Glass Cullet Utilization Study - Pollution Prevention …infohouse.p2ric.org/ref/15/14338.pdf2.2.2 Specific Gravity and Relative Density Specific gravity is a measure of a material’s

Glass Cullet Utilization Study

Civil Engineering Applications

Nebraska State Re cy cl i n g As so c i a t i on

June 1997

HDR Engineering, Inc.

GLASS CULLET UTILIZATION IN CIVIL ENGINEERING APPLICATIONS

PREPARED FOR:

NEBRASKA STATE RECYCLING ASSOCIATION 1941 SOUTH 42ND STREET, SUITE 512

OMAHA, NEBRASKA 68105

PREPARED BY:

HDR ENGINEERING, INC.

JUNE 1997

SECTION 1.0 INTRODUCTION

1.1 Purpose

The purpose of this report is to review available literature, data, and field applications of glass cullet and identify possible uses of glass cullet in civil engineering applications in the State of Nebraska. This project provides the information on glass cullet properties and processing so that engineers could specify the use of cullet as a construction aggregate.

1.2 Background

The background research included review of literature and case history information for applicability to civil engineering applications. Much of this information was based on the Glass Feedstock Evaluation project conducted by the Clean Washington Center, a division of the Washington State Department of Trade and Economic Development. Glass cullet utilized as an aggregate can incorporate mixed glass that have been crushed and screened to remove debris and oversized particles. This system provides a use for glass materials not currently recycled, or difficult to market (2). This report is divided into the following sections:

Processing and Properties of Glass Cullet - presents glass processing (crushing) technologies and the physical properties of glass cullet. Applications - describes glass cullet applications and presents some case histories. Specifications - presents recommended specifications and applicability to State of Nebraska. Economic Considerations - discusses the processing and marketing issues of glass cullet. Conclusions - presents conclusions and discusses implementation issues.

A preliminary range of design parameters, e.g., friction angles, compaction, hydraulic conductivity, specific gravity is presented. This report includes sample economic models (1 1) which can be modified to fit a particular situation.

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SECTION 2.0 PROCESSING AND PROPERTIES OF GLASS CULLET

2.1 Cullet Processing; Methods

This section presents an overview of the processing methods used to produce marketable glass cullet for use in civil engineering applications (9). Processing methods can vary, depending on the anticipated end use. The following discussion is limited to the typical process necessary to produce glass cullet for reuse as a construction aggregate. This category of use includes: general backfill, roadways, utilities, and drainage applications, and miscellaneous applications such as landfill leachate collection or gas venting layers.

Glass crushing equipment has been derived from the rock crushing industry. Several types of equipment can produce cullet which may be used as construction aggregate. Typically, glass crushers will be smaller than rock crushers (glass production capacities of 1 to 20 tons per hour) and designed to handle the abrasive nature of glass cullet.

The basic glass crushing system consists of a crusher (crushing mechanism), a feed hopper, and a discharge chute. The types of crushing mechanisms commonly available are: hammermill, rotating disk and breaker bar, rotating drum and breaker plate, rotating breaker bar, impactor, and helical fluted roller. Optional components to aide in production of glass cullet include infeed and outlet conveyors and a screening mechanism. With this system, glass bottles are loaded into the feed hopper either manually or by a front-end loader, conveyed to the crusher, processed and screened, and conveyed to a bin or the floor. The screening mechanism will likely be necessary to produce aggregate-quality cullet by removing the oversize particles and most of the debris.

Glass crushing may be possible in mills designed for crushing rock; however, several factors need to be considered for crushing glass based on Dames & Moore’s observations of glass crushers (9). Cullet is more abrasive than natural aggregate which will result in greater wearing of surfaces and subsequently more frequent maintenance. Cullet is also less dense than natural aggregate which may cause difficulties in existing crushed rock gravity feed systems. The rock crushing equipment is designed to crush rock to a desired gradation (grain size distribution). The gradation of cullet from this same piece of equipment may be significantly different.

Glass cullet may be handled, spread and compacted with conventional construction equipment. Civil engineering applications of glass cullet include the substitution of cullet or cullet-aggregate mixtures for conventional aggregate materials in backfills, roadway base course, subbase or embankments, utility trench bedding and backfill, drainage fills, and landfills.

Further processing to pulverized or ground glass will require additional equipment and cost. Pulverizing makes glass into particles the size of sand. Civil engineering applications and products of pulverized glass can include glasphalt, concrete additive, building materials, filter media, drainage and erosion control, and reclamation of beaches.

