Recycled Glass Aggregate Research Articles

Performance of normal-weight and lightweight 3D printed cementitious composites with recycled glass: Sorption and microstructural perspective

The development of sustainable mixtures has been a widely researched topic in the last decade, as the cement and concrete industries are among the most polluting sectors. Recycled materials can eliminate the need for extraction of natural materials through re-utilization of waste, reducing the environmental impact. To date, few studies have analyzed the effects of incorporating recycled glass aggregates on the water transport properties and microstructure of 3D printable mixtures.This study assesses the feasibility of incorporating recycled glass as a replacement for natural aggregate in 3D printable mixtures. For this purpose, three normal-weight and three lightweight mixtures containing 0, 50, and 100 vol.% of recycled glass aggregate as basalt aggregate replacement were evaluated in cast and printed samples. Expanded thermoplastic microspheres (ETM) were included to create the lightweight mixture composition. This experimental work evaluated the effects of incorporating recycled glass, ETM, and the impact of the printing process on the microstructure, sorption, and capillary water porosity (CWP).The printing process has proven to be an influential factor affecting the shape, size, and quantity of porosity. In addition, the printing process was demonstrated to be more influential on porosity formation than the inclusion of recycled glass or ETM. Incorporating recycled glass results in a slight decrease in the PHg porosity, more spherical pores, and lower anisotropic tendency. Furthermore, adding ETM has a filling effect, leading to a more compact microstructure.

High-volume recycled glass cementitious and geopolymer composites incorporating graphene oxide

This study presents the development of high-volume recycled glass construction materials using recycled glass aggregate (RGA) as a 100 % sand replacement, recycled glass powder (RGP) as 40 wt% of the binder, and 0.1 wt% graphene oxide (GO) as nano-reinforcement. The research investigates the individual and their combined effects on the engineering performance, reaction kinetics (using calorimetry, X-ray diffraction-XRD, Fourier Transform Infrared-FTIR and Thermogravimetric analysis-TGA), and microstructure (Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy-SEM/EDS) for both cementitious and geopolymer systems. The results indicate that while RGA reduces strength and exacerbates alkali-silica reaction (ASR), the presence of 40 wt% RGP significantly mitigates ASR despite a lower strength gain in both systems. Geopolymers exhibit significantly lower ASR expansion compared to cementitious matrices owing to their superior alkali-binding capacity and denser microstructure, which restricts water and alkali ion mobility. 0.1 wt% GO was found to accelerate geopolymerisation, enhancing the strength of geopolymer mixes, but it decreased compressive strength in cement-based mixes due to self-desiccation-induced micro-cracking under ambient curing condition. The study also highlights that cement and metasilicate, as well as slag, are the main contributors to cost and CO2 emissions in cementitious and geopolymer systems, respectively. Overall, geopolymers exhibit a significantly lower global warming potential (< 180 kg CO2-eq/m3) compared to cement-based mixes (> 365 kg CO2-eq/m3) with a comparable cost (190–230 AUD/m3). The results indicate the potential for sustainable construction applications using high volumes of recycled glass, incorporating over 70 % of the mixture by weight.

Tensile Behavior of Green Concrete Made of Fine/Coarse Recycled Glass and Recycled Concrete Aggregates

