Fly Ash Composites Research Articles

Strength and Microstructural Characteristics of Activated Fly Ash–Cement Paste

Incorporating high volumes of fly ash (FA) in filling materials reduces costs and carbon emissions, but low early strength limits its use. This study investigates the effects of sodium sulfate decahydrate (Na2SO4·10H2O) and calcium hydroxide (Ca(OH)2) as activators at concentrations of 0.5%, 1.0%, 1.5%, and 2.0% on the mechanical properties and microstructure of tailings–cement–fly ash composites. Compressive strength testing, X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used to evaluate performance at different curing stages. Results indicate that all activators enhance early strength, with 2.0% Ca(OH)2 yielding the greatest improvement. Microstructural analysis showed that activators boost quartz reactivity and create denser structures. Na2SO4 promotes ettringite and gypsum formation, while Ca(OH)2 increases alkalinity, enhancing gel formation from FA. These findings clarify how activators improve the performance of activated fly ash–cement paste (AFCP).

Influence of Soilless Growing Media Comprising Industrial By-products on Growth of Foliage Plants Epipremnum aureum and Dracaena sp.

Experiments were conducted during August, 2020 to April, 2021 at the ICAR-Directorate of Floricultural Research, Pune, Maharashtra, India to assess the suitability of industrial by-products fly ash and press mud as growing media component for foliage plants Epipremnum aureum and Dracaena sp. Different growing media compositions comprising of fly ash, press mud, cocopeat and vermicompost were evaluated in varying proportions. Foliage plants growth was monitored for nine months duration. Initial pH and electrical conductivity of growing media compositions were determined and leaf samples were analyzed for macro and micronutrients content at the end of the experiment. pH of growing media compositions ranged from near neutral to slightly alkaline pH and electrical conductivity of all media compositions was less than 1.0 dS m-1. Results indicated that growing media composition Fly ash+Vermicompost+Cocopeat (20:30:50) was the most suited growing media to grow Epipremnum aureum under 50% shade condition. Media compositions Cocopeat+Vermiculite+Perlite (33.3:33.3:33.3) and Fly ash+Vermicompost+Cocopeat (20:30:50) were observed to be more suited for growth of Dracaena sp. under 50% shade condition. Maximum plant height, number of leaves, leaf size and petiole length were recorded in Epipremnum aureum and Dracaena sp. plants grown in above media compositions respectively. Results inferred that fly ash along with vermicompost and cocopeat can be used as a growing media component for production of foliage plants Epipremnum aureum and Dracaena sp.

Synthesization and characterizations of coal fly ash-coffee grounds-based composite as super-absorbent for application in soil

To recycle and utilize two types of harmful solid waste, coffee grounds (CG) and coal fly ash (CFA), a novel and low-cost superabsorbent composite (MCG-PAA/CFA) was synthesized by aqueous solution polymerization with modified coffee grounds (MCG), acrylic acid (AA) and CFA as raw materials, and it was applied to soil to improve its drought resistance. Various reaction conditions were comprehensively investigated and analyzed to assess their influence on the water absorbency of the superabsorbent composite (SAC). After optimization, the MCG-PAA/CFA exhibited water absorbency capacities of 1260(±10.6) g/g and 82(±1.4) g/g in deionized water and physiological saline, respectively. After adding 3 wt% MCG, the water absorption of SAC was improved from 415 to 746 g/g. After further introduction of 2 wt% CFA, the water absorption of SAC increased from 746 to 1260 g/g. Fourier Transform Infrared (FTIR) analysis confirmed that the grafting reaction was successful and that CFA participated in the reaction, while scanning electron microscope (SEM) and thermogravimetric analysis (TGA) results revealed that the grafting reaction and the introduction of CFA improved the surface morphology and thermal stability of the SAC. Kinetic analysis was conducted to investigate how the grafting reaction and the introduction of CFA affected the swelling and water retention kinetics of the superabsorbent composite. In the soil experiment, adding only 0.1 wt% MCG-PAA/CFA can improve the water holding capacity of sandy soil, loam soil and clay soil by 6.65%, 4.42%, and 3.76% respectively This SAC composite has great potential in soil drought resistance.

