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Unread 10-25-2020, 10:02 PM   #28
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,225
In the industry, all cement products are rated for strength after 28-days...they had to pick a time. In reality, cement can continue to cure for many years. Functionally, it will achieve a fair amount in a couple of days, after a month the slope flattens out significantly but never flattens entirely.

Deck mud by its nature given the high sand:cement ratio never is super strong, but it is fine in compression underneath tile. I'd use a kneeboard, or sheet of plywood over it if I was going to walk or work on it. When getting ready to tile it, vacuum any loose material and then wipe it with a wet sponge just prior to spreading thinset. As long as there's no liquid water on the surface it's fine to add the thinset. Adding some moisture prevents it from sucking a lot of moisture out of your thinset and making it stiff prior to setting the tile and having a chance to cure. Curing is a chemical process that incorporates the water into its chemical structure and the lack or excess can weaken things. Excess moisture evaporates, but has nothing to do with it reaching its final strength as long as it has enough during the curing process which continues long after the stuff seems to be dried out.
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Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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