Precast Magazine

the cma – QUaLItY caSt IN cONcRete

• Adding value to paved surfaces

• Precast kerbing – uplifting communities

• The CMA house

PRECASTVOLUME fiVE iSSUE 2 • 2011

Longlife

• In KOBRA »Longlife™« moulds, the critical wearing areas are protected by additional cavities between the insert layout and weld-on frame parts to achieve optimal hardness properties. In the entire mould bottom, no welding seam is weakening the hardness of the mould insert.

• Compared to conventional concrete block moulds, our moulds are designed for optimal standard hardness quality »carbo 68 plus™« to significantly extend service life and reduce cavity wear.

• Tempered and bolted high quality wear plates cleanly and exactly match the top edge of the mould insert to improve the reconditioning of bolted and welded frame variants of each KOBRA paver mould.

Our understanding of durable hardness:

NEW!

KOBRA »Longlife™« MOULDS IN NEW STANDARD HARDNESS QUALITY 68 HRC.

YEARS OF QUALITY AND INNOVATION

Longlife

• In KOBRA »Longlife™« moulds, the critical wearing areas are protected by additional cavities between the insert layout and weld-on frame parts to achieve optimal hardness properties. In the entire mould bottom, no welding seam is weakening the hardness of the mould insert.

• Compared to conventional concrete block moulds, our moulds are designed for optimal standard hardness quality »carbo 68 plus™« to significantly extend service life and reduce cavity wear.

• Tempered and bolted high quality wear plates cleanly and exactly match the top edge of the mould insert to improve the reconditioning of bolted and welded frame variants of each KOBRA paver mould.

Our understanding of durable hardness:

NEW!

KOBRA »Longlife™« MOULDS IN NEW STANDARD HARDNESS QUALITY 68 HRC.

YEARS OF QUALITY AND INNOVATION

QUALITY MOULDS

PRECAST VOLUME 5 • ISSUE 2 • 2011 1

2 SUPER-PLASTICISERS CRUCIAL TO SELF-COMPACTING CONCRETE

3 TERRAFORCE LAUNCHES FULL RETAINING WALL DESIGN SERVICE

4 REMACON SECURES EXCLUSIVE RIGHTS TO TENSARTECH CRB SYSTEM

6 ADVANCED MIXING TECHNOLOGIES BOOST CONCRETE PRODUCTION

6 WORLD EXPERT LEADS SEMINARS ON PRECAST HOLLOW-CORE FLOORING AND LOAD-BEARING STRUCTURES

7 PPC’S NEW PRODUCTS OFFER 15% MORE VALUE

9 SIKA ADMIXTURES STRENGTHEN PRECAST-CONCRETE TOILETS

9 QUESTIONABLE QUEST FOR GREATER SLAB QUOTAS

10 ACTOM WINS BAG-FILTER CONTRACT FOR CEMENT PLANT

13 BOSUN INTRODUCES LARGE DRY-CAST PAVERS

14 MAPEI SUPPORTS ELDOCRETE WITH PURPOSE-SPECIFIC ADMIXTURES

15 TECHNICRETE PAVERS TRANSFORM GRAVEL ROADS

16 CONCRETE BLOCK PAVING – ADDING VALUE TO PAVED SURFACES

20 PRECAST CONCRETE KERBING – UPLIFTING COMMUNITIES, PROTECTING ROADS

22 THE CMA/C&CI LEGACY- HOUSE PROJECT

24 THE CMA HOUSE – PROVIDING A BLUEPRINT FOR SUSTAINABLE SUBSIDISED HOUSING

28 CMA MEMBERSHIP LIST

PRECAST is the official journal of the Concrete Manufacturers Association (CMA)Block D, Lone Creek, Waterfall Office Park, Bekker Road, MidrandPO Box 168 Halfway House 1685Tel: +27 11 805 6742, Fax: +27 86 524 9216E-mail: [email protected], Website: www.cma.org.za

PublishersIsikhova Publishing & CommunicationsPO Box 651793, Benmore, 2010, South AfricaTel: +27 11 883 4627, Fax: +27 11 883 4627Website: www.isikhova.co.za

Publisher: Andrew MeyerTel: +27 11 883 4627, Cell 082 456 5175E-mail: [email protected]: David BeerTel: +27 11 478 0239, Fax: +27 11 678 0254E-mail: [email protected]: Rui ChirindjaTel: +27 11 883 4627, Cell: 082 717 2851,E-mail: [email protected], layout and production: Joanne Brook

The views and statements expressed in this publication are not necessarily those of the editor or the publishers and neither he/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.

contents

Our front page shows a first

course of modular masonry

being laid using hollow-masonry

blocks in Kleinmond, Western

Cape. Modular masonry forms

the backbone of the CMA House

– see article on page 24 - which

was launched by CMA director,

Hamish Laing, at the South African Housing

Foundation Conference in September. Based

on a 40m² design for Government subsidised

housing, the CMA House provides a blueprint for

the more productive construction of sustainable,

aesthetically-pleasing and thermally-efficient

housing units. Plans of the house are available at

no charge from the CMA.

THE CMA – QUALITY CAST IN CONCRETE

• Adding value to paved surfaces

• Precast kerbing – uplifting communities

• The CMA house

PRECASTVOLUME FIVE ISSUE 2 • OCTOBER 2011

The only SABS-approved dry-cast kerb in SA.

At Bosun, our approach to resolving engineering challenges has always been to simplify and innovate.

That’s why we’ve taken the manufacturing of kerbs further with our revolutionary dry-casting process. This allows us to compact the kerb, making a stronger, more durable end product.

And, making kerbs the Bosun way is kinder to the environment. No acids and chemicals are needed as mould release agents. Another great reason to specify Bosun kerbs on your next civil engineering project.

Visit www.bosun.co.za for even more ideas.

GautengTel (011) [email protected]

Eastern CapeTel (041) [email protected]

North West ProvinceTel (012) [email protected]

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Kerbs Dry-casting means no exposed aggregate or blowholes on the

surface of our kerbs.

The Nelson Mandela bridge in Johannesburg where admixtures supplied by Chryso SA played an important role in the self-compacting concrete used for the project.

Admixtures, particularly new-

generation super-plasticis-

ers, play a vital role in self-

compacting concrete’s (SCC)

ability to flow into complex

shapes and to penetrate

seemingly inaccessible spots.

They also assist in achieving

high strengths and superior

surface finishes.

Global construction chemical materials supplier, Chryso, has two

different ranges of SCC super-plasticisers, Premia for the precast

industry, and Optima used by the readymix industry.

Eddie Correia, Chryso’s general manager: technical services, says

SCC doesn’t require mechanical vibration for high-quality blemish-

free finishes in precast concrete applications.

“Other plusses are fast placement and quick mould turnarounds,

not to mention reduced noise levels which assist with Occupational

Health and Safety compliance.

“The Premia range reduces water requirements, and offers

workability retention of between 30 and 45 minutes and high early

strengths,” adds Correia.

Chryso’s Optima range uses a patented phosphonate technology

to produce cohesive, low-viscous readymix concrete.

“Chryso has the ability to match super-plasticisers to the soluble

alkalis and sulphates in the cement. We also assist in finding the

best possible admixture/cement compatibility. This is why there are

so many products within the Optima range,” says Correia.

