US3894686A

US3894686A - Railroad crossing construction

Info

Publication number: US3894686A
Application number: US470819A
Authority: US
Inventors: Lewis C Weinberg; John L Cabanski; Jr John C Moerk
Original assignee: Felt Products Mfg Co LLC
Current assignee: Fel Pro Inc
Priority date: 1974-05-17
Filing date: 1974-05-17
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: BR7502964A; NL7505609A; FR2271338A1; BE828966A; GB1484760A; ES437672A1; IT1035742B; JPS50161035A; AU8121175A; CH603910A5; CA1028673A; DE2521520A1; SE7505534L

Abstract

Railroad crossing structure for a paved roadway over at least a pair of spaced rails mounted on cross ties to form a railroad track and supported by a ballast comprises a flexible center pad which extends transversely between each pair of spaced rails and flexible side pads which extend transversely between each segment of paved roadway and the rail nearest thereto. The flexible center and side pads are bonded directly to the ballast and comprise a resilient base layer containing a cured flexible thermoset resin and a filler of comminuted scrap rubber, and a resilient wear layer on top of the base layer and containing a cured flexible thermoset resin and a filler of finely divided rubber.

Description

United States Patent Weinberg et al.

RAILROAD CROSSING CONSTRUCTION Assignee: Felt Products Mfg. Co., Skokie, 111.

Filed: May 17, 1974 Appl. No.: 470,819

References Cited UNITED STATES PATENTS 1/1947 Abernathy 117/72 X 3/1958 Rennels 238/8 2/1963 Spence 238/8 [451 July 15, 1975 Primary ExamznerM. Henson Wood Assistant Examiner-Randolph A. Reese Attorney, Agent. or FirmDressler, Goldsmith, Clement & Gordon, Ltd.

[ 5 7] ABSTRACT Railroad crossing structure for a paved roadway over at least a pair of spaced rails mounted on cross ties to form a railroad track and supported by a ballast comprises a flexible center pad which extends transversely between each pair of spaced rails and flexible side pads which extend transversely between each segment of paved roadway and the rail nearest thereto. The flexible center and side pads are bonded directly to the ballast and comprise a resilient base layer containing a Cured flexible thermoset resin and a filler of comminuted scrap rubber. and a resilient wear layer on top of the base layer and containing a cured flexible thermoset resin and a filler of finely divided rubber.

11 Claims, 5 Drawing Figures emmeemrz a 40 5 Y7 -24 2" an. v-

e-eeaert-ie was if 1391,1610 i l"1A!- RAILROAD CROSSING CONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to railroad crossing construc' tion. More particularly, this invention relates to a flexible crossing structure which is bonded directly to the ballast for the railroad track.

Vehicular traffic across railroad tracks is subject to shock, the severity of which is dependent on the speed and weight of the particular vehicles, but which may cause extensive damage to the suspensions, wheels and tires of the vehicles and thus high maintenance costs due to broken springs, misaligned front axles which result in unevenly wearing tires, and the like. It is not uncommon for vehicles to slow down substantially when approaching a railroad crossing in order to minimize the passenger discomfort that is experienced during crossing as well as to minimize the likelihood of damage to the vehicle itself. Vehicles having relatively small wheels, such as the so-called compact and subcompact automobiles, receive particularly severe jolts upon crossing.

Moreover, especially heavy jolts are received by small-wheeled utility vehicles of the type used in industrial operations, e.g., small tractors and lift trucks having solid rubber tires, which have to negotiate in-plant railroad crossings frequently during daily operations. The wheels, suspension and frame of such utility vehicles can be damaged and delicate cargo may be broken or damaged during such crossings.

In addition, the impact on and the vibrations of the track rails due to the crossing traffic rapidly deteriorate the crossing structure and cause cracks and further roughness in the crossing surface. The lateral impact of traffic on the rails may shift the rails laterally and may disturb or displace the track ballast so that the shape of the track at the crossing assumes an S-shaped configuration. In addition, the impact of traffic on the rails tends to rotate the rails, thereby pulling out the spikes which secure the rails to the ties, and thus presenting a safety hazard. Water from the roadway surface may seep down into the ballast through cracks in crossing surface and along the rails and will tend to further erode the ballast and the roadbed due to a pumping action which is experienced when a passing load bears down on the track above. That is, a water-and-gravel slurry is formed and is ejected outwardly as a weight bears down on the rail. Upon freezing in cold weather such water will also tend to break up the crossing surface.