2.2 Physical Properties

The technical feasibility of substituting glass cullet or cullet blends for a given soil/aggregate component should be based on demonstrating the equivalency of the cullet performance to that of the conventional aggregate component. The use of conventional aggregate materials in civil engineering construction applications is based on an evaluation of classification and engineering properties (7). Classification properties are those properties which help identify a material and engineering properties are those used for engineering design.

The following summarize a review of the literature on the physical characteristics and properties of glass cullet and their implications for use as construction aggregate components. Project specific testing should be conducted for each glass cullet source to establish adequate physical properties and performance. Existing American Society for Testing and Materials (ASTM) test methods for soils and aggregates are suitable for glass cullet materials. The pulverized glass is not considered, since it has a higher production cost and broader level of reuse in products.

2.2.1 Appearance

The amount of debris in glass cullet can affect its engineering properties. Depending upon the glass collection and sorting procedures, glass cullet may contain the following types of debris (8): paper, foil and plastic labels, plastic and metal caps, cork, paper bags, wood debris, food residue, and grass. Specifications should place a limit on the percentage of debris allowed in the cullet. Generally, debris levels should not exceed a maximum of 10 percent and in many applications 5 percent.

Glass cullet sizes analyzed by Dames & Moore (7, 8, 10) were the 3/4-inch minus (coarse) and %-inch minus (fine) size ranges which relate to standard classifications for fine gravely and sandy soils used for most construction aggregate. The glass cullet particles are mostly angular with a small percentage flat or platy shape. The angular shape indicates a potential to cut or puncture a synthetic liner (geomembrane) or similar material if placed against this material. Applications should avoid this direct contact.

2.2.2 Specific Gravity and Relative Density

Specific gravity is a measure of a material’s density. This determines the amount of voids in the aggregate. Specific gravity values for crushed natural aggregate range from 2.60 to 2.83. Based on test results (10), the specific gravities for coarse glass cullet range from 1.96 to 2.41 and for fine cullet range from 2.49 to 2.52.

ASTM D 653 (1) defines relative density as, " ... the ratio of the difference between the void ratio of a cohesionless soil in the loosest state and any given void ratio, to the difference between the void ratios in the loosest and in the densest states.” In other words, relative density is a measure of a soil’s mass density relative to its possible range of density. Test data shows that the maximum relative densities for 100 percent cullet range from 90.9 to 109.3 pounds per cubic foot. With cullet-aggregate blends, the relative density increases with decreasing cullet content.

The specific gravity and relative density of glass cullet are important baseline properties. They relate directly to engineering properties such as compaction and shear strength.

2.2.3 Gradation

ASTM D 653 (1) defines gradation (grain-size distribution) as the “...proportions by mass of a soil or fragmented rock distributed in specified particle-size ranges.” Gradation is a primary criterion for roadway and engineering fill. It can affect engineering properties such as compaction, permeability, filtration, and shear strength.

The gradation of glass cullet is generally similar to crushed rock and gravely sand and is controlled by the cullet processing method. Gradation is obtained by sieve analysis. Specifications will dictate the gradation required for each application.

Gradation test results from Dames & Moore (10) indicate that significant gradation change occurs when 100 percent cullet is subjected to heavy impact compaction. Therefore, fill applications that use this type of compaction such as fluctuating or heavy stationary loads should not use 100 percent cullet.

2.2.4 Durability and Workability

Durability of a material is based on hardness and toughness. Durability was evaluated by Dames & Moore (1 0) from the Los Angeles (L.A.) abrasion tests using standard method ASTM C 13 1. Durability is a material classification property that affects its suitability for roadway base course and fill under fluctuating loads.

Glass cullet’s resistance to abrasion is lower than that of natural aggregate. The L.A. abrasion test indicated that the percentage wear of glass cullet was 30 percent for 1/4-inch minus size and 42 percent of 3/4-inch minus size (10). This is almost two times greater than that of natural aggregate. The Nebraska Department of Roads (NDOR) specifies limiting values for mineral aggregate used in roadway base courses and foundation courses at 40 percent, and crushed rock used in base courses at 45 percent.

Workability is the ease with which an aggregate is handled and compacted. Glass cullet is generally angular in shape, compared to crush rock (subangular) and gravely sand

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The R-value relates indirectly to the strength of the material. The value is commonly used to specify base or sub-base aggregate. The resilient modulus is a measure of a material’s stiffness used in pavement design. The resilient modulus of natural aggregate is typically about 30 ksi at a bulk stress of 25 psi. Modulus for cullet does not appreciable change with repeated loading (e.g., repeated traffic loads).

Shear strength is a major design consideration for construction with glass cullet in embankments, roadway base courses, and engineering fill under foundations (7). Test results indicate that the strength of cullet is about the same as natural aggregate (1 0). However, for specific applications such as fills under fluctuating loads and roadways, only cullet mixes up to 30 percent are recommended by Dames & Moore.

