You should use a siloxane sealer because it is repels water, de-icing salts and is breathable. See what Tim Carter, a nationally syndicated columnist has to say about them http://www.askthebuilder.com/008_Deicing_Salts_And_Concrete.shtml And here is our product too, http://appliedtechnologies.com/pages/content/concrete_sealer.html Here is a link that might be useful: Concrete sealer

That is poor quality work. It looks like the finish was done when the material was still too wet. That could be because there is too much water added, which makes the concrete weak. Or it could be that the guy ran out of time at the end of the day. Did the workers mix the material on site? Site mixed concrete is often over-watered. If it was delivered pre-mixed, it is probably good concrete. You can verify by calling up the yard and confirming the specs of your particular batch. What kind of finish did you specify? If you had specified a certain level of smoothness, type of finish, or showed him the driveway next to yours and said "Make it like this" you would have a case to make him do it over. But I suspect there was not anything so specific in the contract, so you really can't do anything other than not recommend him to your friends and neighbors. The color will even out eventually. Concrete should be wetted a couple times a day for the first week as it cures, especially in the blazing sun. This helps prevent cracking and surface issues. Conctere likes to cure slowly. You could have the surface ground down to expose the aggregate and then polished smooth and sealed. That could look really neat. The concrete should cure for probably a month first.

Because your slab is suspended above a basement, you could float a plywood subfloor or adhere a subfloor to the slab. When we float a subfloor, it is usually two 1/2" or 5/8" plywood layers installed on a diagonal layout to the room with each layer staggered so no seams line up. The layers are attached to each other only. The plywood needs to be dry and reasonably flat. Garbage sheathing will not suffice. Since yours is such a large space, I would suggest you do a lot of research on different install options and consult with installers who have done solid over concrete slabs. One important thing to note is the fact that even though your slab is suspended construction does not mean it is entirely safe to assume it is dry enough to install wood flooring over without providing for some sort of moisture barrier or retarder. Concrete can take up moisture and emit moisture depending upon the temperature and moisture vapor content in surrounding air at any given time period. There have been remarkable advancements in adhesive technology with some adhesive manufacturers making the claim that now you can install a solid to concrete directly when using their product designed to do just that. I have not done that. Engineered wood flooring construction is basically a quality plywood with a veneer face that is the specie of choice. The veneers differ from product to product; some have a thin peeled veneer and others have a sliced (sawn) veneer. The unfinished Owens engineered is of the sawn type with a veneer that is almost a full 1/4" thick. I did an Owens unfinished over sheet cork over a slab where the product married to an existing 3/4" solid wood floor attached over a portion of the house that had a basement. You could not tell the solid from the engineered. Good luck with your searches.

I've mentioned before that I live in the desert. Most all the drives in my neighborhood are stamped and stained. I was gobsmacked when I moved here and saw all the color and different finishes - in this heat - on driveways. Really, it was a WTH?? moment. A range of products are used. Trojan Color Sealer gets around and a few other ones I can't remember -- but they're out there just gotta look for them.