababa’s volcanic terrain also go into the Koronkoch alley ways that line the city’s dilapidated neighborhoods as well as into our asphalt roads and cement mortar. As we hear often, history, however, has an uncanny way of repeating itself. As has become the custom in the contemporary architecture
of the West, stone is no longer used as a structural element in our mushrooming high-rises. This may be understandable considering the massive weight and consequent foundation requirements. But its use, even as facing or veneer, is being outdone by the omnipresent curtain walls we see in Addis. The city, which hadn’t given in to the hegemony of concrete for a long time is now succumbing to it. High prices and the long waiting needed to get the desired stones have turned this oldest of building materials into something of a luxury. The big irony is that this is happening when the rest of the world is turning its attention back to natural stone, especially since technological progress has dramatically changed the stone trade introducing thinner modules that are easily available. But you can count on stone for a dramatic comeback. Despite giving up its reign to more fashionable materials through the ages and being somewhat sidelined worldwide, stone is transforming construction once again. Dramatic changes in technology within the past 25 years have led to the production of ever-thinner slabs of stone, paving ways for new methods and application of this most ancient of materials in modern design. Architects worldwide have once again embraced stone in their designs thereby forcing suppliers to align themselves with this demand. What until recently had been a luxury item, because of its inaccessibility, is now more available to the general public through improved delivery systems. Nothing beats the beauty of natural stone, as millennia of tangible testimonies and concrete evidence show and stone remains on top as an enduring construction material. After all, easy access, workability and magnetic aesthetics are hard to ignore.
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www.anaimportexport.com
But what really is
Selam Berhe
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n general parlance, stone is that solid, dense and massive substance we use in all types of construction, consolidated enough to be cut, shaped or split into blocks or slabs for use in the construction of buildings and other infrastructure works. This wide definition includes all stones- whether igneous, sedimentary or metamorphic – that widely differ in many aspects but share similarities in composition.
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The classification of stones is not an easy task since there is no international scheme to follow. Some classify building stones based on their properties upon extraction- such as massive stone, when the stone is extracted in squared blocks, or slate when it is extracted as a slab. Another method of classification is based on their mineral composition given that building stones generally contain silica, silicates, or calcareous materials as their main constituents. The primary silica mineral is quartz, the most abundant mineral on the earth’s surface, and the principal component of granite. Feldspar, hornblende, mica, and serpentine, all silicate minerals, are responsible for the rainbow of colors in building stones. Calcareous minerals, on the other hand, include carbonates of lime and magnesia, such as calcite and dolomite, forming limestone, travertine, and marble. Although mineral composition determines much of the mechanical properties of stones, such classifications may not be of much benefit to the builder since the suitability of the stones for construction is by no means made apparent by it. A builder judges stones based on their strength, hardness, workability, durability, appearance and economy. Most builders, however, tend to go for aesthetic qualities such as color, grain size and texture when choosing among building stones. When stonewalls are required to bear loads, for example, a high degree of compressive strength is needed. Now that stones are mostly used as veneers and the load bearing stone elements are low-rise, the compressive load capacity requirements have become not so important. In any case, stones most often used are many times stronger in compression than required by the loads imposed on them. Another required characteristic of stones is the ease with which they can be sawed, shaped, dressed or carved, which has a direct influence on cost of production. Such workability usually decreases as the percentage of siliceous materials increases. For instance, limestone, which has little silica, is easily worked while granite, composed mostly of quartz, is the most difficult stone to cut and finish. Hardness also has a direct influence on workability and is directly proportional to silica content. The degree of hardness in stones varies widely from soft sandstones that are easily scratched to others that are harder than steel. What is of most value for users of building stones is durability since it reflects the long term cost of maintenance and practicality. The life span of a structure also depends heavily on the durability of the stone with which it was built. Some stones like granite age gracefully without loosing their sharp edges and hard contour while other softer stones mellow in tone and outline. Whether age makes a particular stone loose its strength and durability should first be checked before applying it for any purpose.
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The Life of Stone
t is in our nature, we the evanescent creations of earth, to view those that outlast us as eternal and unchanging. Just because some changes have to be witnessed in the course of many lifetimes, we tend to believe however much we are proven wrong, that there is no change at all. It is this same conviction that makes us believe our edifices of stone are immutable. Anyone who is familiar with historic buildings, however, knows this is untrue. The few stones that seem to be unaffected by centuries of weathering are exceptions to the rule while common building stones are prone to deterioration. That is why many buildings that were passed on to us through generations are now on the verge of disappearing. Stone decay takes many different forms, ranging from destructive to desirable, that which affects aesthetics to the one that alters mechanical properties. Many stones, after years of having their surface scratched by the elements and humans, develop a waxy, mellow shine called a patina. This is desirable since it captures and preserves the age of the stone on its façade. Other times the stone slowly weathers away yet maintaining a good surface. But when the weathering is relatively fast, scales of stone may drop away at once doing great damage to facades that are ornately carved. Decay may also be characterized by blistering of the surface or the all-together loss of integrity followed by the crumbling of the stone into pieces. A more deceptive type of decay is one which eats away the core while the stone may look perfectly sound on the surface. The factors that cause decay are present in all environments and can never be entirely mitigated. Of these, air pollutants are taken to be the main culprits of stone decay. This is especially true of industrialized nations but our fair city, Addis, is doing a great job of catching up when it comes to pollution. The effect of air pollution, especially of acid rain, depends both on the immediate environment and the color of stone. Lighter colored stones will exhibit more of the damage than darker stones. The surface of stone prevalently exposed to acid rain will gradually recede every time the surface is washed away while a relatively sheltered stone will only accumulate a tar like slime that blackens the surface and is gradually absorbed into pores. Another common cause of decay on stone is also the most common corrosive substance- salt. Studies have shown that the growth of salt crystals within the pores of a stone can generate stresses that are sufficient to overcome the stone’s tensile strength and turn the stone to a powder. The deterioration of many of the world’s greatest monuments can be attributed to salts. In general, salt crystallization is indicated by the formation of efflorescence, a visible growth or film on the surface of the stone that is usually light in color. The film later dries to form a powder, which will flake off or can be washed off, often taking very small amounts of the stone with it. As a recent research publication has it, biological growths on stone are both a blessing and blight. Many stone buildings can thank the plants that creep on and engulf their surfaces for their look that says ‘I have been here forever’. Remove the lichens and creepers and these buildings may look stark, diminished from their state of grandeur. However, the very same plants, coupled with bacteria and other organisms may contribute to the deterioration of the stone. The plants may even be a magnet of dirt that can become difficult to clean. Instead of thinking of stone as a permanent materials, it may be wise to understand that it has a life of its own. Maybe the old masonry proverb is true: Stone is simply a way-stop for sand in its progress back to the sea.
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Although many builders have abandoned the use of stone as a structural element, they still use it as facing veneer, floor finish, roofing material and in constructing retaining walls, steps, lintels and pathways. Although Ethiopia is not keeping up with the pace of the rest of the world, the extensive use of stones in construction is undeniable. The type of building
Basalt stone are extensively used for fence walls and storm-water channels
stones employed and the purposes these serve have evolved separately depending on the accessibility and abundance of the stones in particular regions. Tigray leads other regions in this respect, where stone is used in every aspect of the vernacular architecture from walls to roofs to pathways. Slate is extensively used in this region; it is not as exploited elsewhere. Most of the building stones used in the rest of the country are of volcanic origin. Hard and brittle basalts are preferred not only because of their abundance but also for their fractured texture that enables easy extraction. Ignimbrites are also used because of their lower cost of finishing. We see gray ignimbrites in Addis competing for attention in walls all over the city along with the red and yellow colored sandstones from Ambo. Contemporary Ethiopian architecture has recently seen the introduction of beige and yellowish limestone from Harer applied in façades and floor tiles. The buildings of Addis are also being adorned by marble from the 34
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country’s many sources including Gojam, Welega and Tigray. Granites, which had been forsaken since the times of Axum, are seeing a renaissance in Addis. It is thus worthwhile to look in detail at some of the outstanding building stones, which are widely used in Ethiopia.
Basalt The word basalt, meaning a black stone, is said to have had an Ethiopian origin. Basalt is an extrusive igneous rock and is often both fine-grained and dense. It is one of the most common volcanic rocks in Ethiopia, the others being ignimbrite and tuff. Basalt is rarely found in the international market as a building-stone, as it is difficult to extract in large blocks and does not normally take a polish. It is nonetheless widely used for housing construction. As far as its genesis is concerned, basalt is formed from the outpouring of lava all along the world’s mid-ocean ridges, where sea-floor spreading continually adds new crust to counterbalance that lost by subduction. In addition to lava flows, basalt is also found in the form of dikes and sills. Basalt is composed almost entirely of dark, fine-grained silicate minerals. It is commonly hard and difficult to work, but since outcrops tend to be pervasively penetrated by fractures, small pieces are easy to extract. Quarrying of basalt is carried out by using crowbars or similar means to open natural fractures. In many places, weathering may already have done the job, leaving behind usable fieldstone on the ground. Perhaps the most famous basalt flow in the world is the Giant’s Causeway on the northern coast of Ireland, in which the vertical joints form hexagonal columns that give the impression of having been artificially constructed. The dark areas visible on the Earth’s moon, the lunar mares, are plains of basalt. In Ethiopia large numbers of basalt
quarries are found throughout the highlands where they are highly fractured and hence easy to extract. Since most of these stones have perfect hexagonal jointing, fitting them together in walls or paved surfaces is made easy.
Granite Granite has been used as a building material almost since the beginning of history. The Egyptians used this stone to construct the Red Pyramid (26th century BC), named for the light crimson hue of its exposed granite surfaces. Many large Hindu temples in southern India were made of the same stone and so were, some claim, the stelae of Axum. Granite is a widely occurring intrusive igneous rock that has visible crystalline formation and texture. Along with other crystalline rocks, it constitutes the foundation of the continental masses, and is the most common intrusive rock found exposed on the earth’s surface. It is very strong, durable and is noted for its hardwearing qualities. These properties, aside from enabling it to take a high polish, also make sawing and cutting it very difficult. True granites, like the ones found in Ethiopia, have a composition with feldspar and quartz, and a
small amount of mica as their main constituents. These minerals determine the color of the stone which usually is whitish or gray with a speckled appearance caused by the darker crystals. Granite may also have a red, greenish or yellow color depending on the weathering it has undergone. Granites in Ethiopia are found in Precambrian regions in all four corners of the country - Sidamo in the south, Harer in the east, Gojam and Welega in the west and Tigray up north. Except in the south, all show promising quarrying potential. The Harer granites, with colors varying from red to brownish pink, are probably older than the others and may represent remnants of the Early Perecambrian (Achaean) granite-genesis of the area. In Gojam and Welega, two main groups of granites have been recognized although the deposits still remain to be investigated. The modern use of granite is as a dimension stone and as a flooring tile in public and commercial buildings and monuments. With increasing prevalence of acid rain in parts of the world, granite has begun to supplant marble as a monument material, since it is much more durable. Polished granite has been a popular choice for kitchen countertops because of its high durability and aesthetic qualities. Granite is also applied in flooring, paneling, veneer, column facings, stair treads, and flagstones, as well as in landscape works.
SEBHATU AND SONS Property Administration and Security Service Plc.
Tel 24Hrs 011-5539525/26/27/28/29 Fax 011-5528677 P.O.Box 101504 Addis Abeba, Ethiopia email: sebhatu_sons@ethionet.et
Asset protection and loss prevention services for: Construction Sites Industries Shopping Centers Residences Hotels Financial Institutions International Organizations Recreation Facilities Agro-industries
Limestone Limestone constitutes approximately 10 percent of the sedimentary rocks exposed on the earth’s surface. Its use as building stone throughout the world is significant especially in making cement and concrete. It is easy to extract, easy to cut and has many applications in the building industry. Direct crystallization from water (usually seawater) or accumulation of shells and their fragments are two of the ways the stone is formed. In the first case, it carries a record of the chemical composition of seawater and it provides evidence of how that composition has changed with time. In the second case, limestone provides a record of the evolution of many important fossils. Limestone usually forms in shallow water less than 20 m deep and thus also provides important geological information on changes in sea level over time. Limestone rocks are frequently riddled with caves. As a sedimentary rock, limestone predominantly consists of carbonate minerals, such as calcite and dolomite. The principal component of limestone is the mineral calcite, but it frequently also contains the minerals dolomite and aragonite. Pure calcite, dolomite, and aragonite limestones Construction Ahead, nov-apr 2007
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are clear or white. However, with impurities, limestone is known to take a variety of colors. Ethiopian limestones are often beige, yellow or brownish, more cemented and fossiliferous. Their production at present is most common in the Harer area. Limestone deposits in the Abay gorge and in Tigray are also being exploited more and more. Many parts of the world use limestone as an important building stone. For example, porous type limestones are used for rubble and ashlars in local housing. Moreover, limestone is used as cut stone for building, and is common throughout Europe in cathedrals and palaces where the relatively soft nature of the stone allows decorative carving. It is also widely used as crushed stone, or aggregate, for general building purposes, roadbeds and railway lines. Finely crushed limestone is also used as filler in industrial products such as asphalt, rubber, plastic, and fertilizers. When heated, the calcium carbonate in limestone decomposes to lime, or calcium oxide, which is important as a flux in smelting copper and lead ores and in making iron and steel. Lime is a key ingredient in the manufacture of cement and concrete.
