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As the demand for environmental sustainability grows in the global construction industry, traditional cement production faces significant challenges due to high energy consumption and substantial CO2 emissions. Therefore, developing low-carbon, high-performance alternative cementitious materials has become a research focus. This paper proposes a new low-carbon cement (alkali-activated lithium slag-fly ash composite cement, ALFC) as a substitute for traditional cement. First, the alkali activation reactivity of lithium slag (LS) is enhanced through calcination and grinding, revealing the reasons behind its improved reactivity. Then, alkali-activated LS and fly ash were partially used to replace cement to prepare ALFC, and the effects of the water-to-binder ratio (W/B), LS content, and NaOH addition on the flowability and mechanical properties of ALFC were investigated. XRD, SEM/EDS, and TG/DTG analyses were conducted to examine its hydration products and microstructure, revealing the hydration mechanism. The results show that the flowability of ALFC increases with W/B but decreases with a higher LS content. When W/B is 0.325 and the LS content is 25 wt.%, flowability reaches 200 mm, meeting construction requirements. LS calcined at 700 °C for 1 h significantly enhanced ALFC's 90-day flexural and compressive strengths by 39.73% and 58.47%, respectively. The primary hydration products of ALFC are C-S-H, N-A-S-H, and C-A-S-H gels, with their content increasing as the NaOH concentration rises. The optimal NaOH concentration and LS content for ALFC are 2 mol/L and 25 wt.%, respectively. [ABSTRACT FROM AUTHOR]

Fly-ash geopolymer composites are an exciting advancement in eco-friendly construction materials. Fly-ash has become a sustainable alternative to regular cement because the approach addresses critical concerns in construction, such as high energy use, excessive carbon emissions and the challenge of managing industrial waste. In this review, a brief discussion on how fly-ash geopolymer composites could transform construction practices and reduce their impact on the environment. The construction industry is a major contributor to climate change, whereas industrial byproducts like fly-ash can also be an environmental challenge. Thus, the fly-ash geopolymer composites offer an innovative solution by reusing this waste to create environmentally friendly binding materials. Fly-ash can effectively replace traditional cement in construction, improving the durability and sustainability of buildings. By reducing our reliance on regular cement, these composites could revolutionise construction practices across various industries. Developing and widely adopting fly-ash geopolymer composites could bring substantial benefits. It could significantly reduce the construction industry's carbon footprint and contribute to global efforts to combat climate change. Additionally, ongoing research aims to enhance these composites' strength, heat resistance, and chemical durability, further promoting sustainable construction and supporting a circular economy by turning industrial waste into valuable construction materials. [ABSTRACT FROM AUTHOR]

This research deals with the improvement in the mechanical properties of pavement quality concrete (PQC) when mixed with Class-F Fly-Ash (FA) and Copper Slag (CS) as replacements for ordinary Portland cement (OPC) and river sand (RS), respectively. Forty-eight different PQC mixes of M40 and M50 grades were prepared, in which RS is replaced by CS to the extent of 100%, and OPC is replaced by FA to the extent of 30%, with each replacement done at a certain increment. The combined effects of CS and FA on fresh and hardened concrete properties such as workability, density, water absorption, volume of voids, cube compressive strength, split tensile strength, flexural strength, cylinder compressive strength and ultrasonic pulse velocity (UPV) are experimentally investigated. All mixes containing up to 20% FA and up to 100% CS replacements showed increased strength compared with that of the control mix. The PQC mix containing 20% FA and 60% CS resulted in superior strength properties at a 90-day curing period. However, PQC mixes with 30% FA showed a decrease in strength properties with respect to the control mix. X-ray diffraction (XRD) and scanning electron microscope (SEM) studies were employed for the characterisation of selected PQC samples. Furthermore, multiple linear regression equations were established to predict all the strength parameters. The PQC mixes made with FA and CS provide superior strength, reduce waste disposal problems and preserve natural resources for future generations, making such developed mixes sustainable. [ABSTRACT FROM AUTHOR]

