US2629669A - Cold-rollable paving mix - Google Patents

Description

Patented Feb. 24, 1953 COLD-ROLLABLE PAVING MIX Benjamin A. Anderton, Cliffside Park, N. J., as-

signor-to- Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application March 16, 1950, Serial No. 150,110

8 Claims.

This invention relates to bituminous paving compositions; more particularly it relates to bituminous paving'compositions comprising-mineral aggregate and bituminous binder, which compositions may be stocked in stock piles and laid and rolled down in a cold state toform a pavement. By cold is meant atmospheric temperatures prevailing where the pavement is formed. This application is a continuation-inpart of and replaces application Serial No. 630,545, filed November 23, 1945, which was abandoned after. the filing of this application.

The production of bituminous paving mixtures comprising aggregate and bituminous binders, which mixtures can be laid cold, is well known. Such bituminous paving mixtures, as heretofore produced, have a tendency to agglomerate in stock piles, rendering it difficult to handle the mixture when it is necessary to transport the.

same from the point of storage to the point. of application. Such agglomeration also interferes with the application of the mixture to produce the desired paving surface. One suggestion for minimizing such difficulties which has been advanced is to add to the paving mixture, coke or crushed brick of a size about the same as that of sand, which crushed particles absorb the liquid binder so as to allow manipulation of the mix on cooling. In the application of such mixtures to form the pavement, the coke or other absorbent particles are crushed to release the binder, which then fulfills its intended function of binding the aggregate particles. In this process, it is necessary to mix the binder at anelevated temperature of the order of 320' F. with the mineral aggregate and crushed coke also at an elevated temperature of the order of 240F: in order to obtain a mixture having the desired properties.

It is an object of this invention to provide a bituminous paving mix which can be stored in stock piles for indefinite periods of time of the order of months and remains friable and workable and when desired can be transported to the place of use and laid and rolled down in a cold state to form a satisfactory paving surface.

It is another object of this invention to provide a bituminous paving mix containing a relatively low percentage of bituminous binder of fluid consistency which binder does not set up while the mix is in storage, resulting in a mixzthat is workable at atmospheric temperatures, including winter temperatures normally encountered. in. this country, and which mix can be laid and rolled cold. When thus rolled the mix sets up or concretes under the pressure of the usual road roller and forms a durable pavement.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

I have found that the incorporation of pulverized coal, preferably pulverized bituminous coal, in a bituminous paving mix containing mineral aggregate and a bituminous binder of the viscosity characteristics hereinafter given to produce a mix containing approximately 1% to 10% by weight of pulverized coal, 3% to 10% binder, and the rest mineral aggregate, results in a paving mix which can be stored in stock piles for long periods of time and remains workable so it can be laid and rolled down in a cold state to form a pavement or other desired surface.

The use of pulverized coal, I have found, in a bituminous paving mix, as above described, greatly increases the consistency of the binder. On account of the low density of the bituminous coal, which approaches that of the usual asphaltic binder, the pulverized coal is readily dispersed in the binder and has relatively little tendency to settle out. Hence, the pulverized coal improves the bond produced by the binder between the particles of aggregate, the binder containing the pulverized coal having less tendency to bleed when the paving is subjected to relatively high. temperatures such as those encountered in the summer. Furthermore, the incorporation of the pulverized coal in the mix permits the use of less binder than could otherwise be used and still obtain a satisfactory paving material. The coal appears to function as a distender for the binder, causing a given amount of the binder to cover more surface area of the aggregate. For example, in practice, as little as 3% to 6% asphaltic binder has been used in a mix. containing 5% to 10% pulverized coal, the rest being mineral aggregate and a pavement of the stone sheet asphalt type obtained which was capable of withstanding the stresses of traffic and weather. The use of such relatively low percentages of binder in the paving mix containing pulverized coal and mineral aggregate results in a mix havingv highly desirable properties, such as the property of retaining a loose and workable condition in storage or in a stock pile for a long period of time and the property of workability over a wide range of temperature when laid for the construction of a pavement.

The pulverized coal employed in the practice of the invention is preferably bituminous. coal, pulverized to suitable fineness, as, for example, in a hammer or attrition mill. The pulverized coal should have a particle size such that from 30% to 100%, preferably at least about 50%, passes a No. 100 sieve; preferably a particle size as follows: 100% should pass through a No. sieve, about 50% to about 70% through a No. 100 sieve, and from to 50% through a No. 200 sieve.

