SUBSTITUTE GROUND SURFACE MATERIAL

Abstract: The invention relates to a substitute soil material for lay­ ing as a sports surface for example a horse-race track. The material may be a sand or other fine granular material with a binder comprising a polymeric material dispersed or dis­ solved in an oil which preferably is a soft grease at ordinary climatic temperatures. When laid, the surface may be main­ tained by periodic raking. Suitable polymeric materials are e.v.a., polystyrene, nylon or p.v.c.

Description: The invention relates to ground surfaces and substitute soil material for use in forming the same. More particularly but not exclusively, it relates to treated particulate material adapted to be laid in defined areas so as to form recreational ground surfaces. Recreational ground surfaces should ideally be little affected by weather or by wear and should offer a durable, resilient superstrate having consistent properties throughout its area. Such ground surfaces, for example the turf on a horse race track, may become slippery when wet, hard and crumbly in drought conditions and unsuitable for use at all in icy conditions or during and after heavy rainfall. Inconsistencies arise in the properties of the track due to the formation of divots thrown up by hooves, uneven treatment by rollers, differences in soil types or various densities of the subsoil beneath the turf. Alternatively, race tracks or other recreational surfaces may be of the kind known as dirt-tracks comprising sand bound by clay compost or other binder, but such surfaces are adversely affected by rain, very dirty in use and require considerable maintenance. In attempts to improve the resilience characteristics of track, it may for example be decided to incorporate wood chippings which will be found quickly to deteriorate in use and eventually to rot. US-A-3 334 556 discloses a substitute soil material for athletic and playing areas which is applied over and supported on a prepared granular base. The material comprises a coarse sand that will not crack or blow and allows water to drain through, planer mill cuttings for wood shavings to form a springy base, and an oil-base product free of asphalt to hold the sand and wood cuttings together to keep them from blowing. GB-A-1 171 discloses a process for making roads consisting of loosening the material constituting the surface upon which the road is to be formed, thoroughly mingling with such loose material a quantity of asphaltic oil or residue of a viscose nature and then consolidating the material. It is well known that tracks of the various kinds mentioned above exhibit very different characteristics in wet conditions. Hard dry surfaces may cause injury to the joints and muscles of the users, for example horses or dogs, due to jarring deceleration on impact. Moreover, dry conditions often results in the formation of so-called dust-bowl conditions, which have a debilitating effect on horses by causing equine cough. Wet, soft surfaces are tiring to the animal and make the performance of the track, i.e. the "going", slow. It is an object of the invention to provide a soil or ground substitute. It is a further objection to provide a soil or ground substitute the use of which minimises the above disadvantages. Accordingly, the present invention provides substitute soil material comprising sand or other particulate or granular mineral material treated with a binder of an oil-based product, characterised in that the binder comprises synthetic polymeric material dispersed or dissolved in an oil, said oil having a viscosity such that it is substantially non-fluid at ambient temperatures so as to produce an inert, discrete material permanently capable of being raked when laid in a layer upon a substrate. The invention further provides a recreational or sports area having a surface formed of said substitute soil material described in the immediately preceding paragraph. The invention further provides a horse race track having a surface formed of said substitute soil material. Advantageously, the particulate material may be of varying particle size. The oil will conveniently have the consistency of a soft grease at normal temperatures and will become fluid at temperatures in a range immediately above climatic temperatures appropriate to the location of use. Suitable oils may be petroleum-based or may be selected from other oils including organic oils. The polymeric material may be ethylene vinyl acetate (E.V.A.), polystyrene, nylon, polypropylene, polyvinyl chloride and the like, as selected, and itself may conveniently be added to the oil in particulate form to facilitate dissolution. Selected oils will also be of a kind for which there is a reasonably wide margin of safety between the dissolution point of the polymeric material and the temperature at which heat degradation commences. It will be appreciated that the addition of the polymeric material to the oil imparts an appreciable degree of resilience to the treated sand. This resilience is such that for example a horse's hoaf landing on the surface of a horse race track formed of material according to the invention deforms the surface to a limited extend i.e. causes a limited shear movement. This allows the hoof to pivot in the track surface as the animal moves forward. However if the binder were not present, the sand would move too freely to assist the next stage of the horse's movement, that is, the pushing bark of the hoof against the track for the next stride. Sand alone does not provide a firm enough reaction surface. However, a track formed of substitute soil material according to the present invention not only possesses the desired limited shear action but also the firm reaction surface to assist the horse's next stride. The track also has a limited capability for retaining air between the treated particles. This entrainment of air contributes to the comfortable under-foot conditions produced by the resilience of the binder in the construction of the track produced according to the invention. Additional resilience may be obtained by the addition of particles of cork or synthetic or natural rubber to the treated sand. There will now be described an example ofa material according to the invention. It will be understood that the description is given by way of example only and not by way of limitation. Example In the example a batch of sand of varying particle size was treated. The range of particle sizes corresponds to the as-dug condition of the sand. However, the sand was dried before treatment. A petroleum oil fraction having a consistency approximating to a soft grease at ambient temperatures (c. 10,000 centipoise at 20°C) was heated to 160°C. Ethylene vinyl acetate (e.v.a.) containing approximately 28% vinyl acetate and having a melt flow index of 25 was then added in particulate form to the heated oil in a ratio of 1 part e.v.a. to 9 parts oil by weight and caused to dissolve by a stirring operation. The dry sand was then added to the binder in the ratio of 100 parts sand to 6.5 parts binder and thoroughly mixed. The resulting mixture was laid to a depth of 15-20cm as a superstrate over subsoil or a suitable porous graded stone base and was found to give agreeable "going" characteristics for a horse. As an alternative the mixture may be laid on a membrane comprising a so-called geotextile, a non woven textile designed to reduce migration of particles between layers. Maintenance of the track has been found to be easy, comprising simply raking or turning over the top 5 to 8 cm. Light rolling will be found to compact a thin upper layer of say 1-2cm which acts to resist the entry of rainwater. If however, rain seeped into the track superstrate, and was unable to drain through the substrate it will be found to be readily expelled by firm rolling, whereupon the water will run off the surface if a suitable slight fall or camber is provided. Advantageously the substrate may be porous to minimise drainage problems. When the track is not in use it may be firmly rolled to become waterproof. As other examples, the oil may be selected from bitumen or gas oil, siliconised oil, suitable latices, alginates or molasses with suitable polymers selected from for example polystyrene, nylon, polypropylene and polyvinyl chloride (p.v.c.). Laid surfaces or tracks according to the invention may be coloured as desired by the addition of pigments during the mixing stage. Superstrates formed according to the invention produce a marked degree of springiness to the laid area or track.