However, in negotiating a railroad crossing the degree of attention a which the driver can be expected to devote to the crossing surface is directly related to the condition of that surface. If the surface is uneven, or if the driver expects the surface to be uneven, the driver will undoubtedly attempt to select the smoothest path over the crossing. The attention that the driver devotes to selecting the smoothest path could very well reduce the attention given to the observance of traffic signals or an approaching train. Furthermore, an unexpected encounter with a rough or uneven railroad crossing surface may cause the driver to lose control of the vehicle and may result in an accident. Thus, continuously providing a reasonably smooth railroad crossing surface is also important for elimination or reduction of hazards at railroad crossings.

Several crossing structures have been developed in attempts to alleviate the foregoing problems. Crossing surfaces of wood fill, asphalt fill, precast concrete panels, reinforced concrete panels, steel-reinforced rubber panels, and the like, have been used to build a crossing surface. Illustrative of such prior art attempts are U.S. Pat. No. 1,693,878 to Wells, U.S. Pat. No. 2,828,079 and U.S. Pat. No. 2,828,080 to Rennels, U.S. Pat. No. 2,950,057 to Speer, and U.S. Pat. No. 3,465,963 to Cailett et al. Yet none of the heretofore proposed crossing structures has been able to fully overcome the hereinabove mentioned problems at a commercially attractive cost. Many of the prior art structures that have been tried under actual service conditions have met with limited acceptance because of relatively high installation costs or the need for frequent repair and maintenance, or both.

It is an object of the present invention to provide a new and improved railroad crossing structure which is long lasting in service and which is relatively inexpensive to install and to maintain.

A further object of this invention is to provide a railroad crossing structure which is resiliently compressible and readily absorbs vibrations, which is less susceptible to damage by the impacts and vibrations normally generated by crossing traffic, and which provides a relatively smooth and safe crossing surface.

Still another object of this invention is to provide a crossing structure which is resistant to water damage and which substantially minimizes water penetration to the underlying track ballast and roadbed.

Yet another object of this invention is to provide a crossing structure which does not require spiking or drilling of cross ties for installation, which can be installed relatively quickly and with a minimal interference with rail traffic.

Still other objects of the present invention will become apparent to the skilled artisan upon reference to the ensuing specification, the accompanying drawings, and the claims.

SUMMARY OF THE INVENTION The present invention contemplates a railroad crossing structure for a paved roadway across at least a pair of spaced rails for guiding railroad vehicles which rails are mounted on cross tie means resting on ballast. A flexible center pad means extends transversely between each pair of spaced rails, is bonded directly to the ballast and to the rails, and provides a roadway surface between the rails. Flexible side pad means extend transversely between each segment of the paved roadway and the rail nearest thereto, are bonded directly to the ballast and are in a sealing engagement with the rail nearest thereto, and provide a roadway surface between the paved roadway and the adjacent rail.

Each flexible pad means preferably forms an elastic bond with an adjacent rail and comprises a base layer containing a cured flexible thermoset resin and a filler of comminuted scrap rubber, and a wear layer on top of the base layer and containing a cured flexible thermoset resin and a filler of finely divided scrap rubber, the scrap rubber preferably being formed from worn automobile tires.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a plan view of a railroad crossing embodying the present invention;

FIG. 2 is a sectional elevation taken along plane 22 in FIG. 1 and enlarged to show interior detail;

FIG. 3 is a sectional elevation taken along plane 3-3 in FIG. 2;

FIG. 4 is a sectional elevation of an embodiment of this invention using filler blocks; and

FIG. 5 is a sectional elevation taken along plane 5-5 in FIG. 1 at a location between two adjacent railroad ties.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, rails and 11 are shown in parallel spaced relationship and mounted on a plurality of cross ties such as cross ties l2 and 13. The cross ties, in turn, are embedded in and rest on ballast 14 in a conventional manner.

The railroad crossing structure of this invention comprises flexible pads l5, l6 and 17 situated between segments 18 and 19 of a paved roadway. If desired,

expansion joints

20 and 21 can be provided between pavement segment 18 and flexible side pad and between pavement segment 19 and adjacent flexible side pad 17, respectively. The upper surface of flexible center pad 16 is provided with a suitable groove along both longitudinal edges so as to provide

flangeways

22 and 23 which accommodate the wheel flanges of the railroad equipment.

