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This study focuses on using activated fly ash to preparate silica aerogel by the acid solution–alkali leaching method and ambient pressure drying. Additionally, to improve the performance of silica aerogel, C6H16O3Si (KH-570) and CH3Si(CH3O)3 (MTMS) modifiers were used. Finally, this paper investigated the factors affecting the desilication rate of fly ash and analyzed the structure and performance of silica aerogel. The experimental results show that: (1) The factors affecting the desilication rate are ranked as follows: hydrochloric acid concentration > solid–liquid ratio > reaction temperature > reaction time. (2) KH-570 showed the best performance, and when the volume ratio of the silica solution to it was 10:1, the density of silica aerogel reached a minimum of 183 mg/cm3. (3) The optimal process conditions are a hydrochloric acid concentration of 20 wt%, a solid–liquid ratio of 1:4, a reaction time of two hours, and a reaction temperature of 100 °C. (4) The optimal performance parameters of silica aerogel were the thermal conductivity, specific surface area, pore volume, average pore size, and contact angle values, with 0.0421 W·(m·K)−1, 487.9 m2·g−1, 1.107 cm3·g−1, 9.075 nm, and 123°, respectively. This study not only achieves the high-value utilization of fly ash, but also facilitates the effective recovery and utilization of industrial waste. [ABSTRACT FROM AUTHOR]

In the context of ongoing rapid industrialization, the increasing deposition of industrial waste has arisen as a persistent global challenge, necessitating immediate attention and subsequent implementation of sustainable remedies. This study convenes on the efficacy of industrial wastes, namely fly ash and ground granulated blast furnace slag, as geopolymer concrete synthesizers in conjunction with the incorporation of reclaimed asphalt pavement (RAP) aggregates as a replacement for natural coarse aggregates varying over 25% to 100%. Under 7 days of ambient curing, employing 14M NaOH and a 50% RAP replacement, the mix achieved significant strengths of 41.80 MPa in compression and 4.72 MPa in flexure, affirming its suitability for pavement quality concrete (PQC). Through this study, the phenomenon of efflorescence could also be explored, which was particularly significant during the winter seasons. Furthermore, the declining coefficient of determination (R2) with the rise in RAP, observed in the correlation between compressive strength and ultrasonic pulse velocity (USPV), likely signified increased variability in the mixture at higher replacement levels. Assessment of long-term performance in terms of resistance to surface abrasion established the mix as durable, depicting minimal depth of wear (0.081 mm). Furthermore, results of the rapid chloride penetration test (RCPT) demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance. Microstructural study was additionally conducted to comprehend the importance of adhered asphalt in impeding crack propagation. ANOVA established a highly significant relationship between the interaction of curing age and RAP fractions with the strength characteristics of the mix. [ABSTRACT FROM AUTHOR]

In light of the urgent need to develop environmentally friendly materials that, at some point, will allow the reduction of concrete and, consequently, cement consumption—while at the same time allowing the reuse of waste and industrial by-products—alkali-activated fly ash (AAFA) geopolymer composite emerges as a material of great interest. The aim of this study was to investigate the physico-mechanical performance of composites based on AAFA binders and the effect of different types of aggregates on these properties. The experimental results indicate variations in flexural and compressive strength, which are influenced both by the nature and particle size distribution of aggregates and the binder-to-aggregate ratio. The analysis of the samples highlighted changes in porosity, both in distribution and pore size, depending on the nature of the aggregates. This supports the evolution of physico-mechanical performance indicators. [ABSTRACT FROM AUTHOR]

Geopolymers are amorphous, quasi-crystalline, three-dimensional networked gel structures formed by the reaction of aluminosilicate raw materials and alkali activators and are composed of silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons. They have excellent mechanical properties, durability and environmental friendliness and can be used as a substitute for Portland cement in civil engineering. In this paper, the current research achievements of geopolymers are reviewed, including the structure type, preparation process, mechanical performance, durability and application of geopolymers in civil engineering. When compared with those of ordinary Portland cement, the mechanical properties of geopolymers not only meet the specification requirements but also show carbonation resistance, acid resistance and high temperature resistance. In addition, the raw materials of geopolymers, such as fly ash and blast furnace slag, are all derived from industrial waste; the use of geopolymers can realize waste recycling, which has extremely high economic benefits. This paper introduces its applications in soil stabilization and silt solidification, curing heavy metals, pavement repair materials and so on. The shortcomings in the current research of geopolymer are also briefly analyzed. This article reviews geopolymers from multiple perspectives, trying to give a more comprehensive understanding of geopolymers. [ABSTRACT FROM AUTHOR]

