Page 62 - New Trends in Eco efficient and Recycled Concrete

38 New Trends in Eco-efficient and Recycled Concrete

Figure 2.8 XRD patterns of BFA (BFA1 BFA5 Vassilev et al., 2013b; BFA6 and BFA7
Berra et al., 2015). BFA, Biomass fly ash.
in BA (61%) is higher than those ashes obtained from coal thermal process (7.2%).
The pH values of the different BFA leachates vary in the range of 4.5 13.4
(Vassilev et al., 2013b). The pH values of woody BFA are normally higher than
straw and cereal BA due to the higher Ca and lower S and Cl concentrations in the
former ashes (Van Loo and Koppejan, 2008).
Since BFA can present high values of K, Cl, Ca and Mg, and it could contain
certain quantities of other hazardous components, environmental risks and health
concerns related to BFA with leaching process could be produced where hazardous
elements, such as K, Cd, Cl, Cr, Mo and others, can induce alkalinity and leaching
in the application of these ashes in civil construction. It is necessary to take into
account the reduction of leaching values when some waste is applied in a cement-
based material (Galvı ´n et al., 2013).