A Tool Kit for
the Use of
Post-Consumer Glass as a Construction Aggregate
FINAL REPORT
Prepared for:
CWC
A
division of the Pacific NorthWest Economic Region (PNWER)
999
Third Avenue, Suite 1060
Seattle,
WA 98104
January
1998
Prepared by:
Soil & Environmental Engineers, Inc.
This recycled paper is
recyclable
Copyright © 1998
CWC. All rights reserved. Federal copyright laws prohibit
reproduction, in whole or in part, in any printed, mechanical, electronic, film
or other distribution and storage media, without the written consent of the
CWC. To write or call for permission:
CWC, 999 Third Avenue, Suite 1060, Seattle, Washington 98104, (206) 464-7040.
Disclaimer
CWC disclaims all warranties to this report,
including mechanics, data contained within and all other aspects, whether
expressed or implied, without limitation on warranties of merchantability,
fitness for a particular purpose, functionality, data integrity, or accuracy of
results. This report was designed for a
wide range of commercial, industrial and institutional facilities and a range
of complexity and levels of data input.
Carefully review the results of this report prior to using them as the
basis for decisions or investments.
Report No. GL-97-5
LINKS
This report contains links
to outside resources and documents that are pertinent to the context of the
information in this report. The
following list will take you to the point in the report where you can use each link:
Home page for the CWC, formerly the Clean Washington Center
The Pacific Northwest
Economic Region (PNWER)
CWC publication Glass Markets Information System
Case
studies associated with this report
Washington State
Department of Transportation (WSDOT)
WSDOT Standard
Specifications naming recycled glass
CWC Fact
Sheet containing WSDOT specifications
Florida
Institute of Technology
Clean Washington Center Best Practices in Glass Recycling
CWC report on the use of
glass in wastewater treatment systems
Direct links to short CWC
reports on specific issues associated with using recycled glass aggregate:
Construction
Inspector's Guide to Recycled Glass Aggregate
Studies
of Glass in Construction Applications
Typical Geotechnical
Parameters of Glass Aggregate
Developing Specifications for
Recycled Glass Aggregate
Model Specifications for Glass
Aggregate
The Behavior of Glass
Aggregate Under Structural Loads
State Specifications for Use
of Cullet as Construction Aggregate
Sampling Procedures for
Recycled Glass Construction Aggregate
Visual Inspection for Glass
Construction Aggregate
Safety Measures for Cullet
Aggregate at Construction Site
Compaction of Glass Fill
Density Testing of Glass
Aggregate Using a Nuclear Densometer
Moisture Content Test of Glass
Fill Using a Nuclear Densometer
Glass Aggregate Dust Control
at Construction Sites
Table of Contents
1.... Introduction.................................................................................. 1
1.
Purpose
of the Tool Kit.................................................. 1
2.
Previous
Investigations Evaluated................................ 1
3.
Information
in the Toolkit.............................................. 2
2... Geotechnical and Engineering
Properties..................................... 7
1... Material
Properties........................................................ 8
........... Specific
Gravity........................................................... 7
........... Relative Density.......................................................... 8
........... Durability.................................................................. 11
........... Soundness................................................................ 13
2... Engineering
Characteristics........................................ 14
........... Compaction.............................................................. 14
........... Gradation.................................................................. 23
........... Permeability.............................................................. 30
........... Shear Strength.......................................................... 35
........... Workability............................................................... 47
........... Safety....................................................................... 48
3... Field
Testing................................................................. 52
........... Density and Moisture Content................................... 50
........... Visual Debris Classification........................................ 53
4... Conclusions
for Construction Aggregate Users......... 58
3... Physical and Chemical Properties, and
Environmental Suitability 64
1... Physical
Properties....................................................... 64
........... Typical Debris Content.............................................. 63
2... Chemical
Properties..................................................... 66
........... Biochemical Oxygen Demand
(BOD)........................ 65
........... Total Phosphorus...................................................... 66
........... Total Kjeldahl Nitrogen (TKN)................................. 66
........... Solids....................................................................... 66
........... Semi-Volatile Organics.............................................. 66
........... pH and Total Organic Carbon................................... 68
........... Priority Pollutant Metals............................................ 68
3... Environmental
Suitability............................................. 73
........... Biological Impacts From
