The versatile applicability of glass products has brought a drastic increase in the amount of glass waste generated, urging to its proper utilization. Light-weight expanded glass is a type of ...sustainable artificial light-weight aggregate produced by mixing glass wastes and expansive agents under special conditions. The highly porous granules are efficient thermal insulating light-weight material primarily used to prepare light-weight concrete. Over the past few years, extensive research has been carried out to improve the properties of concrete incorporated with expanded/foamed glass. This paper is aimed to present an in-depth review of expanded glass aggregate in terms of its composition, flowability, thermal insulation, physical, mechanical, and durability properties. Special emphasis has been given to study the influence of alkali-silica reactions on the behavior of expanded glass concrete, and the results were encouraging despite the presence of a high amount of reactive amorphous silica in the expanded glass. This study is a novel initiative that accumulated the findings of expanded glass aggregate for its broad acceptance and usability in construction industry giving a promising solution to circular economy and an insight to cleaner technologies. There is plenty of research showing feasibility of glass in variant fields but widened research on expanded glass aggregate has not been presented in the past.
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•Gives an insight to circular economy and cleaner technologies.•Suitable to use as a structural concrete for even lower density of 1000 kg/m3.•Excellent frost resistant, prohibits alkali-silica reaction expansion in mortar.•Density and thermal conductivity reduces with Increase in expanded glass aggregate.•Increase in the concentration can increase the risk of carbonation.
Glass residues are available worldwide and are disposed of in large amounts in landfills. However, glass waste presents great potential to be used as raw material to produce foam glass boards, a ...product used in industries such as the construction sector. Conventional foaming agents (e.g. carbon black, carbonates, and sulfates) used in the production of foam glass boards release greenhouse gases into the environment, such as carbon dioxide. Conversely, sodium hydroxide releases only steam during the foaming process. Consequently, an insightful study is necessary to analyze the advantages and disadvantages of sodium hydroxide in comparison to other common foaming agents. Accordingly, the objective of this research is to carry out a cradle-to-gate Life Cycle study with four foam glass boards produced by different foaming agents: sodium hydroxide, carbon black, silicon carbide and dolomite. Global warming potential (GWP), acidification and human toxicity by air were considered as impact categories for Life Cycle Impact Assessment (LCIA). The results from the four foam glass boards were compared to an expanded polystyrene (EPS) board. Results evidenced that the use of sodium hydroxide provides better environmental performance regarding GWP, releasing 0.46 kg CO2 eq., while the use of carbon black has less acidification potential with 1.95. 10−3 kg SO2 eq. Human toxicity by air was the only impact category in which EPS has better performance (8.66. 104 m3 air). LCIA results demonstrate that foam glass boards that stand out as safe (not emitting toxic gases in case of fire) are also interesting materials for the environment.
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•Foam glass boards were analyzed by cradle-to-gate life cycles•The impact of four different foaming agents was compared•The use of sodium hydroxide had the best performance in global warming potential•Carbon black had the best performance in acidification potential•Sintering cycle must be considered to reduce environmental impacts
This paper investigates the contact zone between the binder material, foam glass and its analogues such as block foam glass and sheet glass, using the detachment method. Data is presented on the ...detachment pattern and bond strength between the foam glass and the binder material, which in turn allows the quality of the contact zone to be assessed.
The results of research on the use of such binders as cement, gypsum and modified gypsum binder with the addition of amorphous silica and lime in foam glass concrete are presented. It is shown that the use of modified gypsum binder significantly increases the strength of bond of the aggregate (granulated foam glass) with the binder.
The obtained data can be used to improve the quality of the contact zone and, as a consequence, to increase the quality of expanded glass concrete.
Foamed glass preparation is a complex combination of reactions, greatly influenced by the composition of the used glass and often hindered by simultaneous crystallization. The crystallization ...phenomenon is undesirable in foamed glass production since it decreases the quality of the final product. In this work the influence of different types of additives (foaming agents, flux agents, crystallization inhibitors and nucleating agent) on the crystallization of waste container glass and properties of the sintered samples (density and thermal conductivity) was studied. Results of our study confirmed partial crystallization during sintering stage. We found that waste container glass manifests complex crystallization with the formation of four main crystalline phases, which can be inhibited with the addition of fluxing agents (B2O3 and borax). Moreover, here we show that prevention of the crystallization can lead to a significant decrease of the thermal conductivity.
Foam glass, an inorganic insulation material, is primarily manufactured from recycled glass or sand combined with a foaming agent. During fabrication, gas bubbles are generated in the softened glass, ...causing it to expand and form a cellular structure. Critical parameters such as cell size, type (closed or open cells), distribution, and uniformity significantly influence the physical and chemical properties of foam glass, ensuring sustained thermal efficiency. This research aims to produce foam glass exclusively from waste materials, thereby promoting the circular economy by utilizing container glass, cathode ray tube (CRT) glass, and aluminium dross. A comprehensive microstructural analysis, employing computer tomography and scanning electron microscopy, elucidated key properties including density, thermal conductivity, and water absorption. The manufactured foam glass exhibited lightweight characteristics, with a density ranging from 0.15 to 0.18 g/cm³. Additionally, the foam glass demonstrated low thermal conductivity (between 0.038 W/m·K and 0.05 W/m·K), which can be attributed to the heterogeneous distribution of cells that effectively reduce heat convection. This property makes foam glass an excellent thermal insulator. Furthermore, both high-absorption (open porosity) and low-absorption (closed porosity) foam glasses were successfully produced.