“One such product is Optima 100, a super-plasticiser that

extends slump retention and is compatible with the majority of

cement types. Optima 100 is not water sensitive and produces

robust, non-sensitive mix designs that are easily implemented,”

explains Correia.

A significant challenge is that South Africa typically uses dry-

batch plants for SCC production. This leaves little room for error

as the mix design has to be correct upfront. Therefore it is very

important to receive the correct technical advice.

Brenton Brouard, Chryso’s concrete laboratory manager, says

Chryso can provide all the required technical support. “We look at

a customer’s raw materials, pick the appropriate admixtures, and

create a mix design that meets all requirements.

“Due to the sophisticated nature of SCC, there has to be a

strict control of mix-design technology. In order to make SCC with

consistent accuracy and acceptable quality, a homogenous mix has

to be created using the same raw materials from the same suppliers

and factories,” he adds. P

SUPER-PLASTIcISERS CRUCIAL tO seLF-COMPACtInG COnCRete


[email protected]: +27 11 970 3880 Master Reseller

Microwave Moisture Measurementfor Concrete and Aggregates

The Hydro-Probe Orbiter for mixers:• Rotates through the mix• Rapid response to moisture change• Hardened Ceramic Head• Replaceable sensor arm

The Hydro-Probe II for aggregate bins and chutes.• Accurate, consistent, real time moisture measurement• Linear, with temperature stable output• Remote calibration and confi guration• Easy to interface

The Hydro-Probe Orbiter for mixers:

Birkenmayer half page horizontal 146 x 210 plus 5mm bleed.indd 1 14/04/2011 08:44:42

This retaining wall was built in Williams Lake, British Columbia, Canada, by a Terraforce licensee using Terraforce L18 Split Face retaining wall blocks.

Since 1979, when Terraforce was founded,

the company has assisted specifiers with

design services in the form of purpose-made

tables, design manuals, spreadsheets and

a windows-based design programme for

segmented block retaining walls. And on the

odd occasion the company has also provided

a full design service and site supervision.

This design service has now been formal-

ised with Terrasafe, a first-class engineer-

ing, management, and specialist technical

service available to users of Terraforce

products in many parts of the world.

Holger Rust, managing director of Terra-

force, says that Terrasafe is premised on a

handle the site supervision on our behalf.”

Terraforce has built its name on the

reliability of its retaining walls and superior

product quality. Well before the SABS/

SANS specification for concrete retaining

blocks (CRB’s) came into being, the company

went offshore to ensure that its products

met international standards. For example,

in the 1990s it obtained a comprehensive

evaluation report on its L18 block from the

International Council of Building Officials

(ICBO) in California in compliance with

the USA’s National Concrete Masonry

Association (NCMA) specifications. P

management system which addresses con-

ceptual, feasibility and planning activities as

well as the design, construction, operation

and maintenance phases of each project.

“Terrasafe adds considerable value

by ensuring that high quality levels are

maintained through each stage of the

project cycle. With more than 30 years

experience in the proper design and

execution of retaining wall projects, not

to mention some extensive research and

development work, engineers are happy to

rely on our expertise in providing designs

which meet all the requirements for proper

construction practice and safety aspects.”

“Moreover, in addition to providing proper

and fully-specified retaining wall designs

we have appointed several recommended

installers who know how to follow our

designs to the letter. Based in many parts

of the world, they adhere to our guidelines

and guarantee their workmanship. In remote

areas, where recommended installers don’t

exist, we liaise with local engineers who

TERRAFoRcE LAUncHES FULL RetAInInG WALL DesIGn seRVICe

PRECAST VOLUME 5 • ISSUE 2 • 20114

REMAcon SEcURES EXcLUSIVE RIGHTS tO tensARteCH CRB sYsteM ReMaCon Products has negotiated the

exclusive rights for local manufacture of

the well-proven Tensartech TW1 System

of concrete retaining blocks (CRB) -

designed for constructing retaining walls

over 20m high.

“This is a coup for us because the

Tensartech TW1 System opens the way

for us to provide retaining wall designs

on large civil projects which are more

competitive and advantageous than

incremental panel systems,” commented

Sil v io Ferrar is, ReMaCon Product’s

managing member.

“The maximum height currently attain-

able with locally-produced retaining blocks

is seven metres at a slope of 86 degrees.

“The Tensartech TW1 System can be

built as a single structure up to a height

of 20m plus at a slope of 86 degrees. It is

suitable for highways, railways and other

public embankment structures for which

standard retaining block walls are not

suitable,” Ferraris points out.

Developed by Tensar International

of the UK, the system comprises a

specially designed TW1 block combined

with Tensar uniaxial geogrids made from

high density polyethelene (HDPE). The

geogrids are attached to the blocks and

extend horizontally into the soil mass

behind them, thereby turning the whole

structure into a monolithic solid mass.

Available from Kaytech, the Tensar geogrid

reinforcement and connectors are highly

durable and resistant to chemical and

biological attack.

“The system offers huge construction-

cost savings over conventional reinforced

concrete designs which are extremely

expensive. Cranes have to be used to

install them and metal strips have to be

attached to the panels to secure the

structures. In addition, a high-quality and

more expensive fill material sometimes has

to be used,” explains Ferraris.

By contrast, the TW1 system is

erected without the need for heavy lifting

equipment and can be erected using site-

won or recycled fill materials.” P

A close-up view of the new TW1 concrete retaining blocks and the Tensar uniaxial geogrid.

Birkenmayer Ad x3.indd 1 3/11/11 5:07:47 PM


ADVAncED MIXInG TEcHnoLoGIES BOOst COnCRete PRODUCtIOnEirich RV19 and DEV16 concrete mixers,

supplied locally by Birkenmayer, use ad-

vanced mixing technologies which shorten

mixing times and boost the production

of top quality concrete blocks for paving,

retaining wall and masonry applications.

“The RV19 and DEV16 mixers also offer

optimal homogenisation of cement, aggre-

gates, admixtures, and water,” says Louis

Eksteen, business development manager,

Birkenmayer. “Moreover, shortened mixing

times mean that the risk of spoiled batches

is greatly reduced,” he explains.

Eksteen says that Eirich mixers feature

long-lasting designs which experience little

wear and require minimal maintenance. This

drastically reduces downtime and helps

block-making plants operate at maximum

capacity for maximum profits.

The Eirich RV19 forms part of the

diverse R-type mixer range and features

an inclined pan as well as macro and micro-

mixing technology. The latter ensures

an intensive vertical mixing action –

eliminating the risk of cement and moisture

layers forming.

The Eirich DEV16 mixer has been us-

ing flat-pan technology since 1961 and is

effective in the most arduous of mixing

applications.

Mix qualities in both models can be fur-

ther optimised through the incorporation

of Hydronix moisture measurement and

control instruments.

“Sensors can measure the tempera-

ture and moisture levels inside mixers –

helping to ensure consistent quality with

every batch,” concludes Eksteen. P

An Eirich concrete mixer which is helping block makers achieve top quality results with superior homogenisation and shorter mixing times.

October saw world-renowned precast

concrete expert, Dr K im S. E l l iott

presenting three full-day seminars on

precast hollow-core flooring and loading

bearing structures.

