Effect of Hydrophobic Water Repellent Admixture on the Compressive Strength of Concrete in Highly Aggressive Water (Dead Sea Water as a Case Study)

The compressive strength of concrete may be affected by seepage of salt water. Dead Sea water is a hazardous environment for concrete due to high concentration of salts. The aim of this study was to investigate the effect of Dead Sea water on the compressive strength of concrete containing hydrophobic water-repellent admixture, and to determine the optimum dosage of admixture to be used to reduce this effect. Three types of cement were used (Ordinary Portland Cement, Pozzolanic Cement, and Sulphate-Resisting Cement) with various dose rate of hydrophobic water repellent admixture (0%, 2%, and 4% of cement weight). An experimental approach, in which the specimens were divided based on the type of cement and the specimen’s age, was adopted. Nine control cubic specimens were cured in plain water to ensure that the required compressive strength was reached and (54) specimens were cured in Dead Sea water. The specimens cured in Dead Sea water were tested at 7 and 28 days to investigate the effect of Dead Sea water on the early and long-term strength. The results showed that a reduction in the 28-day compressive strength occurred in all specimens for the three types of cement used, but with the addition of water repellent, this reduction was alleviated, and the optimum percentage of admixture was 2% of cement weight.