We don't install concrete ourselves. But if it's part of a larger landscaping job, we'll take on the work and sub the concrete finishing work out to a contractor we've worked with for years. And that's what happened last October. We subbed part of a large job out to our concrete flatwork contractor (who has always done excellent work in the past). But this time, the concrete patio he installed for our customers didn't turn out so well. Specifically, the patio has large sections that are blotchy. The overall patio is kind of a gray color with these large sections in the middle that are more white in color. It was apparent within a week or so of doing the job. And the homeowner questioned me about it. My contractor told me that since it was fall and the temperatures were fairly low, it would take a while to cure and once it all cured, it would all look the same. Okay, fine. Fast forward to today, and it looks pretty much the same as it did back then. Still very blotchy, still two distinctly different colors throughout the patio. I called him today and he tells me that some patios just take a lot longer to "cure out". He said this has happened to him before and eventually - after 6 months or a year it will all cure out and be the same color. I am no expert in concrete. That's why I sub this stuff out. But I've attached some photos. What do you guys think? It actually stands out more in person than it does in this photo from my cell phone. But you'll get the idea. One other thing, if you go to the gray areas and scratch at it a little bit with a screw driver or pocket knife or something, the gray part sorta comes off and leaves the white color. So that makes me think maybe I could just use some sort of buffing machine or something to get the top layer off. Do they make such a machine? Any suggestions? Comments?