Estudo de adições minerais de cinzas de biomassa de eucalipto no comportamento físico-químico de pastas de cimento

Abstract

Considering the current and future availability of eucalyptus biomass ash in Brazil, this work aimed to study the use of this residue as a mineral addition in cement pastes. In order to better understand the effects that the characteristics of the ash cause in the cement matrix, three different ashes were analyzed: residual eucalyptus ash (CE) donated by a company that performs uncontrolled burning, reburned eucalyptus ash (CER) produced from CE and controlled eucalyptus ash (CEC) produced in the laboratory. The ashes were ground until reaching a D50 lower than that of Portland cement CPV-ARI used in the pastes. The ashes were characterized in terms of specific mass, mineralogical and oxide composition, loss on ignition, morphology and specific surface. Pastes were produced with 0%, 5%, 10% and 20% cement substitution in volume for each of the three ash and water-binder ratio of 0.5. All pastes were analyzed for hydration kinetics, quantification of hydrated products and chemical shrinkage. Based on the results obtained, it was verified that CE was the ash that presented the best performance as a mineral addition in cement hydration due to the high specific surface due to the presence of pores. Thus, a study was carried out on the evolution of the stress versus compressive strain curves of cement pastes with this ash at the ages of 1, 3, 7, 28 and 100 days. The results showed that the 5% replacement of cement by CE presented a significantly better performance than the reference paste in the initial ages for a significance level of 0.05 and after 7 days no significant differences were observed in relation to the paste without addition.