Precast Magazine by Concrete Manufacturers Association (CMA)

PRECAST VOLUME five ISSUE 2 • 2011

the cma – QUALITY CAST IN CONCRETE

• Adding value to paved surfaces • Precast kerbing – uplifting communities • The CMA house

YEARS YEARS OF QUALITY OF QUALITY AND AND INNOVATION INNOVATION

QUALITY MOULDS KOBRA KOBRA»Longlife™« »Longlife™«MOULDS MOULDSININNEW NEW STANDARD STANDARDHARDNESS HARDNESSQUALITY QUALITY68 68HRC. HRC.

Longlife Longlife

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

• Compared • Compared to conventional to conventional concrete concrete block block moulds, moulds, ourour moulds moulds areare designed designed for for optimal optimal standard standard hardness hardness quality quality »carbo »carbo 68 plus™« 68 plus™« to significantly to significantly extend extend service service lifelife andand reduce reduce cavity cavity wear. wear.

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

NEW! NEW!

PRECAST VOLUME 5 • ISSUE 2 • 2011 1

contents 2

SUPER-PLASTICISERS CRUCIAL TO

20 PRECAST CONCRETE KERBING – UPLIFTING

SELF-COMPACTING CONCRETE

TERRAFORCE LAUNCHES FULL RETAINING

22 THE CMA/C&CI LEGACY-

WALL DESIGN SERVICE

COMMUNITIES, PROTECTING ROADS

HOUSE PROJECT

REMACON SECURES EXCLUSIVE RIGHTS

24 THE CMA HOUSE – PROVIDING A

TO TENSARTECH CRB SYSTEM

BLUEPRINT FOR SUSTAINABLE

SUBSIDISED HOUSING

ADVANCED MIXING TECHNOLOGIES

BOOST CONCRETE PRODUCTION

WORLD EXPERT LEADS SEMINARS ON

PRECAST HOLLOW-CORE FLOORing AND

28 cma membership list

PRECAST VOLUME FIVE ISSUE 2 • OCTOBER 2011

THE CMA – QUALITY CAST IN CONCRETE

Our front page shows a first course

modular

masonry

being laid using hollow-masonry

LOAD-BEARING STRUCTURES

blocks in Kleinmond, Western Cape. Modular masonry forms

PPC’S NEW PRODUCTS OFFER

15% MORE VALUE

the backbone of the CMA House – see article on page 24 - which • Adding value to paved surfaces • Precast kerbing – uplifting communities • The CMA house

was launched by CMA director,

Hamish Laing, at the South African Housing

SIKA ADMIXTURES STRENGTHEN

PRECAST-CONCRETE TOILETs

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,

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

aesthetically-pleasing

and

thermally-efficient

housing units. Plans of the house are available at no charge from the CMA.

Precast is the official journal of the Concrete Manufacturers Association (CMA) 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: main.cma@gmail.com, Website: www.cma.org.za Publishers Isikhova Publishing & Communications PO Box 651793, Benmore, 2010, South Africa Tel: +27 11 883 4627, Fax: +27 11 883 4627 Website: www.isikhova.co.za Publisher: Andrew Meyer Tel: +27 11 883 4627, Cell 082 456 5175 E-mail: andrewm@isikhova.co.za Editor: David Beer Tel: +27 11 478 0239, Fax: +27 11 678 0254 E-mail: bigsky@ibi.co.za Advertising: Rui Chirindja Tel: +27 11 883 4627, Cell: 082 717 2851, E-mail: communications@isikhova.co.za Design, 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.

SUPER-PLASTICISERS CRUCIAL TO SELFCOMPACTING CONCRETE Admixtures, particularly newgeneration super-plasticisers, play a vital role in selfcompacting concrete’s (SCC) ability to flow into complex shapes and to pene tr a te 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-

Kerbs

Dry-casting means no exposed aggregate or blowholes on the surface of our kerbs.

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

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

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

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

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

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.

extends slump retention and is compatible with the majority of

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.

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

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

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

so many products within the Optima range,” says Correia. “One such product is Optima 100, a super-plasticiser that 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 dryas 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 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

E+I 15124

consistent accuracy and acceptable quality, a homogenous mix has Gauteng Tel (011) 310-1176 bosunmidrand@bosun.co.za

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

Eastern Cape Tel (041) 405-0100 bosunpe@bosun.co.za

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.

North West Province Tel (012) 250-1711 bosunbrits@bosun.co.za

and factories,” he adds.

PRECAST VOLUME 5 • ISSUE 2 • 2011 3

TERRAFORCE LAUNCHES FULL RETAINING WALL DESIGN SERVICE

management system which addresses con-

handle the site supervision on our behalf.”

ceptual, feasibility and planning activities as

Terraforce has built its name on the

well as the design, construction, operation

reliability of its retaining walls and superior

and maintenance phases of each project.

product quality. Well before the SABS/

“Terrasafe adds considerable value

SANS specification for concrete retaining

by ensuring that high quality levels are

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

maintained through each stage of the

went offshore to ensure that its products

project cycle. With more than 30 years

met international standards. For example,

experience in the pr oper design and

in the 1990s it obtained a comprehensive

Since 1979, when Terraforce was founded,

execution of retaining wall projects, not

evaluation report on its L18 block from the

the company has assisted specifiers with

to mention some extensive research and

International Council of Building Officials

design services in the form of purpose-made

development work, engineers are happy to

(ICBO) in California in compliance with

tables, design manuals, spreadsheets and

rely on our expertise in providing designs

the USA’s National Concrete Masonry

a windows-based design programme for

which meet all the requirements for proper

Association (NCMA) specifications.

segmented block retaining walls. And on the

construction practice and safety aspects.”

odd occasion the company has also provided a full design service and site supervision.

