Cement

Mar 5, 2019
  • 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 includeshells, chalk, marl, shale, clay, blast furnace slag or slate.

Function of Cement

  • To bind the sand and coarse aggregate together to fill voids in betweensand and coarse aggregate particle to form a compact mass
  • For understanding cement composition, one must know the functionality of cement ingredients.
  • By altering the amount of an ingredient during cement production, onecan achieve the desired cement quality.
  • There are eight major ingredients of cement. The general percentage ofthese ingredients in cement is given below:
Sr.No. Ingredient Percentage in cement(%) Function
1. Lime (CaO) 60-65
  • Deficiency in lime causescement to set quickly.
  • Excessive presence of limecauses cement to expand and disintegrate.
2. Silica(SiO2) 17-25
  • Silica imparts strength tocement.
3. Alumina(Al2O3) 3-8
  • Alumina imparts quicksetting property to the cement.
  • Excess alumina weakens thecement
4. CalciumSulphate(CaSO4) 1-3
  • It slows down or retards thesetting action of cement.
5. Ironoxide(Fe2O3) 0.5-6
  • Iron oxide imparts colour tocement.
6. Magnesiaoxide(MgO) 0.1-0.5
  • Excess magnesia will reduce thestrength of the cement.
7. SulphurTrioxide(SO3) 1-3
  • Excess Sulphur Trioxide causescement to unsound.
8. Alkalis(K2O, Na2O) 0-1
  • Excess Alkaline matter causesefflorescence.

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 2000o C.
  • The raw mix burns at 1500o 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.
Sr.No. Ingredients Percentage (%)
1. Alumina : Iron Oxide > 0.66
2. Lime: AluminaLime: IronOxideLime: Silica > 0.66 or < 1.02
3. Loss of Ignition < 4
4. Sulphur Content < 2.75
5. Weight of insolublere side < 1.50
6. Weight of magnesia reside < 5

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.
Sr.No. Types of Cement ReferenceIndian grades Application
1. Ordinary Portland cement Grade33-IS:269Grade43-IS:8112Grade 53-IS:12269
  • Widely used in residential construction where special type ofcement properties is notrequired.
2. Portland Blast furnace Slagcement IS:455
  • It is better suited for usein marine structures asdocks, harbors, andjetties.
  • It is also used in roadconstruction in marshyand alkaline soils
3. Portland Pozzolanacement IS:1489
  • It is mainly used inbuilding constructionwhere strength requiredwith age.
4. Rapid Hardening cement IS:8041
  • It is used in roadpavement works.
  • Itis also used for precastconcrete casting(Beams, Colums etc)
5. Extra Rapid Hardening cement
  • It is used for very high early strength concrete.
6. Acid Resistant cement
  • It is used for acidresistance and heatresistance coatings ofinstallations for chemicalindustry
7. Sulphate resisting cement IS:12330
  • It is used for pilefoundation.
  • It is used in sewage and water treatment plants.
8. Low heat cement IS:12600
  • It is used in massconstruction (dams,marine constructions)
  • It is also used inretaining wallconstruction.
9. Hydrophobic cement IS:8043
  • It is useful where cementis stored for longerduration in wet climaticconditions.
10. Quick setting cement
  • It is used in underwater constructions.
  • It is also used in placeswhere cold and rainyconditions persist.
11. Air entering cement
  • It is used in frost resistance concrete (frostalso makes gap inconcrete like water).
12. Masonry cement IS:3466
  • It is used as masonry mortar for use in brick,block, and stonemasonry construction.
  • It is also used to producestucco.
13. High alumina cement IS:6452
  • It is commonly used inconstruction work nearand along sea-shore.
  • It is also used in workswhere concrete issubjected to high temperatures, frost, andacidic action.
14. Expanding Cement
  • It is used for constructionof water retainingstructures.
  • It is also used for repairing the damagedconcrete surfaces.
15. Oil well cement IS:8229
  • It is used for cementingwork in the drilling of oil wells where they aresubject to high temperatures andpressures.
16. Coloured cement
  • It is used for floor finishing.
17. White cement IS:8042
  • It is used as a base coatbefore painting.
  • It is also used to cover the hairline cracks onconcrete surface to give smooth finish.