Precast July 2014

the cma – QUaLItY caSt IN cONcRete

PRECASTVOLUME EIGHT ISSUE 2 • 2014

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Quality cast in concrete

• Self-compacting concrete in precast applications

• Precast facades used for load-bearing in Germany

• Poor paving specification costs R-millions

PRECAST VOLUME 8 • ISSUE 2 • 2014

1ConTenTS

neWS2 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

CoVeR SToRy8 PeoPLe CoMe FIRST AT SePHAKU CeMenT

ARTICLeS11 SUSPenDeD PAVInG – IT’S In THe BAG

12 HoLLoW-CoRe SLABS FAST-TRACK oFFICe DeVeLoPMenT

14 SeLF-CoMPACTInG ConCReTe BeCKonS LoCAL PReCAST PRoDUCeRS

18 ULTRA-THIn ConCReTe SUPPoRTS HeAVy DUTy LoADS AT n3 WeIGHBRIDGe STATIon

20 HoLLoW-CoRe yIeLDS MoRe SPACe FoR STUDenTS

22 PReCAST FACADeS USeD FoR LoAD-BeARInG In GeRMAny

24 PooR PAVInG SPeCIFICATIon CoSTS R-MILLIonS

26 neW MeMBeRS’ RoLL ConTInUeS To GRoW

APPLICATIonS27 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

30 ARCHITeCTS PLUMB FoR PeRMeABLe PAVInG SySTeM

31 PReCAST PAVeRS SPeCIFIeD FoR InAnDA CLUB ReDeVeLoPMenT

31 PUMPInG ConCReTe To ReCoRD HeIGHTS

MeMBeR DeTAILS33 MeMBeRS’ LIST

PReCAST is the official journal of the Concrete Manufacturers Association NPC (CMA)

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PostNet Suite 8612, Private Bag X32, Kempton Park, 1620

Tel: +27 11 805 6742, Fax: +27 86 524 9216

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Publishers

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Website: www.isikhova.co.za

Publisher: Andrew Meyer

Tel: +27 11 883 4627, Cell 082 456 5175

E-mail: [email protected]

Editor: David Beer

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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 contents

ON THE COVER

Pictured here are the cement si-los at Sephaku Cement’s 155 ton- per-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 effi-ciencies and reduced power consumption. See the full story on page eight.

THE CMA – QUALITY CAST IN CONCRETE

PRECASTVOLUME EIGHT ISSUE 2 • 2014

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• Self-compacting concrete in precast applications

• Precast facades used for load-bearing in Germany

• Poor paving specification costs R-millions

NEWS


2

aFrIsaM LaUNcHes BUsINess DeVeLOpMeNt ceNtre IN sUppOrt OF sMMe grOwtHCMA member, AfriSam recently opened its

Supplier Development Centre in support

of the company’s Enterprise Development

Programme which has been implemented as

part of a transformation drive, especially in

areas where the company operates.

The aim of the Supplier Development

Programme is to identify black-owned Small,

Medium and Micro Enterprises (SMMEs)

close to the company’s operations and

provide these entrepreneurs with the

necessary support and development for

them to grow their business and ultimately

be included in AfriSam’s database of

registered vendors.

To date, AfriSam’s Enterprise Devel-

opment team has held SMME campaigns

and open days with communities around

the company’s Lichtenburg, Roodekrans,

Roodepoort and Eikenhof operations. More

communities will be included as the pro-

gramme is rolled-out to other provinces

in the future.

Situated on a property adjacent to

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

cIVILwOrKs BegINs rIB aND BLOcK MaNUFactUrINgCMA producer member, Civilworks, has

begun manufacturing precast concrete

rib and block flooring material.

A manufacturer of a wide range of

precast concrete products, Civilworks

bought a rib and block production line from

Econoslab in April and re-commissioned

it within two weeks at its Klipriv ier

manufacturing facility in Gauteng.

“While we are pleased with the pur-

chase of the assets, and more so with

the successful and speedy resumption

of production, the biggest gain has been

the transfer of the production and sales

teams. This has ensured a seamless tran-

sition,” says Graham Crooks, Civilworks

managing director.

“We have retained a combined 50 years

of experience within the teams. That

type of transfer is rare, and will ensure

continued quality and service levels.

“Flooring has not formed part of our

traditional civils market, but our strategy

as a precast concrete producer is for

continued growth. We will achieve this both

organically and by acquisition. Rib and block

flooring offers good growth potential and

fits well with our other product lines and

logistic competencies”, he added.

Econoslab was one of the original pro-

ducers of this type of innovative flooring

system, and the product has stood the

test of time over some 18 years. There are

literally thousands of successful installa-

tions spread throughout southern Africa.

“With that reference base and market

footprint, the decision was made a lot

easier, and we are happy to be involved in

this exciting market”.

Civilworks is still an active and growing

producer of miscel laneous v ibrated

products for the civil and structural

industry, and a supplier of manholes to the

sewer, telecoms, and electrical industries.

Other lines include a wide range of municipal

and road products, and a growing list of

bespoke, or special items for individual

clients or applications.

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

AfriSam’s Roodepoort Cement operation,

the Business Development Centre will also

provide SMMEs with a facility where they

will have access to computers that have

already been set up with an accounting

package that will enable them to manage

their statements and invoices.

The Centre for Supplier Development, a

company focusing on SMME development,

has been appointed to provide entrepre-

neurs with training and development that

will enable them to a level where they can do

business with AfriSam and other companies.

In Lichtenburg, Motswiri Consulting

has been appointed to a similar task of

identifying and developing entrepreneurs

from local communities around the

Dudfield operations, and up-skill them to

a level where they operate efficient and

sustainable businesses.

Some entrepreneurs in Gauteng and

Lichtenburg will be enrolled in an acceler-

ated development programme, with the aim

of ensuring they are ready to do business

with AfriSam.

“This is a wonderful example of how

AfriSam lives its values of People and Planet,

making a sustainable difference to the

communities in which we operate. Well done

to the Enterprise Development team for

making this happen. AfriSam looks forward

to contributing towards the sustainable

growth of these businesses”, says Calie

Ehrke, AfriSam’s supply chain manager.


4 neWS

cMa staND attracts sUBstaNtIaL INterest at tOtaLLY cONcreteThere was huge interest in the CMA stand

at this year’s Totally Concrete exhibition

and conference staged at the Sandton

Convention Centre at the end of May.

Twice the size of last year’s display

at 18m², the CMA stand was manned by

executive director, Wally Armstrong and

Pam Zukor. They were assisted by, Shawn

Sewnath of Brickcast, Silvio Ferarris of

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 CMA’s Botswana roadshow.

cMa stages BOtswaNa rOaDsHOw May saw the CMA staging a membership

drive in Botswana together with ABCON

(Association of Botswana Building and

Civil Engineering Contractors). Over 60

delegates comprising architects, engi-

neers, contractors, material suppliers,

government employees, students and four

CMA members, Kwena Concrete Products,

Kwena Rocla, Fastdeck and Panda, at-

tended the event.

CMA executive director, Wally Arm-

strong, introduced the CMA and spoke

about its role as the primary representa-

tive of precast concrete in southern Af-

rica and its expanding African footprint.

Subsequent presentations were made by

Lafarge, Chryso, MTS (Chryso’s Botswana

agent), Techmatik and ABCON.

Lafarge showcased its range of cements

and the success it has had with fly ash in

Botswana and Chryso gave a presentation

on the importance of oiling moulds correctly.