“Moreover, in addition to providing proper and fully-specified retaining wall designs

This design service has now been formal-

we have appointed several recommended

ised with Terrasafe, a first-class engineer-

installers who know how to follow our

ing, management, and specialist technical

designs to the letter. Based in many parts

service available to users of Terraforce

of the world, they adhere to our guidelines

products in many parts of the world.

and guarantee their workmanship. In remote

Holger Rust, managing director of Terra-

areas, where recommended installers don’t

force, says that Terrasafe is premised on a

exist, we liaise with local engineers who

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

Microwave Moisture Measurement for Concrete and Aggregates

The Hydro-Probe II for aggregate bins and chutes.

• • • •

Accurate, consistent, real time moisture measurement Linear, with temperature stable output Remote calibration and conﬁguration Easy to interface

info@birkenmayer.co.za Tel: +27 11 970 3880 Birkenmayer half page horizontal 146 x 210 plus 5mm bleed.indd 1

The Hydro-Probe Orbiter for mixers:

• • • •

Rotates through the mix Rapid response to moisture change Hardened Ceramic Head Replaceable sensor arm

www.birkenmayer.co.za

Master Reseller 14/04/2011 08:44:42

4 PRECAST VOLUME 5 • ISSUE 2 • 2011

REMACON SECURES EXCLUSIVE RIGHTS TO TENSARTECH CRB SYSTEM

cost savings over conventional reinforced

ReMaCon Products has negotiated the

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

structures. In addition, a high-quality and

exclusive rights for local manufacture of

suitable for highways, railways and other

more expensive fill material sometimes has

the well-proven Tensartech TW1 System

public embankment structures for which

to be used,” explains Ferraris.

of concr ete retaining blocks (CRB) -

standard retaining block walls are not

designed for constructing retaining walls

suitable,” Ferraris points out.

over 20m high.

Developed by Tensar International

“This is a coup for us because the

o f the UK , the sy stem compr ises a

Tensartech TW1 System opens the way

specially designed T W1 block combined

for us to provide retaining wall designs

with Tensar uniaxial geogrids made from

on large civil projects which are more

high density polyethelene (HDPE). The

c omp e ti ti v e and ad v an t age ous than

geogrids are attached to the blocks and

incremental panel systems,” commented

extend horizontally into the soil mass

Sil v i o F er r ar is, R eMa C o n P r o du c t’s

behind them, thereby turning the whole

managing member.

structure into a monolithic solid mass.

“The maximum height currently attain-

Available from Kaytech, the Tensar geogrid

able with locally-produced retaining blocks

reinforcement and connectors are highly

is seven metres at a slope of 86 degrees.

durable and resistant to chemical and

“The Tensartech TW1 System can be built as a single structure up to a height

biological attack. “The system offers huge construction-

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

B y c on tr as t, the T W1 sy s t em is erected without the need for heavy lifting equipment and can be erected using sitewon or recycled fill materials.”

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

6 PRECAST VOLUME 5 • ISSUE 2 • 2011

ADVANCED MIXING TECHNOLOGIES BOOST CONCRETE PRODUCTION Eirich RV19 and DEV16 concrete mixers,

The Eirich RV19 forms part of the

supplied locally by Birkenmayer, use ad-

diverse R-type mixer range and features

vanced mixing technologies which shorten

an inclined pan as well as macro and micro-

mixing times and boost the production

mixing technology. The latter ensures

of top quality concrete blocks for paving,

an intensi ve ver tical mixing action –

retaining wall and masonry applications.

eliminating the risk of cement and moisture

“The RV19 and DEV16 mixers also offer

layers forming.

optimal homogenisation of cement, aggre-

The Eirich DEV16 mixer has been us-

gates, admixtures, and water,” says Louis

ing flat-pan technology since 1961 and is

Eksteen, business development manager,

effective in the most arduous of mixing

Birkenmayer. “Moreover, shortened mixing

applications.

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

Mix qualities in both models can be further optimised through the incorporation of Hydronix moisture measurement and control instruments.

wear and require minimal maintenance. This

“Sensors can measure the tempera-

drastically reduces downtime and helps

ture and moisture levels inside mixers –

block-making plants operate at maximum

helping to ensure consistent quality with

capacity for maximum profits.

every batch,” concludes Eksteen.

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

WORLD EXPERT LEADS SEMINARS ON PRECAST HOLLOWCORE FLOORING AND LOAD-BEARING STRUCTURES October saw world-renowned precast

quality materials with the advantages

Africa, Austria, Barbados, Portugal, Spain,

c o n c r e t e e x p e r t, D r K im S . E l li o t t

of production line economy and quality

Scandinavia and six times in Australia. He

presenting three full-day seminars on

assurance, particularly when used as

has lectured at over 30 UK universities.

precast hollow-core flooring and loading

prestressed concrete floor slabs.

bearing structures.

“These seminars encouraged the widest

Aimed at professional design engineers,

possible appreciation of the proper use

architects and graduate students in civil

of precast concrete for innovative and

engineering, building technology and archi-

modern buildings.”

tecture, the seminars were hosted and

Dr Elliott is a self-employed consultant

organised by the Concrete Manufacturers

to the precast industry in UK and Malaysia.

Association (CMA) in collaboration with the

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

Concrete Society in Johannesburg, Port

lecturer in the School of Civil Engineering

Elizabeth, and in Cape Town.

at Nottingham University, UK, and has also

CMA director, Hamish Laing, said the use

worked for Trent Concrete Structures

of precast concrete multi-storey framed

Ltd., one of the UK’s leading precast

buildings was taking hold in South Africa.

concrete manufacturers.

“It is widely regarded as an economic,

S i n c e 19 87, D r E l l i o t t h a s b e e n

structurally sound and architecturally

researching the behaviour of precast

versatile form of construction for buildings

concrete structures, and has published

up to 40 storeys, although the maximum

more than 120 papers and four text books.

height reached in South Africa to date is

He has chaired the European research

five storeys.”

project COST C1 on semi-rigid connection

Dr Elliott commented that prestressed

in precast structures and has lectured on

hollow-core slabs combine the benefits

this subject over 40 times in 16 countries,

o f v er y r apid c onstr uc tion and high

including Malaysia, Singapore, Brazil, South

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.

