Reusable concrete elements vital for sustainability

by Tania Wannenburg
Reusable concrete elements

Recycled building materials make up a big part of Terraforce retaining blocks.
In a recent statement, Bryan Perrie, managing director of the Concrete Institute, pointed out that more attention should be paid to the reuse and recycling of building materials at the design stage to more actively promote sustainability in the construction industry.

Perrie says: “There is growing concern worldwide about the wastage of materials such as concrete, wood, gypsum, metals, bricks, glass, plastics and salvaged building components. Yet there is tremendous potential to recycle so many elements of the construction cycle.”

The Terraforce concrete retaining wall and erosion control system has been a sustainable product since its inception 35 years ago – long before it became fashionable. It is a hollow-core and closed-faced system that allows for maximum water absorption and plant growth, once installed. It is also an easy-to-use, cost-effective mortarless system that requires less material and equipment staging areas, as well as fewer pieces of large equipment for manufacturing and installation than cast in-situ solid concrete.

Crushing clean building rubble

In the Western Cape, Terraforce concrete retaining block manufacturers and contractors, Klapmuts Concrete and Cape Retaining Systems, are also committed to reduce their carbon footprint. Like most Terraforce manufactures locally and abroad, Klapmuts applies a crusher to re-use all broken and reject products.

Johan van Wyk, chief executive officer of Klapmuts Concrete, says: “We recycle all reject blocks as well as blocks that get damaged during the split operation of the rock face blocks. We accept clean building rubble (no timber, plastic, metal, etc.) from builders, as well as rejects from another building block manufacturer in our area. To ensure that the rubble can be used in our products without comprising quality, it was graded by a SANAS-accredited laboratory.”

Adding glass to the mix

When approached in 2013 by Nelson Glass, a major processor of plate glass in Cape Town, Van Wyk immediately took interest in their proposal to use crushed, recycled glass for block production.

Nelson Glass collects off-cuts and broken glass from most big processing companies and runs it through a crushing and screening process, which converts it into a reusable chips or sand format. This can then be supplied to the building industry for the manufacturing of cement blocks or slabs, replacing sand and stone.

Klapmuts Concrete started experimenting with crushed glass late in 2014. Following a series of screening tests and based on studies done in the USA, the decision was made to use crushed glass in limited quantities in almost all their products. “It was the perfect opportunity to use even more recycled products in our concrete mix, replacing more virgin material in the manufacturing of our products,” says Van Wyk.

Klapmuts currently uses two products – a course product that compares favourably with standard 6mm stone and a dust that is very similar to crusher dust.  

Concrete blocks with a sparkle

“The mix designs were adjusted to accommodate these products without jeopardising the strength of the blocks,” explains Van Wyk. “The finishes of the products are exactly the same as with normal aggregates, except that the rock face blocks now have a slight twinkle on the rough face.”

The end-result is that glass waste that would have ended up in a landfill as a hazardous and non-degradable by-product of the glass industry, is transformed into a useful, eco-friendly substitute, reducing the carbon footprint (reduction of mining of raw material and waste disposal) of both Klapmuts and Nelson Glass.

Tel: 021 465 1907
Website: www.terraforce.com

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