Comportamento da cinza de eucalipto em substituição à areia em argamassa de assentamento

Abstract

Civil construction is responsible for a significant part of consumption of natural resources extracted from the planet. The cement production process releases Carbon Dioxide, and mining activities involved in natural sand extraction cause changes in the rivers’ channels and banks, provoking erosion and silting. In the point of turning civil construction processes less aggressive to the environment, an alternative sand, called crushing sand, has started to be tested. At the same time, researches are being developed aiming to find admixtures and substitutions that decrease sand and cement consumption in concrete and mortar production. In the southwest region of the state of Paraná, eucalyptus is largely used for energy generation purposes and, through its burn in grain drying facilities, a residual waste called eucalyptus-burn ash is produced, which does not have a proper environment-friendly final destination. Thus, this study aims to find a way to incorporate eucalyptus-burn ash in mortar production, seeking to decrease consumption of cement or natural or crushing sand. Preliminary experiments show that axial compression resistance resulted more significant in mixtures containing crushing sand with ash-to-sand substitution rates of 2.5% and 5%, and in mortar mixtures containing mixed sand, with ash-to-sand substitution rate of 2.5%. These results were replicated applying these rates to brick-laying mortar. The samples were tested for water retention capacity, consistency, axial compression resistance and drying shrinkage. At the age of 28 days, the samples with eucalyptus-burn ash resulted in superior values for axial compression resistance. In all cases, the addition of eucalyptus-burn ash decreased consistency and water retention capacity of mortar, but not significantly. Mortar expansion decreased compared to benchmarks, in all of the cases.