Dr Kim S. Elliott

PRECAST VOLUME 5 • ISSUE 2 • 2011 7

PPC’S NEW PRODUCTS OFFER 15% MORE VALUE One of the country’s leading cement

According to Richard Tomes, customer

has been used for the past 119 years. It

producers, Pretoria Portland Cement

executi ve at PPC, the r esear ch and

will continue being used to build South

( P P C ), h a s a n n o u n c e d a si g n i f i c a n t

development (R&D) arm and the staff at

African landmarks, its infrastructure

enhancement of its product range. The new

PPC operations have been working together

and major construction projects, just

products facilitate the production of 15%

to achieve higher and tighter specifications

like it did with the Union Buildings, Gariep

more concrete of equal or higher quality

that will ensure that end users get more

Dam, Van Staden’s River Bridge, Gautrain

than they have done in the past using the

yield out of every bag of cement.

in f r as tr uc tur e and A f r ic a’s bigge s t

same amount of cement.

“For example, a project using 100 bags

stadium, Soccer City,” concluded Tomes.

PPC’s OPC (CEM I) cement has changed

of normal general purpose cement for

The new products are available in the

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

casting floors would typically yield 70m2.

Gauteng, Mpumalanga, Polokwane, North

its Surebuild cement has been upgraded

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

West, Free State, Lesotho and Swaziland.

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

Apart from

the same project using the same number

reducing the concrete material cost per

of bags will allow the builder to produce at

cubic metre, these new products also offer

least 10,5m2 more,” says Tomes.

other productivity benefits to builders

“We are taking a clear message to the

and contractors. Some notable examples

nation - that PPC and its cement products

include faster strength development,

not only have the ability to help customers

quicker removal of formwork and faster

realise their construction dreams, but also

floating and finishing of concrete floors – all

the compassion to better the lives of every

of which result in optimal use of labour and

citizen,” commented Tomes.

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

significant downstream savings.

“PPC is an iconic brand and its cement

ECHO

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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: main.cma@gmail.com

Natural Beauty. Engineered Quality.

SIKA ADMIXTURES STRENGTHEN PRECASTCONCRETE TOILETS S i k a’s c o n c r e t e a d m i x tur es 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 Sou th Dube, r ur al ar eas 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

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).

QUESTIONABLE QUEST FOR GREATER SLAB QUOTAS 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 P

0861 SMART1 (0861 762781) E+I 15260

Topfloor’s Cape manufacturing operations.

www.smartstone.co.za

10 PRECAST VOLUME 5 • ISSUE 2 • 2011

ACTOM wins bag-filter contract for cement plant Pretoria Portland Cement Company Ltd

and the bag filter is due for commissioning

Manager on the project, said ACTOM Air

(PPC) has awarded a turnkey contract

in June 2012.

Pollution Control was awarded the bag

to ACTOM Air Pollution Control (formerly

T he new f ilter is being designed

filter contract on the basis of price and

MikroPul) to replace a kiln 6 electrostatic

to reduce dust emissions in line with

conformance to PPC’s tender, technical

precipitator with a reverse-pulse bag-

Minimum Emission Standards as outlined in

sp e ci f ic a tions an d guar an t e e d dus t

filter at its De Hoek cement plant near

Section 21 of the National Environmental

emission limits.

Piketberg in the Western Cape.

Management: Air Quality Act, 2004 (Act

The supply of the new 350 000m3 /hr

No. 39 of 2004) and will be fitted with

capacity bag filter forms part of an extensive

glass-fibre bags capable of withstanding

upgrade and expansion programme which

temperatures of up to 260 degrees C.

includes converting the existing coal-fired

Gerard Pretorius, ACTOM air pollution

system to a new indirect coal-fired system

control’s sales manager, says that the bag

and the installation of a multi-channel

filter and associated equipment will serve

kiln burner. It also involves replacing kiln

the main kiln and raw mill.

shell sections and riding rings, as well as

“The existing forced-draft fan is to be

replacing a satellite cooler with a new

replaced with a higher-capacity induced

generation grate cooler.

draf t fan and a new material handling

T he contract includes the design,

system will collect, transport and feed

manufacture, supply, installation and com-

the collected dust back into the clinker

missioning. Site construction is scheduled

production process,” he explained.

to commence at the beginning of 2012,

L i z é W e l g e m o e d , P P C ’s P r o j e c t

PRODUCTS.CC

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.

* TW1

OFFERING A PROFESSIONAL APPROACH TO RETAINING

* TW1

WALL BLOCK STRUCTURES

011 393 5504 www.remacon.co.za remacon@telkomsa.net

* TW1

* TW1 Retaining block wall, Licensed by Tensar International to ReMaCon for 86 degree slopes to heights exceeding 20m.

* TW1

longrine 04 90 14 48 48 - (9824 - 0508)

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

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Dynamon NRG & Dynamon SP Solutions specially designed for the precast concrete industry

Accelerated development of mechanical strength

of Optimisation 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.

www.mapei.co.za

PRECAST VOLUME 5 • ISSUE 2 • 2011 13

BOSUN INTRODUCES LARGE DRY-CAST PAVERS T he Bosun Group has introduced the

“All three are 60mm thick and are

Urban range of non-bevelled dry-cast

suitable for walkways and driveways.

concrete pavers.

The pavers can either be installed in one

• City Councils have also shown a clear

uniform size or can be combined in either

interest in the pavers for sidewalks and

two or three sizes in various patterns.”

other public areas.

