EPA-670/2-74-014
March 1974
Environmental Protection Technology Series
                SCRAP  RUBBER  TIRE UTILIZATION
                                IN  ROAD  DRESSINGS
                                                lesearch Center
                                    Office of Research and Development
                                   U.S. Environmental Protection Agency
                                            Cincinnati, Ohio 45268

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                                           EPA-670/2-74-014
                                           March 1974
         SCRAP RUBBER TIRE UTILIZATION

               IN ROAD DRESSINGS
                      By
               Benson G. Brand
        BATTELLE-Columbus Laboratories
             Columbus, Ohio  43201
         Project Element No. 1DB314
               Project Officer
              Richard A. Carries
Solid and Hazardous Waste Research Laboratory
    National Environmental Research Center
            Cincinnati, Ohio  45268
   NATIONAL ENVIRONMENTAL RESEARCH CENTER
     OFFICE OF RESEARCH AND DEVELOPMENT
    U.S. ENVIRONMENTAL PROTECTION AGENCY
           CINCINNATI, OHIO  45268

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                     REVIEW NOTICE






     The Solid Waste Research Laboratory of the



National Environment Research Center - Cincinnati,




U.S. Environmental Protection Agency, has reviewed




this report and approved its publication.  Approval




does not signify that the contents necessarily re-




flect the views and policies of this laboratory or




of the U.S. Environmental Protection Agency, nor




does mention of trade names or commercial products




constitute endorsement or recommendation for use.




     The text of this report is reproduced by the




National Environmental Research Center - Cincinnati



in the form received from the Grantee; new




preliminary pages have been supplied.
                           11

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                        FOREWORD
     Man and his environment must be protected from the
adverse effects of pesticides, radiation, noise and other
forms of pollution, and the unwise management of solid
waste.  Efforts to protect the environment require a
focus that recognizes the interplay between the com-
ponents of our physical environment—air, water, and
land.  The National Environmental Research Centers
provide this multidisciplinary focus through programs
engaged in

        o  studies on the effects of environmental
           contaminants on man and the biosphere, and

        o  a search for ways to prevent contamin-
           ation and to recycle valuable resources.

The study described here was undertaken to demonstrate the
feasibility of using rubber from discarded passenger car tires
in emulsions as blacktop dressings for driveways.  Employing
rubber in this manner could increase the demand for used tires
and decrease their solid waste disposal problem.

                                A. W. Breidenbach, Ph.D.
                                Director
                                National Environmental
                                Research Center, Cincinnati
                           iii

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                               EXECUTIVE SUMMARY
          The objective of this study was to demonstrate the feasibility of
using rubber obtained from discarded passenger car tires in water-thinnable
emulsions of asphalt or coal tar for blacktop dressings fqr driveways,
parking lots, streets, highways, etc.  The use of rubber in this large volume
market could result in an increased demand for the used tires, and, thus,
decrease the solid waste disposal problems connected with 200 million dis-
carded tires per year.
          The study has resulted in the production of nine different com-
positions containing from 5 to 25 percent rubber that were promising enough
to apply to a high-traffic area in the BCL parking lot (estimated passage of
1800 cars per day), to determine the respective service lives of the composi-
tions.
          After exposure for one year under the above conditions, performance
appears to have been as good as that of the control samples, and protection
of the underlying blacktop is still being rendered by all samples.
          The goal of the project was the demonstration of the feasibility
of the basic idea that rubber salvaged from discarded auto tires could be
incorporated into water-thinned blacktop dressings, and to utilize the in-
formation obtained to generate interests of industrial companies continuing
the studies to result in marketable products.
          It is felt that the goals of this study have been fully met.  Complete
feasibility of the basic idea has been demonstrated.  Service-life demonstration
have shown good performance characteristics, even though no attempts were made
to optimize the formulation.  One proposed research program was supplied to a
government agency at their request.  This was technically approved but funding
could not be arranged.  Two additional proposals have been submitted to in-
dustrial companies, and are currently under consideration.
          Future plans for Battelle activity in this area will involve attempts
to interest industry in continuing the study to develop improved materials.
                                      iv

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                               TABLE OF CONTENTS

                                                                  Page

INTRODUTION 	     1

SUMMARY 	     1

BACKGROUND  	     2

INDUSTRY SURVEY	.' .     4

DESCRIPTION OF SAMPLES  	     5

     Rubber Reclaimers Association Samples  	     5

     Union Carbide Sample 	     6

     Baker Samples	     6

     Phoenix Sample 	     7

     Uniroyal Dispersion  	     8

     Porter Sample  	     8

     Tall Oil Pitch	     9

     Asphalt Emulsion Base  ..... 	     9

     Coal Tar	     9

EXPERIMENTAL  	    10

     Incorporation of Rubber into Asphalt and
       Coal Tar	    10

     Emulsification of Rubberized Asphalt 	    13

     Rubberized Coal Tar Emulsification 	    14

     Preparation of Experimental Emulsions for Exterior
       Evaluations	    17

     Weather-0-Meter Studies  	    19

     Weather-0-Meter Evaluations  .....  	    19

     Slip Resistance of Experimental Emulsions  	    22

     Application of Nine Experimental and Two
       Control Emulsions  	    24

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                          TABLE OF CONTENTS (Continued)
                                                                   Page
     Three-Week Evaluation of the Applied
       Experimental Emulsions  	    24

     Subsequent Evaluations  	    27

CONCLUSIONS	    29

PATENTS	    30

FUTURE WORK	    32

                                  LIST OF TABLES

Table 1.  Incorporation of Rubber into Asphalt and Coal
          Tar	    11

Table 2.  Emulsified Asphalt-Rubber Mixtures 	    13

Table 3.  Emulsified Coal-Tar Rubber Mixtures  	    16

Table 4.  Experimental Emulsions for Exterior Exposure .....    17

Table 5.  Weather-0-Meter Evaluation of Experimental
          Emulsions	    20

Table 6.  Slip Resistance of Experimental Emulsions  	    23

Table 7.  Three-Week Evaluation of Experiment and Control
          Emulsions	    24


                                 LIST OF FIGURES

Figure 1.  Evaluation of Site Before Application 	    25

Figure 2.  Evaluation Site After Application 	    25


                                     APPENDIX
                                        vl

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                                    INTRODUCTION






            Battelle's Columbus Laboratories has carried out research under Grant



No. R-EP-00500-01 having the following objective:  to explore the feasibility




of effective and advantageous use of ground scrap or reclaimed rubber from




discarded rubber tires that now present a sizeable disposal problem.   The




research was directed toward this objective by studying the development of



improved water-thinned blacktop dressings through incorporation of the rubber




salvaged from used passenger car tires in a bituminous (asphalt or coal tar) base.




                                       SUMMARY






            An exploration of the rubber industry has shown a wide variety of




products is available or can easily be made available from discarded automobile




tires that might have potential in producing materials for use in blacktop




dressing manufacture.  Our laboratory studies under this grant have shown that it is



possible to blend finely ground tire rubber into asphalt or coal tar by either of two

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processes.  The resulting blends have been satisfactorily emulsified to form
materials suitable for use as blacktop dressings.  Nine different blends con-
taining from 5 to 25 percent rubber have been made into emulsions and applied
to a blacktop surface in a high-traffic area (1800 cars/day)*
          Evaluation of the outdoor exposures after one year  shows  good  performance
for all samples.
          Accelerated exposures in the Weather-Ometer indicate  differences
exist,  with some  samples showing better performance than the  controls  containing
no rubber.
          Slip-resistance test indicate a slight superiority  for  the  rubber-
containing samples,  both wet and dry.
          Formulas for the nine experimental products appear  in the Appendix.
                                   BACKGROUND
          Approximately 250 million new automobile tires are manufactured
every year.  The ultimate destination of a large portion of these tires is the
trash heap, where they pose a major disposal problem.  Disposal by burning
contributes to air pollution.  Tires produce unstable landfill, and, hence,
are frequently banned from this method of disposal.
          A sizeable number of tires are retreaded and reused.  The percentage
of truck and bus tires that are retreaded is considerably higher than that
for passenger car tires.   However, the number of retreaded tires is of little
consequence, since the retreading process only delays the discard date, and
the retreaded tire still ends up as a solid waste disposal problem.
          A considerable tonnage of rubber polymer is "reclaimed".  The re-
claiming process involves the separation of fabric and steel wire bead from
the rubber polymer, followed by digestion or depolymerization, and blending with
reclaiming oils. This results in a product that can be used for recycling back
into tire manufacture, tire retreading, and many noncritical materials, such
as elastic webbing, floor mats, sink mats, rubber hose, etc.

