Page 367 - New Trends in Eco efficient and Recycled Concrete

322 New Trends in Eco-efficient and Recycled Concrete

Table 11.6 Influence of each raw material in the environmental performance of concrete
(Braga et al., 2017)

Raw materials EI
CEM I 2
CEM II 1
River aggregate 1
Crushed aggregate 2
Granitic coarse aggregate 1
Limestone coarse aggregate 2
Coarse RCA 11
SP 1

Note:1 represents a reduction of impact;11 represents a significant decrease of impact;2 represents an increase of
impact.
incorporation of CARC contributes to a GWP reduction (Marinkovi´ c et al., 2010).
The same behaviour occurs for the other categories of EI, except for ADP. About
this impact category, is not possible to draw conclusions due to the limited repre-
2
sentation and/or small R values.
In the SP parametric analysis, three intervals were defined: without SP, SP
between 0% and 1% of the cement weight, and above 1%. The analysis of the influ-
ence of SP incorporation on GWP does not provide enough evidence to draw con-
clusions. For some of the remaining environmental categories, the use of SP is
beneficial from an environmental point of view (i.e. for POCP, EP and Pe-Re).
In the parametric study of the W/C ratio, the selected ranges were: less than
0.55; from 0.55 (included) to 0.6; and equal to or greater than 0.6. Regarding the
strength class, it is possible to conclude that an increase of the W/C ratio results in
a decrease of the associated GWP. This trend is confirmed in other environmental
categories. It is also possible to claim that the use of CARC contributes to a
decrease in the EI of concrete.
In summary, the main conclusions of this study were (Table 11.6):

Higher concrete strengths do not necessarily lead to a higher EI;
Mixes with maximum EI do not contain SP in their composition, but is also advised to
use SP to decrease cement content which is the main responsible for the EI;
The w/b (water to binder ratio) reduction does not show significant improvement in EI;
The use of coarse RCA results in a reduction of EI.

11.9 Concluding remarks

In this chapter, the concept of EFU in RA concrete was discussed. It was concluded
that most comparative LCA analyses in the literature do not take into account the
diverse performance of RA concrete relative to equivalent NAC in reinforced con-
crete elements. In other words, the functional units that are compared are not equiv-
alent from a structural point of view.