The utilization of carbon dioxide and combustion products in cost- and energy-efficient technologies is an important element of creating sustainable energy systems, particularly in the transition period towards carbon neutrality and in light of the latest political developments, when solid fuels are still competing for a dominant role in securing energy supplies. Within the study presented, bituminous coal-derived fluidized bed fly ash samples of high calcium content, treated using a dry carbonation method under ambient conditions, were tested in terms of their specific properties to determine their usability in the preparation of injection mixtures for the filling of voids after shallow mining activities and other selected geo-engineering techniques. The study goes beyond the existing literature in terms of the carbonation method used, alkaline earth metal source, scale of the experiment, process conditions employed and product application studied. The results showed that the bituminous coal-derived fluidized bed fly ash, carbonated using the direct method adopted, may be successfully employed as the main solid component (over 82% w/w) of the injection mixtures for filling voids after shallow mining activities. The achievable compressive strength of a few MPa makes these materials applicable also in terms of ground strengthening in case it is required in light of the expected land development options to be employed. All principal materials used in the injection mixtures developed (carbonated fluidized bed fly ash, carbon dioxide, bottom ash) are industrial waste, and the carbonation method employed is simple and performed under ambient conditions, which reduces the required energy and cost input of filling mixture production, avoids the surface waste storage requirements, and contributes to the development of low energy-intensive carbon dioxide utilization and solid waste valorization methods. [ABSTRACT FROM AUTHOR]

The emergence of industrial wastes brings with it a series of global environment issues. However, using these wastes including valuable metals as a source of value-added materials will lead to many advantages. The metals can be recovered and transformed for nanomaterial production which offers utility in many applications such as energy conversion and hydrogen evaluation. In this study, recycling techniques were used to synthesize zinc oxide nanofibers from waste brass flue dust. Initially, characterization and experimental analyses were used to confirm the synthesized nanofibers phase purity, morphology, and optical properties. The X-Ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS) confirmed the nanofibers produced after recycling process were predominantly ZnO and have high purity. It was determined from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis that the produced samples were in fiber form in nanoscale and high crystallinity. According to the ultraviolet visible spectroscopy (UV-Vis) analysis, the optical band of ZnO nanofibers was found as 3.19 eV. It has been demonstrated with this study that the ZnO nanofibers derived from industrial waste can be used in several energy applications. Also, it was revealed that metal-containing wastes can be disposed of by producing value-added nanomaterials directly from industrial wastes with economical value. [ABSTRACT FROM AUTHOR]

In recent years, the reuse of industrial waste has become increasingly important for sustainable development. Therefore, this study investigated the application of granulated blast furnace slag (GBFS) as a cementitious replacement material in fly-ash-based geopolymer mortar containing silica fume (GMS). The performance changes in the GMS samples manufactured with different GBFS ratios (0–50 wt%) and alkaline activators were evaluated. The results indicated that GBFS replacement from 0 wt% to 50 wt% significantly affects GMS performance, including improving the bulk density from 2235 kg/m3 to 2324 kg/m3, flexural-compressive strength from 5.83 MPa to 7.29 MPa and 63.5 MPa to 80.2 MPa, respectively; a decrease in water absorption and chloride penetration, and an improvement in the corrosion resistance of GMS samples. The GMS mixture containing 50 wt% GBFS demonstrated the best performances with notable results regarding strength and durability. Owing to the increased production of C-S-H gel, the microstructure of the GMS sample containing more GBFS was denser, as obtained via the scanning electron micrograph analysis results. Incorporating the three industrial by-products into geopolymer mortars was verified when all samples were determined to be in accordance with the relevant Vietnamese standards. The results demonstrate a promising method to manufacture geopolymer mortars that aid sustainable development. [ABSTRACT FROM AUTHOR]

In the current background of excessive usage of plastic and rubber materials, hardly degradable, when the pollution level and global warming problems due to industrialization are rising, the world turns to new materials, especially composites, with a low impact on the environment, and to using waste formed from other fabrication processes and which after the termination of their life cycle to be easily recycled and reused in the manufacturing of new products with very good qualities. [ABSTRACT FROM AUTHOR]

To reduce the filling cost of high-water backfilling material (HWBM) in mining backfill and improve the recycling utilization of the industrial waste such as the coal fly ash. The ultra-fine fly ash (UFA) was added to the HWBM as a partial replacement in this work. Therefore, a series of experiments were performed to investigate the effect of UFA on the mechanical properties of the HWBM at the different curing conditions, then the hydration mechanism of the HWBM blended with UFA was analyzed by XRD and SEM method. The result indicates that the strength of the HWBM decreased with the increasing of UFA dosages, but the addition of UFA can improve the residual strength of the initial HWBM. Additionally, when the HWBM was cured at the laboratory air condition, its carbonation process was restrained obviously as the UFA dosages were less than 15% at the ages of 28 days, which indicates the UFA can improve the weathering resistance of the HWBM with the curing ages increasing effectively. The XRD and SEM results also shows that the degree of crystallinity of the HWBM increased when UFA dosages were less than 15% effectively, while there were few obvious changes on types of hydration products. It indicates that the main affects of UFA on the performance of HWBM is filler and dilution, which reduced the contact area between hydration products of HWBM and CO2 in the air, further improved the carbonation resistance of HWBM. [ABSTRACT FROM AUTHOR]

