Precast • Issue two • 2018

ISSUE TWO • 2018

R49.00

THE CMA – QUALITY CAST IN CONCRETE

• World beating block maker • 3D printed house • Excellence on display

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3

WORLD-BEATING BRICK, BLOCK AND PAVING PLANT – MADE IN SA

30 PREVENTATIVE MAINTENANCE

ENSURES DURABILIT Y

GLOBAL VIEW

INDUSTRY NEWS

28 ADMIXTURES ROLE IN MEETING

STRICT REQUIREMENTS

FOR CONCRETE

17 NEW AGGREGATE HAS EXCITING

POTENTIAL FOR PRECAST

31 ADVANTAGES OF PRECAST

CONCRETE WINGWALL UNITS

AROUND & ABOUT

PROJECTS

7

CMA PUNTS QUALIT Y CONCRETE TO AVOID FAILURES

9

CEMENT PRODUCER SUPPORTS PRECAST INDUSTRY

32 WEIGHT COLLARS FOR

DESALINATION PLANTS

9

TRAINING ON JBCC BUILDING CONTRACTS

33 AFRICA’S MOST SOUTHERLY

ROAD PAVED WITH EXPOSED

AGGREGATE CBP

10 HONORARY LIFE MEMBERSHIP

FOR FLOORING DOYEN

18

10 ALL SYSTEMS GO FOR

INDUSTRIES TCC 2018 11 EXECUTIVE DIRECTOR RETIRES 12 REGIONAL MEETING WILL

HELP DETERMINE CMA PATH 13 YEAR AT A GLANCE AT

WC REGIONALS

COMPANY NEWS 14 MANUFACTURER

SUPPORTS EDUCATION

14 PRECAST is the mouthpiece for the Concrete Manufacturers’ Association - CMA Concrete Manufacturers’ Association Physical Address: Office 0400, Standard Plaza Building, 440 Hilda St, Hatfield, Pretoria Postal Address: Post Net Suite 334 Private Bag X 15, Menlo Park, 0102 Tel: (+27 11) 805 6742 Fax: (+27) 86 524 9216 E-mail: admin@cma.org.za Website: www.cma.org.za Publishers: Isikhova Publishing & Communications Postal Address: PO Box 651793, Benmore, 2010, South Africa Tel: (+27 11) 883 4627 Fax: (+27 11) 783 2677 Website: www.isikhova.co.za Publisher: Andrew Meyer Tel: (+27 11) 883 4627 E-mail: andrewm@isikhova.co.za Consulting editor: Raymond Campling Tel: 076 297 2775 E-mail: media@mediasavvy.biz

PRECAST | ISSUE TWO | 2018

20 TOP ARCHITECTURE STUDENT

AWARDED FOR NEW DISTRICT

SIX VISION 21 BFT INTERNATIONAL EDITOR

VISITS CAPE CAST STONE MANUFACTURER

1

34 DIVERSE PROJECTS FOR

PIPE MANUFACTURER 37 NEW 3D PRINTED HOUSE 38 PERMEABLE GRASS BLOCKS

USED FOR MASSIVE

STORMWATER CHANNEL 39 CONCRETE CAST STONE

COBBLES – UPGRADE WINE

ESTATE HOUSE

TECHNICAL 22

AVOIDING FAILURES IN THE INSTALLATION OF CONCRETE BLOCK PAVING ON CONCRETE ROOF DECKS

40

26 SOUND PRACTICE CAN EXTEND

CONCRETE DURABILIT Y 27 GLOBAL EXPERTS PRESENT

PIGMENT SEMINARS

42 SA’S SMART CITIES ARE

DRIVING SUSTAINABILIT Y

Coastal editorial: David Beer Tel: 082 880 6726 E-mail: david.bigsky@gmail.com

ISSUE TWO • 2018

R49.00

THE CMA – QUALITY CAST IN CONCRETE

Advertising: Wally Armstrong Cell: 083 701 3278 E-mail: wallyarmstrong@outlook.com Subscriptions/Accounts: Thuli Majola Tel: (+27 11) 883 4627 E-mail: subscriptions@isikhova.co.za Design and layout: Joanne Brook E-mail: joanne.studio@isikhova.co.za The views and statements expressed in this publication are not necessarily those of the editor or the publishers and neither the publishers nor the CMA accept responsibility for them. No person connected with the publication of this journal will be liable for any loss or damage sustained as a result of action following any statements or opinions expressed herein. The same applies to all advertising. Precast© 2018. All rights reserved. No part of this magazine may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage retrieval system, without prior written permission from the publishers.

Endorsed by:

CONTENTS

16 PRECAST MANUFACTURER

CONDUCTS SUSTAINABILIT Y

STUDIES FOR PROJECTS

COVER STORY

• World beating block maker • 3D printed house • Excellence on display

ON THE COVER PMSA has developed the world-beating PMSA Ultra 3000 brick and block manufacturing plant which is 100% focused on meeting high volume manufacturer’s requirements for superior quality products and out-perform their opposition in fiercely competitive market spaces. Its engineering genius allows it to operate rapidly, change setups and machine parameters to produce multiple different products per customer requirements.

COVER STORY 3

The PMSA Ultra range brick, block and paving machine is 100% focused on meeting high-volume manufacturers’ r e quir em e n t s f o r sup e r i o r - qu ali t y products to out-perform opposition in fiercely competitive market spaces.

Simultaneously, its engineering genius allows its operators to rapidly change set-ups and machine parameters in order to produce multiple different products that will meet customers’ requirements.

Thanks to the massive volumes the machine is able to produce, this ability effectively gives manufacturers the

WORLD-BEATING BRICK,

BLOCK AND PAVING PLANT

MADE IN SA

Home-grown technologies developed by PMSA engineers to meet the challenging and demanding requirements of concrete manufacturers over the years are part of the blueprint used by the company to develop its world-beating PMSA Ultra 3000 brick and block manufacturing plant.

scope to manufacture volumes of products such as bricks in the morning and

(Above): PMSA launching the Ultra 3000 at Bauma Africa March 2018.

seamlessly switch to kerbstone, paving

(Left): The feedbox is heavy-duty and guided in closed rails for more accurate feeding and filling of the mould box.

or any other product later in the day, or to effectively become a just-in-time manufacturer. This combination of speed and versatility enables it to do the work

Built to last

of two or more machines, which can dra-

This is echoed by PMSA sales and mar-

matically reduce labour costs, storage

keting manager Quintin Booysen, who

and other requirements.

adds that the Ultra 3000 is an ideal solution for large-scale suppliers with

Experience to bear

diverse product requirements. Like its

PMSA managing director Walter Ebeling

namesake, and derived from its engi-

say s the same design genius also

neering brief, the new plant is designed

ensures that the PMSA Ultra 3000

to be ultra-fast, productive, reliable, efficient, easy to use and able to produce

will last longer and require considerably less maintenance than other types of

3000 has been developed with a rigid

machines. “It’s designed to run two or

frame that absorbs most of the vibration

the best-quality products available.

“We started the design process with

three shift operations per day and night

energy and shock during operation and

the main moving parts and designed the

and is so fast that it’s actually forced

can therefore replace almost any old-

mould and tamper assemblies in a way

us to redesign packaging and product

technology plant on existing foundations

that eliminates movement as far as

handling systems to match the output

and immediately start making more and

possible,” he explains. “As a result, it’s

of the Ultra 3000 block machine.

better products faster.

centred on four large 120mm diameter

“Based on its output and quality, as

“Being fully designed and built right here

chrome shafts to prevent back-to-front

well as the wide range of product types

in SA, the 30-ton block machine delivers

or side-to-side movement. The mould

that it can produce, we feel it’s going to

unsurpassed value-for-money for a ma-

assemblies are then firmly clamped to the

change the game completely. Best of all,

chine that we believe is the best of its type

shaft, rather than sliding down over fixed

despite its imposing size, the PMSA Ultra

in the world at this time,” says Ebeling.

shafts, so that when the mould’s lifted,

PRECAST | ISSUE TWO | 2018

IF YOU THINK PRECAST CONCRETE,

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Address: Office 0400, Standard Plaza Building, 440 Hilda Street, Hatfield, Pretoria, 0083 Tel: (011) 805 6742 • Email: admin@cma.org.za • Website: www.cma.org.za

concerns downstream in the manufactur-

“In order to account for the speed of

mould box and tampers being supported

ing process. The concrete silo draw is

operation and power of the machines,

in this new manner. The tampers have

run by a gearbox and variable speed drive

the hydraulics also make use of two large

additional bushings to further eliminate

which is fast and reliable, combined with

accumulators to store hydraulics under

movement on the shafts.

laser level filling control in the feedbox for

pressure and ensure hydraulic power’s

accurate and consistent filling.

always available during the demanding quick

“Furthermore, the heavyweight, rigid frame is designed to fully absorb shock and

cycle times of the machine. The pumps are

vibration without allowing movements to

Built for speed

also separate from all other systems to

transfer to the operational components

“In order to support the super-fast

ensure cooler operation. Coupled to the

of the machine. This not only ensures

cycle times of PMSA’s Ultra 3000, the

plant’s world-leading PLC control systems

higher-quality products, but reduces

hydraulics and peripheral supply systems

that link vibration, hydraulics and elec-

wear and tear, with obvious benefits for

are designed to be fast and efficient. The

tronic systems, the system provides the

the longevity of the equipment.

hydraulic system, for example, is designed

fastest possible and most accurate cycles

to be uncluttered with a separate valve

that are infinitely repeatable.

Vibration and filling

stand for accessibility. By moving it off the

“And, to complete the picture and

“Aside from its precise construction, our

block machine, it’s unaffected by move-

cater for the large volumes of products

new machine also makes use of our ultra-

ments and vibrations which could disrupt

manufactured, the PMSA Ultra 3000

efficient UltraVibe technology, which

the system over time. It also uses flexible

makes use of over sized 3 000- to

enables the operator to select the exact

hydraulic pipes back to the machine to

3 700-litre planetary mixers, depending

vibration force, vibration frequency

limit any movement on the valve stand.

on the type and size of end products

and amplitude required per product

being manufactured,” says Booysen.

type. T his unique vibratory system allows variation of force and frequency

Productivity tables

independently from each other, which

The Ultra 3000 is designed for the

can be delivered instantaneously to

manufacture of 60 interlocking pavers

provide faster and more optimum filling

per drop, or 30 hollow blocks 390 x 190

of concrete in the moulds.

x 140mm, 21 hollow blocks 390 x 190

“Considering that it can make prod-

x 190 mm, 44 maxi-bricks 290 x 90 x

ucts of 25mm-500mm, it stands to

140mm, 78 stock bricks 210mm long or

reason that the vibration system needs

189 rectangular pavers, 91 maxi and 144

to be infinitely programmable. For dura-

stock bricks on end per drop.

bility, the heavy-duty vibrators are sealed oil bath types requiring no maintenance.

Consider this:

Coupled with the PMSA new filling mecha-

In summar y, Ebeling say s the new

nism and precision tamper, the system’s

PMSA Ultra 3000 machines are the

able to maintain unmatched cycle time

culmination of all the company’s decades

on large 1,4 x 1,1m production boards.

of experience and engineering abilities. It

“Its feedbox in-rail design ensures the

has been designed to be the best of its

feedbox runs straight and true in every

class in the world and operate reliably

cycle, with no possibility of movement

and efficiently to meet the demands of

resulting in under- or over-filling of a mould

modern plants.

which can result in end-product size vari-

Its rigid and precise construction

ations. A hydraulic agitator also ensures

makes it ideal for continuous operation

even coverage between the front and back of the mould to achieve correct filling of the mould cavities. This reduces shortfilling and associated quality and packaging

(Above, from top): Simple touch-screen operation changes parameters on the Ultra 3000 instantly; the Ultra 3000 sports a heavy-duty, overdesigned frame for longevity and containing the machine vibration within the machine frame to reduce wear and tear, as well as maintenance costs.

throughout the year and is backed up

by PMSA’s unsurpassed af ter-sales service throughout the entire region and globally.

Interlocking pavers with topping feed

Hollow blocks 140mm width

Hollow blocks 190mm width

Maxi bricks

Stock bricks

Pavers on end

Maxi on end

Bricks on end

Kerbstones 1 000 x 300mm

Number of products per drop

60

30

21

44

78

189

91

144

5

9 hours production (approx)

150 000

63 000

44 100

110 000

195 000

310 000

200 000

250 000

7 500

Boards per 9 hours (approx)

2 500

2 100

2 100

2 500

2 500

1 650

2 200

1 730

1 500

PRECAST | ISSUE TWO | 2018

COVER STORY

it’s even and very precise due to the

5

EIRICH R-TYPE MIXERS + HYDRONIX MOISTURE CONTROL = TOTALLY CONSISTENT CONCRETE WITH EVERY BATCH

HYDRO CONTROLAUTOMATES MIXING A. BATCH IN MIXER B. CEMENT DISCHARGE BY TIMER C. MONITORED FLAT LINE FOR DRY MIX AND MOISTURE MEASUREMENT D. WATER DISCHARGE E. MONITORED FLAT LINE FOR WET MIX F. TIMED DISCHARGE

COST SAVINGS WITH EIRICH RV19 INTENSIVE MIXER SAVINGS IN CEMENT, PIGMENTS, ENERGY, WATER AND REJECT RATES HAVE BEEN REPORTED FOR 30 YEARS. PRECISE BLENDING AND HOMOGENOUS MIXES ARE ACHIEVED WITH SHORT MIXING TIMES. CONCRETE QUALITY AND SURFACE FINISH SPECIFICATIONS RISE CONTINUOUSLY. THE EIRICH R-TYPE MIXER IS BEST SUITED TO THIS DEMANDING ENVIRONMENT.

EIRICH RV19 INTENSIVE MIXER: INCLINED PAN CREATES STRONG VERTICAL MIXING ACTION AGITATOR BLADES BREAK UP LUMPS AND DISTRIBUTE WATER WATER AND CEMENT IS DRAWN THROUGH THE MIX BY A VORTEX CREATED AT THE SHAFT COMBINED FLOOR AND WALL SCRAPER DIVERTS MATERIAL INTO THE PATH OF THE AGITATOR FLOOR SCRAPER ALSO ASSISTS WITH FAST DISCHARGE

H. Birkenmayer • Website: www.birkenmayer.co.za • Tel: +27 11 970 3880 • E-mail: sales@birkenmayer.co.za

(Above and left): Quality manufactured products are factory-made to exact specifications.

