Cement Hydration
The chemical reaction between cement and water that produces hardened cementitious paste. Hydration generates heat and the binding C-S-H gel that gives concrete its strength.
Hydration begins as soon as water contacts cement. Tricalcium silicate (C3S) reacts first to form C-S-H gel and calcium hydroxide. Dicalcium silicate (C2S) reacts more slowly and contributes to long-term strength. Aluminate phases (C3A, C4AF) react quickly and need gypsum to control setting.\n\nApproximately 25% of cement weight in water is required for complete hydration; in practice 35-40% is typical to maintain workability. Excess water creates voids and reduces strength and durability.\n\nHydration continues for months. Adequate curing keeps the paste moist so reactions can proceed and the concrete reaches its design strength.
Calcium silicate hydrate — the primary product of cement hydration and the main contributor to concrete strength. C-S-H is a nano-structured colloidal gel that binds aggregates together.
The heat released as cement reacts with water. Important for thermal control in mass concrete to avoid cracking from temperature gradients.
The time it takes cement paste to lose plasticity and harden. Measured as Initial Set (start of stiffening) and Final Set (no longer deformable).
The ratio of the weight of water to the weight of cement in a concrete mix. The single most important factor controlling strength and durability.