Marble Commercially the term marble is applied to any rock composed of calcium carbonate that takes a polish, and includes some ordinary 36
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limestones. Marbles are appreciated for their beautiful colors, structures and high gloss on polished surfaces. They are far easier to saw than the harder rocks, and wire sawing is a frequently applied method in extracting them. Marble is formed by metamorphic transformation of limestone many kilometers beneath the earth’s surface over a time span of many millions of years. This process occurs along zones where the earth’s curst is extensively deformed due to collision of continental plates. Most of the mountain chains in the world are formed in such areas and marble deposits are found where such old mountain chains have been stripped and eroded, exposing the rocks following their long journey to the deep interior of the earth and back to the surface. The color of marble depends on the composition of the original limestone from which they evolved. A pure calcite marble is white and the purest form of marble is statuary marble, which is white with visible crystalline structure. Mineral impurities give a variegated pattern of color to marble. For example, organic material in the limestone is altered during metamorphism to graphite, which renders marble gray. Although a variety of colors are possible, more rare colors, such as sky-blue, can be related to impurities or failures within the calcite crystals. Predominantly, Ethiopian marbles are calcites, and coarse grained,
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and are gray and white, although smaller deposits of pink, skyblue and greenish marble are also found. We also find several colors of marble in Tigray, such as white, yellow and violet. The most extensive deposits of marble are found in Italy, UK, and USA. In Italy there is the famous deposit is found in the City of Carrara, northwestern Tuscany. In Ethiopia, the marble deposits are found within the Precambrian metamorphic regions. Some of the most interesting deposits we have are in Welega (Daleti) and Gojam (Mora, Bulen, Mankush and Baruda). Several stone mining companies, including National Mining Company and Ethiopian Marble Industries, work a number of deposits in these areas. Known marble deposits are also found in northern Ethiopia. These marbles differ from the ones in the west because of their fine-grained texture, even though their age is approximately the same as their lithological relatives in Gojam and Welega. This is due to the lower grade of metamorphism undergone by the rocks in Tigray. In other words, the marbles of Tigray remain closer to the limestone from which they originated. The high expense associated with marble is not a new phenomenon. Marble was an expensive building material even in ancient Greece where it was used mainly for decorated sculpture, and not structurally, except in the very
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1. Beautifully polished limestone glows in the well-lit corridors of the Sheraton Hotel. 2. Marble, the ever present stone in our contemporary architecture, is used here as floor finishing. 3. Ambo sandstone has found a new home in Addis on the walls, fences or arcades of the city. 4. Decorative element of old houses in Addis include window quoins made of ignimbrite.
grandest buildings of the Classical period. In more recent times, it is used as finishing material in building construction while its statuary importance has remained significant.
Sandstone These are sedimentary rocks formed by the weathering and erosion of all types or preexisting rocks. They consist of sand or quartz grains held together by natural cementing materials. Their quartz content makes them strong and durable. Sandstones vary in color from buff, pink, and crimson to greenish brown, cream, and blue-gray because of tiny traces of feldspar or mica. Both fine and coarse textures are found, some of which are highly porous and thus cannot be polished. The structure of sandstone lends itself to textured finishes, and to cutting and tooling for ashlar and as dimension stone in veneers, moldings, sills, and cop足ings. Sandstone is also used in rubble masonry as fieldstone. In Ethiopia, sandstone beds are found mainly in Adigrat, Tigray, but also in central regions like
Ambo town, where a highly porous yellow and red sandstone deposit exists; the Bure limestone quarries in Gojam is less known but still of good quality sandstone. The Ambo sandstone is predominantly finegrained and porous allowing easy splitting and chiseling.
Ignimbrite This highly silicate rock occurs worldwide and is associated with many volcanic provinces having high-silica-content magma. Ignimbrite originates from violent eruptions of superheated ash, pumice and gas, and is formed by the deposits of these pumice-rich pyroclastic flows. Ignimbrite is primarily composed of a matrix of volcanic ash, which is made of shards and fragments of volcanic glass, pumice fragments and crystal. The overall colour of ignimbrite is usually quite light: its high silica and feldspar content gives it white, yellow or beige color. The high content of heavy minerals such as magnesium imparts to it dark grey, brown, or an almost black color. Weathering can sometimes alter light coloured ignimbrite to pale pink as a result
of iron oxidation. Ignimbrite deposits can be voluminous with up to hundreds or even thousands of cubic kilometers. Some of such deposits form sheets that can cover thousands of square kilometres or create thick, valley-filling deposits, while others form a landscape-mantling veneer that thickens in valleys and depressions. Soft ignimbrite rocks are common in areas of the Rift Valley in Ethiopia. The most important quarries are, however, located in and around Addis Ababa, where several of these are worked on a cooperative basis. Large deposits of ignimbrite are also present in several other places in the country, including Gonder and Lalibela. Ignimbrite splits into convenient slabs, useful for flagstones and in garden edge landscaping. Its application in Addis Ababa has been extended to surface veneer and structural cladding as well as road surfacing and other construction purposes. Reference ; Building-stones of Ethiopia by Tom Heldal and Haileyesus Walle.
TEPLCO TYRE UNIT
Tel 011 366 0229 Fax 011 466 1562 teplcopirelli@ethionet.et
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Extraction and processing
T
he method of extracting stone is basically the same today as it was some 4000 years ago. Early builders of the time were the first to notice that cliff faces of sandstone, exposed by rains, can be the source of larger amounts of building stones than field-stones strong men gathered through their lifetimes. So they set about scheming on techniques that would enable them to cut out larger units of stones from these deposits. It soon became a no-brainer that natural fault lines would be the ones to hammer at to ease the labor of extraction. Slates faces were then split into thin sheets for roofs, and sandstone boulders were pried out and shaped into smaller blocks with metal pick axes. The smaller units then went into load-bearing walls. The quarry men of Ethiopia have stuck with these simple principles for millennia, working on deposits, very close to the where they will be used. They break their backs digging the topsoil covering the rock mines underneath and then pry the rocks out with a long metal tool they call Mawredga. The larger chunks are then rolled down slopes where laborers at the base of the cliff split them apart using wrenches (Shibelek) of various size that are stuck at focal points and hammered in until the rock breaks apart. The ‘finished’ product is then sold to chiselers at prices which by no means reflect the amount of sweat that goes into production. On an industrial scale, the same old process of drilling and splitting stone is applied but with more sophisticated means that were developed a hundred years ago. The quarry face is initially opened up by exploiting the naturally occurring lines of weakness, provided by joints or bedding planes in the rocks. Stratified sedimentary stones such as sandstone and limestone can easily be cut across their natural cleavage planes. Holes are drilled close together along the face of the rock, and plugs and wedges are then driven in with sufficient pressure to split the rock between holes. Although exploiting the natural fractures facilitates quarrying, it nonetheless limits the thickness of the final product. Alternatively, extraction can be done by blasting. But blasting may not be the best option in quarrying building stones since the requirement is to recover large undamaged blocks from the quarry face that can be subsequently dressed. Blasting
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could have a serious detrimental effect on the structure of the softer stone varieties if not undertaken with care. The use of wire saws, especially of diamond wires, for extraction has also spread across many quarries. These are continuous wire loops that are embedded with diamonds and driven by pulleys and can cut a smoother surface, and subdivide large blocks of stone for easier handling and finishing. Recent improvements in cutting technology have resulted in the capability to cut thick slabs in the quarry, rather than the usual large blocks. The first products of quarries are usually large and have rough, irregular faces. To have an acceptable quality, the blocks should not be smaller than 3-4 tones (or preferably more) and should not have cracks or veins. These blocks are reduced in size by hammer and chisel, as is the case in local quarries, drilling and the use of iron wedges (plug and feathers), by diamond wire saws or using high pressure water jets. The technology has developed so much that advanced machineries are now able to cut the stone into any desired shape and required dimension. The past seven decades have probably brought more change to the ways of quarrying, processing and fabricating natural stone than have the previous two thousand years. The demand of light weight cladding for high-rise architecture was the driving force behind the technological advance. In 1970, a new technology developed by the Italian stone industry in became the salvation stone manufacturers were looking for after years of loosing the market for lighter products. The technology, as innovative as the idea of attaching a non load-bearing skin to a steel building frame, enabled them to produce thin sliced marble and granite panels light enough to clad high-rises using wire saws with diamond tipped blades. While the prices of other cladding materials went up, that of stone came down because of this new capability of producing more for less. Today, processing of stone begins either at the quarry or other cutting plants and involves honing, polishing, hammering or treating the surfaces of
slabs. In addition to sawing, stone may also be dressed with hand or advanced machine tools. Planing machines first prepare the surface for hammered, polished or honed finishes. Honing is done by rubbing the stone surface with an abrasive such as sand while water is sprayed in the process to control dust. Larger surfaces may require to be honed with machines. Polishing is another alternative which provides some measure of sealing the stone pores and helps protect the surface of the stone from deterioration by atmospherÂic weathering agents. It is usually reserved for granite, marble and very dense limestones that can hold a high polish. However, if rough surfaces is desired another finishing technique, flame-cutting or thermal finishing, is a good option especially for granite. A natural gas or oxyacetylene flame is passed over a polished surface that has been wetted. The water that has been absorbed by the stone changes to steam and breaks off the surface, leaving an irregular finish. Most stone products used in the world today are, however, still worked in the old fashion way – with manpower, simple tools and great skill. The mason dresses each face of the stone using pick, hammer and chisels continuing a tradition as old as the art of building. In western countries, the hand tools have been replaced with pneumatic ones to produce more uniform surfaces. In Ethiopia, where the technology for refined finishing is not available to all, if it at all exists, rough blocks are usually exported to European and Far Eastern countries with well-established stone processing industries. Raw blocks are priced depending on their color and structure. Rocks with rare colors like blue, yellow or pure white are more expensive than those with ordinary colors. Such a fluctuation of prices could have been avoided had we been exporting finished products to the major consumers in the US, Japan, Middle East and of course our existing customers in Europe and Asia. Fortunately, much hope can be invested in the burgeoning stone production industry, which started germinating in the 1990s and is still growing. Construction Ahead, nov-apr 2007
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interview
Ato
Beyene Egigu
A
s the right brain is to the left, the analytic versus the synthetic, the speculative as opposed to the practical, there is the menial as a counterpoint to the mental. Artisans, arts and crafts people working with their hands, are men and women of action. In fact, of backbreaking toil. Their occupation is mostly one of using their hands: to grapple usually with hard natural materials, to transform them by fashioning them into something equally as elegant as it is practically functional. Occasionally their work may also mean playing fancifully and freely with natural material and imitating nature’s forms. The clear cut and direct, the definite and tangible, the concrete and solid, the natural and simple are an anathema to academicians, expert consultants, diplomats, politicians and even lawyers when they are on the defensive. Not so with crafts-people. It is the contrary with them since they are short of words and every bit full of deeds. What does a conference, seminar, workshop or even one-to-one interview mean to a potter, a tanner, a smith, a weaver, carpenter or a mason? Especially when the time is seen in terms of how much more can be accomplished by each of these artisans and what that means in earning their livelihood. Besides, from their perspective, what would be the point when the time could be used to do some useful and practical work. You can imagine then why it was impossible to get a mason to give us an interview and talk about his life and work. And yet we know that the trade is an essential, indispensable and key feature of the industry. We knew, of course, we have to have their story, their lot and the value of their skill. And this directly from them and in their own words. But how? We had a go at it by approaching them directly, which was predictably ill fated. Then we tried what 40
Construction Ahead, nov-dec nov-apr 2006 2007
has become an Ethiopian custom: besew. Call it using a presenter, an intermediary, a mutually known lobbyist. This was half successful but it was clear to us that the consent was given on account of the solicitations on our behalf and not because their heart and mind was in it. This did not go with us and the conditions that need to be there for a genuine and true interview. This put us in a serious quandary as to what to do. The subject of the magazine had already been decided on and other features of it were already pretty much in place. It was then that one member of our research team came up with the idea: how about going to them asking for their services? That is exactly what we did: pose as a client. The problem here was that having fixed on our master mason and having negotiated the terms doing business, when we started firing our questions intended to have our mason speak to – the quick response came back: what does that have to do with the job? Hence, though absolutely harmless and good natured, there was at times something of a tassel. So, don’t be surprised if the tone of our dialogue with the master stone worker, Beyene Egigu, comes off more as an interrogative deposition rather than an intimate interlocking – literally an onthe-job conversation about the job. Never mind that it was difficult. It demanded more tact and creativity than usual. But when all is said and done, we believe we have done a fair job in bringing the invaluable work and life of a representative of these master artisans of a great tradition.