CMA member, Techmatik’s Marcin Nowa-

kowski, outlined modern trends in Europe’s

paving and concrete block making industry.

In addition to the CMA, the event was

jointly sponsored by Lafarge, Chryso, MTS

and Techmatik.

ReMaCon, CMA PR consultant, David Beer,

and two overseas members, Marcin Nowa-

kowski (Polish) of Techmatik and Thomas

Schardax (Austrian) of Schlüsselbauer

Technology. The display was sponsored by

nine CMA members; Brickcast; Concrete

Units; Coverland; Echo Group; ReMaCon;

Rocla; Schlüsselbauer Technology; Tech-

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.

A highlight of the CMA’s Totally Concrete

contribution was a seminar on precast con-

crete road construction, Totally Concrete

Roads. It was presented to some 40 con-

ference delegates by independent paving

consultant, John Cairns, who discussed

construction methodologies of precast

concrete roads and the products used to

build them.

Another CMA contribution involved a

panel of experts who answered questions

on precast concrete products and

applications. It comprised: Coenraad

Groenewald of Aveng Manufacturing

Infraset; Graham Crook of Civilworks;

Daniel Petrov of the Echo Group; and Silvio

Ferarris of ReMaCon.

The day after Totally Concrete, Techma-

tik’s Marcin Nowakowski gave a fascinating

two-hour presentation to a select audience

on modern trends in Europe’s paving and

concrete block making industry.

He said that since Poland was trans-

formed into a democracy in the early

1990s, the concrete block and paving

industry had boomed in that country to

the extent that today every major town in

Poland boasts a paving block manufacturer.

He observed that Poland’s current output

was equivalent to that of Germany’s at 85

million paving units a year, and that the two

countries were the world’s biggest paver

producers. Techmatik is one of the world

leaders in manufacturing lines for concrete

paving blocks and decorative products and

sells its equipment worldwide.

5NEWS

Cargo Carriers and Lafarge Cement owner-driver trucks.

Cargo Carriers has assisted Lafarge (one

of its customers) in establishing a B-BBEE

owner-driver scheme. Lafarge saw an

opportunity to develop an owner-driver

scheme based on increased volumes of

its bagged cement products in the Free

State, Northern Cape, and North West

Province and approached Cargo Carriers

for assistance.

Cargo Carriers introduced its own

owner-driver initiative in 2003.

“Owner drivers are contracted directly

to us by means of a service agreement

and we assist them with everything,” says

John Sprenger, Cargo Carriers, owner-

driver manager.

“We source the business opportunity,

provide our own management system,

mentorship and training until the owner-

driver is self-sufficient. This enables us

cargO carrIers assIsts LaFarge wItH OwNer-DrIVer prOgraMMe

business management and communication.

To further increase its B-BBEE rating,

Lafarge owner drivers appointed black

females, either spouses or girlfriends, as

their business partners. This allows Lafarge

to claim at three different B-BBEE levels:

preferential procurement; enterprise devel-

opment; and ownership, with more points

being attained for having black females as

part of the ownership structure.

“We believe our owner-driver scheme is

a win-win initiative. It is about a continuing

partnership in which the drivers are

empowered to determine their own success

and future with the concomitant benefit

of increased productivity and enhanced

service levels,” says Tim Nelson, Lafarge

Cement’s supply chain manager.

“The Lafarge owner-driver initiative

proves that the provision of supply-chain

solutions can go beyond the obvious

areas of application such as performance

and safety. This is what happens when

innovation meets B-BBEE and the results

are truly transformative,” says Sprenger.

to claim for preferential procurement and

enterprise development.”

Cargo Carriers appointed its own drivers

for the Lafarge project as strict selection

criteria are enforced. One of the key condi-

tions for participating in the Lafarge scheme

is compliance with the rigorous Lafarge

South Africa safety standards for driving

and maintenance of the vehicles. Moreo-

ver, drivers underwent intensive training

covering contractual issues, operating pa-

rameters, accounting matters, budgeting,

PReCAST VOLUME 8 • ISSUE 2 • 2014

7neWS

New cMa DIrectION MappeD OUt at agMA 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.


8 CoVeR SToRy

“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.

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

red tape is invaluable and makes for quick

decision making,” he says. “It remains the

most effective way of listening to custom-

ers and responding to their challenges and

requirements appropriately.”

Commenting on the six-and-a half years

it took to bring Sephaku Cement on stream,

Fourie says he and his team had to over-

come some formidable challenges.

“We were entirely success driven and

never lost faith in why we were coming to

market or in the long-term sustainable

growth prospects of the cement industry.

South Africa may have a relatively good

infrastructure but there is still much to

be developed. Sephaku Cement’s modern

technology, its cost-ef f iciencies and

the commitment of its people, give us a

competitive edge. Looking ahead, we will

remain committed to the people who bring

our products to the market, and to making

South Africa’s cement industry more

people focused.

“Building cement production operations

from the ground up has given us the

With the advent of bag and bulk de-livery 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 custom-ers and employees in equal measure.

peOpLe cOMe FIrst At sePHAKU ceMent

Holdings. Sephaku Holdings secured

limestone resources in 2006 when it

invested the initial seed capital. By late

2010, the projects were fully funded, having

attracted South Africa’s largest inward

investment by an African company, Dangote

Cement, one of Africa’s largest cement

producers. Additional debt financing was

provided by Nedbank and Standard Bank.

“We navigated our way through the

global recession by sheer determination

and a belief in our ability to change the face

of the South African cement industry. Ours

is a team passionate about cement-enabled

opportunities. While all of us at Sephaku

have been in the industry for many years,

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

experience. Not only has it made us better

cement technologists, but better people,

and we have learnt more than we ever

thought possible. Above all, we discovered,

at first hand, just how incredible the

results can be when teamwork comes into

play,” concluded Fourie.

opportunity to deploy some of the

world’s best high-tech cement-producing

equipment and to establishing new quality

benchmarks across our three cement

grades: Sephaku 32; Sephaku 42; and

Sephaku 52. Moreover, the greenfield

nature of this project has enabled us

to dictate product quality rather than

be dictated to by existing operational

constraints. Both our Delmas plant, which

began producing cement in January and

our Aganang plant in Lichtenburg, which

comes on stream later this year, have

been equipped with the latest-generation

Loesche vertical roller mills.

“We want to ensure that every customer

gets the best value from our product

offering and to this end our Delmas-based

laboratory is providing technical assistance

such as product testing and special mix

design support.”

Sepahku Cement is a 64% owned

subsidiary of Dangote Cement plc and an

associate company of JSE-listed Sephaku


11ARTICLe

Unlike conventional paving or tiling on a con-

crete surface in which the pavers or tiles

are grouted directly onto a concrete base

layer, in suspended paving the pavers are

mounted on small polythene sandbags (see

top picture) without the use of any adhesive

or binding agent. All that is needed to keep

the pavers firmly in place is their weight.

Moreover, they are laid 10-12mm apart

which creates a water permeable surface.

These and other advantages are why

suspended paving is finding increasing

favour among some of the country’s

leading architectural practices. The

process has already been used on some

major construction projects using pavers

supplied by Cape–based CMA member,

Revelstone. Some recent projects include:

Cape Peninsula-based projects such as:

Liberty Life’s headquarter premises in

Century City; Bloemhof in Tyger Valley;

Wembley Square in Gardens; and some

student residences in Stellenbosch.

