Ordinary Portland Cement (OPC) | Chemical Composition

Ordinary Portland cement is one of the most common type of cement is used in construction industry. The ordinary Portland cement is manufactured by raw material.

The raw material are,

1. Calcareous material that is limestone, Calcium etc.

2. Agrillaceous material that is alumina, shate laterite.

Calcareous material are those material which contain major part of calcium or limestone and Agrlillaceous material are those material which contain major part of alumina.

chemical property and physical properties of ordinary portland cement opc

Chemical Composition of OPC

Chemical constituents (Composition) of Ordinary Portland Cement (OPC) are listed below.

Sr. No.constituentsChemical FormulaPercentage
1.Lime Calcium OxideCaO60 – 65%
2.Silica Silicon OxideSiO217  – 25%
3.Iron Oxide Ferrous Oxidefe2O30.5 – 6%
4.Magnesia- Magnesium OxideMgO0.1 – 4 %
5.Alumina – Aluminium OxideAl2O33 – 8%
6.Soda + PotashNa2O + K2O0.2 – 1%
7.Sulphur oxideSO31- 2.75 %
8.Free lime0 – 1 %

Physical Properties of OPC

Physical Properties of Ordinary Portland Cement (OPC):

Possible Question: Enlist four physical properties of OPC.

Physical properties of OPC are as following:

  1. Fineness
  2. Soundness
  3. Compressive strength
  4. Initial and final setting time
  5. Standard consistency

Determination of Physical Properties:

Possible Questions:

Q. State how fineness of cement is determined by sieving method.

Q. Enlist any four lab test for OPC explain any one of them in brief.

Q. Explain the procedure to determine fineness of cement by dry sieving method, state IS requirement.

The properties are determined according with the BIS codes or IS Codes.

Lab test for OPC are as following:

1. Fineness test

2. Soundness test

3. Compressive strength test (OPC)

4. Initial and final setting time test

5. Standard and normal consistency test

1. Fineness test (OPC)

Fineness test is useful for determine the percentage of fineness of cement. There are two methods in IS code for testing fineness.

a) Sieve test (IS 4031, Part 1 1996)

b) Air permeability method (IS 4031, Part 2 1999)

a) Sieve test (OPC)

Sieve test it very simple test. The procedure is given below,

  1. Weight 100 gram of cement sample as W1 and take it on a standard IS sieve number 9 i.e. sieve of size 90 Microns.
  2. Break down any visible lumps in the sample with fingers. Keep lid at top and pan at bottom.
  3. Continuously sieve the sample for 10 to 15 minute manually by giving wrist motion. Mechanical sieving device may also use.
  4. Weight the Residue left on the sieve W2 gram.
  5. Finally calculate % fineness of cement

% fineness = W2/W1×100

6. Repeat above steps two more times to calculate average percentage of fineness given cement sample.

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