We used a small crusher to process about 300 tons of 4" thick concrete with no rebar. I was pretty impressed with it's capability for such a small portable machine. It took about 4 days to crush the material. We did the same as you by reducing the material into manageable chunks before processing. We found that just because it fits into the hopper doesn't mean it will crush it effectively. It takes much longer for it to grab a large chunk rather than a smaller piece. Once we found the sweet spot, it went remarkably well. I believe it sells for around $12,000 http://www.youtube.com/watch?v=iAGVZIlSegU http://www.ezgrout.com/pages_products/material_recycling_systems/products_hog_crusher.php