Does a concrete slab and the cruise control on a car have anything in common? Well, . . . sort of.Both are influenced by homeostatic principles. Homeostasis simply means that things are regulated so that internal conditions remain the same or stable.
Take the cruise control on a car. It’s set by the driver to maintain a car at a certain speed. If the car begins an uphill climb, naturally the speed of the car begins to slow, which triggers the cruise control to open the throttle to maintain the speed the driver selected. That’s homeostasis.
|Water vapor emission test on a concrete floor. The floor|
tile failure was due to excessive moisture in the floor.
Look at a concrete slab. Concrete is a mix of cement, sand, aggregate, and . . . water. Concrete drying creates moisture vapor emission. This moisture vapor emission occurs whether the slab is below, on, or above grade. Depending on the water table for the location, the earth below the slab may contain high moisture levels also. The water vapor emission moves from the concrete into the drier air around the concrete. That's homeostasis.
The same thing happens in chemistry. Higher concentrations of a chemical move toward areas of lower concentration until an equilibrium is reached (known as Le Chatlier’s principle).
Call it homeostasis or Le Chatlier’s principle, when it happens with concrete and some type of coating or adhesives, problems can occur. Coatings and floor adhesives can be sensitive to high moisture vapor emissions from the concrete and can sometimes result in failures.
Fast construction and short construction deadlines are normal in the business. Concrete may not have sufficient time to dry naturally before coatings are applied. Excessive moisture vapor emissions from concrete that has not dried sufficiently, or from concrete lacking a vapor barrier, will invariably cause problems with bonding of the coating to the concrete.
It’s just homeostasis at work.
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