As shown in FIGS. 2 and 3, a rail, such as rail 10, is mounted on cross tie 24, as by means of a shouldered tie plate 25 and

track spikes

26 and 27. The resulting assembly rests on ballast 14 which provides the necessary support for the railroad track. Flexible center pad 16 is cast in situ between

rails

10 and 11 and extends therebetween. Resilient base layer 28 is cast from a curable base layer composition which is an admixture of comminuted scrap rubber with a curable liquid resin composition. The consistency of the base layer composition is such that a portion of the composition wets cross tie 24 and also ballast 14, preferably flowing at least partially between the individual particles of ballast l4 and forming a substantially continuous network of liquid interspersed with air, i.e., in a funicular state. Upon curing of the base layer 28, the liquid network forms elastic bridges 29 between individual particles of ballast 14 which tend to stabilize and hold ballast 14 together, even when subjected to vibrations of water pumping, without adversely affecting its usual function. Moreover, the need for retamping of the ballast after installation is obviated. Alternatively, ballast l4 and cross tie 24 can be pretreated with the curable liquid resin composition alone to pre-wet ballast l4 and to form the desired liquid network before base layer 28 is cast thereover. If desired, the liquid resin composition can be introduced below each cross tie by drilling spaced through holes in the tie and pouring the liquid resin therethrough. Preferably, the curable liquid resin composition forms an elastic bond between web 30 and flange 31 of rail 10 on one hand and flexible center pad 16 on the other. At any rate, the produced sealing engagement of the rails by the flexible pad prevents surface water from seeping downwardly therebetween and also electrically insulates the rails from the surroundings. The elastic bond is capable of withstanding the vibrations generated by the crossing traffic as well as the usual deflection of the rails when a train passes over.

On top of base layer 28 is provided resilient wear layer 32 which is cast in situ from a wear layer composition which is an admixture of finely-divided rubber in a curable liquid resin composition which can be similar to or different from the liquid resin composition utilized in base layer 28 as long as the thermal coefficients of expansion for base layer 28 and wear layer 32 remain compatible. The flangeways such as flangeway 22 can be conveniently formed during casting by inserting an appropriate form member adjacent to the inside of rail 10 while wear layer 32 is poured. Upon curing, wear layer 32 provides a smooth roadway surface without additional finishing.

Flexible side pads

15 and 17 are of the same construction as flexible center pad 16, and are formed in a similar manner, except that there is no need to form a flangeway along rails 10 and l l. The side pads preferably extend transversely beyond the ends of the cross ties for a distance about equal to the height of the ties. That is, initially base layers 33 and 42 (FIG. 5) are cast over ballast 14 so as to wet at least a portion of the individual particles thereof and preferably to interconnect with base layer 28 below the rails in the regions between ties in a manner shown in FIG. 5. The cast base layers also wet the cross ties such as cross tie 24 (FIG. 3) and portions of rails 10 and 11 (FIGS. 2 and 5). After the base layers have cured, wear layers 34 and 35 are cast thereover and permitted to cure. Suitable expansion joints, such as

resilient strips

20 and 21 can be provided between flexible side pad 15 and adjacent pavement segment 18 and between flexible side pad 17 and adjacent pavement segment 19, if desired. Preferably the expansion joints adhere both to the pads and to the pavement segments.

The use of bulk filler materials in the resilient pads of this invention is illustrated in FIG. 4. Precast concrete slabs 36 and 37 are situated on cross tie 38 on both sides of rail 10 which is mounted thereon by means of shouldered tie plate 39 and track spikes 40 and 41. Base layer 33 surrounds slab 36 and sealingly engages one side of flange 31 of rail 10. In a similar manner, base layer 28 surrounds slab 37 and sealingly engages the other side of flange 3]. Elastic bridges 29, in turn, anchor both base layer 33 and base layer 28 to ballast 14.

The base layer in the flexible crossing pads of this inmention is relatively thicker but more compressible than the wear layer; however, the relative thicknesses of the two layers are not overly critical. Usually the wear layer is about 0.5 to about 3 inches deep, as measured from the pad surface, and preferably about I inch to about 2 inches deep.

The relative amount of comminuted scrap rubber, such as chopped vehicle tires or the like, added to the curable liquid resin in the base layer composition can range from about 2 to about 6 parts by volume of scrap rubber to 1 part by volume of the curable resin composition. Preferably, the fillerto-curable resin volume ratio in the base layer is about 4:1 to about 6:1, respectively. The particle size of comminuted scrap rubber which is used as the filler can vary but should not exceed about one-fourth to about three-fourths inch in the longest dimension. If desired, larger filler materials such as concrete filler blocks, aggregate blocks, stone blocks, fiberglass blocks, or the like can also be incorporated into the base layer by positioning such filler blocks on the cross ties, and then pouring the curable liquid resin-filler composition thereover.

Finely-divided rubber particles having a particle size range of about to 300 mesh are utilized as filler in the wear layer. Fine rubber buffings or finely-ground rubber from old tires and substantially free from tire cord particles are especially desirable filler materials for this purpose. The volume ratio of filler-to-curable resin in the wear layer can be about 1:] to about 4:1, respectively. Preferably the volume ratio is about 3:l, respectively.