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          Present use of tires for the reclaiming industry accounts for about
20 percent of the tires produced (about 50 million tires per year).  Major
inputs to this industry are rubber factory scrap, tire buffings, and inner
tubes. Economic trends indicate a decreasing market for reclaimed rubber,
because several grades of virgin rubber are now selling for less than re-
claimed rubber.  This is especially true if one considers that reclaimed
rubber is usually only about 50 percent rubber polymer, the remainder being
reclaiming oils.
          Considerable interest over the years has been centered on "rubberized
roads".  The technical literature is full of papers describing the use of rubber
with asphalt in the construction of highways.  These papers are presently limited to
two modes of usage.  The most prevalent use is the blending of chopped-up tires
with asphalt for use as a paving composition.  The chopped tires replace a large
portion, or all of the aggregate (crushed rock or gravel) in the paving composi-
tion.  Several state highway departments are known to be exploring this appli-
cation.  Advantages claimed for rubberized roads prepared by this technique
include decreased skidding, longer road life, and decreased cracking and spalling
of the surface.
          The second mode of rubberizing roads described in the literature in-
volves the addition of rubber latex (unvulcanized) to the hot-mix asphalt paving
composition.  The same advantages are claimed as for the above procedure.  How-
ever, it must be pointed out that this procedure is more costly than using
reclaimed rubber, and the unvulcanized rubber tends to contribute less to the
durability than does vulcanized rubber.
          Several valuable bibliographies on the use of rubber in roads have
been prepared.   One particularly valuable list of references, which is kept
up to date, is available from
          Highway Research Board Library
          National Academy of Sciences
          2101 Constitution Avenue
          Washington, D.C.   20418
          Attention D. Bright, Librarian.
          A review of these available bibliographies plus a literature search
by Battelle personnel prior to this study has failed to disclose a single reference
to the emulsification of a dispersion of vulcanized rubber in either asphalt or
coal tar,  for use as a blacktop dressing for coating driveways, parking lots,

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etc.  The closest approach found was the use of an emulsified rubber-asphalt
system as a bond coat between concrete and hot-mix asphalt road surfacing, to
decrease "reflective cracking".
                                INDUSTRY SURVEY
          The study covered by this report was initiated by a survey of the
rubber reclaiming industry to identify materials that could be incorporated
into this program.  Valuable telephone and mail communications with Midwest
Rubber Reclaiming Company, E. St. Louis, Illinois; U. S. Rubber Reclaiming
Company, Vicksburg, Mississippi; and Uniroyal, Naugatuck, Connecticut, were
especially helpful in the early phases.  The Asphalt Institute, College Park,
Maryland, furnished excellent background information.
          The Rubber Reclaimers Association, Naugatuck, Connecticut, was most
helpful.  Through the cooperation of Mr. Tom Fitzgerald, Executive Secretary, it
was possible to arrange for the Association to supply six samples of reclaimed
rubber for use in this study.  Inese samples were selected to be representative ot
the entire industry.  They were prepared by Mr. C. E. Stuecheli of Xylos Rubber Com-
pany, Akron, Ohio. (This company is no longer in existence.) Mr. Louis Baker, Presi-
dent of A. Baker Manufacturing Company, has also been most helpful in supplying
samples of low-cost ground tires, as well as depolymerized rubber.
          Mr. C.  A. Hauck of Union Carbide Corporation, Tarrytown, New York,
has been helpful in supplying freeze-ground tire samples.
          Mr. Charles McDonald of the City of Phoenix, Arizona, has graciously
supplied samples of his high-temperature dispersion of rubber in asphalt for
our emulsification studies, as well as excellent instructions for carrying out
his process.
          Dr. E.  E. McSweeney of Union Camp Corporation, Savannah, Georgia,
supplied samples on high and low penetration tall oil pitch which were also
used in this study.

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                             DESCRIPTION OF SAMPLES
                     Rubber Reclaimers Association Samples

          As mentioned above, through the courtesy of Mr. Tom Fitzgerald,
Executive Secretary of the Rubber Reclaimers Association, arrangements were
made to obtain six samples of reclaimed rubber, representative of materials
that could be made by any reclaimer.  Three compositions were to be made
available in both "slab" and "crumb" form.  These three compositions (six
samples) were prepared by Mr. C. E. Stuecheli, of Xylos Rubber Company, Akron,
Ohio, 44301.  (This company is no longer doing business.)
          Properties of the six samples, as furnished by Mr. Stuecheli, (slab
and crumb form) are recorded as follows:
                                                 Sample No.
                           Ix (Slab & Crumb)  2x (Slab & Crumb)  3x (Slab & Crumb)
Scrap (35 mesh)
  Defiberized                  1UU                1UO                10°

Oil Crowley^                   8                  8                 12

Chem. Softener                   ill
  Pitt-Consol 500                                   ±                  1
Talc                             555
Microcel E                       222
  (in crumb only)
Cooking Time @ 375 F (hrs)       6                 10                  6
Sp.G.                            1.175              1.175              1.170
Mooney ML/4
  (on refined scrap)            M                 M                 OU
Ash %                            8.9                8.9                8.8
Acetone Extract                 21.5               21.0               24.8
Chloroform Extract               7.8                7.2                7.6

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                                                  Sample No.
Ix (Slab & Crumb)
26.1
40
2x (Slab & Crumb)
27.3
40
3x (Slab & Crumb)
26.4
37
Carbon Blac
Approx.
(a)  Rubber reclaiming oil.
(b)  Rubber hydrocarbon content.
          No specific price quotations were given for the above samples.  The
general understanding was that the price would be in the neighborhood of 9 to
14 cents per pound, depending on the volume demand, the cooking (processing) time,
and whether the product was desired in the "crumb" or "slab" form.  Processing of
the samples into the "slab" form represents an additional step in the manufac-
turing, and,.-hence, increases the cost per pound.

                              Union Carbide Sample

          Mr. C. A. Hauck of the Linde Division, Union Carbide Corporation,
Tarrytown, New York, 10591, supplied a sample of cryogenically ground whole
passenger tires.  This sample had the following particle size distribution:

                                             Nominal wt,
                        U.S. Mesh Size       percent past
                             -100               100%
                             -200                50%
                             -325                 5%
          It was prepared from whole passenger car tires (tread plus sidewalls).
It contained no oils or other reclaiming agents.  It was estimated that at least
90% of the fiber had been removed by the preparation process used.  The projected
price was calculated to be 4 to 10 cents per pound, probably nearer the 4-cent
range.  Union Carbide's code for this sample is UCC-B-WT-1.

