Page 395 - New Trends in Eco efficient and Recycled Concrete

350 New Trends in Eco-efficient and Recycled Concrete

Figure 12.8 Performance of the pH-dependency test.

According to Engelsen et al. (2009), results of pH dependence in RCAs of different
fractions and ages have indicated carbonation effects in the components Al, Ca, Fe,
22
Mg, Si and SO 4 .
An evaluation of the environmental impact by leaching is an indicator of the sus-
tainability of recycled concrete and is an extremely important and necessary tool
for an appropriate environmental understanding of the material. In that sense, leach-
ing assessment through a pH-dependency test allows one to obtain qualitative data
necessary to confirm the safe use of recycled concretes.

12.5 Conclusion

Leaching results are a definitive parameter for the application of all type of materi-
als when an environmental impact assessment is taken into account.
Once the different industrial by-products are encapsulated within a cement
matrix, a minimum leaching of these elements is presented. This is of great impor-
tance, since it indicates that these new materials can be used in the manufacture of
recycled concrete.
This chapter also highlights the importance of the reuse of industrial waste that,
in addition to reducing the amount of natural resources used, substantially improves
(in some cases) the mechanical properties of concrete.
The ageing effect is relevant due to the strong alkalinity of concrete and any
cement-based product. This phenomenon leads to progressive changes of pH values
due to carbonation, affecting the release of contaminants due to pH is the most rele-
vant chemical factor that controls the release of many contaminants.