Pulverised Sewage Sludge Ash Partial Replacement of Cement In Concrete

The potential of the ash produced from the incineration of sewage sludge, as partial replacement of cement in concrete has generated research interest in recent times as a result of the increase in its production due to rapid urbanization and the problem of getting functionally adequate landfill sites for its disposal. Physical properties if sewage sludge from one of the two waste treatment plants located at the University of Ibadan were investigated. The properties evaluated were specific gravity, colour, particle size distribution and pH. The colour of the sewage sludge changed from greenish-brown when fresh to brownish-orange after incineration when the organic materials had been burnt off. The specific gravity was 1.9 while the pH was 7.32. The particle size grading of the pulverized sewage sludge was similar to that of cement, which it was meant to partially replace. The properties if fresh and hardened concrete, in which cement was partially replaced with 0, 5, 10, 15 and 20% of pulverised sewage sludge ash by weight, were determined. There was an improvement in workability with increasing sludge ash content. The best performance of sludge ash concrete was attained with 10% sludge ash content. Concrete with up to 20% replacement of cement with pulverized sewage sludge ash produced concrete with properties above grade 20 concrete.