sulfatattack

Sulfatattack refers to the degradation of concrete and mortar caused by sulfate ions. These sulfate ions, commonly found in soil, groundwater, and wastewater, can penetrate the porous cementitious materials. Once inside, they react with components of the hardened cement paste, particularly calcium hydroxide and calcium aluminate hydrates, to form expansive compounds such as ettringite and gypsum.

The formation of these new crystalline structures occupies a larger volume than the original reactants. This volumetric expansion generates internal stresses within the concrete or mortar. Over time, these stresses can lead to cracking, spalling, and a general loss of structural integrity. The rate of sulfatattack is influenced by factors such as the concentration of sulfates, the permeability of the concrete, the temperature, and the presence of moisture.

Common sources of sulfates include industrial waste, sewage, and natural deposits of gypsum. Sulfatattack is a significant concern in civil engineering and construction, particularly for structures like foundations, sewer pipes, and bridges exposed to sulfate-rich environments. Mitigation strategies include using sulfate-resistant cement types, incorporating supplementary cementitious materials like fly ash or slag, applying protective coatings, and improving drainage to reduce exposure.