Recycled Crushed Glass Research Articles

Geotechnical Performance of Recycled Glass-Waste Rock Blends in Footpath Bases

Laboratory and field experiments were undertaken to investigate the possible application of recycled crushed glass blended with crushed basaltic waste rock as a footpath base material. The laboratory experimental program included basic and specialized geotechnical tests including particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and triaxial shear tests. A field demonstration footpath comprising two sections of recycled glass-waste rock blends with 15% and 30% recycled glass content and a third control section with only waste rock was subsequently constructed on the basis of the outcomes of the initial laboratory tests. Subsequently field tests with a nuclear density gauge and Clegg impact hammer were undertaken, as well as laboratory testing of field samples to assess the geotechnical performance of the trial sections. The field and laboratory test results indicated that adding crushed glass may improve the workability of the crushed waste rock base material but subsequently results in lower shear strength. The blend with 15% glass content was found to be the optimum blend, in which the material presented good workability and also had sufficiently high base strength. Higher recycled glass content (30%) resulted in borderline, though still satisfactory, performance. The research findings indicate that recycled crushed glass in blends with crushed waste rock is a potential alternative material to be used in footpath bases. A separate study is recommended to evaluate the environmental risks associated with the usage of these recycled materials.

Instrumented large scale subsurface liquid injection model for bioreactor landfills

Abstract Bioreactor landfills are complex unsaturated systems where liquids are injected at relatively high pressures in on/off dosing cycles. In order to simulate hydraulic scenarios to improve understanding of leachate recirculation systems for landfills, 86 cm long by 30 cm wide by 56 cm tall unsaturated flow physical model was designed and fabricated. A permeable blanket was installed in the model to inject water. The blanket was 50 cm long × 30 cm wide × 2 cm thick and was made up of pea gravel. Uniform fine and coarse sands, which were thoroughly characterized for their hydraulic properties, were used in separate experiments to simulate waste. Pressure transducers and water content sensors were embedded in the model to monitor the migration of injected water in the blanket and in the underlying soils. Water was injected at flow rates ranging from 20 to 150 cm3/s in continuous and on/off modes to achieve transient and steady-state conditions. The responses of the pressure transducers embedded in the blanket in the model mimicked the responses of the pressure sensors embedded in an instrumented field-scale (55 m long × 9 m wide × 0.15 m thick) permeable blanket made up of crushed recycled glass used for recirculation of leachate at a municipal solid waste landfill. The effect of entrapped air present in the voids was evident from greater pressures developed during wetting which dissipated as the entrapped air escaped the system. This finding highlights the need to use of dual phase models for simulating pressures in bioreactor landfills.

Environmental risks of using recycled crushed glass in road applications

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.

Recycled crushed glass in road work applications

A comprehensive suite of geotechnical laboratory tests was undertaken on samples of recycled crushed glass produced in Victoria, Australia. Three types of recycled glass sources were tested being coarse, medium and fine sized glass. Laboratory testing results indicated that medium and fine sized recycled glass sources exhibit geotechnical behavior similar to natural aggregates. Coarse recycled glass was however found to be unsuitable for geotechnical engineering applications. Shear strength tests indicate that the fine and medium glass encompass shear strength parameters similar to that of natural sand and gravel mixtures comprising of angular particles. Environmental assessment tests indicated that the material meets the requirements of environmental protection authorities for fill material. The results were used to discuss potential usages of recycled glass as a construction material in geotechnical engineering applications particularly road works.

Evaluation of Alternative Media for Pebble Matrix Filtration Using Clay Balls and Recycled Crushed Glass

Protecting slow sand filters (SSFs) from high-turbidity waters by pretreatment using pebble matrix filtration (PMF) has previously been studied in the laboratory at University College London, followed by pilot field trials in Papua New Guinea and Serbia. The first full-scale PMF plant was completed at a water-treatment plant in Sri Lanka in 2008, and during its construction, problems were encountered in sourcing the required size of pebbles and sand as filter media. Because sourcing of uniform-sized pebbles may be problematic in many countries, the performance of alternative media has been investigated for the sustainability of the PMF system. Hand-formed clay balls made at a 100-year-old brick factory in the United Kingdom appear to have satisfied the role of pebbles, and a laboratory filter column was operated by using these clay balls together with recycled crushed glass as an alternative to sand media in the PMF. Results showed that in countries where uniform-sized pebbles are difficult to obtain, cla...

