Environmental risks of using recycled crushed glass in road applications

doi:10.1016/j.jclepro.2011.07.020

Journal of Cleaner Production

Volume 20, Issue 1, January 2012, Pages 170-179

https://doi.org/10.1016/j.jclepro.2011.07.020 Get rights and content

Abstract

Recycled crushed glass is the main by-product of the glass recycling industry. Insufficient knowledge of the geotechnical characteristics of recycled glass and its environmental risks are the primary barriers in its application in road works. An extensive suite of geotechnical and environmental tests were undertaken on two common types of recycled crushed glass (fine recycled glass and medium recycled glass) to study the potential of using them in road works as alternatives to natural aggregates. Recycled glass was found to exhibit either equivalent or superior workability, hydraulic conductivity and shear strength to natural aggregates within the same soil classification and demonstrated the potential to substitute natural sand and gravel mixtures in a range of road applications. To address the environmental concerns of using recycled glass in road work applications, a comprehensive series of chemical and environmental tests including total and leachate concentration for a range of contaminant constituents including heavy metals and aromatic hydrocarbons were carried out. Test results were compared with environmental protection authorities’ requirements and indicated that no leaching hazard will be experienced during the service life of recycled glass in road work applications. Other possible environmental risks along with health and safety precautions and management suggestions have also been discussed.

Introduction

The worldwide movement toward a more sustainable society with diverse constituencies including private sectors, governments and universities has resulted in finding new ways of recycling and reusing waste material in a range of applications (Lindsey, 2011). A sustainable society is one that achieves the needs of current generation without jeopardizing the needs of future generations while also reducing wastefulness believed to facilitate the movement toward an improved sustainability (Lindsey, 2011).

Waste material is considered any type of material by-product of human and industrial activity that has no lasting value (Younus Ali et al., 2011). Escalating demand for virgin material and consequent increase in waste material production around the world are major concerns in a sustainable development. Recycling is considered one of the main strategies in waste minimization and provides major benefits including reducing the demand for new resources; cutting down transport and production energy costs and using waste which would otherwise be piled at landfill sites (Tam, 2009, Blengini and Garbarino, 2010).

Several types of waste materials; recycled crushed glass among them are commonly used in geotechnical engineering applications such as road works (Disfani et al., 2009). Waste glass is the mixture of different colored glass pieces collected from municipal and industrial waste streams and is often mixed with a wide range of debris including food remaining, plastic and metal caps, ceramic, paper and soil (Wartman et al., 2004, Landris, 2007, Younus Ali et al., 2011).

Crushed recycled glass is a product of the glass recycling industry and is comprised of mixed colored glass particles which are often angular shaped with a noticeable percentage of flat and elongated particles in the mixture. The waste stream (municipal or industrial) from which the waste glass have been obtained and the crushing procedure used by glass recycling industries are believed to have significant effects on debris content, gradation curve and the flakiness index of the final product (FHWA, 1998, Wartman et al., 2004, Landris, 2007). These parameters subsequently affect other geotechnical characteristics of recycled glass with properties varying from one supplier to another (Landris, 2007, Disfani et al., 2009).

Recycled crushed glass (on its own or in blends with natural or recycled aggregates) can be used in a range of road work applications including subbase, embankments material and drainage media in roads. By the year 2000, no data was available for use of recycled crushed glass in Australian roads (Austroads, 2000). Even today the use of recycled glass in Australian roads is still limited and rare as typically only 3–5% recycled glass is permitted in granular products (Austroads, 2009). This is believed to be the result of a lack of knowledge on the geotechnical engineering characteristics of recycled glass and especially concerns on the environmental suitability of using recycled glass in road works. It is believed that similar barriers are faced in many other developed and developing countries.

This research study firstly investigates the geotechnical engineering characteristics of two different sample types of recycled waste glass produced in the state of Victoria, Australia through a comprehensive laboratory study. Fine Recycled Glass (FRG) and Medium Recycled Glass (MRG) are the main by-products of the glass recycling industry in Victoria with FRG being the more common of the two. The geotechnical engineering properties of FRG and MRG were studied by conducting an extensive suite of laboratory tests including particle size distribution (sieve and hydrometer analysis), specific gravity of the particles, compaction tests, Los Angeles abrasion test, hydraulic conductivity, California Bearing Ratio (CBR), direct shear and Consolidated Drained (CD) triaxial tests. The test results indicated that FRG and MRG exhibit the strong potential to substitute naturally occurring sand and gravel mixtures in a range of road work applications such as filling material in trenches, behind the retaining walls, road pavements and embankment fills.

The next phase of this research was undertaken to cover the knowledge gap on possible environmental risks of using recycled glass in road work applications during its service life. This comprised of a suite of chemical and environmental tests. Total contaminant concentration and leachate concentration tests (using two buffer solutions) were carried out for substances which have an impact on the environment including but not limited to heavy metals, sulfates and chlorides and aromatic hydrocarbons (Valls and Vazquez, 2002, Dalgren et al., 2011). Leaching tests are essential to ensure that no risk will be posed by the seepage water to the water streams and groundwater resources, since the release of contaminant constituents such as heavy metals into the deep soil and the groundwater might have severe consequences (Hellweg et al., 2005). The most reliable method to estimate the contaminant concentration in the seepage water is by means of a leaching test (Susset and Grathwohl, 2011) which will provide information about the impacts on groundwater in the life cycle of the projects (Hellweg et al., 2005).

