As with other masonry materials, cast-in-place concrete is subject to ___________ when exposed to high temperatures, causing damage to the masonry.

• A. Erosion
• B. Cracking
• C. Delamination
• D. Spalling

Answer: (D)

When concrete is heated, moisture inside turns to steam and concrete expands at different rates from the inside to the surface. This creates internal pressure and thermal stresses that can cause the outer layer to peel away in chunks. That surface flaking or breaking off is known as spalling, and it’s a classic form of damage to masonry when exposed to high temperatures.

Erosion describes material loss from flowing fluids, which isn’t the fire-related failure here. Cracking is a general fracture that can occur for many reasons, but spalling specifically refers to the outward bursting and shedding of surface material due to heat. Delamination is the separation of layers, often from bond issues, but the high-temperature surface peeling described matches spalling best.