Cement

Cement

Contents

Define the term Cement 1

Recall different uses of Cement 2

Recall the Composition of Portland Cement 3

Recall the following Bouge’s Compound: i. Tricalcium aluminate ii. Tetra-calcium alumino-ferrite iii. Tricalcium silicate iv. Dicalcium silicate 5

Recall the following Test of Cement: i. Field Test, ii. Lab Test 6

Recall the following Processes of Manufacturing of Cement: i. Dry Process, ii. Wet Process 13

Compare Dry Cement and Wet Cement 14

Classify the Cement 15

Recall the following types of Cement: i. Ordinary Portland Cement, ii. Rapid hardening Portland Cement, iii. Calcium chloride Cement, iv. Quick setting Portland Cement, v. Low heat Portland Cement, vi. Portland pozzolana Cement, vii. Portland slag Cement 17

Recall the following types of Cement: viii. Sulphate Resisting Portland Cement, ix. Supersulphated Portland Cement, x. High alumina Cement, xi. Hydrophobic Cement, xii. White and coloured Portland Cement, xiii. Air entraining Cement 18

Define the term Cement

Cement is a binding material that is used in construction to hold other materials together. It is a powdery substance made by grinding together calcareous compounds like limestone and Argillaceous compounds like clay.

When cement is mixed with water, it undergoes a chemical reaction called hydration, in which the cement powder hardens and binds together the other materials in the mixture.

There are several different types of cement that are used in construction. The most common type is Portland cement, which is made by heating a mixture of limestone and clay to a high temperature and then grinding it into a fine powder. This type of cement is used for making concrete for structures such as bridges, buildings, and roads.

Other types of cement include:

  • Masonry cement, which is used for making mortar to hold bricks, blocks, and other masonry units together.
  • Oil Well cement, which is used to seal oil and gas wells
  • White cement, which is used for making decorative concrete and other architectural applications,
  • Pozzolanic cement, which can be made with pozzolanic materials, is a reactive silica-based material like volcanic ash or fly ash which can improve the strength and durability of the concrete.

Overall, the cement is a versatile binding material that plays a crucial role in construction. Its ability to harden and bind materials together underpins the strength and durability of concrete, which is used to create a wide variety of structures that are essential to modern civilization.

Recall different uses of Cement

Cement is a versatile binding material that is used in a wide range of construction applications. Some of the most common uses of cement include:

  1. Concrete: Cement is an essential ingredient in the production of concrete. When cement is mixed with water, it undergoes a chemical reaction called hydration, in which the cement powder hardens and binds together the other materials in the mixture. The resulting material is called concrete and is widely used in the construction of buildings, bridges, roads, and other structures.
  2. Mortar: Cement is also used to make mortar, which is a mixture of cement, sand, and water. Mortar is used to hold bricks, blocks, and other masonry units together in the construction of walls and other structures.
  3. Stucco: A type of exterior finish for buildings, is a mixture of cement, sand, and water, and it can be applied to the exterior of buildings to provide a decorative finish that is also weather-resistant.
  4. Oil and Gas Wells: Cement is used to seal and stabilize oil and gas wells to prevent leaks and protect the environment. It is also used to keep the well from caving in.
  5. Dam: Cement is a component of the construction of dams and other hydraulic structures. It is used to form the structure and core of the dam, and also used to seal the joints between the various sections of the dam.
  6. Screed and Grout: Cement is also used in flooring and tiling applications, such as screed and grout, which are used to level and smooth surfaces before applying flooring or tile.
  7. Soil Stabilisation: Cement can be used as a component in soil stabilization to improve the compressive strength and durability of soil layers.
  8. Paints and Coatings: Cement can also be used as an ingredient in paints and coatings, which can protect surfaces from weathering and other forms of wear and tear.

In conclusion, cement is an extremely versatile material that is used in a wide range of construction and industrial applications. Its unique properties make it an essential component in the creation of strong, durable structures and infrastructure, as well as in many other industrial and commercial applications.

Recall the Composition of Portland Cement

Portland cement is a type of cement that is made by heating a mixture of limestone and clay to a high temperature, and then grinding it into a fine powder. The composition of Portland cement is composed of several key components:

  1. Calcium oxide (CaO): also known as quicklime, is obtained by heating limestone (CaCO3) to high temperatures, It typically makes up around 60-70% of the raw materials used to make Portland cement.
  2. Silicon dioxide (SiO2): which is obtained from clay and makes up around 15-20% of the raw materials.
  3. Aluminum oxide (Al2O3): which also is obtained from clay, typically makes up around 5-8% of the raw materials.
  4. Iron oxide (Fe2O3): which is obtained from the raw materials, typically makes up around 3-5% of the raw materials.
  5. Sulphur trioxide (SO3): which is obtained as a byproduct of the heating process and typically makes up around 1-3% of the raw materials.

