The correct answer is: A. Lime 63% ; silica 22% ; other ingredients 15%
Portland cement is a hydraulic cement, which means that it sets and hardens under water. It is the most common type of cement in general use around the world. It is a basic ingredient of concrete, mortar, and grout.
Portland cement is made by heating a mixture of limestone, clay, sand, and iron ore to a very high temperature. This produces a clinker, which is then ground into a fine powder. The powder is then mixed with gypsum and other additives to produce Portland cement.
The proportions of raw materials used to make Portland cement vary depending on the type of cement being produced. However, the most common proportions are:
- Lime: 63%
- Silica: 22%
- Other ingredients: 15%
The other ingredients can include iron oxide, alumina, magnesia, and sulfur.
The proportions of raw materials used to make Portland cement are important because they affect the properties of the cement. For example, the amount of silica in the cement affects its strength. The amount of iron oxide in the cement affects its color.
The manufacture of Portland cement is a complex process that requires a high level of technical expertise. The raw materials must be carefully selected and blended to ensure that the final product meets the required specifications. The manufacturing process must also be carefully controlled to ensure that the cement is produced in a consistent manner.