Over the next few blog posts, we shall cover the topic of wear-life of equestrian surfaces. Coated and uncoated surfaces differ in their mechanism of break-down, and we explore these differences. In this post, we address the breakdown of uncoated surfaces.
In the case of uncoated surfaces the integrity of the surface relies both on a fibrous additive to help bind the components, but also, just as important, the moisture present which provides a natural binding mechanism. Chemists call this natural binding hydrogen bonding. If the surface dries out then this bonding is not present so the footing components will separate, and fibres/additives can rise to the surface.
Consider the difference between dry sand in the dunes at the seaside, and that at the shoreline. Any child soon learns that the sand needs to be wet to make sandcastles! But if an equestrian surface dries out and the components separate, the situation is usually recoverable if water is replaced and the footing remixed.
Long term wear in this type of surface tends to be due to a number of factors: loss of fibres/additives in the wind due to the aforementioned separation through drying, fibre disintegration, and sand break-down into fines. Fibre disintegration is inevitable when you consider that the fibre is being abraded against abrasive sand particles. However the type and quality of fibres can play a role in how resistant the fibres are to abrasive damage. The most abrasion resistant fibres are nylon, which is why nylon is routinely used in toothbrushes. Polyester fibres are also tough and are more resistant than polypropylene fibres. Natural fibres such as wool and cotton have poor resistance and have the added disadvantage of rotting.
Sand particles will also break down, especially if a low grade, low silica content sand is used. Silica is a very hard material and will wear out only slowly, whilst a cheaper, low grade sand will most likely contain more limestone which is more than 10 times softer, and will wear quickly. Typically grains will disintegrate into smaller grains, resulting in ‘fines’ which can generate dust if too dry, or in rain will permeate to the bottom of the surface and block drainage membranes/channels. Make sure you ask your supplier of sand what the level of silica is – ideally greater than 95% is preferred.
Stay tuned for Part 2 of wear-life of equestrian surfaces coming out this week!