2.2.6 Compaction

ASTM D 653 (1) defines compaction as the “...densification of a soil by means of mechanical manipulation.” Compaction is a design consideration that effects density control. Compaction characteristics include relationship of density and moisture content, effect of compaction method on density and potential gradation change, and sensitivity of material to weather conditions.

Cullet and cullet-aggregate mixtures have favorable compaction characteristics. Glass cullet-aggregate mixtures generally do not experience appreciable gradation changes with compaction. The maximum density values obtained from the Modified Proctor compaction and vibratory compaction tests are about equivalent for cullet-added fill materials. Density slightly increases with decreasing cullet content. However, heavy field compaction equipment can significantly effect density values for 100 percent cullet fills because of the gradation changes,

The compacted density of cullet is not sensitive to the moisture content (1 0), which means that cullet material can be placed and compacted during wet weather. As a result, construction downtime may be kept to a minimum.

2.2.7 Permeability

ASTM D 653 (1) defines permeability as, “...the capacity of a rock to conduct liquid or gas.” Permeability is a design consideration in civil drainage applications such as foundations drainage, drainage blankets, and french drains, and in leachate collection and gas venting layers. For drainage fill material, high permeability is usually more beneficial than low.

Typical granular soils (washed gravel, sand or sand-gravel mixtures) have permeabilities ranging from 0.01 to 0.001 cm/sec. The permeability of a granular material depends on its gradation and density. Data reported on permeability tests of 100 percent glass cullet have permeabilities ranging from 0.04 to 0.06 cm/sec for fine cullet and 0.18 to 0.26 cm/sec for coarse cullet (1 0). The cullet-aggregate mixtures have



permeabilities between 100 percent cullet and granular soils. In general, permeability will increase with increasing cullet content, cullet size, and debris level but will decrease with increasing compaction. This is comparable to natural sand and gravel. Therefore, drainage applications can use 100 percent glass cullet for fill material.

Cullet also appears to have favorable characteristics for use as filtration media in such applications as septic fields, leachate treatment and water purification. However, further study of the filtration capacity is warranted.

2.2.8 Thermal Conductivity

Thermal conductivity represents the ability of the material to conduct or resist heat flow. Thermal conductivity is a design consideration that effects bedding and backfill for conduits or other heat sources.

Test data results (1 0) indicate that glass cullet and cullet-aggregate mixtures have slightly lower thermal conductivities than natural aggregate. In other words, cullet conducts heat more slowly. This slight difference still allows cullet materials to be feasible for utility trench backfill.

2.2.9 Filtration

ASTM D 653 (1) defines a filter as, "... a layer or combination of layers of pervious materials designed and installed in such a manner as to provide drainage, yet prevent the movement of soil particles due to flowing water.” Filtration is a design consideration that effects clogging and plugging between adjacent layers. The American Water Works Association Standard B 100 was applied to cullet properties (gradation, specific gravity, shape, and hardness) to determine suitability as a filtering media (7).

Typical filtering media such as silica sand have required effective sizes ranging from 0.35 mm to 0.65 mm. The gradation of fine glass cullet (%-inch minus) tested by Dames & Moore (10) ranged from 0.5 mm to 6.5 mm. With additional sieving, the fine cullet appears to be feasible as an intermediate filtering media. Coarse cullet provides high permeability, but is not effective as a graded filter. Dames & Moore recommended further direct measurement and study of cullet filtration capacity.

Filtration is a major design consideration for all drainage type applications in direct contact with adjacent soil layers. Filter fabrics may be used to provide the filtration function and prevent plugging and clogging of the cullet layer. Thick non-woven geotextiles also offer puncture resistance.

2.2.10 Leachability

Glass is a relatively inert material; however, common contaminants from collection methods can influence the chemical characteristics of glass feedstock. Only

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limited chemical test data is available for recycled glass feedstocks. Toxicity Characteristic Leaching Procedure (TCLP) testing for metals, based on analytical data provided by the Clean Washington Center (7) indicates, “...all metals, except lead, occurred at concentrations below the regulatory limit.” The lead levels in some samples may be associated with the lead foil wrappers on wine bottles in various cullet feedstocks. TCLP organic compounds were not detected, suggesting that organic compounds in cullet have a low leachability potential. The semi-volatile organic analysis indicated the presence of phthalate compounds, a biodegradation product of plastics. The variability in presence and concentration of lead and phthalates in cullet samples can be attributed to whether cullet is screened for debris, the color of the cullet, and the sorting and collection procedure for each cullet source.

