Fly Ash Research Articles

UTILIZATION OF WASTE MATERIALS FOR ULTRA-LIGHTWEIGHT AND THERMAL INSULATING CONCRETE BLOCKS

This study investigates the feasibility of utilizing waste materials—specifically fly ash, residual fuel catalytic cracking catalyst (RFCC), and honeycomb briquette ash—in the production of ultra-lightweight concrete blocks for thermal insulation applications. Physical properties such as dry density, water absorption, and compressive strength were evaluated alongside thermal conductivity and microstructural analysis. Additionally, the materials' compliance with hazardous substance regulations and fire resistance were examined. Economic analysis demonstrated substantial cost savings compared to conventional materials. Results indicate that while higher cement replacement ratios with waste materials generally reduce compressive strength, they enhance thermal insulation properties. The study concludes that these materials offer a viable solution for sustainable building construction, aligning environmental benefits with economic advantages.

Characterization and Performance Evaluation of Eco-Friendly Angular-Shaped Fly Ash Aggregates as Base Material in Pavement Construction under Cyclic and Shear Loading

Characterization and Performance Evaluation of Eco-Friendly Angular-Shaped Fly Ash Aggregates as Base Material in Pavement Construction under Cyclic and Shear Loading

Investigation on the behavior of fly ash phosphate-based geopolymer stabilized acidic lead contaminated soil

Investigation on the behavior of fly ash phosphate-based geopolymer stabilized acidic lead contaminated soil

Recycling of fly ash and carbide slag in low-carbon cement composites by pre-depolymerization and pre-dissolution treatment

Recycling of fly ash and carbide slag in low-carbon cement composites by pre-depolymerization and pre-dissolution treatment

From waste to sustainable production: Experimental design and optimization of sustainable concrete using response surface methodology and life cycle assessment

This study focuses on a holistic approach to investigate the engineering properties (microstructural, mechanical, environmental, and economic) of sustainable concretes produced using recycled aggregate and supplementary cementitious material (SCM). Compressive strength tests was conducted on 24 sustainable concrete series for the mechanical properties. Statistical analyses were performed using the response surface methodology, and mathematical models were developed considering the strength values obtained. Developed model-based optimization solutions were applied to determine the mix proportions of the optimization series containing lower cement dosage and SCM with the same hardened concrete properties as the reference concrete series. Considering these mix proportions, life cycle assessments were performed and environmental and economic properties were compared. A comparison of Ref-6 and Opt-6 series reveals that the global warming potential (GWP), energy consumption (EC), and waste generation (WG) values are 422.4-330.9 kg CO2 eq, 1294-1044 MJ, and 1294-1222 kg, respectively. This situation resulted in a reduction of 21.7% in GWP values, 19.3% in EC values, and 5.6% in WG values. Similarly, the economic comparison of these series indicates that the total cost values are 81.9-75.7 €, respectively, resulting in 7.7% reduction. Finally, Scanning Electron Microscopy analyses were conducted to examine the microstructural properties. The use of fly ash at 10% improved the microstructure properties and increased the C-S-H gel formation. It is thought that the process of transition from these waste materials to sustainable production is of critical importance, especially in places that are heavily damaged after devastating earthquakes and where large amounts of waste materials are generated.

Aerated Concrete Made of MSW Incineration Ash: Effect of Blending Materials and CO2 Curing Condition

Municipal solid waste (MSW) incineration ash is used to produce aerated concrete blocks (ACB). To reduce cement usage and improve ACB quality, steel slag and blast-furnace slag were tested as cement substitutes, and CO2 mineralization technology was applied to cure ACB. The effect of steel blending ratios (MSW incineration ash, cement substitutes, water, aluminum powder) and CO2 curing conditions (temperature, pressure) on ACB properties was investigated. Under different conditions, the compressive strength, CO2 uptake and microstructure of ACB were determined. Higher fly ash content in ACB increases CO2 uptake but reduces compressive strength; ACB shows better mechanical properties when the cement is completely replaced by blast-furnace slag, but steel slag will cause ACB to fail to form; the optimal water-to-solid ratio enhances carbonation rate and compressive strength, and reducing aluminum powder content improves compressive strength. As the CO2 curing temperature increases from 25 to 105ºC, the carbonation rate and compressive strength of the ACB initially increase and then decrease, with the maximum CO2 uptake ratio of 20.0% and peak compressive strength occurring at 65ºC. When CO2 pressure increases from 0.2MPa to 1MPa, the carbonation rate rises to 23.4%, and the compressive strength first increases and then decreases, reaching 1.86MPa at a curing pressure of 0.6MPa, meeting the GB/T 11968-2020 B03 A1.5 grade standard. Approximately 0.58 tons of CO2 emissions can be reduced for every ton of ACB produced. This study established an innovative method to produce an environmentally friendly, low-carbon building material.

