A wide variety of permeable pavers and paving systems exist in the Australian market. Traditional permeable pavers are interlocking pavers designed to allow water either between or through the pavers. Alternatively a permeable surface treatment full of small voids such as permeable asphalt, concrete or resin-bound permeable paving may be utilised.
Permeable pavers can be made from a variety of both permeable and impermeable materials. Some concrete pavers are designed to form a traditional interlocking pavement with larger (5-10 mm) gaps in the joints. However, the low surface-to-void ratio means they can readily block up. Other pavers are made of permeable materials such as porous concrete or porous ceramics which allow water to soak through like a sponge. However, the drainage rates can be lower than other pavement types.
A continuous permeable surface treatment (rather than individual “pavers”) can often provide similar durability and better permeability rates. In the UK and USA, permeable concrete systems have been developed and are increasingly being utilised to assist with water sensitive urban design targets. However, the aesthetics of the finished surface are not as good as alternatives, and the surface durability is highly variable on a range of factors including concrete batching and installer skill, and small amounts of surface unravelling can be considered normal.
Resin bound permeable paving uses a UV-stable resin binder (typically a strong, flexible polyurethane) to bind small aggregate together. The mixture can be trowelled to a smooth finish. The final finish, if installed correctly, surpasses the best of exposed aggregate concrete. The smaller stone size and more consistent mixing and batching results in an extremely durable interlocked surface that still obtains a high void ratio resulting in excellent permeability rates.
With all permeable pavement types, the final pavement performance is highly dependent on the subgrade preparation. Numerous differences exist between the materials and installation techniques required compared to “normal” impermeable pavements due to the drainage of water through the paving, subgrade and subsoil. Therefore it is essential when considering permeable paving to compare not only the paving system being used, but also the skill and experience of the installer – the success of your project might just depend on it!