A Comprehensive Review on the Mechanism of Concrete Deterioration in Accelerated Aggressive Environment

Concrete is being extensively utilized for the constructional and other allied works on account of its versatility and mechanical properties. However, it exists to be in a state of disequilibrium with its ambient environment owing to its universal alkaline nature and hence is susceptible to deterioration when exposed to aggressive environments. The reactive species emanating from chemical plants, fertiliser industries, marine water, agro-food industries etc., produce detrimental effects on the concrete structures through the dissolution of calcium bearing phases from the hydrated matrix. This degradation culminates in decalcification, volumetric expansion, salt crystallisation, micro-cracking, surface scaling, delamination, spalling and corrosion. Diffusivity, capillary porosity, permeability, chemical nature of hydrated matrix and pore network are the parameters that influence the chemical mechanism of concrete degradation. The mechanism of concrete degradation is distinct for various aggressive species and its fair comprehension remains as one of the challenges in accomplishing the durability based concrete design. This paper critically reviews the basic mechanism of the concrete deterioration in accelerated aggressive environment of mineral acids, organic acids and inorganic salts. In addition to this, a glimpse of the effect of degradation on different binder systems viz., Ordinary Portland Cement system, blended cement system, special cement system and alkali activated system is provided.