Cement is a glue which acts as a hydraulic binder. It is primarily used to bind fine sand and coarse aggregates together in concrete.
Cement is primarily used in construction for the production of concrete and mortar, and it is always mixed with other materials before use:
Cement mixed with water, sand and gravel forms concrete, which is what the vast majority of cement is used for.
Cement mixed with water, lime and sand forms mortar.
For its high hardness, rigidity and durability, comprehensive material sources, simple production process, low cost, high plasticity, and suitability for use in different types of natural environments, cement is the most used material in civil projects across the world.
Cement is characterized as either hydraulic or non-hydraulic. Hydraulic cements (e.g. Portland cement) harden when mixed with water. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g. lime and gypsum plaster) must be kept dry in order to retain their strength.
There are 27 types of common Cement which can be grouped into 5 general categories and 3 strength classes: ordinary, high and very high. In addition, some special Cements exist like sulphate resisting cement, low heat cement and calcium aluminate cement.
The most commonly used cement types for general construction work are:
Ordinary Portland Cement (OPC): 32.5, 42.5, 52.5 grade (OPC)
Portland Pozzolana Cement (PPC): Both Fly Ash and Calcined Clay based
Portland Slag Cement (PSC)
Special cements are cements that are manufactured for specific applications where normal cements may not be able to perform satisfactorily.
Low-alkali
Low-alkali cements are portland cements that contains a relatively small amount of sodium, potassium, or both; portland cements with a total content of alkalies (Na2O equivalent) not above 0.6 percent. These are used in concrete made with certain types of aggregates that contain a form of silica that reacts with alkalies to cause an expansion that can disrupt a concrete.
Cements Type I / II / III
Type I is ordinary Portland cement, and it is available in white or grey. Type II is a moderate sulfate resistant cement, important when concrete is cast against soil that has moderate sulfate levels. Type III is a high early strength cement
Clinker is the main ingredient used in the manufacture of Portland cement. Clinker is formed in lumps or nodules, usually 3-25mm in diameter, by sintering limestone and alumina-silicate (clay) during the cement kiln stage.
One of the main ingredients of cement. Natural Gypsum is a sulfate mineral compound of Calcium Sulfate Dihydrate. It has a wide variety of uses. Probably the major consumers of Gypsum at present is the Cement Industry. By weight about 4% to 6% Gypsum in crushed condition is utilized in Portland Cement Manufacture after mixing with Cement/Clinker Gypsum acts as a retarder and controls the setting time of cement.
Limestone is the main raw material for clinker and additive ingredient for cement.
Special cement used in the petroleum industry.
Coal is a combustible black or brownish-black sedimentary rock normally occurring in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, with smaller quantities of sulfur, oxygen and nitrogen. Coal is primarily used as a solid fuel to produce electricity and heat through combustion.
Bauxite is an aluminum ore and is the raw material in aluminum production. Typically, bauxite is classified in terms of its intended application: metallurgical, chemical, cement, etc. Bauxite is composed mainly of the minerals gibbsite Al(OH)₃, boehmite y-AlO(OH) and diaspore α-AlO(OH), with iron, clay and silica also present.
Pozzolana is a natural or artificial material which contains silica in the reactive form. It is a siliceous or siliceous and aluminous material that in itself possesses little or no cementitious value, but that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties.
