How quickly should concrete be dried?
Drying and curing are terms that are often used interchangeably when it comes to concrete. Many in the industry will say that concrete is not dried; it is only cured, whilst others will say there is a clear difference. What is not in dispute is that it is necessary to reduce the water vapour within a slab to recommended levels prior to the installation of resilient floor coverings.
Curing refers to the setting of concrete and can happen relatively fast. It is a chemical reaction within the concrete of which water is a necessary component. You can usually walk on it after two to three days and drive on it after seven but concrete will continue to cure for years. Although concrete slabs may be “dry” enough to walk on after a few hours the curing process takes much longer.
It is generally specified that it takes a month for concrete to cure per inch of thickness but this is only a very rough rule of thumb and the actual time depends on many variables like the drying conditions, amount of concrete, moisture levels and any chemicals that have been added to the mixture. The only way to know if a slab is dry enough for its intended use is to measure it.
All about the moisture
The key thing to remember when curing concrete is moisture. Water causes the mixture to bond and is vital to the chemical reaction that takes place to give concrete its strength. If water evaporates too quickly the concrete’s strength can be compromised and you may end up with cracks.
It is widely accepted that to cure correctly, concrete requires sufficient moisture which can be added in a number of ways. You can spray the surface keeping it consistently damp, cover with a wet material, cover with plastic sheeting or use curing compounds. Which method you use will depend on the weather conditions and whether the surface will be painted or covered once cured. It is advised not to alternate wetting and drying as this can cause cracking.
It is also important to note that too much water in the mixture to begin with can cause problems with the drying process. Too much water can result in shrinkage and reduce the strength of the concrete. If you need to make concrete mixture more workable then it is preferable to use chemical additives rather than adding too much water. In hot conditions where concrete sets quickly you should try and cool the area down and begin the curing process immediately after the concrete is laid.
The impact of weather
The weather conditions affect the rate at which concrete will dry or cure. Cold weather increases the drying time and slows down the strengthening of the concrete. It is recommended that you don’t lay concrete at temperatures below five degrees centigrade and when possible try and keep the temperature above 10 by insulating or heating.
Hot weather will accelerate the drying process which could result in shrinkage or cracking so you may need to add additional moisture or protect the concrete from direct sunlight.
Concrete is very sensitive. The drying and curing process is a chemical reaction and even the slightest difference in the mixture, the conditions and the weather can affect that reaction.
Being able to control the drying and curing conditions is extremely advantageous. The Arxell drying system provides many benefits. It can be used to evenly distribute hot or cold air across a surface. It is load bearing so you can walk on it without disturbing drying concrete underneath. The units create a micro-climate that distributes drying air evenly across the wet surface creating optimal drying conditions. Plus the units also provide shelter from direct sunlight.