CEO, David Wertheim Aymes, says the 300mm x 400mm paver forms the

pavers are ideal for trolleys in shopping complexes and hospitals.

back bone o f the Urban r ange but is

Wertheim Aymes comments that it

Wertheim Aymes explains that Urban

complemented by two other paver s,

is very difficult to produce these large

pavers are specialist products and their

the 150mm x 200mm and the 100mm x

pavers using dry-casting.

installation should adhere to strict SANS

200mm blocks.

“However, we have invested in world-

“As with any paving installation, the

advantages are immense. Dry-cast pav-

earthworks are one of the most important

ers yield higher compressive strengths

aspects, and if poorly executed, will result

than their wet-cast alternatives, and

in certain site failure. Apart from this,

do so much more cost-effectively. They

contractors might need special installation

also don’t require cement grouting or

equipment to accurately lay the 300mm x

screeds. This makes it practical to remove

400mm paver and Bosun has launched a

and, if necessary, replace the pavers when

range of installation equipment specifically

doing underground work such as pipe laying

for this purpose.”

or plumbing.” Bosun has identified three diverse target markets for the Urban range.

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

1200MJ specifications.

class manufacturing equipment and the

Contractors interested in becoming authorised installers of Bosun Large Pavers, should contact the company.

• The smooth, unique design comple-

The Urban paver is available in all 10

ments modern architecture in an unprec-

Bosun colours, including the recently

edented manner.

introduced Granite and Marble, which are

• Due to the unbevelled surface, the

produced with imported, white cement.

14 PRECAST VOLUME 5 • ISSUE 2 • 2011

MAPEI SUPPORTS ELDOCRETE WITH PURPOSE-SPECIFIC ADMIXTURES Mapei South Africa Pty (Ltd) is assisting

Mapei admixtures product manager,

Eldocrete, a Centurion-based precast

A n t ony O f f enb er g, sa y s tha t Map ei

concrete manufacturer, boost production

supplies Eldocrete with an accelerating

and profitability with customised

super-plasticiser, Dynamon NRG1020,

admixtures. They reduce setting times,

to speed up production. Although it has

lower production costs, and facilitate

a limited workability period, it allows for

thick. It sets within 30 minutes, and is

the production of consistently superior

substantially improved early strength gains

then already strong enough to carry loads.

precast concrete products.

and increased productivity. It also reduces

As part of its customer service Mapei

the amount of cement required without

offers a purpose-built dosage system.

compromising on strength.

Either weight or volume-specific, the

M a p e g r o u t R a p i d o, a s h r i n k a g e compensation rapid-set repair mortar, also

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.

system allows the accurate and quick dispensing of admixtures.

makes up part of Eldocrete’s comprehensive

Werner Viljoen, a managing member at

Mapei offering. Any deterioration or damage

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

to vertical or horizontal concrete surfaces

ing with Mapei which has demonstrated

can be repaired with Mapegrout Rapido. It

how it can add value to our production.

is a fast-setting, easily-trowelable mortar

Its enthusiasm in proving the effective-

with excellent thixotropic properties, and

ness of its products has built confidence

is suitable for applications up to 2.5cm

between us.”

PRECAST VOLUME 5 • ISSUE 2 • 2011 15

TECHNICRETE PAVERS TRANSFORM GRAVEL ROADS P r e c a s t - p r o d u c t s m a n u f a c t u r e r,

seven separate rural road upgrading op-

Northern Cape; Khuma, Gopane, Sannieshof

Technicrete, is accelerating the pace

erations now under way in the three prov-

and Delareyville in North West Province;

of rural inf rastructural development

inces, serving chiefly rural communities.

and Viljoenskroon and the Alabama location

through the transformation of hundreds of

They include: the Carnivore location in the

outside Klerksdorp in the Free State.

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.

16 PRECAST VOLUME 5 • ISSUE 2 • 2011

CONCRETE BLOCK PAVING –

ADDING VALUE TO PAVED SURFACES

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. According to the Concrete Manufacturers A s s o c i a t i o n ( C M A ), n o t o n l y i s t h e 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 ef ficiently 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 h a v e a v ar i e t y o f di f f e r e n t sur f a c e 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, Concrete block pavers with an exposed aggregate finish are used to good effect on this path.

not all producers supply all types of

PRECAST VOLUME 5 • ISSUE 2 • 2011 17

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 p a v ing sur f aces to w hich landsc ape a r c hi t e c t s, p a v ing c o n sul t an t s an d 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,

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

having first been introduced some 20

EAP offers unlimited colour and textural

exposed aggregate surface improves its

years ago. Five producers, two in Gauteng,

variations and this aesthetic versatility is

performance and appearance.

two in the Western Cape, and one in

what is luring today’s landscape designers.

There are essentially two methods

KwaZulu-Natal, offer the product locally.”

Ideal for public spaces, pavements,

o f manu f ac tur ing E A P. One in v ol v es

EAP’s marginal market penetration to

driveways and patios, EAP requires very

placing a retardant in the concrete mix

date has been largely due to price which is

little maintenance other than sealing

which slows down the curing process on

often the prime driver in the specification

and occasional cleaning. The application

the surface. Surface cement is either

of paved surfaces. EAP comes with a 20 –

of a transparent concrete sealer to an

brushed or washed away to expose the

30% cost premium over conventional CBP

aggregate. A more common alternative,

and must compete with several lower-cost

especially in Germany, involves placing

alternatives.

paper, impregnated with a retardant, on

However, it offers some substantial

the surface of the pavers. The advantage

benefits in both the aesthetic and practical

here is that the retardant only affects

realms, benefits which over the long-term

a few millimetres on the surface of the

far outweigh any initial capital premium.

pavers which can then be brushed away.

Mor e o v er, w hen c omp ar e d t o o ther

An EAP variant is found in terrazzo

decorative CBP products such as con-

finishes. Introduced locally in 2009 by a

crete cobble, clay brick and polished in-situ

small Cape Town-based manufacturer, it

concrete paving, there are considerable

involves burnishing the upper surface of

cost savings to be had, varying from 20 – 60%.