Aimed at professional design engineers,

architects and graduate students in civil

engineering, building technology and archi-

tecture, the seminars were hosted and

organised by the Concrete Manufacturers

Association (CMA) in collaboration with the

Concrete Society in Johannesburg, Port

Elizabeth, and in Cape Town.

CMA director, Hamish Laing, said the use

of precast concrete multi-storey framed

buildings was taking hold in South Africa.

“It is widely regarded as an economic,

structurally sound and architecturally

versatile form of construction for buildings

up to 40 storeys, although the maximum

height reached in South Africa to date is

five storeys.”

Dr Elliott commented that prestressed

hollow-core slabs combine the benefits

of very rapid construction and high

quality materials with the advantages

of production line economy and quality

assurance, particularly when used as

prestressed concrete floor slabs.

“These seminars encouraged the widest

possible appreciation of the proper use

of precast concrete for innovative and

modern buildings.”

Dr Elliott is a self-employed consultant

to the precast industry in UK and Malaysia.

A BTech, PhD, MICE, CEng, he was senior

lecturer in the School of Civil Engineering

at Nottingham University, UK, and has also

worked for Trent Concrete Structures

Ltd., one of the UK’s leading precast

concrete manufacturers.

Since 1987, Dr E l l iott has been

researching the behaviour of precast

concrete structures, and has published

more than 120 papers and four text books.

He has chaired the European research

project COST C1 on semi-rigid connection

in precast structures and has lectured on

this subject over 40 times in 16 countries,

including Malaysia, Singapore, Brazil, South

Africa, Austria, Barbados, Portugal, Spain,

Scandinavia and six times in Australia. He

has lectured at over 30 UK universities. P

WoRLD EXPERT LEADS SEMInARS On PReCAst HOLLOW-CORe FLOORInG AnD LOAD-BeARInG stRUCtURes

Dr Kim S. Elliott

Seen here at the Johannesburg seminar are Monique Eggebeen, managing director of the Echo Group, Dr Kim S. Elliott, Daniel Petrov, technical director of Echo Prestress, and Hamish Laing, CMA director.


EcHo

PPc’S nEW PRoDUcTS OFFeR 15% MORe VALUeOne of the country’s leading cement

producers, Pretoria Portland Cement

(PPC), has announced a signi f icant

enhancement of its product range. The new

products facilitate the production of 15%

more concrete of equal or higher quality

than they have done in the past using the

same amount of cement.

PPC’s OPC (CEM I) cement has changed

from a 42.5N to a 52,5N classification, and

its Surebuild cement has been upgraded

from a 32,5R to 42,5N. Apart from

reducing the concrete material cost per

cubic metre, these new products also offer

other productivity benefits to builders

and contractors. Some notable examples

include faster strength development,

quicker removal of formwork and faster

floating and finishing of concrete floors – all

of which result in optimal use of labour and

significant downstream savings.

According to Richard Tomes, customer

executive at PPC, the research and

development (R&D) arm and the staff at

PPC operations have been working together

to achieve higher and tighter specifications

that will ensure that end users get more

yield out of every bag of cement.

“For example, a project using 100 bags

of normal general purpose cement for

casting floors would typically yield 70m2.

However, with PPC’s new 42,5N Surebuild,

the same project using the same number

of bags will allow the builder to produce at

least 10,5m2 more,” says Tomes.

“We are taking a clear message to the

nation - that PPC and its cement products

not only have the ability to help customers

realise their construction dreams, but also

the compassion to better the lives of every

citizen,” commented Tomes.

“PPC is an iconic brand and its cement

has been used for the past 119 years. It

will continue being used to build South

African landmarks, its infrastructure

and major construction projects, just

like it did with the Union Buildings, Gariep

Dam, Van Staden’s River Bridge, Gautrain

infrastructure and Afr ica’s biggest

stadium, Soccer City,” concluded Tomes.

The new products are available in the

Gauteng, Mpumalanga, Polokwane, North

West, Free State, Lesotho and Swaziland. P

A5 advert Landscape 5/7/09 9:06 AM Page 1

Composite

C M Y CM MY CY CMY K

CONCRETE MANUFACTURERS ASSOCIATION

Block D, Lone Creek, Waterfall Office Park, Bekker Road, Midrand

PO Box 168 Halfway House 1685

Tel +27 11 805 6742 • Fax +27 86 524 9216 • E-mail: [email protected]

RECOURSE

COMPLIANCE

GUARANTEE

CONSISTENCY

EXPERTISE

DURABILITY

VALUE FOR MONEY

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CAST IN CONCRETE

WWW.CMA.ORG.ZA

0861 SMART1 (0861 762781)

www.smartstone.co.za

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60

Natural Beauty.Engineered Quality.

Sika’s concrete admi x-

tures have been used to

strengthen concrete slabs

for the assembly of 5,750

precast-concrete toilets.

Manufactured by Rocla, the

ventilated-pit toilets were

installed in Mkhwanazi and

South Dube, rural areas

located within the greater City of Umhlathuze (Richard’s Bay).

Sika’s admixtures, Viscocrete-3088 (2,000 litres) and

Viscocrete-20HE (5,000 litres) were used in the casting

process and Sika’s MonoTop-610 coating was applied to the

steel reinforcing P

SIKA ADMIXTURES STREnGTHEn PReCAst-COnCRete tOILets

One of 5,750 precast-concrete toilets manufactured using Sika’s concrete admixtures and installed in the rural districts of the City of Umhlathuze (Richard’s Bay).

Topfloor director, Peter Lord, cautions hollow-core concrete

floor slabs users that some Western Cape suppliers are pursuing

questionable quoting practices to secure business in the highly

competitive slab market.

Lord identified three typical examples.

“One is for a supplier to issue a ‘budget’ price when asked

for a quote. This should be an immediate danger signal. Unlike a

quotation, this can be altered at any time after acceptance, with

the excuse that various additional items had not been costed. My

advice to the purchaser is to insist on a formal quote and never

accept so-called budget quotes. This then puts the onus on the

supplier to get it right the first time,” explains Lord.

Another common ruse was for a supplier to fix a price for a

ridiculously short period and then subject the price to an escalation

of up to 2% a month.

“Thirdly, some suppliers in the Cape market give the impression

that they are SABS-certified. The fact is that no supplier in the

Western Cape can claim the SABS mark. Topfloor, however, is

close to achieving the mark and ISO 9002 certification, and will

most probably be the first hollow-core slab manufacturer to

achieve this status.”

Topfloor is a member of the Echo Group, which is SABS- and

ISO-certificated, and is the country’s largest manufacturer

of hollow-core concrete floor slabs. Its advanced hollow-core

technology, developed over 27 years, is being directly applied in

Topfloor’s Cape manufacturing operations. P

QUESTIonABLE QUEST FoR GReAteR sLAB QUOtAs


PRODUCTS.CC

011 393 5504

www.remacon.co.za

[email protected]

OFFERING A PROFESSIONAL

APPROACH TO RETAINING

WALL BLOCK STRUCTURES

* TW1

* TW1

* TW1 Retaining block wall, Licensed by Tensar International to

ReMaCon for 86 degree slopes to heights exceeding 20m.

