EPA-670/2-75-053
May 1975 Environmental Protection Technology Series
USE OF DOMESTIC WASTE GLASS
FOR URBAN PAVING
Summary Report
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-670/2-75-053
May 1975
USE OF DOMESTIC WASTE GLASS
FOR URBAN PAVING
Summary Report
By
Ward R. Malisch
Delbert E. Day
Bobby G. Wixson
Civil Engineering Department
University of Missouri - Rolla
Roll a, Missouri 65501
Program Element No. 1DB314
Project Officer
Norbert B. Schomaker
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
For sale by the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402
rv.uJLGriON AGENCY
„, L
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REVIEW NOTICE
The Solid and Hazardous Waste Research Laboratory of the National
Environmental Research Center - Cincinnati, U.S. Environmental Protec-
tion Agency, has reviewed this report and approved its publication.
Approval does not signify that the contents necessarily reflect 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 summary report is reproduced by the National
Environmental Research Center - Cincinnati in the form received from
the Grantee; new preliminary pages have been supplied. The final
report, including all appropriate background information, has been
published by NTIS. The report accession number is PB-222-052.
11
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FOREWORD
Man and his environment must be protected form 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 components of our physical environment--
air, water, and land. The National Environmental Research
Centers provide this multidisciplinary focus through programs
engaged in
• studies on the effects of environmental contaminants
on man and the biosphere, and
• a search for ways to prevent contamination and to
recycle valuable resources.
In an attempt to solve the problem of solid waste manage-
ment, this study, published by the National Environmental Re-
search Center - Cincinnati, examines research on the use of
waste glass as an aggregate in asphalt paving mixtures. The
potential for using waste glass in asphaltic pavements is
demonstrated in this summary report.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center - Cincinnati
111
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ABSTRACT
Recycling has been suggested as a solution to the problem
of disposing of the increasing quantities of solid wastes gen-
erated in the United States each year. This report summarizes
research on the use of waste glass as an aggregate in asphaltic
paving mixtures. Re-using waste glass in this manner would
provide an outlet for large quantities of the glass and would
permit recycling in urban areas where large accumulations of
glass are found.
Initial laboratory studies showed that asphaltic mixtures
satisfying Marshall design requirements could be designed
using all-glass aggregates and that adequate water-resistance
could be achieved by adding hydrated lime to the aggregates.
Conventional aggregate gradations for dense-graded mixtures
could be used in the mixture and the presence of flat and
elongated particles in the coarse fraction was found to cause
little change in the Marshall properties of glass-asphalt mixtures.
Field installations of asphaltic paving mixtures containing
glass have been placed in several states and in Canada and
field tests as well as observations of the pavement performance
have indicated that these installations have generally main-
tained adequate skid resistance and performed acceptably from
a structural standpoint. Surface deterioration or raveling,
however, has occurred on some of the pavements and further
study of the cause of this raveling is needed.
Based upon the results of a laboratory wear test devel-
oped in this investigation, paving mixtures containing glass
aggregates are more abrasive than mixtures containing some
conventional aggregates. However, the data obtained in the
laboratory wear test are not in agreement with the findings
reported in a British study of tire wear resulting from sur-
faces with varying roughness and micro-texture. Further road
testing to compare tire wear produced by pavements containing
glass and conventional aggregates is recommended.
The economic feasibility of using waste glass as an
aggregate in asphaltic concrete is dependent primarily upon
the development of resource recovery systems which can separate
glass along with other recyclable components and generate
enough revenues from their sale plus disposal and processing
fees to produce an acceptable return on equity. At the present
time it appears that such a system can be economically viable
in a limited number of municipalities. The maximum contribution
to reclaimed product revenues would result if the glass were
color sorted and marketed as cullet. However, if an acceptable
level of color sorting is not possible or if there are no local
markets for the cullet, use of the waste glass as aggregate
should be considered.
iv
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TABLE OF CONTENTS
Page
CONCLUSIONS viii
RECOMMENDATIONS x
ACKNOWLEDGMENTS xii
INTRODUCTION 1
PROPERTIES OF GLASS-ASPHALT MIXTURES 8
FIELD EXPERIENCE WITH GLASS-ASPHALT 21
PAVEMENTS
EVALUATION OF GLASS-ASPHALT PAVEMENT 30
PERFORMANCE
ECONOMIC ANALYSIS 37
REFERENCES 45
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TABLES
Table Page
1 GLASPHALT PAVEMENTS PLACED IN THE 5
UNITED STATES AND CANADA
2 GRADATION OF CRUSHED GLASS USED IN 8
INITIAL DESIGN STUDIES
3 INITIAL MIX DESIGN MARSHALL PROPERTIES 8
AT OPTIMUM ASPHALT CONTENT
4 GRADATIONS USED IN ANGULARITY STUDIES 10
5 MARSHALL PROPERTIES AT OPTIMUM ASPHALT 10
CONTENT FOR GLASS AGGREGATE WITH
MODIFIED GRADATION
6 COMPOSITION OF GLASS-ASPHALT MIXTURES 11
USING GLASS AGGREGATES OF VARYING SHAPE
AND ANGULARITY
7 MARSHALL PROPERTIES OF GLASS-ASPHALT 12
MIXTURES CONTAINING GLASS AGGREGATES
OF VARYING SHAPE AND ANGULARITY
8 IMMERSION-COMPRESSION TEST RESULTS 14
FOR COMMERCIAL ANTI-STRIPPING ADDITIVES
9 IMMERSION-COMPRESSION TEST RESULTS FOR 14
HYDRATED LIME AND LIMESTONE DUST ADDITIVES
10 WHEEL WEIGHT LOSSES ON ASPHALTIC MIXTURES 17
WITH VARIOUS COARSE AGGREGATES
11 WHEEL WEIGHT LOSSES ON ASPHALTIC MIXTURES 18
WITH VARIOUS FINE AGGREGATES
12 WHEEL WEIGHT LOSSES ON FIELD PATCHES 18
WITH VARIOUS AGGREGATES
13 WHEEL WEIGHT LOSSES FOR SURFACES WITH 20
VARYING COEFFICIENTS OF FRICTION
14 AGGREGATE GRADATIONS FOR GLASPHALT 22
FIELD INSTALLATIONS
15 MARSHALL PROPERTIES OF SAMPLES FROM 23
GLASPHALT FIELD INSTALLATIONS
16 RECOMMENDED MINIMUM SKID RESISTANCE 30
REQUIREMENTS
VI
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17 GRADATION OF AGGREGATES USED IN PATCHES 32
FOR SKID RESISTANCE TESTS
18 MARSHALL PROPERTIES OF LABORATORY SPECIMENS 32
FOR SKID RESISTANCE PATCHES
19 MARSHALL PROPERTIES OF LABORATORY 33
COMPACTED FIELD SAMPLES FROM SKID
RESISTANCE PATCHES
20 SKID RESISTANCE OF FIELD PATCHES 33
AFTER 23 MONTHS OF SERVICE
21 SKID RESISTANCE OF FIELD PATCHES 34
AFTER 19 MONTHS OF SERVICE
22 ASSUMED ANNUAL REVENUES FROM RESOURCE 42
RECOVERY SYSTEM
23 ASSUMED RETURN ON EQUITY FROM RESOURCE 43
RECOVERY SYSTEM
VII
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CONCLUSIONS
Asphaltic mixtures satisfying Marshall design criteria
recommended by the Asphalt Institute can be designed using
penetration grade asphalts and aggregates composed entirely
of crushed glass or mixtures of glass and conventional aggre-
gates. Optimum asphalt contents are in the same range (4 to
7 percent) as those required for conventional aggregates.
Water resistance of glass-asphalt mixtures as measured by
laboratory immersion-compression tests is adequate if hydrated
lime is added to the mixture in an amount equal to at least
one percent by weight of the aggregate. Commercial anti-
stripping agents are less effective and the addition of lime-
stone dust does not improve water resistance.
Higher densities for asphaltic mixtures containing glass
aggregates can be obtained by altering the grading ratio
normally used to produce maximum densities with conventional
aggregates. However, this results in air voids and voids in
the mineral aggregate which are below minimum acceptable
values. Thus, higher stabilities which accompany increased
density are obtained at the expense of maintaining a minimum
void content to reduce flushing of asphalt to the surface.
Substitution of angular but nearly equidimensional coarse
glass particles for flat and/or elongated particles obtained
by crushing container glass does not appreciably affect Marshall
properties of asphaltic concrete at a constant asphalt content.
Standard batch plants can be used for mixing asphaltic
mixtures containing glass aggregates, but a mechanical dust
feeder would be desirable since hydrated lime is necessary to
control stripping and manual addition of the lime may result
in delays or inconvenience in the mixing process.
Asphaltic mixtures containing glass aggregates can be
placed and compacted using conventional equipment. These
mixtures may be difficult to compact due to horizontal mix
displacement (crawl) during rolling, and this may necessitate
a delay before breakdown rolling. However, breakdown rolling
should commence as soon as the mat can support the roller
without lateral deformation.
Aggregate degradation as a result of compaction and sub-
sequent traffic over pavements containing glass aggregates is
relatively small for roads carrying light to medium traffic
except when studded tires are used.
The skid resistance of pavements containing glass aggre-
gates is adequate for streets carrying up to 6000 vehicles
per day with speeds up to 30 mph and in service for up to two
Vlll
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years. The substitution of coarse container glass particles
for conventional coarse aggregate may result in lower skid
resistance but the replacement of river sand with crushed
glass fines has no effect upon skid resistance.
Properly designed and constructed asphaltic pavements
containing glass aggregates can be expected to perform well
structurally, with little rutting, cracking, or potholing
occurring. Excessive raveling, however, may develop in
pavements exposed to studded tire traffic and raveling to
a lesser degree may occur due to normal traffic.
Based upon the results of a laboratory wear test devel-
oped in this investigation, paving mixtures containing glass
aggregates are more abrasive than mixtures containing some
conventional aggregates. However, the data obtained in the
laboratory wear test are not in agreement with the findings
reported in a British study of tire wear resulting from
surfaces with varying roughness and micro-texture.
The economic feasibility of using waste glass as an
aggregate in asphaltic concrete is dependent primarily upon
the development of resource recovery systems which can
separate glass along with other recyclable components and
generate enough revenues from their sale plus disposal and
processing fees to produce an acceptable return on equity.
At the present time, it appears that such a system can be
economically viable in a limited number of municipalities.
The maximum contribution to reclaimed product revenues would
result if the glass were color sorted and marketed as cullet.
However, if an acceptable level of color sorting is not
possible or if there are no local markets for the cullet,
use of the waste glass as aggregate is preferable to disposing
of it in a sanitary landfill. This usage would generate some
revenues without incurring additional disposal costs.
IX
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RECOMMENDATIONS
Design of asphaltic paving mixtures containing glass
aggregates should be carried out in accordance with standard
design methods such as the Marshall test procedures outlined
in Mix Design Methods for Asphalt Concrete , published by
The Asphalt Institute. It is recommended that local gradation
requirements commonly specified for dense-graded asphaltic
concrete be used for mixtures containing glass aggregates and
that the aggregate contain at least one percent hydrated
lime by weight.
