I think the better approach would be to stack limestone (density of 170 lb/ft3 vs. concrete's 150 lb/ft3) and have very little environmental impact. Does it de

I think the better approach would be to stack limestone (density of 170 lb/ft3 vs. concrete's 150 lb/ft3) and have very little environmental impact. Does it depend on height to be effective, or could it stack limestone just 30' up or so?