Why is a Moisture Vapor Emission Test Important?

There is no doubt that epoxy concrete floor coatings offer durability and are abrasion resistant which best suit commercial and industrial facilities that are constantly exposed to high traffic and heavy impacts. It is a concrete flooring solution that is very versatile and cost-efficient, offering tons of benefits that cannot be found in other flooring materials. However, there is one major drawback that most epoxies face – moisture vapor emissions from concrete slabs. Because epoxy is so dense, it is non-breathable. Thus, it traps moisture emitted by concrete that has not completely dried. This scenario may lead to several problems and it is for this reason that a standard test for measuring moisture vapor emission is done before the application of epoxies and other coatings.

Importance of a Moisture Vapor Emission Test? 
Thousands to millions of dollars are spent on repair or replacement of concrete flooring due to problems related to moisture. Surely you want your concrete floor to last for as long as possible, right? It is important therefore to conduct a moisture vapor emission test.

This is a test that measures the quantitative value which indicates the rate of moisture vapor emission emitted from the surface of the concrete floor. This is conducted prior to the installation of a new floor or coating such as epoxy. The test should always be done, be it an old or new floor, or one that appears to be in perfect condition. Regardless of age and grade level (above-grade, below-grade, one-grade), all concrete floors should be tested for moisture emission rate.

Calcium Chloride VS Relative Humidity Testing Method
There are two testing methods that provide valuable information regarding the vapor emission rate of a concrete slab, which also includes a pH test. While these tests can be done at the same time, some contractors prefer one from the other.

1. Calcium Chloride Test (ASTM 1869)
Otherwise known as moisture vapor emission rate (MVER), this is a simple and inexpensive test that quantifies the moisture vapor emitted from the slab, and taking into account the fact that calcium chloride is like a sponge that easily absorbs moisture.

The weight difference of the salt before and after it is exposed to the concrete for 60-72 hours gives a percentage of the moisture vapor emitted by the slab. This is usually expressed in pounds per 1,000 square feet of concrete per 24 hours. While the result is a measurement only of the moisture in the top ½ inch and to ¾ inch of the concrete, this test has long been the standard in the United States.

2. Relative Humidity Test (ASTM 2170)
This measures the moisture levels inside the slab, giving you an idea of what’s going on inside the concrete’s body. This is the standard test in several other countries.

The relative humidity test uses a probe that measures the moisture deep within the concrete. The probe is inserted into the concrete through a drilled hole and placed for 72 hours to allow for maximum reading. The results, read on a meter connected to the probe, is expressed as a percentage of relative humidity. While this test is more accurate in terms of the moisture level of the entire concrete, the cost of the relative humidity probe is expensive.

Testing concrete for moisture vapor emission is every important before an epoxy floor is applied. It is ideal to conduct both the calcium chloride and relative humidity tests because these show two different pictures, but doing one is far better than not doing any test at all. So, make sure that your flooring contractor conducts a moisture vapor emission test on your concrete.

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