Effect of Combined Carbon Nano Tubes and Graphene Oxide on the High-Volume Fly Ash Mortar Properties

Abstract Effect of combined carbon nano tubes (CNTs) and graphene oxide (GO) on the high-volume fly ash mortar (HVFAM) properties was presented in this paper. The characteristic of HVFAM mixes were first evaluated using slump flow tests. Then, mechanical properties and microstructure of HVFAM were performed. A scanning electron microscope (SEM) was used to observe the microstructure of HVFAM. A high-volume fly ash was taken as 60% cement replacement. Mortar specimens were produced by adding the combined 0.01% CNTs and GO contents of 0.01% - 0.05% using cement to water ratio of 0.46. The results of study showed that the combined CNTs and GO have substantial impact on the properties of HVFAM. It was further confirmed that adding the combined CNTs and GO cause the microstructure of HVFAM mixes become more compact and the pores that develop become smaller. In such a way, the bridging effect of combined CNTs and GO have successfully reduced the growth and formation of cracks that could led to an increase in the HVFAM performance.

Effect of alkali-activation conditions on microstructure and heavy metal solidification of alkali-activated converter steel slag and municipal solid waste incineration fly ash

Effect of alkali-activation conditions on microstructure and heavy metal solidification of alkali-activated converter steel slag and municipal solid waste incineration fly ash

Efficacy of Biopolymer Treatment in Improving the Dynamic Response of Fly Ash Deposits

Efficacy of Biopolymer Treatment in Improving the Dynamic Response of Fly Ash Deposits

Long-term evaluation of FABA utilization to prevent AMD generation – a review of barrel kinetic test

Abstract The utilization of fly ash and/or bottom ash (FABA) to prevent the generation of acid mine drainage is present in several mining companies to maximize geochemical and geotechnical potentials of FABA. Geochemically, FABA has the potential as a neutralizing material due to its high acid-neutralizing capacity, therefore it can be used as a sealing material for the potentially acid-forming (PAF) overburden in coal mining activities, which has the potential to produce acid drainage. This study aims to ensure that the potential leachate runoff at PAF disposals through neutralizing and sealing is not in acidic condition. A series of kinetic geochemical tests were carried out using a 200-liter volume column, applying various compositions of non-acid forming (NAF) rocks, a mixture of FABA, and PAF to ensure the method reliability. Leachate leaking out of the column was subjected to pH and EC analysis. The test results for a period of 3 years (Jan 2021 – June 2024) showed that the NAF-PAF-FABA sealing system produced a neutral pH compared to the FABA-PAF and NAF-FABA-PAF-NAF sealing. The position of FABA under the PAF layer triggered the carbonate released by acidic water, enabling neutralization. The 9:1 ratio of FA to BA in NAF-PAF-FABA sealing system showed better results than 4:1 ratio, indicative of greater neutralizing capacity of FA than BA. Compositions with smaller amounts of PAF produced better results due to less potential acidity that must be neutralized.

Energy performance and decarbonization evaluation of a novel positive energy building using solar PV

Positive Energy Buildings (PEBs) are vital for reducing energy consumption and promoting renewable energy. This study introduces a progressive method to evaluate the energy performance and decarbonization of a PEB warehouse in Central Taiwan, utilizing Building Integrated Photovoltaic (BIPV) façades and recycled coal ash concrete. The research analyzes building energy performance and renewable energy generation through energy modeling, considering different ventilation configurations and BIPV arrangements. The findings emphasize that a VRF cooling system saves 16.39% energy compared to a chiller system. The study also revealed that improving the arrangement of BIPV on the building façade significantly enhances solar energy generation efficiency even with fewer photovoltaics (PVs). The decarbonization aspect is evaluated by estimating the embodied carbon and CO2 emissions during the operational period. The PEB is projected to have a 70-year operational lifespan, functioning as a PEB for approximately 42 years, a Net Zero Energy Building (NZEB) for the following 10 years, and maintaining energy efficiency for an additional 20 years. The BIPV system enables the building to remain carbon-free for up to 50 years of operation and achieve substantial carbon savings, with 90% CO2 emissions reduction after 70 years, amounting to 243,111 kgCO2e/year. The study concludes that adequate maintenance and preservation can significantly enhance building performance and longevity.

