Cement- it's manufacturing process, uses and types.

Introduction to Cement:

Cement is a binding material that is used in construction to bind other materials together. It is made by heating a mixture of limestone and clay to a high temperature and then grinding it into a fine powder. This powder, when mixed with water, sand, and aggregates, creates concrete, the most widely used construction material in the world. Cement is also used to make mortar, which is used to hold bricks and other masonry materials together. Cement is a key ingredient in many other building materials, including stucco, grout, and tile adhesive. It is an essential material for the construction industry and has played a vital role in the development of modern society. Cement has been used in construction for thousands of years, with the ancient Egyptians, Greeks, and Romans all using variations of the material. However, it wasn't until the 18th century that the modern version of cement, known as Portland cement, was developed by Joseph Aspdin. Portland cement is made by heating a mixture of limestone and clay at high temperatures and is the most used type of cement today.

With the advancement in technology, new types of cement with improved properties have been developed, such as high-strength cement, rapid-hardening cement, low-heat cement, etc. These types of cement have specific applications and are used to achieve specific results in construction projects. Overall, cement is an important and versatile building material that is essential for the construction of a wide range of structures.

The properties of cement are what make it such a valuable building material. It has a high compressive strength, meaning it can withstand a lot of pressure, and it also has a relatively low shrinkage rate, which means it doesn't change shape significantly when it dries. Additionally, it's a very versatile material that can be used in a wide range of construction applications, from bridges and buildings to roads and sidewalks.

Despite its many benefits, there are also some drawbacks to using cement. One major issue is its environmental impact. The production of cement is a very energy-intensive process that releases a significant amount of carbon dioxide into the atmosphere. Additionally, cement is a major contributor to air pollution, with particulate matter and other pollutants released during the production process.

Overall, cement is a vital component in the construction industry, and its properties make it a versatile, durable, and strong building material. However, it's important to consider the environmental impact of cement production and to find ways to reduce its carbon footprint and other negative effects.

The manufacturing process of Cement:

The manufacturing process of cement in India typically consists of the following steps:

1. Mining of raw materials: The main raw materials used in the production of cement are limestone, clay, and sand. These materials are mined from quarry sites and transported to the cement plant.
2. Crushing and grinding of raw materials: The raw materials are first crushed and then ground into a fine powder in a crusher and a roller mill, respectively.
3. Proportioning and grinding of raw meal: The fine powder obtained in the previous step is proportioned with gypsum and other additives as per the desired chemical composition of cement. This mixture is then ground in a ball mill to produce a fine powder called a raw meal.
4. Burning of raw meal: The raw meal is then fed into a kiln where it is heated to a temperature of around 1450 degrees Celsius. This process, known as clinkering, results in the formation of clinker.
5. Grinding of clinker: The clinker obtained from the kiln is cooled and then ground in a ball mill along with gypsum and other additives to produce the final product, cement.
6. Packing and dispatch: The cement produced is then packed in bags or bulk and dispatched to various construction sites.
7. Quality control: Indian Standards have set the guidelines for the quality control of cement. Quality control tests are carried out at every stage of the production process to ensure that the final product meets the required standards.

It is important to note that the manufacturing process of cement can vary depending on the specific type of cement being produced, such as Portland cement, Pozzolanic cement, etc. Additionally, some cement plants may also use alternative raw materials and methods such as the use of waste materials or the use of a dry process instead of a wet process.

Composition of Portland cement

Portland cement is a type of hydraulic cement that is made by grinding clinker (a mixture of limestone, clay, and other materials) and gypsum. The chemical composition of Portland cement varies depending on the manufacturing process, but typically includes the following ingredients:

• Calcium Oxide (CaO): This component is commonly known as lime and is obtained from limestone or chalk. It is the most important ingredient in Portland cement, and typically makes up about 60-65% of the total composition.
• Silicon Dioxide (SiO2): This component is commonly known as silica and is obtained from clay or sand. It makes up about 20-25% of the total composition.
• Aluminium Oxide (Al2O3): This component is commonly known as alumina and is obtained from clay or bauxite. It makes up about 5-8% of the total composition.
• Iron Oxide (Fe2O3): This component is commonly known as iron oxide and is obtained from iron ore. It makes up about 3-5% of the total composition.
• Sulphur Trioxide (SO3): This component is commonly known as sulphate and is obtained from gypsum. It makes up about 1-3% of the total composition.
• Magnesium Oxide (MgO): This component is commonly known as magnesia and is obtained from dolomite or magnesite. It makes up about 1-2% of the total composition.