Incessant generation and mismanagement of industrial waste, resource scarcity, and environmental degradation have created non-sustainability in human life. Though industrial wastes are hazardous or non-hazardous in nature based on their source, open dumping disposal is commonly done for both types of waste. The adversity associated with waste enhances the environmental and health impacts. However, this waste has the potential to recycle and minimize resource scarcity. The circular economy works on the concept of reuse, recycling, and recovery to convert waste into a resource. Thus, industrial waste can benefit the environment and economic growth to build industrial ecology. However, the opportunities and challenges associated with industrial ecology for the reuse and recycling of waste have to be identified and preserved. Therefore, this study has identified challenges associated with waste, analyzed their impact, and industrial regulations, prioritized their criticality, and developed solution strategies to alleviate them. Two case studies on industrial byproducts, i.e., fly ash and red mud, based on different income groups are discussed in this study. It highlights the circular economy has minimized waste generation and enhanced the recovery of secondary resource materials. In addition, this study supports achieving the sustainable development goals (SDGs) 11 and 12 to build a sustainable industrial ecosystem. [ABSTRACT FROM AUTHOR]

Magnesium oxychloride cement (MOC), a type of special construction material, has drawn much research attention in solid waste utilization and environmental protection due to its eco-friendly production. Ammonia soda residue (ASR), a by-product generated from sodium carbonate manufacturing, is one of the industrial wastes that can be recycled in MOC systems. However, ASR exhibits adverse effects on the fresh performance and volume stability of MOC pastes. This paper aims at improving the properties of ASR-MOC by introducing fly ash (FA), solid waste from the power industry. Firstly, the roles of FA in MOC pastes are evaluated and analyzed. Then, three substitution ratios of FA (33.3%, 50% and 66.7% in weight) for ASR are designed for MOC pastes with 10% to 40% industrial wastes. Flowability, setting, strength and expansion of all mixtures were experimentally studied. Furthermore, X-ray diffraction (XRD) and scanning electron microscope (SEM) approaches were adopted to illustrate the microstructure changes. Results show that by adding different amounts of FA, the inferior flowability of MOC caused by ASR can be improved by 6–23%, the setting process can be prolonged by 30–55% and the expansion ratio can be reduced by 14–66%. The intensity of characteristic peaks of 5-phase and Mg(OH)2, together with the degrees of crystallization in XRD curves, well explain the strength variation and volume stability of ASR-MOC pastes. According to the regulation of relative specification, up to 20% of solid wastes in weight (10% FA + 10% ASR) can be consumed, contributing greatly to the greener sustainable development of construction materials. [ABSTRACT FROM AUTHOR]

To satisfy the needs of both an increase of infrastructure construction and a reduction of CO 2 emissions from cement manufacturing, industrial wastes like fly ash (FA) and ground granulated blast furnace slag (GGBFS) have been as substitutes for cement in cementitious infrastructure. This paper partially replaced cement in cementitious material by FA and GGBFS to improve its durability in the chloride and sulfate environments, and the influences of FA and GGBFS on its microstructures like C-S-H gel and binding behaviors of chlorides and sulfates were comparatively analyzed. Results show that, FA can cause an increase of the mean chain length and a reduction of the Ca/Si molar ratio of C-S-H gel, correspondingly changing its microstructure and reducing physical adsorption of cementitious material, but GGBFS has basically no influence on its C-S-H structure and physical adsorption. The hydration of FA can result in higher protonation and aggregation of C-S-H gel than that of GGBFS, and it has a stronger influence on the C-S-H structure than GGBFS, causing a reduction of the adsorption sites on the C-S-H surface. FA can reduce physical adsorption of chlorides and sulfates, but it is more beneficial for improving sulfate binding, while GGBFS is more favorable for improving chloride binding of cementitious materials. In addition, the physical adsorption capacity of cement pastes is associated with not only the structure of C-S-H gel but also its content in cementitious materials serviced in chloride and sulfate environments. This study supplies some insights on the effective incorporation of industrial wastes to improve the durability performance of cementitious materials. • FA and GGBFS increase sulfate and chloride binding capacity of cement paste. • FA enhances sulfate binding while GGBFS enhances chloride binding. • Sulfates are more readily chemically bound than chlorides in paste. • FA reduces Ca/Si ratio and protonates C-S-H gel, decreasing physical adsorption. • GGBFS increases chloride adsorption sites like SiOCaCl on C-S-H surface. [ABSTRACT FROM AUTHOR]

