Cement Manufacturing and Properties

Raw Materials of Cement

• Limestone (CaCO3) is the primary source of calcium oxide
• Clay (SiO2, Al2O3, Fe2O3) is the primary source of silicon dioxide, aluminum oxide, and iron oxide
• Other raw materials include silica, alumina, and iron oxide

Ingredients of Cement and their Functions

• Calcium oxide (CaO): provides strength and binding properties
• Silicon dioxide (SiO2): provides durability and resistance to weathering
• Aluminum oxide (Al2O3): helps in regulating setting and hardening
• Iron oxide (Fe2O3): provides color and strength
• Gypsum (CaSO4.2H2O): regulates setting and hardening

Wet Process of Manufacturing of Cement

• Crushing and grinding of raw materials
• Mixing of raw materials in a kiln
• Burning at high temperatures (1450°C) to produce clinker
• Grinding of clinker with gypsum to produce cement

Properties of Cement

Setting and Hardening

• Cement sets and hardens when mixed with water
• Setting: formation of a hard, rigid mass
• Hardening: strengthening of the set material over time

Heat of Hydration

• Exothermic reaction between cement and water
• Releases heat, which can cause cracks in concrete

Soundness of Cement

• Ability of cement to resist volumetric changes
• Ensures that concrete does not shrink or expand excessively

Raw Materials of Cement

• Limestone (CaCO₃) is the primary component, providing calcium oxide (CaO)
• Clay (SiO₂, Al₂O₃) provides silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃)
• Silica (SiO₂) is present in the form of sand or quartz
• Iron oxide (Fe₂O₃) is typically present in small amounts
• Gypsum (CaSO₄.2H₂O) is added to regulate setting time

Ingredients of Cement and their Functions

• Calcium oxide (CaO): provides strength and hardness
• Silicon dioxide (SiO₂): helps in strengthening and providing durability
• Aluminum oxide (Al₂O₃): assists in regulating setting time
• Iron oxide (Fe₂O₃): provides color and helps in regulating setting time
• Gypsum (CaSO₄.2H₂O): regulates setting time and provides workability

Wet Process of Manufacturing of Cement

• Crushing and grinding of raw materials to produce a uniform powder
• Mixing of raw materials in the desired proportion
• Grinding of the mixture into a fine powder, called raw meal
• Burning the raw meal in a rotary kiln at high temperature (1450°C)
• Cooling the resulting clinker
• Grinding the clinker with gypsum to produce cement

Properties of Cement

Setting and Hardening

• Setting: the process of cement changing from a liquid to a solid state
• Hardening: the process of cement becoming stronger and more durable over time

Heat of Hydration

• The heat generated during the hydration reaction between cement and water
• CaO + H₂O → Ca(OH)₂ + heat
• Heat of hydration affects the setting and hardening of cement

Soundness of Cement

• The ability of cement to withstand the forces of expansion and contraction without disintegrating
• Soundness is tested by measuring the expansion of a cement paste sample

Cement: An Overview

• Cement is a binding material used in construction.

Raw Materials

• The primary raw materials used in cement production are limestone, clay, and silica.
• Other raw materials include iron ore, bauxite, and gypsum.

Ingredients of Cement and their Functions

• Limestone (CaCO3): provides calcium oxide, essential for cement's binding properties.
• Clay (SiO2, Al2O3): provides silica and alumina, which react with calcium oxide to form cement.
• Silica (SiO2): helps to strengthen cement.
• Iron ore (Fe2O3): adds color and helps to strengthen cement.
• Bauxite (Al2O3): provides alumina, which reacts with silica to form cement.
• Gypsum (CaSO4): helps to regulate cement's setting time.

Wet Process of Manufacturing Cement

• The wet process involves mixing raw materials with water to form a slurry.
• The slurry is then fed into a klin, where it is heated to a high temperature, producing cement clinker.
• The clinker is then ground into a fine powder to produce cement.

Properties of Cement

Setting and Hardening

• Cement sets and hardens due to hydration reactions between cement particles and water.
• The setting process is complete when the cement has reached its final shape and strength.

Heat of Hydration

• The heat of hydration is the heat generated during the hydration reaction.
• It is an important factor in cement's strength and durability.

Soundness of Cement

• Soundness refers to cement's ability to withstand chemical reactions and maintain its strength.
• It is an important property of cement, as it affects the durability of structures.