Our conversation started at the site near the towering buildings of Haya Hulet (off Haile Gebreselassie Road) where we first met him working on a new residential building. He took some time off his work to show us around the site and later took us to the place where he buys the stones he works on. CA: How does one tell a good stone carver stone carver? Yesterday, we had gone to 22 looking for a person of the craft and people with paintbrushes, carpentry and plumbing instruments were coming to us saying they can do it. How can we tell if someone is good at it or not? BE: You can tell a carver’s expertise only from his work. Speed does not mean much since this is a trade where finishing first does not have much value. The job actually holds your hands back. In some places, people may claim to be able professionals and then prove otherwise when put to the test. You have to see them at work: how they handle the instruments and when they stop carving and say ‘I am done with this one, this is all I can do with it’- whether that satisfies you or not. But some really do it a rekik sira (refined work). CA: What do you mean by rekik? BE: It means they have done it in keeping with standards. The walls you saw on the site I was working on are rekik. CA: So you are saying you are a good carver? BE: Yes. CA: What makes you good? BE: I stick to measurements and I do good angles (I keep with the squadra). A breeze of wind cannot get in between the masonry blocks I carve and put in place. I don’t give or take a single millimeter of error in the dimensions. Plus, if I weren’t good, why would the engineer I am working for right now choose me over other masons again and again? CA: How do people, who want to contract a good mason, find the kind of skilled craftsman you are talking about? BE: Every engineer has somebody who does such kind of work. So whenever his clients require it one, he will hire him. The engineer I am now working for saw how good my craft was and called me for another job. This was long after I had finished working on one of his sites. I have since been working with him for five years. On one of the projects for which my employer contracted me, I worked on stone that came from Axum and was only 6 cm thick. CA: Do you have other people working under you? BE: Yes, I have both apprentices and experienced masons who work with me on contracts. The other carvers you saw on site are my employees. I saw their work on some sites and I decided that they were the ones I want to work with. I taught all three of them the workings of the trade. CA: Other than engineers, is there any way that a person who is not directly involved in construction but wants to build a home, can contact skilled carvers? BE: You have to know someone who knows such people Construction Ahead, nov-apr 2007
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Masonry Variations: the stone curtain The stone curtain project, undertaken by Matthew Redabaugh, a mason, and Jeanne Gang, an architect, in the US is a remarkable demonstration of exceptional masonry design and craft skills that challenged the traditional use of stone. The project was part of the masonry variations event where architectural students and apprentice masons were given an opportunity to work together, exchanging designer and builder roles. The stone curtain project was an answer to the challenge put up for the design and construct a hut-like structure, with internal space and outside façade, and give stone a futuristic application. The project took nearly one year. Jeanne Gang’s design took stone, a material that performs best when subjected to compressive loads, and put it in tension, linking piece to piece in a series of chains to create a shell-like form, the Stone Curtain. The basic mechanics of the structure was modeled on a jigsaw puzzle, with individual interlocking elements with key and key-hole, hanging in tension from the brick dome of the ceiling without any sort of support or frame. The entire construct, comprised of 620 individual pieces, is 18’ tall and weighs 2000 pounds. A marble called Bianco Limone from Turkey was chosen, a tightly constituted, fine crystalline calcium carbonate that gave out a resounding ring when struck with the knuckle. A battery of tests was imperative to determine if the stone can in fact be hung in tension. However, no tests then existed to determine stone’s strength in tension since there had been no use for them until this project. The results of the tension tests surprisingly exceeded everyone’s expectations when the stones failed under 7 times the expected amount of load. Each individual stone was tested to find any hidden cracks. The back of every piece was then honed to increase its translucency. Blue, bluegreen, white, yellowish and beige colors were used in the curtain and these were randomly shuffled to avoid the potential for any single color based splotches or areas that may occur within the fabric of the curtain. As a fail-safe in case of individual stone fracture, each piece was then reinforced with epoxy resin and fiberglass. After the centering frame was constructed, the architect and the mason built the curtain fitting each piece of the stone jigsaw with its counterpart. Construction Ahead, nov-apr 2007 42 from Abstract Stonexus magazine
and get their phone numbers. There is no other way of doing it. We do not have stationary posts so no one really knows us even around where we live. CA: Are the best masons in Addis known by name and do you know them yourself? BE: Of course, we know each other. There are many whom I admire. The carvers who come from Gurage are reputed to be the best. I myself am from Guranz, which is a place in Gurage zone. CA: What types of stones have you worked on so far? BE: I have carved Kebena stones, Beshale, Bazzola, Nazareth, Kotebe, Legetafo, Ambo and even those that are called Nairobi. The stones are named after the place they come from. CA: Is it the same for the Nairobi stones? BE: No, I don’t know where that name came from. Some also call them Kotebe stones. In fact, the Nairobi stones are now being abandoned since they have low resistance to moisture and in some instances even scratch and disintegrate easily. They fade easily especially when exposed to direct rain although there is a harder variety that is not permeable to moisture. I believe no stone can equal the Kebena stones in quality. But these stones require great skill and a really adept carver. CA: Do you also distinguish the stones according to their hardness? For example, how can we tell the difference between the Ambo stone and the Kebena one? BE: If you look closely, there is a lot of difference. The Ambo stone does not have as much strength as the Kebena. It also fades easily like the Nairobi one once rain falls on it. So, if you are using Ambo stone, it should be under protected condition where rainwater does not directly get to it. Now that you mentioned it, the red stones from Legetafo resemble the Ambo stones
more closely than the Nairobi ones. CA: Aren’t there any other stones that are imported to Addis from nearby places? BE: That depends on how deep abatu’s (the project owner) pockets are. I told you about the stones that were imported from Axum. Sometimes people bring stone from Nazareth. CA: Have you ever worked with marble or granite and do you know their properties? BE: No. That only needs building the masonry so any mason can do it. CA: How are prices these days? BE: They have gone up. Some cost 6 birr per rough block, others come at 5 birr like the Kebena stones. They used to come for half that a couple of years ago. When the cost of living increases the prices of the stones too go up. The Legetafo stones also come at 5 birr. You can buy the Kotebe stones for 1.20 to 1.50 birr. The Nairobi stones are the cheapest at 1 birr. The Ambo stones sell at 12 birr for each meter and the buyer gets to measure them and make sure. CA: Which stones are easier for you to work on? BE: Every kind of stone requires work. You have to sweat it out to carve them all well, no matter where the particular stones came from. There are no easy stones to workbut of all the stones quarried in and around Addis, the Kebena stones are really hard and demanding. But I don’t have preferences- I will work on any stone abatu (the owner) tells me to do. CA: Which stones are preferred these days by people building their homes or fences? BE: If abatu is rich, he goes for the Kebena stones. Kebenan yemiasnek yelem – there is nothing that beats Kebena. CA: How much does the owner have to spend for you to call him rich?
BE: Oh, that is a great deal of money. CA: Assuming we want to build our home – a simple villa - in stone, how much do we need to spend? BE: You should first think it through. You may have to bail out after you have already started. Imagine, you have to buy each piece for five to six birr and pay for laborers like myself. Think of the number of walls that have to be done and honestly, you may end up having a heart attack. CA: But how much do we have to spend? BE: I don’t know. CA: You do. BE: It is the engineer who knows the cost and he does not tell me anything. He deducts his share before paying me so there is no way I can know the actual cost. [When pressured to quote a figure, he says] the rough estimate is at 70 -80 birr per square meter.
40036 Addis Ababa Ethiopia
251-114-420-800
251-114-400-621 251-114-420-153 bde@EthioNet.et
www.cdsco.com.et
CA: How long have you worked as a carver? BE: Forget it. What is it to you? We wonder why: Does he really think that is insignificant or he has smelt something of what we are up to? CA: It must be two years or maybe two years and a half. You are too young to have worked for more than five years. He laughs as he twinkles his mischievous looking eyes. BE: What is two years (Hulet amet min alat)? But why are you so intent on knowing? CA: It can’t be much longer than 15 years. BE: Yeah, you can say that. It is close to 10, 15 years. CA: Where have you worked in the city so far? BE: There isn’t a place that I haven’t set foot in Addis. I have even been in all four directions
Managing Director 251-114-400-960 Design Department 251-114-420-628 Contract Administration 251-114-420-959 Materials Testing 251-114-400-623
of the country– Mekele, Axum, Welo, South- you name it, I have been there. I am one of the masons who worked on the Axum Hotel in Mekele- that was a difficult joband I am among the many who did the Hawelti (Monument) in Mekele. CA: Did you pick up any skills in Tigray? BE: No. There is nothing new to learn. There are stones here and there are stones there. CA: But the stones are different and the skills needed to work them must also be. BE: There was something different in the construction of the Axum Hotel in Mekele. The curved feature on the façade of the building that resembles the Axum stelae was a bit difficult to do and I learned from that. Aside from this, I am telling you there was nothing new except for the fact that they have more stones there.
