Precast • Issue 1 • 2021

CONCRETE MANUFACTURING & CONSTRUCTION ISSUE 1 2021

R49,00

PRECAST

IN THIS ISSUE: Construction industry is united SA product makes it in Spain Shedding light on stormwater purification

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Creating Concrete Possibilities

| CONTENTS |

6 Editor’s NOTE

Rising above the ashes Even as the world’s largest crisis in over 75 years lay at mankind’s doorsteps a year ago, the world’s population was already adapting and seeking ways of defeating the Covid-19 scourge.

That is the nature of us humans.

We a re ha rdw ired to sur v ive against the toughest of odds. If forced to do so, we can adapt to the grimmest of conditions and even thrive in the face of doom. This has been the case in recent months with the pandemic bringing out the best in us and reminding us, seven decades after the Second World War, how formidable the human spirit really is.

The same can be said of the country’s trade media which was forced to adapt overnight to find ways of serving our industries or perish trying to do so. In this regard Precast magazine is at the front of the pack, leading a new wave of communication through digitised databases, social connections and new publishing products that bring readers and advertisers closer than ever before.

Even the look of our flagship printed magazine has changed, so we present you with the new, Covid-proof Precast magazine.

Enjoy!

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Endorsed by:

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Construction industry unites to form a national umbrella body

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MAPEI South Africa awarded ISO 9001 certification

CONCRETE MANUFACTURING & CONSTRUCTION ISSUE 1 2021

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INDUSTRY NEWS

6 Preventing coal ash from reaching dumpsites 8

Finding a way forward for recycled building material IN THIS ISSUE: Construction industry is united

COMPANY NEWS 11 Precasters helping our children 12 Bolted structural connections unlock potential

for construction

PRODUCTS 16 The “BASTION” – a massive retaining wall block 17 Measuring manufacturing environments

GLOBAL VIEW 18 South African retaining wall excellence finds

favour in Spain

SA product makes it in Spain Shedding light on stormwater purification

ON THE COVER Twinstar Precast in Olifantsfontein boldly goes where others fear to tread by manufacturing all types of customdesigned and cast products for civil engineering contractors. While these one-off jobs are usually avoided by typical precasters due to their complexity, size and resource-intensive requirements, Twinstar Precast is specially geared to undertake this type of work and has been doing so for more than six years.

PRECAST is the mouthpiece for the Concrete Manufacturers’ Association – CMA Concrete Manufacturers’ Association Physical Address: Office 0400, Standard Plaza Building,

TECHNICAL 20 UCT research sheds light on PICP stormwater purification 26 Quality precast concrete products need expert control

440 Hilda St, Hatfield, Pretoria Tel: (+27 11) 805 6742 • Fax: (+27) 86 524 9216 E-mail: admin@cma.org.za • Website: www.cma.org.za Publishers: Isikhova Media Address: 10th Floor, Metalbox, 25 Owl Street, Milpark, South Africa

PROJECTS 27 Precast concrete grass blocks line drainage channels 28 Wall blocks used for retaining systems and

stormwater attenuation 30 Finding solutions for residential paving projects 32 Revelstone products used in Baxter Theatre garden upgrade 35 Mix-and-match pavers set the tone for Cape housing estate 36 Important fix for Durban reservoir 38 Paarl bridges widened with precast concrete beams 42 Architecture must pivot around people

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46 Strong culverts for diamond mine 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 © 2021. 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.

Tel: +27 (11) 883 4627 • Fax: +27 (11) 783 2677 www.isikhova.co.za Editor: Raymond Campling Tel: 076 297 2775 | E-mail: media@mediasavvy.biz Coastal editorial: David Beer Tel: 082 880 6726 | E-mail: david.bigsky@gmail.com Managing Director: Imraan Mahomed Tel: +27 (11) 883 4627 | E-mail: imraan@isikhova.co.za Pubishing Director: Jason Aarons Tel: +27 (11) 883 4627 | E-mail: jason@isikhova.co.za Director Brand Strategy: Jenny Justus Tel: +27 (11) 883 4627 | E-mail: jenny@isikhova.co.za Media Specialists: Thuli Majola Tel: +27 (11) 883 4627 | E-mail: thuli@isikhova.co.za Ruwayda Mahomed Tel: +27 (11) 883 4627 | E-mail: ruwayda@isikhova.co.za Design and layout: Joanne Brook E-mail: joanne@isikhova.co.za

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| INDUSTRY NEWS |

CONSTRUCTION INDUSTRY UNITES TO FORM A NATIONAL UMBRELLA BODY As a result of the pandemic and Covid-19’s onslaught on the precast concrete industry, the Concrete Manufacturers’ Association is involved in the transformation of a response task team into a unif ied construction industry alliance. The alliance would form an umbrella body, Construction Alliance South Africa (CASA), which is made up of 29 of the sectors’ professional, contractor, supplier and other bodies.

According to CMA general manager, Henry Cockcroft, the alliance was officially launched on 21 January 2021 and is an important step towards uniting the voice of the industry and facilitating smooth dialogue with government.

I ndust r y sta lwar t John Matthews, the chairperson of CASA, says the need for unity in the sector cannot be over-emphasised and because of the shared vision of an innovative, competitive and transformed industry, the formation of CASA is a historic and welcome achievement.

Future plans “It’s also important as it comes at a crucial time, when the industry is in engagements with the presidency on the roll-out of strategic integrated infrastructure projects to revive the economy,” says Matthews.

Emphasising the need for a united industry voice in confronting the industry’s challenges, Gregory Mofokeng of the Black Business Council in the Built Environment

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(BBCBE), who is the deputy chairperson of CASA, says it is important for the industry to forge a united front to demonstrate a serious commitment to collectively respond to industry issues.

CASA is made up of different industry bodies from across the sector with the broad objective of having joint representation in engagements on matters of mutual concern.

It is expected that the alliance will not only lead a post- Cov id-19 recover y of t he i ndust r y, but also tackle other longstanding issues that include accelerated transformation of the sector and protection of the industry from subsidised foreign competition, as well as dealing with corruption and unethical business practices.

Covid-19 response The construction industr y successfully formed a Covid-19 response team at the beginning of the pandemic in April 2020.

The Construction Covid-19 Rapid Response Task Team was key in developing a wellco-ordinated industry response to the coronavirus pandemic, including the safe reactivation of construction sites as lockdown restrictions were eased.

The task team was also instrumental in co-ordinat ing and present ing the indust r y’s t h in k ing on t he nat iona l economic recovery plan. Following these recorded successes of the joint effort, the industry agreed on the need to form

an alliance built on the shared goal of rebuilding the sector.

The Construction Alliance SA membership consists of: the Association of Architectural Aluminium Manufacturers of SA, the Association of Construction Health & Safety Management, the Association of Construction Project Managers, the Aggregate & Sand Producers’ Association of SA, the BBCBE, Consulting Engineers SA, the Chartered Institute of Building, the Clay Brick Association of SA, the Concrete Manufacturers’ Association, the Construction Management Foundation, Cox Yeats Attorneys, the Institute for Landscape Architecture in SA, Master Builders SA, the National Construction Incubator, the National Spa & Pool Institute of Southern Africa, the South African Affordable Residential Developers’ Association, the SA Association of Consulting Professional Planners, the SA Black Technical & Allied Careers Organisation, the SA Geomatics Institute, the SA Green Industry Council, the SA Institute of Architects, the SA Institute of Black Property Practitioners, the SA Paint Manufacturing Association, the SA Property Owners’ Association, SA Women in Construction & Built Environment, the Association of SA Quantity Surveyors, The Concrete Institute (TCI), the SA Institution of Civil Engineering and the Western Cape Property Development Forum, with Master Builders KwaZulu-Natal as the convenor.

(Left, from top): John Matthews, chairperson of CASA and Gregory Mofokeng, deputy chairperson of CASA.

| INDUSTRY NEWS |

MAPEI SOUTH AFRICA AWARDED ISO 9001 CERTIFICATION Throughout its more than 80 years of operation, the MAPEI Group has sought to uphold the highest international quality standards. The group consistently invests in research and development of quality system solutions, as well as in its technical team, to provide the best possible service to its clients across the broad spectrum of construction.

When the group took the step of investing in its South African subsidiary and making it a full manufacturing facility, the intention was always to achieve certification as acknowledgement of its compliance with both international and local standards. The process of obtaining ISO certif ication in QMS for MAPEI SA began in 2019 and was completed in 2020. Following an extensive audit, the organisation was f inally awarded ISO 9001 certification.

“This is a fantastic achievement for the company and is an ongoing commitment to our customers that we’ll always conduct our business in the best possible manner to

provide them with quality solutions that they know and trust,” says MAPEI SA’s general manager, Antony Offenberg.

“It’s one thing achieving the standard, which is fantastic, but keeping it is now the top priority and the MAPEI team are fully committed to doing so.”

As the project leader in this certification, Simon Molefe – the company’s business unit manager – was heavily involved in the process and oversaw the audit. “One of the key elements in an ISO audit is that your team needs to know what their role is

within the larger mechanics that make up a manufacturing facility – and our team really makes us proud,” he says.

“Achieving the certification meant we had to show that our professionalism, expertise and processes were all in place and effective across all the different principles of a good quality management system – which we did.

“This enables our customers to be confident in the service and the quality they’re getting when using any of the MAPEI system solutions,” adds Molefe.

(Above): MAPEI SA’s head office in Roodekop, Germiston.

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PREVENTING COAL ASH FROM REACHING DUMPSITES Coal ash from power stations and steam generators continues to accumulate across the country, prompting a call from the SA Coal Ash Association (SACAA) to private and public sectors to explore ways of incorporating coal ash into their everyday supply chains.

| INDUSTRY NEWS |

“The association has an important role to play, particularly in promoting the use of coal ash more widely and to a more diverse audience than before.”

SACA A director Belinda Heichler says t here are a my r iad of uses for the coal ash that range from cementblending, cementless concrete production, br ick-mak ing and road stabilisat ion to plastic additives, agricultural uses and neutralising acid mine drainage.

SACAA would like to assist in creating awareness of the benefits of coal ash in these applications. “ T hese compa n ies a re doi ng a n enormous service to the country. They’ve tapped into a resource that has excess supply, is highly versatile and is freely available to users, provided they can provide transport from the point-of-use of the coal. This means that even if the resource needs to be hauled further than traditional supplies, it has a minimal cost attached and should provide a cost benefit to the user,” says Heichler.

Facilitating role She adds that Eskom recently awarded cont racts to new of fta kers and it is envisaged that this will fuel a surge of interest among these companies’ peers.

These new entrants to the market will need to be supported and guided by SACAA and its existing members.

Rather than being left to figure it out on their own, the 30-year-old association has a treasure chest full of resources and skills to assist new and existing entrants to identify markets, facilitate technical challenges and act as an interface between Eskom, offtakers, legislators and other interested parties for the benefit of the industry.

Heichler says that r ight now, the association has an important role to play, particularly in promoting the use of coal ash more widely and to a more diverse audience than before. It is also needed to help promote transparency between the coal ash producers in the country and commercial offtakers of fly ash and other existing and new users of other streams of ash.

Act now “The sad reality is that our country’s running out of space to dump the millions of tons of coal ash that are produced annually and it’s imperative that we support all attempts to take useable ash out of the waste stream at its source. It’s also worth noting that the requirement for fly ash has grown over the past 30 years, but the number of offtakers hasn’t,” she says.

Coarse/Bottom coal ash also needs to be marketed as a greener aggregate for precast concrete and road stabilisation.

In addition, coal ash should be used in our fight to limit acid mine drainage damage to our environments.

