Moisture and Alkalinity. Too much moisture in new concrete can cause paint to bubble. It usually takes at least 30 days for moisture to dissipate enough for paint to adhere. You can test for moisture by taping a piece of foil to the surface, sealing all the edges with tape, and checking for condensation after 24 hours. If there is no condensation, the concrete is dry enough for painting. High alkaline levels also can stop paint from sticking to the concrete. It can take anywhere from 30 to 90 days for alkaline levels to drop enough for painting. Test the pH, and look for levels 9.0 and 10.0.