When water is added to Portland cement, it undergoes a chemical reaction called hydration. During hydration, the cement powder reacts with the water, forming a paste that binds together the other materials in the mixture. The paste then hardens, forming a solid material called concrete.

It’s worth mentioning that there are different variations of the Portland cement and slight variations in the composition based on the source of raw materials and type of the process used to make it .

In conclusion, Portland cement is a type of cement that is made from a mixture of limestone, clay, and other materials. The exact composition of Portland cement can vary depending on the source of the raw materials and the manufacturing process used, but it typically contains calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and sulfur trioxide in different proportions. These components are the key factors that give Portland cement its unique properties, such as its ability to harden and bind materials together.

Recall the following Bouge’s Compound: i. Tricalcium aluminate ii. Tetra-calcium alumino-ferrite iii. Tricalcium silicate iv. Dicalcium silicate

Bouge’s compound is a theoretical compound that was proposed by a French chemist named Louis Victor Pierre Raymond de Broglie, also known as the 7th duc de Broglie. It is a theoretical mix of four different minerals that are present in Portland cement. These minerals are:

  1. Tricalcium aluminate (C3A): This mineral is formed from the combination of calcium oxide (CaO) and aluminum oxide (Al2O3) present in the raw materials. It is responsible for the rapid strength development in the early stages of cement hydration. It also has a big influence on the colour of the cement, The high amount of C3A may lead to the formation of “sulfoaluminate” which can cause cement to set and harden very quickly.
    The Heat of Hydration of Tricalcium aluminate is 860 J/gm
  2. Tetra-calcium alumino-ferrite (C4AF): This mineral is formed from the combination of calcium oxide, aluminum oxide and iron oxide (Fe2O3) present in the raw materials. It is responsible for the heat of hydration, which is the heat generated during the cement hydration process.
    The Heat of Hydration of Tetra calcium alumni Ferrite is 420 J/gm
  3. Tricalcium silicate (C3S): This mineral is formed from the combination of calcium oxide and silicon dioxide (SiO2) present in the raw materials. It is responsible for the majority of the strength development in concrete.
    The Heat of Hydration of Tricalcium silicate is 500 J/gm
  4. Dicalcium silicate (C2S): This mineral is also formed from the combination of calcium oxide and silicon dioxide present in the raw materials. It is responsible for the strength development in concrete, but at a slower rate than C3S.
    The Heat of Hydration of Dicalcium silicate is 260 J/gm

It’s worth noting that the exact proportion of these minerals can vary depending on the type of cement, and that the hydration of these compounds is not a simple matter of mixing them together. The hydration is controlled by various factors, like temperature, humidity and the presence of other compounds like gypsum.

In conclusion, Bouge’s compound is a theoretical mix of four minerals that are present in Portland cement and other types of cement, those minerals are tricalcium aluminate, tetra-calcium alumino-ferrite, tricalcium silicate, and dicalcium silicate. Each of these minerals has a specific role in the cement hydration process, and together they give cement its unique properties, such as its ability to harden and bind materials together, and to develop strength over time.

Recall the following Test of Cement: i. Field Test, ii. Lab Test

Cement is an essential material in construction and as such it is important to evaluate its quality and properties before it is used in a construction project. There are two main types of tests that are used to evaluate the quality of cement, these are:

  1. Field Test: Field tests are tests that are performed on site during the construction process to check the quality of the cement used. These tests are usually simple and quick to perform and they provide a rough estimate of the quality of the cement. Some examples of field tests include:
    a. Date of Manufacturing: As the strength of cement reduces with age, the date of manufacturing of cement bags should be checked.

b. Cement Colour: The colour of cement should be uniform. It should be a typical cement colour i.e. grey colour with a light greenish shade.

c. Whether Hard Lumps are Formed: Cement should be free from hard lumps. Such lumps are formed by the absorption of moisture from the atmosphere.

d. Temperature Inside Cement Bag: If the hand is plunged into a bag of cement, it should be cool inside the cement bag. If a hydration reaction takes place inside the bag, it will become warm.

e. Smoothness Test: When cement is touched or rubbed in between fingers, it should give a smooth feeling. If it feels rough, it indicates adulteration with sand.

f. Water Sinking Test: If a small quantity of cement is thrown into the water, it should float some time before finally sinking.

g. The smell of Cement Paste: A thin paste of cement with water should feel sticky between the fingers. If the cement contains too much-pounded clay and silt as an adulterant, the paste will give an earthy smell.

h. Glass Plate Test: A thick paste of cement with water is made on a piece of a glass plate and it is kept under water for 24 hours. It should set and not crack.

i. Block Test: A 25mm × 25mm × 200mm (1”×1”×8”) block of cement with water is made. The block is then immersed in water for three days. After removal, it is supported 150mm apart and a weight of 15kg uniformly placed over it. If it shows no sign of failure the cement is good.

