The Drying Temperature and Time for Ready-Mix Concrete

Temperatures

• The weather cannot be too hot or cold for concrete to properly cure. If the weather is too dry and hot, then water will evaporate too quickly from the concrete resulting in shrinking and cracking. If the weather is too cold, then the water inside the concrete freezes and the curing process entirely halts. As a general rule, it must be at least 50 degrees F for proper curing.

Humidity

• Moisture is key to triggering the chemical curing process. To maintain proper moisture levels during curing, the concrete must be kept wet. In fact, Portland cement (an ingredient in concrete) will even harden concrete that's completely immersed in water. Different procedures can be used to accomplish this goal. A concrete worker may remain at a work site spraying the concrete down throughout the day to avoid evaporation. Alternatively, a plastic barrier may be placed over the concrete to lock in moisture if someone cannot remain at the site.

Time

• Concrete takes time for the chemical reaction to take place. In fact, concrete is not considered completely cured until 28 days after installation. However, the hydration process does slow down as the concrete cures, so the concrete will not require care and attention for those entire 28 days. On average, concrete only requires hydration for the first 48 to 72 hours, and then is sufficiently hydrated to continue the reaction independently.

Troubleshooting

• While concrete does cure and become very hard, some factors can impact the overall strength and durability of the ready-mix concrete. For instance, in places subject to constant freezes and thaws, concrete is air entrained to give the concrete room for expansion and shrinkage. Otherwise, the concrete will flake. Additionally, subgrades should always be tightly packed under concrete to prevent cracking during the curing process.