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Module: 5 Lecture: 23 Cement industries

Dr. N. K. Patel

Module: 5

Lecture: 23


7. Puzzolana cement

Puzzolana is a volcanic powder. It is found in Italy near Vesuvius. It resembles surkhi which is prepared by burning bricks made from ordinary soils. It can also be processed from shales and certain types of clays. Puzzolana material should be used in between10 to 30%.


Evolves less heat during setting

Possesses higher tensile strength

Imparts higher degree of water tightness

Attains comprehensive strength with age

Can resist action of sulfates

Imparts plasticity and workability to mortar and concrete prepared from it.

Offers great resistance to expansion

It is cheap


Compressive strength in early days is less

Possesses less resistance to erosion and weathering action

This cement is used to prepare mass concrete of lean mix and for marine structures. It is also used in sewage works and for laying concrete under water.

8. Hydrophobic cement

It contains hydrophobic admixtures such as acidol, naphthelene soap, oxidized petroleum etc., which decrease the wetting ability of cement grains and form a thin film around cement grains. When water is added to hydrophobic cement, the absorption films are torn off the surface and they do not in any way, prevent the normal hardening of cement. However, in initial stage, the gain in strength is less as hydrophobic films on cement grains prevent the interaction with water. However, its strength after 28 days is equal to that of ordinary Portland cement.

When hydrophobic cement is used, the line fine pores in concrete are

Module: 5 Lecture: 23 Cement industries

Dr. N. K. Patel


9. Expanding cement

It is produced by adding an expanding medium like sulfoaluminate and establishing agent to ordinary cement. Hence this cement expands whereas other cements shrink.

It is used for the construction of water retaining structures and for repairing the damaged concrete surfaces.

10. Low heat cement

Considerable heat is produced during the setting action of cement. It contains lower percentage of tricalcium aluminate (C3A) and higher percentage of dicalcium silicate (C2S) which reduce the amount of heat produced.

This type of cement possesses less compressive strength. Initial setting time is about one hour and usual setting time is about 10 hours. It is mainly used for mass concrete work.

11. Quick setting cement

It is produced by adding a small percentage of aluminium sulfates and by finely grinding the cement. Percentage of gypsum or retarder for setting action is also greatly reduced. Addition of aluminium sulfate and fineness of grinding accelerate the setting of cement. The setting action of cement starts within five minutes addition of water and it becomes hard like stone in less than 30 minutes. Mixing and placing of concrete should be completed within very short period. This cement is used lay concrete under static water or running water.

12. Sulfate resisting cement

In this cement percentage of tricalcium aluminate is kept below 5 to 6% which increase in resisting power against sulphates.

This cement is used for structures which are likely to be damaged by severe alkaline conditions such as canal linings, culverts, syphons etc.


Raw materials

Basis: 1000kg of cement


= 100-300kg


= 1200-1300kg


= 30-50kg

Module: 5 Lecture: 23 Cement industries

Dr. N. K. Patel


= 250-400kg


= 3000kg


= 80kWH

The most commonly used composition on % basis by mass for the Portland cement manufacturing is given below


% range by mass

Lime ( CaO)


Silica (SiO2)


Alumina (Al2O3)


Iron oxide (Fe2O3)


Magnesium oxide (MgO)


Sulfur trioxide (SO3)


Alkali Oxide (Na2O + K2O)


Significance of constituents


Lime is also defined as non-hydraulic cement mainly consisting of calcium oxide and small amount of magnesium oxide. It is prepared by calcining the lime stone (CaCO3) at temperature that it will slake, when brought in contact with water. It is principal constituent of cement. Proper amount of lime is important as excess of it reduces the strength as well as lesser amount also reduces the strength and makes its quick setting. Lime is mainly used for white washing of mortar for joining bricks, metallurgy and glass industries.


It imparts strength to cement.


It works as an accelerator and makes the cement quick settling. However excess of alumina makes the cement unsound.

Gypsum (Calcium sulfate)

It retards the setting action of cement but enhances the initial setting time.

Iron oxide

It provides colour, strength and hardness of cement.


If present in small amount impart hardness and colour to cement

Module: 5 Lecture: 23 Cement industries

Dr. N. K. Patel

Sulfur trioxide

If present in small amount it imparts soundness to cement but excess of it is undesirable


Most of the alkalis present in raw materials are carried away by the flue gases during heating and cement contains only a small amount of alkalis. If present in excess causes the efflorescent to cement.