Re: repair of concrete underlayment before tiling shower
As for repairing the crack in the concrete ... you could patch it however it may come back depending on the cause for it in the first place.
Personally I would recommend a decoupling membrane for any tile project especially on a concrete slab.
You might want to check out this manufacturer .... Schulter.com for their Kerdi and Ditra decoupling / waterproofing membranes. They also have a great shower system.
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