Effect of fly ash on mechanical properties and microstructural behaviour of injected moulded recycled polypropylene composites

The global challenges of plastic waste and fly ash accumulation demand innovative recycling solutions. In Malaysia, the consumption of 11.2 million tonnes of coal annually generates approximately 2 million tonnes of fly ash, while the recycling of Polypropylene (PP) is hindered by thermo-oxidative and shear-induced degradation during mechanical recycling, resulting in reduced mechanical properties. This study addresses these issues by fabricating recycled PP composites incorporating varying fly ash contents, using a single cycle of mechanical recycling with extrusion and injection moulding methods. The composites were comprehensively tested for tensile, flexural, and compressive strengths, as well as microstructural behaviour. The results reveal a complex relationship between fly ash content and mechanical performance: while tensile strength decreases with increasing fly ash, flexural strength and strain peak at 5 % and 9 % fly ash, respectively. Compressive strength also shows a slight increase up to 7 % fly ash, indicating an optimal range for enhancing mechanical performance. Furthermore, mathematical models were proposed to predict the mechanical properties of rPP – fly ash composites, providing a valuable tool for future material design. These findings demonstrate that optimization of fly ash content can mitigate the effects of polymer degradation, offering a sustainable solution to improving the mechanical performance of this composite.

Comparative study on preparation and hydration mechanism of composite cementitious materials containing copper slag

Copper slag (CS) is a kind of non-ferrous solid waste with low content of aluminosilicate and relatively high content of iron oxide. In this paper, the feasibility and mechanism of CS as the mineral admixture and precursor of alkali activated cementitious material were studied. The effects of CS on mechanical properties were studied and the hydration products were determined by several characterization methods. Scanning Electron Microscopy (SEM) and Mercury Injection Porosimetry (MIP) were performed to characterize the microstructure. The results show that CS composite fly ash (FA) has more advantages than CS alone, but its application as a mineral admixture is limited by the low activity. The alkali activated cementitious material prepared by CS and FA as precursor has excellent mechanical properties. The compressive strength of specimen at 28 days age can reach the maximum of 81.3 MPa when the dosage of CS is 30 %. The 3d and 28d compressive strength of the specimen contained 60 % CS obtained 57.7 MPa and 70.7 MPa, respectively. The research exhibits great potential for the future utilization of CS.

Kaolin–Fly Ash Composite for Pb2+ and AsO43− Adsorption from Aqueous System

The expected benefit of composite adsorbents generally consists in their growing applicability, thanks to the combination of the adsorption properties of individual components. Composite adsorbents were prepared as mixtures of kaolin from a Czech deposit (kaolin Sedlec, SK) and two fly ashes (FAs) from a fluidised bed boiler in Czech operations differing in fuel type. The mixtures of SK with FA in a ratio of 50:50% wt. were prepared at 20 °C, 65 °C, and 110 °C in an autoclave. The source materials and composite adsorbents were tested for the adsorption of lead as Pb2+, and arsenic as AsO43− from model solutions in laboratory conditions. The adsorption of Pb2+ proceeded quantitatively on the source materials except SK, and on both the composites, with an adsorption yield of >97% and a low adsorbent consumption (~2 g.L−1). The AsO43− adsorption proceeded selectively only on both FAs, with an adsorption yield of >97% again. The adsorption of AsO43− on the composite adsorbents achieved a worse yield (˂80%), with about ten times more adsorbent consumption (~20 g.L−1). An increased preparation temperature did not affect the Pb2+ adsorption at all, but it reduced the efficiency of AsO43− adsorption by up to 30%. The SK–FA composites proved to have promising properties, mostly as cation-active adsorbents.

Mechanical, Fire, and Electrical Insulation Properties of Polyurethane Fly Ash Composites.

This paper demonstrates that ash composites, comprising fly ash and polyurethane, can be used to develop value-added products that exhibit an effective decrease in the leaching of coal ash inorganics to less than one-third of the Environmental Protection Agency (EPA)'s maximum contaminant level (MCL) when soaked in a water circulation system for 14 months. Furthermore, the composite blocks remain safe even with ruptured surfaces. The concept of encapsulating fly ash within ash composites by using a polar polymer to bind the fine inorganic particles, mimicking how nature does it in the original unburned coal, ensures the safety of the composite. The ash composites can be formulated to have designed mechanical, fire, and electrical properties by controlling the formulation and the density. The properties of typical density composites were produced, measured, and compared with commercial materials. This paper also demonstrates that ash composite technology can be extended to coal ash stored in ponds. Finally, a typical electric utility box cover was designed, fabricated, and test validated. The box cover has less than one-half the weight of the original box cover for the same design limits. Finally, the benefits of this ash-composite technology for product manufacturers, society, and ash producers are summarized.

