Sealer Popped off

Question:
The sealer on my driveway and patio looks terrible. It isn’t just dirty; I can pressure wash that, but there are some spots that look like the sealer is gone, some flaking, and some spots near the garage door that look like the sealer has popped off the surface or away from the surface. What can I do? I spent too much money to have it look like this.

Answers:
You have several things going on between your concrete and sealer and the seasonal changes.

First, you can cause a lot of damage with a pressure washer. Be careful. A stiff brush and soapy water works great to clean the surface. If you are trying to get rid of hard water spots some white vinegar may help. Muriatic acid works also, but start weak, about 2 cups in 5 gallons of water and work up no higher than 8 cups per 5 gallons of water. Always add the acid to the water, not visa versa. Do not use muriatic acid anywhere it can get to the concrete, only where you are cleaning the sealer.

Second, it is very likely that the sealer applied was a solvent borne acrylic with 25% solids. At that level of solids, there is typically not enough solvent available to carry the sealer into the pores of the concrete, so it creates a skin. If you are experiencing popoffs and scaling, I would bet money on it. Where the driveway abuts the garage, there is a wide and repeated temperature change to the surface of the concrete. If it is just a skin, it cannot forever continue to absorb the expansion and contraction, so it pops off. You probably have plenty of sealer on the surface, just poorly bonded to the surface.

Third, and this is a lot of work. Get a face mask with carbon canisters that states on the package that it is for all hydrocarbon solvents. Do not use solvents without the mask and make sure the filters are fresh. Also, make sure there is no ignition source like pilot lights, motors, smokers, etc. Buy some xylene, Depending on how large your area is, you may need five gallons or more. Use an acid brush (about inch and a half bristles) with a handle so you can stand up to work, and pour some xylene onto the surface to work an area two or three feet square. Scrub the xylene around like it was soapy water, keeping it from leaving puddles, until you see bubbles coming out of the concrete. This means the solvent is carrying the reemulsified sealer into the pores and expelling air. When satisfied you have accomplished the mission in the first area, repeat the process.
Fourth. You probably have enough sealer and do not need to seal again. You probably just needed to get the sealer where it belongs. If you think you need to seal again, I recommend you cut the solids as low as 67% with xylene. All you need to do is give it a uniform gloss. Consider using a slip reducing product as well. Sealers can be slippery. Yes, you are right. You are not supposed to cut the solids with xylene because of the increase of solvent into the atmosphere. Sadly, that rule of good intentions has the opposite result. To fix the failure you had to use a whole lot more solvent. And if someone makes the mistake of re-sealing, you will add more solvent to the atmosphere as well. It is always better to do it right the first time and that means the initial sealing should be no more than 15% solids or you will have a fragile skin on top. Just the facts.

Good luck and good jobs!