This study delved into the utilization of waste glass powder (WGP) and ground granulated blast-furnace slag (GGBFS) as a binder and waste glass cullet (WGC) fine aggregate in fly ash (FA) based geopolymer concrete. The inherent characteristics of WGP, WGC, FA and GGBFS can be significantly altered by multiple factors such as sources, combustion temperatures, particle size, and impurity level. To offset the inconsistent characteristics of listed waste materials, this study provides a universal index to quantify and evaluate its reactivity to be used as aluminosilicate precursor and aggregate feedstock Ten distinct groups were examined: in five groups WG replaced fly ash at varying percentages (0, 10, 20, 30, 40%), and in five groups WG was used as a sand substitute with different fly ash and slag ratios (20, 40, 60, 80%). Alkali leaching tests were conducted on WGP, WGC, FA and GGBFS to determine the dissolubility and dissolution rate of reactive silica (Si) and calcium (Ca) within 3 h. The dissolubility and dissolution efficiency demonstrated decent correlations with the mechanical and durability properties of the resultant FA-based geopolymer. Leaching tests demonstrate that Ca from WGP, WGC, FA and GGBFS readily leaches out and reacts in both ambient and oven curing, while Si only exhibits activity primarily in high-temperature environments. Overall, the reactivity of Ca from GGBFS and WG improved by up to 50% and 30% in compressive strength and water absorption, respectively. Moreover, based on alkali leaching test, the most effective molar ratios (Si/Al=3.5–4) demonstrated the highest compressive strength (60–70 MPa), and verified intensively using scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS). Lastly, this study revealed that WGC as fine aggregate with the size of 20 µm also leached out a significant amount of Ca to the geopolymerization process. [Display omitted] • The feasibility of using waste glass as a substitute for fly ash in geopolymer mortar mixture. • Investigate the leaching behaviour of various industrial waste in geopolymer. • Emphasize the effect of leached calcium from industrial waste on properties of geopolymer in different curing methods. • Influence of Si/Al molar ratio on the performance of waste glass utilization in fly ash/ash-based geopolymer. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synergistic effect of red mud – desulfurized gypsum - fly ash was found. • Sample RDFC6 achieved high content of solid waste and high mechanical performances. • The influence of synergistic effect on the microstructure of materials was elaborated. The use of industrial solid waste to prepare cementitious materials can not only solve the pollution problem of ecological environment, but also help carbon emission reduction and sustainable development. In this work, typical alkaline solid waste - red mud (RM), sulfate solid waste - desulfurization gypsum (DG) and silicon-aluminum character solid waste - fly ash (FA) were used to prepare cementitious materials. The influence of synergistic effect of RM-DG-FA on the mechanical performances and hydration products of cementitious materials were systematically investigated. The hydration products were characterized and analyzed by XRD, TG, FTIR, MIP and SEM-EDS. It was found that the mechanical performances of cementitious materials were significantly improved under the synergistic effect of three kinds of solid wastes. When the content of the three solid wastes was 50%, the compressive strength of the cementitious materials at 28 d was 50.60 MPa, and the mechanical performances at each age were higher than the # 42.5 Portland cement standard. The microstructure results showed that under the synergistic action of alkali and sulfate, the active silicon and aluminum substances in RM and FA can quickly participate in the reaction, which makes the hydration degree of cementitious materials can move to the reaction direction with higher polymerization degree. The hydration products mainly included ettringite, C-S-H and C(N)-A-S-H gel. A large amount of gel and ettringite grew alternately, which reduced the porosity and formed a dense structure of the cementitious materials matrix, and its mechanical performances were improved. The leaching results showed that the synergistic effect also improved the solidification ability of the cementitious materials to Na+. In this work, the synergistic effect of RM-DG-FA significantly increased the utilization of solid wastes and the performances of cementitious materials. The research results provided a scientific basis for improving the utilization rate of alkaline solid wastes, sulfate solid wastes and silicon-aluminum character solid wastes and their collaborative utilization as building materials. [ABSTRACT FROM AUTHOR]

