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Sulphate Resisting Portland Cement (SRC)
Sulphate Resisting Portland Cement is a type of Portland Cement in which the amount of tricalcium aluminate (C3A) is restricted to lower than 5 % and (2 C3A + C4AF) lower than 25%. The SRC can be used for structural concrete wherever OPC or PPC or Slag Cement is usable under normal conditions.
The use of SRC is particularly beneficial in such conditions where the concrete is exposed to the risk of deterioration due to sulphate attack. For example, in contact with soils and ground waters containing excessive amounts of sulphates as well as for concrete in seawater or exposed directly to seacoast. The IS 456 2000 (revised draft code) has made elaborate provisions for use of particular type of cement against different percentages of soluble sulphate salts. These provisions are given in table below:
Class Total SO3 present in soil (wt)% Concentration of sulphates as SO3 Type of Cement (*) Min cement content (kg /m3) Max water /cement ratio
In 2.1 water soil extract In ground (g/I)
1 < 0.2 <1.0 <0.3 OPC,PSC or PPC 280 0.55
2 0.2 - 0.5 1.0 - 1.9 0.3 -1.2 OPC,PSC or PPC 330 0.50
3 0.5 - 1.0 1.9 - 3.1 1.2 - 2.5 SSC or SRC PPC or PSC 310 0.50
4 1.0 - 2.0 3.1 - 5.0 2.5 - 5.0 SSC or SRC 370 0.45
5 >2 >5 5.0 SSC OR SRC with Protective coating. 400 0.40
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