“There are too many other uses to discuss here, but in a depressed economy, it’s safe to say that SACAA will do everything in its ability to help individuals, companies and government departments unpack the characteristics of different types and grades of coal ash and to assist in the use and commercialisation of products derived from this valuable material,” adds Heichler.

Reaching out SACAA will continue raising awareness and providing education through ongoing efforts in the media, webinars, on social med ia platfor ms and other industr y channels. To find out more, contact the offices on tel: 011 791 3327 or visit: www. coalash.co.za.

(Left): Eskom uses both wet and dry ashing on its coal dumps and stockpiles.

(Above): It is imperative to identify ash resources in their original state before they are sent to dump.

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FINDING A WAY FORWARD FOR RECYCLED BUILDING MATERIAL

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| INDUSTRY NEWS |

Robust debate is needed in the construction industry to map a way forward for the recycling of demolition material on construction sites.

Surface mining industry association ASPASA says there is much talk about the recycling of building material, but little research or planning has been done to plot a way forward. Although recycling is a good idea in principle, complexities exist that will need to be resolved before industry-wide recycling will be viable.

ASPASA director Nico Pienaar says it will need close co-operation between all parties concerned to be successful. This must include the civil engineering fraternity, which will be required to compile standards for recycled aggregates and quarries, which have the equipment required to crush and screen material, as well as the demolition industry and recycling experts, who will need to apply certain processes to prevent contamination of the material.

“This kind of separation has its own challenges and will require specialised equipment that is able to deal with foreign objects such as metals, rubber and fines.”

Separation challenge “Recycling of building material for any other purpose than backfill is a complex business. It requires complete separation of materials such as clay bricks, steel, glass, wood and other construction materials in order to guarantee the strength and durability of structures built with recycled constituents. “ T h is k i nd of sepa ration has its own challenges and will require specialised equipment that’s able to deal with foreign objects such as metals, rubber and f ines.

Then there’s the matter of identifying possible contaminants such as oils, chemicals, corrosives and others that may weaken concrete or lead to its degradation in years to come.

“Perhaps more significant is the correct grading of recycled materials that will change from load to load and construction site to construction site. It may even be necessary to have a new breed of specifiers who’re qualif ied in the assessment of structures to be demolished and paths for the recycling and grading of their materials. These kinds of interventions will take time to plan and implement before the industr y can move forward,” says Pienaar.

Finding direction He adds that successful projects are already in operation in other parts of the world where incentives exist and legislation requires the use of a certain percentage of recycled materials. In many instances, these operations are run inside existing quarries where equipment and routes to market already exist.

However, without similar market requirements and incentives, the recycling of building rubble may prove to be too costly or specialised for the local market to grasp. SA has an abundance of suitable sands and aggregates and price-driven (Above): Nico Pienaar of ASPASA (Above left): A typical construction material recycling operation.

market forces are likely to render recycled materials uncompetitive.

Even if a successful industry is launched, the market in even the most advanced recycling countries is only about a 20% substitution and the construction industry will still need to be supported by a strong, healthy and profitable quarrying industry.

Conversely, if the industry wants to use building rubble as backfill or on certain non-load-bearing applications, then the industry may be sufficiently simplified to allow widespread use of construction materials.

Legal route “New legislation regarding the use of recycled materials will need to be devised, as will permitting and standards need to be introduced to ensure quality construction in future. Water usage rights, land rights, the disposal of waste products, safety and health issues and a host of other challenges will also need to be hammered out. However, the longer we leave the issue and soapbox about the virtues of recycling construction materials, the longer the industry will remain in limbo.

“We therefore encourage other government and professional bodies, companies and individuals to make contact with us to begin setting up the process of establishing a forum to drive the way forward. With space running out in the country’s landfills, the time to act is now,” says Pienaar.

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Inca Concrete Products 021 904 1620 info@incaconcrete.co.za www.incaconcrete.co.za

Superior, quality concrete products since 1973

| COMPANY NEWS |

PRECASTERS HELPING OUR CHILDREN Primary school children are cheerfully playing and their school principal, teachers and administrators are comfortable, thanks to the generosity and support of CMA member Infrastructure Specialist Group (ISG), who donated much-needed office accommodation and paving to the Sifunindlela Primary School in Mpumalanga Province recently.

The company – which comprises Technicrete and Rocla, among others – donated a 12m fully insulated, containerised openplan office that will be used by the school’s principal, Jabulani Ndhlovu and some of its administrative staff. The fully insulated container, measuring 12,2m x 2,5m, has four aluminium sliding windows (900 mm x 1 200 mm), complete with fitted burglar bars and a steel panel entrance door with a lock set. In addition, the paving will address the serious problem of dust that is generated by vehicles and foot traffic from pathways and tracks inside the school property.

Principal Ndhlovu explains: “Sifunindlela Primary School has never had offices for staff, who – in the past – met for meetings in passages or under the lapa. Now, with the donation of this containerised office unit,

we have privacy for meetings with staff and visitors. It enables us to house school records and confidential correspondence properly.

We’re incredibly grateful to Rocla and Technicrete for these donations. It creates a proper working environment for myself and members of my team and makes a difference to how we work, giving us all a sense of pride in the school we’re managing.”

According to ISG Group marketing and communications manager Malebusa Sebatane, the company donated 16 sanitation units manufactured by Rocla to the same school in 2019, as it believes that proper sanitation in schools provides human dignity. “It was during this project that we became aware of the fact that Principal Ndhlovu had no dedicated office space not only for himself, but also for some of his administrative staff. ISG decided to donate this fully insulated, open-plan office space to the school to assist in providing a secure and stable office environment for him to carry out his duties,” she says.

Meanwhile, Technicrete also decided to donate 2 574m² of its Double Zig-Zag 60mm grey paving and financed a local contractor to clear the groundwork and install the paving around the school and new office.

Installation is from the entrance to the primary school, around the art class and the netball fields. The paving will improve the health and well-being of these young

“The paving will improve the health and well-being of these young children, in addition to creating safer and more durable walkways.” children, in addition to creating safer and more durable walkways. The containerised open-plan office space is fitted with a 220V distribution board, four 4ft vapour-proof lights, four double-switch plugs, a single light switch and an 1 800 BTU-type air-conditioner. The unit has rubberised f looring with black pigmentation. The exterior of the unit has been wire-brushed, primed and painted in white enamel.

“Educat ion in Sout h A fr ica is of paramount importance. If ISG, in some way, can make a difference by providing a suitable environment for educators to perform their duties in safe and hygienic sanitation units for pupils, like those we’ve donated to Sifunindlela Primary School, then we believe we’ve played a part in the general upliftment of their environment,” says Sebatane.

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| COMPANY NEWS |

(Right and below, right): A warehouse south of Johannesburg under construction with Peikko bolted connections.

“We’re partnering with developers, precast producers, construction companies, consulting engineers and other professionals in SA, familiarising them with the use of our products and systems.”

BOLTED STRUCTURAL CONNECTIONS UNLOCK POTENTIAL FOR CONSTRUCTION

(Above): Peikko bolted connections were used to construct this warehouse in Germiston.

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Faster, more efficient construction is what drives Peikko, the world’s foremost supplier of concrete connections and composite beams for both precast and cast-in-situ construction. In 2018 Peikko extended its reach into Africa, establishing Peikko South Africa as the company’s 34th global outlet.

This had an immediate and positive impact on SA’s construction sector. Peikko’s maiden project was the construction of SA’s largest precast concrete structure to date: a seven-storey parkade at the Fourways Shopping Mall in Johannesburg. Built with precast columns using Peikko bolted connections, the entire installation was completely propless and its repetitive modular technique yielded faster construction, improved engineering, earlier occupation, better safety and minimal- to-no interrup-

| COMPANY NEWS |

tion for shoppers during construction.

Other Johannesburg-based projects using Peikko bolted solutions soon followed: a second parkade at Fourways Mall; an extension to the façade of Cedar Square in Fourways; the construction of Columbine Square, a shopping mall and parkade in Mondeor, and an aquatic centre at King Edward’s School, Houghton, which has been nominated for the 2022 Fulton Awards.

The company is currently supplying bolted connections (namely anchor bolts and column shoes) for the construction of a five-storey tower at a food plant in Durban and it has been commissioned to design and supply Peikko products for a penthouse to be erected on top of an existing multi-storey class II building in Cape Town.

“Last year we supplied Peikko products and systems for a project in Kenya and we’re currently dealing with enquiries for projects in Botswana, Mozambique, Mauritius, Ethiopia and other African countries,” says Peikko SA MD Daniel Petrov.

Peikko was founded in Finland in 1965.

Privately owned, it enjoys a strong global presence with ISO-accredited manufacturing plants in 11 countries. It employs over 1 900 people globally and its turnover for the 2019/20 financial year was €231 million (about R4,4 billion).

“We’re partnering with developers, precast producers, construction companies, consulting engineers and other professionals in SA, familiarising them with the use of our products and systems,” adds Petrov.

He says standardisation and repetition are two of the key elements Peikko brings to the market.

“Repetition embraces every aspect of the Peikko building process, including the detailing, manufacturing and installation.

It yields material-, cost- and time-savings, as well as early returns on investment.

“Pei k ko’s assembly systems a l low columns, beams and hollow-core slabs to be erected without propping. This is a total game-changer for SA and our mechanical connections yield additional advantages over the traditional monolithic connections used in precast concrete (Right, from top): Peikko South Africa managing director, Daniel Petrov (left) and project engineer, Winston Visser, on site at a Johannesburg warehouse construction project; Peikko column shoes.

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| COMPANY NEWS |

construction, such as improved working space and on-site safety.

Faster and more efficient “Our bolted-column connections really do make column installation dramatically quicker, with spin-off benefits for the whole construction site. That’s why they’ve been consistently successful for 30 years. As soon as the nuts are tightened, the columns are self-supporting. This eliminates bracing, reduces crane time and provides more on-site space.

“We once witnessed a contractor safely install a column in just six minutes. And one of our recent projects involved lowering 12m precast columns through the roof of a production plant without disrupting the production process. This wouldn’t have been possible with conventional connecting systems.

System components

A complete system “Another aspect Peikko users appreciate is that bolted-column connections provide them with a complete system. For contractors, this means that everything works smoothly and reliably, while for designers, it facilitates designs with stronger, stiffer concrete, slimmer precast columns and tighter tolerances. And thanks to our anchor bolts and installation templates, contractors can rest assured that their columns will line up as accurately as planned,” says Petrov Design software Peikko offers powerful design software online, which includes 3D components for modelling programs, installation programs, installation instructions and technical manuals.

“Engineers can specify what they need using our software, which we then check to ensure they’ve specif ied correctly,” advises Petrov.

Thirtieth anniversary Over the past 30 years, Peikko’s bolted systems have set the benchmark for column connections. The company’s R&D department was the first to pose the question: “What if we used bolts for column connections?” That is how it all started. Today, Peikko’s bolted-column connections are a global construction industry institution.

For a d e t a i l e d pr e s e nt a t i o n o n Peikko bolted-column connections, visit: www.peikko.com/peikkoway

Bolted connections for columns, walls and beams Peikko bolted-column connections are more than just individual components.

They form complete systems which create strong, reliable connections between columns, walls and beams – in short, they comprise a better way of doing things. And because they resist loads during assembly, temporary bracing is not a requirement.

BOLDA ®

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BECO ®

SUMO ®

BOLDA ® Column Shoe BOLDA ® is our new and most advanced column shoe. It's stronger and more compact, and developed for today's harder concrete, smaller cross sections and higher loads. We tested it to extremes and BOLDA ® has proven its performance.

| PRODUCTS |

THE “BASTION” – A MASSIVE RETAINING WALL BLOCK CMA member, ReMaCon Products, has launched the Bastion, an ultra-large hollow retaining wall block which weighs 280kg and, at 1,82 blocks per m², measures 1,24m (width) x 600mm (depth) x 445mm (height).

