Page 258 - New Trends in Eco efficient and Recycled Concrete

226 New Trends in Eco-efficient and Recycled Concrete

generally accepted assessment tool. Thus, there was a growing need for more
standardisation. The first steps in that direction followed from the 1990s
onwards. The Society of Environmental Toxicology and Chemistry (SETAC)
took a leading role in the continuous improvement and harmonisation of the
LCA framework, terminology and methodology and finally came up with the
SETAC Code of Practice (Consolietal.,1993). The International Organization
for Standardization ISO looked after the standardisation of methods and proce-
dures. This eventually resulted in the publication of the well-known standards
ISO 14040 (2006); ISO 14044 (2006). In compliance with these standards, the
proposed methodology comprised four major steps: (1) the definition of goal
and scope; (2) the inventory analysis; (3) the impact assessment; and (4) the
interpretation. It is quite evident that the very same four-step procedure should
be adopted for life cycle based environmental impact quantification of concrete
with recycled aggregates.

9.3.1 Goal and scope

Setting a clear goal from the start is important because it facilitates the choices to
be made in terms of scope definition (functional unit, system boundaries), and
within the three subsequent steps of the LCA methodology. Usually, the LCA aims
at quantifying the environmental impact of a product/system and compare it with
the impacts of another one. Amongst the LCA applied to recycled aggregate con-
crete, the goal definition is based on the differential environmental performance
compared to conventional concrete mixtures under different scenario constraints
(replacement ratio, coarse/fine substitutions and type of aggregate, etc.). The com-
parative nature of the study implies that both the conventional concrete and the
recycled aggregate concrete need to have the same functional properties in terms of
workability, strength and service life. If not, the functional unit should be chosen as
such that it accounts for performance differences (see Section 9.3.1.1). The aim of
studying this for concrete containing a large portion of recycled materials also has
important consequences when choosing the system boundaries (see Section 9.3.1.2).
Merely focussing on the concrete production stage without including the end-of-life
stage of the concrete and ceramic industry, the actual sources of the recycled aggre-
gate, is obviously not sufficient. In view of data collection for adequate inventory
analysis (see Section 9.3.2), dedicated attention will need to go to detailed docu-
mentation of the end-of-life phase and operations involved to allow for recy-
cling. One will also need to make sure that within the third step of the LCA an
impact method is chosen that actually covers important issues with respect to
recycling, such as avoided waste production, avoided depletion of virgin aggre-
gates and avoided land use for quarry exploitation, etc. (see Section 9.3.3). Only
then, when all LCA steps are well in agreement with the initially defined goal,
the calculation output obtained and analysed in the interpretation phase
(Section 9.3.4)willbeofvalue.