very nice, i would say that all your concrete bits look a little bit too rounded - almost more like pebbles on a beach than broken up concrete. it might be nice to have some cracked bits where the two broken edges conform to each other so you can see they clearly used to be one.
Thank you guys. @Olli I wish I could put crash helicopter in there. I just learned how to make a good concrete debris, block. I will put that in my next project.