Architectural & Engineering Design of Buildings, Roads & Water Works Construction Supervision, Quality Control & Contract Administration Geo-technical Investigation, Materials testing, Analysis & Foundation Recommendation Construction Ahead, nov-apr 2007
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CA: How did you learn your craft? BE: From my father. He learnt from the Greeks who used to work with large blocks all over Addis. So, he then taught me what he learned form and that he knew. CA: Do you know on which buildings your father worked? BE: He used to work for this company called Building Construction that was set up during the Derg period. He was a government employee. When the government changed, the company was dissolved and he didn’t take any employment after that until his death. But I haven’t bothered to know the buildings he worked on. CA: Has anyone else, among your brothers and sisters, followed your father’s steps into this profession? BE: No. CA: How long does it take to learn the craft? BE: Depends on how good the student is. Those who don’t take the time to master the skills will obviously get fired from every job they get. But it takes about a year to learn the trade. You should learn everything in that one year. CA: Everything? BE: Yes, you learn how to make smooth surfaces, how to do perfect corners using the angle metal (squadra). There are many ways of getting the job done and you have to know each of these well. CA: If a young person comes up to you and tells you he or 44
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she wants to learn the trade, would you teach him? BE: Why? What sort of life would they have hammering at hard stone for years on end? I would not recommend it and anyway this is not the sort of life the young kids are looking for. They would rather go to school learn something different. Sometimes, they come to learn and they see how much hard labor is involved and flee back to their schools. I think we are the last in the line still willing to work on stone. You know, I hear things are much better in Tigray in this respect. CA: Why is Tigray better? We were there a couple of weeks ago and the trade is also disappearing there. BE: Many masons have gone to Tigray to work on projects and they seem to be doing well. They also work extra hard. CA: But the craft will disappear. BE: If you are that concerned, you should gather them in one place and teach them how to do it. I can’t say you will find anyone who is interested enough. CA: But what will happen to your jobs if you are unable to hire other able individuals tomorrow? BE: What can we do? Carvers are fed up. You can’t last in this line of job unless you are able to eat well and then sweat it out. It’s too much of a struggle. CA: Don’t you get paid well? BE: You actually get paid well. It is the labor that drives many away. You need a lot of patience in stone carving to get to the stage I am in right now. When
some carvers see how well others are doing in other professions, they simply abandon it instead of waiting until it bears fruit. What is more, it is not a guaranteed job. Sometimes you have to sit idle for two to three months until the next project comes up. Just because I have found jobs constantly doesn’t mean that others are faring as well. CA: Is there still a good working opportunity for stone carvers? Are people still doing their houses in stones? BE: You live in Addis, don’t you? When do you think is better for us – today or yesterday? CA: Yesterday. BE: Wrong. Today is much better. Yesterday’s homes are mud houses. People are getting richer and they can now afford to build in stone. CA: That means you are getting richer. BE: No one gets to become rich in this trade. How can that be possible if you spend your life with stones? You end up dead, that is
what you do. CA: Do you ever get sick on account of the work you do? For example, asthma from the dusty particles that flake off the stone when you chisel? BE: No. I am healthy and so are the other masons and carvers I work with. After a very short drive, we arrive at our destination behind the stables in what is commonly known as Balderas. We wait for a couple of minutes at a closed gate all the while being hustled by some young men trying to sell us blocks of stone, which Beyene insists are of little worth. Wondering if it was the 12th day of the Ethiopian month, St. Michael’s, in which case the quarry would be closed, we patiently await the arrival of someone to open the gate and let us in. Someone does eventually appear, but in no great hurry. Finally, we are let into a huge compound where stones have been piled up in three rows. We found out later that the actual quarry where the stones come from is
within the same compound, down a steep slope. Beyene rushes up to an old man and introduces him to us as Ato Zena, the owner of the quarry, and credits him for his livelihood. Ato Zena, on his part, was quick to start showing us around his quarry and in particular his ‘collection’ of stones. Ato Zena: These stones are quarried in layers. The first layer is the hardest brownish stone. Next comes the whiter variety and finally the stones with perforated surface or eyes, which are called aynama (with eyes). CA: What are the prices? Ato Zena: All three rows sell for 5 birr for each block. The Gimbar (literally, forehead) ones used as corner stones cost 5.50. CA: Which stones should we buy? Which do you think are better? Ato Zena: Buy from all three rows. You should do an ‘aperitif ’ or guramayle (mixture) of the three types which is more beautiful to look at. [He adds, once Beyene
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gets out of earshot]: the masons will always try to avoid the brownish stone since it is difficult for them to work on. But you should trust me and insist on buying it. You won’t regret your decision once you see the finished wall. CA: How long has this quarry been around and working? Ato Zena: I have owned it since the time of Haile Selassie. I started working on it right after I left the army. That means it has been in my hands for forty years. Before the revolution (1972) we used to buy the land from private owners when we wanted to expand but in 1976 (Ethiopian Calendar) the government surveyed it and took it into its possession. Now, we have an agreement with the government to quarry the land as long as we cover back the mined or exhausted quarries with stone and soil. We have been given 46
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the cadastre map according to that agreement. For example, the ground we are standing on right now used to be a quarry a long time ago but has been filled up with soil. BE: The government may take away or confiscate the stones you buy from the vagrants but these here stones are legal. CA: Does that mean you pay taxes on this quarry? Ato Zena: Yes. Three percent of our revenue goes back in taxes and I pay an additional 700 birr every year. They divide this into two and half of it goes to the Ministry of Revenues while the other half goes to the Mining and Energy Ministry. Now I have five laborers and five people of craft working here. CA: Aren’t there any carvers that shape the stone while it is still at the quarry? Wouldn’t selling finished products be more profitable? Ato Zena: A long time ago, we had enough space in our compound to also do the chiseling and we used to sell processed stones. We abandoned it because of lack of enough working space. Upon Ato Zena’s permission, we make our way down the winding pathway, along the steep slope, to where the five quarrymen were hammering away at their wedges and prying out blocks of stone from the quarry face that seems menacing just to look at, let alone work on. There we meet Yimer Mekonnen, who
lets out a sort of tormented grunt every time he raises his hammer above his head and hits a wedge stuck in the rock. When he paused from his work to talk to us, however, he seemed jovial and very willing to answer a couple of our questions. His buoyant spirit was inexplicable, that is, until we spotted a drink- a cup of tella (the local barley brew) - he keeps close to him and takes quick breaks to take long thirsty sips from. He was kind enough to offer us a sip. He was as resistant as Beyene to say how many years he has worked on the quarry but we did finally squeeze it out of him: he has spent fifteen years on this particular site. CA: How did you reach this low down on the ground since the top most soil seems to be some 7 meters up? Yimer Mekonnen: We started quarrying at the top and made our way down. So the cliff you see us climbing up and down today is the one we carved out ourselves with our hammers and axes. You see, the stones at the bottom of this cliff may be easier to quarry since the Kebena River percolates through the rock softening it. The bottom rock has a lot of lime (nora) and wet soil. The sun, however, has dried up the stones on the upper most strata, and they require your sweat and your blood before you can get them out. Ayen ayto leb yeferdal – (The eye sees and the heart judges therefrom). If there is moisture, our work maybe easier but if not then it is the sort of livelihood you would call ‘afer bela yemibalew injera’- it is not injera but soil that he eats. But we go on digging and filling it back in with soil until we arrive at the limits defined by Zena’s cadastre. CA: When do you think this quarry will close shop? When will you reach the cadastre’s limits? Yimer Mekonnen: We never know. For instance, I may be thinking that I will produce a certain number of stone blocks today but who knows, death may overtake me. CA: And if death does not come today? Yimer Mekonnen: If it were up to me I would have it so that I would work everyday and earn the bread that I am used to getting. That is what would make me happy and I don’t do any more calculations than that. I cannot tell how much I will eventually produce. CA: What are the tools that you use and how do you use them in quarrying? Yimer Mekonnen: We use the meradja (a large hammer), the medosha (medium sized hammer), mero (chisel), shebelek (wedge) and degeno (crowbar). The quarry face is opened up by the degeno or larger wedges called the mawredga. The larger blocks are ‘pecked’ with the mero (chisel) and the wedges are placed on those pecks and hit with the meradja (hammer). The rock splits at this point and all you have to do after that is to sell it by cutting it up into pieces like Christmas dabo- the traditional bread). Construction Ahead, nov-apr 2007
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CA: How do you know where to put your wedges and where to hit? Yimer Mekonnen: Only through experience . I cannot really explain this to you. – there are two faces of the stone- the first is the wuha , the longitudinal section, which splits like akirma (the grass used in basalt work) and Gomeda which is the opposite side and less smooth. What I can tell by looking at the cross sections is whether the right face of the quarry has been opened or not. This means that if I open the quarry face in the wuha cross-section, I can only get up to 10 cm thickness of processed stone but I can cut it with a single shebelek (wedge). The other face can produce up to 20 cm thick blocks. CA: But how do you come to know all this? Yimer Mekonnen: I learned it from those who came
before me. When I first came to the quarry to learn how it is done, I thought what my friends were doing was sheer miracle. Now I am a master of the trade just like they are. CA: You were talking about centimeters and we don’t see any measuring instruments around. How do you do your measurements? Yimer Mekonnen: The distance between a man’s outstretched middle finger and his thumb is 20 cm. 48
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That is all we need to know. CA: How much are you paid each day? Yimer Mekonnen: The owner gives us each 18 birr a day and he gives me an additional three birr for transport expense because I come all the way from Kotebe. But that is it. I have seen better times but it wasn’t meant to last. I was a deacon before I abandoned it to come and work here. I guess this is my destiny. Leaving Yimer behind to toil on the rocks like he has become used to, we go back to choosing stones to buy with Beyene the carver. He goes on to explain what methods he uses to choose the stone… CA: How do you tell which ones are good and which are not? Is it like shopping for groceries? BE: I have a good eye. I can tell which stones are likely to crack since these have tiny fractures (ley), which will break apart under a hammer. And I will go for the larger sizes since these are better to work on and allow for amending errors. CA: Why are the larger stones better and why are there still small sized stones on sale? BE: Why are you complicating things? If you do not like the stones I am choosing for you, you can always choose yourself. The smaller stones, for your information, are those left behind after other clients have taken their choice. I am here so you are not fooled into buying such kind of low quality stones. [With the stones of Beyene’s selection loaded in our car, we drove back to the site trying to engage Beyene in more conversation about other carvers’ skills.] CA: Being the good carver that you are, do you go around town looking at the stone masonry faces of many buildings and say this is good and this is not so? For example, would you call the stone wall on the building facing us a good one? BE: How would I know? CA: But we are looking at it. BE: Who cares. If the engineer accepted the final product, don’t you think that is reason enough for it to be good? CA: When you look at masonry done by others, do you investigate how it was done? BE: I already know how it is done so what is the need for questioning how? CA: Can you at least tell the difference between what used to be done in the past and what is being done now? BE: Yes. Today, people can do their walls in any color they choose. Contractors can also change the type of work they do from site to site. Even when a certain type of masonry is abandoned in some parts of Addis, it gains momentum in the extreme opposite corner of the city.
CA: You said you have been to Axum. What did you feel when you looked at the stelae? Did you look at them and say ‘I can do that’ or did you just wish you could? BE: I know I can’t do the top carving – the head. No, I take that back- the whole thing cannot be done with today’s technology. But there is no point wondering about it- it simply cannot be done. [We arrive back at the site Beyene is working at. With a swift change of manners he goes about giving out orders to the other masons that work under him; and in no time, all the stones we have bought are brought to them. He scolds, begs and promises them bonuses for us to photograph them and have them answer some of our questions.] CA: What sort of carving are you doing now? BE: What we are working on here is the gerdef, where we only first chisel the stone to resemble a rectangular block. Then we measure either 10 cm or 15 cm thickness and start chipping away the remaining thickness. The length is determined based on how large or small the originally quarried piece was (endewetaw). Then we start measuring the angle with the angle metal or squadra so that we have a perfect 90° at the corners. We then chisel some part of the interior but leave the middle most part of the face as is. This method is also called the bugnatta. Another style is fino, the smooth work in which the front side is completely chiseled at the end. Right in the middle of walls made of pieces of both types of carving, we insert a single nekes piece. This is different because after smoothening the surface like the fino carving, we tattoo the face with ornamental motifs like intercrossing lines. CA: How much time do you take to carve a single block of stone? BE: I haven’t kept the time. CA: Can you then tell how many pieces a skilled carver finishes in a day? BE: Some do 15 blocks a day; others do 20 while some cannot do more than 10. It depends on how fast the person is. CA: What are your tools? BE: We have the mero (chisel) of different sizes and shapes and the hammer that goes with it. There is the teftafa mero and shul meros of varying diameters and we use the toothed mero for refined work. CA: Do you make your own tools or do you buy them? BE: No, we buy them from metal workers in 22 (Haile Gebreselassie Road) who make the tools from car parts. CA: How long do your tools last? BE: You have to hone your tools everyday or they become too dull to work with. A mero looses some height and body every time it is honed and finishes its
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useful life in two or three months. CA: Do you think a machine can do the same thing you do? BE: No, it can’t. They brought such a machine a couple of years ago and they had to stop working with it because it couldn’t bring out the same quality of stone blocks as we can. It couldn’t produce the desired shape of blocks. CA: Do you also build the walls yourself? BE: Yes. The stone-mason should also be a skilled carver because he needs to correct some angles and chamfer the sides that hold the mortar when necessary. CA: What are the types of masonry works? BE: There is sefulegn masonry, where the mortar is hidden behind the stones, there is sherira or tekus masonry where the mortar can be seen between the stone blocks and there is the sekaram (drunkard) masonry where no order is followed in the arrangement of the blocks- it is just a mosaic of stones. The masonry is done the way the abatu (the owner) wants it. CA: How do you build walls? BE: That is simple really. You lay 50
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the first course, chamfering the four corners and putting enough mortar between the stone cladding and the wall. You also put some aggregate on the mortar to avoid shaking of the courses or slip across the horizontal surface. Then you put the second course on top, which may have the same thickness or not, and repeat the process carefully fitting the stones together and making sure the corners are straight lines with no space between adjacent blocks. CA: Do you feel threatened by the synthetic cladding materials that resemble stone and are now replacing it on the market? BE: I have seen those that were imported from China. There is no comparison between the synthetic and the real stones. And I am sure owners can differentiate between the two so there is no need to worry about those. CA: The building you are working on has brick blocks, unplastered concrete walls, huge glazed windows and, of course, walls done in stone. Do you think this is a good combination of building materials? BE: Yes. It is beautiful. It is good to have a little of everything. If I
ever get rich and build a house for myself, this is the kind I would build myself. CA: Won’t you even consider building the whole house with stone alone? BE: No. Stone is heavy, it is depressing and it is not as beautiful as the house we are doing here. CA: What is down the road for you after this? BE: I will build my own house, as majestic as any rich man can ever build. I will make sure my wife and kid live a good life even if I have to toil everyday for that to happen. Things are looking well. I have gone back to the place I came from in Gurage for the past two Meskel holidays. But I will work more and earn more. After all, God has assigned me to this job and it is my destiny to make a living out of carving stones. I can’t stand against that. CA: And your son? Will you ever teach him the craft? BE: No. The times have changed. I am working so hard so he doesn’t have to see the life I had to see. If he chooses not to listen to me and wants to follow me into the trade, then I would have no choice but to make him the best in the trade.
