US1659554A - Bituminous composition and process of making same - Google Patents

Description

Patented Feb. 14, 1928.

UNITED STATES TWILIJIAM'P. BENTLEY, 01? DALLAS, TEXAS.

BITUMINOUS COMPOSITION AND PROCESS OF MAKING SAME.

K0 Drawing.

This invention relates to improvements in bituminous'compositions and process of making same, and refers more particularly to the treatment of native rock as halt naturally containing a percentage 0 asphalt, with asoftening'agent and a flux, and adding graded mineral aggregate thereto to produce a waterproof, durable composition.

Among the objects of the present invention are to provide a processof combining disintegrated bitumen containing rock mineral aggregate, softening agent and flux to produce a composition having waterproofing properties; to provide a process in which the various substances may be mixed relatively cold, and applied while cold; to produce a composition suitable for pavements and the like in which by proper grading of thennneral aggregate, a minimum of voidswill be roduced; and to produce an economical and durable product of this general character.

A product having the above characteristics is admirably adapted for road coverings, sidewalks and other types of paving, 111 which the wearing surface 'is relatively stable, practically eliminating the danger of creeping or disintegrating even under heavy traffic.

I propose to make a pavement of the asphaltic concrete type, and instead of using mineral aggregate, hot asphalt and sand as is customary in this type of pavement, I use in lieu of the hot asphalt and sand, amortar of pulverized rock asphalt which has been properly fluxed as described in my copending application, Serial No. 643,087 filed June 2nd, 1923, to, which mortar the graded mineral aggregate is added.

The above mentioned application has to do with disintegratin the rock and treating the bitumen containe therein to produce a mixture containing mineral rock and a bituminous substance, and varying the amount of bitumen and consistency of the final roduct by controlling the .percenta e and viscosity of a fluxwhich is added to t e disintegrated mixture, it havin been mixed with a temporary liquefier em; as a light hydrocarbon oil, preferably at atmospheric temperature, to make the bituminous substance in the rock liquid and available.

The careful control of bituminous content within one-half of one percent, and penetration within five points, is desirable for successful results.

, Heretofore, it has been impossible to make Application filed April 18, 1924. Serial m).- 707,497.

cold rock asphalt mixtures using a properly prepared asphaltic, semi-asphalti'c or paratfin base fluxes, that is, material having a hard asphalt that is exposed subsequent to the disintegration or pulverizing of the rock asphalt.

It is essential that a. solvent that will operate readily on the cold bitumen in the rock, be present. In order to supply this necessary solvent, a light distillate such as fuel oil, gasoline, kerosene, gas oil, naphtha, solar oil or the like, is added to the pulverized rock asphalt. The quantity of light distillate solven." will vary considerably with the size of the particles in which the rock asphalt'has been broken, for the reason that when the rock asphalt has been finely comminuted', a greater surface area must be treated, and more bitumen liquefied. This amount of light solvent needed, is not necessarily an exact amount, for the reason that its function is to liquefy the bituminous or asphaltic substance in the rock, only for a very limited period of time. ---Under normal conditions, ten to thirty minutes will be sufficient time in which to perform this function, and it may then be evaporated without harm to the composition. Under certain conditions of disintegration, it has been found that one gallon of light distillate to one thousand ound's of rock asphalt is a satisfactory re ation.

This amount will necessarily vary also with the varying of the percentage of bituminous or asphaltic material naturally contained in the rock as halt.

In certain cases, it is necessary to add asphaltic o r bituminous material to the rock asphalt to supply thereto the desired percentage of bituminous substance and im art the proper consistency. Should the asp alt in the rock be of high enough percentage, and of the proper penetration for the pur' poses for which it is to be used, the composition which has been treated with the distillate may be com ressed into final form immediately by ro ling or tamping, and the process is complete. In the event that the asphalt in the rock be too hard for the purposes for which the composition is to be used, as in the bituminous limestones of Texas and Alabama, whose use is limited practically to paving purposes, or should it be necessary to add asphalt to increase the percentage of bituminous matter in the mixture, then the pulverized rock asphalt, after the addition of a solvent, has supplied there to an asphaltic fluxto increase the asphaltie content. That is, after adding the light distillate which tends to dissolve and soften the bituminous material in the pulverized rock, flux or asphalt having the characteristics necessary to bring the rock asphalt to the desired consistency and proper asphaltie percentage may be added.

For example, the rock asphalt may be placed in any standard type of mechanical mixer, and pulverized so that all will pass a one-half inch screen. The proper amount of pulverized rock asphalt is to be weighed into a pug mill, concrete mixer or the like and the graded mineral aggregate added, either hot or cold. In practice, the percent of rock, asphalt should preferably be not less than 30% and may be higher, up to 100%. After the aggregate has been introduced into the pug mill or concrete mixer, the liquefier .may be poured or sprayed into the mixer in sufficient quantity to liquefy the asphalt in the rock asphalt, which may be from one to three gallons for each ton, depending on the fineness to which the rock asphalt has been pulverized. When the liquefier has softened the bituminous content of the rock, there may be incorporated therewith, the desired asphaltic, semi-asphaltlc or paraffin base fiux in a like manner to that in which the liquefier was added.

The flux, prior to being added to the described mixture, may be preferably heated to temperatures approximating 17 5-200 F. more or less, depending on its viscosity in order that it may be thoroughly liquid. As an illustration, with Uvalde rock asphalt from Texas or Louisiana, may be used a parafiin or mixed base flux of 19 to 21 gravity and having a flash point of not lower than 350 F., it being understood, or course, that any type of flux may be used from a liquid up to a solid asphalt.