Conventional batch plants and paving and compaction
equipment can be used in paving with glasphalt but it is
recommended that a mechanical dust feeder be used at the
batch plant for adding hydrated lime to the mixture. The
hydrated lime may be added manually at the pugmill but this
may result in delays or inconvenience in the mixing process.
Standard construction methods should be used in placing
glasphalt pavements, with care being taken to insure adequate
field density. If horizontal mix displacement occurs during
rolling, a lighter roller, a delay in rolling to permit cooling
of the mix, or a combination of the two should be employed
to compact the pavement.
Although adequate Marshall properties have been obtained
for asphaltic mixtures containing glass aggregates, the
raveling of some glasphalt pavements which has occurred under
service conditions points to the need for further observation
of the abrasion resistance of glasphalt pavements. The inter-
action of factors such as the amount of studded tire traffic,
traffic volume and pavement density which affect the raveling
characteristics of pavements containing glass aggregates
should be studied in more detail. If studded tires are the
primary cause of excessive raveling it will be necessary to
restrict the use of glasphalt to binder or base course appli-
cations in areas where studded tires are in use. If excessive
raveling is caused by higher traffic volumes , regardless of
whether or not studded tires are in use, it may be necessary
to restrict the maximum size of glass particles used in the
pavement or to confine the use of glasphalt mixtures to
binder or base courses.
Since results of laboratory wear tests indicate that the
use of glass aggregates may produce a more abrasive pavement
surface, a comparison of the tire wear resulting from glass
aggregates and conventional aggregates is needed. Road tests
are preferred to laboratory tests on a stationary specimen,
due to the difficulties in interpreting results obtained when
abrasion of the test surface is caused by the test wheel.
x
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While the skid resistance of pavements containing glass
aggregates has proved to be adequate, tests have shown that
replacement of crushed stone coarse aggregate with glass
particles in mixtures of similar gradation and asphalt content
reduces skid resistance. Thus it is recommended that for
surface courses, the use of coarse glass aggregates should
be restricted to roads carrying low-speed traffic (30 mph or
less).
The experimental field installations of glasphalt placed
to this date have utilized clean glass containers which were
crushed to obtain the desired gradation. Placing and per-
formance characteristics of the pavements were of primary
interest and crushing costs for the glass were not a major
concern. However, unit crushing costs are likely to be high
when relatively small amounts of glass are crushed because
of the time consumed in adjusting crusher settings for
feeding the containers, making necessary modifications to
produce the desired gradation and cleaning glass out of the
crusher upon completion of the crushing operation. For this
reason, small volumes of crushed glass prepared in this manner
cannot be processed at as low a cost as conventional aggregate,
and use in glasphalt is not recommended as an economical means
for reusing glass under these conditions. Resource recovery
systems which are currently being developed incorporate
crushing at several stages in the process, though, so that the
glass fraction produced would be in a usable form without
further crushing. It is recommended that this glass fraction
be considered for use as aggregate since such a usage has
been shown to be technically feasible.
XI
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ACKNOWLEDGMENTS
The project is indebted to many individuals and private
as well as public agencies throughout the nation for infor-
mation and assistance in the conduct of the study. The list
of those who have been particularly helpful includes the
following:
John H. Abrahams, Jr., Glass Container Manufacturers
Institute, Washington, B.C.
Harold A. Aschinger, Anchor Hocking Corporation,
Winchester, Indiana
W. R. Bennett, Ontario Department of Highways
H. Elliot Dalton, Glass Container Council of Canada
Charles G. Depew, Owens-Illinois, Inc., Toledo, Ohio
J. J. Kaller (Retired), Municipality of Burnaby,
Burnaby, British Columbia
Henry Kayser (Retired), Industrial Asphalt, Van
Nuys , California
Milton F. Masters, Industrial Asphalt, Van Nuys,
California
De L. Miller, Brockway Glass Co., Brockway,
Pennsylvania
Pickett Scott, Glass Containers Corporation,
Fullerton, California
Thomas A. Smith, Omaha Testing Laboratories, Inc.,
Omaha, Nebraska
and officials of the California, Pennsylvania, Ontario, and
British Columbia Departments of Highways.
Graduate research assistants who participated in the
study included Charles Foster, Michael Korth, John Doyle,
Thomas Keith, Ching-Tzu Lu and Dwarka Gupta.
Xll
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INTRODUCTION
Need for the Study
The increasing quantity and changing character of solid
wastes generated in the United States each year have resulted
in an urgent need to develop improved means for processing
and disposing of these wastes. Recycling and re-use of ma-
terials have been suggested as a solution to this problem.
The rationale for recycling generally includes reduction
of the volume of the waste stream destined for final disposal
as well as conservation of resources. Factors of importance
when considering a recycling program for any waste component
are, therefore, the volume or size of the fraction of the
waste stream constituted by a particular type of waste, and
the nation's source of raw materials from which the item or
group of items were made. Obstacles to recycling are the
heterogenity of wastes, high transportation costs if re-
claimed materials cannot be used in the area where they are
generated, lack of stable markets and prices for salvageable
materials , and absence of a suitable technology for separating
and treating mixed refuse. All these factors have been con-
sidered in the development of a new means for recycling one
of the waste components -- glass.
Approximately 250 million tons of household, commercial,
and municipal wastes are generated in the United States each
year,^ and studies of refuse composition indicate that glass
comprises some 6 to 11 percent by weight of this material3-5
or at least 15 million tons annually." While this does not
represent a major portion of the total waste stream, recycling
a significant amount of glass would decrease the volume of
material destined for ultimate disposal. However, due to the
abundance and low cost of the principal raw materials used for
glass manufacture, conservation of resources is not a major
incentive for recycling at the present time.
Waste glass (cullet) has historically been used in the
manufacture of new glass containers.? This represents the
highest value of re-use since cullet of suitable quality has
a raw material replacement value of 10 to 20 dollars per ton.
However, glass used in this manner must be essentially free
of non-glass components and color-sorted. Even if suitable
technology is developed for separating municipal wastes, the
economic benefits from such a separation will depend upon
the availability of markets, with an important consideration
being the transportation costs involved.
The research described in this final report deals with
the use of waste glass as an aggregate in asphaltic mixtures
used for urban paving and street maintenance operations. Many
of the problems in recycling waste glass to glass furnaces
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can be avoided by using the glass as an aggregate. If waste
glass is to be returned to the furnaces, impurities must be
removed since they may cause erosion of the furnace refrac-
tories or alter the color characteristics of the glass.^ As
little as a tenth percent copper or a few tenths percent iron
will produce appreciable color in clear glass. While the
separation of glass from other refuse is still necessary if
it is to be used as aggregate, contamination by non-glass
components is not as critical. Laboratory tests have indi-
cated that asphaltic mixtures can be designed to meet require-
ments for stability, flow and void content using glass separated
from municipal refuse and containing up to 17 percent non-
glass components. Color separation is not necessary for
glass used as aggregate, and transportation costs are mini-
mized since the waste glass can be used in the urban area
where it is generated. By substituting g,lass for portions
of the conventional aggregates used in city street construction
or maintenance, a steady market would be assured for this
waste component.
The diminishing natural aggregate supplies in some urban
areas further enhance this concept since aggregate costs in-
crease with increasing haul distances. The depletion of
suitable aggregate sources in localized areas and regions
has led national highway officials to study promising re-
placements for conventional aggregates for highway use.
The volume of waste glass is small when compared to the amounts
of aggregate required for highway construction; consequently,
it is not expected that glass will comprise a significant
percentage of the aggregate used for this purpose. However,
this use has the potential for utilizing all of the waste
glass that can be economically separated from refuse in urban
areas of the United States.
Development and Resume of the Study
The possibility of using waste glass as an aggregate in
asphaltic concrete grew out of a special problem assignment
in a ceramic engineering class at the University of Missouri-
Rolla. A preliminary assessment of the potential problems
which might be encountered included consideration of possible
poor adhesion between asphalt and glass in the presence of
water, adverse effects of flat and elongated particles on
mixture density, low strengths and poor skid resistance due
to the smooth surface texture of glass, and increased tire
wear due to the sharp, angular particles.
Promising results obtained in pilot tests conducted on
asphaltic mixtures containing glass aggregates led to the
funding of a research project by the U. S. Public Health
Service Bureau of Solid Waste Management. The overall pur-
pose of this project was to determine whether waste glass
could be used as an aggregate in asphaltic mixtures for street
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construction or maintenance and to demonstrate its potential
use as a method for disposing of urban glass waste. The
specific objectives were to:
1. Acquire engineering data on glass-asphalt mixtures
with respect to suitable particle size ranges for
the glass aggregate, proper type and grade of as-
phalt to be used, and the range of asphalt contents
satisfying stability, durability, and workability
requirements.
2. Institute a field testing program in which glass-
asphalt mixtures would be used in actual paving
operations.
3. Compile the information resulting from the study
for use in recommending design and construction
procedures which permit the effective utilization
of waste glass.
Initial mix design studies showed that asphaltic mixtures
satisfying standard design criteria could be designed using
aggregates composed entirely of glass. However, these mixtures
had very poor water resistance due to stripping of the asphalt
from the glass particles when specimens were immersed in water.
Tests were then conducted to investigate means by which the
water resistance could be improved. Commercial anti-stripping
agents improved the water resistance to a limited extent, but
the most effective additive was hydrated lime. The addition
of one percent hydrated lime by weight of the aggregate
eliminated stripping in laboratory tests.
Upon learning of our work in evaluating glass-asphalt
paving mixtures, Owens-Illinois, Inc. became interested in
the project and volunteered to install a small test section
at their technical center in Toledo, Ohio. In October of
1969, the first pavement containing glass aggregates was
placed by Owens-Illinois and the word "glasphalt" was used
to describe the material. The publicity resulting from this
first field installation generated wide interest in the con-
cept and since then 19 additional experimental glasphalt
pavements have been placed in the United States and Canada.
The Glass Container Manufacturers Institute and several
member glass companies were instrumental in planning and
financing many of these installations , in cooperation with
the project staff at the University of Missouri-Rolla.
Several state and municipal agencies as well as private
industries also became involved in the construction of
glasphalt pavements. A current listing of the glasphalt
test sections installed during the duration of our research
project is given in Table 1. Tests and observations of the
performance of these test sections which were subjected to
varying types and volumes of traffic and climatic conditions
have provided valuable data for assessing the technical feasi-
bility of glasphalt pavements.
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Further laboratory testing was also conducted to deter-
mine the effects of particle size distribution upon mechanical
properties and to compare the abrasiveness of asphaltic
mixtures containing glass with mixtures containing conventional
aggregates.
Results of laboratory and field tests on asphaltic
mixtures containing glass aggregates have demonstrated that
acceptable pavements can be constructed using this material.
Conventional methods for placing and compaction can be
employed and adequate performance has resulted in most
installations. Surface deterioration or raveling has occurred
on some of the glasphalt pavements, but otherwise the struc-
tural performance has been good and the skid resistance has
been found to exceed tentative minimum recommended limits.
