Heavy Metals Leaching of Cementitious Matrices Containing Waste Ash from Brazzaville Landfills (Republic of Congo)

Abstract

Inadequate management of ash generated by household waste burned in open air in Republic of Congo, generates pollution sites especially through heavy metal contamination (Pb, Ni, Cr, Cu, Zn). The aim of this study is to evaluate the chemical durability of cementitious matrices containing waste ashes and their ability to retain in their structure heavy metals contained in these ashes. To do this, we collected 40 kg of waste coming from 4 landfills (A, B, C, D) in Brazzaville city. Waste was then burned and turned into ash. 6 cementitious matrice formulations (P1, P2, P3, P4, P5, P6) based on Dolisie Portland cement were made by varying the cement/ash/lime rations. We carried out static leaching tests with raw ashes and cementitious matrices at pH = 7 and at 25°C in distilled water during 30 days. This study shows that cementitious matrices containing ash have good potentiality for retention of heavy metals (more than 75%). But, cementitious matrices containing ash and lime give better results with retention rates between 90-99%.