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Life cycle assessment applied to recycled aggregate concrete 225

material in the highest-grade application possible to avoid down-cycling. For
instance, crushed concrete from a building structure may be repurposed as recycled
aggregate for road subbase instead of new recycled aggregate for another building
structure. While down-cycling is still an environmental improvement, taking advan-
tage of the full potential of recycled materials is more in line with the sustainability
concept and high-grade applications should be sought for the reutilisation of
recycled aggregates. The resulting trade-offs should be considered since the quality
and final use of a secondary material could carry a different net balance between
direct and avoided impacts between the different management options. The maximi-
sation of the potential benefits arising from the recycling of CDW answers to the
promotion of high-quality recycling routes (e.g., separation) and high-quality uses
(e.g., recycled concrete).

9.3 Life cycle assessment: considerations for recycled
aggregate concrete

In general, a LCA can be defined as an assessment tool to quantify the environmen-
tal impact of products generated over their entire life cycle. The evaluation
addresses all relevant activities necessary to make a product function. Each life
phase of the product (extraction of resources, production, use and disposal, etc.) is
normally considered (Desmyter and Martin, 2001). The value of this methodology
must be understood in view of the increasing importance of sustainable develop-
ment, which can be identified as development that meets the needs of the present
without endangering those of future generations (World Commission on
Environment and Development, 1987). It must be said, though, that the LCA frame-
work was not originally developed for the construction industry. Moreover, in the
beginning it was far from a well-developed methodology. The study of environmen-
tal impact of consumer products began in the late 1960s and early 1970s when envi-
ronmental issues like resource and energy efficiency, pollution control and solid
waste became issues of broad public concern (Guine ´e et al., 2011; Assies, 1992).
Initially, those studies were not much more than simple comparisons between pro-
ducts to see which one was better. Soon it was recognised that for many of these
products the largest portion of the environmental impact was not caused by its use,
but by its production, transportation or disposal (Guine ´e et al., 2011). One of the
first published examples of system analysis quantifying the resource requirements,
emission loadings and waste flows of a production chain from ‘cradle-to-grave’,
dates back from 1974. The study was conducted by the Midwest Research Institute
for the US Environmental Protection Agency (Hunt et al., 1974). In fact, it was a
follow-up of a study performed by the same institute for the Coca Cola Company in
1969 already to enable an environmental comparison between different beverage
containers. Guine ´e et al. (2011) see the period 1970 90 mainly as the period of
conception for LCA. At that time there was not much uniformity among the evalua-
tion approaches, terminologies and results which prevented LCA from becoming a