The picture shows blisters and bubbles in a solvent-based acrylic sealer that was applied over stamped concrete. Over-application of solvent-based acrylic sealers can lead to blisters and bubbles as the top of the sealer skins over trapping excess solvent below. As the temperatures increase, the trapped solvent expands and attempts to escape forming bubbles and blisters in the top film of the sealer. Removing some or all of the sealer is the common remedy for this issue.
This seminar, Troubleshooting Decorative Concrete II, Stains, dyes and sealers, was presented by Chris Sullivan at the World of Concrete 2012.