Laboratory test results have been conducted for total lead and leachable lead by BFI using EPA Method 3010/6010 and EPA Method 13 11/6010 (8). The test results for all samples showed that total lead concentrations were undetectable or at low concentrations similar to levels in natural aggregate. Most cullet source samples showed TCLP lead results below the federal regulatory limit of 5 mg/l or undetected.

Additional laboratory leaching tests were conducted by Dames & Moore (8) in accordance with ASTM D 4793 to assess the chemical characteristics and the potential for contaminant leaching over time. The test protocol involved shaking a known weight of sample with water and separating the aqueous phase ten times over a ten-day period. In general, metal concentrations in glass cullet were at or below the metal concentrations typically found in background levels of natural aggregate. Contaminant levels of the

at concentrations of concern. cullet samples decreased in concentration over time and a

Leachability is a design consideration for glass cullet applications in contact with ground water or subject to infiltration into ground water.

2.3 Safety and Handling

Safety concerns in handling glass cullet during production and construction include: exposure to respirable particles and potential for skin irritations, cuts, or lacerations. Glass is primarily composed of amorphous silica. Amorphous silica is not considered to be a significant health hazard. Crystalline silica, a health hazard known to cause fibrogenic lung disease (7), is not likely to be found, except in very low amounts, in the post-consumer glass stream used for cullet. Test results conducted-by Dames & Moore (9) indicated that cullet samples contained less than one percent crystalline silica which puts glass cullet dust in the nuisance dust category under OSHA.

Skin irritations and cuts can be avoided through the use of protective clothing similar to that worn when working with natural aggregates. This includes heavy gloves, long-sleeve shirts, pants, heavy boots, hard hats, hearing protection and eye protection.



Conventional backfill materials typically consist of granular soils. Design considerations include gradation, compaction, shear strength, and leachability.

In 1992, the Town of Portage La Prairei, Manitoba used crushed glass as an underlayment for cement sidewalks (1 2). Glass cullet processed in the City of Vancouver is used as aggregate or construction fill by several local companies.

3.3 Roadway Construction

Potential glass cullet uses in roadway construction include base course, subbase, subgrade, and embankments. When cullet is mixed with natural aggregate, the resulting mixture will most likely have acceptable strength and resistance to abrasion and traffic loads. Conventional subbase and base course material are granular soils. Design considerations for conventional materials include shear strength, abrasion, R-value, resilient modulus and filtration. The use of glass cullet would add considerations of compaction and leachability.

Imtiaz Ahmed of Purdue University (1 2) concluded that glass cullet is suitable for roadway construction as either an unbound aggregate base layer if it meets gradation standards or as fill material for embankments, if crushed to the appropriate size. The Western Research Institute in Laramie, Wyoming came to similar conclusions.

Glass cullet has been used in several roadway construction projects by the following counties and communities (1 2):

Ocean City, Maryland; City of Regina, Saskatchewan; Town of Dryden, Ontario; Orange County, New York; Pierce County, Wisconsin; Portage County, Wisconsin; Palm Beach County, Florida; and Warner, New Hampshire.

Many of these projects use glass cullet as 10 percent of the road base material. Orange County, New York used 70 pounds of crushed glass per square yard mixed in with reclaimed roadbed aggregate. These projects found that glass cullet can be beneficial for roadbed construction where poor quality gravel exists. In fact, the addition of glass cullet (especially 1/4- inch minus) may enhance the engineering performance of coarse natural aggregate and may even help some of the borderline aggregates meet State’s gradation requirements.

Several state departments of transportation have approved and written specifications for the use of glass cullet in road base and subbase applications. These states include California, New Hampshire, New York, Minnesota, and Washington.

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Others such as South Carolina, Pennsylvania, and Wisconsin have experimented and tested cullet-aggregate mixtures against their specifications. Specifications may then be developed for using glass cullet in unbound base courses, subbase, and/or embankments. In 1994, the State of Wisconsin had already issued a draft exemption for the use of recycled glass in asphalt, roadbed aggregate and drain tile material.

In 1994, the Washington Department of Transportation amended its specifications to allow the use of 3/4-inch minus glass cullet in aggregate applications such as backfill, sand drainage and bedding materials (1 5).

3.4 Utility Construction

Glass cullet can be used for utility trench bedding and backfill. Cullet content up to 100 percent can be used for backfill up to the last two feet below the final grade. Depending on the loading conditions on the backfill area, the last two feet of the backfill may have cullet contents varying from 15 percent to 100 percent. Conventional materials include granular soils. Design considerations for these conventional materials and glass cullet include compaction, permeability, thermal conductivity, and filtration.

