As you new bees have observed typical house construction is hollowblocks with rebars and filled cells
I gave up on trying to buy quality hollowblock I bought a molder and hire native to build my hollow block I get 40 blocks @ bag of portland the retailer gets 80 + hollowblocks @ bag of portland, Imagine my surprise when I picked up my first hollowblock by the web and the web disintegrated then fell the 3' to the ground and exploded