Durability of Laterized Concrete Exposed to Sulphate Attack Under Drying-Wetting Cycles.

Abstract

The study investigated the performance of laterized concrete exposed to drying-wetting cycles of sulphate environments with a view to providing empirical data for laterized concrete specification.  It adopted accelerated ageing method to investigate the effect of sulphate attack on laterized concrete exposed to wetting-drying cycle comprising of 4 days of full immersion and 3 days of drying at ambient temperature at two concentrations (3% and 5%) of magnesium sulphate solution for a total exposure period of 24 weeks.  The test cubes were first cured by complete immersion in water for 28 days and afterward exposed to wetting-drying cycle of magnesium sulphate solution. The compressive strength was determined by using an ELE 2000kN compression testing machine. Data obtained from the experiments were analysed using percentages, mean, ANOVA and regression analysis. The results of the tests carried out showed that conventional concrete had a better resistance (in terms of compressive strength) to sulphate attack than laterized concrete. Conventional concrete exposed cyclically to sulphate solution of concentrations of 3% and 5% lost 18.91% - 30.34% of its compressive strength, after a period of 24 weeks of exposure. Whereas, laterized concrete similarly exposed for the same period; lost 26.54% - 31.79% (at 20% laterite content) and 36.67% - 51.33% (at 40% laterite content) of its compressive strength. It showed that the compressive strength of the tested laterized concrete specimen decreased significantly between 10% and 50%, each at ? = 0.05 with increasing sulphate concentration, laterite content and exposure period. The study concluded that conventional concrete performed better than laterized concrete in intermittently sulphate-laden environments.

Keywords: Laterized concrete, Sulphate, Durability, Compressive strength.