Concrete is the most versatile construction material in history. But, it presents some unique issues when used in combination with other materials, most especially floor coverings. The moisture of concrete is always present to some degree in the concrete slabs, whether suspended in a place on grade or structure. If an exposed concrete surfaces were coated with these:
- Other floor coverings
- Overlaid with tile
These can cause the migration of moisture, which causes significant damage.
Thus, a concrete moisture test is performed to keep updated on the condition of the surface according to your needs.
Moisture in concrete
Excess moisture in concrete slabs reaches the surface and evaporates for the drying process. Once the concrete hardens, the moisture follows these pathways for as long as they stay open. The humidity and ambient temperatures affect drying times.
Concrete moisture testing
Various methods detect and document concrete moisture characteristics. The worst methods will create more questions and then add potential problems. Look at some practices and find out what will work for the application.
- Plastic sheeting. Nothing complicated here; simply take duct tape and a square of plastic to the floor. When coming back the next day and seeing the moisture under the plastic, you will see how the process of plastic sheeting works, such as:
- Know a specific temperature
- Right relative humidity
- Certain barometric pressure
- The right level of sunlight or shade
- Moisture collects under the plastic
If concentrated moisture is present, you still have no idea how much moisture there is, where it comes from, whether it persists at the same level over time, or whether or not going to cause a problem with the particular material you wanted to place over it. If it is dry under the plastic, is it good? Or is there still an issue concealed? In short, some are better methods available for not that much effort.
- Calcium chloride vapor emission test. It is a method that measures the water vapor amount that comes out of the concrete within a given period. A precisely weighed anhydrous calcium chloride pellet dish is placed under the sealed plastic cover at max of 3 days and over. The dish will be weighed and covered again. The dish is recovered and then weighed again.
The weight difference is due to moisture absorbed by the calcium chloride compound permitting a calculated estimate of the moisture vapor pounds emitted through the floor over 24 hours. The practical quantitative test is very simple to execute and accepted by industry standards. This concrete moisture testing method has no limitations.
The environmental conditions influenced the test, and it is not advised or applicable for floors with lightweight aggregates. It can’t be used on floors treated with patching or coatings and leveling compounds.