ALKALI ACTIVATION OF CALCINED LATERITIC SOIL AS ALTERNATIVE BINDER IN CEMENT-BASED PRODUCTS FOR LOW-COST HOUSING

Abstract

In this paper, alkali activation of lateritic soil was investigated to assess its suitability for use as alternative to cement in cement-based products. Lateritic soils were collected and calcined to a temperature of 700 ℃ for 60 minutes, after which it was milled to a particle size of 150 𝜇𝑚 and then characterised using XRF techniques. Mortar prism of size 160 ×40×40 𝑚𝑚 were produced using sodium hydroxide (NaOH) and combined NaOH and Sodium silicate (NaOH/Na2SiO4) as alkali activators at the different concentrations. Specimen were then cured in the oven at 80℃ for 3, 7, 14, 28, 56 days. Strength properties, water absorption and thermal effect of the specimen were determined following standard procedures. The results showed that calcined lateritic (CL) soil contained combined silica, alumina well above 70% as against raw lateritic (RL) soil, while the silica ratio (SR) of CL was 2.1, and that of RL was 1.6, indicating it was a good precursor. The compressive strength of the activated lateritic soil prism with NaOH was about 10.12 N/mm2 at 28 days of curing at 12 M of NaOH, while the strength increased by about 5%, when Na2SiO4 was combined with NaOH as activator at optimum of 10% replacement. In both cases, the strengths were higher than common sandcrete blocks but less than normal cement mortar. Alkali activated CL absorbed water about 27% less compared to normal CL. The study concluded that the alkali activated lateritic soil is a potential material for non-structural building as can be found in low-cost housing unit.