Recently, much attention has been paid to the reuse of bauxite residues from alumina production, also known as red mud, in the cement industry. Red mud bears the potential to improve concrete properties due to its favourable chemical composition and particle size. In this work, the synergy between locally available red mud and common supplementary cementitious materials such as fly ash, slag, calcined clay and limestone in cement mixes is investigated. All materials used were sourced from the immediate vicinity of the cement plant. The study of synergy involved the evaluation of the individual chemical reactivity of each material using the R3 test by isothermal calorimetry as well as their joint contribution to the heat of hydration and the composition of the reaction products of the paste and the compressive strength of the mortar. The results show how, by understanding the synergy between the materials, a higher level of cement substitutions can be achieved without compromising the mechanical properties of the mortar.

Alkali-activated materials (AAM) consist of a precursor, which is a source of aluminosilicates, and an alkali source. The precursors are usually waste materials from various industries such as fly ash from thermal power plants and slags from the metallurgical industry. Due to the increasing use of these materials in the cement industry and strategies for decommissioning coal-fired power plants, alternative raw materials from waste streams are increasingly being explored. One of these materials is waste from the aluminium industry, known as red mud. Due to its chemical composition, which is similar to that of other cementitious materials, red mud is suitable for use in the cement industry. It can also be used as a source of aluminosilicates in the synthesis of AAM. In this study, the corrosion behaviour of steel in chloride exposed AAMs based on fly ash and slag was investigated with and without the addition of red mud. During exposure of AAM to tap water and a 3.5 wt.% NaCl solution, the corrosion process was monitored by corrosion potential and polarisation resistance. AAM mixes containing red mud exhibited better corrosion resistivity and lower current density values compared to mixes without red mud, indicating a possible contribution of the red mud to chloride binding and improving the passivity of the steel.

Storage of large quantities of industrial by-products can pose a serious environmental problem. There is a growing need to recycle these industrial by-products, including red mud, in the construction industry, which is one of the largest consumers of raw materials. A preliminary study of the potential of red mud as a raw material for concrete is presented in this paper. Chemical composition of red mud, determined by X-ray fluorescence and particle size distribution by laser diffraction, is tested as part of its initial evaluation. The reactivity of red mud is evaluated by the R3 test method with isothermal calorimetry. The compressive strength test is carried out on a mortar sample in which 30% by weight of cement is replaced by red mud. Preliminary tests indicate that red mud can be used as raw material in alternative binders.

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