The Civil Engineering Contractor February 2018 | Page 25

INSIGHT
pollution that would result from
the extraction, manufacturing, and
transportation of virgin materials.
“The durability of concrete structures is
a key factor in their suitability for reuse.
The architect or designer needs to apply
many different strategies to ensure that
the structure is sustainable in terms of
its environmental and social impact, to
minimise the use of energy (whether
embodied or consumed during the use
phase), and to minimise the use of water
and the generation of waste during the
entire life cycle of the building. All of
this can only be assessed by carrying
out a full life cycle assessment of the
structure,” Perrie adds.
He says recycling concrete also
has 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
dumping of concrete at landfill sites.
Recycled concrete can be used as
aggregate for building products such
as bricks, blocks, layer works in road
construction, or land reclamation,
thereby reducing the amount of
material sent to landfills.
This recycling also reduces the need
for new virgin materials, thereby
saving resources and the energy
required to process them. Crushed
concrete also absorbs carbon dioxide,”
Perrie contends.
He says that at several ready-
mixed concrete plants, wash water
is collected and reused in fresh
concrete, and aggregate from
returned concrete is screened out
and reused. This reduces the amount
of waste generated at the plants.
Precast components from structures
can also be reused in new buildings
instead of demolishing and recycling
the concrete.
Structures using precast elements
can be designed for such reuse.
“In former industrial areas and
inner-city precincts, there are many
old factories, old warehouses, and
the like that can be converted into
very desirable dwellings. Concrete
buildings can often be adapted
relatively easily for new uses — for
example, unused office space can
be retrofitted for use as residential
accommodation. Effective building
retrofitting usually leaves the building
structure largely intact.”
The benefits of reuse and
retrofitting include:
• Saving natural resources,
including raw materials, energy,
and water required for new
structures;
• Reducing the quantity of solid
waste sent to landfill; and
• Lowering the energy usage and
“If you think about the impact of built
infrastructure 20 years, 30 years, 40
years, 50 years down the road, this
[recycling] will have a big impact in
terms of reducing concrete’s impact
on our environment.”
Yahya Kurama – University of Notre Dame, US
concrete currently is in roads, with 41
states in the US already using recycled
concrete in their road projects. In
Anaheim, California, for example,
700 000 tons of recycled concrete
were used on a new highway 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 000m 3 of recycled concrete,
yielding savings of AUD4-million.
Perrie continues: “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
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