Metal matrix composites (MMCs) are gaining prominence over conventional metals due to their superior strength-to-weight ratio, low density, minimal thermal expansion, and high-temperature resistance. This study investigates the enhancement of MMC properties by reinforcing Al-6061 alloy with fly ash particles. The composites were fabricated using the stir casting method, varying fly ash grain sizes (0-75 μm, 75-90 μm, and 90-150 μm), weight percentages (10%, 20%, and 30%), and melting temperatures (800 ℃, 850 ℃, and 900 ℃). A novel multi-objective optimization technique based on non-dominated sorting with Pareto fronts identified the optimal parameters as 30% fly ash weight, 0-75 μm grain size, and 850 ℃ melting temperature. Microstructural analysis confirmed the uniform distribution of fly ash in the matrix, and hardness testing revealed significant improvement with smaller grain sizes and higher fly ash content. This study highlights the potential of fly ash-reinforced MMCs for applications demanding superior mechanical properties.

Calcium sulfoaluminate–calcium oxide expansive agents (HCSA) are commonly used in mass concrete to compensate for thermal shrinkage. However, the ettringite (AFt) formed by HCSA hydration decomposes when temperatures exceed 70 °C. This study examines the synergistic effects of curing temperature (20 °C to 80 °C), fly ash (FA) content (0%, 40%), and water–binder ratio (w/b, 0.3, 0.4, 0.5) on the expansion behaviour and microstructure of HCSA–cement systems. A critical temperature threshold was identified at 60 °C. Below this limit, elevated temperatures accelerate hydration and enhance expansion, with the restrained expansion ratio peaking at 9.2 × 10−4 mm/mm under 60 °C curing. Beyond 60 °C, expansion capacity significantly diminishes due to the thermal decomposition of AFt into monosulfoaluminate (AFm), as confirmed by XRD and SEM analysis. Calculations of expansive stress reveal a critical mismatch at temperatures ≥ 40 °C, where the expansive stress exceeds the early-age tensile strength, causing microstructural damage. Furthermore, subsequent cooling to standard curing conditions triggers the reformation of AFt from AFm, leading to Delayed Ettringite Formation (DEF), which poses potential risks for late-stage cracking. AFt morphology shifted from needle-like (2–5 μm) to prismatic (5–8 μm). The incorporation of FA suppressed early-stage expansion but improved expansion stability. above 40 °C, although excessive temperatures (>70 °C) led to pore coarsening and reduced mechanical strength. These findings provide a theoretical basis for optimizing the curing regimes of HCSA-admixed mass concrete to ensure structural integrity.

This work describes the results of the study of the impact of by-products of industrial production as a mineral additive to the soil-cement mixture, namely fly ash. The degree of influence of the mineral additive on water absorption and the softening coefficient of soil-cement was studied, since these indicators directly affect the reliability, durability and operational characteristics of the foundations of buildings and structures, especially those operated in conditions of high humidity or in conditions of temperature changes. The use of fly ash as a mineral additive is a promising direction, because fly ash has proven itself well when added to concrete mixtures. Taking into account the fact that one of the most expensive components of the soil-cement mixture is the binder, its partial replacement with available industrial waste will provide a positive impact on the economic and ecological efficiency of the soil-cement. Therefore, in this work, a study of the properties of soil cement with different degrees of replacement of the binding agent on fly ash was carried out. Based on the obtained results, it was found that fly ash as a mineral additive at a certain percentage ratio has a positive effect on the characteristics of soil cement as a material, namely on the reduction of water absorption compared to the control sample in which no fly ash was used, as well as an increase in the softening coefficient. The obtained results clearly demonstrate that the use of fly ash as a mineral additive in the soil-cement mixture is an effective engineering solution that will not only reduce the cost of soil-cement, but also make it possible to dispose of industrial waste and improve the characteristics of the material itself.

Introduction To investigate the influence of fly ash (FA) content on the leaching resistance of shotcrete, this study adopted FA replacement ratios as the main variables (0%, 15%, 20%, 25%). Methods Shotcrete specimens were prepared using the wet-mix spraying method and subjected to accelerated leaching tests in a 6 mol/L ammonium chloride solution. Systematic analyses of compressive strength, porosity, leaching depth, and calcium ion leaching amount were conducted to examine the effect of FA content on the leaching resistance of shotcrete. Microstructural evolution was also analyzed using scanning electron microscopy (SEM). Results The results indicate that the incorporation of FA significantly enhances the leaching resistance of shotcrete. An appropriate amount of FA promotes the formation of additional C–S–H gel through pozzolanic reactions at later stages, improving concrete density and inhibiting calcium ion migration as well as the advancement of the leaching front. With a 20% FA content, shotcrete exhibited optimal leaching resistance: after 90 days of leaching, the compressive strength loss rate was 34.13%, porosity increased by only 3.09%, leaching depth reached 22.09 mm, and the total calcium ion leaching was 3.7 mol/L. The synergistic effect of the pozzolanic reaction and the micro-aggregate effect of FA optimizes the pore structure and reduces the content of soluble calcium phases, thereby enhancing the chemical erosion resistance of concrete. Discussion The results demonstrate that reactive components in FA can react with calcium hydroxide from cement hydration to form more stable calcium silicate hydrate, significantly delaying the leaching process of shotcrete. At a 20% replacement ratio, leaching damage is effectively suppressed while mechanical performance is maintained. This study provides theoretical and technical support for mix design and engineering application of shotcrete in erosive environments.

Green solvents for the extraction and bioutilisation of metals from coal fly ash by Magnetospirillum gryphiswaldense MSR1.

