Civil Engineering Reference
In-Depth Information
converted LCi results are aggregated into a category indicator result, which
is the numerical value of the indicator in appropriate units. The indicator
result is the final result of the mandatory part of a LCia. The examples of
the characterization models are shown in Section 3.5. To date, consensus
has not been reached either for one single default list of impact categories
or for one single characterization model.
normalization, grouping, weighting and additional LCia data quality
analysis are the optional steps within the LCia phase (iSo, 2006a).
normalization is calculating the magnitude of the category indicator results
relative to reference information. Grouping is assigning impact categories
into one or more sets as predefined in the goal and scope definition, and it
may involve sorting and/or ranking. Weighting is the process of converting
and possibly aggregating indicator results across impact categories using
numerical factors based on value choices. Since weighting may include
aggregation of the weighted indicator results, the outcome of this step can be
one number. This score, or index, represents the environmental performance
of the product system under study. it should be noted that according to iSo
14040 there is no scientific way to reduce LCa results to a single overall
score or number, hence it cannot be used for comparative assertions. Data
quality analysis is an additional technique aiming at better understanding
the reliability of the collection of indicator results, i.e. the LCia profile.
interpretation is the fourth phase in LCa containing the following main
issues: identification of significant environmental issues, evaluation of the
results with the aim of establishing their reliability, and conclusions and
recommendations.
The application of this methodology in the case of concrete production
and utilization is discussed in the following sections.
3.3 Life cycle assessment (LCA) of concrete: goal
and scope definition
Within this step, the following items must be defined:
∑ The goal of the study, for example: comparison of two or more different
types of concrete or concrete structural elements, assessment of the whole
building or bridge, determination of the sources of the relevant impacts
and possible optimization potentials, etc.
∑ The function of the product or product system, i.e. functional unit.
∑ The system boundaries.
∑ The relevant impacts.
∑
The necessary data to reach the goal of the study.
The functional unit is defined by the function of the product or product system
(by services it provides with certain quality and for a certain period). For a