Seismic performance of joints in coal ash slag concrete frames

This paper presents experimental investigations on the joints of concrete frame beams and columns with 20% coal ash slag replacing cement. The failure mechanism of concrete frame joints with coal ash slag as a cement replacement is examined, focusing on the impacts of two scenarios—concrete with 20% coal ash slag and ordinary concrete—on the failure mode and seismic performance of beam-column joints, as well as the influence of varying concrete strength grade when the coal ash slag content is 20%. The main research variables are the presence of coal ash slag in the concrete and the concrete strength grade. Findings reveal typical failure modes at the beam-end flexural plastic hinge, progressing through stages of initial cracking, yielding, limit, and failure. Joints without coal ash slag exhibit 10.3–16.2% higher ductility, while those with 20% coal ash slag show a 14% improvement in bearing capacity. The C50 joint with 20% coal ash slag outperformed the C40 joint in bearing and energy dissipation, with robust hysteretic curves meeting seismic requirements. Thus, replacing 20% of cement with coal ash slag enhances durability and seismic performance of concrete components.

Effect of Fosroc Cebex-100 and Fly Ash Stabilization on the Microstructural Properties of Soft Soil

This study investigates the microstructural effects of stabilizing soft soil using fly ash and Fosroc Cebex-100. The soft soil used in this study was collected from the construction site of the Northern Ring Road (JLU) Section 1 in Lamongan regency. Firstly, a series of laboratory soil test was performed to obtain the index properties of the soil sample including unit weight, specific gravity, Atterberg’s limits, optimum moisture content, and maximum dry unit weight. The soil was then treated with three variations of fly ash (20%, 25%, and 30%), while the Fosroc Cebex-100 dosage was held constant at 0.45% of the fly ash weight. A CBR test indicated that a 20% fly ash and Fosroc Cebex-100 mixture achieved the highest CBR value. Consequently, this optimal mix was selected for SEM-EDX (Scanning Electron Microscopy - Energy-Dispersive X-ray Spectroscopy) analysis to further examine microstructural characteristics. Additional fly ash and Fosroc Cebex-100 to the soft soil will influence the microstructural properties of the soil. SEM analysis show that addition of fly ash and Fosroc Cebex-100 results in significant changes in the soil matrix, including increased particle bonding, reduced porosity, and a denser overall structure. Moreover, the addition of fly ash and Fosroc Cebex-100 contribute to the presence of iron (Fe) in the treated soil.

Physical and Mechanical Properties of Mortar Mixed with Paper Mill Waste

The industrial and construction sectors are experiencing continuous growth each year. Concrete, which is used as the main material in construction, is composed of cement, aggregate and water. Research on mortar and aggregate is carried out to create concrete according to the required specifications of certain buildings. However, 8% of global carbon dioxide emissions come from the cement manufacturing process which is one of the main materials in mortar. In the industrial sector, the paper industry is one of the top producers of waste, approximately 48 tonnes for every 100 tonnes of pulp produced. The main wastes of this industry include slaker grits, dregs, lime mud and fly ash which only end up in landfill. To address this problem, this research investigates the modification of mortar mix materials by utilising paper mill waste. Specifically, fly ash and grits are used as substitute for cement and fine aggregate, respectively. Results indicate that the density value of concrete decreased with the increase of fly ash mixture, and the compressive strength value of mortar with varying additions of 0%, 10%, 20%, 30%, 40% and 50% fly ash reached 7.42, 6.68, 6.18, 4.97, 3.93 and 2.97 MPa. The decrease in density and compressive strength with increasing fly ash content can be attributed to the lower adhesive power of waste compared to cement owing to its lower lime oxide content. The value of compressive strength samples 1, 2 and 3 belong to the N type, which can be used as load-bearing walls, while samples 4, 5 and 6 fall into the O type, which can be used as non-load-bearing and decorative walls in accordance with SNI 03-6882-2014 standards.

