Field of the Invention The invention pertains to road markings and compositions for use as road markings that are retroreflective and resistant to conditions that affect the service life of road markings.

Background

Pavement markings serve an important role in delineating the roadway and providing regulatory, warning and guidance information to drivers.

Changes to regulations concerning the use of volatile organic compounds have restricted pavement markings in some jurisdictions to waterborne rather than petroleum based paints. This shift has adversely affected the durability of pavement markings and has resulted in more frequent recoating to maintain visibility. Visibility is important to allow drivers to maintain safe spacing between themselves and other traffic. The frequency of recoating is a particular problem in geographic areas where recoating cannot be carried out due to low temperatures or extended periods of rain or snow. For example, in British Columbia, Canada, the pavement markings on high mountain roads are badly worn by November and cannot be repainted in the winter months until April of the following year. Similarly on the temperate coast of British Columbia, long wet periods in the winter months do not allow sufficient time for road markings to be repainted and cured. In many jurisdictions, particularly in areas prone to heavy rain, pavement markings are preferred to be retroreflective, i.e. able to reflect light back to their source. Glass beads or ceramic elements, for example, are embedded in a binder or tape which adheres to the road surface to reflect light from the vehicles headlamps back towards the headlamps. Because drivers are close to the illumination source, they can see this retroreflected light and better orient themselves and their vehicles.

The service life of a pavement marking is a function of a number of factors, including the number of freeze-thaw cycles, the use of road sand or gravel in very cold weather when road de-icers are ineffective, abrasion and wear from tires, tire chains and studs, impact and wear from snowplows, ultraviolet light-induced and other environmental weathering, the traffic volume, the overlapping of the vehicle wheel path directly over the line marking on corners, the age, condition, and nature of the asphalt or concrete substrate, the abrasion resistance of the pavement marking system, and scouring from wind- or water-borne abrasives including de-icing salts, sands, grits or gravel. Road sand and gravel, which typically has a Mohs hardness of 6 to 7, easily abrades retroreflective glass beads having a Mohs hardness of about 5.5 and also the soft surface layer (typically 10 microns thick) of retroreflective microcrystalline ceramic elements having a Mohs hardness less than 4 (supplied by 3M Corp). The most common materials that incorporate or are embedded with these abrasion-sensitive

retroreflective beads or elements are paint, epoxy paints and thermoplastics. Some temporary road markings incorporate reflective tape with or without a bead component. The net effect of these factors affecting service life is that the measured retroreflectivity of a line marking system decreases from its initial value to a minimum threshold value that indicates that the marking needs to be refurbished or replaced. This can happen in less than one year, especially in very cold climates. A pavement marking can reach the end of its life as a result of forms of deterioration that decrease retroreflectivity, i.e. loss of glass bead or ceramic elements, loss of the base material due to chipping, abrasion or bond failure, and colour change or loss of visual contrast between the base material and the marking.

Furthermore, existing road markings generally fail to have anti-skid properties, especially when they are wet. This is of special concern to motorcyclists in wet weather.

The prior art systems have failed to deal effectively with the durability of retroreflective road markings, especially in the presence of road sand or gravel. US 8,342,700 to Naik et al. describes armoured, retroreflective road markings having the following components: a first dark coloured, non- retroreflective thermoplastic adhesive bonded to a non-recessed road surface; a second light coloured thermoplastic adhesive above the first adhesive with a different chemistry to the first adhesive; and armour above the first non-retroreflective adhesive and above or adjacent to the second adhesive. The second adhesive contains a retroreflective element. This system suffers from certain drawbacks. Being unrecessed, the marking is subject to abrasion due to traffic and snowplows, especially in the presence of road sand or gravel, and particularly in a horizontal direction once the soft glass elements are abraded and the adhesive/armour bond is exposed to abrasive sand or gravel. The dark components including adhesive adjacent to road surface are non-retroreflective. Two sequentially thermoset adhesives are required. It is not possible to repair the road marking once it is partially abraded. Further, the markings can have low anti-skid resistance due to a plethora of smooth elements, e.g. stainless steel balls and glass beads. US 2012/0314290 to Velicky describes un-armoured, recessed reflective road markings having a hot epoxy binder and three different low hardness reflective elements, all abradable by road sand or gravel, bonded to the epoxy binder. This system has certain drawbacks. The soft retroreflective elements are not protected from abrasion as the road surface wears and exposes the elements to traffic, snowplows, sand or gravel, especially abrasion in a horizontal direction. It is not possible to repair a partially abraded road marking since the epoxy adhesive that is used is highly susceptible to abrasion, especially in a horizontal direction by sand or gravel once the soft retroreflective surfaces are abraded, exposing the epoxy adhesive. The low hardness reflective elements (Mohs hardness of about 4 to 5.5) are all susceptible to abrasion by road sand (Mohs hardness of about 6 to 7) or gravel, especially in combination with snowplows.

