Concrete spalling or what?

Hello all,

Question about a customers driveway that I did the other day. They sent pictures to me of the spots in question. It looks like coral almost on the surface. From looking online the closest I can find is “spalling”. Is this caused by the pressure of the washer or the concrete being too old? The concrete is over 25 years old. The driveway hasn’t been cleaned in years either.

Would this be a combination of using the pressure washer in a perfect storm plus the neglect? Before the clean I didn’t notice any major flaws or issues. Maybe the dirt was so bad it filled in these gaps.

Please help so I can give guidance to the customer. No major cracks like crazy in the concrete just about 7 to 8 cracks on a 2500 sq ft driveway. I wash with a 4gpm/4000 psi and 20” surface cleaner with 2502 tips. For next job I will be changing to 25025 from your guys recommendations just hope that I didn’t screw it up too bad.

Really thinking that the owner of the house didn’t properly maintain the driveway. Never seen this before. Wish I investigated more closely before starting the work.


Did you take any before pics?

These are the best ones I have. Looking closely you can see the aggregate. Also, while surface cleaning I did have some sand buildup but not any gray wash or nothing too crazy for me to stop.

Not sure what they were expecting. That driveway looked like crap before with a lot of aggregate showing through. Always undersell especially with old concrete…washing it will clean your driveway not renew it. It is better to use less psi on residential concrete…I use about 2300-2500 psi now but used 4k psi/4gpm on many older driveways with aggregate hoeing through with no problems. That is a little strange looking…haven’t seen any concrete looking like that. Sometimes cleaning a very dirty driveway will expose rust, oil marks, and cracks that were already there


I switched to the 25025 tips. Even thinking at this point of going to 2503 tips. Anybody else here with a 4/4k with any input?

In theory will the larger orifice give me more flow? Always can post treat with a stronger mix if need be but most driveways around this area are very old and it is rare if someone resurfaces or buys a new d/w. One of those things where you don’t do it until you really have to.

Ive done a bunch with a 4x4 and those tips with no damage. Even new concrete has come out clean without hurting it. You just cleaned some ugly concrete