For preparing the base and wear layers having the desired physical properties suitable are glycidyl ether resins cured to a flexible state and preferably having a tensile elongation of at least about 5 percent at break point. Typical of such resins are diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, the glycidyl ethers of glycerol, epoxylated novolacs, and the like, which are derived from epichlorohydrin and a polyhydric material such as polynuclear polyhydroxy phenol, e.g., bisphenol A, bisphenol F, trihydroxyl diphenyl dimethyl methane, 4,4'-dihydroxy biphenyl, and the like, a polyol, e.g., ethylene glycol, 2,3-butane diol, erythritol, glycerol, and the like, a novolac resin and similar materials. The aforementioned curable epoxy resins can be polymerized through the hydroxyl groups in the presence of suitable catalysts such as tertiary amines, inorganic bases, or the like, or the resin chains bearing the oxirane group can be joined by a reactive intermediate such as a polyfunctional primary amine or a polyfunctional secondary amine, i.e., cured, to produce a flexible thermoset resin. Other suitable curing agents for this purpose are organic acids and acid anhydrides, BF; monoethylamine, and the like.

These epoxy resins can be used as the sole ingredient in the liquid curable composition, or resinous modifiers or flexibilizers can be combined therewith. Suitable modifiers are polyepoxides such as diglycidyl ether, butadiene dioxide, glycerol-based epoxy resins, alkylglycidyl ethers, phenylglycidyl ether, and the like. Suitable flexibilizers also are thiol-terminated polysulfides which can be conveniently prepared by condensing organic polyhalides with inorganic polysulfides, the relatively higher molecular weight diisocyanates, e.g., a reaction product of tolylene diisocyanate and polybutane diol, the thermoplastic polyamide resins, polyether polythiols and the like, which will react with the epoxy resin chain and will impart flexibility to the resulting thermoset resin.

For forming the base layer in the railroad crossing pads of this invention a particularly preferred elastomer is the condensation product of diglycidyl ether of bisphenol A and an ethyl formal disulfide polymer of the general formula wherein n is of sufficient magnitude to provide an average molecular weight of about 400 to about 1200. The weight ratio of diglycidyl ether resin to polysulfide polymer in the cured elastomer can range from about 5:1 to about [:2. Preferably, about 3 parts by weight of the diglycidyl ether resin per 1 part by weight of the polysulfide polymer are used. Suitable catalysts or curing agents for producing the foregoing diglycidyl ether resin-polysulfide resin condensation product are the dialkylaminoalkyl phenols such as dimethylaminomethyl phenol, 2,4,6- tri(dimethylaminomethyl) phenol, and the like, which can be present in an amount of about 0.7 to about 0.4 parts by weight.

For the wear layer, a particularly preferred elastomer is a condensation product of diglycidyl ether of bisphenol A with a low-viscosity, flexibilizing polyepoxide resin such as an aliphatic polyglycidyl ether commercially available from Celanese Coatings Co. under the designation EPl-REZ 505 and having an equivalent weight per epoxide of about 550-650, and viscosity at 77F. of about 300-400 cps, cured with an aliphatic amine such as a phenolic accelerated aliphatic polyamine commercially available from Celanese Coatings Co. under the designation EPl-CURE 874 and having an approximate equivalent weight of about 31 and viscosity at 77F. of about l00-200 cps. The diglycidyl ether resin and the flexibilizing polyepoxide resin in the cured elastomer can be present in a weight ratio of about 2:1 to about l:4, respectively. Preferably, about 0.75 parts by weight of the diglycidyl ether resin per 1 part by weight of the polyepoxide resin are used. Optionally, up to about 2.5 weight percent carbon black, based on the weight of the curable wear layer composition, can be added as a colorant for the wear layer. In lieu of the polyepoxide resin, a copolymerizable resin such as a diglycidyl ether of an aliphatic alcohol, and the like can be used, if desired. Suitable curing agents for the wear layer are aliphatic amines or polyamines, amideamine adducts, dimercaptans, aromatic amines, and the like, in an amount of about 0.5 to about 0.9 parts by weight.

Another suitable curable resin for forming the wear layer and having good abrasion resistance is a flexible polyurethane resin made by reacting an organic polyisocyanate with a polyol in a manner well known in the art.

The railroad crossing structure of this invention can be conveniently manufactured in situ be cleaning out any existing pavement as well as some ballast down to about cross tie level or slightly below in the region between the rails, and outwardly from the rails for a distance of about l8 to about 24 inches. If desired, all of the old ballast can be removed in the crossing area and replaced with clean, new ballast.

