Electronic Thesis and Dissertation Repository


Master of Engineering Science


Civil and Environmental Engineering


Moncef Nehdi


Field experience with concrete exposed to sulphates has often shown that concrete can suffer from surface scaling above the ground level caused by physical sulphate attack. This type of attack has been ignored and, in some instances, confused with chemical sulphate attack. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack. This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack. In the current thesis, the performance of concrete exposed to environments prone to physical sulphate attack was investigated. The effects of mineral additives, water-to binder (w/b) ratio, along with various curing conditions on the performance of concrete exposed to physical sulphate attack was studied. In addition, the effectiveness of different surface treatment materials in mitigating physical sulphate attack on concrete was explored. Results show that concrete can experience dual sulphate attack. The lower immersed portion can suffer from chemical sulphate attack, while the upper portion can be vulnerable to physical attack. Lowering the w/b ratio and moist-curing the concrete reduced surface scaling above the solution level since the volume of pores was decreased. Although partial replacement of cement with pozzolans also decreased the pore volume, surface scaling increased due to the increased proportion of small diameter pores and the associated growth of capillary suction and surface area for evaporation. Epoxy- and silane-based surface treatment materials were found to be adequate for protecting both cured and non-cured concrete exposed to physical sulphate attack. However, it was found that adequate curing of the concrete before coating is important to eliminate the separation of the surface treatment based on bitumen and to enhance the resistance of concrete to physical sulphate attack. Using a water-based solid acrylic polymer resin did not provide adequate protection of concrete against physical sulphate attack.