This study aims to investigate the mechanical behavior of reinforced soil under various loading conditions, with a focus on the effects of normal stress, cyclic amplitude, reinforcement angle, reinforcement materials, and pullout rate on its mechanical properties. The findings indicate that the shear strength of soil reinforced at a 30° angle is maximized under monotonic shearing, while the peak strain value is observed at a 180° reinforcement angle during cyclic shearing tests. Both shear stress and stiffness increase with the number of loading cycles, while the interface damping ratio decreases before stabilizing at a constant value. In cyclic pullout tests, the reinforced soil exhibits significant hardening behavior under different conditions, with the peak pullout resistance steadily rising as the number of cycles increases. However, for uniaxial geogrid reinforcement, the pullout resistance initially increases and then declines with continued cycling. Moreover, in post-cyclic pullout tests, a marked reduction in pullout resistance is observed at a displacement of 25 mm, suggesting considerable degradation in the structural integrity and strength of the geogrid.

The production of calcium sulfoaluminate (CSA) cement using hazardous wastes can enhance its sustainability and economic benefits. Incorporating Fe2O3 into ye'elimite can reduce the Al2O3 demand in waste-based CSA cement, while the influence of alkalinity modulus (Cm) on this incorporation remains unclear. This study synthesised CSA cement clinker from hazardous wastes with varying Cm. Results show that forming inert phases like C2AS and Fe2SiO4 hinders the synthesis of hydraulically active minerals, requiring a higher Cm of 1.10 to attain the highest 28-day compressive strength of 76.4 MPa. Additionally, increasing Cm reduces the Fe/(Al + Fe) ratio in ye'elimite, particularly in low-aluminium clinkers. This contributes to the transformation of C4A3S-o to C4A3S-c and the slowed hydration. However, facilitated ye'elimite formation under higher Cm and increased Al2O3 content in feedstock leads to more Fe2O3 being incorporated into ye'elimite. This study provides guidance on regulating Fe2O3 incorporation in the production of waste-based CSA cement clinker.

Microwave-assisted recovery provides a potential approach for restoring fracture damage in asphalt mixtures, but previous studies have mainly focused on heating and curing conditions, while the role of the pre-heating fracture state remains less understood. This study investigated microwave-assisted fracture energy recovery from a damage-state regulation perspective by comparing a control asphalt mixture (CAM) with a basalt fiber-reinforced asphalt mixture (BFAM). Semi-circular bending (SCB) tests were combined with an L9 orthogonal design to evaluate three pre-heating conditions, target surface temperatures of 45-85 °C, and curing times of 6-24 h. Rather than directly enhancing binder recovery, basalt fiber reinforcement increased the initial fracture resistance and altered the relative fracture condition reached under a given external load. The recovery index RI ranged from 20.7% to 55.9% for CAM and from 35.2% to 82.3% for BFAM. Main-effects ANOVA showed that the pre-heating damage condition had the largest main-effect contribution within the adopted L9 framework, reaching 82.3% for CAM and 95.2% for BFAM, substantially exceeding those of target surface temperature and curing time. Under a comparable external load of approximately 2.5 kN, CAM reached the 70% Pmax condition, whereas BFAM remained at the 40% Pmax condition, with corresponding mean RI values of 42.8% and 76.9%. These results support a proposed conceptual damage-state regulation framework within the investigated material and experimental conditions, in which basalt fiber reinforcement preserves a more favorable pre-heating state and thereby greater recovery potential. The findings highlight the importance of improving fracture resistance and applying microwave-assisted treatment before extensive fracture development occurs, while broader validation is required before generalizing the proposed framework to other materials or field conditions.