* TW1

* TW1

AcToM WInS BAG-FILTER conTRAcT FoR CeMent PLAntManager on the project, said ACTOM Air

Pollution Control was awarded the bag

filter contract on the basis of price and

conformance to PPC’s tender, technical

speci f ications and guaranteed dust

emission limits. P

Pretoria Portland Cement Company Ltd

(PPC) has awarded a turnkey contract

to ACTOM Air Pollution Control (formerly

MikroPul) to replace a kiln 6 electrostatic

precipitator with a reverse-pulse bag-

filter at its De Hoek cement plant near

Piketberg in the Western Cape.

The supply of the new 350 000m3/hr

capacity bag filter forms part of an extensive

upgrade and expansion programme which

includes converting the existing coal-fired

system to a new indirect coal-fired system

and the installation of a multi-channel

kiln burner. It also involves replacing kiln

shell sections and riding rings, as well as

replacing a satellite cooler with a new

generation grate cooler.

The contract includes the design,

manufacture, supply, installation and com-

missioning. Site construction is scheduled

to commence at the beginning of 2012,

and the bag filter is due for commissioning

in June 2012.

The new f i l ter is being designed

to reduce dust emissions in line with

Minimum Emission Standards as outlined in

Section 21 of the National Environmental

Management: Air Quality Act, 2004 (Act

No. 39 of 2004) and will be fitted with

glass-fibre bags capable of withstanding

temperatures of up to 260 degrees C.

Gerard Pretorius, ACTOM air pollution

control’s sales manager, says that the bag

filter and associated equipment will serve

the main kiln and raw mill.

“The existing forced-draft fan is to be

replaced with a higher-capacity induced

draft fan and a new material handling

system will collect, transport and feed

the collected dust back into the clinker

production process,” he explained.

L izé We lgemoed, PPC’s Pro ject

This ACTOM Air Pollution Control bag-filter plant, installed several years ago, is similar to the system which will be installed at PPC’s De Hoek cement factory in the Western Cape.

Superiorconcrete surfaces

An environmentally friendly vegetable oil based mould release agent for aesthetic and architectural concrete.

CHRYSO®Dem Aqua 100 is a safe, environmentally friendly and biodegradable product that helps the construction industry to meet its sustainability goals while achieving the perfect concrete finish.

CHRYSO®Dem Aqua 100 offers the following distinct advantages:

■ Environmentally friendly and safe to use■ High quality surface finish■ Formwork protection■ Consistent and economic coverage

CHRYSO: We have the solutions to build the future you imagine

To find out more about the CHRYSO®Dem Aqua 100 range please contact CHRYSO where one of our technical professionals will assist you.

W W W . C H R Y S O . C O M

CHRYSO Southern Africa (Pty) LTD (Head Office - Johannesburg)T : +27 (0) 11 395 9700 F : +27 (0) 11 397 6644 E : www.chryso.comSharecall: 0861 CHRYSO

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ADHESIVES • SEALANTS • CHEMICAL PRODUCTS FOR BUILDING

www.mapei.co.za

Accelerated development of mechanical strength

Optimisation of production cycles and strong reduction of maturing cycles

To solve specific problems encountered in the precast concrete industry and to strongly contribute to the development of this sector, Mapei has developed the DYNAMON NRG and DYNAMON SP product ranges. These products are specifically intended for this type of application and are especially suitable for manufacturing self compacting concrete.

Contact us: +27 11 552 8476 or [email protected]

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D110204 Mapei DYNAMO2 Ad.ai 1 09/05/2011 21:34


The Bosun Group has introduced the

Urban range of non-bevelled dry-cast

concrete pavers.

CEO, David Wertheim Aymes, says

the 300mm x 400mm paver forms the

backbone of the Urban range but is

complemented by two other pavers,

the 150mm x 200mm and the 100mm x

200mm blocks.

“All three are 60mm thick and are

suitable for walkways and driveways.

The pavers can either be installed in one

uniform size or can be combined in either

two or three sizes in various patterns.”

Wertheim Aymes comments that it

is very difficult to produce these large

pavers using dry-casting.

“However, we have invested in world-

class manufacturing equipment and the

advantages are immense. Dry-cast pav-

ers yield higher compressive strengths

than their wet-cast alternatives, and

do so much more cost-effectively. They

also don’t require cement grouting or

screeds. This makes it practical to remove

and, if necessary, replace the pavers when

doing underground work such as pipe laying

or plumbing.”

Bosun has identified three diverse

target markets for the Urban range.

• The smooth, unique design comple-

ments modern architecture in an unprec-

edented manner.

• Due to the unbevelled surface, the

pavers are ideal for trolleys in shopping

complexes and hospitals.

• City Councils have also shown a clear

interest in the pavers for sidewalks and

other public areas.

Wertheim Aymes explains that Urban

pavers are specialist products and their

installation should adhere to strict SANS

1200MJ specifications.

“As with any paving installation, the

earthworks are one of the most important

aspects, and if poorly executed, will result

in certain site failure. Apart from this,

contractors might need special installation

equipment to accurately lay the 300mm x

400mm paver and Bosun has launched a

range of installation equipment specifically

for this purpose.”

Contractors interested in becoming

authorised installers of Bosun Large

Pavers, should contact the company.

The Urban paver is available in all 10

Bosun colours, including the recently

introduced Granite and Marble, which are

produced with imported, white cement. P

BoSUn InTRoDUcES LARGe DRY-CAst PAVeRs

Bosun’s new Urban range of non-bevelled dry-cast concrete pavers in a commercial setting.


MAPEI SUPPoRTS ELDocRETE WITH PURPOse-sPeCIFIC ADMIXtUResMapei South Africa Pty (Ltd) is assisting

Eldocrete, a Centurion-based precast

concrete manufacturer, boost production

and pro f i tab i l i t y w i th customised

admixtures. They reduce setting times,

lower production costs, and facilitate

the production of consistently superior

precast concrete products.

Mapei admixtures product manager,

Antony Of fenberg, says that Mapei

supplies Eldocrete with an accelerating

super-plasticiser, Dynamon NRG1020,

to speed up production. Although it has

a limited workability period, it allows for

substantially improved early strength gains

and increased productivity. It also reduces

the amount of cement required without

compromising on strength.

Mapegrout Rapido, a shr inkage-

compensation rapid-set repair mortar, also

makes up part of Eldocrete’s comprehensive

Mapei offering. Any deterioration or damage

to vertical or horizontal concrete surfaces

can be repaired with Mapegrout Rapido. It

is a fast-setting, easily-trowelable mortar

with excellent thixotropic properties, and

is suitable for applications up to 2.5cm Mapei admixtures shorten curing time and increase Eldocrete’s overall output.

Some of the moulds used by Eldocrete to shape and set concrete using Mapei admixtures.

thick. It sets within 30 minutes, and is

then already strong enough to carry loads.

As part of its customer service Mapei

offers a purpose-built dosage system.

Either weight or volume-specific, the

system allows the accurate and quick

dispensing of admixtures.

Werner Viljoen, a managing member at

Eldocrete, says “We’re excited to be work-

ing with Mapei which has demonstrated

how it can add value to our production.

Its enthusiasm in proving the effective-

ness of its products has built confidence

between us.” P


Pr ecas t -p r oduc ts manu f ac tu r e r,

Technicrete, is accelerating the pace

of rural infrastructural development

through the transformation of hundreds of

kilometers of gravel roads with concrete

block paving (CBP).

Following extensive CBP upgrading

projects in rural and urban areas of Limpopo

Province, the focus has moved to the North

West, Northern Cape and Free State

provinces where government initiatives are

being used to raise road standards.