' The bituminous binder in the mix is fluid at atmospheric temperature and has an absolute viscosity at C. in the case of asphalt binders within the range of 50 to 5000 poises, preferably 200 to 3500 poises, and in the case of tar binders within the range of 20 to 3000 poises, preferably 100 to 2000 poises. It may be derived from asphalts, asphaltic or semi-asphaltic petroleum, coal tar, Water-gas tar or other well-known materials comprising adhesive bitumens. Asphaltic binders may consist of asphalt flux oils, asphalt cut backs, soft asphalts, or residual derived from crude asphaltic or semi-asphaltic petroleum by distillation or by distillation involving cracking. They may be prepared by blending asphaltic materials with fluxes; including petroleum distillates or residuals. The tar binders may consist of residuals derived from the group of bituminous materials comprising coal tar, water-gas tar, oil tar and other tars produced in the destructive distillation of organic materials, such residuals or soft pitches modified in viscosity by blending with fluxes of relatively low volatility.

The asphaltic and tar binders in the mix embodying this invention are materially less viscous than the binders heretofore employed in producing bituminou concretes includin the binders employed in producing cold lay mixes. The preferred binders used are fluid at atmospheric temperatures; examples of such binders are the asphalt flux oils having a viscosity (Saybolt furol at 50 C. in seconds) of from 400 to 8000 seconds corresponding to an absolute viscosity at 25 C. of from 100 to 5000 poises. If desired, however, more viscous binders may be added to the mix along with a flux, which flux blends or combines with the more viscous binder producing in the mix a binder which is fluid at atmospheric temperatures and which has an absolute viscosity in the case of an asphaltic binder within the range of from 50 to 5000 poises, preferably from 200 to 3500 poises, and in the case of a tar binder within the range of from 20 to 3000, preferably from 100 to 2000 poises. The incorporation of pulverized coal in the mix permits the use of such fluid binders; without the coal, the binders would exert insufficient bonding action on the particles of aggregate. The pulverized coal, as above pointed out, increases the consistency of the binder and improves the bonding action, and renders a reduced quantity of binder adequate for suitable performance of the paving mixture.

The mineral aggregate may comprise crushed stone, crushed slag, gravel, stone screenings, natural sand, stone sand, mineral filler and other mineral material customarily used in the production of pavin mixtures. The size and gradation of the aggregate will depend upon the properties desired from the mixture as related to its intended use in service, and is usually controlled by the specifications of the Federal, State, or other government agency for which the pavement is being produced.

The percentage of asphaltic or other bituminous binder incorporated in the mix should be 3% to 10%, based on the weight of all constituents in the mix. As is well known in design of paving mixtures, the percentage of binder for a given mixture should be suitably adjusted, depending on maximum size, gradation and quality of particle in the mineral aggregate. The percentage of binder in pavement surfacing mixtures prepared in accordance with this invention will usually be in the range of about 4% to about 8%. This percentage figure includes the weight of flux incorporated in the mix, as Well as that of the asphaltic or tar binder. The percentage of pulverized coal in the mix should be within the range of 1% to 10%, preferably from 2% to 7%. The remainder of the mix is the aggregate which term is used to include the filler such as mineral fillers. The mineral aggregate may var within the range of to 96% and preferably from to 94%; if 2% to 7% coal and 3% to 10% binder is used, the aggregate will vary within the range of 83% to 95%. For mineral aggregate containing large proportions of fine particles, an amount of binder near the upper portion of the above noted range, namely, up to 10%, should be used and for mineral aggregate of relatively large size an amount of binder near the lower portion of this range, e. g., about 3%, should be used.

The mixing of the constituents may be accomplished in typical paving plant equipment, such as a pug-mill or rotary mixing equipment. Preferably, the mineral aggregate at atmospheric temperature is first introduced into the mixer and is followed by the binder in liquid condition and then by the pulverized coal which is also at atmospheric temperature. In the case of binders at the lower end of the range of viscosity specified hereinabove, generally they are sufliclently liquid at atmospheric temperature under favorable mixing conditions to require no preheating in order to coat the aggregate readily. Accordingly, such low viscosity binders may and preferably are added to the aggregate with the binders at atmospheric temperature. In the case of the more viscous binders, however, it is generally desirable to add them in a heat-liquefied condition to the aggregate so that they will readily coat the aggregate.

