US1671070A - Process of making asphaltic material - Google Patents

Description

Patented May 22, 1928.

UNITED STATES PATENT OFFICE.

JOHN D. FOBRESTER, O12 KANSAS CITY, MISSOURI, ASSIGNOR T PETER J. MOINERNEY OF DALLAS, TEXAS.

PROCESS OF MAKING ASPHALTIC MATERIAL.

No Drawing.

This invention relates to improvements,

for making asphaltic road material, and refers more particularly to a combination of an asphaltic binder and crushed stone adapt able for use both in the binder and surfacing courses of roads or streets.

Among the objects of the invention are to provide a process in which the asphaltic binder is intimately bonded to the crushed stone, a material which .may be shipped in open-topped cars, easily loaded into and removed from the cars as distinguished from the usual type of asphaltic mixes which congeal and set, making it very diflicult without the use of steam to unload asphaltic mixtures transported over any considerable distance.

Describing first the common type of binder course using crushed stone Withan ,asphaltic binder, the crushed stone, termed as crusher run stone, is preferably limestone, granite or crushed gravel sized according to specification. Normally, for the binder course, stone ranging from one and onefourth (1%) inch to one-fourth inch properly graded is satisfactory. With this is a filler of fine material of the same composition sufficiently small in size to pass a one-quarter inch screen and constituting 3 substantially ten percent of the mix. With this is combined from 4% to 5% of asphaltic binder,the same being thoroughly intermixed with'the rock.

Material for the top course or wearing surface, varying somewhat in character from the binder course in that the crushed stone is of smaller size ranging from threefourths inch to one-fourth inch properly graded material. Vvith a top course the filler or fine material passing a one-fourth inch screen constitutes 20% of the mix and the asphaltic binder from 5% to 7%.

The asphalt specifications will vary with climatic conditions. Through the South, in

4 States such as Texas, Alabama and Mississippi, the asphalt penetration will range from to 70, while in the North, through Minnesota and the Dakotas. the penetration is normally in the neighborhood of 95.

0 Ductility in all cases should not be under 85 at 77 F. This brief explanation of the characteristics of the binder and top courses used in connection with asphaltic highways, streets and roads, describes briefly the char- Application filed June 26, 1925. Serial No. 39,815.

acteristic of the particular ingredients or constituents of the road mix.

The greatest trouble experienced in handlmg material of this character and in laymg asphaltic road mixesof this kind, is the fact that itcan not be transported for any considerable distance from the plant where it is prepared without utilizing considerable heat in the way of steam for removing the -mix from the cars due to the congealing of the asphalt and setting to form a tough solid mass. The present invention contemplates the transporting or conveying of such mixes, as described above, for considerable distances in railway cars, truck, or otherwise, due to the use of a liquefier or a relatively light solvent oil used With a mix for a double purpose, first, to carry the asphalt more effectively into the porous stone assuring a more satisfactory bond between the binder and crushed stone and at the same time maintaining the asphaltic binder in a more liquid or slushy condition over a considerable period of time prior to its evaporation facilitating the handling of the material until it can be rolled in place upon a highway or road.

It is recognized that at the present time this practice of using a liquefier or diluent vehicle is used in the preparation with a cold stone mix wherein the crushed rock is combined to the asphalt without heating the stone. In fact, at the present time two methods are employed for mixing crushed stone and asphalt as above described. In

one case, a very satisfactory mix is prepared which is diificult to handle; in the other case, an eas1ly handled mix is prepared which is not altogether satisfactory due to the lack of a proper bond between the asphaltic binder and the crushed stone.

Referring now to the first well known method of preparing this as )haltic material, crusher run stone is heate to 500 F. or more to eliminate the moisture. This heating is carried out in any suitable type of drier. The asphalt binder is then mixe therewith to thoroughly incorporate the bituminous substance with the crushed rock. The particular advantage of a mix of this character is the satisfactory and intimate bond which is effected between the asphaltic binder and the stone due to the removal of the moisture from the stone which increases its porosity and permits the liquid asphalt to penetrate more effectively into the surfaces of the rock. The disadvantage of this mixture is the difficulty in handling when it has cooled due to the setting and congealing of the asphaltic binder into a tough solid mass which is impossible to handle except with a pick and can only be successfully removed from cars by the use of steam. Another difficulty is encountered in properly rolling this material in place on the roa as it necessitates relatively complete dismtegration before the chunks of the'm'aterial can be satisfactorily rolled.

A second well known manner of preparing an'asphaltic crushed stone combination is that prepared under the name of amesite in which the stone is not heated but prepared and graded cold. To this stone is added a liquefier which consists of relative- .ly light oils or distillates having a Baum gravity of 40 to 52. To this combination is added the asphalt heated to a liquid condition. The liquefier, to a certain extent dissolving the asphalt, renders it more fluid and carries it into the stone to a certain limited extent. The cold stone containing considerable moisture has a retardant effect to the penetration of the asphaltic material. The advantage of a mix of this character is, however, that it is easily worked and can be maintained over considerable periods of time in a. relatively liquid slushy condition, thus rendering it especially adaptable to road work situated considerable distances from the plant in which it is mixed. This material ,can be shipped in open-topped cars to any part of the country and there easily unloaded if a liquefier is chosen which evaporates slowly. It has been found that by carefully choosing a suitable liquefier and timing its evaporation period with the distance that the material is to be trans-- ported, a satisfactory mix which has the proper consistency on the job is produced. The disadvantage of a mix of this character, however, is that the presence of moisture in the cold stone prevents a satisfactory bonding or adhesion of the asphaltic binder to the stone.