Chemical Properties............ 71
........... Lead and Leachable Lead
Contamination.................. 72
4... Conclusions
for Construction Aggregate Users......... 80
4... Processing Equipment Guidelines................................................ 83
1... Equipment
Properties................................................... 83
2... Conclusions
for Construction Aggregate Users......... 83
5... General Guidelines and Specifications
for the Use of Glass as a Construction Aggregate in
Proven End-Use Applications................................. 88
1... Summary
of State Policies Regarding Glass Construction Aggregates 88
........... Washington State...................................................... 86
........... Oregon..................................................................... 86
........... California.................................................................. 87
........... Connecticut............................................................... 87
........... New York................................................................ 87
........... New Hampshire........................................................ 87
2... End-Use
Application Specifications............................. 90
........... General Fill and Backfill
Applications......................... 88
........... Roadway Applications.............................................. 90
........... Utility Applications.................................................... 91
........... Drainage Applications............................................... 91
........... Miscellaneous Applications........................................ 92
6... Case Studies............................................................................. 96
1... Case
Studies................................................................. 96
2... Lessons
Learned.......................................................... 97
1. Introduction
Since the publication of the Clean Washington Center’s (CWC)
Glass Feedstock Evaluation Project in 1993, engineers and construction
contractors have implemented a number of projects, in Washington State and
elsewhere, using glass as an aggregate feedstock. Also during the last four years, a number of additional studies
have been conducted to examine the use of glass as a construction
aggregate. Despite these important
developments, acceptance has been slow for the use of glass as an aggregate by
construction professionals
This Glass Construction
Aggregate Tool Kit has been developed for project owners, designers, contractors,
material suppliers, and specifying and permitting agencies.
Its purpose is to increase the quality and focus of information available
on the use of glass as a construction aggregate in order to increase the confidence
with which glass may be used as a replacement for mineral aggregates, and in
other specialty applications. This
Toolkit updates and consolidates technical engineering information on recycled
glass aggregates based on previous research and in-situ material performance.
The Toolkit also couples the technical information with examples of successful
uses of glass in specific construction applications.
This publication is the product of the efforts of many
organizations and individuals. The
majority of this toolkit represents a consolidation of the Clean Washington
Center’s Glass Feedstock Evaluation
Project, Volumes 1-5, prepared by Dames & Moore, Inc. in 1993. These reports are not available in
electronic format.
Information and test results from the following publications
has been incorporated into the consolidated Glass Feedstock Evaluation:
1.
Florida
Department of Transportation, Developing
Specifications for Waste Glass and Waste-to-Energy Bottom Ash as Highway Fill
Materials, Volume 2 of 2 (Waste Glass).
Prepared by Professor Paul Cosentino at the Florida Institute of
Technology, Melbourne, Florida, 1995.
3. Clean Washington Center, Best Practices in Glass
Recycling. Prepared in
cooperation with Soil and Environmental Engineers, Inc. and Re-Sourcing
Associates, Inc., Seattle, Washington, 1996.
4. Browning-Ferris
Industries of Ohio, Laboratory Testing
Results, Glass and Rubber Samples, Lorain County Landfill. Prepared by Woodward-Clyde Consultants,
Oberlin Ohio, 1993.
5. Browning-Ferris
Industries of Ohio, Pulverized Glass Test
Pad, Lorain County Sanitary Landfill, Project No. 93-1359. Prepared by Paul C. Rizzo and Associates,
Inc, Oberlin, Ohio, 1994.
6. Henry,
Karen and Morin, Susan Hunnewell, U.S. Army Cold Regions Research Engineering
Laboratory, The Frost Susceptibility of
Crushed Glass Used as a Construction Aggregate. Draft Report, Febraury, 1997.
7.
Clean
Washington Center,
Crushed Glass as a Filter Medium for the Onsite Treatment
of Wastewater. Prepared by Stuth and Company, Maple Valley, WA., 1977.
The Glass Construction Aggregate Toolkit provides the
information to successfully use recycled glass in value-added construction
applications, organized as follows:
ã Technical Information - Sections 2,3, and
4. This
Toolkit incorporates information from a number of ground-breaking testing and
research reports on the use of glass.
Sections 2, 3, and 4 are focused on those issues that have proven to be
the most critical of those affecting the use of glass in construction
applications: geotechnical and
engineering properties; physical, chemical, and environmental properties; and
equipment guidelines. Each section
contains realistic recommendations for construction aggregate users, suppliers,
and designers based on experiences and lessons learned.