Chemical and Thermal Analysis of Fly Ash-Reinforced Aluminum Matrix Composites (AMCs)

Fly ash has been utilized as a reinforcing material in the production of aluminum matrix composites, and in this investigation, Al-Si (LM6) fly ash composites were fabricated using the compocasting method. Various compositions of fly ash were incorporated into the samples (4, 5 and 6 wt%), and the preparation temperature ranged from 560 to 800°C. This study investigated the thermal (CTE and DTA) and chemical properties (XRD) of fly ash reinforcement and the aluminum melt in the composites. The results revealed that composites with 5 wt% of fly ash exhibited the lowest CTE value compared to those with 4 and 6 wt%. This observation was corroborated by XRD analysis, indicating a reaction between the fly ash particles and the aluminum melt. However, the DTA analysis did not find a significant impact of the addition of fly ash on the melting temperature of the prepared composites. In contrast, this study identified and investigated the existence of reaction effects between the fly ash particles and the aluminum melt.

Impact on casting die diameter size on microstructure and fractographic studies of Al2024 alloy reinforced with fly ash and SiC hybrid composites

AbstractThe development of metal matrix composites is important for industrial applications that require lightweight materials with high strength, stiffness, and wear resistance. In this investigation, Al2024 alloy was reinforced with fly ash and silicon (SiC) carbide hybrid composites using the stir‐squeeze cast technique. Two sets of composites were fabricated: one with 3 wt% fly ash and 3 wt% SiC, and the other with 3 wt% fly ash, 5 wt% SiC, and 3 wt% fly ash, 7 wt% SiC The composites were prepared using 25 and 75 mm diameter dies. Microstructural characterization of the specimens was performed using scanning electron microscope, X‐ray powder diffraction, and energy dispersive X‐ray spectroscopy analysis. Mechanical properties, such as yield strength, ultimate tensile strength, and hardness, were determined according to American Society for Testing and Materials standards. The hybrid composites fabricated in the 25 mm diameter cast iron molds exhibited superior mechanical properties compared to those prepared in the 75 mm diameter molds. The addition of fly ash and SiC particulates enhanced the mechanical properties of the Al2024 alloy. These composites showed improved strength, toughness, and ductility.

Viscoelastic behaviour of poly(ether-ketone)/fly ash composites fabricated by powder metallurgical route

Poly(ether-ketone)/fly ash (FA) composites reinforced with 0-30 wt% FA were fabricated using ball milling followed by hot compaction. The composites were investigated for mechanical and viscoelastic properties. Scanning electron microscopy revealed excellent dispersion and good adhesion of FA particles with the matrix. The addition of FA increased the microhardness by 70% and the storage modulus (below glass transition) by 75%. The reinforcing efficiency was better above the glass transition, which increased to around 177% at 250°C. This research indicates that the FA can be used as an alternative reinforcement of costly ceramic powder for the electronic packaging substrate or printed circuit board applications.

Bulk utilization of steel slag–fly ash composite: a sustainable alternative for use as road construction materials

Bulk utilization of steel slag–fly ash composite: a sustainable alternative for use as road construction materials

Engineering properties and optimal design of foam lightweight soil composite fly ash: An eco-friendly subgrade material

Foam lightweight soil is used frequently in engineering construction for soft soil areas due to its superior lightness and economy, but its greater cement usage will result in cost increase, resource waste, and environmental pollution. This study modified foam lightweight soil with industrial solid waste (fly ash) in place of some cement to propose an eco-friendly and useful lightweight subgrade filling material. A series of macro-micro tests were conducted to investigate the engineering properties and micro-mechanisms of foam lightweight soil composite fly ash (FLS). The results showed that the axial stress-strain and shear stress-displacement curves of FLS showed softening types. The fluidity, compressive strength, toughness and shear strength of FLS first increased and then decreased with the increasing fly ash content. The mechanical strength of 20% FLS was the optimal value for meeting the application requirements of subgrade engineering. Due to the volcanic ash and micro-aggregation effects, fly ash consumed the calcium hydroxide to produce more calcium silicate hydrate for filling the pores of sample and improving its internal structure. According to the results of numerical simulation, the settlement deformation and lateral deformation of subgrade could be better controlled by using 20%FLS as filling material compared with ordinary soil. Consequently, it is feasible to apply FLS in subgrade engineering.