                                 Baker Samples

          The A. Baker Manufacturing Company, South Bend, Indiana, supplied
three samples of ground passenger car tires for our studies.  One of these

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samples was considered to be unsatisfactory for our use, based on its particle
size.  The particles in this sample were roughly 1/2 inch x 1/2 inch.  The two
remaining samples proved to be worthy of investigation.  One sample was ground
whole passenger car tires with an estimated 75% of the fabric removed after
grinding.  The particle size was similar to that of the Union Carbide sample.
A sieve analysis furnished by the supplier indicated it to be -12, +16 mesh.
The price of this material is expected to be in the 4 to 5 cents per pound area,
which might be reduced for large volume uses.
          The third sample was labelled as "depolymerized" rubber.  This sample
had been cooked and blended with reclaiming oils and surfactants.  The exact
composition is considered to be proprietary.  However, the reclaiming oils are
suspected to contain significant amounts of terpenes, disulfides, and highly
polar swelling agents added to improve the handling properties of the rubber.
          The particle-size range of the sample appeared to be about the same
as that of the finely ground sample, approximately -12, +16 mesh.  The presence
of fabric was not nearly as apparent as it was in the ground rubber.
          The depolymerization requires extra processing.  The price is, there-
fore, in the 7 to 8 cent per pound range. If we assume this sample to be 75%
rubber polymer and 25% reclaiming oils, the price is about 10 cents per pound
of rubber polymer, which is considered to be high for the intended application.

                                 Phoenix Sample

          Mr. C. H. McDonald, Engineering Supervisor, City of Phoenix, Arizona,
85034, supplied a sample of rubber that had been incorporated into asphalt by
a heating process developed by him for use in patching and pavement repair
compounds.   This sample was a 25% dispersion of ground tire rubber (-16, +25
mesh) in 120-150 penetration grade Los Angeles Basin asphalt.
          The incorporation process involves heating the mix until a reaction
occurs, yielding a jelly-like composition.  A patent application has been filed
by McDonald covering the process.
          Mr. McDonald has not tried to emulsify the material.  Its use has been
restricted  to paving and pavement patching using the hot-mix technique, and
a hot-melt  spray coating for streets.

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          Care must be used not to overheat the sample,  since depolymerization
of the rubber takes place at about 400 F, which injures  the durability of the
product, according to Mr. McDonald.

                             Uniroyal Dispersion

          Uniroyal Chemical, Naugatuck, Connecticut,  06770, markets a water
dispersion of reclaimed rubber.  This dispersion is 58%  solids,  and is anionic
in nature.  The solids content of the dispersion was

                     	Component	       Parts
                     Ground Whole Passenger Tires        100
                     Tall Oil Pitch                        4
                     Bituminous Petroleum                  3
                     Asphaltic Resin                       5
                     Oleic Acid                            9
          The price, in large quantity, can be expected to be about 20 cents
per dry pound.
          The sample appeared to be of medium viscosity.  Suspended particles
appeared large, much larger than in an emulsion.
          Although this sample was anionic in nature, it was found to be incom-
patible with separately prepared emulsions of either asphalt or coal tar made
by normal procedures.
          Based on the high price and the difficulty of incorporating it in
blends with asphalt or coal tar, this sample was judged to be unsuitable for
this study.

                                 Porter Sample

          The sample received from 11. K. Porter Company was chopped rubber hose,
in the form of rings. It contained considerable fabric.  The particles were too

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large to disperse readily into either asphalt or coal tar.   The sample was,
therefore, judged not suitable for use in this study.

                                 Tall Oil Pitch

          The Union Camp Corporation, Savannah, Georgia,  31402, furnished two
representative samples of tall oil pitch, high and low penetration.   The analyses
of these samples were as follows


                                   High Penetration      Low Penetration
        Acid Number                       64                   31
        Saponificatlon Number            109                   97
        Rosin Acids %                     28.2                 15.1
        Fatty Acids %                     39.7                 48.1
        Unsaponifiables                   32.1                 36.8
          The presence of rosin acids, fatty acids and terpenes in tall oil
pitch make it appear interesting as a dispersing agent for vulcanized rubber.

                             Asphalt Emulsion Base

          The asphalt used as the base in this study is a petroleum residue
asphalt with a penetration of 190.  It was obtained from Ashland Chemical
Company as representing their recommendation for water emulsion use.

                                    Coal Tar

          The coal-tar base used in this study was obtained from Reilly Tar &
Chemical Corporation.  It is a standard emulsion-type base, sold by the supplier
to many blacktop-dressing manufacturers.

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                                        10
                                  EXPERIMENTAL
                          Incorporation of Rubber into
                              Asphalt and Coal Tar

          Several methods were investigated to incorporate the various types
of rubber received into asphalt and coal tar.  The first and one of the most
promising methods was to place the asphalt or coal tar into a jacketed Bramley
mill and add the rubber during agitation.  The best technique was to heat the
mill, after addition of the asphalt or coal tar, to 265 to 275 F with 45 to 50 psig
pound steam.  When the asphalt or coal tar was liquid, the rubber was added.
After sixty minutes, the steam was turned off and cold water at 40 to 45 F was
circulated through the jacket for an additional sixty minutes.  This cycle
was repeated four times.  The Bramley mill is a modified sigma-blade mixer which
places high shear and tearing action on thick mastic materials.  This action
which occurred during the cold-water segment of the cycle tore apart the rubber
particles which had been swollen due to the heat of the first half of the cycle
and the solvency of the oils in the asphalt and/or coal tar.
          The second method tried for incorporating rubber into asphalt and
coal tar was to use a 6-inch rubber mill.  This method resulted in a higher
percentage of rubber being incorporated into the asphalt and the coal tar, but
it was a much more expensive process than any of the other methods explored.
The rubber was milled on heated rolls until it was in sheet form.  Then a
small amount of asphalt or coal tar was added.  The greatest reduction of the
rubber that could be obtained was a composition containing 25% asphalt and
75% rubber.   This mixture was very difficult to remove from the mill even
when the rolls were cooled to 50 F.  Further reduction of the rubber con-
tent was made by heating the rubber-asphalt mixture until liquid, then
adding more liquid asphalt until a 5% rubber-asphalt mixture was obtained.
There did not appear to be any major differences in properties of the rubber-
asphalt and rubber-coal tar blends made by this method and the first method
using the Bramley mill; therefore, due to economics, this method was not in-
vestigated further.
          The third method investigated was to swell the rubber in tall oil
before the addition of asphalt or coal tar.  This work was done in the Bramley

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                                        11
mill using the same cycles as described in the first method.   By swelling the
rubber in the tall oil before adding the asphalt or coal tar,  the final mix-
tures had smoother texture and the rubber appeared to be better incorporated
into the asphalt and coal tar; however, the high oil content  made these mix-
tures very difficult to emulsify.
          The fourth method used to incorporate the rubber was the Phoenix
method.  This process method was developed by Mr.  Charles H.  McDonald,
Engineering Supervisor, Engineering Department, Materials Testing Station,
City of Phoenix, Arizona, 85034.  This process was to heat the asphalt to 350 F
and add 25 % ground rubber (-16 mesh, +25 mesh) to the heated asphalt during
agitation.  Mr.  McDonald emphasized that the mixture should not be heated over
400 F or the rubber would depolymerize.  Mr. McDonald stated  that the rubber
reacted with the asphalt to form a jelly-like composition.  A patent has been
applied for by Mr. McDonald.   Our experiments showed that the 350 F temperature
was fine for incorporation of rubber into asphalt but slightly higher temperatures
(375 to 380 F) were needed to get the rubber into coal tar.
          It was decided, based on economics, ease of incorporation, and appearance
of the mixtures of rubber-asphalt and rubber-coal tar, to use the methods desig-
nated one and four.  The following table lists the name of the rubber used,
percentages of rubber added,  method of incorporation, and the base material
(asphalt or coal tar) to which the rubber was added.
                     TABLE 1.  -INCORPORATION OF RUBBER INTO
                               ASPHALT AND COAL TAR
 Rubber Sample
     (Name)       Rubber Type
% Added    Method
                 (a)
Base Material
Baker
Baker
Xylos Ix
Xylos 2x
Fine ground
tires w/fibers
Full reclaim
Full reclaim
Full reclaim
5 + 25
5+25
5 + 25
5 + 25
1 + 4
1 + 4
1 + 4
1 + 4
Asphalt & Coal tar
Asphalt & Coal tar
Asphalt & Coal tar
Asphalt & Coal tar