Further, the markings can have low anti-skid resistance due to a plethora of smooth elements, e.g. glass beads.

There is a need in the art for improved road markings that are resistant to abrasion from sand and gravel, preferably having antiskid properties due to the presence of coarse, rough components, are resistant to freeze-thaw cycles, and combine high hardness with high retroreflectivity. There is a need for road markings that continue to exhibit sufficient retroreflectivity or contrast with the substrate when any non-armouring retroreflective materials have been worn off. There is also a need for highly durable road markings that are repairable. Summary of the Invention

The invention pertains to a recessed, freeze-thaw resistant road marking comprising particulate semi-retroreflective or retroreflective ceramic, mineral, synthetic crystal or perlite armouring material, and a freeze-thaw resistant adhesive. In some embodiments the road marking is skid-resistant. The particulate ceramic or mineral armouring material may include any high-hardness materials, for example having a Mohs hardness of 6.5 or greater, alternatively 7 or greater. Examples include semi-retroreflective materials such as recycled, crushed and sieved porcelain derived from waste bathroom fixtures or china; recycled, crushed and sieved ceramic tiles; quartz; corundum; perlite grit; and synthetic crystals with a hardness of 7 or greater and high retroreflectivity.

The road marking may optionally further comprise one or more

retroreflective elements having different retroreflectivity than the

armouring material. For example, the retroreflective element may be more reflective than the armouring material in wet conditions, or in dry conditions, or the converse, in order that the road marking has good retroreflectivity in both wet and dry conditions. The optional retroreflective materials may include retroreflective beads or tape, or painted sub-surfaces.

The armouring material is bonded to the road surface via a freeze-thaw resistant thermoplastic adhesive, especially a flexible, abrasion-resistant adhesive. An exemplary adhesive is epoxy-urethane copolymer. The armouring material is designed to both protect the marked surface, and to provide a traction surface for vehicle wheels. In the function of protecting the marked surface including its thermoplastic adhesive, and the optional retroreflective element, if present, from abrasion due to winter road sand or gravel, wheel traffic or snow plows, the protection is by virtue of both the higher hardness of the armouring material as compared to the painted sub-surfaces and the retroreflective element, as well as by the overall height, shape and concentration of the armouring particles relative to the retroreflective elements and the painted sub-surface and road surface. The shape and micro-surface properties of the armouring particles as well as the concentration and distribution of these particles contribute to the traction properties of the surface of the system. For example, spheres of glass half embedded in an adhesive exhibits less traction or surface friction than angular crushed particles embedded in a similar fashion with a surface similar to that of sandpaper. Further, a rough angular surface tends to entrap the abrasives such as sand particles and restrict their scrubbing action, while round particles of similar size would tend not to entrap the abrasives. Glass particles, even if crushed, will not exhibit the same micro texture as ceramic or natural materials due to their glassine surface texture, especially when rounded by abrasive interaction. The optional retroreflective elements can be replaced on partially-abraded road markings by repainting the residual semi-retroreflective or retroreflective armour and applying fresh reflective elements to the freshly painted armour. Brief Description of the Drawings

Figure 1 is a photograph of a road marking comprising a mixture of ceramic beads and crushed porcelain (2.4 - 5 mm diameter porcelain particles), on a dry roadway.

