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**What is Cement ?**

Cement is commonly known as ‘Portland Cement’ in construction works. It is traditionally used as a binding material in concrete, which sets and hardens under water and gives the desired strength. The objective of each grade is similar, that is to bind the ingredients of concrete.

The composition of cement is given below :

Ingredients of cement |
Percentage (%) |

Lime (CaO) | 62 |

Silica (SiO_{2}) |
22 |

Alumina (Al_{2}O_{3}) |
5 |

Calcium Sulphate (CaSO_{4}) |
4 |

Iron Oxide (Fe_{2}O_{3}) |
3 |

Magnesia (MgO) | 2 |

Sulphur (S) | 1 |

Alkalies | 1 |

The ratio of these ingredients matters a lot while manufacturing cement. Changes in these ratios can damage the quality of cement.

The manufacturing process of cement includes grinding the raw materials and mixing them in standard proportion. These mixtures go to a large rotary kiln at a temperature of 1500°C, till the clinkers are out of it.

Then, the final stage is grinding of the clinkers. These clinkers grind to fine powder with sufficient quantity of gypsum and the final product is ‘Portland Cement’.

**Different Grades of Cement**

Grades of cement indicate the avg compressive strength of cement after 28 days of setting. Unit of compressive strength is N/mm^{2 }(Newton per millimetre square) or Mpa (Mega Pascal). These compressive strengths are normally obtained from concrete cubes made out of various grades of concrete.

The different grades of cement such as :

- 33 Grade
- 43 Grade
- 53 Grade

Compressive Strength (N/mm^{2}) |
Min Strength (IS : 269 – 1989) |
Min Strength (IS : 8112 – 1989) |
Min Strength (IS : 12269 – 1987) |

After 3 days | 16 | 23 | 27 |

After 7 days | 22 | 33 | 37 |

After 28 days | 33 | 43 | 53 |

**Grade 33 : **

In 33 grades of cement, the compressive strength of cement after 28 days of setting is 33 N/mm^{2}. This type of cement is used for normal construction work such as flooring, plastering, grouting work and prestressed concrete works etc. Due to upgradation of construction technology and availability of higher grade of cement, this grade of cement is rarely used.

**Grade 43 : **

In 43 grades of cement, the compressive strength of cement after 28 days of setting is 43 N/mm^{2}. This type of cement is used for plain cement concrete, plastering and pathway etc. This grade of cement is not used in civil work where rapid setting is required.

**Grade 53 : **

In 53 grades of cement, the compressive strength of cement after 28 days of setting is 53 N/mm^{2}. This type of cement is used for RCC (Reinforced Cement Concrete), road construction, prestressed concrete etc. Normally 53 cement grade is most commonly used in civil work. The setting time of this cement is faster than the other two grades of cement.

**FAQs on Different Grades of Cement**

#### What does 33 43 and 53 grades of cement mean?

In grade of cement 33,43 and 53, the values 33,43 and 53 show the compressive strength of cube in N/mm2 after 28 days of curing. (cement mould size is 7.06 cm x 7.06 cm x 7.06 cm).

#### Which grade cement is best?

The highest grade of cement is 53 grade in India. It has compressive strength of 53 Mpa after 28 days curing.

#### What are the 6 types of cement?

Six Types of Cement 1. Ordinary Portland Cement 2. Portland Pozzolana Cement 3. Sulphate Resisting Cement 4. High Alumina Cement 5. Rapid Hardening Cement 6. Blast Furnace Slag Cement

#### Which is better OPC or PPC?

OPC is best for industrial and large construction and PPC is best for small residential construction. PPC is useful where possibility of sulphate attack. It has good sulphate resistance property compared to OPC.

#### Which cement is best for slab?

Portland Pozzolana Cement (PPC) is best for slab construction work.

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