CONCRETE MANUFACTURING & CONSTRUCTION ISSUE 3 2022
R49,00
PRECAST SPECIALLY DESIGNED PUMPABLE CONCRETE MIXES
PPC 130
years
Pumpable concrete mixes, ranging from 20MPa to 50 MPa. Pump mixes designed for everyday applications over a wide range of construction elements.
IN THIS ISSUE: Zero carbon by 2050 0800 236 368 | www.ppc.africa
@PPC_Africa
PPC Ltd
Hempcrete building blocks make a world first Get wall-wise Totally precast
2011519
A LOT OF INNOVATION. EVEN MORE DEDICATION. QUALITY CEMENT. WHAT GOES INTO IT MATTERS.
Our range of high quality cement is designed for specialised applications where early strength is required. The fine-particle mineral components mean our cement offers improved durability and a superior quality concrete. When you’re putting everything into delivering a quality product, you need quality cement that delivers every time. Ask for AfriSam.
www.afrisam.com
Creating Concrete Possibilities
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WORK, WEAR SAFETY APPAREL Branding available
Contact Lamees Mahomed | lamees@isikhova.co.za Mobile 084 590 5123 | Landline 011 883 4627 | www.isikhova.co.za
| CONTENTS |
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Editor’s NOTE
New and hybrid technologies show no sign of slowing down the impressive expansion of precast concrete’s functionality and utility – and South Africa is no passive beneficiary: we continue to innovate and contribute, packing a punch that belies our weight. But we still need more inroads into low-cost housing. It is an investment which is inarguably needs-driven and a catalyst for growth that multiplies over time. Precast modular homes have opened up the housing market in countries like Australia and the USA. However, like our preference for bitumen roads, our preference for bricks-and-mortar houses is complex, historic and understandable. It seems, though, that technology could solve this issue too. In this issue, we look at a variety of innovations, driven by the increasingly shared realities wrought by the Covid-19 pandemic in an increasingly globalised economy. From manufacturing to surface treatments, precast construction flourishes in combination with traditional, in-situ methods, blurring the lines of what is exclusively one or the other. We also see the indisputable benefits of this hybrid world, in which sustainability is increasingly the best business case, especially for the full life-cycle of materials and structures.
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| CONTENTS |
COVER STORY PPC’s perfect mix for optimal concrete pumping
SPECIALLY DESIGNED PUMPABLE CONCRETE MIXES
INDUSTRY NEWS
FEATURE Modular building systems – more than just walls The rise of structural precast building systems Totally precast: Complete building systems Getting wall-wise
PROJECTS 32 Mamelodi stormwater upgrades 34 Building reservoirs of talent
CONTRACTUAL 36 Managing a construction contract: The post-award phase
INNOVATIONS
130
years
Pump mixes designed for everyday applications over a wide range of construction elements.
IN THIS ISSUE: Zero carbon by 2050 0800 236 368 | www.ppc.africa
@PPC_Africa
PPC Ltd
Hempcrete building blocks make a world first Get wall-wise Totally precast
ON THE COVER Concrete pumping promises important advantages and realising them depends on the exacting coordination of precise skills. PPC Materials Executive Dave Miles sheds light on the operating world of concrete pumping. PRECAST is independently published by Isikhova Media (Pty) Ltd 10th Floor, Metal Box, 25 Owl Street, Milpark, South Africa Tel: +27 (11) 883 4627 www.isikhova.co.za Pubishing director/Editor-in-chief: Jason Aarons E-mail: jason@isikhova.co.za Editor: Nicholas McDiarmid Tel: 067 672 2503 E-mail: nicholas@isikhova.co.za Director: Brand strategy: Jenny Justus E-mail: jenny@isikhova.co.za Operations director: Thuli Majola E-mail: thuli@isikhova.co.za Creative director: Joanne Brook E-mail: joanne@isikhova.co.za
40 Technological advancements for precast producers 42 The future of precast walls 44 Hemp unlocks sustainable building blocks
GLOBAL VIEW
Managing director: Imraan Mahomed E-mail: imraan@isikhova.co.za Sales manager: Ruwayda Mahomed Tel: 072 383 3203 E-mail: ruwayda@isikhova.co.za Copy editor: Anne Phillips
46 The future of concrete architecture
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PPC
Pumpable concrete mixes, ranging from 20MPa to 50 MPa.
6 Fostering concrete wisdom with live training 7 Maweni Limestone Ltd becomes associate corporate member of WCA 8 Ticking boxes undermines BBBEE 10 AfriSam’s precast value adds benefits to concrete precast manufacturers 11 Zero carbon by 2050 for Cement and Concrete SA members 12 Major Gauteng piling contract for Midrand apartment block foundations 13 A new approach to the regulation of residue stockpiles and deposits 14 T he integration of emerging contractors 15 Coatings sector calls for government action
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CONCRETE MANUFACTURING & CONSTRUCTION ISSUE 3 2022
Find us online @precastmag
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Design intern: Zian Cornellissen Media sales: Tel: +27 (11) 883 4627 / 083 450 6052 / 072 383 3203 The views and statements expressed in this publication are not necessarily those of the editor or the publishers and neither the publishers nor the editor accept responsibility for them. No person connected with the publication of this journal will be liable for any loss or damage sustained as a result of action following any statements or opinions expressed herein. The same applies to all advertising. Precast© 2022. All rights reserved. No part of this magazine may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage retrieval system, without prior written permission from the publishers.
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| COVER STORY |
PPC’S PERFECT MIX FOR OPTIMAL In South Africa, approximately 30% of concrete is placed by pumping and, with its distinct advantages in efficiency, the increasing trend of fast-tracking projects makes concrete pumping indispensable. PPC has refined its response to this market trend through strategic pumping contractor partnerships and optimal pumping mixes. Concrete pumping promises important advantages and realising them depends on the exacting co-ordination of precise skills. PPC has perfected that mix, drawing on its in-house strengths in co-ordination with the best in the business. PPC Materials executive, Dave Miles, explains the operating world of concrete pumping: “Pumping is a lot faster than a crane. You can put the concrete exactly
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where you want to. Therefore, from the contractor’s point of view, a pump saves a significant amount of time. Taking into account the fast-track nature of most projects these days, the pump has become indispensable on any construction site. “In addition, from a ready-mix point of view, one gets faster turnaround on the trucks when they go to a pump. One can send a truck to a pump and 10 minutes later, it’s empty and on its way back to the plant for another load. If one had to do that same load with a crane, the truck could be on site for an hour-and-a-half to two hours. This results in better utilisation of the ready-mix producer’s assets. “The customer gets a one-stop shop with us whereby, on their behalf, we deal
directly with the pumping contractors. This is something we’ve found to be a much more effective operating business model and allows us to focus on producing high-quality concrete. The brand of pump is the contractor’s concern, while customer relations remains our concern. As far as they’re concerned, they’re always dealing with PPC and we're answerable for the job quality,” says Miles.
The right mix for concrete pumping “The mix for pumping aims at reducing the abrasion or friction of the concrete on the machinery. It will therefore have a slightly lower content of stone, probably in the region of 100-150kg/m3 fewer stones and slightly more sand, to achieve more paste in
| COVER STORY |
the mix. It looks fluffier or more cohesive and also has a slightly higher slump. Its slump will be in the region of 100-150mm, so it’s easier to pump. As far as maintaining that slump from plant to site, we use admixtures for workability retention – but there isn’t a big difference in the end product. “The two main differences between the two concretes types lie in its workability and its stone content. When it comes to laying out a slab, it doesn’t make any significant difference which concrete is used in its performance, as long as the engineer’s taken the differences into account with their slab design,” says Miles. “The main difference which the engineer needs to take into account is that the pumped concrete will have slightly more shrinkage because there’s a slightly higher water content and a higher paste content. The engineers take that into account in the steel design in the bigger spans, but on the majority of deck slabs in any building, there’s no difference in performance, strength-wise.” Where a contractor has specialised performance criteria for the end product, PPC Materials’ technical team designs bespoke mixes. The pumping day team The worker in charge of the pump hopper monitors the proceedings and addresses any problems. “The driver requires specialised skills,” explains Miles. “He or she needs a fair
L CONCRETE PUMPING
“The customer gets a one-stop shop with us whereby, on their behalf, we deal directly with the pumping contractors.” understanding of mechanical operation, safety operations and working conditions, as well as a certain amount of concrete technology training. To operate a boom pump, in many cases the operator’s situated on the ground and can’t actually see the end of the pump 20m or 30m up on top of a deck.” Communication between the operator and the team on the deck is critical in these instances. “The pump operator has the final say as to whether they’re going to pump the concrete or not,” cautions Miles. “We have an agreement with our contractors giving the operator the right to reject a load, in order to protect the machines.” Furthermore, if the slump of the concrete is out of specification, the operator may reject the load, as it is an indication that the quality might not be up to PPC’s high standards. “In that event, the batch would be analysed to check what was physically put into the mix by our technical team. After that analysis, if the team feels that adjustments can be made to the mix on site, the operator can do that and still be within specification parameters. If that’s not possible, the truck would normally be returned to the plant and diverted to another site, where the concrete can be used at a much lower strength mix.” Covering all concrete pumping bases From health and safety to maintenance and in-depth client consulting, PPC’s pumping service and products are designed to optimise the whole process. Pumping days on any site can be critical times in a project and it is in everyone’s interests to ensure that they proceed without a hitch or delays. All of this requires complex co-ordination. There are many benef its to PPC’s uniquely curated of fering. Expertise, vetted pumping contractors, mix ing expertise, health, safety and maintenance are managed with years of accumulated skills and experience.
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| INDUSTRY NEWS |
FOSTERING CONCRETE WISDOM WITH LIVE TRAINING Cement & Concrete SA’s School of Concrete Technology is gearing up to present live classes of one of its most important training courses in Durban, Cape Town and Midrand in the second half of this year. The popular “SCT20 – Concrete Practice” course is a vital training tool to ensure best practice and economical concrete works on site, says John Roxburgh, senior lecturer at the school. Roxburgh feels the pandemic has led to rampant cost-cutting in the building industry. “This often leads to neglecting sound site practice which determines concrete performance and infrastructural safety and durability. Saving costs is commendable, but not by sacrificing site expertise. Only contractors with a full grasp of concrete technology will be able to balance pricing and maintaining their company’s credibility,” he explains. “A trained concrete practitioner is needed to assess the quality of the concrete supplied. The concreting team must know
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how the concrete is transported on site and which placement and compaction methods to adopt. They must also ensure that the curing system and staff are fully equipped. “Sound concrete site practice can only be achieved by ‘concrete wisdom’. A trained concrete team will know how to prevent segregation in the concrete both through mix design and handling, and how to prevent crack formation and achieve quality finishing and curing of the concrete. Property-owners whose structures fail prematurely aren’t likely to entrust more work to under-performing contractors. The cost implications are too important for developers and, for the contractors concerned, such failures could mean the end of their business. “That’s why the School of Concrete Technology’s ‘SCT20 – Concrete Practice’ course is such a vital training tool to ensure the best site practice for concrete works. It provides trainees with essential concrete technology concepts and theoretical back-
ground to implement trustworthy and proven methods of dealing with concrete on site.” The SCT20 course is recommended for foremen, clerks-of-work, technicians, supervisors, sales and technical staff. The topics covered include: • Properties of fresh concrete at various stages. • Mix proportion and quantities. • Concrete production and transport. • Placing, compacting, protecting and curing of concrete. • Formwork and reinforcement. • Concreting in cold and hot weather. • Defects and repairs. • Low-density and pre-stressed concrete. • Off-shutter and architectural finishes. • Precast concrete. The four-day course will be presented live in Durban from 25-28 July, in Cape Town from 5-8 September and in Midrand from 20-23 June, 29 August-1 September and 17-20 October. For further information, contact the School of Concrete Technology on tel: (011) 315 0300, e-mail: sct@cemcon-sa.org.za or visit: www.cemcon-sa.org.za.
