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PRECAST VOLUME EIGHT ISSUE 2 • 2014

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the cma – QUALITY CAST IN CONCRETE

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contents

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precast contents NEWS 2

AFRISAM LAUNCHES BUSINESS DEVELOPMENT CENTRE

2

CIVILWORKS BEGINS RIB AND BLOCK MANUFaCTURING

4 CMA STAND ATTRACTS SUBSTAntial interest at totally concrete 4

CMA STAGES BOTSWANA ROADSHOW

5 CARGO CARRIERS ASSISTs LAFARGE WITH OWNER-DRIVER PROGRAMME 7 NEW CMA DIRECTION MAPPED OUT AT AGM

31 PRECAST PAVERS specified FOR INANDA CLUB REDEVELOPMENT 31 Pumping concrete to Record Heights

Member details 33 MEMBERS’ LIST

PRECAST VOLUME EIGHT ISSUE 2 • 2014

ON THE COVER

Pictured here are the cement silos at Sephaku Cement’s 155 tonper-hour cement milling plant in Delmas, Mpumalanga. The plant began producing cement in January and deploys some of the world’s best high-tech cement-producing equipment. It also incorporates the latest environmentally-friendly technology with particular emphasis on high efficiencies and reduced power consumption. See the full story on page eight. THE CMA – QUALITY CAST IN CONCRETE

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COVER STORY

30 ARCHITECTS PLUMB FOR PERMEABLE PAVING SYSTEM

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11 SUSPENDED PAVING – IT’S IN THE BAG

• Poor paving specification costs R-millions

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ARTICLES

• Precast facades used for load-bearing in Germany

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PEOPLE COME FIRST AT SEPHAKU CEMENT

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• Self-compacting concrete in precast applications

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12 HOLLOW-CORE SLABS FAST-TRACK OFFICE DEVELOPMENT 14 SELF-COMPACTING CONCRETE BECKONS LOCAL PRECAST PRODUCERS 18 ULTRA-THIN CONCRETE SUPPORTS HEAVY DUT Y LOADS at N3 WEIGHBRIDGE STATION

Precast is the official journal of the Concrete Manufacturers Association NPC (CMA) 16 Horn Street, Chloorkop, Kempton Park, 1620 PostNet Suite 8612, Private Bag X32, Kempton Park, 1620 Tel: +27 11 805 6742, Fax: +27 86 524 9216 E-mail: admin@cma.org.za, Website: www.cma.org.za

20 HOLLOW-CORE yields more space for students

Publishers

22 PRECAST FACADES USED FOR LOAD-BEARING IN GERMANY

Tel: +27 11 883 4627, Fax: +27 11 783 2677

24 POOR PAVING SPECIFICATION COSTS R-MILLIONS

Publisher: Andrew Meyer

26 NEW MEMBERS’ ROLL CONTINUEs TO GROW

Editor: David Beer

Isikhova Publishing & Communications PO Box 651793, Benmore, 2010, South Africa Website: www.isikhova.co.za

Tel: +27 11 883 4627, Cell 082 456 5175 E-mail: andrewm@isikhova.co.za Tel: +27 11 478 0239, Fax: +27 11 678 0254 E-mail: david.bigsky@gmail.com

APPLICATIONS 27 NEW RANGE OF MOULD RELEASE AGENTS 28 PERMEABLE PAVING BLOCK PROVIDES ECO FRIENDLY MOBILITY FOR NATURE RESERVE 28 ALFABLOC – ROCLA’S PORTABLE RETAINING WALLING SYSTEM 29 COST-SAVING GEOGRID CHOSEN FOR RETAINING WALL

Advertising: Charlene Pillay Tel: +27 11 883 4627 E-mail: andrewm@isikhova.co.za Design, layout and production: Joanne Brook Tel: +27 11 883 4627 E-mail: joanne.studio@isikhova.co.za The views and statements expressed in this publication are not necessarily those of the editor or the publishers and neither he, the publishers nor the CMA 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.

PRECAST VOLUME 8 • ISSUE 2 • 2014


2

NEWS

AFRISAM LAUNCHES BUSINESS DEVELOPMENT CENTRE IN SUPPORT OF SMME growth CMA member, AfriSam recently opened its

AfriSam’s Roodepoort Cement operation,

neurs with training and development that

Supplier Development Centre in support

the Business Development Centre will also

will enable them to a level where they can do

of the company’s Enterprise Development

provide SMMEs with a facility where they

business with AfriSam and other companies.

Programme which has been implemented as

will have access to computers that have

In Lichtenburg, Motswiri Consulting

part of a transformation drive, especially in

already been set up with an accounting

has been appointed to a similar task of

areas where the company operates.

identifying and developing entrepreneurs

The aim of the Supplier Development

f r o m l o c a l c o mm u n i t i e s a r o u n d t h e

Programme is to identify black-owned Small,

Dudfield operations, and up-skill them to

Medium and Micro Enterprises (SMMEs)

a level where they operate efficient and

close to the company’s operations and

sustainable businesses.

provide these entrepreneurs with the

Some entrepreneurs in Gauteng and

necessary support and development for

Lichtenburg will be enrolled in an acceler-

them to grow their business and ultimately

ated development programme, with the aim

be included in AfriSam’s database of

of ensuring they are ready to do business

registered vendors.

with AfriSam.

To date, AfriSam’s Enterprise Devel-

“This is a wonderful example of how

opment team has held SMME campaigns

AfriSam lives its values of People and Planet,

and open days with communities around

AfriSam CEO Dr Stephan Olivier at the launch of the business development centre.

making a sustainable difference to the

Roodepoort and Eikenhof operations. More

package that will enable them to manage

to the Enterprise Development team for

communities will be included as the pro-

their statements and invoices.

making this happen. AfriSam looks forward

the company’s Lichtenburg, Roodekrans,

gramme is rolled-out to other provinces in the future. Situated on a property adjacent to

communities in which we operate. Well done

The Centre for Supplier Development, a

to contributing towards the sustainable

company focusing on SMME development,

growth of these businesses”, says Calie

has been appointed to provide entrepre-

Ehrke, AfriSam’s supply chain manager.

CIVILWORKS BEGINS RIB AND BLOCK MANUFaCTURING CMA producer member, Civilworks, has

traditional civils market, but our strategy

Other lines include a wide range of municipal

begun manufacturing precast concrete

as a precast concrete producer is for

and road products, and a growing list of

rib and block flooring material.

continued growth. We will achieve this both

bespoke, or special items for individual

A manufacturer of a wide range of

organically and by acquisition. Rib and block

clients or applications.

precast concrete products, Civilworks

flooring offers good growth potential and

bought a rib and block production line from

fits well with our other product lines and

Econoslab in April and re-commissioned

logistic competencies”, he added.

it within two weeks at its K lipri v ier manufacturing facility in Gauteng.

Econoslab was one of the original producers of this type of innovative flooring

“While we are pleased with the pur-

system, and the product has stood the

chase of the assets, and more so with

test of time over some 18 years. There are

the successful and speedy resumption

literally thousands of successful installa-

of production, the biggest gain has been

tions spread throughout southern Africa.

the transfer of the production and sales

“With that reference base and market

teams. This has ensured a seamless tran-

footprint, the decision was made a lot

sition,” says Graham Crooks, Civilworks

easier, and we are happy to be involved in

managing director.

this exciting market”.

“We have retained a combined 50 years

Civilworks is still an active and growing

of experience within the teams. That

p r o du c e r o f m i s c e ll a n e o u s v ib r a t e d

type of transfer is rare, and will ensure

products for the civil and structural

continued quality and service levels.

industry, and a supplier of manholes to the

“Flooring has not formed part of our

PRECAST VOLUME 8 • ISSUE 2 • 2014

sewer, telecoms, and electrical industries.

The first blocks produced by Civilworks’ rib and block team at the new facility.


4

NEWS

CMA STAND ATTRACTS SUBSTANTIAL INTEREST AT TOTALLY CONCRETE There was huge interest in the CMA stand

ReMaCon, CMA PR consultant, David Beer,

at this year’s Totally Concrete exhibition

and two overseas members, Marcin Nowa-

and conference staged at the Sandton

kowski (Polish) of Techmatik and Thomas

Convention Centre at the end of May.

Schardax (Austrian) of Schlüsselbauer

Twice the size of last year’s display

Technology. The display was sponsored by

at 18m², the CMA stand was manned by

nine CMA members; Brickcast; Concrete

executive director, Wally Armstrong and

Units; Coverland; Echo Group; ReMaCon;

Pam Zukor. They were assisted by, Shawn

Rocla; Schlüsselbauer Technology; Tech-

Sewnath of Brickcast, Silvio Ferarris of

matik; and Technicrete. Wally Armstrong says the interest in the CMA extended to several requests for membership. Most came from local companies but there was foreign interest, including a block-making machinery company from China.

Marcin Nowakowski of Techmatik during his presentation at the CMA.

The Totally Concrete Roads seminar.

Wally Armstrong shares a joke with some visitors to the CMA stand.

The day after Totally Concrete, Techmatik’s Marcin Nowakowski gave a fascinating

A highlight of the CMA’s Totally Concrete

two-hour presentation to a select audience

contribution was a seminar on precast con-

on modern trends in Europe’s paving and

crete road construction, Totally Concrete

concrete block making industry.

Roads. It was presented to some 40 con-

He said that since Poland was trans-

ference delegates by independent paving

formed into a democracy in the early

consultant, John Cairns, who discussed

1990s, the concrete block and paving

construction methodologies of precast

industry had boomed in that country to

concrete roads and the products used to

the extent that today every major town in

build them.

