Most paving has been designed to cast water off its surface and to avoid water penetration, and the consequent frost–thaw damage to wearing surface, base and sub-base. However, concern about groundwater levels with the fall in the levels of aquifers and the decline of water levels in streams and rivers has led to the development of porous paving—both unit paving and asphalt varieties.
Currently, the following materials are available as porous pavings:
- concrete blocks;
- permeable clay pavers;
- permeable asphalt;
- permeable resin-bound asphalt;
- cell-matrix pavers—e.g. concrete-reinforced grass paving; and
- no-fines concrete.
Unit-paving has developed using no-fines precast concrete blocks and clay pavers with wide, nibbed joints. Resin-bound ...