Avaliação do uso de cinza de casca de arroz residual no controle de fissuras em argamassas de revestimento

Abstract

Facades made of mortar coatings are often the subject of cracks throughout their life cycle, compromising their performance. On the other hand, the use of industrial by- products by the construction industry is viable for application in cement-based products, in order to improve their properties. Even though some studies have addressed the use of rice husk ash (RHA) and its impact on the hardened properties of mortars, there is a need to develop a study that specifically explores shrinkage in mixtures containing residual mineral additives. This work aims to analyze the feasibility of using residual and ground RHA as a partial substitute for Portland cement in coating mortars, as a way of mitigating the retraction originated from temperature and humidity variation cycles. In this analysis, mortars have a 1:2:9 mix design, containing cement, hydrated lime and fine natural sand, with samples containing 15% RHA contents as a replacement for the cement. Impacts on the consistency index, mass density, incorporated air content, voids index, water absorption, permeability, microstructure analysis using Scanning Electron Microscopy, mechanical resistance, restricted shrinkage and in an accelerated test of cycles of humidity and temperature variation were evaluated. An analysis of the tests concludes that RHA samples, especially without grinding, are a suitable solution for use in coating mortars, in view of their superior performance in shrinkage tests, while meeting the minimum slump and strength requirements required by Brazilian standards. The results show that it is recommended to use residual ash as a partial replacement for cement, both from the perspective of sustainability and the reuse of residue, as well as the increase in the properties of the mortar in its hardened state.