Using Urban Sewage Filtration Sludge for Producing Construction Material

Abstract

Management of sludge produced in urban sewage filtration plants is essential and inevitable due to great volume of water, contamination with pathogens, organic material and high expenses of such filtrations. Purpose of this research is to evaluate the possibility of using urban sewage sludge in producing light concrete. In order to conduct this study, mouldswith dimensions of 15 x 15 x 15 cm were prepared. In each series of production of light concrete samples, dry sludge was taken from Ghods filtration plant and lime was added to the sludge 24 hours before making concrete samples, in order to increase its pH to 12 and destroy microorganisms. Sludge was used at the weight percentages of 0. 10, 20, 30, 40 and 50 of the cement , and the produced concretes were tested for pressure resistance after being processed with the moisture caused from perspiration of the blocks at the ages of 7, 28 and 90 days and determination of the specific gravity. Evaluating average pressure resistance of the samples shows that up to 30%, sewage sludge works as a fine granular material or filler and the pressure resistance of the samples increases with the increase in sludge percentage compared to control group. Nevertheless, we observe a decrease in pressure resistance of the samples with the increase in dry urban sewage sludge percentage at 30, 40 and 50 percents of sludge compared to control group, which is due to higher water absorption of the dry sludge and its increased impurity (particularly, organic impurities)resulting in inappropriate hydration operation.