In New London, New Hampshire (12), glass cullet of 1/2-inch minus is being used for fill around sewer connections from homes to the city’s line, as fill for electrical conduit, as backfill and drainage aggregate along walls, and as frost-heave protection fill under pathways and parking lots. The State of Hawaii, by law, also requires the use of glass cullet as cushioning backfill of underground utilities. Other usage requirements include drainage backfill behind retaining walls, surrounding leachlines and perforated drains, and similar uses.

The 1991 National Standard Plumbing Code allows the use of glass crushed to 3/4- inch as aggregate in storm drains, which are used to drain water away from the parts of the buildings that are below ground.

3.5 Drainage

Glass cullet can be used for construction of drainage facilities such as drainage blankets, french drains, foundation drains, and behind retaining walls. Conventional materials include granular soils and geosynthetics (geotextiles and geonets). Design considerations include compaction, permeability, filtration and puncture resistance. Drainage backfill behind retaining walls will also have considerations of lateral earth pressure coefficient, settlement of underlying soils, Poisson’s ratio, and unit weight. In drainage applications, a geotextile filter should be used to separate glass cullet from the surrounding soil and to prevent clogging of the drain, similar to conventional aggregate filtration requirements.


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Glass cullet was used in french drains and trench drains by the Town of Dryden, Ontario in parkland and residential subdivision work and by Palm Beach County, Florida at its landfill (1 2). The City of Seattle, Washington used glass cullet for filtration purposes in a storm water treatment project (7). Glass cullet was used in the trenches along with a mineral aggregate and geotextile. Performance of this system is being monitored by the City. The City also used glass cullet as drainage aggregate at its landfill.

3.6 Landfill Construction

Potential glass cullet uses in landfill construction include the leachate collection layer, gas venting layer, and landfill cover.

3.6.1 Leachate Collection Layer

The purpose of a leachate collection layer is to provide positive control and discharge of landfill leachate. These layers are typically located directly above the geomembrane component of the composite liner system. Conventional materials used in leachate collection layers include granular soils and geosynthetics (geotextiles and geonets). Design considerations for these conventional leachate collection materials include shear strength (side slopes), permeability, filtration and puncture resistance. The use of glass cullet would add a consideration of compaction and durability.

Glass cullet of 3/8-inch minus was tested in the laboratory and field as a landfill leachate layer by the Ohio Environmental Protection Agency (13). This glass cullet was found to be feasible for a 12-inch thick leachate collection layer, compacted using standard equipment. The non-carbonate nature of glass made it preferable to natural aggregates that are highly carbonate. A non-woven geotextile provided cushioning between the glass and the geomembrane. Vancouver, British Columbia, a Connecticut landfill, and a private firm in San Jose, California (1 2) have all used glass cullet as a filter media between soil and coarse aggregate or some other component of the leachate collection system.

Section 003.04B 1 of the Nebraska Department of Environmental Quality (NDEQ) Title 132 states that “leachate collection systems shall be designed and constructed to maintain less than a 30 cm depth of leachate over the liner.” The permeability required to meet this criterion, whether granular soil, a geosynthetic, or glass cullet, is a function of the slope and drainage path length of the leachate collection layer. Glass cullet permeability is comparable to sands and fine gravels.

3.6.2 Gas Venting Layer

The purpose of a gas venting layer is to provide control and discharge of landfill gas under active or passive extraction. These layers typically are located directly beneath the infiltration layer in the closure cap. Conventional materials used in these layers


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include granular soils and geosynthetics (geotextiles and geonets). Design considerations for these conventional materials include shear strength (on side slopes), permeability, and filtration. The use of glass cullet would add considerations of puncture resistance (against a synthetic liner) and leachability.

Glass cullet has been used or approved for several projects in the construction of gas venting systems at landfills in the State of New York (14). The cullet passed New York’s Department of Environmental Conservation regulations for gas venting layers without further processing as delivered from the material recovery facility. A geotextile should be placed on top of the glass cullet layer to prevent cuts or puncture of the flexible membrane liner.

3.6.3 Landfill Cover

The purpose of daily and intermediate cover is to control disease, fires, odors, blowing litter, scavenging, and minimize infiltration and leachate generation. Intermediate cover also serves to support vegetative growth. Conventional materials used in these layers are soils and synthetic materials.

The higher permeability of glass cullet can be a limitation for this application, since this may limit the glass cullet layers effectiveness in controlling disease vectors, odors, and infiltration. However, several landfills have used glass cullet as daily landfill cover (1 2):

NDEQ Title 132 allows for the use of alternative materials of an alternative thickness for daily cover if it can be demonstrated to perform all the functions of a daily cover without presenting a threat to human health and the environment.

