Shanyang Wei

The efficacy of foamed concrete for CO₂ sequestration is critically governed by its pore topology, yet the time-dependent evolution of transport pathways remains poorly understood. This study systematically investigates the evolution of pore structure in steel slag-biochar incorporated foamed concrete across curing ages (3–28 d) using X-ray computed tomography (X-CT), three-dimensional reconstruction, and pore network modeling. A steady-state CO₂ diffusion model grounded in real pore geometries was established to link structural descriptors to transport performance. Results reveal that both total and connected porosity follow a unimodal trend, peaking at 14 d (21.02% and 20.18%, respectively), with connected pores accounting for over 90% of total porosity. At this optimal age, the median pore-throat diameter (D50) reaches 220 μm, permeability attains 1285.5 D, and tortuosity declines to 1.567—yielding an effective CO₂ diffusion coefficient of 2.94 × 10⁻⁶ m²/s, which is 43.4% higher than that at 3 d. Notably, the 14-d sample exhibits the highest pore fractal dimension (2.766) alongside the lowest tortuosity, demonstrating that topological connectivity, rather than local geometric complexity, dominates mass transport. XRD Rietveld refinement confirms significantly enhanced carbonation uniformity from surface to center, with calcite content remaining above 90% throughout. These findings establish 14 d as the optimal curing window that balances pore expansion and hydration-product filling, providing a rational structural basis for designing high-performance carbon-sequestering foamed concrete. This work offers a paradigm for integrating solid waste utilization with CCUS through microstructure-informed process optimization.

The efficacy of foamed concrete for CO₂ sequestration is critically governed by its pore topology, yet the time-dependent evolution of transport pathways remains poorly understood. This study systematically investigates the evolution of pore structure in steel slag-biochar incorporated foamed concrete across curing ages (3–28 d) using X-ray computed tomography (X-CT), three-dimensional reconstruction, and pore network modeling. A steady-state CO₂ diffusion model grounded in real pore geometries was established to link structural descriptors to transport performance. Results reveal that both total and connected porosity follow a unimodal trend, peaking at 14 d (21.02% and 20.18%, respectively), with connected pores accounting for over 90% of total porosity. At this optimal age, the median pore-throat diameter (D50) reaches 220 μm, permeability attains 1285.5 D, and tortuosity declines to 1.567—yielding an effective CO₂ diffusion coefficient of 2.94 × 10⁻⁶ m²/s, which is 43.4% higher than that at 3 d. Notably, the 14-d sample exhibits the highest pore fractal dimension (2.766) alongside the lowest tortuosity, demonstrating that topological connectivity, rather than local geometric complexity, dominates mass transport. XRD Rietveld refinement confirms significantly enhanced carbonation uniformity from surface to center, with calcite content remaining above 90% throughout. These findings establish 14 d as the optimal curing window that balances pore expansion and hydration-product filling, providing a rational structural basis for designing high-performance carbon-sequestering foamed concrete. This work offers a paradigm for integrating solid waste utilization with CCUS through microstructure-informed process optimization.

This study develops a novel foam concrete incorporating steel slag and biochar for synergistic CO2 sequestration and strength enhancement, targeting applications in mine backfilling. Using response surface methodology (RSM), the effects of steel slag content (10–20%), biochar content (1–3%), and curing time (3–14 days) on carbonation behavior were systematically evaluated. Results reveal that curing time is the most critical factor governing the CO2 uptake rate (p < 0.0001), with influence far exceeding that of steel slag or biochar content. The quadratic regression model reliably predicts carbon sequestration performance (R² = 0.9715), with a validation error of only 5.84% between predicted (16.35%) and measured (15.39%) values. Microstructural analysis confirms extensive formation of calcium carbonate, achieving up to 83.68% crystallinity. Notably, while Group 17 exhibited the highest carbon sequestration, its mechanical properties (compressive strength: 7.46 MPa; Young's modulus: 0.2 GPa) were compromised by carbonation-induced microcracking. Conversely, Group 2 achieved superior mechanical performance (12.62 MPa; 1.98 GPa) through biochar-mediated microstructural regulation, which promoted uniform and dense carbonate precipitation. This study demonstrates that optimized mix design can simultaneously achieve high carbon sequestration and satisfactory mechanical properties, offering a viable pathway for large-scale utilization of industrial solid wastes in low-carbon construction materials for mining engineering.