The study conducted axial tensile strength tests on concrete samples that replaced conventional aggregates with recycled aggregates. In Series I, using FNG instead of FNA resulted in a reduction in compressive strength by 12.8–49.8% and tensile strength by 14.5–44.6%. If the proportion of FNG exceeds 50%, compressive strength decreases by more than 24.5% and tensile strength by more than 27.5%. In Series II, replacing CNA with CRG reduced compressive and tensile strengths by 18.4–32.8% and 5.1–24.9%, respectively; exceeding 40% CRG results in a compressive strength reduction of more than 32.8% and a tensile strength reduction of more than 24.9%. In Series III, samples made with RCA, CNA, and 20% CRG showed a compressive strength decrease of 8.8–22% and a tensile strength decrease of 10.7–26%; RCA80 samples showed maximum reductions. In Series IV, replacing CNA with RCA resulted in compressive and tensile strength reductions of 15.4–34.7% and 13.9–24.3%, respectively; RCA80 samples again showed maximum reductions. Maximum stress unit deformation values (εo) increased by 3–58.4% in Series I, 9–80% in Series II, 10–44.9% in Series III, and 9–32% in Series IV. Tensile toughness values showed the highest increase of 35.15% in the CRG40 sample and the lowest of 0.13% in the RCA40-20 sample. The use of glass aggregates in concrete is feasible, but exceeding certain ratios can significantly reduce strength. Concrete can effectively use waste glass as a partial substitute for cement, fine aggregates, or as a filler material, potentially enhancing compressive strength.

Influence of recycled rubber and glass aggregates on magnesium sulfate resistance of geopolymers: Physio-mechanical properties and mechanisms

Recycled rubber aggregates (RRA) and recycled glass aggregates (RGA) are sustainable alternatives to natural aggregates. However, the influences of RRA and RGA on the magnesium sulfate resistance of geopolymers remain unclear. Previous studies have focused on the influences of binder type and composition on magnesium sulfate resistance but have neglected the role of aggregates. This study bridges this gap and demonstrates the influences of RRA and RGA on the magnesium sulfate resistance of geopolymers. This study investigated the physical properties, mechanical properties and phases of FA and GBFS-based geopolymers containing 0:10 – 10:0 RRA and RGA after being exposed to 5 % MgSO4 solution for 90 days. The results showed that compared to 100 % RGA, the 90-day length and mass of 100 % RRA increased by 50.48 and 33.22 times, respectively, and the 90-day compressive, flexural and splitting tensile strengths of 100 % RRA decreased by 65 %, 43.28 % and 56.75 %, respectively. However, the changes in length and mass of 100 % RGA were very small, and the mechanical properties even slightly increased rather than decreased. RRA + RGA showed an interval performance between 100 % RRA and 100 % RGA. The different magnesium sulfate resistance of RRA and RGA were attributed to the following mechanisms. RRA caused much higher drying shrinkage of geopolymers than RGA because the soft nature of RRA increased uncoordinated deformation, leading to micro-cracks in the matrix before magnesium sulfate exposure. The pre-existing micro-cracks served as physical transportation paths for external ions to diffuse into the interior of specimens, leading to expansive gypsum crystals formed in these micro-cracks. The accumulation of expansive gypsum crystals enlarged these micro-cracks and facilitated their propagation, leading to the expansion, cracking and degraded mechanical properties. By contrast, RGA reduced drying shrinkage due to its hard nature, which limited the availability of micro-cracks as physical transportation paths for external ions and therefore reduced the formation of expansive gypsum crystals and improved the magnesium sulfate resistance of geopolymers.

Improving the mechanical performance of railway concrete sleepers using recycled materials: An experimental and numerical study

This paper explores the use of three waste materials available in vast quantities, including waste tires, glass bottles and bamboo furniture, in the manufacture of railway sleepers. Mechanical properties of recycled concrete have been studied to establish an optimal mix suitable for concrete railway sleeper manufacturing. Thus, 5%, 10%, 15% and 20% recycled rubber sands (RRS) by volume of fine aggregate are used instead of 30# and 60# mesh sizes of fine aggregate. Moreover, 20%, 40%, 60%, 80% and 100% of aggregate volume are replaced by recycled glass aggregate (RGA) particles. Furthermore, different percentages of recycled bamboo fibers (RBF) have been used as 1%, 2% and 3% by volume of concrete. According to the optimal concrete mixtures of RRS, RGA and RBF, twelve concrete railway sleepers are manufactured and tested for middle and rail seat bending strengths. Results show that ref. sleeper has almost 16% and 24% lower strengths than RGA sleeper in middle and rail seat, respectively, while ref. sleeper have higher strengths by 16% and 13%, and 18% and 7% than RRS sleeper (M60-R5) and RBF sleeper (B2) in middle and rail seat, respectively. The FEM results show that the ([Formula: see text]) of the RGA sleeper is the minimum ratio by 1.11 and 1.13 for rail seat and middle of sleeper, respectively, which is the best performance. In RBF sleeper FEM model, Bamboo fiber can only bear 5% and 8% of total stress in middle and rail seat, respectively, due to low mechanical properties of fibers.

