Oftentimes, a construction schedule fails to allow for proper drying of the concrete slab. The basic reason that this occurs is lack of understanding and/or unrealistic scheduling..
The fact is that when flooring is installed over a concrete slab before it has dried sufficiently:
An informed, responsible contractor who wants to protect the interests of the client, will help the client understand the necessity of a realistic construction schedule as regards the drying of the slab.
Contractors who lack understanding about the importance of a properly dried concrete slab often push for premature flooring installation.
Before the drying process for the concrete can begin, the concrete must be cured. What curing does is to maintain a satisfactory moisture content which allows the cementitious material to react to the hydration process and develop into a quality product. If the concrete isn’t cured, the surface can be ruined and the odds of future problems with the slab are greatly increased. Proper curing of the slab helps establish compressive strength and overall durability of the concrete.
During the first few days of curing, the goal is to keep the concrete saturated as much as possible in order to achieve 70% hydration. Fresh concrete needs to be kept moist for five days minimum during the curing process.
There are different methods used to slow down the evaporation process in a slab while it’s curing. They include covering the wet concrete with:
Wet curing is considered by many to be the superior way to cure concrete because the results are a less permeable slab than you get when a curing agent is used. Wet curing uses ponding, fogging, sprinkling, or covering the concrete with wet burlap.
Being able to achieve a shortened length of drying time begins before the slab is poured. Steps which allow for optimum slab curing and drying times include:
The amount of time required for a concrete slab to dry properly varies, but, in general, the ideal drying time is one month for every one inch of slab. Some additional factors besides the thickness of the slab which affect drying time include:
Dehumidification equipment is available which is specially designed for construction sites and for speeding up the drying time of concrete slabs.
Moisture meters such as the Rapid RH 4.0 are the most effective method for determining whether a slab is sufficiently dry. See more details under “Installation.”