Microwave-assisted concrete recycling - Microwave-Assisted Concrete Technology: Production, Demolition and Recycling - page 129

Microwave- assisted
concrete recycling
4.1 INTRODUCTION
The construction industry is the largest consumer of raw materials world-
wide, with an estimated consumption of up to 50% of all materials. As
a result of the enormous amount of energy consumed in the production
and transportation of materials together with the energy consumed by con-
struction operations and the operation of buildings, the global construction
industry has been estimated to be responsible for up to 40% of the total
energy use and up to 30% of the total associated carbon emissions. In addi-
tion, up to 50% of the total waste generated in some countries has been esti-
mated to be directly or indirectly related to the construction industry [1,2].
The substantial amount of materials used by the construction industry
contributes to some of the biggest environmental concerns. The major envi-
ronmental concerns related to construction materials include (1) upstream
impacts related to the depletion of nonrenewable natural resources as well
as the energy used and the waste generated during the production of materi-
als; and (2) downstream impacts concerned with the huge amount of mate-
rial waste generated at the end of the service life of the materials as well as
the energy and associated carbon emissions incurred during processing of
demolition wastes. Dealing with the waste material generated during the
production of construction materials as well as during the construction and
demolition (C&D) phases of buildings and other structures has been a major
focus of research over the past few decades. The United States alone pro-
duces around 140 tons of C&D waste each year, accounting for almost 29%
of the total solid waste generated in the country [3]. Europe is estimated to
produce about 970 tons of C&D waste annually [4]. In Australia, about
14 million tons of solid wastes are dumped in landfills annually, and 44%
of this total is estimated to be attributed to the construction industry [5].
The most common way of dealing with the huge amount of C&D waste
generated every day is to invest waste with new usable life (as the same
or a different material) through recycling. The benefits of effective C&D
waste recycling are economic, environmental, and social. Recycling reduces
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