Poland boasts a paving block manufacturer.

Another CMA contribution involved a

He observed that Poland’s current output

panel of experts who answered questions

was equivalent to that of Germany’s at 85

on precast concrete products and

million paving units a year, and that the two

applications. It comprised: Coenraad

countries were the world’s biggest paver

Gr oenewald o f Av eng Manu f ac tur ing

producers. Techmatik is one of the world

Infraset; Graham Crook of Civilworks;

leaders in manufacturing lines for concrete

Daniel Petrov of the Echo Group; and Silvio

paving blocks and decorative products and

Ferarris of ReMaCon.

sells its equipment worldwide.

CMA STAGES BOTSWANA ROADSHOW May saw the CMA staging a membership

rica and its expanding African footprint.

drive in Botswana together with ABCON

Subsequent presentations were made by

(Association of Botswana Building and

Lafarge, Chryso, MTS (Chryso’s Botswana

Civil Engineering Contractors). Over 60

agent), Techmatik and ABCON.

delegates comprising architects, engi-

Lafarge showcased its range of cements

neers, contractors, material suppliers,

and the success it has had with fly ash in

government employees, students and four

Botswana and Chryso gave a presentation

CMA members, Kwena Concrete Products,

on the importance of oiling moulds correctly.

Kwena Rocla, Fastdeck and Panda, attended the event. CMA executive director, Wally Arm-

CMA member, Techmatik’s Marcin Nowakowski, outlined modern trends in Europe’s paving and concrete block making industry.

strong, introduced the CMA and spoke

In addition to the CMA, the event was

about its role as the primary representa-

jointly sponsored by Lafarge, Chryso, MTS

tive of precast concrete in southern Af-

and Techmatik.

PRECAST VOLUME 8 • ISSUE 2 • 2014

The CMA’s Botswana roadshow.


NEWS

5

CARGO CARRIERS ASSISTs LAFARGE WITH OWNER-DRIVER PROGRAMME

business management and communication.

Cargo Carriers has assisted Lafarge (one

to claim for preferential procurement and

to claim at three different B-BBEE levels:

of its customers) in establishing a B-BBEE

enterprise development.”

preferential procurement; enterprise devel-

To further increase its B-BBEE rating, Lafarge owner drivers appointed black females, either spouses or girlfriends, as their business partners. This allows Lafarge

owner-driver scheme. Lafarge saw an

Cargo Carriers appointed its own drivers

opment; and ownership, with more points

opportunity to develop an owner-driver

for the Lafarge project as strict selection

being attained for having black females as

scheme based on increased volumes of

criteria are enforced. One of the key condi-

part of the ownership structure.

its bagged cement products in the Free

tions for participating in the Lafarge scheme

“We believe our owner-driver scheme is

State, Northern Cape, and North West

is compliance with the rigorous Lafarge

a win-win initiative. It is about a continuing

Province and approached Cargo Carriers

South Africa safety standards for driving

par tnership in which the drivers are

for assistance.

and maintenance of the vehicles. Moreo-

empowered to determine their own success

ver, drivers underwent intensive training

and future with the concomitant benefit

covering contractual issues, operating pa-

of increased productivity and enhanced

rameters, accounting matters, budgeting,

service levels,” says Tim Nelson, Lafarge

Cargo Carriers introduced its own owner-driver initiative in 2003. “Owner drivers are contracted directly to us by means of a service agreement

Cement’s supply chain manager.

and we assist them with everything,” says

“The Lafarge owner-driver initiative

John Sprenger, Cargo Carriers, owner-

proves that the provision of supply-chain

driver manager.

solutions can go beyond the obvious

“We source the business opportunity,

areas of application such as performance

provide our own management system,

and safety. This is what happens when

mentorship and training until the ownerdriver is self-sufficient. This enables us

innovation meets B-BBEE and the results Cargo Carriers and Lafarge Cement owner-driver trucks.

are truly transformative,” says Sprenger.


NEWS

7

NEW CMA DIRECTION MAPPED OUT AT AGM A new operating structure was announced by CMA executive director, Wally Armstrong, at the Association’s annual general meeting which was held at Caesar’s Palace on June 19. Armstrong advised that the new structure will commence from March 2015. Other presentations were given by CMA financial director, John Simpson, and by guest presenters who included: CMA member, Envirotan’s Business Development manager, Chantel Maree; CMA member, ASPASA’s director, Nico Pienaar; and FSC Consulting Engineers consultant, Fred Crofts. Armstrong said the new executive board would comprise one executive director and atleast three non-executive directors. The board is to be supported by several committees and a panel of experts. Comprising seven individuals, the panel of experts will provide members with access to a range of consultancy expertise in the manufacture, application and promotion of precast concrete. This service is to be delivered at competitive rates by individual panel members. Details on the panel of experts and their experience can be viewed on www.cma.org.za. Armstrong stressed that the success of the CMA essentially rested on the level of involvement and input from members. He suggested that members identify ways in which the CMA can assist them, be this through joint participation in exhibitions such as Totally Concrete, the publication of technical literature, or through staging technical seminars, among other avenues. He also spoke about the Association’s social responsibility projects. Current projects include the Vrederfort Bridge, the Rhodes Park Junior Traffic Centre and assisting CMA member, The Job Club in building precast concrete structures for a business development initiative. The latter involves establishing unemployed members of Mamelodi and Moloto communities in forming commercial ventures.

Wally Armstrong makes his presentation at the CMA’s AGM at Caesar’s Palace.

PRECAST VOLUME 8 • ISSUE 2 • 2014


8

COVER STORY

With the advent of bag and bulk delivery by Sephaku Cement, some may wonder what to expect from this new entrant to the South African cement market. Chief executive, Pieter Fourie, observes that the company is primarily people-focused, and values its customers and employees in equal measure. “Our operation is based on a combination of non-negotiable quality checkpoints. A high quality product, which in our industry means consistency, strength and durability, is imperative and this demands optimal performance from every employee. Achieving this means we must equip ourselves through ongoing skills acquisition in all aspects of our business while remaining attuned to the changing needs of our customers. This, and state-of-the-art equipment, will enable us to provide consistent levels of customer service excellence down the years.

red tape is invaluable and makes for quick

PEOPLE COME FIRST AT SEPHAKU CEMENT

decision making,” he says. “It remains the

oppor tunity to deploy some of the

Holdings. Sephaku Holdings secur ed

most effective way of listening to custom-

world’s best high-tech cement-producing

limestone resources in 2006 when it

ers and responding to their challenges and

equipment and to establishing new quality

invested the initial seed capital. By late

requirements appropriately.”

benchmarks across our three cement

2010, the projects were fully funded, having

Commenting on the six-and-a half years

grades: Sephaku 32; Sephaku 42; and

attracted South Africa’s largest inward

it took to bring Sephaku Cement on stream,

Sephaku 52. Moreover, the greenfield

investment by an African company, Dangote

Fourie says he and his team had to over-

nature of this project has enabled us

Cement, one of Africa’s largest cement

come some formidable challenges.

to dictate product quality rather than

producers. Additional debt financing was

“We were entirely success driven and

be dictated to by existing operational

provided by Nedbank and Standard Bank.

never lost faith in why we were coming to

constraints. Both our Delmas plant, which

“We navigated our way through the

market or in the long-term sustainable

began producing cement in January and

global recession by sheer determination

growth prospects of the cement industry.

our Aganang plant in Lichtenburg, which

and a belief in our ability to change the face

South Africa may have a relatively good

comes on stream later this year, have

of the South African cement industry. Ours

infrastructure but there is still much to

been equipped with the latest-generation

is a team passionate about cement-enabled

be developed. Sephaku Cement’s modern

Loesche vertical roller mills.

opportunities. While all of us at Sephaku

Fourie adds that customer dialogue will be pivotal to Sephaku Cement’s modus operandi, so much so, that customers will have direct access to Fourie and his executive team. “Face-to-face customer service without

technology, its cost-ef f iciencies and

“We want to ensure that every customer

have been in the industry for many years,

the commitment of its people, give us a

gets the best value from our product

this project has been a once-in-a-lifetime

competitive edge. Looking ahead, we will

offering and to this end our Delmas-based

experience. Not only has it made us better

remain committed to the people who bring

laboratory is providing technical assistance

cement technologists, but better people,

our products to the market, and to making

such as product testing and special mix

and we have learnt more than we ever

South Africa’s cement industry more

design support.”

thought possible. Above all, we discovered,

people focused.

Sepahku C ement is a 64% owned

at first hand, just how incredible the

“Building cement production operations

subsidiary of Dangote Cement plc and an

results can be when teamwork comes into

from the ground up has given us the

associate company of JSE-listed Sephaku

play,” concluded Fourie.

PRECAST VOLUME 8 • ISSUE 2 • 2014


ARTICLE

11

Suspended paving is installed at Wembley Square, Cape Town.

SUSPENDED PAVING –

IT’S IN THE BAG

How does one convert a dull bitumen-coated flat roof or terrace into an attractive paved surface without the use of grout or any other form of binding agent? One answer is to be found in suspended paving, a process which uses concrete flagstone pavers without the use of any binding agent.

which is sloped for drainage purposes. Flat surfaces are achieved by altering the thickness of the supporting sandbags to compensate for the slope. Secondly, because the paved surface is permeable, there is no water pooling even during the heaviest of storms. This means that as soon as the rain has abated, the surface can be walked on without any concerns for wet feet. “Another major advantage is the fact that the paved surface creates a protective layer which shields the waterproofing on the base layer from the sun’s UV rays and from other forms of possible damage.

