Influence of Concrete Mixture Composition on Acid Resistance of Concrete: A Review
Cementitious materials are highly susceptible to rapid and severe degradation by a wide range of acids that are found immensely in ground water, sewage systems, industrial effluents, acid rain etc. which may cause microstructure deterioration. The factors influencing acid attack is generally categorised as material related factors and test related factors. Material related factors can be either related to acid solution or concrete mixture composition. Composition of concrete mixture greatly impacts the acid resistance of concrete. Factors related to composition of concrete mixture are type of cement, type and proportion of binders, water binder ratio, aggregate binder ratio and mineralogical nature of the aggregates. Even though the type of cement influences acid attack, the magnitude of variation is negligible. Consumption of calcium hydroxide and refinement of pore structure makes the use of supplementary cementitious materials favourable for acid resistance. Decrease in water binder ratio and increase in aggregate binder ratio reduces the porosity of concrete and thereby improves the acid resistance of concrete. Calcareous aggregates are preferred for concretes exposed to acids having less soluble salts and not preferred for acids forming soluble salts. This paper highlights the influence of composition of concrete mixture on acid resistance of concrete. A proper formulation of concrete is expected to enhance its acid resistance.
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