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Technology Brief
WASHINGTON STATE DEPARTMENT OF |
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The reverse side of this technology brief provides the Washington State
Department of Transportation (WSDOT) specifications for recycled glass in
unbound construction aggregate applications.
Use of crushed glass in these applications represents a major
breakthrough in the acceptance of recycled materials in construction. The specifications are precedent-setting in
terms of the number of applications permitted and the high percentage
content of glass aggregate allowed.
With these specifications, aggregate producers will be able to
capitalize on the cost and performance advantages of using glass as
a construction aggregate. Practical considerations to supplying glass
aggregate are discussed below. Aggregate
Producer Considerations While aggregate mills can be used to produce a product meeting gradation
specifications, the high abrasiveness of glass may require a separate,
dedicated system for crushing glass. |
The WSDOT specifications reference the American Geological Institute (AGI) visual classification method that provides a field-verifiable standard for judging contamination levels. Copies of AGI Data Sheets 15.1 and 15.2 are available from ReTAP. In practice, qualification under this contamination standard may require that the producer screen-off contaminants after crushing, particularly if the glass source is the mixed color byproduct of color sorting performed for bottle manufacture. Typical glass contaminants (aluminum caps, paper labels, etc.) do not crush as efficiently as glass and are easily screened and removed. No level
of hazardous materials is acceptable.
Environmental testing has determined that the only material
in glass recycling programs that is of potential environmental concern
is lead foil, which is sometimes used for wine bottle wrappers.
The specifications require five random samples to be tested
quarterly for total lead. Total
lead tests cost less than $25 per test. |
| Amendment to 1994 Standard Specifications Section 9-03.21, 1994 Standard Specifications for Road, Bridge, and Municipal Construction. Washington State Department of Transportation. 1994. |
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9-03.21(1): Reclaimed Glass (Mixed Waste Cullet) Additive to Aggregates. Reclaimed
glass may be blended with the following:
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Ballast 9-03.9(1)
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Shoulder Ballast 9-03.9(2)
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Crushed Surfacing Base
Course 9-03.9(3)
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Aggregate for Gravel
Base 9-03.10
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Gravel Backfill for
Foundations, Class A 9-03.12(1)A
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Gravel Backfill for
Foundations, Class B 9-03.12(1)B
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Gravel Backfill for
Walls 9-03.12(2)
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Gravel Backfill for
Pipe Bedding 9-03.12(3)
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Gravel Backfill for
Drains 9-03.12(4)
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Backfill for Sand Drains
9-03.13
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Sand Drainage Blanket
9-03.13(1)
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Gravel Borrow 9-03.14
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Bedding Material for
Rigid Pipe 9-03.15
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Bedding Material for
Flexible Pipe 9-03.16
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Foundation Material
Class A and B 9-03.17
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Foundation Material
Class C 9-03.18
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Bank Run Gravel for
Trench Backfill 9-03.19 Aggregates containing reclaimed glass shall conform to the requirements of these Specifications for each item listed above. No aggregate shall contain more than 15% glass. No more than 10% of the material retained on an individual sieve 1/4 inch or larger shall be glass, based upon visual examination and weight. |
9-03.21(2): Recycled Glass Aggregate. Aggregate composed solely of glass may be used as gravel backfill
for walls, pipe bedding, and sand drains; sand drainage blanket; gravel
borrow; and bedding material for flexible pipe. One hundred percent of the glass shall pass a 3/4 inch square sieve
and not more than 5% by mass shall pass a U.S. No. 200 sieve.
Sieve analyses shall be conducted according to WSDOT Test Method 103-C on at least a quarterly basis by
the product supplier. All test
results shall be kept on file by the product supplier. The maximum debris level shall be 10%.
Debris is defined as any deleterious material which impacts the
performance of the engineered fill and includes all non-glass constituents
of the glass feedstock. The percentage of debris in cullet shall be
quantified using the following visual method:
Approximately 200 grams of processed cullet shall be placed in
a flat pan or plate. The percentage of debris shall be estimated using
American Geological Institute (AGI) Data Sheets 15.1 and 15.2, "Comparison
Charts for Estimating Percentage Composition", 1982. Total lead content testing shall be performed quarterly by the product
supplier. Tests shall include
a minimum of five samples. Sample
collection shall be conducted according to ASTM D75. The mean of these tests shall not exceed 80
ppm. Total lead content testing
will be conducted according to EPA Method 3010/6010.
All test results shall be kept on file by the product supplier. |
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