Throughout these sections, the toolkit refers to
samples of glass cullet that were used to test material properties, engineering
characteristics, and environmental impacts during the CWC and FDOT
studies. The chart below describes the
sample names and sample configurations for the major studies referenced.
|
Samples
Referenced in the Toolkit.
|
|
Cullet Sample
Number
|
Debris Levels
|
Cullet Contents
(%)
|
Cullet Gradations
|
Collection and
Sorting Source
|
|
CWC Glass Feedstock Study
|
|
CA-14
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Blue Bags - Commingled Bottles/Cans/Paper
|
|
CA-15
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled Only - Non-color sorted
|
|
AZ-01
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Dropbox/Barrels - Unattended
|
|
OR-05
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled Glass Only - Color Sorted at Curb
|
|
WM-10
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Negative Sort
|
|
CA-13
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Redemption
|
|
OR-01
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Dropbox/Barrels - Unattended
|
|
WM-14
|
High
|
15, 50, 100
|
¼” minus
¾” minus
|
Blue Bags - Commingled Bottles/Cans/Paper
|
|
WM-11
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Mixed Fraction
|
|
BFI-06
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled Glass Only - Facility Sorted - Positive Sort
|
|
CA-09
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Positive Sort
|
|
BFI-07
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside -
Commingled Glass Only - Facility Sorted - Negative Sort
|
|
OR-12A
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Deposit Collection
|
|
AZ-02
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Dropbox/Barrels - Attended
|
|
AZ-06
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled Glass Only - Positive Sort
|
|
OR-12
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Deposit Collection
|
|
WM-09
|
Medium
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Positive Sort
|
|
MN-08
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled Glass Only - Mixed Cullet Fraction
|
|
WA-11
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With other Containers - Mixed Fraction
|
|
WA-10
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Negative Sort
|
|
MN-04
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - source Separated by Consumer
|
|
WA-09
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Curbside - Commingled With Other Containers - Positive Sort
|
|
WA-15
|
Low
|
15, 50, 100
|
¼” minus
¾” minus
|
Furnace Ready Cullet - Beneficiated
|
|
Florida
Department of Transportation Study
|
|
WPBMRF
|
Medium
|
100
|
ASTM D 448 #8, #9, #10
|
West Palm Beach Material Recycling Facility
|
|
BSMG
|
Medium
|
100
|
ASTM D 448 #8, #9, #10
|
Southeast Recycling Corporation (Brevard Shredded Mixed Glass)
|
ã Model specifications for specific
aggregate applications - Section 5. The authors evaluated guidelines and
specifications developed in several studies, and have modified them based on a
comparison to the specifications used in the case history and in-situ
performance. Section 5 presents model
specifications for several end-use applications.
ã Lessons Learned from previous uses of
glass in construction applications - Section 6. This Toolkit has the benefit of learning from
years of in-field use of glass. Section 6 presents case histories of
five projects in Washington, and four projects in other states. Information for these case histories was
collected by interviewing project owners, designers, contractors, material suppliers,
specifying and permitting agencies, or a combination of all. Washington State projects were visited in
person, and photographs are included in the Appendix.
The resulting case history portfolio of successful uses of
glass in construction applications includes project
descriptions/characteristics and valuable in-field lessons learned. Material specifications and construction
information have been detailed as part of each case history, when available. Cost information has been captured to the
extent that the documentation maintains the proprietary aspects of the project.
2. Geotechnical and Engineering
Properties
This
section of the Toolkit presents material properties of glass cullet and the
engineering characteristics of cullet aggregate. Table 1 lists potential applications for cullet along with the
level of importance (H=High, L=Low) material properties and engineering
characteristics have on the performance of cullet in these applications.