Unlike conventional paving or tiling on a con-

suspended-paving pioneers – the process

However, in the event that the base layer

crete surface in which the pavers or tiles

of fers some distinct advantages over

does require some routine or other main-

are grouted directly onto a concrete base

conventional roof-top or terrace paving.

tenance work, it is easily effected by simply

layer, in suspended paving the pavers are

“In the first instance it allows for the

mounted on small polythene sandbags (see

creation of a level paved surface on a base

lifting the pavers and then re-inserting them once the job has been completed.

top picture) without the use of any adhesive

“Contrast this with the expense and

or binding agent. All that is needed to keep

inconvenience of lifting and replacing pavers

the pavers firmly in place is their weight.

which have been grouted to the base layer.

Moreover, they are laid 10-12mm apart

Moreover, no expansion joints are needed

which creates a water permeable surface.

with suspended paving and there is no

These and other advantages are why

chance that the pavers will crack or lift

suspended paving is finding increasing

due to wind or earth induced movement,”

f avour among some of the countr y’s

says Schwartz.

leading ar chitec tur al pr ac tices. T he

Revelstone director, Alex Cyprianos,

process has already been used on some

says that suspended paving is generally

major construction projects using pavers

used in low-traffic areas such as concrete

supplied by Cape–based CMA member, Revelstone. Some recent projects include: Cape Peninsula-based projects such as:

roofs, balconies and terraces. A balcony at Liberty Life’s head office premises at Century City, Cape Town, where concrete flagstone pavers were used for a suspended paving contract.

“The pavers tend to be large, averaging 600mm² and 55mm thick. We produce a

Liberty Life’s headquarter premises in

wet-cast flagstone paver for the purpose

Century City; Bloemhof in Tyger Valley;

which is steel reinforced, and we can also

Wembley Square in Gardens; and some

make up special shapes to accommodate

student r esidences in Stellenbosch.

curved borders.”

Suspended paving has also been used

The sandbags used in suspended paving

at Dainfern Square in Johannesburg and

are filled with a mixture of sand and cement

Liberty Life’s Umhlanga offices in KwaZulu-

which hardens once the laying process has

Natal, among other high-profile projects. According to Johnny Schwartz, a partner of Louis Karol Architects – one of the

been completed. Over time the polythene The completed suspended paving surface at Wembley Square.

outer casing will deteriorate leaving a hard and durable concrete core.

PRECAST VOLUME 8 • ISSUE 2 • 2014


12

ARTICLE

A section of Clearwater Phase 2 under construction.

HOLLOW-CORE SLABS FAST-TRACK OFFICE DEVELOPMENT Hollow-core concrete slabs – manufactured by CMA member, Echo Prestress – in combination with structural steel frames and raft foundations were used for the fast-track construction of a new office development at Clearwater Estate in Boksburg.

photovoltaic power generation units in future. Moreover, the roofs have created ideal catchment areas for harvesting rainwater which is to be stored in subterranean tanks,” said Mann. Echo’s prestressed hollow-core slabs were specified by PDS Civil and Structural Engineers and slabs totalling ± 3 100m² were used for Phase one. Phase two will make use of ±3 750m² of Echo slabs. Slabs up to 10m were deployed on the first floor sections and slabs of between five and seven metres were installed on the roof. Both the first floor and roof panels were topped with steel reinforced screeds and a bitumen coating was used to waterproof the roofs. In addition, Echo also supplied nine metre

Built in two phases, the first compromising

“The design uses overhangs above all

H-shaped universal steel columns to provide

a gross lettable area (GLA) of ± 3 100m²

the windows and doors to minimise the

slab support for the internal cantilevering.

and the second, 3 700m² GLA , the project

impact of the sun and to reduce heat loss,”

was the initiative of local property devel-

says Marais.

oper, Krisp Properties.

Completed by the end of November

“We already had a lease agreement with

2013, Phase 1 comprises two double

Michelin Tyre Company South Africa for

storey buildings, each measuring 1 550m²

Phase 1 well before the first sod had been

(GL A ), which ar e linked by a central

turned, which meant we only had seven

entrance atrium.

months to erect the building,” said Jordan

“We deployed hollow-core slabs for the

Mann, executive director of Krisp Properties.

first floors as well as the roofs, and this

Francois Marais of Francois Marais Ar-

assisted us in reducing construction time

chitects said the construction of the build-

by several weeks. Hollow-core slabs were

ings embraced new energy efficiency legis-

used for the roofing which would allow the

lation rather than being restricted by it.

necessary support for the installation of

PRECAST VOLUME 8 • ISSUE 2 • 2014

According to structural engineer, Spiros Sdralis, of PDS, Echo’s role involved

Clearwater Phase 1.


ARTICLE

13

considerably more than simply supplying the slabs. “We provided Echo with a set of drawings and they then prepared a layout which took all the servicing requirements into account. Echo’s engineer, Daniel Petrov, was involved from the outset and he was always on site when we needed him,” said Sdralis. “For example, some of the slabs had to be modified so that the upper-section of steel skeleton could be anchored to the first floor on a solid platform. This meant that the hollow-core end sections of some slabs had to be packed with concrete to provide

completion dates on both buildings by

the solid base. Echo filled in the voids with

several weeks.

concrete according to our specifications

“Extensive use was made of cantile-

and this enabled us to drill out the holes for

vering, both internally and for the shade

the bolt anchor sleeves in the same way as

overhangs, and Daniel assisted with rede-

we had done on the ground floor.

signing some of the cantilever sections on

“The builders were able to begin the assembly of the upper level steel frame

Phase 1 of Clearwater Park Boksburg, where Echo Prestress hollow-core slabs were used to fast track the development.

Phase 2. He also helped us with changing the direction of some of the slabs.”

as soon as the slabs had been installed

Echo also allowed for service ducts and

and this was the prime advantage of

suspended ceilings were created 600mm

using hollow-core slabs. If in-situ flooring

below the soffits of the roofs and first

had been used it would have delayed the

floors to accommodate piping and cabling.

The upper-level steel framework of Phase 2 which was bolted to solid concrete sections of Echo slabs.

P O Box 124, Sanlamhof, 7532 PRECAST VOLUME 8 • ISSUE 2 • 2014


14

ARTICLE

SELF-COMPACTING CONCRETE

BECKONS LOCAL PRECAST PR

Self-compacting concrete (SCC) has been used in the developed world for over three decades, yet until recently, it has remained off limits to most South African precast concrete manufacturers. Complex mixes, increased costs, extreme sensitivity to even the smallest changes in chemical composition and production processes, and the hands-on attention it demands for achieving consistent results, go some way to clarifying this apparent local reluctance. But for those brave enough to grasp the nettle, the rewards are substantial.

for a new range of precast products and for improving the quality of its existing product line up. A CMA producer member and part of the ISG Group, Rocla began experimenting with SCC in early 2012 shortly after it realised that some new products such as the Alfabloc retaining walling system, REBLOC road barriers, wing walls for stormwater outlets, and mor e r ecently, pr ecast

This explains why so many precast produc-

quicker, neater and easier.

concrete cabins for photovoltaic plants,

ers in other parts of the world use SCC

Further time savings, long workability

would be better and more easily produced

exclusively in place of conventional vibrated

( one hour) and an impr o v ed wor k ing

with SCC. Using European guidelines and

concrete (CVC). Having no slump, SCC can

environment are other benefits. But

standards (none exist in SA as yet), it took

flow over dense reinforcement and fill voids

arguably its major advantages are high

a year of research and experimentation

under its own weight. And it does this with-

durability combined with substantially

before the company was producing SCC

out the need for any post-cast vibration.

superior finishes, factors which have

to consistent best-practice standards.

As a result moulds can be less robust and

not escaped one of the country’s leading

A formidable group of concrete

last much longer, noise pollution is greatly

precast concrete producers. Since the

technologists was assembled to conduct

reduced, and the casting process is much

middle of 2013 Rocla has been using SCC

Rocla’s SCC research. They included: Rocla

PRECAST VOLUME 8 • ISSUE 2 • 2014


ARTICLE

15

as we did without the use of SCC. This

the average cement or fly ash particles,

achievement led us to introduce SCC at

and like fly ash, it’s also an eco-friendly

several other Rocla branches, the ultimate

by-product material. We found that fly ash

goal being to produce all our wet-cast

improved flow and mobility and decreased

products with SCC. Our Virginia branch

water demand whereas silica fume pre-

is already using SCC for the manufacture

vented bleeding.”

of culverts and special products such as Alfablocs and road barriers. “The requirement for optimal chemical

Roberts added that conveying SCC from mixer-to-hopper-to-mould presented additional challenges.

balances meant we had to prepare specific

“We observed that even when moving

SCC designs for each of our branches

SCC over a distance of 50-100m, the ensu-

across the country, due to chemical

ing vibration, which varied in line with ground

variations in raw materials and the manner

surface conditions, could cause the mix

in which they react with each other.

to separate. The obvious and more costly

Rocla’s SCC trials began with smaller

alternative involved pumping the concrete

products such as manhole cover slabs and

directly from the mixer to the moulds.

the Alfabloc. Initially several obstacles

However, getting this right meant further

were encountered in achieving consistent

changes to an already successful SCC mix

levels of repeatability and robustness.

design and considerable trial and error.