Additionally, trace amounts of other materials, such as titanium dioxide and chromium oxide, may also be present in Portland cement. The exact composition will depend on the source of the raw materials and the manufacturing process used.

Hydration Reaction

Hydration reaction refers to the chemical reaction that occurs between the cement and water, which leads to the formation of a solid, hardened mass. The main components of Portland cement, tricalcium silicate, dicalcium silicate, and tricalcium aluminate, react with water to form a series of compounds, including calcium silicate hydrate (C-S-H) and calcium hydroxide (CH).

The reaction starts with the dissolution of the cement particles in water, followed by a nucleation process where new solid phases are formed, and finally the growth of the solid phases to form the hardened cement paste. The reaction is exothermic, meaning it releases heat, and it can be divided into two stages: the induction period and the acceleration period. The induction period is the time it takes for the initial reaction to begin, while the acceleration period is the period of rapid reaction and heat release.

The hydration reaction continues over time, resulting in the formation of a microstructure that is composed of C-S-H and CH. The C-S-H is the primary binding phase that provides the mechanical strength of the cement paste, while the CH acts as a filler and helps to regulate the setting time of the cement. The hydration reaction also leads to the formation of other compounds such as ettringite and mono sulphate, which can contribute to the expansion and cracking of the cement paste if formed in excess.

Setting Time of Cement:

Setting time is the time it takes for cement to harden and gain strength after being mixed with water. It is an important property of cement as it determines the time frame within which the concrete should be placed and finished. There are two types of setting time: initial setting time and final setting time.

Initial setting time, also known as initial stiffening time, is the time taken for cement to lose its plasticity after water is added. This time is determined by Vicat’s apparatus method, which measures the time it takes for a needle to penetrate and cease at a specific depth. The initial setting time of Portland cement is typically around 30-45 minutes.

Final setting time, also known as final stiffening time, is the time measured from the instant when the water is added to the cement and the time when the cement has gained enough strength to withstand a definite amount of pressure. This is determined by Gilmore’s needle method, which measures the time it takes for a needle to create a dent in the cement paste sample that does not recover upon removal of the needle. The final setting time of Portland cement is typically around 10-12 hours.

It is important to note that the setting time of cement can be influenced by factors such as temperature, humidity, and the type and amount of cementitious materials used.

Contribution of Bogue’s Compounds on Setting and Hardening of cement:

Portland cement is composed of several compounds, including tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetra-calcium alluminoferrite. Each of these compounds contributes to the properties of the final concrete in different ways.

1. Tricalcium silicate, also known as C3S, is responsible for the initial set and early strength development of concrete. It hydrates quickly, forming calcium silicate hydrate (CSH) and contributing to the strength of the concrete in the first few days after it is mixed.
2. Dicalcium silicate, also known as C2S, hydrates more slowly than C3S, but it continues to contribute to strength development for several weeks.
3. Tricalcium aluminate, also known as C3A, and tetra calcium alluminoferrite, also known as C4AF, are both responsible for the heat of hydration in cement. They both react with water to produce significant heat, which can be a problem in mass concrete pours. C3A also accelerates the initial set of concrete, and C4AF contributes to the final strength and durability of the concrete.
4. Tetra-Calcium Aluminofettite, also known as C3AF, is comparatively inactive.

Bogue compounds are the compounds formed during the hydration process of cement. The major Bogue compounds are C-S-H (Calcium Silicate Hydrate), C-A-H (Calcium Aluminate Hydrate), Ettringite and Hydrogarnet. Their composition and quantity vary depending on the type of cement used and the water-cement ratio. C-S-H is the most important contributor to the strength of the concrete, while C-A-H contributes to the durability and resistance to chemical attack. Ettringite and Hydrogarnet also contribute to the strength and durability of the concrete.

Types of Cement:

1. Ordinary Portland Cement (OPC)

Ordinary Portland Cement (OPC) is the most common type of cement used in construction. It is made by grinding together clinker and gypsum. It is available in different grades, such as 33, 43, and 53, which refer to the strength of the cement after 28 days of curing.

