How Long Does it Take Cement to Harden?

Curing

• The process of concrete hardening is called curing. The curing process occurs through a chemical reaction between the cement and the water. The different chemical compounds that make up the cement react and harden at different times during the curing process, and the concrete will continue to harden as long as moisture is present. The general rule of thumb is the longer the curing process, the harder the concrete.

Time Frame

• The curing process for concrete used in household applications should take at least three days, but curing for five to seven days will provide optimum strength and hardness, according to the Concrete Basics website. Concrete that is allowed to cure for three days is approximately twice as strong as three day-old concrete that was not allowed to cure.

States of Hardening

• Concrete goes through three states of hardening during the curing process. The first state is known as the plastic state. This is freshly mixed concrete which can be poured into molds, shaped and worked. It is the least hard of all the states. Concrete in the setting state is stiff and is not workable, but you can still make an impression on it. A person or animal walking across concrete in the setting state would leave footprints on the surface. The final state is the hardening state. Hardened concrete can be walked on without leaving an impression. Concrete is usually hard enough to walk on within one day of curing, and concrete driveways can usually be driven on after three days, according to the Rainier Asphalt and Concrete website.

Considerations

• Concrete hardens due to a chemical reaction between the cement and the water, and not due to the drying process. Concrete will actually harden underwater, according to the Portland Cement Association. Temperature is an important factor in the curing process. For best results you should cure your concrete when the temperatures are not likely to fall below 50 degrees Fahrenheit. Extreme temperatures, wind and low humidity may cause the moisture in the concrete to evaporate too quickly, resulting in weaker concrete. The concrete must be kept wet during the curing process. You can use a light misting spray, cover the concrete with wet burlap cloth, or use a commercial sealing agent to help seal in moisture.