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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 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]

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]

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]

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]

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]

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]