Avaliação de propriedades físico-mecânicas de concretos com fíler calcário, em altos teores, cinza de casca de arroz e ativadores

Abstract

Construction is one of the largest sectors of the economy by virtue of meeting basic demands. The main material the construction activities is Portland cement. It is known that its substitution by mineral additions provides gains regarding mechanical properties and reduction of environmental impacts of concrete. Among the inert additions most commonly used by the cement industry is ground limestone. Thus, seeking to develop structural concrete mixtures with high content of cement replacement by limestone filler, but also presenting mechanical performance similar to the usual characteristic resistances (20 to 50 MPa). The experimental program was developed with granulometrically optimized mixtures using the Emma software, binary mixtures of limestone and ternary limes of rice carcass ash chemically activated by calcium sulfate and calcium hydroxide. With substitution contents of up to 70% in relation to cement volume, the aim was to evaluate the mechanical properties, axial compression at 7, 28 and 91 days, traction by diametrical compression at 28 and 91 days, modulus of elasticity at 28 and 91 days and drying shrinkage at 7, 14, 28 and 56 days compared to a control mixture. The results showed that it is possible to use high strength limestone fillers, with significant strength gains in binary mixtures with 50% and 60% cement substitution. The addition of calcium sulfate increased axial compression strength in the advanced ages for the 70% substitution mixture. Calcium hydroxide enhanced the strength gain at the age of 28 days for the ternary mixture with rice husk ash when compared with the addition of calcium sulfate. With respect to drying shrinkage, all substitution mixtures had lower shrinkages than the control mixture. Through the study developed it is possible to reduce clinker consumption, contributing to the reduction of environmental impacts.