Chloride and Sulfate Resistance of Calcined Lateritic Clay-Based Geopolymer

The dissemination of chloride and sulfate ions greatly affects the quality and strength of concrete obtained from cementitious materials. The current research is focused on the development of good quality geopolymer from calcined lateritic clay, sodium metasilicate, and aluminum hydroxide with optimum Si to Al ratio (by mass) and study of its resistance in aggressive environments of chloride and sulfate. Different geopolymer samples with Si to Al ratio of 3 to 1 were prepared and exposed in 8 wt.% sodium chloride and sodium sulfate solutions for 7, 14, 21, 28, and 35 days. The geopolymer sample with Si to Al ratio = 1.5 offers greater resistance in aggressive environments. The resistance of geopolymer remained better in sodium chloride solution than in sodium sulfate solution. The reduction of compressive strength of the geopolymer is 7% less in sodium chloride solution than in sodium sulphate solution. FTIR and XRD investigation proved that both chloride and sulfate do not affect the bonding and structural features of geopolymer however slight erosion of the surface morphology confirmed by SEM analysis. It can be concluded that an impure clay can be utilized to obtain a valuable product.