What is Cement? Types of Cement and its uses
What is Cement?
Cement is a powder of lime, silica, iron oxide, alumina, and magnesium oxide burned together in a furnace and finely crushed and used as an ingredient of concrete and mortar. It is a substance used for construction that hardens, sets, and sticks to other materials to bind them together. It is used to bind sand and aggregate together.
Types of cement →
- White Cement
- Low Heat Cement
- Quick Setting Cement
- Rapid Hardening Cement
- Coloured Cement
- High Alumina Cement
- Ordinary Portland Cement (OPC)
- Portland Pozzolana Cement (PPC)
- Air Entraining Cement
- Expansive Cement
- Sulphate Resisting Cement
- Hydrophobic Cement
- Blast Furnace Slag Cement
White Cement →
- White cement or white portland cement or white ordinary Portland cement is similar to ordinary grey cement except for its colour.
- Prepared from raw materials free from iron oxide.
- It is used for architectural purposes such as facing panels, terrazzo surfaces, curtain walls, etc.
- Also used for interior or exterior decorative works like floor finishing, facing slabs, the path of the garden, swimming pool.
- Used to fix marbles and glazed tiles.
- Costlier than ordinary portland cement (OPC).
Low Heat Cement →
- It is a specially customized cement that generates low heat of hydration during setting.
- Less reactive than ordinary portland cement (OPC).
- It is suitable for mass concrete construction like gravity dams, large footings, wind turbine plinths, large raft slabs as the low heat of hydration prevents the cracking of concrete due to heat.
- A small quantity of Tricalcium Aluminate makes the concrete to generate low heat of hydration.
- Its initial setting time is higher than ordinary portland cement (OPC).
- Low heat cement contains 5% of Tricalcium ALuminate(C3A) and 46% of Dicalcium Silicate (C2S).
- The amount of water required for hydration is low.
- The cost of the cement is higher than that of ordinary cement and needs more curing time.
- It cannot be used in cold weather conditions.
Quick Setting Cement →
- It is used where the quick setting is required.
- Setting time is very high as compared to ordinary portland cement (OPC).
- The initial setting time is 5 minutes and the final setting time is 30 minutes.
- Manufactured by grinding cement clinkers with Aluminium Sulfate which accelerates the setting time of cement.
- Used in underwater constructions such as river bridges.
- We use this cement in higher-temperature areas where water evaporates easily.
- Due to the quick setting, a large amount of heat discharged during the hydration of cement may lead to shrinkage cracks.
Rapid Hardening Cement →
- It is also called high early strength cement.
- The initial setting time is 30 minutes and the final setting time is 600 minutes.
- The specific surface is greater than 3250 cm2/gm.
- It is mostly used to construct roads where the traffic cannot be suspended for a long time.
- Also used in manufacturing electric poles, precast slabs, etc.
- Shrinkage during curing and hardening of cement is less.
- It is costlier than OPC.
Coloured Cement →
- It is prepared by grinding 5 to 10 per cent of suitable shade with white or ordinary grey portland cement.
- The cobalt gives blue colour, the chromium oxide gives green colour, the iron oxide in different proportions gives red, yellow, or brown, the manganese dioxide gives brown or black coloured cement.
- It is used for the finishing of floors, artificial marbles, stair treads, external surfaces, textured panel faces, window sill slabs, etc.
High Alumina Cement →
- Manufactured by grinding clinkers formed by lime and bauxite.
- It has high refractoriness and high durability in sulphuric acid.
- It is used in the construction of sewage pipes, water pipes, factory drains and chimneys, coastal constructions, etc.
- Release great heat during setting, therefore not affected by frost.
- The initial setting time is more than 3.5 hours and the final setting time is about 5 hours, therefore it allows more time for mixing and placing operations.
Ordinary Portland Cement (OPC) →
- Ordinary portland cement is simply known as ordinary cement.
- It is the most common type of cement.
