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Comparative studies of the life cycle analysis between conventional and recycled aggregate concrete 287

both NAC and RAC slabs were designed according to Eurocodes’ requirements.
The following conclusions were drawn.
In the case of attributional modelling:
1. RAC made of RCA which water absorption was 4.4% (RAC1) caused environmental
impacts similar to those of NAC, while RAC made of RCA with water absorption equal
to 5.7% (RAC2) had slightly larger impacts, up to 8%.
2. Similar results were obtained for more severe exposure conditions, that is, XC3 class.
When comparing only RAC, impacts of RAC mix in the XC3 environment were larger
than impacts of the same mix in XC1 environment at 6% 7%.
3. Modelling of CO 2 uptake in indefinite time perspective made GWP of both RAC mixes
and for both XCs lower than GWP of NAC mix. In RAC2 and XC3 the decrease was 1%.
In the case of consequential modelling:
4. Both RAC mixes for both XCs had similar, or lower, impacts than NAC mixes.
Compared to attributional modelling, the decrease was especially significant for ADP_FF
and POCP indicators and was mostly caused by avoided burdens of pig-iron production.
Looking at RAC2 mix in XC3, for instance, consequential modelling brought about a
5% 27% decrease of impacts compared to attributional modelling.
5. Modelling of CO 2 uptake in indefinite time perspective made GWP of both RAC mixes
and for both XCs significantly lower than GWP of the NAC mix: 20% for RAC1 and
17% for RAC2. When NAC mixes were examined separately, reduction of GWP was
about 30%, while for RAC mixes reduction of GWP was slightly larger, at about 35%.
By putting into the context of specific RC structure it was possible to evaluate
the importance of analysed parameters in comparative LCAs. When RCA quality,
that is, strength and structure’s durability aspects are regarded, results will probably
be different for other structural members’ type, like beams or columns, and for
other XCs. However, influence of the LCI modelling approach on all indicators and
influence of the CO 2 uptake on the GWP indicator is straightforward and in per-
formed case studies, very significant; much more significant than RCA quality or
XC influence. Even for less favourable scenarios in the RAC life cycle, such as for
instance in the case of different modelling of displaced processes, consequential
modelling would still have a positive influence on RAC impacts making the differ-
ence between NAC and RAC smaller.

References

Allacker, K., Mathieux, F., Manfredi, S., Pelletier, N., De Camillis, C., Ardente, F., et al.,
2014. Allocation solutions for secondary material production and end of life recovery:
proposals for product policy initiatives. Resour. Conserv. Recycl. 88, 1 12. Available
from: https://doi.org/10.1016/j.resconrec.2014.03.016.
Andersson, R., Fridh, K., Stripple, H., H¨ aglund, M., 2013. Calculating CO 2 uptake for exist-
ing concrete structures during and after service life. Environ. Sci. Technol. 47 (20),
11625 11633. Available from: https://doi.org/10.1021/es401775w.
BSI, 2006. BS 8500-2:2006, Concrete Complementary British Standard to BS EN 206-1,
Part 2: Specification for Constituent Materials and Concrete. BSI, London.