Figure 2 is a photograph of a road marking comprising a mixture of ceramic beads and crushed porcelain (2.4 - 5 mm), on a wet roadway. Figure 3 is a photograph of a road marking comprising a mixture of ceramic beads and crushed porcelain (1.2 - 2.4 mm), on a dry roadway.

Figure 4 is a photograph of a road marking comprising a mixture of ceramic beads and crushed porcelain (1.2 - 2.4 mm), on a wet roadway.

Figure 5 is a photograph of a road marking comprising stripes of ceramic beads and crushed porcelain (2.4 - 5 mm), on a dry roadway.

Figure 6 is a photograph of a road marking comprising stripes of ceramic beads and crushed porcelain (2.4 - 5 mm), on a wet roadway.

Figure 7 is a photograph of a road marking comprising stripes of ceramic beads and crushed porcelain (1.2 - 2.4 mm), on a dry roadway. Figure 8 is a photograph of a road marking comprising stripes of ceramic beads and crushed porcelain (1.2 - 2.4 mm), on a wet roadway. Figure 9A is a schematic plan view of a road marking comprising sequentially laid unblended and striped fine porcelain with reflective ceramic bead striped gauze tape. Figure 9B is an elevational view of the road marking of Figure 9A.

Figure 10 is a schematic perspective view of the application of retroreflective or luminescent paint on and inside fine crushed porcelain armour.

Figure 11 is a schematic perspective view of the application of retroreflective or luminescent paint in between stripes of fine crushed porcelain armour. Figure 12 is a schematic perspective view of a road marking comprising colour tinted epoxy-urethane copolymer in between and under stripes of fine crushed porcelain armour.

Figure 13 is a photograph of a road marking according to Example 11, when freshly applied.

Figure 14 is a photograph of the road marking of Figure 13, after four months. Figure 15 is a photograph of the road marking of Figure 13, after nine months. Figure 16 is a photograph of a road marking according to Example 12, when freshly applied.

Figure 17 is a photograph of the road marking of Figure 16, after four months.

Figure 18 is a photograph of the road marking of Figure 16, after nine months. Description

The road markings of the invention are freeze-thaw resistant, preferably skid resistant, and comprise retroreflective or semi-retroreflective armouring material, optionally also containing one or more additional retroreflective elements or paint having retroreflectivity higher than the armour.

The Mohs scale of hardness compares the scratch resistance of various materials. The hardness of a material is a measure of its resistance to abrasion or crushing. Glass beads have a Mohs hardness of about 5.5, and some porcelains have a hardness of 7, i.e. porcelain is harder (more scratch and abrasion resistant) than glass. Ceramic tiles have a typical Mohs hardness of 7. Therefore pulverized and sieved porcelain, e.g. porcelain derived from recycled bathroom fixtures and china, and pulverized and sieved ceramic tiles are suitable as armoring materials for road markings.

The hardness of the ceramic, mineral, synthetic crystallite or perlite armouring material is greater that of the optional supplementary retroreflective elements and of the painted sub-surface. It may have a hardness greater than 6.5, or great than 7, and preferably greater than the hardness of road sand or gravel, typically in the range of 6 to 7. The thickness and/or top of the armouring materials in the road marking are higher on average than the supplementary reflective elements or painted sub-surface. The armouring material therefore functions as a sacrificial wearing surface. The initial retroreflectivity of the retroreflective material/armouring material composite can be controlled in a variety of ways, including: the dosing ratio or concentration of the armouring material and the

supplementary retroreflective element, e.g. glass beads; management of the average armouring material particle diameter to the thickness ratio, weight ratio or volume ratio; the dispersion of the optional retroreflective element or paint and armouring material across the surface of the pavement marking line, e.g. either as a set of coherent alternating armouring material stripes with paint or retroreflective bead stripes or a mixture of retroreflective beads and armouring material to form a single stripe.