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Figure 1 - The new marble façade on Finlandia Town Hall – approximately 6 months after a re-cladding of the building. Figure 2 - A close-up of the bowed Carrara marble panels on Finlandia Town Hall few months before the panels were replaced by new Carrara marble panels. Figure 3 - The town hall in Malmo, Sweden features a 27 year old Carrara marble facade that is in perfect condition.
Deterioration of Thin Marble Cladding a major international study
This intriguing article reveals that problems can and do occur, even with materials like Carrara marbles that have been used extensively for many years. The article also confirms that solutions can be found and improvements can be made. There is no sense in assuming that everything in the garden is rosy, when it patently is not. These images could be enough to deter any specifier from choosing thin marble as a cladding material. However, despite the cost of repairs and the apparent severity of the highlighted problem, the majority of marble façade installations perform adequately. This article serves to highlight the critical need for architects to be well informed about the materials they have at their disposal, and how and where they can be used effectively. This report was partially funded by the European Commission and conducted by TEAM (Testing and Assessment of Marble and Limestone). 52
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by Bent Grelk Ramboll, Copenhagen, Denmark, Björn Schouenborg SP Swedish National Testing and Research Institute, Borås, Sweden, Katarina Malaga SP Swedish National Testing and Research Institute, Borås, Sweden Discoveringstone magazine
Background Natural stone has been used for facade applications since time immemorial. Originally, the stone employed was rather thick, when used as a construction element, and the strength and durability was very consistent . Scientific research on properties of marble began in the late 19th century. In the years following, the thickness of natural stones used on facades decreased from over 1000 mm (as in construction elements) to 20-50 mm (in cladding applications) as a result of new cutting technologies and equipment that was developed by industry. The use of thin marble and limestone slabs as facade cladding has increased substantially during the last few decades. Even though the vast majority of marble claddings perform satisfactorily, durability problems began to occur, following the advent of thin cladding materials. During recent years reports of facade failures have increased dramatically.
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Prominent buildings such as the Amoco building in Chicago, the Finlandia City Hall in Helsinki, La Grande Arch and SCOR Tower in Paris and IBM Tower in Brussels have all experienced serious problems with their thin marble clad facades. The problems include expansion, bowing, loss of strength, and in the most serious cases complete detachment from the anchoring system. The bowing of marble is not only restricted to buildings. Marble tombstones have also been known to bow. At the present time, most of the recorded cases of façade failures emanate from Europe or North America, because of the more widespread use of thin marble claddings in those parts of the world. However, failures have also been recorded in Lebanon, Australia, India and Cuba. The problems regarding limestone facades are slightly different. Apparently, limestone does not bow, however it can expand causing serious problems if the joints are not sufficiently wide enough to tolerate the expansion. The industry urgently needs to develop a repair system for existing facades that develop problems. Despite several European research projects, the prime solution relies on replacing the panels at a cost of approximately 600-900 AUD $/m². The fairly recent example of the City Hall in Helsinki, where all panels were replaced in 1998, came in at a cost of 6.5 Million AUD$ (a figure that was not dissimilar to the entire cost of the TEAM project). This provides an economic perspective of the problem. The problem did not cease because it would appear that the new panels which were chosen incorrectly started to bow 6 months after installation! (Figure 1) It is estimated that the known cost of repairs to damaged facades located in Europe will exceed AUD$400 million. This figure is based on current strategies used to effect repairs. Although the vast majority of reported durability problems with thin marble or limestone
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slabs relate to use of Italian Carrara marble, which is the most widely used marble in the world, other marbles e.g. American, Norwegian and Portuguese have also been reported to bow on facades. However, the reports on performance of Carrara marble are inconsistent, since in some cases Carrara marble apparently performs satisfactorily. Note that there are about 200 different stone quarries in operation in Carrara, Italy! The direction of the observed bow may be either convex or concave relative the facade, this is probably determined by local climatic conditions. However, despite considerable effort the exact physicochemical processes responsible for the degradation of thin marble and limestone slabs exposed to outdoor conditions have not been established by the research community. As a consequence of the reported durability problems and the lack of fundamental understanding of the problem, both producers and users (architects and building owners) of marble and limestone are almost desperate for more knowledge and in particular they are eager to find a test method that will distinguish durable building stones from nondurable building stones. Objectives The main objectives in the TEAM were: • To understand and explain the mechanisms of the expansion and loss of strength, probably the most important phenomena leading to degradation of marble and limestone clad facades. • To prevent the use of deleterious marble and limestone by introducing drafts for European standards. • The project also aimed to develop a concept for assessment of facades, including a monitoring system in order to predict strength development and improve safety and reliability. • To analyse if surface coating and impregnation could prevent or diminish the degradation. Construction Ahead, nov-apr 2007
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Figures 4-6 - Examples from Croatia depict a building façade that exhibits severe bowing. Figure 7 - Bowing measurement on a façade.
• The project has also addressed quality control aspects in order to optimise the production conditions.
various levels of detail. This includes 26 Buildings that have been selected for further investigation.
Work carried out
• All of the 26 Buildings were considered as suitable for dismantling of the facade panels for laboratory testing purposes.
The TEAM project consortium, representing 9 EU countries, comprised 16 partners representing stone producers and trade associations, testing laboratories, standardisation and certification bodies, consultants, building owners and care-takers and producers of fixing and repair systems. A state-of-the-art report has been written and is based on an extensive compilation of more than 300 papers on marble and limestone deterioration dating from late 1800s to 2005. A survey of about 200 buildings has given a clear picture of the extent of the problem in geographical, geological and climatic terms. Detailed case studies of 6 buildings have resulted in a methodology for assessment of facades including monitoring system and risk assessment. Research, both in the laboratory and the field was performed on a large number of different natural stones from various countries utilised in varying climates. This provided an explanation of degradation mechanisms and lead to the determination of the critical influencing factors. Two tests methods, including precision statements: one for bowing and one for thermal and moisture irreversible expansion have been prepared for submission to CEN TC 246. Repair techniques based on the use of surface coating and impregnation systems has been tested in the laboratory and in field. Positive side effects including increased durability and easier cleaning have been observed. Guidelines for production and product control have been proposed. An instruction for stone sampling and description has been developed.
Observation and results from the project Inspection and investigation of buildings During the project a total of 194 Building Projects have been identified and reported on, providing 54
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• Six buildings were selected for detailed field studies, measurements of bowing and supplementary investigations. • Two buildings were selected for long term monitoring. Based on the investigations we have concluded that the phenomenon of bowing of thin marble is actually rather common. Deformation by bowing is experienced in buildings of various ages, in buildings exposed to various weather conditions and for slabs of various thickness and dimensions and with different anchoring methods. Finally, and what is most interesting, bowing is registered for marble of seemingly different composition and structure. It is important to note that the problem of bowing is not restricted to one type of marble or one climatic zone. The buildings are situated in Northern, Central and Southern Europe, and there are buildings with bowed slabs in all countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom). Many of the buildings with problems have been visited and a preliminary investigation has been conducted. During these investigations several different marble types from Greece, Italy, Portugal, Spain, Norway and USA have been identified as having durability problems in terms of bowing. It is also equally important to draw attention to the fact that many marble and limestone claddings and pavements tend to be durable and robust, provided that the correct quality has been specified. The report also considered the possible effects of climate. It is reasonable to discuss the effects of different locations of the stone facade slabs on
the building itself – height above the ground and directions of the compass. As for these parameters, our studies are in accordance with the literature:
various origins) that may bow. Marble selected from same region or even same quarry can demonstrate bowing as well as non-bowing behaviour.
• most pronounced bowing on the upper parts of the buildings and • most pronounced bowing on the facades that face southeast and southwest. Pronounced bowing also occurs on facades that face south. The claddings facing to the north display less tendency to bow.
• Problems other than bowing and deterioration have been registered and noted.
This implies that the facades which are subjected to the most sunlight exhibit the highest percentage of bowing panels and the largest amplitudes. • The bowing seems to be related to some types of marble and marble/limestone while other stone types (travertine, slate, granite, sandstone etc) do not demonstrate this problem. • Both concave and convex bowing can occur on the same facade with the same marble. • There is a clear correlation between bowing behaviour and deterioration leading to loss of strength. • It cannot be stated that non-bowing stone slabs are not deteriorating and losing strength (e.g. mortised facade slabs seem to be hindered from bowing but might still deteriorate) • There are quite a few different types of marble (with
• Marble types with known or measured bowing problems and marked strength loss should be avoided in thin building claddings. Based on the observations it is also possible to conclude that revisions in e.g.: • Application system (fixing methods) • Thickness of stone slabs • Panel face dimensions • Placement on the building may not totally hinder or reduce the deterioration in such marbles. Investigations of selected buildings show large strength loss in the order of 80 % after 35 years for one calcitic marble and 40 % for one dolomitic marble. Laboratory studies clearly indicate that there is no correlation between the amount of bowing and the loss of strength. This is especially worrying since there is a potential risk of severe strength loss without any evident bowing of claddings.
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Figure 8 Bowed marble panels on a building in Helsinki, Finland. Figure 9 Microphoto (1.0x 1.5 mm) Carrara marble with granoblastic microstructure, marble with potential bowing behaviour. Figure 10 Microphoto (1.0x 1.5 mm) Carrara marble with xenoblastic microstructure. A marble that does not bow.
It is surprising that, despite several reports of severe loss of strength, field investigations in relation to this topic are rare. Main Conclusions The TEAM project has significantly increased our knowledge of marble and limestone deterioration processes. We hope that the findings will contribute to an increase in the use of marble and limestone for cladding and thus help restore some of the trust lost in these materials in particular countries and climatic conditions. The main conclusions are given below: • A deeper understanding of the properties influencing the durability of marble and limestone as an outdoor cladding material has been gained, not the least through compiling and reviewing most of the literature (over 300 articles) in this field and making it available to anybody through the homepage (see www.sp.se/ building/team). • A comprehensive building survey, of about 200 buildings, has given a very good picture of the extent of the problem both geographically and geologically. Bowing is a worldwide phenomenon not confined to one type of marble or one type of climate, e.g. frosty conditions are not necessary for this phenomenon to occur. Subsequent detailed case studies have provided the possibility of testing several deterioration hypotheses and yielded important information about the variables to be used in the test methods which were developed later in the project, and are especially relevant to variations in temperature. • Sampling and testing of panels from the buildings have provided further information about the deterioration process and the rate of thickness and dimensions and with different anchoring methods. Finally, and what is most interesting, bowing is registered for marble of seemingly different composition and structure. It is important to note that the problem of bowing is not restricted to one type of marble or one 56
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climatic zone. The buildings are situated in Northern, Central and Southern Europe, and there are buildings with bowed slabs in all countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom). Many of the buildings with problems have been visited and a preliminary investigation has been conducted. During these investigations several different marble types from Greece, Italy, Portugal, Spain, Norway and USA have been identified as having durability problems in terms of bowing. It is also equally important to draw attention to the fact that many marble and limestone claddings and pavements tend to be durable and robust, provided that the correct quality has been specified. The report also considered the possible effects of climate.It is reasonable to discuss the effects of different locations of the stone facade slabs on the building itself – height above the ground and directions of the compass. As for these parameters, our studies are in accordance with the literature: • most pronounced bowing on the upper parts of the buildings and • most pronounced bowing on the facades that face southeast and southwest. Pronounced bowing also occurs on facades that face south. The claddings facing to the north display less tendency to bow. This implies that the facades which are subjected to the most sunlight change, together with the inspection methodology, this has provided a sound basis for building a model to predict the remaining service life, including analysis of the associated risk. • Long-term monitoring underlined the importance of repeated measurements in order to enable reliable conclusions to be made. One time measurements are of little use due to large diurnal and seasonal variations.