Synthesis, Characterization, and Thermal Properties of Mg-3Ca/Fly Ash Composites

Synthesis, Characterization, and Thermal Properties of Mg-3Ca/Fly Ash Composites

Effects of alkali activator types and fly ASH replacement rate on mechanical properties of geopolymer

In this study, C-class fly ash (FA) and ground granulated blast-furnace slag (GGBS)-based geopolymer activated in NaOH and NaOH+Na2SiO3 were used to study setting time, compressive strength, porosity, etc. As a result of comparing the effects of alkali types on FA and GGBS geopolymer composites, NaOH + Na2SiO3 showed increased strength and density compared to NaOH, since the addition of Na2SiO3 provides the silica source to develop more compact structure. For the Class-C FA and GGBS mix, increased fly ash content resulted in prolonged setting times, reduced strength, and loose matrix. In addition, the non-reactivity of calcium in the mixture was observed as the fly ash content increased, leading to strength loss.

Engineering and microstructural properties of carbon-fiber-reinforced fly-ash-based geopolymer composites

Alkali-activated fly ash and slag-based geopolymer composites offer sustainable cement alternatives to conventional cement materials. Incorporating fibers mitigates issues such as brittleness, insufficient toughness, and cracking in geopolymers. However, limited systematic research exists on the influence of carbon fiber characteristics on geopolymer performance. In this study, the effects of carbon fibers having varying lengths (6 mm and 12 mm) and volume fractions (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) on multiple properties of geopolymers, including workability, water absorption, porosity, mechanical strength, drying shrinkage, uniaxial tensile properties, fracture toughness, and microstructure, are investigated. Results indicate that the incorporation of carbon fibers diminishes the flowability of the geopolymer mix and accelerates its setting time. Parameters such as water absorption, porosity, and compressive and flexural strengths initially decrease and then increase with increasing fiber content. Carbon fibers positively affect drying shrinkage, particularly during the early stages. The fiber bridging effect enhances uniaxial tensile properties, reducing brittleness. Carbon fiber addition improves the fracture toughness of the composite, achieving an optimal volume fraction at 0.6%. At this volume fraction, carbon fibers of 6 mm length exhibit better crack initiation toughness and resistance to instability cracking than fibers of 12 mm length. Moreover, the presence of carbon fibers promotes the formation of hydration products, minimises the occurrence of microcracks, and interacts synergistically with the slurry matrix to enhance overall crack resistance and material toughness. This study provides a valuable reference for the development and application of fiber-reinforced geopolymer materials.

Polydopamine/β-cyclodextrin/coal fly ash composite for the highly efficient extraction of uranium from water environment

To obtain a green, low-cost and efficient adsorbent, polydopamine (PDA) and β-cyclodextrin (β-CD) were adopted to modify coal fly ash (CFA) to prepare polydopamine/β-cyclodextrin/coal fly ash composite (PDA/β-CD/CFA). The successful introduction of PDA and β-CD was proved by FT-IR, XRD and XPS. The uranium extraction efficiency on PDA/β-CD/CFA reached 95.6% (pH = 5.0, T = 298 K, C0 = 10 mg/L and m/V = 0.2 g/L) and the whole adsorption process was perfectly fitted by the Pseudo-second-order model (R2 = 0.999), illustrating that uranium was extracted via chemisorption. The correlation coefficient R2 of Langmuir model was 0.999, which was higher than other models, meaning that uranium extraction behavior on PDA/β-CD/CFA was uniform monolayer adsorption. The maximum extraction capacity of uranium on PDA/β-CD/CFA calculated by Langmuir model was 537.6 mg/g, which was larger than most of reported adsorbents, indicating that PDA/β-CD/CFA was a potential candidate for uranium extraction from water environment. Moreover, PDA/β-CD/CFA performed excellent uranium extraction properties with the existence of coexisting ions and the desorption efficiency of uranium by PDA/β-CD/CFA was higher to 95.8% at the fifth cycles, fully suggesting that PDA/β-CD/CFA possessed good selectivity and cycle stability. Characterization results demonstrated that uranium was immobilized on PDA/β-CD/CFA through chelation, complexing action, electrostatic interaction and hydrogen bonding.

