Final answer:
The answer identifies feldspar as not a common cement type. While silica, iron oxides, and calcite are involved in cement production, feldspar is not commonly used in cement.
Step-by-step explanation:
The question asks to identify which item is not a common cement type. Cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Portland cement is the most common type of cement in general use around the world, made from a combination of calcium, silicates, and other materials. When considering the options provided:
- Silica (SiO₂) is a major component of sand and is indeed a component of cement, as it reacts with calcium hydroxide to form the calcium silicate hydrates that give cement its strength.
- Clays, which contain silicates, are also used in the production of cement.
- Feldspar, while a silicate mineral, is not commonly used in cement.
- Iron oxides are used in cement for color and to help facilitate the process of clinker formation.
- Calcite (CaCO₃) is another name for calcium carbonate, which is a source of calcium in the manufacturing of cement.
Therefore, feldspar is not a common cement type and does not significantly contribute to the cement's properties.