US2884841A - Hot bituminous concrete surface treatment and process - Google Patents

Description

"zap-hi- United States Patent HOT BITUMINOUS CONCRETE SURFACE TREATMENT AND PROCESS Howard "E. Dickinson, Wethersfield, Conn., assig'nor of forty percent to, Joseph F. Briganti, New Britain, Conn., and twenty percent to I. Jordan Kunik, New York, N .Y.

No Drawing. Application August 21, 1957 a Serial No. 679,513

Claims. (CI. 94-23) ture within the range of 300 to 340", F., and to a method o'f'applying the-same to highway pavements.

When highways disintegrate or deteriorate by scaling, cracking or the like, inevitably the expense of repaving or restoring the defective areas adds considerably to the already heavy burden upon state and municipal funds. It has beenthe general practice, therefore, to apply temporary surface treatments in order to maintain reasonably adequate road surfaces until repaving becomes mandatory.

Existing methods of maintenance, such as RC-2 brush patching or tar treatments, have proven somewhat less than satisfactory. Where asphalt cutback has been applied to scaled areas, squeegeed across said areas and sand covers applied, the resultant protective coating is comparatively short lived and unsightly. The application of tar to scaly concrete pavements, with a sand covering and a honing, also has proven somewhat unsatisfactory since a considerable portion of this coating soon wears Off. This establishes a rough surface and an unsightly appearance, thereby requiring an application of tar and sand annually in order to maintain the highway in suitable condition. 1

It is well known that the method of applying road oil to "a road surface with'a' bituminous oil distributor and thereafter-applying a sand or gravel aggregate, which is impacted into the oil by highway trafi'ic, has the obvious disadvantage of prolonged curing time and of unfavorable working conditions 'for the men engaged in the operation, as well as for pedestrians who track the oil on their shoes when crossing such a treated highway. The highway traffic which is utilized to pack the aggregate into the tacky oil causes a large portion of the aggregate to be cast upon the shoulders of the road. Simultaneously, deleterious and unsightly deposits of oil are spattered on the undersides and painted exterior of the bodies of passing vehicles. This operation often results in the unintentional spraying of bitumen on curbs, bridges, sign posts and guide rails, thereby disfiguring the aesthetic attractiveness of the roadsides.

It has been apparent for some time that there is need for a low cost, fastcuring, surface treatment mix and for 'amethod of applying the same. To be acceptable, a new:

method should provide improved means for maintaining and preserving the surface of highway pavements and provide longer life to such surfaces, whereby the need for resurfacing and repairing will be diminished.

.I provide, therefore, anew bituminous mixture and a method of applying the same to a'highway surface, whereby great savings can be realized. This new mixture and method are advantageous in providing a correction for disintegrated pavement and as a retardant to scaling until such surface can be resurfaced or repaved by bituminous concrete. Since the mixture cures substantially immedi- ICC ately upon application, it can also be used in lieu of tar and sand treatments, thereby eliminating complaints re sulting from tracking of tar into stores and homes, the spattering of motor vehicles and comparable nuisances arising from the spraying of liquid bitumen.

Since the mixhas high non-skid value, it can be used to correct slick pavement conditions resulting from highly polished aggregate or from bleeding of the bituminous tack coat on stone surfaced roads, thereby preventing accident hazards. It can be used for sealing and renewing pavement surfaces and, in this connection, it is particularly advantageous in that it is not necessary to appreciably increase present pavement thickness, for the treatment merely adds a thin coating to obtain a renewal of the riding surface. It can also be used to correct uneven.

sections of old pavements as it eliminates dips and irregularities.

Since this mix cures rapidly and the desired results areachieved immediately, adverse weather conditions do not affect the results. It can be used in lieu of liquid bituminous surface treatment at a more reasonable cost. If the initial application of the mix becomes worn, a second application can be made over the old treatment. The mix can be used on city streets and town roads to correct pavement failures and to improve the riding qualities, at minimum cost regardless of the existing pavement characteristics.

v The mix has also proven successful in covering bridge decks where the original surface consists of Portland cement concrete, Wood, bituminous concrete, sheet asphalt, or steel. Since the mix adheres very well to a steel surface, it can be used for filling adjacent to or covering unused trolley car rails.

The process described herein is also adaptable for producing new pavements or resurfacing treatments, the composition and thickness of which will be determined by the use to which the pavement is to be put.

In order to accomplish the foregoing, I provide, according to the present invention, a relatively low cost, hot

surface appearance is produced and the treated highway is in condition promptly to carry heavy traffic loads.

