Which statement about cement hydration is true?

• A. Cement hydration only occurs at high temperature
• B. Cement requires no water to hydrate
• C. Cement hydrates with water to bind aggregates into a solid matrix.
• D. Cement hydration is reversible

Answer: (C)

Cement hydration is the chemical reaction between cement and water that forms the binding paste. When water is added, reactive clinker minerals chemically react to produce calcium silicate hydrate (C-S-H) and calcium hydroxide. The C-S-H gel fills the spaces between cement grains and aggregates, creating a cohesive solid matrix that binds sand and gravel into concrete and gives it strength as it hardens. Water is essential for this reaction, so without moisture hydration won’t occur properly. It doesn’t require high temperatures; it happens at ordinary ambient conditions, though heat can speed it up. And it’s not reversible—once the hydrated products form, the material doesn’t revert back to cement and water.