GB2053331A - A Prefabricated Covering for Road Surfaces, a Process for Manufacturing the Covering and an Apparatus for Applying It - Google Patents

Abstract

A covering for road surfaces comprises a base of woven material 1 made impermeable by impregnation with a resin composition and an upper surface resinous coating 2 containing very hard abrasive particles 3, said coating having a hardness which approaches that of the abrasive particles. When a roadway or the like is needing to be re-surfaced, a thin layer of hot tar or the like is applied to the road and, over this layer, the covering of the present invention is compressed so as to produce a new surface in a fraction of the time necessary for carrying out a conventional re-surfacing operation. <IMAGE>

Description

SPECIFICATION A Prefabricated Covering for Road Surfaces and the Like as well as a Process for Manufacturing the Covering and an Apparatus for Applying It Background of the Invention The present invention refers to a prefabricated covering for road surfaces and the like as well as a process for manufacturing the covering and an apparatus for applying it.

Prior Art Asphalt surfaces which practically all over the world consist of hot rolled asphalt, have the disadvantage of deteriorating due to general exposure, friction from vehicle wheels, rain water, petroleum derivatives and the like. Prefabricated elements have been used, including bricks or slabs of asphalt but they never met with any real success due to the fact that they suffer from the same type of problems.

Another serious disadvantage is the so-called "polishing" of the asphalt surface which happens in heavy traffic stretches after about only one-fifth of the useful life of the road, this resulting in smooth, skid and dangerous surfaces.

Apart from the above, asphalt surfaces subject to normal conditions of use tend to crack, this giving rise to the penetration of water and the very serious problem of "pumping" in the base and even the substrate, producing serious structural damage in the road.

Summary of the Invention An object of the present invention is to overcome the problems associated with the prior art, particularly in dangerous stretches of road or stretches subject to conditions which are highly prejudicial to an asphalt surface, by means of a special covering to be applied directly to the surface of the roadway. This covering base on the exposed surface of the road has properties suitable for meeting the conditions to which the road is subjected, including wheel friction.

According to one aspect of this invention, a prefabricated covering for the physical and chemical protection of driving surfaces, such as a roadway or the like, comprises a base of permeable woven material made impermeable by impregnation with a resin composition and having its upper surface covered with a resinous coating layer containing and adhering therein very hard abrasive particles so that the particles cannot be removed even with high friction forces, said layer having a hardness which approaches that of the abrasive particles themselves.

Preferably the abrasive particles comprise aluminum oxide and/or silicon carbide in grain size between Tyler screens 24 and 1 15, normally between 30 and 80.

In general, the abrasive particles will have a hardness of at least 7 Moh, preferably at least 9 Moh.

In a preferred embodiment of the invention a covering is manufactured by the steps of providing a permeable base of woven material, impregnating said base with a resinous composition to make it impermeable to liquids, allowing the impregnation composition to cure, applying a coating layer to one surface of said impregnated base, having the same chemical nature as the impregnation composition and containing very hard abrasive particles and then drying and curing the product so that said particles remain fixed thereto even when subject to large friction forces and so that the coating layer thus formed has a hardness which approaches that of the abrasive particles.

The resinous impregnation and coating compositions should be such as not only to provide the surface of the covering with a hardness approaching that of the abrasive particles but also to provide the covering with a certain flexibility so that it can be stored in rolls and then applied to a road surface without the formation of any cracks in its exposed surface.

The base may comprise a raw cotton canvas woven with high density triple strands and may further comprise up to 50%, based on the amount of cotton, of synthetic fibers, preferably polyester, so as to increase its tensile strength.

In normal use the covering, preferably in the form of a roll, is applied directly to a surface which has already been covered with asphalt, by placing a bonding agent between the lower surface of the covering and the surface of the asphalt of a smooth compression roller or the like. The bonding of the covering to the asphalt can be carried out cold or by means of special resins (for example, guttapercha) and asphalt slurry, or hot tar such as is normally used.

According to yet another aspect of the invention, an apparatus for applying the new covering to a road surface comprises support means for a roll of said covering, a compression roller having a width at least as much as that of the roll to be placed on said support means and adapted to be rolled over the surface of the road as it is advanced therealong, and means for applying a bonded agent to the road across the width and in front of said compression roller, behind the point of application of the bonding agent, so that the advance of the apparatus and the consequent rotation of the compression roller continuously withdraws the covering from the roll and compresses it over the bonding agent on the surface of the roadway.