Contrary to the older practice of first applying warm oil to a pavement surface and thereafter applying the aggregate, leaving much to be desired in the end result, I now provide a mixture of medium curing cutback asphalt and aggregate which is heated to a temperature ranging between 300 and 340 F., preferably at 300 F., or above, and which is applied to the road surface at substantially within this temperature range. For pur poses of illustration only there follows a typical mix for mula and the general composition thereof:

Mix Formula, Percent Composition Limits by Weight,

Percent Crushed Rock Aggregate Passing #200 Sieve Passing Sieve... Passing #40 Sieve Bitumen Recommended weights of aggregate and bitumen used in one typical ton of mixture:

. Pounds 1 Sand (passing M sieve) 1, 400

Stone M size (retained on sieve)... 450

mineral filler such as calcium chloride flakes in the amount of approximately 18 to 20 pounds per ton of mixture. Also, the mix formula may include a portion of crushed rock aggregate that passes a /2 sieve in the above formulation depending upon particular surfacing requirements. Other suitable variations in composition of aggregate and cutback asphalt formulas may be prescribed depending upon the desired design of the pavement and the use to which the highway is to be put.

The aggregates are graded within the composition limits set forth above and are heated in an asphalt plant to such temperature that, when inserted into the mixing chamber and coated with the MC-S cutback asphalt (the bitumen having been heated previously to about 150 F.), the resulting mixture has a temperature of between 300 F. to 340 F. prior to being discharged from the mixer. The hot mixture is then loaded on dump trucks or other suitable conveyances which may be provided with fitted covers or the like, which prevent any substantial cooling of the mixture while being conveyed to the paving site.

The hot mixture may then be dumped in small piles directly upon the previously cleaned and brushed pavement ahead of a self-propelled grader which distributes the material over the required width of the highway. The grader blade is adjusted to the requisite height to provide the desired finished highway cross-section elevation.

Alternatively, the hot MC-S mix may be dropped into a skid-mounted hopper attached to the front end of a truck. The hopper continually releases a sufficfent amount of the mixture to keep its strike-off blade filled at all times. This blade is set at a suitable forward angle from the vertical in order to provide a wedging action which forces the hot MC5 mixture into the depressions of the road surface, sufiicient extra material being carried along by the blade to leave a smooth surface to the depth required.

In some applications, a wheighted canvas, fabric or rug is towed behind the truck in such manner that the entire bottom surface of the drag is in intimate contact with the surface of the roadway, thereby effectively backfilling tire-tread depressions, smoothing out irregularities and minimizing any fluffing" that may be produced. This drag operation makes unnecessary the assignment of numerous workmen to follow behind the truck, using rakes and lutes to dress-up the area being covered.

About five minutes thereafter, a tandem roller makes a single pass over the freshly applied mix to provide a final smoothing operation. The tandem roller is utlized not for the purpose of compacting the surface application but merely to complete the smoothing of the surface treatment. The rollers are equipped with a sprinkling system to keep the wheels wet to prevent pick-up of the material. As soon as the rolling operation has been completed, a light dusting of sand may be applied to the treated area. Traflic then may be permitted on the new surface inasmuch as the newly applied MC-S mix will not pick up on passing vehicles or shift in position.

The principal purpose of the foregoing operation is to provide comparatively simple and inexpensive means for maintaining highways whose conditions have not deteriorated to the extent that a complete repaving job is necessary. The outstanding advantage of the surface treating mixture disclosed herein is that it cures very soon after it is applied to the highway, thereby preventing the tracking of hot oils or tars into business establishments and homes, and sticking to and hardening upon vehicles that pass over the highways.

The medium curing cutback designated herein is a product described as an asphalt cement fiuxed with a kerosene type of distillate. See page 13 of the Asphalt Handbook, published by The Asphalt Institute, College Park, Maryland, copyright 1947, and identified as Construction Series No. 81 (1957 edition). The medium curing cutback asphalt as described herein is also defined on page 1419 of the publication A.S.T.M. Standards of 1955 (part 3), issued by the American Society for Testing Materials, as liquid petroleum products, produced by fluxing an asphaltic base with suitable distillates, to be used in the treatment of road surfaces in the manner designated for the respective grades. These A.S.T.M. standards designated D-59846 were originally published tentatively in 1940 and were permanently adopted in 1946. The same A.S.T.M specifications for medium curing cutback asphalt are also incorporated on page 44 of the Asphalt Handbook referred to hereinabove. The foregoing standards include a description of MC-S cutback asphalt which is one typical medium curing grade that is useful in the practice of the present invention. While MC-S has for many years been used as a hot liquid surface treatment, and in so-called cold laid pavement mixtures, it has never heretofore been utilized in an asphalt mixing plant for mixing with aggregates at the elevated temperatures prescribed herein and for producing a hot-laid pavement in the manner described.