“For instance, we wer e unable to

“Initially we encountered frequent

achieve robust mixes at first and slight

blockages in the pipes which could cause

variations would cause a mix to fail and not

delays of up to an hour. The pumps were

self-compact. Furthermore, when using

so powerful that if not properly controlled

precisely the same ingredients in exactly

and monitored, they would force the

the same quantities, some of the mixes would yield variable results and it took time to work out why,” said Kretzmar. Commenting on the research work, A newly cast photovoltaic cabin prior to delivery.

PRODUCERS

Roberts said that he found SCC to be extremely water sensitive and that anything above a two percent water variance could throw out the total mix design in contrast to about five percent for CVC. “We made extensive use of fly ash and condensed silica fume in all the mixes.

civil technologist, Jason Roberts; Murray

Silica fume is a super fine powder, its par-

& Roberts group concrete and research

ticles being about 50-100 times finer than

The photovoltaic cabin mould at Rocla’s Johannesburg premises.

manager, Cyril Attwell, and Warren Mc Kenzie of the Murray & Roberts Centre of Concrete Excellence (CCE). Antony Offenberg of Mapei SA and Rocla head office personnel added further expertise to the team. The latter included sales engineer, Justin K retzmar and Rocla technical executive, Gerhard Rossouw. Commenting on the development work, Kretzmar said the research team relied extensively on CCE’s ARC Technology which focuses on establishing optimal chemical balances between all the components of concrete mixes, such as cement, stone, sand, fly ash, silica fumes, various chemicals and additives. “We could no t ha v e managed our photovoltaic cabin project as successfully

SCC is pumped into a photovoltaic cabin mould.

PRECAST VOLUME 8 • ISSUE 2 • 2014


ARTICLE

17

cement/water paste inside the pipes past

and affected other quality aspects as well.

the aggregates. With the assistance of

By introducing steam heating we were

Mapei and CCE we examined the aggregate

able to reduce the amount of accelerator

ratios and other material combinations,

and still realise our early 18MPa strength

and managed to create a mix suitable for

requirement. Moreover, after seven days

pumping. Moreover, the pumps had variable

we were achieving around 60MPa, well in

flows and this enabled us to match pump

excess of our 40MPa target.

outputs to the rate of production.

“Other stripping problems encountered

“B e s i d e s b e i n g m u c h s a f e r t h a n

during the development phase included pull

transporting hoppers with dump trucks,

outs, pin holes and blow holes, blemishes

forklifts or cranes, we found that pumping

which could be seen even after painting.

made the casting process a lot faster,

We solved this by changing the releasing

by a factor of five at the very least. For

agent and further tweaking the mixes,”

example, we were able to cast a complete

said Roberts.

photovoltaic cabin shell (outer walls and

Kretzmar added that the photovoltaic

base slab), using approximately eight cubic

cabins are relatively thin-walled, being only

metres of SCC in 30 to 40 minutes as

100mm thick at the bottom and tapering

opposed to the 160-210 minutes it would

to 75mm at the top.

have taken had we used CVC and more

“Although some sections required dense

conventional modes of shifting and then

reinforcement, we still had to comply

vibrating the concrete.

with the required cover. SCC’s flowability

“Another challenge was mould stripping,

made this very easy for us. Traditional

especially off the cabins and other thin-

concrete in a similar application would have

walled sections such as the roof and

resulted in extensive honeycombing with

internal walls, which required exceptionally

the coarse aggregates being visible after

smooth finishes and very early strengths.

stripping. One very seldom, if ever, finds

In order to meet our client’s delivery

honeycombing in SCC.

schedule, we needed to produce five to

“One of the reasons SCC is so difficult

six complete cabins a week using only a

to implement in SA is that our aggregates

single mould. This meant we had to strip

tend to be flaky, unlike those in America and

and recast one cabin a day. Requiring 12m³

Europe, which are more rounded. Needless

of concrete, completed cabins comprised:

to say, we have managed to circumvent

outer walls; base floor; suspended floor; a

the problem.”

roof and internal walls; and weighed close on 28 tons.

Kretzmar concluded by saying that although SCC traditionally costs up to

“Meeting this production schedule meant

40% more than CVC, the adoption of ARC

we had to achieve compressive strengths

technology for mix design, resulted in an

of 18MPa after 12 to 16 hours and we

SCC mix at a very similar costing to that

relied on a combination of accelerators

of previous CVC mix designs.

and steam heating to do so. To begin with

“However, SCC does require a higher

we used accelerators without the steam

degree of hands-on attention than CVC and

but we found that the former impinged on

the equipment used to produce it must be

the self-compacting properties of the SCC

better and more frequently maintained.”

An installed photovoltaic cabin which was manufactured under license to Spanish company, Prephor.

PRECAST VOLUME 8 • ISSUE 2 • 2014


18

ARTICLE

ULTRA-THIN CONCRETE SUPPORTS HEAVYDUTY LOADS at N3 WEIGHBRIDGE STATION Some 600m of ultra-thin continuously reinforced concrete pavement (UTRCRCP) has been used in the rehabilitation of the access and egress roads at the Heidelberg weighbridge stations on the N3 highway, the main corridor between Johannesburg and Durban. Specified by The South African National Roads Agency SOC Limited (SANRAL), the 65mm concrete was used to replace a confalt asphalt surface which had failed in places. SANRAL project manager Rajan Padavattan, said that UTCRCP was specified because of its superior performance properties as well as level constraints which are critical for the screening and prosecution of illegally loaded vehicles. The professional team comprised King Civil Engineering Contractors (main contractor) Aurecon/Blue Quartz, (consulting A bag of premixed concrete ingredients is poured into the pan mixer.

engineers) and PC Floors (sub-contractor). King Civil Engineering’s contracts manager, Hugh Crofford, said that this was the first

King Civil Engineering’s contracts manager, Hugh Crofford.

time King Civil had used ultra-thin concrete.

premixed off-site. It was important that

“It obviously entailed a considerable

we achieved very accurate slumps and to

amount of trial and error and we worked

this end the super plasticisers were added

with Allan de Kock of Beton Lab to design

electronically down to the last millimetre.

the concrete so that it met SANRAL’s

What’s more, the amount of water used

80MPa specification. Initially the intention

in the mix had to be equally accurate,”

had been to source ready-mix concrete

Crofford commented.

from an AfriSam depot in Nigel, but a very

Before the concrete was placed, the

short workability time of only 15 minutes

existing confalt asphalt surface was milled

meant that we had no option but to design

down to provide a suitable base. Steel

our own mixing platform and to do the final

mesh which measured 100 x 75mm was

mixing on site.

then fastened to the base prior to placing

“E xperimenting with concrete is a

The concrete is vibrated before setting, which takes 15 minutes.

PRECAST VOLUME 8 • ISSUE 2 • 2014

Concrete with a slump of 90mm, is shovelled down the chute onto the road base.

the UTCRCP.

lengthy process and it took us three months

Once mixed, the concrete was dis-

to get a suitable mix design approved us-

charged from the back of the truck off

ing AfriSam’s 50.2 cement. Moreover, the

a metal chute onto the steel mesh. Side

stringent specifications for all the materials

discharging, which would have been prefer-

used in the mix required that all ingredi-

able, was not possible due to insufficient

ents had to be tested. We also included

space for vehicular access.

three types of sand which were difficult to

‘The concrete had a slump of 90mm and

source. Other materials used in the mix in-

it only took 15 minutes to set. This meant it

cluded steel fibres at 80kg/m³ for additional

had to be vibrated immediately to eliminate

strength and 2kg/m³ of polypropylene fibres

voids. We attained an average production

to assist against cracking.

rate of 12m³ per day which equates to a

“We installed an 800lt generator-

surface area of around 20m², while the

powered pan mixer on the back of the

compressive strengths of 65MPa were

truck. Apart from the plasticisers, steel

achieved after two days rising to 100MPa

fibres and the water, all the materials were

after 28 days,” concluded Crofford.


20

ARTICLE

HOLLOW-CORE yields more space for sTudents The use of prestressed hollow-core slabs, supplied by CMA producer member, Portland Hollowcore, has significantly increased floor space to a student apartment development currently under construction above Eikestad Mall, a modern shopping centre in the heart of Stellenbosch. The apartments are being built on the concrete roof of the mall by NMC Construction Group. Given that all roofs have a limited weight-bearing capacity, the weight of the building materials used in the construction of the apartments was a crucial design consideration. NMC projects manager, Johan Bezuidenhout, said that hollow-core slabs were an obvious choice for the apart-

A hollow-core slab is lowered into position at Eikestad Mall.

ment flooring at Eikestad Mall because

Portland Hollowcore supplied over 950

they weigh some 35% less than an in-situ

prestressed hollow-core slabs in lengths

concrete flooring equivalent.

varying between 1.5 and eight metres. Most of them were 160mm thick, although

“Further weight savings were made through the use of a light clay brick which

some sections required 200mm slabs, es-

weighs 2.5kg. By applying these light-

pecially where load-bearing walls had been

weight materials we were able to build

removed to combine two flats into one. The apartments are being built on three

116 apartments. “Speed of construction was another

levels and a 900mm services void has been

important design consideration because

created between the roof of the mall and

the development is taking place on two

the bottom floor of the apartments. Most of the apartments vary between 35m² and

main streets in the heart of Stellenbosch’s CBD and we wanted to minimise disruption to vehicular and pedestrian traffic as much

Dirk Thiart, Portland Hollowcore’s site manager, seen here above a hollow-core flooring deck at Eikestad Mall.