As the demand for environmental sustainability grows in the global construction industry, traditional cement production faces significant challenges due to high energy consumption and substantial CO2 emissions. Therefore, developing low-carbon, high-performance alternative cementitious materials has become a research focus. This paper proposes a new low-carbon cement (alkali-activated lithium slag-fly ash composite cement, ALFC) as a substitute for traditional cement. First, the alkali activation reactivity of lithium slag (LS) is enhanced through calcination and grinding, revealing the reasons behind its improved reactivity. Then, alkali-activated LS and fly ash were partially used to replace cement to prepare ALFC, and the effects of the water-to-binder ratio (W/B), LS content, and NaOH addition on the flowability and mechanical properties of ALFC were investigated. XRD, SEM/EDS, and TG/DTG analyses were conducted to examine its hydration products and microstructure, revealing the hydration mechanism. The results show that the flowability of ALFC increases with W/B but decreases with a higher LS content. When W/B is 0.325 and the LS content is 25 wt.%, flowability reaches 200 mm, meeting construction requirements. LS calcined at 700 °C for 1 h significantly enhanced ALFC’s 90-day flexural and compressive strengths by 39.73% and 58.47%, respectively. The primary hydration products of ALFC are C-S-H, N-A-S-H, and C-A-S-H gels, with their content increasing as the NaOH concentration rises. The optimal NaOH concentration and LS content for ALFC are 2 mol/L and 25 wt.%, respectively.

A comprehensive manual review of the use of slag and fly ash in engineered cement-based composites (ECBCs) was conducted. The extensive use of supplementary cementitious materials and integrated fibers in engineered cement-based composite (ECBCs) in seawater composite structures can help to enhance the durability of infrastructure in marine environments and minimize the extensive use of cement and CO2 emissions in the construction industry. This paper retrieved journal and review articles on slag/fly ash utilization in ECBCs from the Scopus database, mainly from 2015 to 2022, and performed an analysis using a suitable software tool. It also provided an up-to-date review of the literature on eco-friendly engineered cementitious composites’ (ECC) durability, with in-depth discussions on the effects of temperature fluctuation on ECCs, supplementary cementitious material, frost and salt corrosion resistance, pre-cracking, seawater resistance, and microstructural alteration. The durability of ECCs is closely related to the behaviors of the fiber distribution, matrix, and fiber-matrix interface under various environmental conditions. The main factors causing the deterioration of the engineering cement-based composites are fiber orientation and dispersion, frost resistance, corrosion, and alkaline environment. Fiber dispersion is mainly assumed to be highly homogeneous in theory, but in practice, due to the uneven dispersion of the fibers the property of each composite structure is not uniform. Further, among all issue associated with durability, sulfate salt attack considered as the most significant environmental deterioration process that affect the resilience of hydraulic structure. At last, it is necessary to conduct additional research on the durability of ECC under various environmental conditions to comprehend its behavior in the actual world. The experimental data currently available on the short-term durability of ECC fluctuate over time. Which indicates that the mechanisms for the long-term degradation of ECC under specific environmental conditions remain unknown.

Micropiling is an extensively used method for improving the stability of building foundations and load-carrying capacity of the soil. Unlike regular piling, it can be employed without pile driving equipment and, hence, it is a versatile option of soil reinforcement under space-restricted situations. Since, it is an economical and easy to implement option for soil improvement, this paper intends to study the improvement in bearing capacity and settlement behaviour of a fly-ash bed using fine micropiles under isolated footings, for low-cast and lightweight structures. Fly-ash, a by-product of coal-fired power plants, is used in the experiment because it is extensively used as a filling material for housing projects in low-lying areas and pavements. Micropiles were installed underneath the footing as well as beyond the periphery of footing with varied spacing and extent ratio. The results are depicted through two dimensionless constants, namely bearing capacity ratio (BCR) and settlement reduction factor (SRF). Significant improvements have been observed in load-carrying capacity and settlement potential due to decrease in spacing and increase in lateral extent of micropiles. The optimum configuration of spacing and lateral extend achieved 135% bearing capacity improvement with 71% decrease in settlement. [ABSTRACT FROM AUTHOR]

This study explored self-healing in geopolymer mortar cured at ambient temperature using polypropylene fibers and bacterial co-cultures of Bacillus subtilis and Bacillus megaterium. Damage degree, compressive strength, ultrasonic pulse velocity (UPV), strength-regain percentage, and self-healing percentage were evaluated. A full factorial design was used, which resulted in an eight-run complete factorial design with four levels in the first factor (polypropylene content: 0%, 0.25%, 0.5%, and 0.75%) and two levels in the second factor (bacteria concentration: 0 (without) and 1 (with)). The results indicate that increasing the polypropylene fiber content enhanced strength regains up to 199.97% with 0.75% fibers and bacteria. The bacteria alone improved strength-regain percentages by 11.22% through mineral precipitation. The analysis of variance (ANOVA) showed no interaction between fibers and bacteria, but both independently improved the compressive strength. Only bacterial samples exhibited positive self-healing, ranging from 16.77 to 147.18%. The analysis using a scanning electron microscope with energy dispersive X-ray (SEM-EDX) and X-ray fluorescence (XRF) also revealed greater calcite crystal formation in bacterial samples, increasing the strength-regain and self-healing percentages. The results demonstrate that polypropylene fibers and bacteria cultures could substantially enhance the strength, durability, and self-healing percentage of geopolymer mortars. The findings present the potential of a bio-based self-healing approach for sustainable construction and repair materials. [ABSTRACT FROM AUTHOR]

