A binder, also known as a chemical substance that sets, hardens, and attaches to other materials to bind them together, is a cement. Typically, cement is used to combine sand and gravel rather than being utilized on its own. It is used for various purposes like dams, construction of buildings, bridges, etc, and is in different chemical compositions.
Chemical composition of Cement
There are different types of ingredients are present in cement and have their own specific function. They are described below:
Chemical composition of Cement with the percentage
| Ingredients | Percentage |
| Lime | 60-65 |
| silica | 17-25 |
| alumina | 3-8 |
| magnesia | 1-3 |
| iron oxide | 0.5-6 |
| calcium sulfate | 0.1-0.5 |
| sulfur trioxide | 1-3 |
| alkaline | 0-1 |
Function of ingredients
Every ingredient has its own specific function which is essential for the composition of cement.
- Lime: Lime is also known as calcium oxide or quick lime. It helps increase the strength of cement properties. Lime deficiency causes the cement to firm up too quickly. Lime in excess weakens cement. The cement expands and breaks down when there is too much lime present.
- Silica: With the chemical formula SiO2, silicon dioxide is also known as silica. Cement should include enough silica to form dicalcium and tricalcium silicate. Cement gains strength from silica. Cement typically contains roughly 30% silica by volume.
- Alumina: Aluminum oxide is alumina. Al2O3 is the chemical formula. The cement gains a quick-setting quality from alumina. The necessary amount of alumina is present, which reduces the clinkering temperature. Alumina in excess weakens cement.
- Magnesia: MgO is the chemical symbol. Cement shouldn’t include more than 2% magnesium. Magnesia buildup will weaken the cement’s strength.
- Iron oxide: Cement acquires color from iron oxide. Acting as a flux, it. Tricalcium alumino-ferrite is created at extremely high temperatures when it participates in the chemical reaction with calcium and aluminum. The tricalcium alumino-ferrite in cement gives it hardness and strength.
- Calcium sulfate: Gypsum (CaSO4.2H2O), which is a component of cement, inhibits or delays the setting process of cement.
- It shouldn’t make up more than 2% of the sample. Sulfur trioxide in excess renders cement unstable.
- Alkaline: It shouldn’t be more than 1% present. Efflorescence is a result of too much alkaline material.
Types of cement
Generally, cement is classified into two categories on the basis of hardening and setting mechanisms.
- Hydraulic
- Non-hydraulic
Hydraulic cement: The word “hydraulic cement” refers to materials that harden by hydration in the presence of water. To make non-hydraulic cement, the key raw materials are limestone, clay, and gypsum. To create hydraulic cement, this raw ingredient is burned at a very high temperature.
Non-hydraulic cement: Water is not necessary for the non-hydraulic cement to solidify. Carbon dioxide (CO2) from the air aids in its growth. For this sort of cement to harden, dry conditions are required. The primary materials needed to make non-hydraulic cement include lime, gypsum plasters, and oxychloride. Slaked lime, for instance, is a non-hydraulic cement.
Generally, we will discuss two main types of cement :
Ordinary Portland cement(OPC)
Portland cement clinker is a hydraulic material that must have at least two-thirds by mass of calcium silicates (3 CaOSiO2 and 2 CaOSiO2), with the remaining portion made up of various compounds and phases of clinker that contain iron and aluminum. SiO2 to CaO2 must be less than a 2.0 ratio. Magnesium oxide (MgO) cannot contain more than 5.0% of the mass.
Uses of ordinary portland cement
- It is used to construct buildings.
- It is also used in the majority of masonry works.
Portland pozzolano cement(PPC)
Pozzolans are substances, either natural or artificial, that have reactive forms of silica. When it is finely split, it combines with the calcium hydroxide produced by hydrating cement to form additional cementation materials. Portland Pozzolana Cement is made of:
- OPC clinker
- Gypsum
- Pozzolanic Materials (Fly ash, volcanic ash, and Calcined clay or silica fumes.
Uses of PPC cement
- PPC is frequently utilized in the construction of dams, maritime structures, and hydraulic structures.
- Additionally, it is utilized in pre- and post-tensioned concrete members.
- It is utilized in decorative and artistic structures because it provides a better surface polish.
- Additionally, it is employed in the production of precast sewage pipes.
Difference between OPC and PPC cement
| OPC | PPC |
| In the early stages, it is stronger than PPC. In the long run, PPC’s strength is superior to OPC. | In the long run, PPC’s strength is superior to OPC. |
| It is not suitable for mass concreting because of its high heat of hydration. | Due to the slower hydration rate than OPC, there is less heat generated during hydration. It is therefore appropriate for mass concreting. |
| Sulphates, alkalies, chlorides, etc. are more prevalent and less resistant than PPC. | The concrete is durable because it contains little in the way of sulfate alkalis, chlorides, magnesia, and free lime. |
| The rainy season is unfavorable for OPC. | Increase your ability to withstand harsh weather. |
| Three grades of OPC cement are offered, including 33 Grade, 43 Grade, and 53 Grade. | PPC is offered in a variety of grades. |
| It is a little more expensive than PPC. | less costly than OPC. |
Types of OPC grades
There are generally three grades of ordinary portland cement.
Grades 33
This grade of cement is generally used for construction under normal environmental conditions. The average compressive strength of at least 3 mortar cubes.
Grades 43
This is the most popular grade of cement belonging to OPC cement. It is used for the construction of blocks, tiles, pipes, sheets, flooring, etc.
Grades 53
It is used when we need higher-strength concrete and used in the construction of bridges, runways, roads, etc.
MCQs/FAQs
What is the full form of OPC AND PPC cement?
The full form of OPC and PPC is an ordinary portland cement and portland pozzolana cement.
What are the three grades of OPC cement?
The three grades of cement are 33, 43, and 53.
What is clinker?
The foundation of cement manufacture is clinker. It is primarily a mixture of minerals and limestone that has been fired and changed by heat in a kiln.
What is concrete?
A paste is made by mixing portland cement (10–15%) with water (15–20%) to build concrete. Then, this paste is combined with aggregates (65-75%), such as crushed stone or sand and gravel. The cement and water combine to harden and bind the aggregates into a solid mass that resembles rock.
What is mortar?
In order to provide a dense, homogenous lining that will stick securely to the surface of the substance, cement mortar must be made up of cement, sand, and water, be well mixed, and have the right consistency.
