Proper curing is very important because curing controls the rate of hydration of the cement, so proper curing is very important to obtain the total compressive strength of the cement.
Ordinary Portland cement has 3 grades 33, 43, and 53. According to the Bureau of Indian Standard, these grades are differentiated by their compressive strengths and expressed in megapascals (Mpa), which is N / mm2.
Compressive strength is a proportion of load per unit area. The load is calculated in newton (N), and the area is calculated in mm2. The differences between 33, 43, and 53 grades cement are as follows:
Generally, three different types of cement are used, which are,
- Grade-33 Cement
- Grade-43 Cement
- Grade-53 Cement
Grade 33 Cement:
Fineness = 300 kg / m2
Crush strength 3 days later = 16 N / mm2 after 7 days later, force = 22 N / mm2 after 28 days later, force = 33 N / mm2
Grade 43 Cement:
Portland Grade 43 cement was generally used in the construction of reinforced concrete, also called R.C.C. Class 43 is also used in R.M.C, which is also called pre-mixed concrete and is also used in precast concrete for construction purposes.
The fineness will be = 225 kg / m2
Crush resistance 3 days later = 23 N / mm2 after 7 days later, force = 33 N / mm2 after 28 days later, force = 43 N / mm2
Grade 43 cement has a good ability to resist sulfate, and grade 43 has a low chloride content. Class 43 cement has a good working capacity, and, using this class, we obtain a good and smooth exit surface.
Grade 53 Cement:
In grade 53, Portland cement, low chloride content was present, and grade 53 cement has a good ability to resist sulfate.
The amount of cement is required in a smaller volume because this grade has high strength as compared to other grades of Portland cement.
Grade 53 cement is mainly used in:
- C.0 Bridges.
- Construction of precast civil construction.
- Construction of factories, construction of buildings, etc. (Strength required for buildings).
- Construction of concrete sleeper (for railways).
The fineness of grade 53 will be = 225 kg / m2 Crush resistance 3 days later = 27 N / mm2 after 7 days, force = 37 N / mm2
After 28 days, force = 53 N / mm2
Grade 53 cement has high strength after 28 days after proper curing. Without proper healing, strength is not achieved properly.
1. IS codes
- For 33 grade IS 269 is used
- For 43 grade IS 8112 is used
- For 53 grade IS 12269 is used
2. Compressive strength
For calculating the compressive strength, sand and water from the cement are mixed, vibrated and cured, and cubes are made.
These cubes are tested in the laboratory at 27 ° C after 3 days, 7, and 28 days. The cement classification indicates the compressive strength of the concrete after 28 days of laying.
3. Initial strength
Here you can see that the initial strength of cement 53 is greater than 33grde or 43.
The strength of grade 53 does not increase much after 28 days due to the initial strength gain, while grade 33 and 43 cement continues to gain strength after 28 days.
Over time, 33 and 43-grade cement will achieve the same maximum strength as 53-grade cement.
4. Heat of Hydration
During the initial setup, the 53-grade cement releases heat of hydration at a much faster rate compared to the 33 and 43 cement.
Therefore, the chances of microcracks are much greater; these micro-cracks may not be visible on the surface. Often, site supervisors or masons increase the amount of cement in the mix.
They think this will increase the strength and durability of the concrete. But it creates micro-cracks in the concrete.
Therefore, grade 53 cement should only be used where such applications justify the manufacture of concrete with greater strength, where there are good supervision and quality assurance measures and where appropriate precautions are taken to reduce the greatest heat of hydration through an appropriate healing process.
The 43-grade cement releases medium heat of hydration. The 33-grade cement releases low heat of hydration.
- The price of 33-grade cement is lower than 43-grade cement.
- The 43-grade cement price is higher than 33 but lower than 53.
- The price of cement 53 is higher than 33 and 43.
Currently, 33-grade cement is rarely used. As most manufacturers have adopted PPC. 33-grade cement is commonly used to manufacture low strength concrete, as below M20 concrete.
It is also used to finish all types of buildings, bridges, culverts, roads, water retention structures, etc.
Grade 53 OPC cement is recommended in all RCC structures, such as feet, columns, beams, and slabs, where initial and final strength is the main structural requirement. Can also be used for RCC jobs where the concrete grade is M30 and above
Building – Activity,
- A precast concrete item, such as paving blocks, tiles, building blocks, pipes, sleepers, masts, etc.
- Work in prestressed concrete, such as bridges, silos, etc.
- Track, concrete roads, bridges.
- Concreting for cold weather, cement grout, instant clogging, etc.
Every type of cement is suitable for a different set of tasks. Each of them has a variable level of resistance, the use of incorrect resistance levels for a specific job can affect your overall structural design.