Avaliação da potencialidade reativa da sílica de casca de arroz por meio da mitigação da reação álcali-sílica

Abstract

The use of rice husk silica in concrete aims to contribute to the sustainability applied to civil engineering, giving an appropriate destination for this material that is considered as a high value-polluting waste. However, tests are required in order to investigate the effect of replacing part of the Portland cement per rice husk silica in the production of concrete and mortar. One of these analyses would be the alkali-silica reaction, which is highly detrimental decay process that may affect the functionality of a structure. In this context, this study aims to analyze the durability, through the degree of mitigation provided by the substitution of rice husk silica in mortar bars subjected to accelerated method recommended by the ABNT NBR 15577: 2008 standard, analyzing also the materials mechanical strength. For this, mortar specimens should be molded with a partial substitution of 3, 5 and 10% of rice husk silica to the Portland cement. Specimens of Portland cement CPII-Z 32 and natural sand of the city Manoel Viana-RS were performed. One part of the samples was analyzed during a period of 45-days under the alkali-silica reaction while others were checked for mechanical strength at ages 7, 28, and 56 days. Finally, the reference mixtures and those samples with 3% substitution showed innocuous behavior while the mixtures containing 5% to 10% of substitution exhibited potentially reactive behavior due to the use of rice husk silica with Potland cement, especially for the age of 30 days.