The potential for using waste glass in asphaltic pave-
ments has been demonstrated and there are no insurmountable
technical problems associated with this usage. However,
present techniques for recovering glass from refuse impose
economic limitations on the successful utilization of this
method for re-using the glass. Hand-picking is expensive
and even if containers are collected at recycling centers
using donated labor, crushing is required. Due to the
relatively small volume of glass involved, unit crushing
costs are high. Consequently, the economic feasibility of
employing waste glass as aggregates will depend on the
development of large scale systems for separating refuse
into usable components including a glass fraction which
could preferably be used in glasphalt with a minimum of
further processing.
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PROPERTIES OF GLASS-ASPHALT MIXTURES
Marshall Properties
To determine the feasibility of using waste glass as
aggregates, initial studies were conducted using mixtures
consisting of asphalt and all-glass aggregates. Non-returnable
glass containers were washed to remove labels and other foreign
material, dried and then crushed and separated into size
fractions ranging from 1/2-in. through minus 200 mesh material.
Using the gradation shown in Table 2, and ah 85-100 pene-
tration asphalt cement, a mixture was designed which met
requirements for stability, flow and voids recommended by The
Asphalt Institute for pavements subjected to medium traffic.
The properties of this mixture containing 5.5 percent asphalt
on a total weight basis are shown in Table 3.
TABLE 2
GRADATION OF CRUSHED GLASS USED IN INITIAL
DESIGN STUDIES
Sieve Size Percent Passing
1/2-in.
3/8-in.
No.
No.
No.
No.
No.
No.
No.
4
8
16
30
50
100
200
100
88
67
48
37
28
18
11
6.
3
TABLE 3
INITIAL MIX DESIGN MARSHALL PROPERTIES AT
OPTIMUM ASPHALT CONTENT
Stability, Ibs 770
Flow, .01-in. 8
Air Voids, % 3.39
VMA, % 15.52
Unit Weight, pcf 139.4
Initial mix design studies with glass aggregates utilized
a gradation which produces maximum density for aggregates with
nearly equidimensional particle shapes. However, since the
-------
coarse crushed glass contained a large number of flat or
elongated particles, studies were conducted to determine whether
higher stabilities could be obtained by modifying the gradation
to produce a denser mixture. Dry density tests were conducted
on mixtures of glass particles with varying shape and angu-
larity by altering the gradation and noting the effects upon
density. Types of glass used in this investigation included
crushed container glass with a large number of flat and elon-
gated particles and an angular shape, drain cullet and tempered
glass which consists of angular nearly equidimensional particles
and glass beads which were rounded and equidimensional. The
gradations used were computed from the relationship:
P = (-)n
VD
where P is the cumulative percent passing a sieve having an
opening of size d for an aggregate having a maximum size of
D. The grading ratio, n, was varied from 0.30 to 0.55 and
the resulting changes in density were noted. It was found
that maximum density for the glass spheres occurred at
n = 0.475, but at n = 0.375 for crushed container glass and
0.400 for the drain cullet and tempered glass combination.
Since maximum bulk density was obtained with the container
glass at a grading ratio of 0.375, Marshall test specimens
were molded using this gradation (Table 4) and asphalt contents
ranging from 4.0 to 6.0 percent. Results of stability, flow,
air voids and voids in the mineral aggregate determinations
for these mixtures indicated that there was no asphalt content
at which acceptable mixture properties were obtained since air
voids and voids in the mineral aggregate were too low. The
gradation was then modified as shown in Table 4 and a second
series of specimens was made with asphalt contents ranging
from 3.5 to 6.0 percent. Specimens with an asphalt content of
5.25 percent met Marshall requirements specified by The Asphalt
Institute. The properties of this mixture are shown in Table
5. However, the stability obtained with this gradation was
approximately equal to the stability of specimens using the
initial gradation shown in Table 2. Consequently, although
higher densities did produce larger stability values, low air
voids for the high density mixtures made them unacceptable,
and when gradation was modified to produce high enough void
contents, the stability decreased to previously obtained
levels.
The effects of angularity and sphericity of aggregates on
Marshall properties were determined from specimens made using
the modified gradation shown in Table 4, and an asphalt content
of 5.25 percent. The four different combinations of glass used
are shown in Table 6. Mixes A, B, and C all contained crushed
container glass in sizes smaller than a No. 8 sieve, but con-
tainer glass coarse aggregate was used in Mix A, drain cullet
and tempered glass coarse aggregate were used in Mix B, and
glass spheres were used as coarse aggregate in Mix C. The
aggregate for Mix D consisted entirely of glass spheres. Three
-------
specimens were molded and tested for each aggregate combination
and the results are shown in Table 7.
TABLE 4
GRADATIONS USED IN ANGULARITY STUDIES
Percent Passing
Sieve Size n = .375 n = .375 (modified) n = .550
1/2-in.
3/8-in.
No. 4
No. 8
No. 16
No. 30
No. 50
No. 100
No. 200
100
90
69
50
38
28
20
15
10
100
91
71
57
45
30
19
9
5
100
85
58
41
28
18
13
9
6
TABLE 5
MARSHALL PROPERTIES AT OPTIMUM ASPHALT
CONTENT FOR GLASS AGGREGATE WITH MODIFIED GRADATION
Stability, Ibs. 750
Flow, .01-in. 10
Air Voids, % 3.5
VMA, % 15.25
Unit Weight, pcf 139.6
Substitution of the more nearly equidimensional drain
cullet and tempered glass for coarse bottle glass particles
caused a slight increase in air voids and VMA with a slight
decrease in stability. When glass spheres were substituted
for the coarse container glass, air voids and VMA decreased,
but there was also a substantial decrease in stability. The
decrease in stability was probably due to a reduction in the
interlocking resistance developed between the coarse particles.
This effect was even more pronounced when container glass was
replaced by glass spheres in all sizes , with the specimens
having virtually zero stability and a higher air void content.
This mixture was very difficult to compact since it rebounded
after each blow of the compaction hammer.
To further assess the effects of angularity and sphericity
of coarse particles, a second series of tests was made using
a gradation containing a higher percentage of material coarser
than the No. 8 sieve. A gradation computed with an exponent of
0.55 (Table 4) was used at an asphalt content of 5.25 percent
10
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and mixtures with crushed container glass, drain cullet and
tempered glass, and glass spheres were compared. Substitution
of drain cullet for container glass had little effect upon air
voids and VMA and decreased stability only slightly. Glass
spheres in the coarse fraction once again reduced air voids and
VMA and resulted in a significant decrease in stability as shown
in Table 7.
The large percentage of flat and elongated particles in
the coarse fraction of the crushed container glass aggregates
had little effect upon the Marshall properties of the glass-
asphalt mixtures, since the substitution of more nearly equi-
dimensional particles in the coarse sizes did not improve the
stability and there was little change in void content or flow.
The results show that particle angularity, however, has a
pronounced effect on stability with less angular particles
producing lower stabilities. Thus the large percentage of
flat particles in the coarse fraction of glass aggregates
should not be a problem with respect to their effects upon
Marshall properties, and the angularity of these particles
is beneficial to the stability of the mixture. Spherical
glass particles should be avoided due to the adverse effect
upon stability, but since little if any of a crushed waste
glass fraction is likely to contain spherical particles, a
restriction on such particles should not create any diffi-
culties in producing glass aggregates.
Water Resistance
In initial mix design studies it was noted that stripping
or loss of adhesion betwaen the asphalt and glass occurred when
specimens were immersed in water. Immersion-compression tests
were used to evaluate the effectiveness of several anti-stripping
agents added at varying addition levels.
The agents investigated included three commercially manu-
factured asphalt additives, hydrated lime and limestone dust.
These were used in specimens containing all-glass aggregates
and having an asphalt content of 5.5 percent by weight. The
aggregate gradation is shown in Table 2. The commercial anti-
stripping agents were added to the asphalt at three addition
levels of 1, 2 and 4 percent by weight of the asphalt. Hydrated
lime was substituted for minus 200 mesh glass at three different
addition levels (5.4, 1.9 and 0.9 percent by weight of the
aggregate) and limestone dust was substituted for minus 200
mesh glass at one addition level (6.5 percent by weight of
the aggregate).
Results of the tests are given in Tables 8 and 9. The
percent retained strength given is the average strength of
three specimens tested dry divided by the average strength of
three specimens tested after immersion in water at 140F for
24 hours. The commercial anti-stripping agents were only
13
-------
marginally effective in improving water resistance. At the
4 percent addition level, which is more than double the
manufacturer's recommended amount, the maximum retained strength
was 71 percent. The addition of limestone dust resulted in no
improvement in water resistance but a substantial increase in
water resistance was achieved by additions of hydrated lime.
The use of approximately 1 percent hydrated lime by weight of
the glass aggregate resulted in 100 percent retained strength
which was considered to be satisfactory.
TABLE 8
IMMERSION-COMPRESSION TEST RESULTS FOR
COMMERCIAL ANTI-STRIPPING ADDITIVES
Additive
Retained Strength, %
Control
Pavebond
2%
4%
No-Strip
1%
2%
4%
De-Hydro
H86C
1%
2%
4%
0
0
41
71
0
47
67
18
0
32
^Percent added by weight of asphalt
Additive
TABLE 9
IMMERSION-COMPRESSION TEST RESULTS FOR
HYDRATED LIME AND LIMESTONE DUST ADDITIVES
Retained Strength, %
Hydrated Lime
5 . 4%*
1.9%
0.9%
Limestone Dust
6.5%
110
192
100
^Percent added by weight of aggregate
14
-------
Degradation of Glass Aggregates
Sieve analyses were conducted on all-glass aggregates
recovered from Marshall specimens which had been tested for
stability. This was done to assess the degree to which the
gradation of glass aggregates changed due to breakage caused
by laboratory mixing, compacting and testing procedures.
Six specimens were chosen from each of two trial mix
series and Hudson's A was calculated for uncompacted and
compacted mixtures. Hudson's A is one-hundredth of the sum
of the percentages passing the ten U. S. Standard sieves
starting with the 1 1/2-in. and including the No. 200 sieve.
In the first trial mix series, Hudson's A increased from 5.03
for uncompacted mixtures to an average of 5.11 for compacted
specimens which had been tested at asphalt contents varying
from 4.5 to 7.0 percent. In the second trial mix series the
increase was from 5.03 to an average of 5.19. In previous
studies of aggregate degradation^1-1 an increase in the Hudson's
A value of 0.25 due to field compaction and an increase of
0.39 due to field compaction and traffic were both considered
to be minor and insufficient to affect the service behavior
of the pavement. Thus, the degradation of glass aggregates
due to laboratory mixing, compacting and testing was not
considered to be excessive.
Abrasiveness of Glass-Asphalt Mixtures
In order to determine the effects of glass aggregates
upon tire wear, a laboratory testing apparatus was developed
to determine the relative abrasiveness of compacted paving
mixtures containing varying combinations of glass and con-
ventional aggregates. The apparatus consisted of a rubber
wheel of standard composition which was rotated while in
contact with the surface of a small sample of the compacted
paving mixture. Weight loss for the wheel was measured and
used as an indication of the abrasiveness of the surface.
Two sets of sixteen specimens each were molded in the
laboratory. Each compacted specimen was 3 1/2-in. wide and
6-in. long with a thickness of 1 1/2-in. One set contained
four different coarse aggregates (plus No. 8 material): glass,
traprock, limestone and river gravel, combined with a crushed
container glass fine aggregate. The asphalt content was 5.5
percent and 1 percent hydrated lime by weight of the aggregate
was added. Each specimen was compacted with 100 blows using
a standard Marshall compaction hammer which was modified by
adding a rectangular compaction plate 3 1/2-in. wide and 6-in.
long.