3.7 Summary

Glass cullet may be used in numerous civil engineering applications, many of which are mentioned in Section 3.1. Conventional soils and aggregate laboratory test results and design analyses can address the major design considerations identified in Section 2 and further establish the feasibility of using glass cullet in the civil engineering applications described in this Section 3. The key to utilizing glass cullet is identifying and matching the minimum performance requirements for each application.

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SECTION 4.0 SPECIFICATIONS

4.1 Introduction

The data collected by Dames & Moore for the Glass Feedstock Evaluation (7, 8, 9, 10, 1 1) can be used to evaluate engineering performance of glass cullet for a variety of aggregate applications. However, not all glass sources will be suitable for all civil engineering applications that utilize aggregate. For each application proposed, the suitability of a particular glass source for aggregate-quality cullet should be reviewed.

Glass can be processed into construction-grade cullet using any convenient mechanical method described in Section 2.1. For cullet-aggregate blends, glass cullet can be blended with natural aggregates by any convenient mechanical method. Normal precautions should be followed to prevent segregation.

Physical properties and performance of aggregate materials are presented in the State of Nebraska Department of Roads (NDOR) “Standard Specifications for Highway Construction, 1985,” and supplemental specifications, 1993. Some of the civil engineering applications identified in this report for glass cullet as an aggregate may be governed under other state regulations. Typical aggregates in Nebraska for construction include sands, gravels, crushed rock and recycled concrete. The glass cullet and cullet- aggregate blends should be compared with these standard specifications for each specific application. The intent of this report is to encourage NDOR and other regulatory departments within the State of Nebraska to amend specifications to allow glass cullet and cullet-aggregate blends as an alternative to conventional aggregate in numerous applications. Several states, including the Washington State Department of Transportation (6), have already included specifications for glass aggregate.

4.2 Application Specifications

Dames & Moore developed model specifications for using cullet in aggregate applications. These specifications include recommendations on threshold values for cullet content, debris level, and compaction level which are summarized in Table 4- 1 for the various applications. The cullet contents for utility and drainage application listed in this table would apply to backfill which is not subjected to surcharge loading such as from a roadway. If the utility trench backfill or drainage fill are subject to surcharge loads, then the specifications for general backfill or roadway applications would apply, as appropriate.

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Landfill Leachate Collection Layer4 100 10 Landfill Gas Venting Layer4 100 10 Landfill Cover 100 10

Data Source: Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 5 - Evaluation of Cullet as a Construction Aggregate, Clean Washington Center, June 1993.

Notes:

90 90 90

Percent by weight. Percent using the AGI visual method. Percentage of maximum dry density. Use ASTM D1557 (Modified Proctor) for cullet - aggregate mixtures or ASTM D698 (Standard Proctor) for 100% cullet fills. Based on case histories from references (1 3) and (1 4) and data from Dames & Moore, Inc.

1

2

3

4

Cullet gradation specifications are provided for structural fill (backfill, roadway and utility applications) and drainage fill in Table 4-2. Both the 3/4-inch minus or 1/4-inch minus gradations should perform well. However, Dames & Moore found that the 1/4-inch minus cullet appeared to be more durable and complimented the gradation of natural aggregates better.

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4.3.1 Debris Level

Debris is any material which can negatively impact the performance of the engineered fill and includes all non-ceramic components of the glass cullet. No hazardous materials should be allowed in the glass cullet. The percentage of debris in glass cullet can be quantified visually in the field by using the “Comparison Chart for Estimating Percentage Composition”, by the American Geological Institute, 1982 (AGI Data Sheets 15.1 and 15.2). Dames & Moore (1 1) recommends a sample size of approximately 200 grams of processed glass cullet, avoiding segregation of debris from the glass. The debris level determined by the AGI method should not exceed the values given in Table 4-1 or as allowed by the State of Nebraska.

4.3.2 Laboratory Testing

Laboratory testing should be conducted to establish values for the appropriate physical properties used in the design (Table 2-2). Existing ASTM test methods for soils and aggregates are suitable for cullet and cullet-aggregate mixtures.

A minimum suite of index tests should include:

1.

2.

3.

Maximum dry density of cullet-aggregate mixtures determined by Modified Proctor Test in accordance with ASTM Dl557 test procedure. Maximum dry density of 100 percent cullet determined by standard proctor test in accordance with ASTM D 698 test procedure. Gradation test of cullet or cullet-aggregate in accordance with ASTM D422.

In addition, environmental testing for total lead may also be required. For example, the Washington State Department of Transportation requires five random samples to be tested quarterly for total lead by the product supplier (6). The sample collection should be conducted in accordance with ASTM D 75. The mean of these tests should not exceed 80 ppm. Total lead content testing should be conducted according to EPA 3010/6010.

