Abstract
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.
Highlights
Bauxite residue (BR), commonly known worldwide as red mud, is a highly alkaline material generated from the production of alumina in the Bayer process, in which bauxite is dissolved in caustic soda
The iron content in the waste NE-BR, 56%, was higher than for the other residues, 29.5% and 37.1%, respectively for SE-BR1 and SE-BR2. Due to this large amount found in the waste, some works are reported in literature trying to recover iron from the bauxite residue [26], [27], but the process is not yet economically viable, and the remaining waste is still discarded
The ratio between aluminum, calcium, and silicon oxides obtained for these residues, illustrate that both are in accordance with the results presented by Romano et al [12] in the ternary diagram of supplementary cementitious materials
Summary
Bauxite residue (BR), commonly known worldwide as red mud, is a highly alkaline material generated from the production of alumina in the Bayer process, in which bauxite is dissolved in caustic soda. Romano et al, “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” Rev. IBRACON Estrut.
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