What is concrete moisture testing (calcium chloride test)?
A calcium chloride test (ASTM F1869) measures the moisture vapor emission rate from concrete by placing a dome over a calcium chloride salt sample on the floor surface for 24-72 hours to determine if concrete is dry enough for epoxy coating.
The calcium chloride test follows the ASTM F1869 standard to measure how much moisture is being released from a concrete slab. A technician places a small sealed dome containing anhydrous calcium chloride directly on the concrete floor for 24 to 72 hours. The salt absorbs moisture vapor rising from the slab, and the gain in weight of the salt indicates the moisture vapor emission rate (MVER), typically expressed in pounds per 1,000 square feet per 24 hours.
Epoxy flooring requires the concrete substrate to be sufficiently dry. Excess moisture trapped in the slab can cause the epoxy coating to blister, peel, or fail to cure properly, leading to costly repairs or complete re-work. Before applying epoxy, Ontario flooring installers run this test to verify that moisture levels meet ASTM standards, usually a maximum of 3 to 5 pounds per 1,000 square feet per 24 hours depending on the epoxy system specified.
The test is non-destructive and provides a site-specific reading rather than a general assumption about the concrete's condition. Results help installers determine whether additional drying time, moisture barriers, or preparation methods are needed before proceeding. Many concrete flooring providers include this testing as part of their pre-installation process to protect against adhesion failures and warranty issues.