Grain Size Correction of Pavement Unbound Granular Material Using Recycled Glass Aggregate

Millions of tons of used glass are recovered worldwide each year. As an environmental friendly solution, the glass waste are collected and recycled to manufacture new glass products. Nevertheless, the additional cost associated with separating waste glass materials can be seen as an inconvenience in this closed loop recycling method. This is why it is very interesting to valorise this waste material in other areas. Using glass waste in geotechnical applications and road construction has showed a particular interest. However, using such technique is hampered by insufficient knowledge on geotechnical characteristics of mixtures of natural materials and glass waste. This research investigates using Recycled Glass (RG) to correct the grain size of an unbound granular material for road pavement. The reference material is a crushed limestone of a class 0–20 mm which presents a deficiency of fine aggregates. Bearing tests, mainly Proctor and CBR tests, were conducted on the reference material and the mixtures composed of natural material and RG. The hydraulic conductivity was also measured. The findings indicated that the addition of the fine part of glass waste allowed correcting the grain-size distribution and therefore the bearing capacity has been improved. Furthermore, the mixture of natural material and RG upgrades the permeability class, which contributes to the durability of pavement layers.

A comprehensive evaluation of the photo-catalytic performance of recycled glass aggregate incorporated permeable cement-based mortar with TiO2 as a photo-catalyst

This study aims to investigate the effectiveness of incorporating recycled glass aggregate (RGA) in TiO2-containing cement-based permeable mortars in terms of their photo-catalytic performance. To do this, standard and permeable mortars were produced with the RGA utilization rates of 15% and 30% (by weight of total aggregate content). Photo-catalytic activity of the mortars was evaluated through the determination of NOx and NO degradation capacities, NO2 transformation ratio and the selectivity, and their photo-catalytic activity performances were compared with each other and with reference specimens without any RGA to assess the efficiency of RGA utilization in terms of photo-catalytic degradation. Microstructural and mechanical properties of the mortars were also evaluated by performing scanning electron microscope (SEM) analysis and compressive strength test, respectively. According to the experimental results, regardless of curing age, utilization of RGA as aggregate caused decrements in the strength results because of the lower adherence capability with matrix. NOx degradation results indicated that permeable structure of the photo-catalytic mortars allows NOx species to diffuse to the inner part of the hardened specimen in favor of stimulation of photo-catalytic degradation reactions in deep along with the surface. RGA utilization was also allowed to penetration of UV lights throughout the matrix providing improved the photo-catalytic activity for the TiO2-containing specimens. The correlation between the selectivity results and the degradation rates of NOx demonstrates the reliability of selectivity as a parameter for evaluating the photo-catalytic performance.

Mechanical properties of unbound limestone aggregates replaced by recycled glass aggregate for pavement in Canada/Quebec

This study investigated the use of recycled glass aggregate (RG) as unbound base/subbase material. The experimental tests included compaction, Los Angeles, Micro-Deval, and California bearing ratio (CBR) tests. In this regard, a fine proportion of course limestone aggregate (MG20) was replaced by RG with size ranging from 0 to 5 mm based on the volumetric method. Adding RG to the coarse aggregate improved durability in wet conditions, which is more representative of the field condition of Canada/Quebec, but decreased in dry conditions. CBR values decreased with increasing RG inclusion, but all blends with 0%–100% RG in the fine fraction of MG20 met minimum requirements for unbound granular layers in Quebec. A simple model predicting the resilient modulus values of these materials based on CBR values at different stress levels was suggested. This equation estimates Mr values of various aggregate-RG blends under a wide range of mean stresses based on their CBR values.

