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#1 - danlathegreat
Reply 0 123456789123345869
(06/29/2013) [-]
It's a type of concrete called Pervious. It's usually used to deal with a lot of runoff. Whereas normal concrete is made of cement/fine stone/coarse stone/and sand, Pervious exchanges the sand for coarser aggregates, allowing the water to pass through. Think of it as almost a stone sponge.