ReMaCon is bringing the Bastion block to the market for the construction of boldfaced retaining walls, as well as free-standing vertical walls. The block’s exceptionally large dimensions and weight lend additional mass stability and strength to both types of walling. The face can also be textured and coloured to simulate rock.

Despite its size, the Bastion block is surprisingly versatile and can be deployed for the erection of stepped-down walls with special sloped elements, curved walls and for building 90° convex and concave corners. When used in combination with geogrid reinforced backfill in retaining walls, they offer standard slope angles of 58°, 69°, 74°, near-vertical 87° and vertical 90°. And, as in conventional concrete block retaining walls, the blocks’ voids are filled with soil for growing plants in retaining

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walls with flatter slopes.

Rated at over 50MPa, Bastion blocks are exceptionally strong. For example, if a Bastion wall is built next to a road, the bottom rows can be filled with concrete to form a solid barrier. This means a bastion wall is better able to withstand accidental knocks from cars and other vehicles, unlike normal retaining walls or gabion walls, which would usually be damaged and could collapse in such circumstances.

The block’s high strength rating also makes it ideal for security wall construction.

“We’ve achieved the high strength on the Bastion block with self-compacting concrete,” says ReMaCon CEO Silvio Ferraris.

“And it gives us very high early strengths, enabling us to demould in 15 hours.

“Because of their weight, the blocks require mechanical aides such as TLBs, Bobcats and cranes to place them in position. They’re also easily stacked on trucks and, with sufficient site access, they can be offloaded and placed directly in final position with a truck-mounted crane, so no double handling is required.

“They may also be cast on site using ReMaCon moulds, although quality is better controlled and more easily managed when cast at our plant,” says Ferraris.

(Top): A bastion wall with a curved section and a 90° corner.

(Right, from top): A stepped-down retaining wall built with Bastion blocks; a 74° Bastion wall and one of the first walls built with Bastion blocks.

| PRODUCTS |

MEASURING MANUFACTURING ENVIRONMENTS Electronic measuring equipment supplier RS South Africa has introduced a wide range of meters for measurement of environmental factors within manufacturing plants such as heat, moisture, sound and light.

Among the most useful for precast concrete manufacturers is the RS PRO infra-red thermometer, which is designed for taking quick, non-contact temperature measurements and features an easy-toread display. It has two modes of operation for body and surface measurements, taking them from up to 10cm away with an accuracy of approximately 0,3°C. Up to 32 measurements can be stored in the memory and an alarm value can be set.

Applications include measuring room temperature, as well as temperatures of solids or liquids from 10-60°C. Another option for curing chambers is the company’s RS PRO thermal imaging camera, which provides accurate, fast and reliable temperature screening of objects or items. A typical application would be spotting heat leaks in thermal insulation or cold spots in curing chambers. It includes a blackbody to ensure consistent and accurate temperature calibration to approximately 0,3°C. Thermal images are displayed on a large screen, making

“The camera provides accurate, fast and reliable temperature screening of objects or items.” the results easy to read, with an option of relaying readings to a larger screen via video output.

Data logging is done via an 8GB microSD card, which is included, and there is a variety of internal storage settings for data capture. In addition, the camera is supplied complete with batteries, video cable, lens cover, card reader, handrails, packing list, carrying case, QC certificate, USB speaker, tripod, client software, a power adaptor and associated power cables

for the camera and blackbody.

For more permanent installations, the RS PRO thermal imaging system allows users to visualise heat sources at a safe distance of 3-10m in real-time, using the video output connection to a display. It can be set up for continuous recording 24/7, with critical temperature conditions triggering an automatic alarm for abnormal temperatures.

In addition to thermal measurement and monitoring equipment, the RS PRO environmental T&M range includes a microwave emissions detector. This instrument is typically used by facilities and maintenance engineers to monitor and detect electromagnetic leakage. The RS PRO sound level meter has a dynamic range from 35-130dB. Measurement data can be transferred to the user’s mobile phone via Bluetooth for further analysis.

The RS PRO environmental T&M equ ipment ra nge has been t hrough high-calibre compliance and quality testing to ensure quality, durability and consistency, and comes with the RS PRO Seal of Approval. The range is available from RS South Africa.

(Left, from far left): The RS PRO infra-red thermometer, the RS PRO thermal imaging camera and the RS PRO thermal imaging system.

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| GLOBAL VIEW |

Olé!

CMA member, Terraforce, can be justifiably proud of a retaining wall constructed in 2020 at the Salamanca Hospital in Salamanca, Spain.

Demonst r at i ng a h igh deg ree of technical excellence in retaining wall construction, the Terraforce L16 rock face retaining wall covers a surface area of 2 300m² and rises to a maximum height of 7,86m.

The wall was built by ORBE Técnicas Y Medioambiente, an environmental engineering company which specialises in the construction of reinforced soil structures.

ORBE Técnicas Y Medioambiente civil engineer Miguel Seller says the main section of the wall supports a new access road to the hospital.

“Special consideration had to be given to the placement of geogrids in some sections of the wall due to the presence of a large drainage pipe (2,5m in diameter) near the wall face. One of our challenges was having to adapt the slope of the wall to meet a vertical reinforced concrete wall, a

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PRECAST | ISSUE ONE | 2021

SOUTH AFRICAN RETAINING WALL EXCELLENCE FINDS FAVOUR IN SPAIN

very complex topographical undertaking.

“Another interesting technical aspect is that a section of the wall is set in a floodplain of the river Tormes, so in this instance we used a permeable soil with better geotechnical characteristics as the reinforcing soil.”

Seller adds that Huesker (Fortrac) geogrids with nominal tensions of 3580kN were used in the construction of the wall.

“The natural foundation ground was a slate soil, with 28º of internal friction, 10kN/m² of cohesion and 19,95kN/m³ of specific weight. In addition, we used a soil with 30º internal friction and a density of 20,00kN/m³ for the reinforcing soil – without cohesion, of course.”

The new road, the Paseo de la Transición

Española, adds almost 600m to the existing road system and provides direct access to the hospital emergency zone. A central roundabout provides further access to the hospital complex and future parking.

Landscaping and a bicycle path are still to be completed.

Additional coping blocks and fencing along the top of the wall, as well as the large rock strip lining the base, add eyecatching visual dimensions to the wall.

(Right): The completed wall with the coping and fencing in place.

(Above, from left): The Salamanca Hospital retaining wall under construction and a section of the completed wall showing the reinforced concrete retaining wall and the river Tormes on the left.

“One of our challenges was having to adapt the slope of the wall to meet a vertical reinforced concrete wall, a very complex topographical undertaking.”

| GLOBAL VIEW |

G e n u i n e

c o m p e t i t i o n i s

good

for

the

c o n s u m e r Imitators are

Project participants Client: Salamanca City Council Project manager: Excelentísimo Ayuntamiento de Salamanca Main contractor: Ferrovial Construcción Sub-contractor: ORBE Tecnicas Y Médioambiente Block supplier: Prensagra Prefabricados

NOT

TERRA FORCE

Find your nearest supplier www.terraforce.com

Te l : 0 2 1 4 6 5 1 9 0 7

| TECHNICAL |

UCT RESEARCH SHEDS LIGHT ON PICP

STORMWATER PURIFICATION

Permeable interlocking concrete paving (PICP) provides two functions: controlling the rate, as well as the quality of stormwater drainage from roads and parking areas in urban environments. The flow rate is managed by temporary storage within the PICP structure.

The quality is improved through a variety of different mechanisms, depending on the pollutants, which include heavy metals, hydrocarbons, pathogens and nutrients.

Sedimentation plays an important role in the removal of some of these pollutants, through deposition in the openings between the pavers. However, nutrients are generally soluble and thus tend to pass through the openings into the underlying aggregates from where they are released back into the environment.

In Sout h A fr ica, PICP ’s nutr ient removal (ie the removal of orthophosphates and nitrates) has generally been treated as secondary to its drainage capacity: more as a nice-to-have than an essential function.

However, nutrient removal plays a vital role in preserving urban stream- and river-based ecosystems and the more it is researched, studied and understood, the more effectively it can be achieved.

Pollution control Engineers who design for pollution as well as drainage control must contend with factors such as the quality of the local stormwater, the type of pavers, the possible use and location of different geotextiles, the difference in performance between washed and unwashed aggregates, the impact of piped outlets and the timing of rainfall events.

Studies on pollutant removal from PICP stormwater have been conducted worldwide, but no common agreement has yet been reached on the most effective designs. For example, there is is a lack of consensus on the inclusion of a geotextile to enhance water purification because its presence has been observed to accelerate the clogging of PICP systems. Furthermore,

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PRECAST | ISSUE ONE | 2021

conditions vary from location to location, A f inal layer of “pea-sized” gravel let alone country to country, so without (2-4mm quartzite/gritstone) was placed local knowledge on the type and nature between the pavers to provide a f low of pollutants and how best to deal with path for the surface water. Some cells them, design engineers are left shooting in included a layer of geotextile between the the dark; a situation which base and bedding layers, has prevailed in SA since while others did not. In the inception of permeable certain cells the aggregate paving in 2007 – until now. was carefully brushed clean, Kimberley Liu BSc (Eng), while in others, the stone a civil engineering Master’s was left in conditions more student at the University typical of installations in of Cape Town (UCT) and the field. In one case, there her supervisor, Prof Neil was a raised outlet to create Armitage, published a paper a permanent wet sump at in 2020 which sheds light the bottom of the cell. Three on local pollutant removal. types of pavers were used in Entitled The Link Between (Above): Kimberley Liu. the research: Aquaf low® Permeable Interlocking Concrete and Permealock® ( both Paving and Nutrient Removal, it covers research specifically designed for PICP designs) into the nutrient removal performance of 10 and a standard exposed aggregate paver PICP test cells constructed at UCT’s civil laid with gaps for water infiltration. Three engineering laboratory. types of geotextile were trialled: Fibertex® (non-woven), Kaytech® bidim (non-woven) Test cells and Inbitex (non-woven).

Each test cell comprised a HDPE container In addition, field testing was carried out ensuring 1 200mm x 1 100mm x 400mm on the new engineering building parking lot (depth). They were fitted with perforated located on UCT’s upper campus in a bid drains with a valve-controlled outlet. Each to verify the laboratory investigations in a cell was filled with a 250mm sub-base layer more realistic setting. Monitoring chambers of 50-63mm aggregate, covered with a were installed at the underdrain outlets to 100mm base layer of 19-25mm aggregate allow for water quality testing. and topped with a 50mm layer of 2-6mm Infiltration tests were carried out to bedding gravel. determine the inf iltration rate of each

| TECHNICAL |

PICP test cell with the use of a single-ring infiltrometer, following the test procedure given by the ASTM C1781: Standard Test Method for surface inf iltration rate of permeable unit pavement systems.

Each test cell was pre-flushed with 10 litres of clean potable tap water, applied with a watering can (to simulate rainfall). The outflow from each cell was then tested to determine the “baseline” water quality, prior to the addition of any external pollutants.

The pH, temperature and electr ical conductivity (EC) of the discharged water from the bottom of each PICP cell were measured in situ using hand-held probes.

Grab samples were analysed for total suspended sediment, orthophosphatephosphorus, ammonia-nitrogen, nitritenitrogen and nitrate-nitrogen.