The understanding of relationship between densification and foaming for preparation of foam glasses is still lacking. In this study, 128 powder compacts of glass-CaCO3 mixture were foamed ...isothermally for different time by varying glass particle size, foaming temperature and initial density of green compacts. The results showed that densification tends to take place in the early stage by viscous flow sintering prior to predominant foaming expansion. Therefore, there exists a critical time at which the maximum apparent density is reached, and it is correlated with both the densification rate and kinetics of CaCO3 decomposition. Such a densification has a minor effect on the minimum apparent density, however, it significantly impacts the evolution of pore structure including pore size and homogeneity, depending on glass particle size. Coarse-particle glass and high load applied on the green compacts, leading to higher green density, is favorable for slow development of pore structure with time. In this case, the foam glasses were endowed with small size of pores and homogeneity. This study provides an insight into how to obtain low apparent density and the optimum microstructure by the interplay between densification and foaming.
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•Densification and foaming behaviors of glass-CaCO3 mixture were investigated.•Densification always takes place in the early stage by viscous flow sintering.•Densification affects pore structure in a higher degree than the apparent density.•Foam glasses with low apparent density and optimum microstructure were prepared.
Lately, energy-saving attempts in the construction and building materials industry have become more popular due to the diminishing natural resources. With this motivation, we investigated the first ...foam glass consisting of ferrochrome slag (FS) and waste soda-lime glass (SLG) for potential use as a heat insulation material. For this, FS and SLG waste materials were valorized as main constituents, whereas a mixture of water glass (WG) & glycerol (G) and a sufficient amount of water (W) was used as a foaming agent and a moisturizer in the batch mixture, respectively. The studied series was prepared with the composition of 20FS-70SLG-xG-(8-x)WG-2W where x: 2, 4, and 6 wt%. After that, three different process temperatures (800, 825, and 850 °C), two distinct heating rates (5 and 10 °C/min), and two discrete dwell times (15 and 30 min) paved the way for the synthesis of 36 different foam glass samples. Eventually, the fabricated 36 different samples were subjected to physical, thermal, mechanical, and microstructural evaluations. According to the findings, one can say that samples synthesized with a lower G-to-WG ratio, higher process temperature, lower heating rate, and higher dwell time have the best features. From the physical property determinations, we found out that bulk density (ρbulk) varied between 233 and 903 kg m−3 while the estimated porosity (P) ranged from 59.4 to 89.5%. Further, thermal conductivity (k) measurements demonstrated that the fabricated foam glass series provides lower values, namely from 0.038 to 0.130 W m−1 K−1. Besides, compressive strength (CS) values were found to be changing from 0.127 to 2.225 MPa. Microstructural evaluations via scanning electron microscopy (SEM) revealed the pore formations and the relevant alterations as a result of the different parameters. All in all, the authors concluded that a heat insulation material composed of nearly fully waste substances can effectively be produced.
Foam glasses have potential of using in several fields due to their high porosity. Usually, the foam glasses are prepared though chemical approach where the powdered glass is mixed with foaming ...agents at high temperatures. However, in such approach, the emission of gaseous pollutants (e.g. CO2) from the most used foaming agents can be harmful to the environment. Thus, understanding the mechanisms of foam formation is quite important to eliminate the drawbacks afore mentioned, as well as, give us more information on the processing steps. Herein, we propose a new chemical route to obtain foam glasses from soda-lime glass waste using sodium hydroxide and borax as foaming and flow agents, respectively. The reaction mechanism was investigated by thermogravimetric and differential thermal analysis, mass spectroscopy, mercury porosimetry, optical dilatometry, X-ray diffraction, and infrared spectroscopy. At the glass transition temperature (587o C), the crystallization of a new phase of hydrated sodium and calcium silicate (Na2CaSi2O6.2H2O) was observed. As demonstrated by mass spectrometry, when the mixture was heated to a temperature above the softening point, the foaming occurred only due to steam released from the hydrated sodium and calcium silicate. This foaming process provided a foam glass with 86% of porosity, low permeability and bulk density of 0.3 g/cm3. The results indicate the proposed approach is environmentally safe, besides being relatively cheap and easy to prepare.
•Reactions between NaOH and soda-lime glass were analyzed in a foam glass composition.•Above Tg a new hydrated Na-Ca silicate phase (Na2CaSi2O6·2H2O) is crystallized.•Steam was the only gas responsible for the expansion of foams.•After foaming process a stable phase of devitrite (Na2Ca3Si6O16) is formed.
Foam glass-ceramics were successfully prepared with the powder sintering method using granite tailings as the main raw material, and silicon carbide (SiC), and manganese dioxide (MnO2) as the mixed ...foaming agent. The effects of the mixed foaming agent and sintering temperature on the crystalline phase, pore-wall structure, and the properties of the prepared foam glass-ceramics were systematically studied. Moreover, the foaming mechanism of the foam glass-ceramics prepared by using the mixed foaming agent was revealed. The results showed that, with a decrease of SiC content, the thermal conductivity and compressive strength decreased, and with an increase of MnO2 content, a special connected pore structure formed in the pore wall of the sample. The optimum mass ratio of MnO2: SiC in the mixed foaming agent was 1: x (x = 3‒7). Foam glass-ceramics with good thermal insulation performance, a bulk density of 0.35–0.50 g/cm3, a porosity of 85.05–88.12%, a thermal conductivity of 0.037–0.046 W/(m·K), and high compressive strength (0.46–3.11 MPa) were obtained at the sintering temperature of 880 °C.
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