Geopolymer fly ash composites modified with cotton fibre

The work’s primary goal is to assess the influence of the cotton fibres addition and their proportion on the strength properties and thermal conductivity of foamed geopolymer composites based on fly ash.Fly ash from a thermal power plant was used as the foundation material to create the geopolymer composites in this study. Volcanic silica was used as an additional source of silicon. As an additive, the recycled cotton flock was used in amounts of 0.5%, 1% and 2% by weight of dry ingredients. The density, compressive, and three-point bending strength of the created geopolymers were measured. Moreover, the thermal conductivity measurements for three temperature ranges: 0–20C, 20–40C, and 30–50C for all investigated geopolymers were conducted. The structure of tested materials was observed using a scanning electron microscope (SEM).It was demonstrated within the context of the study that the addition of cotton fibres to foamed fly ash-based geopolymers aids in slightly reducing their density. Cotton fibres can be used to boost the strength of the examined geopolymers; for samples with 1% cotton fibres added, compressive strength rose by around 22% and flexural strength by about 67%. Additionally, it is feasible to lower their thermal conductivity coefficient by incorporating cotton fibres into foamed fly ash-based geopolymers.The results obtained highlight the potential of fly ash-based geopolymer composites with the addition of cotton flocks for application as insulating materials in the building industry.The novelty of this work is the demonstration of the possibility of producing foamed geopolymers based on fly ash with the addition of recycled cotton fibres, with properties that make them suitable for use as building insulation materials.

A novel approach of fabricating low-cost high temperature printed circuit board substrate based on poly(ether-ketone)/fly ash composites

A novel approach of fabricating low-cost high temperature printed circuit board substrate based on poly(ether-ketone)/fly ash composites

Integrating Fly Ash-Controlled Surface Morphology and Candle Grease Coating: Access to Highly Hydrophobic Poly (L-lactic Acid) Composite for Anti-Icing Application

New ways of recycling fly ash are of great significance for reducing the environmental pollution. In this work, biodegradable hydrophobic poly (L-lactic acid)/fly ash composites for anti-icing application were successfully fabricated via a facile solvent-volatilization-induced phase separation approach. A silane coupling agent of 3-(Trimethoxysilyl) propyl methacrylate was used to decorate a fly ash surface (FA@KH570) for strengthening the interface bonding between fly ash and poly (L-lactic acid). Moreover, FA@KH570 could obviously enhance the crystallinity of poly (L-lactic acid) (PLLA)/FA@KH570 composites, which accelerated the conversion from the liquid-liquid to the liquid-solid phase separation principle. Correspondingly, the controllable surface morphology from smooth to petal-like microspheres was attained simply by adjusting the FA@KH570 content. After coating nontoxic candle grease, the apparent contact angle of 5 wt% PLLA/FA@KH570 composite was significantly increased to an astonishing 151.2°, which endowed the composite with excellent anti-icing property. This strategy paves the way for recycling waste fly ash and manufacturing hydrophobic poly (L-lactic acid) composite for potential application as an anti-icing material for refrigerator interior walls.

The Effects of Curing Temperature on CH-Based Fly Ash Composites.

Curing temperature affects the compressive strength of cement paste systems via the pozzolanic reaction. However, different processes, climates, and weather conditions often result in different initial curing temperatures. The relationship between curing temperature and compressive strength is still an underexplored domain. To explore the effect of curing temperature on calcium hydroxide (CH)-based fly ash composites, fly ashes from different carbon sources were used to make CH-based composites, and the compressive strength, reaction rate, CH content, and C-S-H generation were analyzed. The correlation between the reaction rate and C-S-H content was analyzed. High-temperature curing improved the compressive strength of the cement paste system by affecting the CH-based reaction rate in the initial stage, with the highest initial reaction rate reaching 28.29%. However, after cooling to constant temperature, high-temperature curing leads to a decrease in CH and C-S-H content. The average decrease rate of calcium hydroxide content under high temperature curing is 38%, which is about 2.38 times that of room-temperature curing conditions. This led to a decrease in the compressive strength of the cement paste. Therefore, the performance of CH-based fly ash composites produced by low-temperature curing was superior to that of composites produced by high-temperature curing.