Which of the following factors can affect spalling in concrete?

Spalling in concrete is primarily influenced by moisture content and rapid cooling. Spalling occurs when there is water absorbed within the concrete structure that freezes and expands during colder temperatures. If the concrete cools quickly, especially after being heated during a fire situation, the rapid temperature change can lead to internal stresses that result in flaking or chipping of the surface.

The moisture content is critical because when excess water is present in the concrete mix, and the freezing occurs, it exacerbates the spalling effect. Rapid cooling creates conditions that can cause the surface of the concrete to crack and flake off, manifesting as spalling. Other factors, such as the age of the concrete and the methods of mixing or materials used, may contribute to the overall condition of concrete but are not direct causes of spalling in the way that moisture content and temperature changes are. Thus, understanding the dynamics between moisture levels and temperature variations is essential for assessing the risk of spalling in concrete structures exposed to sudden temperature changes.