Suspended paving has also been used

at Dainfern Square in Johannesburg and

Liberty Life’s Umhlanga offices in KwaZulu-

Natal, among other high-profile projects.

According to Johnny Schwartz, a partner

of Louis Karol Architects – one of the

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 thick-

ness of the supporting sandbags to com-

pensate 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 protec-

tive layer which shields the waterproofing

on the base layer from the sun’s UV rays

and from other forms of possible damage.

However, in the event that the base layer

does require some routine or other main-

tenance work, it is easily effected by simply

lifting the pavers and then re-inserting

them once the job has been completed.

“Contrast this with the expense and

inconvenience of lifting and replacing pavers

which have been grouted to the base layer.

Moreover, no expansion joints are needed

with suspended paving and there is no

chance that the pavers will crack or lift

due to wind or earth induced movement,”

says Schwartz.

Revelstone director, Alex Cyprianos,

says that suspended paving is generally

used in low-traffic areas such as concrete

roofs, balconies and terraces.

“The pavers tend to be large, averaging

600mm² and 55mm thick. We produce a

wet-cast flagstone paver for the purpose

which is steel reinforced, and we can also

make up special shapes to accommodate

curved borders.”

The sandbags used in suspended paving

are filled with a mixture of sand and cement

which hardens once the laying process has

been completed. Over time the polythene

outer casing will deteriorate leaving a hard

and durable concrete core.

Suspended paving is installed at Wembley Square, Cape Town.

The completed suspended paving surface at Wembley Square.

sUspeNDeD paVINg –

suspended-paving pioneers – the process

offers some distinct advantages over

conventional roof-top or terrace paving.

“In the first instance it allows for the

creation of a level paved surface on a base

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.

It’s In tHe BAG


12 ARTICLe

Built in two phases, the first compromising

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

and the second, 3 700m² GLA , the project

was the initiative of local property devel-

oper, Krisp Properties.

“We already had a lease agreement with

Michelin Tyre Company South Africa for

Phase 1 well before the first sod had been

turned, which meant we only had seven

months to erect the building,” said Jordan

Mann, executive director of Krisp Properties.

Francois Marais of Francois Marais Ar-

chitects said the construction of the build-

ings embraced new energy efficiency legis-

lation rather than being restricted by it.

“The design uses overhangs above all

the windows and doors to minimise the

impact of the sun and to reduce heat loss,”

says Marais.

Completed by the end of November

2013, Phase 1 comprises two double

storey buildings, each measuring 1 550m²

(GLA), which are linked by a central

entrance atrium.

“We deployed hollow-core slabs for the

first floors as well as the roofs, and this

assisted us in reducing construction time

by several weeks. Hollow-core slabs were

used for the roofing which would allow the

necessary support for the installation of

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.

HOLLOw-cOre sLaBs FAst-tRAcK oFFIce DeVeLoPMent

photovoltaic power generation units in

future. Moreover, the roofs have created

ideal catchment areas for harvesting rain-

water 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

H-shaped universal steel columns to provide

slab support for the internal cantilevering.

According to structural engineer, Spi-

ros Sdralis, of PDS, Echo’s role involved

Clearwater Phase 1.

A section of Clearwater Phase 2 under construction.

13


ARTICLe

P O Box 124, Sanlamhof, 7532

considerably more than simply supplying

the slabs.

“We provided Echo with a set of draw-

ings and they then prepared a layout which

took all the servicing requirements into ac-

count. 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

the solid base. Echo filled in the voids with

concrete according to our specifications

and this enabled us to drill out the holes for

the bolt anchor sleeves in the same way as

we had done on the ground floor.

“The builders were able to begin the

assembly of the upper level steel frame

as soon as the slabs had been installed

and this was the prime advantage of

using hollow-core slabs. If in-situ flooring

had been used it would have delayed the

completion dates on both buildings by

several weeks.

“Extensive use was made of cantile-

vering, both internally and for the shade

overhangs, and Daniel assisted with rede-

signing some of the cantilever sections on

Phase 2. He also helped us with changing

the direction of some of the slabs.”

Echo also allowed for service ducts and

suspended ceilings were created 600mm

below the soffits of the roofs and first

floors to accommodate piping and cabling. The upper-level steel framework of Phase 2 which was bolted to solid concrete sections of Echo slabs.

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


14 ARTICLe

This explains why so many precast produc-

ers in other parts of the world use SCC

exclusively in place of conventional vibrated

concrete (CVC). Having no slump, SCC can

flow over dense reinforcement and fill voids

under its own weight. And it does this with-

out the need for any post-cast vibration.

As a result moulds can be less robust and

last much longer, noise pollution is greatly

reduced, and the casting process is much

quicker, neater and easier.

Further time savings, long workability

(one hour) and an improved work ing

environment are other benefits. But

arguably its major advantages are high

durability combined with substantially

superior finishes, factors which have

not escaped one of the country’s leading

precast concrete producers. Since the

middle of 2013 Rocla has been using SCC

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 Afri-can precast concrete manufacturers. Complex mixes, increased costs, extreme sensitivity to even the smallest changes in chemical composition and produc-tion 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.

BecKons LocAL PRecAst PRoDUceRsfor 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 more recently, precast

concrete cabins for photovoltaic plants,

would be better and more easily produced

with SCC. Using European guidelines and

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

a year of research and experimentation

before the company was producing SCC

to consistent best-practice standards.

A f ormidab le group o f concrete

technologists was assembled to conduct

Rocla’s SCC research. They included: Rocla

seLF-cOMpactINg cONcrete

15


ARTICLe

BecKons LocAL PRecAst PRoDUceRsA newly cast photovoltaic cabin prior to delivery.

SCC is pumped into a photovoltaic cabin mould.

as we did without the use of SCC. This

achievement led us to introduce SCC at

several other Rocla branches, the ultimate

goal being to produce all our wet-cast

products with SCC. Our Virginia branch

is already using SCC for the manufacture

of culverts and special products such as

Alfablocs and road barriers.

“The requirement for optimal chemical

balances meant we had to prepare specific

SCC designs for each of our branches

across the country, due to chemical

variations in raw materials and the manner

in which they react with each other.

Rocla’s SCC trials began with smaller

products such as manhole cover slabs and

the Alfabloc. Initially several obstacles

were encountered in achieving consistent

levels of repeatability and robustness.

“For instance, we were unable to

achieve robust mixes at first and slight

variations would cause a mix to fail and not

self-compact. Furthermore, when using

precisely the same ingredients in exactly

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,

Roberts said that he found SCC to be ex-

tremely 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.

Silica fume is a super fine powder, its par-

ticles being about 50-100 times finer than

the average cement or fly ash particles,

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

by-product material. We found that fly ash

improved flow and mobility and decreased

water demand whereas silica fume pre-

vented bleeding.”

Roberts added that conveying SCC

from mixer-to-hopper-to-mould presented

additional challenges.

“We observed that even when moving

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

ing vibration, which varied in line with ground

surface conditions, could cause the mix

to separate. The obvious and more costly

alternative involved pumping the concrete

directly from the mixer to the moulds.

However, getting this right meant further

changes to an already successful SCC mix

design and considerable trial and error.

“Initially we encountered frequent

blockages in the pipes which could cause

delays of up to an hour. The pumps were

so powerful that if not properly controlled

and monitored, they would force the

civil technologist, Jason Roberts; Murray

& Roberts group concrete and research

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 Kretzmar 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 chemi-

cals and additives.