The other set of specimens contained four different fine
aggregates (minus No. 8 material): glass, traprock sand,
limestone sand and river sand combined with a limestone coarse
15
-------
aggregate. Composition and preparation procedures for the
specimens were identical to those used for the coarse aggre-
gate test series.
In order to assess the abrasiveness of asphaltic mixtures
which had been subjected to traffic and weathering, specimens
were cut from field patches which had been placed for use in
studying the skid resistance of mixtures containing glass
and conventional aggregates. Samples were sawed from patches
containing five different combinations of glass and conventional
aggregates which had been subjected to traffic for 23 months.
These combinations were: all-glass, limestone-glass, gravel-
sand, gravel-glass, and limestone-sand.
Ten locations on the specimen surface were chosen by
superimposing a numbered grid on the surface and randomly
choosing ten numbers corresponding to ten different locations.
The test wheel was weighed and mounted in the apparatus,
placed on the first location, then rotated for three minutes
at 100 rpm while in contact with the surface. It was then
moved within thirty seconds to a new location and rotated
for three minutes at 100 rpm. This procedure was repeated
at each of the remaining locations with a thirty second inter-
val in which to position the wheel, after which the wheel was
removed from the apparatus and weighed to determine weight
loss.
A test was conducted on both sides of each laboratory
compacted specimen and a different wheel was used for each
of the four mixtures containing different aggregates which
were made on the same day. Thus, there were four replications
requiring four wheels for each the coarse and fine series
testing.
In testing the samples cut from patches which had been
in service for two years, six specimens were cut from each
of the five patches. Three different wheels were used and
each wheel was used on two specimens.
During testing, as the temperature of the wheel increased,
the specimen surface was severely abraded by the wheel. An
attempt was made to decrease this abrasion by inserting a
spring between the top sleeve bearing and the loading plat-
form. This reduced the contact pressure on the wheel from
55 to 31 psi. However, in tests conducted at this loading,
wheel weight losses were extremely small, making it difficult
to draw conclusions about differences in specimen composition.
A further attempt to decrease the abrasion was made by in-
creasing the number of locations on the test specimen from 10
to 15 and decreasing the test period from 3 to 2 minutes per
location. This procedure, however, still produced surface
16
-------
abrasion. Consequently, it was decided to conduct the tests
at 10 locations with a three minute duration at each location,
Wheel weight losses measured in the three sets of tests
conducted are shown in Tables 10 through 12. An analysis of
variance procedure was used to compare mean weight losses
produced by the varying aggregate combinations. Where sig-
nificant difference among the means was indicated, single
degree of freedom comparisons were made to compare mixtures
containing glass aggregates with conventional aggregate
mixtures.
TABLE 10
WHEEL WEIGHT LOSSES ON
ASPHALTIC MIXTURES WITH VARIOUS
COARSE AGGREGATES
Replications
Weight Loss
(g.)
Glass
Traprock-
Limestone
Gravel
Top
Bottom
2 Top
Bottom
TOD
Bottom
4 Top
Bottom
Mean
Weight
Loss
1.9
1.7
1.8
1.4
1.35
1.70
2.4
1.2
1.70
1.1
1.1
2.15
1.80
1.65
1.00
1.4
1.2
1.45
1.0
0.8
1.30
1.50
0.95
1.10
1.1
1.0
1.10
1.4
1.0
1.2
1.3
1.1
1.3
1.5
1.0
1.25
17
-------
TABLE 11
WHEEL WEIGHT LOSSES ON
ASPHALTIC MIXTURES WITH VARIOUS
FINE AGGREGATES
Replications
, Top
Bottom
2 Top
Bottom
3 T°P
Bottom
H Top
Bottom
Mean
Weight
Loss
Weight Loss
(g.)
Glass
0.8
0.6
1.2
0.4
1.3
0.8
1.2
0.9
0.9
Traprock
0.6
0.8
0.6
0.2
0.8
0.3
0.6
0.2
0.5
Limestone
0.4
0.6
0.6
0.6
0.9
0.4
0.8
0.6
0.6
Sand
0.8
0.6
1.1
0.8
0.9
1.1
0.7
1.0
0.9
TABLE 12
WHEEL WEIGHT LOSSES ON
FIELD PATCHES WITH
VARIOUS AGGREGATES
Replications
All-
Glass
1
2
3
First
Second
First
Second
First
Second
Mean
Weight
Loss
1.
2.
2.
1.
2.
1.
2.
7
5
0
3
8
6
0
Weight
(g
Loss
.)
Limestone- Gravel-
Glass Sand
0.
0.
0.
0.
1.
0.
0.
8
8
6
9
0
9
85
0.
0.
0.
1.
0.
0.
0.
5
9
6
1
6
6
70
Gravel-
Glass
1.
2.
1.
1.
1.
1.
1.
3
0
6
1
7
4
50
Limestone-
Sand
0
0
0
0
0
0
0
.4
. 8
.6
.4
.4
.6
.55
In the set of specimens containing different coarse
aggregates, a statistically significant difference among means
was indicated at a 0.05 significance level. The mean wheel
weight loss for tests on mixtures containing coarse glass was
18
-------
greater than that for mixtures containing either limestone or
gravel coarse aggregates, but was not significantly different
from the weight loss produced by mixtures containing traprock.
For specimens containing different fine aggregates, a
statistically significant difference among means was also
indicated at a 0.05 significance level. The mean wheel
weight loss for tests on mixtures containing glass fines
was greater than that for mixtures containing either lime-
stone or traprock fine aggregates, but was not significantly
different from the weight loss produced by mixtures containing
river sand.
Results of wear testing on the field samples were in
agreement with the tests on laboratory compacted specimens
when mixtures containing coarse glass aggregates were com-
pared with mixtures containing conventional coarse aggregates.
The mean weight loss resulting from tests on all-glass mixtures
was significantly higher than weight losses measured for
gravel-glass and limestone-glass mixtures. Comparison of
weight losses between limestone-glass and limestone-sand
mixtures also confirmed the finding that no significant
difference in wear resulted from the substitution of fine
glass for river sand. However, a significant difference in
weight loss was found when comparing gravel-sand and gravel-
glass mixtures. The gravel-glass mixture produced higher
weight losses than were found with gravel-sand mixtures.
It is interesting to compare these results with the
results of studies by Lowne-'--'- on the effects of road surface
texture on tire wear. His data indicate that wet coefficient
of friction and a factor related to the density and shape of
asperity tips can be used to predict tire wear ratings for
differing surfaces, with higher coefficients of friction and
greater density and sharpness of the asperity tips resulting
in higher wear. Macro-texture, indicated by surface rough-
ness which can be seen by eye, was found to be only a slightly
modifying factor in tire wear.
In our studies, the coefficient of wet friction was
measured with a British Portable Tester on the field patches
immediately before they were tested in the laboratory wear
apparatus. The average wear corresponding to differing
coefficients of friction is shown in Table 13. There is a
trend toward decreasing weight loss with increasing skid
resistance, whereas Lowne's study indicates that the reverse
should be true. Furthermore, the data from tests on labora-
tory compacted specimens with differing fine aggregates show
a trend toward decreasing wear or wheel weight loss with
increasing angularity, while Lowne's data suggests that
sharper asperity tips should increase wear. Since the surface of
19
-------
specimens tested in the laboratory wear test was severely
abraded by the spinning wheel, the effect of initial coef-
ficient of friction was minimized. Abrasion would also be
expected to continuously expose new particle tips so that
polishing of the surface which might take place under traffic
conditions would not occur in the laboratory test. Conse-
quently, the laboratory testing method may not accurately
reflect differences in tire wear resulting from surfaces of
varying composition.
TABLE 13
WHEEL WEIGHT LOSSES FOR SURFACES
WITH VARYING COEFFICIENT OF FRICTION
Mixture Wet Coefficient Av. Wt. Loss
of Friction (g. )
All glass O.H85 2.0
Limestone-glass 0.528 0.85
Limestone-sand 0.561 0.55
Gravel-glass 0.503 1.50
Gravel-sand 0.483 0.70
20
-------
FIELD EXPERIENCE WITH GLASS-ASPHALT
PAVEMENTS
Asphaltic concrete pavements utilizing glass aggregates
have been placed at several locations in the United States
and Canada. In all of these installations, glass has been
blended with conventional aggregates with varying percentages
of glass being used. Design and construction data for several
of these pavements are summarized in Tables 14 and 15 and in
the following discussion.
University of Missouri-Rolla
A road to the University general services building and
central receiving area was paved with glasphalt on July 10,
1970. Traffic density on this road is approximately 700
vehicles per day with 10 percent heavy trucks. The portion
paved was 525 feet long and 20 feet wide with a thickness of
1 1/2 inches. It was placed over an existing surface treat-
ment in which chuck-holes had been patched with cold mix
prior to tacking with a diluted SS-1 emulsion.
The glass used for this project was donated by member
companies of the Glass Container Manufacturers Institute and
was a relatively coarse mixture of drain cullet and clean
broken bottle glass. The mix was designed to include 63
percent glass, 33 percent fine sand and 4 percent hydrated
lime. While only 1 percent hydrated lime is necessary to
provide adequate water resistance, 4 percent was used because
the fine aggregate employed in the mixture did not contain
enough minus 200 mesh material and only two cold bins were
available so that a third aggregate could not be blended
into the mixture. Thus, the hydrated lime was used as a
source of fines as well as an anti-stripping agent.
During construction, the material was mixed in a batch
plant at 275F with an 85-100 penetration asphalt cement at an
asphalt content of 5.75 percent (total weight basis). Aggre-
gate gradation based upon hot bin analysis is given in Table
14. After placing half of the pavement the supply of coarse
glass was nearly exhausted and the gradation was modified as
shown in Table 14. This gradation with an asphalt content of
5.5 percent was used for the remainder of the paving operation,
Marshall properties of laboratory compacted field samples for
both mixtures are given in Table 15.
A conventional paver and 2-ton roller were used for
placing and compaction. Both mixtures were tender and it
was necessary to defer breakdown rolling until the mixture
temperature had dropped to 225F.
21
-------
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Sawed samples of the compacted pavement were taken 3 days
after compaction and at one year intervals thereafter. After
2 years the coarse mixture had reached 98.0 percent of the 50
blow Marshall density while the fine mixture had reached 98.2
percent. After extracting the asphalt from these samples,
washed sieve analyses were conducted on the aggregate.
Hudson's A had increased from 5.12 for an uncompacted plant
sample to 5.27 for a pavement sample of the coarse mixture
after two years of service. The fine mixture Hudson's A had
increased from 5.43 to 5.60 after two years.
A British Portable Skid Tester was used to measure the
skid resistance of the pavement at approximately 1 to 3
month intervals for the first year and at approximately 6
month intervals thereafter. Measurements were made in the
wheel tracks at 10 different locations for each mixture. After
two years of service the average British Pendulum Number was
49.5 for the coarse mixture and 52.0 for the fine mixture.