CMA PUNTS QUALITY CONCRETE TO AVOID FAILURES A sure way of ensuring the procurement

CMA membership should be a non-nego-

of quality precast concrete products is

tiable starting point for building profes-

by dealing with Concrete Manufacturers

sionals, as well as for end-users wanting

Association (CMA) member companies.

quality precast concrete products. End-

Frans Minnaar, outgoing executive

users, in particular, need to be aware of

director of the CMA, explains that the

the value of dealing with CMA members.

association is a non-profit company

“The CMA logo is used in various

with the well-being of end-users and

ways, either as an additional logo on

the industry at heart. It therefore only

stationery or as a sticker on a vehicle,

allows membership from producers of

or on social media, etc. The use of this

precast concrete products that comply

logo is limited to valid members of the

with strict standards set by the CMA

CMA, a list of whom is published on the

and the industry.

CMA website (www.cma.org.za) or in

As a result, member companies must

Precast magazine. Misuse of the logo is

have in place a quality management sys-

difficult to control, although the media

tem which has been entrenched in the

and stationery are regularly scanned and

manufacturing process of its products.

action is taken against those who falsely

Furthermore, where South African Na-

claim to be members.

tional Standard (SANS) specifications

“If a quality management system is

are required for the product manufac-

entrenched by a producer, the quality

tured, the applicant must also prove

of the product should always be under

that the product complies consistently

control. For a product to comply with the

with the requirements of the relevant

requirements of a specification naturally,

specification.

the quality of the concrete will play a

In these instances, the producer will either obtain the CMA Certification Services mark of approval or the SABS mark of approval, in which case the producer will be audited and its products tested for compliance on a regular basis by qualified auditors.

Fighting for quality “In an otherwise unregulated industry,

PRECAST | ISSUE TWO | 2018

major role in success.

“Informal manufacturing of precast concrete products should not be encouraged.”

Self-test measures

wire (if used at all), moulds or formers which

“This brings us to the question: what is

are of very poor quality or custom-made

good-quality concrete? With an imple-

out of scrap metal, mixing done by hand in

mented quality system, every aspect of

inconsistent ways, contaminated river or

the manufacturing of the concrete will

dam/pond water, uneven working surfaces,

be controlled, including procurement of

soil being mixed into concrete mixes, lack

raw materials from legitimate suppliers,

of control over compaction of the concrete,

confirmation of the quality of the raw

dimensions which are out of specification,

materials, the quality

and green product which

and calibration of equip-

is damaged during de-

ment with which the con-

moulding and handling,

crete is manufactured,

or which is placed on un-

the condition of plant

even surfaces for short

and forms (moulds), the

periods of drying out (no

assembly of moulds or

curing) before being sold

forms, the proper design

as final product.

of concrete mixes, the

There is no inspection

controlled application of

and testing done in most

raw materials to the mix,

ins t anc e s and ther e -

mixing times of mixes,

f or e also no c onsis t-

testing or inspection of

ency in the dimensions

freshly-mixed concrete,

and strengths of these

handling of freshly mixed

products. Employees

concrete, application to

are seldom paid minimum

the f orms or moulds,

wages and are usually not

compaction of the fresh concrete, strip-

trained thoroughly. No PPE is made available

ping of green product from mould or forms,

to employees and they do not have official

handling of green product, after-care and/

appointments. As a result, these informal

or curing of new products, handling of

producers cannot fulfil the necessary

products after curing, storage facilities

requirements and manufacture inferior-

and delivery to clients.

quality products which do not comply with

“Then there’s the quality control part of

any specification or standards.

the process: inspection of raw materials for compliance with required specifications,

Informed decisions

checking of measuring and test equipment,

End-users of precast concrete products

inspection and testing of equipment and

should therefore be informed about the

plant before manufacturing, pre-deter-

detrimental ef fects of using inferior-

mined in-process inspections and testing,

quality precast products. The use of these

final product inspection and testing, keeping

products is the cause of many failures of

of evidence of compliance and release of

structures, the loss of huge amounts of

complying product to the client. All these

money and even the loss of lives. In ad-

processes must be controlled and managed

dition, it causes mistrust in the use of

to ensure the client always receives a good-

precast products.

quality product,” says Minnaar.

“Government, local authorities, municipalities, developers and the general public

Quality first

should be informed in every possible way

From the above, it is clear that informal

about the pitfalls of using the cheapest

manufacturing of precast concrete prod-

or inferior products. Reputable producers

ucts should not be encouraged. In order to

will be able to provide customers with the

manufacture good-quality concrete, manu-

necessary evidence of good quality and any

facturers require access to good-quality

customers using contractors should insist

raw material, which is not always readily

on seeing evidence of materials compliance

available to informal producers. As a result,

before accepting them for a project. It is

they use raw materials and practices which

easy to confirm whether a precast con-

are totally unsuitable for manufacturing of

crete product supplier is a member of the

precast concrete, such as inferior-quality

CMA or whether products bear the CMA

cement, stone and sand being replaced by

CS mark of approval,” says Minnaar.

soil or building rubble, proper reinforcing being replaced by pieces of scrap metal or

(Above): Frans Minnaar, outgoing executive director of the CMA.

PRECAST | ISSUE TWO | 2018

CEMENT PRODUCER SUPPORTS PRECAST INDUSTRY

innovations that add value to customers’ quality efforts, as well as their bottom lines. Having these local resources, plus an abundance of global knowledge and skills, is a major benefit for the entire precast concrete industry in SA. In order to ensure our customers can out-compete their opposition, our focus always remains on being customer-centric and providing sustainable solutions that are tailored to the needs of each customer.

The precast concrete manufacturing

our business. However, this segment is

What would you consider the biggest

industry is one of the largest single

the area with the most potential to offer

opportunity to increase market share

markets for cement producers in SA. In

additional value offerings and services.

among precasters?

this market the price of raw materials,

Our customer-centric approach is not

such as cement, has a large role to play

The precast industry is a major user

only our biggest thread, but our most

in the overall profitability of the precast

of your cement. How do you see your

important one. With that as the basis, the

operation.

involvement with this sector of the

entire process from start to finish cen-

industry, going forward?

tres on the customer’s desired outcomes.

and price-sensitive environment, but as

As the leader in construction materi-

Our golden thread is innovation and provid-

seasoned campaigners know, there is

als globally, Lafarge Industries SA re-

ing solutions that are sustainable

far more to buying cement than merely

mains committed to this market. Going

choosing the bag with the cheapest

forward, we’ll also remain innovative

What effect does imported cement have

price tag.

through technology and solutions in an

on South African producers?

As a leading cement producer locally,

effort to provide for our customers’ re-

As a global-based company, we’ve in-

Lafarge Industries SA views the success

quirements. We believe that we’re best

vested in the country not only to grow

of the precast industry as a key ingredient

positioned to add value to the customers

its wealth, but also to create decent

in its own success. Commercial director

in this segment.

jobs in line with our National Development

This makes for a highly competitive

Alta Theron and country manager: com-

Plan. Imported cement is countering this

munications, Thami Nkadimeng, recently

How do you differentiate yourself and

very notion and putting pressure on the

opened the lid on the company’s plans for

your product from the other major

industry.

the industry in an exclusive question and

South African producers?

answer session with Precast magazine:

Lafarge SA prides itself on innovative

* Precast magazine approached all the

solutions, quality products, consistent

major producers in SA to comment on

How important is the precast market

performance and superior technical sup-

the importance of the precast concrete

sector to you as a cement producer?

port. We operate one of the largest civil

industry. Lafarge Industries SA was the

The precast market makes up a signifi-

engineering laboratories in the country,

only producer to respond.

cant portion of the volumes sold by any

with highly skilled personnel. These tech-

cement producer. Any market sector is

nical resources are designed to support

imperative, given the diverse nature of

our technical sales teams on a daily basis.

(Above): Lafarge bagged products for the precast concrete manufacturing industry. The company also supplies bulk cement sales, as required.

TRAINING ON JBCC BUILDING CONTRACTS The Joint Building Contracts Commit-

constituents’ regional offices and offers

• 15 August: Garden Court,

tee (JBCC) has announced the dates of

short, intensive training courses on the

its training workshops for the second

appropriate application of these agree-

• 16 August: The Beach Hotel,

half of 2018. The JBCC comprises nine

ments throughout the subcontinent.

East London.

Marine Drive, Port Elizabeth.

constituents that represent the con-

Uwe Putlitz, CEO of the JBCC, per-

struction industry (owners and develop-

sonally conducts the one-day training

ers, contractors, subcontractors and

workshops from 8am-4.30pm, which – in

• 12 September: Sports Science

related professions) and whose members

all cases – earn delegates one Continuing

volunteer their services and knowledge

Professional Development credit.

• 3 October: Bytes Conference

• 5 September: The Country Club Johannesburg, Auckland Park.

Institute of SA, Cape Town.

to draft building contracts containing

Training in the “Principal Building

an equitable distribution of contractual

Agreement and Nominated/Selected

Johannesburg.

risk. The JBCC supplies these agreement

Subcontract Agreement” for the second

• 14 November: 18 Burlington B&B

documents to all users through the

semester of 2018 will take place on:

PRECAST | ISSUE TWO | 2018

INDUSTRY NEWS

Together they’re able to come up with

Centre, Halfway Gardens, Midrand,

& Conference Venue, Durban.

9

INDUSTRY NEWS 10

HONORARY LIFE MEMBERSHIP FOR FLOORING DOYEN Neil Duncan, a respected leader in

Training Association (FITA) which regis-

the South African flooring and building

ters, accredits and provides training of

industry, has been awarded Honorary

flooring installers nationally, and serves

Life Membership by Master Builders

as one of FITA’s directors.

Association (MBA) North.

Apart from his involvement in the

D un c an, cur r en tl y dir e c t or an d

flooring industry, Duncan has also played

formerly chief financial officer of KBAC

voluntary and key roles in the building

Flooring, is among the pioneer s of

industry overall over the past 44 years.

training in the flooring sector, having

A qualified Chartered Accountant, he

successfully implemented an internal

has, for example, served as trustee

training programme at KBAC Flooring –

and principal of ficer of the Gauteng

an initiative which has already resulted

Building Industry Pension & Provident

in 30 KBAC flooring installers acquiring

Fund, honorary treasurer of MBA North,

SAQA/CETA-accredited qualifications.

executive committee member of MBA

He has also been instrumental in the

North and president of MBA North in

establishment of the Flooring Industry

2006 and 2007.

(Above): Neil Duncan (right), director of KBAC Flooring, receives the Honorary Life Membership bestowed on him by MBA North from the association’s president, Jason Wilmot.

ALL SYSTEMS GO FOR INDUSTRY’S TCC 2018 Afrisam has shown its commitment

He adds that the first day’s pro-

to the concrete industry associations

ceedings will culminate in a gala dinner

through its headline sponsorship for

where the SARMA ready-mix awards

The Concrete Conference 2018 (TCC).

will be presented, bolstered by top-rack

Other corporate companies that

entertainment and acts that include

have invested in the success of the

singer/drummer/comedian and the even-

conference are Chryso, PPC, Sephaku

ing’s MC, Gino Fabbri.

Cement and KonkreteGlobal with sponsorships of breakaway events such as

Highlights and speakers

the Concrete Quiz, which takes place

• Prof Henk Jonkers from the Delft Uni-

the night prior to the conference on

versity of Technology will be present-

31 July 2018 at High Flyers on the

ing a paper on technology behind self-

same premises, as well as sponsoring

healing concrete.

refreshments, lunch and pre-dinner

• Max Moyo, world-renowned speaker,

drinks respectively.

will motivate and lead delegates into

the future.

Underlining the importance of this joint event is the strong support from

• L e o n v a n d e r We s t h u i z e n f r o m

some of the best-known names in the

industry who will be exhibiting at the

• Allesandro Bernacchia from Germany

event, including Afrisam, Mapei, Chryso,

and Andrea Bonomi from Italy will be

Sika, Nissan, Basilisk Self-Healing Con-

presenting case studies on extrusion

crete, Isuzu and Carmix.

kerbing and mobile batching respectively.

Johan van Wyk, organiser of TCC,

BrainRx will do some brain training.

• TCC will feature feedback on the

says: “Basilisk will be launching its self-

state of concrete standards, includ-

healing concrete at the conference.

ing concrete test methods, aggre-

Imagine that – concrete which heals

gate test methods, water-retaining

cracks! And KonkreteGlobal will show

structures and design codes.

the first robotic non-entry ready-mix

• There will also be a feedback and panel

truck cleaning system in SA. At the

discussion on the consolidation of the

same time, Isuzu Truck World will have

concrete industry associations.

a surprise for ready-mix concrete op-

• Other speakers will discuss energy-

erators and several other exhibitors will launch new ranges of equipment, concr e te addi ti v es, adhesi v es and much more.”

(Above, from top): TCC 2017 brought together the industry associations and all the role-players; Johan van Wyk is the chairman of the organising committee of The Concrete Conference.

ef ficient concrete roofs, cellular

concrete and case studies on the

Bosjes Chapel, Fourways Mall pre-

cast concrete and Zeitz MOCAA.

PRECAST | ISSUE TWO | 2018

EXECUTIVE DIRECTOR RETIRES

A strong foundation for infrastructure success

Af ter a productive and event-filled time as executive director of the CMA, Frans Minnaar has decided to step down from his busy role to enjoy the finer things in life and spend quality time with his family.

Under Frans’s tenure at the CMA, the association has achieved much recognition for its role in promoting and representing the views of the precast concrete manufacturing industry in SA. Chief among these is undoubtedly the successful launch and implementation of the Concrete Manufacturers Association Certification Service (CMACS) as an alternative to the SABS system.