  1. Lab Test: Laboratory tests are tests that are performed in a laboratory to evaluate the quality of the cement. These tests are more detailed and accurate than field tests, but they also take longer to perform. Some examples of laboratory tests include:

The following tests are conducted on cement in the laboratory are as follows:

  1. Fineness Test
  2. Consistency Test
  3. Setting Time Test
  4. Strength Test
  5. Soundness Test
  6. Heat of Hydration Test
  7. Tensile Strength Test
  8. Chemical Composition Test1. Fineness test on cement
    The fineness of cement is responsible for the rate of hydration, rate of evolution of heat and the rate of gain of strength. Finer the grains more is the surface area and faster the development of strength. The fineness of cement can be determined by the Sieve Test or Air Permeability test.

    a. Sieve Test: Air-set lumps are broken, and the cement is sieved continuously in a circular and vertical motion for a period of 15 minutes. The residue left on the sieve is weighed, and it should not exceed 10% for ordinary cement. This test is rarely used for fineness.

Blaine Air Permeability Apparatus

b. Air Permeability Test: Blaine’s Air Permeability Test is used to find the specific surface, which is expressed as the total surface area in sq.cm/g. of cement. The surface area is more for finer particles.

2. Consistency test on cement: This test is conducted to find the setting times of cement using a standard consistency test apparatus, Vicat’s apparatus. Standard consistency of cement paste is defined as that water content which will permit a Vicat plunger of 10 mm diameter and 50 mm length to penetrate depths of 33-35 mm within 3-5 minutes of mixing.
Consistency Test Apparatus

The test has to undergo three times, each time the cement is mixed with water varying from 24 to 27% of the weight of cement. This test should be conducted at a constant temperature of 25°C or 29°C and at a constant humidity of 20%.

3. Setting Time of cement

Vicat’s apparatus is used to find the setting times of cement i.e., initial setting time and final setting time.

Initial Setting Time: For this test, a needle of 1 mm square size is used. The needle is allowed to penetrate into the paste (a mixture of water and cement as per the consistency test). The time taken to penetrate 33-35 mm depth is recorded as the initial setting time.

Vicat'S Apparatus

Final Setting Time: After the paste has attained hardness, the needle does not penetrate the paste more than 0.5 mm. The time at which the needle does not penetrate more than 0.5 mm is taken as the final setting time.

4. Strength test of cement: The strength of cement cannot be defined directly on the cement. Instead the strength of cement is indirectly defined on cement-mortar of 1:3. The compressive strength of this mortar is the strength of cement at a specific period.

5. Soundness test of cement

This test is conducted in Le Chatelier’s apparatus to detect the presence of uncombined lime and magnesia in cement.

6. Heat of Hydration Test

During the hydration of cement, heat is produced due to chemical reactions. This heat may raise the temperature of concrete to a high temperature of 50°C. To avoid these, in large scale constructions low-heat cement has to be used.

Hydration Test Apparatus

This test is carried out using a calorimeter adopting the principle of determining heat gain. It is concluded that Low-heat cement should not generate 65 calories per gram of cement in 7 days and 75 calories per gram of cement in 28 days.

7. Tensile Strength of Cement

This test is carried out using a cement-mortar briquette in a tensile testing machine. A 1:3 cement-sand mortar with the water content of 8% is mixed and moulded into a briquette in the mould.

Tensile Strength Apparatus

This mixture is cured for 24 hours at a temperature of 25°C or 29°C and in an atmosphere at 90% relative humidity.

The average strength for six briquettes tested after 3 and 7 days is recorded.

Chemical Composition Test

Different tests are conducted to determine the amount of various constituents of cement. The requirements are based on IS: 269-1998, is as follows:

  • The ratio of the percentage of alumina to that of iron oxide should not be less than 0.66.
  • Lime Saturation Factor (LSF), i.e., the ratio of the percentage to that of alumina, iron oxide and silica should not be less than 0.66 and not be greater than 1.02.
  • Total loss on ignition should not be greater than 4%.
  • Total sulphur content should not be greater than 2.75%.
  • Weight of insoluble residue should not be greater than 1.50%.
  • Weight of magnesia should not be greater than 5%.