A covering and an apparatus according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an amplified diagrammatic section of a covering manufactured by the present invention; and Figure 2 is a diagrammatic illustration of a system, including apparatus in accordance with the invention, for applying the covering shown in Figure 1 to a roadway.

Referring first to Figure 1 of the drawings, a covering for coating road surfaces or the like in accordance with the present invention, comprises a base 1 of raw cotton canvas No. 10 which has been impregnated with a saturated polyester resin composition including an isocyanate adduct and aromatic solvents. Over base 1 there is a coating 2 of an organic-inorganic composition containing a resin of the same chemical nature as that of the impregnation composition so as to ensure mutual compatibility and bonding therewith and also an inorganic filler such as quartz, aluminum oxide or the like. Coating 2 also contains a spreading of very hard abrasive particles comprising aluminum oxide and/or silicon carbide (Mohs hardness between 9-9.3) in grain size which may vary according to the conditions to be met during use.

Coating 2 is sufficiently compact with filler so that the organic-inorganic composition serves principally as a bonding agent but is not so compact as to affect unduly the flexibility of the covering.

Its flexibility should be sufficient for the product to be able to assume a curvature having a radius of approximately 50 cm without any cracks being noted in coating 2.

With respect to the spreading or distribution density of the abrasive particles in the coating layer and to their grain size, it is clear that with larger particles there will be more friction between the tires of vehicles and the covering, and vice versa.

A reduction in the density of distribution of the particles, on the other hand, will make the covering more flexible and, up to a point, will reduce friction. This latter, however, is not true at the greatest densities since it has been found that maximum friction is produced when there is a certain spacing between the abrasive particles, this being because the rubber of the vehicle tires penetrates to a certain extent between the particles to produce a positive drive somewhat similar to a rack and pinion. In any case the particles must not be superimposed with respect to each other and there should in fact be a certain spacing between individual particles.

In a preferred embodiment of the invention, the distribution was defined by applying the particles at a rate of approximately 400 g/m2 with a grain size of Tyler screen 3040, such covering being used in the region of a curve in a roadway used by heavy trucks.

With respect to the nature of the compositions used for the impregnation of the base and the coating, they may be based on any suitable substances, specifically epoxy- alkyde- phenol- and acrylic resins with plastifiers. In the case of the impregnation composition, it is important that the canvas base be made impermeable to water, mineral and vegetable oils and chemical solutions so as to prevent penetration from underneath whereas, in the case of the upper coating, the composition must ensure that the product will have a certain flexibility, but retain the abrasive particles so that they cannot come off during use, and must have an extra resistance to chemical products and the like, including acids and petroleum derivatives.A specific example of the covering and its manufacture will now be given: Base or Substrate The substrate chosen was a high density raw cotton canvas No. 10 woven with triple strands.

The canvas was impregnated by passing it continuously through two impregnation tanks, after which it was dried in an oven.

The following impregnation composition was used: Components 1st tank 2nd tank (1) Saturated polyester resin with 69-71% dry matter, xylol solvent, Gardner density Z-Z4, maximum acidity index of 7, hydroxyl index of 140-160 (%=4.24 to 4.84) soluble in aromatics, esters, ketones, glycol, ether and acetates 53.95 53.95 (2) Ethyl-glycol acetate or toluene 19.42 9.71 (3) Ethyl-acetate . 35.96 17.98 (4) Toluene diisocyanate adduct containing 75% of dry matter and 25% ethyl-acetate 18.34 18.34 It should be observed that the first tank contained twice as much solvent (components (2) and (3)) whereby it had about half the viscosity of the second tank.

Drying and curing was carried out in an oven in a non-continuous process, taking about 90 minutes with the temperature being increased from 840C to 1 320C and then lowered to 500C. This step may also be carried out continuously.

The impregnated and cured base or substrate had the following characteristics: a) porosity of approximately 2%; b) continuous strength after 24 hours of approximately 13.71 6 kg. m/m. linear matter; c) excellent resistance to degradation by micro-organisms (for example, molds and fermentations-six months in bi-degraded soya without any attack); and d) excellent resistance to ultraviolet and infrared rays.

