11.2 : התקפה סולפטית על בטון

Concrete subjected to sulfate attack typically exhibits a distinct whitish appearance, often first noticeable at the edges and corners, with subsequent cracking and flaking.

Cracking in concrete results due to enhanced permeability, allowing water with sulfate to infiltrate the structure.

The infiltrated sulfate forms calcium sulfate and calcium sulfoaluminate, which take more space, causing hardened concrete to expand and break apart, leading to issues like shifting of building walls due to lateral pressure exerted by an expanding slab.

Soil or groundwater is the usual source for sulfates, such as sodium, potassium, magnesium, ammonium, and calcium sulfates, which lead to damage when coming in contact with concrete.

Laboratory tests for concrete's resistance to sulfate attack involve immersing or alternate wetting and drying samples in sodium or magnesium sulfate solutions or a combination of both.

The impact is gauged by the specimen's loss of strength, expansion, weight loss, or visual examination.

Utilizing sulfate-resistant cement or reducing the calcium hydroxide in hydrated cement paste and casting dense concrete with a lower water-cement ratio boosts concrete's defense against sulfate attack.