Features:

• Available in different grades (33, 43, and 53)
• Common and widely used in construction.
• Good strength and durability

Key Points:

• Made by grinding together clinker and gypsum.
• Grades refer to strength after 28 days of curing.
• Can be used in a variety of construction applications.

Uses:

• Building and construction of bridges, roads, buildings, and other structures
• Concrete production

Advantages:

• Widely available
• Inexpensive
• Good strength and durability

Disadvantages:

• Not suitable for certain harsh environments
• Not suitable for certain specialized construction project

2. Portland Pozzolana Cement (PPC):

Portland Pozzolana Cement, also known as PPC, is made by mixing Portland cement with pozzolanic materials such as fly ash, calcined clay, or silica fume. It has a lower heat of hydration and improved resistance to sulphates and acids compared to OPC. It is commonly used in the construction of dams, bridges, and marine structures.

Features:

• Lower heat of hydration Improved resistance to sulphates and acids Used in the construction of dams, bridges, and marine structures

Key Points:

• Made by mixing Portland cement with pozzolanic materials Contains 10-15% pozzolanic materials Sets and hardens at a slower rate than OPC Has lower strength than OPC.

Uses:

• Construction of dams Bridges Marine structures.

Advantages:

• Lower heat of hydration Improved resistance to sulphates and acids Used in the construction of dams, bridges, and marine structures 

Disadvantages:

• Has lower strength than OPC Slower setting and hardening time compared to OPC.

3. Rapid Hardening Cement:

Rapid Hardening Cement is a special type of cement that hardens faster than OPC. This type of cement is often used in the construction of precast products, pavements, and other projects where the time of construction is a critical factor.

Features:

• Rapid hardening
• Suitable for precast products and pavements

Key Points:

• Hardens faster than OPC.
• Used in projects where the time of construction is critical.

Uses:

• Precast products
• Pavements

Advantages:

• Rapid hardening
• Suitable for precast products and pavements

Disadvantages:

• Lower strength compared to OPC.
• Not suitable for massive

4. Blast Furnace Slag Cement (BFSC):

Blast Furnace Slag Cement, also known as BFSC, is made by mixing granulated blast furnace slag with Portland cement. It has a lower heat of hydration and improved resistance to sulphates and acids compared to OPC. It is commonly used in the construction of roads, bridges, and marine structures.

Features:

• Lower heat of hydration Improved resistance to sulphates and acids Used in the construction of roads, bridges, and marine structures.

Key Points:

• Made by mixing granulated blast furnace slag with Portland cement Contains 40-70% granulated blast furnace slag Sets and hardens at a slower rate than OPC and Has lower strength than OPC

Uses:

• Construction of roads Bridges Marine structures

Advantages:

• Lower heat of hydration Improved resistance to sulphates and acids Used in the construction of roads, bridges, and marine structures.

Disadvantages:

• Has lower strength than OPC Slower setting and hardening time compared to OPC.

5. Low Heat Cement:

Low Heat Cement is made by inter-grinding OPC clinker with a small quantity of gypsum and then granulated blast furnace slag. It generates less heat of hydration during setting which results in reduced thermal cracking and crazing. It is commonly used in the construction of massive concrete structures such as dams, large foundations, and other large concrete structures.

Features:

• Generates less heat of hydration during setting Reduced thermal cracking and crazing Used in the construction of massive concrete structures.

Key Points:

• Made by inter-grinding of OPC clinker with a small quantity of gypsum and granulated blast furnace slag Contains 5-15% granulated blast furnace slag Sets and hardens at a slower rate than OPC Has lower strength than OPC

Uses:

• Construction of massive concrete structures such as dams large foundations Other large concrete structures.

Advantages:

• Generates less heat of hydration during setting Reduced thermal cracking and crazing Used in the construction of massive concrete structures

 Disadvantages:

• Has lower strength than OPC Slower setting and hardening time compared to OPC.

6. Sulphate Resistant Cement

Sulphate Resistant Cement, also known as SRPC, is a special type of cement that is used in areas where the soil or water is high in sulphates. It is made by adding gypsum to the cement clinker during the grinding process. It has a lower rate of expansion, which makes it ideal for use in foundations, floors, and other parts of the building that are in contact with the ground.

