Durability index of dry sludge incorporated concrete when used as sand replacement

Abstract

It is paramount to look for alternative ways of disposing dry sludge, as present disposal methods are environmentally unsustainable. Hence, the investigation on the possible inclusion of dry sludge in concrete. More specifically, this paper presents and discusses the effect of dry sludge used as a partial sand replacement on concrete durability indexes. Two durability indexes were assessed in this article, which are Oxygen permeability index (OPI) and chloride conductivity index (CCI). The OPI gives an indication of concretes resistance to the flow of water through continuous pores, at a given pressure and temperature, while the CCI provides an indication of concretes resistance to chloride infiltration. Dry sludge was used as a sand replacement, in the proportion of 0 %, 1 %, 3 % and 5 %. The 0 % sample served as the control sample. Three water cement ratios (W/C), of 0.67, 0.69 and 0.80, were assessed. The samples were water cured for 28 and 90 days before testing. The results showed that higher W/C and higher sludge replacement had a detrimental effect on concrete OPI. In addition, the CCI results show that dry sludge had a positive ionic reaction and good sulphuric attack resistance on concrete.