Microestrutura e durabilidade a cloretos de protótipos de concreto com cinza de casca de arroz com e sem moagem prévia

Abstract

Cement is the main component of concrete, which is the second most common material used by man. The cement manufacturing process is largely responsible for the emission of carbon dioxide in the atmosphere. The construction industry has been studying the possibility of using agroindustrial byproducts for cement mortars, which aims to reduce the environmental impact of cement production and promote improvements in the performance of concrete. In this context, the rice husk ash is one of the most studied mineral additions, as well as being an industrial waste widely available, generally provides a longer service life of reinforced concrete structures. This paper investigates the microstructure and durability of rice husk ash and residual natural, unprocessed prior production of structural concrete. We studied prototypes of concrete with dimensions of 20 x 20 x 75 cm with partial replacement of cement by rice husk ash and milled in natural levels of 0%, 15% and 25% in the relations / ag 0.45; 0 55 and 0.65. These prototypes were exposed to natural environmental conditions, up to 540 days. We conducted tests of compressive strength, water chemically combined (AC), mercury intrusion porosimetry (MIP), accelerated penetration of chlorides (EAPC) by the method of ASTM C 1202 and total chlorides retained. The results showed that the compressive strength at 540 days showed the highest values for mixtures with crushed CCA, while mixtures containing natural CCA showed the lowest resistance being lower than the reference blend. In assay mixtures containing CCA AC ground showed the best performance. For testing PIM, mixtures that showed the highest amounts of mesopores and pores of gel mixtures were milled with CCA, where there was the refinement of the pores of the 91 days to 540 days, thereby reducing the porosity of these mixtures. For the test of EAPC, mixtures ground with CCA showed the lowest cargo bystanders, especially the mixture with 25% substitution. The blends with natural CCA showed loads passers below the reference mixture, showing a good performance. For the assay of the total content of chloride retained, mixtures with CCA ground showed the lowest levels, confirming that the best performance of CCA promotes grinding on concrete. The blends with natural CCA showed values very close to the reference mixture. The results show the technical feasibility of CCA natural levels in 15% of partial replacement of cement.