MAWENI LIMESTONE LTD BECOMES AN ASSOCIATE CORPORATE MEMBER OF WCA The World Cement Association (WCA) has announced that Maweni Limestone, a subsidiary of Huaxin Cement Group, has joined the international network as a corporate member. “We’re delighted to welcome Maweni Limestone among our membership, as one of the WCA’s key ambitions is to more effectively engage emerging-market players across the global cement ecosystem,” explains Ian Riley, the association’s CEO. “We look forward to the contribution it will make to our efforts to share and improve best practice among members.” Maweni Limestone is one of East Africa’s leading manufacturers of cement operating in Tanzania. In 2020, it was acquired and reconstructed by China Huaxin Cement, becoming one of the largest cement manufacturers in the region, with an output of 1,5 million tons per annum of cement, which provided important support for the industrialisation of Tanzania. “We’re very proud that we’ve not only managed to develop a strong market position in Tanzania, but have also maintained high standards for our business,” says Changxi Jing, country manager of Maweni Limestone. “We’ve admired the work already done by the WCA to raise awareness of pressing issues and opportunities faced by our industry today and we look forward to contributing to this global discussion.” About the World Cement Association The WCA is the original international cement association and represents the cement industry and its stakeholders. Corporate members are cement producers and have equal rights, regardless of size or nationality. The WCA connects members across the world and provides practical help to improve competitiveness and sustainability.
| INDUSTRY NEWS |
TICKING BOXES UNDERMINES BBBEE The prominence of skills development and training in the broad-based black economic empowerment (BBBEE) codes recognises its centrality to transformation. It is equally central to companies’ BBBEE scorecards, contributing an entire level, independently of all other measures. Despite this, sk ills development and training has been identified as a failing area of BBBEE. Sk i l l s development a nd t r a i n i ng empowers employees to perform their jobs to the best of their ability and rise up the ranks to play a more meaningful role in the growth of their companies and the economy. Importantly, proper training should also contribute towards the personal growth and development of individuals and, in this way, make a positive contribution to society at large. Still ticking boxes “Unfortunately, many companies are still ‘ticking boxes’ when it comes to training and skills development. They’re training just for the sake of it, simply to meet their scorecard requirements. This is opposed to ensuring that people who really require skills are selected for appropriate training. Their training initiatives therefore aren’t having the intended impact – a problem that’s again been brought to the fore by the government, considering the slow rate of economic transformation,” says Marco Maree, expert training and development advisor of Triple E Training. The organisation is a leading provider of adult literacy and numeracy training to industr y. The accredited training provider’s skills development programmes are geared for equipping people with
The National Qualification Framework is a highly under-utilised resource that has the power to change lives.
workplace literacy skills. Also referred to as functional literacy, these are skills needed by employees to perform jobs at optimal levels. They are also used in just about every facet of life outside the world of work in their broader communities and society. Wasting potential, wasting money There are many ways in which companies “t ick boxes”, includ ing by spend ing money on super f luous tra ining t hat will not improve the core skills of their workforce. There have even been instances where companies have intent iona l ly conducted training that provides scant or no opportunity for employees to improve t heir circumstances. Employees are deliberately being held back because there is no clear career development path and rationale for the training in the first place. In extenuating circumstances, companies have also been caught simulating training without actually transferring skills to
(Above): The power of literacy to transform lives is more powerful than any box-ticking exercise.
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employees, simply to improve their BBBEE scorecards. It is expected that this will become a major concern of the new BBBEE advisory panel. Solving the skills crisis However, South Africa is grappling with a severe skills crisis, including for tradespeople who hold a qualification at a National Qualification Framework level. Despite being proficient in their jobs, many young adults are being deprived of an opportunity to attain such a qualification simply because they lack literacy and numeracy skills. They struggle to grasp the technical content presented in vocational training and write their trade tests in the language of business and learning. There are adult literacy and numeracy training programmes geared specif ically to prepare individuals for vocational training and more companies should be taking advantage of them. Facing the technology reality At the same time, there is also a need to fast-track the upskilling of the many employees who perform general roles that are gradually being replaced by technology. Their jobs are at risk in a modern economy which relies increasingly on skilled and experienced employees. The changes that the economy has undergone since 1994 is also fuelling persistently high unemployment in the country, especially among black youth and
black women. These individuals need to be equipped with at least the most basic skills that will help them to improve their prospects of securing employment. This is particularly relevant to community training interventions which companies are supposed to undertake as part of their corporate social investment initiatives and social-labour plans. It is imperative that these projects are undertaken correctly. A passion for equality Appropriate individuals need to be selected for training and placed at the correct adult literacy and numeracy training levels to ensure a successful outcome. The private sector has a prominent role to play in helping the government break the back of illiteracy in poor areas of the country. It is an enormous challenge that cannot be addressed solely by the adult basic education and training programmes which are being delivered by municipalities, non-government organisations and universities. An equal opportunity investment In turn, high unemployment and lack of appropriate skills are fuelling growing inequality. To address this, SA needs to focus on creating skilled jobs for the poor. Adult literacy and numeracy training is the first step towards upskilling these citizens for the jobs of the future. The ultimate outcome of formal and structured adult literacy and numeracy training is to prepare individuals to embark on a journey of lifelong learning. This is in addition to instilling a passion for learning in participants in adult literacy and numeracy training programmes. A business case for a multiplier profit centre However, an investment in training also benefits employers in many other ways than just contributing points to their BBBEE scorecards. These are also further incentives for companies to invest more in human resource development and to take this requirement of the BBBEE codes more seriously. Adult literacy and numeracy training, for example, improves the productivity, efficiency and accuracy of workers. These advantages can be measured by a reduction in waste, shorter times taken to complete tasks and improved customer satisfaction, among others. There is also a strong correlation between literacy and health and safety in the workplace and on worksites – an important advantage for the construction, mining and manufacturing industries, in particular. “While skills development has once again been placed under the spotlight by the authorities, it’s important to note that many companies take skills development and training very seriously. It’s a vital component of their human capital, so their approach transcends merely training to gain points for their BBBEE scorecard. They’re investing in building strong teams who’re contributing to economic growth and inclusivity. A lot can be gleaned from their approach, which also challenges their training service providers to innovate and break perceived boundaries in skills development,” says Maree.
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| INDUSTRY NEWS |
AFRISAM’S PRECAST VALUE ADDS BENEFITS TO CONCRETE PRECAST MANUFACTURERS AfriSam’s offering to concrete precast manufacturers (CPMs) operat ing in today’s highly competitive marketplace incorporates several value-adds, designed to improve the performance of their products and help contain costs. Underpinning the primary products supplied to the market – Rapid Hard Cement in the 52.5R strength class, High Strength Cement (HSC) in the 42.5R strength class in the northern market and the 52.5N HSC product in the southern market – AfriSam’s value-adds include on-site technical services. Concrete mix, testing and customercentric delivery services T hese ser v ices, wh ich are rendered by staf f from the A friSam Centre of Product E xcel lence, help customers determine the ideal mix desig ns for their specific applications and propose aggregates that meet these requirements. SANAS-accredited laboratory services are used to verify and test the efficiency of mixes, while product deliveries can be specifically scheduled to suit customers’ individual activities.
(Above): AfriSam’s Rapid Hard Cement has been developed for specialist concrete product manufacturers and achieves more than the SANS 50197 minimum of 30MPa mortar strength at the two-day mark.
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“In the CPM market, we focus on assisting our customers to operate as efficiently as possible,” says Mike McDonald, manager of AfriSam’s Centre of Product Excellence. “This involves evaluating their existing mix designs and helping them reduce unnecessarily costly components without compromising the quality or aesthetics of the end product.” High-strength cement enables highspec precast production The “R” early strength factor in AfriSam’s 52.5R CEM I Rapid Hard Cement and 42.5R CEM II High Strength Cement is proving to be a real dif ferentiator in the CPM market. Top-of-the-range 52.5R Rapid Hard Cement, developed for specialist concrete product manufacturers, is performing particularly well, achieving more than the SANS 50197 minimum of 30MPa mortar strength at the twoday mark. This is enabling CPMs to develop a variety of new high-specification products, such as highway barriers, roof tiles, retaining wall systems, culverts and concrete pipes. Its 42.5R High Strength Cement has been specially formulated and activated to allow for further extension with additional
(Above): AfriSam’s value-add to concrete precast manufacturers includes on-site technical service, SANAS-accredited laboratory services and product deliveries to suit customers’ requirements.
mineral components in the production of structural concrete. The “R” rating of the HSC is supported by AfriSam’s strict quality control plan and this product is achieving in excess of the SANS 50197 minimum of 20MPa mortar strength at the two-day mark. High Strength Cement is commonly used to achieve concrete strengths of 10-60MPa, but it is also suitable for high-strength concrete, with strengths of 80MPa and higher. Customer va lue management initiative “These market-leading products, together with our value-adds, are part of AfriSam’s in-house customer value management initiative that seeks to unlock value for our customers across the board in new ways,” says McDonald. “Our CPM customers are experiencing tangible benefits and this has led to measurable growth in this market for us. Our innovative approach allows us to make a genuine contribution to optimising their operations.”
| INDUSTRY NEWS |
ZERO CARBON BY 2050 FOR CEMENT AND CONCRETE SA MEMBERS Cement and Concrete SA (CCSA) has noted the United Nations Framework Convention on Climate Change (UNFCC) position that parties should act to protect the climate system “on the basis of equality and in accordance with their common, but differentiated responsibilities and respective capabilities”, based on Principle 7 of the Rio Declaration at the first Rio Earth Summit in 1992. “In response, to comply with CCSA climate change commitments in line with the national NDC and Paris agreement, CCSA member companies aspire to net zero emission by 2050 with milestones informed by decarbonisation along a 1,5˚ trajectory. The key initial milestone will be set at 2030,” says Dr Dhiraj Rama, CCSA industry executive. “The net zero target boundary is based on the Greenhouse Gas [GHG] inventory target, as per RSA GHG technical reporting guidelines for the cement sector in line with the Inter-Governmental Panel on Climate Change reporting framework,” he adds. Rama will provide adequate support, direction and leadership to members and will also monitor progress at sector level. He says key matters to note include that: • The net zero target monitoring covers
both Scope 1 and Scope 2 emissions of the company. • With supported technology interventions, as well as improved overall nationally developed Scope 3 emission monitoring programmes implemented by stakeholders, the GHG inventory would be expanded accordingly. • The trajectory is based on the understanding that the cement sector is hard to abate and would be supported by: • Technical, technological and fiscal support, as per the CCSA overall nat iona l N DC com m it ment to UNFCCC provisos. • Appropriate policy implementation and support to secure both green energy and alternate fuels and resources. • Optimising operation of current pro duction plants as practically feasible until the end of the plant’s life-cycle. • All future plants will ensure emission efficient technologies. • Access to carbon offsets. • The climate response action will be underpinned by a “ just transition”. • The overall consolidated CCSA sector performance of the GHG emission profile will be transparent by reporting performance on a regular basis. CCSA
(Above): Dr Shiraj Rama, CCSA industry executive.
will ensure sectoral support to its members to comply with regulatory requirements. Key requirements include compliance with: • Draft methodological guidelines for quantification of greenhouse gas emissions. The draft methodological guide lines can be downloaded by members of the public at the website link: www. env i r on ment .g ov.za/ leg i s l at ion/ gazetted_notices (Government Notice 135 dated 19 February 2021). • Technical guidelines for the validation and verification of GHG emissions as per Technical Guidelines for Monitoring, Reporting and Verification of GHG Emissions by Industry: A Companion to the South African National GHG Emission Reporting Regulations Version No: TG-2016. 1 June 2016 (Government Notice 1496 dated 12 November 2021). • For further information, contact Dr Dhiraj Rama at: dhiraj.rama@cemcon-sa.org.za.