Crushed recycled glass as a filter medium and comparison with silica sand

AbstractThe objective of this work was to evaluate crushed recycled glass as a medium for rapid filtration. In the first part of this work, physical and hydraulic characteristics of the glass medium were studied. In the second part, pilot scale inline filtration experiments were carried out using raw waters from three different water sources. Two physically identical filter columns were operated in parallel in all the experiments. One filter contained a silica sand medium that is widely used in Turkey, whereas the other filter contained crushed recycled glass. Experiments were repeated five times as follows: (i) Without the use of a coagulant, (ii–iii) with 5 mg/L and 10 mg/L of alum, and (iv–v) with 5 mg/L and 10 mg/L of ferric chloride. Turbidity, particle counts, and head losses were measured and compared as functions of time. The following were observed: (1) Provided that a coagulant was used, the filter containing crushed glass produced effluent turbidities and particle counts similar to those obtained with the sand filter. (2) The crushed glass medium generated both a smaller clean‐bed head loss and smaller clogging head losses than those of the sand filter. It is concluded that crushed glass shows significant promise as an alternative to silica sand in rapid filtration.

Investigating the Alkali-Silica Reaction of Recycled Glass Aggregates in Concrete Materials

Application of crushed recycled glass in concrete materials can offer significant economical and environmental benefits provided that the alkali-silica reaction (ASR) of glass in concrete is properly controlled. Previous work on the use of glass sand in mortars shows that the reactivity of glass is influenced by its particle size as mortars containing finer glass sand show reduced ASR expansions. This may be counterintuitive since ASR is considered to be a surface reaction and should accelerate by increasing the surface area (i.e., reducing the size) of reactive aggregates. This paper presents a more in-depth investigation of the size-effect phenomena using scanning electron microscopy (SEM)/energy dispersive spectroscopy imaging of mortars containing different size glass particles. The SEM micrographs reveal that ASR does not occur at the glass-paste interface; rather, it occurs inside microcracks that exist inside glass particles which were generated during the glass bottle crushing operations. Larger size glass particles show larger and more active microcracks which render their high alkali-silica reactivity. At its interface with cement paste, glass shows evidence of pozzolanic reaction which leads to the formation of nonexpansive CSH. For particles smaller than #30 sieve (0.6 mm), the intraparticle ASR is minimal and only the interfacial pozzolanic reaction proceeds. This agrees well with the results of ASTM C1260 tests showing that mixed color glass aggregate smaller than #30 sieve does not produce deleterious ASR expansions in mortars even when no ASR suppressant (e.g., fly ash) is used.

The effect of aggregate-to-cement ratio and types of aggregates on the properties of pre-cast concrete blocks

The effects of aggregate-to-cement (A/C) ratios and types of aggregates on the properties of pre-cast concrete blocks are evaluated in this study. A/C ratios between three and six and three types of aggregates (i.e., natural crushed aggregate (NCA), recycled crushed aggregate (RCA) and recycled crushed glass (RCG)) were used in the experiments. It was found that the compressive strength of the paving blocks decreased as the A/C ratio increased. The results showed that the strength was directly proportional to the crushing strength of the aggregates (i.e., 10% fines value). Moreover, the water absorption of the blocks had a good correlation with the water absorption ability of the aggregate particles. The use of RCA as a replacement of NCA in the production of concrete blocks reduced the density and strength but increased the water absorption of the blocks. However, the potential high water absorption of the blocks as a result of the incorporation of RCA could be ameliorated by the use of RCG since RCG particles had a low water absorption value.