The utilization of industrial waste as a partial replacement in construction materials has been increasing rapidly in recent years. This Paper investigates the performance of reinforced concrete columns comprising of recycled aggregates, fly ash and synthetic fibres in varying percentage, under monotonic and thermal loads. Ten full scale reinforced concrete columns of size 150 x 150 x 750 mm were experimentally studied under compressive loads. Results of the experiment showed that the polypropylene (PP) fibre reinforced fly ash column with recycled aggregate consisting of 1.5% PP fibre, 15% fly ash and 25% recycled aggregates exhibited better load carrying and deflection capacities and was further considered for numerical analysis. The conventional column was modelled as a control specimen and the behaviour of polypropylene fibre-reinforced fly ash column with recycled aggregate was comparatively studied under the action of thermal loads in ABAQUS. In order to understand the effect of fibre-reinforced polymer (FRP) rebar reinforcement in columns under thermal loads, a parametric study was carried out by varying the type of reinforcement, using carbon fibre-reinforced polymer rebar (CFRP) and glass fibre-reinforced polymer rebar (GFRP). The polypropylene fibre-reinforced fly ash column with recycled aggregate reinforced with CFRP rebars exhibited better performance under thermal loads. [ABSTRACT FROM AUTHOR]

• Em-CEF model combines carbon emission factor with emergy analysis to assess carbon emissions of different concrete production methods. • Gangue concrete reduces emissions by influencing particle gradation choices in solid waste concrete production. • Em-CEF model uses emergy data to calculate index and analyze building energy consumption accurately with emergy phase diagram. The carbon emission emergy factor (Em-CEF) model is applied to evaluate the carbon emissions associated with the traditional concrete production method, fly ash concrete production method, coal gangue concrete production method, and recycled aggregate concrete production method in the complete lifecycle. The highest emission reduction can be achieved when solid industrial waste is used to replace part of the traditional raw materials, and the processing and treatment of industrial waste are simplified. Among the four production methods, gangue concrete production corresponds to the highest emission reduction. When solid waste recycled concrete is applied to reduce carbon emissions, coal gangue concrete can be prioritized. [ABSTRACT FROM AUTHOR]

• Resource utilization of industrial wastes in energy storage system. • Synergistic adsorption-electrocatalysis effectively suppresses the shuttle effect. • MCFA separator can effectively reduce internal resistance and polarization of LSBs. • MCFA helps to improve the transformation kinetics of LiPSs. The notorious shuttle effect severely limits the practical application of Lithium-Sulfur Batteries (LSBs). In line with the concept of "green chemistry", industrial solid waste is reasonably applied to the design of battery's interlayer. The modified coal fly ash (MCFA) can effectively accelerate the redox kinetics of the electrode and optimize the nucleation and decomposition of Li 2 S. The synergistic adsorption and catalytic action from rich pore structure and polar metal oxides can effectively capture and fix free polysulfide (LiPSs), which realizes the inhibition of shuttle effect. The LSBs with MCFA interlayer exhibit good cycle stability (decay-rate: 0.05% per cycle) and rate capability (703 mAh g−1 at 3C). Even under extreme conditions of poor electrolytes (E/S = 7.8 μL /mg), Cell-MCFA/PE with a high S loading (7.5 mg cm−2) still performs well (732 mAh g−1 after 100 cycles). This work provides an economical and environment-friendly strategy for the design of interlayer, which is conducive to the commercialization process of LSBs. [ABSTRACT FROM AUTHOR]

In response to the requirement for the comprehensive utilization of industrial waste, high-strength geopolymers were prepared from red mud (RM) and Class 1, 2, and C fly ash (FA) rich in active substances (FA1, FA2, and FAC, respectively) in the presence of an alkali activator (AA). Increasing the curing temperature from room temperature (22 °C) to 60 °C rapidly increased the strength of the geopolymer, while maintaining a certain level of humidity during curing inhibited crack formation in the geopolymer. The use of a sodium hydroxide (NaOH) solution improved the strength of the geopolymer. However, an excessively high concentration of NaOH solution induced considerable efflorescence. The strength of the geopolymer prepared with a mixed solution (MS) composed of a NaOH solution and a water glass (WG) solution increased as the concentration of the MS increased and reached 63.5 MPa when the NaOH concentration in the MS was 10 mol/L. [Display omitted] • A red mud–fly ash geopolymer with a strength >60 MPa is developed. • The physical/chemical mechanism of the high-strength characteristics is revealed. • The microstructural evolution of the geopolymer is examined by SEM, XRF and XRD. • The necessity of increasing the curing temperature for strength is emphasized. [ABSTRACT FROM AUTHOR]