• The sampling of test materials is very critical for any project. Detailed sampling and sample marking instructions have to be used for any sampling. Our findings have been reported to CEN TC 246 Natural Stone. • Laboratory testing of almost 100 different types of marble has taken us much further in our search for the mechanism and allowed us to refute many “old” hypotheses. The main extrinsic influencing factor is elevated temperature in the presence of a moisture gradient. This creates the external stresses that different marbles will then respond to in different ways. The most crucial intrinsic parameter is the complexity of the grain boundaries and the grain size distribution of mineral grains in the rock. This provides different bonding strength between the mineral grains due to the complexity of the arrangement of the grain boundary and in combination with the crystal structure. The irregular grain structure that all marble considered suitable for outdoor cladding have in common is the product of the metamorphism that turned limestone into a marble combined with a dynamic re-crystallisation event. Weaker bonds will cause granular de-cohesion, ’sugaring’, of the marble and significant strength losses. •The work in developing the test methods has proved that every marble is unique and has a unique response to climatic stresses with its own degradation curve. The acceleration factor of the laboratory bow-test is therefore different for different marble types. The test methods developed enable a relevant evaluation that determines whether a marble is suitable for outdoor cladding or not. The bowtest can be adapted and used for predicting the remaining service life of a specific marble on a particular building. •Field exposures have shown that it is possible to inhibit or decrease the degradation of marble by coating the surface with a hydrophobic treatment. The effect is most pronounced on marble already exposed and it should not be used to support the selection of an unsuitable marble for a new building project. •Guidelines for designers and producers/ suppliers have been given to ensure a proper selection of suitable marble and limestone for outdoor cladding and to insure production with a homogeneous and acceptable quality respectively.
Your Partner in Building and Construction Activities !
Head Quarter Factory Location In Oromia Region at Alem Gena area 20 Km South West of Addis Ababa on the route to Butajira. Tel. 011 387 0843, 011 387 0845 Mob. 091 154 7458, 091 154 7457 Fax 011 387 0846 waliasteel@ethionet.et P.O.Box 181218 Addis Ababa, Ethiopia Addis Ababa Liason Bureau Tel 011 440 0275
opinion
A chip of the old Bu Yves Stanger
G
ebre Egziabher has left no stone unturned in his long and back breaking career as a stonemason. A still sturdy man who looks to be in his early sixties, he sports a red bob and clothes the colour of the rock dust produced by his relentless pounding and chiseling. Right now, he’s working on the foundations of a bridge on the Maganania to Hayat road. The bridge is at the top of an equilateral triangle with the new Mariam church and the Ethiopian Management Institute at its base. The river is a stream, a bare trickle that doesn’t seem to warrant the hefty structure being erected here, but come the next rain season, it will no doubt prove useful and the improved road will mean an end to traffic jams for the Hayat and CMC commuters. But this is no concern of Gebre Egziabher. He has a job to do. He chooses a round boulder and cracks away. With a hammer and a rudimentary chisel, he knocks the rock into the shape he’s looking for. Stone fragments whiz past his uncovered face and a faint mineral odor lingers in the air as he pounds away purposely. He stops, turns the rock on its side and hammers some more. In a few minutes he’s got the rough flattened-out rectangle he was looking for. Just another 58
Construction Ahead, nov-apr 2007
BLOCK stone in the wall, Gebre Egziabher fits the block neatly into the space that was waiting for it. Six days a week, eight hours a day. It gets the job done, and earns him forty birr per shift. Gebre Egziabher doesn’t know the name of the stream but thinks it might be called ‘Maryam.’ It might just as well be called ‘Management’ I put to him, at which he shakes his head at first, then cracks a slow, hesitant smile. He tells me he lives nearby, so the early start is no problem. I ask him if he’s been to Lalibela, and seen the rock hewn churches there, but he shakes his head again. But he has seen it on TV, he adds. I ask him if he’s seen the unfinished rock hewn church of Washa Mikael (The ridge where the church is found can be seen from the road where we stand, and is nearly in his neighborhood). No, he hasn’t been there either but he may have seen it, some time ago, on TV as well. Starting at Axum and Yeha, and arching its way to the present by way of Lalibela and Gondar, rock has always been a cornerstone of Ethiopian architecture. Let’s go back a little, all the way to Axum and its carved stelae. These monumental structures, some twenty three meters high for the tallest, are intricately carved with false windows, doors and a
certain architectural feature called a monkey head, in which the round end of supportive beams protrude from the stone walls. All these features were no doubt found on the now crumbled palaces of Ezana, Kaleb, and why not, Sheba as well. In the hills around Axum, there are stelae still attached to the cliffs from which they were partly detached, very much like the small blocks of Gebre Egziabher, back there, toiling away on the bridge near Maganania. Be it the megaliths at Tiya, the anthropomorphic statues of the Butajra area, or the age-worn tradition of cave and rock hewn churches stretching all the way from Tigray to Addadi Mariam, just south of Addis Ababa, rock has always been a favored medium for Ethiopian builders. Modern stonemasons have a feel for their material that casts solid roots back to antiquity and Gebre Egziabher the stonemason knows quite a bit about rocks. Oh, not their names for sure, but he knows which ones are going to crumble, and where to find that little fault line; which stones to discard, and which to keep. He has spent, after all, years banging away at them with all his might and know-how. I ask him if he thinks he could build a new Lalibela. A question he finds, I’m afraid, a little blasphemous, for he
Alfalum
turns a stony face to me and declares the sacred place to have been built by angels, or at least ‘with their help and that of the Holy Spirit.’ Rome was not built in a day, so they say, but Lalibela was built in a night, so they also say –at least for one of the churches. Finding myself between a rock and a hard place, I ask our stonemason if, being a servant of God, he wouldn’t like to enlist the help of the Holy Spirit to finish his bridge, and have it completed in one night. At this, Gebre Egziabher cracks another of his slow smiles that deepen the creases around his eyes. Who would be paid, me or the angels? He wants to know. History, they say, is written by the victors and not laid down in stone. Nowhere is that more true than in Ethiopia, where the scarcity of written material often makes history a guessing job. But nowhere, as well, is it more false than in Ethiopia, where history has been remembered for its landmarks built of stone. The Arc of the Covenant itself, the foundation stone of Ethiopian history if one is to believe the Kebra Negast, and certainly a cornerstone of the Ethiopian state’s modern nation building exercise, was built to contain the tables of the law, two stone slabs inscribed with the ten commandments given to Moses by Yahweh, and later ‘borrowed’ by Menelik I. Who built the monoliths of Lalibela? Who erected the stelae of Axum, their tips decorated with the crescent moons and suns of Southern Arabia? Who shaped the smooth stone walls of Yeha to the state of perfection where they still find themselves, some 2 600 years after their architect breathed his last sigh? What was the purpose of the thousands of megaliths of southern Ethiopia and who raised them there? Or indeed, who built even the modest church ruin atop Addis, where I was standing, the sky outlined by the jagged edges
of the stone box cut out of the mountain summit? It was easy to believe that angels had a hand in it. To walk through the tunnel at Washa Mikael, bored through solid rock and to come out into the courtyard where the church stood with its monolithic walls and arches was to wonder how such a structure could come into existence by the hand of man alone. It was tempting to see the work of God, or at least of his minions, in this sacred place.
doors
But if we look back at the churches and cathedrals of Europe, built for the same purpose as Lalibela –to strike awe in the hearts of believersone reads a different story, a story of labor and sweat, of masons inspired by angels in their dreams but spending their woken lives toiling away. Those fantastical structures of stone, the pyramids of Egypt –not that far from Ethiopia- and the even closer ruins of Meroe, with their gigantic architecture of stone, were built with the sweat of the thousands of slaves of Pharaoh and the kings of Nubia. Gebre Egziabher was down there, under the road, toiling away in the sun at his bridge. It’s simple, he’d said, of his work. Tap, tap, tap… all you have to do, is never stop, be relentless, and just keep tapping away with your hammer all day. When I’d asked if it weren’t hard, especially at his age, he’d answered that it wasn’t really that difficult, once you knew where to hit. It was more technique than brute strength; you just had to be relentless and you could move mountains. And that’s when I understood; when he said that. Gebre Egziabher’s skills run in his blood and it has been running there since Axum started some 2000 years ago. The hands of his ancestors had grown crooked holding tools, just like his. And before Axum, there had been Yeha and the other cities, so old that they’d disappeared under the sand of time, blown to smithereens by relentless winds and
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A New Way of Looking at Stone by Scott Engering Geologist & Building Stone Consultant - Contributing European Editor, discoveringstone magazine
S
ince ancient times, rocks and minerals have been highly valued, with gems, semi-precious stones and slabs of marble and granite being cut and polished and used lavishly in the very finest artefacts, architecture and jewellery. On a much more modest scale, there are surely very few households where an attractive pebble, mineral, fossil or rock, picked up from a beach, can’t be found.
Using photography and digital technology to take the subject matter to another level, the saturated colours and repetitive forms have been since described as “resembling the abstract graphics for a psychedelic trance party flyer, with an overall effect that is bizarrely futuristic”
However, one of the most spectacular ways of displaying the inherent natural beauty of rocks and minerals is very rarely seen outside universities and analytical laboratories. In 1849, Henry Sorby of Sheffield pioneered a new branch of geology – “Microscopical Petrography” – a technique of examining thin sections of rock, only a thousandth of an inch, using plane and polarised light. Considered a source of great amusement at the time, especially by the Swiss geologist Saussure who thought it “especially ridiculous to look at mountains through a microscope”, the technique is now widely accepted by geologists as an essential tool for studying rocks. When polarised light is shone through these rock thin sections, it is refracted by the internal crystallographic structure of the minerals to produce an astonishing array of vivid colours which vary according to both the chemical composition and orientation of the individual interlocking crystals. Although this microscopic technique is primarily used to identify minerals and help the geologist to understand how rocks are formed, the subject material inspired John Ruskin, a friend of Sorby and mineral collector, to write lyrically of the beauties to be seen.
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Construction Ahead, nov-apr 2007
Main picture LHERZOLITE: deep fractures in the Earth reflect surface structures. Figure 2: Graphic Granite, these inter-twining crystal structures were well known to the Egyptians. Figure 3: Olivine, crystals dissolve and melt, but these are frozen in time. Figure 4: Twin, the repetitive form of nature is one of it’s greatest assets.
the plundering nomads, nothing left to even let us wonder, their memory itself erased from the surface of the earth. Tap, tap, tap… he’d gone, Gebre Egziabher –the slave of Godand in five minutes his little block for the Maganania bridge was finished, and he’d barely placed it in the gap in the wall that he’d already started on another, relentless, slowly but surely working his way through the pile of stones to his left, moving his own little mountain. I looked up at the rugged walls of stone that silhouetted the sky above the old church’s courtyard where I lay. Centuries ago –a millennium and a half if one were to believe the explanatory placard- this mountain top had been carefully chosen by an architect or a monk for its beautiful position, overlooking Finfinne, and its pure rock –how were they to know there was a fault deep down? Soon, the mountain had teemed with slaves and peasants, doing their good deed. With crude hammers, with blunt chisels burnished in wood fires, with their nails if need be, they had gone to work, digging-in to the mountain. How long did it take? Nobody knows. One generation, perhaps two? What is time when you have all the time in the world? With their bare hands, and a few primitive tools they had dug this sacred place. Slaves of God, they had moved a mountain with their work and their faith. Tap, tap, tap… I must have fallen asleep in the courtyard of Washa Mikael, thinking of angels, because I thought I awoke to the metallic sound of hammers on chisels, echoing from a bygone past. But perhaps it was a Kado bulldozer starting in the plain below that had awoken me, driving over Gebre Egziabher’s bridge. Gebre Egziabher, the stonemason, a chip of the old block, moving his own mountain, stone by stone, in Ethiopian time worn fashion.
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what’s new
In this section, Construction Ahead presents new products and services entering the Ethiopian Market. To advertise here, please contact our sales department. Tel 011 515 2477
Personal navigator The eTrex is a handheld full-function GPS. When moving, the eTrex provides you with your speed, direction and movement, time, distance to destination, and more.
Kid-Tek provides professional Web design and Web development services to help make your company’s online presence stand out from the crowd. Kid-Tek Computer Technology Tel 011 554 0857 Fax 011 554 0862 info@kid-tek.com www.kid-tek.com
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Nothing establishes a mood as fast as colour. Our reactions to different colours are instant and instinctive. The atmosphere of your space is a result of the colours you use in it. So, you need to be sure it is the effect you want.