A concrete block paver with a charcoal bush-hammered topping.

the paver to expose the aggregate which is densely packed beneath. The surface then

So what is EAP? In a nutshell it is a

gives the impression of movement similar

form of concrete block paving which uses

to those in other types of EAP, but has

embedded aggregates, in the first instance

the advantage of being completely smooth.

for its decorative attributes, but equally for

The appearance mimics that of traditional

its outstanding durability. Either sourced

terrazzo, and because the aggregate is

from quarries or manufactured, exposed

so dense, the result is a finish which is

aggregates can achieve spectacular and

much finer than those achieved with normal

unique visual effects at a reasonable cost.

polished concrete pavers.

For example, high concentrations of

Today’s specifier must also decide

aggregate mean that a path paved with

whether the paving surface should be

exposed aggregate pavers can be made to

traditional, in which case rain water is

look like a gravel path. With hard wearing surfaces capable of handling heavy traffic,

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

prevented from penetrating the paved surface, or permeable which is designed

18 PRECAST VOLUME 5 • ISSUE 2 • 2011

to allow water to inf iltrate beneath it. Still in its infancy in South Africa, permeable paving comes with considerable environmental plusses including water c o n s e r v a t i o n, m o r e c o s t - e f f e c t i v e 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

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

mould and will only retain its shape some

R200. However, huge advances have been

24 hours later.

made with dry-casting and it produces an

“The advantage of wet-casting is that it

excellent product.”

swimming pool surrounds. “Half the reason why wet-casting is so expensive is that it is very labour intensive.

yields a perfect replica of the materials being

Because of these advances dry-

Also the colour blending in wet-casting

imitated such as stones, rocks, granite or

cast flagstone pavers are now being

is difficult, being part art, part science,

marble. However, it is a considerably more

manufactured locally. South Africa looks

and manufacturers are still limited to

expensive process. For example, the selling

set to follow the trend in Europe where

three colours. The Germans have made

price of a typical dry-cast paver would be

the use of flagstone pavers is on the

considerable progress in automating wet-

between R60 – R75/m², whereas exactly

increase. These pavers are ideally suited

casting and the Italians are using a wet/dry

the same material content using wet-

to public squares, paths and pavements,

process with 75 – 80% of the tile being

casting would fetch anything from R150 –

shopping malls, inner courts, patios and

dry-cast,” concludes Laing.

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20 PRECAST VOLUME 5 • ISSUE 2 • 2011

PRECAST CONCRETE KERBING –

UPLIFTING COMMUNITIES, PROTECTING ROADS

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

introduction of paved roads with kerbing

of urban and suburban roads, providing

and pavements can rapidly transform

defined demarcation between roads and

shanty towns into aspirational suburbs.

pavements, various types of barriers, as

This fact was not lost on Soweto resi-

well as drainage conduits. Roads without

dents who have insisted on the kerbing of

kerbing develop ragged edges which are

all their roads as part of a road-surfacing

prone to water ingress, potholes and the

programme completed recently on behalf

eventual disintegration.

of the Johannesburg Roads Agency. The

Un-kerbed roads, according to Nico

project, which involved the installation of

Swart, technical director of Bigen Africa,

more than 700km of kerbing at +-R200

a major civil engineering consultancy,

a linear metre, was begun in 2003 and

require far more maintenance and

completed in 2005, a year before the

can break up within 10 to 15 years,

target date.

whereas they should last 20 years or more when kerbed.

“The then mayor of Johannesburg, A mos Masondo, said he wanted the

“Without the ef ficient stormwater

project completed within five years and we

drainage kerbing provides, most roads

bettered that thanks in the main to the use

have to be rebuilt in less than 20 years.

of precast concrete kerbs. Similar kerbing

T here is no doubt that viewed solely

projects are now being run in other areas

in financial terms, let alone from any

such as Orange Farm in the south and

other standpoint, kerbing is a sound

Diepsloot and Ivory Park in the north. And

infrastructural investment,” says Swart.

the Ekurhuleni Metropolitan Municipality is

It has another equally important role; it

running various street upgrade projects in

appears formal and properly finished and

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

Kerbing under construction in a commercial district.

its townships.

is one of the factors which differentiate

“The Soweto road upgrade demon-

suburban from rural landscapes. It also

strated conclusively that precast con-

has a very positive and uplifting effect on

crete is the most suitable material for

the communities in which it is installed,

township kerbing in the South African

especially in less affluent areas where the

environment. However, we began the

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

PRECAST VOLUME 5 • ISSUE 2 • 2011 21

project using cast in-situ and extruded

up generally. Many township roads are

Metropolitan Council and many of the

concrete. This proved to be the wrong

tarred but it is the kerbing which provides

people trained by us, both in Soweto and

choice and within the first few weeks

the psychological boost for community

Ekurhuleni, are now using these skills to

we realised that it wasn’t working. In

members to improve their immediate

lay driveways and other forms of paving.”

the first instance the skills required to

environments. In fact it’s plain to see that

Some of the older suburbs in

cast neat kerbs were hard to come by,

the JRA’s road and kerbing programme

Johannesbur g and Pr e tor ia ar e still

and secondly, members of the community

has transformed Soweto from township

without kerbing and the local authorities

vandalised the freshly constructed kerbs

to suburban status.

are currently running kerbing installation

with graffiti, foot/hand prints and bicycle

“We used local contractors and local

tracks. Kerb extrusion is a first-world

labour to lay the kerbing in Soweto. We

process where one operator can produce

initiated accredited training programmes

“In suburbs such as Pretoria’s Brooklyn

500m of kerbing in a day. By contrast,

and registered the workers with ASETA.

the roads were built quite deep so the main

we found that precast kerbing creates

Sub-contracting teams generally comprised

motivation for kerbing in this instance is

jobs and is more socially acceptable in

eight people and they were responsible for

aesthetic rather than function based. New

South Africa.