75m² although 10% comprise duplex units of ±100m².

as possible. Precast slabs have certainly

we laid the structural topping on the slabs

In addition to NMC Construction Group

assisted in this regard as they only take

which comprised a 50mm 25MPa concrete

the professional team comprised: DHK,

hours or at most days to install unlike in-

reinforced with 100 rev mesh. The topping

principal agents and exterior architects;

situ concrete which takes two to three

abuts the walls, and in doing so, creates

Macgregor Forsyth, interior architects;

weeks. Moreover, there is no formwork or

an automatic joint which allows for wind-

KLS, structural engineers; IQS, quantity sur-

rebar to offload in the streets below.

induced movement.

veyors; Eppen Burger & Associates, health

“Another advantage of hollow-core slabs

“We also caulked the joints where the

and safety; Arcu Gibb, electrical consultants;

is that building operations can resume as

slabs meet end-on-end to prevent the con-

WSP, wet services engineers; Landmark

soon they are installed. At Eikestad we

crete topping from seeping into slab hollows

Studios, landscaping architects; Aurecon,

started building the apartment walls before

and wasting material’” said Bezuidenhout.

mechanical engineers; Ecko, fire engineers.

PRECAST VOLUME 8 • ISSUE 2 • 2014


22

ARTICLE

Image courtesy Rößner, Ed. Züblin AG

A ground-floor corner column with a match-cast head beam section.

The new Ohligsmühle building merges aesthetics with functionality.

PRECAST FACADES USED FOR with the legal requirements for thermal

Image courtesy Yasar, Ed. Züblin AG

Precast concrete technology has been evolving rapidly in Europe, paving the way for solutions that meet sophisticated architectural and economic requirements. In this article, which was first published by BFT International, an example of how precast concrete facades can now be used for load-bearing as well as aesthetic purposes is examined.

insulation. Various facade elements were gr ouped together accor ding to their technical features and prefabricated as a unit. Internally, the facade extends over the entire floor without the use of columns or supports and the floor is linked to the beam supports using a thermal barrier. This approach enlarged the floor space available for letting and provided greater flexibility for partitioning because the need for internal facade supports was completely eliminated. Furthermore, construction times were shortened significantly.

Previously any attempt at using precast

The concrete facade was designed and

concrete facades for load bearing was sub-

built within approximately 10 months. This

ject to tight constraints. However, recent Image courtesy Franke, Ed. Züblin AG

developments in precast concrete technology have ushered in fresh options. The new Ohligsmühle building in Wuppertal-Elberfeld, Germany, is a case in point. A prominent feature of this six-storey building’s envelope is the use of sculptural architectural concrete components and windows which

Facade view with panoramic windows.

ambitious project required close cooperation between architects, structural engineers and the precast plant. HPP Architects

extend from floor to ceiling. Yet its major

prepared a design which included beams

achievement lies in its ground-breaking

and columns arranged as a right-angled tri-

technical approach to facade design.

angle. Structural engineers, Schüßler-Plan

The architectural concrete components

Ingenieurgesellschaft discarded the option

used on this project facilitated important load-bearing functions whilst fully complying

PRECAST VOLUME 8 • ISSUE 2 • 2014

of mounting solid cast stone elements on First-floor cantilevered element during assembly.

the facade and suggested an external load-


ARTICLE

23

Image courtesy Franke, Ed. Züblin AG

Image courtesy Yasar, Ed. Züblin AG

Arrangement of joints in the panoramic window area.

LOAD-BEARING IN GERMANY bearing facade design instead. Precast

architectural concrete were included in

had to be split below floor level to comply

concrete manufacturers, Züblin AG added

the general contractor’s brief.

with maximum transpor t dimensions.

further details to the proposal.

A rapid assembly schedule of one storey

The regular floor grid began on the first

The design team decided to merge entire

per week per building section necessitated

storey. T he standard elements were

facade components and to make the load-

a very high prefabrication rate. Site

approximately 3.50m high and 5.40m wide

bearing material out of precast concrete.

cranes lifted each of the elements from

and each of these elements defined the

Columns were connected to each other

the trailers to final installation positions.

height of a storey. They were inserted on

via the beams to facilitate and assemble

Socke t dowels wer e inser ted in the

top of each other floor-by-floor.

large facade elements. Overall, 1 215

precast elements and in the cast-in-situ

The pointed internal and external cor-

columns were merged with 770 elements

floor. The facade elements were then

ners of the envelope formed the special el-

using 180 tons of reinforced steel. The

assembled, aligned and filled in whilst being

ements of the building. Panoramic window

precast elements had a total weight of

held in place by diagonal struts. The next

areas that project from the structure,

about 2,600 tons.

step entailed the in-situ casting of the

starting on the first and second floors,

The design of the connecting points

floors. Due to their full-storey height of

made it impossible to transfer the loads of

between the beams and the columns posed

about 4.70m, the ground-floor columns

these floors directly via the columns. This was why cantilevered elements were used.

lines of the isosceles triangle formed by

Non-load bearing columns were split for

the column and the lines of the beam’s unequal triangle intersection created two adjacent roof areas with varying pitches. This challenge was overcome by applying the precast elements so that the fabrication of sharp-edged intersections without

Image courtesy Rößner, Ed. Züblin AG

a particular challenge. This was where the

joints yielded both aesthetic and functional

the assembly of larger precast elements. A tailor-made solution was also required for the facade sections of the attic. The area designed for connecting the roofing seal had to be integrated with the precast elements during prefabrication whilst adhering to the geometrical specifications.

benefits. The design team tested the

The interdisciplinary collaboration of

feasibility of all plans at an early stage

architects, structural engineers and the

using mock-ups at Züblin’s precast plant

precast plant resulted in a long-lasting

in Gladbeck. These were inspected and

facade design. Sustainable facade elements

approved by the client, and as a result, load-bearing facade columns made from

and state-of-the-art precast components Formwork stripping from a cast corner column element.

provided a high degree of design freedom.

PRECAST VOLUME 8 • ISSUE 2 • 2014


24

ARTICLE

These pavers are not appropriate for heavy construction traffic.

POOR PAVING SPECIFICATION The Concrete Manufacturers Association NPC (CMA) warns that R-millions are being wasted on concrete block paving (CBP) roads which fail due to poor specification. In many instances paving is simply specified as being 25MPa without any reference to the SABS mark. One of the CMA’s technical consultants,

percentages, and these properties are

civil engineer and independent paving

addressed in SANS 1058:2012. The old

consultant, John Cairns, says that many

standard, SANS 1058:2006 was based

of the engineers and landscape architects

solely on a single compression test which

who design paved roads are not aware of

measures resistance to crushing.

the most important specification criteria when using CBP.

“Paving blocks never crush under load which is why the compression test is not a

“I participate in regular paving seminars

good performance indicator. In fact pavers

and workshops and am amazed at how

can have a very high compressive strength

many professionals don’t know that the

but poor abrasion resistance. This is why

new CBP standard, SANS 1058:2012, is

the standard was changed.

These pavers do not meet the dimensional tolerances specified in SANS1058:2012 which results in excessive highs and lows in the finished road.

based on tensile strength and abrasion

“This lack of awareness is resulting in

resistance rather than the old standard

failed CBP installations and unnecessary

of compression resistance. Some are

remedial expense. For instance, I was

not even aware that the standard has

recently asked to submit a report on a new

occur in shopping centres, office parks

changed. Therefore it is hardly surprising

car park paved with CBP at an East London

and housing developments, where paved

that so many pr of essionals ar e still

shopping mall. Serious abrasion had taken

surfaces tend to be regarded as simple,

specif ying for CBP projects based on

place even though the paved surface was

not requiring an engineering design.

compression strength,” says Cairns.

barely six months old. The reason for this

“By contrast industrial CBP surfacing

“In most instances, pavers fail either

was that the pavers were simply specified

is generally designed correctly, especially

by cracking and then splitting, or through

on the basis of compressive strength

wher e the pav ing pr ov ides a critical

surface abrasion due to factors such

rather than the SABS standard.”

functional element such as the working

as par ticle distribution and binder

PRECAST VOLUME 8 • ISSUE 2 • 2014

Cairns says that most paving failures

surface of a container yard or steel mill.”


ARTICLE

25

Pavers at an intersection in Randfontein which have worn badly due to poor abrasion resistance.

COSTS R-MILLIONS C air ns a d ds th a t C BP r o a ds c an

of sand and stone. Then if damage occurs

also fail when they are not designed for

responsibility for the repairs will fall to

construction loading.

the contractor.”

“This often occurs on housing estates

CMA director, Wally Armstrong, notes

where roads are designed to handle light

that most CMA producer members hold

traf fic only. What normally happens is

the SABS mark . T his means they do

that the roads are built before other

regular batch testing and manufacture

construction takes place. This means that

with a r ecognised quality assurance

they must then handle the heavy-duty

system in place.

trucks and other construction equipment

“Some of our members and other CBP

while the estate is being built and this

producers comply with the standard but

obviously causes damage. Further damage

don’t actually hold the mark which is also

is caused by the spillage of sand and stone,

acceptable. However, holding the mark is

especially at traffic circles where most of

obviously first prize, especially if there

the braking and turning takes place.

are comebacks due to poor specification.

