Moisture Content Of Concrete Slab

If excess moisture is present in a concrete slab when an impermeable surface treatment is installed it will become trapped under that covering.

Moisture content of concrete slab.

Why concrete moisture is tested. Moisture tests for concrete slabs. A definitive test that measures the amount of moisture released from the concrete requires a calcium chloride kit or a relative humidity meter. Gravimetric this is a direct and accurate method of determining moisture content by weight in the concrete slab.

Most concrete moisture meters only check surface moisture. The second source is moisture rising from below the slab. Armstrong recommends conducting a calcium chloride test per astm f 1869 the relative humidity in situ probe test per astm f 2170 or the armstrong 72 hour bond test hygrometer test relative humidity meter placed on floor surface and covered with plastic. Every slab of concrete has moisture and will always have moisture.

Internal relative humidity of concrete slab. Testing with either method will tell you how. So you re never going to achieve nor would you want 100 percent dry concrete. What you re looking for is moisture condition that s within manufacturer s specifications to accept the flooring product you are going to apply.

Three methods for testing concrete moisture levels. Pieces of concrete are removed by chiseling or stitch drilling and dried in an oven to constant weight. Concrete slabs often have thicknesses measured in feet not inches. If an effective low permeance vapor retarder material is not installed directly in contact with the underside of the slab the concrete will be exposed to a perpetual source of moisture rising from below.

Moisture meters can only check the moisture near the surface of a concrete slab which is not sufficient for predicting how the slab will react to having sealant applied or other building materials installed over it. The moisture content is then calculated as a percentage of the dry sample weight.