Page 329 - New Trends in Eco efficient and Recycled Concrete

286 New Trends in Eco-efficient and Recycled Concrete

Figure 10.10 Influence of CO 2 uptake on GWP of NAC and RAC mixes in (A) attributional
and (B) consequential modelling. NAC, natural aggregate concrete; RAC, recycled aggregate
concrete; GWP, global warming potential.

From all the selected indicators, CO 2 emissions influence only GWP. The impact
of CO 2 uptake in a unlimited time perspective is significant for both NAC and
RAC mixes, see Fig. 10.9. GWP reduction for RAC mixes (35%) is larger than for
NAC mixes (27% 29%) due to the larger cement amount in FU and the assump-
tion of a slightly larger CaO content in RAC.
Even if attributional modelling is applied, GWP of both RAC mixes is lower
than GWP of NAC mixes, see Fig. 10.10. When consequential modelling is applied
and CO 2 uptake is taken into account, GWP of RAC mixes is smaller than GWP of
NAC mixes at approximately 20%. Bearing in mind that RAC2 mix is made with
relatively low-quality RCA and XC3, this reduction is significant.

10.6 Conclusions

Ten comparative LCAs of RC slab life cycles were performed. Analysed slab was a
typical floor structure of residential buildings and made either from NAC or RAC.
The goal was to investigate the influence of RCA quality, durability, LCI modelling
approach and CO 2 uptake on the assessment results. Results were locally con-
strained as the investigated building is located in the capital of Serbia, Belgrade.
Beside local conditions regarding transport types and distances, raw material types,
production technologies and construction practice, an important assumption was
made: RCA was transported over a 20 km distance while a transport distance for
NA, both river and crushed, was 100 km. The influence of transport types and dis-
tances was not investigated.
All comparisons were based on FU which provided full functional equivalences
between RC slab alternatives. In order to calculate the amount of reference flows,