In the rest of the world, three regions in particular
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are at evident risk of volcanic activity. The Pacific The colours with which you decorate your room, home or office, Rim is also known as the “Ring of Fire” from can make it feel and look spacious or confining, warm or cold, its extensive history of volcanic eruptions and casual and relaxed or formal and dramatic. many countries around the Rim are at great risk.
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This lets you create contrasting moods as distinct as the changing similar risks and so does the Great Rift Valley
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in eastern Africa, which has many volcanoes in Ethiopia and Kenya. Eleven volcanic activities were recorded around the world, including Ethiopia, in 2006.
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Not every picture is worth a thousand words. And there may be some that are worth more. We hope ours fall at least somewhere in between. In any case, we want to end Construction Ahead with a photograph that we hope will always be interesting enough and constructive. So, if you have an unusual picture, that attempts to capture an intriguing coincidence of space and time, do send to it and share it with our readers. Sorry, but we will not be able to return submitted photographs but appropriate credit will be made.
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Among the many volcanoes known to exist in Ethiopia are Dubi, Ziquala, Aluto, Erta’ Ale, and Chebi, which is a dormant volcano located 15 kilometers south of Shashemene that is capable of destroying both Awasa and Shashemane in case it erupts in the future. Erta’ Ale, in Afar, is an active volcano that erupted recently (see sidebar). The Aluto volcano is the site for the only geothermal energy project of the nation.
There are some indicators that help us know about volcanic eruptions in advance. Unusual increase of heat in the area and steam and gas coming out of the volcano are the main indicators cited. Experts advise that communities should be educated about these indicators and be ready to be mobilized whenever the need arises. Related events such as earthquakes, plate movements and Construction Ahead Website www.constructionahead.com other records of geophysical instruments should generally distinguished from the in some rocks. changed. also be studied to help in predicting volcanic The by Magazine and its associated more modest kinds of time studies by other scientists using More than 200 eruptions. years ago James web site Careful complement each being called “geologic time”’. relative time scale showed that Hutton proposed that wherever in their coverage of the whole Like earthquakes, volcanic eruptions are difficult the had industry, diverse each origins. Some un-contorted layers were exposed, The geologic time is the fourgamut and a ofrocks to predict andfirst completely unpreventable. Unlike of its particular rock layers contain fossil remains the bottom layer was deposited half billion years or more thetaking earth advantage medium. earthquakes, no structure can be made to be is estimated to have existed. This of fish, or plants and animals succeeded by progressively younger ‘volcano-resistant’. Whereas the inmagazine is the ocean. Other layers ones up to the topmost. During the Some volcanoes are almost time is difficult to understand in formed continuously eruptive, which obviously means better suited reviews of consist for of separated sand grains same year William Smith, a civil the familiar time units of months new construction technology after observing poor quality human rocks working CA: What is being done to ensureOther settlement them is impossible. cleaned the long wave rolling engineer and surveyor in near 00251-11-439-1037, 1040 - Fax by 00251-11-439-0254,440-0207 - Kadisco@ethionet.et and years, Tel or even centuries.techniques and tools, you need on the surface may have invaluable that environmental volcanoes become active only degradation over very long in the fromwww.kadgroup.com the lake or sea, formed southern England observed that to log more interactive reservesthe underneath. doesn’t around A great part of the Earth’s age into periodsareof time,occur at least on quarry humansites? time scales. as beach deposits marking limestoneDetail and studies shells layered and constantly updated web site should be done and they are In not.areas where such volcanoes are found, most is locked up in its rocksto get andthe shoreline of ancient lakes or seas. like slice of bread and butter. latest prices for building HW: He Production is on a minor our centuries-old search for the Certain people perceive littlelevel or nountil threat from them. materials and projects Canof thiscollected be recommended forfrom layers are being in theCA: form fossil shells rocks excavation now which is Here key led to the beginning tendered. of the sand bars and heap of gravel destruction caused by volcanoes is small-scale producers? - rock quarry as a hobby, and lessening catalogued them, tothe say that noticeable environmental development of geologic science. dependent on not careful concerns beenmonitoring raised as and debris overmore. theHW: land This by which him entirely to discover that have But the Web site spread has much groupledfaces more There is evidence that records It does give a synopsis of were the once lava certain layers contained warning systems to alert people of anwhere imminent yet. Most of the quarry sites streams. Some rocks fossils and problems. It is either they buy plus: or beds of cinders and ash are different from astounding episodes, which magazine certify flows are life those dimension inHowever, other stones eruption. these are saveproduced only human the land on which the quarry that the earth is billions ofDiscussions years thrown located incrops remote areas, far away out under of ancient volcanoes; layers. Using these key or index Forums three is and not property, or livestock. situated and conduct further So dependable, so durable, old. Two scales are used to date others are parts of large masses of fossils as markers, Smith categories; from human settlement, which could studies later on (if at all) orSlope failureshave dulled their effect on the thatvery fruitfulness can beface these episodes and to measure molten rock that cooled identify certain kind of rock technical once (addressing theoretical price escalations on athe value of may the age of the earth - a relative environment. Still, movements studies need Slope failures are down slope of rock, slowly beneath the earth’s surface. layer wherever was exposed. That and technical matters); land onceentrusted they are seen the foritby life to same be fill carried concern time scale, based on the sequence Other rocks were so transformed is he discovered that the soil, or artificial underout the with influence of gravity such studies. business (dealing with practical owners conducting starting now, processes we have and of layering of the rocks and theof the by construction heat and pressure during lift rock layer contained the now. Until caused by atmospheric, geologic It isthe understandable thatusually many opt issues business conducted somethestudies on theSlope evolution of life, and a radiometric up and crumple up of the assemblage of fossils,interference whereas with and trade); human environment. for Earth’s the first same choice, which affects cultural and historical heritage time scale based on the natural crust(taking during building rocks abovelower andfailures below that layer natural are major disasters in many areas but helps initial social/public the mountain concerns productivity associated with deposits and radioactivity of chemical elements that oftheir features were cost. contained different assemblage investment and interests the original wider public whether or not production will and society with regard to CA: Is there a centralized system affect these heritage. Effects on topics ranging from architectural aesthetics, building codes and for production (and export) or is wildlife are also considered. But Tel. Off 011 663 6671 -Fax/Tel 662 3548 -P.O.Box 27101Addis Ababa, Ethiopiapgatech@ethionet.et The011 Better Machine. environmental implication of this undertaken individually by each all in all, we do not fear that certain construction materials or exporter working alone? remarkably hazardous effects are practices) HW: Everything is done through occurring because of production of Advisory directing your particular individual effort in Ethiopia. In dimension stones. questions or problems to the Europe, the case is different. The CA: Are there abandoned quarries experts and getting a direct company that owns the quarry and what can be done to revive response. may only be involved up to the these? Events related to the industry. production of blocks. Another company takes over the processing HW: I am not aware of sites that Tenders work and hands over semi-finished have been depleted enough to Price watch of basic building be abandoned. However, quarry materials updated every 2 weeks. slabs to yet another company, which produces the final products that owners should by default rehabilitate Market the classified-buying and enter the market. Marketing may quarries with overhauled or native selling, exchanging bartering, not necessarily be handled by the material to maintain the right leasing, renting and so on. final producer either. Such a system morphology. Directory of key sectorial operators is recommendable in the Ethiopian CA: Any last words? and services. context since it divides the huge cost of investment among many HW: I think the construction companies. Quarry production is industry has to benefit from not a cheap endeavor. Although geological investigations on the cost varies with the type of dimension stones more than Sole Agent: Tel:+251 11 618 5576 - Fax:+251 11 618 3768 rock being quarried, the minimum it is doing today. Designers and P.O.Box:550 code 1110 Addis Ababa, Ethiopia e-mail:yb.berhane@beyo-ct.com, y.megerssa@beyo-ct.com requirement of equipment cannot builders should make informed Beyo Plc. Haile Bldg. #2 on 5th floor be covered at lower costs. At decisions on what type of rock to minimum, you may need a diamond use on their buildings and other structures. to cover the saw wire to cut out a good qualityAhead, Construction sep-oct 2006 Attempting 21 quarry face and that is expensive. façade of a whole building after Add to this the costs of loaders, sampling just two three slabs is not cranes, compressors and the like a recommendable practice. More and you will get the picture of what considerations should be given to is involved. If the cost of processing, accommodate better quality and marketing and delivering is divided uniformity. Traditional small-scale within a centralized system the rate production may not be enough to and quantity of production can meet increasing demand and this benefit. should also be given due attention.
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technology
Diamond loses its stiffness crown to new material
A
material that is stiffer than diamond has been created by mixing particles of the mineral barium titanate and molten tin. Diamond was previously the stiffest material known. The new material was made by a team from Washington State University and Wisconsin-Madison University, both in the US, and from Ruhr-University Bochum in Germany. They mixed molten tin, heated to about 300ºC, with pieces of a ceramic material called barium titanium - often used as an insulator in electronic components. The particles were each about onetenth of a millimetre in diameter and were dispersed evenly through the tin using an ultrasonic probe. Once ingots of the new composite had cooled, rectangular or cylindrical samples 3 centimetres long and 2 millimetres across were tested for stiffness. The response of the samples to bending was tested by gluing one end to a strong support rod and the other to a magnet with a small mirror attached.
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light bouncing off the mirror. The tests were carried out at a variety of temperatures. Between 58ºC and 59ºC the samples became stiffer than diamond. Some were nearly 10 times as resistant to bending. “This is very clever,” says composite materials researcher Mark Spearing of Southampton University, UK. “They’ve come up with an interesting material.” The material’s stiffness results from the properties of the barium titanate pieces, Spearing says. As the material cools, its crystal structure changes, causing its volume to expand. Tin matrix ”Because they are held inside the tin matrix, strain builds up inside the barium titanate,”
Spearing explains, “at a particular temperature that energy is released to oppose a bending force.” Since energy has to be stored in the material to make it super-stiff, the creators have only really measured an “apparent Young’s modulus”, says Spearing. A true Young’s modulus is an inherent property of a material, and would also be more constant across a greater range of temperatures, he notes. Nevertheless, the new material could still have useful applications, says Spearing, perhaps for making shock-protective casings. “You might be able to make a tune-able damper that transmits force very well under certain conditions but behaves differently and is softer the rest of the time,” he says. Journal reference: Tom Simonite, Science
Low-Maintenance Composite Decking Weyehaeuser ChoiceDek® boards are made using a process that encapsulates recycled wood fiber in recycled polyethylene, and they do not require staining, sealing, or treating. The manufacturer’s limited-lifetime warranty includes saltwater contact installations and
Rhythmic force
termite resistance. The boards are suitable for decks, dock surfaces,
An electromagnet was used to exert a rhythmic force on the material one hundred times per second. The resistance of the composite to the bending force - called the Young’s modulus - was recorded by a light sensor monitoring laser
playground equipment, boardwalks, wheelchair access ramps, and
Construction Ahead, nov-apr 2007
walkways. Available in six colors: gray, redwood, sandstone, wood tone, driftwood, and spice. The product line includes matching railing systems. choicedek.com
Flexible Trim for Curves and Arches ZāGO’s Flexible Trims and Mouldings can be used in place of or as an accessory to wood. They are easily bent or shaped to fit around any circular architectural detail, curve, or arch. This versatile material can be molded or routed to add accents to cabinetry, furniture and display units. ZāGO’s flexible trims and mouldings are creative products; their uses are limited only by the boundaries of your imagination. Ranked “Top 100 Products” in Building Products Magazine. For more information visit flexibletrim.com
Designed by nature, made for life... The quartz surface is made of 93 percent of natural materials – namely quartz and granite combined with 7 percent of additives. The additives consist of resins (binding the individual components together and lending the stone the necessary strength) and color pigments (ensuring excellent aesthetics and color stability). The product has virtually identical and in some respects even better characteristics than natural stone. The wide range of slabs, edges and the extensive variety of available colors are, among others, the advantages of this Hi-Tec product.