Each cell was then subjected to multiple “seasons” of accelerated rainfall events, using pre-prepared synthetic stormwater containing suitable soluble pollutants to test their treatment efficacy. The synthetic stormwater testing was carried out in two distinct phases. In the first phase, three rainfall seasons were simulated in October 2017, September 2018 and April 2019 respectively, using water containing t he commercia l fer t i l iser “Grow ing Orchid” at an appropriate concentration as the pollutant. Each season comprised nine distinct “storm” events that were applied one per day, using a 10 -litre watering can.

Close control The pH, temperature and EC of the outflow were determined for each cell and for each rainfall event. Samples were analysed in the water laboratory on the first, fifth and ninth days for the concentrations of ammonianitrogen, nitrite-nitrogen, nitrate-nitrogen and orthophosphate-phosphorus.

The second phase of the research took place during August–September 2019. The use of “Growing Orchid” as the source of stormwater contamination was abandoned because of problems with inconsistent nitrogen-to-phosphorus ratios, which gave rise to inconsistent influent quality – and thus, potentially, outflow quality.

Sy nt h e t i c s t o r m w a t e r w a s t hu s produced in the laboratory by adding NH4Cl, K2H2PO4 and KNO3 to tap water in carefully measured quantities in

(Above): Permeable interlocking concrete pavement (PICP) test cells (Cell A and Cell F laid with Aquaflow® pavers, Cell B, C, D, E, G, H laid with Permealock® pavers, and Cell I and Cell J laid with ‘traditional’ exposed pavers).

a 500-litre tank. A new rainfall regime was purposed with intermittent dry and wet periods to represent the four months of the “typical” Cape Town rainy season, but in an accelerated 1,5-month period (see Table 3). The pH, temperature and EC of the outflows from each cell were measured daily, while samples were analysed in the water quality laboratory for ammonianitrogen, nitrite-nitrogen, nitrate-nitrogen and orthophosphate-phosphorus on a weekly basis.

The flow over and through the NEB park ing area was tested during four significant storm events (ie >7mm) between 2018 and 2019. The pH, temperature and EC were tested in situ using hand-held probes. Grab samples were then taken to the water quality laboratory for measurement of the ammonia-nitrogen, nitrate-nitrogen, nitrite-nitrogen and orthophosphatephosphorus concentrations.

The paper outlines the lab testing procedures and their results in extensive

PRECAST | ISSUE ONE | 2021

21

| TECHNICAL |

detail, which was too long to be covered in this article. However, as mentioned above, influent pollutant concentrations were not always consistent during Phase 1 and the use of two different fertiliser concentrations made it difficult to compare influent and effluent concentrations from the samples collected during this phase.

They were therefore only regarded as indicative and were discarded in favour of the results obtained from Phase 2 testing.

After the lab test results had been analysed, some of the results were as follows: • The cells using washed aggregates had higher ammonia-nitrogen removal efficiencies than those with unwashed aggregates, while the cell with the raised out let (creat i ng a “sump” i n t he underlying stone aggregate) had the highest ammonia-nitrogen removal efficiency of all.

• All the experimental cells appeared to add significant quantities of nitrate nitrogen in quantities which ranged from 160-2 580%. This was probably due to the nitrif ication process of ammonia to nitrate.

• The cells with exposed aggregate pavers produced less nitrite-nitrogen and nitrate-nitrogen than the other two types of pavers.

• The cell with the raised outlet produced the most nitrate-nitrogen.

• The presence of geotext ile had a negative impact on the nitrate-nitrogen removal efficiencies.

• When the pH levels were within the optimum range of 7,6-8,8 for the growth of nitrifying bacteria, the nitrification process resulted in a reduction of the ammonia-nitrogen concentration and an increase in nitrate-nitrogen concen tration. Lower pH levels resulted in higher nitrate-nitrogen concentrations.

• The removal eff iciencies of ortho phosphate-phosphorus ranged from

•

•

•

37-11%, compared with the mean of 47,7% removal rate of orthophosphatephosphorus in other studies.

The presence of a geotextile resulted in a higher orthophosphate-phosphorus removal efficiency than those without.

The cells with washed aggregates had higher orthophosphate-phosphorus removal efficiencies than those with unwashed aggregates.

The cell with the raised outlet had the lowest orthophosphate-phosphorus removal efficiency of all, which might have been caused by the fine particles being slowly washed t hrough t he permeable paving and desorption due to the lack of useful adsorption sites.

T h e p a p e r c o n c l u d e d w it h t h e observation that while PICP is effective in removing ammonia-nitrogen, it does so at the expense of an increase in nitritenitrogen and nitrate-nitrogen. The authors recommend further research to establish whether the creation of an anoxic zone, coupled with introduction of a suitable electron donor to the PICP, could address this shortcoming.

• A full copy of the paper can be down loaded at: http://dx.doi.org/10.3390/ w12061714.

(Above): A typical cross-section of the PICP test cells.

(Below): Paver types: (a) Aquaflow®, (b) Permealock® and (c) standard exposed aggregate.

| IN THE MIX |

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| TECHNICAL |

“The precast concrete sector can no longer rest on its laurels when it comes to maintaining quality.”

In the highly competitive and pandemicplagued precast concrete industry, the input of a well-trained and experienced concrete technologist to ensure quality and durable products is now essential, says John Roxburgh, senior lecturer at The Concrete Institute’s School of Concrete Technology.

“The precast concrete sector can no longer rest on its laurels when it comes to maintaining quality. A concrete specialist will ensure that performance specifications with regard to strength and durability are met, and that the manufacturing process employs cost- ef fect ive concrete m i x designs that still meet vital performance requirements. This specialist will also have to control quality assurance, which is essential for the reputation and survival of a producer. Therefore we at the school strongly recommend that at least one person in a precast operation has the necessar y t ra in ing and ex per t ise in concrete technology,” says Roxburgh.

He says precast concrete is a wide and diverse f ield, ranging from highly engineered elements such as bridge beams, pipes, culverts, tilt-up panels and hollow core flooring to smaller and simpler items such as bricks, pavers, kerbs, blocks, roof tiles, floor tiles and lintels.

“There are endless possibilities when it comes to the design and manufacture of precast concrete items and the use of large precast items in mainstream construction is also becoming increasingly popular.

There are some important reasons: ease and speed of production, economical costs for the repetitive work involved, and the easy demolishing and recycling of precast structures at the end of their service life.”

Roxburgh believes that precasting offers many entrepreneurial possibilities.

“Producing smaller precast elements, such as bricks, blocks, kerbs, lintels, tiles and roof tiles, offers entrepreneurs a relatively easy entry to the market, particularly those

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PRECAST | ISSUE ONE | 2021

QUALITY PRECAST CONCRETE PRODUCTS

NEED EXPERT CONTROL with factories close to clients, as heavy transport costs make it difficult for more distant, large operators to compete with well-located smaller firms. In fact, a brick producer which precasts 5 000 bricks a day

can successfully compete with a company that produces 300 000 a day, but needs to transport the bricks longer distances.

Strategic location also benefits precast producers of decorative items such as floor tiles, cobblestones, garden retaining wall blocks, garden furniture and pots.”

Roxburgh adds that the School of Concrete’s “SCT20 Concrete Practice” provides detailed knowledge of all the important concrete concepts and practices needed to produce top-quality precast and other concrete products. The course is suitable for foremen, clerks-of-work, technicians and supervisors, as well as sales and technical staff in the building, mining and related industries. The fourto eight-day online training includes a virtual laboratory session, detailed video recordings and authoritative tutoring by the School of Concrete Technology, which has trained thousands of South Africans and has a respected reputation dating back to 1974.

(Left): John Roxburgh

| PROJECTS |

Precast concrete grass blocks line

DRAINAGE CHANNELS

Drainage channel sections have been lined with grass blocks supplied by CMA member CEL Paving Products on a 12km section of the old Malmesbury road in the Western Cape. The road, which runs between Philadelphia and Kalbaskraal, is being completely rebuilt with new layer works, fence lines and drainage, and is due for completion in May 2021.

The project’s professional team includes consulting engineers MPAMOT, a joint venture consortium comprising Amandla Construction and Umzali Civils, and a local paving contractor, Esau Holdings.

Jako Kriel of Amandla is the senior member on site and is being assisted by Les Groenewald of MPAMOT and François Lourens of Umzali Civils.

CEL supplied 10 000m² of grass blocks, which were used to line some of the drainage channel sections on both sides of the road. The blocks were laid by Esau Holdings, which employed members of the local community, trained by Umzali Civils. The blocks were laid two abreast on one in two slopes on either side of a 1 000mm x 125mm concrete base.

Umzali site agent Lourens says that once laid, the blocks were filled with soil for greater stabilisation and plant growth.

“The blocks were installed to prevent erosion and, being open-faced, will allow water infiltration between the block openings. This controls water flows, especially during heavy downpours, and assists with flood prevention,” he explains.

The channels drain into stormwater pipes and box culverts which, in turn, drain into the Diep River to the west of the new road. Water from east-lying channels drain under the road via culverts into stormwater pipes and box culverts. From there, it flows overland to the river.

(Left): A water channel section paved with grass blocks supplied by CEL Paving Products.

PRECAST | ISSUE ONE | 2021

27

| PROJECTS |

Wall blocks used for retaining systems and

STORMWATER ATTENUATION Retaining block walls have been used for the construction of extensive retaining systems and erosion control measures at one of the grassroots sites at Lanseria Corporate Estate, an environmentally sensit ive industr ia l park adjacent to Gauteng’s Lanseria International Airport.

Dubbed “One on 75” and developed by Erf 844 Joint Venture, the project entails the construction of a plastic mouldings factory which is due for completion in October 2021.

One of t he estate’s reg ulat ions is that all developments must comply with an approved JR A form of stormwater at tenuat ion to prevent dow nst rea m flooding, erosion and pollution. In addition to two retaining systems, three attenuation ponds were built for the “One on 75” project using retaining wall blocks supplied

by CMA member, MVA Bricks.

A bb e yd a le Bu i ld i n g & C i v i l s i s the development’s principal building contractor and Jodan Construction the project’s bulk earthworks contractor.

Ret a i n i ng wa l l specia l ist , P G Con, constructed the retaining block systems, which included the retaining systems for the attenuation ponds. Civil design,

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PRECAST | ISSUE ONE | 2021

stormwater attenuation and site planning were completed by Tribid Projects and the design of both the building platform block walls and the attenuation pond block walls was handled by Crossman Pape & Associates, in compliance with the design and construction contract.

Attenuation ponds Over 6 500m² MVA-7 concrete retaining wall blocks were used to construct the attenuation ponds and the retaining systems. Two large ponds were built on the western perimeter of the site and a third subsidiary pond was sunk at the northeastern corner.

“A lt hough t he attenuat ion ponds are unusually large, their footprint in relation to the overall size of the site is relatively small,” says James Croswell of Tribid Projects. “The north-western pond measures 50m x 20m and has 3 000m³ capacity; the south-western pond measures 75m x 15m and has a 2 000m³ detention capacity; and at 40m x 15m, the north-eastern pond has a water detention capacity of 1 500m³. Two further ponds will be built along the property’s eastern boundar y when a proposed building extension is unveiled at a future date.

“This is the f irst time we’ve used concrete retaining block walls exclusively

| PROJECTS |

“All developments must comply with an approved JRA form of stormwater attenuation to prevent downstream flooding, erosion and pollution.”

11,5m in the south-western corner.

B ot h t he pond a nd t he bu i ld i ng platform walls were built with the lower half of each in closed-face configuration, using MVA-7 blocks and sliders supplied

by MVA Bricks. The top sections were constructed in open-face configuration.