Frans had responded to calls from members who had waited in vain for months or years for the old certification service to test their products by the SABS. This led to the rapid deployment of the association’s own CMACS service, which will also serve as a model to partially fund the association in future. He was also responsible for a host of other innovations which were introduced to assist members and streamline the operation of the business.

Unfortunately, during the same period, the country’s economy had stagnated and funding of the association was becoming increasingly challenging. The withdrawal of a major long-term sponsorship plunged the CMA into further financial difficulties, which Frans had to overcome in order to ensure the survival of the association. However, with frugal spending and careful manoeuvering, he ably steered the CMA to relative safety and has decided to use the current peaceful period to announce his retirement.

“I plan to join my wife in Cape Town and travel with her wherever her contracts take her. I’ll also pursue a quieter work life with some consulting, less pressure and more time to myself.” In addition, he will focus on recuperating to full fitness, having spent several months recovering from a major back operation at the beginning of this year.

The association will be placed in the capable hands of the current marketing manager, Henry Cockcroft, who will be promoted to the position of general manager. He will be assisted by Charlotte Swanepoel as financial manager. They will report to the board of directors on a monthly basis during the monthly meetings normally held in the CMA boardroom.

The board of directors has requested that a notice be served to all members that there is a need for at least one extra nonexecutive director to serve on the board. In the best interests of the CMA, it is important to have a diverse

ROCLA is South Africa’s leading manufacturer of pre-cast concrete products. Surpassing 100 years of product excellence, including pipes, culverts, manholes, poles, retaining walls, roadside furniture, sanitation and other related products within infrastructure development and related industries.

board of directors to represent all the different pillars of the association. Members will receive nomination forms before the AGM. Thank you, Frans, and good luck with your future endeavours!

PRECAST | ISSUE TWO | 2018

Visit us on www.rocla.co.za for our nationwide branches

INDUSTRY NEWS 12

REGIONAL MEETING WILL HELP DETERMINE CMA PATH The Gauteng regional meeting held in Ger-

Either way, obtaining sufficient funds

Other topics of discussion included

miston recently marked a watershed for

to keep the association running ef-

the urgent need to address skills short-

the Concrete Manufacturers Association

fectively remains a moot point and one

ages in the industry, training, policing

(CMA) and its members as the floor was

that was put to the floor for discussion.

of false claims of membership and main-

opened for discussions on several path-

Members also heard how the current

taining high standards within the indus-

changing decisions that lie ahead for the

tough economic climate has eaten into

try. Findings based on input from the

association in the near future.

the association’s reserves and requires

nationwide round of regional meetings

future funding models to be cognisant of

will be further collated and discussed,

these challenges.

whereafter findings and suggestions will

Firstly, outgoing executive director Frans Minnaar updated delegates on the status of talks to consolidate the

Simultaneously, members heard that

various concrete-related bodies into a

the CMA Certification Services is find-

single representative body. While tra-

ing traction and is increasingly being

ditional funding from the country’s six

recognised as the de facto concrete

major cement producers will potentially

product certification of discerning engi-

be withdrawn from separate entities

neers. In fact, so high is the demand for

(including the CMA, the Southern Africa

certifications that the company and its

Readymix Association, The Concrete

team are being thoroughly stretched to

Institute and the Concrete Society of

ensure fast and efficient turnaround. It

Southern Africa) unless the consolidation

was also noted that CMA CS is already

takes place, CMA members also voiced

nearing break-even point in terms of

their concerns that a single umbrella

profitability and will soon be in a position

body may not adequately represent the

to begin repaying the CMA’s initial and

association in future.

founding loan.

be tabled to all members in the weeks that follow.

(Above): CMA members attended the recent Gauteng leg of the 2018 round of regional meetings.

The CMA hosted a members’ feedback

Cockcroft’s presentation covered the

had been the best competition to date.

meeting in Cape Town on 22 May 2018.

past year’s achievements, the member-

This year’s panel of independent judges

Presented by CMA outgoing executive

ship drive, the CMA CS and its website,

were drawn from the Universities of the

director Frans Minnaar and marketing

Precast magazine, the 2018 Awards for

Witwatersrand and Pretoria, the Master

manager Henry Cockcroft, the event

Excellence Competition, conferences,

Builders’ Association, ILASA and SAIA.

was held to apprise members of what

expos and technical workshops.

Cockcroft said that the structure of the

the association had achieved during the

He said a roof tile workshop which

competition had been reconfigured on a

previous 12 months and its plans for the

was jointly sponsored by Aveng Infraset,

product category basis, which meant

forthcoming year.

Monier Coverland and Marley had been

that more companies stood a chance of

The association’s financial position

a great success. It was presented by

winning an award. There were 100 en-

was first on the agenda. While there were

Danie Hattingh of Monier Coverland and

tries, 18 of which garnered awards and

some notable fundraising successes,

attended by close on 80 delegates, mainly

four of which received overall trophies.

such as various workshops and the CMA

roofing contractors.

He noted that this had already seen

Awards function, Minnaar said that if

Cockcroft also mentioned that the

the CMA active in several concrete

current conditions prevailed, the CMA

CMA CS had revolutionised precast

promotional events: The Concrete Con-

would post a net loss for the current

unit quality standard assessment and

ference which was held in August 2017,

financial year. This was mainly due to a

certification and was attracting the at-

jointly organised by the CMA, TCI, SARMA

lack of major sponsorships. In addition,

tention of some of the major players in

and the CSSA . T he CM A member s

several action plans are being investi-

the concrete industry. Moreover it was

presented several case studies at the

gated to improve the financial position

anticipated that by the end of the year,

conference. The CMA also participated in

of the association.

60 permits would have been issued by

the KZN Construction Expo in February

the CMA CS.

2018, in another joint initiative with TCI,

On a more positive note, Minnaar mentioned that the CMA’s Certification

Several technical manuals and publica-

SARMA and the CSSA and in two other

& Mark of Approval (CMA CS) arm, which

tions have been proposed for the current

joint events this year, BAUMA in April

specialises in the auditing of precast

year. They include a wet cast specifica-

and Totally Concrete in May.

concrete production, was financially

tion which has been submitted to the

In the immediate wake of Bauma, the

self-sufficient and in a position to begin

SABS Standards Committee, a cost

CMA was a joint organiser and host, to-

paying back a CMA loan.

comparison survey on roof tiles versus

gether with Pan Mixers SA, of a seminar

The CMA is not alone in feeling the

other coverings, cement bricks versus

on pigmentation and advanced colour

impact of a spluttering economy and is

clay bricks, a concrete versus plastic

metering systems. It was presented by

one of five associations which the cement

pipes manual and a new segmented paving

two global experts on pigment dosing and

producers are no longer willing to support

installation manual.

dispensing: Hans J de Witte, a world-

as independent entities. In light of this,

Cockcroft added that the main focus

leading specialist in inorganic pigments

Minnaar mentioned that discussions are

of the membership drive was on reviving

and Michael Finke, managing director

underway with local cement producers

membership in KwaZulu-Natal and the

of Finke Dosiertechnik GmbH, Germany.

to consolidate the country’s cement and

Western Cape. The CMA is also seeking

The meeting was concluded when

concrete organisations into one body.

to rekindle relationships with resigned

delegates were given two questions to

members.

ponder on during the coming months: “Of

The consolidation initiative is being driven by a working group (CWG) to

T he 2018 Awards for E xcellence

what value is CMA membership to you?”

formulate proposals for presentation

competition was a resounding triumph,

and “How can the CMA improve its of-

to the cement industry. Other associa-

with many of the participants saying it

fering to members?”

tions being considered for inclusion are the Concrete Institute, the SA Readymix Association (SARMA) and the Association of Cementitious Material Producers (ACMP). Minnaar said that the CMA’s board of directors had expressed reservations about the consolidation, especially as CMA CS was now financially viable. Likewise, the ACMP felt that its association would not fit into the new structure.

While preliminary discussions are underway, the CMA board has agreed that Minnaar should represent the association on the CWG.

PRECAST | ISSUE TWO | 2018

INDUSTRY NEWS

YEAR AT A GLANCE AT WC REGIONALS

13

COMPANY NEWS

MANUFACTURER SUPPORTS EDUCATION The IS Group has provided funding in the form of a donation in cash and kind to the value of R743 000 to assist in the construction of 10 new classrooms for

14

the Lompec Education Centre in Mamelodi East.

The centre is providing much-needed educational facilities to the local community and growing demand recently made it necessary to expand the centre and separate the junior school from the high school. The IS Group of companies came on board to assist in the expansion of the centre by donating materials and funding.

T h e d o n a ti o n w a s us e d f o r th e manufacture and delivery of 1 635m2 of Technicrete Bond Brick pavers, 77m

(Above): A classroom at the Lompec Education Centre nears completion.

of Figure 7 1 000mm kerbs, 2 200

much-needed expansion programme. In

“Access to education is crucial for

Technicrete Earthform grey retaining wall

addition to the bricks and kerbs, we were

the upliftment and skills development of

blocks and 87 000 Ocon Brick clay stock

able to complete two sections of the

previously disadvantaged communities.

bricks. A cash portion of R456 590 was

school with ready-mix concrete, which

Without education, there’s no future.

also donated to Lompec and used to fund

was cast on the first floor. Reinforcement

When we heard about the need for extra

the new classrooms, as well as a library

steel was purchased and, along with the

classrooms and learning facilities at

and a computer facility.

donated bricks, enabled us to complete

Lompec Education Centre, we offered

two wings,” says Barnard Mashiane, Emis

to donate, through the manufacture and

officer: Lompec Education Centre.

transportation of materials required,

“We were delighted when the IS Group informed us it would be assisting in the

and assist in the centre’s expansion,” Education for the future The Lompec Education Centre offers conventional education from pre-grade

says Malebusa Sebatane, group marketing and communications manager for the IS Group.

R up to Grade 12, delivering good results. In 2017, the centre was staffed by

“The financial donation by the IS Group

41 educators overseeing 924 pupils. Lompec engages in skills development

will enable us to buy paint and floor tiles,

by partnering with local universities in teacher training and during 2017,

as well as complete the stormwater erec-

it monitored four Unisa students and one University of Pretoria student.

tion, paving installation, electrification

Additionally, it awarded bursaries to five pupils.

elements and finishing touches to Section C of the school,” says Mashiane.

ATTRACTIVE, FUNCTIONAL AND DURABLE PAVING Appearance is a key selling point for

autumn, terracotta, plum, grey, slate

residential and commercial properties,

and tan.

as it is for attracting customers to

It is a very functional and durable paver,

petrol stations and parking facilities, so

which enhances the final appearance of

the choice of paving plays an important

any petrol station forecourt, municipal

role in the final design of developments.

parking area, pathway, commercial or

It is therefore not surprising that

residential development, factory road

Technicrete’s Conleaf smart and durable

or suburban street.

pavers are often specified by architects

T he C onle a f is manu f ac tur e d in

and developers in order to obtain the

a 55mm or 60mm thickness, with a

desired attractive finish to a project.

200 x 200mm length/width. A larger

T he C onlea f p a v ing block o f f er s

80mm paver is available upon request.

attractive patterns and lines through

Te c h n i c r e t e I S G i s p a r t o f t h e

its unique, sof t, curved appearance

Infrastructure Specialist Group, which

and a choice of colours that includes

also comprises Rocla and Ocon Brick.

PRECAST | ISSUE TWO | 2018

INSTALL

CERTIFIED

PRECAST CONCRETE

PRODUCTS TO OBTAIN A LIST OF CERTIFIED SUPPLIERS, CONTACT CMA CERTIFICATION SERVICES OR VISIT WWW.CMA.ORG.ZA. Address: Office 0400, Standard Plaza Building, 440 Hilda Street, Hatfield, Pretoria, 0083 Tel: (011) 805 6742 • Email: admin@cma.org.za

CMA

YOUR MARK OF QUALITY IN PRECAST CONCRETE

COMPANY NEWS 16

PRECAST MANUFACTURER CONDUCTS SUITABILITY STUDIES FOR PROJECTS Precast concrete manufacturer Elematic

a precast concrete solution, namely

required for adapting precast construc-

is offering a service to developers and

choosing the most suitable concept de-

tion, such as basis of structural analysis

contractors to determine the benefits

sign office, preparing for concept design

and design, outline structural framing

of moving from traditional construction

project and concept design.

and precast arrangement.

methods to construction of precast concrete structures.

When considering a new construction

In addition, typical connection details

method, it is important to have a profes-

of various precast elements, sizing, geo-

While precast structures offer many

sional partner to work with in order to

metrical details and number of precast

cost- and time-savings for construction

achieve the best possible outcome. It is

product types, including reinforcement,

projects, evaluation of these benefits

also important to consider whether en-

pre-stressing and concrete strengths,

in terms of clear cost calculations and

gineers on the project have sound knowl-

are required. The final report should

precast product selection is essential.

edge of precast industry developments,

also consider suggested changes to

For this reason, the company is offering

practical knowledge and geographically

architectural design for efficient building

a concept design service to those wishing

varied experience.

and details of production set-up/precast

to make the switch.

The engineers should also have a good

machinery and equipment requirements.

“The service is available globally and

knowledge of precast production, plant

assists our customers in understanding

operations and efficient working meth-

Local assistance

the feasibility of adopting this technology,

ods, as well as structural connections

Elematic technology and assistance are

as it includes an evaluation of how their

and solid experience.

already being successfully utilised in

current and future projects could be

Gauteng and the Western Cape in SA for

structured using precast and whether to

Scope of projects

affordable housing developments by local

use complete or composite structures.

The starting point in evaluating the

municipalities, as well as private property

The performance of the precast building

suitability of precast for a project is

developers.

in local gr ound conditions and the

understanding the project in totality.

“Besides the feasibility studies, we

required precast product types are also

Architectural drawings – including lay-

assist in the finalising of building details

evaluated,” says Prakash Shah, head

outs, elevations, sections and special

and the setting up of a precast plant. Our

technical support of Elematic India.

features – are required, as well as de-

commitment is to our customer base and

tails of building utility service arrange-

we promise a lifetime commitment from

The process

ments, local seismic details and costs

design to the complete life-cycle of the

With its global experience in precast

of structural materials.

factory” says Shah.

production and application, Elematic can

The end result of a concept design

provide assistance throughout the pro-

project is the final reporting, which

cess required to successfully implement

includes all the information that will be

(Above): A typical precast structure using Elematic units.