My present method is an improvement upon the above explained methods in that I heat the crusher run stone in a drier to a temperature of over 200 F., or in no event in the first instance, is dumped into a pug mill or other type of mixer in which the liquefier is introduced. Asphalt heated to temperatures of from 250 to 325 F. is then added and thoroughly mixed to the combination of the crushed stone and liquefier. It is advisable that neither the crushed stone nor the asphalt be heated to the flash point of the liqueiier. the combination of the asphalt, crushe stone and liquefier, a filler material, comprising not ess than one-half percent or more than one percent of the total weight of the mix, is added. This filler material is preferably calcium hydrate or oxide, limestone dust pulverized to the extent that it will pass a two hundred mesh screen, or by draulic cement.

The particular advantages of preparing the mix in this manner are first there is removed substantially all of the moisture from the stone which assures a better bonding between the asphaltic binder and the stone as the heat in removing the moisture increases the porosity of the stone. The liquefier dissolves to a considerable extent the asphalt, reducing its surface tension and accelerates the penetration of the asphalt into thesurface of the stone and the adhesion of the asphaltic binder to the stone, effecting an intimate bond therebetween. It is particularly advantageous to select a liquefier which has a flash point above the boiling point of water in order that the moisture may be more effectively removed from the stone without danger of flashing the liquefier. Also, a liquefier having a relatively high flash point permits the heating of the asphalt to a more fluid condition in which case it is more readily absorbed into the surface of the stone. As described, a liquefier should be chosen where the mix is to be transported a short distance which will readily evaporate, while in the case where the mix is to be conveyed for a relatively long distance from the plant in which it is prepared, a slowly evaporating liquefier isbetter adapted to such a mix as it maintains the crushed rock and asphalt combination in a slushy condition over a longer period of time and prevents its congeal1ng,making it diflicult to remove the mix from the cars in which it is transported.

While it is recognized that to heat crushed stone and combine it with asphalt or to use a liquefier in preparing a cold crushed stone asphalt mix, is well known in the art, it is thought to be new to prepare a mix in the manner described, that is, heating the crushed stone to a temperature below the flash point of the liquefier, combining the liquefiertherewith, and adding an as haltie binder, thus assuring a proper bon ing of the asphaltic binder and crushed rock by elimination of the moisture in the rock and After thoroughly mixing efl'ecting an'easily workable mass by the use mixture adapted to be laid cold, comprising the steps of heating graded crushed stone of a liquetier of the proper character.

The amount of liquefier used and the char- I acter of the liquefier will vary according to the particular asphalt and the character of the crushed stone as well as other varying conditions.

A further advantage of my process lies in the fact that a more uniform product is produced and better'plant control may be had by drying all the crushed rock preliminarily to eliminate the moisture. Some rocks are notoriously deliquescence and rapidly acquire moisture in the atmosphere. Unless such materials are first heat treated or dried, the bonding of the asphalt is very unsatisfactory and stripping and peeling of the binder results.

Crushed stone aggregate is heated to temperatures of from 200 F. to 300 F. to substantially eliminate the moisture. To this hot stone is added a volatile oil liquifier, preferably in a closed retort, the liquefier having a flash oint about the heat of the stone. Such a liquefier as naphtha, kerosene, light gas oil, or a combination of theseloils, is satisfactory for this purpose. After being thoroughly combined with the heated rock, the bituminous or asphaltic composition which comprises an asphalt of from 60 to 95 penetration having a ductility normally not less than, 85 at 77, is added, having first been suliiciently heated to facilitate its handling.

This composition comprises; of from 2.5% to 7% of the final mix.

I claim as my invention:

1. A process of making an asphaltic road mixture, comprising the steps of preparing the crushed stone aggregate by heating to a temperature to eliminate the moisture there from. adding to the crushed stone while hot a light oil having a flash point above the temperature of the drying heat and finally adding and thoroughly incorporating therewith an asphaltic binder.

. material 2. A process of making an asphaltic road in a drier to substantially eliminate the moisture therefrom, adding to the crushed stone while hot a hydrocarbon solvent thereto having a flash point above the temperature used in drying the stone and subsequently incorporating an asphaltic binder to produce a mix of easily workable consistency.

3. A process of making asphaltic road mixture adapted to be handled and laid cold and remaining at a workable consistency from the time of its preparation to its application, comprising the steps of heating crusher run stone in a drier to temperatures above the boiling point of water to substantially eliminate the moisture therefrom and increase the absorbent qualities thereof, adding to the crushed stone while hot a hydrocarbon solyent having a flash point above the temperature used in drying the stone and subsequently incorporating an asphaltic binder to produce a mix of a predetermined consistency, said solvent adapted to improve the penetration and bonding effect of the binder with the stone.

4. A process for making an asphaltic road mixture, comprising the steps of drying the crushed stone by applying heat to remove the moisture therefrom, adding a lightsolvent to the stone while in the heated state and subseguently adding an asphaltic binder.

5. rocess for making an asphaltic road comprising the steps of heating graded crushed stone in a drier to substantially eliminate the moisture therefrom, then adding to the crushed stone while in a heated condition a hydrocarbon solvent having a flash point above the drying temperature and subsequently incorporating an asphaltic binder to produce a mixof easily workable consistency.

,JOHN D. FORRESTER.