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                                        12
                              TABLE 1.  (Continued)
 Rubber Sample
     (Name)       Rubber Type
                       % Added    Method
                                        (a)
                        Base Material
 Xylos 3x
Full reclaim
5+25      1+4     Asphalt & Coal tar
 Union Carbide    Cryogenic Ground
                   90% Fibers removed    5+25      1+4     Asphalt & Coal tar
 (a) 1 - Battelle method (Bramley mill)
     4 - Phoenix method.
          The Baker fine ground rubber with fiber was incorporated into asphalt
and coal tar with no difficulties by both the Battelle and Phoenix methods at
both the 5 and 25 percent level.
          The Baker full reclaim rubber was extremely difficult to incorporate
by the Phoenix method when added to either .the hot asphalt or hot coal tar at
both the 5 and 25 percent level; the rubber would cause heavy foaming and in
most cases foamed out over the container.  This reaction was most likely caused
by boiling of the oils used to reclaim the rubber.
          Also the Baker reclaimed rubber was fairly difficult to incorporate
into asphalt and coal tar at the 5 percent level in the Bramley mill and the
resulting mixture was granular in appearance.  At the 25 percent level the Baker
reclaimed rubber had lumps about 1/4 inch in diameter.
          Xylos Ix crumb was the only one of the three reclaimed rubbers from
Xy]os Rubber Company that could be incorporated smoothly into the asphalt and
coal tar in the Bramley at both the 5 and 25 percent level.  The other two
rubbers, Xylos 2x and Xylos 3x, looked similar to the 5 percent Baker reclaim.
They all had a very granular texture.  All the Xylos crumb rubbers were incor-
porated into asphalt and coal tar by the Phoenix method and looked good at both
levels of addition (5 and 25 percent).
          The Union Carbide cryogenic ground rubber was easy to incorporate
into both asphalt and coal tar by both methods at the 5 and 25 percent levels.
          All three slab rubber samples proved to be very difficult to disperse
in both asphalt and coal tar, and their use was abandoned.

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                                        13
                      Emulsification of Rubberized Asphalt

          All asphalt emuIsification work was conducted with an Asphalt Emulsion
Base obtained from Ashland Chemical Company.  During the first attempts to emulsify
the asphalt, various clays and talcs were used as fillers and Indulin W-l was
used as an emulsifying agent.  Most of these emulsions were very poor and heavy
settling occurred when the emulsions stood overnight.  The most stable emulsions
resulted when Mistron ZCS talc was used as the filler.  The following was selected
as the standard method for evaluating rubberized asphalt.
          Three hundred grams of water and 100 grams of United Sierra's Mistron
ZCS talc were placed in a quart container.  A Premier mill mixer was used to
provide high-speed agitation ("\-5000 rpm) of the water-talc slurry.   The slurry
was heated to 160 to 170 F during constant agitation.  Two grams of calcium
chloride and 85 to 90 grams of hot (180 to 200 F) asphalt-rubber mixture were
added.  As soon as the addition of asphalt-rubber mixture was made, the agitation
was increased to 7500 to 8000 rpm for one minute.  Table 2 lists the asphalt-
rubber mixtures emulsified and comments on their stability and appearance.
                  TABLE 2.   EMULSIFIED ASPHALT-RUBBER MIXTURES
Asphalt-Rubber
Xylos Ix
Xylos Ix
Xylos Ix
Xylos Ix
Union Carbide
Union Carbide
Union Carbide
Union Carbide
Baker Reclaim
% Rubber
5
25
5
25
5
5
25
25
5
Method (a)
BCL
Phoenix
Phoenix
BCL
Phoenix
BCL
Phoenix
BCL
BCL
Comments
Appearance
Very Good, Smooth
Good, Smooth
Good, Smooth
Good, Slightly Granular
Excellent, Very Smooth
Excellent, Smooth
Good, Smooth
Good, Smooth
Good, Slightly Granular

Stability
Good
Good
Good
Good
Very Good
Very Good
Good
Good
Fair

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                                        14
                              TABLE 2.  (Continued)
'Asphalt-Rubber %
Baker Reclaim
Baker Reclaim
Baker Reclaim
Baker Ground
Baker Ground
Baker Ground
Baker Ground
Phoenix- Asphalt
Rubber Mix
Xylos 2x
Xylos 2x
Xylos 3x
Xylos 3x
(a) BCL - Battelle1
Rubber
5
25
25
5
25
5
25
25
5
5
5
5
s Columbus
Method (a)
Phoenix
Phoenix
BCL
BCL
Phoenix
Phoenix
BCL
Phoenix
Phoenix
BCL
Phoenix
BCL
Comments
Appearance
Good, Slightly Granular
Fair, Lumpy
Fair, Granular
Very good, Very Smooth
Good, Smooth
Good, Smooth
Good, Very Slightly
Granular
Fair, Lumpy
Good, Slightly Granular
Fair, Granular
Fair, Granular
Fair, Granular

Stability
Good
Fair
Good
Good
Good
Good
Good
Fair
Fair
Fair
Fair
Fair
Laboratories .
Rubberized Coal Tar
Emulsif ication

          All coal tar emulsification work was conducted with a coal tar emul-
sion base from Reilly Tar and Chemical Company.  Initial work on eraulsification
was to evaluate several different clays and emulsifiers.  The following list
gives the clays and emulsifiers tried.

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                         15
    	Clays	




    Hydrite PXS




    Kaogen A3




    Hydrite RS




    Kaophobe 45




    #20 Clay




    Hydrite Flat "D"
      	Supplier	




      Georgia Kaolin Co.
      Burgess Figment Co.




      Georgia Kaolin Co.
 Emulsifiers




Kricinol 35




Indulin C




Indulin W-l




Westvaco M-50




Westvaco Resin 90




Arizona DRS 42




Arizona DRS 43




Dresinate X




Dresinate XX




Redicote E-l




Redicote E-3




Redicote E-5




Redicote E-9




Redicote E-ll




Redicote E-12




Redicote E-14




Redicote E-23




Redicote E-27




Redicote i:-28
          Supplier
Arthur C. Trash Co.




Westvaco Corp. Chem. Div.
Arizona Chemical Co.
Hercules, Inc.
Armour Industrial Chemicals

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                                         16
           The following was selected as the standard method for the evaluation
 of rubberized coal tar.  One hundred and twenty grams of water, 20 grams of Burgess #20
#20 clay, and 10 grains of Mistron ZCS Talc were placed in a quart container.  A Premier
mill mixer was used to provide high-speed agitation (~5000 rpm) of the water-clay-
 talc slurry.  The slurry was heated to 160-180 F with constant agitation.
 When the slurry reached the desired temperature, 1 gram of Indulin W-l and
 1 gram of calcium chloride was added slowly to the slurry during constant
 agitation.
           When approximately 50 percent of the rubberized coal tar had been
 added the mixer speed was increased to 7500-8000 rpm.  After all the rubberized
 coal tar was added, 1 gram of potassium ricinoleate was added.  Before the
 addition of the potassium ricinoleate the rubberized coal tar was suspended
 in little globules in the slurry.  The addition of the potassium ricinoleate
 caused the breaking up of the globules and resulted in a good emulsion.
 Table 3 lists the coal-tar rubber mixtures emulsified and comments on their
 stability and appearance.
                   TABLE 3.  EMULSIFIED COAL-TAR RUBBER MIXTURES
Coal- Tar Rubber
Xylos
Xylos
Xylos
Xylos
Union
Union
Union
Baker
Baker
Ix
Ix
Ix
Ix
Carbide
Carbide
Carbide
Reclaim
Reclaim
% Rubber
5
25
5
25
25
5
5
5
5
Method
BCL
Phoenix
Phoenix
BCL
Phoenix
Phoenix
BCL
Phoenix
BCL


