US1955077A - Method of surfacing roadways - Google Patents

Description

Patented Apr. 17, 1934 PATENT OFFICE METHOD OF SURFACING ROADWAYS Leon R. MacKenzie, Des Moines, Iowa, assignor to L. R. MacKcnzie Incorporated, Tulsa, Okla., a corporation of Delaware No Drawing. Application August 19, 1931, Serial No. 558,103

3 Claims.

The purpose of the present invention is to provide a simple and very economical method for surfacing roadways to render them waterproof, to increase their stability and to make them dustless.

In accomplishing these purposes, I preferably precoat the material of the roadway surface, after suitable preparation with a highly volatile fluid, acid or non-acid as desired, and apply to the surface of the road cold bituminous emulsion to which there may or may not have been added, subsequent to emulsification, a neutral or alkaline highly volatile fluid. I have found that a bituminous emulsion to which has been added non-acid highly volatile fluid is to be preferred in many instances.

The nature of the highly volatile fluid is such that when the steps of my process are properly followed, the pre-coating of the mineral surface material of the road with such fluid facilitates the rapid spread of the bituminous emulsion, serves as a partial temporary flux for the bitumen, then contributes to the setting of the bitumen on the road material and accelerates the hardening of the bitumen.

I am aware of the fact that previous applications have used oils for the pre-coating of mineral particles but in all such applications known to me, these oils are complete solvents of bitumen, having a low degree of volatility which prevents rapid evaporation and thus retards instead of accelerates the hardening action of the bitumen applied, and such oils are therefore not adapted for the purposes of this invention.

With these general objects in'view, the invention of my present application consists of the method whereby these objects are attained as hereinafter more fully explained.

In some sections of the country there are many miles of highway that are peculiarly adapted for the practice of the method. Efforts have been made to use asphalt treatments for such highways, but these efforts have been only relatively successful and in only a few localities due to peculiar soil conditions.

Treatments of crude oil well worked into the earth or gravel surfaces have also been used with fair success, but oil treatments have the decided disadvantage that they are detrimental to rubber tires and that in a relatively short time the crude oil loses its volatile constituents and there is left a rather sticky mass which is very detri mental to paint on vehicles when deposited on them, and after the crude oil has stood for some time longer the roads again become dusty, and

the oil treated dust from such roads is particularly obnoxious and detrimental to traffic.

Such treatments of this kind as have been most successful have required repeated applications, the cost of which finally approaches too closely to the cost of a high type improvement to be sound expenditure economically.

I will now illustrate how my method would be applied to the surfacing of a road of the character mentioned.

The road surface material is first loosened by scarifying or any other desirable method to any desired depth. It is then pulverized by harrowing or otherwise. The surface is then permitted to dry thoroughly. In case time or weather conditions are such that drying cannot be properly clone, artificial drying of some sort may be practiced, as for example by running a heating machine over the loosened surface.

Under certain conditions it may be necessary where moisture cannot be removed from the loosened particles to treat them with a dilute acid or alkaline solution, the purpose of which will more fully appear below.

The loosened surface is then preferably given a coat of highly volatile fluid, such for instance as certain grades of gasoline, benzol, naptha, carbon-tetrachloride, or alcohol or the like. This may be sprayed, sprinkled or otherwise applied and thereupon the surface is preferably immediately harrowed'or otherwise agitated so as to assist the highly volatile fluid to penetrate quickly to the depth of the loosened part of the surface and as nearly as possible to coat all the loose particles.

As promptly thereafter as possible, and in any event before substantial evaporation of the high- 1y volatile fiuid,I deposit on the road surface a cold bituminous emulsion which likewise may be sprinkled or sprayed or otherwise deposited on the road and immediately thereafter the harrowing, blading or an equivalent operation should be repeated for assisting the bituminous emulsion to penetrate and coat all of the loosened particles.

The mechanical mixing in place, is not an essential operation in all cases but will expedite the penetration of the mass and the coating of the individual particles. It will also greatly assist in securing a good riding surface. The highly volatile fluid even without the mechanical mixing will facilitate the rapidity of the spread of the bituminous emulsion by causing it to form into a thin film or coating on the loosened particles of the road surface and cause quick and permanent adherence of the bitumen to the particles.

On account of the fact that the loose particles have been pre-coated with the highly volatile fluid I find that certain results can be obtained with the bituminous emulsion that would not otherwise be possible.

By way of illustration, if there is a layer of dry dust in a wheel rut and bituminous emulsion is poured into the dust without suchpre-coating, it will not penetrate the layer of dust at all. If, on the other hand, the same dust is pre-coated with a highly volatile fluid of the kind mentioned above and the bituminous emulsion is then poured into the rut, the emulsion will immediately spread throughout the layer of dust and thinly coat each particle of dust.

The use of a highly volatile fluid also promotes adherence of the bitumen content of the emulsion to the particles, and the highly volatile fluid acts as a partial and temporary flux.