Lightweight and Alternative Backfills for Highway Applications: State-of-the-Art Practice in the U.S.A.

The use of lightweight and alternative materials in geotechnical applications may be advantageous when compared with more conventional structural backfills. This paper focuses on using seven lightweight and alternative backfill materials in highway applications: controlled low-strength materials (CLSM); expanded shale, clay, and slate (ESCS); foamed glass aggregates (FGA); lightweight cellular concrete (LCC); polystyrene geofoams; recycled glass aggregates; and tire-derived aggregates (TDA). The current knowledge and the state-of-the-art practice for using these materials in highway geotechnical applications of interest, that is, retaining walls, bridge abutments, pipes/culverts, embankments, and slope stabilization, were evaluated. The paper first introduces the materials, including the unit weight ranges for each lightweight and alternative fill material, and their applications. Then, the key aspects and advantages of each material for highway geotechnical applications are listed and evaluated. Further, for each material, the physical, chemical, and mechanical material properties are discussed, as well as the design requirements and guidelines, construction and placement guidelines, and the environmental considerations. Finally, the technology-ready aspects of each material studied with regard to its application to highway geotechnical problems, and the identified barriers to the deployment of each one were summarized and discussed. Based on the current knowledge, some lightweight and alternative materials (e.g., ESCS, CLSM, TDA) have been more widely used in the U.S.A. for geotechnical applications, whereas others are still emerging technologies. Further, certain materials (e.g., LCC, TDA, geofoam) have well-developed design guidelines, whereas others (e.g., CLSM, FGA) require more research.

Effect of recycled of recycled glass aggregates on mechanical and physical properties of structural concrete

The exponential expansion in concrete use has put the environment under immense pressure to supply cement, aggregates, and water. Natural resource consumption impacts the environment and undermines the concrete industry. A swift shift towards sustainable concrete is required considering the emergency triggered by human activity on the climate. Glass concrete (GC) has sparked the curiosity of the construction industry owing to its environmentally friendly approach. The study uses recycled glass aggregates (RGA) to partially replace natural aggregates (NA) to produce sustainable structural concrete with superior mechanical properties. 20% glass concrete outperformed all others in fresh and hardened concrete. Only 75% glass blend demonstrated a slight decrease in compressive strength due to drop in density. Glass concrete showed a lower water absorption capacity. However, glass has triggered an alkali-silica (ASR) reaction, reducing the durability of the concrete significantly.

Environmental assessment of recycled glass aggregates in reinforced concrete

The sustainability of the concrete industry is in jeopardy due to the use of natural resources which impacts the environment. A swift shift towards sustainable thinking is required considering the emergency triggered by human activity on the climate. Glass concrete (GC) has sparked curiosity of the construction industry owing to its environmentally friendly approach. This article examines the environmental implications of partially replacing natural aggregates in concrete with recycled glass aggregate at various percentages i.e. 10%, 25%, 50%, and 75% which is then compared to controlled concrete specimen (CC). The assessment indicated 287 kgCO2Eq were generated for control concrete (CC), whereas concrete with 20% glass aggregate (GA) resulted in 258 kgCO2Eq. global warming potential. Likewise, M25 concrete was reported to have 1.68 kgCFC-11Eq compared to 1.85 kgCFC-11Eq for natural aggregate concrete. Even though glass concrete demonstrates lower values in several environmental effects, there is need for improvement in impact categories including acidification and respiratory organics.

