Cement is used to make concrete products such as roads, buildings, bridges, dams, etc. Concrete is widely used for constructing our roads, airfields, buildings, monuments, etc. Cement is used as a binder material in concrete. Portland cement (or portlandite) is the most commonly used type of cement around the world.

 The basic components of cement are limestone, clay minerals, iron oxide, and 2 types of sulfate; calcium sulfoaluminate, which makes 60-70% of concrete, and sulfo-magnesia, which makes 30-40%. When water reacts with these two compounds, they form hydrated lime, known as slag, which hardens and bonds the solid particles together into cement paste.

 Limestone Calcium Carbonate CaCO~3~ – contains ~20% of carbon from CO~2~ that was released from atmosphere through photosynthesis over eons of time.

 Clay Minerals Kaolinite Alumina Silica

 Kaolin has high aluminum content, which gives it good heat insulation properties. In addition, kaolin has good adsorbent capacity for gases and many chemical substances.

Types of Cement –

1. Portland Cement (CEMI 1)

 Portland cement is produced from limestone by heating, grinding, mixing water, and adding lime. This results in calcium carbonate and silicate hydrate compounds that react together to form portlandite, a chemical reaction occurring through a hydration process. Hydration occurs when the cement encounters water, which is needed for the cement to harden. In addition, the curing time of this material can vary based on the type of aggregate used, the temperature of the environment, and the amount of moisture present.

 2. Concrete (CEM II/A-32)

 Concrete is composed of cement, sand, gravel, iron oxide pigments, and other additives. There are two types of concrete: ordinary concrete and high-performance concrete. Ordinary concrete is used in many different applications, including foundations, walls, flooring, and pavements. High performance concrete is used mainly in large projects that require exceptional durability and long service life at extremely harsh conditions.

 3. ECC30/ECC 32

 Eco-friendly cement, or ECC30/ECG32, was developed to reduce emissions and pollution associated with cement manufacturing. Today, over 90% of the world’s cement production is derived from conventional clinker technology. However, traditional methods produce significant amounts of CO2. Moreover, these processes do not consider the waste generated during their use. Thus, they create serious environmental problems. To address some of these issues, modern manufacturing technologies have been introduced into the process. These include using alternative fuels for fuel combustion, recovering heat energy, recycling materials, and producing low ash content cements.

Raw Material used in Manufacturing of Cement –

1. Raw Materials –

 Cement is principally composed of limestone (CaCO3), clay minerals (kaolin, montmorillonite, illite) and silica sand (SiO2). These raw materials are then ground into fine powder, mixed with water, and placed together into a mold where they harden into cement. Depending on how the raw material is processed before mixing, the type and quantity of additives used, and the composition of the mix, different types and grades of cement can be produced.

 2. Manufacturing Processes –

 The manufacturing processes of cement are quite complex and involve many chemical reactions that take place at high temperatures and pressures. Cement production begins with quarrying limestone from quarries, crushing the stone into small pieces, and grinding them into a powdery form known as clinker. Clinker is then formed into large blocks called “bricks” and combined with other ingredients to make ready-to-use cement.

 3. Manufacturing Technologies –

 In both conventional and advanced technologies, cement manufacture relies heavily on energy-intensive kilns and presses, and heat generated from these devices has a significant impact on the environment. In addition, to produce cement using traditional methods requires large amounts of water, which contributes to further environmental pollution.

4. Burning Process –

 The first step in manufacturing cement is burning. Here, coal or natural gas is burned in air to produce heat that heats the mixture of lime and clay. As soon as the temperature reaches 900 degrees Celsius, the chemical reaction begins. Lime undergoes calcination, turning into quicklime and producing various gaseous compounds. The gases are then collected and separated through several stages. After these steps, the remaining solid residue contains 60-70 percent clinker, 15-20 percent gypsum, and the remainder is water.

 5. Sintering Process –

 After the clinkers have been ground down, they are sintered together into larger pieces. These pieces are formed using either cold pressing or hot pressing. Cold pressing uses only pressure, whereas hot pressing adds heat. Today, hot pressing has become popular due to its ability to produce dense products while avoiding the expansion of materials caused by water absorption.

Cement is used in any form of construction whether it be concrete, mortar, clay bricks, etc. Cement is made from two major components, lime and silica. Lime is derived from limestone while silica is extracted from sand and rock. These two ingredients are mixed together along with water to make a slurry that hardens into a solid mass over time.

 The different types of cements vary in consistency and durability, however, they are primarily classified as either hydraulic cements or chemical cements.

 Hydraulic cements (e.g., Portland cement) do not require curing agents in order to set completely; however, they have a lower tensile strength than chemical cements. When exposed to moisture, this type of cement will begin to harden within minutes.

 Chemical cements like calcium aluminate cements require curing agents to set effectively. They can withstand higher temperatures and are resistant to chloride salts and other corrosive chemicals.

Cement is a substance that can be used as a binder to bind other materials together. Cement has been around since ancient times and its production was recorded in the Ebers Papyrus from 1550 BC. Today, there are two ways to produce cement; either through hydration or calcination. In this video we learn about the manufacturing of Portland cement via calcination. Calcined cement is white and provides the strongest binding properties relative to hydrated cement. This type of cement is used for concrete, mortar, grout, stucco, plaster, and even some types of pottery glaze. Calcining cement produces lime, silica, alumina, ferrous sulfate, and calcium oxide.