Improving the efficiency of coal seam gas extraction is essential for safe coal mining and the clean utilization of coalbed methane. The combined use of ultrasound and alkaline fracturing fluids enhances the modification of the micropore structure in the coal matrix, thereby increasing the effectiveness of alkaline fracturing. In this study, the improvement effect of ultrasound-alkaline fracturing fluid on coal permeability was investigated using FTIR, XRD, BET, SEM-EDS, contact angle measurements, and other methods. The results indicate that ultrasound and alkaline solution interact synergistically. Ultrasound provides physical impact, while the alkaline solution drives chemical dissolution. Together, these effects increase hydrophilic groups, reduce oxygen-containing groups, break the compact internal structure of coal, and dissolve as well as fragment certain minerals, leading to a marked increase in internal pores and expanded pore channels. An alkaline solution containing 2% NaOH demonstrates the most significant improvement in coal pore development. Additionally, ultrasound-alkali treatment enhances the hydrophilicity of the coal surface, which facilitates gas release. This study provides a theoretical foundation for the efficient extraction of coal seam gas.

This study addresses limitations in single-alkali research by investigating mineral dissolution-precipitation dynamics and functional group transformations under multi-alkali conditions. Comparative experiments with concentration gradients were conducted to analyze chemical structure evolution and methane adsorption performance in alkalized anthracite. Brunauer–Emmett–Teller, scanning electron microscopy, x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses revealed alkaline solutions' synergistic regulation of hierarchical pore structures. Results show 1 mol/l potassium hydroxide (KOH) increased average pore diameter by 32% while reducing specific surface area by 24.6%, shifting pore dominance from microporous to macroporous structures with H3 hysteresis loops. High-concentration sodium hydroxide (NaOH) elevated surface fractal dimension (D1 = 2.53) and enhanced pore connectivity by 3.2-fold. XRD/FTIR characterization indicated KOH is superior mineral dissolution capacity, reducing aromatic lamellae stacking height by 37.8% and increasing alkyl chain (–CH) content while decreasing reactive adsorption sites (–CH2/–CH3). Alkaline conditions (pH > 12) promoted OH− driven aluminosilicate dissolution to alleviate pore blockage, alongside catalytic dissociation of carboxyl/phenolic hydroxyl groups facilitating aromatic layer disassembly. This mineral-organic synergy generated interconnected nano-micro fracture networks, supporting methane desorption-seepage channel enhancement through structural reconstruction. The findings demonstrate coupled effects of mineral dissolution and organic matrix transformation in optimizing coalbed methane recovery efficiency with solution parameters quantitatively correlating to adsorption-seepage behavior modifications.

Sealing materials play an important role in the safety of coal mine production. To improve the efficiency of coal mine gas mining, it is necessary to optimize the performance of the sealing materials. In order to develop new sealing materials with better performance, it is necessary to improve the formula of the cement materials. In this study, poly­(vinyl alcohol) fiber (PVAF), polypropylene fiber (PPF), nanosilica (NS), and their composite materials were added to the composite cement-based materials of Portland cement and sulphoaluminate cement, respectively, and a new cement-based hole sealing material was prepared. The effects of these additives on fluidity, setting time, and compressive strength of cement-based sealing materials were studied through experiments. X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and pore size analysis were used to study the influence of composite fiber and nanosilica on the properties of the cement system. The results show that PVAF, PPF, and NS all effectively improve the mechanical properties and stability of the cement system, in which PPF: PVAF = 3:1 and the content of nanosilica ranges from 0% to 3%, and the performance of the cement system can be improved. When the content of NS is 3%, PPF is 0.05%, and PVAF is 0.15%, the compressive strength at 28 days reaches 30.5 MPa. The addition of NS can make the hydration degree of cement materials higher, and PVAF and PPF can improve the distribution of hydration products, reduce the generation of harmful pores with pore size greater than 10 nm in the cement pore system, and significantly improve the properties of materials. This effectively maintains the stability of the borehole in the process of gas drainage, improves the gas drainage concentration of the borehole, and enhances the gas drainage effect.