A Word About Damp Curing
All portland cement mortars (screed beds, thin-set mortars, grouts, etc.)
will not reach their full strength and serviceability if they dry out before
curing. Generally, the only way to retain water in an installation is by
preventing its loss through the use of polyethylene film or Kraft paper.
Also, water can be added to the mortar after it has initially set. And it
may need to be added for several days in a row. Drier, hotter conditions
only reinforce this need. Wherever weak, crumbling mortars have appeared
the usual problem is lack of a proper cure. Considering the cost of labor
and tile in today's market, damp curing is a low cost insurance policy indeed.
The graph below depicts the strength advantage of damp cured mortars.