where is the quote from.... Did I say it... Eek!! Must have been a wobbly moment.... It's not correct. All screeds dry by evaporation of moisture from the surface with the additional drying effect of
cement hydration in the sand
cement version. I hear the drying from the bottom upwards thing a lot. I think it is because of some of the misunderstandings that go on with screeds and how people measure and interpret results. In general what happens is that the surface of the screed begins to dry and this effect reduces the moisture in the top part of the screed. The body of the screed then wants to equilibrate as nature does not like unevenness. Thus " drawing moisture from the body of the screed. More moisture evaporates and more moisture is pulled through the screed in a bid to equilibrate. And so on... It's much easier to explain I pictures but I can't get them uploaded on here.....
I do explain it in my tiling to anhydrite screeds course....
the relative rates of drying in a sand
cement screed are much more linear than you see with anhydrite primarily because of surface texture and porosity. It is not however possible to measure either accurately along it's drying phase using anything other than direct moisture measurement eg oven dried sample or carbide bomb because all the other methods are affected by the moisture levels in the screed in relation to the atmospheric humidity.
