National Occupational Competency Testing Institute (NOCTI) Carpentry Practice Exam

What is cement primarily composed of?

1. Sand and gravel

2. Lime and clay

3. Water and soil

4. Bitumen and oil

The correct answer is: Lime and clay

Cement is primarily composed of lime and clay, along with other materials such as gypsum and various additives, depending on the specific type of cement being produced. The key ingredient, lime, often comes from limestone, and the clay component provides essential silicates. When heated in a kiln, these components undergo a chemical transformation that produces clinker, which is then ground into the fine powder we recognize as cement. This chemical process ensures that cement can bind with aggregates, such as sand and gravel, to form concrete, a critical construction material. Options that mention sand and gravel, water and soil, or bitumen and oil do not relate to the core composition of cement. While sand and gravel are critical components of concrete, they are aggregates mixed with cement rather than being constituents of the cement itself.