Kiele Molingo Mbemba^1,, Mithé Brice Mabiala Loubilou¹, Jean Maurille Ouamba¹

Inadequate management of ashes generated by household waste burning in open air leads to sites pollution, particularly through contamination with heavy metals (Pb, Ni, Cr, Cu, Zn...). The objective of this study is to evaluate the chemical durability of cementitious matrices containing ashes from waste burning by using static leaching tests. To do this, several cementitious matrices were synthesized with different ash/cement/lime ratios (P0, P1, P2, P3, P4, P5 and P6). These cementitious matrices then underwent leaching static tests at 25°C in acid (pH=4) and neutral (pH=7) media. Static leaching tests carried out on monoliths made it possible to evaluate heavy metals immobilization effectiveness in cementitious matrices network. The results of this study highlighted the good chemical durability provided by the stabilization/solidification of ashes in cementitious matrices. All cementitious matrices leachates present very low heavy metals concentrations with are below the standard applicable to leachate discharge. Heavy metals concentrations in cementitious matrices leachates are also very largely below the heavy metals concentrations released by raw ashes leaching. Heavy metals retention rates inside cementitious matrices range between 80 and 99% for arsenic, lead, chromium, copper, nickel and zinc.

heavy metals, cement, ashes, leaching, stabilization, solidification