Experimental Study on Lightweight Concrete through Partial Replacement of Cement with Fly Ash and Fine Aggregate with Thermocol

Abstract: Lightweight concrete provides a sustainable way to decrease the weight of structures, improve heat insulation, reduce environmental impact and make buildings more resistant to earthquakes. This research looks at creating lightweight concrete using fly ash (30%, 40%, 50%, and 60%) instead of some cement and thermocol (0.2%, 0.4%, and 0.6%) instead of some fine aggregates. We made 78 cube samples (each 150 mm × 150 mm × 150 mm) and 26 cylindrical samples (150 mm in diameter and 300 mm in height). These samples were made and then kept for different periods before testing. The samples are classified into two groups: one was left for 7 days of curing and the other for 28 days. Each group has three cubes to study how much pressure they could handle and for the cylindrical samples, we tested one from each group to see how much force they could resist. The aim is to make the concrete lighter while maintaining the required strength. Fly ash, which comes from burning coal, makes the concrete easier to work with and more environmentally friendly. Thermocol makes the concrete much lighter and better at insulating heat. The concrete samples were tested for their compressive and tensile strength during testing. The results showed that the concrete became much lighter maintaining the required strength, making it compatible for the desired purpose. By including waste materials such as fly ash and thermocol, this method provides a more environmentally friendly and cheaper alternative to regular cement concrete mixture. The results show that it can cut material costs, reduce CO₂ emissions, and encourage sustainable building practices. This approach of using lightweight concrete significantly contributes to the development of sustainable infrastructure while addressing the growing demand for less environmentally conscious construction practices.

Influence of Fly Ash Content on Macroscopic Properties and Microstructure of High-Performance Concrete

To investigate the influence of the fly ash (FA) content on the performance of high-performance concrete (HPC), seven groups of tests were conducted, aiming to evaluate both the macroscopic properties (workability and compressive strength) and microscopic pore structure. Low-field nuclear magnetic resonance (NMR) technology and SEM images were employed to analyze the changes in the internal pore structure of the concrete. The results showed that the workability of HPC initially increased and then decreased with the increase in the FA content. When the FA content was 15%, the slump of HPC reached a maximum of 264 mm, and the 28-day compressive strength exhibited a 23.2% increase compared to the 7-day compressive strength. The pore size distribution of the concrete varied with different fly ash content. At 15% FA content, secondary hydration of the FA was sufficient, refining the pores to between 0 and 0.1 µm. Excessive FA substitution deteriorated the internal structure of the HPC matrix and reduced the workability and mechanical properties of the HPC. When the content of FA was 35%, the slump of HPC decreased to 176 mm, while the macropores within the matrix significantly increased, resulting in porosity of 6.81%.

A two-step hydrothermal synthesis of fly-ash-based ZSM-5 zeolite and its catalytic properties in NO removal

The pursuit of carbon peaking and carbon neutrality goals necessitates flexible operation and deep peaking of coal-fired units, thus placing heightened demands on nitrogen oxide (NOX) emission control. Fly ash, a solid waste rich in silicon (Si) and aluminum (Al), should be fully leveraged, and the high-value synthesis of zeolite represents a viable utilization method. In this context, fly ash-based zeolite was prepared as a catalyst to facilitate the generation of active oxides from H2O2, combined with alkali solution absorption, to achieve efficient denitrification. This approach effectively transforms ‘waste to pollution’ mitigation. The optimal synthesis conditions for FA-ZSM-5 zeolite were established using the alkali fusion hydrothermal synthesis method, with fly ash as the raw material. The specified conditions were NaOH/FA = 1.2, SiO2/Al2O3 = 40, H2O/Al2O3 = 1325, TPAOH/Al2O3 = 10, ZSM-5-seed addition of 5 %, and a hydrothermal temperature and time of 140 °C for 24 h. Experimental parameters were meticulously investigated to ascertain their impact on nitric oxide (NO) removal efficiency. The highest removal efficiency was achieved under specific conditions: a reaction temperature of 140 °C, an H2O2 concentration of 6 %, a catalyst dose of 0.3 g, an NO concentration of 600 mg/m3, and an SO2 concentration of 1000 mg/m3. Finally, analysis of the catalytic oxidation mechanism revealed that H2O2, when catalyzed by FA-ZSM-5 zeolite, generates ·OH radicals with strong oxidizing properties, thereby facilitating the oxidative removal of NO.

Feasibility of coal bottom ash as fine aggregate in strain-hardening cementitious composites: A study on strength, durability, and sustainability

