Material: Recycled Glass Issue: Glass aggregate can include 100% glass cullet, or a mixture of cullet
and natural aggregate. In
general, glass aggregate is durable, strong, and easy to place and
compact. The material can be used in various construction
applications including general backfill, roadways, utility backfill,
drainage media, and miscellaneous uses such as landfill cover and
underground storage tank backfill.
For each application, specifications based on material performance
are required. These specifications
should be developed based on laboratory tests and refined based on
long-term field performance data. Best Practice: This best practice presents model specifications that
were developed based on material behaviors tested in the laboratory. These specifications are conservative in terms
of the amount of cullet and debris allowed, and compaction levels
required. The gradation specifications
below have been found to be acceptable in all of the applications
described here. Sieve Size 3/4” 1/4”
No. 10 No.40 No. 200 Percent Passing (by weight) 100 10-100 0-100
0-50 0-5 General Backfill: General backfill applications include fills that support heavy stationary
loads such as beneath footings and slabs, fluctuating loads such as
beneath reciprocating pumps and compressors, and non-loaded conditions
such as landscaping fill or fill placed beneath pedestrian sidewalks. Model specifications for general backfill
are presented below. Loading Maximum Cullet Maximum Debris Minimum Compaction Conditions Content (%) Content (%) Level
(%) Stationary Loads 30 5
95 Fluctuating Loads 15 5
95 Non-Loading General Fill 100 10 85 Roadways: Roadway applications include the use of cullet aggregate in base
course, subbase, subgrade, and embankments.
Model specifications for these applications are presented below. Maximum Cullet Maximum Debris Minimum Compaction Applications Content (%) Content (%) Level (%) Base Course 15 5 95 Subbase 30 5 95 Embankments 30 5 90 Utilities: Utility applications involve the use of cullet aggregate for trench
bedding and backfill. The
specifications listed below apply to backfill, which is not subjected
to surcharge loading such as from a roadway or slab.
If the trench backfill lies within five feet of a loading area,
then the specifications provided in General
Backfill above would apply. Maximum Cullet Maximum Debris Minimum Compaction Applications Content (%) Content (%) Level (%) Water & Sewer Pipes 100
5 90 Electrical Conduit 100 5
90 Fiber Optic Lines
100 5 90 Drainage: Drainage applications include
retaining wall backfill, footing drains, drainage blankets, and french
drains. Recommended specifications on cullet content, debris content
and compaction level are listed below. Maximum Cullet Maximum Debris Minimum Compaction Applications Content (%) Content (%) Level (%) Retaining Wall 100 5 95 Footing Drain 100 5 95 Drainage Blanket 100 5
90 French Drain
100 5 90 Miscellaneous: Miscellaneous uses of cullet aggregate include landfill cover and
underground storage tank (UST) backfill.
Model specifications for these applications are presented below. Maximum Cullet Maximum Debris Minimum Compaction Applications Content (%) Content (%) Level (%) Landfill Cover 100 5 90 UST Backfill 100 5 90 Implementation: The use of these specifications
should be confirmed by a qualified geotechnical engineer, who should
also inspect and approve the material at its storage location prior
to import to the project site. Also,
placement and compaction should be monitored and tested by engineering
personnel. Benefits: Model specifications provide guidelines to the specification
of glass aggregate. These
guidelines help owners, engineers, and contractors to evaluate glass
aggregate as an alternative to natural aggregate. Application Sites: Design offices, glass processing facilities,
construction sites and test labs. Contact: For more information about
this Best Practice, contact CWC, mailto:info@cwc.org. References: Case Studies for the Use of Post Consumer
Glass as a Construction Aggregate, report GL97-5rpt, Clean Washington
Center, 1997. Issue Date /
Update: January 1997
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