PRECAST | ISSUE TWO | 2018

POTENTIAL FOR PRECAST ECA manufacturers claim the material is up to four to five times lighter than traditional aggregates, with a host of benefits that can be harnessed to produce special concretes ranging from

Worldwide, the use of expanded clay aggregates (ECA) is finding favour among concrete manufacturers for the production of lightweight, yet strong blocks and slabs for use in the construction of thermally efficient buildings and other specialised applications.

chemical-resistant, sound-dampening and thermally efficient varieties to fire-

market, including for the manufacture

results for use on non-load-bearing

resistant and lightweight concretes.

of blocks, thermal panels, landscaping

walls and would surely find applications

products, fire, acoustic and other con-

in southern Africa. Different mixes and

crete units.

aggregates sizes may produce even

The properties of the material are made possible through careful control

better results for external walls, slabs,

of different types and sizes of expanded

ECA is usually produced in different

clay products as they are processed.

sizes and densities from 0-30mm, com-

During the cycle, the clay pellets are

monly 0-1mm, 0-2mm, 2-8mm, 2-8mm

However, looking at the specifications

heated and cooled to temperatures

Crushed, 8-15mm and 15-30mm and

of the company’s commonly manufac-

exceeding 1 200˚C in a rotary kiln. This

densities from 260-700kg/m3.

tured blocks, it produces good properties

roof tiles, etc.

provides the desired effect of expand-

This provides characteristics such

in post-curing, with good overall finish

ing the clay particles and gives them a

as lightness, thermal insulation by low

and thermal insulation properties. These

honeycombed void structure.

conductivity co-ef ficient (as low as

are typical technical specifications:

0,097W/mK ), soundproofing by high

• Dry density: 600-750kg/m3

Speciality mixes

acoustic resistance, moisture imperme-

Overseas, it seems that a large part of

ability, incompressibility under perma-

• Drying shrinkage: 0,005%

the appeal of the material is its predict-

nent pressure and gravity loads, non-

• Compressive strength:

able density, geometry and shape, which

decomposition against severe condition,

3,5-5,0N/mm2 (MPa)

can be harnessed to give accurate cal-

fire-resistance, ease of transport and

• Flexural strength: 1,05N/mm2

culations of performance and strength

a reduction of construction dead load.

• Thermal conductivity: 0,14-0,18W/mk

(average value = 700kg/m3)

• Sound insulation index: Up to 46dB

for use in speciality mixes. Moreover, its spherical surface is rough with a

Some examples

for 100mm-thick walls and up to 52dB

semi-porous finish which provides good

Examples of blocks manufactured using

for 2 30mm-thick walls.

adhesion for concrete crystallisation.

ECA, fly ash and cement produce good

All these properties previously popularised the aggregate in the horticultural industry, where it has been extensively used for drainage and moisture retention purposes and for the growing of seeds. Other large-scale applications in geotechnical and earth stabilisation applications have led to the material being made more widely available and contributed to its cost-effectiveness for use in specialised concrete mixes.

A quick search also reveals that at least one locally manufactured product

“At least one locally manufactured product is available, with several overseas suppliers also seeking to establish themselves in the market.”

Potential benefits The blocks are also marketed to have a number of benefits that are potentially useful in certain applications, including the lightweight ability to reduce structural loads by 40-50%, excellent thermal performance, sound insulation abilities and high compressive strength, as well as resistance to fire, chemicals, water absorption, termites and pests.

Concrete manufactured using ECA can be drilled, carved, nailed and shaped and is easily plastered or coated.

is available, with several overseas suppli-

With competition mounting in the

ers also seeking to establish themselves

precast concrete industry, the introduc-

in the market. One such company is

tion of new technologies may carve new

Rivashaa Eco Design Solutions from

niches for manufacturers who are willing

India, which has been actively marketing its services and products in SA.

to take a chance and explore new opportunities. Whether ECA or other newer technologies will find favour

Numerous applications

among our concrete manufactur-

Accor ding to the company’s

ers and lead to the proliferation

literature, there are a number

of exciting new products remains

of products suited to the local

to be seen.

PRECAST | ISSUE TWO | 2018

GLOBAL VIEW

NEW AGGREGATE HAS EXCITING

17

AROUND & ABOUT 18

EXCELLENCE ON DISPLAY The CMA Awards for Excellence 2018 held recently at The Venue in Melrose Arch, Johannesburg, provided all the glitz and glamour expected from one of the construction industry’s premier events.

It also allowed the CMA’s members to show what the industry is capable of, while simultaneously offering a muchneeded opportunity to network among peers. Above all, the event provided a chance for everyone to let their hair down and celebrate the industry’s success.

The pictures say 1 000 words….

PRECAST | ISSUE TWO | 2018

PRECAST | ISSUE TWO | 2018

TOP ARCHITECTURE STUDENT AWARDED FOR NEW DISTRICT SIX VISION An architectural student with a modern

Swett Arquitectos and is a respected

vision for District Six has walked away

writer and designer;

with top honours at this year’s PPC

• Maria Fernanda Derntl, author and

Imaginarium Awards for Architecture

held in Pretoria recently.

• Award-winning architect Nadia Tromp

R o a r k R o b i n s o n, a 2 2 - y e a r - o l d

professor at the University of Brasilia; of Ntsika Architecture; and

student from the University of Cape

• Award-winning studioMAS architect

Town, received the award including a cash

Heidi Boulanger (Van Eeden).

prize of R50 000 for his outstanding

The judges chose Robinson’s proposed

design project which envisages a “public,

Artisan Centre for District Six in Cape

connective architecture” for a District

Town as the overall winner. According to

Six of the future.

this budding young architect: “District

Architecture schools across south-

Six stands vacant and scarred as one of

ern Africa were invited to submit works

the greatest exhibitions of apartheid-era

by final-year students for consideration.

planning reinforcement. As one of the

All 21 finalists’ projects were on exhibi-

pioneering redevelopments of the area,

tion at the 012 Central Gallery as part

the building aims to set a precedent for

of the Architecture ZA (AZA) Confer-

future developments, encouraging acts

ence programme. In keeping with the

of public, connective architecture and

AZA’s theme of resilience and memory,

creating the first framed public space

entrants were asked to locate a “hole”

in the area.”

in urban infrastructure caused by rapid

Fellow UCT students Anna Stelzner

growth and change, and to contribute

and Ilaena Napier were declared the

to spatial transformation by addressing

runners-up and received a cash prize of

connections between the community’s

R20 000 each. Two additional commen-

memory and resilience.

dations were bestowed on the entries

The entries were judged at the AZA

of Nelson Mandela University students

by an international panel of architects,

Robert Duvenage and GP Greyvenstein.

some of whom formed part of the AZA

Robinson’s winning project will join the

speaker line-up. The judges included:

national travelling exhibition of the PPC

• Hermann Kamte, Cameroonian archi-

Imaginarium Awards, which includes all

tect and founder of the award-winning

category winners across fashion, sculp-

firm HKA | Herman Kamte & Associates;

ture, jewellery, film and industrial design.

• Prolific Chilean architect Enrique

The PPC Imaginarium Awards travelling

exhibition will be at the Turbine Art Fair

Browne, who co-founded Browne &

(12-15 July 2018) and 100% Design South Africa (8-13 August 2018).

T he PP C Imaginar ium Awar ds is SA’s most supportive arts and design competition for emerging creatives. The BASA award-winning initiative encourages up-and-coming creatives to produce innovative designs from concrete. The 2018 round of the competition witnessed a record number of finalists chosen from the six entry categories, namely film, fashion, sculpture, jewellery, industrial design and ar chi t e c tur e. T he PP C Imaginarium Awards has now extended its reach from SA to Zimbabwe and is (Above): Roark Robinson won the 2018 PPC Imaginarium Award for Architecture.

running its first PPC Imaginarium Awards in Zimbabwe in 2018.

PRECAST | ISSUE TWO | 2018

(Above): Silvio Schade (left) seen here with Revelstone managing director, Andrew Cyprianos.

BFT INTERNATIONAL EDITOR VISITS CAPE CAST STONE MANUFACTURER Among the many visitors to this year’s Bauma Conexpo Africa was BFT International editor Silvio Schade, who stopped over in Cape Town en route to the exhibition in Johannesburg.

BFT International is a widely respected publication which covers all aspects of precast concrete. Published in Germany in several languages, its readership extends to Europe and Russia, the USA, China, the Middle East, South East Asia, Australia, Africa and South America.

Schade’s work has taken him to close on 30 countries and while in Cape Town, he took the opportunity to visit CMA producer member, Revelstone, one of the country’s most innovative producers of paving blocks and wall cladding.

“We’re interested in monitoring developments in the precast concrete industry all over the world and at Revelstone, I was astonished to find something I hadn’t seen before, namely rubber moulds,” says Schade. “Besides being recyclable and eco-friendly, they enable Revelstone to produce a vast range of pavers to order, giving architects and landscape professionals huge scope for bespoke design options.”

BFT International is in it’s 84th year and is issued by Bauverlag BV GmBH, the German construction industry publishing house, which publishes 17 other construction-related magazines covering architecture, the cement industry, masonry production, building trade and contractors, among others. The journal offers a mix of research material sourced from German universities, as well as project-and product-orientated material.

“German academia has an excellent relationship with the construction industry and nine of our leading universities conduct ongoing research into the precast industry on an ongoing basis.

Both sides benefit from the relationship; industry is fed a continuous stream of technological developments and the universities benefit from the financial backing of industry,” says Schade.

He adds that precast concrete is the dominant material in multi-storey construction in Europe.

“Masonry still plays a significant role in domestic construction, although wooden houses predominate in southern Germany.

Some of the masonry units used in Germany are: autoclaved aerated concrete (AAC), clay white silicate stone, lightweight concrete blocks, and cement blocks which are mainly used in the construction of outbuildings,” says Schade.

PRECAST | ISSUE TWO | 2018

TECHNICAL 22

AVOIDING FAILURES IN THE INSTALLATION OF CONCRETE BLOCK PAVING ON CONCRETE ROOF DECKS Concrete block paving (CBP) is a very functional and attractive method of surfacing concrete roof decks and is SA’s most widely used roof deck covering. Nevertheless, failures are all too common because crucial design elements are often side-stepped. Poor drainage is the major culprit, for several reasons: inadequate falls in the concrete slab; insufficient provision for surface run-off and, at times, a complete lack of drainage for subsurface water in the bedding sand.

These and other issues are addressed in

its relevance. Cairns highlights the ele-

this article which has been culled from a

ments which must be taken into account

paper presented to an international pav-

under South African conditions for the

ing conference in 2000 by independent

design and installation of CBP on concrete

paving consultant, John Cairns. Given

slabs, particularly on outdoor roof decks.

the incidence of recurring roof deck pav-

Various types of drainage are examined in

ing failures, this topic has lost none of

detail and he makes recommendations,

(Left, from top): Expansion joints in the concrete slab must be continued through to the pavers to allow movement without opening or closing the gaps between pavers; An example of good drain detailing. Aesthetically pleasing and correctly sized, the drain has no unsightly in-situ concrete surround and it also captures the sub-surface water in the bedding sand (see Figure 2 detail).

illustrated with examples.

A number of old asphalt roof decks (over 15 years) have been replaced with CBP due to deterioration in the asphalt and damage to the waterproofing membrane. However, even roof decks designed

PRECAST | ISSUE TWO | 2018

TECHNICAL 23

(Left): Different coloured pavers are used for the roadway and parking bays. Besides being aesthetically pleasing, they eliminate the need for painted bay lines.

able, but they must be designed to catch

(Above): Expansion joints in concrete slab must be continued through to the pavers to allow movement without opening or closing the gaps between pavers.

typical drain detail.

the sub-surface water from the bedding sand or deck drain. Figure 2 shows a It is also essential that the paving blocks are laid approximately 5mm above the level of the drain to ensure that the

Paving blocks do not require special consideration because they are only a

water flows into the drain and does not pond around it.

wearing surface. Pavers 50mm thick for pedestrian traffic or 60mm for vehicle

Surface water

traffic are more than adequate. Perme-

Roof decks are of ten designed and

able pavers can also be considered for ap-

constructed without considering rain-

plications in which rainwater is required

fall drainage and concrete decks are

to pass through the CBP surface into a

frequently cast without falls. Falls can

drainage system below.

be created with screeds, but due to several constraints – such as fixed levels

Drainage

at entrances and exits, as well as weight

An adequate number of correctly sized

restrictions which limit screed thick-

drainage outlets must be strategically

ness – decks often do not cater for drain-

positioned at the low points of the slab

age adequately.

to ensure ef fective drainage. Of ten

It is essential that decks are con-

with CBP from the outset can present

100mm diameter full-bore outlets are

structed with minimum falls in compliance

problems, either because certain critical

used and these are too small to cope

with SABS 1200 MJ, which are 1% in

aspects have not been included in the

with the large volumes of water during

the longitudinal direction and 2% in the

design, or the laying process has not been

severe downpours. In addition, during

transverse direction. This will prevent

properly executed. Besides slab move-

the dry season these outlets become

ponding, which is inconvenient to pedes-

ment, caused by temperature variations,

blocked with extraneous materials such

trians and causes excessive amounts of

drainage, vibration and edge restraints

as cigarette butts, plastic paper and

water to penetrate through the CBP. It

are all critical design considerations.

other debris.

will also ensure that surface water and

A typical section through a roof deck is shown in Figure 1.

Figure 1

PRECAST | ISSUE TWO | 2018

Large rectangular drains (minimum 500mm x 500mm) are far more prefer-

Figure 2

any water that penetrates the paving flows into the drains.

TECHNICAL

SUB-SURFACE WATER In a study by the late Prof Shackel², it was shown that approximately 25% of stormwater can penetrate the joints in newly-laid and unsealed CBP and even with sealing, some penetration still occurs.

Therefore provision must be made to drain

24

any water which penetrates the paving.