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| INDUSTRY NEWS |
MAJOR GAUTENG PILING CONTRACT FOR MIDRAND APARTMENT BLOCK FOUNDATIONS Gauteng Piling has secured a major contract to provide extensive foundation piling for the Grand Central Towers apartment block which, with a ground floor and nine storeys, will become a lofty landmark in Midrand. Keoatlaretse Tema, contracts manager for Gauteng Piling, who is in charge of the project, says 302 piles will be required for the new high-rise structure, which will incorporate 990 social housing walk-up units. The apartment block, near Grand Central Airport, is being developed by Bridgeport, with Tri-Star Construction as the main contractor. Geology challenges “The site is roughly triangular and covers 1 259ha. The property’s bounded to the east by Diagonal Street, to the south by Exchange Street and on the north and west by Market Street,” says Tema. In providing the piles with an average depth of 5m, Gauteng Piling encountered shallow rock at 200-900mm below ground surface, which will require specialist d r i l l ing. “However, Gauteng P i l ing provided a piling rig to conduct a pre-piling geotechnical investigation, so we were aware and prepared for the shallow rock on a portion of the site,” she adds. The diameter of the 302 piles being installed for the apartment block varies from 650mm-1,15m. Steel reinforcement cages 500mm-1m in diameter are being installed to support the piles. Gauteng Piling also has to install four additional piles per crane to secure the three tower cranes being used by Tri-Star for the construction. Concrete preparations Tema says that, apart from the shallow rock, the main challenge for the Grand Central Towers project is the casting of column starter bars into the piles. “No pile caps will be installed, so we’re working closely with the steel-fixing crew from TriStar Construction to ensure the starter bars are in place before the piling concrete’s poured,” she adds.
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(Above): A piling rig was used to conduct a predrilling geotechnical investigation. In the absence of pile-caps, starter bars were placed before any concrete was poured.
Gauteng Piling, which is using three rigs for this contract, was founded in 1996 by building industry veteran Nico Maas. He is still heading the company, which has completed over 1 800 piling contracts over the past 26 years, including the massive Mall of Africa in Midrand, Greenstone Mall in Edenvale, Clearwater Mall in Roodepoort and Alex Junction in Alexandra.
“In providing the piles with an average depth of 5m, Gauteng Piling encountered shallow rock at 200-900mm below ground surface, which will require specialist drilling.”
| INDUSTRY NEWS |
A NEW APPROACH TO THE REGULATION OF RESIDUE STOCKPILES AND DEPOSITS By Kirsty Kilner, partner and Lerato Molefi, associate, both of Webber Wentzel Climate change has put the spotlight on various sectors to ensure that they comply with specific regulations governing pollution control. The mining sector, in particular, is currently facing environmental legal over-regulation which has created a negative atmosphere with regard to residue stockpiles and deposits regulations. The National Environmental Management Amendment Act IV (NEMLAA IV) will introduce a shift in the regulation of residue stockpiles and deposits when it is signed into law. Residue stockpiles and deposits are currently regarded as waste and are therefore regulated under the National Environmental Management: Wa ste Act 59 of 20 0 8 ( Wa ste Act). NEMLAA IV will amend the definition of “waste” to exclude residue stockpiles and deposits. This removes the regulation of residue stockpiles and deposits from the Waste Act. Residue stockpiles and deposits will instead be regulated in terms of the National Environmental Management Act 107 of 1998 (NEMA). Transitional arrangements will be imposed to facilitate this change. This means that: • Any approval granted or waste management licence (WML) issued in relation to residue stockpiles and deposits under the Waste Act will remain valid until it
lapses, or until it is replaced under NEMA. • The regulations regarding the planning and management of residue stockpiles and deposits, 2015 that were published under the Waste Act remain in force and will be deemed to have been promulgated in terms of NEMA. W hen N EM L A A I V becomes operational (and subject to the transitional arrangements), a WML will no longer be required to authorise residue stockpiles and deposits. It is expected that residue stockpiles and deposits will, in future, be required to be regulated in terms of environmental authorisation and approved environmental management programmes,
(Above): New South African stockpile legislation needs to be factored in by all users of aggregate materials.
issued in terms of NEMA. We anticipate that further changes will need to be made to the NEMA-listed activities to facilitate this regulatory shift. We similarly anticipate that the residue stockpile and deposit regulations will also be amended to bring them in line with the changes that will be imposed by NEMLAA IV. The proposed amendments to the regulation of residue stockpiles and deposits should be kept in mind when considering the planning and management of residue stockpiles and deposits.
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| INDUSTRY NEWS |
THE INTEGRATION OF EMERGING CONTRACTORS An Eastern Cape company has become the first member of Cement & Concrete SA’s (CCSA’s) new “Emerging Contractors” membership category, created for this important part of the construction industry and the national economy. Hanlie Turner, business development manager of CCSA, says the new Emerging Contractors category – which falls under the CCSA Corporate Members section – is specifically designed to support and uplift cement and concrete industry micro-enterprises with BBBEE Level 1 status and an annual revenue of up to R5 million. “The category aims to provide important market exposure and CCSA corporate membership benefits to emerging contractors, who very often have limited marketing capacity and budgets. CCSA’s also fixed an affordable membership fee of R3 000 per year for contractors who qualify for inclusion in this category,” she says. Turner explains that up to three individuals can be listed under an Emerging Contractor membership, while their company receives a listing in the CCSA directory and digital listing in the CCSA journal Concrete Beton, as well as hyperlinking of the company’s logo to the CCSA website. The listed individuals benefit from cost discounts on CCSA publications, technical events and educational courses.
(Above): GloQ's membership of CCSA marks a very important inroad into the formalisation of professional services intrinsic to rural development of the Eastern Cape. (Left): GloQ Construction and Projects, the first emerging contractor to join CCSA under its new category, specialises in concrete ready-mix products and a range of construction services.
Experiencing the benefits The first company joining CCSA under this category is Eastern Cape-based GloQ Construction & Projects. Owned and managed by Qaqamba Gloria Selikane, it describes itself as a “leader in various phases of construction projects that demand ready-mix concrete products and consulting in design development, tender documentation and procurement, construction documentation and management, as well as the ‘closing-out’ phases of residential and rural developments, commercial building and civil engineering projects”. Selikane has over 15 years’ experience in the construction industry and is a member and registered mentor of the SA Council for the Project and Construction Management Professions (SACPCMP) as a professional construction manager. She serves as a non-executive director of the Construction Management Foundation.
Her professional experience includes working for Murray & Roberts, Sasol and Eskom. She holds a BSc Honours degree in construction management and an MSc in project management (construction). GloQ’s operating base is Bizana, on the border of the Eastern Cape and KwaZuluNatal. The small town is the birthplace of Struggle icons Oliver Tambo and Winnie Madikizela-Mandela. Opening market doors CCSA’s comprehensive corporate membership structure is open to medium and micro-enterprises, suppliers, contracting and consulting firms, government organisations, provincial and national producer companies, as well as professional bodies in the cement and concrete industry, which can join as organisational members at various levels of benefits and costs. “The members benefit from affordable and targeted marketing levels to broaden their reach, create brand awareness and remain competitive and relevant in the market,” says Turner. Interested parties can find further infomation at: www.cemcon-sa.org.za.
(Left): Qaqamba Selikane, owner and MD of GloQ Construction & Projects, CCSA’s first Emerging Contractor member.
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| INDUSTRY NEWS |
The South African coatings sector urgently needs government assistance to counter growing challenges that could endanger its entire future, says Sanjeev Bhatt, who was recently re-elected as chairperson of the SA Paint Manufacturing Association (SAPMA). Bhatt says that in addition to issues such as disruptions in electricity supply, crumbling infrastructure and inefficient management of parastatal entities which the coatings sector has to face, competition from other African countries is also major problem. Rates and imports “The employment rates that some African governments, such as Egypt, grant their manufacturing sectors make production costs there much lower than in SA. If these cheaper imports from Africa are allowed to flood the local market, the local coatings manufacturing sector will suffer serious economic consequences and ultimately cease production. We’re hoping that relief will come, as the Department of Trade, Industry & Competition [DTIC] has confirmed that an African Free Trade Agreement has been ring-fenced for SA. This will mean that coatings and associated raw material imports from the likes of Egypt won’t be allowed duty-free into this country. “Due to the cost of electricity – and lack of its constant supply – as well as the cost of labour in SA, we believe that the government must also assist the coatings sector with rebates for electricity, in addition to any other possible rebates needed. If not, many SA PM A members will consider moving to alternate countries to set up plants where labour costs are lower and electricity supply more assured,” says Bhatt. Co-operation and streamlining He believes that government departments need to work more closely with the coatings sector to ensure that current policies that are in place, or planned, are reconsidered or revised to help the sector streamline operational processes. “Take permits required at ports of entry, for example. These are
COATINGS SECTOR CALLS FOR GOVERNMENT ACTION now required in writing for every single individual consignment brought into SA. As some coatings companies have consignments of the same chemicals and raw materials coming into port four or five times a year, the importers must laboriously repeat the same paper-based permit applications over and over again. We’d like government departments to make these import permit processes more streamlined – and def initely place them online. “Government departments generally should consult members of the coatings sector to better understand our manufacturing process, as well as our supplier needs. SAPMA’s hoping to meet with key government departments such as the DTIC, the International Trade Administration Commission and Invest SA (which is part of the DTIC) as soon as possible to
seek help in this regard,” he adds. Bhatt believes there is a worrying skills shortage in the coatings sector – especially at industrial chemist level. “SAPMA’s never stopped training – we’re just not doing it anymore via our SA Paint Industry Training Institute, which we’ve shut down. Instead, we’re working closely with the British Coatings Federation [BCF], which recently updated its training modules to make it more user-friendly and also cover more fields such as powder coatings, inks and printing, in addition to only general coatings tuition. Through SAPMA locally, these BCF courses are available online, which make them more accessible to students all over the country. The other benefit of using the BCF training material is that modules completed are recognised both locally and internationally through the federation,” he says. • To contact the SA Paint Manufacturing Association, visit: www.sapma.org.za. (Left): Sanjeev Bhatt, chairperson of the SA Paint Manufacturing Association (SAPMA).
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| FEATURE |
(Above): Since precast wall panels are manufactured in a production facility, the impact that they impose on site is minimal.
MODULAR BUILDING SYSTEMS – MORE THA There are dif ferent t y pes of precast concrete buildings, which can be grouped as total precast, partial precast and mixed-construction structures. Total precast building comprises various precast components such as footings, beams, slabs, columns, walls, façades and frames. Precast walls can combine both structural and loadbearing functional properties, or simply function as dividers – as is the case with frame-panel buildings, where the loads are carried by a framework. A partial precast building can be made of the precast components and cast-in-situ concrete members. This type of building is also known as hybrid construction. Mixed-construction buildings consist of precast components along with cast-in-situ concrete, steel, masonry or timber members. The different systems of precast concrete buildings can be grouped under the following headings: • Overall structural systems. • Systems for lateral load-resistance. • Floor and roof systems.
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(Right): A partial precast building can be made of the precast components and cast-in-situ concrete members.