Influence of seawater concentration on alkali-silica reaction of seawater sea-sand concrete: Mimicking through NaCl solution and recycled glass aggregate

Seawater sea-sand concrete (SSC) is one environment-friendly and promising construction material. Nevertheless, limited research shed favorable light on alkali-silica reaction (ASR) of SSC. This work provided a novel insight regarding the fast test method that (i) the recycled glass aggregate (RGA) was used for fast assessing the effect of seawater concentration on ASR, reusing its characteristic resource; (ii) the NaCl solutions with different concentrations were used to mimic different salinities of sea waters; and (iii) a modified curing method was adopted. The results showed that the NaCl solution could be used for assessing ASR risk of SSC instead of seawater. The specimens mixed with twice and above the sodium concentration of seawater would exhibit ASR expansion, strength reduction, coarsening of nanopore distribution, and the cracks on the macro and micro levels. However, the change of NaCl concentration scarcely affected the composition and content of hydration products. Additionally, with increasing the mixing Na+ concentration, the ASR crack would firstly appear in the interface between the cement paste layer and the glass layer, and then developed in the internal zone of RGA matrix with different hardness, elastic modulus, and Si contents based on the destroyed degree.

Application of recycled crushed glass in road pavements and pipeline bedding: An integrated environmental evaluation using LCA

The study aims to conduct a comprehensive life cycle assessment (LCA) of mixed glass waste (MGW) recycling processes to quantify the environmental impacts of crushed glass as a partial substitute for virgin aggregate. Upstream washing, crushing, and sorting conducted at material recycling facilities (MRF) are the prime activities to assess whether reprocessed MGW in pavement construction is an alternate feasible solution. None of the previous studies explicitly account for the relative uncertainties and optimization of waste glass upstream processes from an environmental perspective. The study calculates environmental impacts using the LCA tool SimaPro considering design factors attributed to transportation, electricity consumption, use of chemicals, and water for reprocessing glass waste. Relative uncertainties of design variables and the national transition policy (2021−2030) from non-renewable to renewable energy sources have been validated by performing detailed Monte Carlo simulations. The correlation coefficients (r = 0.64, 0.58, and 0.49) of successive variables explain how the higher environmental gains of the glass recycling process are outweighed by diesel, energy consumption, and transportation distances. Compared to natural quarry sand, the recycled glass aggregate produced through crushing and recycling of its by-products reduces CO2eq emissions by 16.2 % and 46.7 %, respectively. The need for a washing line at the plant, in addition to crushing, results in a higher environmental impact over natural sand by 90.1 % and emphasizes the benefits of collecting waste glass through a separate bin, hence avoiding contamination. The result indicates that the benefit of lowering emissions varies significantly when considering waste glass landfilling. Moreover, this study evaluates the potential impacts on asphalt and reinforced concrete pavements (RCP) with 5 %, 10 %, 15 %, and 20 % replacement of natural sand with recycled glass aggregate. The LCA emphasizes the limitations of energy-intensive waste glass reprocessing. The obtained results and uncertainty analysis based on primary MRF data and recycled product applications provide meaningful suggestions for a more fit-for-purpose waste management and natural resource conservation.

Effective management of waste glass: Application in the production of eco-friendly concrete

Aggregates are one of the main components of concrete as they give volumetric stability to concrete structures. However, consuming natural aggregates dramatically impacts the environment destroying the ecosystem. Thus, it is crucial to find secondary resources that can provide an acceptable performance level as natural aggregates. Many countries, especially in Asia, have limited for natural aggregates; hence, making natural aggregate expensive. Therefore, recycling waste materials with the potential to be used as aggregates would mitigate this challenge thereby reducing the impact on the environment. Hence, researchers worldwide are replacing various kinds of waste materials with partial or complete replacements for the natural aggregates in concrete. In this research work, recycle waste glass aggregates are used to partly substitute natural fine and coarse aggregates in producing eco-friendly concrete. In this regard, 5–20% of recycled glass aggregates were used to replace natural aggregates in concrete. Concrete slump test, mechanical properties such as compressive and split tensile strength tests are conducted on eight concrete mixes. As the percentages of aggregates increased due to the angular shape of fine glass aggregates, it decreases the slump value of concrete. Nevertheless, from the results, it is stipulated that recycling of waste glass aggregates can be an alternative to natural aggregates for concrete if used properly. Successful uses of these aggregates can save the environment and waste disposal costs and significantly save the total production cost of concrete as the density of glass concrete is lighter than the concrete made from conventional aggregates.