“We could not have managed our

photovoltaic cabin project as successfully

The photovoltaic cabin mould at Rocla’s Johannesburg premises.


17ARTICLe

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

cement/water paste inside the pipes past

the aggregates. With the assistance of

Mapei and CCE we examined the aggregate

ratios and other material combinations,

and managed to create a mix suitable for

pumping. Moreover, the pumps had variable

flows and this enabled us to match pump

outputs to the rate of production.

“Besides being much safer than

transporting hoppers with dump trucks,

forklifts or cranes, we found that pumping

made the casting process a lot faster,

by a factor of five at the very least. For

example, we were able to cast a complete

photovoltaic cabin shell (outer walls and

base slab), using approximately eight cubic

metres of SCC in 30 to 40 minutes as

opposed to the 160-210 minutes it would

have taken had we used CVC and more

conventional modes of shifting and then

vibrating the concrete.

“Another challenge was mould stripping,

especially off the cabins and other thin-

walled sections such as the roof and

internal walls, which required exceptionally

smooth finishes and very early strengths.

In order to meet our client’s delivery

schedule, we needed to produce five to

six complete cabins a week using only a

single mould. This meant we had to strip

and recast one cabin a day. Requiring 12m³

of concrete, completed cabins comprised:

outer walls; base floor; suspended floor; a

roof and internal walls; and weighed close

on 28 tons.

“Meeting this production schedule meant

we had to achieve compressive strengths

of 18MPa after 12 to 16 hours and we

relied on a combination of accelerators

and steam heating to do so. To begin with

we used accelerators without the steam

but we found that the former impinged on

the self-compacting properties of the SCC

and affected other quality aspects as well.

By introducing steam heating we were

able to reduce the amount of accelerator

and still realise our early 18MPa strength

requirement. Moreover, after seven days

we were achieving around 60MPa, well in

excess of our 40MPa target.

“Other stripping problems encountered

during the development phase included pull

outs, pin holes and blow holes, blemishes

which could be seen even after painting.

We solved this by changing the releasing

agent and further tweaking the mixes,”

said Roberts.

Kretzmar added that the photovoltaic

cabins are relatively thin-walled, being only

100mm thick at the bottom and tapering

to 75mm at the top.

“Although some sections required dense

reinforcement, we still had to comply

with the required cover. SCC’s flowability

made this very easy for us. Traditional

concrete in a similar application would have

resulted in extensive honeycombing with

the coarse aggregates being visible after

stripping. One very seldom, if ever, finds

honeycombing in SCC.

“One of the reasons SCC is so difficult

to implement in SA is that our aggregates

tend to be flaky, unlike those in America and

Europe, which are more rounded. Needless

to say, we have managed to circumvent

the problem.”

Kretzmar concluded by saying that

although SCC traditionally costs up to

40% more than CVC, the adoption of ARC

technology for mix design, resulted in an

SCC mix at a very similar costing to that

of previous CVC mix designs.

“However, SCC does require a higher

degree of hands-on attention than CVC and

the equipment used to produce it must be

better and more frequently maintained.”


18 ARTICLe

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.

ULtra-tHIN cONcrete sUPPoRts HeAVY-DUtY LoADs At n3 WeIGHBRIDGe stAtIon

premixed off-site. It was important that

we achieved very accurate slumps and to

this end the super plasticisers were added

electronically down to the last millimetre.

What’s more, the amount of water used

in the mix had to be equally accurate,”

Crofford commented.

Before the concrete was placed, the

existing confalt asphalt surface was milled

down to provide a suitable base. Steel

mesh which measured 100 x 75mm was

then fastened to the base prior to placing

the UTCRCP.

Once mixed, the concrete was dis-

charged from the back of the truck off

a metal chute onto the steel mesh. Side

discharging, which would have been prefer-

able, was not possible due to insufficient

space for vehicular access.

‘The concrete had a slump of 90mm and

it only took 15 minutes to set. This meant it

had to be vibrated immediately to eliminate

voids. We attained an average production

rate of 12m³ per day which equates to a

surface area of around 20m², while the

compressive strengths of 65MPa were

achieved after two days rising to 100MPa

after 28 days,” concluded Crofford.

A bag of premixed concrete ingredients is poured into the pan mixer.

King Civil Engineering’s contracts manager, Hugh Crofford.

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

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

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 con-

tractor) Aurecon/Blue Quartz, (consulting

engineers) and PC Floors (sub-contractor).

King Civil Engineering’s contracts manag-

er, Hugh Crofford, said that this was the first

time King Civil had used ultra-thin concrete.

“It obviously entailed a considerable

amount of trial and error and we worked

with Allan de Kock of Beton Lab to design

the concrete so that it met SANRAL’s

80MPa specification. Initially the intention

had been to source ready-mix concrete

from an AfriSam depot in Nigel, but a very

short workability time of only 15 minutes

meant that we had no option but to design

our own mixing platform and to do the final

mixing on site.

“Experimenting with concrete is a

lengthy process and it took us three months

to get a suitable mix design approved us-

ing AfriSam’s 50.2 cement. Moreover, the

stringent specifications for all the materials

used in the mix required that all ingredi-

ents had to be tested. We also included

three types of sand which were difficult to

source. Other materials used in the mix in-

cluded steel fibres at 80kg/m³ for additional

strength and 2kg/m³ of polypropylene fibres

to assist against cracking.

“We installed an 800lt generator-

powered pan mixer on the back of the

truck. Apart from the plasticisers, steel

fibres and the water, all the materials were


20 ARTICLe

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.

HOLLOw-cOre YIeLDs MOre sPAce FoR stUDents

The apartments are being built on the con-

crete 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 Be-

zuidenhout, said that hollow-core slabs

were an obvious choice for the apart-

ment flooring at Eikestad Mall because

they weigh some 35% less than an in-situ

concrete flooring equivalent.

“Further weight savings were made

through the use of a light clay brick which

weighs 2.5kg. By applying these light-

weight materials we were able to build

116 apartments.

“Speed of construction was another

important design consideration because

the development is taking place on two

main streets in the heart of Stellenbosch’s

CBD and we wanted to minimise disruption

to vehicular and pedestrian traffic as much

as possible. Precast slabs have certainly

assisted in this regard as they only take

hours or at most days to install unlike in-

situ concrete which takes two to three

weeks. Moreover, there is no formwork or

rebar to offload in the streets below.

“Another advantage of hollow-core slabs

is that building operations can resume as

soon they are installed. At Eikestad we

started building the apartment walls before

we laid the structural topping on the slabs

which comprised a 50mm 25MPa concrete

reinforced with 100 rev mesh. The topping

abuts the walls, and in doing so, creates

an automatic joint which allows for wind-

induced movement.

“We also caulked the joints where the

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

crete topping from seeping into slab hollows

and wasting material’” said Bezuidenhout.

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

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

Portland Hollowcore supplied over 950

prestressed hollow-core slabs in lengths

varying between 1.5 and eight metres.

Most of them were 160mm thick, although

some sections required 200mm slabs, es-

pecially where load-bearing walls had been

removed to combine two flats into one.

The apartments are being built on three

levels and a 900mm services void has been

created between the roof of the mall and

the bottom floor of the apartments. Most

of the apartments vary between 35m² and

75m² although 10% comprise duplex units

of ±100m².

