National Occupational Competency Testing Institute (NOCTI) Carpentry Practice Exam

Which of the following is NOT an ingredient in concrete?

1. Water

2. Sand

3. Cement

4. Wood

The correct answer is: Wood

In the composition of concrete, the primary ingredients include cement, sand, gravel (or coarse aggregate), and water. Cement acts as the binder that holds the mixture together when it hydrates. Sand provides bulk and helps fill the spaces between the larger gravel particles, contributing to the overall strength of the hardened concrete. Water is essential for the chemical reaction that allows the mixture to cure and harden properly. Wood is not included in the standard formulation for concrete. Instead, it is a separate construction material often used in framing, formwork, or other applications related to building, but it does not contribute to the chemical structure or physical properties of concrete itself. Concrete relies on its specific aggregate components to achieve desired strength, durability, and workability, making wood an unsuitable ingredient for its mix.