Alteration of a cement matrix subjected to biolixiviation test

This paper reports on the assessment of durability and long-term performance of a cement matrix subjected to heterotrophic microbial mediated degradation. In near surface disposal facilities for hazardous and radioactive wastes, microbial activities may likely, in a long-term perspective threaten the integrity of cement-solidified wastes. To investigate the detrimental impact of heterotrophic microorganisms on cement matrices, Aspergillus niger reputed as versatile and prevalent fungus in soil flora was selected as candidate. It was shown that this fungus has the potential of severely degrading ordinary Portland cement pastes through organic acids production. Cement pastes experienced chemical alterations such as substantial leaching of calcium, and mechanical degradation was evident as highlighted by the drastic decline in Young’s modulus. Their poor behaviour with respect to heterotrophic biodeterioration and susceptibility to failure were therefore demonstrated. Consequently, biolixiviation scenario should be seriously considered in order to ensure safe long-term disposal for cement-solidified wastes.