Claims: 1. Substitute soil material comprising sand or other particulate or granular mineral material treated with a binder of an oil-based product, characterised in that the binder comprises synthetic polymeric material dispersed or dissolved in an oil, said oil having a viscosity such that it is substantially non-fluid at ambient temperatures so as to produce an inert, discrete material permanently capable of being raked when laid in a layer upon a substrate. 2. Soil material as claimed in claim 1 wherein the sand or other particulate or granular material is of varying particle size. 3. Soil material as claimed in either one of claims 1 and 2, wherein the oil has the consistency of a soft grease at ambient temperatures. 4. Soil material as claimed in either one of claims 1 and 2, wherein the oil has the consistency of a soft grease at normal climatic temperatures and becomes a liquid at temperatures in a range immediately above said normal temperatures. 5. Soil material as claimed in any one of the preceding claims wherein the oil is petroleum based. 6. Soil material as claimed in any one of claims 1 to 4, wherein the oil is an organic oil. 7. Soil material as claimed in claim 5, wherein the oil is a bitumen or gas oil. 8. Soil material as claimed in claim 5 wherein the oil is a siliconised oil. 9. Soil material as claimed in claim 6 wherein the oil is selected from the group comprising latices, alginates and molasses. 10. Soil material as claimed in any of claims 1 to 4 wherein the polymeric material is ethylene vinyl acetate. 11. Soil material as claimed in claim 10 wherein the ethylene vinyl acetate contains approximately 28% vinyl acetate by weight. 12. Soil material as claimed in any one of claims 1 to 4 wherein the polymeric material is selected from the group consisting of polystyrene, nylon and polypropylene. 13. Soil material as claimed in any one of claims 1 to 4 wherein the polymeric material is polyvinyl chloride. 14. Soil material as claimed in any one of the preceding claims to which colouring pigments are added. 15. A recreational or sports area having a surface formed of substitute soil material as claimed in any one of the preceding claims, wherein the material is laid in a layer upon a substrate.

Inventors: DACHTLER, JOHN DAVID, HAWKINS, PAUL
Applicants: EN-TOUT-CAS PLC
Application year: 1987
Main classification: E01C13
IPC codes: E01C13, C08L77, C08L27, C08K3, C09K17, C08L7, C08L101, C08L1, E01C7, C08L23, C08L21