Although it is quite possible to use rapid curing or slow curing cutback asphalts that are applied hot for various surface treatments, the rapid curing cutback asphalt cannot be used in the method described herein because of the lower flash point admixtures of naphtha or gasoline, which might create a hazard from explosion or combustion when being mixed with the preheated aggregates.

In the case of a slow curing cutback liquid asphalt, while it is possible to heat the mixture to a higher degree than the MC cutbacks, such slow curing asphalts will require a longer waiting period before traflic may be permitted to move over the treated pavement. The MC-S appears to be the preferable asphalt grade to be used in the mixture described hereinabove inasmuch as it gives to said mixture the requisite characteristics of pliability and adhesiveness which are its advantageous features for surface maintenance of deteriorated highways.

A salient feature of the invention is that the MC-S medium curing cutback asphalt is mixed with the other ingredients that have been raised in temperature to such a degree that, when it is later applied to the highway, its application temperature is within the range of 300 to 340 F. As the mixture is applied to the highway at that elevated temperature, volatilization of a substantial portion of the cutback ingredients takes place quickly so that a prompt curing of the mix is effected. After this, the asphaltic residues which act as a binder film between the aggregates in the mixture, serve to maintain the resilience of the application under varying traffic conditions and under ambient temperatures ranging through summer and winter as may be experienced in the different areas of the United States.

The application of the MC-S and aggregate mixtures at elevated temperatures is considerably different in process and effect from that where a hot liquid asphalt or tar application is applied at approximately F. The so-called hot liquid asphalt process is, in effect, a cold application because of the attenuation of the liquid over the pavement which rapidly cools the liquid, thereby decelerating the rate of vaporization of the volatile components. This accounts for the fact that such an application remains tacky for a considerable length of time, even after a layer of sand or gravel has been spread over the surface of the liquid.

In the application of the present invention, however, the residual heat in the aggregates is believed to cause a more rapid volatilization of the cutback ingredients whereby a fast cure is effected and trafiic is permitted to proceed over the highway a very short time thereafter.

The asphalt residuum not only acts as a binder for the particles of the aggregates and causes them to cohere into a long lasting resilient cover layer, but it also causes said layer to form a bond with the surface of the pavemerit upon which it has been applied so that the cover layer does not peel off or blister. At the same time, this cohesiveness coupled with the resiliency of the application of the present invention provides a surface highway coating which withstands heavy trafiic loads under widely varying temperature conditions throughout the various seasons of the year.

The composition of the present invention is also useful as an intermediate binding layer in the construction or reconstruction of roads and highways. Where a standard bituminous concrete layer is to be applied as a new surface on a road, it is essential to insure the adherence of said layer to the base upon which it rests. Heretofore, a hot liquid bituminous application has been made prior to the laying down of the bituminous concrete course with the intention of causing the latter to adhere to the base. This procedure, however, has proven inadequate and buckling of the top layer of the road has been experienced.

The buckling and blistering of a standard bituminous concrete surface course can be prevented by the application of an intermediate layer of the cutback and aggregate mixture described hereinabove. Such an intermediate course retains its resiliency and adhesiveness whereby an effective and long lasting bond is established between the bituminous concrete riding course and the base upon which it rests. This is due to the characteristics of the mixture described herein which adheres both to the bituminous concrete material and to the material that forms the base for the highway.

The compositions described herein have such flow characteristics that, upon application with a grader blade, they adapt themselves readily to all gradations of depth in the pavement surface from paper thin to any desired degree of thickness as determined by the level at which the grader blade is moved in respect of said pavement.

In the specification, I have explained the principles of my invention and the best mode in which I have contemplated applying those principles, so as to dishinguish my invention from other inventions; and I have particularly pointed out and distinctly claimed the part, mode or combination which I claim as my invention or discovery.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the function and scope thereof, as will be clear to those skilled in the art.

I claim:

1. The method of surface treating a pavement with a bitumen and crushed rock and sand aggregate mixture, comprising heating said aggregates to an elevated temperature, heating a medium curing cutback asphalt containing asphalt and kerosene to an elevated temperature, mixing said heated aggregates and said heated cutback asphalt intimately, the respective elevated temperatures of said aggregate and of said cutback asphalt being controlled whereby the final temperature of the aggregate and cutback asphalt mixture is between 300 F. and 340 F., conveying said mixture to the pavement site in a manner as to substantially maintain said temperature, and spreading the mixture at substantially said temperature across the width of the pavement area to be treated.