Water which does penetrate the paved surface should be kept to a minimum and to this end, proprietary water-activated jointing sand and/or liquid sealants should be applied to the joints. In both cases, it is essential that the joints are completely filled and regular sampling should be carried out by lifting the pavers for verification purposes. The loss of jointing sand due to trafficking is one of the

(Above): Good examples of aesthetically pleasing concrete block paved surfaces.

major causes of paving block movement, leading to saturation of the bedding sand

drains and this can cause differential

between adjacent paving blocks to open

and pumping and, ultimately, the failure of

settlement of the CBP.

up, resulting in a loss of jointing sand,

The preferred system is a continuous

excessive water ingress, CBP movement

Provided the falls are adequate and the

deck drainage layer beneath the bedding

and, eventually, the failure of the paving.

right quality of bedding sand is used, any

sand. This can be an open-graded granu-

It is therefore essential that control

water which penetrates the paving will

lar base or, alternatively, one of several

joints, complete with edge restraints on

flow to the drains. However, it is essential

proprietary membranes can be used.

either side, extend into the CBP. This can

that the grading of the bedding sand con-

The most common and suitable is a geo-

be simply achieved by casting an in-situ

forms to SABS 1200 MJ and it is prefer-

composite drain consisting of a studded

concrete upstand on either side of the

able that fine material (ie <0,075mm) is

polystyrene core covered with a strong

joint (see Figure 3) or bolting a steel angle

eliminated completely.

woven polypropylene filter fabric. This

onto the slab on either side of the joint

For non-trafficked roof decks, single-

woven fabric filter allows water to pass

(see Figure 4). The gap must naturally be

size pea gravel can be used as the bedding

into the drain core, while restricting any

suitably sealed to prevent water ingress.

layer and the joint can be left open for

dispersion of the bedding sand. Various

Alternatively, a proprietary expansion

rapid drainage. If the falls are inadequate

cores are available to suit the predicted

joint assembly as used on bridge decks

for suitable drainage of the bedding sand

volume of water and traffic loading.

can be attached to the concrete slab.

sand may become saturated, then a drain-

Movement of the concrete deck

coincide with the highpoints of the slab

age system must be installed beneath the

Concrete slabs are subject to substan-

to reduce the volume of water flowing

bedding sand.

tial movement, mainly due to tempera-

across the joint.

the paved surface.

It is preferable for the control joint to

or if there is a concern that the bedding

One system which has been used is

ture variations, especially in instances

There will also be a certain amount of

a herringbone drainage pattern using

where there is no insulation layer above

deflection and vibration of the roof deck,

geotextile wick drains as the drainage

the slab. This movement is handled by

depending on spans, traffic intensity and

material. However, these drains tend to

installing control joints in the concrete

method of construction. If the deck is

become blocked and local pumping of the

slab at regular intervals and these must

post-tensioned, the vibrations may be sig-

bedding sand can occur as described in

extend through the CBP layer. There have

nificant and cause the dispersion of joint-

a paper by KnoesenÂł. It also results in

been many cases in which this provision

ing sand. In such cases, it is necessary to

the dispersion of bedding sand around

was ignored. This causes the joints

inspect the paved surface regularly and refill the joints until lock-up occurs.

Edge restraints Typical edge restraints for roof deck CBP include buildings, protrusions and perimeter parapet walls. If there are segregated vehicle traffic lanes and pedestrian walkways, these can be normally demarcated with precast concrete kerbs in the standard manner.

Figure 3

If a masonry parapet wall is used as the edge restraint, it must be designed

PRECAST | ISSUE TWO | 2018

The normal precautions which are

ated by concrete slab movement. There

taken when laying CBP on steep slopes

are many cases of masonry walls crack-

should be used for access ramps, es-

ing due to these forces and in extreme

pecially the drainage aspects. If in-situ

cases, parapet walls have been pushed

concrete beams are used as anchor

off the edge of the slab.

blocks, they must include weep holes to

TECHNICAL

to withstand the horizontal forces cre-

It is recommended that an expansive

allow the free passage of water. And if

material be placed between the wall and

an insulation layer is placed above, rather

CBP and it is essential that the CBP slopes

than beneath a slab, it must be able to

away from the wall to prevent water pond-

withstand the static and dynamic loads

• All edge restraints must be capable of

ing. The joint between the wall and the CBP

of the traffic.

withstanding the loadings, both verti-

cal and horizontal.

should be sealed to prevent high volumes of water from entering the bedding sand. (See

Recommendations

typical details in Figures 5 and 6.)

25

Figure 4

• The drainage systems for both sur-

Conclusion

Two other aspects which are not only

face and sub-surface water are of

Roof deck CBP must be properly de-

related to roof decks, but need care-

paramount importance for roof deck

signed, detailed and constructed if it is

ful consideration are speed bumps and

CBP to perform adequately.

to perform without mishap.

access ramps, which tend to be fairly

• The volume of water penetrating

steep. Speed bumps must be designed

the CBP should be minimised by using

inspections – especially during their

to prevent high-impact forces causing

proprietary jointing sands and surface

early life – will highlight any minor faults,

movement of the CBP and it is strongly

sealants.

which can generally be addressed at

recommended that they do not coincide

• The movement of the concrete deck

relatively small cost before they develop

with control joints.

into major problems.

must be catered for in the paved surface.

As with all CBP installations, regular

REFERENCES 1. SA Bureau of Standards standardised

specification for civil engineering

construction, 1200 MJ: Segmented

Paving, 1984.

2. Shackel, B (1988). An Experimental

Study of Methods for Sealing Concrete

Block Pavements. Proceedings of the

Third International Workshop on Con-

crete Block Paving, pp38-1 to 39-11.

3. Knoesen, L (2000). Rehabilitation of

Damaged Asphalt Paving Using

Concrete Block Paving on a National

Road in South Africa. Proceedings of

the Sixth International Conference

on Concrete Block Paving.

Figure 5 These images of a well-executed CBP installation on a concrete roof deck were taken in April 2018 at the Canal Walk Shopping Centre in Cape Town, 18 years after the pavers were laid.

Article courtesy John Cairns, JC Paving Consulting 079 884 7986 • jcpaving@gmail.com.

• Day courses on all aspects of concrete block paving.

• Advice on design and detailing of concrete block paving for residential, commercial and industrial applications.

• Providing an expert opinion

Figure 6

PRECAST | ISSUE TWO | 2018

on failed paving or disputes.

TECHNICAL

caused by wheeled traffic on floors and pavements, as well as abrasive material, as in ore passes and silos, wearing down the surface of the concrete. Strong concrete with little surface laitance, well cured and finished off along with abrasive-resistant large aggregate, will slow down the rate at which the concrete

26

sur f ace we ar s. Specialist sur f ace hardeners will also help reduce wear.

Cavitation: The collapse of very highpressure vapour bubbles, created by fluid jumping off the surface of the concrete due to sudden changes in direction of that fluid, can cause massive damage to the concrete within a short period. Aerating the fluid – as is often done on dam spillways – to prevent pressure build-up is an effective way of preventing cavitation.

Salt crystallisation: This is often called “salt jacking” and tends to occur along the coast, where the concrete is subject to high concentrations of salt.

SOUND PRACTICE CAN EXTEND

CONCRETE’S DURABILITY

Although concrete is an extremely robust and forgiving construction material, with almost all concrete placed outlasting its designed service life, some durability issues do crop up and can be overlooked.

Salt in solution is transported into the concrete and, when the concrete dries out, it recrystallises, with the resulting expanding salt crystal exfoliating the surface of the concrete.

Freeze-thaw: Ingress of water into the concrete that subsequently freezes can cause the formation of cracks, due to the expansion of the ice. Air entrainment can effectively prevent this. The size and – more importantly – the spacing of the air bubbles are key factors in how effective the air entrainment will be.

Chemical deterioration mechanism

Dissolution of hydration products: Acid attack: The calcium in the concrete hydrates has a high solubility in acids.

Often a sacrificial calcareous aggregate

John Roxburgh, lecturer at The Concrete

known mechanisms that could lead to

is used to get an even wear and slower

Institute’s School of Concrete Technol-

deterioration of concrete. Durability

disintegration of the concrete surface.

ogy, outlines some of the less common

issues can generally be categorised

With strong acids, a sacrificial layer or an

durability issues that may be encoun-

under two main headings: mechanical

acid-resistant coating is more effective

tered in concrete practice. The corrosion

(and physical) deterioration, and chemical

in protecting the concrete.

of steel within the concrete is the most

deterioration. Chemical deterioration,

Soft or pure water attack: Waters

prevalent durability problem associated

furthermore, can be subdivided into the

with very low ion contents will cause

with concrete. For this reason, great

chemical dissolution of the hydration

the dissolution of the hydrates within

care is usually taken to ensure that the

products and the chemical conversion of

concrete. Soft or pure waters are often

correct reinforcing steel is placed in the

the hydration products.

those which have not come into contact

correct position with enough concrete

with calcareous rock.

Chemical conver sion of hydration

cover to it. However, what is sometimes

Mechanical (and physical) deterioration

overlooked is the environment into which

mechanisms

products

the concrete is placed – a factor that

Erosion and abrasion: Erosion is caused

Alkali silica reaction (ASR): Silica

could negatively impact the planned du-

by fluids, most often water, containing

contained in the aggregate can react

rability targets.

abrasive particles wearing down the

with active alkalis within the concrete

surface of the concrete. Abrasion is

pore structure. This forms an expansive

Listed below are a few of the better-

PRECAST | ISSUE TWO | 2018

Interestingly, all of the above deterio-

by ensuring excellent compaction and

Avoiding aggregates containing reactive

ration mechanisms can be mitigated or

optimising curing. By doing this, the con-

silica, minimising the active alkalis within

even prevented by designing the concrete

crete will be less permeable, which is key

the concrete and preventing the ingress

mix with a lower water-to-cement ratio

to a more durable concrete.

of water into the concrete are effective

and implementing good site practice

measures in preventing ASR.

Although the mechanisms mentioned above are by no means exhaustive with

Sulphate attack: A combination

regard to concrete’s durability, they

of sulphates, calcium hydroxide and

serve to illustrate the wide spectrum

tricalcium aluminates in the concrete can

of environments to which concrete

lead to the formation of two expansive

may be subjected. There are many well-

compounds: gypsum and ettringite.

researched methods of ensuring that

This can cause the concrete to soften

concrete will perform for its service

and crack. Using sulphate-resisting

life within any specific environment.

cement or extending the cement with

However, it is important that engineers

fly ash or slag can help prevent sulphate

and concrete practitioners take heed of

attack on the concrete. In addition,

these environments to avoid potential

ensuring that the sulphate content in

durability problems.

the aggregate and mixing water is kept

(Left): Surface exfoliation of concrete pavers caused by salt crystallisation.

low and preventing the ingress of water into the hardened concrete will prevent

(Far left): Corrosion of steel reinforcement is a major cause of concrete deterioration, particularly in harsh coastal environments.

sulphate attack.

GLOBAL EXPERTS PRESENT PIGMENT SEMINARS Two global experts on pigment dosing and

and the manner in which these factors

versal System for pneumatic transfer of

dispensing, Hans J de Witte, a world-

can be controlled.

powder pigments in 2004.

leading specialist in inorganic pigments

Finke, who has worked with the con-

One of its more recent innovations

and Michael Finke, managing director

crete industry for 30 years, covered

is a water-soluble bag, UniPac, which is

of Finke Dosiertechnik GmbH, Germany,

some of the latest developments in

produced from water-soluble film. The

gave a seminar on pigments and advanced

Finke pigment handling systems and

bag is filled with pigment and conveyed

colour metering systems for local pre-

the advantages of each system. He also

to the mixer, where it dissolves. This

cast concrete producers shortly after

described steps which can be taken to

makes for a very clean mixing process.

this year’s Bauma Conexpo Africa.

match existing colours and the creation

Other Finke dosing systems include the

of new colour shades.

UniGran for granules and the UniMicro

Initiated by local Finke agent Pan Mixers SA (PMSA), the seminar was held in

Family-owned, Finke Dosiertechnik is

Cape Town and Johannesburg and was

world-renowned for its innovative solu-

for very small doses.

The Finke factory is based in Detmold,

jointly hosted by PMSA and the Concrete

tions for dosing and dispensing powder,

close to Hanover, and was founded by

Manufacturers Association NPC.

granular and liquid pigments, chemical

Finke’s father in 1985. It is run by

De Witte, a chemical engineer with

admixture sealers and other materials.

Michael Finke and his brother, Ingo,

40 years’ experience in concrete pig-

The company is highly innovative and

employs 40 people and sells its dosing

ments, coatings and concrete produc-

was responsible for inventing the Uni-

equipment worldwide.

tion, was technical service manager at one of the world’s largest inorganic pigment manufacturers, where he ran the inorganic pigment laboratory for the construction industry.

His pr esenta tion de f ined colour and how to produce coloured concrete products more effectively. He reviewed the spectrum of pigments available for colouring concrete, illustrated their inherent advantages and described the f actor s which af f ect colour in cementitious pr oducts and how to ma t ch them . He also c o v er e d the advantage of using sealers and explained how raw materials, mix designs and processing conditions can affect colour

PRECAST | ISSUE TWO | 2018

(Above): The Cape Town pigment seminar participants included (from left): Roann Heunis of Chryso, Abdul Galiek of Wondercrete, Peter Visser of CEL Paving Products, Simamkele Ngcaba of Cape Brick, Ben Punt of DBL Precast Decking, Bartlett Barnard of Van Dyk Stene, Michael Finke of Finke Dosiertechnik GmbH and Hans J de Witte, chemical engineer and international pigment expert.

TECHNICAL

gel that results in the concrete cracking.

27

TECHNICAL 28

ADMIXTURES’ ROLE IN MEETING STRICT What exactly are admixtures?

Basically, they’re chemicals used to modify and enhance concrete’s freshly mixed, setting or hardened properties.

They’re added to the batch before or during mixing.

What led to admixtures’ development?

There’s been a change in building practice over the past few decades, with more expected of concrete than ever before.