The pavement was in good condition after two years of service
except for an area of alligator cracking caused by base failure.
Glass Containers Corporation
A street in the Fullerton Air Industrial Park in Fuller-
ton, California, was paved with glasphalt on October 26,
1970. The street was 600 feet long and HO feet wide. Thirty
feet of the width was paved with a 3-in. thick layer of
glasphalt with the other 10 feet of width being paved with
conventional asphaltic concrete. The base course was a 7 1/2-
in. thick layer of crushed rock equivalent to California
Division of Highways Class 2 aggregate base. The subgrade
was a silty sand which had been compacted to at least 90
percent of maximum density as determined in the laboratory
in accordance with the requirements of the California
Standard Specifications.
All of the glass used for this project was obtained by
crushing clean non-returnable bottles in a hammermill. The
glass was blended with rock dust and hydrated lime in a
mixture of 63 percent glass, 36 percent rock dust and 1
percent hydrated lime.
The design asphalt content chosen was 5.5 percent (total
weight basis) with a 60-70 penetration asphalt cement being
used. Aggregate gradation based on hot bin analyses is shown
in Table 14. Results of Marshall tests on a sample taken at
the plant are given in Table 15.
The material was mixed in a batch type plant with a
4000 Ib pugmill and the hydrated lime was added by hand at
the pugmill. The 3-in. thick layer was placed and compacted
with an 8-10 ton tandem roller. Initial attempts at compaction
resulted in excessive crawl even at temperatures of 220F.
Breakdown rolling was carried out at temperatures of 22OF and
below.
24
-------
Tests conducted on cores removed from the compacted
pavement indicated a unit weight of 131.4 pcf or 93.5 percent
compaction. This low unit weight is believed to be due to the
difficulties in compacting the mixture at temperatures above
220F. Little further increase in density had occurred after
one year when additional cores were obtained. Aggregate
gradations based upon wet sieve analyses of the cores after
extraction were used to_calculate changes in Hudson's A due to
degradation. Hudson's A had increased from 4.58 for a plant
sample to 4.87 for a pavement sample after one year of service.
On March 2, 1971, skid tests were conducted on the glas-
phalt pavement by the California Division of Highways. The
towed trailer method (ASTM E-274) was used at a test speed of
25 mph and the skid number at 25 mph ranged from 61 to 69
which converts to 54 to 62 at 40 mph.
After one year of service, the pavement surface exhibited
some raveling caused by the fracture of larger glass particles
at the surface. However, the overall condition of the surface
was good and its performance has been considered to be satis-
factory .
Bramalea, Ontario
A private road at the Dominion Glass Company's Bramalea,
Ontario, plant was paved with glasphalr on August 29, 1970.
The roadway width paved was 18 feet and the length was
approximately 500 feet. The mix was placed in two courses,
each of 1 1/2-in. compacted thickness, giving a total com-
pacted thickness of 3 inches.
Glass bottles for the project were crushed in a Pioneer
Model 40V duplex crusher to produce coarse and fine fractions
which were blended with a natural sand. Trial mixes at
various asphalt contents using an 85-100 penetration asphalt
cement were tested and the mix selected consisted of 39
percent coarse glass, 29.5 percent fine glass, 29.5 percent
natural sand, 2 percent hydrated lime and 5 percent asphalt
on a total weight basis. The gradation of the combined
aggregate is shown in Table 14.
A Barber-Greene 4000 Ib. Batch-o-matic batch plant was
used for mixing the material at 275F and the haul distance
from the plant to the Bramalea project was approximately 25
miles. The paving operation used a Barber-Greene Model
SA-40 paver and three rollers were used on the project: a
Buffalo-Springfield KT8-4-6 ton steel-tired roller, a Gallon
Rollomatic 12-14 ton steel-tired roller and a Bros 7-wheeled
SP-6000 rubber tired roller. The first two loads of glasphalt
were breakdown-rolled with the 14-ton steel-tired roller. The
mix was too tender to support this heavy roller initially and
the mix had to be left to cool. The procedure was then changed
25
-------
to breakdown with the 5-ton steel tired roller followed by the
pneumatic-tired roller. This sequence gave good results with
no difficulty in rolling or pick-up. Average Marshall proper-
ties of field samples are shown in Table 15.
In September 1970, four skid tests were conducted using
an ASTM skid trailer at 20 mph. The skid numbers obtained
were 47, 56, 53, and 61 with an average of 54. Skid tests
are normally carried out at speeds of 30 and 60 mph but these
speeds could not be obtained because of the configuration of
the test area. The minimum skid number fo a 30 mph speed is
36 and based upon experience, as well as a study of the sur-
face texture, it was concluded that the glasphalt skid number
at the higher speeds would be higher than the minimum require-
ment .
Approximately 10 weeks after the glasphalt had been placed
cores were cut from the pavement. The average percent compaction
for four cores was 95.9 percent.
Inspection of the pavement 14 months after placing re-
vealed little raveling or loss of surface material. In one
area, however, there were several "punching" failures con-
sisting of rectangular depressions approximately 4 inches long,
2 inches wide, and over an inch deep. These were found to
have been caused by large steel garbage bins which were parked
filled on the pavement for a period of three months during
hot weather due to a strike at the plant. The 6 cu yd capacity
bins with an empty weight of 650 Ibs rested on steel casters
and this resulted in large concentrated loads under the casters.
Other than these holes , the pavement surface was in good con-
dition and its performance has been satisfactory.
Scarborough, Ontario
Scarden Avenue, a public road in the Borough of Scar-
borough, Ontario, was paved with glasphalt on October 17,
1970. Approximately 600 feet of 26-foot wide pavement was
placed in one course of 1-in. compacted thickness on a pre-
viously placed conventional binder course.
Materials used and the design mix were similar to those
used for the Dominion Glass Company installation except that
one load of the mix was modified by the addition of 2 percent
asbestos and an additional 2 percent of asphalt cement to
determine characteristics of asbestos-modified glasphalt.
The gradation of the combined aggregate is given in Table 14.
The paving operation was performed using a Barber-Greene
Model SA-35 paver and an 8-10 ton Galion steel-tired roller
for breakdown with a 9-ton rubber-tired roller for finishing.
No difficulties were encountered in compacting the mixture in
that pushing, rutting or pick-up did not occur. However,
26
-------
the air temperature was 35F and the mix temperature in the
paver varied from 200 to 380F.
Field Marshall test results for the regular glasphalt and
asbestos modified mixture are given in Table 15. The addition
of asbestos resulted in increased flow, and a marked decrease
in air voids due to the increased asphalt content but a slight
decrease in stability. No cores were obtained from the com-
pacted pavement.
On May 3, 1971, the pavement was skid-tested using an
ASTM skid trailer. At 30 mph the skid numbers ranged from
47 to 61 with an average of 55. These values are well above
tentative minimum requirements and indicate good skid re-
sistance.
Inspection of the pavement 14- months after placing re-
vealed a considerable degree of raveling with many of the
larger glass particles being dislodged from the surface.
This may have been due to fracture of the surface particles
by studded tires, although inadequate density resulting from
low mix temperatures during compaction may also have con-
tributed to the deterioration.
Brockway Glass Company
Approximately 1600 square yards of roads through the
employees parking lot at the Brockway Glass Company in Brock-
way, Pennsylvania, were paved with glasphalt on October 28,
1970. Three strips were paved with the longest being 212
feet by 24- feet wide. Thickness was 1 inch except for 156
square yards which were placed in two layers to a total
depth of 5 inches. The 1-in. layer was placed as a surface
course over two 2-in. layers of conventional Pennsylvania
Department of Highways ID-2 binder which had been placed
one week previously. The subgrade under all paving was
composed of shale and ash spread over old refractory rubble
and compacted through years of use.
Glass used for the project was obtained by crushing non-
returnable bottles in two passes through a jaw crusher. The
glass was blended with sand to produce an aggregate mixture
containing 54 percent glass and 46 percent sand. The design
asphalt content was 5.0 percent (total weight basis) and the
composition of the mix based upon cold feed quantities is
given in Table 14. No hydrated lime was used in the mixture.
Marshall properties of laboratory compacted specimens are
shown in Table 15.
A Cedar Rapids spreader-finisher was used to place the
material with a 10-12 ton tandem steel wheel roller and 2
ton vibratory roller being used for compaction. No diffi-
culties were encountered in compacting the mixture. However,
the unit weight of cores obtained on the day following con-
27
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struction was only 132.5 pcf or 92.9 percent of the labora-
tory compacted unit weight.
On July 8, 1971, cores were taken from the pavement
for testing by the Pennsylvania Department of Transportation.
Using the British Portable Tester, the cores provided skid
numbers of 62, 63, 58 and 63 with 55 being generally regarded
as acceptable by the Pennsylvania Department of Transportation.
An inspection of the pavement one year after placing
revealed a slight amount of raveling but in general the
surface was in good condition. Since no hydrated lime was
used in this installation, the absence of any significant
stripping indicates that under some conditions the water-
resistance may be adequate without the use of anti-stripping
agents.
Burnaby, British Columbia
A 700 foot section of Royal Oak Avenue in Burnaby,
British Columbia, was paved with glasphalt on June 18, 1971.
The 20 foot wide existing asphalt pavement was tacked with a
diluted emulsion before placing a 1 1/2-in. overlay. Traffic
density on the road is 6000 vehicles per day (both lanes) at a
maximum posted speed of 30 mph, with deceleration and acceler-
ation occurring at the intersection with Moscrop Avenue.
Approximately 90 tons of bottles were crushed for use in
the glasphalt and blended with conventional aggregates to
produce the combined gradation given in Table 14. The com-
bined aggregate consisted of approximately 67 percent glass,
31 percent conventional aggregate and 2 percent hydrated
lime with 4.75 percent (total weight basis) of 85-100 pene-
tration asphalt cement added to the mix.
The glasphalt was delivered to the job site at tempera-
tures between 270 and 29OF. Breakdown rolling was carried out
at 230 to 270F with an 8-ton tandem roller, and subsequent
rolling was done with a 7-ton pneumatic roller at temperatures
from 180 to 230F. The mix was tender and required a cooling
period before rolling. Results of Marshall tests on plant
samples are given in Table 15.
Seven cores were cut from the compacted pavement and
the density ranged from 96.4 to 98.5 percent of the labora-
tory density with an average density of 97.0 percent.
On September 16, 1971, skid tests were conducted on the
glasphalt pavement as well as a conventional asphalt pavement
placed during the same time period. The average British
Pendulum Number (BPN) measured in the wheel paths was 48.9
for the glasphalt and 56.0 for the conventional asphalt.
28
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Inspection of the pavement on March 30, 1972, indicated
that severe raveling had occurred in the wheel paths. Loose,
uncoated glass particles were prevalent along the shoulder and
surface pitting was extensive. One pothole had developed.
This deterioration was attributed primarily to heavy studded-
tire traffic resulting from an abnormally severe winter.
However, low pavement density and insufficient asphalt content
may also have contributed to the condition.
On May 23, 1972, additional skid tests were conducted on
the glasphalt and conventional asphalt pavements. The average
BPN measured in the wheel paths had risen to 64.0 for the
glasphalt and to 57.4 for the conventional asphalt. The
substantial increase in skid resistance for the glasphalt
was probably due in part to the surface raveling.
