3. What is cement Cement ?
• A powdered materials which initially have plastic
flow when mixed with water or other liquid, but
has the property of setting to a hard solid
structure in several hours with varying degree of
strength and bonding properties”
• Picture of cement
4. Types of cement
• Generally 4 types …….
1. Portland cement: - generally mixture of tri -calcium silicate , di-calcium silicate, and
tri-calcium aluminate.C3S and C3A is more important of them.
2. Pozzuolana cement:- generally made from tofus of volcano. (pozzuola in Itali).
Tofus turned into cement when only it is finely grounded and mixed with lime.
3. Calcium aluminate cement: -some time it is called high alumina cement . when the
mixture of Al2O3 and CaCO3 is melting for industrial production.
4. Special or corrosion resistance cement:- phenolic Sulphur, Silicate cement.
5. History
• In 1824, Portland cement was invented and named by Joseph
Aspdin.
• Portland cement: He named because the cement he made was as
same as ,Portland rock (stone)
• Natural cement (puzzoli ) in Itali: mixture of burnt silicate and
lime , from volcanic stuff ,volcanic tufa.
6. What is Portland cement
• It is the mixture of fine powder at definite
ratio of calcium aluminate and hydraulic
(jalbahi) calcium silicate when come in
contact with water , hardening to make
strong concrete.
7. Types of Portland cement
• Depending upon the rate of setting ,heat evolution and strength characterstics, Portland
cement is of various types;
Type 1. regular Portland cements- generally used to make concrete ,e.g . white cement
,which contain small amount of Fe2O3.
Type 2. modified Portland cements-used where waters heat neutralization is necessary.it
produced for the neutralized reaction of sulfate.
Type 3. high early strength Portland cements-ratio of lime and sand is greater than
regular Portland cement . contain greater tri calcium silicate and quickly hard than regular
Portland cements. Used appropriate for road construction.
Type 4. low heat Portland cements-contain high rate of tetra calcium aluminate ferrite
and di calcium silicate. low heat emit during setting.
Type 5. sulfate resisting Portland cements-resist sulfate reaction. contain tetra calcium
alumina ferrite in high rate and tri calcium aluminate in low rate than regular Portland
cement .
8. Other types of cement
Acid resisting cement- capable of resisting corrosion by acids in the post hardening stage.
It is used in concrete and reinforced concrete structures to be exposed to corrosive action of
mineral and organic acids.
White cement- the color of the ordinary Portland cement is greyish-black due to presence of
iron oxide present. If iron oxide can be avoided by suitable selection of raw materials and
produce white cement.
Colored cement- obtained by mixing white or grey Portland cement with suitable colored
pigments. For getting blue, green, black and red cements, the pigments that are respectively
cobalt blue, chromium oxide, carbon black and iron oxide.
9. Raw materials for the manufacture of portland
cement
Limestone: CaO, Fe2O3
Clay: SiO2, Al2O3
The raw materials include
a) Calcareous materials: eg.limestone (containing 65-80%
CaCO3), calcium carbonate sludge, marl, chalk and
alkali waste.
b) Siliceous or Argillaceous materials: e.g silica, iron oxide
and alumina.
10.
11. Cement manufacturing process
• Two process:
1.Wet process: older and used mostly in INDIA & EUROPE
2. Dry process: invented in America and used there
The choice between two process is usually govern by the following factors
1.Physical condition of available raw materials.
2.Climate surrounding the place of manufacture
3.Cost of fuel.
12. Comparison between dry and weight process
• If limestone and clay are soft, climate is fairly moist, and the fuel is cheap, the wet process is
preferred.
• The dry process is employed, if the limestone and clay are hard.
• Wet process is more common and is almost universally employed for the manufacture of
cement.
• Dry process is slow and cement produced is of low quality.
• In wet process, the fuel consumption is higher, process is comparatively faster, the cement
produced is of superior quality.
13. • Manufacture of Portland cement
Figure: Manufacture of Portland cement
14.
15. Clinker
1.Raw materials are crushed, screemed & stockpiled.
2.Raw materials are mixed with definite proportions to obtain
“raw mix”. They are mixed either dry (dry mixing) or by water
(wet mixing).
3.Prepared raw mix is fed into the rotary kiln.
4.As the materials pass through the kiln their temperature is rised
upto 1300-1600 °C. The process of heating is named as
“burning”. The output is known as “clinker” which is 0.15-5 cm
in diameter. Clinker is cooled & stored.
5.Clinker is ground with gypsum (3-6%) to adjust setting time.
6.Packing & marketting.
16. Reaction at the kiln
• Evaporation zone (100-500)c: To remove crystal water.
• Calcining water (600-900)c: To break Calcium carbonate to form calcium oxide and
carbon dioxide.
• Reaction zone (900-1400)c: C2S, C3S, C3A, C4AF.
17. Reactions:
• CaCO3 = CaO + CO2
• 2CaO+SiO2 = 2CaOSiO2
• 3CaO+SiO2 = 3CaO.SiO2
• 3CaO+Al2O3 = 3CaO.Al2O3
• 4CaO+Fe2O3+Al2O3 = 4CaO.Fe2O3.Al2O3
Generally (2-3%) Gypsum is also added to the clinker before grinding. The function of
gypsum in cement is to slow down the time of setting.
C3A + 6H2O = C3A.6H2O + Heat
18. Function of cement manufacturing
constituents
• Lime( CaO)- is the principal constituents of cement. Excess of lime and lesser than needed both
reduce the strength of cement.
• Silica(SiO2)- imparts strength to cement.
• Alumina(Al2O3)- increase the rate of setting but excess of Alumina weakens the strength of cement.
• Gypsum(CaSO4.2H2O)- retards the rate of setting of cement and actually enhances the initial
setting time of cement.
• Iron oxide(Fe2O3)- gives color, strength and hardness to cement
• SO3- in excess reduces the soundness of cement.
• Alkalies- should be present in small amounts. In excess, they cause the cement to become
efflorescent.
19. Setting of cement
The various compounds that contributes to the heat of hardening are:
C3A>C3S>C4AF>C2S
Strength contribution of various compounds in Portland cement is ,
1 day C3A>C3S>C4AF>C2S
3 days C3A>C3S>C4AF>C2S
28 days C3A>C3S>C4AF>C2S
2years C2S>C3S>C4AF>C3A
20. Soundness of cement
Soundness is defined as the volume stability of cement paste.
The cement contain definite amount of free lime is called sound cement.
The cement contain lime greater or lower than definite amount is called
unsound cement.
If free lime in cement is not have required amount, the cement quality is
not well.
21. Uses
Main use is in the fabrication of concrete and mortars
Modern uses
Building (floors, beams, columns, roofing, piles, bricks, mortar, panels, plaster)
Transport (roads, pathways, crossings, bridges, viaducts, tunnels, parking, etc.)
Water (pipes, drains, canals, dams, tanks, pools, etc.)
Civil (piers, docks, retaining walls, silos, warehousing, poles, pylons, fencing)
Agriculture (buildings, processing, housing, irrigation)
USES
