US2701213A - Process for reclaiming asphaltic pavement and a composition so formed - Google Patents

Description

2,701,213 Unlted States Patent 1C6 Patented Feb. 1, 1955 A class of softeners or conditioners for asphalt has 2,701,213 been discovered which act as such without stripping the asphalt from the aggregate, and in addition they leave a PROCESS FOR RECLAIMING ASPHALTIC PAVE- desirable residue of nonasphaltic flux oils in the surface. MENT AND A COMPOSITION S0 FORMED 5 ghese Iflux oils blencli witlg the oxiccilizeddresiduall aspllilalt in teria to e treate an revita ize t e as- Charle A. Neville, Sacramento, Calif assignor to Re- 6 Su ace claimix Inc. San Jose, Calif. a corporation of Cali restoring its original quallty of resillency and flexl fomla These conditioners, which may be employed in the N0 Drawing Applicafion December 16, 1950, 10 process described hereinafter, are of several important serial No. 201227 classifications, dependent upon their sources. The essential criterion upon which the broad classification is 5 Claims. (Cl. 106-278) based is that the conditioner must contain a minimum of 40% aromatics. Preferably the conditioner has a boil- This invention relates to asphaltic compositions and g range of from 400 to F, Since Such materials not has particular reference to bituminous or asphaltic comonly provide optimum softening for asphalt surfaces but positions for use in road building or the like, and to also restore thereto the flux oil fractions which have disprocesses for making such compositions. appeared for one reason or another from the asphalt dur- One of the principal objects of my invention is to ing 1ts aging or weathering. provide a novel process for salvaging or reclaiming the Conditioners Within this boiling range and having more dry and brittle asphaltic surface material of roads, landthan about 40% aromatics include especially catalytically ing field runways and the like and restoring the material to Cracked g C031 tar extracts, h g ly thermally Cracked its original condition. oils and extracts of the Edeleanu type. The latter type Anothepimpoftant bj f my i ti i to proof extracts includes those prepared by the extraction of vide a novel process for reclaiming asphaltic material with P t l um fra ns W h lv nts Such as liquid Sulf r which process roads and the like may be rebuilt and redioxide, furfural, phenol, aniline and similar well-known stored to a condition equal to that of a new surface, but solvents which have a preferential solubility of aromatic at a cost considerably less than the cost of building a new constituents. surface. Catalytically cracked gas oil is a preferred type of con- Another object of my invention is to provide a novel ditioner since it contains not only a high percentage of process for reclaiming asphaltic surface material whi h aromatics but is an oil having suitable boiling range and includes the steps of removing the old surface, reducing containing fractions which beneficially restore the asthe particles to size, mixing with the recovered material a phalt to its original state. Typical gas oils which have quantity of a softener or conditioner to a consistency been found highly effective for the present process are equal to that of a new asphaltic surface. described in Examples 1-6 given hereinafter. A similar Another object of my invention is to provide novel corntype of oil having a lower A. P. I. gravity and a higher positions of matter having an asphalt binder and adapted boiling range is clarified oil. Both of these oils have arofor use in road surfacing and the like. matic contents which usually are above about 50% by Another object of my invention is to provide novel weight. The thermally cracked stocks which are suitasphaltic compositions for use in road building and the able as softeners for use in the present process are usually like, which compositions may be applied at ordinary temprepared by multiple cracking procedures wherein a preperatures without the use of the heat which is convenviously cracked oil is subjected to further cracking steps tionally required in order to render the asphalt workuntil it has a sufficiently high aromatic content. The ble, Edeleanu type of extracts usually have very high aromatic Other objects and advantages of my invention it is contents in the neighborhood of 70-80%. These may believed will be readily apparent from the following debe used without modification or may be diluted down to tailed description of preferred embodiments thereof. the minimum effective aromatic concentration specified In the past, attempts have been made to reclaim old herein either with a non-aromatic oil or with one of the and worn asphalt or bituminous pavements. One methother preferred types of aromatic softeners. od has been to rip up the old surface and reduce the The following examples are illustrative of preferred material in size by means of various mechanical crushers catalytically cracked gas oils which have proved to be or grinders and to blend with this material an added quaneffective softeners or conditioners for asphalt in paving tity of asphalt cutback. This mixture was then relaid as compositions in accordance with my invention:

