A right selection of cement may increase the life of the structure and prevent the chemical attack. 

Generally, the concrete will face chemical attacks such as

  • Sulphate Attack – Seawater
  • Acid attack
  • Chloride attack – groundwater sometimes contains chloride.
  • Carbonation – Carbon dioxide in the surrounding

Special Types of Cement required for these kinds of acid attacks.

We can use SRC for a normal construction structure; however, it will be beneficial only when the structure is under the attack of sulphate like seawater piers.

In this post, we are going to discuss the sulphate resisting cement and its advantages & disadvantages.

What is sulphate resisting cement?

The sulphate resisting cement is a type of cement that has low Tricalcium aluminate (C3A) & Tetracalcium aluminoferrite (C4AF) content and high Tricalcium silicate (C3S) content than the normal chemical composition of OPC. 

sulphate resisting cement

Composition Of Sulphate Resisting Cement

Tricalcium aluminate & Tetracalcium aluminoderrite will be reduced in % by weight (< 5%), making the cement as sulphate resistant.

In nature 

  • Tricalcium aluminate (C3A) liberates much heat during the early stage of hydration.
  • Tricalcium silicate (C3S) is responsible for quick hydration and cement hardening.

Chemical Composition of Portland Cement

Compounds of OPC Clinker Formula Shorthand form % by weight1
Tricalcium aluminate Ca3Al2O6 C3A 10
Tetracalcium aluminoferrite Ca4Al2Fe2O10 C4AF 8
Belite or dicalcium silicate Ca2SiO5 C2S 20
Alite or tricalcium silicate Ca3SiO4 C3S 55
Sodium oxide Na2O N (Up to 2)
Potassium oxide K2O K
Gypsum CaSO4.2H2O CSH2 5

Properties of Sulphate Resisting Cement

PROPERTIES VALUE
Initial setting time 30 minutes
Final setting time 10 Hours
Average Compressive Strength @
3 Days 10 Mpa
7 Days 16 Mpa
28 Days 33 Mpa
Soundness
Lechatelier (mm) 2 (max)
Autoclave 0.25(max)

Advantages

  • High durability under aggressive conditions.
  • Low heat development during hydration comparing other types.
  • SRC cement protects the structure from the sulphate attack.
  • Mostly sulphate resisting cement is used to construct the underground structure where sulphate resistant is needed much.

Disadvantages of Sulphate Resisting Cement

  • Costly
  • Not suitable for marine construction
  • Not ideal for the areas where there is a danger of chloride attack
Author

Bala is a Planning & QS Engineer working at Megha Engineering & Infrastructure Limited who has more than 9+ Years of experience in Building & Infrastructure. He is the author, editor of Civil Planets.

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