Coating Layer The working face of the covering was coated by means of a first application of an organicinorganic compositing using either paint rolls or spray techniques. The composition used was as follows: Weight Percent 1Saturated polyester resin (as in the impregnation composition) 17.58 2-Ethyl-glycol acetate (as in the impregnation composition) 3.16 3-Ethyl-acetate (as in the impregnation composition) 17.58 4 Quartz (*) 26.31 5-3F-AA aluminum oxide (*) 8.77 6-Titanium oxide (*) 5.84 7-Colloidal carbon black 0.17 8-A thixotropic agent (pyrogenic silica) 4.35 9-lsocya nate adduct (as described) 15.59 (*) Grain size STyler screen 200.

With the first application still sticky, abrasive particles of electrofuse aluminum oxide (Tyler screens 30-40) were applied by jet at a pressure of about 100 psi at a rate of approximately 400 gr/m2, after which another application of the organic-inorganic composition was made. Thus the coated product was then cured during 80 minutes in an oven with the temperature being increased from 900C to 1 360C and then lowered to 60 C. This curing can be made either in batches or continuously and also in the open air, in which case it takes about 24 hours.Depending on the conditions of use, the rate of distribution of the particles may vary approximately from 300--600 gr/m2 so that there is always a small spacing betwoen the new particles for ensuring the "rack and pinion effect" mentioned above.

The application of the new covering to a roadway or the like is extremely simple and rapid, the application time being no more than one-third of the time necessary to effect a conventional resurfacing operation whereas the road may be re-opened to traffic almost immediately. A process of application is illustrated in Figure 2 which shows a small tractor 4 towing an apparatus which embodies another aspect of this invention. The apparatus comprises a tar boiler 5 on wheels 6, provided with a hot tar distributor bar 7 which, during use, applies a layer of hot tar to the surface of the road as tractor 4 advances.

Immediately behind the boiler 5 the tractor tows a smooth compression roller 8 rotatable in an upper frame 9 having a support 10 for a roll 11 of the covering illustrated in Figure 1. The covering has a width equal to half that of the roadway being re-surfaced. As can be seen from Figure 2, the free end of the covering passes in front of frame 9 and under compression roller 8 where it is squeezed against the roadway. Behind the roller the covering is already united with the road.During operation the very advance of tractor 4 and those of compression roller 8 cause the covering to be unrolled from roll 11, the roller compressing the covering against the road surface with the layer of hot tar therebetween at a temperature of about 1 800C which softens the covering slightly so that it accommodates any variations in the profile of the roadway and becomes perfectly incorporated therewith. The compressing and rolling effect of roller 8 is sufficient to ensure a substantially immediate fixture of the covering, producing a new, smooth and extremely resistant surface. The road may be re-opened to traffic immediately.

The tar layer between the covering and the road being re-surfaced may have any thickness from about 1 mm to about 5 mm depending upon the state of the road and serves as a type of cushion to protect the covering against penetration by pebbles or the like. A thickness of 1-1.5 mm is normally sufficient and this should be compared to the 50 mm necessary in the case of conventional re-surfacing techniques.

The new process of re-surfacing roadways in accordance with the present invention using the new covering or sheet suitably prefabricated, produces the following advantages: a) it avoids the problem of skidding on old surfaces which suffer from "polishing" during their otherwise useful life; b) the new covering completely seals any cracks in the road being re-surfaced, preventing penetration of water and consequent "pumping"; c) the exposed surface of the covering is of such a nature that it completely eliminates the effect of the weather on the asphalt surface, be it new or old; d) due to its impermeability the new covering eliminates the action of petroleum derivatives, Diesel oil, detergents and the like; e) since it is possible to mix dyes in the resin of coating 2 (Figure 1) the new covering may be used to provide colored surfaces;; f) it is also possible to provide the new covering pre-painted with any traffic markings desired, such as white or yellow lines, pedestrian crossings and the like. This eliminates the necessity to send personnel to paint the re-surfaced stretches of road; g) the application of the new covering leaves practically unaltered the level of the surface of the road (the covering has a thickness of approximately 1.2-1.4 mm compared with the 3 to 5 cm or more of a well-made conventional new surface); h) the process of application is about three times quicker and much more simple than conventional re-surfacing techniques and permits the road to be re-opened immediately; i) the new covering may be used to protect and seal the junction areas at the beginnings of bridges and the like. This is highly desirable since it avoids any penetration by rain water; j) transport costs are reduced considerably since the bulk of material necessary to re-surface the road is reduced many times. In addition this reduction in weight is of great importance when resurfacing structures such as bridges which are not then overloaded; and k) the cost of the covering and of its application is comparable with that of a conventional wellmade new surface whereas its useful life is at least twice as long.