As in the Limpopo projects, Technicrete’s

Double Zig-Zag interlocking concrete

pavers have been the surface of choice

for specifiers. These heavy-duty blocks

are being manufactured at the Murray

& Roberts Building Product’s plant in

Stilfontein, Free State.

Tens of thousands of square metres of

60mm and 80mm blocks are being laid in Technicrete’s interlocking double zig-zag concrete paver has transformed what was a dusty track into a modern road.

Birkenmayer Ad x3.indd 2 3/11/11 5:06:31 PM

TEcHnIcRETE PAVERS tRAnsFORM GRAVeL ROADs seven separate rural road upgrading op-

erations now under way in the three prov-

inces, serving chiefly rural communities.

They include: the Carnivore location in the

Northern Cape; Khuma, Gopane, Sannieshof

and Delareyville in North West Province;

and Viljoenskroon and the Alabama location

outside Klerksdorp in the Free State. P


The days when one could buy concrete block paving (CBP) in any colour, provided it was grey, are long gone. On the contrary, today’s specifier is spoilt for choice.

concRETE BLocK PAVInG – ADDInG VALUe tO PAVeD sURFACes

According to the Concrete Manufacturers

Association (CMA), not only is the

traditional concrete block paver available

in virtually any colour combination but

there are several different types of paving

surfaces ranging from cobbles which mimic

natural stone, to high gloss finishes and

exposed aggregate surfaces. They are also

available in numerous sizes, thicknesses,

shapes and strength ratings.

CMA director, Hamish Laing, says many

value-added surfaces have been available

for decades, and in the early days, the

challenge lay in developing machinery to

produce large volumes efficiently and

consistently.

“For example a typical bush-hammered

surface was initially manufactured by

hand with only a few square metres being

produced daily. Machines by contrast can

produce 1 000s of square metres per shift.”

Most European and American producers

have a var iety of di f ferent sur face

processing options, Holland and Germany

having been the initial innovators. This

diversity is now global and the standard

grey concrete paver has been transformed

into a product which offers great versatility

and added-value potential.

Laing comments that surfaces which

have been washed (exposed aggregate),

bush-hammered (chipped surface, facing

aggregates and corners) ground surfaces,

ground and polished surfaces, shot-blasted

surfaces and tumbled or artificially aged

surfaces are available in South Africa.

“These are usually suitable for the

majority of regular applications, however,

not all producers supply all types of Concrete block pavers with an exposed aggregate finish are used to good effect on this path.


value-added paving surfaces, and some

varieties, such as bush-hammered, are

only manufactured on demand. Although

there is a cost premium, due to the special

materials and additional work in value-added

CBP, this is offset by improved durability

which in most instances is higher than the

specified standards.”

Specialised machinery and computerised

concrete batching play a substantial role

in obtaining the required results and the

best finishing technologies are to be found

in Germany and Italy.

Laing adds that one of the value-added

pav ing sur faces to which landscape

architects, pav ing consultants and

specifiers are paying increasing attention

is exposed aggregate paving (EAP).

“Although the technology has been

around since the early 1900s, its adoption

in South Africa is much more recent,

having first been introduced some 20

years ago. Five producers, two in Gauteng,

two in the Western Cape, and one in

KwaZulu-Natal, offer the product locally.”

EAP’s marginal market penetration to

date has been largely due to price which is

often the prime driver in the specification

of paved surfaces. EAP comes with a 20 –

30% cost premium over conventional CBP

and must compete with several lower-cost

alternatives.

However, it offers some substantial

benefits in both the aesthetic and practical

realms, benefits which over the long-term

far outweigh any initial capital premium.

Moreover, when compared to other

decorative CBP products such as con-

crete cobble, clay brick and polished in-situ

concrete paving, there are considerable

cost savings to be had, varying from

20 – 60%.

So what is EAP? In a nutshell it is a

form of concrete block paving which uses

embedded aggregates, in the first instance

for its decorative attributes, but equally for

its outstanding durability. Either sourced

from quarries or manufactured, exposed

aggregates can achieve spectacular and

unique visual effects at a reasonable cost.

For example, high concentrations of

aggregate mean that a path paved with

exposed aggregate pavers can be made to

look like a gravel path. With hard wearing

surfaces capable of handling heavy traffic,

EAP offers unlimited colour and textural

variations and this aesthetic versatility is

what is luring today’s landscape designers.

Ideal for public spaces, pavements,

driveways and patios, EAP requires very

little maintenance other than sealing

and occasional cleaning. The application

of a transparent concrete sealer to an

exposed aggregate surface improves its

performance and appearance.

There are essentially two methods

of manufacturing EAP. One involves

placing a retardant in the concrete mix

which slows down the curing process on

the surface. Surface cement is either

brushed or washed away to expose the

aggregate. A more common alternative,

especially in Germany, involves placing

paper, impregnated with a retardant, on

the surface of the pavers. The advantage

here is that the retardant only affects

a few millimetres on the surface of the

pavers which can then be brushed away.

An EAP variant is found in terrazzo

finishes. Introduced locally in 2009 by a

small Cape Town-based manufacturer, it

involves burnishing the upper surface of

the paver to expose the aggregate which is

densely packed beneath. The surface then

gives the impression of movement similar

to those in other types of EAP, but has

the advantage of being completely smooth.

The appearance mimics that of traditional

terrazzo, and because the aggregate is

so dense, the result is a finish which is

much finer than those achieved with normal

polished concrete pavers.

Today’s specif ier must also decide

whether the paving surface should be

traditional, in which case rain water is

prevented from penetrating the paved

surface, or permeable which is designed

An example of permeable interlocking concrete paving blocks during the laying process.

A concrete block Terrazzo paver with a quartzite and sandstone blend topping.

A concrete block paver with a charcoal bush-ham-mered topping.


• Long lasting• Labour intensive and interlocking• Projects remain as good as new after many years

precast products

paving concrete masonry

retaining walls

erosion protection

drainage kerbs

Tel: 0861266267www.technicrete.co.za

PAVED ROADS

Technicrete Double Zig-Zag Interlock pavers are the answer to low-maintenance roads:

Paved Roads.indd 1 8/11/10 4:31 PM

An example of a locally-manufactured non-bevelled dry-cast flagstone paver.

to allow water to inf iltrate beneath

it. Still in its infancy in South Africa,

permeable paving comes with considerable

environmental plusses including water

conser vat ion, more cost-e f f ect i ve

stormwater and pollution control.

Laing says that dry-casting is the more

common method of CBP manufacture,

accounting for at least 90% of pavers

produced in South Africa. It uses a damp

or semi-dry mix which holds its shape

before curing. By contrast wet-casting

involves pouring a porridge-like mix into a

mould and will only retain its shape some

24 hours later.

“The advantage of wet-casting is that it

yields a perfect replica of the materials being

imitated such as stones, rocks, granite or

marble. However, it is a considerably more

expensive process. For example, the selling

price of a typical dry-cast paver would be

between R60 – R75/m², whereas exactly

the same material content using wet-

casting would fetch anything from R150 –

R200. However, huge advances have been

made with dry-casting and it produces an

excellent product.”