A synergistic ternary geopolymer system based on dechlorinated and detoxified municipal solid waste incineration fly ash (MSWI FA), waste glass powder (GP), and ground granulated blast furnace slag (GGBS) was developed to enhance mechanical performance and durability. MSWI FA is a potential resource for geopolymer synthesis. However, its independent reactivity is constrained by the scarcity of reactive aluminosilicate phases, and the coexistence of chlorides and heavy metals threatens structural durability. In this study, dechlorinated and detoxified MSWI FA was combined with GP and GGBS, and activated by a mixture of sodium hydroxide (NaOH) and sodium silicate solutions (Na2O·nSiO2). The ternary geopolymer system showed synergistic formation of calcium-aluminum–silicate-hydrate (C–A–S–H) and sodium-aluminum–silicate-hydrate (N–A–S–H) gels, which further crosslinked into C–A–S–H gels, enhancing structural compactness. At 8

Sodium sulphate-activated slag has been recognised as an eco-friendly binder, although it faces issues of slow setting and strength development. In this study, magnesium oxide (MgO) is introduced as a co-activator alongside sodium sulphate (SST) to tackle these challenges. The results demonstrate that SST-MgO-activated slag (SSTMS) pastes exhibit favourable fresh and mechanical properties, with the fastest setting time of around 12 h and compressive strength of up to 55 MPa at 28 days. During hydration, MgO partially dissolves and primarily provides an alkaline environment to initiate slag dissolution. Afterwards, SST actively participates in the alkali-activation process by reacting with Ca2+ and Al(OH)4- ions released from slag to form ettringite at early ages. This not only promotes self-alkalinisation for accelerating slag dissolution, but also enhances strength through the pore-filling and bridging effects of ettringite. However, the competition for aluminium sources between ettringite and C-A-S-H gel results in some retardation of the initial gel polymerisation. As the pore solution alkalinity exceeds a level aborting ettringite precipitation, the hydration of SSTMS paste gradually resembles that of MgO-incorporated alkali-activated slag (AAS) paste. The excess Al(OH)4- ions then tend to react with Mg2+ ions, leading to the generation of hydrotalcite at a later stage. Overall, understanding the hydration mechanism for the SSTMS system provides a theoretical basis for optimising its mechanical performance. The SSTMS paste, as a weakly AAS system, offers favourable long-term compressive strength and improved operational safety compared to conventional AAS systems.

The skid resistance of early-stage Hot In-Place Recycled (HIR) asphalt pavements deteriorates significantly, raising safety concerns. This study aimed to enhance the long-term skid resistance of secondary recycled pavements by evaluating coarse aggregate types, polymer admixtures, and basalt fibers through accelerated polishing tests, British Pendulum Number (BPN) measurements, and laser texture scanning. The results showed that diabase and steel slag aggregates achieved final BPN values of 61.5 and 62.2, respectively, which were 7.9

The crude disposal of construction wastes generates recycled concrete fines (<4.75 mm) characterized by complex morphologies and high heterogeneity. Although cold-bonding granulation combined with the alkaline activation method can convert such wastes into uniform core-shell artificial lightweight aggregates (CLWAs), the role of particle morphology in governing granulation behavior and performance remains unclear. To clarify this effect, recycled concrete fine aggregate (RFA), glass fine aggregate (GFA), and quartz fine aggregate (QFA) with identical size ranges but distinct morphologies were selected as core materials, while recycled concrete powder was used as the shell material to prepare CLWAs. Morphological parameters were quantified via image analysis, and principal component analysis was employed to extract key morphological features. By monitoring the particle size growth rate and adhesion rate at multiple time intervals, the granulation kinetics of CLWAs were elucidated. Multiscale characterizations were conducted to assess the physical, mechanical and microstructural properties of CLWAs. Results indicate that the highly irregular RFA morphology induced mechanical interlocking and capillary adhesion between the core and shell, leading to rapid yet unstable growth, high water absorption (15.5%), and low bulk crushing strength (9.6 MPa). GFA's inert and smooth surface produced weak interfacial bonding and the widest ITZ (8 mu m), constraining aggregate performance. In contrast, QFA's spherical and moderate roughness promoted stable granulation, enabling strong core-shell bonding and facilitating abundant C-A-S-H gel formed in the shell matrix to fill voids, thereby imparting superior performance of aggregate. This study provides a theoretical foundation for turning construction wastes into high-performance CLWAs.

