Sulphate Resisting Cement

What is Sulphate Resisting Cement?

Sulphate resisting cement is used to protect structures from sulphate attack. It is a specialized cement used in building structures that will be submerged or exposed to soil or water for extended periods of time when sulphate quantity is high.

Sulphate resisting cement contains low amount of tricalcium aluminate. The content of tricalcium aluminate in cement is responsible for its interaction with sulphate ions in the soil or water, causing expansion of concrete and the appearance of cracks. Due to low tricalcium aluminate, these are very low probability of chemical reaction with sulphate ions.

Composition

As we knows that this type of cement have very low quantity of tricalcium aluminate. A tiny amount of calcium aluminate is formed due to hydration.

The making of calcium sulpho- aluminates which made due to reaction of calcium sulpho-aluminates and sulphate salts is highly decreased with use of sulphate resisting cement. The sulphate aluminates are present in huge quantity in nature.

Properties of Sulphate Resisting Cement

Here are the main characteristics of sulphate resisting cement.

• Provides maximum resistance to chloride ions and minimizes risk of rebar corrosion.
• High concrete performance and structural integrity in highly aggressive sulphate and acidic environments.
• Workability of this cement is high.
• Placing is more easy compared to conventional cement.
• As it ages, significant improvement in concrete strength.

Sulphate Resisting Cement Uses

The most common uses are:

• Soil containing high amount of sulphate.
• Underground RCC tanks.
• Offshore structures.
• Chemical, fertilizer and sugar plants.
• Food processing.
• Petrochemical projects.
• Coastal works.

Pros

• The use of sulphate-resistant cement provides excellent protection against the formation of sulfoaluminates and consequently resistance to sulfuric acid attack of concrete.
• Very high compressive strength due to economical concrete recipe.
• Very low heat of hydration prevents cracking due to shrinkage.
• Improves structure life and durability in aggressive conditions.
• Prevents sulfate attack and improves corrosion resistance of steel.

Cons

• Sulphate resistant cement is not suitable where there is a risk of chloride attack. This leads to corrosion of the reinforcement.
• If both chlorides and sulfates are present, regular portland cement with a C3A of 5-8 should be used.
• The curing process should be carried out with great care for at least 8-10 days.
• Not mandatory for use in shipbuilding.