Effect of slag and calcium carbonate addition on the development of geopolymer from indurated laterite

This paper reports the development of inorganic polymers from laterite, for a potential use at least as non-load bearing building materials. The effect of blending laterite with Ground Granulated Blast Furnace Slag (GGBS) and calcite (CaCO3) was investigated. Laterite was substituted by calcite at 2 to 20% in mass and by GGBS at 5 to 50% in mass. X-ray diffraction, Fourier Transform Infrared spectroscopy and differential thermal analysis evidenced the presence of kaolinite, hematite, and quartz minerals in the laterite. Sodium silicate solutions of modulus ranging from 1.6 to 2.2 were used to prepare inorganic polymers from laterite that had been thermally treated at 700 °C. The strength increased with the reduction of the modulus of the activating solution, achieving a 28 days maximum compressive strength of 36 MPa at 25 °C. The substitution of laterite by calcite was found to have little effect on the compressive strength meanwhile the substitution of laterite by slag was beneficial for strength development, mainly from 20% substitution, achieving a 28 days compressive strength of 65 MPa at 50% slag. Mercury Intrusion Porosity and Scanning Electron Microscopy analysis evidenced a better refinement in microstructure with slag addition in the system. The results of compressive strength were found to be in agreement with ASTM C216-17 standard for building bricks, suggesting a potential interest for the valorization of laterite and blended laterite/slag in the development of at least non-load bearing building materials, using geopolymer technology.