Overall structural systems The structural system of a building is that part of it which resists the loads acting on it. It can be broadly categorised under four groups:
Structural System Skeletal Frame System Large Panel System Cell System Hollow Block System
Skeletal frames Skeletal frames are commonly used for relatively low-rise buildings which do not have many partitions. A common usage is
Low-rise Portals and frames Multi-Storeyed frames Slab-column system with shear walls
in large-scale car parking buildings. Other common buildings built using frames are office blocks and commercial buildings. The frames can be designed as moment-
| FEATURE |
frames and are often either combined with precast shear wall systems or cast-in-situ shear walls. The speed of construction and the high quality of the components are the main benef its of using precast skeletal systems. A building using a fully precast system can often be built at approximately 10-14 days per floor, depending on the area and logistic limitations. The frame system can be designed for resisting lateral loans. However, there may be a need for supplemental lateral loadresistance through the use of braces or walls. Hence, core or shear walls are provided. It incorporates a network, or system, of columns and connecting beams which support the building’s interior floors and exterior walls and carry all loads to the foundations. Skeleton frames can be constructed from t imber, concrete or st r uctura l steel components, with the building envelope formed by glazing, brick, cladding, etc hung on the outside.
AN JUST WALLS (Above): A building using a fully precast system can often be built at approximately 10-14 days per floor, depending on the area and logistic limitations. (Below): Large-panel structures for exterior walls consist of panels one or two storeys in height and one or two rooms in width.
The skeletal frame was introduced in the late 19th and early 20th centuries and allowed for the rapid erection of buildings, such as the early skyscrapers. It enabled interior floor layouts to be free of immovable walls, making them more flexible spaces, and meant that different materials could be used for the façades. This reduced the importance of masonry from something that was a structural element to having a more decorative role. Large-panel system Large-panel structures are one of the most progressive industrial types of structural elements. In modern construction, they are used when building apartment blocks, public and industrial buildings, roads, airf ields, dams and canals. They have become most widespread in large-scale housing and civil construction, where the erection of buildings from large panels manufactured at housing construction combines and plants reduces the construction time by a factor of 1,5-2,0 in comparison with erection of the buildings from brick or other traditional materials, as well as a decrease of 30-40% in labour expenditures at the construction site. A ll the main parts of a building, including the exterior and interior walls, floor slabs, roofs and staircases, may be made up of large-panel structures. These structures are used in two main design schemes: frame-panel and panel (frameless) buildings. In frame-panel buildings, all the base loads are borne by the building’s
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| FEATURE |
frame, while the panels are usually used to fill the frame and as enclosure elements. Frameless buildings are assembled from panels that perform the load-bearing and enclosing functions simultaneously. Single-layer and sandwich-layer walls Large-panel structures for exterior walls consist of panels one or two storeys in height and one or two rooms in width. The panels may be blind (without openings) or with window or door openings. In terms of design, the wall panels may be single-layer (solid) or multi-layer (sandwich). Solid panels are manufactured from materials that have insulating properties and supporting functions, such as lightweight concrete, cellular concretes and hollow ceramic stone. Sandwich wall panels are made with two or three layers; their thickness depends on the climatic conditions of the region and the physico-technical properties of the materials used for the insulating layer and the exterior (supporting) layers. The exterior layers of the panels are usually made from heavy, lightweight or solid silicate concrete, or from brickwork or sheeting (asbestos cement, steel or aluminium). Polystyrene foam, rigid and semi-rigid rock wool panels or cellular concretes may be used for the insulating layer. Wall panels are produced in completely finished form, with ready-to-paint surfaces and with windows and doors. The piping for heating and other systems and for wiring may also be installed in the panels. The surface of exterior wall panels is covered with decorative mortar or is faced with ceramic or other f inishing tiles. After assembly, the joints between panels are filled with mortar or with lightweight or ordinary concrete and then sealed with elastic packing and special mastics. Large-panel roof elements are used in housing and public buildings, mainly in the form of combined attic-less roofs. In industrial buildings, the roof panels have a span of up to 12m. The weight of largepanel structures depends on the method of dividing the building into pre-fabricated elements; it is usually 1,5-7,5 tons. Cell/Box system Orthogonal walls and slabs are cast together as integral units to create box-type structures. As with carcass construction or pre-fabricated structures with load-
bearing wall panels, modular box unit systems are composed of a combination of rods or surface load-bearing elements. The basic problem in the modular box unit construction system is how to join the individual box together. The tolerances between the individual box units are essential. Box units systems have a high level of industrialisation. They are threedimensional spatial elements formed by the combination of wall panels and floor units. These systems, constituting an advancement of heavy- and lightweight panel systems, are preferred for achieving a high degree of completion off-site. The development of the box unit system makes it possible to manufacture an entire completed product in the factory. “Box-module structures” are buildings with a fireproof and permanent design in steel and concrete construction. Here the entire structure is factory-built, then split into modules and transported to the construction site. Wall system Precast walls are energy-efficient due to a high thermal mass that enables materials to absorb and store temperatures at a more constant rate. This system reduces the fluctuation of temperatures within the building. Since precast wall panels are manufactured in a production facility, the impact that they impose on site is minimal. This helps reduce the space needed on a job site. Precast wall panels can be customised to the architect’s or owner’s desire. Some architectural features that can be found in a wall panel system include bullnoses, reveals, chamfers and a vast assortment of form-liners. Conclusion The concept of precast construction includes buildings where the majority of structural components are standardised and produced in plants in a location away from the building and then transported to the site for assembly. These components are manufactured by industrial methods based on mass production in order to build a large number of buildings in a short time at low cost. • We have discussed the divisions of building systems of concrete in this article. In the next one, we will discuss the components.
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THE RISE OF STRUCTURAL PRECAST BUILDING SYSTEMS
Precast concrete beams, columns and stairs are the ideal solution for owners and builders who want to achieve wide-open spans, fire-resistance, energy-savings and attractive design in one structural system. These components are suitable for both low- and high-rise structures. Highly durable, the concrete units can be installed in all weather conditions. Precast beams may be either continuous, with single-storey columns or singlespan, with multi-storey columns. The use of standardised forms accelerates the manufacturing process. The quality of smooth formed finishes produced in a precast plant saves money by allowing designers to expose the structure in a finished building. Single-source provider As a single unit, even with stone or brick inset, precast panels require only one source to create the entire exterior wall system. When a precast structural system
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of columns, beams and double tees is also specified, it concentrates the complete shell construction with one certified and reliable producer. This approach ensures that all the responsibility and accuracy for meeting design specifications rest with one supplier. Consistency, tolerances, deadlines, budget and other requirements are assured. Precast’s advantages are maximised when the precaster is brought onto the design team early in the planning stage. This allows the company’s full expertise in designing efficient shapes, textures and finishes to be exploited, as well as its stateof-the-art knowledge of connection and erection methods. (Above and left): The economy and functionalities of architectural panels make them a highly attractive option.
“Architectural precast concrete can be cast in almost any colour, form, or texture (within budget guidelines) to meet aesthetic and practical requirements.”
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Precast components meet all needs A wide range of precast concrete architectural and structural components can be used in commercial buildings. The key pieces used most often in these designs include: Architectural panels Architectural precast wall panels are the solution of choice for the cladding on many office buildings, institutional facilities and mixed-use retail projects of all types. A key reason is that they offer beauty and affordable economy without sacrificing design freedom. That economy results from the low initial cost, the ability to enclose the structure quickly, the ability to continue construction through winter weather and the panel’s long-term durability. In some cases, further economies can be achieved by designing load-bearing precast walls or using insulated wall panels to improve energy-efficiency. These budget, scheduling and design benefits combine with precast’s mouldability to create dramatic and cost-effective looks for all types of commercial buildings. Gl a ss -f ibre -rei n forced (GF RC) panels and decorative elements GFRC concrete can expand the options for attractive exteriors by being used for architectural panels and decorative accent elements, such as balusters, medallions and cornices. It consists of a Portland cementbased composite with alkali-resistant glass f ibres randomly dispersed throughout. These f ibres add f lexural, tensile and impact strengths. The use of GFRC can save costs in a variety of ways, including
(Above): From brick façades… (Right): …to exposed aggregate surfaces.
“The use of precast columns and beams makes an ideal framework for hanging precast panels, creating a design that offers fast construction, structural stability and enhanced fire-resistance.”
(Above): Precast concrete components have opened up options for architectural design and function.
the use of lighter structural framing, faster erection using lighter cranes and creative rehabilitation of older, detailed buildings. GFRC also provides energy-savings and will last the lifetime of the building, ensuring an attractive and consistent look through the years. Beams and columns A complete precast concrete structural system offers tremendous advantages and value for commercial buildings. The use
of precast columns and beams makes an ideal framework for hanging precast panels, creating a design that offers fast construction, structural stability and enhanced fire-resistance. A wide range of options is available for creating the perfect system to achieve the size and shape of commercial building required. Double tees These components provide excellent roof and flooring units, spanning considerable distances and providing quick erection to close in a structure faster. In some cases, they can also be used as wall panels on low-rise commercial buildings, creating distinctive designs that require little maintenance and offer fire-resistance and durability, as with architectural wall panels. Hollow-core planks Precast hollow-core flooring units provide long spans with cross-sections that reduce the height of the building, saving material costs, while their inorganic composition enhances fire protection. Local precasters can help determine which sizes, shapes and styles of components will best suit
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| FEATURE |
any ind iv idual commercial build ing project. Bringing the precaster into the planning early in the design process will ensure the precast components maximise their effectiveness in aesthetic appeal, functionality and cost-effectiveness. Architectural precast cladding was developed to combine the maximum freedom of architectural expression with the economies of mass production of repetitive precast elements. With this precast specialist help, proper functional, structural and mechanical feat ures ca n t hen be det a i led. T he results will accurately ref lect material characteristics, manufacturing and erection efficiencies, cost factors, quality control standards and local trade practices. A continuing dialogue between designer and precaster will ensure the optimum quality of the product and its economical, efficient installation on the construction site. Architectural variety Architectural precast concrete can be cast
in almost any colour, form or texture (within budget guidelines) to meet aesthetic and practical requirements. Special sculptured effects can provide such visual expressions as strength and massiveness or grace and openness. The long-term effects of weathering often enhance the appearance of properly designed shapes. Design flexibility is achieved by varying aggregates and matrix colour, the size of aggregates, finishing processes and depth of exposure. Combining colour with texture highlights the natural beauty of aggregates. Panel geometry (shape details) has a major influence on fabrication economy and engineering requirements, with overall size and conf iguration being the most important elements. Generally, the smaller the elements, the higher the cost. Surface textures range from smooth to rough, through a variety of ribbed, sandblasted and exposed aggregate finishes. Texture allows the natural concrete ingredients to be expressed, provides the mass with scale, expresses the plasticity of
the material and improves its weathering characteristics. Supplementing the freedom of aesthetic e x pr e s s ion a nd e c onom ic fe at u r e s achievable with the use of architectural concrete are a number of other important functional and construction advantages. A rchitectural cladding panels are sometimes used as permanent concrete exterior formwork, thus becoming an integral part of the structure. Insulated architectural wall panels contribute substantially to the overall thermal efficiency of a building. Since the thermal resistance of glass is less than that of concrete, reducing window areas minimises heat gains and losses. In suitable environments, properly designed precast sunscreens help to reduce air-conditioning loads. Off site pre-assembly of all the components comprising a total precast wall system, including insulation, air gap, flashing, window-washing tracks, window sash and glazing, can be very cost-effective.
