Pour a small amount of Xylene on an area that is still coated by sealer and allow the Xylene to sit for 20 seconds. Remove any excess. Touch the area and if it is tacky or sticky the surface was sealed with a solvent-based sealer. If the concrete is not tacky or sticky the concrete was sealed with a water based sealer.
Also asked, what temperature should it be to seal a concrete driveway?
As a general rule, 50 degrees F is the minimum ambient air and surface temperature needed when applying most concrete sealers and coatings. All sealers and coatings have a minimum film-forming temperature, or MFT.
How long does concrete need to cure before sealing?
Other reactive penetrating sealers (silanes and siloxanes) and most high-performance coatings, such as epoxies and urethanes, should only be applied after the concrete is fully cured (generally 28 days). Almost all sealers can be applied after the concrete is 28 days old. Again, that depends on the product you use.