|
Table
1
Construction
Application and Property Matrix
|
|
|
Material Properties
|
Engineering Characteristics
|
|
Applications
|
Specific Gravity
|
Gradation
|
Workability
|
Durability
|
Compaction
|
Permeability
|
Shear Strength
|
|
General
Backfill
|
|
|
|
|
|
|
|
|
Non-Loaded Conditions
|
H
|
H
|
H
|
L
|
L
|
L
|
L
|
|
Fluctuating Loads
|
H
|
H
|
H
|
H
|
H
|
L
|
H
|
|
Heavy, Stationary Loads
|
H
|
H
|
H
|
L
|
H
|
L
|
H
|
|
Roadways
|
|
|
|
|
|
|
|
|
Base, Subbase
|
H
|
H
|
H
|
H
|
H
|
H
|
H
|
|
Embankments
|
H
|
H
|
H
|
L
|
H
|
L
|
H
|
|
Utilities
|
|
|
|
|
|
|
|
|
Pipe Trench Bedding/Backfill
|
H
|
L
|
H
|
L
|
H
|
L
|
L
|
|
Conduit Bedding & Backfill
|
H
|
L
|
H
|
L
|
H
|
L
|
L
|
|
Fiber Optic Cable Bedding & Backfill
|
H
|
L
|
H
|
L
|
H
|
L
|
L
|
|
Drainage
|
|
|
|
|
|
|
|
|
Foundation Drainage
|
H
|
H
|
H
|
L
|
H
|
H
|
L
|
|
Drainage Blanket
|
H
|
H
|
H
|
L
|
H
|
H
|
L
|
|
French Drains
|
H
|
H
|
H
|
L
|
H
|
H
|
L
|
|
Septic Fields
|
H
|
H
|
H
|
L
|
H
|
H
|
L
|
|
Leachate Treatment
|
H
|
H
|
H
|
L
|
H
|
H
|
L
|
|
Miscellaneous
|
|
|
|
|
|
|
|
|
Landfill Cover
|
H
|
L
|
H
|
L
|
H
|
L
|
L
|
|
Underground Tank Fill
|
H
|
L
|
H
|
L
|
H
|
L
|
L
|
Specific Gravity Specific gravity, a measure
of a material's density, is a widely used parameter in establishing the
density-volume relationship of a soil mass.
Typical values of specific gravity for natural aggregate are 2.65 to
2.68 (Bowles, 1988), and typical values for commercial glass are 2.49 to 2.51
(BCIT, 1991; HWA, 1992). Since density
relates directly to engineering properties such as compaction and shear
strength, specific gravity is an important baseline property.
Advantage
The specific gravity of glass
cullet test results show that at the same weight, 10% to 15% more volume of
glass aggregates can be shipped compared with natural aggregates, resulting
in lower shipping costs.
|
|
The CWC’s Glass Feedstock
Evaluation conducted fourteen specific gravity tests on on samples comprised of
two cullet sources, three cullet contents (100%, 50%, and 15%), and two cullet
sizes (1/4 inch minus and 3/4 inch minus).
Crushed rock was the natural aggregate used in all of the mixed
samples. Two repetitive tests were
conducted for statistical analysis.
Additionally, specific gravity tests were conducted on the two types of
natural aggregate (gravelly sand and crushed rock) with no added cullet.
The Glass Feedstock Evaluation test results indicate that
the specific gravities of the coarse cullet range from 1.96 to 2.41 and the
specific gravity of the fine cullet range from 2.49 to 2.52. The difference in these ranges is believed
due to the difference in the test procedure used for the coarse and fine cullet
and the difference in the debris levels of these cullet samples. These values agree with values obtained in
the testing performed in the Florida Department of Transportation (FDOT)
Study. The 3/4 inch minus CA-14 cullet
tested by the CWC had a debris content of about 5% by visual classification,
while the 1/4 inch minus CA-14 cullet had a debris content of 2%-3%, both by
visual classification. Both the 3/4
inch minus and 1/4 inch minus gradations of the WA-09 cullet had about 1%
debris, by visual classification. The
lowest specific gravity of 1.96 measured for the one sample of 3/4 inch minus
cullet reflects the higher debris level of the sample, while the specific
gravity of the other sample of 3/4 inch minus cullet was 2.41.
The specific gravities of the 1/4 inch minus cullet are
close to the typical value of glass.
This closeness confirms the fact that both 1/4 inch minus cullet samples
had a low debris level. On the other hand,
the specific gravity of the WA-09 cullet was slightly higher than the CA-14
cullet. This difference may be the
result of slight difference in debris level of these two cullet samples.
The specific gravities of the crushed rock and gravelly
sand ranged from 2.60 to 2.83. These
values are typical of natural aggregate and were higher than those of the
cullet. The specific gravities of the
mixed samples were found in between those of the 100% cullet and 100% natural
aggregate.
The difference in the specific gravities of the cullet
and natural aggregate and the difference in the specific gravities of the CA-14
and WA-09 cullet samples are believed to affect the relative density and the
unit weight of the compacted samples.
These effects are presented in the sections that follow.
Relative Density Relative density is
a measure of a soil mass's density relative to its possible range of
density. For cohesionless, granular
material such as cullet, the possible range of density is determined by the
maximum density and minimum density index tests. The standard methods for determining these values are ASTM D 4253
(maximum density) and D 4254 (minimum density). The maximum and minimum index density results can be used to
correlate with density determinations from compaction tests such as the Proctor
and WSDOT 606. The relative density
procedure used in the CWC’s Glass Feedstock Evaluation was a vibratory
procedure that did not create much crushing of the cullet particles. This produced different results than the
Proctor compaction tests, which produced substantial crushing of the cullet
particles.