Example Example Example Example Example Example 1 2 a 4 5 6 57.5 385 460 500 694 400 500 423 644 463 634 Viscosity S 39 a new surface. The principal difficulty with this method I have found that old and worn asphalt surfaces may is that due to the basic difference in surface resistance of be effectively reclaimed by using specific amounts of conthe relatively soft asphalt and the hard mineral aggregate ditioners of the type described above, the amounts dewith which it is combined, the two substances are very pending upon several factors, principally the amount and difficult to separate and break down to their original comconsistency of the worn asphaltic material, and the screen ponent sizes. This results in a rough, loosely bound suranalysis of the aggregate present. face which ravels and disintegrates in a comparatively I have further found that the softener must be intishort time. 7 mately mixed with the material to be reclaimed. In ac- Another method which has been attempted is to add cordance with my invention this is accomplished by resolvents, such as kerosene, diesel fuel, etc. to the surface moving the worn asphaltic surface from the roadbed or material. This has been unsuccessful since the use of such other base and pulverizing or fracturing the material, solvents has resulted in stripping the asphalt from the mixing the material and simultaneously adding the condi aggregate and total destruction of the material as a sur- 0 tioner in the desired proportions. face-forming substance. The following examples are illustrative of compositions in accordance with my invention in the proportions by weight indicated:

Example A Parts Asphalt 185 Conditioner 51 In this example the asphalt recovered from the road surface was a soft asphalt having a penetration (at 77 F.) of 300 and the conditioner used corresponds to Example 6 above. It is to be understood in this and the following examples that the asphaltic material recovered from the road surface included a major proportion of a mineral aggregate such as sand and crushed rock. In Example A set forth above the screen analysis of the pulverized surface material was as follows:

Screen size: Percent passing No. 4 99 No. 8 98 No. 16 96 N0. 30 86 No. 50 71 No. 100 55 No. 200 44 It will be noted that the above analysis of the surface material indicates what is termed in the art an extremely dense mixture. Due to the lack of adequate voids the stability of this composition as relaid was poor and therefore an amount (about 33%) of 7 to No. 8 crushed rock was added.

Example B Parts Asphalt 118 Conditioner 18 Here the asphalt recovered from the road surface had a penetration of 150 and the conditioner used corresponds to Example 6 above. The screen analysis of the pulverized surface material was:

The asphalt component of this surface material had a penetration of and the conditioner used corresponds to Example 6 above. The screen analysis of the pulverized surface material was:

Screen size: Percent passing 1" 100 3/8! No. 4 30 No. 8 22 No. 16 20 No. 30 13 No. 50 9 No. 100 6 No. 200 4 In carrying out my invention the first step is to an alyze a representative sample of the surface material to be reclaimed. As will be apparent from the above example the amount of conditioner required depends principally upon the amount and grade of asphalt present, as well as the screen analysis of the surface material to be reclaimed. It is generally desirable in order to obtain maximum wearability to add only so much of the conditioner as is necessary to accomplish the desired softening action and to leave the proper amount of flux oils necessary to properly condition the mixture. It may be desirable to add new asphalt and/or more aggregate, depending upon the analysis of the used material as well as upon the properties desired in the new road Surface itself, which latter properties are governed by contemplated traffic conditions, atmospheric conditions and the funds available. After the amount of conditioner required has been determined, and as indicated above this preferably will be in the range of l0-30% based on the asphalt present, the mixture may be designed in accordance with standard practices known to those skilled in the art in designing new road mixes.

The remainder of the process is carried out in the field. The old surface is first torn up by means of toothed scarifiers or rooters or the like. After the initial breaking up and uprooting has been accomplished the slabs of surface material, some of which are over two square yards in area, are reduced in size by heavy grid rollers. The rollers are followed by a conventional mobile cornbination feeder and rock breaker. These machines are provided with a conveyor belt which delivers the broken surface material from the road bed into a crusher or impact breaker of the revolving hammer type. One pass of this machine which deposits the crushed material in a windrow has been found to be generally sufficient to reduce the material substantially to the size of the original aggregate. Next, a conventional road mixer which is a self-propelled unit, including rotating drums mounted in tandem on which are placed staggered spades alternately angled to provide maximum mixing in addition to pulverizing, is passed over the windrow. The mixer is further provided with a series of spray nozzles through which the conditioner is introduced in a fine spray while the mixer is in operation. While not essential, it is very important that the conditioner is added simultaneously with the mixing so that the motion of the asphaltic particles will assure even distribution of the conditioner throughout the mix.