Results of total and leachate concentration tests were compared with Environmental Protection Authority of Victoria (EPA Victoria) requirements for fill material and also different categories of waste material. Results of leachate concentration tests were also compared with US EPA guidelines to provide a better insight into the environmental impacts of using recycled glass in road work applications. The results of this study will facilitate the move toward increasing recycling of glass worldwide and especially toward the 75% overall recycling rate by 2013 strategy for the Victorian government, Australia (Clay et al., 2007).

Section snippets

Review of past studies

Several studies are available on the suitability of using recycled glass in concrete mixtures (Meyer and Xi, 1999, Corinaldesi et al., 2005, Taha and Nounu, 2008) and also on using recycled glass in asphalt layers (Halstead, 1993, Meyer, 2001; Huang et al., 2007, Landris, 2007). Available research studies indicate that recycled glass can be used as a free-draining material in filters and drainage blankets (Clean Washington Center, 1998). Recycled glass can be used as load bearing material in

Production and sampling

Sustainability Victoria is the State Government agency working with Victorians in order to use resources in a more sustainable way and to reduce the everyday impacts of communities and business on the environment (Clay et al., 2007). With a population more than 5 million people (Clay et al., 2007), over 186,000 tons of waste recycled crushed glass was recovered in the year 2008–2009 in the state of Victoria (Sustainability Victoria, 2010). Municipal recycled glass comprises mostly of food and

Geotechnical characteristics

Various international standards (ASTM, British and Australian) and test methods are currently available for geotechnical laboratory testing of recycled aggregates (Sivakugan et al., 2011). The geotechnical engineering properties of FRG and MRG were studied by conducting an extensive suite of laboratory tests and the results are presented in Table 1. Fig. 2(c) presents gradation curves of FRG and MRG sample types.

Both FRG and MRG sample types are classified as well graded sand size particles

Debris level, organic content and pH

Debris levels of FRG and MRG were determined using American Geological Institute Data sheet 23.1 and 23.2 (Clean Washington Center, 1998). Table 2 shows that the debris level determined by the weight method is less than one fifth and less than half of the value obtained by the visual method for FRG and MRG samples respectively. The primary reason for this is that a high percentage of debris in the FRG sample comprises of very low density material, predominantly paper. For the MRG sample, the

EPA guidelines

EPA Victoria is responsible for protecting human health, amenity and the environment from the hazards that may be posed by industrial wastes in Victoria, Australia (EPA Victoria, 2005). In waste management hierarchy charts introduced by different environmental protection organizations worldwide including EPA Victoria, it is recommended that where practicable, waste should be avoided, reduced, reused, recycled or used for energy recovery before being treated or disposed to landfills (EPA

Total and leachable concentration Results

Determining the leachate concentration of a material involves preparation of the leachate through a leaching process. The preparation of leachate involves contact between the solid matrix with the liquid (leaching fluid) to form leachate solutions in order to determine which elements initially present in the solid will be dissolved (Quina et al., 2011). The properties of the leachate depend on several variables such as leaching fluid composition (e.g. pH), method and time of contact, and

Discussion

Prior to using recycled glass in road work applications (such as embankment fills and pavement layers) all the possible environmental risks including the leaching hazard, exposure of contaminant constituents into soil, surface and ground water as well as the potential to spread into surrounding areas during the service life of the project should be investigated.

Conclusions

Results of an extensive series of geotechnical engineering tests on two sample types of recycled crushed glass produced in Victoria, Australia indicate their excellent workability and hydraulic conductivity which is especially beneficial in the event of using recycled glass in geotechnical fills. Shear strength test results suggest that recycled crushed glass exhibit shear strength behavior similar to naturally occurring sand and gravel mixtures with angular particles. The test results provide

Acknowledgement

The authors would like to thank Alec Papanicolaou, Geomechanics laboratory technician of Swinburne University of Technology for his technical support during the experimental works.

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¹: Present address: Faculty of Engineering and Industrial Sciences (H38), Swinburne University of Technology, PO Box 218, Hawthorn VIC 3122, Australia. Tel.: +613 92144679.

²: Tel.: +1807 626 1312.

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Environmental risks of using recycled crushed glass in road applications

Abstract

Introduction

Section snippets

Review of past studies

Production and sampling

Geotechnical characteristics

Debris level, organic content and pH

EPA guidelines

Total and leachable concentration Results

Discussion

Conclusions

Acknowledgement

J. Waste Manage.

J. Cleaner Production

J. Cleaner Production

J. Waste Manage.

J. Waste Manage.

J. Cleaner Production

J. Resour. Conserv. Recycl.

J. Cleaner Production

Soils and Foundations

J. Waste Manage.

J. Resour. Conserv. Recycl.

J. Waste Manage.

J. Constr. Build Mater.

J. Cleaner Production

J. Waste Manage.

Crushed brick blends with crushed rock for pavement systems. Proceedings of ICE (UK)

Waste Resource Manage.

Use of recycled materials and the management of roadside vegetation on low trafficked roads

Guide to pavement technology part 4E: recycled materials

A tool kit for the use of post-consumer glass as a construction aggregate

Soil mechanics

Shear strength behavior of recycled glass-biosolids mixtures, Proceedings of 62nd Canadian Geotechnical Conference, 20–24 September