The CWC’s Glass Feedstock Evaluation conducted fourteen
maximum and fourteen minimum index density tests using the ASTM D 4253 and ASTM
D 4254 test procedures, respectively.
The tests were conducted on samples comprised of two cullet sources
(WA-09 and CA-14), three cullet contents (100%, 50%, and 15%), and two cullet
gradations (1/4 inch minus and 3/4 inch minus). The gravelly sand was the natural aggregate used in all of the
mixed samples. Additionally, two
repetitive tests were conducted for statistical analysis.
|
Table 2
Relative
Density Test Results.
|
|
Cullet Sample
Number2.
|
Type of Natural
Aggregate
|
Cullet Content
(%)
|
Cullet
Gradation
|
|
|
Maximum index
Density
|
|
|
|
Maximum Index
Density (pcf)
|
|
CA-14
|
|
100
|
¼" minus
|
98.4
|
|
CA-14
|
|
100
|
¾" minus
|
90.9
|
|
WA-09
|
|
100
|
¼" minus
|
106.6
|
|
WA-09
|
|
100
|
¾" minus
|
109.3
|
|
CA-14
|
gravelly sand
|
50
|
¼" minus
|
122.6
|
|
CA-14
|
gravelly sand
|
50
|
¾" minus
|
130.0
|
|
WA-09
|
gravelly sand
|
50
|
¼" minus
|
126.7
|
|
WA-093.
|
gravelly sand
|
50
|
¼" minus
|
126.7
|
|
WA-093
|
gravelly sand
|
50
|
¼" minus
|
128.8
|
|
CA-14
|
gravelly sand
|
15
|
¼" minus
|
137.9
|
|
CA-14
|
gravelly sand
|
15
|
¾" minus
|
137.0
|
|
WA-09
|
gravelly sand
|
15
|
¼" minus
|
135.9
|
|
WA-09
|
gravelly sand
|
15
|
¾" minus
|
140.3
|
|
Minimum Index
Density
|
|
|
|
Minimum Index
Density (pcf)
|
|
CA-14
|
|
100
|
¼" minus
|
81.2
|
|
CA-14
|
|
100
|
¾" minus
|
76.8
|
|
WA-09
|
|
100
|
¼" minus
|
86.3
|
|
WA-09
|
|
100
|
¾" minus
|
89.5
|
|
CA-14
|
gravelly sand
|
50
|
¼" minus
|
102.3
|
|
CA-14
|
gravelly sand
|
50
|
¾" minus
|
105.9
|
|
WA-09
|
gravelly sand
|
50
|
¼" minus
|
102.7
|
|
WA-093.
|
gravelly sand
|
50
|
¼" minus
|
102.5
|
|
WA-093.
|
gravelly sand
|
50
|
¼" minus
|
104.2
|
|
WA-09
|
gravelly sand
|
50
|
¾" minus
|
104.4
|
|
CA-14
|
gravelly sand
|
15
|
¼" minus
|
116.6
|
|
CA-14
|
gravelly sand
|
15
|
¾" minus
|
115.8
|
|
WA-09
|
gravelly sand
|
15
|
¼" minus
|
114.2
|
|
WA-09
|
gravelly sand
|
15
|
¾" minus
|
116.5
|
|
|
|
|
|
|
|
|
|
|
NOTE: 1. All tests performed using the ASTM D 4254 test procedure.
2. CA-14 is the high debris level sample. WA-09 is the low debris level sample.
3. Repetitive test for statistical analysis.
The data indicates that the maximum index density of the
test samples was affected largely by the cullet content, and to a lesser degree
by the cullet size and debris level.
The trend of increasing density with decreasing cullet content is also
true for the minimum index density.
When a maximum density test was conducted
using Proctor compaction energy in accordance with ASTM D 698-83 for the FDOT
Study, glass particles spilled from the mold as the compaction hammer contacted
the waste glass surface. It was assumed
that this phenomenon could be attributed to the low surface tension and
rigidity of the glass particles. The
study thus concluded that the conventional Proctor moisture-density
relationship did not exist.
Maximum densities obtained using the
Modified Marshall-Proctor method during the FDOT Study produced results close
to those of the CWC’s Glass Feedstock Evaluation The grain size distribution of the glass determined from a sample
after compaction indicated no change in grain size distribution and therefore
no significant degradation of the particles.
