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Ordinary Portland Cement(OPC) is the most widely used cement in the construction world. It is the basic ingredient for producing concrete, mortar, stucco, and non-specialty grouts. Ordinary Portland Cement is graded based on its strength. The grade indicates the compressive strength of the mortar cube that will be attained after 28 days of setting.
Contents:
Grades of Ordinary Portland Cement
The different grades of OPC are discussed below:
1. OPC 33 Grade Cement
This grade of cement is used for general construction under normal environmental condition. But low compressive strength and availability of higher grades of cement have impacted the use and demand of OPC 33.
Compressive Strength of OPC 33 - The average compressive strength of at least three mortar cubes, having a face area of 50 sq.cm is taken into account while checking the compressive strength. These mortar cubes are composed of one part of cement and three parts of standard sand.
| a) 72 +/- 1 hour | Not less than 16 N/mm2 |
| b) 168 +/- 2 hours | Not less than 22 N/mm2 |
| c) 672 +/- 4 hours | Not less than 33 N/mm2 |
IS Code - IS 269 : 1989 for Ordinary Portland Cement, 33 Grade.
2. OPC 43 Grade Cement
This grade of cement is the most popular cement used in the country today. OPC 43 is used for general RCC construction where the grade of concrete is up to M30. It is also used for the construction of precast items such as blocks, tiles, asbestos products like sheets and pipes, and for non-structural works such as plastering, flooring etc.
Compressive Strength of OPC 43 -
| a) 72 +/- 1 hour | Not less than 23 N/mm2 |
| b) 168 +/- 2 hours | Not less than 33 N/mm2 |
| c) 672 +/- 4 hours | Not less than 43 N/mm2 |
IS Code - IS 8112: 1989 for 43 Grade Ordinary Portland Cement.
3. OPC 53 Grade Cement
OPC 53 is used when we need higher strength concrete at very economical cement content. In concrete mix design, for concrete M20 and above we can achieve 8 to 10% saving in cement with the use of OPC 53. This cement grade is used for specialized works such as prestressed concrete components, precast items such as paving blocks, building blocks etc, runways, concrete roads, bridges, and other RCC works where the grade of concrete is M25 and above.
Compressive Strength of OPC 53
| a) 72 +/- 1 hour | Not less than 27 N/mm2 |
| b) 168 +/- 2 hours | Not less than 37 N/mm2 |
| c) 672 +/- 4 hours | Not less than 53 N/mm2 |
IS Code - IS 12269 : 1987 for Specification for 53 grade ordinary portland cement
Physical Properties of OPC Cement
Physical requirements other than
Fineness
When tested for fineness by Blaine’s air permeability method, the specific surface of cement shall not be less than 225 m2/kg. This is applicable to all grades of cement.
Soundness
When tested by ‘Le-Chatelier’ method, unaerated cement shall not have an expansion of more than 10mm. When tested by Autoclave test, unaerated cement shall not have an expansion of more than 0.8
Setting Time
When tested by Vicat apparatus method, the setting time of cement shall conform to the following requirement:
a) Initial setting time - not less than 30 mins.
b) Final setting time - not less than 600 mins.
The setting time requirements mentioned above are applicable to all grades of cement.
Chemical Requirement of OPC Cement
The chemical requirements for OPC 33, OPC 43 and OPC 53 are as follows :
| Sl. No. | Characteristics | Requirements | ||
|
OPC 33 Grade |
OPC 43 Grade |
OPC 53 Grade | ||
| 1 | Ratio of percentage of lime to percentages of silica, alumina and iron oxide | Not greater than 1.02 and not less than 0.66 | Not greater than 1.02 and not less than 0.66 | Not greater than 1.02 and not less than 0.8 |
| 2 | Ratio of percentage of alumina to percentage of iron oxide | Not less than 0.66 | Not less than 0.66 | Not less than 0.66 |
| 3 | Insoluble residue, percent by mass | Not more than 4 | Not more than 2 | Not more than 2 |
| 4 | Magnesia, percent by mass | Not more than 6 | Not more than 6 | Not more than 6 |
| 5 | Total Sulphur content calculated as Sulphuric anhydride (SO2), percent by mass | |||
| (a) When tricalcium aluminate is less than or equal to 5 | Not more than 2.5 | Not more than 2.5 | Not more than 2.5 | |
| (b) When tricalcium aluminate is greater than 5 | Not more than 3 | Not more than 3 | Not more than 3 | |
| 6 | Total loss on ignition | Not more than 5 % | Not more than 5 % | Not more than 5 % |
References:
- IS 269 : 1989 for Ordinary Portland Cement, 33 Grade.
- IS 8112 : 1989 for 43 Grade Ordinary Portland Cement.
- IS 12269 : 1987 for Specification for 53 grade ordinary portland cement.
