Page 152 - New Trends in Eco efficient and Recycled Concrete

126 New Trends in Eco-efficient and Recycled Concrete

Figure 5.2 Size distribution of the original SSA and their sieved fractions (Monzo ´ et al.,
1996). SSA, Sewage sludge ash.

Table 5.3 Chemical composition of the original SSA and their size fractions
% Sewage sludge ashes

SSA SSAC SSAM SSAF
20.8 30.1 16.2 15.5
SiO 2
14.9 11.9 14.7 14.0
Al 2 O 3
7.4 7.1 8.2 8.3
Fe 2 O 3
CaO 31.3 25.9 32.9 32.1
MgO 2.6 2.2 2.4 2.6
12.4 10.7 13.1 13.7
SO 3
6.7 6.3 7.6 6.9
P 2 O 5
Moisture 0.5 0.5 0.4 0.4
LOI 5.1 3.6 5.2 5.2
I.R. 16.1 28.0 11.7 11.3
SSA, Sewage sludge ash
Adapted from Monzo ´, J., Paya ´, J., Borrachero, M.V., Co ´rcoles A., 1996. Use of sewage sludge ash (SSA) cement
admixtures in mortars. Cem. Concr. Res. 26 (9), 1389 1398. Available from: https://doi.org/10.1016/0008-8846(96)
00119-6.

conductivity of the aqueous ash suspension (9.57 mS/cm) revealed that the ash had
2 22
a high soluble salt content (Cl 5 7.8 mg/g, SO 4 5 37.2 mg/g) (Garcı ´a-Alcocel
et al., 2006). In Fig. 5.3, SEM micrographs of SSA are shown, revealing irregularly
shaped particles with a rough surface.
More recently, Pe ´rez-Carrio ´n et al. (2014) used the SSA from Pinedo (Spain) as
a substitute for cement in the manufacture of precast concrete blocks. In this case,