"Cast Stone" Stains

[Mountain View 14]

I have a customer with a "Cast Stone" balcony over his front porch. It's essentially a concrete facade laid over a steel frame. There are lots of high end ($1mil and up) houses around here that have this kind of stuff. Attached is a before and after photo of part of this balcony. The problem is, I just can't get all of the stains (mold, algae, leaf tannins from roof run off) out of the concrete. In the after picture the surface is stained but feels perfectly smooth. My theory is the concrete has lots of micro pores and micro cracks that moisture and mold has crept into. Everything on the SURFACE has been cleaned off. I used concrete cleaner from Delco and SH with cold water (don’t have HW rig yet). I even went back after words with a strong SH (about 6% hitting the surface) with the hopes that it would creep into the cracks and pores to kill the mold, no help. This is the north side of the property and NEVER gets direct sunlight. I’ve had a couple of these before but none this bad. I did tell the customer that it was doubtful I could get all of the stains out and other parts of the balcony do look considerably better, however, I’m pretty gun shy of this type of material now and will think seriously before tackling this type of surface again. Either that or tell the customer, “Hey, I’ll do what I can but no promises”. Having said all of the above, the customer was cool about the whole thing, we agreed that regular cleaning over time would certainly help, and he did pay me for the job. It still bugs me that stains aren’t all gone!!

Any advise about something else I could try?:confused:

[MMI Enterprises 289]

That type deco brick facade (not painted right?) can likely take a turbo if ya got no heat. May need turbo even with heat.

The flat balcony looks thin on paint like it's been oxidized and worn through from the runoff. A strong house mix of the 6-8% level, a butyl gutter type cleaner, or even some Clorox Cleanup should of sufficed if the stuff was on a solid top coat of paint. Following up with some citric is about all ya can do after the cleaners.

[Mountain View 14]

Never painted, just concrete. I've thought about the butyl gutter cleaner I have. I may go back and try a small patch with that, then an ox rinse. I did try the turbo nozzle, no difference. Up close you can see little micro cracks running through this stuff like the veins of a leaf. Supposed to look like Mediterranean stone I guess.

[Beth n Rod 1,279]

Saferestore from Eachochem will do it.

Rod!~

[John Orr 206]

I would go with 12.5% chlorine, applied directly to the stained area. (Be sure to rinse any over-spray.) Give it some dwell time, then pw. Hot water is not needed.

[MMI Enterprises 289]

Pete,

No paint on fake bricks but is there paint on the balcony?

If not then then them phosphoric type restore products a good choice and or the stronger bleaching...sorta looked painted on my screen.. :)