Moreover, the cut-and-fill walls and the backfill in the attenuation pond walls were cement-stabilised. Maccaferri’s WG-6 geofabric was used to reinforce the fill material behind each wall at every fifth block course.

for building attenuation ponds and to save space, we made the ponds relatively deep.

We looked at several building materials to meet our design criteria, but in the end, the MVA-7 block proved the most economical option,” says Croswell.

Balancing act Croswell explains that all the material for general f ill and the selected layer works was sourced on site. “However, we did find some unsuitable material (about 20 000m³) at a depth of 300-400mm which had to be removed. This meant we had to adjust the level of the platform so that the cut-and-fill and the fill behind the block walls balanced and we used a sophisticated software program to do it. Moreover, there wasn’t as much rock on site as we’d anticipated, although there was enough to stabilise the critical areas.”

The retaining system walls and the pond walls were built at 70º. The northern boundary platform wall is a f ill wall 260m long, r ising from 0,5m in the north-western corner to a height of 9m in the north-eastern corner. The western wall is a cut structure 315m long, rising from 0,5m in the north-western corner to

Future developments All the walls were built with 45º wick drains every 1,5m. They discharge into bottom drains and, in walls higher than 4m, into mid-level drains as well. Croswell adds that the ponds were designed for attenuating a 25-year post-development run-off, discharging at the five-year predevelopment outflow.

The ponds have a weir capacity which accommodates a 1:100-year storm event.

All the water collected off the building and the concrete platform which surrounds it drains into both western ponds. Lined (Armorflex) channels have been installed

along the bottom of the ponds to cater for low flows and an overflow culvert was constructed at +1,5m for draining high outflows from the south-western pond.

The discharge from the south-western pond is routed through the north-western pond before being discharged into a 10 000m³ sub-reg ional pond via the township’s stormwater system. The northeastern pond drains into an open channel which runs along the township’s eastern boundary. It also discharges into the subregional pond, which is used to distribute greywater to the entire estate, primarily for the flushing of toilets and for watering plants.

“The greywater is partially purified through the removal of hydrocarbons by the vegetation which grows at the bottom of all the attenuation ponds on the estate.

Each developed site is allocated a greywater quota at a ratio determined by its catchment area and the water is pumped through a set of solenoid valves. Smaller sites use header tanks for storing the water, whereas two 10 000-litre JoJo tanks will be installed at the ‘One on 75’ site,” says Croswell.

(Top left): The grass-covered bottom of one the attenuation ponds shortly after a severe thunderstorm.

(Far left): A close-up of an attenuation pond closed-face wall which was built using MVA-7 retaining wall blocks and sliders.

(Left): One of the attenuation ponds under construction.

(Above right): A water channel runs adjacent to one of the attenuation walls which was constructed in a closed- and open-face configuration.

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29

| PROJECTS |

Two large-scale paving projects with completely different requirements were recently completed by CMA member, Technicrete, in the North West and Gauteng provinces respectively.

In the f irst project in North West, Technicrete was able to assist Ikageng in its attempt to set aside stands for development below the 100-year flood line and take preventive measures to reduce the possibility of stormwater or flood damage to the area. Technicrete’s Armorflex proved to be the most effective and sustainable option to meet their requirements.

“The project was initiated after it became apparent that some residential stands were set out w it h in t he 1:50 year f lood line. The formalisation of the trapezoidal channel to contain the 1:100 -year f lood meant these stands would be available for development. The construction of a lined channel could increase the capacity with a smaller crosssectional area,” says Dries Joubert, design engineer from FHP Consulting Engineers on the Ikageng project.

Drainage channel Technicrete’s internationally licensed Armorflex 180 was recommended as the best option for the Ikageng project from the range of products available. The 180 is

Finding solutions

FOR RESIDENTIAL PAVING PROJECTS an open block suitable for stormwater and drainage channels, erosion control, roadside drains, strip roads and access roads.

“We originally thought that a combined

“The channel had a natural alignment and the Armorflex improved the natural flow characteristics.”

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PRECAST | ISSUE ONE | 2021

concrete and concrete-filled geo cell-type lined canal would serve the purpose, but due to poor soil conditions which required substantial earthworks, Armorflex was the preferred option and offered a reduced construction period – mainly because of the interlocking pattern that offered flexibility, should settlement occur. The channel had a natural alignment and the Armorf lex improved the natural flow characteristics of the channel during f lood conditions, hence its gently curved installation which eliminates the small radius bends that could have created overtopping,” explains Joubert.

The project required the Armorflex 180 blocks to be tied to adjacent blocks with galvanised wire to form long mats. As and where required, these were also anchored into in-situ soil to further assist with stabilisation of the blocks and mat in general.

Flexible fit The blocks provided a loose, but sophisticated interlocking design, allowing the surface to remain flexible to movement without the cracking and spalling issues that occur with in-situ cast concrete when exposed to regular stormwater or flooding incidents.

| PROJECTS |

The project showed the versatility of the Technicrete solution, which offers a good lining for drainage channels. At aprons at pipe inlets and outlets, Armorflex eliminates pipe undercutting that can lead to severe problems such as surrounding bank failure and hence additional siltation downstream.

One of the challenges on site at Ikageng was groundwater seepage, which impacted the delivery of project products. “Due to water seeping from underground at the project site, which resulted in wet and muddy surfaces, we built a temporary roadway so that Technicrete could deliver the daily quantity of 1 000m² blocks required,” says Anton Muller, managing director of Born Free Civils, a contractor at the Ikageng project.

Approximately 40 000m² of blocks were placed in three months just before the summer rains. To achieve this, the channel profile was pre-prepared to allow the installation team to finalise and smooth out levels, place geofabric and Armorflex, wire up the system and backfill.

Conformity first While the technical challenges on the Ikageng project were many and varied, the other project had the opposite requirement, concerning mainly the aesthetics of the

paving to complement the cultivated sprawling garden in Groenkloof, Tshwane.

Whether it is a residential estate or a commercial park, style conformity always plays an important role in the success of such developments. The choice of paving plays a role not only in appearance, but also in future maintenance planning. These were the key factors when the owner of a house in a residential complex in Herbert Baker Street decided to demolish and revamp their home after 15 years.

Maxi Pave, the contractors for the owner’s house rebuild, contracted Technicrete to supply 1 500m 2 of Conleaf Autumn 60mm pavers and 150m 2 of Bond Brick Autumn 55mm pavers for the parking and driveway areas of the refurbished property. Managing director of Maxi Pave, Leon Veldsman, says: “The company’s Conleaf and Bond Brick pavers are aesthetically attractive and the longevity of the products makes them ideal for this residence.

Attractive patterns “Technicrete supplied the original paving to this small complex many years ago, but after seeing the Conleaf design and colour installed at one of the residences, the owners decided to re-pave the driveways and entrances in the same manner of the

“Technicrete supplied the original paving to this small complex many years ago.” other three units as well.”

The Conleaf paver introduces gentle curves into paving, creating attractive patterns, pleasing lines and durability.

This block is available in all standard colours, such as Autumn, Terracotta, Grey, Plum, Slate and Tan and is suitable for domestic driveways, municipal parking areas, pedestrian pavements, pathways and commercial developments. The larger 80mm thickness can be installed at petrol station forecourts, industrial and factory roads, as well as suburban streets.

Technicrete’s Bond Brick is a traditional paver that is not only economical, but durable. It is also available in various colours and thicknesses and is mainly applied to park ing areas, pathways, commercial and domestic surfaces.

(Above): Preparation work in progress for the Ikageng project and the completed drainage channel.

(Left): The paving project in Groenkloof, Tshwane.

PRECAST | ISSUE ONE | 2021

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| PROJECTS |

(Below): One of the retaining wall benches dressed with Saxon Split Cladding and topped with Kent Random Edge paving. and some of the stairs dressed with Revelstone’s Saxon Split Cladding and paved with Kent Random Edge paving. (Photographer: David Beer)

Cladding and flagstone paving, manufactured by CMA member Revelstone, has played a crucial role in the redesign and revamp of the garden at Cape Town’s Baxter Theatre. The revamp was undertaken to prepare an outdoor venue for the Rolex Arts Weekend, one of the world’s most important and prestigious international arts events, part of which was staged at the Baxter on 7 and 8 February 2020.

Project architect Julius Burmeister van der Merwe of Masterpiece Architects says that prior to the revamp, the garden consisted largely of grassed slopes fringed w it h f lowerbeds. “ T he Rolex event required level spaces where furniture could be accommodated and where people could gather and mingle. Timber decking had initially been mooted, but on closer analysis, this solution proved impractical.

As an alternative, I proposed levelling the slopes into a series of stepped terraces which would not only provide a venue for the Rolex event, but also serve as a userfriendly outdoor sanctuary for students and theatre-goers, as well as for staging subsequent events.

“This approach required extensive

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Revelstone products used in

BAXTER THEATRE GARDEN UPGRADE earthworks and an upgrading of the garden. In addition to four level terraces, a retaining wall was built to shore up t he cut face of t he ensuing ver t ica l embankment below what remained of the upper-slope section. We wanted to use natural rock for dressing the retaining wall and for the paving, but we had neither the budget nor the time to quarry natural rock. Instead, I approached Revelstone, whose cast-stone concrete

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products show no discernible difference from their quarry-sourced equivalent; in fact, they look completely natural.

Aesthetic appeal “ Fo r e x a m p l e , R e v e l s t o n e ’s K e n t Random Edge flagstone pavers mimic the striations and colour of the surrounding rocks at Falling Waters, a residence in Pennsylvania, USA, designed in 1935 by the famous American architect, Frank Lloyd Wright.

“We chose Revelstone’s Saxon Split Cladding to dress the retaining wall, as it presents an uneven, stone-like surface which resembles cut sandstone. We also used it to clad the plant boxes built into the retaining wall and to dress the risers on the stairs which link the terraces.

We opted for another natural-looking (Left): Visitors to the Rolex Arts Weekend enjoy the newly-created terraced garden.

(Photographer: Marc Wessels) (Below left): The Baxter Theatre garden prior to the commencement of the earthworks. (Photographer: Julius van der Merwe) (Below): The revamped Baxter Theatre gardens showing the terraces, stairs and retaining wall which were dressed with various cast-stone precast concrete products manufactured by Revelstone.

(Photographer: David Beer)

“Well over 500 000 patrons attend over 2 700 performances at the Baxter annually.”

Revelstone product, Devon Wall Capping, for overlaying the top of the wall.”

Revelstone MD Alex Cyprianos says that although Saxon Split Cladding is manufactured in one standard size for ease of installation, no face repetition is apparent after installation. The lower and largest of four terraces was surfaced with a combination of Kent Random Edge paving and grass. This large flagstone paver has a slightly irregular edge and a subtle hewn surface with natural indentations, which lend it a time-worn appearance. It was also used to pave the top of the steps and the stone benches which were built into the retaining wall.

“The Revelstone products were much quicker to install than natural stone and they’ll last much longer,” says Van der Merwe. “We had to create a path on the lawn for high-heeled users and we laid the Kent pavers in a random pattern, which I designed for the other terraced areas as well.”

Green space Masterpiece Architects was responsible for the conceptualisation and all the design work. Landscape architects Annette Zulch Designs handled the project management of the installation work. It also managed the greening of the new spaces and a garden upgrade, which included plant selection w ith input from Signature Gardens.

The earthworks, the construction of the retaining wall and the paving and cladding work were done by main contractor, the Uvuyo Group.

Baxter Theatre marketing director Fahiem Stellenboom says upgrading the Baxter garden was a great decision on several levels. “It’s created a beautiful s pace wh ich pat ron s a nd aud ience members can enjoy while visiting or attending performances at the theatre.

