colored concrete self locking flooring blocks assembled on a substrate of sand - type of flooring permeable to rain water as

concrete permeable water paving stone drainage permeability self locking interlocking color colored pavement floor interlocked sidewalk flooring brick sand substratum beton outdoors construction site limited slip installation assembly durability outdoor solid building activity strength materials solidity driveway material coating urban square road architecture stability industry footpath parking cobblestone blocks assembled substrate type rain required laws laws