Chao Qun Lye

Production and Properties of Glass Cullet

This chapter, which in many ways can be viewed as the foundation chapter for what follows, begins with describing briefly the barriers to the use of waste glass, as well as its market opportunities, instead of sending it to the landfill, together with the related financial and environmental benefits. The types of waste glass and the collection schemes in operation and how these may influence the quality of the final product and the classification and handling of unprocessed waste glass are dealt with. This is followed by the processing of waste glass into recyclable glass cullet for the primary glass market and secondary markets, with specific focus on the use of glass cullet in the construction market and ceramics. The chemical and physical properties of glass cullet, mainly relating to the use of glass cullet as a fine aggregate, as a filler or cement in mortar and concrete, and in geotechnical and road pavement applications, are discussed, based on widely published data over a period of time.

Use of Glass Cullet in Geotechnical Applications

This chapter assesses the performance of glass in geotechnical applications, dealing with the material characteristics, geotechnical properties, durability, environmental impact, case studies and guidance relating to the use of this material. Glass cullet (GC) tends to be used in the coarse sand-to-medium gravel size range and its grading does not change significantly after compaction. The material is almost impermeable and is slightly lighter than natural sand and gravel. The compaction characteristics and permeability of GC are similar to those of natural material. Depending on the size, the frictional angle of GC is about 40–50 degrees. GC is inert and safe to use provided that its debris content is low. GC has been successfully used as a full and partial replacement for sand and gravel in various geotechnical applications such as trench backfill, structural fill and artificial beach/dune fill.

Use of Glass Cullet in Road Pavement Applications

This chapter assesses the appropriateness and performance of glass cullet (GC) as an aggregate in road pavement, dealing with its use in unbound, hydraulically bound and bituminous bound applications. The California bearing ratio of GC has been found to be comparable to that of natural aggregate. In hydraulically bound applications, GC fine aggregate is shown to be compatible with other waste materials for use in subbase and base, such as steel slag, ladle furnace slag and foundry sand. The performance of GC in concrete rigid pavement was generally satisfactory. It is shown that the Marshall method can be adopted when designing bituminous mixtures made with GC in coarse, fine and filler aggregate size fractions. The use of GC at up to 10% does not adversely affect the stiffness modulus, rutting resistance or moisture damage resistance of bituminous mixtures. Antistripping agent is effective in improving the performance of mixtures containing GC. The material does not have a negative environmental impact. Case studies with GC in road pavement applications are also included.

Use of Glass Cullet in Ceramics and Other Applications

Synopsis This chapter deals with the use of glass cullet as a new material in alternative markets, other than the previously covered concrete, geotechnical and road pavement applications. The results of several experimental investigations have been compiled and analysed on the use of waste glass in the manufacture of ceramic-based products, namely, glass-ceramics, foam glass-ceramics, ceramic bricks and tiles, porcelain products and glazing material. Other applications of waste glass have also been identified and succinctly addressed in this chapter, such as the production of aesthetic finishing materials, filtration medium, epoxy resins, glass fibres, blast abrasive, paint filler, elastomeric roof coatings, amongst others.

Use of Glass Cullet as Filler Aggregate

Synopsis The performance of glass cullet (GC) filler as a fine aggregate replacement in concrete and as a filler component in self-compacting concrete (SCC) is examined in this chapter. The fresh properties of concrete and SCC are largely unaffected when GC filler is used, except for consistence, in which high contents of GC filler can lead to a reduction. At a fixed water/cement ratio, the use of GC filler tends to increase the compressive strength of concrete and SCC. The pozzolanic effect of GC filler can be beneficial to the long-term strength. Although limited, other data show that the impact of GC filler on flexural strength, elastic modulus and shrinkage is generally positive. The use of GC filler as a fine aggregate in concrete or a filler component in SCC results in either an improvement or no significant change in the permeation and durability properties, except for the resistance to carbonation, which could be affected if the pozzolanic effect of the GC filler is pronounced. The use of GC filler at low content is not likely to give rise to alkali–silica reaction concern. No relevant information has been found on the environmental impact or in case studies related to the use of GC filler.

Use of Ground Glass Cullet as Cement Component

Finely ground glass cullet (GGC) exhibits pozzolanic properties. Its inclusion with Portland cement does not significantly change the characteristics of cement apart from prolonging the setting times. In the fresh state, the consistence and stability of concrete are almost unaffected, but the density is slightly reduced when GGC is used. It also reduces the temperature rise and heat of hydration of the concrete. Depending on the content and fineness of GGC, its use can maintain or improve the compressive strength of concrete. The relationship between compressive strength and tensile strength also remains unchanged. The use of GGC reduces the modulus elasticity of concrete and increases shrinkage. Other than carbonation, GGC is shown to generally improve the permeation and durability properties of concrete. The use of this material is safe in terms of environmental impact and it has been used in the concrete construction industry since the 2000s.

Environmental Impact, Case Studies and Standards and Specifications

This chapter discusses the leaching of toxic elements of copper slag (CS), the associated environmental impact and case studies in which CS is used in various construction applications. CS is a non-hazardous waste material and its leaching behaviours are not affected by its type, but its particle size and the pH condition can affect the leaching behaviours. The leaching studies on CS used as either raw feed for cement clinker, in ground form as cementitious material, or an aggregate in concrete, geotechnical and road pavement applications, show that the leached element concentrations are generally not to be of concern. Although limited in number and scope, the available information that can be drawn from the case studies of CS suggest that the material is generally suitable for use in construction material. The relevant standards and specifications for CS use in various construction applications are also discussed.

Production and Properties of Copper Slag

This chapter deals with the production, chemical and physical properties and potential applications of copper slag (CS), as well as its associated environmental impact. Air-cooled and quenched slags are the outcomes of different cooling rates applied during the production of copper. Spent CS is a reuse material from its application as an abrasive. CS is an angular, smooth, hard, dense and low-absorption material, composed mainly of iron oxide and silicon dioxide. It has low loss on ignition, has low chloride and sulphate contents and is innocuous to alkali–silica reaction. Air-cooled slag can be crushed to coarse and fine aggregate fractions, whilst quenched slag is granular, similar to sand. The impact and crushing values and friction angle of slag are similar to or better than those of the natural aggregate.

Use of Copper Slag in Road Pavement Applications

The effect of copper slag (CS) on the engineering properties of road pavements is described based on the literature published since 1992. CS has a similar California bearing ratio to natural sand. When used in hydraulically bound applications, it increases workability and compressive and flexural strengths, and decreases drying shrinkage of concrete. It may also improve the abrasion resistance of concrete. The Marshall method can be adopted when designing a CS bituminous mix. The material reduces the modulus, but increases fatigue life of the bituminous mix and has no effect on its water sensitivity. Though little is known about its use in real applications, CS should not present any threat to the environment. The study of copper tailings has also been included.

Use of Copper Slag in Geotechnical Applications

The data published relating to the geotechnical performance of copper slag (CS) since 1964 have been systematically analysed and evaluated. CS is a non-plastic material, which has better compaction characteristics than sand. Its permeability and consolidation rates are similar to those of sand, but it may be more compressible. The material has a friction angle close to that of well-graded sand, and its use as backfill reduces the active lateral pressure on retaining walls. The material does not cause any adverse environmental impact. The views of the construction industry about its use have been mostly positive, and CS has been considered in the development of the new prEN 13242 (2015). The potential for the use of copper tailings in geotechnical applications is also very briefly discussed in this chapter.