Most importantly, it’s enabled the Baxter to offer the public the opportunity of hiring the space for weddings, functions

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and corporate events. This means we can generate additional income for the theatre, especially after its seven-month closure during lockdown. A little-known fact is that the Baxter isn’t funded by the Department of Sport, Arts & Culture, so it’s vital that we find innovative ways to generate additional income by attracting new audiences and the public to our spaces and venues.

“The Rolex Arts Weekend was the culmination of a year’s planning which saw more than 200 renowned artists and arts leaders from SA and around the world gathering at the Baxter. The weekend involved a ser ies of ta l k s, read ings, exhibitions and performances and featured the work of the 2018/19 protégés of the Rolex Mentor & Protégé Arts Initiative, along with their mentors. Highlights included dance, architecture, literature, music, arts symposia and cinema.

Well attended “Distinguished guests included celebrated artists such as Wole Soyinka [playwright,

(Left): The revamped Baxter Theatre gardens showing the terraces, stairs and retaining wall which were dressed with various cast-stone precast concrete products manufactured by Revelstone. (Photographer: David Beer) Garden furniture blends in perfectly with the newly-created terrace garden in preparation for the Rolex Arts Weekend. (Photographer: Marc Wessels)

poet, writer and Nobel Prize laureate for literature], American cellist Yo-Yo Ma, South African artist William Kentridge, Sir David Adjaye [Ghanaian-born British architect], Colm Tóibín [renowned Irish novelist, short story writer and playwright],

film-maker Mira Nai and Zakir Hussain [Indian musician and composer[, among many others. Tennis star Roger Federer also made an appearance,” says Stellenboom.

Well over 500 000 patrons attend over 2 700 performances at the Baxter annually, making it one of the busiest theatres in southern Africa. Founded in 1978, it has stayed true to its promise of always being open to all and to stage work of the highest artistic quality. It aims to reflect the cultures of all South Africans on its stages and in its foyers and spaces, thereby promoting an interactive and meaningful relationship with its audiences and patrons, while generating a spirit of goodwill and nurturing creativity.

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Mix-and-match pavers set the tone

FOR CAPE HOUSING ESTATE O ver 6 0 0 0 m² of c onc r et e p aver s manufactured by CMA member Inca Concrete Products have been used to pave the roads of Bonsai Estate, a new housing project being brought to the market in Langerberg Ridge, Cape Town, by MSP Developments.

The central and by far the largest section of the roads was surfaced with Inca’s Table Mountain (Tan) Exposed Aggregate interlocking pavers, while the road edging and the colour breaks were laid with Inca’s Double Cobble pavers in two colours – red and charcoal.

Produced to SANS 1058:2015 Class 2.0 specifications, the pavers are 70mm thick.

In addition, over 1 000m of kerbing was installed in four derivatives: CK5, MK10, BK2 and C1. It was supplied by Lascokerbs, a specialist kerb manufacturer which produces kerbs in a state-of-the art plant in Philippi, Cape Town.

The paving layout design was supplied

by JVE Consulting Engineers and the paving was done by paving contractor GLC. “We’re extremely proud of this project because it’s unleashed a very attractive layout which is unique to Inca. This is the first time that this paving combination has been used and it’s refreshing to note how one can achieve almost limitless diversity

in design and appearance through the creative application of texture and colouring,” says Schalk van Wyk, Inca director of operations.

The layer works of the paved area comprise 150mm G5 sub-base aggregate and the pavers were bedded in 20mm of sand.

“One of the advantages of using our exposed aggregate pavers is that they’re less prone to showing tyre marks. More-over, the aggregate is imbedded throughout the whole paving block, so should any wear

occur, the pavers will retain the same appearance,” says Van Wyk. “Our pavers are tested on a regular basis for tensi le spl itt ing, abrasionresistance and water absorption at our in-house laboratory and our Tan Exposed A gg reg ate mater ia l t h rough-m i x is specifically designed to achieve a uniform, natural look that mimics and blends in with the natural environment.

“Another advantage of our interlocking paver is that once laid, it doesn’t move and for ms an integ rated whole. It’s also extremely strong, which is why the interlocker is so popular across the world.

Furthermore, sections of paving can be removed for remedial work or new belowground installations and then replaced without patches or visible evidence,” explains Van Wyk. Bonsai Estate is being developed in three phases. Phase 1, which comprises the construction of three-bedroomed homes, was begun in February. The construction of two-bedroomed apartments will follow.

(Above and left): Inca Concrete Products’ Tan Exposed Aggregate interlocking pavers and its TwinBlock Cobble are used creatively on Bonsai Estate’s roads.

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Important fix for

DURBAN RESERVOIR

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Concrete panels forming the roof of a 350ML reservoir in Durban have been repaired and sealed to prevent potentially harmful contaminants from polluting the potable water supply to more than 500 000 people in the region.

Durban Heights Reservoir 3 is situated in the suburb of Reservoir Hills, KwaZuluNatal. Constructed in 1971, it is one of the biggest concrete reservoirs in southern Africa. The reservoir design is unique, as it has a single support in the middle and a roof shaped like a circus tent. The roof is made up of 120 steel post-stressed cables that radiate from the centre roof support to the outer base support.

In 2003, a full diagnostic survey of the concrete roof panels was done. A variety of issues were identified, but of particular interest was the existence of a micro-climate within the reservoir. This micro-climate, with wet-dry cycles, creates a favourable environment for contaminants to be absorbed into the reinforced concrete panels, causing corrosion of the reinforcing.

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Operational reservoir Based on the original diagnostic survey, rehabilitation proposals and the subsequent product trials, a tailored solution from speciality chemical company Sika was evaluated and chosen to perform the repairs. Umgeni Water appointed Royal HaskoningDHV to take on this rehabilitation project as the project engineer and Sika products were specified on the tender. Smart Civils Construction was the specialised civil contractor.

As the work was being done in an operational reservoir, the product choice was paramount to health and safety in ensuring they posed no risk of water contamination. The project’s other challenges were identifying alternative methods of gaining access to the roof structure and shortening the repair time. Smart Civils developed an inventive idea where access to the roof was provided by a design innovation.

This involved erecting 550 tonnes of scaffolding, in a bird-cage configuration, from the floor to just under the soffit. The scaffolding would give the contractor access to one-quarter of the roof at any given time, before being dismantled and re-erected as the works progressed.

Sika solutions To fulf il the intended task, a decision was made to use SikaTop Armatec-110 EpoCem as the primary rebar protective coating for the concrete repair to protect the reinforcing of steel and inhibit corrosion.

Due to the dif f icult conditions, Sika MonoTop-610 was used as a primer to the concrete substrate. The decision to use Sika MonoTop-412 NFG as a repair mortar was because of its unique properties as an excellent wet spray mortar.

This application method improved the compaction of repair mortar and increased the application rate of the product. Sika MonoTop-412 NFG also differentiates itself as a single-component, polymer-modified, fibre-reinforced, low-shrinkage structural repair mortar with Sika FerroGard-903 Plus corrosion inhibitor. That is a threein-one solution which delays the start of corrosion and reduces the corrosion rate when it occurs. It also increases the service (Left and right): Rehabilitation of the 350ML Durban Heights Reservoir 3.

“The micro-climate, with wet-dry cycles, creates a favourable environment for contaminants to be absorbed into the reinforced concrete panels.”

life of a reinforced concrete structure.

Sika’s carbon fibre fabric impregnated with a structural epoxy resin, SikaWrap-230C, was used due to the age of the structure and minimal concrete cover. Sika Injection-307 was used for refilling the ducts.

Sika Injection-307 is a low-viscosity elastic polyacrylic injection resin that can be adjusted to set at a pre-determined time, forming a passivating permanently elastic matrix.

Protective coatings Two protective coating systems were appl ied to t he pa nels, na mely Si k a FerroGard-903 Plus, which is a corrosion inhibitor that penetrates down to rebar level over time and forms a protective

monomolecular layer on the surface of the reinforcing steel.

The final protective coating in the solution was Sikagard-705 L, a singlecomponent, low-viscosity, solvent-free and reactive impregnation product for concrete and cementitious substrates based on silane.

Its unique properties allow moisture vapour to escape from the concrete panels, ensuring they stay dry and thus preventing further ingress of contaminants.

Other Sika systems used on site were Sika Primer-3 N and Sikaf lex PRO-3 i-cure, a single-part, moisture-curing elastic joint sealant with high mechanical resistance used to seal the expansion joints of the soffit. Sikadur-43 ZA is a solventfree, three-component repair and filling mortar used to do roof repairs next to the cable ducts.

Smart Civils generated 100 local jobs for the duration of 14 months in the Reservoir Hills community. The use of exceptionally durable and high-performing Sika products in the refurbishment of this reservoir will lessen the future refurbishment cycles, saving on material consumption and time throughout the structure’s lifespan.

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Paarl bridges widened with

PRECAST CONCRETE BEAMS

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A project being headed by UDS Africa to upgrade Berg River Boulevard and Oosbosch Street in Paarl was commissioned by the employer, Drakenstein Municipality, in 2013. The first phase, which included the upgrading of Berg River Boulevard from Lady Grey Street to Optenhorst/Oosbosch Streets, was started in 2016 and completed in 2018.

This phase included the construction of the abutments and piers for the subsequent widening of the 100m-long Oosbosch Street bridge over the Berg River. The bridge traverses a railway line some 600m from the Berg River bridge. Both bridges are being widened using precast concrete beams manufactured by Cape Concrete.

The bridge-widening project was begun in August 2019 and is due for completion in August 2021.

The bridge-widening forms part of upgrading a section of Oosbosch Street between the Berg River Boulevard and Jan van Riebeeck Street. Members of the bridge-widening professional team include main contractor, Martin & East, A ECOM SA , Empa St r uct ures and Mowana Engineers.

Old bridges Both bridges were first built as beam-andslab structures in the 1960s. The river bridge is now being transformed from two to four traffic lanes, whereas the rail bridge, which was originally built as a narrow four-lane thoroughfare, is being widened on either side to accommodate new pedestrian walkways and allow the full width of the original bridge to be used solely for traffic.

The original river bridge was constructed with post-tensioned beams, building technology which was considered for the current project. However, UDS finally approved the contractor’s proposal for pre-tensioned precast beams as being the more cost-effective and time-efficient option and Cape Concrete was commissioned to cast 20 T-beams, 26m apiece.

The rail-bridge extension required four 10m reinforced concrete beams and balustrades to be cast as single full sections by Cape Concrete. Two of these beam/balustrade units were placed on either side of the bridge. By casting the beams and balustrades as a single unit,

no staging was necessary, saving much valuable time. Moreover, the use of precast elements meant that the manufacture of the beams for both bridges, and the precast permanent shuttering for the river bridge, could take place during the early stages of the project and be run concurrently with other construction work.

Time-saving A ECOM SA desig ned both br idges.

AECOM engineer, Jacobus Kritzinger, says that having extended abutments and piers for the river bridge already in place saved further construction time. “In addition, the benefit of several construction activities taking place simultaneously reduced pressure on the programme and yielded savings for the client and all parties involved. In order to achieve uniformity throughout the new river bridge structure, we adopted the same type of cross-section

“It includes the widening of the 20m-long Oosbosch St bridge, which traverses a railway line.”

(Left): One of four precast concrete beam/balustrade units being lifted off the truck bed and lowered into position on the rail bridge.

(Above): Elements of the partially constructed river bridge.

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profile we found in the original design – but, of course, using pre-tensioned, rather than post-tensioned beams,” says Kritzinger.

“It was essential that the structural behaviour of the new beams mirrored the structural behaviour of the existing post-tensioned beams as closely as possible, because construction tolerances were very tight. This meant we had to model and analyse the deflections and the induced movements of the pre-tensioned beams to match those of the existing beams as much as we could.”

