Epoxy resin-bound gravel - review

Landscape and Garden Product Directory

The distinction between plastics and resins is 'arbitrary' (Encyclopedia Britanica). They are polymers, which are very long-chain molecules. It is the great length of the chains which produces their characteristic flexibility and ability to soften when heated (hence the name 'thermoplastic'). Natural resins, containing cellulose, are exuded from coniferous trees and have a delightful aroma. Artificial resins use oil as a feedstock.An epoxy resin is is a polymer with oxygen and carbon atoms in the ratio 1:2 bonded into long chains. Epoxy derives from epi-, above and oxygen. Epoxy resins are used in paints, glues and bonding agents. Epoxy resins set hard when two components are mixed. They can be clear or have an amber or brown colour. Epoxy resins are highly durable and have great adhesive strength.Weeds do no grow through resin bound paving.

Given the above properties, resin is superior to bitumen as a binding agent for paving: you see the natural colour of the gravel aggregate instead of the sticky blackness of bitumen. The disadvantage is that resin is much more expensive than bitumen. It has therefore become common practice to lay a base of bitumen-bound paving and surface it with a thin layer (4-8mm) of resin-bound gravel. To produce a thin layer, and save money on the resin, small-size gravel aggregate is used. The resultant paving is much pleasanter than bitumen paving - but very much more expensive than unbound gravel paving.

Permeability to water is another issue. From a sustainability standpoint, it is much better if a paving surface is permeable. The water can then trickle back to replenish underground water supplies, instead of flowing into drains and causing downstream flooding. From this point of view, two different types of resin-bound gravel should be distinguished:

• If a layer of resin is applied to an impermeable base course, then the resin-bonded gravel will also be impermeable. to water.
• If a pre-manfactured resin-gravel compound is used, the pavement can be permeable if laid on a permeable concrete or macadam base.