Good,
Good,
Good,
Good,
Good,
Good,
Good,
Fair,
Good,
Comments
Appearance
smooth
slightly granular
very slightly granular
slightly granular
smooth
smooth
smooth
granular
granular

Stability
good
good
good
good
good
good
good
fair
good

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                                        17
                              TABLE 3.  (Continued)
Coal-Tar Rubber
Baker Ground
Baker Ground
Baker Ground
Baker Ground
Xylos 2x
Xylos 2x
Xylos 3x
Xylos 3x
% Rubber Method
25
5
5
25
5
5
5
5
Phoenix
Phoenix
BCL
BCL
Phoenix
BCL
BCL
Phoenix
Comments
Appearance
Good, very slightly granular
Good, smooth
good, smooth
good, very slightly granular
Fair, granular
Fair, granular
Poor
Fair, granular

Stability
good
good
good
good
fair
fair
poor
fair
Preparation of Experimental Emulsions
for Exterior Evaluations
Asphalt


          Five experimental asphalt-rubber emulsions and four experimental
coal-tar rubber emulsions were prepared in 4-gallon lots for exterior exposure
evaluation.   Table 4 designates the experimental emulsions made.
                        TABLE 4.   EXPERIMENTAL EMULSIONS
                                  FOR EXTERIOR EXPOSURE
Emulsion
Number
TE-1
TE-2
Rubber
Xylos Ix
Baker Fine
% Rubber
5
5
Method (a)
Rubber Incorporation
BCL
BCL
Base Material
Asphalt
Asphalt

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                                        18
                             TABLE 4.  (Continued)
Emulsion
Number
TE-3
TE-4
TE-5
TE-6
TE-7
TE-8
TE-9
Rubber
Union Carbide
Baker Fine
Baker Fine
Xylos Ix
Union Carbide
Union Carbide
Baker Fine
% Rubber
5
25
5
5
5
25
5
Method *a*
Rubber Incorporation
BCL
Phoenix
Phoenix
BCL
BCL
Phoenix
BCL
Base Material
Asphalt
Asphalt
Asphalt
Coal tar
Coal tar
Coal tar
Coal tar
  (a) BCL - Battelle's Columbus Laboratories.


          All the emulsions were made on a laboratory model Cowles Dissolver.
The asphalt control and five experimental emulsions were formulated as follows.
          Added to Dissolver tank
               9 kilograms water
               3 kilograms Mistron ZSG talc
              60 grams Calcium Chloride
          Heated to 160 F with constant agitation then added 4.5 kilograms
asphalt or asphalt-rubber mix heated to 200 to 210 F during constant agitation.

Coal Tar
follows.
The four experimental coal-tar rubber emulsions were formulated as

Added to Dissolver tank
     7.2 kilograms water
     1.2 kilograms Burgess it20 Clay
      .6 kilograms Mistron ZSC talc
     60  grams Indulln W-l
     60  grams Calcium Chloride

-------
                                         19

          Heated above to 180 F with constant agitation then added 5.4 kilograms
coal tar-rubber mix.
          Heated to 220 to 230 F during constant agitation.  Immediately after
all the coal tar-rubber mixture was added, 60 grams of potassium ricinoleate
was added.
          All the experimental emulsions were smooth and looked good.  After
standing for 14 days, TE-4 had a granular appearance and it was fairly difficult
to reincorporate the surface liquid.  TE-8 was extremely difficult to stir;
however, after the surface liquid was reincorporated, it had a very smooth
texture.  All of the other experimental emulsions mixed as well as the coal tar
and asphalt controls.


                             Weather-0-Meter Studies

          Table 5 lists the emulsions that were applied to 2-1/2-inch x 6-inch as-
bestos boards for evaluation in the Weather-0-Meter.  The twin-arc Weather-0-Meter
was cycled so that the panels would have 108 minutes dry, high temperature
(100 to 120 F) and 12 minutes of water spray directly on the panels.
          Evaluation of the Weather-0-Meter exposed samples is given in Table
5.

                            Weather-0-Meter Evaluations

          It was noted early in the exposure life of the panels in the
Weather-0-Meter, that atypical behavior was being encountered.  The changes
observed did not agree with the noted performance of the samples applied to
Battelle's driveway.  Failure by forming large alligator-skin-like cracks was
almost universal.
          This variance in performance is felt to be due to the facts that
          (1)  The samples in the Weather-0-meter series are much
               thicker (1/8 inch) than the driveway samples.

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                                          TABLE  5.  WEATHER-0-METER EVALUATION
                                                   OF EXPERIMENTAL EMULSIONS
Specimen    Emulsion
 Number      Number     Comp Components
          Method of Rubber
Rubber    Incorporation^)
                                                                   100  hr Evalua-
                                                                    tion Comments
                                                                              1000  hr Evaluation
                                                                                   Comments
  1,  2       TE-1      Asphalt-Xylos Ix
  3,  4       TE-2      Asphalt-Baker fine
  5,  6       TE-3      Asphalt-Union Carbide
  7,  8       TE-4      Asphalt-Baker fine
  9, 10       TE-5      Asphalt-Baker fine
 11, 12       TE-6      Coal tar-Xylos  Ix
 13, 14       TE-7      Coal tar-Union Carbide
                                      25
                                                   BCL
                                                  BCL
                                                   BCL
                                         Phoenix
                                                  Phoenix
                                                   BCL
                                                  BCL
                              Very slightly
                               checked smooth
                               film

                              Slightly checked
                               soft film, few
                               rubber chunks

                              Medium checking
                               mud cracking,
                               dull film, soft,
                               rubbery

                              Very rough rub-
                               bery, heavy
                               cracks

                              Smooth film, gray
                               rubber chunks

                              Thin, heavy alli-
                               gatoring medium-
                               hard film

                              Very heavy alli-
                               gatoring, flat
                               film, medium
                               hard film
                                                                              Smooth,  very
                                                                               slightly checked
                                                                               gray

                                                                              Slightly checked
                                                                               whitish,  few
                                                                               rubber  chunks

                                                                              Considerable check-
                                                                               ing,  whitish
                                                                               eroded
                                                                                                                         ro
                                                                                                                         o
                                     Rough, slight
                                      cracks, rubbery
                                                                              Smooth,  gray,  very
                                                                               slighly checked

                                                                              Dull,  heavily  alii-
                                                                               gatored,  pinholed
                                                                              Dull,  very heavily
                                                                               alligatored,  pin-
                                                                               holed
 15, 16
TE-8
Coal tar-Union Carbide
 25
Phoenix
Gray, hard, no
 cracks, few
 craters
Slight surface
 cracks, whitish
 pinholed

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                                                 TABLE 5.   (Continued)
Specimen
 Number
Emulsion
 Number
     Components
     Components
% Rubber    Method of Rubber   100 hr Evalua-
°L Rubber    Incorporation^)    tion comments
                      1000 hr Evaluation
                           Comments
 17, 18
  TE-9
Coal tar-Baker fine
               BCL
 21, 22
 23, 24
 27, 28
 29, 30
  CTC
  AC
Coal tar-Control
            Coal tar-Baker fine         25
            Coal tar-Union Carbide
Asphalt-Union Carbide       25
               Commercial
                                        Phoenix
                                        Phoenix
               Phoenix
Heavy coating
 very, very heavy
 alligatoring
 healed, soft
 rubbery

Very smooth, high
 gloss, black
 medium soft

Slightly gray
 very rough,
 rough chunks

Black, smooth
 hard, flat

Medium cracking
 slightly gray
 soft, rubbery
 thin film
Extremely alli-
gator, pubby blis-
ters
Bronzed flat, pin-
 holed thin
Very rough, no
 checks, no pin-
 holes

Black, Smooth,
 few pinholes

Considerable check-
 ing, gray, thin-
 eroded

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                                         22

           (2)   The Weather-0-Meter  samples  are  applied  to Transite®
                board  (asbestos-cement composition) rather than blacktop.
           (3)   The Weather-0-Meter  samples  are  subject  to sudden  tempera-
                ture changes of wider excursion  than  the driveway  samples.
           (4)   The Weather-0-Meter  samples  are  not subject  to the pres-
                sure of traffic, which can cause a healing of small
                cracks to occur.
           Even  though the Weather-0-Meter exposures  were exhibiting atypical
failures,  they  were continued on exposure to obtain  valuable comparative data.
           After only 100 hours of exposure, it  became apparent that cracking of
coal-tar-rubber blends was related  to the amount of  rubber  in the blend.  Cracking
was restricted  to the coal tar samples containing only  5 percent  rubber.  Those
samples containing 25 percent rubber did not crack.  Although no  cracking has been
observed in any samples exposed in  the Battelle driveway, the results indicate
that a higher amount of rubber than 5 percent might  be  desirable  in coal tar
compositions, in order to obtain maximum flexibility.
           The differences observed  early in the exposure period continued through-
out the exposure life.

