Ordinary Portland Cement (OPC) is an essential component in the construction industry, as it is used to produce concrete, mortar, stucco, and non-specialty grouts. This type of cement is widely utilized due to its versatility and durability in various applications. OPC is graded based on its strength, which is measured by the compressive strength of the mortar cube that forms after 28 days of setting.
The grading system of OPC is an essential aspect of its application, as it helps determine the strength of the material. The strength of the cement is determined by the amount of compressive force that it can withstand after 28 days of setting. The higher the grade, the more robust the cement will be, indicating its suitability for specific construction applications.
OPC is commonly used in the construction of buildings, bridges, dams, and other structures. Its versatility and durability make it a popular choice for a wide range of applications. Additionally, OPC’s properties make it ideal for use in harsh environments, as it can withstand extreme temperatures, high humidity, and corrosive chemicals.
In conclusion, OPC is an essential component in the construction industry due to its versatility, durability, and strength. Its grading system helps determine its suitability for specific applications, making it a reliable and efficient material for various construction projects.
Grades of Ordinary Portland Cement
The different grades of OPC are discussed below:
1. OPC 33 Grade Cement
OPC 33 is a type of cement that is commonly used in general construction projects under normal environmental conditions. However, due to its low compressive strength and the availability of higher grade cements, the demand for OPC 33 has been impacted.
When assessing the compressive strength of OPC 33, at least three mortar cubes with a face area of 50 sq.cm are tested. These mortar cubes are made up of one part cement and three parts standard sand. The average compressive strength of these cubes is then calculated to determine the overall compressive strength of the OPC 33 cement.
| 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 |
The IS Code IS 269:1989 pertains to the specifications of Ordinary Portland Cement, 33 Grade. This code provides guidelines on the physical and chemical requirements of the cement, such as fineness, compressive strength, soundness, and setting time. It also outlines the testing procedures that must be followed to ensure that the cement meets the specified standards.
This code is important for the construction industry as it helps to maintain the quality of cement used in various construction projects. The specifications mentioned in the code ensure that the cement is suitable for use in structures that require moderate strength, such as residential buildings, bridges, and dams.
Overall, the IS Code IS 269:1989 plays a crucial role in ensuring the safety and durability of structures by providing standards for Ordinary Portland Cement, 33 Grade.
2. OPC 43 Grade Cement
OPC 43 is the most widely used grade of cement in the country at present. It is typically employed in general RCC construction applications where the concrete grade is up to M30. In addition, it is used in the production of precast items like blocks, tiles, and asbestos products such as sheets and pipes. This grade of cement is also used in non-structural works such as plastering and flooring. When it comes to compressive strength, OPC 43 exhibits high performance.
| 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 a type of cement that is specifically used when higher strength concrete is required, while still maintaining economical cement content. It is particularly useful in concrete mix design for grades M20 and above, as it can achieve significant savings of 8 to 10% in cement.
This cement grade is commonly utilized in specialized works, such as prestressed concrete components, precast items like paving blocks and building blocks, as well as in the construction of runways, concrete roads, bridges, and other RCC (reinforced cement concrete) structures where the grade of concrete required is M25 and above.
The compressive strength of OPC 53 is an essential consideration when determining the suitability of this cement grade for specific applications. It is a reliable option for achieving high compressive strength in concrete, making it a preferred choice for projects where durability and strength are crucial factors.
| 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 |
The IS Code IS 12269:1987 provides a specification for 53 grade ordinary Portland cement. This type of cement is commonly used in construction projects that require high strength concrete. The code outlines the various physical and chemical requirements that the cement must meet to qualify as 53 grade cement.
According to the code, the cement must have a minimum compressive strength of 53 MPa (megapascals) after 28 days of curing. The chemical composition of the cement must also meet certain criteria, with limits on the percentages of different compounds such as silica, alumina, and iron oxide.
In addition to these requirements, the code also specifies the fineness of the cement, which is determined by measuring the amount of cement that passes through a specific sieve size. The code also outlines the setting time and soundness requirements for the cement.
Overall, the IS Code IS 12269:1987 serves as a standardized guide for the production and use of 53 grade ordinary Portland cement in various construction applications. Compliance with the code ensures that the cement meets the necessary strength and quality requirements, which is essential for ensuring the safety and durability of concrete structures.
Physical Properties of OPC Cement
The approval process for cement involves more than just checking its compressive strength. There are other physical requirements that must be verified before cement can be approved for use.
These additional requirements may include factors such as the cement’s setting time, which refers to the amount of time it takes for the cement to harden after it has been mixed with water. Another important factor is the consistency of the cement, which can affect its workability and performance. Cement’s fineness, or particle size, is another important consideration, as this can impact its strength and durability.
Other physical properties that may be evaluated include the cement’s heat of hydration, which measures the heat generated during the chemical reaction that occurs when cement is mixed with water. This property can be particularly important in applications where excessive heat buildup could cause damage or compromise the integrity of the cement structure.
In addition to these physical requirements, there may be other factors that need to be considered depending on the specific application for which the cement will be used. These could include environmental factors such as exposure to extreme temperatures or corrosive materials, as well as performance criteria such as resistance to cracking or abrasion.
Overall, the approval process for cement involves a thorough evaluation of its physical properties and performance characteristics to ensure that it will meet the specific needs of the intended application.
Fineness
The Blaine’s air permeability method is used to determine the fineness of cement. It is required that the specific surface of cement must be at least 225 m2/kg according to this method. This requirement applies to all types of cement, regardless of their grade.
Soundness
Unaerated cement must meet certain standards to ensure its quality and suitability for use. Two tests are commonly used to measure the expansion of unaerated cement: the Le-Chatelier method and the Autoclave test.
According to the Le-Chatelier method, unaerated cement should not exhibit an expansion of more than 10mm when tested. This test is used to evaluate the soundness of cement, which refers to its ability to retain its volume after setting.
The Autoclave test is another commonly used method for evaluating the soundness of unaerated cement. This test involves subjecting a sample of cement to high pressure and temperature in an autoclave. The expansion of the cement is then measured, and it should not exceed 0.8 percent.
Both the Le-Chatelier method and the Autoclave test apply to all grades of cement. Adherence to these standards ensures that the cement is of good quality and will perform as expected in various applications.
Setting Time
The setting time of cement is determined using the Vicat apparatus method, and it must meet certain requirements. For all grades of cement, the initial setting time should not be less than 30 minutes, and the final setting time should not be less than 600 minutes. These requirements are mandatory and must be adhered to during testing.
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:
There are three different specifications for Ordinary Portland Cement in India, each with their own specific grade designation. The first specification is IS 269:1989 for Ordinary Portland Cement, 33 Grade. This standard defines the requirements and specifications for OPC with a minimum compressive strength of 33 megapascals at 28 days of curing.
The second specification is IS 8112:1989 for 43 Grade Ordinary Portland Cement. This standard sets the requirements and specifications for OPC with a minimum compressive strength of 43 megapascals at 28 days of curing.
Lastly, there is IS 12269:1987, which defines the specifications for 53 Grade Ordinary Portland Cement. This standard specifies the requirements for OPC with a minimum compressive strength of 53 megapascals at 28 days of curing.
It is important to note that the different grades of OPC are used for different applications, with higher grade cement typically used in construction projects where greater strength is required. All three specifications set the minimum requirements for the physical and chemical properties of OPC, such as fineness, setting time, and soundness, among others.