- OPC is a fine powder manufactured by heating clay minerals and limestone in a furnace to form clinkers, grinding the clinkers and add 2 to 3 per cent of gypsum.
- The initial setting time is 65 minutes and the final setting time is 275 minutes.
- The fineness of OPC is 330 kg/m2 and soundness is 2.5 mm.
- Specific gravity is 3.12 and bulk density is 830-1650 kg/m3.
- It has great resistance to shrinkage and cracking but less resistant to chemical attacks.
Portland Pozzolana Cement (PPC) →
- PPC is mainly used in hydraulic constructions.
- Reacts with calcium hydroxide to form a compound with cement properties.
- The initial setting time is 30 minutes and the final setting time is 600 minutes.
- The fineness of PPC should not be less than m2/kg.
- Drying shrinkage should not be higher than 0.15%.
- Lower rate of strength development than OPC.
- PPC is environment-friendly cement because the materials used in construction are made from natural recycled waste.
- It is used in prestressed and post stressed concrete members.
Air Entraining Cement →
- Air entraining cement is a different kind of cement that generates air bubbles in the cement or concrete.
- Air bubbles allow the space for concrete expansion due to freezing and melting and defend concrete from damage and cracks.
- The workability and compressive strength of concrete are affected by air-entrained concrete.
- Increased the workability of concrete without increasing the water-cement ratio.
- Compressive strength decreases automatically when the workability of concrete increasing.
- Air entrained concrete contains billions of microscopic air pockets and these air pockets relieve internal pressure on the concrete by creating a small air void for water to expand when it freezes.
Expansive Cement →
- When expansive cement is mixed with water creates a paste that tends to increase in volume to a greater degree than portland cement paste.
- It contains anhydrous tetra calcium alumino sulphate, which burns simultaneously with a portland cement composition or burns separately.
- It is a mixture of portland cement, calcium sulphate and calcium aluminate cement.
- Types of Expansive Cement:- (a) Type K (b) Type M (c) Type S
Sulphate Resisting Cement →
- It is a type of portland cement in which the amount of tricalcium aluminate (C3A) is controlled to lower than 5% and (2C3A+C4AF) lower than 25% which decreases the formation of sulphate salt.
- The possibility of sulphate attack on the concrete becomes lower due to the reduction of sulphate salt.
- A very small quantity of calcium aluminate is formed on hydration due to the very low range of tricalcium aluminate in sulphate resisting cement.
- The initial setting time of this cement is 80 minutes and the final setting time is 240 minutes.
- Increased pumpability and workability.
- Minimize the risk of corrosion of reinforced steel and maximize resistance to chloride ions.
- Provides a high level of structural integrity and concrete performance in highly aggressive sulphate and acidic environment.
- This cement is generally used in foundation, chimney, cooling towers, tetrapods, sea walls, sumps, drainage works, chemical industries, piling works, etc.
Hydrophobic Cement →
- It is also known as hydrographic cement.
- After grinding portland cement clinkers with a film-forming substance, we obtain this cement.
- The initial setting time of this cement is 30 minutes and the final setting time is 600 minutes.
- Water absorption of this cement is 0.3% to 1%.
- The fineness of this cement is 350 m2/kg.
- It is used in Manholes, Drainage system works, dams, retaining walls, water treatment plants, green roofs, parking structures, spillways, underwater constructions, etc.
- The strength of this cement is the same as ordinary portland cement.
Blast Furnace Slag Cement →
- It is a mixture of finely granulated blast furnace slag and ordinary portland cement.
- Constituents of the ground granulated blast furnace slag:-
- The initial setting time of blast furnace slag cement is 60 minutes and the final setting time is 600 minutes.
- The specific surface area of this cement is 4050 cm2/gm.
- The density of this cement is 3.04 gm/cm3.
- It is used in dams, foundations, bored piles, marine structures, retaining walls, river ports, tunnels, etc.
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