A curable base layer composition is then prepared from a selected polymerizable liquid composition by admixing therewith comminuted scrap rubber to form a castable slurry having a desired consistency. If the resulting curable base layer composition is relatively viscous, preferably the cleaned out crossing region, including the filler blocks, is prc-wetted with a polymerizable liquid composition.

Next the curable base layer composition is deposited into the cleaned out region between the rails and between the adjacent pavement segment (or an expansion joint abutting the pavement segment) and the rail nearest thereto, and is tamped into place to completely fill all void space up to a level about 2 to 3 inches below roadway surface.

Depending on what portion of the rail web is covered by the base layer when poured in place, a temporary form for providing a flangeway along the inside of the rails may or may not be needed while the base layer is poured. in any event, a flangeway form is provided ad jacent the inside of each of the rails when the wear layer is poured in place.

A curable wear layer composition prepared from a selected polymerizable liquid composition and a finelydivided rubber filler is then poured over the base layer. The wear layer composition usually has a higher resin content than the underlying base layer composition and is more fluid so as to provide good wetting and ultimate adhesion between the base layer and the wear layer and also between the rails and the wear layer. The wear layer composition is poured to the level of the rails themselves and is brought over contiguous to the rails on the outside and over to the removable flangeway forms in the region between the rails. Thereafter the poured wear layer is tamped down on top of the base layer and permitted to cure so as to provide a smooth, finished roadway surface.

The base layer and the wear layer usually cure to an extent sufficient to bear traffic within about 4 to about 6 hours, depending on the curing agent that is employed and also, of course, on the ambient temperature. If a faster cure rate is desired, the curable compositions can be heated before pouring.

A railroad crossing has been built in accordance with the present invention, and has satisfactorily withstood one winter season at below freezing temperatures while subjected to daily train and vehicular traffic. The flexible center pad and the flexible side pads were about 6 inches thick, having a flexible base layer thickness of about 4 inches and a flexible wear layer thickness of about 2 inches.

The curable liquid resin formulation for the base layer was made up of about parts by weight diglycidyl ether of bisphenol A, about 2 parts by weight ethyl formal disulfide polymer having a molecular weight of about 1000, and about 0.5 parts by

weight

2,4,6- tri(dimethylaminomethyl) phenol. Comminuted scrap rubber from automobile tires and having particles ranging in size from about one-fourth inch to about threefourths inch in the longest dimension thereof was admixed with the curable liquid resin formulation to form a slurry having a filler-to-curable resin volume ratio of about 4:1.

Concrete slabs measuring about 24 X 16 X 4 inches were utilized as an inorganic filler, and were positioned at a transverse spacing of about 8 to 12 inches between adjacent slabs and a longitudinal spacing of about 1 inch between adjacent slabs.

An aliquot of the curable liquid resin formulation was used to wet the ballast, the cross ties, and the concrete slabs at the railroad crossing in a region from which old pavement and some ballast had been previously removed to a level of about the top surface of the cross ties supporting the rails. Thereafter, the slurry for the base layer was poured into the cleaned-out region and leveled off about 3 inches from the pavement surface. Care was taken that the slurry was in intimate contact with the rails, the cross ties, and the supporting ballast.

Thereafter a curable liquid resin formulation for the wear layer was prepared containing about 1.65 parts by weight diglycidyl ether of bisphenol A, about 2.15 parts by weight polyepoxide resin prepared from a polyhydric alcohol and having an approximate weight per epoxide of about 600, and about 0.8 parts by weight of phenolic accelerated aliphatic amine. Additionally about 0.15 parts by weight of carbon black was stirred into the curable wear layer formulation as a colorant and enough finely-divided rubber buffings were added to the formulation to give a slurry having a filler-to curable resin volume ratio of about 3:1.

Flangeway forms were then placed along the inside of the rails at the crossing, and the obtained slurry was cast over the base layer already in place and tamped down about level with the pavement surface and the rails. Surface of the wear layer was smoothed out and finished, and the cast pads were permitted to cure at ambient temperature for about 4 hours. After this time period the flangeway forms were removed, and the railroad crossing was placed in service and periodically examined. The side pads and the center pad were observed to flex when a heavy load passed thereover, but after about 8 months of use no deterioration of the pad surface is apparent.

The foregoing specification and the drawing are intended as illustrative and are not to be taken as limiting. Still other variations and modifications are possible without departing from the spirit and scope of this invention.

