May sound crazy, try a product called Gorilla Glue. Depending on the size of the cracks it could be your answer. It expands to about three times the amount you put in. It bonds concrete and just about anything else. It's sandable, paintable and stainable. I tried it on a wood floor and it worked great. Distibuted by Lutz File and Tool Co. 3929 Virginia Ave. Cincinnati, Ohio www.gorillaglue.com
You may think I'm pulling your chain, but this stuff is for real. I swear by it. Lots of luck.