Types of Portland Cement
Code (IS: 456:2000) permits the use of the following Portland cement for a specific work:
1. Ordinary Portland Cement (OPC)
Ordinary Portland Cement of grades 33, 43 and 53 are permitted. Only these cements are most commonly used in general concrete construction.
2. Rapid Hardening Portland Cement (RHPC)
This cement conforms to IS 8041:1990, which is similar to OPC. Here the percentage of C3S is more and less C2S and ground more finely. It has the quality of attaining high strength in a short period of time. Thus, it is used for construction purposes where speed is of importance.
3. Portland Slag Cement (PSC)
This cement conforms to IS 455:1990. Here the cement is made by inter-grinding Portland Cement clinker and granulated blast furnace slag. Slag is a waste product obtained from the manufacture of pig iron. Here the tricalcium content is restricted to a minimum. This has fairly high resistance to sulphates. Hence, it is suitable for environments exposed to sulphates.
4. Portland Pozzolana Cement (PPC)
Pozzolanic material is siliceous or aluminous material which by itself has no cementitous properties. However, in the presence of water it reacts with calcium hydroxide liberated in the hydration process of cement.
Fly ash and calcinated clay are pozzolanic materials used in the manufacture of PPC. Fly-ash-based and calcinated-clay-based Portland Pozzolana Cements conform to Parts 1 and 2 of IS 1489:1991. These cements hydrate and gain strength relatively slowly, and hence need more curing time. Because of the long curing time, this cement is preferred for construction purposes where time is not of prime importance, such as mass concreting.
5. Hydrophobic Portland Cement (HPC)
Hydrophobic is the water-repellent property of material. This cement conforms to IS 8043:1991. This type of cement is produced by inter-grinding Portland cement with 0.1–0.4% of oleic acid or stearic acid.
This water-repellent property is due to the formation of a water-repellent film around each particle of cement, but during mixing the film breaks and makes room for normal hydration to take place. This hydrophobic quality of cement facilitates its storage for longer periods in extremely wet climate conditions.
6. Low Heat Portland Cement (LHPC)
This contains low quantities of tricalcium aluminate and high quantities of dicalcium silicate. This cement conforms to IS 12600:1989. Compared to PPC the hydration process is slow because of which generation of heat is also low. This property is desirable for mass concreting purposes, such as the construction of gravity dams. Because of slow strength gain, care should be taken while removing the formwork early.
7. Sulphate-resisting Portland Cement (SRPC)
This cement contains a very low quantity (about 5%) of tricalcium aluminate and is ground finer than OPC. This cement conforms to IS 12330:1988. This cement is highly sulphate resistant caused by the reaction of C3A in hardened cement. This is ideal for use in locations where sulphates are present in the atmosphere or soil.
Physical and chemical properties of different Ordinary Portland Cements are presented in Table 6.3.
Table 6.3 Specifications for physical properties of cements (as per the Indian Standard)
Leave a Reply