“One way around this problem is to build

“Most South African paving producers

road bases to handle the construction and

manufacture pavers with two layers. The

early resident traffic and only pave them

bottom and thicker layer provides the

once the estate is close to completion. Not

required strength and the top layer can

only will this save the pavers from unneces-

be coloured with pigments for enhanced

sary wear but it will also ensure that the

aesthetic appeal. And now that the new

road base has been constructed properly.

standard measures abrasion resistance

“However, in instances where it is

this topping layer is also being designed

deemed necessary to install complete

with excellent surface-wear properties.

roads before the construction of the

Even lower-grade blocks with a good

estate commences they should be built

topping layer can of fer high abrasion

with a paver which can handle heavy-duty

resistance, proving that the topping

traffic. And once built, the contractor

layers do more than offer colour variation,”

should ensure that the roads are kept free

concludes Armstrong.

PRECAST VOLUME 8 • ISSUE 2 • 2014


26

ARTICLE

NEW MEMBERS’ ROLL CONTINUEs TO GROW Four new members have joined the CMA since April and new member enrolment since November 2012 now stands at 34. The new members are: Envirotan; Schlüsselbauer (Austria); Smartstone and The Job Club. Outlined below are brief profiles.

pressure pipes, manhole elements, roadside channels, and so on. A newsworthy innovation, PERFECT PIPE, produces a durable and dense sewage pipe with an integrated plastic liner, distinguished by a high static load-bearing capacity and a long-lasting resistance to chemical attack. The pipe is suitable for both trench construction and pipe jacking/ micro-tunneling.

Envirotan

SmartStone paving at Melrose Arch.

Furthermore, PERFECT is a wet-cast

Env ir otan is an innovati ve chemicals

system which enables the production of

The Job Club

company that specialises in anti-microbial

fully customised dense products as well as

A registered NPO, The Job Club was es-

additives for the cementitous coatings

mould-hardened concrete manhole bases,

tablished in 2010 in association with the

industry. It has developed and tested

risers and cones. (www.sbm.at, www.per-

SA Council for Business Women and SA

various additives based on customers’

fectsystem.eu).

United Employers to facilitate practical

specific needs. These include anti-microbial

and sustainable job creation in partnership

additives for tile adhesives and tile grouts,

with the business community, government

as well as anti-algae products for marbelite

and civil society.

pools. It also offers a range of products

The organisation’s primary objective is

- all based on cementitious coatings - to

to generate employment by providing people

keep floors, walls, counters, kitchen and

with the necessary skills to establish and

bathrooms hygienic. Envirotan also offers a technical service to concrete product producers to deter-

sustain their own businesses. Schlüsselbauer state-of-the-art concrete pipe production.

Already active in all nine provinces, the organisation manages a range of innovative

mine the origin of stains, be they organic,

SmartStone

skills training, internship, host employment

in-organic or biological. Once identified,

SmartStone was founded in 1980. The

and entrepreneurship programmes in as-

several solutions are offered which can be

original SmartStone concept was to create

sociation with host employers, businesses

used by manufacturers and their custom-

concrete products that simulated the look

and experienced professionals.

ers. http://www.envirotan.co.za

and feel of natural stone, but the company

Businesses and professionals share

quickly evolved into much more. It pioneered

their expertise in programmes aimed at

the idea of exterior design systems, which

youth, women and start-up entrepreneurs,

was achieved by creating products with

and also assist in identifying host employ-

natural textures, others which remained

ment and job opportunities.

Envirotan’s laboratory.

Schlüsselbauer

true to concrete and some that could only

The Job Club works in collaboration with

be described as authentic SmartStone.

community representatives, as well as local

Subsequently, SmartStone became a ge-

health, social and education departments.

neric name and its manufactured product

It also forms social partnerships with gov-

range expanded to include various paving

ernment and private sector organisations,

shapes, textured pavers, wall cladding, tiles

such as the National Youth Development

and landscaping features.

Agency (NYDA).

A significant achievement was winning a

Based in Austria, Schlüsselbauer operates

premier CMA excellence award for a paving

worldwide as a solution provider and sup-

installation at Melrose arch in 2002 and

plier of plant equipment for the production

then winning the Vintage Award for the

of precast concrete components for sew-

same project at the Association’s Awards

erage and stormwater drainage systems,

for Excellence competition in 2012.

as well as water mains.

SmartStone has branches in Bloemfon-

Schlüsselbauer’s manufacturing tech-

tein, Cape Town, George, Durban, Nelspruit,

nology for wet and dry cast concrete

Midrand, Port Elizabeth, Potchefstroom and

products is designed to produce concrete

Pretoria. It also has branches in Namibia,

pipes, concrete pipes with plastic liner,

Zambia and Mozambique.

PRECAST VOLUME 8 • ISSUE 2 • 2014

Some of The Job Club executives: Hester Du Bruyn, CFO (left); Tabea Magodielo, chairlady and corporate governance; and Elise Coetser, CEO.


APPLICATIONS

NEW RANGE OF MOULD RELEASE AGENTS

27

In addition to the clean and easy release of the mould or formwork from concrete, some other advantages of the ChrysoDem range include: • Protecting and extending the life of the formwork/mould • Reducing the likelihood of imperfections

CMA member, Chryso South Africa has

and surface damage, particularly blow holes,

launched a new range of application-driven

to create more durable and attractive

mould release agents.

concrete surfaces

Hannes Engelbrecht, Chryso S.A. gen-

• Elimination of staining and colour changes

eral manager: marketing, says the new

• Plaster, paint and other coatings may be

ChrysoDem release agents have been

applied subsequent to the mould removal

designed to meet the needs of specific

as ChrysoDem release agents do not

industries and applications.

adversely affect adhesion of finishes and

“Choosing the appropriate release agent

coatings applied to the concrete

may be critical to the success of a project,

• Water repellent and not affected by rain

as it affects both the quality and colour of

• No effect on the hydration of concrete

the surface finish,” says Engelbrecht .

• Ready-to-use release agents which re-

“The cost of a release agent is low in

duce the possibility of errors during mixing

proportion to the formwork or mould itself,

• Two-year storage life for virtually all the

so simply choosing the cheapest release

new release agents.

agent available on the market, is false econ-

“There has been exceptionally positive

omy. The top quality release agents in the

response from the concrete industry

ChrysoDem range may cost a little more but

to this new range which Chryso S.A. is

provide greater coverage, are easier to use,

planning to export to the rest of Africa as

and add consistent quality to the production

well,” added Engelbrecht.

line. This is important, particularly in the

For further information, contact Hannes

precast industry, where high temperature

Engelbrecht on tel 011 395 9700 or email

steam curing forms a formidable challenge

hannes@chrysosa.co.za or visit www.

in the production process.

chryso.com

“The new range is a ground-breaking de velopment f or Sou th A f r ica, longawaited by industries which for years have had to use one-size-fits-all mould release agents. ChrysoDem, which is locally manufactured by Chryso S.A. at our production plants in Gauteng, KZN and the Western Cape, also includes a vegetable-based, environmentally-friendly release agent.” Mould release agents are primarily used to assist in the clean, easy release of moulds or formwork from concrete, without damaging the concrete, the moulds or formwork. “In or der to achie v e sa tisf ac tor y results, it is imperative that the correct release agent for specific applications is chosen. The new ChrysoDem range features dif ferent release agents for moulds made of metal, wood, plywood, resin ply, and shutter board as well as for those made from plastic, polystyrene, rubber, latex, and fibreglass,” said Engelbrecht.

Chryso SA has launched a new range of applicationdriven mould release agents for the concrete industry.

PRECAST VOLUME 8 • ISSUE 2 • 2014


28

APPLICATIONS

PERMEABLE PAVING BLOCK PROVIDES ECO-FRIENDLY MOBILITY FOR NATURE RESERVE Garden Route Terraforce licensee, CMA

keeping its shape and integrity. We decided

stability and loose substrate is used to fill

member, Mobicast, is building two-wheel

to use the Terracrete block because of its

any gaps in and around the blocks.

jeep tracks with Terracrete paving blocks

permeability, low environmental impact and

for Cape Nature at Geelkrans Nature

cost-effectiveness.”

“The blocks are relatively easy to work with, compared to other paving methods

Reserve in Stillbaai, Western Cape. The

The blocks are laid after 100-150mm

which involve more sophisticated machinery

Terracrete block is providing a hard wearing

of substrate is removed. Binding wire is

and labour,” says Du Plessis. “We are

all-weather surface which is water perme-

threaded through them to increase overall

finding that approximately two percent of

able, unlike surfaces such as asphalt or

the blocks are broken during transport and

conventional paving which are impermeable.

handling over rough terrain but on the whole

Jean du Plessis, conservation manager,

the process is straightforward and causes

Geelk r ans Cluster & Stilbaai Marine

very little disturbance in the reserve.”

Protected Area (MPA) says:

The tracks are being installed in 250m

“We have a network of maintenance jeep

stages and 7 000 blocks have already been

tracks on the reserve and the substrate

laid. Carpobrotus edulis (Sour Fig) is being

comprises mostly deep dune sand unsuited

planted on the verges of the tracks to

to normal paving. As an alternative we

rehabilitate any destabilisation that occurs

sought a hard surface that was water

during construction. Maintenance of the

permeable and allowed the growth of vegetation. Another proviso was that it should move with the substrate while

tracks is quick and easy, and should blocks Terracrete paving blocks on track at Geelkrans Nature Reserve.