Because of these advances dry-

cast f lagstone pavers are now being

manufactured locally. South Africa looks

set to follow the trend in Europe where

the use of flagstone pavers is on the

increase. These pavers are ideally suited

to public squares, paths and pavements,

shopping malls, inner courts, patios and

swimming pool surrounds.

“Half the reason why wet-casting is so

expensive is that it is very labour intensive.

Also the colour blending in wet-casting

is difficult, being part art, part science,

and manufacturers are still limited to

three colours. The Germans have made

considerable progress in automating wet-

casting and the Italians are using a wet/dry

process with 75 – 80% of the tile being

dry-cast,” concludes Laing. P


Road-side kerbing is comparable to the soil upon which it rests – something we see every day but take for granted, rarely giving a thought to the essential structural and environmental role it plays.

Kerbs are typically located at the edge

of urban and suburban roads, providing

defined demarcation between roads and

pavements, various types of barriers, as

well as drainage conduits. Roads without

kerbing develop ragged edges which are

prone to water ingress, potholes and the

eventual disintegration.

Un-kerbed roads, according to Nico

Swart, technical director of Bigen Africa,

a major civil engineering consultancy,

require f ar more maintenance and

can break up within 10 to 15 years,

whereas they should last 20 years or

more when kerbed.

“Without the efficient stormwater

drainage kerbing provides, most roads

have to be rebuilt in less than 20 years.

There is no doubt that viewed solely

in financial terms, let alone from any

other standpoint, kerbing is a sound

infrastructural investment,” says Swart.

It has another equally important role; it

appears formal and properly finished and

is one of the factors which differentiate

suburban from rural landscapes. It also

has a very positive and uplifting effect on

the communities in which it is installed,

especially in less affluent areas where the

introduction of paved roads with kerbing

and pavements can rapidly transform

shanty towns into aspirational suburbs.

This fact was not lost on Soweto resi-

dents who have insisted on the kerbing of

all their roads as part of a road-surfacing

programme completed recently on behalf

of the Johannesburg Roads Agency. The

project, which involved the installation of

more than 700km of kerbing at +-R200

a linear metre, was begun in 2003 and

completed in 2005, a year before the

target date.

“The then mayor of Johannesburg,

Amos Masondo, said he wanted the

project completed within five years and we

bettered that thanks in the main to the use

of precast concrete kerbs. Similar kerbing

projects are now being run in other areas

such as Orange Farm in the south and

Diepsloot and Ivory Park in the north. And

the Ekurhuleni Metropolitan Municipality is

running various street upgrade projects in

its townships.

“The Soweto road upgrade demon-

strated conclusively that precast con-

crete is the most suitable material for

township kerbing in the South African

environment. However, we began the

UPLIFtInG COMMUnItIes, PROteCtInG ROADs

PREcAST concRETE KERBInG –

Kerbing under construction in a commercial district.

An example of neat kerbing which formalises the border between township roads and pavements.

Where the rot begins – the verge of an unkerbed road showing signs of early disintegration.


project using cast in-situ and extruded

concrete. This proved to be the wrong

choice and within the first few weeks

we realised that it wasn’t working. In

the first instance the skills required to

cast neat kerbs were hard to come by,

and secondly, members of the community

vandalised the freshly constructed kerbs

with graffiti, foot/hand prints and bicycle

tracks. Kerb extrusion is a first-world

process where one operator can produce

500m of kerbing in a day. By contrast,

we found that precast kerbing creates

jobs and is more socially acceptable in

South Africa.

“It worked very well in Soweto. It

was easy to install and the end result

was very satisfactory. And it definitely

does uplift communities. If one drives

down any kerbed street in Soweto it

looks neat and inviting. We found that

soon after the kerbing was completed

people were creating gardens and tidying

up generally. Many township roads are

tarred but it is the kerbing which provides

the psychological boost for community

members to improve their immediate

environments. In fact it’s plain to see that

the JRA’s road and kerbing programme

has transformed Soweto from township

to suburban status.

“We used local contractors and local

labour to lay the kerbing in Soweto. We

initiated accredited training programmes

and registered the workers with ASETA.

Sub-contracting teams generally comprised

eight people and they were responsible for

the preparation work, the laying and the

alignment. If the kerbs were not neatly

aligned we insisted on them being re-done

until they met our specifications.

“Each time we moved into a new ward

we trained a new team and this process

was repeated many times over. We are

currently running a similar roads and

kerbing project on behalf of the Ekurhuleni

Metropolitan Council and many of the

people trained by us, both in Soweto and

Ekurhuleni, are now using these skills to

lay driveways and other forms of paving.”

Some o f the o l de r subur bs i n

Johannesburg and Pretoria are stil l

without kerbing and the local authorities

are currently running kerbing installation

programmes to improve pavements in

their areas.

“In suburbs such as Pretoria’s Brooklyn

the roads were built quite deep so the main

motivation for kerbing in this instance is

aesthetic rather than function based. New

roads definitely need kerbing, to prevent

water ingress, to set an even height for

pavements and to prevent damage to them

and the roads.”

Swart concluded by commenting that

not all kerbing projects go according to

plan and examples of badly installed kerbs

do exist. This is mainly due to a lack of skills

and poor training. P


THE cMA/c&cI LeGACY-HOUse PROJeCt Initiated by a common interest in human settlements, the Concrete Manufacturers Association (CMA) and the Cement & Concrete Institute (C&CI) have embraced the opportunity to showcase the sustainable use of concrete in the International Housing and Home Warranty Conference (iHHWC) South Africa 2011 Legacy Project. CMA members donated modular concrete masonry blocks and other precast concrete building materials, and architectural and technical expertise was provided by the C&CI.

The CMA Legacy House Project under construction in Cape Town using two types of modular masonry and precast hollow-core slabs.

legacy to the International Housing and

Home Warranty Conference (IHHWC), an

event which was hosted by the NHBRC and

which took place on African soil for the

first time this year. The actual conference

was held at the CTICC in Cape Town from

the 25th to 28th September .

Besides the donation of bui ld ing

material by CMA members, the CMA

appointed local professionals and modular

masonry experts to ensure the success

of the project. The CMA shared design

and buildng costs with the NHBRC on a

50/50 basis.

The houses were built in Blue Downs, a

suburb of Cape Town some 30km from the

CBD. Each double-housing unit comprises

two 60m² semi-detached double-storey

apartments. Ground floor sections include

a living area, a kitchen and a bathroom

Manufactured using 100% South African

concrete, the building materials were

used for the construction of one of

four affordable double-housing units to

demonstrate the cost–effectiveness of

building with proper modular masonry and

other precast concrete elements. The

other units were built using alternative

building materials and methods.

“This project was for a worthy cause

and formed part of the CMA social

responsibility programme. The houses were

given to particularly needy people on the

Government’s waiting list for subsidised

housing,” said CMA Director Hamish Laing.

“The project also gave us the opportu-

nity to showcase our members’ concrete

products as a live billboard side-by-side

with other building methods,” said Laing.

The project was officially and appropri-

ately launched during a sod-turning cer-

emony on July 18th, Madiba Day (Nelson

Mandela’s birthday), by the Minister of

Human Settlements, Tokyo Sexwale. Also

in attendance were Cape Town’s mayor,

Patricia de Lille and acting CEO of the

NHBRC, Jeff Mahachi.

The houses were built as a tangible


while the upper levels accommodate two

bedrooms. The houses share a central

stairwell divided by a wall to provide each

semi-detached unit with its own staircase.