It is desirable for the road marking to be light in colour to increase its visibility, including its visibility when it becomes worn. In some

embodiments, the adhesive is colourless or is lighter in colour than the retroreflective marking material, or the armouring material and the retroreflective marking material are the same colour or are both colourless, or the armouring material is lighter in colour than the retroreflective armouring material. The light colour of the armouring material and the resistance of the armouring material to abrasion results in a road marking that still has reasonably good visibility when it becomes worn. That visibility can be enhanced by refurbishing the road marking, for example by cleaning it, spraying it with white or yellow paint, and then spraying particulate retroreflective marking material, such as glass beads or ceramic particles, onto the wet paint.

In forming the road markings, the application of the armouring material and the optional retroreflective elements can be simultaneous or sequential. Examples

Experimental pavement markings were made by applying a 100 mm (four inch) wide strip of about 40 mil (1 mm) thick wet epoxy-urethane copolymer (Pro Poxy Type III DOT, Dayton Superior Corporation,

Maimisburg, Ohio). The following materials were applied onto this wet epoxy-urethane copolymer coating:

1. White or whitish armouring porcelain flakes (Mohs hardness >6 and <8 prepared by crushing and sieving a used white china toilet to either a 1.2 to 2.4 mm maximum width or a 2.4 to 5 mm maximum width particles.

2. A supplementary retroreflective element comprising ceramic beads having a Mohs hardness of 4 or less, between 0.85 to 2.0 mm maximum width with one-third of the particles between 0.85 to 1.25 mm (AW50E White Bioptic Elements or AW51E yellow Bioptic Elements, 3M Corporation, St Paul, Minnesota). 3. Crushed glaciated basalt (known as 6 x 10, supplied by

Manufacturers Minerals, Renton, Washington).

In Examples 1 and 2 below, a premixed blend of 70 weight % porcelain armouring flakes and 30 weight % white ceramic beads was dropped onto the wet epoxy-urethane copolymer coating to form a 100 mm wide marking.

In Examples 3 and 4 below, reflective white or yellow beads were dropped through a slot onto the wet epoxy-urethane copolymer coating to form lines approximately 20 mm (¾ inch) in width. Porcelain flakes were then dropped onto the adjacent wet epoxy-urethane copolymer surfaces to form contrasting lines so that the bead lines were inside the porcelain flake armouring lines while forming a 100 mm composite stripe marking.

In Examples 1 to 4, crushed glaciated non-retroreflective basalt was applied to a wet epoxy-urethane copolymer surface adjacent to both sides of the 100 mm wide markings to simulate a road surface. In Examples 1 to 4, the epoxy-urethane copolymer was allowed to cure for a number of hours in laboratory air and the excess reflective element and porcelain flakes were swept from the surface.

Example 1 Simultaneously Laid Blended Coarse Porcelain Flakes and Supplementary Retroreflective Bead Road Marking

The pre-mixed blend of 2.4 to 5 mm porcelain flakes and white ceramic beads was dropped onto the wet adhesive coating. Figures 1 and 2 show the resulting 100 mm wide marking, after curing, on a dry and wet basis respectively on exposure to a camera flash.

Example 2 Simultaneously Laid Blended Fine Porcelain Flakes and Supplementary Retroreflective Bead Road Marking

The pre-mixed blend of 1.2 to 2.4 mm porcelain flakes and white beads was dropped onto the wet adhesive coating. Figures 3 and 4 show the resulting 100 mm wide marking, after curing, on a dry and wet basis respectively on exposure to a camera flash.

Example 3 Sequentially Laid Unblended and Striped Coarse Porcelain Flakes and Supplementary Retroreflective Bead Road Marking The 2.4 to 5 mm porcelain flakes were used in sequential combination with the white and yellow ceramic beads by application of three odd rows of porcelain flakes with two even rows of white or yellow beads to form a five-stripe single road marking. Figures 5 and 6 show the resulting 100 mm wide marking, after curing, on a dry and wet basis respectively on exposure to a camera flash.

