14 / 48
12
CONSTRUCTION WORLD
JULY
2016
“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 environ-
mental 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 Johan-
nesburg 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 reduc-
tion 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 Insti-
tute 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 increas-
ingly consider the use of recycled concrete
when designing new buildings,” he added.
Concrete
RECYCLING’S
BENEFITS
More emphasis should be placed worldwide on the recycling of
concrete, the most commonly used building material on earth,
Bryan Perrie, MD of The Concrete Institute, has urged.
>
The quality of the concrete in demolished structures
will determine the concrete's suitability for reuse, says
The Concrete Institute MD, Bryan Perrie.
“Eight billion tons of concrete are used annually -
twice as much as any other building material. ”
ENVIRONMENT AND SUSTAINABILITY