Potential use of natural red mud as pozzolan for Portland cement

Abstract

Red mud, the main waste generated in aluminum and alumina production by the Bayer process, is considered hazardous due to its high pH, according to the Brazilian standard NBR 10004/2004, and worldwide generation of this waste exceeds 117 million tons/year. In this work, non-calcined red mud was used, thus requiring less energy and time and reducing costs, which is the ideal condition for reusing wastes. Mortars containing 30 wt. (%) of cement substituted by red mud showed higher strength of hardened products. The pozzolanic activity index was evaluated based on physical and mechanical parameters (Brazilian NBR 5751 and NBR 5752 standards) and on a chemical analysis . A comparison of the reference mixture (without red mud) and the results obtained with red mud confirm the potential of non-calcined red mud for use a as pozzolanic additive in cementitious materials. The setting time (according to the MERCOSUL NM 65 standard) tends to increase but workability remains almost unchanged.

Engineering properties of controlled low strength material (CLSM) incorporating red mud

“…Therefore, the setting process was accelerated. This result is identical to that reported by Ribeiro et al [33].…”

“…Figure 9 shows the unconfined compressive strengths in . These also hydrate to produce cementitious compounds in reactions which are fairly well known from the fact that they are responsible for strength of mixtures with high alumina content in a highly alkaline environment [29,33]. Furthermore, an increase in amount of hydroxide ions OH − might be another reason explained for a gain in strength.…”

Effect of Calcination Temperature on the Pozzolanic Activity of Brazilian Sugar Cane Bagasse Ash (SCBA)

“…As shown in Figure 7, the reference Portland cement does not qualify as a pozzolanic material because the cement alone is not pozzolanic. It is the addition of the pozzolan in the presence of water that binds the calcium hydroxide that is formed by the cement hydration and lowers the calcium oxide content of the liquid phase of the cement paste 8,9,17 . The CaO and OH -ion concentrations decrease in the solution when SCBA is added, and a clear pozzolanic action is observed for mixtures containing SCBA independent of the calcination temperature of the ash.…”

“…This replacement is possible because of the potential ability of these materials to enhance the properties and performance of concrete through their filler effect and through the pozzolanic reaction [6][7][8][9] . According to Johari et al 7 , different types of materials used as partial cement replacement materials or as mineral additives can have different effects on the properties of cementitious matrices due their different chemical and mineralogical compositions, as well as different particle characteristics, which determine their water requirement, packing ability, and their reactivity when used as part of a binder for concrete.…”

Application of bauxite waste from amazon region in the heavy clay industry

“…Thus, a number of efforts have been made in order to find possible applications for this material, as for example, as catalysts materials 10 , fillers in PVC 11 , pigment 12 , for the recovery of some valuable elements 13 , cements manufacturing 8,[14][15][16] , water treatment 17,18 , among others. Unfortunately, several reuse techniques consume relatively small amounts of waste compared to the huge amount produced.…”