When it is desired to incorporate fine aggregate or fine mineral filler in the mix, either or both of the constituents may be introduced after the introduction of the bituminous binder or after the introduction of the pulverized coal. To avoid loss of the pulverized coal by the formation of dust in an open mixer of the pug-mill type, it is preferred to combine the pulverized coal with the aggregate which has previously been mixed with all or a portion of the bituminous binder or has been otherwise wetted, as, for example, by a solvent or flux for the binder.

The bituminous binder may be introduced in two or more stages. It may comprise two or more bituminous materials; thus the total asphaltic binder may consist of a heavy asphaltic oil or a soft asphalt and an appropriate proportion of flux of relatively low viscosity. To facilitate mixing, the aggregate may be primed with a solvent such as a petroleum distillate, a thin tar, or other such material.

Examples of preferred embodiments of the invention are as follows:

In all of these examples, pulverized bituminous coal was used, having a particle size such that passed through a No. 10 sieve, 50% through a No. 100 sieve and from 20% to 40% through a No. 200 sieve. In the specification and claims, all percentages are by Weight.

In all examples the mineralaggregate and pulverized coal were introduced. at atmospheric temperature'and the binder wasintr'oduced in liquid condition; where thetemperature of the binder was above atmospheric, this is indicated by ref-' erence to the-temperature of the binder. In all cases the mixing was carried out without supplying extraneous heat to the mix.

Example 1 .A- mix was produced containing 89% mineral. aggregate, 6% asphaltic flux oil (125'poises at 25 C. or 625 seconds Saybolt furol at 50 C.) and pulverized coal. aggregate consisted of. stone screenings. having the following grading: passing. No. 4. sieve 100%., passing No. 10 sieve 90%, passing. No. 40. sieve 32%, passing No, 80. sieve 18%, passing No. 200 sieve 9.5%.

In mixing the constituents, the mineral aggregate was first introduced into the mixer and"v the asphaltic flux oil at a temperature of'about C. and pulverized coalv thereafter introduced simultaneously.

Example 2.-A mix was produced containing 87.4% mineral aggregate, 1.1% heavy petroleum di tillate flux boiling within. the ran e of 200 to 360 C., 6.5% asphaltic flux oil (1780 poises at 25 C. or 3910 seconds Saybolt furol at 50C.) 5% pulverized coal.

Of. the 87.4 mineral aggregate, 77.4% was stone screenings and 10% stone dust. The grading of the mineral aggregate was as follows: passing No. 4 sieve 100%, passing No. 10 sieve 91.5%,

passing No. sieve 41.4%, passing No. 80 sieve 25.4%, passing No. 200 sievel4.9%.

The mix was produced by introducing the stone screenings in the mixer, then adding the heavy petroleum distillate flux, then the pulverized coal, thereafter the asphaltic flux oil at temperature of about 150 C,and finally incorporating thestone du t.

The mix thus produced \vas'laid cold on a roadway to form an experimental pavement which was subjected to traific and found. satisfactory.

Example 3.A mix was produced. containing 90% mineral aggregate, 6% asphaltic' flux oil (135 poises at 25 C. 01*573 seconds Saybolt furol at C.) 4% pulverized coal.

Oi the 90% of the mineral aggregate, 85% was stone screenings and 5% stone dust. The'grading of the mineral. aggregate-was as follows: passing inch sieve 100 passing No. 4 sieve 99.1%, passing No. 10 sieve 79.4%, passing No. 40 sieve 22%. passing No. 80 sieve 12.3%, passing No. 200 sieve 6.9

The mix was made by introducing stone screenings in the mixer, then adding the asphalt flux oil at a temperature of about 125 F., then the pulverized coal, and finally the stone dust..

The mix thus produced was laid cold toforman experimental pavement which was? subjected to traffic and found satisfactory.

Example 4.The composition of the mix was as follows: mineral aggregate 88.2%, petroleum distillate, volatile solvent (having aboiling'range of 85 to 160 C.) 3%, asphaltic. flux oil (135 poises at 25 C. or 673. seconds Saybolt furol at 50 C.) 6%, pulverized coal 5%.

Of the 88.2% mineral aggregate, 53.2% was stone screenings, 30% sand and 5% stone dust.