the preparation work, the laying and the

roads definitely need kerbing, to prevent

“It worked very well in Soweto. It

alignment. If the kerbs were not neatly

water ingress, to set an even height for

was easy to install and the end result

aligned we insisted on them being re-done

pavements and to prevent damage to them

was very satisfactory. And it definitely

until they met our specifications.

and the roads.”

programmes to improve pavements in their areas.

does uplif t communities. If one drives

“Each time we moved into a new ward

Swart concluded by commenting that

down any kerbed street in Soweto it

we trained a new team and this process

not all kerbing projects go according to

looks neat and inviting. We found that

was repeated many times over. We are

plan and examples of badly installed kerbs

soon after the kerbing was completed

currently running a similar roads and

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

people were creating gardens and tidying

kerbing project on behalf of the Ekurhuleni

and poor training.

22 PRECAST VOLUME 5 • ISSUE 2 • 2011

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.

legacy to the International Housing and

Manufactured using 100% South African

housing,” said CMA Director Hamish Laing.

appointed local professionals and modular

concrete, the building materials were

“The project also gave us the opportu-

masonry experts to ensure the success

used f or the construction o f one o f

nity to showcase our members’ concrete

of the project. The CMA shared design

four affordable double-housing units to

products as a live billboard side-by-side

and buildng costs with the NHBRC on a

demonstrate the cost–effectiveness of

with other building methods,” said Laing.

50/50 basis.

building with proper modular masonry and

The project was officially and appropri-

The houses were built in Blue Downs, a

other precast concrete elements. The

ately launched during a sod-turning cer-

suburb of Cape Town some 30km from the

other units were built using alternative

emony on July 18th, Madiba Day (Nelson

CBD. Each double-housing unit comprises

building materials and methods.

Mandela’s birthday), by the Minister of

two 60m² semi-detached double-storey

“This project was for a worthy cause

Human Settlements, Tokyo Sexwale. Also

apartments. Ground floor sections include

and f or me d p ar t o f the C M A so cial

in attendance were Cape Town’s mayor,

a living area, a kitchen and a bathroom

responsibility programme. The houses were

Patricia de Lille and acting CEO of the

given to particularly needy people on the

NHBRC, Jeff Mahachi.

Government’s waiting list for subsidised

The houses were built as a tangible

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 . B e si d e s t h e d o n a t i o n o f b u i l d i n g material by CMA members, the CMA

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

PRECAST VOLUME 5 • ISSUE 2 • 2011 23

while the upper levels accommodate two

around the house and driveway.

having recently completed a substantial modular housing project in Kleinmond,

bedrooms. The houses share a central

“Precast hollow-core slabs speed up

stairwell divided by a wall to provide each

the entire construction process, allowing

semi-detached unit with its own staircase.

masonry and other construction work

Laing concluded by saying that the

Two types of modular masonry, one us-

to continue as soon as they are laid.

experience gained on the Legacy project

ing conventional mortar (10mm thick) and

Another advantage is that they are made

will be put to good effect in the design

blocks made from recycled material and

in a controlled manufacturing environment

of the double-storey version of the CMA

the other with thin-bed mortar blocks,

which ensures the structural integrity and

House. The CMA House is a project which

were used to build the CMA unit.

quality of the product.

promotes the use of full modular masonry

Western Cape.

“O n e o f o u r o b j e c t i v e s w i t h t h e

“Concrete roof tiles, besides offering

by making architectural drawings on a

L egac y P r oje c t,” sa y s L aing, “is t o

excellent thermal and weather-pr oof

40m² house freely available to interested

demonstrate how modular masonry and

properties, can convert a very ordinary

parties – see CMA House article in this

pr ecast concr e te building ma ter ials

lo ok ing h ouse in t o som e thing r e all y

issue on page 24.

offer anyone investing in entry level or

special, simply through their outstanding

affordable housing a building system which

aesthetic appeal. This is why an increasing

is difficult to beat in terms of productivity,

number of entry-level housing projects are

durability and aesthetic appeal. And unlike

opting for this type of roofing.

alternative building methods, there is

“Concr ete block pav ing (CBP ) laid

a large labour component in the CMA’s

around the Legacy house finished off the

Legacy house.”

project very neatly. CBP also added a

B e side s masonr y blo ck s, o ther

practical dimension, by preventing mud

precast concrete products donated by

from spattering the walls during the rainy

CMA members included precast hollow-

season,” comments Laing.

core slabs for the first floors, precast

The main contractor on the two CMA

c oncr e t e s t air c ases, c oncr e t e r o o f

houses was Breekon Construction, a

tiles, polymer concrete door and window

construction company familiar with and

frames, and concrete blocks for the apron

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.

24 PRECAST VOLUME 5 • ISSUE 2 • 2011

THE CMA HOUSE – PROVIDING A BLUEPRINT FOR SUSTAINABLE SUBSIDISED HOUSING The Concrete Manufacturers Association has launched the CMA House, an initiative, which if adopted by the construction industry, will improve the quality and building productivity 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 constructed. However, very little of the R60 billion invested in these structures was allocated to design and detailing. Maximum profit, rather than delivery excellence appears 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 qualit y,” say s L aing, “and the f unds 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 zer o-tolerance appr oach to poorly Superior strength, one of the facets of the CMA house, is graphically illustrated in this caricature, which is being used to promote the house.

constructed subsidy houses. “It is generally accepted that for the

PRECAST VOLUME 5 • ISSUE 2 • 2011 25

foreseeable future the concrete masonry

block or brick will be the walling material

using two different block sizes, one which

of choice for subsidised housing,” com-

is largely used inland and the other which is

ments Laing.

generally found in coastal regions.

