Caracterização de cinza de lodo de eta para uso no concreto – (resistência a compressão axial)

Abstract

The importance of civil construction for humanity is unquestionable. Today, environmental concerns and more stringent legal requirements have fueled research on the possible uses of agricultural and industrial byproducts in concrete as a way of creating more sustainable constructions. This study investigated the effect of sewage sludge ash (SSA) additions in the compressive strength of concrete samples. The optimal temperature and calcination time of SSA were first determined to ensure a product with maximum pozzolanic activity was obtained. The pozzolanic potential was determined using the modified Chapelle method and the pozzolanic activity index in Portland cement was determined according to Brazilian Standard ABNT NBR 5752. Compressive strength was determined according to Brazilian Standards ABNT 5738 and ABNT 5739. Substitutions of WWTP sludge ash for Portland cement ranged from 0% to 30%, and samples were prepared using water/binder ratios of 0.35, 0.50 and 0.65 and wet curing periods of 7 and 28 days. Data obtained using the modified Chapelle method and the performance index of Portland cement showed that the optimal treatment for SSA was calcination at 600ºC for 1 hour, followed by grinding in a steel ball mill. Concrete tests showed that the partial substitution of WWTP sludge ash for cement resulted in an increase in compressive strength when compared with the reference mix at 7 and 28 days. Compressive strength values increased from 3% to 30%, depending on the water/binder (w/b) ratio used and the concentration of the substitution. The use of SSA seems to be an economically sound alternative as it reduces cement consumption and offers an alternative to disposal, a costly procedure.