Oh dear. The "concrete tiles" issue. Concrete is more sensitive than marble. It is more porous and easier to stain than marble. Which means it must be seal like marble. Marble tiles must be sealed at least once before install and then SEVERAL TIMES after installation but BEFORE grouting. Traditionally 3 sealant applications need to be used on marble. That means concrete tiles can/should receive the same treatment.

I'm sorry to say, but the tiles needed to be dealt with BEFORE they were installed and then sealed AFTER installation (can be as many as 3 times) but BEFORE grouting. You will need to ask the installer how MANY TIMES the tiles were sealed BEFORE being installed (some homeowners take matters into their own hands and seal the tiles a few WEEKS before the installation happens so the tiler does not spend DOZENS of hours doing this).

Then you will need to ask how many times the tiles were sealed AFTER installation...and if it happened BEFORE or after the grout was put down. And most importantly, you will need to know the name of the sealant...so that you can go out and get more if needed.

And while you are waiting for this detailed answer from the tiler, go ahead and splash some water on your tiles. If they are properly sealed, the water should "bead" as if sitting on the finish of a newly waxed car. If it does NOT bead, you know where the problem lies...not enough sealant.

And just for fun, let us know what you use for a floor cleaner. It will have to be rated for marble or cement tiles....in other words it cannot be too harsh.