EFFECT OF CEMENT CONTENT AND CEMENT TYPE ON THE RESISTANCE OF CONCRETE AGAINST CHEMICAL ATTACK

Abstract

Mortar and concrete are two important construction materials widely used in both domestic and industrial constructions all over the world. A durable concrete is able to withstand the attacks of destructive processes of chemical, physical or mechanical origin, acting externally or arising internally. Chemical salt attack is caused by ingressing salts into cementitious materials, and the reactions with cement hydrates resulting in either the deterioration of the matrix or loss of corrosion protection of the steel reinforcement. The chemical resistances of the materials against deleterious reactions determine the performance of the materials. Cement type and mix proportions are keys to the resistance of concrete against chemical attack. In this paper, the resistance of concrete against sulfate and chloride attack was investigated in the laboratory by storing different specimens of concrete cubes in a solution of calcium chloride with concentration 5%, or solution of magnesium sulphate with concentration 5% or in solution of magnesium sulphate with concentration 5% + sodium chloride with concentration 5% at different ages (7, 28, 59, 90 and 180 days). Compressive strength is determined for specimens submerged in the previous chemical solutions. The chemical resistance of concrete is expressed by the percentage of compressive strength losses for those specimens exposed to the chemical attack compared with those similar ones submerged in fresh water. Both specimens were kept in the condition of laboratory temperature. It is of importance to mention that, only external attack was implemented in this research because it is the more common type and typically occurs where water containing dissolved chloride and sulphate penetrate the concrete. It can be concluded that, the highest values of compressive strength were obtained from concrete mix cured in water (control mix) meanwhile, the lowest values were resulted from mixes cured in a solution of magnesium sulphate with concentration 5%+sodium chloride with concentration 5%.