ConMIS 2006 Invaluable Software for Construction Project Management • Creating a database of construction activities; resource prices and rates; and productivity norms • Cost Estimation and Bid Preparation • Planning of Material quantities, Man-hours and Equipment-hours • Prediction of budget for Materials, Manpower , equipments and for the project • Payment Processing (from Takeoff/ Backup sheet up to Payment Certificate preparation) • Planned vs. Actual Comparison • Cost Controlling. (Profit / Loss)
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software review
Aftermarket Solutions for CAD Third-party programs increase AEC productivity. H. Edward Goldberg, Cadalyst
R
ight out of the box, AEC software is excellent, but there’s always room for improvement. Since the beginning of the digital AEC revolution, third-party programs have filled the niches that major software developers missed or omitted. These thirdparty developers often start by creating programs for their own use and then offer them to the public. Probably the most successful of these developers was Softdesk, which started with an architectural add-on for AutoCAD and was ultimately purchased by Autodesk. Though fewer third-party developers exist today (partly because the basic AEC products are becoming more complete and partly because of development costs), their products are excellent. Figure 1. WinEst Virtual Takeoff, which works with AutoCAD, Architectural Desktop, Revit and Bentley Architecture, quickly generates takeoffs directly on your computer screen using electronic plans.
IN THIS ARTICLE Ameri-CAD • www.visionrez.com Autodesk •www.autodesk.com Bentley Systems • www.bentley.com Construction Industry Solution •www.constructionindustrysolutions.com DSI Digital • www.dsi-digital.com Encina • www.encina.co.uk Google SketchUp • www.sketchup.com Graphisoft • www.graphisoft.com Nemetschek North America • www.nemetschek.net
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Today, most third-party programs are aimed at the architectural, structural, engineering and estimating areas. But, as you may recall from my last column about the state of BIM (building information modeling), users have great interest in any program that helps to complete the BIM process. Access to a program’s API (application program-ming interface) is very important to third-party developers. If an API is open— that is, available to the programmer— developers can easily integrate their code with the main program. AutoCAD, which Architectural Desktop is based on, has always had an open API, so a wide range of applications is available. Revit, on the other hand, until recently had a closed API. This situation is changing, though, and
more developers are beginning to consider plug-ins for this software. Graphisoft and VectorWorks have fewer available plug-ins, probably because of their smaller user base. Bentley doesn’t have many architectural plug-ins, either, because it has a unified interface. Bentley also offers many of its own integrated modules to fill anticipated niches, so plug-ins and third-party programs aren’t typically necessary. In preparing this column, I was confounded by the overwhelming number of plug-ins—literally hundreds. Some are even free. So here I try to highlight some of my favorite third-party programs.
Google SketchUp This conceptual design program is probably the most downloaded of all the third-party applications. Although it’s a stand-alone program, plug-ins or integrated import capability are available for Architectural Desktop, Revit Building, Bentley Architecture, Archicad and VectorWorks.
AutoCAD and Architectural Desktop Plug-Ins Because AutoCAD and Architectural Desktop have the largest installed user base as well as an open API, they attract the greatest number of thirdparty products. Solutions are as diverse as WinEST (figure 1) for estimating and CAD Pipe for plant design. Because of limited space, I chose to illustrate just a few of the solutions, primarily for building construction. VisionREZ. Although I don’t have figures, I get the impression that most residential architecture is designed with AutoCAD or Architectural Desktop. Several years ago, Ameri-CAD, which had been a long-time developer of custom AutoCAD routines, decided to customize Architectural
Desktop specifically for the residential market. VisionREZ provides drawing functionality and processes that leverage the power of the building information model specifically for the residential industry (figure 2, p. 45). Its suite of solutions is optimized for those areas most likely to hinder overall residential design performance, such as roof design, trim detailing, labeling, framing and BOM (bill of materials). This software, in my opinion, is the best residential version of Architectural Desktop available. Its Roof Object tool is superior to Architectural Desktop’s own tool. The program is available as a stand-alone version for $2,495 (does not include curtain walls) or as a plug-in for Architectural Desktop 2005–2007. COINS. COINS Framing from Construction Industry Solutions complements Autodesk Architectural Desktop 2004–2007 and produces sophisticated timber and lightweight steel framing models (figure 3). COINS Framing is optimized to produce detailed material takeoffs and full production of manufacturing drawings with the ability to link to CNC machines. This framing application is built on the Architectural Desktop platform and focuses on the specific requirements of the United States, United Kingdom, Europe, the Middle East and Asia. DSI Digital. DSI Digital’s products are designed for metal-roof trussing, wood framing and trussing, tiltup construction, concrete and masonry construction and steel framing design. It automates the creation of roof, truss and wall elements and then generates shop drawings and BOMs. Although the company plans a whole series of modules for AutoCAD and Architectural Desktop, only IntelliModel, IntelliRoof and IntelliWall are currently available.
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Figure 2. VisionREZ add-ons for Architectural Desktop are specifically optimized for those areas most likely to hinder overall residential design performance, such as roof design, trim detailing, labeling, framing and BOM.
Figure 3. COINS Framing works with Autodesk’s Architectural Desktop to produce timber and lightweight steel framing models.
IntelliModel is a parametric application that allows rapid production of 3D building models within the AutoCAD or Architectural Desktop DWG environment. It automates the production of architectural isometrics, plans and elevations and performs automated building framing and analysis for structural engineers, including the production of pertinent engineering drawings. IntelliRoof is aimed at architects, structural engineers, estimators, fabricators and erectors. Integrated solutions allow the entire design team to quickly and accurately model, detail, analyze and share information about buildings, roofs, truss systems and stud walls. IntelliWall creates 3D models of wall framing with plans, schedules, fabrication drawings, BOM and cut lists.
Bentley Architecture Plug-Ins As I mentioned previously, Bentley Systems’ portfolio is fairly complete. On top of that, Bentley claims to be the largest third-party developer for the AutoCAD platform. Among the Bentley products for AutoCAD are AutoPlant, Haestad Methods, InRoads, MX, RAM, CAD Studio and Speedikon. For a complete listing of Bentley’s third-party solutions, see www.bentley. com/en-US/Products/All+Products. Figure 4. FrameWright Pro by Encina models timber and metal framing for Archicad using GDL (graphic design language) objects.
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Graphisoft Archicad Plug-Ins Graphisoft refers to its add-ons as productivity tools, and most are developed by European
developers, where the majority of Graphisoft’s Archicad customers are located. ArchiGlazing is an Archicad add-on that enables architects to design a broad range of glass structures. Custom windows can be created based on sketches, and vertical or slanted glass walls can be quickly built on any type of curve. The program supports the placement of conical and shed glass structures as well as winter gardens, adjusting them to fit the building. The parametric behavior of these objects enables users to change most of their properties at any time in the design process. ArchiGlazing fulfills the needs of ambitious architects seeking to exceed the capabilities of the standard Archicad library.
UPF SHUTTERS
HVAC for Archicad provides tools to model ductwork efficiently without an in-depth knowledge of HVAC. Architects and designers who receive simple 2D data from their HVAC consultants can use this add-on to quickly model the data in their projects to effectively coordinate the systems and visualize the model using Archicad’s 3D tools. Interior designers can use HVAC for Archicad to model HVAC systems for their projects and customize the ductwork’s appearance to create cutting-edge designs for their clients. FrameWright Pro by Encina is a timber framing add-on for Archicad developed in partnership with the Oak Frame Carpentry Company (figure 4). Designing the software in cooperation with a framer has ensured that the objects and tools are relevant, familiar and easy to use. VectorWorks Plug-Ins Nemetschek North America’s VectorWorks has a long list of free and for-sale add-ons. They are organized in five categories: symbols, textures, plug-ins, miscellaneous and useful sites. The Vector plug-ins site (www.vectorplugins.com/) offers many useful routines for $36 each.
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Join the Party Third-party solutions will probably always be with us, not because developers of the primary application are remiss, but because there’s always room for a different point of view or a better way to meet a specific need. H. Edward Goldberg, AIA, NCARB, is a practicing licensed architect and AEC industry analyst. Ed’s full-length book, Autodesk Architectural Desktop 2007: A Comprehensive Tutorial (Prentice Hall, www.prenhall.com/ ) is now available. His new Revit Building tutorial book will be available in spring 2007. Visit www.hegra.org/ or e-mail ed.goldberg@cadalyst.com for more information.
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books Spaces: Offices, Restaurants, Commercial Spaces by Fernando de Haro, Omar Fuentes How do clients ensure a great design for their commercial space? By using a great architectural firm. Spaces includes topquality examples of office buildings, shops, restaurants, hotels, learning centers, health clubs, country clubs, and even industrial warehouses — a full spectrum of fabulous commercial spaces that respond to the needs of the client and the demands of our times.
Lifestyles, Nature & Architecture: Mexican Weekend Homes By: Lourdes Legooreta Mexicans have a real passion for life. A unique flair that is expressed in their customs, interpersonal relations and lifestyles. Lifestyles, Nature & Architecture offers an intimate glimpse into this culture through the signature, solutions some of its leading architects have achieved in integrating space, light, color, and local building materials and decorative elements - all anchored in traditional design features - into a oneness with a resplendent natural setting renowned for its recreational activities, water sports and powers for renewal: Lake Valle de Bravo. We hope you enjoy the weekend homes illustrated in this book. We are certain that you will find many design ideas worthy of being incorporated into your own living space.
Facade & Signage Works chosen for the book represent outstanding achievements, selected through a rigorous screening process among entries by designers from all over the world. Each realization is accompanred by detailed photos and plans presenting every step of the process, from initial design concepts to the construction stage and finishing touches, so as to provide readers with a complete experience of the varied world of interior design and its highest accomplishments. The wide palette of quality works in this anthology edition is sure to offer the rare opportunity of exploring jewels of total interior design to all those involved in the field, including interior Designers, architects and contractors, as well as consumers. 72
Construction Ahead, nov-apr 2007
Construction Materials: Their Nature and Behavior by J.m. Illston Thoroughly revised and updated, the third edition of Construction Materials continues to provide a comprehensive coverage of the main construction materials for undergraduate students of civil engineering and construction related courses. It creates an understanding of materials and how they perform through a knowledge of their chemical and physical structure, leading to an ability to judge their behavior in service and construction. With its wealth of illustrations and reader-friendly writing style and layout this book is ideal for both the student and the practicing engineer.
Materials for Architects and Builders by Arthur Lyons Materials for Architects and Builders provides an introduction to a wide range of building materials. It explains in detail the manufacture, key physical properties, specification and uses of the standard building products, everything a student would need to know. The book also describes many recent technological innovations and rediscovered materials, reflecting an increased concern for environmental issues within the Industry. This new edition has been completely updated to reflect the amended Building Regulations, the latest British and European Standards as well as incorporating current advice and information from the Building Research Establishment. Dr Arthur Lyons is a teacher fellow and principal lecturer in building materials at the Leicester School of Architecture within the Faculty of Art and Design at De Montfort University, UK. He has taught the subject of building materials for thirty five years to a wide range of students within the built environment disciplines. All books are available in stock at
Reliable Book Store Visit our book store, in front of Meridian Hotel, Bole Road Tel 00251 11 663 5399, 651 1497 Fax 00251 11 663 82842 Mob 00251 91 124 8353 P.O.Box 849/1110 Addis Ababa, Ethiopia remsethiopia@yahoo.com
Construction Ahead, nov-apr 2007
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snapshot
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Construction Ahead, nov-apr 2007
Not every picture is worth a thousand words. And there may be some that are worth more. We hope ours fall at least somewhere in between. In any case, we want to end Construction Ahead with a photograph that we hope will always be interesting enough and constructive. So, if you have an unusual picture, that attempts to capture an intriguing coincidence of space and time, do send to it and share it with our readers. Sorry, but we will not be able to return submitted photographs but appropriate credit will be made.
Construction Ahead Website www.constructionahead.com
The Magazine and its associated web site complement each other in their coverage of the whole gamut of the industry, each taking advantage of its particular medium. Whereas the magazine is better suited for reviews of new construction technology techniques and tools, you need to log into the more interactive and constantly updated web site to get the latest prices for building materials and projects being tendered. But the Web site has much more. It does give a synopsis of the magazine plus: Discussions Forums under three categories; technical (addressing theoretical and technical matters); business (dealing with practical issues of the construction business and trade); social/public (taking the concerns and interests of the wider public and society with regard to topics ranging from architectural aesthetics, building codes and environmental implication of certain construction materials or practices) Advisory directing your particular questions or problems to the experts and getting a direct response. Events related to the industry. Tenders Price watch of basic building materials updated every 2 weeks. Market the classified-buying and selling, exchanging bartering, leasing, renting and so on. Directory of key sectorial operators and services.
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