REQUIREMENTS FOR CONCRETE Just how important are admixes in the manufacture of quality concrete products? Norman Seymore, head of admixture producer, Chryso Southern Africa, explains the role of admixtures in concrete design

The trend now is to use fluid concrete that

What are the main categories of admix-

When did the construction industry be-

can be fitted and moulded into any shape.

tures used in concrete mixes today?

come converted to the role admixtures

However, concrete strength is non-

Admixtures can be classified into five

can play to enhance performance and

negotiable and that’s why chemicals such

main categories: plasticisers, super-

durability? Was there substantial early

as admixtures were developed: to enhance

plasticisers, air-entrainers, accelerators

resistance?

concrete without sacrificing strength.

and retarders.

It was during the 1980s that admixtures

How do admixtures improve concrete

Briefly, what are the individual charac-

essential part of concrete mix design.

performance?

teristics of these admixtures?

In the early years, there was scepti-

Admixtures can improve workability,

When plasticisers are added to the con-

cism from some quarters, but as the

develop high early strength, increase

crete mix, they enhance workability by

industry’s advanced – and become able

ultimate strength, compensate for

repelling binder particles and distribut-

to really measure the benefits of admix-

temperature fluctuations and improve

ing the particles more evenly throughout

tures – there are very few projects on

resistance to corrosion, shrinkage or

the concrete. Super-plasticisers can re-

which admixtures aren’t included in the

freezing and thawing. They’re also used

duce the required water content of the

concrete mix design today.

to overcome placement emergencies

concrete mix by 15-20%. Air-entrainers

such as equipment failure and other un-

introduce bubbles to the concrete mix

Is there a facet of the construction op-

expected delays. Admixtures also reduce

to provide maximum protection against

erations that particularly benefits from

the cost of the concrete mix and com-

f r eezing and thawing and incr ease

the use of admixtures in the concrete?

pensate for poor aggregate properties.

workability when the mix lacks fines.

Many precast operations now use self-

Accelerators speed up the chemical

compacting concrete (SCC). This is a

reaction of the cement and water and,

highly flowable type of concrete that

consequently, the rate of hydration,

spreads into the form without the need

really started to be regarded as an

“The new-generation admixtures are based on specific raw materials or polymers (polycarboxylates).”

improving the setting or early gain in the strength of concrete. Retarders, on the other hand, slow the chemical reaction of cement and water, providing longer setting times and slower initial strength gain.

(Top, from left): Evaluation of the alkali content of cement and admixtures by Donald Khoza in the Chryso Centre of Excellence laboratory, which provides a testing and advisory service to customers; the towering pylons of the Nelson Mandela Bridge in Johannesburg were filled with self-compacting concrete based on an admixture supplied by Chryso.

PRECAST | ISSUE TWO | 2018

of admixtures not only in this country,

admixtures are used to meet a project’s

segregating concrete that’s placed by

but worldwide?

specific needs.

means of its own weight.

The new-generation admixtures are

With careful mix design, SCC admix-

based on specific raw materials or

How important are the advisory role

tures produce a concrete that’s fully

polymers (polycarboxylates). These raw

and after-sales service in the admixture

flowing and self-compacting and can be

materials and formulations radically im-

industry?

placed with no vibration. SCC functions

prove the performance of the admixture

Accurate dosing is essential to fully

in the same manner as super-plasticised,

in terms of water reduction/workability

capitalise on the benefits of admixtures.

flowing concrete, but doesn’t need any

retention and strength development,

Dosage rates and admixture selection

compacting ef fort. It’s also

compared with traditional or

are determined through a series of trial

less susceptible to bleed and

old-generation admixtures. A

mixes to optimise concrete properties.

segregation.

key benefit for Chryso is that

This is why it’s vital for suppliers of ad-

A dmi x tur es, speci f icall y

we produce our own raw mate-

mixtures to provide detailed guidelines

super-plasticisers, produce

rials for the formulation of our

to assist with design of mix proportions

fluid SCC, which is cohesive

new-generation products.

and admixture dosages.

Which sectors of the construc-

cerned, Chryso recently substantially

tion industry are the main us-

expanded its laboratory testing facilities

with high flow retention. SCC is also extremely pumpable. For example, the towering pylons

As far as after-sales service is con-

of the Nelson Mandela Bridge in Johan-

ers of your admixtures?

with the opening of a new Centre of Ex-

nesburg were filled with SCC based on

Ready-mix concrete users mainly use

cellence in Jet Park. The centre features

a super-plasticiser supplied by Chryso.

admixtures to adjust the workability

ultra-modern equipment and temperature

retention of concrete; precast users

control systems to offer cement, concrete

What exactly is new in Chryso’s New

use admixtures to speed placing and set-

and construction system technology as an

Generation range of admixtures, which

ting times so that they can get faster

added-value service to customers.

have been around for a few years now?

turnaround time of the moulds and im-

And how radically did these relatively

proved surface finishes, while for on-site

“green” chemicals change the fortune

mixing for new construction, different

(Above): Admixtures were developed to enhance concrete performance without sacrificing strength, says Chryso chief Norman Seymore.

TECHNICAL

for mechanical vibration. It’s a non-

29

TECHNICAL 30

PREVENTATIVE MAINTENANCE ENSURES DURABILITY The durability of concrete structures, in-

especially in zones where chloride ingress

Crack repairs

cluding precast, can be greatly increased

or carbonation are a reality. Repairing

“Among the most common challenges of

by a proper preventative maintenance and

deteriorated concrete and restoring its

concrete rehabilitation are crack repair,

repair programme, says Warren Trew,

structural integrity should consequently

patching, using strengthening methods

Gauteng sales manager: General Con-

form part of the initial design, but these

(in lieu of repair) like carbon fibre plate or

struction of abe Construction Chemicals.

measures are frequently resorted to only

wrap, and generally choosing the most ap-

when emergencies arise.

propriate repair materials for an effective

Trew says many key South African building and civil structures have eroded

“The first and most crucial step in

long-term solution. A decision should also

with age, neglect, misuse, weather fac-

a successful repair project involves

be taken on whether strengthening meth-

tors, rebar corrosion, extraneous load-

early damage assessment and arriving

ods should be opted for instead of repair.

ing and natural disasters. “Neglecting

at a proper diagnosis. The

Fortunately, the range of con-

the need to introduce proper repair and

owners shouldn’t wait until

crete repair products avail-

maintenance systems for these struc-

the concrete shows obvious

able today have made it pos-

tures results in reduced capital value and

signs of distress. To properly

sible to economically refurbish

wastage of resources, which could lead to

repair any damage, it’s im-

structures that just a few

poor quality of life for communities. With

portant to understand what

decades ago would have had

large parts of SA currently experiencing

c ause d th e p r ob l em an d

to be demolished and rebuilt.

devastating drought, the need for ad-

then determine the correct

The input from specialists in

equate maintenance of water reservoirs

method of repair.

concrete rehabilitation – and

and dams particularly comes to mind.

“Experience is vital for

the selection of the correct

“In a sustainably built environment,

the diagnosing and planning of concrete

products – will avoid common pitfalls of

structural maintenance is non-negotiable.

repairs. While a high level of expertise

concrete repairs,” observes Trew.

As soon as a concrete structure is

goes into concrete construction, the

He says abe Construction Chemi-

completed, the need for a maintenance

skills, understanding and experience

cals’ range of concrete repair products

programme must start. Maintenance

required to repair damaged or deterio-

is based on epoxies, synthetic resins,

shouldn’t be driven simply by the need to

rated structures are decidedly differ-

silanes and cementitious materials. Ap-

correct defects that occur over time,

ent from those required to build new

plications include flexible slurries and

but to avoid these defects in good time,”

structures. That’s why it’s important

coatings for protecting and waterproofing

says Trew.

to consult reputable suppliers of con-

the concrete parts of bridges, silos, build-

crete repair products – companies that

ing and water containment structures

Dire need

can offer not only the product, but also

against attack from their environment.

He says concrete is a durable, but not

advice on its suitability, as well as the

eternal material. Over time, it will deteri-

system and procedures to be followed

orate and require repair or replacement,

for concrete repair projects.

(Above): Repairing deteriorated concrete and restoring its structural integrity should form part of the initial design, says abe’s Warren Trew.

PRECAST | ISSUE TWO | 2018

ADVANTAGES OF PRECAST CONCRETE WINGWALL UNITS Precast concrete products offer many advantages and Rocla’s precast concrete wingwall units are no exception. Wingwall units are used at both the inlet and outlet of a pipe system in both culvert and stormwater applications. Precast wingwall units offer the client a faster installation time, reduced material usage and no site-mix concrete or reinforcing on site, resulting in project cost-efficiencies.

The natural flow path of water upstream of a construction is wider than the culvert or pipe structure. Transition sections are therefore required to receive and direct the flow of this upstream water through the culvert/pipe. This is also true of the downstream end of the culvert/pipe, where the flow of water is to be returned to the natural width of the stream. Where water velocities reach up to 4m/s and above, the precast concrete wingwall unit is the most effective structure to use for the transfer of this water.

In stormwater applications, the primary focus is to direct water into a flow path that results in the least amount of turbulence. This, in turn, optimises the hydraulic capacity of the conduit. The wingwall portion directs the water, while the wingwall, floor slab and toe provide protection for the embankment and surrounds against scouring and possible collapse.

Rocla’s precast concrete wingwall units offer: • Fast and easy installation.

• A reduction in the quantity of materials required.

• No waste or clean-up required.

• No formwork.

• Making remotely located sites simpler to manage.

• Guaranteed concrete strength.

• Guaranteed quantity and positioning of designed reinforcing.

• No curing of concrete or formwork stripping required,

thus saving time.

• Units capable of fitting a wide range of pipe diameters

and culvert sections.

• Lifting anchors cast into the structure.

“We believe that the time- and cost-savings associated with the utilisation of precast concrete wingwall units can be enormous for infrastructure-related projects. The full range of wingwalls can be manufactured at all Rocla factories nationwide, optimising transportation costs. Rocla’s well known for its manufacturing capabilities and quality standards, in addition to its technical team available to assist with technical support required by the customer,” says Justin Kretzmar, Rocla’s sales engineer.

Rocla has been supplying precast concrete products to most of the major infrastructure projects in SA, Mozambique, Namibia and Botswana. Its entire product offering is manufactured to the ISO 9001:2008 standard at various plants throughout SA, Namibia and Botswana.

PRECAST | ISSUE TWO | 2018

PROJECTS

Part of the process involved the assembly of two small desalination plants on the False Bay coastline, which used precast concrete collars for attachment to inlet and outlet pipes.

The weight of the collars, which were manufactured under extremely tight time

32

constraints by CMA member Concrete

CONCRETE COLLARS FOR DESALINATION PLANTS Precast concrete has played a crucial role in assisting Cape Town implement emergency measures to alleviate the city’s unprecedented water shortage.

Units, provided the pipelines with the re-

positioning of the 100m sections and

quired ballast and stability to keep them

the connecting required excellent co-

firmly anchored to the seabed.

ordination and could only be undertaken

Concrete Units manager Brian Cook

during calm seas.

says that due to the pressing nature of the projects, there was very little time

Discharge section

to tender for and execute the contracts.

The outlet (or brine pipe, as it is called) is considerably shorter at 250m and has

Fast turnaround

a narrower diameter of 350mm. This is

“Our delivery targets were extremely

due to the fact that roughly 55% of the

challenging and, in meeting them, we

intake volume is retained and only 45%

redesigned the shape and size of the

of the original volume is returned to the

collars. This enabled us to produce fully

sea. Nevertheless, the assembly of the

workable moulds using our own technolo-

brine pipe sections followed the same

gy within seven calendar days of receiving

production process used on the Gordon’s

the order – something which has never

Bay pier and by the time the contract

been achieved before and which none of

had been completed, Concrete Units had

our peers believed was possible.

delivered 128 collars for the inlet pipe and 19 collars for the outlet pipe.

“We bent plates and took other extraordinary measures to produce

Cook says that the first cast began

the moulds in record time without any

at 6am and the second star ted at

outside help. In addition, other steps to

4.30pm. “We required a strength of

increase the rate of production included:

18MPa to remove the units from the

creating an extra week’s production by

moulds, which meant that we achieved a

working on the last three weekends be-

final strength of 70MPa, far higher than was actually required.”

fore the December holiday break, casting twice a day and using special concrete and acceleration systems.”

(Above, from top): Concrete collars on the pier at Gordon’s Bay prior to the assembly process; two pipe sections are butt-welded together.

These desalination plants are regarded as short-term emergency measures and are due to be decommissioned

Using mobile and containerised desalination equipment from Europe, the

15km to a barge 1,5km offshore of the

after two years in operation. This is due

first plant was installed at Monwabisi off

Monwabisi site.

to the fact that desalination is energy-

Baden Powell Drive, which links Stellen-

Each pipe section was hauled inland by

intensive, very expensive and decidedly

bosch to Muizenberg. With a daily output

a winch and, once in position, was flooded

non-eco-friendly. After decommissioning,

capacity of seven megalitres, the plant is

and guided to the seabed by professional

the concrete collars will be recycled. The

linked to the sea via two separate pipes.

divers. The divers also did the final con-

steel will be separated from the concrete

nection on the seabed by bolting the

and recycled and the concrete will be

flanges of each section together. The

crushed and sold for use as sub-base

Clean water The inlet pipe has a diameter of 630mm

material. The HDPE pipes will either be

and extends 850m out to sea. It was

redeployed as pipes or recycled. Very

assembled off-site by the main contrac-

little will be wasted.

tor, Subtech, in Gordon’s Bay harbour in 100m lengths using 12m HDPE pipe sections. This involved welding the pipes together on the pier and then fitting the collars around the pipes at 6m intervals.

Once a 100m section was assembled, it was capped at either end to trap the air inside so that it could float. Cranes were used to launch completed sections off the pier into the water and a tug towed two sections at a time some

(Left): A floating pipe section with concrete collars attached.

(Above): A 100m pipe section is attached to a tug prior to towing out to sea.

