the only other thing i may add to this is that the concrete blocks in the u.s. is solid like a rock and unless you use all force with a hammer, the u.s. concrete block is indestrubtible. at 8" x 16" it is dense, and massivery heavy. the philippines concrete blocks however at (4" or is it 6") is fragile. it will crumble on your handles with the slightest pressure. it is not uncommon for this blocks to crumble when picked up.
stacked vertically without any support, the u.s. concrete blocks is formidable. the same arrangement with the philippines concrete blocks is unstable.