In addition to NMC Construction Group

the professional team comprised: DHK,

principal agents and exterior architects;

Macgregor Forsyth, interior architects;

KLS, structural engineers; IQS, quantity sur-

veyors; Eppen Burger & Associates, health

and safety; Arcu Gibb, electrical consultants;

WSP, wet services engineers; Landmark

Studios, landscaping architects; Aurecon,

mechanical engineers; Ecko, fire engineers.


22 ARTICLe

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

precast FacaDes UseD FoR LoAD-BeARInG In GeRMAnY

Previously any attempt at using precast

concrete facades for load bearing was sub-

ject to tight constraints. However, recent

developments in precast concrete technol-

ogy 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 enve-

lope is the use of sculptural architectural

concrete components and windows which

extend from floor to ceiling. Yet its major

achievement lies in its ground-breaking

technical approach to facade design.

The architectural concrete components

used on this project facilitated important

load-bearing functions whilst fully complying

with the legal requirements for thermal

insulation. Various facade elements were

grouped together according 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.

The concrete facade was designed and

built within approximately 10 months. This

ambitious project required close cooperation

between architects, structural engineers

and the precast plant. HPP Architects

prepared a design which included beams

and columns arranged as a right-angled tri-

angle. Structural engineers, Schüßler-Plan

Ingenieurgesellschaft discarded the option

of mounting solid cast stone elements on

the facade and suggested an external load-

The new Ohligsmühle building merges aesthetics with functionality.A ground-floor corner column with a match-cast head beam section.

Image courtesy rößner, ed. Züblin ag

Facade view with panoramic windows.

First-floor cantilevered element during assembly.

Image courtesy Franke, ed. Züblin ag

Image courtesy Yasar, ed. Züblin ag

23


ARTICLe

precast FacaDes UseD FoR LoAD-BeARInG In GeRMAnY

Formwork stripping from a cast corner column element.

bearing facade design instead. Precast

concrete manufacturers, Züblin AG added

further details to the proposal.

The design team decided to merge entire

facade components and to make the load-

bearing material out of precast concrete.

Columns were connected to each other

via the beams to facilitate and assemble

large facade elements. Overall, 1 215

columns were merged with 770 elements

using 180 tons of reinforced steel. The

precast elements had a total weight of

about 2,600 tons.

The design of the connecting points

between the beams and the columns posed

a particular challenge. This was where the

lines of the isosceles triangle formed by

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 fabrica-

tion of sharp-edged intersections without

joints yielded both aesthetic and functional

benefits. The design team tested the

feasibility of all plans at an early stage

using mock-ups at Züblin’s precast plant

in Gladbeck. These were inspected and

approved by the client, and as a result,

load-bearing facade columns made from

architectural concrete were included in

the general contractor’s brief.

A rapid assembly schedule of one storey

per week per building section necessitated

a very high prefabrication rate. Site

cranes lifted each of the elements from

the trailers to final installation positions.

Socket dowels were inserted in the

precast elements and in the cast-in-situ

floor. The facade elements were then

assembled, aligned and filled in whilst being

held in place by diagonal struts. The next

step entailed the in-situ casting of the

floors. Due to their full-storey height of

about 4.70m, the ground-floor columns

had to be split below floor level to comply

with maximum transport dimensions.

The regular floor grid began on the first

storey. The standard elements were

approximately 3.50m high and 5.40m wide

and each of these elements defined the

height of a storey. They were inserted on

top of each other floor-by-floor.

The pointed internal and external cor-

ners of the envelope formed the special el-

ements of the building. Panoramic window

areas that project from the structure,

starting on the first and second floors,

made it impossible to transfer the loads of

these floors directly via the columns. This

was why cantilevered elements were used.

Non-load bearing columns were split for

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 ad-

hering to the geometrical specifications.

The interdisciplinary collaboration of

architects, structural engineers and the

precast plant resulted in a long-lasting

facade design. Sustainable facade elements

and state-of-the-art precast components

provided a high degree of design freedom.

Image courtesy Yasar, ed. Züblin ag

Image courtesy Franke, ed. Züblin ag

Arrangement of joints in the panoramic window area.

Image courtesy rößner, ed. Züblin ag


24 ARTICLe

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,

civil engineer and independent paving

consultant, John Cairns, says that many

of the engineers and landscape architects

who design paved roads are not aware of

the most important specification criteria

when using CBP.

“I participate in regular paving seminars

and workshops and am amazed at how

many professionals don’t know that the

new CBP standard, SANS 1058:2012, is

based on tensile strength and abrasion

resistance rather than the old standard

of compression resistance. Some are

not even aware that the standard has

changed. Therefore it is hardly surprising

that so many professionals are still

specifying for CBP projects based on

compression strength,” says Cairns.

“In most instances, pavers fail either

by cracking and then splitting, or through

surface abrasion due to factors such

as partic le distr ibution and b inder

occur in shopping centres, office parks

and housing developments, where paved

surfaces tend to be regarded as simple,

not requiring an engineering design.

“By contrast industrial CBP surfacing

is generally designed correctly, especially

where the paving provides a critical

functional element such as the working

surface of a container yard or steel mill.”

percentages, and these properties are

addressed in SANS 1058:2012. The old

standard, SANS 1058:2006 was based

solely on a single compression test which

measures resistance to crushing.

“Paving blocks never crush under load

which is why the compression test is not a

good performance indicator. In fact pavers

can have a very high compressive strength

but poor abrasion resistance. This is why

the standard was changed.

“This lack of awareness is resulting in

failed CBP installations and unnecessary

remedial expense. For instance, I was

recently asked to submit a report on a new

car park paved with CBP at an East London

shopping mall. Serious abrasion had taken

place even though the paved surface was

barely six months old. The reason for this

was that the pavers were simply specified

on the basis of compressive strength

rather than the SABS standard.”

Cairns says that most paving failures

pOOr paVINg specIFIcatION costs R-MILLIons These pavers are not appropriate for heavy construction traffic.

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

25


ARTICLe

pOOr paVINg specIFIcatION costs R-MILLIons Cairns adds that CBP roads can

also fail when they are not designed for

construction loading.

“This often occurs on housing estates

where roads are designed to handle light

traffic only. What normally happens is

that the roads are built before other

construction takes place. This means that

they must then handle the heavy-duty

trucks and other construction equipment

while the estate is being built and this

obviously causes damage. Further damage

is caused by the spillage of sand and stone,

especially at traffic circles where most of

the braking and turning takes place.

“One way around this problem is to build

road bases to handle the construction and

early resident traffic and only pave them

once the estate is close to completion. Not

only will this save the pavers from unneces-

sary wear but it will also ensure that the

road base has been constructed properly.

“However, in instances where it is

deemed necessary to install complete

roads before the construction of the

estate commences they should be built

with a paver which can handle heavy-duty

traffic. And once built, the contractor

should ensure that the roads are kept free

of sand and stone. Then if damage occurs

responsibility for the repairs will fall to

the contractor.”

CMA director, Wally Armstrong, notes

that most CMA producer members hold

the SABS mark. This means they do

regular batch testing and manufacture

with a recognised quality assurance

system in place.

“Some of our members and other CBP

producers comply with the standard but

don’t actually hold the mark which is also

acceptable. However, holding the mark is

obviously first prize, especially if there

are comebacks due to poor specification.

