What is the reason or cause of concrete waterproofing cracks?
The elements and weather. Has it been cold? What did the can or bucket say about temperature or weather conditions?
I agree with weather conditions. Also improper prep could do it. Reaction of the sealer with cleaners used on the concrete.
You mean the sealer cracked? The concrete had too much moisture before you applied it. Run a heater to dry out, and test it with a moisture meter, check the label on the sealer for instructions or call the manufacturer for their suggested level of moisture.
Outside or inside concrete location?
If you have not solved the groundwater issue outside, nothing you do inside will be permanent. In addition to what others have mentioned, continuous hydrostatic pressure from the outside will cause your concrete to wick moisture to the inside. If that water vapor is trapped behind an impermeable layer, it will eventually push the coating off. What ever you apply to the inside walls will eventually fail. It may take a few years, but you will need to reapply at some point. Start outside in terms of managing runoff, gutter extensions, grading away from your foundation, etc.
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Copy and paste.
You need certain grading for cement to have water run off
When the cement isn’t waterproofed that’s when it cracks