Since moisture, if any, in the road surface particles has already been rendered acid by appropriate treatment, and since the highly volatile fluid is also usually slightly acid, or can be readily'rendered slightly acid, whereas the bituminous emulsion is always slightly alkaline, it follows that acid acting upon the alkaline bituminous emulsion causes the emulsion to break down and causes the bitumen to separate from the liquefier content of the emulsion and remain deposited upon the particles of the road surface in thin films.

Bituminous emulsion always has a specific degree of alkalinity at which it is most stable. By rendering the mass strongly alkaline, considerably beyond the degree of alkalinity necessary to retain the bitumen in an emulsified form, I am able to produce the same result whereby the emulsion is caused to break down and the bitumen to be deposited upon the particles.

The evaporation of the highly volatile fluid then greatly facilitates the evaporation of the liquefler leaving the bitumen as originally spread in the emulsified form in a condition to harden rapidly. Proper time should be permitted to elapse for the hardening of the bitumen and thereafter the loose surface particles should be compacted. The compacting is preferably done with a roller, but may in some instances be left to. the action of trafiic.

A road surface made in this way will be waterproof for all practical purposes so that surface water will flow off. There will be formed a substantial surface coat which will maintain the stability of the road both on account of the waterproof nature of this coat and because it serves to hold the particles together. It is also true that the coating would largely prevent trafiic from displacing any under layer of earth, gravel or the like. Aroad surface constructed in this way originates no dust.

In event of later excessive traffic, by adding another thin surface coating before the original has been broken up, and continuing to so add layers from time to time as needed, it is possible to build up a thick durable hard surfaced road.

It is, of course, obvious that the nature of different kinds of soils, loams, gravels, clays and so on will require different relative amounts of highly volatile fluid and bituminous emulsion. The viscosity of the emulsion may be varied for different road materials, if necessary or desired.

In addition to the advantages already mentioned, attention is called to the ease and simplicity with which the method may be practiced.

Light traffic graveled roads may be changed into roads with dense waterproof surfaces with a minimum of trouble and cost. On account of the economy of this method, many roads which otherwise could not be surfaced on account of the expense, may be provided with satisfactory surfaces.

Any surplus of highly volatile fluid will penetrate the hard surface under the separated and treated particles, and will help the bonding of the bituminous coated particles with the base and it is often desirable to use a surplus for this purpose. A surplus of emulsion will penetrate somewhat into the base and thus form a bond.

Beneficial results to the mass of particles constituting the road surface may be obtained at times by omitting the step of pre-coating the material with a highly volatile fluid and instead applying, after the material has been suitably prepared a bituminous emulsion to which has been added a suitable highly volatile fluid. The highly volatile fluid which is added to the emulsion should be non-acid in character, either alkaline or neutral. The beneficial results obtained in this way may be greatly enhanced by immediate thorough agitation of the mass after the application of the emulsion has been made.

At other times the step of pre-coating the particles with highly volatile fluid (either alkaline, acid-or neutral) may be followed by an application of a liqueous bituminous emulsion to which, has been added a non-acid highly volatile fluid. In this way quicker results may be obtained as to penetration and spread of the bitumen, particularly when followed by immediate thorough agitation.

From the foregoing, it is obvious that the use of oils as brought out by previous applications will not accomplish the results obtained through my process in which I use a highly volatile fluid for the precoating of mineral particles.

I claim as my invention:

1. A method of preparing a roadway comprising loosening and pulverizing the upper surface, applying to the finely divided resulting particles a coating of highly volatile fluid, then before evaporation of such fluid coating has substantially progressed, pouring upon the particles bituminous emulsion, agitating the particles and emulsion to cause coating of the particles by the emulsion and to insure that the coated materials shall be in a loosened state for aeration, allowing the loosened mass to lie and aerate and the emulsion to break and then compacting the mass.

2. A method of treating a roadway having an upper surface of finely divided loosened material, comprising applying to the finely divided particles a coating of highly volatile fluid, then before evaporation of such fluid coating has substantially progressed, pouring upon the particles bituminous emulsion, agitating the particles and emulsion for insuring the thorough coating of the particles by the emulsion and for insuring that the coated material shall be in a loosened state for aeration, allowing the loosened mass to lie and aerate and the emulsion to break and then compacting the mass.

3. A method of preparing a roadway having an upper surface of finely divided loosened material, comprising applying to the finely divided particles a coating of highly volatile fluid, then before evaporation of such fluid coating has substantially progressed, pouring upon the particles bituminous emulsion in an amount sufficient to provide a slight excess over the amount required 1.

loosened state for aeration, allowing the excess of the emulsion to penetrate downward to and into the undisturbed portion of the roadway, and allowing the loosened mass to lie and aerate and the emulsion to break, and then compacting the mass.

LEON R. MACKENZIE.