What is claimed is:

l. A railroad crossing structure for a paved roadway across at least a pair of spaced rails for guiding railroad vehicles and mounted on cross tie means supported on ballast which comprises a flexible center pad means extending transversely between each pair of spaced rails, providing a roadway surface therebetween, and being bonded directly to said ballast and being in a sealing engagement with said rails; and

a flexible side pad means extending transversely between each pavement segment and the rail nearest thereto, providing a roadway surface therebetween, and being bonded directly to said ballast and being in a sealing engagement with said nearest rail;

each of said flexible pad means having a base layer comprising a flexible thermoset resin which is a cured glycidyl ether resin, comminuted scrap rubber, and an inorganic bulk filler, and a wear layer of a cured flexible thermoset resin and finelydivided scrap rubber on top of said base layer, scrap rubber-to-cured resin volume ratio in said base layer being about 2:1 to about 6:1 and scrap rubber-to-cured resin volume ratio in said wear layer being about 1:1 to about 4:1; and said cured glycidyl ether resin in said base layer bonding together individual ballast particles below said base layer and bonding said base layer to said ballast.

2. The railroad crossing structure in accordance with claim 1 wherein said flexible pad means further include an elastic bridge network of said cured glycidyl ether resin holding together individual particles of said ballast.

3. The railroad crossing structure in accordance with claim 1 wherein said inorganic bulk filler is a plurality of blocks.

4. A railroad crossing structure for a paved roadway across at least a pair of spaced rails for guiding railroad vehicles and mounted on cross tie means supported on ballast which comprises a flexible center pad means extending transversely between each pair of spaced rails, providing a roadway surface therebetween, and being bonded directly to said ballast and being in a sealing engagement with said rails; and

each of said flexible pad means comprising a base layer of a cured flexible thermoset resin which is a condensation product of a glycidyl ether resin and a thiol-terminated polysulfide resin and a filler which is comminuted scrap rubber, and a wear layer of a cured flexible thermoset resin which is an aliphatic amine-cured glycidyl ether resin and a filler which is finely-divided scrap rubber on top of said base layer, a filler-to-cured resin volume ratio in said base layer being about 2:1 to about 6:1, and the tiller-to-cured resin volume ratio in said wear layer being about 1:1 to about 4:1.

5. The railroad crossing structure in accordance with claim 4 wherein said flexible thermoset resin in the base layer is a condensation product of diglycidyl ether of bisphenol A and ethyl formal disulflde polymer in a weight ratio of about 5:1 to about 122, respectively, the ethyl formal disulflde polymer having the general formula where g is of sufficient magnitude to give a molecular weight of about 400 to about 1200, and about 0.7 to about 0.4 parts by

weight

2,4,6- tri(dimethylaminomethyl) phenol; and wherein said flexible thermoset resin in the wear layer comprises a diglycidyl ether of bisphenol A and a flexibilizing polyepoxide in a weight ratio of about 2:1 to about 1:4, respectively, and about 0.5 to about 0.9 parts by weight of an aliphatic polyamine curing agent.

6. A method for manufacturing a resilient railroad crossing pad to provide a crossing structure across at least a pair of spaced rails mounted on cross tie means supported on ballast which comprises the steps of preparing a curable base layer composition comprising a glycidyl ether resin and a thiol-terminating polysulfide resin, a dialkylaminoalkyl phenol curing agent, and a particulate resilient filler; said filler and said resin being present in said curable base layer composition in a volume ratio of about 4:1 to about 6:1, respectively; casting said curable base layer composition over said ballast to form a base layer for said pad 1L1 it u;

curing the cast base layer so as to form a condensation product of said glycidyl ether and said polysultide;

preparing a curable wear layer composition comprising a glycidyl ether resin, a polyepoxide resin, an aliphatic amine cross-linking agent, and a particulate resilient filler; said filler and said resin being present in said second curable composition in a volume ratio of about 3:1, respectively;

casting said curable wear layer composition to form a wear layer on top of said base layer; and

curing the cast wear layer so as to form an aliphatic amine-cured glycidyl ether polymer.

7. The method in accordance with claim 6 wherein the curable liquid resin for the base layer composition is a mixture of glycidyl ether resin and thiol-terminated polysulfide in a weight ratio of about 5:1 to about 1:2, respectively, and about 0.7 to about 0.4 parts by weight dialkylaminoalkyl phenol, and wherein the curable liquid resin for the wear layer composition is a mixture of glycidyl ether resin and a flexibilizing polyepoxide in a weight ratio of about 2:1 to about 1 :4, respectively, and wherein about 0.5 parts to about 0.9 parts by weight of an aliphatic amine curing agent are present in the mixture.