Eco-Efficiency Assessment Utilizing Recycled Glass Aggregate in Concrete

This paper reviews specific technical and eco-efficiency performance issues in using glass waste as an aggregate in the production of concrete. Eco-efficiency is a relatively modern tool in the pursuit of sustainability. Eco-efficiency is the concept of maximising the benefits from the use of non-renewable resources while minimising the use of non-renewable resources. The paper details a life cycle assessment and eco-efficiency review of a potentially sustainable alternative to traditional concrete, made from ordinary Portland cement. The study follows the ISO framework, which includes goal and scope, a life cycle inventory, life cycle impact assessment, life cycle costing, normalising of data and the creation of an eco-efficiency portfolio. SimaPro life cycle assessment software has been used to further analyse the use of recycled glass aggregate as a replacement for naturally occurring stone aggregate in geopolymer concrete. The study found that the use of geopolymer concrete as a non-cement based alternative concrete was a viable way to reduce emissions with a high global warming potential but faced challenges in other environmental impact areas. There is a need for ongoing research and study on the application of eco-efficiency as a tool in the pursuit of sustainable practices in society.

A review of 3d printing technology-the future of sustainable construction

The construction industry has traditionally been slow, labour-intensive, and faced challenges in sustainability. However, recent advancements in 3D concrete printing (3DCP) offer promising solutions for faster, more precise, and sustainable construction practices. This critical review examines the developments and advances in 3D printing of concrete, as well as the challenges and future potential of this technology in sustainable construction. Our study highlights the advantages of 3D printing technology, such as reducing costs, materials, and time, enhancing safety, and minimizing environmental pollution. Moreover, 3D printing enables the creation of complex and intricate designs that were previously challenging to achieve through traditional methods. To address sustainability concerns, we explore eco-friendly alternatives like high-volume fly ash, geopolymers, and recycled glass aggregates that can be utilized in 3D printing. These materials not only reduce environmental impact but also enhance the long-term strength performance of building components. While discussing the different 3D printing methods, including extrusion and powder-based techniques, we emphasize the potential applications of each method in sustainable construction. In conclusion, 3D printing technology has the potential to transform the construction industry by offering low-cost, efficient, and environmentally responsible solutions. However, challenges like job implications and structural stability must be addressed through further research.

Flexural Capacity of Fire-Affected Concrete Members with Recycled Glass Aggregate and Glass Pozzolan

Adding recycled glass components to concrete mixes is a novel and sustainable option. Prior studies have recommended replacement ratios of 30% glass aggregates and 20% ground glass pozzolan as optimum substitutions in concrete mixes. The compressive strength of glass concrete has been shown to increase when glass components are used with these proportions. Less information is available on the flexural strength of such concrete, and no previous research has been conducted on the flexural capacity of glass concrete exposed to high temperatures. To bridge this knowledge gap, cured concrete cylinders and beam samples using various glass coarse aggregate and ground glass pozzolan replacement ratios were heat-treated in a furnace. The heat-affected samples were then tested for their compressive and flexural capacities. It was found that glass pozzolan increased the mix workability, while glass aggregates reduced it. The compressive strengths were modesty increased and the flexural capacities were drastically reduced (up to 93%) after heat exposure. Therefore, recycled sustainable glass concrete may be efficiently used in concrete compressive members and in properly designed flexural members. It can also be used efficiently in architectural non-load-bearing members for insulating and aesthetic effects.