“Most South African paving producers

manufacture pavers with two layers. The

bottom and thicker layer provides the

required strength and the top layer can

be coloured with pigments for enhanced

aesthetic appeal. And now that the new

standard measures abrasion resistance

this topping layer is also being designed

with excellent surface-wear properties.

Even lower-grade blocks with a good

topping layer can of fer high abrasion

resistance, proving that the topping

layers do more than offer colour variation,”

concludes Armstrong.

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


ARTICLe26

New MeMBers’ rOLL contInUes to GRoW

Envirotan

Envirotan is an innovative chemicals

company that specialises in anti-microbial

additives for the cementitous coatings

industry. It has developed and tested

various additives based on customers’

specific needs. These include anti-microbial

additives for tile adhesives and tile grouts,

as well as anti-algae products for marbelite

pools. It also offers a range of products

- all based on cementitious coatings - to

keep floors, walls, counters, kitchen and

bathrooms hygienic.

Envirotan also offers a technical service

to concrete product producers to deter-

mine the origin of stains, be they organic,

in-organic or biological. Once identified,

several solutions are offered which can be

used by manufacturers and their custom-

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

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. Out-lined below are brief profiles.

Envirotan’s laboratory.

Schlüsselbauer state-of-the-art concrete pipe production.

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

SmartStone paving at Melrose Arch.

pressure pipes, manhole elements, road-

side channels, and so on.

A newsworthy innovation, PERFECT

PIPE, produces a durable and dense sew-

age 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.

Furthermore, PERFECT is a wet-cast

system which enables the production of

fully customised dense products as well as

mould-hardened concrete manhole bases,

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

fectsystem.eu).

The Job Club

A registered NPO, The Job Club was es-

tablished in 2010 in association with the

SA Council for Business Women and SA

United Employers to facilitate practical

and sustainable job creation in partnership

with the business community, government

and civil society.

The organisation’s primary objective is

to generate employment by providing people

with the necessary skills to establish and

sustain their own businesses.

Already active in all nine provinces, the

organisation manages a range of innovative

skills training, internship, host employment

and entrepreneurship programmes in as-

sociation with host employers, businesses

and experienced professionals.

Businesses and professionals share

their expertise in programmes aimed at

youth, women and start-up entrepreneurs,

and also assist in identifying host employ-

ment and job opportunities.

The Job Club works in collaboration with

community representatives, as well as local

health, social and education departments.

It also forms social partnerships with gov-

ernment and private sector organisations,

such as the National Youth Development

Agency (NYDA).

SmartStone

SmartStone was founded in 1980. The

original SmartStone concept was to create

concrete products that simulated the look

and feel of natural stone, but the company

quickly evolved into much more. It pioneered

the idea of exterior design systems, which

was achieved by creating products with

natural textures, others which remained

true to concrete and some that could only

be described as authentic SmartStone.

Subsequently, SmartStone became a ge-

neric name and its manufactured product

range expanded to include various paving

shapes, textured pavers, wall cladding, tiles

and landscaping features.

A significant achievement was winning a

premier CMA excellence award for a paving

installation at Melrose arch in 2002 and

then winning the Vintage Award for the

same project at the Association’s Awards

for Excellence competition in 2012.

SmartStone has branches in Bloemfon-

tein, Cape Town, George, Durban, Nelspruit,

Midrand, Port Elizabeth, Potchefstroom and

Pretoria. It also has branches in Namibia,

Zambia and Mozambique.

Schlüsselbauer

Based in Austria, Schlüsselbauer operates

worldwide as a solution provider and sup-

plier of plant equipment for the production

of precast concrete components for sew-

erage and stormwater drainage systems,

as well as water mains.

Schlüsselbauer’s manufacturing tech-

nology for wet and dry cast concrete

products is designed to produce concrete

pipes, concrete pipes with plastic liner,


27APPLICATIonS

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

New raNge oF MoULD ReLeAse AGentsCMA member, Chryso South Africa has

launched a new range of application-driven

mould release agents.

Hannes Engelbrecht, Chryso S.A. gen-

eral manager: marketing, says the new

ChrysoDem release agents have been

designed to meet the needs of specific

industries and applications.

“Choosing the appropriate release agent

may be critical to the success of a project,

as it affects both the quality and colour of

the surface finish,” says Engelbrecht .

“The cost of a release agent is low in

proportion to the formwork or mould itself,

so simply choosing the cheapest release

agent available on the market, is false econ-

omy. The top quality release agents in the

ChrysoDem range may cost a little more but

provide greater coverage, are easier to use,

and add consistent quality to the production

line. This is important, particularly in the

precast industry, where high temperature

steam curing forms a formidable challenge

in the production process.

“The new range is a ground-breaking

development for South Africa, long-

awaited 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 order to achieve satisfactory

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.

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

and surface damage, particularly blow holes,

to create more durable and attractive

concrete surfaces

• Elimination of staining and colour changes

• Plaster, paint and other coatings may be

applied subsequent to the mould removal

as ChrysoDem release agents do not

adversely affect adhesion of finishes and

coatings applied to the concrete

• Water repellent and not affected by rain

• No effect on the hydration of concrete

• Ready-to-use release agents which re-

duce the possibility of errors during mixing

• Two-year storage life for virtually all the

new release agents.

“There has been exceptionally positive

response from the concrete industry

to this new range which Chryso S.A. is

planning to export to the rest of Africa as

well,” added Engelbrecht.

For further information, contact Hannes

Engelbrecht on tel 011 395 9700 or email

[email protected] or visit www.

chryso.com


28 APPLICATIonS

Terracrete paving blocks on track at Geelkrans Nature Reserve.

Rocla’s Alfabloc.

Garden Route Terraforce licensee, CMA

member, Mobicast, is building two-wheel

jeep tracks with Terracrete paving blocks

for Cape Nature at Geelkrans Nature

Reserve in Stillbaai, Western Cape. The

Terracrete block is providing a hard wearing

all-weather surface which is water perme-

able, unlike surfaces such as asphalt or

conventional paving which are impermeable.

Jean du Plessis, conservation manager,

Geelkrans Cluster & Stilbaai Marine

Protected Area (MPA) says:

“We have a network of maintenance jeep

tracks on the reserve and the substrate

comprises mostly deep dune sand unsuited

to normal paving. As an alternative we

sought a hard surface that was water

permeable and allowed the growth of

vegetation. Another proviso was that

it should move with the substrate while

The need to store or partition fertilizer,

coal, sand, stone and other granular or

loose particles in discrete batches is

critical for many sectors of industry.

These requirements are easily facilitated

by the installation of CMA member, Rocla’s

Alfabloc A-framed precast concrete

retaining walling system.

Manu f actured under l i cense to

Poundfield Products Ltd in the UK, Alfabloc

is a naturally stable and robust retaining

wall block which requires little or no ground

fixing while offering limitless configurations

and quick installations.

“Alfabloc is a versatile product that

can be deployed across many applications.

The type of stored material determines

whether the blocks are free-standing

or bolted into place,” says Rocla sales

engineer, Justin Kretzmar.

“The traditional retaining wall concept is

well suited for the separation and storage

of granular materials, however, Alfabloc’s

quick and easy alignment, its even weight

distribution, sturdiness and durability, are

what make it an efficient alternative.

“And the inner cavity formed by the

two A-frame legs can be used for placing

electrical cabling for CCTV alarms or any

other wiring requirements.

