Types of cement

INTRODUCTION

TYPE OF CEMENT: A cement is a binder, a substance that sets and hardens and can bind other materials together. The word “cement” can be traced back to the Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were later referred to as cementum, cimentum, cement, and cement.

Cements used in construction can be characterized as being either hydraulic or non-hydraulic, depending upon the ability of the cement to set in the presence of water.

Non-hydraulic cement will not set in wet conditions or underwater; rather, it sets as it dries and reacts with carbon dioxide in the air. It can be attacked by some aggressive chemicals after setting.

Hydraulic cements (e.g., Portland cement) set and become adhesive due to a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack. This allows setting in wet condition or underwater and further protects the hardened material from chemical attack.

The most important uses of cement are as a component in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material.

 TYPES OF CEMENT

The following are the types of cement that are in practice:

1. Rapid Hardening Cement
2. Quick setting cement
3. Low Heat Cement
4. Sulphates resisting cement
5. Blast Furnace Slag Cement
6. High Alumina Cement
7. White Cement
8. Coloured cement
9. Pozzolanic Cement
10. Air Entraining Cement
11. Hydrographic cement

Rapid hardening cement: As the name indicates it develops the strength rapidly. This cement develops at the age of three days, the same strength as that expected of Ordinary Portland cement at seven days. The rapid rate of development of the strength is due to the higher fitness and higher C₃S and lower C₂ Used for the Road repair work, early removal of the formwork, Cold weather concrete.

Sulphate resisting cement: Ordinary Portland cement is successible to the sulphate attack. Sulphate react with the free calcium hydroxide to form calcium sulphate and the hydrate of calcium aluminate to form calciumsulphoaluminates., the volume of which is approximately 227% of the volume of the original aluminates. Their expansion results in cracks. To remedy this. The use of the cement with the low C₃A is recommended. Such cement with the low C₃A and content is known as the Sulphate resisting cement. Used for Marine condition, Foundation in soil infested with sulphates and Concrete used for the fabrication of pipes etc

Quick setting cement: As the name indicates this type cement set quickly. This property is brought out by reducing the gypsum content at the time of the clinker grinding. This cement is required to mix, place and compacted very easily. Used for the underwater construction.

Super sulphated cement: Super sulphated cement is manufactured by grinding together a mixture of 80 to 85 % of the granulated slag, 10 to 15 % of the hard burnt gypsum, and 5% Portland cement clinker. This cement is high sulphate resistant. Because of this property it is used for the Foundation where chemically aggressive condition exists.

Low heat cement: Hydration of the cement is exothermic process which liberates high quantity of the heat. This will cause the formation of the cracks. A low heat evolution is brought by Reducing the C₃A and C₃S which are the compounds evolving the greater heat of hydration and increasing C₂ Rate of evolution of heat of hydration will therefore will be less and evolution of heat will extend over a large period. Therefore Low heat cement rate of the development of the strength is very low. Used for the mass construction works

Table below shows different types of cement, their composition and uses:

Types of Cement	Composition	Purpose
Rapid Hardening Cement	Increased Lime content	Attains high strength in early days it is used in concrete where form work are removed at an early stage.
Quick setting cement	Small percentage of aluminium sulphate as an accelerator and reducing percentage of Gypsum with fine grinding	Used in works is to be completed in very short period and concreting in static and running water
Low Heat Cement	Manufactured by reducing tri-calcium aluminate	It is used in massive concrete construction like gravity dams
Sulphates resisting Cement	It is prepared by maintaining the percentage of tricalcium aluminate below 6% which increases power against sulphates	It is used in construction exposed to severe sulphate action by water and soil in places like canals linings, culverts, retaining walls, siphons etc.,
Blast Furnace Slag Cement	It is obtained by grinding the clinkers with about 60% slag and resembles more or less in properties of Portland cement	It can used for works economic considerations is predominant.
High Alumina Cement	It is obtained by melting mixture of bauxite and lime and grinding with the clinker it is rapid hardening cement with initial and final setting time of about 3.5 and 5 hours respectively	It is used in works where concrete is subjected to high temperatures, frost, and acidic action.
White Cement	It is prepared from raw materials free from Iron oxide.	It is more costly and is used for architectural purposes such as pre-cast curtain wall and facing panels, terrazzo surface etc.,
Coloured cement	It is produced by mixing mineral pigments with ordinary cement.	They are widely used for decorative works in floors
Pozzolanic Cement	It is prepared by grindin pozzolanic clinker with Portland cement	It is used in marine structures, sewage works, sewage works and for laying concrete under water such as bridges, piers, dams etc.,
Air Entraining Cement	It is produced by adding indigenous air entraining agents such as resins, glues, sodium salts of Sulphates etc during the grinding of clinker.	This type of cement is specially suited to improve the workability with smaller water cement ratio and to improve frost resistance of concrete.
Hydrographic cement	It is prepared by mixing water repelling chemicals	This cement has high workability and strength

REFERENCES

Robert G. Blezard, “The History of Calcareous Cements” in Hewlett, Peter C., ed.. Leaʼs chemistry of cement and concrete. 4. ed. Amsterdam: Elsevier Butterworth-Heinemann, 2004. 1-24. Print.

Brabant, Malcolm (12 April 2011). Macedonians created cement three centuries before the Romans, BBC.

Hill, Donald (1984). A History of Engineering in Classical and Medieval Times, Routledge, p. 106, ISBN 0415152917.

Ridi, Francesca (April 2010). “Hydration of Cement: still a lot to be understood” (PDF). La Chimica l’Industria (Società Chimica Italiana) (3): 110–117.