Two types of modular masonry, one us-

ing conventional mortar (10mm thick) and

blocks made from recycled material and

the other with thin-bed mortar blocks,

were used to build the CMA unit.

“One o f our objecti ves with the

Legacy Project,” says Laing, “is to

demonstrate how modular masonry and

precast concrete building materials

offer anyone investing in entry level or

affordable housing a building system which

is difficult to beat in terms of productivity,

durability and aesthetic appeal. And unlike

alternative building methods, there is

a large labour component in the CMA’s

Legacy house.”

Bes ides masonr y b l ocks, o ther

precast concrete products donated by

CMA members included precast hollow-

core slabs for the first floors, precast

concrete staircases, concrete roof

tiles, polymer concrete door and window

frames, and concrete blocks for the apron

around the house and driveway.

“Precast hollow-core slabs speed up

the entire construction process, allowing

masonry and other construction work

to continue as soon as they are laid.

Another advantage is that they are made

in a controlled manufacturing environment

which ensures the structural integrity and

quality of the product.

“Concrete roof tiles, besides offering

excellent thermal and weather-proof

properties, can convert a very ordinary

look ing house into something real ly

special, simply through their outstanding

aesthetic appeal. This is why an increasing

number of entry-level housing projects are

opting for this type of roofing.

“Concrete block paving (CBP) laid

around the Legacy house finished off the

project very neatly. CBP also added a

practical dimension, by preventing mud

from spattering the walls during the rainy

season,” comments Laing.

The main contractor on the two CMA

houses was Breekon Construction, a

construction company familiar with and

committed to modular construction,

Tokyo Sexwale, Minister of Human Settlements, addresses visitors, professionals and construction workers at the CMA Legacy House Project on Madiba Day (Nelson Mandela’s birthday), at the project’s sod turning ceremony. Other celebrities included Cape Town’s mayor, Patricia de Lille and acting CEO of the NHBRC, Jeff Mahachi.

having recently completed a substantial

modular housing project in Kleinmond,

Western Cape.

Laing concluded by saying that the

experience gained on the Legacy project

will be put to good effect in the design

of the double-storey version of the CMA

House. The CMA House is a project which

promotes the use of full modular masonry

by making architectural drawings on a

40m² house freely available to interested

parties – see CMA House article in this

issue on page 24. P


THE cMA HoUSE – PROVIDInG A BLUePRInt FOR sUstAInABLe sUBsIDIseD HOUsInG

The Concrete Manufacturers Asso-ciation has launched the CMA House, an initiative, which if adopted by the construction industry, will improve the quality and building productiv-ity of government subsidy housing dramatically. As with any successful venture the devil is in the detail and the CMA House is no exception. The project was officially launched by CMA director, Hamish Laing, at the South African Housing Foundation Conference in September.

Since the advent of South Africa’s new

political dispensation in 1994, 1.5 million

government subsidy houses have been con-

structed. However, very little of the R60

billion invested in these structures was

allocated to design and detailing. Maximum

profit, rather than delivery excellence ap-

pears to have been the main motivation in

many of the projects. Minimum standards

were often ignored and materials were

sourced strictly on price. The results were

inevitable; poorly constructed houses

which have either had to be rebuilt or

repaired at considerable expense.

The CMA has always held that shoddy

construction practice is inexcusable.

“Low-cost should not equate to low

quality,” says Laing, “and the funds

allocated to subsidy housing were certainly

sufficient to build to minimum standards

and better.”

The Minister of Human Settlements,

Tokyo Sexwale, agrees and is pursuing

a zero-tolerance approach to poorly

constructed subsidy houses.

“It is generally accepted that for the Superior strength, one of the facets of the CMA house, is graphically illustrated in this caricature, which is being used to promote the house.


foreseeable future the concrete masonry

block or brick will be the walling material

of choice for subsidised housing,” com-

ments Laing.

“ Market research shows that South

Africans want their houses, even the most

humble of abodes, to be constructed with

traditional and dense materials such as

concrete masonry, preferring them to the

numerous and often lighter alternatives

which as yet have not penetrated the

market to any significant degree.

“Given that the concrete block is here

to stay it goes without saying that it

should be deployed in the most productive

and durable manner. Quicker construction,

minimal wastage and an adherence to

documented building standards all form

part of the process, and the most

effective way to achieve these objectives

is through a modular approach.”

Modular construction using concrete

blocks forms the backbone of the CMA

House. Fundamental to the whole process

are the architectural drawings which

not only include wall, door and other

dimensions, but unlike traditional plans,

detail each and every block used.

“Building any house, even a small basic

structure, is not a simple exercise if

it’s to be done properly,” advises Laing.

“And it is attention to detail, especially

in the plans and schedules, which make

the difference between modular and non-

modular masonry. Working out precise

block layouts is a complicated process,

especially at the corners, but the results

more than justify the effort.”

Based on a 40m² unit, The CMA House

or, more accurately, two houses, were

designed by Pretoria architect, Isia Ortner,

using two different block sizes, one which

is largely used inland and the other which is

generally found in coastal regions.

Each version includes: a full set of

drawings; a normal raft foundation or an

alternative Agrément-approved precast

concrete hollow-core option; modular

concrete-block walls; and aesthetically-

pleasing and thermally-efficient concrete

roof-tiles. The plans also include schedules

for block-cutting and for matching door

and window frames to block sizes, as well

as recommendations for cost-effective

waterproofing of external wall surfaces,

and some energy-efficiency options.

“The benefits of the modular approach

are obvious. By religiously sticking to a

set of modular plans wastage is minimised

by reducing the need for odd-sized blocks

which is so prevalent in the non-modular

approach. Furthermore, by following a

disciplined and identical building procedure

time-after- time, the benefits of repetition

and mass production come into play.

Although it takes longer to produce a

set of modular masonry drawings the

downstream savings far outweigh any

additional investment the preparation

of such drawings may incur. Moreover,

the modular approach is ideally suited to

subsidised housing, given the one-design-

fits-many approach.”

Both sets of drawings on the CMA

House are available on the CMA website,

www.cma.org.za, at no charge to anyone

wishing to use them.

The inland set is based on a solid block

which measures 290mm long 140mm wide

and 90mm high. The coastal set is based on

the 390mm long x 140mm wide by 190mm

high hollow block. The 140mm width of both

units has sufficient structural integrity

based on the SANS 10400-K standard and

is more economical than the 230mm width

of a standard wall.

When used in a wall with a 10mm layer

of mortar the solid block forms a 300 x

100mm module (the old imperial module

of one foot). Traditionally, window and

doorframes are also based on the old

imperial system, door frames measuring

900mm and window frames being either

600mm or 900mm.

“Therefore, the ef fective way to A modular masonry house under construction at Kleinmond.

A first course of modular masonry using hollow masonry blocks measuring 390 x 190 x 140mm is carefully laid out on some damp course sheeting. Note the L-shaped corner block.

design with solid blocks and imperial sized

frames is first to make all the dimensions

multiples of full blocks (300mm minus

the vertical 10mm of mortar lost at the

corners),” advises Laing.

“If this design philosophy is followed,

half blocks, either cut on site (preferably

by diamond cutting discs) or precast will

be required at door and window cavities.