Rocla’s Alfabloc is available in three

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

“The mini-Alfabloc, at 1.2m high, has

been very successful at offering a quick,

flexible option for storage requirements

as well as an alternative to the New

Jersey Barrier for many non road-related

applications.

The Port of Durban has used 22 mini-

Alfablocs as a temporary security measure

for crowd control, and a Durban-based

logistics company has used the large 2.4m

Alfablocs for stock piling manganese.

The Alfabloc has also been used at chem-

ical factories, farms and mines as well as

at airports, railways and other transport-

perMeaBLe paVINg BLOcK prOVIDes eco-FRIenDLY MoBILItY FoR nAtURe ReseRVe

aLFaBLOc – rOcLa’s pOrtaBLe RetAInInG WALLInG sYsteM

stability and loose substrate is used to fill

any gaps in and around the blocks.

“The blocks are relatively easy to work

with, compared to other paving methods

which involve more sophisticated machinery

and labour,” says Du Plessis. “We are

finding that approximately two percent of

the blocks are broken during transport and

handling over rough terrain but on the whole

the process is straightforward and causes

very little disturbance in the reserve.”

The tracks are being installed in 250m

stages and 7 000 blocks have already been

laid. Carpobrotus edulis (Sour Fig) is being

planted on the verges of the tracks to

rehabilitate any destabilisation that occurs

during construction. Maintenance of the

tracks is quick and easy, and should blocks

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

block has two sockets cast into the top

surface, which can be used with eye-bolts

to easily lift and move the blocks or to

attach additional items such as roofing,

razor wire or electric fencing.

keeping its shape and integrity. We decided

to use the Terracrete block because of its

permeability, low environmental impact and

cost-effectiveness.”

The blocks are laid after 100-150mm

of substrate is removed. Binding wire is

threaded through them to increase overall

29


APPLICATIonS

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

Some 14 800m2 of CMA member, Kay-

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

to reinforce 10 open-faced concrete block

retaining (CRB) walls at Olivedale Retire-

ment Village, currently under construction

in Randburg, Johannesburg. Situated on

sloping ground, the site required extensive

terracing and embankment buttressing

to provide level building platforms for the

construction of houses, apartments and

communal buildings.

Completed in April, the retaining walls

were designed and built by Engineered

Interlock Solutions (EIS) in close collabo-

ration with main earthworks contractors,

Lone Rock, and consulting engineers, Pro

North Consultants, to ensure that all

statutory requirements were met.

Building 10 CRB walls reinforced with

Kaytech’s Miragrid GX 80/30 in combination

with Aveng Manufacturing Infraset’s split-

face Terrace Blok® 300 proved to be an

effective and cost saving decision for the

developers.

Miragrid GX geogrids are manufactured

from high tenacity polyester (PET) yarns

with a protective polymeric coating. They

are especially suitable for the reinforcement

of vertical or inclined soil walls with modular

block or panel facings and are available in a

wide variety of strengths and sizes.

Quick and easy to install, Miragrid GX

80/30 was placed at every second block

with tie back lengths of up to 5.4 metres. It

is an economical alternative to conventional

geogrids and provides superior interfacing

with concrete block structures.

The walls were built at a 75° angle

and reached heights of up to 7.5m. To

prevent the possible build-up of hydrostatic

pressure behind the walls, blanket drains

were constructed, consisting of a layer of

bidim A2 covered with a 120mm layer of

19mm stone followed by a second layer of

bidim A2. Outlets were provided at every

three metres.

A layer of PC100/100 was installed on

the second last tier of blocks for erosion

control and reinforcement.

With its performance properties having

been independently verified and tested,

Miragrid GX provides guaranteed long-

term durability (>100 years) and low creep

resistance.

For more information on Kaytech prod-

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

cOst-saVINg geOgrID cHosen FoR RetAInInG WALL


30 APPLICATIonS

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.

arcHItects pLUMB FOr PeRMeABLe PAVInG sYsteMPermeable interlocking concrete paving

(PICP) is a prominent landscaping feature

at Alchemy Architects’ new office premises

in Edenvale, Johannesburg. Completed

in December 2013, the modern three-

storey building is surrounded by 935m² of

PICP which serves both as driveways and

parking areas.

Alchemy Architects’ permeable paving

system was based on an infiltration-based

PICP design provided by CMA member,

Aveng Manufacturing Infraset, one of

the country’s leading PICP suppliers. The

manufacturer also supplied Uni-Ecolok, its

interlocking paving block system, for the

installation of the paved surface.

Amândio Castanheira, a senior partner

at Alchemy Architects, says that PICP

using Uni-Ecolok made both environmental

and aesthetic sense.

“We were very aware of how widespread

urbanisation, and through it the creation of

impermeable surfaces, is placing mounting

pressure on stormwater drainage. Imper-

meable surfaces increase the risk of flood-

ing, spread pollution and disrupt aquatic

eco systems in rivers, streams and vleis.

“Research has shown that only 30%

of rain water infiltrates surface areas in

urban centres, and in towns and cities

the figure is as low as five percent. This

is why these areas are often flood-prone.

PICP reverses this imbalance allowing up to

95% of rain water to infiltrate the ground,

a figure which largely mirrors what happens

in undeveloped landscapes.

“Minimising pollution, albeit in a small

way, was another motivating factor in

our choice of permeable paving. During

Gauteng’s dry winter months, heavy

metals, hydrocarbons, oil, rubber and other

pollutants are deposited on impermeable

surfaces. When it rains they are washed

into stormwwater systems and are then

discharged into streams and rivers where

they destroy fauna and flora.

“PICP is very effective at removing

pollutants from run-off. The sub-base of

any PICP system is largely comprised of

coarse-graded aggregate and geotextile

sheeting and both materials harbour

natural microbes which devour water-borne

pollutants and prevent them from clogging

PICP systems.

“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 load-

bearing 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 aggre-

gate. 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

of PICP systems, the other being attenua-

tion. Infiltration allows water to flow through

the crushed stone gradually before ground

infiltration takes place. In attenuation the

water is temporarily stored in the crushed

stone before being slowly released through

outflow pipes into conventional stormwater

drainage systems. This reduces peak flows

during heavy rainfall and reduces water tem-

peratures by 30ºc, both factors minimising

downstream damage considerably.

“There are other PICP options. For in-

stance, some systems store water below

the surface to be used for watering plants,

washing cars and equipment, and for sanita-

tion purposes. And some systems combine

infiltration with attenuation, especially in

instances where ground infiltration rates

are low. However, the final specification of

any permeable paving structure depends on

the hydraulic properties of the sub-grade

and anticipated traffic loading.

“The Uni-Ecolok system covers all these

requirements and its L-shaped concrete

block is ideal for driveways, car parks,

suburban streets and township roads,

light and heavy duty industrial yards,

as well as bus terminals and suburban

arteries. Moreover, the 80mm Uni-Ecolok

block conforms to the new SANS 1058

standard for paving block performance,”

concludes Soupen.

Contact Charlene Soupen on 012 652

000 or via email on [email protected].

31


APPLICATIonS

precast paVers specIFIeD FOr InAnDA cLUB ReDeVeLoPMentCMA member, Colonial Stone, has supplied

4 600m² of concrete block paving (CBP)

for the paving of private roads at the

prestigious Inanda Club redevelopment

project in Sandton, Johannesburg.

Two types of CBP were supplied, a 222

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

smaller unit being used for a herringbone

layout. Both pavers have granite finishes

and both have a compressive strength of

over 42MPa.

