Chemical Durability And Mechanical Properties Of Cementitious Matrices Containing Ashes Obtained After Combustion Of Waste From Moukondo Landfill In Brazzaville, Republic Of Congo.

The regular burning of solid waste in the open air and on the ground is commonplace in the Republic of Congo. Burning waste produces pollutants and ashes that can be hazardous to the soil and surrounding waters. Inadequate management of the ash generated by the open burning of household waste results in site pollution, particularly heavy metal contamination (Pb, Ni, Cr, Cu, Zn...). The aim of this study is to develop cementitious matrices containing burnt ashes that are sufficiently effective to retain the heavy metals contained in these ashes in their structure. To this end, in order to assess the chemical durability of these cementitious matrices, we carried out static leaching tests at pH=4 and 7 at 25°C in distilled water on the raw ashes firstly, and then on the 24 cementitious matrices synthesized with different ash/cement/lime ratios. The mechanical durability of the cementitious matrices was assessed using flexural and compressive strength tests. The leaching results obtained demonstrated the effective immobilization of heavy metals in cementitious matrices, whose leachates contain very low levels of heavy metals compared with those of raw ash. Flexural and compressive strength tests showed an improvement in strength from 25°C to 60°C. Several cementitious matrices doped with waste ashes show flexural strengths higher than the recommended standard for flexural strength EN1339 (5 MPa) and compressive strength X31-211 (1 MPa) after 28 days curing at 60°C