Phosphogypsum, the primary solid waste from the wet-process phosphoric acid industry, poses significant environmental and health risks due to large-scale stockpiling. To promote its resource utilisation, this study systematically evaluated the solidification and stabilisation performance of phosphogypsum–coal fly ash cementitious material (PAC) for Cr(VI)-contaminated soil under high-chloride conditions. Phosphogypsum reactivity was enhanced via mechanical activation and high-temperature calcination. An orthogonal experimental design was employed to analyse the effects of multiple factors—including calcination temperature and duration—on compressive strength and heavy metal leaching behaviour. Results show that PAC prepared from coal ash calcined at 600 °C for 3 h exhibits excellent mechanical properties and Cr(VI) stabilisation efficacy under high-chloride conditions, achieving a maximum compressive strength of 28.75 MPa and a Cr(VI) leaching concentration as low as 15.69 μg/L. Microstructural characterisation revealed the synergistic formation of a dense framework between C–S–H gel and calcium aluminate, conferring superior mechanical strength. Substitution and chelation mechanisms of Cl− ions played a key role in enhancing corrosion resistance. This study provides theoretical support and technical guidance for the high-value utilisation of phosphogypsum-based materials in remediating saline–alkali-contaminated soils.

Pioneer plants drives initial pedogenesis in fly ash: Mechanisms of iron mineral transformation and microbial community reorganization.

This study aims to develop artificial intelligence (AI) models for predicting the compressive strength and flow value of cementitious systems containing fly ash, influenced by various high-range water-reducing admixtures (HRWRAs) that differ in molecular weight and chain length. A database comprising 180 mixes was created, encompassing cement and fly ash dosages, HRWRA characteristics (including molecular weight, main and side chain lengths) curing period, and flow time. Two AI-based modelling approaches were employed: a classical artificial neural network (ANN) and a new hybrid model that integrates ANN with biogeography-based optimisation (ANN–BBO). The modeling results showed that the hybrid model achieved a compressive strength performance with an R2 of approximately 0.99 and an RMSE of around 1.37 MPa, while the single ANN model attained an R2 of about 0.91 and an RMSE of 4.40 MPa. For flow value prediction, the ANN–BBO model also demonstrated high accuracy (R2 ≈ 0.98; RMSE ≈ 0.32 cm). Furthermore, the ANN–BBO model reduced the prediction error by approximately 60% across the evaluation criteria compared to the single ANN model, highlighting its enhanced performance. The importance of the input variables indicated that curing time and cement content have the greatest impact on compressive strength, while flow time and the molecular weight of the HRWRA significantly influence the flow value. Since AI models rely solely on virtual trials, they significantly reduce laboratory time and material usage while aiding in the design of mixes with lower water-to-binder ratios and higher fly ash content, which ultimately helps to reduce the CO2 footprint. The proposed models provide a practical route to low-clinker, FA-rich mix designs that satisfy strength/workability targets with less cement, supporting embodied-carbon reductions and straightforward integration into ready-mix/precast quality-control workflows.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-32972-1.

Catalytic pyrolysis of waste biomass via coal fly ash for synergistic production of cost-effective artificial humic acid.

Mechanism of biomass driving microbial community assembly in eco-engineering bauxite residues: Based on molecular traits of dissolved organic matter.

Remediation of soil contaminated by waste drilling slurry in oilfield with mixed bacteria immobilized by fly ash modified biochar.

Abstract Expansive black cotton (BC) soils pose significant challenges for pavement subgrades due to their high plasticity, low strength, and moisture sensitivity. This study investigates the stabilization of BC soil using cement, lime, fly ash, and ground granulated blast furnace slag (GGBS), combined with machine learning (ML) for predictive modeling of strength and bearing capacity. Laboratory experiments evaluated Atterberg limits, unconfined compressive strength (UCS), and California Bearing Ratio (CBR) across varying dosages and curing periods. The untreated soil exhibited poor performance (LL = 58%, PI = 31%, UCS ≈ 1.2 kg/cm², CBR ≈ 8.8%). Cement showed the greatest strength enhancement, with 8% cement achieving ~ 19 kg/cm² UCS and ~ 19% CBR after 28 days. Lime was most effective in improving subgrade performance, with 9% lime yielding ~ 7.7 kg/cm² UCS and the highest CBR of ~ 27–28%. GGBS at 30% provided ~ 8.9 kg/cm² UCS and ~ 9% CBR, while fly ash (40%) achieved only ~ 3 kg/cm² UCS and 6% CBR. To complement the experimental program, ML algorithms—Decision Tree, Random Forest, and XGBoost—were developed to predict UCS and CBR. Random Forest delivered the best accuracy for UCS (R² = 0.99, RMSE = 0.25, MAE = 0.13), while XGBoost excelled for CBR prediction (R² = 0.99, RMSE = 0.20, MAE = 0.11). SHAP analysis identified cement dosage and curing time as dominant factors for UCS, and lime as the most influential for CBR. The integration of laboratory data with ML models establishes a robust framework for optimizing stabilizer blends, reducing experimental effort, and promoting sustainable, low-carbon pavement design.

Dual catalytic system using industrial solid waste and zeolite for enhanced aromatic hydrocarbon conversion from waste bamboo biomass.

High-quality Al Si alloy fabrication via efficient green synergistic recovery of aluminum and silicon from coal fly ash

Electrochemical extraction of water-reactive silicon from coal fly ash in molten CaCl2-CaO

Trace element quantification in solid fuel wastes by LA-ICP-MS: a review.

Multifunctional amino acid promoters: Overcoming CO2 mineralization limits in fly ash

Soil reconstruction using coal industry solid wastes: Linking pollution control with climate variability across scales.

Freeze-thaw response and macro-micro evolution of saline soil stabilized with lime and fly Ash

Extraction of silicon and aluminum components from fly ash by mixed alkali-step heating synergistic activation process: mechanism analysis and resource application exploration