Example 4 Sequentially Laid Unblended and Striped Fine Porcelain Flakes and Supplementary Retroreflective Bead Road Marking The 1.2 to 2.4 mm porcelain flakes were used in sequential combination with the white retroreflective beads by application of three odd rows of porcelain flakes with two even rows of white and yellow beads to form a five-stripe single road marking. Figures 7 and 8 show the resulting 100 mm wide marking, after curing, on a dry and wet basis respectively on exposure to a camera flash.

Example 5 Sequentially Laid Unblended and Striped Fine Porcelain with Supplementary Retroreflective Bead Striped Gauze Tape

Referring to Figures 9 A and 9B, a recessed road surface marking channel 10 is prepared by grinding a 100 mm wide shallow groove into a road surface 12 and coating it with liquid epoxy-urethane copolymer 14. Prior to set, the groove containing the liquid adhesive is overlaid with a porous tape 16 bonded with retroreflective bead stripes 18, e.g. 13 mm (½ inch) bead stripe widths having three 25 mm (linch) gaps 20 from 1) the edge of the porous tape to the left edge of the first bead stripe, 2) the right edge of the first bead stripe to the left edge of the second bead stripe, and 3) the right edge of the second bead stripe to the right edge of the porous tape. The three bead-free channels above the porous tape are then filled with armouring material 22 so that the beads are mostly or all below the top surface of the armouring material. Example 6 Supplementary Retroreflective or Luminescent Paint on or Inside Porcelain Armour

Referring to Figure 10, the armouring material 22 is embedded into the epoxy-urethane copolymer bedding 14 layer in a roadway marking channel 10 and allowed to set. Reflective or luminescent paint 24 is applied over the entire surface of the road marking line. Optionally, the paint is formulated to abrade from the highest points of the armouring material. The paint in between the high points of the armour, i.e. in the "valleys," is protected by the armouring material and resists abrasion. Optionally, the armouring material can be repainted to refurbish the marking.

Example 7 Supplementary Retroreflective or Luminescent Paint in Between Porcelain Armour or Porcelain Armour Retroreflective Bead Composite

Referring to Figure 11. the armouring material 22 or armouring material reflective bead composite is embedded into an epoxy-urethane copolymer bedding layer 14 and allowed to set. Reflective or luminescent paint 24 is applied in one or more stripes between armouring stripes.

Example 8 Colour Tinted Epoxy Adhesive in between and under Fine Porcelain Armour Stripes

Referring to Figure 12, the armouring material 22 is embedded into an epoxy-urethane copolymer bedding layer 14 and allowed to set. Colour- tinted epoxy 26 is applied between armor stripes to give a colour stripe effect.

Example 9 Supplementary Retroreflective White Element(s) plus Paint on or Inside Retroreflective Armour

Armouring material comprising white quartz and/or white corundum ranging in size from 1.25 mm to 5.0 mm (Bosun Abrasives, Shanghai, China) is embedded into a recessed (e.g. up to 8 mm recess) tinted or untinted adhesive layer which comprises or is similar to Unitex DOT Type 3 (Dayton Superior of Miamisburg, Ohio), optionally tinted at the factory with pigments suitable for use in epoxy-urethane copolymer. The adhesive and armouring is applied adjacent to an asphalt road surface and allowed to set. Reflective or luminescent paint and retroreflective beads are sequentially or simultaneously applied over the previously-applied entire armouring surface/adhesive laminate so that paint and retroreflective elements lie over and between the high points of the armor, i.e. the valleys resist direct mechanical abrasion of the reflective or luminescent paint and/or retroreflective elements. A white pavement marking paint that complies with US Federal Specification 595b White 17886, such as Standard Dry paint (Ennis-Flint) is spray applied at the manufacturer's recommended thickness. Glass beads conforming to AASHTO M247, such as Potters Visi Max (Potters Industries LLC) are dispensed on to the wet surface of the paint at a rate whereby the retro-reflectivity after the surface has dried has an average reading of 250 millicandelas or higher.