Recent years have witnessed a large surge in energy consumption by the building sector, for maintaining a pleasant atmosphere inside the building. Keeping in mind the possible energy crisis in future, the use of thermal insulators can present an extensive solution to reduce energy consumption. Due to the high demand for energy, a higher amount of coal is used in thermal power plants, which produce a large amount of fly-ash as industrial waste that poses a serious environmental problem. In this direction, the extensive utilization of fly-ash to make useful materials could provide helpful societal benefits. This strategy will offer a dual advantage in transforming waste to wealth coupled with potential to serve in the energy sector through effective thermal insulation. On a similar line, we have fabricated biomass-derived cellulose nano-fiber based thermal insulators and incorporated fly-ash as a reinforcer to increase the mechanical strength and fire-retardancy. Interestingly, after incorporation of fly-ash, low thermal conductivity of 0.034 W m−1 K−1 was achieved in the nanohybrid material with reinforcement of mechanical strength up to 2.9 MPa. Furthermore, the thermal stability was enhanced in this novel organic–inorganic nanohybrid, which may create a sustainable solution for energy related issues in future. [ABSTRACT FROM AUTHOR]

Bentonite is the most common binder in iron ore pelletization. In the present work, laboratory experiment as well as basket trials were carried out with partial replacement of bentonite by fly-ash as a binder. Fly-ash is a coal combustion residue produced from power plants. Laboratory tests were carried out with different proportion of fly-ash replacement in the pellet. Pellets prepared in the laboratory with up to 20% replacement of bentonite by fly-ash show favorable green ball properties such as green compressive strength, drop number and dry compressive strength. Based on laboratory tests, basket trials were carried out using 10% fly-ash replacement. Pellets prepared for basket trial show no major variation in green ball properties. However, drop-in cold compressive strength (CCS) of pellet was observed in fly-ash-based pellet as compared to base case (100% Bentonite). Microstructure characterization of the fired pellets indicated the presence of large pores in the case of the pellets containing fly-ash, which are believed to reduce their compressive strength. [ABSTRACT FROM AUTHOR]

The mechanical, microstructural and statical interpretation of the Alkali Activated Concrete (AAC), prepared using fly ash with crushed granulated corex slag as the binder ingredient, are examined in this work. Here, cast in-situ alkali-activated concrete strengths and substitute slag concentrations of 0-50% by fly-ash weight were undertaken to determine a workable manufacturing process and were all considered for up to 28 days. Moreover, in microstructural research, C-A-S-H gel is produced by adding Ground Granulated Corex Slag (GGCS) to the binder-generated structural changes in the in-situ alkali-activated concrete. As a result, this research obtained perfect mixture fractions by synthesizing 25% GGCS with 0.4% of the liquid-to-binder ratio, in addition, a unified desirability of 80% was attained. [ABSTRACT FROM AUTHOR]

The study examined the use of waste materials such as fly ash and bauxite laterite soil in concrete to address waste disposal issues and reduce the cost of concrete products. Bauxite laterite soil is a byproduct of aluminum extraction, while fly ash is a byproduct of coal-fired power plants. To produce bauxite laterite concrete, 20% fly ash was utilized as a partial cement substitute, and 10%, 20%, 30%, and 40% bauxite laterite soil was utilized as a fine aggregate substitute. The mechanical properties of bauxite laterite concrete were studied and compared to those of conventional concrete. The test results indicate that a 10 % substitution of bauxite laterite soil is the optimal amount. After 28 days of curing, the mixture achieved a 58% improvement in compressive strength compared to conventional concrete. In addition, bauxite laterite concrete exhibited high early compressive strength and a unit weight decrease of between 6% and 8%. However, as more bauxite laterite soil was incorporated into the mix, the concrete's workability decreased. Moreover, a Response Surface Model was developed to predict the compressive strength of the bauxite laterite concrete. It can be inferred that both bauxite laterite soil and fly ash are viable alternatives to fine aggregates and cement. [ABSTRACT FROM AUTHOR]

