Development of alkali-activated composites from calcined iron-rich laterite soil

Abstract

Abstract An experimental investigation was carried out to investigate the feasibility of using calcined iron-rich aluminosilicate (i.e. laterite soil) as a precursor for making alkali-activated mortars (AAMs). Laterite soil was calcined at a temperature of 600\xa0°C and activated with an alkali solution in order to produce the AAMs. The developed AAMs were cured at 27\xa0°C and 80\xa0°C for 4\xa0h followed by continuous curing at 27\xa0°C until testing. The corresponding mechanical and durability performance of the AAMs were evaluated at 7, 28 and 90 days. The findings from this study showed that the use of initial elevated curing (i.e. at 80\xa0°C) enhanced the performance of the AAMs. AAMs cured at 80\xa0°C exhibited compressive strength and flexural strength up to 32.2\xa0MPa and 12.1\xa0MPa, respectively at 28 days. It was also found out that the mechanical performance of the AAMs can be correlated with the apparent porosity and water absorption. The microstructure evaluation of the AAMs revealed that the binder phases are a mixture of amorphous Na-aluminosilicate and iron silicate binder phases surrounding the sand particles. Similar to the mechanical performance, AAMs cured at 80\xa0°C exhibited better resistance to the acid environment (H2SO4 solution of pH=1) than the ones cured at 27\xa0°C. The higher degree of deterioration in AAMs cured at 27\xa0°C was due to the lower rate of reaction and higher porosity in the AAMs. The properties of the end products showed that calcined laterite is a decent alternative precursor for alkali-activated materials.