The search for cost-effective and sustainable materials for strain-hardening cementitious composites (SHCC) has led researchers to explore alternatives to silica sand, a critical yet costly and environmentally unfavorable material. Although river sand seems like a cheaper and viable alternative, its extraction is linked to severe environmental degradation. This study aims to investigate the potential of coal bottom ash (CBA) as a replacement for silica sand in SHCC, targeting to meet the minimum requirements for structural applications. The novelty of this research lies in its comprehensive exploration of CBA as a partial to full replacement for silica sand (at 0 %, 25 %, 50 %, 75 %, and 100 %), extending beyond the replacement limit investigated in previous studies on SHCC, and provides an extensive evaluation of the composite’s fresh, mechanical, durability, and microstructural properties. Additionally, it includes a thorough assessment of the leaching potential, CO₂ emissions, energy consumption, and cost implications of the CBA-SHCC, which have not been fully explored in earlier CBA-SHCC research. The findings indicate that the reduction in mechanical strength was minimal (0.5 %-10 %) across all CBA replacement levels. Notably, all mixes demonstrated typical strain-hardening behavior, sustaining higher flexural loads beyond the first crack, with increased deflection capacity observed at higher CBA contents, peaking at 50 % replacement. Durability metrics, including water absorption and HCl acid attack resistance, exhibited a downward trend with higher CBA content but remained within acceptable limits up to 75 % replacement. Toxicity characteristic leaching procedure results confirmed the non-leachability of toxic elements in both the CBA and CBA-SHCC mixes. Economically and environmentally, CBA proved advantageous, resulting in 1.5–5 % lower CO2 emissions, 0.4–1.5 % lower energy consumption, and 18–84 % cost savings at 25–100 % CBA replacement. Additionally, a multicriteria analysis using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was employed, which identified 25 % as the optimal CBA content that balances fresh properties, mechanical strength, durability, environmental sustainability, and cost efficiency. The study is significant because it demonstrated that CBA can be used as a sustainable and cost-effective alternative to silica sand in SHCC, with lower environmental impact while maintaining structural integrity.

Mechanical performance of polyurethane polymer mortar—A novel sealing material for CAES man-made caverns

This work aims to investigate the feasibility of polyurethane polymer mortar (PPM) as a sealing material for compressed air energy storage (CAES) caverns. The effect of polymer content, aggregates ratio (fine sand to medium sand) and filler types (bentonite, clay, and fly ash) on gas permeability, tensile strength, and resistance to high and low temperature of PPM were conducted. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were performed to characterize the microstructure of PPM. Additionally, numerical simulations were performed to analyze the stress distribution characteristics of PPM when used as a sealing structure. The results demonstrate that PPM exhibits low gas permeability (10−21 m2), high tensile strength (up to 2.96 MPa), and significant tensile strain (up to 27.02 %), with a relatively low elastic modulus (11.87–35.05 MPa). Meanwhile, PPM containing fly ash showed the highest strength, followed by those with clay, while PPM with bentonite exhibited the lowest strength. However, only the PPM with bentonite as a filler remained stable and did not collapse under high temperatures. The hoop stresses in the PPM are only compressive and not tensile, and the maximum hoop tensile strain remains well below the ultimate tensile strain of the material, thus preventing the tensile damage and ensuring the gas-tightness. These findings provide a theoretical basis for using PPM in CAES sealing applications, and advance the understanding and application of sealing materials in CAES man-made caverns.

Integrating fiber with new cement trends to create a greener future for sustainable concrete

The need for innovation in the construction sector is increasingly pressing, propelled by rising environmental issues and the ongoing quest for structural efficiency. This study investigates the transformational potential of fiber-reinforced concrete (FRC), analyzing its ability to improve mechanical performance and promote environmental sustainability. By using diverse fibers, including natural, synthetic, and industrial waste fibers, FRC enhances qualities like as tensile strength, fracture resistance, and durability while promoting more sustainable building techniques. This research carefully explores current improvements in the processing and handling of various fibers and assesses their effects when integrated into concrete. Particular emphasis is placed on the use of recovered industrial by-products, including slag, fly ash, and recycled plastics, in conjunction with natural fibers such as bamboo, kenaf, and flax. These materials are recognized for both augmenting the structural integrity of concrete and substantially decreasing the carbon footprint of construction by lowering dependence on virgin resources and encouraging the recycling of industrial waste. Experimental investigations and life cycle evaluations were performed to measure the improvements in performance and sustainability provided by FRC. The study results indicate that FRC has enhanced durability and performance attributes, making it a suitable choice for both structural and non-structural applications. Moreover, the incorporation of sustainable fibers has shown a decrease in greenhouse gas emissions, consistent with international sustainability objectives. Nonetheless, the implementation of FRC encounters obstacles pertaining to the inconsistency of fiber characteristics, economic viability, and industrial scalability. Confronting these obstacles via continuous research and interdisciplinary cooperation is essential for the widespread adoption and use of FRC in the construction sector. This study emphasizes the significance of new materials, such as fiber-reinforced concrete, in promoting sustainable building methods, illustrating its potential to profoundly influence the future of construction regarding environmental responsibility and structural efficacy.