Maintenance of the retro-reflectivity where surface wear has occurred is accomplished by cleaning the surface of the marking with a high pressure power washer (5,000 psi), allowing the surface to dry, and repeating the painting process. This combined process provides a marking system wherein a failure of the retroreflective coating leaves behind a semi- retroreflective base of sufficient contrast and visibility as to continue to indicate to vehicle drivers their relative position on the roadway.

Example 10 Supplementary Retroreflective Yellow Element(s) plus Paint on or Inside Retroreflective Armour

Sintered yellow quartz (Merkury SP, Gdynia, Poland), with or without crushed, yellow porcelain is embedded into a recessed tinted or untinted adhesive layer adjacent to an asphalt road surface and allowed to set. Reflective or luminescent paint and retroreflective elements comprising glass beads are sequentially or simultaneously applied over the previously- applied entire armouring surface/adhesive laminate. Paint and

retroreflective elements between the high points of the armor, i.e. in the valleys, resists abrasion of the reflective or luminescent paint and/or retro reflective elements. Optionally, or where the retroreflective components of the assembly have become damaged, a yellow tinted pavement marking paint conforming to US Federal Specification 595b colour identification 33538 such as Ibis brand Formulation number 44-4955 (Ennis Traffic Safety Solutions, Pickering, Ontario) or other suitable coating or material is applied at the manufacturers recommended coating thickness. Yellow glass beads such as Visi Max (Potters Industries LLC) are dropped onto the surface of the wet paint by suitable means. Examples 11 and 12 Freeze-thaw Resistant Retroreflective

Armoured Road Marking Trials

In the following Examples 11 and 12, experimental road markings were made using vehicle equipped with rotary head diamond cutter to a mill 100 mm (4 inch) wide by 4.5 m (15 feet) long recesses in the worn surface of an asphalt roadway. The resulting recesses were swept with a rotary brush equipped skid/ steer vehicle and were blown free of dust with a leaf blower.

Example 11

In this example, the asphalt recess depth was 2 mm. 820 grams combined weight of un-tinted Pro Poxy "DOT Type 3" Parts "A" and "B" epoxy- urethane copolymer (Dayton Superior) were mixed with a low speed drill equipped with a one pint-sized stainless steel rotary mixer. This mixed epoxy was poured into the recess and spread by hand with a notched 100 mm wide squeegee. Immediately after spreading the adhesive, crushed porcelain ceramic particles 1.25 mm to 2.5 mm in size were spread over the surface of the adhesive completely inundating the surface. The adhesive was allowed to set for approximately two hours and the excess material was manually swept with a push broom to remove excess aggregates. These rejected aggregates were collected and weighed. This weight was

subtracted from the known initial aggregate weight and the quantity left in place determined to be 2.34 kg. The marking was photographed three times, upon completion (Figure 13), four months later (Figure 14), and nine months later after a winter (Figure 15). In Figure 14, the surface slush and abrasives are visible, and some painted line margins are visible where the milled recess did not fully overlap the prior painted line marking. In Figure 15, evidence of scouring is apparent as no painted line margins are visible and the surface of the road has been worn in the wheel path.

Example 12 In this example, the asphalt road recess was cut to a depth of 8mm. 1000 g of the aforementioned DOT Type 3 epoxy-urethane copolymer was used and 3.85 kg of a 50/50 blend of 1.25 mm to 2.5 mm and 2.5 mm to 5 mm of crushed porcelain was applied as in Example 11. Photographs were taken on day of installation (Figure 16), four months later (Figure 17) and nine months later after a winter (Figure 18). The weeping of excess armour is visible in Figure 16. In Figure 17 slush-borne abrasives are visible on and in the recess and the painted margins on either side of the recess. In Figure 18, painted line margins are absent and the road surface is abraded. Example 13 Reflectivity of White and Yellow Beaded Road Markings on used Asphalt containing Aggregate with and without Supplementary White or Yellow Retroreflective Bead Elements and their Repair