Omaha, Nebraska
One block of a city street in Omaha, Nebraska, was paved
with a 1-in. glasphalt overlay on August 6, 1971. The roadway
width paved was 60 feet and the length was approximately 280
feet.
Glass for the project was gathered during a bottle
collection drive and crushed at a local gravel pit. Con-
siderable difficulty was encountered in crushing the bottles .
They were crushed in a Pioneer Three Roll Crusher normally
used for crushing gravel with a maximum size of one inch.
Several times , broken bottles became wedged in the opening to
the crusher and severely cut the rubber input feed belts.
Bits of glass flew from the crusher and were a definite safety
hazard, resulting in several workers receiving cuts. Due to
this , the time required for crushing the glass was much longer
than the contractor had estimated and the cost was extremely
high.
The mixture was designed to include 20 percent crushed
glass, 30 percent crushed gravel, 10 percent blow sand and 40
percent limestone screenings. Design asphalt content was 6.25
percent and no hydrated lime was used to control stripping.
Aggregate gradation based upon cold feed quantities is shown
in Table 14 and Marshall properties of plant samples are given
in Table 15.
Paving operations using conventional equipment proceeded
smoothly and performance of the mat has been satisfactory.
During the winter months, larger glass particles at the
pavement surface were broken by studded tires and whipped out
by traffic leaving numerous pock marks. Otherwise, there have
been no indications of poor performance.
29
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EVALUATION OF GLASS-
ASPHALT PAVEMENT PERFORMANCE
Skid Resistance
The skid resistance measured on several of the glasphalt
pavements described has, with one exception, been adequate
after periods of service up to two years in duration.
A British Portable Tester was used to measure skid resis-
tance on the Rolla, Brockway and Burnaby installations. After
two years of service, the average British Pendulum Number
(BPN) for the Rolla Street was 4-9.5 for the coarse mixture
and 52.0 for the fine mixture. Natural rubber sliders were
used for these measurements rather than ASTM E249 synthetic
rubber sliders. Tests conducted by Kummer and Moore-^ show
that the synthetic rubber sliders give BPN values that are
10 to 15 percent higher than numbers obtained with natural
rubber sliders. In "Tentative Skid-Resistance Requirements
for Main Rural Highways"13, Kummer and Meyer list tentative
minimum skid resistance requirements for various testing
methods and test speeds. These requirements for the British
Portable Tester are given in Table 16. A 10 percent correction
for use with data obtained with natural rubber sliders has
been applied to these figures and is shown in the table.
Based upon these corrected figures, the minimum recommended
BPN for both coarse and fine mixtures is above this minimum
value.
TABLE 16
RECOMMENDED MINIMUM SKID RESISTANCE
REQUIREMENTS
Mean Traffic
Speed (mph)
0
10
20
30
40
50
60
Skid
SN*
60
50
40
36
33
32
31
Number
SN40 +
__
—
—
31
33
37
41
British
^SR*
—
--
50
55
60
65
Pendulum No.
BPNNR$
__
—
—
45
50
55
59
*Measured at mean traffic speed
+Measured at 40 mph
tMeasured in accordance with ASTM E 303 using ASTM E 249 rubber
^Corrected for use of natural rubber sliders as suggested
by Kummer and Moore
30
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The average BPN for cores from the Brockway parking lot
was 61.5, which is well above the recommended minimum value
of 50 for 30 mph speed using ASTM E249 sliders.
The average BPN measured in the wheel paths of the Burnaby
glasphalt road after 3 months of service was 48.9 which is
slightly below the recommended minimum value of 50. The BPN
had risen to 64.0 after 11 months of service, but raveling
probably caused much of this increase. Measurements were
also made on an adjacent conventional asphalt pavement which
had been placed at the same time and the average values
obtained in the wheel paths were 56.0 and 57.4 after 3 and
11 months respectively.
The Fullerton, Bramalea, and Scarborough roads were
tested using the ASTM towed trailer (ASTM E274). The Fuller-
ton tests were conducted at 25 mph and yielded skid numbers
(SN) ranging from 61 to 69. These values, converted to 40
mph were 54 and 62 respectively, which are well above minimum
requirements shown in Table 16.
Tests on the Bramalea road, conducted at 20 mph, yielded
SN values ranging from 47 to 61 with an average of 54.
Skid test results on the Scarborough street tested at 30
mph ranged from SN47 to SN61 with an average of SN55. These
values are also well above minimum requirements shown in
Table 16.
The results of these skid tests show that pavements con-
taining glass aggregates have generally maintained adequate
skid resistance levels under the service conditions described
and for the time periods indicated.
Only limited data were available from the Burnaby instal-
lation to permit a comparison of the skid resistance of glas-
phalt and conventional asphaltic concrete. However, additional
data were obtained from a series of test patches with varying
composition which were placed in a Rolla city street.
Five different combinations of aggregate were used in the
test patches. One mixture contained an all-glass aggregate
with particles ranging in size from 1/2-in. through minus
200 mesh material. Two mixtures contained crushed limestone
in the coarse sizes (1/2-in. to plus No. 8 material) with
river sand fines in one mixture and glass fines in the
other. The other two mixtures consisted of river gravel in
the coarse sizes, with river sand fines in one mixture and
glass fines in the others.
Since specific gravities for the different aggregates
varied from 2.50 to 2.57, the weight of aggregate was ad-
justed so that the volume of aggregate in each size fraction
remained the same regardless of the aggregate composition.
The gradation used, based on volume, is given in Table 17.
31
-------
Each mixture was designed with an effective asphalt content
of approximately 5.5 percent (total weight basis) and all
mixtures contained one percent hydrated lime by weight of
the aggregate. Results of laboratory Marshall tests on the
mixtures are given in Table 18.
TABLE 17
GRADATION OF AGGREGATES USED IN PATCHES
FOR SKID RESISTANCE TESTS
Sieve
Percent Passing (by Vol.)
1/2-in.
3/8-in.
No.
No.
No.
No.
No.
No.
No.
4
8
16
30
50
100
200
100
87
69
50
38
28
22
11
3
TABLE 18
MARSHALL PROPERTIES OF LABORATORY SPECIMENS
FOR SKID RESISTANCE PATCHES
Effective Unit
Mix Type
All Glass
Stone-Glass
Gravel- Sand
Gravel-Glass
Stone-Sand
Asphalt
Content
5.
5.
5.
5.
5.
50
40
50
60
40
Weight
(pcf)
138.
140.
140.
136.
143.
8
4
0
7
4
Air
Voids
(%)
3.
3.
2.
4.
2.
64
63
91
06
70
VMA Stability Flow
(%) (Ibs) (.01-in.)
15.
15.
15.
16.
14.
72
71
15
12
91
515
760
1230
750
1275
9
10.
9
8
10
5
Two lines of five 12 by 18 inch patches were placed in
one lane of the road and each line of patches contained all
five of the different mixtures. A vibrating plate compactor
was used to compact the patches. Results of tests on labora-
tory compacted field samples from each of the mixtures are
given in Table 19.
Skid resistance of these patches was measured periodic-
ally over a 23 month period with the British Portable Tester.
Eight individual measurements were made on each patch each
time the skid resistance was evaluated, from which an average
BPN was calculated.
32
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TABLE 19
MARSHALL PROPERTIES OF LABORATORY COMPACTED
FIELD SAMPLES FROM SKID RESISTANCE PATCHES
Effective Unit
Mix Type
All Glass
Stone-Glass
Gravel-Sand
Gravel-Glass
Stone- Sand
Asphalt.
Content
5.40
5.50
5.50
5.60
5.50
Weight
(pcf)
138.1
138.3
137.5
135.8
143.4
Voids
(%)
4.43
4.96
3.45
4.63
2.49
VMA Stability
(%) (Ibs)
16.24
16.33
15.59
16.61
15.01
350
510
1360
1095
1650
Flow
( .01- in.)
7.3
10.3
11.3
9.7
9.3
Data obtained after 23 months are shown in Table 20.
Comparisons between the average British Pendulum Numbers for
the various treatments were made using a t-test and only two
significant differences between treatment means were indi-
cated at a 0.05 significance level. The average BPN for the
all-glass mixture was significantly lower than the BPN for
the stone-sand mixture and the stone-glass mixture. However,
there was no significant difference between the stone-sand
and the stone-glass mixtures or the gravel-sand and gravel-
glass mixtures. Nor was there a significant difference be-
tween the all-glass mixture and the gravel-glass or gravel-
sand mixture. This indicates that a replacement of stone by
coarse glass lowered the skid resistance, but the replace-
ment of gravel by coarse glass has no effect upon skid re-
sistance. The replacement of river sand by fine glass
resulted in no significant change in skid resistance for
mixtures with either gravel or stone coarse aggregate.
TABLE 20
SKID RESISTANCE OF FIELD PATCHES
AFTER 23 MONTHS OF SERVICE
Mix Type
British Pendulum Number (BPN)
Average
Range
All Glass
Stone-Glass
Gravel-Sand
Gravel-Glass
Stone-Sand
47.4
53.3
47.8
48.5
54.6
43.8 -
47.5 -
44. 3 -
43.1 -
47.2 -
51.4
61.2
52.5
55.5
62.7
Since the measured skid resistance was lower during the
summer months, and differences among the skid numbers of the
various mixtures were not as pronounced, a similar analysis
was conducted using the British Pendulum Numbers obtained
after 19 months and shown in Table 21. The results of this
33
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analysis indicate several significant differences among the
mixtures. The average BPN for the all-glass mixture was
significantly lower than the BPN for either stone-sand or
gravel-sand mixtures. Stone-glass and gravel-glass mixtures
also had higher average BPN's than the all-glass mixture.
There was again no significant difference between the stone-
sand and stone-glass mixtures or the gravel-sand and gravel-
glass mixtures. This indicates that the replacement of
either gravel or stone by coarse glass lowered the skid
resistance while replacement of fine sand by fine glass had
no effect upon skid resistance.
TABLE 21
SKID RESISTANCE OF FIELD
PATCHES AFTER 19 MONTHS OF SERVICE
British Pendulum Number (BPN)
Mix Type
All Glass
Stone-Glass
Gravel-Sand
Gravel-Glass
Stone- Sand
Average
50.4
62.7
56.1
56.1
64'. 1
Range
60.0 -
51.6 -
50.4 -
58.4 -
58.6
65.6
62.4
58.6
69.4
Based upon the above analyses, the replacement of river
sand by fine glass results in no significant change in skid
resistance. Substitution of coarse glass for crushed stone
reduces the skid resistance, but the effect of substituting
coarse glass for gravel is inconclusive. After 19 months of
service the results indicated that the glass for gravel re-
placement lowered the skid resistance, while results obtained
after 23 months showed no difference in the skid resistance.
Aggregate Degradation
There was no indication of excessive aggregate degrada-
tion based upon sieve analyses of pavement samples taken
from the Rolla and Fullerton glasphalt roads. A comparison
of plant samples and samples sawed from the Rolla pavemenl:
after two years of service shows an increase in Hudson's A
of 0.15 and 0.17 for the coarse and fine mixtures respectively.