                    Slip Resistance of Experimental  Emulsions

           The experiment emulsions were brushed onto a  damp piece of 1/8-inch asbestos
board.  Three specimens were evaluated for each experimental emulsion and a con-
trol.  The slip resistance was measured in wet  and dry  conditions. The test pro-
cedure was to apply a piece of tread from a rubber tire to  the coated surface and
to place a 500-gram weight on the rubber tread.  A Chatillon measuring device
was used to determine the pull in pounds necessary to move  the weighted rubber
tread from at rest to a sliding position.  The  rubber tread had an area of 1.68
square inches.  The measuring device is calibrated in 0.05-lb increments and is
Model No.  DPP-5.  Table VI lists the specimens and the pull in pounds necessary
to break friction hold,  wet and dry.  The figure given  represents an average
of three readings per specimen and  the average  of the three specimens evaluated.

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                                        23
                          TABLE 6.  SLIP RESISTANCE OF
                                    EXPERIMENTAL EMULSIONS
Specimen No.
TE-1
TE-2
TE-3
TE-A



TE-5
TE-6
TE-7
TE-8
TE-9
TE-10
TE-11
Description
5% Xylos Ix-Asphalt
5% Baker fine-Asphalt
5% Union Carbide-Asphalt
25 % Baker fine-Asphalt



5% Baker fine-Asphalt
5% Xylos Ix-Coal tar
5% Union Carbide Coal tar
25% Union Carbide Coal tar
5% Baker fine Coal tar
Asphalt Control
Coal tar Control
Average pull, Ib
Dry Wet
1.27 1.19
1.49 1.40
1.83 1.27
Unable to evaluate
because of large
chunks of rubber
on surface of coating
1.61 1.49
1.07 0.96
1.09 1.05
1.05 0.99
1.04 1.04
1.43 1.56
0.99 0.91
          All of the experimental coal tar-rubber emulsions have improved slip
resistant both wet and dry when compared to the commercial control.  The same
is true with the experimental asphalt-rubber emulsions with one exception.
The asphalt emulsions all show greater skid resistance than the coal tar
emulsions.  This effect is mostly likely due to the slightly softer films of
asphalt.

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                                       24
                       Application of Nine Experimental
                          and Two Control Emulsions
         The nine experimental and two control emulsions were applied on an
evaluation site in the north drive of Battelle's Columbus Laboratories' entrance
to the parking area.  (See Figure 1.)
         Most of the experimental emulsions were applied with no difficulty.
Emulsion TE-4, Baker fine rubber at 25 percent level, was fairly hard to apply
in a smooth coating because the rubber particles had swollen and agglomerated
during standing in the container.  Emulsion TE-8 was very difficult to apply
because of a very rapid break time.  Several of the experimental emulsions were
gray when dried, indicating that too much extender material (talc and clay) was
used in the formulation.
         The emulsions were applied on Saturday, May 20, 1972, between 1:00 p.m.
and 4:00 p.m.  The temperature was between 80 and 85 F during the time of appli-
cation.  Figure 2 shows the evaluation site after application of the experimental
and control emulsions.  It is estimated that a minimum of 1800 cars pass over
the experimental emulsions every weekday.

                         Three-Week Evaluation of the
                        Applied Experimental Emulsions

         The experimental emulsions and the two controls were given brief
observations three weeks after their application.  It is estimated that ap-
proximately 28,000 cars had passed over the experimental emulsions in this
time period.  Table 7 lists the emulsions and observations made.
                      TABLE 7.  THREE-WEEK EVALUATION OF
                                EXPERIMENT AND CONTROL EMULSIONS
               Emulsion                     Observations

           TE-1                 Very good crack sealing
           Asphalt              Not very soft
           5% Xylos Ix          Slightly streaky application
           TE-2                 Grayish-white at edges
           Asphalt              Black in traffic areas
           5%                   Thick spots very soft
                                Streaky application

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FIGURE 1.  EVALUATION SITE BEFORE APPLICATION
 FIGURE 2.  EVALUATION SITE AFTER APPLICATION

-------
                             27
                   TABLE 7.  (Continued)
    Emulsion
            Observations
TE-3
Asphalt
5% Union Carbide
TE-4
Asphalt
25% Baker
TE-5
Asphlat
57. Baker
TE-6
Coal tar
5% Xylos Ix
TE-7
Coal tar
5% Union Carbide
TE_8
Coal tar
257. Union Carbide
TE-9
Coal tar
Asphalt Control
Coal tar Control
Tire abrasion marks
Gray
Thick areas soft
Fair crack sealing
Slightly streaked from application

Grayish-white
Very granular, rubbery, sticky
Very streaky, Rubber appears to be
separating

Gray
Tire abrasion marks
Fairly tough
Uniform appearancy
Very slightly granular

Very dark gray
Thick areas slightly soft
Cracks not very well sealed oil
oil drippage resulted in soft spots

Black
Very good general appearance
Thick areas soft
Cracks appear well sealed

Considerable tire abrasion marks
Harder than TE-7
Considerably grayer than control
Oil drippings not soft
White in nontravelled areas

Very thick spots are soft
Few tire abrasion marks
Dark gray-darker than asphalt
control

Puddled
Soft in deep areas
Tire abrasion marks
Slight gray general appearance

Very uniform
Fair cracking filling
Fairly hard in thick area

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                                         28
          The observations made on the control and experimental emulsion after
three weeks were very general and the differences were slight.  No major trends
were detected at that time.

                              Subsequent Evaluations

          Periodic observations of the conditions of the applied stripes were
made throughout the period from May 20, 1972, through May 20, 1973.
          On July 28, 1972, observations indicated that all samples were showing
wear on the tops of aggregate particles, including both controls.  All samples
continued to exhibit good sealing between aggregate particles.  No major differences
were noted between samples.  Those samples appearing white or light gray shortly
after application appeared to be darkening, so that very little difference (if any)
could be seen between exposed samples.
          Examination again in late December, 1972, showed some differences be-
ginning to appear.  However, they were decided to be not definitive enough to
permit identification of any trends.   Those samples containing 25 percent rubber,
based on the bitumen content, appeared to be losing some of the granules of rubber
by its working out of the surface, particularly in the high-traffic areas.
          It also appeared at this time that the finer ground (cryogenic) rubber
produces a more penetrating dressing that appeared to seal cracks better than those
dressings made from coarser rubber particles.
          Examination of the test patches was again made on March 20, 1973.  In
general, the winter of 1972-73 had been moderate, with only a small amount of snow-
fall in Columbus, Ohio.  These conditions did, however, result in an unusual
amount of freezing and thawing.  In spite of this, all coatings including the con-
trols appeared to have lasted through the winger remarkably well.  Although the
tops of the aggregate particles were worn clean of the dressing material, all
coated areas, regardless of the coating material, were still well sealed between
the aggregate particles, providing water-tightness.  The conclusion was reached
that all experimental samples were at least as good as the controls.  Indications
continued to be present that the 5 percent rubber was giving superior performance
to the 25 percent rubber samples, and that the finer-ground rubber had apparently
penetrated further into the pores and cracks of the substrate.

