[scociny]

We moved to Henderson this summer and noticed the brown stamped concrete has some white residue that doesn't wash off. It's not over the entire area but some spots are worse than others. I also noticed it in some of the desert landscaping we have. Does anyone know what this is and how to remove it? I tried scrubbing with a scrub brush, but maybe I need a real stiff brush to get it off. I was thinking of renting a power washer but don't want to spend the money and not have it work. I also have plants around the perimeter so using harsh chemicals would be out. I lived in Phoenix and never remembered seeing this problem. Any suggestions? Thanks so much for your help!

[jpk]

Most likely it's hard water spots (calcium deposits, as you guessed). Check that your drip irrigiation isn't spraying water onto the driveway or isn't running so long that there is runoff onto your driveway.

You can probably take it off with some CLR or other cleaning product from the hardware store.

[SportyandMisty]

It can also be coming up from underneath if there is no vapor barrier underneath. There is a simple test. Get a 3 foot by 3 foot thick sheet of plastic and tape it to the stamped concrete using duct tape - sealing it all the way around. Wait at least 24 hours. Then pull up the plastic & tape. If it is damp underneath - the moisture & lime are coming up from underneath the concrete. If so, then your best bet at this point is elbow grease. The right way to pour a concrete slab is with a vapor barrier underneath, but many contractors cut corners.

[Buzz123]

Here is a Google page on efflorescence: Efflorescence - Google Search

And here is company that deals with it I guess. Look at the bottom of this page for efflorescence: Frequently Asked Questions | ArtCon | Las Vegas Concrete | Decorative Concrete | Stamped Concrete | Stained Concrete | Concrete Pavers

I take it they are saying it comes from the salts in the cement, but I've always been told that it comes from our alkaline soil, and maybe the caliche. The lowest parts of the valley have the worst soil and it takes a lot of soil preparation to build on it. Years ago they didn't do that and many homes were wrecked because they didn't.

After moving into my first house in the Wilbur Clark Estates, near Lamb and Charleston, in the 60's, we found out just how bad it was when I stepped out into the back yard after a rain and went in up to my knees. In those days builders and realtors didn't have to reveal everything like they do now. We later found out that every house in that development had been recalled (for lack of a better term). They had to remove every slab under every house, and then raise the houses on blocks to keep them off the ground, and then put in wooden floors. Homes all over the east side of town were sinking and walls were cracking. Our friends on Rio Mayo, near Boulder Highway and DI, had to do a lot of work on theirs.