This document discusses cement, including its manufacture and composition. It notes that cement is made by heating limestone and clay at high temperatures which forms calcium silicates and other compounds. The raw materials are finely ground and mixed with water to form a slurry, then heated in a kiln at 1400-1500°C. This process forms cement clinker which is then cooled, ground into a powder, and mixed with gypsum. When cement is mixed with water, it undergoes hydration and hardening reactions that cause it to set and strengthen over time. The main uses of cement are in construction applications like buildings, bridges, and concrete.

1. CEMENT
Dr.Bincy Joseph
Assistant Professor
Dept.of chemistry
St. Mary's college Thrissur

2. CEMENT
 Cement or Portland cement is a fine grey
powder consisting of calcium silicate and
aluminate that hardens under water.

3. Manufacture of cement
Raw materials
 Limestone – calcium carbonate,CaCO3
 Clay - rich in silica and alumina and containing
some Fe2O3

4. Manufacture of cement
 Finely powdered limestone mixed with finely
powdered clay
 Made into a slurry in water
 Raw slurry heated at 1400-1500oC in steel rotary kiln
 Dehydration occurs
High temperature form CaO, decomposition of
CaCO3

5. Manufacture of cement
CaO combines with silica & alumina of clay ,give a mixture of
silicates, aluminates & aluminoferrites.
CaCO3 → CaO + CO2
 2CaO + SiO2 → (2CaO).SiO2 (dicalcium silicate)
 3CaO + SiO2 → (3CaO).SiO2 (tricalcium silicate)
 3CaO + Al2O3 → (3CaO).Al2O3 (tricalcium aluminate)
 (3CaO).Al2O3 + CaO + Fe2O3 → (4CaO).Al2O3. Fe2O3
(tetracalcium aluminoferrite)

6. Manufacture of cement
Cement clinker, form of marble sized lumps
having greenish - black colour.
 Clinker from the kiln ,cooled to 150oC by
circulating cold air
 Then it is mixed with 2-3%
gypsum(CaSO4.2H2O),ground to a fine powder.
Gypsum act as retardant of quick initial setting
of cement
Portland cement

7. Composition of Portland
cement
 10-20 % dicalcium silicate (2CaO).SiO2
 50-70% tricalcium silicate (3CaO).SiO2
 5-10% tricalcium aluminate (3CaO).Al2O3
 3-8 % tetracalcium aluminoferrite
(4CaO).Al2O3. Fe2O3

8. Composition of Portland cement
 CaO = 50 - 60%
 SiO2 = 20-25%
 Al2O3 = 5-10%
 MgO = 2-3%
 Fe2O3 = 1-2%
 SO3 = 1-2 %

9. Setting of cement
 The plastic mass obtained when cement is
mixed with water becomes stiff and hard due to
the precipitation of colloid gels formed by the
hydration and hydrolysis of cement
constituents, the process is called setting.
 The constituents lose water and change into
interlocking crystalline products by the rupture
of the gel coatings ,the process is called
hardening.

10. Setting of cement-Reactions
 Hydration of tricalcium aluminate -
3CaO .Al2O3 + 6H2O → 3CaO .Al2O3 .6H2O
Hydrated gel of tricalcium aluminate
 Hydrolysis of tricalcium silicate –
3CaO.SiO2 + H2O → Ca(OH)2 + 2CaO .SiO2
Dicalcium silicate
Ca(OH)2 binds the calcium silicate particles together

11. Setting of cement-Reactions
 Hydration
2CaO.SiO2 + xH2O → 2CaO.SiO2. xH2O
Hydrated gel of dicalcium silicate
 Partial hydrolysis
3CaO.Al2O3 + 6H2O → 2Ca(OH)2 + 2Al(OH)2
Al(OH)2 fills all the interstices in the cement, sealing all
the pores, making the mass leak proof.

12. Setting of cement-Reactions
 Hydration
4CaO.Al2O3. Fe2O3+ 6H2O → 3CaO.Al2O3 .6H2O+ CaO. Fe2O3
 Addition of gypsum
3CaO.Al2O3 + 3CaSO4.2H2O → 3CaO.CaSO4.Al2O3.6H2O
Calcium sulphoaluminate
Calcium sulphoaluminate does not have the property
of quick hydration, increases setting time & improves
the strength.
The hydrated salts formed lose water slowly ,by
evaporation, sets to a hardened mass.

13. Uses of cement
 Construction of bridges, dams, buildings,
plastering of walls.
 Used to make concrete & reinforced
concrete.

14. THANK YOU