-------
                                         29

          A final examination was made on May 22, 1973, after the applications had
been on exposure for one full year.  During that year, a conservative estimate
indicated more than 450,000 vehicles had passed over the center portions of the
applications.  Although most of these vehicles were passenger cars, a significant
number were trucks, many of them of the heavy, tractor-trailer type.  The area
also included a portion of each application exposed to parking, including oil
drippage (on the south edge).
          Prior to examination, the strips were hosed with cold water, and brushed
dry with a push-broom, to insure the removal of loose dirt.  The strips were also
photographed when dry.  These photographs are presented as Figures A-l to A-1L in
the Appendix of this report.
          Observation of the general appearance of the exposed samples showed that
all materials were in fair conditions.  Although the sealer had been worn off the
tops of aggregate particles, the area between particles remained filled, and the
surface appeared to be well sealed for all samples.  Cracks in the pavements that
were present at the time of application either remained filled and sealed, or had
not enlarged from their conditions prior to sealing.
          Intercomparing the samples, all experimental materials appeared to be in
at least as good condition as either of the two controls.  The asphalt control
appeared slightly more worn than the coal tar control.
          Sample TE-1 remained quite smooth.  The large crack in the base pave-
ment remained fairly well sealed by the sealer.  It had not enlarged from the pre-
application state.  It was not injured in the parking area in the foreground of the
oil drippage.
          Sample TE-2 showed some application marks due to thick areas.  However,
it remained in very good condition, and appeared to still be giving good protection
and sealing.
          Sample TE-3 appeared very uniform in application.  It remained dark.  No
damage could be seen due to oil drippage.
          Sample TE-4 showed marked application marks due to thick areas.  The
granular appearance that was evident just after application has, for the most part,
disappeared.  Due fo its heavy nature, it did not penetrate the large crack very
deeply.  However, tlic crack still appeared sealed for the most part, and had not
enlarged noticeably from its original size.

-------
                                         30
          Sample TE-5 still retained its original uniform appearance.  It re-
mained dark, having lost most of the original gray appearance.  Good protection
of the base asphalt seemed to be maintained.
          Sample TE-6 shows some application marks.  The large crack is incom-
pletely sealed, probably because of its large size.  Generally good protection
is being maintained by the coating.
          Sample TE-7 is, for the most part, quite uniform.  A few application
marks can be seen in the foreground.  Small cracks appear to be well sealed.
The light spots in the foreground are due to oil drippage from parked cars.  No
injury to the coating was noted in these areas.
          Sample TE-8 has lost its early whiteness and has now become dark gray.
Very few application marks can be seen.  Excellent protection seems to be main-
tained.  Small cracks remain well sealed.
          Sample TE-9 remains gray in color.  Some application marks are visible.
The large crack in the foreground remains well sealed.  Generally good performance
was noted.
          Sample CTC, the coal tar control, appears very thin.  The large crack at
the left of the application was still well sealed.  Show-through of the aggregate
was very noticeable.
          Sample AC, the asphalt control, appears slightly worn in the center,
high traffic area.  The large crack on the right remained well sealed.

                                   CONCLUSIONS
          Many conclusions are possible from the study as described in this report.
However, it appears that the following are among the most important.
          (1)  It has been demonstrated beyond doubt that it is
               feasible to incorporate ground rubber from discarded
               automobile tires in bitumens such as coal tar or
               asphalt to prepare a product suitable for us<_ as a
               blacktop dressing.
          (2)  The economics, although not completely resolved, seem
               to be favorable since it appears possible to improve
               the performance of asphalt to essential!) match that
               of coal tar.

-------
                                         31

          (3)  The economics will, of course, depend on the optimum
               level of rubber in bitumen.
          (4)  The optimum level of rubber appears to lie somewhere
               between 5 and 25 percent of the rubber-bitumen blend.
          (5)  The rubber may be incorporated into the bitumen by
               several processes.  Both the Battelle and the Phoenix
               process used in this study appeared to give satisfactory
               results.
          (6)  Satisfactory durability was observed for all experimental
               samples exposed after one year of service.
          (7)  Assuming 10 percent rubber to be the optimum con-
               centration, each gallon of emulsion would contain
               approximately 1/2 pound of ground rubber.  This
               gallon would normally cover about 40 square feet
               (optimistic estimate).

          One passenger car tire, after removal of the bead and the major part
of the fabric, will yield approximately 10 pounds of ground rubber, or enough to
prepare 20 gallons of emulsion.
          The average driveway is estimated to contain about 800 square feet
(8* x 100'), and should require about 20 gallons of dressing for good protection.
          It, therefore, appears that about one tire per average driveway would
be used.
          In addition, the millions of square feet of blacktop in shopping center
parking lots, city streets, airport loading aprons, taxi strips, etc, could furnish
enough area to use up all the roughly 200 million discarded passenger car tires
per year.
                                     PATENTS
          It is believed that the process for emulsification of a vulcanized
tire rubber-bitumen blend is new and novel.  Before proposing the research pro-
gram covered by the subject grant, a fairly comprehensive literature study failed

-------
                                          32

to uncover any reference to such an emulsification.  The early phases of the
study included contacts with many asphalt, coal tar, and rubber specialists.
These contacts failed to reveal any emulsification of rubber-bitumen blends.
          Although no patent novelty search has been made of the process, the
intelligence obtained from the above-noted sources substantiates that the emulsi-
fication of rubber-bitumen blends is a novel process, resulting in a new, useful
material that might be patentable.
          After examining the many facets of this situation, the following course
of action is recommended.
          (1)  The first step should be a patent novelty search of
               the process of preparing vulcanized rubber-bitumen
               (asphalt or coal tar) blends, and emulsification of
               such blends to prepare water-thinnable systems.  This
               step would permit a decision regarding the possible
               patentability of the process, and the advisability of
               preparing an application for a patent.
          (2)  The preparation of a strong patent application will
               doubtless require some additional studies to establish
               limits of composition and preferred formulas.  It should
               be remembered that the study covered by this report was
               designed to demonstrate feasibility of the basic idea.
               Neither tisie ncr funds were available to obtain the
               comprehensive information and mutitude of examples,
               required for a strong patent application.  Since the
               present contract has terminated, and no extension is being
               anticipated, funds for supporting these additional studies
               will need to be sought elsewhere.
          (3)  Assuming a patent application is made and a patent is
               granted for the process or product, the rights thereto
               would be governed by the patent provisions in the grant.

          Since the fundamental purpose of this study is to stimulate widespread
interest in and use of this method of solving one difficult phase of the urgent
solid waste disposal problem, it is urged that any obtained patent become an
item of public domain, in order to encourage as widespread use of the process as
possible.

-------
                                          33

          A report of invention has been prepared and is being submitted to the
Grants Officer.  This invention report covers the basic concept of blending
ground automobile tires with bitumens (asphalt or coal tar) and emulsifying the
resulting blends to form water-thinnable compositions suitable for use in treating
blacktop driveways, parking lots, highways, etc.