Enhancing the performance of pre-cast concrete blocks by incorporating waste glass – ASR consideration

Abstract There is a growing interest of using recycled crushed glass (RCG) as an aggregate in construction materials especially for non-structural applications. Although the recycled crushed glass is able to reduce the water absorption and drying shrinkage in concrete products due to its near to zero water absorption characteristics, the potential detrimental effect of using glass due to alkali–silica reaction (ASR) in cementitious materials is a real concern. The extent of ASR and its effect on concrete paving blocks produced with partial replacement of natural aggregates by crushed glass cullet are investigated in this study. This study is comprised of two parts. The first part quantified the extent of the ASR expansion and determined the adequate amount of mineral admixtures that was needed to reduce the ASR expansion for concrete paving blocks prepared with different recycled crushed glass contents using an accelerated mortar bar test in accordance with ASTM C 1260 (80 °C, 1 N NaOH solution). In the second part, concrete paving blocks were produced using the optimal mix proportion derived in the first part of this study and the corresponding mechanical properties were determined. It was found from the mortar bar test that the incorporation of 25% or less RCG induced negligible ASR expansion after a testing period of 28 days. For mixes with a glass content of higher than 25%, the incorporation of mineral admixtures such as pulverized fuel ash and metakaolin was able to suppress the ASR expansion within the stipulated limit but the results need to be confirmed by other test methods such as the concrete prism test. The study concluded that the optimal mix formulation for utilizing crushed waste glass in concrete paving blocks should contain at least 10% PFA by weight of the total aggregates used.

Leachate Recirculation Using Permeable Blankets in Engineered Landfills

Subsurface leachate recirculation or liquid injection methods for municipal solid waste (MSW) landfills are horizontal trenches, vertical wells, and permeable blankets. In this study, results of field-scale testing and numerical modeling of a recently developed subsurface leachate recirculation system called permeable blankets have been presented. In the field, at a MSW landfill located in Michigan, the travel of injected leachate in a 60-m-wide by 9-m-long by 0.15-m-deep blanket made up of crushed recycled glass was measured using an automated sensing system consisting of sensors embedded in the blanket. Leachate injection rates used in the field and simulated in this study ranged from 1.1 to 3.6 m3 ∕h per meter length of the injection pipe embedded in the permeable blanket. HYDRUS-2D was used to simulate the travel and pressure head of injected leachate in permeable blankets. The influence of the following parameters on the hydraulic performance of permeable blankets was evaluated: (1) hydraulic propert...

Geotechnical Sensor System to Monitor Injected Liquids in Landfills

Abstract A field-scale horizontal permeable blanket made up of crushed recycled glass was built in an active municipal solid waste (MSW) landfill to recirculate leachate. The permeable blanket is a new method for subsurface leachate recirculation or liquid injection. Leachate injection rates in the blanket ranged from 1.1–3.6 m3/h/m. An automated sensing system consisting of moisture content sensors, pressure transducers, and temperature sensors was designed to monitor the migration of injected leachate inside the blanket. The sensors were embedded in the blanket and connected to a data logging system. All sensors were able to detect the leachate migration within the blanket. The TDR and impedance moisture content sensors could not detect the migration of injected leachate once the surrounding medium got saturated. The pressure transducers and temperature sensors were able to detect leachate migration irrespective of the degree of saturation of the blanket. Unlike thermistor sensors, temperature readings measured by thermocouple sensors were influenced by air temperature.

Use of recycled crushed glass as a filtration medium in municipal potable water treatment plants

The aim of this study was to investigate the use of recycled crushed glass as a filtration medium for municipal potable water treatment plants. It evaluated the main physical parameters of recycled glass and its performance in a potable water treatment application. Pilot-plant testing was used to compare the performance of recycled glass to a typical sand filter medium in a conventional treatment process. Laboratory analysis was used to determine media characteristics. Pilot-plant testing determined that the filtration performance of the glass medium was similar to that of a typical sand medium of similar effective size and uniformity under all conditions tested. The glass medium had the benefit of taking 10-15% longer than the sand to reach particle breakthrough. The glass also appeared to accumulate headloss in most runs at a slightly lower rate than the sand. Backwashing observed during pilot-plant testing also showed that the glass expanded more than the sand under the same backwash water rates. This was noted to be a potential benefit to installations that have low backwash water flow.