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Volume 5 issue 2 - Sept/Oct 2011
Citation preview
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]
E+
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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
PRECAST VOLUME 5 • ISSUE 2 • 2011 3
[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
PRECAST VOLUME 5 • ISSUE 2 • 20116
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.
PRECAST VOLUME 5 • ISSUE 2 • 2011 7
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
TIME SAVING
CAST IN CONCRETE
WWW.CMA.ORG.ZA
0861 SMART1 (0861 762781)
www.smartstone.co.za
E+
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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
PRECAST VOLUME 5 • ISSUE 2 • 201110
PRODUCTS.CC
011 393 5504
www.remacon.co.za
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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Solutions specially designed for the precast concrete industry
Dynamon NRG & Dynamon SP
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]
C
M
Y
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MY
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CMY
K
D110204 Mapei DYNAMO2 Ad.ai 1 09/05/2011 21:34
PRECAST VOLUME 5 • ISSUE 2 • 2011 13
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.
PRECAST VOLUME 5 • ISSUE 2 • 201114
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
PRECAST VOLUME 5 • ISSUE 2 • 2011 15
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
PRECAST VOLUME 5 • ISSUE 2 • 201116
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.
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
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.
PRECAST VOLUME 5 • ISSUE 2 • 201118
• 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
PRECAST VOLUME 5 • ISSUE 2 • 201120
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.
PRECAST VOLUME 5 • ISSUE 2 • 2011 21
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
PRECAST VOLUME 5 • ISSUE 2 • 201122
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
PRECAST VOLUME 5 • ISSUE 2 • 2011 23
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
PRECAST VOLUME 5 • ISSUE 2 • 201124
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.
PRECAST VOLUME 5 • ISSUE 2 • 2011 25
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
PRECAST VOLUME 5 • ISSUE 2 • 201126
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]
Their piece of heavenYOUR PEACE OF MIND
Use CMA concrete roof tiles for the best all-round roofi ng solution
PRECAST VOLUME 5 • ISSUE 2 • 201128
Producer membersM = Masonry P = Paving Pi = Pipes R = Retaining Blocks S = Floor Slabs T = Roof Tiles
CoMPAny nAME TElEPhonE PRoDuCT CoMPAny nAME TElEPhonE PRoDuCT
ARW Concrete Holdings
A Fick Cement Works
Bafokeng Concor Technicrete
Baybrick
Boland Concrete
Bosun Brick Brits
Bosun Brick Midrand
Brick and Concrete Industries
Brickcast Industries
Brickbuild T/A Panda
Cape Brick
C.E.L. Paving Products
Cast Industries
Columbia DBL
Concrete Units
Conframat
Corobrik
Deranco Blocks
Deranco Paving
Deranco Precast
Eagle Roof Tiles
Echo Floors
Echo Prestress
Echo Prestress Durban
Fort Concrete
Inca Concrete Products
Inca Masonry Products
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
(031) 560 3111
(041) 463 3338
(041) 933 2755
(041) 463 3338
(044) 874 0290
(011) 662 4600
(011) 589 8800
(031) 569 6950
(00263) 448 6620
(021) 904 1620
(043) 745 1215
(011) 876 5500
(012) 652 0000
(031) 569 6900
(00267) 392 2850
(021) 875 5151
(00267) 393 2850
(021) 873 1154
(011) 316 2121
(013) 933 3351
(032) 944 4155
082 324 7277
R
M
MPRT
P
M
P
MPR
MP
MPR
MP
MPR
P
P
MPR
Pi
P
PR
MR
P
S
T
S
S
S
Pi
MP
MPRT
Pi
MPR
PR
MP
R
Pi
M
T
T
T
T
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 (Mpumalanga)
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
(051) 432 5089
(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
(011) 357 7600
(011) 914 8500
(051) 434 2218
(041) 372 1933
(032) 457 0237
(012) 802 1496
(011) 674 6900
(013) 758 1203
(017) 689 2100
(013) 696 1153
(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
P
P
T
T
T
T
T
T
T
T
T
MPRS
R
P
Pi
Pi
Pi
S
S
MP
P
MPRT
MPRT
MPR
MPR
MPR
MPR
MPRT
MPR
MPR
MP
S
PR
P
MP
M
P
PRECAST VOLUME 5 • ISSUE 2 • 2011 29
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
CoMPAny nAME TElEPhonE
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
CoMPAny nAME TElEPhonE
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
CoMPAny nAME TElEPhonE