                                   FUTURE WORK
          An inspection of the exposure series was made with the Project Officer
of this study on May 24, 1973.  At that time, it was mutually agreed between the
Project Officer and Battelle's Columbus Laboratories' personnel that the objective
of the present study had been reached.  Complete feasibility of the basic idea
of bitumen-rubber blends that could be emulsified had been demonstrated.  Therefore,
the objectives of the grant were judged to have been met, and no further work was
judged to be necessary.
          However, the complete success of this study has opened up many in-
triguing possibilities.
          First and foremost, it must be emphasized strongly that the materials
exposed in this study represent only starting point recipes.  The limited program
did not permit (1) selection of the optimum raw materials used to make the emul-
sions, (2) establishment of optimum rubber-bitumen ratios, (3) identification of
best preparation techniques, or (4) conduct long-range storage stability tests.
All of these studies should be carried out before suitable assurance of a marketable
product can result.
          In addition, the observed properties of rubber-bitumen blends point
towards many possibilities for other uses than blacktop dressings.  These might
include
          (1)  Vehicle under-coats
          (2)  Coatings for underground protection of steel structures
               (tanks, pipes, etc.)
          (3)  Roofing (composition and built-up)
          (4)  Marine paints
          (5)  Adhesives
          (6)  Acid-proofing (battery cases, etc.)
          (7)  Waterproofing

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          (8)  Expansion joints (concrete construction)
          (9)  Sound and vibration dampeners
         (10   Sealants
         (11)  Caulking compounds
         (12)  Paper impregnants
         (13)  Ammunition case enamels
         (14)  Thermal insulation
          Each of the above end-uses would require study to develop optimum
compositions.
          Considerable interest in this program has been exhibited by both
government agencies and industrial organizations.  The successful completion
of a study such as this can be expected to result in aiding the solution of a
solid waste disposal problem, and at the same time, development of a saleable
product of improved quality and favorable economics.

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                  APPENDIX

                     A-l


                FORMULA TE-1

Water

Mistron ZCX talc

Calcium Chloride

Asphalt - 5% rubber mix

  Asphalt - 4.275 kg
  Xylos Ix - 0.225 kg


                FORMULA TE-2


Water

Mistron ZCS talc

Calcium Chloride

Asphalt - 5% rubber mix

  Asphalt -  4.275 kg
  Baker Fine - 0.225 kg
 9 kilograms

 3 kilograms

60 grams

 4.5 kilograms
 9 kilograms

 3 kilograms

60 grams

 4.5 kilograms
                FORMULA TE-3


Water

Mistron ZCS talc

Calcium Chloride

Asphalt - 5% rubber mix

  Asphalt - 4.275 kg
  Union Carbide - 0.225 kg
 9 kilograms

 3 kilograms

60 grams

 4.5 kilograms

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                      A-2



                FORMULA TE-4


Water

Mistron ZCS talc

Calcium Chloride

Asphalt - 25% rubber mix

  Asphalt - 3.375 kg
  Baker Fine - 1.125 kg



                FORMULA TE-5


Water

Burgess If20 Clay

Mistron ZCS talc

Indulin W-l

Calcium Chloride

Potassium ricinoleate

Coal tar - 5% rubber mix

  Coal tar - 5.130 kg
  Baker Fine - 0.270 kg
 9 kilograms

 3 kilograms

60 grams

 4.5 kilograms
 7.2 kilograms

 1.2 kilograms

 0.6 kilograms

60 grams

60 grams

60 grams

 5.4 kilograms
                FORMULA TE-6
Water

Burgess //20 Clny

Mistron ZCS talc

Indulin W-l

Calcium Chloride

Potassium ricinoleatf
 7.2 kilograms

 1.2 kilograms

  .6 kilograms

60 grams

60 grams

60 grams

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                      A-3
           FORMULA TE-6 (Continued)
Coal tar - 5% rubber mix

  Coal tar - 5.130 kg
  Xylos Ix - 0.270 kg
 5.4 kilograms
                FORMULA TE-7


Water

Burgess #20 Clay

Mistron ZCS talc

Indulin W-l

Calcium Chloride

Potassium ricinoleate

Coal tar - 5% rubber mix

  Coal tar - 5.130 kg
  Union Carbide - 0.270 kg
 7.2 kilograms

 1.2 kilograms

 0.6 kilograms

60 grams

60 grams

60 grams

5.4 kilograms
                FORMULA TE-8


Water

Burgess #20 Clay

Mistron ZCS talc

Indulin W-l

Calcium Chloride

Potassium ricinoleate

Coal tar - 25% rubber mix

  Coal tar - 4.05 kg
  Union Carbide - 1.35 kg
 7.2 kilograms

 1.2 kilograms

 0.6 kilograms

60 grams

60 grams

60 grams

 5.4 kilograms

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                      A-4
                FORMULA TE-9
Water

Burgess //20 Clay

Mistron ZCS talc

Iftdulin W-l

Calcium Chloride

Potassium ricinoleate

Coal tar - 5% rubber mix

  Coal tar - 5.130 kg
  Baker Fine - 0.270 kg
 7.2 kilograms

 1.2 kilograms

 0.6 kilograms

60 grams

60 grams

60 grams

 5.4 kilograms

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FIGURE A-l.   1 YEAR EXPOSURE - SAMPLE TE-1
FIGURE A-2.  1 YEAR EXPOSURE - SAMPLE TE-2

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                          <*|*&';. .; •. |...- .
                                                i
                                                'i
FIGURE A-3.  1 YEAR EXPOSURE - SAMPLE TE-3
                              t
FIGURE A-4.  1 YEAR EXPOSURE - SAMPLE TE-4

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FIGURE A-5.  1 YEAR EXPOSURE - SAMPLE TE-5
FIGURE A-6.  1 YEAR EXPOSURE - SAMPLE TE-6

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FIGURE A-7.  1 YEAR EXPOSURE - SAMPLE TE-7
FIGURE A-8.  1 YEAR EXPOSURE - SAMPLE TE-8

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-. MMfa.
     FIGURE A-9.  1 YEAR EXPOSURE - SAMPLE TE-9
     FIGURE A-10.  1 YEAR EXPOSURE - SAMPLE CT-C

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FIGURE A-ll.  1 YEAR EXPOSURE - SAMPLE AC

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                                  TECHNICAL REPORT DATA
                           (Please read Instructions on the reverse before completing)
 1 REPORT NO.
     EPA-670/2-74-014
                             2.
                                                         3. RECIPIENT'S ACCESSION-NO.
 4. TITLE AND SUBTITLE
                                                         5. REPORT DATE
                                                          March  1974; Issuing  Date
   Scrap Rubber Tire Utilization in Road Dressings
                                                         6. PERFORMING ORGANIZATION CODE
 7 AUTHOR(S)
                                                         8. PERFORMING ORGANIZATION REPORT NO.
  Benson G. Brand
 9. PERFORMING ORGMWIZATION NAME AND ADDRESS
  Battelle
  Columbus Laboratories
  505 King Avenue
  Columbus, Ohio  43201
             10. PROGRAM ELEMENT NO.

             1DB314;ROAP  24AIN;Task 24
             11 CONTRACT/GRANT NO.
               EP-00500-01
 12 SPONSORING AGENCY NAME AND ADDRESS
  National  Environmental Research Center
  Office of  Research  and Development
  U.S.  Environmental  Protection  Agency
  Cincinnati ,  Ohio  45268
             13. TYPE OF REPORT AND PERIOD COVERED
               Final	
             14. SPONSORING AGENCY CODE
 15. SUPPLEMENTARY NOTES
 16. ABSTRACT
  Research  to demonstrate the feasibility of using rubber from discarded passenger car
  tires  in  water-thinnable emulsions of asphalt or coal tar for blacktop dressings for
  driveways,  etc.,  was conducted.   Nine different compositions containing from 5 to 25
  percent rubber were applied to field test site.  After one year of continuous exposure
  in  a high traffic area, the performance of the experimental compositions appeared to
  be  as  good  as  control  samples.  No attempts at composition optimization were made but
  complete  feasibility of the basic idea has been successfully demonstrated.
 7.
                               KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS  C. COSATI Field/Group
kTires
 Automobile  tires
 Emulsions
 Asphalts
 Road surfacing
kUtilization
 Coal tar
*Scrap rubber  tires
*Road dressings
       11J
       13B
 8 DISTRIBUTION STATEMENT
 Release  to  public
                                             19. SECURITY CLASS (ThU Report)

                                              Unclassified	
                          21. NO. OF PAGES

                                57
20. SECURITY CLASS (This page)

 Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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