Wet Water on Concrete Won't Dry

Temperature

• The air temperature where the concrete sits affects how warm or cold the concrete is, and how quickly it dries. As with clothing, hair and other objects, concrete dries slower in cold temperatures and quicker in hot temperatures. Evaporation is slowed when there is less heat or thermal energy in the air, which is why you should try to perform concrete work on warmer days whenever possible. If your concrete is taking too long to dry, then you can heat up the surrounding air by running a space heater, if the concrete is indoors.

Relative Humidity

• Water evaporates at a slower rate if the humidity levels in the air are high. If you are laying concrete outdoors, try to avoid days where rain or other precipitation is predicted, if at all possible. You may decrease the humidity in your house with a dehumidifier, if you are laying concrete indoors, to help speed up the drying process.

Precipitation

• If your concrete is sitting outdoors, precipitation can not only slow the drying process, but it can lengthen the process by introducing more moisture into the concrete. You must protect the concrete from precipitation, taking steps to do so if you suspect there is any chance for precipitation falling in the near future. Place a plastic tarp over the concrete, but you must leave some distance between the concrete or any container it sits inside and the tarp, otherwise you trap the water that evaporates from the concrete, slowing the concrete’s drying even further.

Air Flow

• If the air around the concrete sits stagnant, as opposed to air that is moving around rapidly, this can increase the concrete’s drying time. As the water in the wet concrete evaporates, the air above the concrete can begin to become saturated with water vapor. Once the air reaches a relative humidity of 100 percent, the air can no longer hold more water vapor and the concrete stops drying. Placing a fan directed at the concrete helps move the air around, preventing the air from becoming saturated with water vapor and speeding up the concrete’s drying time.