Recall the following Processes of Manufacturing of Cement: i. Dry Process, ii. Wet Process

The manufacturing of cement involves a series of complex processes, and two of the most commonly used methods are the dry process and the wet process.

The dry process, also known as the “dry method,” is the most traditional method of cement production and dates back to the early 20th century. In this process, the raw materials, such as limestone, clay, and iron ore, are crushed and then fed into a rotary kiln. The rotary kiln is a large rotating cylinder that is heated to a high temperature, typically around 1450 degrees Celsius, by burning a fuel, such as coal. The raw materials are heated to a point where a chemical reaction takes place, resulting in the formation of clinker, which is the main component of cement. The clinker is then cooled and ground into a fine powder, which is known as cement. This process is called clinkerization

The wet process is a more modern method of cement production and involves the mixing of the raw materials with water before they are fed into the kiln. The water helps to form a slurry, which allows for better homogenization of the raw materials. The slurry is then fed into the kiln, where it is heated and a clinker is formed. The clinker is cooled and ground into a fine powder, just as in the dry process. The main difference between the two methods is the use of water in the wet process, which can lead to a more efficient mixing of the raw materials and a more homogeneous final product. However, the wet process is more energy-intensive and also generate more CO2 emission

Both of these processes have their own advantages and disadvantages. The dry process is more energy-efficient and generates less CO2 emissions, but it can result in a higher level of dust emissions. On the other hand, the wet process generates more CO2 emissions but results in a more homogeneous final product. The choice of which process to use will depend on factors such as the availability of water, the local regulations on emissions, and the desired properties of the final product.

Overall, the manufacturing of cement is a complex and energy-intensive process that involves the careful control of temperature, chemical reactions, and the properties of the raw materials to produce a high-quality final product.

Compare Dry Cement and Wet Cement

Dry cement and wet cement are two different methods of producing cement, each with its own unique characteristics and properties.

Dry cement, also known as the dry process, is produced by crushing and grinding the raw materials, such as limestone, clay, and iron ore, into a powder. This powder is then fed into a rotary kiln, where it is heated to a high temperature, typically around 1450 degrees Celsius. The intense heat causes a chemical reaction, known as clinkerization, that produces clinker, which is the main component of cement. The clinker is cooled and ground into a fine powder, which is known as cement.

On the other hand, wet cement, also known as the wet process, is produced by first mixing the raw materials with water to form a slurry. The slurry is then fed into the kiln, where it is heated and a clinker is formed. The clinker is cooled and ground into a fine powder, which is also known as cement.

The main difference between dry and wet cement is the use of water in the wet process. This water allows for better homogenization of the raw materials and can result in a more consistent final product. However, the wet process is more energy-intensive and generates more CO2 emissions.

In terms of properties, dry cement typically has a higher strength and lower setting time compared to wet cement. This is because the dry process allows for better control of the chemical reactions taking place in the kiln, leading to a more consistent final product.

Wet cement, on the other hand, tends to have a lower strength and a higher setting time. But it also has some advantages, such as increased workability, better water tightness and reduced water demand. This can make it a better option for certain types of construction, such as dams, and other structures that need to be waterproof.

Both dry and wet cement have their own unique properties and characteristics and the choice between the two will depend on the intended application and the desired properties of the final product.

Overall, both dry and wet cement production methods are in use throughout the world. Each one has its own advantages and disadvantages, and the choice of method will depend on factors such as the availability of resources, the local regulations on emissions, and the desired properties of the final product.

Classify the Cement

Cement is a key construction material used in a wide range of applications, from building homes and bridges to laying roads and creating infrastructure. Cement can be classified into several different types, based on its properties and intended use.

One way of classifying cement is based on its composition. The most common type of cement is called Portland cement, which is made from a combination of limestone, clay, and iron ore. These raw materials are heated to high temperatures in a rotary kiln, where a chemical reaction called clinkerization takes place. The resulting clinker is then cooled and ground into a fine powder, which is known as Portland cement.

Another way of classifying cement is based on its strength. Cement is available in different strength grades, such as ordinary Portland cement (OPC) which has a compressive strength of 33, 43 and 53 grades, depending on the ratio of raw materials and the fineness of grinding.

Additionally, cement can be classified based on its setting time. Rapid hardening cement sets quickly and has a faster strength development, while slow hardening cement sets more slowly but develops strength over a longer period.

Another classification of cement is based on its fineness, including normal cement and fine cement. Normal cement is less fine than fine cement and has less specific surface area.

Another way to classify cement is by its application. Some types of cement, such as blast-furnace slag cement and pozzolanic cement, are used in specific types of construction projects, such as bridge foundations and marine structures.