The present investigation addresses the influence of fly ash filler material on physico-mechanical properties (water absorption, tensile, flexural, impact, and hardness) and abrasive wear on alkali-treated (2% NaOH) chopped Himalayan agave fiber randomly oriented compound with polyester resin. The physico-mechanical properties such as void fraction, water resistance capability, tensile, flexural, impact, hardness, and dry abrasive wear characteristics of Himalayan agave fiber/polyester composites was determined. The maximum tensile strength (30.09 MPa), flexural strength (54.51 MPa), impact strength (30.24 J/m2), and hardness (42.5 HV) were observed at 15 wt.% of Himalayan agave fiber and fly ash. The abrasive specific wear rate of the composite was studied at four different factors, i.e., fiber loading (5–15 wt.%), normal load (10–30 N), fly-ash content (5–15 wt.%), and speed (50–150 rpm) using Taguchi’s method L9 orthogonal array. The study determined that the control parameters of fiber loading (15 wt.%), normal load (10 N), fly-ash content (15 wt.%), and speed (100 rpm) exhibited the least specific abrasive wear rate. The SEM analysis of worn abrasive surfaces revealed the micro-cuts, fiber breakage, micro-plowing, cracks, and wear debris as the dominant wear mechanism.

Recently, the demand for strengthening and rehabilitation of existing RC structures has increased due to the corrosion of internal steel reinforcement, variations in temperature, and increasing loading. As a result, several experimental studies have been performed to investigate the structural behaviour of strengthening RC beams with CFRP sheets, but few for GPC beams; therefore, this investigation focuses on the behaviour of strengthening GPC beams with CFRP sheets. In this experimental work, a set of ten specimen beams with the same cross section of 100 × 250 mm and 850 mm length with a 750 mm clear span were cast in two groups of five beams each. First group (flexural group) to study the flexural behavior, and the second one for the shear behaviour (shear group). In each group, the first beam was carried out as an RC control beam and the second as a GPC control beam without strengthening, while the other three beams were cast as GPC beams and strengthened with various schemes of CFRP sheets. All specimens were tested up to failure under two-sided static loading (four-point bending). The first cracking, yielding, and ultimate failure loads, the deflection values at midspan, the longitudinal bar strain, and the concrete strain were recorded for all tested specimens. The experimental results indicated that the Flextural Strengthening of GPC with CFRP sheet increased the First Cracking, yield and ultimate load capacity by 25.33%, 15.3% and 15% respectively, as well as, deflection was decreased by 16% on average while ductility and toughness have improved by 10% and 12% on average compared to R.C Beam.On the other side, the Shear Strengthening of GPC with CFRP strips increased the First Cracking, yield and ultimate load by 43%, 70% and 68% respectively, as well as, shear ductility has improved by 8% on average compared to R.C Beam. Overall, the different schemes of externally bound CFRP sheets have improved the flexural and shear behaviour of GPC beams.

The construction industry is on the lookout for cost-effective structural members that are also environmentally friendly. Built-up cold-formed steel (CFS) sections with minimal thickness can be used to make beams at a lower cost. Plate buckling in CFS beams with thin webs can be avoided by using thick webs, adding stiffeners, or strengthening the web with diagonal rebars. When CFS beams are designed to carry heavy loads, their depth logically increases, resulting in an increase in building floor height. The experimental and numerical investigation of CFS composite beams reinforced with diagonal web rebars is presented in this paper. A total of twelve built-up CFS beams were used for testing, with the first six designed without web encasement and the remaining six designed with web encasement. The first six were constructed with diagonal rebars in the shear and flexure zones, while the other two with diagonal rebars in the shear zone, and the last two without diagonal rebars. The next set of six beams was constructed in the same manner, but with a concrete encasement of the web, and all the beams were then tested. Fly ash, a pozzolanic waste byproduct of thermal power plants, was used as a 40% replacement for cement in making the test specimens. CFS beam failure characteristics, load–deflection behavior, ductility, load–strain relationship, moment–curvature relationship, and lateral stiffness were all investigated. The results of the experimental tests and the nonlinear finite element analysis performed in ANSYS software were found to be in good agreement. It was discovered that CFS beams with fly ash concrete encased webs have twice the moment resisting capacity of plain CFS beams, resulting in a reduction in building floor height. The results also confirmed that the composite CFS beams have high ductility, making them a reliable choice for earthquake-resistant structures. [ABSTRACT FROM AUTHOR]

The study of pressure loss along pipelines during slurry transportation has become a core research concern. However, the simulation research on non-Newtonian flows in mining backfill operations is limited. In this study, a validated Herschel-Bulkley model is deployed to simulate and quantify the pressure evolution and flow characteristics of backfilling slurry inside an L-shaped pipe, showing that both the total and dynamic pressures decrease gradually from the central region to the layers close to the pipe walls. Through a numerical analysis, this paper introduces an unprecedented pressure loss calculation formula simultaneously taking into consideration, both the pipe diameter and the slurry flow velocity. [ABSTRACT FROM AUTHOR]

