Estudo das propriedades mecânicas e dos parâmetros de durabilidade de concretos autoadensáveis com elevados teores de adições minerais submetidos à carbonatação

Abstract

Self-compacting concrete (SCC) is an innovative product that has fluidity and cohesion to traverse the entire length of the part and fill the spaces between armatures, optimizing the execution of concrete and reducing costs with labor. The use of mineral admixtures rich in amorphous silica and aluminum such as metacaolin, pozzolan rice husk and sugarcane biomass are an alternative to the reduction of cement, since they confer benefits to the cement matrix and are industrial waste, contributing to their correct disposal in the environment. However, the mineral admixtures cause the reduction of Calcium Hydroxide, which acts as a protective barrier of carbonation in concrete. This aggressive agent causes reduction of alkalinity and forms carbonaceous products that alter the porous structure of the matrix, making the environment aggressive to the reinforcements. The present study investigated the influence of accelerated chamber carbonation on the mechanical properties and durability indicatives of self-compacting concretes, with low cement content and high levels of mineral additions from agroindustrial residues, with RBC and PCA. The properties of the SCC were correlated with the carbonation process, evaluating the action of Carbon Dioxide (CO2) and the concrete realcalinization through the hydrated lime (Ca(OH)2) and the performance of the RBC compared to the PCA. The results obtained were considered satisfactory, where the mixtures with mineral admixtures presented mechanical properties equivalent to the reference mix and the carbonation fronts didn´t reach the depth equivalent to the nominal cover of 25 mm, determined by NBR 6118 (ABNT, 2014). The mineral admixtures also promoted a significant increase in the electrical resistivity, even the samples being saturated, making negligible the occurrence of carbonation and ratifying the use of the mix produced. The RBC performed less than PCA, but its good results enabled its use, mainly with a 20% content, ideal replacement content. The lime has positively influenced the carbonation combat and has given concrete resistance. The traces with 20% RBC and 30% PCA, both with lime, presented the best results in most of the trials, being the optimal traits of the research. Finally, an eco-efficient and sustainable concrete was obtained.