Physicomechanical Properties of Mortars Based On Ordinary Portland Cement with Bauxite as Mineral Additives

Guinea has one of the world's main reserves of bauxite that can be used as an industrial mineral to produce low-cost building materials and other parts to address the housing and industrial development difficulties in this country. In this line, mortars were manufactured by replacing 5–25 wt.% of Portland cement with raw and 600 °C calcined. Workability and setting time of fresh mortars were measured. Hard products were characterized by linear shrinkage, porosity, and structural and microstructural investigations. The two mineral additives are chemically active since they favored the reduction of the workability and setting time of mortars. In the case of calcined bauxite, ettringite and monosulfoaluminate coexisted regardless of the rate of substitution due to the higher reactivity of alumina, whereas, for raw bauxite, ettringite is only found at 5 and 10 wt.%. Heterogeneous microstructures and increased porosity were revealed with the rate of cement replacement for raw bauxite, whereas for calcined bauxite, the porosity decreased. Even the minimum compressive strengths of both series of mortars, 13 MPa for raw bauxite and 17 MPa for calcined one, enabled their application as construction materials. Favouring the porosity increase, raw bauxite is more appropriate for applications using porous materials.