SRPC (cement), chemical composition, pros and cons of SRPC.

Articles > SRPC (cement), chemical composition, pros and cons of SRPC.

Sulfate Resisting Portland Cement:

Sulfate-resisting Portland Cement (SRPC), simply called Sulfate Resistant Cement is a unique purpose cement which is used in areas where sulfates are present in high concentrations. Sulfate would damage concrete made using CEM I(Composite Epoxy Material)  or CEM II cements. In cement, the Sulfate resistance is achieved by limiting the level of C3A in the cement. SRPC is synthesized by mixing ground limestone, shale, and iron-oxide together at a very high temperature, which results in cement clinker. Gypsum is also added in a very small quantity. Then the mixed gypsum and the cement clinker is ground into a very fine powder, thus producing Sulfate Resistant Portland Cement. This type of cement is used in areas prone to sulfate attack. Sulfate weakens the strength and durability of a common type of cement. This type of cement is invincible only in areas enriched with sulfate. It can not face chloride attack. In seawater construction, as there is hight concentration of chloride, this type of cement is allowed to be used. 

Chemical Composition of SRC:

Sulfate Resistant Cement is different from ordinary Portland cement because of the reduced quantity of Tricalcium Aluminate up to 5% and Calcium Aluminate (2C3A) and Tetracalcium aluminoferrite (C4AF) up to 25%. The reduction of these compounds results in reduced formation of Sulfate Salts. Reduced sulfate salts result in better strength and durability of the cement structure. Detail of its chemical composition is given in the following table;

Uses of SRC:

In order to reduce the risk of the chemical attack which deteriorates the structure, Sulfate resisting cement is highly recommended in the following applications:

  1. Food processing plants, feedlots of livestock, pig farms (piggeries), and slaughterhouses.
  2. SRC is recommended in construction near geothermal areas.
  3. It is highly recommended in the construction of drainage, and sewerage plants.
  4. SRPC (Sulfate Resisting Portland Cement) is used in construction in the acidic soil environment.
  5. Constructions of dairying, animal husbandry, fishing, forestry, and other buildings prone to chemical attack.
  6. This type of cement is recommended to minimize chloride-induced corrosion to the steel reinforcing concrete.
  7. SRPC should be specified in ship-wharfs and marinas.
  8. Sea walls, reservoirs, and dams, and water retaining structures are susceptible to chemical attack, therefore, this type of cement is recommended in the construction of water-contact structures.
  9. Construction of Off-shore platforms, bridges, and any other submerged structures in tidal and splash zones, are specified to this type of cement.
  10. SRC is recommended to use in the construction of below-ground level apartments.

Pros of SRC:

  1. It provides maximum resistance to the chloride ions. The maximum resistance to the chloride ions results in a minimum risk of corrosion of reinforcing steel in the concrete mass.
  2. A high level of concrete durability and structural integrity can be attained by the use of this type of cement instead of the OPC.
  3. This type of cement survivability to the structures constructed in acidic and sulfate environment.
  4. SRPC provides good workability and pumpability (the property of flowing easily through lines and vessels).
  5. SRPC has a significant and improved later age strength.

Cons of SRC:

Generally, the concrete structures face chemical attacks like chloride attack, sulfate attack, and carbonation attack. Sulfates are present in seawater, therefore, offshore regions are prone to sulfate attack. Chlorides are present in groundwater, therefore, all the buildings present in regions of water-logging and salinity are prone to chloride attacks. Carbon dioxide is present in the atmospheric air, therefore, the carbon dioxide attack is likely almost in all areas of the world. As far as, the SRPC (cement) is concerned, it is resistant to sulfate. Buildings near shores are vulnerable to sulfate attack only, therefore, this type of cement is recommended in off-shore construction. Undersea water construction, SRPC is not recommended because, in the sea, water chlorides are present in an excessive concentration, and the buildings constructed with SRPC are not resistant to chloride attack, therefore, this type of cement is not allowed to use in constructions under seawater.

  1. A sulfate resistant Portland cement is not suitable for constructions in the areas of chloride-concentration, this is why it is not recommended in under-sea constructions. In case of the presence of both chloride and sulfate, an Ordinary Portland Cement with 5 to 8% of Tricalcium Aluminate is recommended.
  2. The cost of SRPC is higher than an ordinary Portland cement, therefore, it is specified in very specific cases.
  3. Not suitable in the areas where there is a risk of chloride attack.

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