Occurs when concrete is heated and the moisture expands within concrete causing fractures and chips to flake off, exposing the metal framework. What is this phenomenon?

• A. Tensioned framework within concrete
• B. Type I - Fire Resistive
• C. Cast in Place
• D. Spalling

Answer: (D)

Spalling is the phenomenon at play when heat causes moisture inside concrete to turn to steam, creating internal pressure. As the pore water expands, the resulting tensile stresses in the outer layer cause cracks to form and pieces of the surface to break away or flake off. This can expose the reinforcing steel and significantly weaken the concrete, especially in fires where temperatures rise rapidly. The appearance of chips or flakes on the surface is a hallmark of spalling, not just a simple crack or normal cracking, and it signals moisture-driven damage from heat.