Características de pastas de cimento Portland com adição de cinza de lodo de ETA

Abstract

Currently, it is increasing the search for alternatives to minimize the environmental impact on inputs production. Concrete, highly polluting, is the second most natural material used by man, losing just for the water. Mineral additions have been investigated as partial replacement of cement in concrete, because, besides of providing the use of industrial waste, it can offer improvements in material characteristics. This study analyzed the microstructure of cement pastes composed by sludge produced in water treatment plants (WTP). Seven different traces were investigated: a reference one and 6 traces adding WTP sludge ash in different levels of 5, 10, 15, 20, 25 and 30%. Each trace has been developed to three water/binder (w/b) ratios (0.35, 0.50 and 0.65), ending in 21 different traces, which were studied for different healing ages. Assays of Calorimetry, thermogravimetric analysis (TGA/DTA), setting time, DRX, porosity by mercury intrusion (PIM), chemically combined water, electrical conductivity and hydrogen potential (pH); were performed. From the results, it appears that the increased cement replacement content by WTP sludge ash resulted in an increase in the start and end times of the setting time and decrease in electric conductivity and pH testing. Likewise, a reduction in remnant CH amounts with the increase in WTP sludge ash content shown in TG and XRD tests, as well as reduction in hydration heat because of less formation of side C-S-H. The results for combined chemical water increased when the relations w/b and the WTP sludge ash also increased. When compared to the reference mixture, the increase in WTP sludge ash content resulted in PIM values and the like, although an increase is found in the total area of pores due to change in pore size distribution.