According to Friedel Weihe, director

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

pUMpINg cONcrete tO RecoRD HeIGHtsBosch Rexroth has supplied its latest

axial piston pump, the A4VG, to Zoomlion

in China for installation in a hydraulically-

operated portable concrete pump capable

of pumping concrete to heights of over

100 metres.

“Pumping concrete to these heights

entails very specific requirements. For

instance, the placing boom must be

robust yet sufficiently flexible for versatile

service,” as Binxing Wu, chief engineer at

Zoomlion, explains.

“Moreover, a limited load-bearing capac-

ity meant that all the main components

had to be highly efficient with the intrinsic

weight as low as possible.”

High operating pressures, large dis-

placement volumes and no critical vibra-

tion in the placement boom were some of

Zoomlion’s requirements for the A4VG.

“The A4VG switches so rapidly and

gently that no such vibration occurs,” says

Christian Frick, project engineer at Bosch

Rexroth in Germany.

As is almost always the case in inter-

national assembly projects, integrating

the different components was a challenge.

The engineers had to make a number of

adjustments to joints and connections for

the axial piston pump to run smoothly in

Chinese machines.

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

gional company in the country concerned

makes our work a lot easier,” explains

Frick. “Working closely with our Chinese

colleagues we were able to grasp all of

Zoomlion’s needs very rapidly.”

Work on the machine began in early-

mid 2012, and was complete by October

that year.

“The use of our axial piston pump in

the concrete pump has had a favourable

effect on the Chinese market and places

products from Zoomlion and Rexroth on

a new level,” says Zhicai Zhang, Bosch

Rexroth’s trade sector manager for

concrete machines in China.

Both Bosch Rexroth and Zoomlion are

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. Pav-

ing Contracts was responsible for laying

the pavers.

Michael Hartley of R.E.E Paving Con-

tracts 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

material comprised 150mm layer of G5

aggregate and all the paving was cement

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

which meant we did not have to cart pavers

up to 50-60m using wheelbarrows.”

The Inanda Club’s redevelopment includes

an exclusive residential component, a new

clubhouse which overlooks a polo field, meet-

ing rooms and a large function ballroom.

convinced that even more world records

will soon be broken in China with the aid

of modern hydraulic technology.

A section of road at Inanda Club paved with 222 x 55mm supplied by Colonial Stone.


32 MeMBeRS’ LIST

Producer members

COMPANy NAME TElEPHONE PROVINCE/COuNTRy PIllAR

A Fick Sementwerke Bk 022 913 2370 Western Cape PB

Aveng Manufacturing Infraset

011 876 5500 Gauteng PB/PI

Bass Beams 031 784 1920 Kwa-Zulu Natal PB

Bay Brick 035 792 5218 Kwa-Zulu Natal PB

Beta Tiles 002634 2925303 Zimbabwe PB

Boland Concrete 021 875 5365 Western Cape PB

Bosun Brick Midrand 011 310 1176 Gauteng PB

Brickbuild t/a Panda 00267 244 2107/8 Botswana PB/PI

Brickcast Industries cc 031 507 5525 Kwa-Zulu Natal PI

C.E.L. Paving Products 021 905 5998 Western Cape PI

Cast Industries 011 316 2375 Gauteng PB/PI

Civil Works 011 903 7023 Gauteng PI

Concrete Units016 362 2236021 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

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 PB/PI

Keystone Walling 082 850 3512 Gauteng PB/PI

Lategan Cement Works 021 873 1154 Western Cape PB

Mobicast (Pty) Ltd 044 874 2268 Western Cape PB

Monier Roofing South Africa 011 222 7300 Gauteng PB

MVA Bricks 012 386 0050 Gauteng PI

Technicrete 011 674 6900 Gauteng PB/PI

Portland Hollowcore Slabs Pty Ltd

021 972 1111 Western Cape PB

COMPANy NAME TElEPHONE PROVINCE/COuNTRy PIllAR

ReMaCon Products cc 011 393 5504 Gauteng PI

Revelstone (Cape) Pty Ltd 021 761 9734 Western Cape PB

Reya Pele Bricks Ltd 016 363 0340 Gauteng PB

Rocla 011 670 7600 Gauteng PB/PI

Shukuma Flooring 041 372 1933 Eastern Cape PB

Smartstone 011 310 1161 Gauteng PB

Southern Pipeline Contractors

011 914 8500 Gauteng PB/PI

Style Décor Pty Ltd 012 376 2454 Gauteng PB/PI

Swakop Tiles cc t/a Namib Roof Tile Company

00264 6446 3717 Namibia PB

Topfloor Concrete 021 951 7700 Western Cape PB

Vanstone Precast Pty Ltd 012 541 2056/1808 Gauteng PI

West End Cement Bricks Pty Ltd

011 851 1005/1063 Gauteng PI

AssociAte members COMPANy NAME TElEPHONE PROVINCE/

COuNTRy

Aspasa 011 791 3327 Gauteng

ARQ Consulting Engineers Pty Ltd 012 348 6668 Gauteng

British Precast Concrete Federation 044 116 253 6161 United Kingdom

Concrete Society 012 348 5305 Gauteng

ILIFA Africa Engineers Pty Ltd 012 362 1473 Gauteng

JC Paving Consulting 011 431 0727 Gauteng

Sekhukhune & Associates 012 993 4776 Gauteng

SNA Civil & Structural Eng 012 842 000 Gauteng

SARMA 011 791 3327 Gauteng

The Job Club 012 661 1099 Gauteng

Terraforce Pty Ltd 021 465 1907 Western Cape

Tjeka Training Matters 011 665 2777 Gauteng

Young & Satharia Consulting Civil Engineers

031 207 7252 Kwa-Zulu Natal

PI - Precast Infrastructure PB - Precast Building


33MeMBeRS’ LIST

cement membersCOMPANy NAME TElEPHONE PROVINCE/

COuNTRy

AfriSam South Africa 011 670 5500 Gauteng

PPC Ltd 011 386 9000 Gauteng

Sephaku Cement 012 684 6300 Gauteng

contrActor membersCOMPANy NAME 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

Valcal International Export 011 867 2471 Gauteng

non-Producer members

COMPANy NAME TElEPHONE PROVINCE/COuNTRy

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

HawkeyePedershaab 00 45 9645 4040 Denmark

Kavango Block & Brick cc 00 264 61 213 632 Namibia

Kaytech 031 717 2300 Kwa-Zulu Natal

Kerenos Southern Africa Pty Ltd 011 444 3090 Gauteng

Kobra Moulds B.V. 003111 356 2460 Netherlands

Manitou SA (Pty) Ltd 011 975 7770 Gauteng

Pan Mixers SA Ltd 011 578 8600/8701 Gauteng

SamJung Industries Ltd 0082542607722 Korea

Schlüsselbauer Technology GmbH & Co KG

004377357144 201 Austria

Sika South Africa Pty Ltd 031 792 6500 Kwa-Zulu Natal

Techmatik S.A. 00484 803 690 811 Poland

MaKe sUre YOU secUre


PRECAST

VOLUME EIGHT ISSUE 1 • 2014

co

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manufacturers

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uality cast in concrete

• Building practice antiquated

• Precast transforms factory into showroom

• Record retaining wall height

YoUR sPot

Contact Charlene for more information:

Tel: 011 883 4627 or E-mail: [email protected]


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anufacturers

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Precast July 2014

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