What is the heat of hydration?

• A. The heat released when water chemically reacts with cement during curing
• B. The heat required to boil water
• C. The heat produced by ambient temperature
• D. The heat generated during drying of concrete

Answer: (A)

Heat of hydration is the heat released when cement reacts chemically with water as concrete cures. When water mixes with cement, hydration reactions form products such as calcium silicate hydrate and calcium hydroxide, and energy is released as heat. This exothermic process makes the concrete warm as it hardens, and the amount of heat depends on factors like how much cement is in the mix, cement fineness, temperature, and mix design. It’s distinct from heating required to boil water, heat produced by the environment, or heat from drying out moisture, which are different phenomena.