Which of the following is NOT listed as a factor influencing the heat of hydration?

• A. Type of cement used
• B. Water-to-cement ratio
• C. Ambient temperature
• D. Slump

Answer: (D)

Heat of hydration is the energy released when cement reacts with water. The amount and rate of that heat depend mainly on the cement’s makeup (different cement types hydrate differently and release varying amounts of heat), the amount of water available for the reaction relative to cement (the water-to-cement ratio, which changes how completely hydration proceeds and how much heat can build up), and the temperature of the surroundings during curing (ambient temperature affects how fast reactions occur and how quickly heat is drawn away). Slump, which measures mix flowability, doesn’t directly control the chemical heat produced; it’s influenced by water content and aggregate characteristics and only affects heat indirectly through any changes in water content.