Sustainability is a growing area of concern, especially amid the concrete industry. Concrete, especially traditional concrete, which contains Portland cement, is extremely harmful to the environment producing mass amounts of carbon dioxide. Additionally, the harvesting of these materials, like lime, cause significant damage to waterways and the ecosystem. For years, studies have found numerous, more sustainable, alternatives that are structurally equivalent to traditional concrete. The Connecticut Department of Transportation does allow for the use of alternative “green” concretes as long as the mix designs meet the required specifications. Nevertheless, heavy highway construction seems reluctant to dabble with new substances and continues to falls back on the use of fly ash concrete. This solution, however, is not perfect, as fly ash is a finite material. By conducting a nationwide survey to the Departments of Transportation (DOT), the reliance on fly ash was evident. It was also found that the biggest concerns for DOTs would be the cost and availability of the material. This study investigates presently accepted alternative concrete mixture designs and also explores the solutions of volcanic ash concrete and ground glass concrete. Based off the results of the survey and practicality, this study suggests the incorporation of ground glass concrete for heavy highway construction. This solution provides the needed strength requirements per DOT specs and is within the same price-range as fly ash concrete.

A facile and green approach to extract silica from the coal fly-ash waste is extremely critical for environmental sustainability and economically suitable. In this study, we have used acid-alkali coupled approach to improvised the proficiency of the extraction process. The sodium hydroxide (NaOH) soaking results the formation of the sodium silicate (Na2SiO3) solution then pure silica was obtained by heating at high temperature; this coupled route-way results better yield of silica (SiO2) which is ∼ 40 g. The efficiency of pure silica is not enough to remove toxic effluents from the aqueous media. A highly versatile approach of composite formation was adopted to fabricate silica-clay composite using kaolinite-clay and extracted silica. Both materials, extracted silica and its silica-clay composite were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) method, X-ray diffraction technique (XRD) and Fourier transform infra-red spectroscopy (FTIR). The silica-clay composite showed plate-tubular like morphology with enormous binding sites available for the sorption pollutants like organic dyes. It has shown excellent sorption of methylene blue (MB) efficiency of 131.5 mg/g, while silica furnished the sorption of 70.5 mg/g. Results revealed that the synthesized material could probably have better potential for dye removal from industrial effluents. [ABSTRACT FROM AUTHOR]

Solid particle erosion at room and elevated temperatures of filled and unfilled hot-cured epoxy resin using an anhydride hardener were experimentally tested using an accelerated method on a special bench. Micro-sized dispersed industrial wastes were used as fillers: fly ash from a power plant and spent filling material from a copper mining and processing plant. The results showed that the wear of unfilled epoxy resin significantly decreases with increasing temperature, while the dependence on the temperature of the wear intensity at an impingement angle of 45° is linear and inversely proportional, and at an angle of 90°, non-linear. The decrease in wear intensity is probably due to an increase in the fracture limit because of heating. Solid particle erosion of the filled epoxy compounds is considerably higher than that of unfilled compounds at impingement angles of 45° and 90°. Filled compounds showed ambiguous dependences of the intensity of wear on temperature (especially at an impingement angle of 45°), probably as the dependence is defined by the filler share and the structural features of the samples caused by the distribution of filler particles. The intensity of the wear of the compounds at impingement angles of 45° and 90° has a direct and strong correlation with the density and the modulus of elasticity, and a weak correlation with the bending strength of the materials. The data set for determining the correlation between the mechanical properties and the wear included compound filling characteristics and temperature. [ABSTRACT FROM AUTHOR]

Four‐point bending tests were conducted to investigate the flexural properties of fly‐ash‐based geopolymer concrete beams. Although geopolymer concrete has a stress–strain relationship with brittle compressive softening behavior, it can be used as a flexural member because it exhibits ductile bending moment–deflection relationships when used with compression reinforcing bars and transverse reinforcement. The test results revealed that the conventional design method can be used to estimate the bending moment–deflection relationship of geopolymer concrete beams. However, the stiffness reduction ratio for yielding must be modified to consider the difference in the modulus of elasticity between geopolymer concrete and ordinary Portland cement concrete. [ABSTRACT FROM AUTHOR]

