Explanation: Sulfate attack: ● Sulfate attack of concrete is a complex process, which includes physical salt attack due to salt crystallization and chemical sulfate attack by sulfates from the soil, groundwater, or seawater. ● Sulfate attack can lead to expansion, cracking, strength loss, and disintegration of the concrete. ● Sulfate attack is generally attributed to the reaction of sulfate ions with calcium hydroxide and calcium aluminate hydrate to form gypsum and ettringite. ● The formation of ettringite leads to an increase in solid volume, resulting in expansion, cracking, and mass loss, particularly when restrained. ● The formation of gypsum can lead to softening and loss of mass and strength. In addition to the formation of ettringite and gypsum and its subsequent expansion, the deterioration due to sulfate attack is partially caused by the degradation of the calcium silicate hydrate through leaching calcium compounds. This process leads to a loss in calcium silicate hydrate gel stiffness and an overall deterioration of the cement paste matrix.