Allowing for creep and shrinkage in this alternative beam design proposed by the contractor entailed some specialist eng i neer i ng i nput , wh ich wa s why consulting engineers, Mowana Engineers, was appointed to design the pre-tensioned concrete beams.

Creeping bridge Edward Smuts, Mowana Engineers bridge eng ineering director, says there was evidence that considerable creep had taken place on the bridge over its 50-year lifespan.

“Armed with the concrete and section properties of the old bridge structure, we were able to simulate theoretical deflections in order to match the behaviour of the new beams as closely as possible with the performance of the original beams.

Part of this exercise involved calculating instantaneous and long-term creep. Based on these calculations, we compiled a report which was submitted to AECOM in the first instance and, once approved by them, to Cape Concrete,” says Smuts.

Cape Concrete factory manager Johan Nel says that as a result of Mowana’s calculations, some additional detailing was required in casting the river bridge beams and this aspect was handled by Mowana. “We’ve done numerous post-topre-tensioned conversions with Mowana Engineers and they get involved with the pre-stressing and checking procedures.

“The river bridge beams were specified as W40MPa and the rail bridge beams as a W50MPa mix. However, we used the W50 mix for the river bridge beams as well because it also covers ASR durability issues. We’ve used this formula historically on ot her br idge project s, w it h ver y satisfactory results.

“Steam-cured, the road bridge beams

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“The extension of the abutments and centre pier required approximately 30 working occupation permits.” reached the desired de-tensioning strength after 18 hours. However, we only detensioned on the third day because earlier de-tensioning leads to greater hog and deflection issues. It was essential that we controlled the deflection of the beams very carefully so that they matched the camber alignment of the existing bridge beams,” explains Nel. Work-in-progress Empa Structures was appointed by Martin & East to handle the actual construction of both bridges. Work on the river bridge involved the installation of bearing pads, beam placement, cross-bracing with insitu cast diaphragm beams and casting a reinforced concrete deck on reinforced concrete permanent shutters. It also involved demolishing the old balustrade above the

midpoint of the new bridge structure and replacing it with an in-situ cast safety barrier between the two sets of traffic lanes.

Unlike the river bridge, the abutments and centre pier of the rail bridge had to be extended under extremely constrained conditions. Once this was accomplished, the precast beam/balustrade units were placed on the bearing pads and attached to the existing bridge structure. Work still to be done at the time of writing includes demolishing the two original balustrades, constructing new pavements and resurfacing the road.

José Dos Reis of Empa Structures says the river beams were placed on the bearing pads using two mobile cranes.

(Above): Workers involved with attachment of a precast concrete beam/balustrade unit to the rail bridge.

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“Because the bridge has a high mid-point, the abutments and piers were sloped for stormwater drainage. This meant that when the bearing pads were installed, they had to be offset with epoxy to attain a level resting position,” he says.

River beams “The river beams were cast with bendout bars for attachment to the diaphragm beams. They were also cast with seven 50mm PVC ducts at the point where they crossed the diaphragm beams to enable Y25 continuity rebar to be installed along the full length of the diaphragm beams for additional strength. This required a high level of precision in casting the precast beams because the ducts had to run parallel to the slope of the diaphragm beams.

“Once all the precast beams were placed, we started with the in-situ casting of the diaphragm beams. The river bridge has 28 diaphragm beams at seven beams per span, which resulted in a massive and extremely strong monolithic bridge structure. The main diaphragm beams were installed at each abutment end and above each pier. As each diaphragm beam has six sections, the bridge required 196 diaphragm casts.

“Two of the spans are positioned above the river and we had to comply with very strict environmental conditions; we used long through-ties to support a gangway below the diaphragm beams. As soon as the diaphragm beams in each span were completed, we installed permanent concrete shutters between the precast beams. We’d cast 1 500 on site and some of them needed trimming, because we were working to very tight tolerances. Any gaps of 3mm or more were sealed with multi-bond epoxy. This was done to prevent any grout loss when we poured the deck concrete,” says Dos Reis.

Deck slab “Once the deck shuttering was in position, we installed the rebar for the deck slab, which took about a week to 10 days to do.

We then inserted our level rails and cast the deck to a thickness of 125mm. Each span took 40 cubes of concrete and once the screeding and floating were done, the deck was water-cured for seven days. This process was repeated for each span,” says Dos Reis.

When the old outer balustrade, which was used as a safety barrier during construction, is demolished, an infill beam – which will form the foundation for the median/central traffic barrier – will be cast along the full length of the bridge. The barrier and a new outer balustrade will be cast in-situ, with extensive reinforcing.

Dos Reis says that before the beams could be placed on the rail bridge, a colossal amount of preparation work went into widening the central pier and the abutments. “What made it tricky was that we were working above and under two 3kV power lines and three live fibre lines running right next to the one abutment.

In addition, we had to found 3m below natural ground level within 1m of the live track and then tie the new abutment and pier superstructure into the existing structure.

Weekend work “ We h a d to apply to Tr a n snet for occupation permits, which gave us a very limited time to do the work. The extension of the abutments and centre pier required approximately 30 working occupation

(Above): The underside of the newly constructed river bridge showing the T-beams and the permanent concrete shuttering.

(Below): Workers attach a precast concrete beam/ balustrade unit to the rail bridge.

permits. This was extremely challenging.

For example, we had to cast the 3m-deep foundation base over a weekend, starting on Friday evening and finishing on Sunday afternoon. To accomplish this and meet other targets, we had to double up on all our plant, equipment and human resource capacities.

“The foundation trench had to be retained and we had to steel-fix, place the formwork and pour the concrete, which needed to set within our allotted 72 hours.

Scaffolding and drilling into the existing structure to insert the rebar followed. All of this work was done under occupation permits, which take roughly 28 days to be granted. So if one fell behind with anything due to a freak thunderstorm or some other event, one would have had to re-apply for a permit and wait another 28 days before work could resume.

“Empa is fortunate in having a great team and we managed by working on multiple fronts. We began working on the side of the bridge where occupation permission wasn’t required. It provided a valuable learning curve that enabled us to plan our working schedules for the ‘live’ side properly. We conducted timeand-motion studies and we actually beat our targets through every site occupation.

During one of our working windows, there was a massive storm when 90mm fell in one day. We had to erect temporary roofs on our scaffolding so that our team could continue working,” says Dos Reis.

Challenging project Once the precast beams were placed on the bearing pads, they were held in position with push-pull props until they were permanently attached to the rail bridge. This was done by drilling into the existing bridge and inserting rebar, which was then tied to the exposed rebar of the new beam. Concrete was poured over the rebar and when it was set, the push-pull props were removed. After that, the old balustrades were demolished and new raised pavements were cast by Martin & East using premix.

Dos Reis says that despite the challenging nature of the project, everything was well executed, primarily due to all the members of the professional team working extremely well together.

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Architecture must pivot

AROUND PEOPLE

By Patrick McInerney and Christoph Malan, directors at Co-Arc International Architects

Architecture is fundamentally important to the human experience, as it frames the world in which we live. At its core, arch itect ure is about people, about humanity and the human condition. As British prime minister Winston Churchill observed in 1944: “We shape our buildings and afterwards, our buildings shape us.”

It stands to reason, therefore, that we approach architecture with our humanity fully engaged.

Whereas countries such as the Netherlands can demonstrate exemplary models of well-integrated social housing devel-

opment and management, the world is, unfortunately, also replete with failures, from Pruitt-Igoe in St Louis, Missouri to the Komtar Tower in Malaysia, Cabrini-Green in Chicago, Pink Houses in Brooklyn and the infamous Grenfell Tower in London.

South Africa has also failed to shine in this respect.

From the outset, the development of new South African housing policies in the 1990s buckled under the social pressure of demand, leading politicians to regard housing delivery as a purely statistical exercise. This approach has sidelined

architectural and urban design professions.

In spite of lip service being paid to social integration in the later “Breaking New Ground” housing policy, the settlements that continue to be developed across SA remain a sprawl of carelessly designed and built, anonymous, disconnected and sterile huts.

If the pressure to deliver housing by numbers was meant to prevent SA from spinning into revolution, some might argue that the country’s highly unequal society puts us on the verge of just such (Top, from left): Patrick McInerney and Christoph Malan.

(Above): Grenfell Tower in London.

(Left): Four modern social housing units in terra colours containing modest family apartment houses in Ypenburg, The Hague, Netherlands.

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a revolution today; one fuelled in part by the lack of respect afforded to many South Africans in the design, development and management of their living environments.

Image vs identity When architecture loses its focus on humanity, and the particular social and physical context, the process becomes more about image than identity. This is highly problematic and a great deal of the commercial architecture around SA has certainly fallen foul of that search for image while neglecting the community, pedestrians and the liveability of the space.

A remarkable project from Urban-Think Tank, a global interdisciplinary design practice, shows us that architecture and humanity can effectively merge to create

(Right): Komtar Tower in Malaysia.

something truly special. The Empower Shack project found a home in Khayelitsha, Cape Town under the watchful eye of local architects Design Space Africa.

The concept is simple: develop a new open-source housing prototype and urban plan which could be a model for informal settlement upgrading across SA. Using the existing footprint of the shack and working closely and transparently with residents and city planners, structures are built using local labour and materials according to architectural principles focused on creating homes, not just houses.

Key obstructions Empower Shack is an extraordinary and in-

“When architecture loses its focus on humanity, and the particular social and physical context, the process becomes more about image than identity.”

novative way of working, and an approach SA should certainly replicate. But standing squarely in the way of a fully-formed, human-focused approach to architecture are several threats: • In our focus on the individual housing unit, we fail to design for communities on an urban scale.

• Our obsession with security fragments society and results in areas like Fourways in Johannesburg, which has a dearth of urbanity and is exclusionary by nature.

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•

•

•

Economic forces persistently trump the social and human factors in favour of treating buildings solely as assets to be draped in billboards and neglected when times get tough.

Political inconsistency undermines our ability to translate policies into long-term projects and to see these through to completion. Constant changes in focus within government inevitably alter the focus of the city and make it harder to deal with critical issues like restitution.

A disregard for natural environmental considerations a nd oppor t u n it ies erodes t he ver y fou ndat ions of susta inable sett lement development. A reas such as Johannesburg and Soweto could capitalise and preserve their watercourses as ecological footprints which could form the sort of urban planning green areas that make the likes of Edinburgh’s Princes Street Gardens and New York’s Central Park such outstanding features.

Instead, developers have been allowed to build right up to river banks, in spite of possible ecological concerns.

There are other evolving considerations of which architects should also be aware, such as mankind’s growing technological addiction, which creates opportunities to re-think social congregation through interventions like free Wi-Fi coupled to public spaces. In Argentina, free Wi-Fi has resulted in city squares and parks filled with young people on their cellphones or interacting. It is impossible to ignore this new force shaping our society.

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Listen and learn While adaptation is critical, fundamental human needs continue to underpin the essence of good architecture – and that begins with a sense of belonging and community. This is

“While adaptation is critical, fundamental human needs continue to underpin the essence of good architecture – and that begins with a sense of belonging and community.”

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Sealants

ASPHALT PAVEMENTS ACOUSTIC INSULATION ARCHITECTURAL STONE PAVING PAVIMENTAZIONI BITUMINOSE SEALANTS AND ADHESIVES ISOLAMENTO ACUSTICO PAVIMENTAZIONI ARC. IN PIETRA SIGILLANTI E ADESIVI ELASTICI

522 527

B STRUCTUR MARINE RINFOR INDUSTR

523

520 521 522 demanding that we, as architects, listen to and engage with 529 530 531 532 533 534 524 525 526 527 the communities we serve. After all, the success of any project 536 537 538 requires buy-in and Icons a sense of community ownership.

