Combined evaluation of oscillatory rheometry and isothermal calorimetry for the monitoring of hardening stage of Portland cement compositions blended with bauxite residue from Bayer process generated in different sites in Brazil

Avaliação combinada de reometria oscilatória e calorimetria isotérmica para o monitoramento do estágio de endurecimento de composições de cimento Portland misturadas com resíduos de bauxita do processo Bayer coletados em diferentes locais no Brasil

Abstract

Bauxite residue (BR), a by-product of alumina and aluminum production, consists of high aluminum, silica, and iron content, and sodium from the bauxite ore digestion during the Bayer process. This waste is still being disposal into the lakes of mud, causing some environmental problems. So, the search for its application has gained interest. Studies reported in literature point out that one of the most promising applications is in association with Portland cement, which can also help to reduce the environmental impact caused by the CO2-emissions in its production. In this work, a combined evaluation of oscillatory rheometry and isothermal calorimetry was performed for the monitoring of the hardening stage of Portland cement (PC) compositions blended with BR generated in different sites in Brazil. The time-sweep test was applied to obtain the consistency gain of suspensions over-time, allowing us to understand the physical parameters of consolidation, while the changes in the hydration reaction showed considerable differences in the chemical contribution. As a conclusion, it was clear the impact of each BR, mainly due to the aspects related to soluble aluminates, silicates, and sodium, which in association with the soluble ions from PC, affected the chemical reaction and agglomeration/flocculation forces of particles.

Keywords:
rheological properties; reuse of bauxite residue; Portland cement; chemical reactions