Features:

• Lower rate of expansion
• Resistant to sulphate attacks

Key Points:

• Made by adding gypsum to cement clinker.
• Ideal for use in foundations and floors
• Used in areas with high sulphates in soil or water

Uses:

• Foundations
• Floors
• Other parts of the building in contact with the ground

Advantages:

• Lower rate of expansion
• Resistant to sulphate attacks

Disadvantages:

• May have lower strength than OPC.
• Limited availability

7. Fly Ash Cement:

Fly Ash Cement, also known as FAC, is made by grinding fly ash, a by-product of coal combustion, with clinker and gypsum. It has a lower carbon footprint compared to OPC and has a higher resistance to sulphate attacks. It is commonly used in the construction of marine structures, foundations, and roads.

Features:

• Lower carbon footprint compared to OPC.
• Higher resistance to sulphate attacks
• Used in marine structures, foundations, and roads.

Key Points:

• Made from fly ash, a by-product of coal combustion.
• A model with clinker and gypsum
• Sets and hardens slowly.
• Has lower strength than OPC.

Uses:

• Marine structures
• Foundations
• Roads

Advantages:

• Lower carbon footprint compared to OPC.
• Higher resistance to sulphate attacks

Disadvantages:

• Lower strength than OPC
• Sets and hardens slowly.

8. Super Sulphate Cement:

Super Sulphate Cement, also known as SSC, is made by adding a large amount of gypsum to OPC during the grinding process. It has a higher resistance to sulphate attacks and has a lower heat of hydration compared to OPC.

Features:

• Higher resistance to sulphate attacks
• Lower heat of hydration

Key Points:

• It is made by adding gypsum to OPC during grinding.
• It has a higher resistance to sulphate attacks.
• It has a lower heat of hydration compared to OPC.

Uses:

• Construction in areas with high sulphate content in soil or water
• Repair and rehabilitation of concrete structures

 Advantages:

• Higher resistance to sulphate attacks
• Lower heat of hydration

Disadvantages:

• Lower strength compared to OPC.
• Not suitable for massive concrete structures

9. Special Cement:

Special cement includes cement like quick setting cement, low-heat cement, coloured cement, etc. They are manufactured by adding special chemical compounds to the raw materials during the grinding process.

Features:

• Quick setting
• Low heat of hydration
• Can be coloured.

Key Points:

• Manufactured by adding special chemical compounds to raw materials during grinding.
• Quick setting
• Low heat of hydration
• Can be coloured.

Uses:

• Construction of bridges, roads, and other structures
• Repair and rehabilitation of concrete structures
• Decorative concrete

Advantages:

• Quick setting
• Low heat of hydration
• Can be coloured.

Disadvantages:

• Lower strength compared to OPC.
• Not suitable for massive concrete structures

10. Natural Cement:

Natural cement is made from natural materials such as limestone and clay. They have a lower strength compared to OPC and are not commonly used in construction today.

Features:

• Made from natural materials.
• Lower strength

Key Points:

• Made from natural materials such as limestone and clay.
• Lower strength compared to OPC.
• Not commonly used in construction today

Uses:

• Historically used in the construction of buildings and structures

Advantages:

• Made from natural materials.

Disadvantages:

• Lower strength compared to OPC.
• Not commonly used in construction today

11. High Alumina Cement:

High Alumina Cement, also known as Calcium Aluminate Cement, is made from limestone and bauxite. It contains a higher percentage of alumina (about 40-50%) compared to OPC. It has a lower heat of hydration and a higher resistance to chemical attacks. It is used in the construction of refractory linings, and furnace beds, and in the manufacture of precast products.

Features:

• High resistance to chemical attacks
• Lower heat of hydration
• Used in refractory linings and furnace beds.
• Used in the manufacture of precast products.

Key Points:

• It is made from limestone and bauxite.
• Contains 40-50% alumina.
• Sets and hardens rapidly.
• Has lower strength than OPC.
• Not suitable for massive concrete structures

Uses:

• Furnace linings
• Precast products
• Refractory linings
• Furnace beds
• Flooring
• fireproofing
• Protective linings

Advantages:

• High resistance to chemical attacks
• Lower heat of hydration
• Used in refractory linings and furnace beds.
• Used in the manufacture of precast products.