“ Market research shows that South

Each version includes: a full set of

Africans want their houses, even the most

drawings; a normal raft foundation or an

humble of abodes, to be constructed with

alternative Agrément-approved precast

traditional and dense materials such as

concrete hollow-core option; modular

concrete masonry, preferring them to the

concrete-block walls; and aesthetically-

numerous and often lighter alternatives

pleasing and thermally-efficient concrete

which as yet have not penetrated the

roof-tiles. The plans also include schedules

market to any significant degree.

for block-cutting and for matching door

“Given that the concrete block is here

and window frames to block sizes, as well

to stay it goes without saying that it

as recommendations for cost-effective

should be deployed in the most productive

waterproofing of external wall surfaces,

and durable manner. Quicker construction,

and some energy-efficiency options.

minimal wastage and an adherence to

“The benefits of the modular approach

documented building standards all form

are obvious. By religiously sticking to a

p ar t o f th e p r o c e ss, an d th e m o s t

set of modular plans wastage is minimised

effective way to achieve these objectives

by reducing the need for odd-sized blocks

is through a modular approach.”

which is so prevalent in the non-modular

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.

Modular construction using concrete

approach. Furthermore, by following a

blocks forms the backbone of the CMA

disciplined and identical building procedure

House. Fundamental to the whole process

time-after- time, the benefits of repetition

design with solid blocks and imperial sized

are the architectural drawings which

and mass production come into play.

frames is first to make all the dimensions

not only include wall, door and other

Although it takes longer to produce a

multiples of full blocks (300mm minus

dimensions, but unlike traditional plans,

set of modular masonry drawings the

the vertical 10mm of mortar lost at the

detail each and every block used.

downstream savings far outweigh any

corners),” advises Laing.

“Building any house, even a small basic

additional investment the preparation

“If this design philosophy is followed,

structure, is not a simple exercise if

of such drawings may incur. Moreover,

half blocks, either cut on site (preferably

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

the modular approach is ideally suited to

by diamond cutting discs) or precast will

“And it is attention to detail, especially

subsidised housing, given the one-design-

be required at door and window cavities.

in the plans and schedules, which make

fits-many approach.”

The result is practically zero wastage, fast

the difference between modular and non-

Both sets of drawings on the CMA

construction and full structural integrity,

modular masonry. Working out precise

House are available on the CMA website,

especially where it matters most, around

block layouts is a complicated process,

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

the door and window frames.”

especially at the corners, but the results

wishing to use them.

more than justify the effort.”

The inland set is based on a solid block

Laing cautions, however, that it is impor tant for raf t foundations to be constructed accurately.

Based on a 40m² unit, The CMA House

which measures 290mm long 140mm wide

or, more accurately, two houses, were

and 90mm high. The coastal set is based on

“If they are not, adjustments must

the 390mm long x 140mm wide by 190mm

be made either through larger or smaller

high hollow block. The 140mm width of both

vertical joints. Smaller joints can work

units has sufficient structural integrity

without compromising the modular princi-

based on the SANS 10400-K standard and

ple but larger joints tend to become even

is more economical than the 230mm width

bigger at door and window openings and

of a standard wall.

builders may be tempted to insert small

A modular masonry house under construction at Kleinmond.

When used in a wall with a 10mm layer

pieces of blocks into the gaps. This is

of mortar the solid block forms a 300 x

wasteful in terms of both time and materi-

100mm module (the old imperial module

als and compromises structural integrity.”

of one foot). Traditionally, window and

In coastal areas where the hollow

doorframes are also based on the old

390mm block is preferred for its better

imperial system, door frames measuring

thermal and damp proofing properties,

900mm and window frames being either

the working module, allowing for 10mm

600mm or 900mm.

of mortar, is 400mm long x 140mm wide

“ T h er e f o r e, th e e f f e c ti v e w a y t o

by 200mm high. This module does not

26 PRECAST VOLUME 5 • ISSUE 2 • 2011

enjoy the benefit found in the solid blocks

These and other details are fully covered in

available in either 800mm or 1 000mm

300mm module where the width of the

the plans of the coastal house.

widths and the choice of windows is vast

block is half its length, and steps must be

There is another important considera-

taken during corner construction to retain

tion in addition to the cornering details.

“Once the importance of module com-

full modularity. This is either achieved us-

Hollow 400mm blocks (390mm + 10mm

patibility is better understood by designers

ing precast L-shaped corner blocks which

mortar) are based on 200mm modules,

and then specified, frame suppliers will

require an additional mould, or more cost-

which are not compatible with the 300mm

quickly adapt. Getting structural engineers

effectively, using a smaller 340mm block

module of traditional imperial sized door

attuned to the significant benefits of

at the corners.

and window frames. Cutting blocks to fill

modular construction is another challenge.

(400, 600, 800mm etc).

There are certain procedures which

+-100mm gaps is not advised. What usually

“The CMA House provides a blueprint

must be adhered to in both instances. For

happens in such instances is that blocks

for the productive construction of sustain-

example, if one uses the 340mm block, the

are hacked to size with a trowel, produc-

able, aesthetically-pleasing and thermally-

wall must always start with a 340mm block

ing inaccurate fill-in pieces and massive

efficient housing. It is a turnkey subsidy

laid either lengthwise or perpendicularly

amounts of waste.

housing solution, which if followed in a

and end with a 340mm block laid either

The preferable solution is to source

disciplined manner, can be executed ef-

lengthwise or perpendicularly depending on

200mm module door and window frames

ficiently and profitably to the benefit of all

the overall required dimensions of the wall.

from CMA recognized suppliers. They are

participants,” concludes Laing.