Fly ash, a by-product of high temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amount of industrial solid wastes generated in China. Its improper disposal has become an environmental problem. Now it is widely realized that fly ash should be considered as a useful and potential mineral resource. Fly ash is rich in alumina, making it a potential substitute for bauxite. With the diminishing reserves of bauxite resources, as well as the increasing demand for alumina, recovery of alumina from fly ash has attracted extensive attention world-wide. The present review describes, firstly, the generation and physicochemical properties of high alumina fly ash found in northern China and then focuses on the various alumina recovery technologies, the advantages and disadvantages of these processes, and in particular, the latest industrial developments. Finally, the directions for future research are also considered. [ABSTRACT FROM AUTHOR]

• The use of CDP reduced water demand and increased the setting time of paste blends. • CDP improved the early strength of concrete, contributing positively to industrial waste recycling. • Mortar mixtures incorporating up to 50% CDP exhibited comparable 28-day compressive strength to the control mixture. • CDP type and curing procedure have no significant effect on the 28-day strength of concrete. This study evaluated the strength development in hyperalkalized concrete mixtures incorporating cement waste-derived Portlandite (CDP), synthesized from two variants of cement kiln dust (CKD). The source CKDs (coded CKD1 and CKD2) and synthesized CDPs (coded CDP1 and CDP2) were characterized physically and mineralogically, after which the CDPs were used as cement replacement, from 0 to 60 %, in the mortar phase of a base concrete mixture at w/b of 0.5 and 0.425. After in-mold curing, the mortar mixtures were subjected to 12 h of accelerated carbonation curing (ACC), and then moist–cured until 28 days. The strength development and alkalinity of mortar mixtures were investigated using the strength activity factor (SAF) and pH analysis, respectively. The incorporation of more alkaline and fine-grained CKD1 (D50 = 14.74 µm) was found to increase the water demand and setting time of CKD-cement paste blends, compared with the coarse-grained CKD2 (D50 = 27.51 µm). Additionally, the use of CDP reduced water demand but increased the setting time of paste blends. Further, the incorporation of CDP increased the early-age compressive strength of mortar, but its effect diminished as the mixtures matured, with SAF reduction of over 50 % in most cases. Finally, CDP1 mixtures exhibited about 30 % higher early–age compressive strength than CDP2 counterparts but the difference evened out at a later age, with the studied mixtures exhibiting 28-day compressive strengths varying between 23 and 54 MPa. [ABSTRACT FROM AUTHOR]

The fabrication of bricks commonly consumes relatively high natural resources. To reduce the carbon footprint in the brick production industry, repurposing industrial wastes in the making of sustainable bricks is a recent trend in research and application. Local wastes, such as oil palm shell (OPS), palm oil fuel ash (POFA), and quarry dust (QD), are massively produced annually in the palm oil-exporting countries. Moreover, QD from mining industries is hazardous to both water and air quality. For better waste management in marching towards sustainability, these wastes should be given their second life as construction materials. Therefore, this paper investigates the possibility of incorporating agro-industrial wastes into the brick mixture by examining their properties by means of several standardized tests. For the mix design, a 100% replacement of coarse aggregate with OPS, 20% replacement of cement with POFA, 20% cement weight of limestone as admixture, and 0 to 50% replacements of fine aggregate with QD are experimentally considered. The optimum mix of these wastes is preliminarily determined by focusing on high compressive strength as an indicator. Other examinations include splitting tensile, flexural strength, water absorption, and efflorescence tests. Although the agro-industrial waste cement brick is 18% lower in the strength to weight ratio compared to that of conventional, it is observed that it has better late strength development due to its POFA pozzolanic properties. Moreover, the proposed green cement brick is further checked for compliance with several standards for feasible use in the construction industry. Financially, the cost for the brick with the new mix design is almost equivalent to that of conventional. Hence, this green cement brick is reasonable to be employed in the construction industry to promote material sustainability for better waste management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Area of bloating clays by Riley and Wilson is used to assess the bloatablity of CDW to make LWA. • Brick and fly ash in Vietnam is suitable for producing LWAs, GBFS is not. • SiC is suitable as a blowing agent to produce LWAs from CDW and fly ash. • Optimum sintering temperature to make LWA from CDW is 1220–1250 °C. • Necessary residence time for burning is 6–9 min. The amount of construction and demolition waste and industrial by-products are increasingly high in Vietnam recently. The recycling of these wastes as new construction materials is an effective solution for sustainable development. This paper presents a method for the recycling of construction and demolition waste and other industrial by-products, such as fly ash and slag in Vietnam to produce lightweight aggregate. Experimental results show that masonry wastes including brick and mortar as well as fly ash are suitable materials for producing lightweight aggregates with a granule density of less than 1000 kg/m3 with the optimum sintering temperatures and the residence time in the range from 1220 °C to 1250 °C and, 6 to 9 min, respectively. These recycled lightweight aggregates can be used as valuable substitutes for natural aggregates to make lightweight concrete for new structures and therefore contribute to the construction industry's sustainability. [ABSTRACT FROM AUTHOR]

