maxit floor Moisture Environment Concepts  
   
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Background
Risk Factors
Damage Processes
When tp Use Adhesives?
Drying
Drying Phases
Concrete Beams
Calcium Sulphate
Concrete with levelling
Single-side Drying
Optimal Drying
Humidity Measurement
Questions

Drying Phases

Drying Phases


The course of drying can be divided into two phases: 
First drying phase

In the first phase the surface of the concrete is wet and the rate of drying is determined by evaporation from the wet surface. This drying process phase will continue as long as the movement of moisture from the concrete by capillary action is sufficient to keep the surface wet so that evaporation can continue. Various measures can be taken to increase the rate of drying, for example, ensuring that RH is low, air speed across the surface is high and the material temperature is high. Water evaporation from the material surface removes heat so that the surface will cool down unless heat is applied.
Second Drying Phase


In the second phase, the properties of the concrete beam structure and the state of the moisture in it affect the rate of drying. A 'water front' gradually recedes into the structure. This means that the moisture must be moved over a steadily increasing distance, predominantly in the form of vapour. This longer route creates ever greater resistance to moisture transport, and drying slows down.


During the second phase of drying, transport of moisture to the surface of the material should be as great as possible. This is important when the concrete or levelling material completes the first phase of drying in a very short time. Factors for achieving this include having a low RH. This requires adequate ventilation and high material temperatures. Drying proceeds more slowly in the second phase so that air speed across the surface of the material has less significance, but a sufficiently high room temperature is important to promote speed of drying.