The result is practically zero wastage, fast

construction and full structural integrity,

especially where it matters most, around

the door and window frames.”

Laing cautions, however, that it is

important for raft foundations to be

constructed accurately.

“If they are not, adjustments must

be made either through larger or smaller

vertical joints. Smaller joints can work

without compromising the modular princi-

ple but larger joints tend to become even

bigger at door and window openings and

builders may be tempted to insert small

pieces of blocks into the gaps. This is

wasteful in terms of both time and materi-

als and compromises structural integrity.”

In coastal areas where the hollow

390mm block is preferred for its better

thermal and damp proofing properties,

the working module, allowing for 10mm

of mortar, is 400mm long x 140mm wide

by 200mm high. This module does not


enjoy the benefit found in the solid blocks

300mm module where the width of the

block is half its length, and steps must be

taken during corner construction to retain

full modularity. This is either achieved us-

ing precast L-shaped corner blocks which

require an additional mould, or more cost-

effectively, using a smaller 340mm block

at the corners.

There are certain procedures which

must be adhered to in both instances. For

example, if one uses the 340mm block, the

wall must always start with a 340mm block

laid either lengthwise or perpendicularly

and end with a 340mm block laid either

lengthwise or perpendicularly depending on

the overall required dimensions of the wall.

These and other details are fully covered in

the plans of the coastal house.

There is another important considera-

tion in addition to the cornering details.

Hollow 400mm blocks (390mm + 10mm

mortar) are based on 200mm modules,

which are not compatible with the 300mm

module of traditional imperial sized door

and window frames. Cutting blocks to fill

+-100mm gaps is not advised. What usually

happens in such instances is that blocks

are hacked to size with a trowel, produc-

ing inaccurate fill-in pieces and massive

amounts of waste.

The preferable solution is to source

200mm module door and window frames

from CMA recognized suppliers. They are

available in either 800mm or 1 000mm

widths and the choice of windows is vast

(400, 600, 800mm etc).

“Once the importance of module com-

patibility is better understood by designers

and then specified, frame suppliers will

quickly adapt. Getting structural engineers

attuned to the significant benefits of

modular construction is another challenge.

“The CMA House provides a blueprint

for the productive construction of sustain-

able, aesthetically-pleasing and thermally-

efficient housing. It is a turnkey subsidy

housing solution, which if followed in a

disciplined manner, can be executed ef-

ficiently and profitably to the benefit of all

participants,” concludes Laing. P

Two plan options of the CMA House, both of which are available at no charge from the CMA.

CONCRETE MANUFACTURERS ASSOCIATION • Block D, Lone Creek, Waterfall Office Park, Bekker Road, Midrand • PO Box 168 Halfway House 1685

Tel +27 11 805 6742 • Fax +27 86 524 9216 • E-mail: [email protected]

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Fort Concrete

Inca Concrete Products

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Infraset

Infraset

Infraset

Kwena Concrete Products

Klapmuts Concrete & Cape Retaining

Kwena Rocla

Lategans Cement Works

Marley Roofing

Marley Roofing

Marley Roofing KZN

Marley Roofing Cape Town

(082) 850 3512

(022) 913 1921

(014) 538 0818

(035) 792 5218

(021) 875 5365

(012) 250 1711

(011) 310 1176

(00264) 61 321 3000

(031) 507 5525

(00267) 244 2106

(021) 511 2006

(021) 905 5998

(011) 316 2375

(021) 905 1665

(021) 386 1923

0861 33 5599

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(041) 463 3338

(041) 933 2755

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(021) 904 1620

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(012) 652 0000

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(00267) 392 2850

(021) 875 5151

(00267) 393 2850

(021) 873 1154

(011) 316 2121

(013) 933 3351

(032) 944 4155

082 324 7277

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MPR

MP

MPR

MP

MPR

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MPR

Pi

P

PR

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MP

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Pi

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Mobicast Mossel Bay

MVA

Monier Roofing South Africa (H.O.)

Monier Roofing South Africa

Monier Roofing South Africa (Free State)

Monier Roofing South Africa (North West)

Monier South Africa (Cape Town)

Monier Roofing South Africa (DBN)

Monier Roofing South Africa (ELN)

Monier Roofing South Africa (George)

Monier Roofing South Africa (PE)

Neat Contech

ReMaCon Products

Reya Pele Bricks

Rocla

Salberg Concrete Products

Southern Pipeline Contractors

Stabilan

Shukuma Flooring System

Stanger Brick & Tile

Stone Age Concepts

Technicrete

Technicrete (Mpumalanga)



Technicrete (Free State)

Technicrete (North West)

Technicrete (Limpopo)

Technicrete (Gauteng)

Technicrete (North West)

Technicrete (E.Cape)

Topfloor

Vanstone Precast

Vibro Bricks

Watson Concrete

Western Granite Bricks

West End Cement Bricks

(044) 874 2268

(012) 386 0050

(011) 222 7300

(016) 430 8000

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(012) 250 2218

(021) 534 1441

(031) 565 1312

(043) 743 2191

(044) 878 1325

(041) 463 2629

(046) 624 3377

(011) 393 5504

(016) 363 0340

(011) 670 7600

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(011) 914 8500

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(041) 372 1933

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(012) 802 1496

(011) 674 6900

(013) 758 1203

(017) 689 2100

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(057) 391 4200

(018) 790 4380

(015) 293 8083

(011) 203 7700

(018) 484 6234

(041) 372 2230

(021) 951 7700

(012) 541 2056

(012) 374 0205

(011) 740 0910

(021) 904 1620

(011) 851 1098

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non-Producer members

Abel Equipment

Ash Resources

Birkenmayer H

BASF Construction Chemicals South Africa

C&CI

Chryso Southern Africa

Dick King Lab Supplies

Kaytech

Kobra Moulds

Manitou SA

Pan Mixers SA

Rampf Formen GmbH

Sika South Africa

Soillab

Smartstone

Techincal Finishes

(044) 874 1876

(011) 886 6200

(011) 970 3880

(011) 203 2400

(011) 315 0300

(011) 395 9700

(011) 499 9400

(031) 717 2300

(003) 111 356 2460

(011) 975 7770

(011) 397 3754

(0049) 7391 5050 148

(031) 792 6500

(021) 988 7410

(011) 310 1161

(021) 535 4455

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AssociAte members

ARQ Consulting Engineers

ILIFA Africa Engineers

J C Paving Consultant

Pipes

Sekhukhune and Associates

SNA Civil & Structural Engineers

Terraforce

Young & Satharia Structural Civil Engineers

(012) 348 6668

(016) 981 0591

(011) 431 0727

(012) 644 0043

(012) 993 4776

(012) 842 0000

(021) 465 1907

(031) 207 7252


contrActor members

Cape Wall

Daron Construction

Decorton Retaining Systems

Friction Retaining Structures

Galaxy Paving

Kalode Construction

Mondo Paving & Retaining Walls

PYW Paving

Roadstone Civil & Paving

SA Paving Gauteng

The Paving Creations

Vesles Civils

Valcal International

(021) 856 3745

(034) 955 1333

(021) 875 5155

(011) 608 4321

(011) 815 1175

(011) 781 3814

(011) 708 0800

(031) 763 5771

(011) 683 7080

(011) 483 1350

(031) 765 4083

(012) 662 3031

(011) 867 2471


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