Avaliação do pré-tratamento superficial de resíduo de borracha e sílica ativa no comportamento físico-mecânico e microestrutural das propriedades do concreto

Abstract

The increasing accumulation of tire waste has become a social environmental and public health problem because rubber degradation is extremely difficult to achieve and time consuming. The use of rubber in concrete has become an alternative to assist in the disposal of this solid waste. It also contributes to reduce the use of non-renewable natural resources. Therefore, the present work evaluated the effect of a chemical pretreatment with sodium hydroxide solution (NaOH) on the physical, mechanical and microstructural properties of a concrete. The relation of water/binder ratio of 0.5 for all the mixtures. The different rubber residue contents (15% and 30%) as a substitution for natural fine aggregate (for volume) and the addition of silica fume (7.5% and 15%) to replace Portland cement (for weight). The statistical significance of the physical-mechanical results for absorpition, porosity, bulk density, compressive strenght, tensile strenght and modulus elastic were analyzed using the analysis of variance. Scanning electron microscopy and X-ray microtomography were used to investigate the influence of treatment rubber and silica fume in the microstructure of concretes. The results showed that the use of rubber in the cement matrix, regardless of the treatment (or lack thereof), decreases the physical-mechanical properties of the concrete. The rubber pre-treatment did not significantly influence the concrete behavior. In contrast, the use of silica fume showed significant strength gains. These gains were confirmed by the microstructural analysis and the densification of the interfacial transition zone between the aggregates and the cement paste.