• Using industrial wastes in bricks increases performance and prevents pollution. • Kiln burnt bricks incorporated 2–10% silica fume (SF) and fly ash (FA) as additives. • 4% SF and FA was determined optimal which enhanced strength by 27.55% and 17.36%, respectively. • The addition of SF and FA reduced density, water absorption, and efflorescence. • The additives caused variation in brick dimensions; however, it was within acceptable range. Rapid industrialization over the past few decades has increased the disposal of waste materials in open-air landfills. The utilization of industrial wastes for the preparation of bricks can improve its functional characteristics and reduce the environmental pollution caused by landfill sites. This research investigated the effects of silica fume (SF) and fly ash (FA) on the structural and durability properties of burnt clay bricks (BCB) manufactured at the industrial kiln site. The SF and FA were added to the brick earth with a percentage variation of 2–10%. Results showed that the addition of 4% SF in brick earth increased the compressive strength of BCB by 27.55%, while 4% FA increased the compressive strength by 17.36%. Results also revealed that the addition of SF and FA reduced the weight of BCB, water absorption, and efflorescence while increased the structural efficiency. The incorporation of SF and FA resulted in variation of all dimensions of the burnt clay bricks. Nonetheless, the variation was observed within the range of testing standards. [ABSTRACT FROM AUTHOR]

Several industrial wastes including biomass, fly ashes, red mud, mill scales, water treatment residues, have significant concentrations of metal oxides: Fe 2 O 3 , Al 2 O 3 , TiO 2 , SiO 2 etc. Several efforts have been made towards recovering metals within these wastes. Rather than recovering one metal at a time, we report a novel approach for simultaneously extracting multiple metals from mixed oxides in a single process step. Using three distinct furnaces/heating regimes, the carbothermic reduction of Fe 2 O 3 /Al 2 O 3 /SiO 2 system was investigated at 1450–1700 °C for up to 2 h over a wide composition range. Complete reduction was achieved for both Fe 2 O 3 and SiO 2 in all cases leading to the formation of Fe and Fe–Si alloys. The reduction of alumina at moderate temperatures was the key challenge. No alumina reduction was observed during reductions at 1450 °C. A partial reduction of alumina and the formation of Fe–Al alloys was detected in the Al 2 O 3 /Fe 2 O 3 /C system at 1550 °C. The formation of Fe–Si–Al alloys was also observed in the Fe 2 O 3 /SiO 2 /Al 2 O 3 /C system at 1550 °C. Complete reduction of alumina was observed at 1600–1700 °C, even for up to 50 wt% alumina in the system. Optimal operating conditions and reference standards were established for the simultaneous recovery of multiple metals from waste oxides. While conserving natural resources, this novel route will lower the burden on waste storage facilities with significant contributions to the economic and environmental sustainability of industrial waste management. [Display omitted] • Carbothermic reduction of mixed oxides at 1450–1700 °C under argon atmosphere. • Simultaneous extraction of multiple metals from waste oxides in a single process. • Novel route applicable to biomass, fly ashes, red mud, mill scales and other wastes. • Benefits include resource conservation and associated reductions in waste storage. [ABSTRACT FROM AUTHOR]

• Formulated rammed earth mix using pulp mill fly ash as low carbon cementing agent. • Synthesized strong calcium aluminosilicate binder from fly ash by alkali activation. • Combination of non-activated ash and bentonite showed excellent frost resilience. • Cementitious products immobilized toxic elements within the rammed earth matrix. • Study showcases new greener approach to achieve sustainable growth in construction. Sustainable rammed earth (RE) material was formulated using pulp mill fly ash (PFA), an industrial waste product, as an alternative low carbon cementing material. The alkali-silicate activation of PFA in RE showed substantial strength improvement. However, combinations of calcium bentonite clay and raw PFA without activation imparted significantly better frost resilience properties. The recommended RE formulation with 5% PFA, 5% Portland cement and 15% bentonite showed 3.56 MPa compressive strength at 28 days curing and retained 92% strength after 12 freeze–thaw cycles. Further, the leachate analysis revealed that the cementitious reaction products immobilized toxic elements within the stabilized RE matrix. [ABSTRACT FROM AUTHOR]

The aim of this research is to evaluate the possibility of using an eco-sustainable geopolymer binder, through the development of innovative technologies capable of offering tools for the water systems management, for the enhancement and protection of environmental resources. Specifically, a hydraulic pipeline made of geopolymer mortar has been designed as prototype. A detailed comparative environmental assessment analysis of unreinforced and reinforced geopolymer prototypes has been conducted using the Life Cycle Assessment (LCA). The LCA study has been performed to determine the environmental performance of the different mix designs and to identify the most important factors contributing to their environmental burdens. The results of the analysis indicate that the advantages of geopolymers make them a valid alternative to traditional binders in many industrial environments and in this case in the realization of useful artifacts for hydraulic engineering. [ABSTRACT FROM AUTHOR]

