I have seen this in a few places around town. A few possible reasons: You may be seeing 'efflorescence', which is where the salt in the water dries and cakes up on any hard surface. You see it a lot on concrete. This may be especially noticable if your granite is darker in color. It could also be related to the soil in your yard. I have seen extreme efflorescence to the point of the salts actually eating away at concrete and CMU block walls, due to high levels of salt in the soil. You can have your soil tested to determine if this is the cause. And, it could also be the granite further breaking down due to exposure to moisture, and revealing different colors as a result. I notice some granites break down more easily than others. As to how to deal with it, obviously it is difficult to change your water or soil. If your granite depth is 2" or more that should be fine. Im not sure what to advise here, but hopefully this has helped a little determining the cause.

Well, The engineer did provide an updated design and stamp of approval on the poured product. The builder moved quick to remedy the situation. I'm still a bit concerned though, as I contacted several structural engineers and 2 of them said they would NEVER add-on as described and the other 2 said it was perfectly acceptable. I'm waiting to hear back from the PTI (Post-Tensioning Institute) to see what they say. I don't know that I have any recourse except to walk away from my deposit which is not an insignificant amount of money. Any yes, the soil conditions and cost both contribute to the use of the post-tensioned slab which is the most common construction method here in Houston.

First you'll need to vacuum or remove any loose concrete from that area. You may need to sand the area around the crack, to give it some texture so that you can feather out the patching material. Here's one products we've used but there are many others out there. Schonx SL

Best way to do this is to chase the crack with a chisel and clean up the edges. Buy 1/4-1/2" closed cell backer rod, you can get it on amazon for $6. Put that inside the crack along entire length about 1/2" deep and in the same place you can order and get Quikcrete Cement Crack Filler (home depot might be cheaper for this item) You can also use Sika or Quikrete self leveling concrete filler it sold in most Home depot stores HD also sells the backer rod, but I'm not sure if they have 1/4" or 1/2" I think they only have 3/4"... just make sure to get the one intended for concrete not windows (frost king brand), it would be Sika brand usually, they would know "hopefully". Good luck