Finally, it will be understood that the surfaces to which the new covering may be applied are not limited to roadways as such nor even to asphalt surfaces. For example, the covering may be used for factory floors since it provides excellent characteristics where chemical products are being used which are highly prejudicial to the surfaces conventionally employed.

Claims (14)

Claims

1. A prefabricated covering for the physical and chemical protection of driving surfaces such as a roadway or the like characterized by comprising a base of permeable woven material made impermeable by impregnation with a resin composition and having its upper surface covered with a resinous coating layer containing and adhering therein very hard abrasive particles so that the particles cannot be removed even with high friction forces, said layer having a hardness which approaches that of the abrasive particles thamselves.

2. Covering according to Claim 1 characterized in that said abrasive grains comprise aluminum oxide and/or silicon carbide in grain size between Tyler screens 24 and 11 5, preferably between 30 and 80.

3. Covering according to Claim 1 or 2 characterized by having a flexibility such that no cracks are formed in said coating layer when the covering is bent with a radius of curvature of approximately 50 cms.

4. Covering according to any of Claims 1-3 characterized in that said coating layer contains an organic filler, the resin thereof being of the same chemical nature as that of the resinous impregnation composition.

5. Process for manufacturing a prefabricated covering for the physical and chemical protection of driving surfaces such as a roadway or the like, characterized by the steps of: providing a base of a permeable woven material; impregnating said base with a resinous composition to make it impermeable to liquids; curing the impregnation composition; applying a coating layer to one surface of said impregnated base, having the same chemical nature as the impregnation composition and containing very hard abrasive particles; and drying and curing the product so that said particles remain fixed thereto even when subject to large frictiontforces and so that the coating layer thus formed has a hardness which approaches that of the abrasive particles.

6. Process according to Claim 5 characterized in that said step of applying the coating layer comprises the application of a resinous composition, spreading the abrasive particles over said application before the resinous composition cures and a final second outer application of the same composition.

7. Process according to Claim 6 or 7 characterized in that said abrasive particles are spread at a rate of 300-600 gr/m2 and preferably about 400 gr/m2.

B. Process according to Claim 6 or 7 characterized in that said abrasive particles are applied by means of a pistol.

9. Process according to Claim 5, 6, 7 or 8 characterized in that said abrasive particles comprise aluminum oxide and/or silicon carbide in grain size between Tyler screens 24 and 11 5, preferably between 30 and 80.

10. Apparatus for applying the covering according to Claim 1 to a driving surface characterized by comprising support means for a roll of said covering, a compression roller having a width at least as much as that of the roll to be placed on said support means and adapted to be rolled over the surface as it is advanced therealong, and means for applying a bonded agent to the road across the width and in front of said compression roller, so that the covering may pass under the compression roller, behind the point of application of the bonding agent, so that the advance of the apparatus and the consequent rotation of the compression roller continuously withdraws the covering from the roll and compresses it over the bonding agent on the surface of the roadway.

11. A covering for road surfaces and the like, substantially as described herein with reference to, and as shown in, Fig. 1 of the accompanying drawings.

1 2. A process for manufacturing a prefabricated covering for road surfaces and the like, conducted substantially as described herein with reference to Fig. 1 of the accompanying drawings.

1 3. A covering for road surfaces and the like, whenever made by a process as claimed in any one of Claims 5 to 9 or 12.

14. Apparatus for applying a prefabricated covering to a road surface or the like, substantially as hereinbefore described with reference to, and as shown in, Fig. 2 of the accompanying drawings.