Creative development of ferrocement technology in the construction industry has enhanced dynamically due to its faster construction, lighter weight, higher strength, durability and economical advantages than the reinforced concrete structures. The use of smaller diameter closely spaced mesh layers which is uniformly distributed throughout the cross section improved the moment of resistance, deflection and ductility of the ferrocement members. To achieve the environmental friendliness and sustainability in the durable ferrocement technology, this paper aims to provide a comprehensive implication reviewed from the previous research works carried out to explore the application of industrial waste materials in the ferrocement construction. Influence of various industrial waste materials on the behaviour of both mortar and meshing reinforcement were discussed separately. The optimum level replacement, effect on the structural behaviour and the suitability in the various environmental conditions were inferred. For instance, Ground Granulated Blast furnace Slag (GGBS) could be utilized as a binder at the maximum of 50% by weight, where as the use of metakaolin in ferrocement construction is optimum at 15% by weight as further addition caused the undesirable effect on the mechanical properties due to the delay in hydration process and inefficient filler effect. Grain size modified nano industrial wastes like nano silica and nano fly ash resulted in improved mechanical and micro structural behaviour of ferrocement products due to its nano filling effect. The use of nano fly ash was found to be successful as nano binder to the maximum of 10% which is not possible in case of other costlier nano materials like nano silica, alumina, titanium oxide, etc. The major issues of corrosion and chemical attack in ferrocement mesh were easily solved by the implementation of high molar geopolymer mortar which also resulted in cleaner and greener production of ferrocement products. [ABSTRACT FROM AUTHOR]

The production of lightweight aggregates (LWAs) involves much energy consumption and emission of pollution during the sintering process. The increasing worldwide demand for functional concrete for use in modern construction has promoted this negative trend to a more serious level. This study reports an artificial lightweight capsule aggregates (CAs) based on an encapsulation technology from the viewpoint of green manufacturing. The novel CAs are composed of a fly ash-cement inorganic shell and sodium alginate organic core. A series of experiments were conducted to study the influences of the rotation rate, duration time, curing conditions and surface conditions for sodium alginate beads (SAB) on the physical and mechanical characteristics of the CAs. The results indicate that CAs with a wet density of 1340 kg/m3 and corresponding crush strength of 2.46 MPa can be achieved. The CAs density can be further decreased by a third via sodium alginate dehydration. CAs with optimized performance can be synthesized by using a rotation rate of 150 rpm, duration time of 30 s and C/A ratio of 2.0. A low rotation rate and high duration time have a negative effect on the CAs characteristics. A saturated surface dry (SSD) condition process for the SAB was found to greatly contribute to the optimization of CAs density. Findings from this study can provide a novel and viable way to reuse industrial wastes and biomass resources to manufacture core-shell structured LWAs with stable and adjustable performance. These artificial LWAs have great application potential in the preparation of the advanced lightweight concrete. • Novel LWAs with a core-shell structure were produced with a biomass resource and industrial waste. • The encapsulation method consumes no additional energy and emits no greenhouse gas. • Effect of production parameters, surface condition of SAB and curing condition on CAs performance was investigated. • Hydrogel core locked internal water to delay its release, and cementitious shell resisted possible mechanical damage. [ABSTRACT FROM AUTHOR]

Mineral carbonation, involving reactions of alkaline earth oxides with CO2, has received great attention, as a potential carbon dioxide sequestration technology. Indeed, once converted into mineral carbonate, CO2 can be permanently stored in an inert phase. Several studies have been focalized to the utilization of industrial waste as a feedstock and the reuse of some by-products as possible materials for the carbonation reactions. In this work municipal solid waste incineration fly ash and other ashes, as bottom ash, coal fly ash, flue gas desulphurization residues, and silica fume, are stabilized by low-cost technologies. In this context, the CO2 is used as a raw material to favor the chemical stabilization of the wastes, by taking advantage of the pH reduction. Four different stabilization treatments at room temperature are performed and the carbonation reaction evaluated for three months. The crystalline calcium carbonate phase was quantified by the Rietveld analysis of X-ray diffraction (XRD) patterns. Results highlight that the proposed stabilization strategy promotes CO2 sequestration, with the formation of different calcium carbonate phases, depending on the wastes. This new sustainable and promising technology can be an alternative to more onerous mineral carbonation processes for the carbon dioxide sequestration. [ABSTRACT FROM AUTHOR]