Utilization of wastewater sludge for lightweight concrete and the use of wastewater as curing medium

The increasing population have resulted in a higher generation of domestic and industrial wastewater sludge. The sludge ends up as a landfill in designated areas which makes the land unusable. The search for lightweight materials for construction has led to the use of sludge as a viable replacement for the basic composition of concrete due to its low density. The dry sludge collected from Polokwane Waste Water Treatment Works (WWTW) in Limpopo Province was used as a partial replacement of sand in concrete. The sludge content in the sand was varied from 2.5, 5, 7.5, 10, to 12.5 %. The outcomes of the analysis indicate that the partial replacement of sand with dry sludge in the concrete mix is viable and useful. The result showed that up to 7.5 % of sand could be replaced with dry sludge in concrete for structural applications. Also, wastewater can be used as a curing medium. The unit weight of the concrete decreased with increasing sludge content, which was attributed to the lower density of the sludge. The SEM image revealed a porous nature and irregular surface morphology of the sludge and the concrete.