The curing process is particularly important with dry-cast mixes. Adequate curing enhances the desirable properties of concrete, such as strength, impermeability, surface hardness, and crack resistance. Early curing periods are most critical to ensure protection from extreme temperatures and dryness. Dry cast products must be protected from drafts to prevent cracking due to surface moisture.

Concrete can not cure properly without an adequate amount of water in the mix. And, because the forms are removed immediately, dry cast products have an undesirable tendency to dry too quickly. Consequently, a dedicated curing area, such as an insulated enclosure with misters, is generally required.

A normal curing cycle for dry cast products includes a preset period of about two hours, a ramp period (to raise ambient temperature to the desired curing temperature) of four to six hours. These curing cycles will vary with the type of product being cured.

Curing in a controlled, moist environment dramatically increases the concrete's rate of strength development. In many cases, full design strengths can be achieved in one day.

Note: Curing begins after the exposed surfaces of the concrete have hardened sufficiently to resist marring. Curing ensures the continued hydration of the cement and the strength gain of the concrete. Concrete surfaces are cured by water. The longer the concrete is kept moist, the stronger and more durable it will become. The rate of hardening depends upon the composition and fineness of the cement, the mix proportions, and the moisture and temperature conditions. Most of the hydration and strength gain take place within the first month of concrete's life cycle, but hydration continues at a slower rate for many years. Concrete continues to get stronger as it gets older.

Hyrdration Begins

Soon after the aggregates, water, and the cement are combined, the mixture starts to harden. All portland cements are hydraulic cements that set and harden through a chemical reaction with water. During this reaction, called hydration, a node forms on the surface of each cement particle. The node grows and expands until it links up with nodes from other cement particles or adheres to adjacent aggregates.