The Modified Marshall-Proctor method for compaction was found to be
satisfactory to determine the maximum densities of glass aggregate.
Durability The durability of a material
has historically been regarded as essential to good aggregate for
roadways. Durability relies on
hardness, toughness, and abrasion resistance. The properties of hardness and
toughness are closely related. Hardness
is made up, in part, by abrasion resistance and toughness is generally
understood to mean the power possessed by a material to resist fracture under
impact.
Crushing and grinding of cullet are expected to occur during
mixing, transportation, placement and compaction. To evaluate the durability of cullet and cullet-aggregate
mixtures, the CWC’s Glass Feedstock Evaluation conducted Los Angeles (L.A.)
abrasion tests using standard method ASTM C 131. At present, most highway agencies specify a limit on abrasion
resistance of aggregate based on the Los Angeles test. The test results, along with those of the
sieve analysis provide valuable insight into the suitability of the material
for roadway base course and fill under fluctuating loads.
The first sample was
comprised of 100% WA-09 cullet with a gradation of 1/4 inch minus. A second sample consisted of 100% WA-09
cullet with a gradation of 3/4 inch minus.
A third sample consisted of 100% CA-14 cullet having a gradation of 1/4
inch minus. The fourth sample was 100% crushed
rock. The test results are presented in
Table 3, below.
|
Table 3
L. A.
Abrasion Test Results1.
|
|
Cullet Sample Number2.
|
Type of Natural Aggregate
|
Cullet Content (%)
|
Cullet Gradation
|
Percent Loss
|
|
WA-09
|
-
|
100
|
¼" minus
|
29.9
|
|
WA-09
|
-
|
100
|
¾" minus
|
41.7
|
|
CA-14
|
-
|
100
|
¼" minus
|
30.9
|
|
-
|
crushed rock
|
0
|
-
|
13.6
|
Notes: 1. All tests performed using the ASTM C
131 test procedure.
2. CA-14 is the high debris level
sample. WA-09 is the low debris level
sample.
No tests were conducted for mixed
cullet-aggregate samples. However, it
is reasonable to assume that the percent loss of mixed samples would lie
somewhere between the percent loss of the two components. The percent loss of the 100% cullet samples
represents the worse condition if the materials are used as a construction
aggregate. The CWC test results
indicate that cullet was not as sound, mechanically, as crushed rock. The percent loss of the 1/4 inch minus
cullet was about 30%, and that of the 3/4 inch minus cullet was about 42%. These losses were at least two times greater
than that of the crushed rock.
Of course, natural aggregate durability
is dependent on the characteristics of the local supply. For example, a study conducted by the U.S.
Army’s Cold Regions Research Engineering Laboratory in New Hampshire conducted
L.A. Abrasion tests on 30% by weight glass-70% aggregate and 100% aggregate. Test results indicated that the percent wear
of 100% aggregate samples ranged from 33% to 52.3%, while the cullet-aggregate
mix ranged from 25.3% to 31.2%. The
first of the two aggregates used in the New Hampshire test was classified as a
well-graded sand with gravel, and the second as a poorly graded sand with
gravel.
As mentioned above, the percent losses of
the 100% cullet results in the CWC study represent a worse case scenario. The test values for 100% cullet samples in
that study were relatively close to the normal limiting values for roadway
aggregate. For instance, the Washington
State Department of Transportation (WSDOT) specifies that the not-to-exceed
value for a crushed surface course is 35% and the value for ballast is
40%. From the CWC test results shown in
Table 3, the 100% ¼-inch minus cullet will meet this requirement. Based on the results of 100% ¾-inch minus
cullet, it is projected that 50% ¾-inch minus cullet will also meet this requirement.
The CWC study also shows that the debris level appears to
have an effect on the percent loss.
This can be seen from the slightly higher loss of the CA-14, 1/4 inch
minus cullet than the WA-09, 1/4 inch minus cullet. The difference was small since the difference in the debris level
of these two materials was small.
Soundness The
soundness of aggregates, or their resistance to the forces of weathering, is
another important consideration in the selection of a material for roadway
construction. The primary exposure is
freezing and thawing. Most aggregate
specifications from northern states include a provision for soundness. The most common soundness requirement for
aggregates is based on exposure to sodium or magnesium sulfate solution (ASTM C
88). Container glass is inert to
exposure to these solutions. As such,
the CWC’s Glass Feedstock Evaluation found that soundness is a property which
can not be measured for cullet. It is
more appropriate to use the L.A. abrasion test to determine the degradation
properties of cullet .
