Considerações sobre o concreto composto com cinza de lodo de ETA exposto a altas temperaturas

Abstract

The use of concrete admixtures coming from industrial waste or by-products from other activities has already been a reality with several positive impacts in a world where it is necessary to predominate the conscious consumption of resources and its sustainability. In this study, it was evaluated the effects of the partial replacement of cement to the water treatment plant sludge ash (CLETA) regarding the behavior of concrete under high temperatures, isolated or with the presence of ground limestone. The specimens were exposed to temperatures of 200 °C, 400 °C, 600 °C and 900 ° C and then compared with a reference at ambient temperature. Axial compressive strength test and dynamic modulus of elasticity test, indirectly measured using the ultrasonic pulse velocity test (UPV), were performed. Water/binder (w/b) ratios of 0.35 and 0.50 were adopted and cement was replaced with 15% of CLETA, 15% of CLETA + 7.5% of ground limestone and 24% CLETA + 12% of ground limestone. From the obtained results it was verified a behavioral pattern similar to that of other concretes with cement replacements, and that the replacement of cement by 15 % of CLETA and 7,5% of ground limestone is beneficial considering the technical and environmental aspect for w/b ratios of 0.50 (used for usual concretes). For lower w/b ratios, or for increased substitution rate, a more detailed study should be performed because the risk of spalling occurrence increases noticeably. Likewise, the use of the UPV test to assess the material integrity conditions is valid and feasible, but the viability of using the dynamic modulus in this situation was not conclusive.