Hudson's A increased from 4.58 for the plant sample taken at
Fullerton to 4.87 for cores obtained after one year of service
giving a total increase of 0.29. Thus, the effect of field
compaction and subsequent traffic on the aggregate gradation
was minimal.
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Surface Deterioration
Raveling has been a problem in two of the glasphalt
installations. The Burnaby road exhibited the greatest
degree of deterioration. Pronounced raveling was noted in
the wheel paths after the first winter. Glass aggregates
which had been dislodged from the pavement had no asphalt
remaining on the surface. A similar, though not as severe,
deterioration had occurred on the Scarborough street after
a year of service. The material lost from the surface in
this case was primarily coarse glass particles which had
fractured and then been dislodged by further traffic. The
deterioration in both of these cases was probably initiated
by studded tire traffic with subsequent asphalt stripping
from the loose particles.
Raveling in the Fullerton, Brockway and Omaha pavements
was less severe and was confined primarily to the loss of
large particles at the surface. Little raveling had occurred
on the Rolla and Bramalea pavements.
In a laboratory study of raveling characteristics of
hot mix asphalt paving mixtures, Gallaway and Vavra^1^ found
that increasing voids in the pavement (lower densities) re-
sulted in increased raveling. In their studies, raveling
was not found to be significant except where the void content
was 10 percent and higher for specimens made with good
aggregates. Specimens made with poor aggregates showed
significant raveling at all void contents, but the raveling
definitely increased with increasing void content. Based
upon field density tests of the Burnaby glasphalt, the void
content of the compacted pavement was 8.67 percent. Since
this is below the 10 percent figure suggested by Gallaway
and Vavra, it is unlikely that inadequate density alone
accounts for the raveling which occurred, although it may
have contributed to the severity of the problem.
No cores were taken from the Scarborough pavement and
thus the void content of the compacted pavement could not
be computed. However, due to the low ambient temperatures
during construction, it is possible that a high void con-
tent in the pavement may have been a contributing factor
in the raveling observed.
The void content of the compacted pavements at Fullerton
and Brockway was higher than 10 percent, but the lower traffic
volumes at these sites may explain the fact that extensive
raveling has not occurred.
There was little deterioration of other types occurring
in the glasphalt pavements described. One pot hole had de-
veloped in the Burnaby road and alligator cracking was found
in one small area of the Rolla road. Punching failures due
35
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to sustained concentrated loads during hot weather occurred
in the Bramalea road, but there was no rutting or other
evidence of low stability in any of the other pavements
containing glass aggregates.
36
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ECONOMIC ANALYSIS
The economic feasibility of using waste glass as an
aggregate is dependent upon several factors which include
the cost of disposing of waste by conventional methods of
disposal such as sanitary landfilling or incineration, the
cost of separating refuse into recyclable components and
the cost of conventional aggregates.
Costs of Conventional Disposal Methods
Cost ranges for sanitary landfill disposal have been
estimated at $0.50 to $2.00 per ton by Cannela-^ and more
recently at $1.50 to $3.00 per ton.16 Incineration costs
are generally somewhat higher with an average operating
cost of $5.00 per ton being reported by DeMarco et all' on
the basis of results from a 1968 National Survey of Community
Solid Waste Practices. Based upon data from 78 facilities
at which incoming refuse was actually weighed, 73 percent
of the incinerators studied had operating costs below $5.00
per ton while four of the 78 plants reported operating costs
above $10.00 per ton.
Costs of Refuse Separation Facilities
Costs of separating refuse for the purpose of recycling
the separated components vary with the methods used for
separation. Non-profit organizations and community action
groups have set up recycling centers throughout the United
States using volunteer labor, and industry groups such as
glass container and can manufacturers have also established
reclamation centers. Materials such as paper, glass con-
tainers and metal cans are collected for recycling and, in
some cases, donors are paid for material brought to the center.
Up to $20 per ton has been paid for reasonably clean glass
containers. The volume of material collected in this manner,
however, is relatively small. In Los Angeles, for instance,
130,000 tons per year of residential materials are salvaged,
but 4.20 million tons of solid wastes are landfilled.
If recycling is to be practiced on a large scale, auto-
mated systems for segregating and recovering portions of
residential solid waste will be necessary. Several such
resource recovery systems are currently being developed by
the U. S. Bureau of Mines1 , Black Clawson Company^, Combus-
tion Power Company and Garrett Research. These include both
dry and wet separation systems for treating either incinerator
residue or raw refuse. Processing steps that have been uti-
lized include crushing, screening, air classification, heavy
media separation, and magnetic separation. Detailed data on
37
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the capital and operating costs for these systems is scarce,
however. Costs of treatment for the Black Clawson system
have been reported to be an estimated $7.50 per ton of raw
refuse processed^! minus the credits for salable separated
components. Sullivan and Stanczyk^2 give cost data on the
Bureau of Mines system which treats incinerator residue.
The most comprehensive analysis of the costs for separ-
ating refuse is given in an engineering feasibility study for
a materials recovery system which is being developed by the
National Center for Resource Recovery, Inc.^3 Their plan
calls for a facility which would process 500 tons of refuse
per day and would incorporate "off-the-shelf" equipment used
in other process industries. Major separation equipment items
would include a shredder, air classifier, magnetic belt
separator, roll crusher, electrostatic separator and optical
separator along with the required hoppers, conveyors and
other processing equipment.
Recovered material from the system is predicted to be
15 to 20 percent of the input by weight, with the remainder
being disposed of by conventional methods. Since the value
of recovered products does not cover the cost of extracting
them from the refuse, economic viability of the system requires
benefits as a result of shredding -- either lowering the cost
of landfill due to less cover requirements or increasing the
efficiency of an incinerator. Also, there are savings in-
curred by simply not having to dispose of the recovered
materials.
A cost analysis for the system details estimated capital
requirements of $2,416,000 which includes $100,000 working
capital. Under the conditions outlined in the report, annual
revenues from sale of materials and collection of dumping and
processing fees would approximate $1,030,000 while annual net
expenses would be $818,000. Thus, an expected profit of
$212,000 per year would yield a return on equity of 1H.6 per-
cent for a debt-equity ratio of 40-60. Several assumed
conditions, especially those relating to the glass fraction,
are of interest.
The facility was targeted for a city that has a disposal
cost of $6.50 per ton or higher. Thus the facility charges
the city $6.50 for every ton of solid waste that is delivered
and therefore does not have to be disposed of by traditional
means. A $2.00 per ton processing charge is assumed for
shredding and removing the inerts from the unrecovered refuse.
Estimated revenues generated by the recoverable glass
fraction are dependent upon whether color sorting is employed.
Glass is assumed to comprise 10 percent by weight of the raw
feed input to the system or 50 tons per day. Of this 50
tons, 32 tons are expected to be recovered while the remainder
38
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is landfilled. Twenty of the 32 tons recovered may be color
sorted and are assumed to have a market value of $12 per ton
after color sorting while the remaining 12 tons consists of
material smaller than a 3/16-in. screen but retained on a 20
mesh screen and suitable for aggregate with a market value of
$1 per ton. Since color sorting equipment is optional,
however, one portion of the economic analysis assumes that no
color sorting is carried out and all recovered glass has a
market value of $1 per ton. This lowers the return on equity
from the previously stated 14.6 percent to 10.2 percent.
Costs of Conventional Aggregates
Costs of conventional aggregates generally range from
$1.00 to $7.00 per ton depending upon the locality and type
of aggregate. Monthly market quotations reported by Engineer-
ing News Record21* for January 1973, give sand prices ranging
from $1.00 per ton in Detroit to $5.40 per ton in Pittsburgh.
The price of 3/4-in. gravel in Birmingham was $1.65 per ton
while in New Orleans the price was $7.00 per ton. Crushed
stone with a 3/4-in. maximum size had a price range from $1.55
per ton in St. Louis to $6.50 per ton in Minneapolis. The
average aggregate prices per ton in the twenty U.S. cities
surveyed were $3.17, $3.79, and $3.55 for sand, gravel and
crushed stone respectively.
The variations in aggregate prices for different cities
reflect the availability of aggregates in these areas. The
Gulf Coast in Texas, Louisiana, Alabama and portions of Florida
is an area in which quality aggregates are lacking and conse-
quently the prices are higher in this area. A study by the
American Road Builders' Association was used in NCHRP Report
No. 135 to estimate the yearly tonnage of aggregates needed
in various regions of the United States through 1985. The
results of this study indicated that the aggregate demands for
highways in the Northwestern United States will not be met in
the future unless:
1. Aggregate production increases in excess of 5
percent per year are encountered,
2. The amount of aggregate for highway consumption
expressed as a percentage of total aggregate pro-
duction for the region is greatly increased over
40 percent,
3. Conventional aggregate is transported into the
region from other regions,
4. Supplemental aggregates are manufactured and
used for highway construction, or
39
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5. Low quality aggregates are beneficiated and used.
Some of these possibilities such as transporting aggre-
gate into the region, would probably increase the cost of
aggregate while the effect of others, such as increasing aggre-
gate production, might have little effect on cost or even
reduce aggregate prices.
Economic Feasibility of Using Waste Glass as Aggregate
It is apparent from the above discussion, that the eco-
nomic feasibility of using waste glass as aggregate will vary
considerably in different localities throughout the United
States. The optimum conditions for successful utilization of
this approach to recycling glass would include high landfill
costs and high aggregate costs in an area. Even with these
conditions present, however, the cost of separating refuse
and processing the glass would be a critical consideration.
It is very unlikely that glass collected at recycling centers
can be economically recycled as aggregate. If donors are paid
for the glass bottles at rates as low as $10 per ton, it is
obviously not practical to use this material as a replacement
for aggregate costing at most $7.00 per ton. Even if the
bottles and labor at the recycling center are donated, crushing
is required and, due to the relatively small volumes of glass
involved, unit crushing costs would be high. Thus, when
waste glass is collected at recycling centers, recycling
into new containers offers more promise for economical utili-
zation of the glass than using it as aggregate.
For a materials recovery system such as the one proposed
by the National Center for Resource Recovery, however, the
prospects for economical utilization of the glass fraction as
an aggregate are more promising. The estimated revenues for
this system have been calculated by assuming that 63 percent
of the recovered glass is color sorted and marketed at $12
per ton. However, if color sorting equipment is not used in
the system, due either to the absence of a market for cullet
in the area or an inability to sort the glass to the desired
degree of purity, use of the glass as an aggregate is preferable
to simply disposing of it in a landfill. Crushing and screen-
ing equipment are included in the plant facilities and thus
gradation control would not require additional equipment.
Although the glass would have a lower value when used as
aggregate, this usage would make a contribution to product
revenues rather than incurring an additional cost for dis-
posal. The variations in estimated annual revenue for
varying end uses of the glass from a resource recovery system
are shown in Table 22 and the return on equity for each of
these assumptions is given in Table 23. The figures given
in these tables are based upon data contained in the report
by the National Center for Resource Recovery.