4.3.3 Field Placement and Compaction

Prior to field placement, surfaces and adjacent areas should be protected in accordance with specified conventional construction techniques. Field placement and compaction should include the following requirements (1 1):

1. Lifts shall not exceed 8 inches in loose thickness. 2. Place each layer of glass cullet or cullet-aggregate blends over full width of

section. Use conventional equipment, as needed, to obtain a uniform layer thickness.

3. Cullet and cullet-aggregate blends shall be well mixed.

4. Compact each lift to specified minimum dry density. 5. Compacted fill shall be tested by engineer using the method described

subsequently prior to approval.

With fills containing cullet, some consideration should be made regarding the exposure to the general public. Depending on the application, landscaping soil and vegetation, asphalt pavement, or reinforced concrete could be used to cover the cullet fills. Some applications may place glass cullet directly against a synthetic liner. Glass cullet may puncture a synthetic liner. Current practice suggests using a heavy geotextile between the glass cullet and a synthetic liner.

4.3.4 Field Quality Control

Field quality control should include the following tests (1 1):

1.

2. Field density testing:

Minimum of one density test per 1000 square feet of fill, but not less than one test per lift.

a) b)

Sand replacement method, ASTM D 1556, or Nuclear densometer method, ASTM D 2922. The nuclear method shall be field-verified by the engineer prior to its use as a means of compaction control.

Quality assurance should include the following procedures:

1. 2. 3.

Obtain samples from on-site stockpiles in accordance with ASTM D75. Conduct gradation tests in accordance with ASTM D 422. Sample and test at a frequency of 1 test per 500 tons.


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SECTION 5.0 ECONOMIC CONSIDERATIONS

5.1 Introduction

In 1995, Nebraskans recycled 4,663 tons of glass as compiled by the Nebraska State Recycling Association (NSRA). This was estimated to be approximately six percent of the total glass generated in the State. The majority of this was recorded as mixed glass. Low prices, high transportation costs, and more stringent specifications make it difficult to sell post-consumer glass back to distant packaging manufacturers. In addition to municipal recycling programs, manufacturers and industrial generators also need more and better outlets for their waste glass. Currently, there are no viable markets for ‘waste industrial glass’ anywhere in the midwest region. The Nebraska Business Development Center had identified about 50 manufacturers of glass products (i.e. bottlers, flat glass, bottles, glass/lock structural, glass products made from purchased glass, and surgical and medical instruments) and another 275 firms for glass, auto plate and window. These firms will be targeted for a more in-depth survey to be conducted by NSRA in 1997.

The economics of glass recycling are very case and geography specific. The competitiveness of glass cullet to the natural aggregates will primarily depend on the glass collection and processing costs, conventional aggregate costs, and local market demand. The sections below discusses these considerations in more detail.

5.2 Glass Collection and Processing

Collection of glass in many communities may depend upon the price and market for glass. Some may collect all three colors of glass (clear, green, brown), while others may only collect clear glass. The cost of collection will vary between curbside collection and drop-off centers. After collection, glass is either processed locally or shipped to distant processors or markets. A community or county may want to consider a glass crushing system to process glass locally.

Before selecting a glass crushing system, the purchasing objectives should be determined. These may include capital costs, operational and maintenance costs, minimum production capacity, system configuration and size, portability, power requirements, operational factors (e.g. noise and dust levels), desired product characteristics, etc. Suggested purchasing guidelines and recommendations by Dames & Moore (9) include the following:

Equipment relatively easy to operate and maintain; Screening system to control particle size and debris level; Adjustable crushing mechanism to adjust the gradation of the cullet to specific applications; Wearing surfaces constructed of abrasion-resistant materials;

5.4 Economic Model

Dames & Moore (11) developed an economic model that helps identify the criteria and parameters important to the economic viability of glass aggregate production. “The key to usage is production of glass cullet that is comparable to rock aggregate for a variety of applications.” Economics become more favorable if there are many applications and a stable demand for glass aggregate production. Local conditions and operations can be entered into the model to evaluate the economic tradeoffs. (See Appendix B).

A further analysis would compare the three available options for glass: landfill disposal, the bottle market, and the aggregate market. A sample spreadsheet by Dames & Moore (1 1) which evaluates these options is provided in Appendix C. The cost inputs for landfill disposal, collection, labor, shipping, and glass processing can vary from region to region. The cost of rock aggregate can also vary significantly depending on the location of the aggregate supply and project application. The spreadsheet could be modified to reflect these local conditions.