In the 1990s we were asked by our partners, Aziz Tayob Architects, to assist with urban design in Marabastad, the Products WOODE CERAMIC ANDINSULATION STONE MATERIAL RESILIENT,BUILDING LVT, TEXTILE MATERIALS WOODEN FLOORING RESIN FLOORING ACOUSTIC ADMIXTURESSPORT FOR CONCRETE SPORT PA CERAMICA E MATERIALI LAPIDEI RESILIENTI, LVT,MATERIAL TESSILI Pretoria Six. The initial community PARQUETequivalent of District RESINA ISOLAMENTO ACUSTICO EDILIZIA ADDITIVI PER CALCESTRUZZO SPO CERAMIC AND STONE RESILIENT, LVT, TEXTILE MATERIALS for Resilient, SPO CERAMICA E MATERIALI LAPIDEI RESILIENTI, LVT, TESSILI Admixtures for participation meeting wasSTRUCTURAL tense andSTRENGTHENING fuelled by anger at MASONRY the BUILDING LVTWALL & Textile RESIN FLOORING ACOUSTIC INSULATION ADMIXTURES CONCRETE ARCHITECTURAL STONE PAVING RESTORATION THERMALFOR INSULATION PROTECTIVE WAT RESINA ACUSTICO EDILIZIA EDIFICI ADDITIVI PER CALCESTRUZZO RINFORZO STRUTTURALE PAVIMENTAZIONI ARC. IN PIETRA RISANAMENTO ISOLAMENTO TERMICO ANDMARINE DECORATIVE COATINGS IMPER SEALANTS AND ADHESIVES INDUSTRY CEM Concrete Materials constant re-planning of theISOLAMENTO environment from which the IN MURATURA FINITURE COLORATENAVALE E PROTETTIVE SIGILLANTI E ADESIVI ELASTICI INDUSTRIA 524 525 526 527 528 529 530 531 531 523 532 533 534 535 community had been expropriated. It took a series521 of about 520 522 523 524 528 529 530 20 community participation meetings for us to structure the 537 538 539 532 533 534 535 process and gradually identify the stakeholders and interest groups, take note of all the concerns and workshop designs and management processes. It became self-evident that land THE BACTERIOSTATIC, rights restitution issue, so we made that the THE BACTERIOSTATIC, WOODEN FLOORING was the driving RESIN FLOORING ACOUSTIC INSULATION BUILDING ADMIXTURES FOR CONCRETE STRUCTURAL STRENGTHENING ARCHITECTURAL PAVING ARCHITECTURAL STONE PAVING MASONRY MASONRY RESTORATION THERMAL INSULATION WALL PROTECTIVE WATERPROOFING UNDERGROUND CONSTRUCTION Sports Products for PARQUET RESINA ISOLAMENTO ACUSTICO EDILIZIA ADDITIVI PER CALCESTRUZZO RINFORZO PAVIMENTAZIONI PAVIMENTAZIONI ARC. IN PIETRA RISANAM RISANAMENTO EDIFICI TERMICO AND DECORATIVE COATINGS IMPERMEABILIZZANTI COSTRUZIONI INSTRUTTURALE SOTTERRANEO SPORT WOODEN FLOORING CERAMICISOLAMENTO AND STONE MATERIAL RESILIENT, LVT, TEXTILE MATERIALS STRUCTURAL ST ARCHITECTURAL PAVING ARCHITECTURAL STONE PAVING heart of our urban development framework.

ARCHITETTONICHE IN M IN MURATURA FINITURE COLORATE PROTETTIVE RINFORZO S PAVIMENTAZIONI PAVIMENTAZIONI ARC. IN PIETRA Flooring SPORT PARQUET CERAMICA E MATERIALI LAPIDEI RESILIENTI, LVT,ETESSILI Underground HIGH-PERFORMANCE, HIGH-PERFORMANCE, ARCHITETTONICHE MARINE INDUSTRY CEMENT ADDITIVES ASPHALT PAVEMENTS THERMAL INSULATION WALL PROTECTIVE WATERPROOFING UNDERGROUND CONSTRUCTION Ultimately, the project was successful only in that a Construction Solutions INDUSTRIA TERMICO NAVALE C-ADDCOATINGS PAVIMENTAZIONI BITUMINOSE ISOLAMENTO AND DECORATIVE IMPERMEABILIZZANTI COSTRUZIONI IN SOTTERRANEO FINITURE COLORATE E PROTETTIVE restitution process was completed.

However, it took too long.

MULTIFUNCTIONAL, MULTIFUNCTIONAL, 531 532 533 534 535 536 537 538 539 539 Regrettably, the city dragged its feet in investing in the area, 536 537 538 528 529 530EPOXY 531 532 EASY-TO-USE GROUT. EASY-TO-USE EPOXY GROUT. allowing Marabastad to sink even deeper into decline. By the time the small core of remaining business-owners and residents secured ownership of the land, nobody was really interested in investing – a missed opportunity in an area so Cement MASONRY RESTORATION THERMAL INSULATION WALL PROTECTIVE WATERPROOFING UNDERGROUND CONSTRUCTION SEALANTS AND ADHESIVES MARINE INDUSTRY CEMENT ADDITIVES ASPHALT ASPHALT PAVEMENTS rich in diversity and heritage.ISOLAMENTO Waterproofing RISANAMENTO EDIFICI TERMICO AND DECORATIVE IMPERMEABILIZZANTI COSTRUZIONI IN SOTTERRANEO SIGILLANTI E ADESIVI COATINGS ELASTICI INDUSTRIA NAVALE PAVIMENTAZ PAVIMENTAZIONI BITUMINOSE SEALANTS AND ADHESIVES MARINE C-ADD INDUSTRY CEMENT A Additives IN MURATURA FINITURE COLORATE E PROTETTIVE SIGILLANTI E ADESIVI ELASTICI INDUSTRIA NAVALE C-A What Marabastad ARCHITECTURAL did underlinePAVING was the need toARCHITECTURAL engage STONE PAVING STRUCTURAL STRENGTHENING MASONRY RESTORATION TH RINFORZO STRUTTURALE PAVIMENTAZIONI PAVIMENTAZIONI ARC. IN PIETRA RISANAMENTO EDIFICI ISO and the patience required when working closely with ARCHITETTONICHE IN MURATURA communities. It takes time to break down barriers to trust 539 and to interact openly and honestly – the starting point of MAPEI is and supplier 537 is no 538a trusted manufacturer 539 any human-centred536 architectural process. But there of the highest quality building materials to the easy work-around to this process of engagement if humanity construction sector.

The MAPEI Group consists of is truly to be brought to the forefront.

90 subsidiaries with 83 plants in five continents.

Ultimately, the buildings we create today will shape the ASPHALT PAVEMENTS PAVIMENTAZIONI societies ofBITUMINOSE tomorrow. Without putting people at the centre, Our team is committed to providing pre-sales we can never hope to develop sustainable and healthy SEALANTS AND ADHESIVES MARINE INDUSTRY CEMENT ADDITIVES ASPHALT PAVEMENTS advice, technical on-site support and training and communities; instead, we perpetuate a cycle of reinforcing SIGILLANTI E ADESIVI ELASTICI INDUSTRIA NAVALE C-ADD PAVIMENTAZIONI BITUMINOSE after-sales support f rom the conception of your old divides and, in the process, erode the importance of our project to the completion. own profession.

Product Lines / Linee di prodotto

KERAPOXY CQ KERAPOXY CQ

(Above): New York’s Central Park.

(Left): Soweto Townships in Johannesburg.

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KERAPOXY CQ is aCQ easy-to-use, anti-acid, easy-to-clean, two-component epoxy epoxy filler with KERAPOXY is a easy-to-use, anti-acid, easy-to-clean, two-component filler with BioBlock® technology for grouting the joints ceramic tiles and mosaics.

BioBlock® technology BioBlock® technology for grouting theof joints of ceramic tiles and mosaics.

BioBlock® technolo prevents the growth of unwanted micro-organisms and mould on the on joints prevents the growth of unwanted micro-organisms and mould thesurface. joints surface.

KERAPOXY CQ is ideal grouting joints where a high alevels hygiene are required such as KERAPOXY CQ isfor ideal for grouting joints where high of levels of hygiene are required such as industrial &, commercial kitchens, residential environments, swimming pools, worktops, etc. etc. industrial &, commercial kitchens, residential environments, swimming pools, worktops,

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| PROJECTS |

Extra-heavy equipment and a harsh mining environment were some of the challenges Kwena Rocla in Botswana had to overcome in order to complete a complex culvert project in Jwaneng, in the south-central area of the country, recently.

The company was awarded a contract to design, manufacture and supply bespoke culverts to one of the world’s richest diamond mine operations in order to allow for the expansion of the open-cast mine.

The culverts had to withstand the 530ton weight of the mine’s Komatsu 930E tippers and giant electric shovel with only a 1,2m-thick fill layer above the culvert.

According to Philip Smith, operations director of Kwena Rocla, the company also had to meet the challenge of the culverts having to stand on double- and triple-base slabs due to the soil conditions experienced.

This called for special moulds to be created in order to produce the slabs. Yet despite this and strict contractual milestones, the extremely tight deadlines were met and the company delivered culverts of exceptional quality and strength.

Tough conditions “Our plant maintenance department excelled in the design and manufacture of the new moulds on a very tight schedule.

We were also audited on a monthly basis for compliance to the set health, safety, environment and quality assurance criteria laid down before commencement of the contract. A cashf low analysis needed to be submitted to the client in order to monitor payment milestones and control the retention portion. Another contractual requirement was the submission of monthly progress reports.

“A dedicated production supervisor and quality assurer were client requirements, with every load having to have a detailed quality control pack for the products on board – 171 QCPs in total were submitted.

Kwena Rocla a lso w rote new work methodology statements pertaining to the production and handling of the bespoke 8,2-ton products and all drivers and crane operators had to be cleared and certified by the mine,” says Smith.

Kwena Rocla supplied 102 units of 2 000 x 1 000 at 1,2m fill culverts, 244 units of 2 000 x 1 500 at 1,2m fill culverts and 288 units of 2 000 x 2 000 at 1,2m fill culverts.

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Strong culverts

FOR DIAMOND MINE (Above): Triple bases of 8,2 tons each for the Jwaneng project.

(Left, from top): The production area at Kwena Rocla in Botswana and a grid ready to be inspected.

It also supplied 217 units of 2 000 double bases and 72 units of 2 000 triple bases to the project. It delivered these bespoke culverts ahead of deadline with a level of attention to detail commended by the client.

In addition, it received client recognition for zero life-threatening incidents on site or at the factory throughout the project.

“The culverts needed to stand on double- and triple-base slabs due to the soil conditions.”

Ongoing work “We’re extremely pleased with our capability and performance on this project, which was an extension of a previous project in which we were involved. We’re very optimistic about becoming involved in similar projects, going forward,” says Smith.

The plant maintenance department of Rocla provides services to both Rocla and Technicrete plants. It manufactures and repairs anything the plants require, including the concrete moulds used in daily production runs.

Inca Concrete Products Pty Ltd

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PRECAST | ISSUE ONE | 2021

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PRECAST | ISSUE ONE | 2021

IM/02/2021

YOUR PRECAST CONCRETE SPECIALIST PRODUCTS Storm Water Electrical Markers Water Reticulation Outdoor & Building Polymer Products Mining Solutions Kerb Inlet & Road Products Custom Products SERVICES Moulds Drawings

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