The result of combining a flux in this manner by first softening the bitumen in the rock with a temporary liquefier, is to cause the flux to intimately commingle and permanently unite with the bitumen which has been rendered temporarily liquid by the liquefier. Without the use of a liquefier. it is impossible to make a satisfactory union of the heated fluxes with the cold bitumen in the cold rock asphalt, as it has been neces- It is clear that the function of the distillate.

is merely temporary, enabling rock asphalt to be properly fiuxed in a cold state, whereas,

it would otherwise be necessary to heat the rock in order to effect a proper union.

The asphalt mortar could be mixed separately and after being fiuxed, the stone aggregate could be added. Sand, chats or other suitable aggregate may be used as well as crushed stone. This type of mixture has all the advantages of a hot mixed pavement and in addition, has the advantage that inasmuch as the rock asphalt mortar is not heated, nor the aggregate or flux subjected to high temperatures, the product is not exposed to the danger arising from calcined or burned material. In addition, no expensive paving plant is required. Another advantage of this type of construction, is the cheapness with which it may be constructed as compared with other compositions of this character. The only apparatus required is a pug mill or concrete mixer and a pulverizer for the rock asphalt.

I-Ieretofore, it has been the common practice to add an unrefined oil to the rock asphalt and produce a softening of the asphaltic substance while the asphalt is in a cold and pulverized condition. Such oils however, vary greatly in gravity, viscosity, asphaltic content and volatile constituents. and normally have a certain amount of objectionable water contained therein. These factors being variable, naturally produce varying results which are objectionable in the production of uniform products. lVhere the bitumen is of too hard a consistency, as in Uvalde rock asphalt, the use of an unrefined asphalt oil, regardless of resulting consistency, must be restricted to an amount to prevent an excess of bitumen in the final product.

A further advantage of the addition of the flux to the cold rock asphalt and aggregate is that the consistency of the bitumen can be made the same as in the hot asphalt processes, or even higher with an equal quantity of flux, owing to the fact that there is no hardening due to the heating process.

A further advantage of the process is the fact that cold mixed paven'ients will he in all respects very similar and as uniform as the pavements that are made by methods of heating the rock asphalt. Treating cold in this manner eliminates the objectionable features accompanying the heating of the rock asphalts by a fuel oil blast directed on the inside or to the exterior of the cylinder in which therock asphalt is contained. The working temperature inside of the cylinders frequently runs as high as 1800 F., resulting in a loss of valuable properties in the native bitumen and rock asphalt, factors which are totally eliminated by the use of a distillate solvent and the addition of a flux as explained.

The-salient elements of the invention consist in pulverizing or breaking up the asphalt containing rock, mixing therewith regulated proportions of mineral aggregate, and adding a liquefier thereto to soften the bituminous or asphaltic substance contained in the rock, and incorporating with thepulverized or broken up material a flux to .supply thereto certain desirable characteristics such as increasing or decreasing the consistency and hardness of the bituminous-or asphaltic substance contained therein, and increasing to theamount desired, the percentage of bituminous material present. The preparation of the material for laying is done while the rock asphalt is in a cold state- A further advantage of the process arises from the fact that very much simplerand inexpensive equipment. may be utilized than that required for the hot process.

Batches can be made up at any time to be used in the future, thus permitting the transporting of the material from place to place and 'eliminating the necessity of heating and reheating whenever it is to be used.

I claim as my invention:

1. A method of producing a paving mixture of the bituminous-concrete type, which comprises mixing with graded non-bituminous mineral crushed bitumen-containing rock, controlling the grading of the mineral so as to produce a mixture with a minimum of voids, liquefying the bitumen in the rock by adding a volatile liquefier thereto, adding a bituminous flux in li uid condition to combine with the natural y contained bitumen, said flux being added in such quantity that when combined with said naturally contained bitumen the total quantity of bitumen will be suflicient to coat the mineral and fill the voids in the mixture but insufiicient to produce a substantial excess in bitumen content. I

2. A method of producing a paving mixture of the bituminous-concrete type, which comprises mixing with relatively cold graded nonbituminous mineral crushed relatively cold bitumen-containing rock, controlling the grading of the mineral so as to produce a mixture with a minimum of voids, liquefy ing the bitumen in the-rock by adding avolatile liquefier thereto, adding a bituminous fiux in liquid condition to combine with the naturally contained bitumen, the amount of added flux being so controlled that when combined with the naturally contained bitumen the total quantity will be sufiicient to coat the mineral aggregate and fill the voids in the mixture but insufiicient to produce a substantial excess in bitumen content.

3. paving mixture of the bituminousconcrete type comprising crushed bitumeneontaining rock, graded non-bituminous mineral aggregate, a volatile solvent and a hydrocarbon flux, the crushed bitumen-containing rock acting as the mortar constituent,

the quantity of bitumen being sufficient to coat' the non-bituminous mineral aggregate and fill the voids in the mixture but insufiicient to produce a substantial excess of bitumen content.

4. A method of producing a paving mixture of the bituminous-concrete type, which comprises mixing graded non-bituminous mineral with crushed relatively cold bitumen-containing rock, controlling the grading of the mineral so as to produce a mixture with a minimum of.,voids, liquefying the bitumen in the rock by adding a volatile liquefier thereto, adding a bituminous flux in liquid condition to combine with the naturally contained bitumen, the amount of added flux being so controlled that, when combined with the naturally contained bitumen, the total quantity'willibe suificient to coat the non-bituminous mineral and fill the voids in the mixture, but insuflicient to pronaturally, contained bitumen the total.