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Wednesday, February 08, 2017

Sulphate resisting portland cement

Sulphate resisting portland cement

SRPC counters what is commonly known as " sulphate attack". Soluble sulphate salts when present  in groundwater or in the soil penetrate through the pores of the hardened concrete and chemically react with the tricalcium aluminate (C3A) constituent of the cement. The reaction product, occupies a volume, which is more than the reacting compounds. This creates internal pressure resulting in the cracking of the concrete, which eventually disintegrates. This is called "sulphate attack".

SRPC has low C3A content which helps in reducing sulphate attack. The use of  SRPC is strongly recommended for structures in marshy lands, creek areas, coastal areas, in seawater, and in all areas where soluble sulphate salts are present beyond tolerable limits. Whenever sulphate concentration measured in terms of SO3 content exceeds 300 ppm in ground water, or 0.2 percent in the soil, the use of SRPC is recommended. When chlorides are present besides sulphate beyond permissible limits, it would be preferable to use Blended cement instead of SRPC.