The Importance of relative humidity in a concrete slab.

Sources of Moisture in Concrete

Multiple factors can influence the level of relative humidity in a concrete slab, thus contributing to high relative humidity 6 months or more after pouring concrete:

The initial amount of water in the concrete (from a high water/cement ratio);Ambient conditions such as high ambient relative humidity, cold temperatures, additional sources of water, and limited air movement;Wet curing;The use of pozzolans, such as silica fume, which have a tendency to retain water and take longer to dry; andMissing or inadequate moisture barrier in a slab on grade, causing outside moisture to penetrate the slab.

Prevent Flooring Failures With Concrete Humidity Meters

Before a flooring system is installed, it is crucial to measure the relative humidity of the concrete. Only when the relative humidity has reached a certain level is it safe to install a floor while avoiding failure.

Once the floor is installed, it seals the surface and prevents further drying of the concrete underneath. If the floor is installed too early, excess relative humidity will be trapped inside the concrete. It will try to evaporate, leading to pressure and changes in the alkalinity at the flooring and concrete interface.

Typical concrete failures due to relative humidity include:

Delamination of the floor adhesive;Blistering of the epoxy coating;Re-emulsification of the adhesive (stain); andCurling, cracking, or bubbling of flooring materials

Inappropriate flooring prior to installation can lead to these types of recurring and costly failures

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