More emphasis should be placed worldwide on the recycling concrete, the most commonly used building material on earth, Bryan Perrie, MD of The Concrete Institute, has urged.

“Modern civilisation is built on concrete and its positive social impacts are immense. However, as a result of its extensive usage, concrete has a relatively large environmental footprint which could be reduced by increasing the volumes of recycled concrete,” Perrie told the Concrete Society of Southern Africa’s ReCon 2016 seminar held in Johannesburg recently.

He said there were many misconceptions about the extent of concrete’s effect on the environment but worldwide, the cement industry was responsible for only about 5% of man-made carbon dioxide. Of this, 40% is derived from the burning of coal and 60% from the calcination of limestone. “Eight billion tons of concrete are used annually – twice as much as any other building material. This means that the volumes of Construction and Demolition Waste (C&DW) also reach substantial volumes. In Europe, for example, the annual volume is estimated to be around 510 million tons, in the USA it is 325 million tons, and in Japan, 77 million tons. The totals for China and India – where half of the world’s concrete is produced – are not known. Enormous volumes of C&DW are ending up in landfills, completely ignoring their recycling potential.”

Perrie said recycling concrete also had many other benefits, including the reduction of natural resource exploitation, lower transport costs of new building materials, and increased employment opportunities – an important element in a country such as South Africa where many people are jobless.

The most common usage of recycled concrete currently is in roads, with 41 states in the USA already using recycled concrete in their road projects. In Anaheim, California, for example, 700 000 tons of recycled concrete were used on a new freeway project, resulting in savings of about USD5-million. In Australia, building materials for the construction of the Western Link highway at Melbourne included around 15 000 cubic metres of recycled concrete, yielding savings of AUD4-million.

“But concrete can also be recycled for other purposes. Old demolished concrete structures provide a potentially rich source for recycling concrete for a wide range of applications; precast concrete components are often reused in new buildings; and old factories and warehouses can be converted into dwellings. The quality of the concrete in structures will determine its suitability for reuse.”

Perrie said there were, however, some challenges to be overcome in the quest for using higher volumes of recycled concrete. “Included are aspects such as irregularity of supply, contamination and lack of consistent quality, coupled with the high cost of quality concrete recovery, site sorting, noise and pollution resulting from recovery and processing on site, as well as potential legal aspects.

“But the benefits, particularly for countries with shrinking economies, by far outweigh the challenges. The Concrete Institute believes there is a need for legislation banning construction and demolitiion waste from landfills, or the introduction of taxation to limit the volumes ending up in landfills. This must be coupled with increased policing to stop illegal dumping of construction waste. Architects and specifiers also need to increasingly consider the use of recycled concrete when designing new buildings,” he added.

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