PRECAST | ISSUE TWO | 2018

AFRICAâ&#x20AC;&#x2122;S MOST SOUTHERLY ROAD PAVED WITH EXPOSED AGGREGATE CBP Exposed aggregate concrete block pavers (CBP) have been used to pave a section of road which runs parallel to the Western Cape coast between the Cape Agulhas lighthouse and the coastal village of Suiderstrand. Situated in the Agulhas National Park on the southernmost tip of Africa, the road was constructed for the SA National Parks Board (SANParks) during the latter half of 2017 and early part of 2018.

The paved section extends 1,2km across gently undulating topography from the lighthouse to a new outdoor museum which was recently built to commemorate this unique geographic location. The road has a paved width of 6,8m and was paved with 8 100m² of 70mm Muddy exposed aggregate interlocking paving blocks, manufactured by CMA member CEL Paving Products.

SANParks specified that the road should make as little visual impact on the surrounding topography as possible.

This was achieved by giving the road a low profile and using a paver which blends in with the colours of the sand and rocks of the region.

Designed by consulting engineers Ingerop SA as a cambered road with cross-culvert drainage, it was constructed by grading and compacting an existing gravel road. The sub-grade, which was formed with material from the existing road, was covered with a sub-base of imported G5 aggregate, cementstabilised to a C4 quality. Excavated material was used to form a berm on the landward side of the road, which was heaped above road height to channel stormwater away from the road and into the cross-culverts.

The project also involved precast concrete kerbing, the construction of 1,0m-deep mole barriers using 2mm-thick HDPE sheeting and a raised pedestrian crossing which links a boardwalk between the lighthouse and the open-air museum.

The paving contractor was Mapitsi/Masiqhame Joint Venture, which used local labour to lay the pavers in a herringbone pattern. The concrete kerbs were supplied by Blueportwetcast based in Eersterivier.

PRECAST | ISSUE TWO | 2018

PROJECTS

CMA member Rocla is undertaking several large-scale sewer and stormwater projects with some challenging requirements along the way.

In Waterkloof Quarry, a 58ha landmark

34

situated on the border of Waterkloof Ridge and Monument Park, Rocla was selected to manufacture and supply all the stormwater (spigot and socket) and interlocking pipes for an upmarket retirement estate known as the Waterkloof Marina Retirement Estate, due to be launched early in 2019.

Hannes Bezuidenhout, estimator from Advance Projects, comments: “This exciting development will consist of a mixed-use development which will offer a large selection of sectional title and full ownership retirement units and full support facilities, such as a 24-hour

DIVERSE PROJECTS FOR

I believe the Waterkloof Dam’s still good

PIPE MANUFACTURER

for bass fishing!”

ability, that secured it the contract to

for the delivery of our large stormwater

supply over 614 assorted stormwater

pipes, so that no major inconvenience or

Tough ask

pipes and fit in with the project’s six-

disruption to excavation scheduling oc-

“However, it wasn’t without its chal-

month duration.”

curred. I believe Rocla successfully met

frail care centre, medical centre, restaurants and recreation facilities. And

these specific challenges,” says Brendon

lenges. The size of the pipes required

van Vuuren, sales consultant for Rocla.

for the development and proximity of

Large pipes

the pipe trenches to existing roads

“Obviously, when there are existing

Rocla’s spigot and socket storm-

created some logistic issues in terms

roads nearby or trench excavation work-

water pipes use the rolling rubber ring

of excavation materials, pipe deliveries

ing space is small, the delivery of large

principle and no lubricant is required.

and existing traffic flow.

stormwater pipes can be problematic

Pipes within this category may be or-

for contractors at site.

dered as both stormwater culvert (SC)

“Rocla understood these issues and ensured that pipe deliveries were as we

“At the Waterkloof Marina Retire-

or stormwater and irrigation (SI) pipes.

requested and that pipes were offloaded

ment Estate project, these factors

SI pipes are hydrostatically tested after

as close to the excavated trenches as

needed to be addressed, particularly

manufacturing.

possible for ease of installation,” says Bezuidenhout.

“The timeframe for pipe delivery was a mere three months and it was Rocla’s capability to meet this timeframe, its competitive pricing and product avail-

“The timeframe for pipe delivery was a mere three months.”

Sewer augmentation The increase in residential and commercial developments in the Walmer area of Port Elizabeth, in addition to the estimated increasing requirement by 2020, was a crucial factor for the Nelson Mandela Bay Municipality to increase the capacity of the existing Driftsands Collective Sewer Augmentation.

The construction of a 1 400mm concrete high-density polyethylene (HDPE)lined sewer of 1 850m in length forms part of Phase One of this four-phase project, which commenced in the second quarter of 2017. Rocla was selected

(Above): Sewer pipe laid on stone bedding for the Driftsands Collective Sewer Augmentation.

(Left): Rocla pipes ready for transport.

PRECAST | ISSUE TWO | 2018

and continued with production for the

come the accepted and required stand-

and manhole access pipes. The sewer

remainder of the year. Ten manhole ac-

ard for all future outfall sewer projects.

star ts f r om the Drif tsands Waste

cess pipes were also ordered and these

Water Treatment Works and terminates

were cut in the Rocla yard to specifica-

Second phase

at the ACSA boundary.

tion, which allowed the laying of pipes to

“With Phase One completed, the sec-

The existing sewer was constructed

continue uninterrupted, thus giving the

ond phase is due to start during 2018,

in 1983 and is a gravity sewer which is

contractor the opportunity to achieve

which will certainly present Rocla with

unable to be upgraded from a technical

good production on site.”

new and interesting challenges, as the

perspective, so a realignment of the line

conditions include rock and very deep

route is currently being undertaken. The

trenches, but we’re more than confident

first 1 460m is parallel to the existing

in our ability to overcome these, as well

1 050m Driftsands Collector sewer and

as in our manufacturing capabilities,”

then branches off to bypass the planned

says Howell.

ACSA extension of the Port Elizabeth

PROJECTS

to supply Class 75D HDPE-lined pipes

35

The value of the Phase One project is

Airport runway.

R52,8 million and consists of 1 850m of 1 400 concrete HDPE-lined sewer pipes,

Improving designs

26 manhole structures, one diversion

Graham Howell, Rocla sales consultant

chamber and bulk earthworks.

in Port Elizabeth, explains: “We started

On completion, the 4,2km four-phase

manu f ac tur ing the 780 leng ths o f

project will have addressed the sewer-

1 400mm diameter Class 75D HDPE-

age requirements for existing and future

lined pipes in May 2017 at an average rate of eight pipes per day. We achieved this by double-stripping our four available moulds and we delivered the first

developments for the western suburbs (Above): Pipes being installed at the new Waterkloof Marina Retirement Estate.

Rocla made further design changes

of the Nelson Mandela Bay Municipality.

Calling municipalities

during the manufacture of the manhole

Effective stormwater management can

“We made minor improvements to the

rings and offered rings and cover slabs

prevent pollution, flooding, erosion and

product after numerous on-site visits

with internal HDPE liners. This could be-

damage to the environment and infra-

pipes to site in July 2017.

We are there when you repair

TCI

Need to maintain your concrete? Our Information Centre has extensive information on assessment and repair techniques.

Improve concrete with us. www.theconcreteinstitute.org.za +27 11 315 0300

PROJECTS 36

structure. It therefore makes financial

potentially threatening pollutants into

Projects from Mozambique to Cape Town

sense for local municipalities to invest in

local rivers, dams and municipal water

have utilised technical support and prod-

products and technologies to ensure that

services, creating a breeding ground for

uct quality that is associated with the

the quality of infrastructure, be it stabil-

diseases that could seriously affect the

Rocla range.

ity or sustainability, of both the built and

health of humans and livestock.

natural environments is not compromised.

Rocla has been contracted for the

Storms and the resulting floodwater

supply of precast concrete storm-

Rocla’s stormwater pipes with both in-

can carry toxic particles such as oil, pes-

water pipes to numerous projects over

terlocking and spigot and socket joints

ticides, pet waste, fertiliser and other

the 100 years it has been in operation.

are available in a range of strength

Technical support

ratings. The spigot and socket joints utilise the rolling rubber ring principle, where no installation lubricant is required. All pipes conform to the SANS 677 standard.

Af ter consultations with Rocla’s technical team, interlocking joint pipes were selected for installation at the Great North Plaza in Limpopo, while the Borwa project in Westonaria selected Rocla spigot and socket joint stormwater pipes. Technical support from Rocla ensures that correct product and technology is selected with consideration for the financial constraints of each project.

Rocla’s entire product of fering is manufactured to the ISO 9001:2008 standard at various plants throughout SA, Namibia and Botswana.

PROJECTS 37

NEW 3D PRINTED HOUSE Arup and CLS Architects unveiled 3D Housing 05 – a new 3D printed house in central Milan – as part of the Salone del Mobile design festival.

Printed on-site by a portable robot, the house showcases the role 3D printing can play in reducing construction waste; it increases efficiencies during the building process and allows materials to be re-used at the end of the building’s life, rather than ending up as landfill.

the end of their lives. 3D printing technology is critical to helping our industry become far more accurate, efficient and less wasteful.”

“This building represents a milestone for 3D printing applied to construction,” says Luca Stabile, Italy building practice leader at Arup. “The industry’s fast moving towards increased levels of automation. Robots are opening up a number of possibilities for realising

The construction industry is currently one

the next generation of advanced build-

Advantages of 3D-printed buildings

of the world’s biggest users of resources;

ings. Digital tools combined with new

• Sustainability: They of fer a

in the UK alone, it accounts for 60% of

technologies will enable the production

sustainable alternative to the

all raw materials consumed. The concrete

of custom-made shapes that can’t be

traditional construction pro-

3D-printed house, the first of its kind

produced otherwise. We’re pushing the

cess, reducing material waste

within the EU, can be taken apart and re-

boundaries and contributing to radical

and allowing recycled concrete

assembled elsewhere. Arup, a knowledge

innovation through new manufacturing

to be used. 3D-printed buildings

partner of the Ellen McArthur Foundation,

technologies and materials.”

can be designed to ensure that

has applied learnings from its innovative

A robot from Cybe Construction was

the components can be re-used

Circular Building, which was constructed

used to print the walls, while the roof,

in the future, according to the

out of fully re-usable components.

windows and doors were completed af-

principles of the Circular Economy.

T he one-stor ey concr ete house,

terwards. Italcementi, one of the world’s

• Flexibility: They also offer great-

located in the grand Piazza Cesare Bec-

largest cement suppliers, provided advice

er f lexibility in the building

caria, covers 100m2; it has curved walls,

for the base concrete mix used during the

shape, allowing engineers and

a living area, a bedroom, a kitchen and a

printing operations.

architects to generate more

bathroom. The project differs from many

complex structures, such as

other 3D processes in its use of a robotic

double-curved walls, at lower

manipulator, mounted on a movable base

cost. In addition, the process

for increased flexibility compared with

allows for on-site construction

fixed 3D printers. The house is made up of

with few limitations regarding

35 modules that have each been printed

site location.

in 60-90 minutes; the full house has been

• Affordability: 3D printing is less

printed in just 48 hours’ effective time.

expensive than traditional con-

The building will be moved from the square

str uc tion due to the mor e

to a new location after the festival.

efficient use of materials and

“We’re at Salone del Mobile to build

a more structured and faster

momentum,” says Guglielmo Carra, Eu-

building process.

rope materials consulting lead at Arup.

CONCRETE

MOULDS STEEL FIBREGLASS POLYURETHANE SILICONE

• Accuracy: 3D printing offers a

“We need to make a major shift in the

dir ect transf er of inf orma-

way the construction industry oper-

tion from the 3D design model

ates, away from today’s ‘make, use and

to construction operations,

dispose’ mentality. We’ve shown with

082 774 4657 Unit 8, Ken Smith Industrial Park, Rand Street, George Industria

thereby drastically reducing

this building that 3D printing technology

building inconsistencies and

is now advanced enough to take on more

potential mistakes.

complex structures and we can design buildings to be re-purposed or re-used at

PRECAST | ISSUE TWO | 2018

www.concretemoulds.co.za

RPOJECTS

The channel forms the major component of a sustainable urban drainage system (SUDS) designed to protect the new housing estate from water flows during heavy downpours. Specified by the Western Cape’s Provincial Government, it was designed by consulting engineers

38

Over 76 000 precast concrete Terracrete grass blocks, manufactured by Terraforce licensee and CMA member, Klapmuts Concrete, have been used to line a 6,5m-wide section of 1,8km stormwater drainage channel next to what will become the Vlakkeland low-cost housing estate in a peri-urban area on the outskirts of Paarl, Western Cape.

Lyners & Associates, based on input from Guillaume Nel Environmental Consultants and some initial stormwater surveys undertaken by Graham McGill of Graham McGill Consulting.

T he channel is par t of a system which has been designed to ensure that stormwater flows are managed and dispensed in a controlled manner. Several tributaries and stormwater pipes which previously flowed into several evaporation ponds, situated on the land earmarked for the new housing estate, now drain into the main channel, Channel 1, and into two tributary channels, named 2 and 3.

PERMEABLE GRASS BLOCKS USED FOR

MASSIVE STORMWATER CHANNEL Water management

to minimise dust during dry periods and

The unlined section of the main channel

encourage water infiltration.

was designed to accommodate a 1:100

The main channel is composed of four

year flood (50,2m³/s), whereas the lined

material layers: the sub-soil which was

section can accommodate a 1:5 (18m³/s)

compacted with rollers to 93% MOD

year flood.

AASHTO, a layer of Grade A2 geofab-

The deployment of the Terracrete

ric, which prevents the blocks from

blocks and mini gabion dams, which were

settling too much and allows filtration,

built into the downstream section of

while preventing the wash-out of locally

Channel 1, reduce flow rates and allow

sourced bedding sand, and the Terra-

the SUDS system to better filtrate any

crete grass blocks.

run-off. The other major component of

These Terracrete blocks are being

the system is a large attenuation pond

filled with a bio-charcoal material and

which was excavated at the bottom end

mushroom spores, the former to absorb

of Channel 1.

pollutants in the water and the latter

The pond further reduces the flow

to recharge the charcoal and keep it fit

rate and prevents surges by releasing

for purpose. The channel banks above

water gradually through a 450mm outlet

the blocks are being planted with grass.

pipe at the far end of the pond. However,

The main channel and the bulk earth-

when water volumes are such that

works, including the attenuation ponds

the pond fills to capacity, the overflow

and other channels, were constructed

pushes back into the main channel at the

by JVZ Construction.

entrance to the pond.

