Learn About Cement Raw Materials, Types, & How to Make It

Cement is one of the most important building materials in construction. Almost all modern building structures, from houses to skyscrapers, use cement as an adhesive to hold bricks, concrete, and other building materials together. Therefore, construction workers need to understand cement raw materials, types, and how it's made.

This basic knowledge can help people who work in the construction sector choose the right type for a particular application, ensure construction quality, and avoid possible renovation mistakes resulting from the improper use of cement.

This article aims to provide information about cement raw materials, cement types, and how to make cement. We hope that this information will help you better understand the properties and applications of cement for construction purposes.

Cement Raw Materials

As an important material in construction, cement must be made from the best quality materials. The following are some of the raw materials used in making cement:

1. Clay

The first raw material for cement is clay. It has the chemical formula Al2O3.K2O.6SiO2.2H2O, the raw material needed to make cement. Clay is rich in silicate and aluminate compounds, with a small amount of iron compounds. With a molecular weight of 796.40 g/mol, clay generally has a reddish-brown color.

Clay is a water-soluble substance. In small amounts, clay sometimes contains alkaline compounds such as Na and K, which can affect cement quality.

In general, clay is an easily obtainable cement raw material, which makes it relatively cheap. Using clay in making cement possesses many benefits, such as increasing the strength and durability of cement and slowing down its hardening progress.

Despite its many benefits, it is important to note that the quality of clay can vary. Therefore, it is necessary to carefully select and process clay before using it as a raw material for cement.

2. Limestone

Limestone, especially pure ones such as calcite and aragonite, is the main source of calcium (Ca) compounds, which are abundant in nature. The calcium in this limestone comes from Calcium Carbonate (CaCO3), an important component in geological formation and is the main raw material for making Portland cement.

The process of making cement here involves transforming CaCO3 in limestone into Calcium Oxide (CaO) and Dolomite (CaMg(CO3)2) into free Magnesium Oxide (MgO) crystals, or Periclase. This combination produces Portland cement, an important material in building construction.

3. Silica Sand

Silica sand is one of the raw materials for cement, aside from limestone and clay. Silica sand can add strength and durability to cement, making it an ideal material for building construction.

4. Optional Raw Materials

Apart from limestone, clay, and silica sand, there are several other raw materials used in making cement, namely:

Gypsum: Regulate the hardening time of cement and increase its strength. Iron sand to maintain temperature stability and increase the fluidity of the cement mixture during the firing process.
Limestone ash (fly ash): An additional material to replace some cement and reduce the use of main raw materials.
Slag: An additional material and a source of silica to increase the strength and durability of cement.
Pozzolan: An additional material and source of reactive silica to increase the strength and durability of cement.
Industrial waste: An alternative raw material to replace some of the main raw materials and reduce environmental pollution.

Types of Cement

Cement has three main types, namely Portland cement, non-Portland cement, and composite cement. The following is an explanation of the three types of cement:

1. Portland Cement

Portland cement is known for its adhesive quality, which holds building materials together into a sturdy structure. It's made of a combination of cement raw materials like limestone, clay, iron, silica, and alumina, making it ideal for various projects.

There are several types of Portland cement that can be used in projects, namely water-resistant and fire-resistant. Each type of Portland cement has its advantages and uses to ensure long-lasting and safe buildings. The correct use of Portland cement in construction is the key to creating a sturdy and durable structure.

2. Non-Portland Cement

In contrast to Portland cement, non-Portland cement has a particular characteristic. Therefore, it is not as widely used as Portland cement in construction. Non-Portland cement comes in several variations, such as:

Aluminate cement: Made from a composition of alumina cement and calcium aluminate. Commonly used in projects such as chemical tanks and drain pipes.
High-resistance sulfate cement: Contains cement in the form of calcium sulfate and clinker. It is ideal for construction in coastal areas.
Polymer cement: Made with synthetic polymers, this cement is a great choice for building projects that require high flexibility.

It's worth noting that non-portland cement needs adjustment according to the needs and conditions of the construction project.

3. Composite Cement

Composite cement is an innovative solution in the world of construction. Different from ordinary cement, composite cement is made from a mixture of several of the same cement raw materials, such as Portland and non-Portland cement. What makes it different is that it contains other materials, namely fly ash or slag.

There are three main types of composite cement, namely mixed cement, geopolymer cement, and glass cement. Each has its advantages.

Mixed cement combines Portland and non-Portland cement to produce building-weather-resistant and high-compression-strength materials. Utilizing fly ash, slag, and chemicals can produce a geopolymer cement that has good tensile strength and corrosion resistance. Meanwhile, the combination of glass waste and chemicals produces glass cement, which is known for its strength and corrosion resistance.

Choosing the right composite cement not only provides benefits for the structure but also for the environment. This is because the use of materials such as fly ash and slag in composite cement can help reduce industrial waste and carbon emissions, making it beneficial for sustainable development.

How to Make Cement

After knowing the raw materials for cement and their types, you need to pay attention to the process of making good-quality cement. Here's how to do it:

1. Mining and Raw Material Extraction

Cement production requires limestone with a percentage of 75–90% and clay (7–20%) as the main raw materials. Additionally, balancing raw materials such as 1-3% iron sand and 1-6% silica sand is required to achieve the ideal cement composition.

2. Raw Meal Grinding

The next step in making cement is mixing all the raw materials. This raw material processing aims to reduce the size and increase the surface area of the material to produce a homogeneous mixture.

This process will also aid chemical reactions during clinkerization. This raw material is processed using hot gas from a hot gas generator or kiln exhaust gas.

3. Mixing and Preheating

The next stage is burning, where the raw meal is processed in the kiln once the raw cement material is homogenized in the CF Silo. With the help of various means of transportation, the raw flour will be transferred to the kiln and then fed as kiln feed. In the kiln, raw flour will be burned at high temperatures (around 1450°C) to produce clinker.

This combustion process is divided into three stages:

Drying and dehydration: Heating raw flour in the preheater to remove air.
Decomposition: Decomposing compounds in raw flour at high temperatures in the preheater.
Clinkerization: Burning raw flour in a kiln to produce clinker.
Cooling: Cooling down hot clinker on a cooling grate before being ground into semen.

4. Clinker Formation

The grinding process is first carried out using a roller press to obtain a certain size. Next, the grounding begins again using a tube mill equipped with iron balls as a crushing medium.

The fine material is then separated from the carrier air using several dust separation devices. The final milling results are stored in airtight cement silos.

5. Cement Packaging

The cement packaging process begins by removing it from the storage silo. This cement is then moved by conveyor belt to a steel silo. Using the steel silo, a rotary packer bagging machine is utilized to pack cement into 50-kg bags. These cement bags are then loaded onto trucks and taken to their destination.

That's all the information regarding the raw materials, types of cement, and the manufacturing process. Cement is a fundamental material in building construction, essential knowledge for contractors, engineers, and construction workers.

Learning the information above may help you understand that raw materials for building construction, especially cement, are very important. Therefore, it's necessary to choose high-quality cement.

Semen Merah Putih is the ideal choice for premium cementitious material base products to fulfill a wide range of building construction needs. Reach out to us now to get professional assistance for your construction projects.