8. The method in accordance with claim 6 wherein the curable liquid resin for the base layer composition contains about 5 parts by weight diglycidyl ether of bisphenol A, about 2 parts by weight ethyl formal disulfide polymer of the general formula where n is of sufficient magnitude to give a molecular weight of about 1000, about 0.5 parts by

weight

2,4,6- tri(dimethylaminomethyl) phenol; and wherein the curable liquid resin for the wear layer composition contains about 1.65 parts by weight diglycidyl ether of bisphenol A, about 2.15 parts by weight of a flexibilizing polyepoxide, and about 0.8 parts by weight aliphatic polyamine.

9. The method in accordance with claim 6 wherein that portion of the ballast which is covered by said crossing pad is pre-wetted with a curable liquid resin composition before said curable base layer composition is cast thereover.

10. A method of repairing an existing paved roadway crossing over a railroad track which includes a pair of spaced rails supported on ties supported by a ballast material and wherein roadway pavement extends up to and transversely between the rails, which comprises cleaning out existing pavement and a portion of said ballast down to at least tie level in the region between said rails and also in a region immediately adjacent to each pair of spaced rails;

casting a base layer comprising a curable liquid resin composition and a filler of comminuted scrap rubber in said cleaned out regions to a level above the tie level but below the pavement level;

curing the cast base layer so as to produce a flexible base;

casting a wear layer comprising a curable liquid resin mixture and a filler of finely-divided scrap rubber substantially level with said rails and said pavement; and

curing the cast wear layer so as to produce a flexible wear layer over said flexible base;

the filler-to-curable resin volume ratio in the base layer being about 2:1 to about 6:1, respectively, and the filler-to-curable resin volume ratio in the wear layer being about 1:1 to about 4:1, respectively.

l 1. The method in accordance with claim 10 wherein the filler-to-curable resin volume ratio in the base layer is about 4:1 to about 6:1 and the filler-to-curable resin volume ratio in the wear layer is about 3:1.

Claims

1. A RAILROAD CROSSING STRUCTURE FOR A PAVED ROADWAY ACROSS AT LEAST A PAIR OF SPACED RAILS FOR GUIDING RAILROAD VEHICLES AND MOUNTED ON CROSS TIE MEANS SUPPORTED ON BALLAST WHICH COMPRISES A FLEXIBLE CENTER PAD MEANS EXTENDING TRANSVERSELY BETWEEN EACH PAIR OF SPACED RAILS, PROVIDING A ROADWAY SURFACE THEREBETWEEN, AND BEING BONDED DIRECTLY TO SAID BALLAST AND BEING IN A SEALING ENGAGEMENT WITH SAID RAILS, AND A FLEXIBLE SIDE PAD MEANS EXTENDING TRANSVERSELY BETWEEN EACH PAVEMENT SEGMENT AND THE RAIL NEAREST THERETO, PROVIDING A ROADWAY SURFACE THEREBETWEEN, AND BEING BONDED DIRECTLY TO SAID BALLAST AND BEING IN A SEALING ENGAGEMENT WITH SAID NEAREST RAIL, EACH OF SAID FLEXIBLE PAD MEANS HAVING A BASE LAYER COMPRISING A FLEXIBLE THERMOSET RESIN WHICH IS A CURED GLYCIDYL ETHER RESIN, COMMINUTED SCRAP RUBBER, AND AN INORGANIC BULK FILLER, AND A WEAR LAYER OF A CURED FLEXI LE THERMOSET RESIN AND FINELY-DIVIDED SCRAP RUBBER ON TOP OF SAID BASE LAYER, SCRAP RUBBER-TO-CURED RESIN VOLUME RATIO IN SAID BASE LAYER BEING ABOUT 2:1 TO ABOUT 6:1 AND SCRAP RUBBERTO-CURED RESIN VOLUME RATIO IN SAID WEAR LAYER BEING ABOUT 1:1 TO ABOUT 4:1, AND SAID CURED GLYCIDYL ETHER RESIN IN SAID BASE LAYER BONDING TOGETHER INDIVIDUAL BALLAST PARTICLES BELOW SAID BASE LAYER AND BONDING SAID BASE LAYER TO SAID BALLAST.

4. A railroad crossing structure for a paved roadway across at least a pair of spaced rails for guiding railroad vehicles and mounted on cross tie means supported on ballast which comprises a flexible center pad means extending transversely between each pair of spaced rails, providing a roadway surface therebetween, and being bonded directly to said ballast and being in a sealing engagement with said rails; and a flexible side pad means extending transversely between each pavement segment and the rail nearest thereto, providing a roadway surface therebetween, and being bonded directly to said ballast and being in a sealing engagement with said nearest rail; each of said flexible pad means comprising a base layer of a cured flexible thermoset resin which is a condensation product of a glycidyl ether resin and a thiol-terminated polysulfide resin and a filler which is comminuted scrap rubber, and a wear layer of a cured flexible thermoset resin which is an aliphatic amine-cured glycidyl ether resin and a filler which is finely-divided scrap rubber on top of said base layer, a filler-to-cured resin volume ratio in said base layer being about 2:1 to about 6:1, and the filler-to-cured resin volume ratio in said wear layer being about 1:1 to about 4:1.