TECHNOLOGICAL INNOVATION IN THE CONCRETE INDUSTRY STARTS WITH MAP PRODUCTS. • • • • • • • • • • • • • • • • • • • Learn more at mapei.co.za Tel: +27 11 552 8476 Email: info@mapei.co.za
Precast concrete plasticising admixtures Ready-mixed concrete plasticising admixtures Extended workability polymers Set retarding admixtures Hardening accelerators Viscosity modifying admixtures Form release agents Synthetic fibres Pozzolan-activity mineral additions Permeability-reducing admixtures Water-repelling admixtures Anti-washout admixtures Expanding agents Drying shrinkage-reducing admixtures Clay mitigating admixtures Pumping aides Air entraining and foaming agents Concrete rescue packs Evaporation-retarding admixtures
HISTORY TWINSTAR PRECAST was founded in 2014 with the express aim of assisting specifying Civil Engineers and Civil Engineering Contractors with complicated sites and situations where currently available Precast Concrete Products just won’t work. TWINSTAR PRECAST strives to be the problem solver, and are solution driven in all aspects of precast concrete. With products ranging in weight from 2 kgs up to 6 tons, they are capable of solving almost all precast problems and turning nightmare requirements into a quick and affordable solution. MINISUB PLINTH
To date it is the only company in SA specializing only in custommade and one-off precast concrete products, only keeping a few fast-moving products in stock which are standard spec in tenders and drawings. Companies who previously made them
WATER RETIC
have either stopped or have closed down.
YOUR GO-TO PROBLEM SOLVER FOR THOSE DIFFICULT, ONCE-OFF JOBS THAT MAKE CIVIL ENGINEERING & CONSTRUCTION CHALLENGING
TWINSTAR PRECAST’S UNIQUE OFFERING
ELECTRICAL
With 26 years of experience in the precast industry, owner-operator Coetzee realised that there was a gap in the precast concrete market for custommade products and once-off items. SOME OF OUR BESPOKE CREATIONS INCLUDE
In the concrete pipe and manhole market, for example, the emphasis is on high volumes. The effort and time required to
bicycle racks
design and build once-off moulds for non-standard products
bollards
disrupt any normal well-oiled production line and also
copings
require specialised skills and supervision. This makes custom-made, once-off product manufacture an unprofitable business for mainstream, high-volume operations. Moreover, not all building contractors have the necessary expertise, manpower and facilities to manufacture such products on site.
pier caps entrance sign structures floating steps umbrella stands mop basins custom tree rings recreational facility braai stands park benches
Did you know? We can also assist with drawings and moulds
industrial studio counter-tops gutter shoes.
MINING S
POLYMER PRODUCTS
Unit 21, Hunky Dory business Park, 9 Goedehoop Avenue (M57), Olifantsfontein Telephone: (012) 670 9083 E-mail: info@twinstar.co.za (Annemerie Coetzee) or andre@twinstar.co.za (Andre Claassens) admin@twinstar.co.za (quotes) Website: www.twinstar.co.za
CUSTOM PRODUCTS
MANUFACTURE We manufacture all products to strict quality standards, ensuring all products are free of any defects. EXPERT DESIGN ASSISTANCE We can help you custom design your product to suit your specific precast building requirements.
CULATION
CRANE PLACEMENT SERVICES We can assist in placing the products onsite including delivery.
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| FEATURE |
TOTALLY PRECAST: COMPLETE BUILDING SYSTEMS
Total precast concrete building systems are becoming a popular choice for many construction projects. Architectural and structural precast, pre-stressed concrete components can be combined to create the entire building. This design approach can take several forms, including precast columns and beams with panelised cladding or loadbearing precast walls and double-tee or hollow-core flooring. These advantages benefit every member of the construction team – especially the owner, whose goals are always paramount. ARCHITECT: In addition to helping to meet all of the building-owner’s goals, total precast concrete systems provide specific advantages to architects that can make the design process smoother. CONTRACTOR: General contractors find the use of precast concrete components make their job easier at the site, ensuring a smooth process for the owner and designer in both the short and long terms. There are fewer trades to co-ordinate with precast construction. (Left): Precast concrete manufacturing plants work with a variety of moulds and injections, with recent advances allowing for rapid mould-making and a greater variety of concrete mixes.
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ENGINEER: Structural engineers report no difficulty in learning to design with total precast concrete systems. They also benefit from the material’s ease of use and efficiency. Fast construction Developers who use total precast systems say these can shorten the project timetable by six to eight weeks, compared with steel and even more, compared with castin-place concrete construction. Those savings can be critical in bringing a new building into a competitive marketplace or in meeting a tenant’s need for occupancy on a specific date. A total precast system’s speed helps keep projects on track. Scheduling advantages One-stop shopping sources much of a building’s shell in one efficient, precast contract. Fabrication of precast elements during permitting and/or site preparation saves time, resulting in fast, efficient construction, regardless of weather conditions. Precast components can be erected in winter, maintaining tight schedules. With total precast systems, speedy erection allows the contractor to enclose the building quickly, giving interior trades faster access. Precast components are naturally fire-protected because they will not burn. Precast’s inherent fire-resistance eliminates the messy and time-consuming fireproofing
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(Left): From pillar to post, the evolution of precast moulds, and the increased use of latex moulds, means custom designs are readily available.
Effective pricing Because of precast concrete’s tightly controlled and shorter production process, costs can be more accurately estimated earlier in the process. Changes during design development can be quickly reassessed to verify that estimates remain stable. The contractor, owner and design team are assured that project budgets remain sound.
“Precast structures require less maintenance than buildings erected with other materials.”
Safety Precast construction keeps the site cleaner and eliminates trades from the construction zone, improving logistics and enhancing worker safety. Site storage is usually not required – precast components are lifted by crane directly from the truck into position in a building. A clean site is particularly vital on building additions and existing campuses and in dense urban areas, where adjacent businesses can maintain nearnormal activities. Early input Precast manufacturers support design and co-ordination at the schematic stage. They can ensure that the building takes full advantage of state-of-the-art fabrication and connection techniques. This input allows the project to remain cost-effective and efficiently designed.
required for a steel structure and subsequent repairs caused by other trades. Aesthetic variety Precast concrete panels offer a wide range of styles. Panels can be produced in a variety of colours, textures and finishes, providing an almost endless range of aesthetic options. Precast panels can replicate granite, brick or stone, achieving a strong, institutional image at a fraction of the cost.
(Above): New design possibilities have completely altered the traditional aesthetic expectations of precast palisade fences, and today's designs are lightweight and functional, while retaining secure visibility.
Low maintenance Precast structures require less maintenance than buildings erected with other materials. Incorporating the architecture into the structure using large panel sizes minimises the number of joints.
Interior design flexibility Long-span precast concrete systems help building-owners adapt to changing client needs in future years. Hollow-core slabs and double-tees can span 14-16m to match typical composite-steel framing and minimise the need for interior columns required with cast-in-place systems. Precast can span as far as 21m to provide flexibility for challenging interior requirements. It also provides high loading capacity at little added cost. Efficient design Responsible manufacturers can provide early and precise design assistance to help select the most efficient sizes and shapes for components, for structural efficiency and optimisation for casting, transporting and erecting precast components. Fabrication repetition reduces form costs and aids design
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| FEATURE |
speed, while retaining design f lexibility. These cost-efficiencies can free up more of the budget for other critical design areas. Strong finish-approval process Precasters can provide finish samples, range samples and large-scale mock-ups, ensuring that design concepts translate into reality. Designers can inspect window interfaces, joint connections and other critical elements to ensure that they are visually acceptable and will properly interface between trades. Plant visits to discuss technical and aesthetic concerns provide control without requiring constant site supervision. Green design Precast concrete offers a number of benefits that make it environmentally friendly – a growing need as green building criteria become more popular. Precast’s energyefficiency, recyclability and re-usability, along with minimal waste in the precast plant and on-the job site, are key to meeting environmental standards that are gaining client interest. Precast offers high thermal mass that has become a feasible element of building design. With its ability to aid in meeting LEED standards, the benefits of thermal mass w il l become more apparent to designers in the future. The use of fly-ash, slag and other waste materials aids its environmental friendliness. Precast’s high durability produces buildings with a total service life that far outpaces other designs. Construction speed Time is money for the entire construction team. Precast concrete’s speed through design, fabrication and erection helps meet
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tight deadlines. This particularly aids contractors when permitting processes slow down or unforeseen delays arise at the site due to soil conditions or other factors. Precast structural systems are ready to be erected when the foundations are prepared. All-weather construction Contractors can minimise the added “cushion” created in schedules to accommodate bad weather conditions, since precast components can be produced and erected all year round. Efficient erection Because precast concrete pieces are fabricated in precast plants under controlled conditions using high-quality materials, designs more exactly meet specifications. Field adjustments are reduced, creating a smooth erection process with minimal surprises. All-in-one components Total precast concrete systems allow the architectural panels to serve structural functions, limiting the need to incorporate multiple materials and trades. Combining arch itecture and st r ucture prov ides efficiencies in a building’s lateral support systems. Spandrel panels can support floor systems and windows, while providing architectural exterior f inishes. Precast elevators and stair cores can support floor systems, while providing secure and firerated enclosures. Comprehensive drawing A total precast concrete system ensures onestop shopping for the entire core/shell design. Professional manufacturers can design and supply the entire system, generating a
“A total precast system ensures one-stop shopping for the entire core/shell design.” better co-ordinated set of drawings to allow construction to proceed more efficiently. This eliminates the added effort needed to co-ordinate various trades when using mixed systems controlled by different suppliers. Easy handling Site construction moves smoothly because no special equipment or techniques are required to transport or lift a combination of structural and architectural components. These types of activities can often require additional structural review and exposure to risk. Shape and design Precast/Pre-stressed components are custom-manufactured to match design requirements. Unusual shapes, sizes and specific technical requirements are expertly fabricated in the top precast plants. Repetition of shapes and sizes will greatly enhance the economical use of precast components. Precast efficiency The continuous, uninterrupted erection of precast structural components lends itself perfectly to fast-track construction schedules. Saving on financing costs (faster return on investments, resulting from bringing the structure into productive life sooner) is just one of the benefits provided by a complete precast building system.
Precast walls-fronts are now a regular feature of internal walls.
GETTING WALL-WISE Exterior perimeter walls are among the most important features of homes. In recent years, they have become increasingly popular due to the prevailing harsh security climate. The days of open gardens are long past. Surrounding walls demarcate the boundary of one’s property, as well as adding an aesthetic quality. Most people, when they think of enclosing their property, think first of security and then of privacy. A wide choice of precast walls is available. These mater ials include facebrick (chipbrick), concrete and steel. Interesting combinations of these products are much in evidence around the suburbs. Atop many of the walls, one often finds razor wire. Concrete palisade fencing is available in 1,8m and 2,4m heights. Razor wire or electric fencing may be added for additional security. It is the perfect fencing solution for industrial, as well as domestic properties. Concrete palisade fencing is virtually maintenance-free. Among its advantages is that it enables one to see passers-by.
Palisade fencing Palisade fencing’s open-slat structure makes it a popular choice, as it provides visibility to the outside of the premises, while still acting as a robust security barrier. It is also difficult to climb, which helps deter intruders. What is concrete palisade fencing? Lascocrete’s industrial palisade fencing is a cost-effective, high-quality solution which is perfect for securing the boundary of a commercial property. It comprises vertical poles secured onto horizontal rails that result in a secure fencing solution. We produce this fencing by manufacturing precast concrete pieces (slats and rails) that can be installed on site. These pieces are then bolted into place and come in one standard height of 2,4m. This fencing can be installed quicker than other forms of perimeter security methods due to our precasting methods, saving our clients precious operational time and offering them almost instant security.