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The first column in Table 22 gives product revenues
for a 500 ton per day plant assuming that the glass fraction
is not marketable and must be disposed of in a sanitary land-
fill. In column 2, glass revenues and disposal and processing
fees are calculated assuming that 4-0 percent of the glass
input is color sorted and marketed at $12 per ton while 24-
percent is too small for sorting and is sold as aggregate for
$1 per ton. Column 3 gives glass revenues and disposal and
processing fees assuming that 64 percent of the glass input
is marketed as aggregate at $1 per ton. Return on equity
for these options is given in Table 23 for a case where 40
percent of capital is borrowed. Return on equity is only
6.4 percent if all of the recovered glass is landfilled, but
rises to 10.2 percent if the recovered glass is sold as
aggregate for $1 per ton and 14.6 percent if 63 percent of
the recovered glass is sold for cullet at $12 per ton and
37 percent is sold for aggregate at $1 per ton. The $1 per
ton value for glass used as aggregate is quite conservative,
based upon the previously stated aggregate prices throughout
the United States. If a value of $3 per ton is assumed, the
return on equity rises to 11.7 percent when all of the glass
is used as aggregate. It should be noted again that these
figures are based upon assumed disposal fee of $6.50 and
processing fee of $2.00 per ton. Other assumptions concerning
operating costs, equipment costs, and product revenues are
detailed in the report by the National Center for Resource
Recovery.
This analysis indicates that waste glass can be economic-
ally reclaimed from municipal refuse for use as aggregate only
if the recovery system produces revenues from marketing
additional components such as ferrous metals, aluminum, other
non-ferrous metals, and paper and from disposal or processing
fees. Disposal and processing fees are of particular im-
portance since the value of recovered products does not
cover the cost of extracting them from the refuse. This means
that recycling of refuse components in general, and glass in
particular, is not likely to be economical in a classical
sense (not considering social costs) when costs for landfill
disposal are low. In areas where conventional disposal
costs are relatively high, and recycling offers an alternate
means for treating solid wastes, the use of glass as aggre-
gate can contribute revenues to the system even though the
glass is not color sorted or the system is not conveniently
located for transporting glass to a container manufacturer.
The advantage of a local market for the glass as aggregate,
especially in areas which have a deficiency in conventional
aggregate supplies, may make this usage more attractive than
shipping the glass some distance to a container manufacturer.
Under conditions of high disposal costs and adequate market
prices for other recoverable components, resource recovery
systems may be able to obtain an adequate return on equity
even though the glass aggregate brings in revenues of only
$1 per ton. Higher aggregate prices will enhance the desira-
-------
bility of using glass as aggregate under these same conditions
but even at $7.00 per ton, revenue generated by the use of
glass as aggregate would represent less than 10 percent of
the total revenue necessary to insure a profitable operation
of the resource recovery system.
TABLE 22
ASSUMED ANNUAL REVENUES FROM RESOURCE RECOVERY SYSTEM
Revenue Source Conditions Outlined Below
1 23
Product Revenues
Ferrous $105,760 $105,760 $105,760
Aluminum 218,400 218,400 218,400
Glass 0 78,624 9,984
Fiber 62,400 62,400 62,400
Non-ferrous Materials 124,800 124,800 124,800
Total Product Revenues $511,360 $589,984 $521,344
Disposal Fee $120,458 $185,354 $185,354
Refuse Processing Fee 274,936 254,968 254,968
Total Revenues $906,754 $1,030,306 $961,666
1. No optical sorting and no market for recovered glass.
All glass landfilled.
2. Optical sorting. 63% of recovered glass selling at $12
per ton, 37% selling at $1 per ton.
3. No optical sorting. All recovered glass selling at $1
per ton.
Other assumptions:
a. 6.8% of input stream assumed to be recovered ferrous
selling at $10 per ton.
b. 0.7% of input stream assumed to be recovered aluminum
selling at $200 per ton.
c. 6.4% of input stream assumed to be recovered glass.
d. 4.0% of input assumed to be a mixture of hand picked
newspaper, Kraft and corrugated selling at $10 per ton.
e. 0.4% of input assumed to be other non-ferrous metal
selling at $200 per ton.
f. Assumes a fee of $6.50 per ton charge for every ton of
refuse that does not have to be disposed of.
g. Assumes a $2 per ton refuse processing fee for shred-
ding and air classifying the refuse.
42
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TABLE 23
ASSUMED RETURN ON EQUITY FROM RESOURCE RECOVERY SYSTEM
Conditions Outlined Below
123
Equity $1,429,045 $1,445,513 $1,429,045
Debt 970,000 970,000 970,000
Capitalization $2,399,045 $2,415,513 $2,399,045
Annual Revenue $906,754 $1,030,306 $961,666
Annual Operating Cost 814,770 818,511 814,770
Profit $ 91,984 $ 211,795 $146,896
Return on Equity 6.4% 14,6% 10.2%
1. No optical sorting and no market for recovered glass.
All glass landfilled.
2. Optical sorting. 63% of recovered glass selling at $12
per ton, 37% selling at $1 per ton.
3. No optical sorting. All recovered glass selling at $1
per ton.
43
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REFERENCES
1. Golueke, C. G. Recycling and reusing resource residues.
Compost Science 12(3): 14-8, May-June 1971.
2. Vaughan, R.D. Reuse of solid wastes: A major solution
to a major national problem. Waste Age 1(1):
10-15, Apr. 1970.
3. Hickman, H.L. Characteristics of municipal solid wastes.
Scrap Age 26(2) 305-307, Feb. 1969.
4. Bell, M. Characteristics of municipal refuse. In
National Conference on Solid Waste Research,
Chicago, 1963. American Public Works Association.
p. 28-38.
5. Kaiser, E.R. Chemical analyses of refuse components.
Paper 65-WA/PID-9. In Proceedings, American Society
Mechanical Engineers, Nov. 7-11, 1965. 5p.
6. Resource recovery from incinerator residue. Vol. 1
Findings and conclusions. A report for the Bureau
of Mines, U.S. Department of the Interior prepared
in cooperation with the Institute for Solid Wastes
of the American Public Works Association (Chicago)
Nov. 1969. p. 2.
7. Glass Containers, sub-council report. National Industrial
Pollution Control Council (Washington D.C.) Feb.
1971. 21 p.
8. Golueke, C.G. and P.H. McGauhey. Comprehensive studies
of solid waste management. Public Health Service
Publication No. 2039, Washington, U.S. Government
Printing Office, 1970. p. 111-112.
9. Malisch, W.R., T.E. Keith, D.E. Day, and E.G. Wixson.
Effect of contaminants in recycled glass utilized
for glasphalt. In Proceedings; Third Mineral
Waste Utilization Symposium, Chicago, Mar. 14-16,
1972. U.S. Bureau of Mines and IIT Research
Institute, p. 371-384.
10. Goode, J.F., and E.P. Owings. A laboratory-field
study of hot asphaltic concrete wearing course
mixtures. American Society for Testing and Ma-
terials Special Technical Publication 309. 1962.
p. 1-21.
11. Lowne, R.W. The effect of road surface texture on tyre
wear. Wear 14(1): 57-70, 1970.
44
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12. Rummer, H.W., and D.F. Moore. Concept and use of the
British portable skid resistance tester. Joint
Road Friction Program: Pennsylvania Department of
Highways and the Pennsylvania State University,
Report No. 6, June 1963. 27 p.
13. Kummer, H.W. and W.E. Meyer. Tentative skid-resistance
requirements for main rural highways. National
Cooperative Highway Research Program Report 37.
Highway Research Board. 1967. 80 p.
14. Gallaway, B.M., and G.R. Vavra. The effect of silicone
on the raveling characteristics of hot mix asphalt
paving mixtures. In Proceedings; Association of
Asphalt Paving Technologists, Atlanta, Feb. 26-28,
1968. p. 422-433.
15. Cannella, Albert A. The refuse disposal problem. Public
Works 99(2) 116-120, Feb. 1968.
16. Quimby, Thomas. Resource recovery. Waste Age 4(1) 24-28
Jan.-Feb. 1973.
17. DeMarco, Jack, D.J. Keller, J. Leckman and J.L. Newton.
Incinerator Guidelines 1969. Public Health Service
Publication No. 2012, Washington, U.S. Government
Printing Office, 1969. p. 8-10.
18. Bargman, Robert D. Urgent need to recycle wastes? Civil
Engineering 42(9) 107-109, Sept. 1972.
19. Stanczyk, M.H. ,. and J.A. Ruppert. Continuous physical
beneficiation of metals and minerals contained in
municipal incinerator residues. In_ Proceedings;
Second Mineral Waste Utilization Symposium, Chicago,
Mar. 18-19, 1970. U.S. Bureau of Mines and IIT
Research Institute. p. 255-262.
20. Herbert, W. Solid waste recycling at Franklin, Ohio.
In Proceedings; Third Mineral Waste Utilization
Symposium, Chicago, Mar. 14-16, 1972. U.S.
Bureau of Mines and IIT Research Institute. p.
305-310.
21. Solid Waste Report 2(1) 4, Jan. 11, 1971.
22. Sullivan, P.M. and M.H. Stanczyk. Economics of recycling
metals and minerals from urban refuse. Bureau of
Mines Solid Waste Research Program Technical Progress
Report-33, Apr. 1971, 19 p.
23. Materials Recovery System Engineering Feasibility Study.
National Center for Resource Recovery, Inc.
Washington D.C., Dec. 1972.
45
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24. Engineering News-Record 190(1) 30-31, Jan. 4, 1973.
25. Marek, Charles R., M. Herrin, C. Kesler and E. Barenberg.
Promising replacements for conventional aggregates
for highway use. National Cooperative Highway
Research Program Report No. 135. Highway Research
Board. 1972.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-670/2-75-053
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
USE OF DOMESTIC WASTE GLASS FOR URBAN PAVING
Summary Report
5. REPORT DATE
May 1975; Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Ward R. Malisch, Delbert E. Day, and Bobby G. Wixson
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Civil Engineering Department
University of Missouri-Rolla
Roll a, Missouri 65501
10. PROGRAM ELEMENT NO.
1DB314, ROAP-24AIN, Task 19
11. CONTRACT/GRANT NO.
EP-00329
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
Summary -
14. SPONSORING AGENCY CODE
is. SUPPLEMENTARY NOTESSummary to EPA-670/2-73-038, PB-222 052
Project Officer: Norbert Schomaker 513/684-4487
16. ABSTRACT
This report summarizes research on the use of waste glass as an
aggregate in asphaltic paying mixtures. Reusing waste glass in this manner would
provide an outlet for large quantities of the glass and would permit recycling in
urban areas where large accumulations of glass are found. Field tests as well as
observations of pavement performance have indicated that field installations of
asphaltic paving mixtures containing glass have generally maintained adequate skid
resistance and performed acceptably from a structural standpoint. The economic
feasibility of using waste glass as an aggregate in asphaltic concrete depends
primarily on developing resource recovery systems that can separate glass along
with other recyclable components and generate enough revenues from their sale,
plus disposal and processing fees, to produce an acceptable return on equity.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Skid resistance, *Urban areas, *Glass,
*Asphalts, Bituminous concretes, Aggregates,
Pavements, Economic analysis, Revenue,
Surface properties^ Texture, Sieve analysis
Recycling; *Solid waste
management; *Resource
recovery; Marshall de-
sign; Hydrated lime;
Glass-asphalt; Cullet
11B; 13B
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO OF PAGES
59
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
•&U.S. GOVERNMENT PRINTING OfFICEt 1975-657-593/5381 Region No. 5-11
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