The grading of the mineral aggregate was as follows: passing inch sieve 100%, passing No. 4 sieve 99.2%, passing No. 10 sieve 88.9%, passing No. 40 sieve 48.1%, passing No. 80 sieve 26.9%, passing No. 200 sieve 7.4%.

The mix was produced by placing the stone screenings in the mixer, then adding the sand,

The. mineral 6;: then the: petroleum distillate; solvent, thereafter introducing the pulverized coah. then the. asp'halti'c: flux: 011;, and. finally: the: stonedust: and

continuing the mixing until. a workable, mix; was

produced;

Example. 5.-The-- composition of the was as follows: miner-a1. aggregate 8819-92, asphaltic' flux oil (1100 poises at. 251 C. or 287 2: seconds Saybolt furol, at. 50 C.) 5.4%, pulverized coal 5.7%.

Of the- 88.9'%.- mineral: aggregate. 62.4% was stone-screenings; 22% sand, and.4.-.5-% stone dust... The. grading of the mineralaggregate was as.

follows: passing /{3- inch sieve.- 100%, passing No. 10,-sie.ve 90.2%, passing No. 20 sieve 63.3%,, pass-- ing. No..40 sieve. 19.4%, passing No. 8.0 sieve.2 8.%., passing.No 200 sieve 14.7%.

The mix was produced by first placing" the stonescreenings and the sand in the mixer, then simultaneously adding the asphaltic. flux, oil at. a temperature of. about 200 F. and the pulverized coal. while continuing, the mixing, and finally in.- troduoing. the stone dust.

An experimental pavement section waslaidby applying the mixture-at an atmospheric temperature of 35 to. 40 F.. and rolling to produce. thev desired road surface. The pavement section was subjected tocity traflic and was. found satisfactory, requiring no supplementary treatment for aperiod of several years.

Example 6.The' composition of the mixwas as follows:; mineral aggregate 84.6%, asphaltic flux oil (1100poises' at 25 C. or 2872 seconds Saybolt furol at 50 C.) 5.4%,, pulverized coal. 10%.

Of the 84.6%, mineral aggregate 58.61% was stone screenings, 18% sand, 8% stone dust.

The grading of the mineral aggregate was as follows; passing inch sieve 100%, passing No. 10 sieve 84.1%, passing No. 20 sieve 65.4%, passing No. 4.0 sieve 45%, passing No. sieve 29.1%, passing No. 200 sieve 16%.

The mix was produced by placing the stone screenings and the sand in the mixer, then incorporating the asphaltic flux oil at a temperature of about 200 F., while mixing, thereafter adding the pulverized coal while continuing the mixing and nally introducing thestone dust.

The mix was laid on a city street at an atmospheric temperature of 20 to 30 F. and was rolled to form an experimental road section, subsequently subjected to traffic for several years without requiring further construction or treatment.

Thus, it will be noted this invention results in the production of a mix which remains workable even though stored in stock piles for long periods of time and which mix may be laid and rolled cold to form a pavement. In view of the. low cost of pulverized coal and since the use of this material results in a saving of the more expensive binder, my invention results in important economies in paving construction both from the standpoint. of the cost of the mix and the cost of" laying same in highway construction and maintenance- A substantial saving in laying expense is obtained due. tothe loose and workable condition of the mix. even after storage. for months in stock piles and the fact that the mix can be laid cold.

Since certain changes in the mix which embody this invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A bituminous paving mix comprising mineral aggregate, pulverized coal and a bituminous binder fluid at atmospheric temperatures, said binder being from the group consisting of asphaltic binders having an absolute viscosity at 25 C. within the range of 50 to 5000 poises and tar binders having an absolute viscosity at 25 C. within the range of 20 to 3000 poises, the constituents of said mix being in the proportions of approximately 1% to pulverized coal, 3% to 10% binder and 80% to 96% mineral aggregate, said paving mix having the property of remaining friable and workable in storage at atmospheric temperature and can be laid at atmospheric temperatures to produce the paving surface.

2. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperature and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal of particle size such that from 30% to 100% passes a No. 100 mesh sieve, and a bituminous binder fluid at atmospheric temperatures from the group consisting of asphaltic binders having an absolute viscosity at 25 C. within the range of 50 to 5000 poises and tar binders having an absolute viscosity at 25 C. within the range of 20 to 3000 poises, the constituents of said mix being in the proportions of approximately 1% to 10% pulverized coal, 3% to 10% binder and 80% to 96% mineral aggregate.

3. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperature and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal of a particle size such that from 30% to 100% passes a No. 100 mesh sieve, and an asphaltic flux oil having a viscosity (Saybolt furol at 50 C. in seconds) of from 400 to 8000 seconds in the proportion of approximately 1% to 10% pulverized coal, 3% to 10% asphaltic flux oil and 80% to 96% mineral aggregate.

4. A bituminous paving mix comprising mineral aggregate, pulverized coal and a bituminous binder fluid at atmospheric temperatures from the group consisting of asphaltic binders having an absolute viscosity at 25 C. within the range of 50 to 5000 poises and tar binders having an absolute viscosity at 25 C. Within the range of 20 to 3000 poises in the proportions of approximately 2% to 7% pulverized coal, 3% to 10% binder and 83% to 95% mineral ag gregate, which paving mix has the property of remaining friabl and workable in storage at atmospheric temperature and can be laid at atmospheric temperatures to produce a paving surface.

5. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperature and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal of a particle size such that about 30% to about 100% passes a No. 100 mesh sieve, and an asphaltic binder fluid at atmospheric temperatures having an absolute viscosity at 25 C. within the range of 200 to 3500 poises in the proportion of approximately 2% to 7% pulverized coal, 3% to 10% asphaltic binder and 83% to mineral aggregate.

6. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperature and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal having a particle size such that approximately passes a No. 10 sieve and 20% to 50% a No. 200 sieve, and an asphaltic binder fluid at atmospheric temperatures having an absolute viscosity within the range of from 200 to 3500 poises in the proportion of 1% to 10% pulverized coal, 3% to 10% binder and 80% to 96% mineral aggregate.

7. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperature and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal of a particle size, such that from 30% to 100% passes a No. 100 mesh sieve and a tar binder fluid at atmospheric temperatures having an absolute viscosity at 25 C. within the range of 20 to 3000 poises in the proportion of approximately 1% to 10% pulverized coal, 3% to 10% tar binder and 80% to 96% mineral aggregate.

8. A bituminous paving mix having the property of remaining friable and workable in stock piles maintained at atmospheric temperatur and which mix can be laid at atmospheric temperature to produce a paving surface, said mix comprising mineral aggregate, pulverized coal of particle size such that from 30% to 100% passes a No. 100 mesh sieve and a tar binder fluid at atmospheric temperatures having an absolute viscosity at 25 C. within the range of from 100 to 2000 poises in th proportion of approximately 1% to 10% pulverized coal, 3% to 10% tar binder and 80% to 96% mineral aggregate.

BENJAMIN A. ANDERTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,531,723 Alsdorf Mar. 31, 1925 2,037,147 Radsclifie Apr. 4, 1936 2,113,794 Leaute Apr. 12, 1938 FOREIGN PATENTS Number Country Date 179,664 Great Britain May 11, 1922 431,474 Great Britain July 8, 1935 OTHER REFERENCES An Encyclopedia of the Ceramic Industries," Searles, vol. 2, 1930, pp. 451-2.

Claims (1)

1. A BITUMINOULS PAVING MIX COMPRISING MINERAL AGGREGATE, PULVERIZED COAL AND A BITUMINOULS BINDER FLUID AT ATMOSPHERIC TEMPERATURES, SAID BINDER BEING FROM THE GROUP CONSISTING OF ASPHALTIC BINDERS HAVING AN ABSOLUTE VISCOSITY AT 25*C. WITHIN THE RANGE OF 50 TO 5000 POISES AND TAR BINDERS HAVING AN ABSOLUTE VISCOSITY AT 25*C. WITHIN THE RANGE OF 20 TO 3000 POISES, THE CONSTITUENTS OF SAID MIX BEING IN THE PROPORTIONS OF APPROXIMATELY 1% TO 10% PULVERIZED COAL, 3% TO 10% BINDER AND 80% TO 96% MINERAL AGGREGATE, SAID PAVING MIX HAVING THE PROPERTY OF REMAINING FRIABLE AND WORKABLE IN STORAGE AT ATMOSPHERIC TEMPERATURE AND CAN BE LAID AT ATMOSPHERIC TEMPERATURES TO PRODUCE THE PAVING SURFACE.