While the total amount of conditioner may be added in one pass of the road mixer I have found it preferable to add the conditioner in at least two portions to increase its effectiveness and to facilitate control by allowing visual inspection between additions. After the first application the material is thoroughly mixed, left in a windrow for at least several hours, and then the remaining amount of conditioner is applied in the same manner by use of the road mixer. At this point a rest period is provided to permit the conditioner to act upon the hard oxidized asphalt. This curing period will vary from a few hours to several days, depending upon weather conditions and the hardness of the asphalt up n which the conditioner must act. Experience has indicated that an average period of 48 hours is required.

After the material has been cured it is mixed th roughly to blend and integrate the mixture. A sample of the finished mix is taken and analyzed as a check on the design and if found correct the surface may be completed by any of the accepted methods or the material may be stockpiled for future use.

I have found that the above described asphaltic conditioners may be advantageously employed in the construction of road surfaces, roofing, etc. with air-bl wn asphalt. The present practice is to ship solidified asphalt in barrels, and in order to render the material workable it is necessary to liquify it by heating before mixing with the aggregate. With the use of the c nditioners described above the asphalt may be comminuted and furnished in sacks. This material may then be mixed cold with the conditioner and aggregate and l id without the use of the heat which is generally re uiredv While I have fully described preferred embodiments of my invention, it is to be understood that I do not wish to be limited to the details herein set forth. but my invention is of the following scope of the appended claims.

I claim:

1. A process for reclaiming used asphaltic surface material which includes the following steps: removing the material from its foundation; reducing the material in size; adding between about 10 and about 30 percent bv weight, based on the asphalt content of the material. of a relatively non-volatile liquid hydrocarbon conditioner having an aromatic content of not less than approximately 40 percent by weight; thoroughly mixing the conditioner and asphaltic material; and curing the mix.

2. A process for reclaiming used asphaltic surface material which includes the following steps: removing the material from its foundation; reducing the material in size; adding a liquid hydrocarbon conditioner having an aromatic content of not less than approximately 40 percent by weight and boiling from about 400 to about 750 F.; thoroughly mixing the conditioner and asphaltic material; and curing the mix.

3. An asphaltic composition to be used for road surfaces and the like, comprising a major proportion of ag: gregate; a minor proportion of asphalt; and 10 to 30 percent by weight, based on the asphalt content of the material, of a liquid hydrocarbon conditioner having an aromatic content of not less than approximately 40 percgnt 1%}! weight and boiling from about 400 to about 7 4. An asphaltic composition to be used for road surfaces and the like, comprising a major proportion of aggregate; a minor proportion of asphalt; and 10 to 30 percent by weight, based on the asphalt content of the material, of a relatively non-volatile liquid hydrocarbon conditioner having an aromatic content of not less than approximately 40 percent by Weight.

5. An asphaltic composition to be used for road surfaces and the like, comprising a major proportion of aggregate; a minor proportion of blown asphalt; and 10 to percent by weight, based on the asphalt content of the material, of a liquid hydrocarbon conditioner having an aromatic content of not less than approximately percent by weight and boiling from about 400 to about 750 F.

References Cited in the file of this patent UNITED STATES PATENTS 657,799 Varney Sept. 11, 1900 711,115 Lober Oct. 14, 1902 760,051 Amies May 17, 1904 2,308,245 Ortynsky Jan. 12, 1943 FOREIGN PATENTS 16,657a Great Britain of 1902

Claims (1)

1. A PROCESS FOR RECLAIMING USED ASPHALTIC SURFACE MATERIAL WHICH INCLUDES THE FOLLOWING STEPS: REMOVING THE MATERIAL FROM ITS FOUNDATION; REDUCING THE MATERIAL IN SIZE; ADDING BETWEEN ABOUT 10 AND ABOUT 30 PERCENT BY WEIGHT, BASED ON THE ASPHALT CONTENT OF THE MATERIAL, OF A RELATIVELY NON-VOLATILE LIQUID HYDROCARBON CONDITIONER HAVING AN AROMATIC CONTENT OF NOT LESS THAN APPROXIMATELY 40 PERCENT BY WEIGHT; THROUGHLY MIXING THE CONDITIONER AND ASPHALTIC MATERIAL; AND CURING THE MIX.