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Comparative studies of the life cycle analysis between conventional and recycled aggregate concrete 281

10.5 Results and discussion

Input parameters in conducted case studies are summarised in Table 10.9.
Designations of the case study consists of three parts. The first part stands for RCA
quality (1 5 high quality; 2 5 low quality), the second stands for XC (XC1 and
XC3) and the third part for modelling approach (A 5 attributional; C 5 conse-
quential). Lastly, two case studies include CO 2 uptake modelling. Only selected
results are presented and discussed.

10.5.1 Quality of recycled concrete aggregate

Results of 1_XC1_A and 2_XC1_A case studies are jointly presented in Fig. 10.3.
Firstly, ADP_FF and POCP of both RAC mixes are slightly lower than those of
NAC mixes due to the much shorter transport distance of RCA compared to the
transport distance of crushed NA (20 km compared to 100 km). Secondly, impacts
of RAC1 mix are similar to those of NAC mixes. The largest increase compared to
NAC1 mix is 3% which is within the limits of NAC mixes’ differences in impact.
RAC2 has slightly higher impact, with 8% larger GWP and AP compared to the
NAC1 mix.
When only RAC mixes are considered, it can be seen in Fig. 10.4 that the RAC2
mix exerts 3% 6% larger impact compared to the RAC1 mix, depending on the
impact category. The lower the RCA quality, the larger the impact of RAC is to be
expected.
However, RCA with larger absorption than that used in the RAC2 mix probably
would not be used in the structural concrete for design reasons. This may lead to
significant self-weight increase which affects not only the studied structural mem-
ber, but also columns, walls and foundations due to the increase of vertical and
seismic loads on the structure.

Table 10.9 Input parameters in case studies

Case study RCA quality Exposure Modelling CO 2 uptake
class approach
1 1_XC1_A NAC1 versus RAC1 XC1 Attributional No
2 2_XC1_A NAC2 versus RAC2 XC1 Attributional No
3 1_XC3_A NAC1 versus RAC1 XC3 Attributional No
4 2_XC3_A NAC2 versus RAC2 XC3 Attributional No
5 1_XC1_C NAC1 versus RAC1 XC1 Consequential No
6 2_XC1_C NAC2 versus RAC2 XC1 Consequential No
7 1_XC3_C NAC1 versus RAC1 XC3 Consequential No
8 2_XC3_C NAC2 versus RAC2 XC3 Consequential No
9 2_XC3_A_CO 2 NAC2 versus RAC2 XC3 Attributional Yes
10 2_XC3_C_CO 2 NAC2 versus RAC2 XC3 Consequential Yes

NAC, Natural aggregate concrete; RAC, Recycled aggregate concrete; RCA, Recycled concrete aggregate.