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Customisable These walls can be produced with various textures and finished with a colour of the customer’s choice.
The benefits of industrial concrete palisade fencing include the following: Longevity Our concrete palisade fencing can last for many years, giving customers peace of mind that their premises will always be safe without their having to be on site. Low maintenance The slats we manufacture for our fencing require little to no maintenance over their lifespan. Cost-effective Our industrial concrete palisade fencing is a wonderful alternative to its steel variant, as it is considerably more affordable, but also extremely durable. Excellent quality Our solutions are professionally engineered with meticulous quality control. We strive to fulfil the highest security standards in our manufacturing. Strong and robust Industrial palisade fencing is sturdy and can withstand the harshest weather conditions, ensuring world-class perimeter protection, no matter what the environment. No scrap value Unlike steel fencing, concrete palisade fencing has no scrap metal value, so it is not a desirable option for stealing and selling. Visually deterring The height of our concrete palisade fencing makes it visually deterring to possible trespassers. (Right): Precast walls can be shaped in a number of different structures.
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(Above): New advances in surface treatments allow for almost any aesthetic.
Privacy Lascocrete’s palisade fencing offers a great solution for security that does not block out the outside world. The spaces between each slat enable a clear line of vision to the outside. Good versatility These products can be shaped to be used in the construction of a number of different structures. Mobility As they are precast panels, they are easy to transport and move around on location.
How secure is palisade fencing? Our palisade fencing is manufactured with high-grade concrete, an extremely durable and resilient building material. Since the main purpose of the fencing would be to keep intruders out, concrete is an ideal material: it is rust- and corrosion-resistant and can also be tweaked to improve certain existing qualities. Concrete palisade fencing has been designed to make climbing it nearly impossible – it achieves this through the no-grip design and significant height. These structures can also be reinforced with wall spikes as an extra deterrent. Our concrete palisade fencing is made to last for years. It is the easiest and most economical way of securing premises at all times, while still boasting a beautiful finish that shows character and sophistication. Raising walls The main aim of raising walls is to add height to the existing structure in the easiest way possible. There are several factors
“Concrete palisade fencing has been designed to make climbing it nearly impossible – it achieves this through the no-grip design and significant height.”
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to consider when doing this, such as whether the foundation is strong enough to support it. This is where Lascocrete can assist. We have years of experience in the industry and can provide excellentlooking precast wall raising that will last. We are also familiar with the relevant municipal requirements pertaining to wall height restrictions. If vibracrete walls have cracked or broken poles, these need to be replaced before our teams can raise the walls to ensure that your extension lasts. The existing walls need to be correctly aligned before raising can commence. The walls’ foundation needs to meet the minimum strength and maximum height requirements. Cracked or broken panels will also have to be replaced. If the wall is shared with a neigh-
(Above): Security is a key advantage in using precast walls and slabs.
bour, the home-owner needs to negotiate their intentions to them and obtain their approval. How are precast walls made? Our precast concrete items are manufactured indoors to prepare t hem properly for their outdoor use. Our process begins with a mixture of crushed rock and sand that can be altered with different additives for various finishes. This is then transferred to a mixer to speed up the curing process. After this, it is mixed until it achieves a thick, gritty consistency. Nex t , we conduct test s on t he concrete’s strength by casting some of it for a day and then crushing it with a ram. Before we cast the final slabs, any necessary moulds are put into place and sprayed with a release agent. We place welded wire onto the sheet before the concrete is poured, which helps maintain the wall’s integrity. The next day the wall is taken outside, where it is sand-blasted. We then cure it for a minimum of three days before declaring it ready for use. Whatever a home-owner’s concrete or vibracrete palisade requirements, Lascocrete can offer the highest quality and service.
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Mamelodi stormwater
UPGRADES
Upgrades to major stormwater systems are currently underway in Mamelodi Extensions 4 and 5 north-east of Pretoria. T he project , u nder t a ken by Tef l a , was awarded by the City of Tshwane Metropolitan Municipality and Armorflex 140 selected as the product of choice by the engineers due to its fitness for purpose, flexibility (during installation and in the long term) and labour creation through ease of installation. A tough selection Based on a trapezoidal channel analysis of water volumes and velocity, Armorflex 140 was selected as the best system to install for the gradual channel to be constructed. The area has been recognised as one which is frequently waterlogged. Nevertheless, it was determined that because there was a high volume of water, the expected flow velocity was low, so Armorflex 140 blocks would suffice, rather than using the heavier 180 blocks used to offset higher velocities. “The Armorflex 140 system’s flexibility (Right): Accommodating both high- and low-flow water channels was necessary due to the varying inclines in topography.
is in its ability to conform to ground contours. It settles without cracking and requires limited ground preparation. When installed and anchored correctly, the system offers a superior lifespan with minimum maintenance required,” says Thatho Moruke, site manager for Tefla. “Part of the contractual requirement was to outsource 30% of the work to labourers from the local community. Armorflex’s easy installation enabled us to meet this requirement with training and some supervision, thereby adding skills to the local building labour force.” In-situ hybrid preparations Before lay ing A rmor f lex blocks, the channel must be roughly profiled to form
(Above): Heavy blocks were required to offset high-velocity water flow.
the trapezoidal shape with dimensions approximate to those of the final design. T h i s i n- s it u a rea mu st be su it ably compacted before placing a thin layer of river sand-type material used to get final levels and clear, straight lines without any highs or lows. Obstructions such as roots and projecting stones must be removed prior to placement of the river sand “bedding” layer, as poor preparation will be reflected in the finished surface and leave high corners that create friction points and turbulence in the f lowing water. “This is an important factor,” stresses Justin Kretzmar, technical sales and new product development engineer at Technicrete. “The channel profile must be level in order for the water to flow smoothly and the blocks correctly interlocked in order for the Armorflex system to stay together and resist uplift of individual blocks.
(Above): The Mamelodi stormwater upgrades used a system which is an engineered alternative for a wide variety of erosion control and drainage projects.
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Lining with geotextiles “A geotextile (woven or non-woven) is then placed on top of the levelled river sand layer. This must extend wider than the block width of the channel and must be continuous (or overlapped) along the length of channel. It’s imperative that the geotextile extends into the embank ment and is anchored and protected against water ingress below this layer. When f lowing water gets under the geofabric, the channel’s started to fail and large sections could be washed away,” explains Kretzmar. Another feature of Armorflex, specifically relevant to this project, is the capacity for water to flow vertically up or down through the openings in the blocks. Accordingly, the high levels of groundwater in this area will be able to seep up through the block voids and into the channel, where it will flow away. The geofabric resists migration of bedding sand when water flows up and blocks infill sand when water flows down, ensuring continued structural integrity of the layerworks. Among the fundamental advantages of A r mor f lex are t he sma l l sleeve openings inside each block that run per pend icu la r to t he d irect ion of water flow. These openings typically accommodate a 3,5-4,5mm galvanised steel wire, threaded through the system after installation of the blocks. This wire assists with overall stability of the system until such time as the natural vegetation can grow and take root (typically one or two rainy seasons). Should Armorflex need to be installed in pre-assembled mat s for under water i nst a l lat ions like harbours, the contractor can use these openings to thread a structural polypropylene cable strong enough to support 6m x 2,4m mats during lifting and placement. Maintenance is a simple annual process of ensuring that the vegetation growth is cut back to block level, as overgrowth will cause settlement of silt. This then spirals into larger islands of vegetation and silt, eventually blocking free-flow dynamics within the channel. It is important to note that the vegetation (Right): Connecting a trench drain to a concrete manhole cover.
must not be removed, but simply cut down, as the roots help lock the blocks to the channel bed. Precast blocks intrinsic to the system “For this project, with steep vertical sides to the channel, Technicrete’s earthretaining Florawall blocks have been proposed for placement on top of the edge blocks to protect the embankment from eroding when stormwater volumes exceed base flow of the channel. Florawall is a versatile block, as it can be filled with concrete, soil or vegetation to improve overall aesthetics to a project while still maintaining its earth-retaining function,” adds Kretzmar. “We’re very satisfied with the support from Justin and his technical team, who were on site ensuring that all blocks were laid correctly and that the channel profile and levels were at the required ‘smoothness’. The delivery scheduling from Technicrete was spoton. Not only do we now have a strong, effective and long-lasting solution in place for stormwater control, but we’ve also upskilled many members of the surrounding communities,” says Moruke. Erosion control and stabilisation The Armorf lex 140 Erosion Control System is an engineered alternative for a wide variety of erosion control and drainage projects. The matrix of open cells and projections retains soils, relieves hydrostatic pressure and provides the perfect environment for establishing natural vegetation Armorf lex is supplied palletised in loose block form for manual or specialised installations, pre-formed into mats for mechanical installation. The result is a stable protection designed to withstand high water velocities and wave attack with a finish which is aesthetically pleasing and environmentally friendly.
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Building reservoirs Lee-Ann Dippenaar, an up-and-coming young engineer, is among the members of the Tango’s Consulting team who participated in the design and construction of a unique precast concrete 30ML reservoir in Selcourt, Springs, Gauteng. Notably, the reservoir wall, roof, columns and beams consist of precast concrete elements that are being manufactured and installed by Corestruc, which is working alongside Selby Construction, the principal contractor, on this project. The value of controlled manufacturing Ta ngo’s C on su lt i ng dec ided to use this technology instead of traditional construction methods to signif icantly accelerate the construction of the reservoir in a rapidly developing area of the East Rand on behalf of the City of Ekurhuleni Metropolitan Municipality. The system will also provide a higher-quality final structure, considering that the components are being manufactured in a controlled factory environment which is far removed from the many variables encountered on a traditional construction site. The foundations of a strong career This project is the junior resident engineer’s first construction supervision assignment since she joined Tango’s Consulting in 2018, after completing her BSc in civil eng ineer ing at the Universit y of the Witwatersrand in 2017. The valuable experience gained on this project will also contribute towards achieving one of her short-term career goals, namely registering as a professional engineer with the Engineering Council of SA. D ippena a r laud s her col leag ues, especially Nadia Stoycheva, a senior professiona l eng i neer w it h Ta ngo’s Consulting, for their willingness to share their experience with her, as well as providing the support she needed to settle in at this leading firm of consulting engineers. “While I learnt a lot during the early
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OF TALENT
engineering design phases, construction of the reservoir has provided immense oppor tunit ies for fur t her mentor ing f rom Way ne Went wor t h, who’s t he senior resident engineer on this project and anot her reser voir bui ld in Pam Brink, Springs, that’s also based on the same modular system. I’ve learnt a lot from Wayne, considering his extensive experience in helping to deliver complex water infrastructure and his background working with precast concrete specialists, such as Corestruc, over the years,” she says.
Pooling talent Dippenaar is also joined on site by other young built-environment professionals, such as Gift Mohwaduba Moroe, a director of Pamsensive Projects. The Springs-based small, medium and micro-enterprise was appointed to undertake parts of the in-situ concrete work, including the column bases and ring-beam foundation which support the precast wall panels. This has contr ibuted towards the excellent team dynamics between the engineer and the various contractors, as is mirrored by the favourable outcome thus
“All the precast concrete columns that support the roof structure, comprising beams and hollow-core slabs, were installed in only three weeks to support the centre portion of the roof structure.”
