Cement Manufacturing Functions, Composing Properties Application & Characteristics

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  • Cement, one of the most important building materials, is a binding agent that sets and hardens to adhere to building units and made up of limestone(calcium), sand or clay, bauxite (aluminum) and iron ore, and may include shells, chalk, marl, shale, clay, blast furnace slag or slate.

Function of Cement

  • To bind the sand and coarse aggregate together to fill voids in between sand and coarse aggregate particle to form a compact mass.

Composition of Cement

  • For understanding cement composition, one must know the functionality of cement ingredients.
  • By altering the amount of an ingredient during cement production, one can achieve the desired cement quality.
  • There are eight major ingredients of cement. The general percentage of these ingredients in cement is given below:
Sr.No. Ingredient Percentage in cement(%) Function
1. Lime (CaO) 60-65
  • Deficiency in lime causes cement to set quickly.
    Excessive presence of lime causes cement to expand and disintegrate.
2. Silica(SiO2) 17-25
  • Silica imparts strength to cement.
3. Alumina(Al2O3) 3-8
  • Alumina imparts quick setting property to the cement.
    Excess alumina weakens the cement.
4. CalciumSulphate(CaSO4) 1-3
  • It slows down or retards the setting action of cement.
5. Ironoxide(Fe2O3) 0.5-6
  • Iron oxide imparts colour to cement.
6. Magnesiaoxide(MgO) 0.1-0.5
  • Excess magnesia will reduce the strength of the cement.
7. SulphurTrioxide(SO3) 1-3
  • Excess Sulphur Trioxide causes cement to unsound.
8. Alkalis(K2O, Na2O) 0-1
  • Excess Alkaline matter causes efflorescence.

Manufacturing of Cement

Stage of Cement Manufacture

There are six main stages of cement manufacturing process:

Stage 1: Raw Material Extraction/Quarry

  • The raw cement ingredients needed for cement production are limestone (calcium), sand, clay, etc.
  • The raw materials are blasted from the quarry.

Stage 2: Crushing

  • The raw ingredients are quarried and crushed to smaller pieces.

Stage 3: Raw Grinding

  • The crushed raw ingredients are then combined them with additives and grinding them to ensure a fine homogenous mixture.
  • It can be done through 2 process: a. Dry Process (modern technology) b. Wet Process (old technology)

Stage 4: Burning

  • The raw mix is pre-heated before it goes to the kiln, which is heated by a flame that can be as hot as 2000° C.
  • The raw mix burns at 1500° C producing Clinker.

Stage 5: Grinding

  • The Clinker and the Gypsum are very finely ground giving pure Cement.
  • Other secondary additives and material can also be added to make a blended cement.

Stage 6: Storage, Packing and Dispatch

  • Cement is conveyed from grinding mills to silos (large storage tanks) where it is packed in 20-40 kg bags.
  • Most of the product is shipped in bulk quantities by trucks, trains or ships.

Characteristics of Good Cement

1. The color of cement should be uniformly grey with greenish shade. It gives an indication of excess of lime or clay and the degree of burning.

1. Construction

  • It is used in mortar for plastering, masonry work, pointing, etc.
  • It is used in concrete for laying floors, roofs and constructing lintels, beams, stairs, pillars etc.
 

2. Transport

  • It is used in the construction of roads, pathways, crossings, bridges, tunnels, parking, sleepers, and runways etc
 

3. Hydrophilic Construction

  • It is used in the construction of important engineering structures such as pipes, culverts, drains, canals, dams, weirs, reservoir, tanks and pools etc.

4. Miscellaneous

  • It is used for constructing piers, docks, retaining wall and breast wall etc.

Types of Cement

Sr.No. Types of Cement Reference Indian grades Application
1. Ordinary Portland cement Grade 33-IS: 269 Grade 43-IS: 8112 Grade 53-IS: 12269
  • Widely used in residential construction where special type of cement properties is not required.
2. Portland Blast furnace Slag cement IS:455
  • It is better suited for use in marine structures as docks, harbors, and jetties.
  • It is also used in road construction in marshy and alkaline soils
3. Portland Pozzolana cement IS:1489
  • It is mainly used in building construction where strength required with age.
4. Rapid Hardening cement IS:8041
  • It is used in road pavement works.
  • It is also used for precast concrete casting(Beams, Columns etc)
5. Extra Rapid Hardening cement
  • It is used for very high early strength concrete.
6. Acid Resistant cement
  • It is used for acid resistance and heat resistance coatings of installations for chemical industry
7. Sulphate resisting cement IS:12330
  • It is used for pile foundation.
  • It is used in sewage and water treatment plants.
8. Low heat cement IS:12600
  • It is used in mass construction (dams,marine constructions).
  • It is also used in retaining wall construction.
9. Hydrophobic cement IS:8043
  • It is useful where cement is stored for longer duration in wet climatic conditions.
10. Quick setting cement
  • It is used in underwater constructions.
  • It is also used in places where cold and rainy conditions persist.
11. Air entering cement
  • It is used in frost resistance concrete (frost also makes gap in concrete like water).
12. Masonry cement IS:3466
  • It is used as masonry mortar for use in brick,block, and stone masonry construction.
  • It is also used to produces tucco.
13. High alumina cement IS:6452
  • It is commonly used in construction work near and along sea-shore.
  • It is also used in works where concrete is subjected to high temperatures, frost, and acidic action.
14. Expanding Cement
  • It is used for construction of water retaining structures.
  • It is also used for repairing the damaged concrete surfaces.
15. Oil well cement IS:8229
  • It is used for cementing work in the drilling of oil wells where they are subject to high temperatures and pressures.
16. Coloured cement
  • It is used for floor finishing.
17. White cement IS:8042
  • It is used as a base coat before painting.
  • It is also used to cover the hairline cracks on concrete surface to give smooth finish.

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