CEMENT PROPERTIES

The cement is obtained by burning at very high temperature a mixture of calcareous and argillaceous materials. The mixture of ingredients should be intimate and they should be in correct proportion. The calcined product is known as clinker. A small quantity of gypsum is added to the clinker and it is then pulverized in to very fine powder, which is known as cement.

          Among the various types of cement, ordinary Portland cement (OPC) is by far the most important type of cement. The OPC was classified in to three grades, namely 33 grade, 43 grade and 53 grade depending upon the strength of the cement at 28 days when tested as per IS 4031-1988. If the 28 days strength is not less than 33 N/mm², it is called as 33-grade cement.

The chemical composition of ordinary Portland cement is tabulated below

Oxide	Percentage (%)
CaO	60-67
SiO2	17-25
Al2O3	S3-8
Fe2O3	0.5-6
MgO	0.1-4
Alkalies (K2O, N2O)	0.4-1.3
SO3	1.3-3

Following are the important properties of good cement, which primarily depend upon its chemical composition, thoroughness of burning and fineness of grinding.

o   It gives strength to the masonry.

o   It is an excellent binding material.

o   It is easily workable.

o   It offers good resistance to the moisture.

o   It possesses a good plasticity.

o   It stiffens or hardens easily.

Physical Characteristics Of OPC

Types of cement		33grade	43grade	53grade
Finess(m2/kg)Mm		225	225	225
Soundness by	Le chatelier (mm) max	10	10	10
	Auto clave (%)max	0.8	0.8	0.8
Setting time	Initial(mts)mm	30	30	30
	Final(mts)mm	600	600	600
Compressive strength	1day Mpa	N.S	N.S	N.S
	3days Mpa	16	23	27
	7days Mpa	22	33	37
	28days Npa	33	43	53

Chemical Characteristics Of OPC

Type of cement	33grade	43grade	53grade
Lime saturation factor (%)	0.66Mm 1.02max	0.66Mm 1.02Max	0.8Mm 1.02max
Alumina iron ratio (%)Mm	0.66	0.66	0.66
Insoluble residue (%)max	4	2	2
Magnese(%)max	6	6	6
Sulphuric anhydride	2.5% max when C3A is 5	2.5% max when C3A is 5	2.5% max when C3A is 5
	3% Max when C3A is >5	3% Max when C3A is >5	3% Max when C3A is >5
Less on ignition(%)max	5	5	4