There are various categories of cement used in building works for various purposes. Thus, it is important to understand properties of each type of cement and their uses. There are commonly three types of cement used in general construction purposes i.e. Ordinary Portland Cement (43 Grade & 53 Grade), Portland Pozzolana Cement and Portland Slag Cement.
Type#1. Ordinary Portland Cement (OPC)
OPC is manufactured by grinding together OPC Clinker (95 – 97%) along with gypsum (3-5%). Ordinary Portland Cement (OPC) is graded according to their compressive strength. The grade indicates the minimum compression strength (MPa or N/mm2) that the cement will attain after 28 days of setting.
Compression Strength of OPC cement
OPC 43 Grade cement attains a minimum compression strength of 43 MPa in 28 days of setting as compared to OPC 53 which attains a strenth of 53 MPa in the same time.
Initial Strength
OPC 53 Grade cement is used for fast paced construction were initial strength is to be achieved rapidly. 53 Grade cement is fast setting as compared to 43 grade cement. 53 Grade attains a minimum strength of 27 MPa in 3 days as compared to only 23 MPa achieved by 43 grade cement.
Uses and Application
53 Grade OPC cement is recommended in all RCC structures like footing, column, beam and slabs, where ever initial and ultimate strength is the major structural requirement.
43 Grade OPC Cement is recommended for plastering ,tiling , masonry works, Non-RCC structures, pathways etc. where initial days strength is not of prime importance. PPC is best substitute to OPC 43.
Type#2. Portland Pozzolana Cement (PPC)
PPC is blended cement manufactured by grinding together OPC Clinker (63-83%) and fly ash (15-35%) along with gypsum (3-5%) or by intimately blending OPC and fly ash. Fly ash is a byproduct from burning pulverised coal in electric power generating plants. The percentage of fly ash in PPC permitted by BIS varies from 15 per cent (minimum) to 35 percent (maximum).
Compression Strength
PPC need to attain minimum compression strength of 33 MPa in 28 days of setting compared to 53 attained by 53 Grade OPC cement. In PPC the development of strength at initial stages, between 1 to 7 days, is lower; however PPC progressively improves its strength at later ages.
PPC improves the strength of concrete over a period of time (28 to 90 days and beyond) whereas OPC improves strength hardly beyond 28 days. As per the BIS, a minimum curing period of 10 days is prescribed for PPC and 7 days for for OPC in dry and hot climates.
Uses and Applications
PPC is useful for general construction works and strongly recommended for Masonry, Plaster, Tiling works as initial strength not being a prime factor of performance in this application.
PPC has an edge on OPC for non-structural/masonry applications as PPC has slower rate of heat of hydration. Due to less heat of hydration PCC is prone to less cracks & has reduced shrinkage). It also has better workability and finishing (as fly ash based cement are spherical in shape and finer in size).
Type#3. Portland Slag Cement (PSC)
Portland Slag Cement, commonly known as PSC, is also a kind of blended cement. It is manufactured by either inter-grinding or blending, OPC Clinker (35% – 50%),slag (45- 65% ) and gypsum (3-5%). Slag is by product of steel production, essentially, a non-metallic product comprising of more than 90% glass with silicates and alumino-silicates of lime. The percentage of slag in PSC permitted by BIS varies from 25 per cent (minimum) to 70 percent (maximum).
Compression Strength
PSC need to attain minimum compression strength of 33 MPa in 28 days of setting compared to 53 attained by 53 Grade OPC cement. In PSC the development of strength at initial stages, between 1 to 7 days, is lower; however PSC progressively improves its strength at later ages.
PSC improves the strength of concrete over a period of time (28 to 90 days and beyond) whereas OPC improves strength hardly beyond 28 days. As per the BIS, a minimum curing period of 10 days is prescribed for PSC and for OPC it is 7 days in dry and hot climates.
Uses and Applications
PSC is Useful for general construction works and strongly recommended for Masonry, Plaster, Tiling works as initial strength not being a prime factor of performance in these applications.
PSC has an edge on OPC for non-structural/masonry applications, as PSC has slower rate of heat of hydration (thereby prone to less cracks & reduced shrinkage), better workability and finishing.
PPC & PSC are substitutes to each other; the economical one may be opted for recommended use.
