Concrete Cleaning

[Brian 14]

Any thoughts as to what might cause a stain like this?

Thanks,

Brian

[Beth n Rod 1,279]

Brian,

What's at the top of the picture? Is that a garage door? What's on the bottom of that door? Is this on a downhill slope? Looks like possibly rust, but I'm not sure. I'll ask Rod to take a look.

Beth

[Brian 14]

Hello, Beth,

Here's another shot...

[Brian 14]

Up close...

[One Tough Pressure 580]

Groundwater seeping up, or a broken water pipe and the rebarb of the concrete eroding. Or a very leaky Radiator.

Have the person turn on the sprinklers and see if it seeps out. See where the meter box is and where the line enters the house. Make a path and see if it runs thru there.

[Brian 14]

OTP, I'll give that a try.

Thanks,

Brian

[Beth n Rod 1,279]

Brian,

Rod agrees with OTP. He also says you can remove it with an acid and then seal it with a concrete sealer or stain.

Bth (for Rod) :)

[ron p 500]

you can see from the close-up of the pic that 2 diffrent contractor's have poured the diffrent slab's.

Whatever the prob is, im betting it's not the first time one of the slab's has been poured.

[Brian 14]

ron p,

That's exactly what I learned today. The electric company made some sort of repairs under that section of the driveway in the last year. Thanks, all, for the suggestions.

Brian

[One Tough Pressure 580]

And during that repair, what did they break? Something is leaking underground, question is what?

[Beth n Rod 1,279]

I hate to think it's from wire that's exposed.... Looks more like its from a pipe But I don't know. They wouldn't have to rupture it to have that would they, if they put something under there that wasn't meant to be exposed to minerals and wet and so forth?

Beth

[Aplus 525]

Could there be an underground sprinkler pipe under the drive? OTP may be on to something.

Those stains look like they could be caused from iron rich well water, or maybe even from the re-bar in the concrete.

Water will always emerge from the point of least resistance, in this case, thru the felt expansion strips that separate the concrete flags.

I can't imagine a city water or sewer pipe in that location. Usually those go straight out from the house to either the street, or an easement area.

One last remote thought..... was there ever an old car parked there? I've seen brake rotors and calipers, which are made of iron corrode and leave stains on a driveway.

[Big Bill 14]

My guess is that when the electric co. poured the new section of slab, they might have or probably did use rebar & wire mesh, then had CaCl2 (Calcium Chloride) added to the ready mix concrete to speed the curing time of the concrete. CaCl2 is very, very, corosive. You can bet that rain water is seeping through the expansion joint, hitting either plastic or clay mud under the slab, then coming back up to the top of the driveway. It is bringing up the corrosion of the steel w/ it. Generally, when you order ready mix concrete, you can request CaCl2 in 1% or 2% be added to the mix to speed the curing time.

Big Bill

[ron p 500]

they could have used a cast pipe to route the wire's and now that pipe is rusting.

[Paul B. 523]

It looks like water seeping thru the concrete and I would suspect rebar to be the causing the corrosion on the surface. Looks like the expansion joint and concrete are failing in one area.

Is the grass wet or muddy on either side of the concrete (in line with the expansion joint)?

Water lines are normally under frost line (in MD that must be at least 2 ft). That doesn't mean it's not leaking, but the customer can usually tell a leak by differences in their water bills. The water company can also check at the meter to see if there is a leak before/after the meter. (If it's before the meter it's the utility co's. $$ to fix, if it's after the meter, it's the homeowners $$$.)

If it's a sprinkler system, the homeowner can turn it off and leave it off.

Newer power lines are normally at least 3ft underground and are not encased in corrosive pipes.

Again, if it's an underground water leak, it should be repaired first. Looks like the concrete should also be repaired and the rebars that are exposed during the repair should be coated before concrete is poured, otherwise the problem will remain.

"The Must For Rust" is a pretty decent corrosive inhibitor and provides a coating. For cleaning the concrete, a phosphoric acid based product is most effective, but there are others out there such as Oxalic acid, White Ox, Prosoco's Ferrous Stain Remover, etc.

[Paul B. 523]

It looks like water seeping thru the concrete and I would suspect rebar to be the causing the corrosion on the surface. Looks like the expansion joint and concrete are failing in one area.

Is the grass wet or muddy on either side of the concrete (in line with the expansion joint)?

Water lines are normally under frost line (in MD that must be at least 2 ft). That doesn't mean it's not leaking, but the customer can usually tell a leak by differences in their water bills. The water company can also check at the meter to see if there is a leak before/after the meter. (If it's before the meter it's the utility co's. $$ to fix, if it's after the meter, it's the homeowners $$$.)

If it's a sprinkler system, the homeowner can turn it off and leave it off.

Newer power lines are normally at least 3ft underground and are not encased in corrosive pipes.

Again, if it's an underground water leak, it should be repaired first. Looks like the concrete should also be repaired and the rebars that are exposed during the repair should be coated before concrete is poured, otherwise the problem will remain.

"The Must For Rust" is a pretty decent corrosive inhibitor and provides a coating. For cleaning the concrete, a phosphoric acid based product is most effective, but there are others out there such as Oxalic acid, White Ox, Prosoco's Ferrous Stain Remover, etc.

[Jon 533]

I see one more thing here, not only the two slabs poured at different times but look closer, about a foot or so on each of them appear to have been removed and re-poured, so whatever it is I would say has been fixed or tried to be fixed before.

It also could be anti-freeze but rust is my first guess. There is some type of tool that can locate leaking water, plumbers use them, rent one and check for the leak if the water company or other utility won't do it.

My opinion only, some will not agree with me but I will still consider you friends of mine.

[Mike Williamson 198]

Jon:

Where do you see it repoured? The only thing I see is about a 2" border on each slab, which was done when it was poured...not sure why they'd do this on a driveway, but they did. Whoever poured it did a lousy job.

Is that what you're talking about, or did I miss something you noticed.

[Brian 14]

I want to thank everyone for responding. You have come up with many very interesting ideas.

There is no underground sprinkler system and I didn't notice wet or muddy areas near the expansion joint. I had not considered anti-freeze because of the pattern of the stain. After further questioning, the home owner remembers a contractor's van that was leaking radiator fluid being parked there for the better part of one day. If this were the cause, what sort of treatment would be appropriate?

At this point, because the concrete needs more attention than just cleaning, they have decided to pursue this with the electric company first. We'll see where that leads and take it from there.

Again, thanks for the help,

Brian

[Jon 533]

Mike could be what you see is right, they don't do it that way here so it did appear to me it was dug up and repoured.

Yes a crappy job indeed, bet it was the homeowner who mixed and poured that driveway.

Or it was over runs of concrete and why the mixed batch or looks.

Ok out West they call any left over concrete in the trucks over runs, they either sell it cheap or dump it so they mix batches and sell it cheap.

Still that is going to be one nasty job and you should charge accordingly too!

Jon