Cambridge 8 Test 3 Writing Task 1 Cement & Concrete Production

Cambridge 8 Writing Task 1 Test 3

Writing Task 1
You should spend about 20 minutes on this task.
The diagrams illustrate the stages and equipment used in the cement making process, and how cement is used to produce concrete for building purposes.
Summarise the information by selecting and reporting the main features and make comparisons where relevant.
Write at least 150 words

Source: Cambridge IELTS 8 Practice Tests Academic Writing Test 3 Task 1

Cement and Concrete Production Task 1 Sample Answer

Producing concrete for construction purposes begins with making cement. The diagrams illustrate that the first step in the cement making process is mixing the raw materials limestone and clay and then crushing it using a special machine. The result is a fine powder, and the powder then passes through a mixer and a rotating heating tube. A grinder then processes the heated powder, producing finely ground powdered cement, ready to be bagged.

Concrete is made from a mixture of this fine cement, water, sand, and gravel in the ratio of 15%, 10%, 25%, and 50%, respectively. This combination is mixed together in a concrete mixer, and the final product is concrete ready to use in construction.

Cement production requires fewer ingredients than concrete but more equipment, namely the crusher, mixer, rotating heater, and grinder. Also, the process has various stages, whereas concrete is a simpler process involving mixing cement with only three other elements: water, sand, and gravel, in a rotating concrete mixer.

Cement and Concrete Production

Cement Production Overview

Cement can be produced industrially by combining water with limestone and clay. The cement making process starts by mixing raw materials, lumps of burnt limestone (calcium carbonate) and clay silts (clay minerals like kaolinite), in varying proportions to undergo slow hydration.

Industrial production requires heating - typically up to 2800 °F/1538 °C in a rotating heater to drive off any volatile matter in a process referred to as calcining. The resulting dry powder is then mixed with water before it is ready to use for building purposes.

How do you describe the cement making process?

Cement production involves 4 steps.

1. The limestone and clay crushing process produces a powder
2. A rotating heater heats the powder to 1500 degrees °C
3. The calcining process removes the water and volatile matter from the powder
4. The now dry powder is combined with water and other ingredients to form cement

How do you describe the concrete making process?

Concrete Production Overview

The raw materials to make concrete are cement, water, aggregate (usually crushed stone or gravel), and various admixtures.

In the concrete mixer, the water reacts with the cement to form calcium silicate hydrate in a process called hydration.

These chemical reactions provide most of the energy needed for this type of construction. More complicated formulations are possible when non-Portland cement is used.

Aggregates typically are natural materials, such as sand or rock mined from the earth's surface. Large quarries produce aggregates convenient for concrete production.

Concrete production involves 5 steps.

1. Excavation: the first step in producing aggregate is excavation. Heavy machinery such as bulldozers and excavators extract the material from the earth.
2. Primary Crushing: the next step is to crush the material into smaller pieces using a crusher, a large machine that reduces the size of the rocks.
3. Screening: the smaller pieces are screened to remove unwanted materials, such as soil or clay. This is done by using a screen, which separates the rocks into different sizes.
4. Secondary Crushing: the rocks are then crushed again into smaller pieces using a smaller crusher.
5. Mixing: cement and water are then mixed with the rocks in a concrete mixer to produce concrete.

Frequently Asked Questions

Are cement and concrete the same?

Yes and no. Cement is a powder that, when mixed with water, becomes concrete. So in that sense, they are the same.

However, cement is not always used to make concrete – there are other ingredients that can be added to the mix to change the properties of the final product.

For example, Portland cement is a type of cement that contains limestone and clay which makes it more resistant to weathering and erosion than other types of cement.

What are the main raw materials in cement production?

The most important raw materials for concrete production are limestone, clay, and sand or aggregate.

• Limestone is used to create the cement that binds the other ingredients together.
• Clay is used as a binder and to help control the setting time of the concrete.
• Sand is used as a reinforcing agent and to help control the porosity of the concrete.

How do you form concrete

Concrete is made by combining cement, aggregate (such as gravel or crushed stone), and water. The concrete is formed when the water reacts with the cement to create a paste that binds the aggregate together.

Is making concrete difficult?

The process of making concrete can be difficult because it's hard to get the materials to meet specifications.

The difficulty in achieving desired qualities in a finished product often stems from the variability inherent in obtaining required materials.

For example, cement processing plants often start with poor-grade limestone or low-quality clays, and their final product will reflect this limited input material quality.

Furthermore, newer cement types such as fly ash cement result in substantially increased attention to the consistency of input materials.

Clays may contain wide ranges of unwanted particles such as flint which must be removed before using higher compressive strength cement; otherwise, they cause damaging thixotropy when mixed with water.

Which countries produce cement?

China is the world's largest producer of cement, followed by India. The United States is in third place.

What are the stages and equipment used in cement and concrete production?

The equipment used in cement and concrete production depends on the type of cement or concrete that is being produced.

For wet, semi-dry, dry and pre-cast concretes, most of the production process can be done by hand.

For high-strength concretes, more specialized equipment is needed.

The following steps are involved in concrete manufacturing:

1. Breaking up raw materials
2. Mixing water with raw materials to create a slurry (a combination of ingredients suspended in liquid)
3. Transporting slurry to creation/casting site

Cement production typically involves the following equipment:

• A cement mill to grind the clinker
• A kiln to calcine the limestone and other materials
• A PRE [Pulverized Fuel Ash Recovery Equipment] system to recover fly ash from the exhaust of the boilers
• An air separator to remove dust from the air stream and produce a white cement product
• Various storage and handling systems.

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