In the CWC Glass Feedstock Evaluation Engineering
Performance Testing Program, samples were tested by investigating three
independent variables. These included
cullet content in the aggregate mix (15, 50, or 100% by weight), aggregate mix
gradation (1/4" minus or 3/4" minus), and relative debris level (high
or low). The lower bound of cullet
content (15% by weight) was selected to correspond to the maximum use content
for cullet specified in the Washington and California departments of
transportation specifications prior to the CWC study. The mix gradations of 1/4" minus and 3/4" minus were
intended to cover the majority of applications for cullet aggregates. By varying the relative debris levels, it
was possible to investigate the sensitivity of the chemical and engineering
properties to this parameter.
Compaction The
compaction characteristics of engineering fill include the relationship of the
density and moisture content, the effect of compaction method on this
relationship, the potential of gradation change during the compaction process,
and the sensitivity of the material to weather (moisture change)
conditions. Since almost all
engineering fill requires compaction during placement, the characteristics are
relevant to almost all potential cullet applications. By testing materials of different constituents with different
compaction methods, the compaction characteristics of cullet and cullet
mixtures can be evaluated. Compaction
test results and curves can be used to develop a data base for correlation with
other materials. The results of the
compaction densities can also be compared with the densities from the relative
density tests. Through a common
parameter - dry density - other engineering properties such as shear strength,
can be correlated, and the sensitivity of these properties to the material
constituents and compaction methods can be studied. The CWC Glass Feedstock Evaluation study used three compaction
test methods:
ã ASTM
D 698, the standard Proctor test.
ã ASTM
D 1557, the modified Proctor test.
ã Washington
Department of Transportation (WSDOT) test method 606.
Proctor tests are widely used for field control of fill
materials. Typically, engineers will
specify the materials be compacted to a state such that the field density
exceeds a specific percentage of the maximum density obtained from the Proctor
tests. Since the engineering properties
of the fill materials are related to their density, controlling this parameter
in the field ensures the engineering performance (strength for instance) of the
materials.
ASTM D 698 results represent the effects of light compaction
equipment. It uses impact compaction,
and the input energy produced in the laboratory is comparable to light field
compaction equipment. The test results
are typically used for the field control of unloaded or lightly loaded
fill. ASTM D 1557 results represent
heavy impact compaction conditions.
Test input energy is comparable to heavy compaction equipment. The test results are used for the field control
of heavily loaded conditions. WSDOT
test method 606 is used for the field control of base course material for
roadway construction. The test uses
vibratory compaction and its effort and mechanism are comparable to vibratory
compaction equipment.
Advantage
The small gradation change seen
during the hydrostatic compression and triaxial shear tests implies minimal
breakage of the cullet under normal working loads. In other words, the cullet particles,
like the crushed rock particles, have adequate strength to behave like an
elastic body which deforms under hydrostatic loads, and displaces or
rotates near shear planes.
|
|
In the Proctor test, a sample is compacted in a
mold by a steel hammer, weighing 5.5 and 10 pounds for the standard and
modified tests, respectively. Field
compaction equipment, on the other hand, does not use impact compaction. Generally, the difference in compaction
modes between laboratory and field is not critical if the materials are
granular, natural materials. However,
when a material consists of fragile or angular particles, the difference in
compaction may be significant.
A previous study found that the standard Proctor test
created minor crushing of the cullet particles (Metro Testing Laboratory,
1991). The degree of crushing is
expected to increase with increasing cullet content and particle size. The degree of change in gradation was investigated
by conducting a sieve analysis after each compaction test. The gradation change created by each
compaction method was then determined.
Compaction quality control of construction aggregates is
usually achieved through control of the in-situ density. Nuclear density gages are commonly used to
measure in-situ density. The standard
test methods are: ASTM D 2922 for
density, and ASTM D 3017 for moisture content.
See Part 3 - “Field Testing” - of this Section for a discussion of
compaction quality control using nuclear density gages.
The CWC’s Glass Feedstock Evaluation compaction tests were
conducted on samples consisting of two sources (WA-09 and CA-14), three cullet
contents (100%, 50%, and 15%), and two cullet sizes (1/4 inch minus and 3/4
inch minus). For each method,
repetitive tests were conducted for statistical analysis. Also, tests on 100% natural aggregate were
conducted for comparison.