Overall, Figure 5(d) has a minimum wear rate as compared to Figure 5(a), Figure 5(b), and Figure 5(c) due to fewer cavities and better interlocking of fiber with polyester resin form in HA15/15 fabricated composite in comparison to untreated polyester resin (PC) and other alkali-treated agave fiber composites. Keywords: Natural fiber; composite; fly-ash; agave fiber; physical and mechanical properties; abrasive wear; Taguchi analysis; ; ; ; ; ; ; EN Natural fiber composite fly-ash agave fiber physical and mechanical properties abrasive wear Taguchi analysis ZH 9269 9282 14 11/21/22 20221220 NES 221220 Introduction Nowadays, natural fiber (NF) extracted from the lignocellulosic plant along with surface modification or without surface modification as reinforced in the polymer-based composite are used frequently in many engineering applications like automotive and aerospace industries, gears, braking systems, naval architecture, low-level transportation, rollers, and other automatic office machinery (Acharya and Mishra [1]; Kumar et al. [16]). Usually, the alkali-treated fiber with the composition of FA and fiber content enhanced the fabricated composite modulus to improve the hardness of the composite (Goriparthi, Suman, and Mohan Rao [7]). [Extracted from the article]

The current study compares and analyses the fly-ash–epoxy composite structure with alloys for bracket applications. A dispersed reinforcement composite is created by combining epoxy and fly-ash. Three different prototypical brackets are modelled and analysed using the finite element method, and their results are compared to common alloys used in the manufacture of L-shaped brackets. The mechanical properties of the composite material are calculated using a rule of mixtures, and the properties of the composite material are modified by changing the percentage composition of fly-ash. Based on equivalent stress and total deformation, all geometrical models are analysed and compared. The analysis results appear to be appropriate for broadening the scope of the application of epoxy-based composites for small-scale and large-scale applications. The results also show that the composite material can be used to make a variety of structural elements with high design complexity, such as bulkheads and other structural components. [ABSTRACT FROM AUTHOR]

Annually, the thermal coal industries produce billion tons of fly-ash (FA) as a waste by-product. Which has been proficiently used for the manufacture of FA based geopolymer concrete (FGC). To accelerate the usage of FA in building industry, an innovative machine learning techniques namely gene expression programming (GEP) and multi expression programming (MEP) are employed for forecasting the compressive strength of FGC. The comprehensive database is constructed comprising of 311 compressive strength results. The obtained equations relate the compressive strength of FGC with eight most effective parameters i.e., curing regime (T), time for curing (t) in hours, age of samples (A) in days, percentage of total aggregate by volume (% Ag), molarity of sodium hydroxide (NaOH) solution (M), silica (SiO2) solids percentage in sodium silicate (Na2SiO3) solution (%S), superplasticizer (%P) and extra water (%EW) as percent FA. The accurateness and predictive capacity of both GEP and MEP model is assessed via statistical checks, external validation criteria suggested by different researcher and then compared with linear regression (LR) and non-linear regression (NLR) models. In comparison with MEP equation, the GEP equation has lesser statistical error and higher correlation coefficient. Also, the GEP equation is short and it would be easy to use in the field. So, the GEP model is further utilized for sensitivity and parametric study. This research will increase the re-usage of hazardous FA in the development of green concrete that would leads to environmental safety and monetarist reliefs.

A hydrometallurgical treatment under ambient conditions was proposed in order to eliminate and recover the lead and zinc contained in a sample of thermal coal fly ash used to produce energy. By using leaching solutions with conventional inorganic acids (HCl, HNO3, and H2SO4), ferric chloride, and sodium citrate, more than 90% zinc and approximately 40% lead were obtained. The most favorable leaching conditions were set at 0,5 M, with a pH value of 8 for citrate. Two leaching stages were necessary to optimize metal recovery: the first with nitric acid for zinc extraction and the second one with citrate for the lead. The sulfur phases of the metals limited a complete metal extraction.

Abstract Four‐point bending tests were conducted to investigate the flexural properties of fly‐ash‐based geopolymer concrete beams. Although geopolymer concrete has a stress–strain relationship with brittle compressive softening behavior, it can be used as a flexural member because it exhibits ductile bending moment–deflection relationships when used with compression reinforcing bars and transverse reinforcement. The test results revealed that the conventional design method can be used to estimate the bending moment–deflection relationship of geopolymer concrete beams. However, the stiffness reduction ratio for yielding must be modified to consider the difference in the modulus of elasticity between geopolymer concrete and ordinary Portland cement concrete.