5. The railroad crossing structure in accordance with claim 4 wherein said flexible thermoset resin in the base layer is a condensation product of diglycidyl ether of bisphenol A and ethyl formal disulfide polymer in a weight ratio of about 5:1 to about 1:2, respectively, the ethyl formal disulfide polymer having the general formula H ( SCH2CH2OCH2OCH2CH2S )nH where n is of sufficient magnitude to give a molecular weight of about 400 to about 1200, and about 0.7 to about 0.4 parts by weight 2,4,6-tri(dimethylaminomethyl) phenol; and wherein said flexible thermoset resin in the wear layer comprises a diglycidyl ether of bisphenol A and a flexibilizing polyepoxide in a weight ratio of about 2:1 to about 1:4, respectively, and about 0.5 to about 0.9 parts by weight of an aliphatic polyamine curing agent.

6. A method for manufacturing a resilient railroad crossing pad to provide a crossing structure across at least a pair of spaced rails mounted on cross tie means supported on ballast which comprises the steps of preparing a curable base layer composition comprising a glycidyl ether resin and a thiol-terminating polysulfide resin, a dialkylaminoalkyl phenol curing agent, and a particulate resilient filler; said filler and said resin being present in said curable base layer composition in a volume ratio of about 4:1 to about 6:1, respectively; casting said curable base layer composition over said ballast to form a base layer for said pad in situ; curing the cast base layer so as to form a condensation product of said glycidyl ether and said polysulfide; preparing a curable wear layer composition comprising a glycidyl ether resin, a polyepoxide resin, an aliphatic amine cross-linking agent, and a particulate resilient filler; said filler and said resin being present in said second curable composition in a volume ratio of about 3:1, respectively; casting said curable wear layer composition to form a wear layer on top of said base layer; and curing the cast wear layer so as to form an aliphatic amine-cured glycidyl ether polymer.

7. The method in accordance with claim 6 wherein the curable liquid resin for the base layer composition is a mixture of glycidyl etHer resin and thiol-terminated polysulfide in a weight ratio of about 5:1 to about 1:2, respectively, and about 0.7 to about 0.4 parts by weight dialkylaminoalkyl phenol, and wherein the curable liquid resin for the wear layer composition is a mixture of glycidyl ether resin and a flexibilizing polyepoxide in a weight ratio of about 2:1 to about 1:4, respectively, and wherein about 0.5 parts to about 0.9 parts by weight of an aliphatic amine curing agent are present in the mixture.

8. The method in accordance with claim 6 wherein the curable liquid resin for the base layer composition contains about 5 parts by weight diglycidyl ether of bisphenol A, about 2 parts by weight ethyl formal disulfide polymer of the general formula H ( SCH2CH2OCH2OCH2CH2S )nH where n is of sufficient magnitude to give a molecular weight of about 1000, about 0.5 parts by weight 2,4,6-tri(dimethylaminomethyl) phenol; and wherein the curable liquid resin for the wear layer composition contains about 1.65 parts by weight diglycidyl ether of bisphenol A, about 2.15 parts by weight of a flexibilizing polyepoxide, and about 0.8 parts by weight aliphatic polyamine.

10. A method of repairing an existing paved roadway crossing over a railroad track which includes a pair of spaced rails supported on ties supported by a ballast material and wherein roadway pavement extends up to and transversely between the rails, which comprises cleaning out existing pavement and a portion of said ballast down to at least tie level in the region between said rails and also in a region immediately adjacent to each pair of spaced rails; casting a base layer comprising a curable liquid resin composition and a filler of comminuted scrap rubber in said cleaned out regions to a level above the tie level but below the pavement level; curing the cast base layer so as to produce a flexible base; casting a wear layer comprising a curable liquid resin mixture and a filler of finely-divided scrap rubber substantially level with said rails and said pavement; and curing the cast wear layer so as to produce a flexible wear layer over said flexible base; the filler-to-curable resin volume ratio in the base layer being about 2:1 to about 6:1, respectively, and the filler-to-curable resin volume ratio in the wear layer being about 1:1 to about 4:1, respectively.

11. The method in accordance with claim 10 wherein the filler-to-curable resin volume ratio in the base layer is about 4:1 to about 6:1 and the filler-to-curable resin volume ratio in the wear layer is about 3:1.