Can premixed thinset be used to lay tiles on a concrete floor (or any surface). Is it reliable? The reason I ask is that “no mixing required” is an incentive to use the stuff. But I don’t wantthe job to fail down the road. Thanks
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Depends...
Read the directions.
Usually should not be used on large format tiles on floors. With larger tiles, mastic can take too long to dry. It doesn't cure via a chemical reaction like portland cement based thinsets. Mastics cure by drying out.
Should not be used in wet areas like shower floors. It may re-emulsify (soften) nd lose its bond. If your slab passes excessive moisture? Might not want to use it.
Might not want to use it if you're tiling with natural stone. It can stain or give a blotchy apearance if it bleeds through the stone.
My opinion? Mastics are good for decorative ceramic tiling on walls. Backsplashes, etc. Everything else? Use a true modified thinset instead of a mastic.
second that
Thinset is really easy stuff to mix.