Before discussing the methods of moisture testing and its importance to ensuring successful commercial and industrial flooring, including epoxy flooring, it is important to understand a little about the process of concrete manufacture. Concrete is made by mixing a combination of water, cement and sedimentary materials in appropriate quantities so that a precise consistency is achieved. The water in the mixture is prevented from evaporating out of this mixture until the initial curing phase is over and the concrete is at setting point.
It is at this point that you require any excess water droplets or moisture to evaporate out of the mixture so that the concrete can begin to harden and dry. Depending on the surrounding temperature and humidity, this process can take a matter of days or weeks. The general rule is 28 days to full cure. If moisture is retained in the mix and sealant applied prior to this general rule (28 day full cure) then the water droplets are trapped and after a period of time due to hydrostatic pressure, will begin to force any liquid upwards and bubbles will begin to appear in the flooring material. Over time cracking can occur, with mould and mildew getting in between and the flooring will no longer be waterproof for example, or safe to walk or drive on, which is a waste of your time and money.
Carrying out a moisture test, particularly if installing an epoxy floor finish, is always recommended by National Waterproofing & Industrial Flooring and any other professional contractor. Epoxy floors can be buckled or lifted off the concrete base if there is excess moisture that rises to the surface destabilizing the concrete. Any surplus water droplets that are alkaline in content can also eat away at epoxy coatings which cause it to split and bubble up. Fortunately, moisture testing is a routine process for professional waterproof and commercial flooring companies based in and around the Melbourne, Port Melbourne, Moorabbin, Cheltenham, Croydon, Sunshine and Preston areas. They may use one of four methods which are:
A non-destructive moisture meter is a hand-held electronic moisture meter operating on the principle of impedance measurement. Parallel co-planer electrodes are mounted on the base of the unit which, during operation, transmit low-frequency signals into the concrete floor screed to a depth of approx. 12.5mm (.5 inch). While concrete under normal conditions can never be completely dry, the instrument has been calibrated on acceptably dry material. In operation it compares the change in impedance caused by the presence of dampness and displays this on a clear, easy to read analogue dial. This type of moisture meter will give you an instant reading of moisture content from 0% to over 6%.
The flooring is prepared by being swept clean and vacuumed dry using a commercial or industrial vacuum cleaner. Then the surrounding air temperature and humidity are checked, because moisture tests are most accurate during relative humidity levels not more than 60% and during an air temperature between 18-30°C (65-85°F). The test kits can be bought from a number of manufacturers but they basically contain the same equipment and it is recommended using a ratio of 1 kit to 333 square feet (sq. ft.) of flooring. The kit is placed on the floor and a weighed amount of anhydrous calcium chloride is placed on the dish that is supplied with the kit, and a plastic dome, which is used to cover the dish and chloride. The precise weight of the chemical compound is noted at the start of the test period and depending on the size of flooring, there may be one, two, three or more kits set out at the same time.
Then not before 60 hours are up and no more than 72 hours, the kits are removed and the calcium chloride weighed using precision scales. Any excessive moisture will have been absorbed by the chemical, making it heavier and it is possible to work out the level of safe vapour transmission levels. If you have a flooring of 1000 sq. ft. then you will have 3 kits in operation, and for new concrete the safe level of moisture or vapour transmission cannot be more than 3 pounds per 1000 sq. ft. So if each of your 3 kits picked up less than one pound each, the moisture level is acceptable but any more and the sealing process should not take place. A lot of new concrete floors will test around 10 to 15 pounds per 1000 sq. ft. and further curing time is needed until the moisture level is safe enough to pour on an ePoxy waterproof covering for example.
Alternate moisture tests involve taping a plastic sheet to the surface of the flooring very securely around the edges ensuring a tight seal. This is left for 72 hours and a dew point hygrometer used which records how much evaporation took place by testing the moisture content of the air under the sheet.
For this test, holes are drilled into the concrete and an electronic meter inserted in or embedded before the concrete has dried out. Over the following 72 hours the relative humidity of the concrete is tested and the software in the meter can work out the amount of moisture present in the core of the concrete slab.
Whichever method is used, moisture testing is an important part of ensuring you get the professional commercial, industrial, waterproof or Epoxy flooring that will stand the test of time and continue to work hard on your behalf, day after day.
At NWIF, we are the industrial flooring melbourne specialists. For any work on commercial or industrial flooring, just contact us on 03 9555 0655.