This study explored self-healing in geopolymer mortar cured at ambient temperature using polypropylene fibers and bacterial co-cultures of Bacillus subtilis and Bacillus megaterium. Damage degree, compressive strength, ultrasonic pulse velocity (UPV), strength-regain percentage, and self-healing percentage were evaluated. A full factorial design was used, which resulted in an eight-run complete factorial design with four levels in the first factor (polypropylene content: 0%, 0.25%, 0.5%, and 0.75%) and two levels in the second factor (bacteria concentration: 0 (without) and 1 (with)). The results indicate that increasing the polypropylene fiber content enhanced strength regains up to 199.97% with 0.75% fibers and bacteria. The bacteria alone improved strength-regain percentages by 11.22% through mineral precipitation. The analysis of variance (ANOVA) showed no interaction between fibers and bacteria, but both independently improved the compressive strength. Only bacterial samples exhibited positive self-healing, ranging from 16.77 to 147.18%. The analysis using a scanning electron microscope with energy dispersive X-ray (SEM-EDX) and X-ray fluorescence (XRF) also revealed greater calcite crystal formation in bacterial samples, increasing the strength-regain and self-healing percentages. The results demonstrate that polypropylene fibers and bacteria cultures could substantially enhance the strength, durability, and self-healing percentage of geopolymer mortars. The findings present the potential of a bio-based self-healing approach for sustainable construction and repair materials.

Reusing or recycling waste into new useful materials is essential for environmental protection. Herein, we used discarded polystyrene (PS) and fly-ash (FA) particles and a fabricated fly-ash incorporated polystyrene fiber (FA/PS fiber) composite. The electrospinning process produced continuous PS fibers with a good distribution of FA particles. The prepared nanofibers were characterized by state-of-the-art techniques. The performances of the composite nanofibers were tested for fire-retardant applications. We observed that the incorporation of FA particles into the PS fibers led to an improvement in the performance of the composite as compared to the pristine PS fibers. This study showed an important strategy in using waste materials to produce functional nanofibers through an economical procedure. We believe that the strategy presented in this paper can be extended to other waste materials for obtaining nanofiber membranes for various environmental applications. [ABSTRACT FROM AUTHOR]

Aluminosilicates are the base precursors that combined with alkali solutions manufacture geopolymers. A wide variability of aluminosilicate precursors can be found in the market worldwide, which may be an issue when proposing single designs. The goal of this study is to compare the use of different precursors in the hardening mechanisms of geopolymers. For this, two types of metakaolin (a low (MK LR) and a high-reactive (MK HR) one), and partial replacements made with fly-ash (FA) and blast furnace slag (BFS) are used in SiO 2 /Al 2 O 3 = 4.00, Na 2 O/SiO 2 = 0.25, and H 2 O/Na 2 O = 11.00 fixed design ratios. Fresh state (viscosity and squeeze flow), transient state (Vicat needle and sonic strength), and hardening measurements (compression tests under room and high temperature conditions), were used, supported by chemical analysis (calorimetry and SAM/HCl extraction) and materials characterization (particle analysis, density, BET and XRD). In general, the reactivity, chemical composition, and morphology of each precursor, as well as solid/liquid portions of each mix were major factors influencing the hardening process. The use of MK LR achieved shorter setting times and enhanced viscosities due to its particles larger surface area, solid/liquid ratios, and unreactive portions, reaching the highest values of strength and diminished thermomechanical performance. Partial substitutions made with FA and BFS increased the amorphous part of the binder, increasing also its flowability, setting time, and its stability to thermal exposure. The geopolymer made with MK HR presented the lowest viscosity and longer setting time due to its almost constant dissolution rate, attributed to its enhanced reactivity from highly amorphous parts and diminished solid-to-liquid ratio mixture. Therefore, the use of varied aluminosilicates significantly modifies the materials properties, leading to different potential applications that should be considered when designing geopolymers. [ABSTRACT FROM AUTHOR]

Fly-ash, a kind of large solid waste in energy industry, has brought about serious environmental problems and safety consequences. No efficient way has been found yet to deal with it worldwide. The focus of contemporary research are mainly placed on the reuse of aluminum and iron, but with a low utilization rate less than 30%. Having destroyed the ecological balance, fly-ash has become a challenge drawing the attention of people in the solid waste industry. In this paper, a smoke-suppressant and flame-retardant layered double hydroxide (LDH) featuring Mg-Al-Fe ternary was successfully synthesized by fly-ash after coprecipitation. XRD results presented LDHs successful synthesis. Then, exploration on the flame retarding properties of LDHs in composites composed by ethylene vinyl acetate (hereinafter referred to as EVA)/LDHs was carried out by UL-94, limiting oxygen index (LOI), cone calorimeter (CCT), smoke density (SDT), and thermogravimetry-Fourier transform infrared spectrometry (TG-IR) tests. UL testing results showed that most of the samples had a vertical combustion rating of V-0. LOI results showed the highest LOI value of ELDH-1, amounting to as high as 28.5 ± 0.1 while CCT results showed that the rate of heat releasing, mass loss, and smoke production of composite materials were decreased significantly compared with corresponding data of pure EVA. The ELDH-1 sample displayed the lowest peaks of heat release rate (pHRR) value of 178.4 ± 12.8 Kw·m−2 and the lowest total heat release (THR) value of 114.5 ± 0.35 KJ·m−2. Then, SDT indicated that under respective ignition and non-ignition conditions, all composite materials present a good smoke suppression performance. Additionally, digital photographs after CCT demonstrated that EVA/LDHs composites could enhance the formation of compact charred layers, and prevent their splitting, which effectively prevent the underlying materials from burning. Finally, TG-IR findings showed that compared with pure EVA, EVA/LDHs composites also achieved a higher-level thermal stability. [ABSTRACT FROM AUTHOR]