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

Their piece of heaven

YOUR PEACE OF MIND

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: main.cma@gmail.com

Use CMA concrete roof tiles for the best all-round roofing solution

28 PRECAST VOLUME 5 • ISSUE 2 • 2011

Producer members M = Masonry

Company Name

P = Paving

Pi = Pipes

Telephone

R = Retaining Blocks

Product

S = Floor Slabs

Company Name

T = Roof Tiles Telephone

Product

ARW Concrete Holdings

(082) 850 3512

Mobicast Mossel Bay

(044) 874 2268

A Fick Cement Works

(022) 913 1921

MVA

(012) 386 0050

Bafokeng Concor Technicrete

(014) 538 0818

MPRT

Monier Roofing South Africa (H.O.)

(011) 222 7300

Baybrick

(035) 792 5218

Monier Roofing South Africa

(016) 430 8000

Boland Concrete

(021) 875 5365

Monier Roofing South Africa (Free State)

(051) 432 5089

Monier Roofing South Africa (North West)

(012) 250 2218

Monier South Africa (Cape Town)

(021) 534 1441

Bosun Brick Brits

(012) 250 1711

Bosun Brick Midrand

(011) 310 1176

MPR

Brick and Concrete Industries

(00264) 61 321 3000

Monier Roofing South Africa (DBN)

(031) 565 1312

Brickcast Industries

(031) 507 5525

MPR

Monier Roofing South Africa (ELN)

(043) 743 2191

Brickbuild T/A Panda

(00267) 244 2106

Monier Roofing South Africa (George)

(044) 878 1325

Cape Brick

(021) 511 2006

MPR

Monier Roofing South Africa (PE)

(041) 463 2629

C.E.L. Paving Products

(021) 905 5998

Neat Contech

(046) 624 3377

MPRS

Cast Industries

(011) 316 2375

ReMaCon Products

(011) 393 5504

Columbia DBL

(021) 905 1665

MPR

Reya Pele Bricks

(016) 363 0340

Concrete Units

(021) 386 1923

Rocla

(011) 670 7600

Conframat

0861 33 5599

Salberg Concrete Products

(011) 357 7600

Corobrik

(031) 560 3111

Southern Pipeline Contractors

(011) 914 8500

Deranco Blocks

(041) 463 3338

Stabilan

(051) 434 2218

Deranco Paving

(041) 933 2755

Shukuma Flooring System

(041) 372 1933

Deranco Precast

(041) 463 3338

Stanger Brick & Tile

(032) 457 0237

Eagle Roof Tiles

(044) 874 0290

Stone Age Concepts

(012) 802 1496

Echo Floors

(011) 662 4600

Technicrete

(011) 674 6900

MPRT

Echo Prestress

(011) 589 8800

Technicrete (Mpumalanga)

(013) 758 1203

MPRT

Echo Prestress Durban

(031) 569 6950

Technicrete (Mpumalanga)

(017) 689 2100

MPR

(00263) 448 6620

Technicrete (Mpumalanga)

(013) 696 1153

MPR

(021) 904 1620

Technicrete (Free State)

(057) 391 4200

MPR

Inca Masonry Products

(043) 745 1215

MPRT

Technicrete (North West)

(018) 790 4380

MPR

Infraset

(011) 876 5500

Technicrete (Limpopo)

(015) 293 8083

MPRT

Infraset

(012) 652 0000

MPR

Technicrete (Gauteng)

(011) 203 7700

MPR

Fort Concrete Inca Concrete Products

Infraset Kwena Concrete Products Klapmuts Concrete & Cape Retaining

(031) 569 6900

Technicrete (North West)

(018) 484 6234

MPR

(00267) 392 2850

Technicrete (E.Cape)

(041) 372 2230

(021) 875 5151

Topfloor

(021) 951 7700

(00267) 393 2850

Vanstone Precast

(012) 541 2056

Lategans Cement Works

(021) 873 1154

Vibro Bricks

(012) 374 0205

Marley Roofing

(011) 316 2121

Watson Concrete

(011) 740 0910

Marley Roofing

(013) 933 3351

Western Granite Bricks

(021) 904 1620

Marley Roofing KZN

(032) 944 4155

West End Cement Bricks

(011) 851 1098

082 324 7277

Kwena Rocla

Marley Roofing Cape Town

PRECAST VOLUME 5 • ISSUE 2 • 2011 29

Associate members

Company Name

Telephone

ARQ Consulting Engineers

(012) 348 6668

ILIFA Africa Engineers

(016) 981 0591

J C Paving Consultant

(011) 431 0727

Pipes

(012) 644 0043

Sekhukhune and Associates

(012) 993 4776

SNA Civil & Structural Engineers

(012) 842 0000

Terraforce

(021) 465 1907

Young & Satharia Structural Civil Engineers

(031) 207 7252

CONTRACTOR members

Company Name

Telephone

Cape Wall

(021) 856 3745

Daron Construction

(034) 955 1333

Decorton Retaining Systems

(021) 875 5155

Friction Retaining Structures

(011) 608 4321

Galaxy Paving

(011) 815 1175

Kalode Construction

(011) 781 3814

Mondo Paving & Retaining Walls

(011) 708 0800

PYW Paving

(031) 763 5771

Roadstone Civil & Paving

(011) 683 7080

SA Paving Gauteng

(011) 483 1350

The Paving Creations

(031) 765 4083

Vesles Civils

(012) 662 3031

Valcal International

(011) 867 2471

non-producer members

Company Name

Telephone

Abel Equipment

(044) 874 1876

Ash Resources

(011) 886 6200

Birkenmayer H

(011) 970 3880

BASF Construction Chemicals South Africa

(011) 203 2400

C&CI

(011) 315 0300

Chryso Southern Africa

(011) 395 9700

Dick King Lab Supplies

(011) 499 9400

Kaytech

(031) 717 2300

Kobra Moulds

(003) 111 356 2460

Manitou SA

(011) 975 7770

Pan Mixers SA

(011) 397 3754

Rampf Formen GmbH

(0049) 7391 5050 148

Sika South Africa

(031) 792 6500

Soillab

(021) 988 7410

Smartstone

(011) 310 1161

Techincal Finishes

(021) 535 4455