This example simulates the reflectivity of clean worn road markings with a low dose (e.g. 10 % retroreflective element) and with no dose of

retroreflective element ahead of repainting and recoating with

retroreflective beads. White and yellow pigments suitable for use in epoxy were added and mixed into component A of Epco 30 epoxy-urethane copolymer (Cornerstone Epoxy, Kansas City, Missouri). The resulting unheated blended epoxy was weighed, dispensed and spread onto the weathered surface of asphalt panels to a thickness of 1 mm (40mils). These panels were obtained by removing sections of an existing weathered asphalt pavement and subsequently trimming them to a rough rectangular shape. White quartz and white corundum (Bosun Abrasives, Shanghai, China), were premixed with white retroreflective elements manufactured by 3M Corp. and were sprinkled onto the wet epoxy surface until the surface was entirely covered. After curing, the samples were tested for retroreflectivity with measurements taken in millicandelas with an AR Stripemaster (Road Vista). The surface of the test samples was then wetted with water and the test repeated. The average retroreflectivity readings, in millicandelas, measured before and after the wetting, are recorded in the table below. The surface of the asphalt parking lot and a painted white stripe on the parking lot were also tested for comparative purposes. Adhesive Armour and Retrore- Retrore- Retrore- dose (wt ) flective flectivity flectivity wet element and dry (mcd) (mcd) dose (wt )

White epoxy White quartz None 44 22

cp* (100)

White epoxy White quartz White beads 96 58

cp (90) (10)

White epoxy White none 55 30

cp corundum

(100)

White epoxy White White beads 75 49

cp corundum (90) (10)

White epoxy White quartz none 49 22

cp (50) white

corundum (50)

White epoxy White quartz White beads 115 36

cp (45) (10)

White

corundum (45)

Yellow epoxy Yellow glass none 51 36

cp (100)

Yellow epoxy Yellow glass Yellow beads 110 88

cp (90) (10)

Used asphalt None none 37 17 Used white None none 38 Not measured parking lot

painted stripe

In the above table, "epoxy cp" means epoxy-urethane copolymer. Repair of these simulated used retroreflective road markings can be carried out as follows: 1. Water flushing via high pressure water sprayer to remove debris including sand and dirt; 2. dry by heat or air; and 3. spray painting (e.g. white or yellow) onto residual retroreflective armor followed by spraying of supplementary retroreflective element(s) onto the paint.

The purpose of this approach is to use residual recessed reflective armour such as quartz, corundum, perlite or synthetic crystals, having a hardness exceeding that of the winter abrasives in use such as sand or gravel, to protect the freshly re-applied supplementary retroreflective element(s) from abrasion. Glass can also be used provided it has a hardness exceeding that of the winter abrasives in use where the pavement marking will be in service. This approach allows the retroreflectivity of an initial armoured road marking to be enhanced above its initial value by using a

supplementary retroreflective element(s) upon repair or upgrading the retroreflectivity of supplementary retroreflective element(s) during any repair. Example 14 Bond Strength of Retroreflective Road Markings Applied to Used Asphalt containing Aggregate

