The Effects of Varying Water-Cement Ratio on the Degradation of Concrete by Sulphate Salts

Abstract

This study assessed the extent of degradation by seawater on the physical properties and strength characteristics of concrete. It evaluated the extent of deterioration of concrete by MgSO4. Three concrete mixes corresponding to grade 20 with water-cement ratios of 0.45. 0.6 and 0.75 were prepared. 324 concrete cylinders of 100 mm dia × 200 mm were partially immersed in exposure regimens of Distilled Water (DW), 5% Magnesium Sulphate Solution (MSS) and Seawater (SW) for a period of 180 days. Physical tests involving visual assessment of degradation and expansion measurements were employed along with mechanical tests of compression and splitting tensile tests. Results of the physical examination showed that the specimens in MSS, after 120 days, developed blooms of salt crystals above the evaporation front. At the end of 180 days the 0.75 w/c specimen in MSS expanded slightly by 1.01%. The compression test result showed a progressive increase in strength. However at 150 days, the 0.60 w/c and 0.75 w/c specimens in MSS dropped. At 180 days, the 0.45 w/c specimens showed that DW and SW strengths were higher than MSS by 1.06% and 1.02% respectively. The lower water-cement ratio could possibly reduce sulphate induced damage as the magnesium sulphate did not penetrate the concrete easily.