The efficiency of recycled glass powder in mitigating the alkali-silica reaction induced by recycled glass aggregate in cementitious mortars

With the potential for a decline in fly ash (FA) production over time, due to the phasing down of coal fired power plants, alternative supplementary cementitious materials need to be identified. The efficiency of pulverised glass powder (PGP) was studied for its reactivity and its capacity for inhibiting alkali-silica reaction (ASR) that results from utilisation of recycled glass as a fine aggregate (sand) replacement. Characterisations of pastes containing PGP reveal that PGP may possess latent hydraulic properties, resulting in a more than 75% strength activity index, together with better strength gain than FA-blended pastes. PGP also offered increased heat of hydration compared to FA, from a combination of the dilution effect, filler effect and early-age reactions of PGP. A comparable efficiency of PGP and FA in ASR expansion mitigation was confirmed with mortar bar expansions of less than 0.10% at cement replacement levels of at least 10%. Both PGP and FA provided alkali dilution and reduced the mass transport in hydrated cement paste from the refinement of larger pores to below 60 nm. The FA mix consumed calcium hydroxide and, thus, performed marginally better than the PGP mix in mitigating ASR. This pozzolanic reactivity is not evident for PGP, whereas in the literature glass powders are often regarded as pozzolanic. Microscopic images confirm that PGP and FA significantly limit the occurrence of ASR gels without altering its composition. It was concluded that PGP is a comparable ASR inhibitor to FA, despite the underlying differences in their mechanisms. The result of this research support the utilisation of recycled glass both as an aggregate, and as an ASR-inhibiting SCM in cementitious systems.

A ternary blended binder incorporating alum sludge to efficiently resist alkali-silica reaction of recycled glass aggregates

Recycled glass has been widely used as aggregates in cement-based materials. However, it may lead to a severe alkali-silica reaction (ASR) due to high reactive silica content in glass, causing cracks and failures in concrete structures. Our previous research indicated that utilization of alum-based drinking water treatment sludge (DWTS) as partial cement replacement could mitigate ASR. However, such mitigation only occurred when a high volume of DWTS was used and resulted in significant mechanical property deterioration. This study developed ternary blends containing ground granulated blast furnace slag (GGBFS) and DWTS content to overcome the strength loss. Up to 30% of the cement were replaced with DWTS and GGBFS at a mass ratio of 1:1. The results showed that the mortar made with the ternary blends had considerable compressive strength (37 MPa) compared with reference (34 MPa) when 30% cement by mass was replaced, and this replacement proportion could effectively control the ASR expansion under 0.1% in samples. The microstructural analysis was conducted using X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF), and backscattered electron (BSE) coupled with energy-dispersive X-ray spectroscopy (EDS) techniques. The results indicated that the Al in the DWTS could limit the precipitation of the detrimental ASR gels by promoting the generation of calcium aluminum silicate hydrate (C-A-S-H), binding alkaline and preventing ASR gels from transforming into low-flowable gels.

Sustainable shotcrete production with waste glass aggregates

This study employs statistical and experimental procedures to assess the applicability of crushed waste glass to replace natural sand in shotcrete production for use in tunneling, mining and excavation industries as a support system. Mechanical strength under different uniaxial and biaxial load combinations, fracture properties, and ultra-high-speed photography of the crack growth mode in the newly developed shotcrete mixes were studied and compared against the control mix at 0% waste glass inclusion. Results suggest that shotcrete mixes containing synthetic glass aggregates exhibit similar or higher strength properties (compared with conventional shotcrete with natural aggregates) at early and late ages in both fresh and hardened shotcrete samples. Under biaxial stress conditions, in particular, the new glass shotcrete designs demonstrate a higher load-bearing capacity of up to 35% increase. Compared to conventional shotcrete, replacing sand with recycled glass aggregates further exhibited the need for less water and binder consumption owing to the glass water-reducing effect. This in return could leave more water available for improved workability in the mixture hence producing a more cost-effective and eco-friendly shotcrete product. From the results, no impairment of performance was recorded by substituting sand with crushed waste glass even at a high substitution percentage of up to 100%; suggesting high improvement potential of crushed waste glass re-use in the shotcrete industry.