Page 337 - New Trends in Eco efficient and Recycled Concrete

294 New Trends in Eco-efficient and Recycled Concrete

This chapter is comprised of six parts: the definition of the declared and func-
tional unit, where these concepts are clearly defined in order to understand the sub-
sequent discussion; the discussion of how RA concrete performs relative to NAC,
with the explanation of how this relative performance depends not only on the
aggregates’ type and content, but also on the property analysed; the methodology
for the definition of EFU for RA concrete is described next; an EFU for RA con-
crete is then proposed and the calculations needed to quantify it are described in
detail; the methodology is then applied and validated in reinforced concrete slabs;
finally, a survey of previous life cycle assessment (LCA) studies is presented, with
emphasis on a recent one.

11.2 Definition of declared unit and functional unit

11.2.1 LCA analyses and balanced comparisons

The environmental LCA methodology is an integrated approach that considers the
environmental impacts along the life cycle of products (Ortiz et al., 2009). The
evaluation of these impacts of each construction material should be made from a
life cycle point of view, and a LCA can be used for that purpose. This implies con-
sidering the resources used in the manufacture of the construction material, the
maintenance operations, their expected service life, and the replacement or demoli-
tion operations.
The LCA methodology comprises four analytical phases interlinked by iterative
cycles (ISO, 2006a,b; Blok et al., 2007; Ortiz et al., 2009):
1. Definition of the goal and scope of the assessment;
2. Life cycle inventory (LCI) analysis;
3. Life cycle impact assessment (LCIA);
4. Life cycle impact interpretation.

The definition of the goal and scope of the assessment comprises the description
of the product to be assessed, the boundary of the associated system (including the
definition of the cut-off criterion) and the functional unit. It also comprises the
selection of the environmental interventions and of the method (or methods) of
environmental impact assessment and the definition of the goal of the study, among
other issues.
LCI comprises the inventory, quantification and compilation of the relevant
inputs and outputs of the processes included along the life cycle of the product
being studied. Therefore, to complete the LCI of a product, each flow (e.g., of mass
or quantification of materials, energy and emissions to the air, water or soil) is iden-
tified, quantified and compiled for each life cycle and its corresponding processes.
The LCIA phase starts with the selection of impact categories, category indica-
tors and characterisation models. The classification procedure assigns LCI results to
the selected impact categories. The calculation of each category indicator result is
made during the characterisation stage. A characterisation model converts LCI