Weathered asphalt panels were prepared as in Example 13. The panels were placed on a scale and a number of adhesive binders (detailed below) were mixed and weighed onto the surface of the test panels. Pre-weighed blended and unblended mixtures of aggregates (detailed below) and retroreflective elements were weighed to provide a target aggregate concentration of 3.6 kg/m ² (0.75 pound per sq. ft). This pre- weighed blend was evenly distributed onto the surface of the test panels and the samples were allowed to cure. To determine the direct tensile bond strength of the adhesive binder, the samples were placed on the table of a drill press and a 50 mm hollow core diamond drill was used to cut through the aggregates and coating. A 50 mm diameter steel disc was affixed to the surface of the samples concentric to the circular groove cut by the core with Hilti RE500 resin (Hilti Group, Liechtenstein). This epoxy was allowed to cure and the disc and the adhered coating were tensile loaded to failure by use of a mechanical loading jig with a Honeywell LKW5KKZ load cell and display unit. The ultimate test force applied was recorded. The samples were weighed and placed in plastic containers, inundated with a watery 4% CaCl ₂ solution and placed in a freezer at a temperature of approximately minus 10 degrees C. After approximately 16 hours the samples were removed from the freezer, allowed to thaw out for approximately 8 hours and then returned to the freezing environment. After 17 cycles of freezing and thawing, the samples were allowed to thaw out and solid material which had de-bonded from the sample surface was collected, dried and weighed. Finally, tensile bond tests were conducted on the samples similar to the initial round of tensile bond testing described above. The results are set out in the table below. They show that certain epoxies and epoxy- urethane copolymer are examples of high strength, freeze-thaw resistant adhesives useful in the present invention. Epoxy-urethane copolymer has the advantage of being more abrasion resistant than epoxy and is considered as a preferred adhesive.

All the samples showed little if any deterioration after the freeze-thaw test. * The meaning of the symbols in the above table is:

E- Epco 30 clear untinted epoxy-urethane co-polymer, (Cornerstone Construction Materials, LLC, Harrisonville, MO), applied at a thickness of 1 mm (40 mil).

H- Dayton Superior J56 high-mod epoxy, untinted, (Dayton Superior, Miamisburg Ohio), applied at a thickness of 1 mm (40mil). QW - white quartz coarse sand (Bosun Abrasives, Shanghai, China). CW - white corundum 1.5 - 2.5 mm, (Bosun Abrasives). b- 10 weight % retro reflective white ceramic elements 70E, (3M Corp.) on CW or QW

Example 15 High Hardness Retroreflective Road Marking without optional Retroreflective Element(s)

A synthetic crystalline grit and/or beads comprising aluminum oxide, calcium oxide and silicon dioxide are produced using the chemistry as described in U.S. Patent No. 3,431,125 to Gordy. The crystals have a Mohs hardness of about 8.5 and a refractive index of 1.9. A refractive index of 1.9 has been shown to be highly retroreflective under dry conditions. The crystalline grit and/or beads are used as a retroreflective armouring material in combination with a suitable adhesive such as epoxy-urethane copolymer. Example 16 High Hardness Retroreflective Road Marking with optional Retroreflective Element(s)

A synthetic crystalline grit and/or beads as in Example 15 is used in combination with a suitable adhesive such as epoxy-urethane copolymer and a supplementary retroreflective component having high retroreflectivity under wet conditions. The synthetic crystalline grit is used to armour the retroreflective material. Example 17 High Hardness Retroreflective Road Marking with Perlite

Translucent perlite glass beads formed of refined, unexpanded perlite, having a Mohs hardness of 7, (Sigma Engineering, White Plains, New York) are used as the armouring material or as a component of a blended armouring material for a road marking. The bead sizes are either 0.60 - 0.85 mm, 0.85 - 1.00 mm or less than 2 mm. The perlite beads have a refractive index of 1.5 and are retroreflective, especially under dry conditions. In some embodiments, the armouring material is (a) the perlite beads alone; (b) a mixture of perlite and quartz particles; (c) a mixture of perlite and corundum particles; or (d) a mixture of perlite and beads that have high retroreflectivity under wet conditions such as product code 70E manufactured by 3M corporation. In some embodiments, the perlite is in the form of a grit, having rough, irregular particle shapes to enhance antiskid properties of the marking. In some embodiments a mixture of perlite grit and beads is used. A 40 mils thick layer of epoxy-urethane copolymer adhesive is applied in a recessed groove on an asphalt road surface. The armouring material is embedded in the adhesive and the adhesive is allowed to set. In one embodiment, retroreflective paint is applied to the entire armouring surface and adhesive; in use, as the paint becomes worn, the armouring material is exposed and provides retroreflectivity to the worn marking. As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of the invention without departing from the scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the following claims.