Disadvantages:

• Lower strength than OPC
• Not suitable for massive concrete structures
• Sulphate Resistant Cement

12. Oil well Cement:

Oil Well Cement, also known as API Class G cement, is a type of cement that is specifically designed for use in oil and gas wells. It is made from a blend of ordinary Portland cement, ground granulated blast furnace slag, and pozzolanic materials such as fly ash or silica fume. It is formulated to have a high resistance to the high temperatures and pressures found in oil and gas wells, as well as to resist the corrosive effects of the fluids found in these wells.

Features:

• High resistance to high temperatures and pressures
• Resistant to corrosive effects of fluids found in oil and gas wells.
• Formulated to meet API (American Petroleum Institute) standards.

Key Points:

• Made from a blend of ordinary Portland cement, ground granulated blast furnace slag, and pozzolanic materials.
• Designed specifically for use in oil and gas wells.
• Can be formulated to meet the specific needs of different types of oil and gas wells.

Uses:

• Cementing of oil and gas wells
• Plugging and abandonment of wells

Advantages:

• High resistance to high temperatures and pressures
• Resistant to corrosive effects of fluids found in oil and gas wells.
• Formulated to meet API standards.

Disadvantages:

• Not suitable for general construction use
• Higher cost compared to ordinary Portland cement.

Uses of Cement:

Cement has a wide range of uses in the construction industry. Some of the most common uses of cement include:

1. Concrete production: Cement is an essential ingredient in the production of concrete. Concrete is a mixture of cement, water, and aggregate (sand, gravel, or crushed stone) that is used as a building material for foundations, walls, floors, bridges, and other structures.
2. Mortar production: Cement is also used to make mortar, which is a mixture of cement, water, and sand. Mortar is used to bond bricks and other masonry units together in the construction of walls and other structures.
3. Plastering: Cement is also used in the production of plaster, which is a mixture of cement, water, and sand. Plaster is used to finish the interior and exterior surfaces of buildings.
4. Road construction: Cement is used in the construction of roads and highways as a binder for aggregate materials such as gravel, sand, and crushed stone.
5. Dams and other hydraulic structures: Cement is used in the construction of dams, locks, and other hydraulic structures to provide stability and water resistance.
6. Marine construction: Cement is used in the construction of ports, harbours, and other marine structures to provide stability and water resistance.
7. Pipe and precast products: Cement is used in the production of pipes and precast products such as manholes, drainage structures, and other underground structures.
8. Oil and gas well cementing: Cement is used to secure the steel casing that lines the good bore and to seal the annular space between the casing and the good bore.
9. Other industrial uses: Cement has various industrial uses such as in the production of glass, and ceramics, and as a binding agent in foundry sands.
10. Art and sculpture: Cement is also used in the art world to create sculptures and other decorative objects.

Cement has many other uses; these are some of the most common.

Sustainability:

Sustainability in the cement industry involves reducing the environmental impact of the manufacturing and use of cement, while also meeting the demands for cement in a growing global population.

• Energy efficiency: One of the main ways the cement industry can improve sustainability is by reducing the energy required to produce cement. This can be done through better kiln design, using alternative fuels, and increasing the use of waste heat recovery systems.
• Carbon dioxide emissions: The cement industry is a significant source of carbon dioxide emissions, largely due to the high temperature required to produce cement. Technologies such as carbon capture and storage can be used to reduce emissions.
• Use of alternative materials: The use of alternative materials, such as fly ash and slag, can reduce the number of raw materials required for cement production, thus reducing the environmental impact.
• Recycling of waste: The recycling of waste materials, such as used tires, can also be used as fuel in cement production.
• Water conservation: The cement industry also has a significant water footprint, and water conservation measures can be implemented to reduce this impact.
• Life Cycle Assessment (LCA): Life cycle assessment is a tool used to evaluate the environmental impact of a product or service throughout its entire life cycle. This can be used to identify areas for improvement in the cement industry.
• Sustainable design: In the construction industry, sustainable design principles can be applied to the use of cement-based materials, such as using fly ash in concrete to reduce the environmental impact and designing buildings to reduce energy use.

Overall, sustainability in the cement industry involves a combination of technical solutions, process improvements, and changes in behaviour. With new technologies and approaches, the industry can work towards reducing its environmental impact while meeting the growing demand for cement.