ALFABLOC – ROCLA’S PORTABLE RETAINING WALLING SYSTEM The need to store or partition fertilizer,

quick and easy alignment, its even weight

coal, sand, stone and other granular or

distribution, sturdiness and durability, are

loose particles in discrete batches is

what make it an efficient alternative.

break during the course of their lifetime, they are easily replaced.

related locations. The mini Alfabloc has found a home along railway lines keeping people, wildlife and farm animals safe from moving trains. And Rocla itself has used the 3m Alfabloc for a river-sand bunker at its Polokwane manufacturing plant. Alfablocks interlock with a cast-in concrete tongue-and-groove joint. Each

critical for many sectors of industry.

“And the inner cavity formed by the

block has two sockets cast into the top

These requirements are easily facilitated

two A-frame legs can be used for placing

surface, which can be used with eye-bolts

by the installation of CMA member, Rocla’s

electrical cabling for CCTV alarms or any

to easily lift and move the blocks or to

A l f abloc A-f r amed pr ecast concr e te

other wiring requirements.

attach additional items such as roofing,

retaining walling system. Manufactured under license to

Rocla’s Alfabloc is available in three

Poundfield Products Ltd in the UK, Alfabloc

“The mini-Alfabloc, at 1.2m high, has

is a naturally stable and robust retaining

been very successful at offering a quick,

wall block which requires little or no ground

flexible option for storage requirements

fixing while offering limitless configurations

as well as an alternative to the New

and quick installations.

Jersey Barrier for many non road-related

“Alfabloc is a versatile product that

applications.

can be deployed across many applications.

The Port of Durban has used 22 mini-

The type of stored material determines

Alfablocs as a temporary security measure

whether the blocks are free-standing

for crowd control, and a Durban-based

or bolted into place,” says Rocla sales

logistics company has used the large 2.4m

engineer, Justin Kretzmar.

Alfablocs for stock piling manganese.

“The traditional retaining wall concept is

The Alfabloc has also been used at chem-

well suited for the separation and storage

ical factories, farms and mines as well as

of granular materials, however, Alfabloc’s

at airports, railways and other transport-

PRECAST VOLUME 8 • ISSUE 2 • 2014

razor wire or electric fencing.

height options of 1.2m, 2.4m and 3m.

Rocla’s Alfabloc.


APPLICATIONS

29

Kaytech’s Miragrid GX 80/30 is covered with soil at Olivedale Retirement Village.

COST-SAVING GEOGRID CHOSEN FOR RETAINING WALL Some 14 800m 2 of CMA member, Kay-

of vertical or inclined soil walls with modular

tech’s Miragrid GX 80/30, has been used

block or panel facings and are available in a

to reinforce 10 open-faced concrete block

wide variety of strengths and sizes.

retaining (CRB) walls at Olivedale Retire-

Quick and easy to install, Miragrid GX

ment Village, currently under construction

80/30 was placed at every second block

in Randburg, Johannesburg. Situated on

with tie back lengths of up to 5.4 metres. It

sloping ground, the site required extensive

is an economical alternative to conventional

terracing and embankment buttressing

geogrids and provides superior interfacing

to provide level building platforms for the

with concrete block structures.

construction of houses, apartments and communal buildings.

The walls were built at a 75° angle and reached heights of up to 7.5m. To

Completed in April, the retaining walls

prevent the possible build-up of hydrostatic

were designed and built by Engineered

pressure behind the walls, blanket drains

Interlock Solutions (EIS) in close collabo-

were constructed, consisting of a layer of

ration with main earthworks contractors,

bidim A2 covered with a 120mm layer of

Lone Rock, and consulting engineers, Pro

19mm stone followed by a second layer of

North Consultants, to ensure that all

bidim A2. Outlets were provided at every

statutory requirements were met.

three metres.

Building 10 CRB walls reinforced with

A layer of PC100/100 was installed on

Kaytech’s Miragrid GX 80/30 in combination

the second last tier of blocks for erosion

with Aveng Manufacturing Infraset’s split-

control and reinforcement.

face Terrace Blok® 300 proved to be an

With its performance properties having

effective and cost saving decision for the

been independently verified and tested,

developers.

Miragrid GX provides guaranteed long-

Miragrid GX geogrids are manufactured from high tenacity polyester (PET) yarns

term durability (>100 years) and low creep resistance.

with a protective polymeric coating. They

For more information on Kaytech prod-

are especially suitable for the reinforcement

ucts and systems, visit www.kaytech.co.za.

PRECAST VOLUME 8 • ISSUE 2 • 2014


30

APPLICATIONS

“Moreover, we were also impressed with the Uni-Ecolok paver’s L-shaped design, which not only creates a very attractive paved surface, but offers exceptional loadbearing capacity, durability and stability properties,” says Castanheira. The Alchemy Architects PICP system was installed by Lushaka Construction. After excavating to approximately 500mm below surface, an A4 bidim geofabric was placed on the sub-grade. This was followed by a 350mm layer of course-graded aggregate. Uni-Ecolok pavers, 80mm thick, were then laid on 50mm of bedding grit which had been placed on top of the aggregate. Charlene Soupen, Aveng Manufactruring Infraset’s marketing manager and paving specifier, says that the PICP installation at Alchemy Architects is a typical infiltration PICP system. “Infiltration is one of two common types L-shaped Uni-Ecolok permeable pavers, supplied by Aveng Manufacturing Infraset, make attractive visual and important eco statements at Alchemy Architects’ new HQ premises in Edenvale, Johannesburg.

of PICP systems, the other being attenuation. Infiltration allows water to flow through

ARCHITECTS PLUMB FOR PERMEABLE PAVING SYSTEM

the crushed stone gradually before ground

Permeable interlocking concrete paving

“Research has shown that only 30%

drainage systems. This reduces peak flows

(PICP) is a prominent landscaping feature

of rain water infiltrates surface areas in

during heavy rainfall and reduces water tem-

at Alchemy Architects’ new office premises

urban centres, and in towns and cities

peratures by 30ºc, both factors minimising

in Edenvale, Johannesburg. Completed

the figure is as low as five percent. This

downstream damage considerably.

in December 2013, the modern three-

is why these areas are often flood-prone.

“There are other PICP options. For in-

storey building is surrounded by 935m² of

PICP reverses this imbalance allowing up to

stance, some systems store water below

PICP which serves both as driveways and

95% of rain water to infiltrate the ground,

the surface to be used for watering plants,

parking areas.

a figure which largely mirrors what happens

washing cars and equipment, and for sanita-

in undeveloped landscapes.

tion purposes. And some systems combine

Alchemy Architects’ permeable paving

infiltration takes place. In attenuation the water is temporarily stored in the crushed stone before being slowly released through outflow pipes into conventional stormwater

system was based on an infiltration-based

“Minimising pollution, albeit in a small

infiltration with attenuation, especially in

PICP design provided by CMA member,

way, was another motivating factor in

instances where ground infiltration rates

Aveng Manufacturing Infraset, one of

our choice of permeable paving. During

are low. However, the final specification of

the country’s leading PICP suppliers. The

Gauteng’s dr y winter months, heav y

any permeable paving structure depends on

manufacturer also supplied Uni-Ecolok, its

metals, hydrocarbons, oil, rubber and other

the hydraulic properties of the sub-grade

interlocking paving block system, for the

pollutants are deposited on impermeable

and anticipated traffic loading.

installation of the paved surface.

surfaces. When it rains they are washed

“The Uni-Ecolok system covers all these

Amândio Castanheira, a senior partner

into stormwwater systems and are then

requirements and its L-shaped concrete

at Alchemy Architects, says that PICP

discharged into streams and rivers where

block is ideal for driveways, car parks,

using Uni-Ecolok made both environmental

they destroy fauna and flora.

suburban streets and township roads,

and aesthetic sense.

“PICP is very effective at removing

light and heav y duty industrial yards,

“We were very aware of how widespread

pollutants from run-off. The sub-base of

as well as bus terminals and suburban

urbanisation, and through it the creation of

any PICP system is largely comprised of

arteries. Moreover, the 80mm Uni-Ecolok

impermeable surfaces, is placing mounting

coarse-graded aggregate and geotextile

block conforms to the new SANS 1058

pressure on stormwater drainage. Imper-

sheeting and both materials harbour

standard for paving block performance,”

meable surfaces increase the risk of flood-

natural microbes which devour water-borne

concludes Soupen.

ing, spread pollution and disrupt aquatic

pollutants and prevent them from clogging

eco systems in rivers, streams and vleis.

PICP systems.

PRECAST VOLUME 8 • ISSUE 2 • 2014

Contact Charlene Soupen on 012 652 000 or via email on csoupen@infraset.com.


APPLICATIONS

31

of Colonial Stone, both pavers were strip tested for a period of six months prior to installation with regular traffic, including 34 ton cement bulk deliveries. The road was designed by Landmark Studios and the civil and earthworks were handled by P&R Construction. R.E.E. Paving Contracts was responsible for laying the pavers. Michael Hartley of R.E.E Paving Contracts said that the paving was begun in September 2013 and had been completed in January. “We laid the pavers on a river sand base using screed rails. The sub-base A section of road at Inanda Club paved with 222 x 55mm supplied by Colonial Stone.

material comprised 150mm layer of G5

precast PAVERS specified FOR INANDA CLUB REDEVELOPMENT

aggregate and all the paving was cement

CMA member, Colonial Stone, has supplied

x 222mm and a 222 x 55mm block, the

which meant we did not have to cart pavers

4 600m² of concrete block paving (CBP)

smaller unit being used for a herringbone

up to 50-60m using wheelbarrows.”

for the paving of private roads at the

layout. Both pavers have granite finishes

The Inanda Club’s redevelopment includes

prestigious Inanda Club redevelopment

and both have a compressive strength of

an exclusive residential component, a new

project in Sandton, Johannesburg.

over 42MPa.

clubhouse which overlooks a polo field, meet-

Two types of CBP were supplied, a 222

According to Friedel Weihe, director

slurry grouted. The paving plated very nicely and snagging was minimal. We were also impressed with the fact that Colonial Stone staggered the off-loading of the pallet loads

ing rooms and a large function ballroom.

