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TECHNICAL PAPER COLLECTOR’S EDITION

contamination and the presence of dangerous
substances have been investigated. The current
state of this research is now directed towards
developing the technology to a level of marketable
products, and practical application.

The use of granulated rubber from waste tyres is
an example of how recycled materials can improve
the performance of concrete, as research has
shown that concrete incorporating tyres can be
used as an alternative to air-entrained concrete
to improve freeze/thaw resisting performance
[Figure 10] and for enhancing thermal insulation
through reductions in the thermal conductivity of
concrete [Figure 11]. 46 - 48
Incineration is an increasingly common method for
reducing the bulk mass and volume of municipal THE WAY FORWARD
wastes. Incinerator bottom ash aggregate (IBAA)
This paper has shown examples of how research
may be used as a coarse aggregate in concrete
construction, although it should be restricted and practice are making a positive contribution
towards realising the best use of RSA in concrete
to low strength concrete and must not be used
and concrete products. Indeed, the benefits of
in reinforced or prestressed concrete due to
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potentially high chloride contents. As a material, using RSA, where they are appropriate, is being
increasingly recognised, for example, the range of
it is perhaps best restricted to precast blocks or
to cement-bound road and sub-bases (Figure 8). applications for recycled aggregates described at
the AggRegain website is promising and it needs
Sewage sludge ash (SSA) is a potential alternative
to be said that the concrete construction industry
to natural fine aggregate, and research has
concentrated on this outlet. Incinerator fly ash in itself is now more receptive to the use of RSA, as
(IFA) may have some potential as filler aggregate. a recognised valuable resource material. 49, 50

Oil drill cuttings are a sand-like material, produced However, as to be expected, there are still numerous
through offshore oil extraction (Figure 9). While barriers to cross before recycled aggregates
they are composed of natural granular materials become a common concrete constituent.
consisting of stable minerals with relatively Indeed, it is becoming increasingly clear that the
good mechanical properties, they do suffer from governments and industry need to invest heavily
contamination by oil. A feasibility study by Dhir et in meaningful and responsible research, which is
al has shown that they may be used at up to 20% capable of being packaged in a form that clearly
by mass of sand in concrete without affecting shows how these materials can be used in concrete
main engineering properties of concrete or construction and which is of direct interest to
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water-tightness of the product. Concerns with industry. For example, the previous research and

The Indian Concrete Journal | November 2018 123