In summary, cement can be classified in various ways, based on its composition, strength, setting time, fineness, and intended application. Each classification has its own unique properties and characteristics and is used in different types of construction projects, depending on the specific requirements of the project. It’s important to select the appropriate type of cement in construction as it will affect the performance of the structure over its lifespan.

Recall the following types of Cement: i. Ordinary Portland Cement, ii. Rapid hardening Portland Cement, iii. Calcium chloride Cement, iv. Quick setting Portland Cement, v. Low heat Portland Cement, vi. Portland pozzolana Cement, vii. Portland slag Cement

Cement is a key construction material that can be classified into several different types, based on its properties and intended use.

  1. Ordinary Portland Cement (OPC) is the most common type of cement and is made from a combination of limestone, clay, and iron ore. OPC is available in different strength grades such as 33, 43, and 53 grades, depending on the ratio of raw materials and the fineness of grinding. It is generally used in general construction, such as in buildings, bridges and roads.
  2. Rapid hardening Portland cement, also known as high early strength cement, sets quickly and develops strength faster than regular Portland cement. This type of cement is useful in construction projects that require a rapid pace of work or need to be completed quickly, such as repairs and precast concrete.
  3. Calcium chloride cement is a specialised type of cement that contains calcium chloride. This cement hardens quickly and generates heat during the hardening process, which can be useful in certain cold weather construction applications. However, it also generates more heat than normal OPC which could cause cracking if not properly handled.
  4. Quick setting Portland cement, also known as fast setting cement, sets quickly, similar to rapid hardening cement but also hardens faster and with a lower strength. This type of cement is used in applications where a fast setting time is required, such as in repair work and underground construction.
  5. Low heat Portland cement is specially formulated to generate less heat during the hardening process. This type of cement is used in large-scale construction projects, such as dams, where the generation of excessive heat can cause cracking or other problems.
  6. Portland puzzolana cement is a specialised type of cement that contains a combination of Portland cement and pozzolanic materials such as fly ash or microsilica. This cement generates less heat during hardening and has a slower rate of strength development. This cement is mainly used for marine structures, foundations and massive concrete works.
  7. Portland slag cement is a specialised type of cement that contains granulated blast furnace slag, a byproduct of the iron manufacturing process. It has a slower rate of strength development compared to ordinary Portland cement and generates less heat. This type of cement is mainly used in marine structures, foundations and massive concrete works as well.

In summary, each type of cement has its own unique properties and characteristics that are suited for specific applications and construction projects. The selection of the appropriate type of cement is an important consideration in construction to ensure the structure performs well over its lifespan.

Recall the following types of Cement: viii. Sulphate Resisting Portland Cement, ix. Supersulphated Portland Cement, x. High alumina Cement, xi. Hydrophobic Cement, xii. White and coloured Portland Cement, xiii. Air entraining Cement

Cement is a key construction material that can be classified into several different types, based on its properties and intended use.

  1. Sulphate resisting Portland cement is a specialised type of cement that is specifically formulated to resist the damaging effects of sulphates present in soil or groundwater. This type of cement is used in construction projects where the foundation or building will be exposed to high levels of sulphates, such as in coastal or marine environments.
  2. Supersulphated Portland cement is a specialised type of cement that contains a high amount of gypsum. It has high sulphate resistance, high early strength and good durability. The cement is used in marine and other sulphate-bearing soil conditions.
  3. High alumina cement is a specialised type of cement that contains a high amount of aluminum. It is used in construction projects that require a high level of chemical resistance, such as in wastewater treatment plants, sewage systems, and other projects that are exposed to acidic environments.
  4. Hydrophobic cement is a specialised type of cement that contains a chemical admixture that makes it resistant to water. It is used in construction projects that require a high level of water-tightness, such as dams, water-treatment plants, and underground structures.
  5. White and coloured Portland cement is a specialised type of cement that can be manufactured with white or coloured pigments. This type of cement is used for decorative purposes, such as for architectural finishes, facades, and artistic creations.
  6. Air entraining cement is a type of cement that contains air-entraining agents, which produces tiny air bubbles in the concrete mixture. It improves the workability of the concrete and increases resistance to freeze-thaw cycles. It is used in construction projects that are exposed to freeze-thaw cycles, such as roads and bridges in cold weather climates.

In summary, each type of cement has its own unique properties and characteristics that are suited for specific applications and construction projects. The selection of the appropriate type of cement is an important consideration in construction to ensure the structure performs well over its lifespan. Depending on the condition of the environment, structure design and the desired properties of the final product, the appropriate type of cement must be used.