Pumping concrete to Record Heights Bosch Rexroth has supplied its latest

As is almost always the case in inter-

convinced that even more world records

axial piston pump, the A4VG, to Zoomlion

national assembly projects, integrating

will soon be broken in China with the aid

in China for installation in a hydraulically-

the different components was a challenge.

of modern hydraulic technology.

operated portable concrete pump capable

The engineers had to make a number of

of pumping concrete to heights of over

adjustments to joints and connections for

100 metres.

the axial piston pump to run smoothly in

“Pumping concrete to these heights

Chinese machines.

entails very specific requirements. For

“In cases like this, of course, our re-

instance, the placing boom must be

gional company in the country concerned

robust yet sufficiently flexible for versatile

makes our work a lot easier,” explains

service,” as Binxing Wu, chief engineer at

Frick. “Working closely with our Chinese

Zoomlion, explains.

colleagues we were able to grasp all of

“Moreover, a limited load-bearing capac-

Zoomlion’s needs very rapidly.”

ity meant that all the main components

Work on the machine began in early-

had to be highly efficient with the intrinsic

mid 2012, and was complete by October

weight as low as possible.”

that year.

High operating pressures, large dis-

“The use of our axial piston pump in

placement volumes and no critical vibra-

the concrete pump has had a favourable

tion in the placement boom were some of

effect on the Chinese market and places

Zoomlion’s requirements for the A4VG.

products from Zoomlion and Rexroth on

“The A4VG switches so rapidly and

a new level,” says Zhicai Zhang, Bosch

gently that no such vibration occurs,” says

Rexr oth’s trade sector manager f or

Christian Frick, project engineer at Bosch

concrete machines in China.

Rexroth in Germany.

Both Bosch Rexroth and Zoomlion are

Zoomlion’s hydraulically-operated portable concrete pump fitted with Bosch Rexroth’s A4VG axial piston pump.

PRECAST VOLUME 8 • ISSUE 2 • 2014


32

MEMBERS’ LIST

Producer members telephone

PROVINCE/ country

Pillar

telephone

PROVINCE/ country

Pillar

A Fick Sementwerke Bk

022 913 2370

Western Cape

PB

ReMaCon Products cc

011 393 5504

Gauteng

PI

Aveng Manufacturing Infraset

011 876 5500

Gauteng

PB/PI

Revelstone (Cape) Pty Ltd

021 761 9734

Western Cape

PB

Bass Beams

031 784 1920

Kwa-Zulu Natal

PB

Reya Pele Bricks Ltd

016 363 0340

Gauteng

PB

Bay Brick

035 792 5218

Kwa-Zulu Natal

PB

Rocla

011 670 7600

Gauteng

PB/PI

Beta Tiles

002634 2925303

Zimbabwe

PB

Shukuma Flooring

041 372 1933

Eastern Cape

PB

Boland Concrete

021 875 5365

Western Cape

PB

Smartstone

011 310 1161

Gauteng

PB

Bosun Brick Midrand

011 310 1176

Gauteng

PB

Southern Pipeline Contractors

011 914 8500

Gauteng

PB/PI

Brickbuild t/a Panda

00267 244 2107/8

Botswana

PB/PI

Style Décor Pty Ltd

012 376 2454

Gauteng

PB/PI

Brickcast Industries cc

031 507 5525

Kwa-Zulu Natal

PI

Swakop Tiles cc t/a Namib Roof Tile Company

00264 6446 3717

Namibia

PB

C.E.L. Paving Products

021 905 5998

Western Cape

PI

Topfloor Concrete

021 951 7700

Western Cape

PB

Cast Industries

011 316 2375

Gauteng

PB/PI

Vanstone Precast Pty Ltd

012 541 2056/1808

Gauteng

PI

Civil Works

011 903 7023

Gauteng

PI

West End Cement Bricks Pty Ltd

011 851 1005/1063

Gauteng

PI

Concrete Units

016 362 2236 021 386 1923

Western Cape/Gauteng

PB/PI

Conframat

0861 33 5599

Gauteng

PB/PI

Colonial Stone

011 794 9737

Gauteng

PB/PI

Corobrik Pty Ltd

031 560 3111

Kwa-Zulu Natal

PI

Deranco Precast

041 933 2755

Eastern Cape

PB/PI

Eagle Roof Tiles Pty Ltd

044 874 0290

Western Cape

PB

British Precast Concrete Federation

Echo Prestress Pty Ltd

011 589 8800/8899

Gauteng

PB

Fastdeck Pty Ltd

0026737 71321528

Botswana

PB

Inca Masonry Products

043 745 1215

Eastern Cape

Keystone Walling

082 850 3512

Lategan Cement Works

company name

company name

PI - Precast Infrastructure PB - Precast Building

Associate Members telephone

PROVINCE/ country

Aspasa

011 791 3327

Gauteng

ARQ Consulting Engineers Pty Ltd

012 348 6668

Gauteng

044 116 253 6161

United Kingdom

Concrete Society

012 348 5305

Gauteng

ILIFA Africa Engineers Pty Ltd

012 362 1473

Gauteng

PB/PI

JC Paving Consulting

011 431 0727

Gauteng

Gauteng

PB/PI

Sekhukhune & Associates

012 993 4776

Gauteng

021 873 1154

Western Cape

PB

SNA Civil & Structural Eng

012 842 000

Gauteng

Mobicast (Pty) Ltd

044 874 2268

Western Cape

PB

SARMA

011 791 3327

Gauteng

Monier Roofing South Africa

011 222 7300

Gauteng

PB

The Job Club

012 661 1099

Gauteng

MVA Bricks

012 386 0050

Gauteng

PI

Terraforce Pty Ltd

021 465 1907

Western Cape

Technicrete

011 674 6900

Gauteng

PB/PI

Tjeka Training Matters

011 665 2777

Gauteng

Portland Hollowcore Slabs Pty Ltd

021 972 1111

Western Cape

PB

Young & Satharia Consulting Civil Engineers

031 207 7252

Kwa-Zulu Natal

PRECAST VOLUME 8 • ISSUE 2 • 2014

company name


MEMBERS’ LIST

33

non-producer members Abel Equipment

044 874 1876

Western Cape

Ash Resources (Pty) Ltd

011 657 0230

Gauteng

H Birkenmayer (Pty) Ltd

011 970 3880

Gauteng

Chryso Southern Africa Pty Ltd

011 395 9700

Gauteng

Doubell Brick Machines

041 585 9060

Eastern Cape

Delta Bloc South Africa (Pty) Ltd

011 024-4604

Gauteng

Dick King Lab Supplies

011 499 9400

Gauteng

Envirotan

011 452 7906

Gauteng

00 45 9645 4040

Denmark

00 264 61 213 632

Namibia

Kaytech

031 717 2300

Kwa-Zulu Natal

Kerenos Southern Africa Pty Ltd

011 444 3090

Gauteng

003111 356 2460

Netherlands

011 975 7770

Gauteng

011 578 8600/8701

Gauteng

0082542607722

Korea

Schlüsselbauer Technology GmbH & Co KG

004377357144 201

Austria

Sika South Africa Pty Ltd

031 792 6500

Kwa-Zulu Natal

HawkeyePedershaab Kavango Block & Brick cc

Kobra Moulds B.V. Manitou SA (Pty) Ltd Pan Mixers SA Ltd SamJung Industries Ltd

Techmatik S.A.

00484 803 690 811

make sure you secure

your spot PREC AST VOLU

ME EI

Poland

cement members

ISSUE

1 • 2014

the

telephone

PROVINCE/ country

AfriSam South Africa

011 670 5500

Gauteng

PPC Ltd

011 386 9000

Gauteng

Sephaku Cement

012 684 6300

Gauteng

company name

GHT

ItY ca

m

an

ufactur

St IN

cONc

Rete

er

ass

ociat

CONTRACTOR members

– QUaL

s

• Build ing pr actic • Prec e antiq ast tra uated nsfor • Reco ms fac rd ret tory aining into wall show heigh room t

cma

e

PROVINCE/ country

concret

telephone

company name

io n

Q

u

al

telephone

PROVINCE/ country

Decorton Retaining Systems

021 875 5155

Western Cape

Friction Retaining Structures Pty Ltd

011 608 4321

Gauteng

Powergate Construction

071 603 5070

Gauteng

PYW Paving

031 903 1736

Kwa-Zulu Natal

facturer

Contact Charlene for more information:

s

ncrete

iatio

Q

PRECAST VOLUME 8 • ISSUE 2 • 2014

Tel: 011 883 4627 or E-mail: communications@isikhova.co.za

n

co

Gauteng

nu

soc

011 867 2471

a

as

Valcal International Export

yc ast te in concre

Don’t miss out! Book your advertising space in the next issue of Precast magazine.

m

company name

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the cma – QUALITY CAST IN CONCRETE


Precast July 2014  

The official publication of the Concrete Manufacturers Association of South Africa.

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