Standard
Proctor: A total of 15 Standard
Proctor tests were conducted using the ASTM D 698 test procedure. The test results are summarized in Table
3. Plate 29 (following page) shows the
relationships between the moisture contents and the dry densities of the
compacted samples. Plate 29 contains
the results of samples with the same cullet debris level and size but different
mix percentages. For ease of
comparison, the result for the non-cullet sample is also plotted. Two repetitive tests were conducted for
statistical analysis. These results are
not plotted, but are included in Table 4 below.
|
Table 4
Standard
Proctor Compaction Test Results1.
|
|
Cullet Sample Number2.
|
Type of Natural Aggregate
|
Cullet Content (%)
|
Cullet Gradation
|
Maximum Dry Density (pcf)
|
Optimum Moisture Content (%)
|
|
CA-14
|
|
100
|
¼" minus
|
104.4
|
4.7
|
|
CA-14
|
|
100
|
¾" minus
|
99.3
|
5.5
|
|
WA-09
|
|
100
|
¼" minus
|
104.9
|
5.0
|
|
WA-09
|
|
100
|
¾" minus
|
107.5
|
5.3
|
|
CA-14
|
gravelly sand
|
50
|
¼" minus
|
119.5
|
6.5
|
|
CA-14
|
gravelly sand
|
50
|
¾" minus
|
124.6
|
6.0
|
|
WA-09
|
gravelly sand
|
50
|
¼" minus
|
121.4
|
6.0
|
|
WA-093.
|
gravelly sand
|
50
|
¼" minus
|
121.0
|
6.6
|
|
WA-093.
|
gravelly sand
|
50
|
¼" minus
|
121.8
|
5.3
|
|
WA-09
|
gravelly sand
|
50
|
¾" minus
|
126.7
|
5.7
|
|
CA-14
|
gravelly sand
|
15
|
¼" minus
|
126.5
|
6.5
|
|
CA-14
|
gravelly sand
|
15
|
¾" minus
|
130.5
|
5.7
|
|
WA-09
|
gravelly sand
|
15
|
¼" minus
|
127.0
|
8.6
|
|
WA-09
|
gravelly sand
|
15
|
¾" minus
|
130.5
|
6.0
|
|
-
|
gravelly sand
|
0
|
-
|
132.5
|
8.8
|
Notes: 1. All tests performed using the ASTM D 698 test
procedure.
2. CA-14 is the high debris level sample. WA-09 is the low debris level sample.
3. Repetitive test for statistical analysis.
Plate 29 and the data summarized in Table 5 indicate that
the compacted density of the test samples was affected largely by the cullet
content, and to a lesser degree by cullet size and debris level. These effects are summarized below:
1. The
density increases with decreasing cullet content.
2. The
optimum moisture content increased slightly with decreasing cullet content.
3. In
general, all the moisture-density curves are relatively flat. The only exception to this was the sample
comprised of 100% WA-09, 3/4 inch minus cullet.
4. The
densities of the low debris WA-09 samples were slightly higher than those of
the high debris CA-14 samples.
5. The
sample of 100% CA-14, 3/4 inch minus cullet had the lowest density. All other samples with 3/4 inch minus cullet
had a higher density than the samples with 1/4 inch minus cullet.
Modified
Proctor: A
total of 16 Modified Proctor tests were conducted using the ASTM D 1557 test
procedure. The test results are
presented in Plate 34 and summarized in Table 4. Plate 34 shows the relationship between the moisture contents and
the dry densities of the compacted samples, and the table summarizes the
maximum
dry densities and their corresponding moisture contents.Plate 34 contains the results of samples composed of
the same cullet debris level and size but different mix percentages. For ease of comparison, the result of the
crushed rock sample is also plotted.
Two repetitive tests were conducted for statistical analysis. These results are not plotted but are
summarized in Table 5.
|
Table 5
Modified
Proctor Compaction Test Results1.
|
|
Cullet Sample
Number2.
|
Type of Natural
Aggregate
|
Cullet Content
(%)
|
Cullet
Gradation
|
Maximum Dry
Density (pcf)
|
Optimum
Moisture Content (%)
|
|
CA-14
|
|
100
|
¼" minus
|
111.0
|
5.6
|
|
CA-14
|
|
100
|
¾" minus
|
111.4
|
7.5
|
|
WA-09
|
|
100
|
¼" minus
|
113.0
|
5.2
|
|
WA-09
|
|
100
|
¾" minus
|
117.8
|
6.0
|
|
CA-14
|
crushed rock
|
50
|
¼" minus
|
126.0
|
9.2
|
|
|