Glass Cullet Utilization in Civil Engineering Application HDR Engineering, Inc. n:\waste\nsra\cuIlet.doc June 1997

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SECTION 6.0 CONCLUSIONS

6.1 Summary

A review of the literature on glass cullet utilization in civil engineering applications indicated that glass cullet usage is viable as an aggregate or blended with conventional aggregate. The findings are as follows:

Glass cullet and cullet-aggregate blends have been used in numerous civil engineering applications as an alternative to conventional granular materials. Glass cullet has physical properties similar to granular materials. The computational methods and tests to demonstrate glass cullet performance essentially are the same methods and tests used for granular materials. Several states have amended specifications or approved the usage of glass cullet in unbound construction aggregate applications. Cullet content is dependent upon the application and allowable percentages by the state.

6.2 Implementation Issues

The acceptance of glass cullet as an aggregate relies on the technical equivalency compared to conventional granular materials. As noted in the previous sections, the physical properties fall within the ranges for conventional granular materials. Analytical methods, combined with laboratory test results, are available to demonstrate the technical equivalency of glass cullet.

Implementation issues which may impact the acceptance of glass cullet for unbound aggregate applications include:

Current physical tests on glass cullet have been conducted using ASTM methods for soils or aggregate. ASTM had established a committee in 1993 to evaluate the use of recycled material, including glass cullet, for highway construction.

The water quality issue could be a concern for applications where the glass cullet is in contact with ground water or infiltration. However, the only material in glass recycling programs that is of potential environmental concern is lead foil, which is typically used for wine bottle wrappers. Specifications can address this issue by requiring random samples for total lead of the glass cullet supply.



Cost savings for a specific glass cullet application will depend on local materials costs, glass cullet processing costs, and additional design features, i.e., geotextiles between a glass cullet layer and synthetic liner.

6.3 Potential Benefits

The utilization of glass cullet in civil engineering applications is an emerging market, subject to variability in costs of materials and contractors’ perceptions of risk associated with glass cullet construction. However, the viable applications for glass cullet utilization offer many benefits which may include:

Creation of a product market for mixed glass; Diversion of recyclable glass from disposal in a landfill; Reduction in need for natural mineral resources; Improving the performance of poor quality gravel in cullet-aggregate mixtures; and


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REFERENCES

ASTM, “Standard Technology Relating to Soil, Rock and Contained Fluids,” Annual Book of ASTM Standards, Vol. 04.08, No. D 653-90, American Society for Testing and Materials, Philadelphia, PA., 1994.

Broughton, A.C., “Glass Recyclers Seek Quality, Alternatives,” Recycling Today, December 1992, pps. 62-65.

Clean Washington Center, Washington State Department of Trade and Economic Development, Glass Markets Information System Application Summary Reports, December 1993.

Clean Washington Center, Washington State Department of Trade and Economic Development, Recycling Burden Turned Into Local Resource Fact Sheet, September 1994.

Clean Washington Center, Washington State Department of Trade and Economic Development, Respiratory Health Aspects of Ground Glass vs. Ground Silica Fact Sheet, September 1994.

Clean Washington Center, Washington State Department of Trade and Economic Development, Washington State Department of Transportation Specifications for Glass Aggregate Fact Sheet, September 1995.

Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 1 - Testing Program Design, Clean Washington Center, March 1993.

Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 2 - Environmental Suitability Evaluation, Clean Washington Center, June 1993.

Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 3 - Equipment Evaluation, Clean Washington Center, June 1993.

Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 4 - Engineering Suitability Evaluation, Clean Washington Center, June 1993.

Dames & Moore Inc., Glass Feedstock Evaluation Project, Task 5 - Evaluation of Cullet as a Construction Aggregate, Clean Washington Center, June 1993.

Reindl, J., “Reuse/Recycling of Glass Cullet For Non-Container Uses,” Dane County Department of Public Works, State of Wisconsin, May 20, 1996.

Schmucker, Bruce O., and Buffalini, Rick J., “Pulverized Glass and Landfill Liner Systems,” Waste Age, April 1995, pps. 25 1-262.


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(14) Swyka, Mark A., “Alternative Construction Materials in Waste Containment Applications,” Waste Age, March 1996, pps. 1 14- 1 1 6.

(1 5 ) Washington State Department of Transportation, Amendment to 1994 Standard Specifications Section 9-03.2 1, Standard Specifications for Road, Bridge, and Municipal Construction, 1994.



APPENDIX A GLASS PROCESSING COST PER TON ANALYSIS

APPENDIX B GLASS FEEDSTOCK ECONOMIC MODEL

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Documents

Glass Cullet Utilization Study - Pollution Prevention …infohouse.p2ric.org/ref/15/14338.pdf2.2.2 Specific Gravity and Relative Density Specific gravity is a measure of a material’s