2. The method of producing a pavement, comprising heated crushed rock and sand aggregates to an elevated temperature, heating a medium curing cutback asphalt containing asphalt and kerosene to an elevated temperature, mixing said heated aggregates and said heated cutback asphalt whereby the resultant temperature thereof is between 300 F. and 340 F., transferring said mixture at said temperature to a conveyance, covering said mixture to prevent any substantial loss of heat, conveying said mixture to a paving site and spreading said mixture at said temperature across the pavement area.

3. The method of producing a pavement, comprising heating aggregates to an elevated temperature, heating a. medium curing cutback asphalt containing asphalt and kerosene to an elevated temperature, mixing said heated aggregates and said heated cutback asphalt whereby the resultant temperature thereof is between 300 F. and 340 F., transferring said mixture at said temperature to a conveyance, covering said mixture to prevent any substantial loss of heat, conveying said mixture to a paving site and spreading said mixture at said temperature across the pavement area, and thereafter dragging a piece of fabric across the freshly laid pavement in order to produce a smooth surface thereon.

4. The method of surface treating a pavement with a bitumen and crushed rock and sand aggregate mixture, which comprises placing and spreading said mixture at a temperature of at least 300 F. over a base, said mixture having been prepared by heating said aggregate to an elevated temperature, heating a medium curing cutback asphalt containing asphalt and kerosene to an elevated temperature, and mixing said heated aggregates and said heated cutback asphalt intimately, the respective elevated temperatures of said aggregate and of said cutback asphalt being controlled whereby the final temperature of the aggregate and cutback asphalt mixture is between 300 F. and 340 F.

5. The method of surface treating a pavement with a bitumen and crushed rock and sand aggregate mixture, comprising heating said aggregates to an elevated temperature, heating a medium curing cutback asphalt containing asphalt and kerosene to an elevated temperature, mixing said heated aggregates and said heated cutback asphalt intimately, the respective elevated temperatures of said aggregate and of said cutback asphalt being controlled whereby the final temperature of the aggregate and cutback asphalt mixture is between 300 F. and 340 F., and thereafter spreading said mixture within said temperature range over the pavement area.

References Cited in the file of this patent UNITED STATES PATENTS 935,572 Amies Sept. 28, 1909 1,291,361 Babst Jan. 14, 1919 1,549,656 Drummond Aug. 11, 1925 1,576,045 Greene Mar. 9, 1926 1,671,070 Forrester May 22, 1928 1,683,382 Carr Sept. 4, 1928 1,883,683 Gardner Oct. 18, 1932 2,347,233 Abernathy Apr. 25, 1944 2,742,372 Colvin Apr. 17, 1956 2,783,162 Mollring Feb. 26, 1957 OTHER REFERENCES Asphalt Pocket Reference for Highway Engineers, published by the Asphalt Institute, 1941, page 61.

Asphalt Handbook, published by the Asphalt Institute as Construction Series No. 81, 1947.

Specifications for Liquid Asphaltic Road Materials, published by the Asphalt Institute as C.S. No. 6, page 8.

Claims (1)

1. THE METHOD OF SURFACE TREATING A PAVEMENT WITH A BITUMEN AND CRUSHED ROCK AND SAND AGGREGATE MIXTURE, COMPRISING HEATING SAID AGGREGATES TO AN ELEVATED TEMPERATURE, HEATING A MEDIUM CURING CUTBACK ASPHALT CONTAINING ASPHALT AND KEROSENE TO AN ELEVATED TEMPERATURE, MIXING SAID HEATED AGGREGATES AND SAID HEATED CUTBACK ASPHALT INTIMATELY, THE RESPECTIVE ELEVATED TEMPERATURES OF SAID AGGREGATE AND OF SAID CUTBACK ASPHALT BEING CONTROLLED WHEREBY THE FINAL TEMPERATURE OF THE AGGREGATE AND CUTBACK ASPHALT MIXTURE IS BETWEEN 300* F. AND 340* F., CONVEYING SAID MIXTURE TO THE PAVEMENT SITE IN A MANNER AS TO SUBSTANTIALLY MAINTAIN SAID TEMPERATURE, AND SPREADING THE MIXTURE AT SUBSTANTIALLY SAID TEMPERATURE ACROSS THE WIDTH OF THE PAVEMENT AREA TO BE TREATED.