Cement is the most widely used construction material with both adhesive and cohesion qualities, allowing it to join and bind solid matter particles into a compact, long-lasting solid mass.
Cement is mainly classified into two categories based on hardening and setting mechanisms.
Hydraulic cement: Hydraulic cement is a block of cement that hardens when mixed with water due to an independent chemical process. When mixed with water, hydraulic cement sets in 3 to 5 minutes.
Non-hydraulic cement: When lime or gypsum plaster is exposed to water, it does not harden. It is necessary to keep it dry to maintain its strength; however, drying takes a long time. Slaked lime, for example, is a non-hydraulic cement that hardens through a carbonation process in the presence of carbon dioxide in the air.
Many Types of cement have been developed to suit different conditions, such as:
Ordinary Portland cement (OPC)
The most prevalent type of cement used in construction is Portland cement. It's made by grinding clinker with a little amount of gypsum, water, and less than 1 percent air-entraining agents. Portland clinker is made up of calcium silicate. It is made by calcining to incipient fusion a predefined and homogeneous mixture of minerals, including 59–64 percent lime (CaO) and 19–24 percent silica (SiO2), together with 3–6% alumina (Al2O3) and 1%–4% iron oxide (Fe2O3).
After the water is added to cement, it sets and hardens due to the dissolution and reactivity of its constituents. The constituent's calcium aluminate sets and hardens the cement, and the calcium trisilicate generated is important for the cement's early strength gain.
Portland Pozzolana Cement (PPC)
Portland pozzolana cement is made by blending Portland cement with fine pozzolana or by grinding clinker and pozzolana together. Pozzolana accounts for 10 to 25% of the cement's weight. This type of cement is appropriate for waterfront or maritime structures, such as dams, bridge piers, thick foundations where mass concrete is employed, and sanitary systems like sewers. The pozzolana has no cementitious or binding qualities. Still, when finely divided and exposed to water at a suitable temperature, it can react with calcium hydroxide to create compounds with sufficient binding capabilities.
Rapid Hardening Cement
Blending Portland cement with fine pozzolana or grinding clinker and pozzolana together produces Portland pozzolana cement. Pozzolana makes from ten to twenty-five percent of the cement's weight. This type of cement is suitable for waterfront or maritime buildings such as dams, bridge piers, heavy foundations, and sanitary systems such as sewers. Although the pozzolana has no cementitious or binding properties, when finely divided and exposed to water at an appropriate temperature, it can react with calcium hydroxide to produce compounds with significant binding properties.
Extra Rapid Hardening Cement
Calcium chloride is ground with rapid hardening Portland cement to make extra rapid hardening cement. Calcium chloride accounts for 2% of the cement's weight. After adding water, a large amount of heat is generated in a short time, as well as hydration. As a result, this type of cement is ideal for cold-weather concreting. This cement has a 25 percent higher strength than rapid-hardening cement.
Portland Slag Cement
Portland slag cement is made by combining Portland cement clinker, granulated blast furnace slag, and gypsum in the appropriate proportions and grinding the mixture to finer particle size. It can also be made by combining Portland cement with finely powdered granulated slag and vigorously mixing it. Granulated slag is a non-metallic substance made primarily of glass with silicate and aluminum silicates of lime and other bases. This slag is made from molten slag swiftly chilled or quenched with water, steam, or air. The waste product from blast furnaces is typically used to create this sort of cement.
Hydrophobic Portland cement
Ordinary Portland clinker is combined with water-repellent film-forming cement such as oleic acid and stearic acid to produce hydrophobic cement. The water-repellent coating that forms around each grain of cement slows the cement's degradation. These films will be broken when the cement is mixed with the aggregate, allowing the cement particles to hydrate normally. On the other hand, these water-repellent materials let a certain amount of air into the concrete, boosting its workability.
Low-heat Portland cement
Low-temperature cooking Portland cement is made the same way as regular Portland cement. The main difference is that the amount of c3s and c3A compounds is reduced, while the amount of c2s is raised. The chemical activity of hardening is slowed by this reduction of components. As a result of this activity, the cement gains strength at a slower rate. Their ultimate strength, however, is the same as standard Portland cement.
Sulphate Resisting Portland cement
In general, conventional Portland cement is prone to sulfate attack. Resistant to sulfate Cement was created for usage in soils afflicted with sulfates. This type of cement has a high silica concentration and contains a low proportion of c3A and c4AF. Resistance to sulfate Portland cement is made by grinding and combining calcareous, silica, alumina, and iron oxide-containing minerals nearby. The clinker that results is pulverized to make cement.
Quick Setting Cement
Quick-setting cement is employed for difficult foundation conditions, such as when pumping is required. This cement can be set quickly. This cement feature is acquired by lowering gypsum content during the clinker grinding process. Some common grouting operations also employ this sort of cement.
High Alumina Cement
High alumina cement is made from an aluminous and calcareous substance by sintering and grinding the clinker, which is made by fusing 40 percent bauxite, 40 percent lime, and 25 percent iron oxide with a little amount of ferric oxide, silica, magnesia, and other minerals at a very high temperature. This type of cement should have a total alumina concentration of at least 32 percent. Monocalcium aluminate is the major constituent, which combines with water to generate dicalcium octahydrate hydro aluminate and aluminum oxide hydrate. The dicalcium octahydrate hydro aluminate gels consolidate, and hydration occurs, resulting in product crystallization.
Compared to OPC, the crystallization rate is fast, resulting in a rapid increase in strength. Because this cement lacks c3A, it is resistant to sulfate attack. This type of cement is utilized as a refractory concrete in industries and is commonly used for precast concreting because it is resistant to the action of seawater and sulfates.