Absorbing pollutants In addition, a secondary and smaller attenuation pond has been excavated immediately above some culverts which have been installed under a main tarred road adjacent to the estate. Grass has been planted on the floors of both ponds

(Top): The lined section of Channel 1 under construction.

(Left, from top): The partially completed Channel 1 in which the bio-charcoal fill material can be seen inside the Terracrete blocks; newly-laid Terracrete grass blocks in Channel 1; the main attenuation pond under construction; the partially completed entrance to the main attenuation pond where Channel 1 forks, one arm leading into the pond and the other feeding into an extension of the channel.

PRECAST | ISSUE TWO | 2018

PROJECTS

CONCRETE CAST STONE COBBLES UPGRADE WINE ESTATE HOUSE Situated on the Libertas Wine Estate in

39

Stellenbosch, House Van Heerden underwent wide-ranging renovations during the second half of 2017. The project involved a complete redesign of the garden, which was wild and hilly, and extensive use was

because the house was to be painted

forecourt also included a grass block sec-

made of CMA member Revelstone’s char-

white and because the roof and window

tion, adding colour diversity and softening

coal Kent and Jura cobbles, in combina-

frames were also coloured charcoal.

the whole area.

tion with Ravine tiles and pavers.

Moreover, as Tone Alexander explained,

Further design differentiation was

charcoal provided an excellent backdrop

achieved by paving a patio and a section

to green foliage.

between the driveway and front door,

The design of the new paved areas involved collaboration between the landscape designer, Tone Alexander Design

Kent and Jura cobbles were used to

with larger Ravine tiles in the same char-

Solutions and paving contractor, Adrien

good effect on the large driveway and

coal colour. Other paved areas included

of Progressive Paving, and it included

forecourt in front of the house. They

the courtyard and kitchen patio.

repaving the original red brick driveway

were laid in grid formation together with

in Kent and Jura cobbles.

rectangular Jura cobbles, which were

Char coal cobbles wer e specif ied

used as edging and accent lines. The

(Above): Revelstone’s Jura and rectangular cobbles form the perfect contrast to the green foliage in the forecourt of House Van Heerden.

granite inlays per square metre of paving. Paving contractor Cox Civils did this by cutting into and removing the middle section of G-Bloks and inserting granite block pieces between the remaining two pieces of G-Bloks.

The G-Bloks were supplied in thicknesses of 80mm and 60mm, the former for areas of heavy traffic and the latter for light-trafficked areas and walkways.

In addition, Aveng Infraset supplied

EXPOSED AGGREGATE PAVERS FOR SUPERIOR PAVING FINISH

12 000m² of 60mm grey G-Bloks for the

In what may well be a first for SA, just

paving gives an established look which im-

designed by Craft of Architecture. Apart-

under 3 000m2 of exposed aggregate

proves with weathering, a process which,

ments are being marketed from R1 million

paving blocks have been used in combina-

over time, renders the jointing invisible.

for a single-bedroom unit and up to R3,7

tion with polished granite inserts for the

Another plus was that Aveng Infraset’s G-

million for a three-bedroom unit. Luxury

paving of parking areas and driveways

Blok pavers passed all engineering tests.

four-bedroom units are also available.

at OceanDune Sibaya, a 260-unit luxury

Uys & White also suggested the use

Occupation of OceanDune Sibaya

apartment development some 10km

of granite blocks for enhanced aesthetic

began at the end of May this year and

north of Umhlanga Rocks, close to the

appeal and their glitter effect at night

final occupation will take place at the

Sibaya Casino on the KwaZulu-Natal

and specified the insertion of roughly four

end of August, when further units are

(KZN) North Coast.

paving of the parking basements.

OceanDune Sibaya is being brought to market by Construction ID and was

completed. A neighbouring development,

The paving, which comprised CMA

Pebble Beach, which is also being devel-

member Aveng Infraset’s exposed ag-

oped by Construction ID, is earmarked for

gregate G-Blok paver, was specified by

completion by mid-2019.

Uys & White Landscape Architects KZN. The inspiration came from the exposed aggregate paving used in the parking areas of Cape Town’s Kirstenbosch National Botanical Garden. Exposed aggregate

PRECAST | ISSUE TWO | 2018

(Above): A newly-completed section of exposed aggregate paving at OceanDune Sibaya.

(Left): Polished granite blocks are installed between exposed aggregate G-Blok pavers at OceanDune Sibaya.

PROJECTS

CAPE TOWN LUXURY HOUSING UNITS BUILT WITH PRE-STRESSED RIB AND BLOCK DECKING Due for completion in April 2019 and varying between 250-340m², the triple-

40

storey houses comprise four-car basement garages and luxury finishes, as well as eco-friendly features such as watersaving devices and integrated heat pumps combined with solar panels, among numerous other options. Priced between R7,95 million-R8,95 million, five units had been sold as Precast went to press.

The R&B system was supplied by Western Cape-based DBL Precast Decking. Manufactured in standard 150mm widths and 60mm depths, the ribs were pre-stressed and came in lengths of 1,27,5m. A Classico Developments project, 3 Mona is being constructed by main contractor WJC Projects, which has been using R&B construction for the past 15 years. WJC managing director, John Watson, notes that the major advantages of R&B over pure in-situ construction

A new triple-storey cluster housing project, 3 Mona, situated in a secure residential estate near Cape Town’s Newlands cricket ground, is being built using prestressed concrete rib and block (R&B) decking.

are speed, price and simplicity.

Fast erection “A 100m² deck, including the propping and all the servicing and reinforcing, takes us three days to install before the concrete is poured and it took us a mere eight weeks to cast all 18 decks on this project. 3 Mona’s completed slabs are 300mm thick and once the concrete had been poured on the R&B formwork, it was only a matter of days before we were able to begin work on the upper-storey structures,” says Watson.

of mesh with the engineer’s consent, but

“We’ve been using a combination of

we prefer mesh because it can be used to

100mm-, 150mm- and 200mm-high deck-

keep conduits in place and prevents them

ing blocks to achieve various deck depths.

from floating up during casting.”

The low 100mm block is very useful to accommodate services within the depth

Versatile solution

of the slab without compromising its

DBL has been in the R&B business since

structural integrity. It’s also used where

1986 and has worked solely with inde-

bottom reinforcing, such as transverse

pendent consulting engineers on all its

stiffeners, is required.

(Top): Y32 rebar was used in the construction of small cantilevered balconies outside the main bedrooms on the second-floor decks.

(Above, from left): The underside of a second-floor structure at 3 Mona, showing the steel support beam as well as the R&B assembly; a recently installed floor showing Y16 rebar stiffeners laid down the middle of a second-floor deck at 3 Mona.

Also visible are 6mm hard-drawn loop-shear connectors, which are cast into the ribs to anchor the poured concrete to the R&B assembly.

projects. This is one of the reasons there

slabs. In this instance, the project engi-

“Ribs contain all the primary bottom

are very few engineers in Cape Town who

neer, Ted Kelly, made good use of R&B’s

reinforcing for the decks. This is why engi-

do not have considerable experience in

versatility to overcome the numerous

neers design the top reinforcing elements

R&B. All engineers have their own pref-

design challenges on these triple-storey,

such as cantilevers, continuity and hog-

erences in design and some of them are

open-plan houses. He designed the houses

ging steel, as well as transverse reinforc-

more cautious than others.

with a mix of steel and concrete beams

ing to run in the opposite direction to the

R&B can be very successfully designed

as additional load-bearing mechanisms

span of the ribs. On this project we used

to work compositely with both steel and

over large openings to transfer loads to

Ref-100 mesh as anti–cracking reinforce-

concrete beams, particularly as the depth

foundation. He also made innovative use of

ment. Fibre concrete can be used instead

of the beams is equal to the depth of the

span direction changes to accommodate

PRECAST | ISSUE TWO | 2018

traditionally reinforced lattice systems.

Less concrete

the staircases.

These include reduced long-term de-

Punt adds that pre-stressed R&B con-

Several deck sections at 3 Mona

flection, superior fire- and corrosion-

struction has a fairly green footprint

were up to 10m wide, which meant the

resistance and enhanced sheer capacity.

because it uses up to 75% less steel

spans needed to be broken by beams.

The most important factor, however, is

than traditional in-situ slabs and lat-

Although the majority of the beams on

the cost-savings, which are passed on

tice R&B slabs. And because the blocks

this project are concrete, Kelly used

to our clients.

are hollow, they use less concrete and

shallower steel beams over the open-

reduce dead weight.

plan lounge, kitchen and dining areas,

“The other big benefit of R&B is

where the architect and clients wanted

that it’s labour-intensive, both in its

uninterrupted, open soffits.

manufacture and application. Installation doesn’t require skilled labour and

Hybrid system

can take place as soon as some of the

“A major plus of R&B construction is

load-bearing walls reach slab height. One

that it’s a hybrid system, offering the

doesn’t have to wait until all the walls

best of both worlds, precast and in-

reach slab height and because they’re

situ construction,” says Ben Punt, MD of DBL Precast Decking. “It has all the

(Above): One of the 10m steel beams which were used by the engineer for R&B support.

adaptability and flexibility that come with

easy to install, we’re finding that bricklayers can easily do the decking installation as well.

in-situ, while providing a solid composite

“We produce ribs to stock lengths

“This means the masonry work and

structure. It also provides the speed of

in 100mm increments and we always

slab work can be done in tandem. This

construction of precast concrete and

have about 15 000m² of stock ready

also gives the plumber and electrician

the structural integrity of in-situ con-

and cured, available for delivery as soon

additional time to tube the slab, prevent-

struction, due to the reinforced in-situ

as the engineer’s design has been ap-

ing a last-minute rush and subsequent

concrete topping.

proved. This is in contrast to lattice R&B

errors. This is a convenient and flexible

“We’ve chosen to specialise in pre-

construction, where the ribs are only

way of keeping a building team on site

stressed R&B construction because

manufactured after the design measure-

all the time, which builders find very

of the undeniable benefits gained over

ments have been confirmed.”

beneficial,” says Punt.

PROJECTS

cantilever balconies and the voids around

41

PROJECTS 42

SAâ&#x20AC;&#x2122;S SMART C Property development and nature might not automatically go hand in hand, but more and more developers are moving towards incorporating nature into building design.

Green spaces prove popular, even in major city centres where they are seemingly rare. Rooftop gardens are springing up in central business districts in the likes of Hong Kong, Tokyo, Rotterdam and New York. Likewise, urban farming initiatives

PROJECTS 43

CITIES ARE DRIVING SUSTAINABILITY makes a smart city? Combining the

opers are under pressure to drastically

perks of modern technology with the feel

minimise water usage and incorporate

In SA, Johannesburg has long been

of old-time village living – with walkable,

eco-friendly technologies that will ben-

considered the world’s largest man-

pedestrianised streets and green spaces.

efit the planet in the long term. “Modern

made urban forest, boasting more than

Yet “green can mean many things. It’s

trends in development and construction

6 million trees. And Cape Town’s CBD is

the colour you allegedly turn when you’re

are predominantly focused on issues re-

set to change with the arrival of its first

sick, envious or inexperienced. You’re

lating to sustainability,” says Stopforth.

environmentally friendly mixed-use de-

encouraged to “eat your greens” to stay

“Residents and investors want to know

velopment: Harbour Arch. Perhaps sur-

in good health. You can green an urban

what’s being done to reduce impact on

prisingly, one of the most eye-catching

area by planting trees, or even green

the environment.”

features of this 5,8ha mixed-use precinct

your home to make a positive impact on

will be the complex’s green roof top

the environment.

to boost food resources are fast becoming a global trend.

Sustainability now

New-urbanist pr ecincts such as

“Everything about development today

Melrose Arch and Harbour Arch revolve

is about sustainability and energy-wise

Smart cities

around the principle of being close to

innovation, water-saving technology,

With the rise of “smart cities” – mixed-

everything you need in daily life, with all

heat-reducing aspects, etc. And when

use precincts – developers are driven

your requirements accessible by foot.

you use sustainable technology, you also

to find ways of creating green spaces

But it’s the outdoor spaces – the piazza-

reduce the cost of occupation in the long

innovatively in a bid to bring nature to

style squares and courtyards for dog-

term and obtain a competitive edge,”

the concrete jungle.

walking or people-watching – that give

says Stopforth.

towering over the city’s harbour.

Nicholas Stopforth, managing director of Amdec Property Developments

these inner-city developments a sense of community.

Sustainability and eco-friendly innovation are a key focus area of Amdec’s developments, with green building initia-

– the group behind SA’s award-winning Melrose Arch and the new Harbour Arch

Growing need

tives including refuse recycling, water-

– says green spaces are essential for

There has been huge demand for busi-

saving devices, low-energy LED lighting

people to feel safe and secure in an envi-

ness, retail and residential spaces within

and rainwater harvesting. With water

ronment. Nature has long been lauded for

Melrose Arch. So much so that a new

scarcity being the new normal for SA,

its positive impact on the human psyche.

residential complex – One on Whiteley

developers must implement water-wise

There are countless studies and reports

– within the precinct is currently under

strategies from the ground up. Harbour

on the benefits of green spaces for our

construction.

Arch, for example, has been designed to

mental health.

But just what The world over, devel-

harvest rainwater to reduce the load on municipal supply.

“There’s huge benefit in executing water-saving measures at the construction stage, rather than retro-fitting. Not only is it better to have systems in place at the start, but it saves money in the long run,” explains Stopforth.

Recycled water – either rain-harvested or grey water – will be used for flushing, gardening and landscaping.

“Ultimately, we need to reduce our impact. It’s better for business and it’s better for the planet,” says Stopforth.

PRECAST | ISSUE TWO | 2018

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PI – Precast Infrastructure PB – Precast Building

PRECAST | ISSUE TWO | 2018

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