Sulfates present in soil or water can cause serious damage to concrete. The methods given below can be adopted to protect concrete from sulphate attack.
Use of sulphate resistant cement
The most efficient way to resist sulfate attack is with a low C. to use cement with3a material. It is found that a C3The content of 7% in sulfate water gives a rough division between cements of good and poor performance.
A well designed, placed and compacted concrete that is dense and impervious, exhibits a high resistance to sulfate attack. Similarly, concrete with a low water/cement ratio also exhibits high resistance to sulfate attack.
use of air-trained mixture
The use of air-penetration to the extent of about 6% has a beneficial effect on the sulfate resistant properties of concrete. The beneficial effect is probably due to the reduction in separation, improved workability, reduced bleeding and generally better impermeability of the concrete.
use of pozzolana
The sulphate attack is reduced by incorporating or replacing a portion of the cement with pozzolanic material. A mixture of pozzolana converts the leached calcium hydroxide into a non-leached cementitious product. This pozzolanic action is responsible for the impermeability of the concrete. Secondly, the removal of calcium hydroxide reduces the sensitivity of concrete to magnesium sulfate attack.
high pressure steam curing
Improves resistance to sulfate attack of high pressure steam treated concrete. This improvement c. is due to the change of3AH6 To remove or reduce calcium hydroxide in a less reactive phase and by reaction of silica which is always mixed when high pressure steam curing method is adopted.
use of high alumina cement
The reason for the great resistance shown by high alumina cement to the action of sulfate is still not fully understood. However, this is attributed to the absence of any free calcium hydroxide in set cement, unlike Portland cement. High alumina cement contains approximately 40% alumina, a compound that is susceptible to sulfate attack in ordinary Portland cement. But this percentage of alumina present in high alumina cement behaves differently. The primary cause of resistance is attributed to the formation of protective films that prevent the penetration or diffusion of sulfate ions into the interior. It should be remembered that high alumina cement may not show high resistance to sulfate attack at high temperatures.