Does pressure washing driveways remove a little bit of concrete off the surface?

Ralph Q

Ralph Q

New member
I've been doing some driveways in a development that I never worked in, and it seems whenever I'm done I see a little more exposed aggregate. And sometimes you can see lines from my surface cleaner, not dirt lines, exposed rocks in the concrete. I have reduced the pressure to 1500 psi, and it still happen. So far it seems I'm the only one who notices. Does anyone have an explanation for this?
 
If the concrete is less than fully cured you absolutely can remove excessive amounts of the creme. It takes a good year to fully cure. Even older concrete I often see some sand. What spray nozzles are you using? What psi and gpm? I don't reccomend using anything smaller than 25 degree nozzles if you question the integrity Of the concrete. Also if you think you're pressure is too high I suggest using larger orifice nozzles and leave that unloader alone..... you want full flow messing with the unloader cuts your flow and slows you down.
 
Pat Norman said:
If the concrete is less than fully cured you absolutely can remove excessive amounts of the creme. It takes a good year to fully cure. Even older concrete I often see some sand. What spray nozzles are you using? What psi and gpm? I don't reccomend using anything smaller than 25 degree nozzles if you question the integrity Of the concrete. Also if you think you're pressure is too high I suggest using larger orifice nozzles and leave that unloader alone..... you want full flow messing with the unloader cuts your flow and slows you down.
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I am using a 4200 psi. 4. GPM machine. I replaced the 2502's. With 25 degree 3.5's. I would never even think of using the unloader. I thought for sure that would be low enough pressure. All the driveways were at least a couple of years old. Is this just a Florida thing? I never had a problem like this in New Jersey. Should I go even lower and up the chemical strength. Can you softwash concrete effectively?
 
Yes you can soft wash it. But...florida crete does suck. Rated at 2500psi on a good day. So ya aggregate will be exposed after washing on some surfaces. Just make sure the obvious has been out ruled. Tips are alighned propey and pattern is clear..bar not bent..and so one. The smooth creme concrete doesnt seem to be abundant down here. Pics would help do determine if this was abrasion or if itsjust the elusive mildew stripes.
 
palm beach said:
Yes you can soft wash it. But...florida crete does suck. Rated at 2500psi on a good day. So ya aggregate will be exposed after washing on some surfaces. Just make sure the obvious has been out ruled. Tips are alighned propey and pattern is clear..bar not bent..and so one. The smooth creme concrete doesnt seem to be abundant down here. Pics would help do determine if this was abrasion or if its just the elusive mildew stripes.
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According to one nozzle calculator I used those 3.5 s should have brought my pressure down to 1500 psi. That seems awful low to me for concrete, but it did come clean and still left marks. I don't have a pic that shows this clearly. I did observe that there were patterns in the concrete before I started. Bit they definitely were more pronounced when I was done. I guess I'll throw some 4.5 s on there and see what happens. I have another one tomorrow in the same area. I'll take pics and post them.
 
I have the same problem here in NY...surface cleaned 2 1/2 year old cement and you can see a light haze of grey coming off the cement. There were areas where you can see the exposed rock like you mentioned. Its just cheap concete.
 
There is cheap concrete everywhere, try to do some test spots so you know what the concrete can handle.
 
Number 4.0's on a 4000psi@4gpm will bring you down to 1000psi. Check with a gauge at the end of your hose and you will get a better reading than at the pump. You have friction loss with the longer hoses. Chazz is right about cheap concrete. The mix rates vary. If you ever have the chance to go in the control room at a concrete plant you will see what I mean. Computer monitor system for the mix.
 
Well. I didn't follow the unwritten forum rule...read ,read ,read(search, search, search!) I found a similar thread where guys were having the same problem with the hammerhead. I think I found the answer. The swivel is adjustable and the nozzles were pretty much touching the ground. I lifted the swivel up at least 1.5 inches and I didn't carve up the concrete, but now I need to try some more nozzle sizes. I think I will go for a #3 40 degree and see what that does. The 3.5's were too weak and left mold and dirt behind. thanks everyone for the input.
 
I have heard that most surface cleaner nozzles are anywhere from 1.25" to 1.5" from the ground so you should be ok, but.......always remember that not all concrete is indestructible and a lot of it is just weak.

It is not the manufacturer that makes it weak as they make huge batches for all kinds of places, it is the workers that are adding water that destroys the strength or other types of manipulation that makes it weak so when you pressure wash it, the cream rinses off, even with low pressure, even after months or years of curing.
 
Christopher said:
I have heard that most surface cleaner nozzles are anywhere from 1.25" to 1.5" from the ground so you should be ok, but.......always remember that not all concrete is indestructible and a lot of it is just weak.

It is not the manufacturer that makes it weak as they make huge batches for all kinds of places, it is the workers that are adding water that destroys the strength or other types of manipulation that makes it weak so when you pressure wash it, the cream rinses off, even with low pressure, even after months or years of curing.
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I am starting to wonder if softwashing is the way to go, or a sort of hybrid softwash... say with 4 or 500 psi and stronger cleaning solution. Do you think that would be an effective means to get a driveway cleaned, or do strong cleaners weaken the crete too?. I really want to come up with a method that does the least harm to the concrete (or at least very minimal harm) There is a vast sea of concrete here to work with and I want to become an expert, so I can stay on the ground and off a ladder. I'm half a century old! I started my pressure washing business in 1996 in New Jersey, so I did mainly decks and house washes. There wasn't enough concrete work for me to justify buying surface cleaner. But now, being in Florida, I am on a concrete cleaning learning curve. Thanks everyone for the help.
 
Ralph Q said:
I am starting to wonder if softwashing is the way to go, or a sort of hybrid softwash... say with 4 or 500 psi and stronger cleaning solution. Do you think that would be an effective means to get a driveway cleaned,
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No.
Soft wash and concrete don't go together.
 
Pat Norman said:
What's the ladder for ? If you aren't softwashing roofs sounds like you need to learn about some special downstreaming techniques and spray nozzles to keep you off a ladder. We'll be glad to help.
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Gutter cleaning. And I definitely want to learn more about softwashing and special downstreaming techniques.
 
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Pat Norman said:
What's the ladder for ? If you aren't softwashing roofs sounds like you need to learn about some special downstreaming techniques and spray nozzles to keep you off a ladder. We'll be glad to help.
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Also Pat, can you whiten gutters effectively from the ground? That's the only time I break out my ladder anymore on house washes. sometimes they just don't come clean enough without that soft bristle brush!
 
Ralph Q said:
Also Pat, can you whiten gutters effectively from the ground? That's the only time I break out my ladder anymore on house washes. sometimes they just don't come clean enough without that soft bristle brush!
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They make 32 foot extension poles that are great for brushing gutters. Let's not hijack this thread and start a new one on the softwashing. I hardly ever break out my ladder. Call me at 662 316 7685 anytime.
 
I have tried softwashing concrete a few times, you can't bleach out dirt. Sure you can bleach the mold, mildew and algae but when there is dirt embedded into the concrete, soft washing will not get it out, you just need pressure on concrete.

Always do test spots to see how weak the concrete is so you know. As you are finding out, not all concrete is the same.
 
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