Heavy metal removal by constructed wetland (CWs) is becoming the most efficient and greener technology around the world where plants are used in phytoremediation to degrade, stabilize and remove contaminants from soils, water and waste. The design of CWs for successful phytoremediation in heavy metals contaminated wastewater should not affect the local environment. By‐product generation is another crucial part of phytoremediation's success. In the study, phytoremediation plants (Canna indica and Acorus calamus) biomass has been successfully used in the manufacture of 70 fly‐ash bricks. Further, these bricks are used for CWs to see the efficiency in removing heavy metals pollution. Results found that high rates of Cu (96 %), Zn (95 %), (Fe 93) and Cr (91 %) removal from Canna indica and Acorus calamus were found as compared to the Typha latifoliya, Myriophylhum aquaticum, Ludwigina palustris, Eichhornia crassipes, Schoenoplectus californicus, Cyperus papyrus and Phragmites australis reported by others global researchers which indicates C. indica is the high potential for heavy metal removal and can be strongly used for industrial wastewater. The use of ornamental plants for phytoremediation of contaminated sewage wastewater would also change the landscape of the aquatic environment. This study summarizes viable avenues in the method of using phytoremediation plant biomass for environmental protection and sustainable environmental management. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to investigate the effect of fly-ash(FA) as a fine aggregate on filling performance. The effect of FA content on the gradation distribution and compactness of the dry mixture is tested. Slump, bleeding rate, and unconfined compressive strength (UCS) of cemented waste rock-FA backfill (CWFB) samples were also tested at different FA content, solids content, and cement-sand ratio conditions. Results show that FA as a fine aggregate can effectively improve the mixture gradation performance. Short-term (3d/7d) strength increases with FA content, while long-term (28d) strength and slump first increase and then decrease, reaching a maximum value of 8.58 MPa and 27.4 cm respectively at 30% FA content. The bleeding rate first decreased and then stabilized (about 5.2%) with FA content. The UCS showed higher sensitivity to high solid content. The slump reduction rate of samples with high FA content decreases with solid content. Larger cement content will weaken the fluidity. When the cement-sand ratio increased from 1:6–1:4, the slump decreased from 27.5 cm to 23.5 cm, and the bleeding rate decreased to 4.05%. However, the mechanical properties are significantly improved with cement content. This study has positive implications for recycling the FA.

In many countries, the use of waste materials in the construction sector is a viable option due to rising raw material costs and the continuous depletion of natural resources. Waste materials have shown to be valuable as construction materials when properly processed, and they readily fulfil design criteria. Natural aggregate extraction is still prevalent, but it's wreaking havoc on the environment. Aggregate extraction alters the landscape and may cause other issues, such as weathering, which frequently results in lasting harm to rural areas. Fly ash aggregates, which are created from industrial waste, not only supply additional aggregate sources but also aid in pollution reduction. Fly-ash is a finely dispersed waste produced by the combustion of powdered coal that is carried by flue gases and collected using an electrostatic precipitator. Fly ash is an environmentally toxic waste product that is difficult to decompose. Fly ash from power stations is utilized in a variety of civil engineering applications, including blended cement, lightweight aggregates, fly ash bricks and blocks, and lightweight concrete. India's energy industry is currently reliant on coal-fired thermal power plants, which generate a considerable quantity of fly ash (about 200 million tons per year). Fly ash has mostly been used in concrete as a cement replacement element or as aggregate fillers. Fly ash is utilized to substitute cement in around 30% of concrete applications. This degree of replacement must be increased. Future additions of high-volume fly ash are projected. Fly ash aggregates are a novel breakthrough in the construction industry, directly replacing coarse aggregates which are typically a major constituent of buildings. The strength characteristics of fly ash aggregate concrete were investigated in this experimental investigation by manufacturing aggregates with cement and fly ash in the ratios of 10:90, 15:85, and 20:80. The tests were performed on concrete to look at qualities like compressive and split tensile strength. [ABSTRACT FROM AUTHOR]