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Simultaneous pieces of time-sensitive puzzle Working towards completing the reservoir by the end of this year, the specialist contractor will then install the post-tensioning ducts and cables between the joints of the wall panels, in addition to the numerous threedimensional printed components to secure the rubber cast through which the grout will be pumped. The grout has been designed to reach a compressive strength of 100MPa within four days and to further react when the medium comes into contact with water while the reservoir is being filled. T he a b i l it y t o c o n s t r u c t v a r i o u s components which make up a reservoir structure simultaneously has significantly accelerated construction time, with the professional team having shaved as much as five months off the construction schedule by using Corestruc’s technology. Savings in construction costs have also been achieved by eliminating the need for extensive formwork and shuttering for the walls and roof. This is a significant additional benefit for municipalities, especially at a time when budgets for essential infrastructure services have come under severe pressure. (Left): Factory production of the precast concrete components of the reservoir delivers quality only achievable in a controlled environment.
(Above): Lee-Ann Dippenaar, a young engineer on the project, was involved at all stages, from design to construction.
far, despite the severe interruptions which the Covid-19 level 5 lockdown caused on most construction projects in the country. For example, all the precast concrete columns that support the roof structure, comprising beams and hollow-core slabs, were installed in only three weeks to support the centre-portion of the roof structure. Corestruc began installing the wall panels and buttresses that reinforce the reservoir while it completed the in-situ concrete floor slab.
(Above): Construction workers installing the precast concrete walls.
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(Above): Managing any construction project is all about meeting the conditions laid out in the contract.
MANAGING A CONSTRUCTION CONTRACT
THE POST-AWARD PHASE By Bilaal Dawood, Bilaal Dawood Attorneys The post-award phase commences once the contract has been awarded. The employer (project-owner) has now chosen a contractor according to their selection criteria and has presented a contract for signature by the parties. The first step is to review the contract presented for signature. The parties should ensure that the terms contained in it do not differ from the tender phase contract. As a matter of good practice, the contract should clearly capture the rights and obligations of each party. In addition, the parties should ensure that the following are annexed to the contract and signed: • Concise scopes of works. • Pricing information, together with the pricing basis. • The schedule for managing progress
on the works, with an updated start and completion date (reflecting the timing of the award). • All other relevant documents with which the parties are expected to comply. Once the contract has been reviewed and signed, the parties will be required to manage the project according to its terms. The form of the contract may be a bespoke agreement or one of the various recognised standard form contracts. Standard form contracts have the advantages of representing good practice and being easier to understand, since they are widely used. Both parties need to be familiar with the standard form contract being used. After signing the contract, the parties will be required to ensure that the necessary payment guarantees, bonds and insurances are in place. Both the employer and the contractor should know what
“When the contract requires notices and/or claims from a party to the contract, it is imperative for the parties to comply with this.”
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is required of them and comply. In the absence of compliance, the party requiring the guarantee, bonds or insurances must request them from the party who should be providing them. The parties should take note of the contract periods for providing these. Once the project has commenced, both parties should: 1. Ensure that frequent progress meetings are held and that minutes of these meetings are taken. These meetings will allow both parties to resolve issues. 2. Both parties should be represented by sufficiently skilled human resource practitioners who understand the terms of the contract. Currently, more emphasis is placed on contracts, rather than verbal agreements. Therefore, the parties representing the contractor and employer should be conversant with the terms, rights and obligations of the parties, as stipulated in the contract. 3. The employer should implement good contract management processes, including management of the commercial commitments of the employer. At a minimum, the following management aspects are recommended for the parties: i. Contract cost vs projected contract value, taking into account variations still to be approved. ii. The contract cost should be updated to reflect the approved variations. This then becomes the contract price. iii. The planned completion date in terms of the schedule vs the actual completion date. iv. A schedule of variations to the con tract value, what is approved and
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what is currently under assessment. v. Delay registers – what are the root causes of the delays? What is their extent? 4. Where the contract requires notices and/or claims from a party to the contract, it is imperative for the parties to comply with this. The contractor, in particular, faces a risk of being time-barred if he does not comply with the notice periods for claims. The following aspects are some of the most referred-to matters during the postaward phase and close attention should be paid to them. The basis of the assumptions made below is in terms of the JBCC agreement. However, there are other standard term agreements and the parties should refer to their specific requirements when addressing these matters. These are addressed below generically, as each contract may have different requirements: • Notices of intention to claim money or delay: The contractor should refer to the contract, including the terms that sometimes modify standard term agreements, to ensure compliance with the periods for submitting notices of delays or claims. This is important, as the contractor
“Employers often change the scope of works with different specifications or requirements, or alternatively add to the scope of works.”
may be time-barred for failure to comply and would lose their right to the claim. The notice should include all aspects referred to in the contract clause dealing with notices. It should clearly identify the nature of the claim, what caused it, when it ceased or when it is anticipated to cease, or what is required in order for it to cease. • Claim: The contractor should claim according to the relevant clause of the contract. These clauses are well defined in standard form contracts. The reason for the claim, the clause on which the contractor is relying, the cost of the claim and – if additional time is required – the basis thereof must be stated. Here again, different contract forms have different requirements and the contractor must familiarise themselves with the terms of their specific contract. Where a standard form agreement is used, the parties should also pay attention to any modifications of its terms. • Variation orders: Employers often change the scope of works with different specifications or requirements, or alternatively add to the scope of works. These should be dealt with as variation orders. The general rule is that approval from a cost and schedule perspective must be obtained before executing the variation orders. However, the contractor must refer to the contract terms dealing with variation orders. • Interim payment certificates: These usually refer to monthly payments made for works complete up to a specific point. The contractor usually provides the basis of their monthly
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claim to the agents of the employer to process a payment certificate. Some contracts require the employer and/ or their agent to make fair assessments on a monthly basis. Cash flow is critical for project success. Therefore, the parties should use this mechanism of the contract as intended by the contract. • Practical completion: The date of practical completion indicates when the works will be fit for use. It is an important milestone on the project and there are usually penalties for late completion levied against the contractor. The standard terms contract addresses the requirements for the
contractor to meet this milestone. These requirements usually include ensuring that the works are complete prior to this date and thereafter inviting the employer or their agent, where required, to inspect the works and certify practical completion. There may be a list of items that the contractor needs to address for practical completion to be certified. • Defects liability period: This is the period pursuant to practical completion and usually spans three to 12 months, depending on the terms of the contract. During this period, there may be defects that the contractor must address. • Retention monies: The contractor may sometimes put up a performance bond up to the value of 10% of the contract sum. In instances where the contractor does not put up a performance bond, the employer may withhold 10% on each payment
certificate to serve as the performance bond. The contract provides for the terms of release in percentages at certain milestones towards the end of the project or, in other instances, the full retention to be released when a certain milestone is reached. • Latentdefectsliabilityperiod: The latent defects liability period relates to defects that arise after completion which could not be found through a reasonable inspection at the time of completion. This is usually a period of five years, although the terms of the contract would specify it. The contract plays a key role during the entire project, but having role-players who understand it is equally important. Compliance with the requirements of the contract offers protection to both parties, who should act in good faith and agree on most matters.
| INNOVATIONS |
Technologically advanced concrete and construction technologies, both hardware and software, have been increasing in importance on job sites and among producers. These solutions help precast manufacturers speed up their operations and improve safety and sustainability. Building information modelling (BIM) A BIM tool is an all-in-one technology combining digital technology, project management, design and architecture, making it easier to build, manage and design structures. This software collects and imports project data and creates a cloud-based data environment, enabling collaboration between engineers, architects and construction companies. BIM can help manufacturers model precast concrete walls and floors and help with connection placement. Examples of BIM software include Tekla by Trimble and BIM 360 by Autodesk.
(Above): BIM goes further than any of its predecessors as an integrator of analogue and digital tools.
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TECHNOLOGICAL ADVANCEMENTS FOR PRECAST PRODUCERS
| INNOVATIONS |
(Left): Bionic exoskeletons are adding a new dimension to the scope of human possibility. (Below): The exploration of possibilities when it comes to precast mould-making and integrated technologies is in its early days.
material that result in precise dimensional structures, thereby eliminating human error. When it comes to precast concrete, 3D printing is especially useful for creating re-usable, durable formwork. Bionic exoskeletons Bionic exoskeletons work as an extension of the body, increasing the lifting capacity of the average human. This helps people carry and lift heavy items more easily. Exoskeletons are currently available as full-body suits or for specific areas, such as the upper body, lower body or back braces, minimising pressure on the body when doing repetitive work or heavy lifting, reducing the risk of injury and maximising efficiency. This technology can be useful for any part of the construction process to increase labour productivity.
Virtual reality (VR) and augmented reality (AR) VR and AR provide real-time scanning of a jobsite, helping accurately track the progress of construction without actually visiting the site. This improves communication with all stakeholders and boosts productivity. For precast manufacturers who send concrete to job sites, this process aligns concrete curing timeliness more accurately with site progress. 3D printing 3D pr int ing is all the rage in ever y industry, from the modelling of chocolate sculptures to entire housing structures. It uses computer software to create layers of
Loader cranes Improving site organisation and safety is of the utmost importance. When it comes to precast manufacturers, the loading, transportation and placement of panels is a complicated process. A lorry loader like the Hiab allows for eff icient, safe movement and installation of precast panels. Rather than needing a crane or a second vehicle on site to unload the lorry and an additional team to install the sections, this crane can easily lift and move the panels into position. Retractable enclosures Retractable enclosures, like Chameleon’s products, provide protective environments for indoor and outdoor curing, concrete production, aggregate storage and dust control. These enclosures prevent product defects and shrinkage cracking by blocking weather conditions, helping to contain humidity, control curing temperature and prevent temperature gradients. P24 Delta Tie Insulation System Dayton Superior’s P24 Delta Tie Insulation
“Improving site organisation and safety is of the utmost importance. When it comes to precast manufacturers, the loading, transportation and placement of panels is a complicated process.” System is a non-conductive, non-corrosive fibre composite which is used as a wythe connector for concrete sandwich panel construction. The product is produced from a geometrically conf igured, twodimensional truss manufactured from continuous wound fibreglass embedded in an alkali-resistant resin. The design produces a connector of remarkable strength and durability. CarbonCure Precast CarbonCure Precast works by injecting recycled carbon dioxide into fresh concrete during mixing. Once injected, the CO₂ undergoes a chemical reaction where it transforms into a mineral. This improves the compressive strength of the concrete mix, allowing for the reduction of cement content while maintaining strength and performance. CarbonCure Precast involves the installation of two boxes at the plant: the CarbonCure valve box and the CarbonCure control box. The valve box connects to a CO₂ tank and delivers a metered quantity of CO₂ into the concrete mix. The control box monitors the performance of the valve box system in real-time and feeds usage data back to CarbonCure (which syncs with the customer portal myCarbonCure). The control box’s software integrates seamlessly with all existing batching software, so adding CO₂ to a mix is just like adding an admixture – there is no impact on batching or loading cycle time. With so many technologically advanced opt ions ava i lable in t he market for improving precast operations, it is not surprising that this adaptable, sustainable model of construction is increasing in popularity.
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| INNOVATIONS |
(Left): The use of precast façades offers an almost limitless choice of surface aesthetics.
surface treatments: wood or steel trowelling, rolling, brushing and several types of washing can be carried out when the concrete is fresh. Precast walls with graphic concrete patterns (a Finnish innovation) can be manufactured by placing a printed membrane into the mould. Polishing, hammering, acid etching and sand-blasting can be applied to hardened concrete. Precast walls can also be coated with plaster or paint, brick, ceramic tiles or natural stone.
