Whether it’s wood or concrete construction, knowledge empowers all players to assess moisture content for optimum results.
MVER (Moisture Vapor Emissions Rate)
Commonly called the calcium chloride test, MVER is a traditional measure of concrete moisture content. Due to its longevity, building contractors still use it. However, installers had used calcium chloride to measure concrete moisture content for decades without any real sense of the science (or lack thereof) behind it. MVER reads the pounds of water per thousand square feet per 24 hours of drying. Most manufacturers recommend readings of between “3″ and “5.”
Calcium chloride fails to address the moisture measurement technology that has developed in recent years. While MVER testing estimates concrete moisture content to a very limited depth, it is imprecise. Calcium chloride only measures surface concrete conditions. Building projects continue to be defined by time constraints and budget. Accordingly, installers utilize more curing, sealing and bond-breaking compounds to speed up the process. This is anathema to calcium chloride. An MVER reading depends on the absence of exactly those compounds that builders increasingly use. Therefore, calcium chloride assessment has become passe in construction and, in fact, has been disallowed for certain concrete applications.
Relative Humidity (RH)
Testing for relative humidity provides a statement of overall moisture content in concrete. Because the RH in-situ probes take their readings at a 40% depth, an equilibration moisture content can be determined. Building contractors and building inspectors conduct RH tests to determine the proportional presence of moisture content throughout a concrete slab. The RH test of moisture content via in-situ probes is a certified method of satisfying ASTM Standard F2170. An RH test is deployed to identify variations in moisture content in a body of building material which needs to reach a specified moisture content. Industry uses the RH test method for continuous spots checks during a building process. Concrete builders deploy RH tests at multiple locations on a slab to determine its drying status.
Put simply, RH tests scrutinize the interactive relationship between moisture content of building materials and the relative humidity of its surroundings. Building contractors apply RH tests by implanting in-situ probes in the slab. Done repeatedly, building contractors can build data libraries which indicate the eventual onset of equilibrated moisture content (EMC). This data would certainly interest building inspectors.