Yea, but I haven't figured out how to make a concrete ROOF for the coal bin yet...
Those blocks were cheap, the local concrete companies make them from left-over mix in the trucks. Because of the price, compared to pressure-treated wood, and the ease of just stacking the blocks, they were ideal for making my bin.
It took just a few hours to stack the blocks, and I can remove them just as easily if I need to move the coal bin, or decide to get fancy and put down a concrete slab under the bin.
I have a tarp stretched over the bin now, to keep rain and snow off the coal. I had my coal freeze last year, had to use a pick-ax to break it up. I looked like a 'real' coal miner then!!