Finland is renowned for its innovations in precast construction technology and in addition to increasing the speed, cost-effectiveness and quality of construction, precast technology offers developers and contractors endless possibilities in terms of appearance and design. Elevating thermal responsiveness Precast sandwich panels enable strict requirements for thermal insulation to be met. Concrete structures have great insulation qualities, keeping buildings warm in cold weather and cool in hot weather, stabilising the moisture and temperature inside. For the precast façade, a calculated age can be defined. In real life and in the conditions for which the material is designed, a precast façade can last up to 200 years. Precast façades tolerate harsh weather conditions, including sub-zero temperatures combined with salt strain and long rainy seasons. A world of possibility with surface treatments To complete the desired look on the four precast wall panel types – sandwich, plastered sandwich, inner layer and cladding panels – there are virtually limitless possibilities for the surface. The cement can be white or grey, bearing in mind that the colour and size of the aggregate certainly make a difference. (Right): With the right frameworks, precast façades offer an endless choice in appearance and design.
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THE FUTURE OF PRECAST WALLS Different colours, pigments and paints can be added. The shape and surface of the precast concrete moulds also have an effect on the appearance – the mould can be made of timber, steel, plastic, rubber or fibreglass, with each material giving a unique finish. Concrete façades allow for different
Architectural design In addition to the surface finish, there are several ways to give the façade a unique look. In plastered sandwich walls, the façade seams are not visible. Joints can be hidden by designing the positions of windows, balconies and doors so that they break the lines, utilising the discontinuities. The joint form and profile can create the desired look, while horizontal or vertical lines give the façade character. With no limitations to the shape of the moulds (even curved walls can be manufactured), an industrial building method such as precast concrete is superior to any other façade construction when it comes to freedom of design choice. Elematic continuously shares knowledge in order to ensure that architects, designers and the global building industr y are aware of the effective ways to manufacture
| INNOVATIONS |
quality precast concrete façades with an outstanding look. Examples of successfully installed and functional façades include: • A black precast wall inside with a surface shaped for an optimal acoustic experience in a music hall in Kristiansand, Norway. • Sandwich wall panels used as façades in wood-drying plants with a relative
humidity of 100% inside the building. • Massive wall panels used as acoustic barriers with a surface designed to absorb traffic noise. Elematic invests heavily in precast concrete research and new applications which enable the company to offer design soft-
ware, machinery and automated solutions that can be tailor-made to customers’ requirements. Technical and service support is offered via its 24-hour global online help centre. Customer support for South Africa and the rest of Africa is serviced from its warehouse in Dubai.
(Below): Black Precast wall, shaped for acoustic purposes.
(Above): Massive wall panels have structural, functional and acoustic advantages.
• Tel: + 27 11 822 2320 • Fax: + 27 11 822 2354 • e-mail: cindy@ashak.co.za
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| INNOVATIONS |
Hemp is 100% natural, CO₂-absorbing, energ y-saving and durable.
A global first, 8 4 Harrington Street in Cape Town is officially the world’s tallest building, constructed using hempcrete blocks and building materials. A partnership between two Cape Townbased companies, Hemporium and Afrimat Hemp, 84 Harrington Street is setting the benchmark for how to build a safe, carbon-neutral, multi-storey building using hemp blocks and hemp systems. The origin of hemp as a building product “I bought 84 Harrington in 2016, with the idea that it would become the flagship Hemporium store, a steak restaurant, and house the ‘Hemp Hotel’, a place where people could experience living in a hemp-constructed space. From a sustainability and eco-construction perspective, we wanted to take hemp construction in South Africa to the next level, while also contributing to the inspiring hemp construction projects being undertaken globally,” says Duncan Parker, Hemporium’s founding partner and CEO. “We also believed that once licences for the commercialisation of hemp in SA were issued, having innovative examples of what
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HEMP UNLOCKS SUSTAINABLE
BUILDING BLOCKS
The superior acoustic performance ensures privacy between units.
| INNOVATIONS |
could be achieved with hemp would lead the way for the fledgling hemp industry in SA.” The sustainability race There is a massive increase in the global demand for bio-based construction, driven by the need for the reduction of CO₂ emissions. Hemp construction is considered the gold standard for CO₂ reduction in buildings. The South African government has initiated a drive to create employment within the industrial hemp sector, so the timing for developing hempcrete-based construction materials is ideal. Previously, hemp houses built in SA used hempcrete. For a project of 84 Harrington’s scale, however, this was not feasible and inspiration was taken from hemp blocks developed in Europe. The creation of hemp blocks is a viable way of commercialising hemp in the construction industry. Passionate partnerships “With this in mind, Hemporium naturally looked for strategic partners on this project, which we found in Wolf & Wolf Architects and Afrimat Hemp,” notes Tony
“There is a massive increase in the global demand for bio-based construction, driven by the need for the reduction of CO2 emissions.” Budden, founding partner and director of Hemporium. Wolf & Wolf Architects is a small practice specialising in contemporary and sustainable architecture and is considered a pioneer of hemp construction in SA. It is passionate about pushing the envelope of hemp construction. Jumping into sector’s mainstream “Afrimat, a mid-tier mining company, prides itself on having an innovative and entrepreneurial culture, always looking (Below): Using hemp blocks reduces the CO₂ footprint of a building, as well as its operational CO₂ footprint.
at global trends. Our subsidiary, Afrimat Hemp, focuses on carbon-neutral construction and unlocking value in the industrial hemp sector. Afrimat has developed its own formulated lime binder for hempcrete and is producing hempcrete blocks at one of its commercial block plants,” says Afrimat’s MD Boshoff Muller. The company is blazing a trail in SA and the continent for a new era of carbonneutral building materials and investing in a sustainable future in construction, and proudly supplied the hempcrete blocks and building systems for 84 Harrington Street. Future goal Hemporium’s long-term goal is to continue promoting legislative change so that cultivation of industrial hemp in SA becomes a mainstream reality. This could provide solutions to many of the challenges that the country faces in terms of sustainable housing, nutrition and job creation. Afrimat Hemp also expands its upstream hemp processing capabilities through its built technology. This will help enable the hemp value chain to be unlocked cost-effectively in SA for all. (Above): Vapour-permeability: The ability of hempcrete to easily absorb and release moisture helps regulate the building’s internal humidity, thus maintaining a healthy indoor air quality.
PRECAST | ISSUE THREE | 2022
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| GLOBAL VIEW |
THE FUTURE OF
CONCRETE ARCHITECTURE
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| GLOBAL VIEW |
(Left): This landmark underwater restaurant in Norway relied on precast concrete structures for highly idiosyncratic angles and design. (Right): This architectural garden in Beijing demonstrates incorporation of precast masts and blocks, as well as ventilation modules. (Below): Torquay concrete house, Australia.
By Juliet Taylor There are two different types of concrete in construction: architectural and decorative. Architectural concrete serves a structural purpose. It is used in many different types of structures, from garages to internal façades. Decorative concrete serves an aesthetic purpose, such as flatwork or panels with no structural responsibility. However, concrete homes are blending the two categories together. These are houses constructed almost entirely out of concrete, usually including the walls, floors and often even ceilings. Concrete is an extremely durable material that will not rust, rot or burn. Concrete homes are
“Concrete houses have a sense of raw brutalism, which is becoming an increasingly attractive stylistic alternative in a decade marked by the opulence of ultrawealthy society.”
likely to last decades longer than traditional buildings – sometimes even two or three times longer – and concrete can be cast into any case, making it a very flexible material to use in designing. The trend towards precast concrete So why are all houses not concrete? Well, smaller concrete sub-contractors capable of building completely concrete homes can be hard to find. The cost of precast concrete slabs is relatively high compared with cheaper materials like timber, which is also very popular in Australia because it is cheap, fast, easy to build and can be locally sourced. However, trends are beginning to change. Concrete has gained huge attention in the global design world recently as an attract ive and minimalist desig n material. Concrete houses have a sense of raw brutalism, which is becoming an increasingly attractive stylistic alternative in a decade marked by the opulence of ultra-wealthy society. Raw materials like concrete, steel and architectural glass gain a sense of industrial chic when contrasted with elegant interior design styles and bursts of a warm décor. This style has become very popular recently and the trend shows no sign of slowing down.
Concrete is one of the eco-friendliest home building options available. The primary ingredient in the production of concrete is limestone, the single most abundant material on the planet. It can also be made from other materials, including waste by-products from manufacturing companies. Concrete lasts much longer than traditional buildings and can even be recycled towards the end of its life. Fur t her more, it can save on energ y production, as concrete houses are more effective at temperature moderation than many traditional materials. The significance of concrete’s benefits All of this indicates concrete becoming one of the world’s most popular housing materials over the next few decades. Its practicality is another huge factor, as it is low-maintenance, wind/fire/water/pest/ rust/rot/earthquake-resistant, allergen-free and can even help muffle sounds. Concrete homes have become a stylishly practical housing choice for many different landscapes and settings. Whether a concrete home is contrasting its man-made industrial materials against the raw beauty of a natural beachscape or blending in with the urban steel-painted skyline of a big city, it is sure to catch the eye.
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| GLOBAL VIEW |
Concrete house design: the best examples of concrete architecture around the globe Torquay concrete house, Australia A marvel of raw materials, this breathtaking prefab Australian home contrasts natural hardwood with unrefined concrete. The effect is stylish and inviting, with an effortless beauty that captures the eye. Designed by Auhaus Architecture for a family of concreters, this home embraces the beauty of the material by leaving surfaces untreated and emphasising the industrial aesthetic at every opportunity – inside and out. The cool grey walls leave each room open to various colours and textures.
Concrete farmhouse, New Zealand Featured on the hit architecture show Grand Designs New Zealand, this magnificent farmhouse was overseen by architects Richard Naish and Natalie Stebben from RTA Studio. Every room in the 280m² home has a view of the lush surrounding countryside. The concrete house blends in seamlessly with the landscape, even appearing to change colour at times – homeowner Lachlan MacDonald has said that it appears grey and moody after rain, but brightens to a white, stone-like colour in direct sunlight.
Suburban concrete house, Australia This concrete refuge is nestled in the heart of Sydney’s suburbs, providing respite from the hustle and bustle of the city without distancing itself too far from its roots. Designed by Ian Bennett Design Studio, this home is a wonderful example of how
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PRECAST | ISSUE THREE | 2022
minimalism and concrete can go hand in hand. The design process of this house is particularly interesting, as it was subject to specific requirements by the CDC. These regulations specified that the house had to occupy limited space on the block, the first floor needed to be narrower than the ground floor and the house had to be set back from the road. These regulations actually turned into the home’s greatest strengths, as they inspired the minimalist design and allowed its architects to utilise the northerly aspect of the home and promote privacy.
London concrete apartment, England This 240m² apartment in Clerkenwell was renovated by Stephen Kavanaugh of London’s Inside Out Architecture. Although it is not technically a “concrete house” in the same way as other homes featured on this list, concrete is certainly its central design feature. The strikingly dramatic geometry of the room design is perfect for raw materials and creates a sense of sophisticated industrialism.
Lewes concrete house, UK This house is easily one of the most beautiful concrete homes in the world. Designed by Raw Architecture Workshop and manufactured by Cemex in 2020, it has gained national attention for its intelligent design, thoughtful decoration and stunning materials. The use of raw materials such as concrete walls, industrial steel fittings, exposed pipes, leather and live house plants emphasises the natural aspect of the house, helping it blend into the surroundings, while still offering the twist of elegant comfort needed in a home. A marvel of modern architecture, it is sure to pave the way for many other luxury concrete designs.
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CONCRETE MANUFACTURING & CONSTRUCTION ISSUE 2 2022
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WE ARE OUR IN THIS ISSUE:
PEOPLE
Formwork release agents Towards sustainability Precast business development
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AVOIDING REPEATTYPE INJURIES
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POSITIVE TURNOUT FOR INDUSTRY TRADE SHOWS
Leaders in Construction and Leaders in Transformation
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development Precast business sustainability Towards release agents Formwork
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