The self-healing behavior of concrete is crucial for enhancing the durability of underwater concrete structures. Cementitious Capillary Crystalline Waterproofing material (CCCW) interacts with substances within the concrete to generate crystals that fill the pores and cracks, thereby improving its self-healing capacity. This study systematically investigates the self-healing behavior of cracked concrete following the incorporation of CCCW and curing in a water environment. The effects of CCCW dosage on the crack healing process for concrete with different strength and crack width were studied and analyzed. The healing performance and microscopic mechanisms were analyzed via permeability tests, surface crack monitoring, and SEM/XRD characterization. Results indicate that the incorporation of CCCW material significantly enhances the self-healing performance of cracks. At a 5% CCCW content, the self-healing rates for 0.1 mm, 0.3 mm, and 0.5 mm cracks increased by 94.7%, 65%, and 45.39%, respectively, compared to the specimen without contain CCCW. However, with 5% CCCW content, the healing performance gradually weakened as both crack width and concrete matrix strength increased. Microstructural characterization analysis revealed that CCCW promotes crack self-healing and guides the formation of C-S-H gel, leading to a dense microstructure of hardened cement hydration products. Furthermore, a multi-factor theoretical model for water permeability, based on the principle of mass conservation, was established, showing high consistency between theoretical calculations and experimental values. These findings provide crucial theoretical guidance and technical support for crack control and self-healing design in hydraulic concrete structures.

The widespread application of alkali-activated soil-based artificial aggregates (AAs) is limited by their low early strength and high-water absorption, creating an imperative for effective enhancement methods. This study investigates the efficacy of thermal treatments (heat curing and microwave curing) and surface treatments (alkaline solution immersion, double pelletisation, and slurry immersion) in enhancing their performances. The properties of AAs were evaluated through crushing strength, water absorption, and apparent density tests, with underlying mechanisms elucidated by microstructural analyses. The results demonstrate that both heat curing and microwave curing significantly enhance the early-age strength, improving the 1-day crushing strength by over 140% and 100%, respectively. This enhancement is attributed to the accelerated formation of C-(A)-S-H gels and hydrotalcite. However, a slight increase in water absorption and a reduction in 28-day crushing strength are observed, primarily due to microcracking induced by the rapid drying process. Among the surface treatments, alkaline solution immersion and double pelletisation increase apparent density by-3.6%, reduce water absorption by-22.3%, and enhance crushing strength by-30.9%, primarily due to the formation of a denser outer shell. In contrast, slurry immersion adversely affects the properties owing to its uneven coating and potential aggregate swelling. This study provides practical strategies and mechanistic insights for optimising the performance of AAs, facilitating their industrial production and application.

Small Modular Reactors (SMRs) offer advantages over traditional large-scale nuclear power plants, including scalability and cost-effectiveness. While mat foundations are commonly used for SMR structures, they have limitations in some seismic scenarios. Pile foundations present a promising alternative, yet their impact on the floor response spectrum (FRS) of SMR structures remains largely unexplored. This study examines the FRS characteristics of SMR structures with pile and mat foundations, accounting for soil-structure interaction (SSI). Analyses are conducted for three types of soil sites (hard, stiff, and soft) and two embedment depths (10 m and 25 m). Results show that at a 10 m depth, foundation type significantly influences spectral shape and amplitude of FRS, especially on soft soil sites. At a 25 m depth, however, the foundation type has minimal impact. These findings provide essential insights for seismic design and foundation selection in SMR structures across diverse site conditions. As the SSI analyses employed equivalent-linear soil behavior and tied mat-soil interfaces, the obtained FRS variations represent an upper-bound stiffening response, particularly for the 10 m embedment cases.

As the capacity of offshore wind turbines continues to increase, more stringent demands are placed on the bearing capacity and stability of foundation structures. The pipe pile with interior restraint plate (PPIRP) can significantly enhance the bearing capacity of pile foundations by inducing the soil plug formation within the pile. However, existing research has yet to comprehensively elucidate the penetration behavior of PPIRP and the soil response mechanisms. In this study, a coupled finite element and discrete element method is employed to precisely simulate the penetration behavior of open-ended pipe pile (OEPP) and PPIRP. The numerical simulations provide insights into the structural response during pile penetration, offering a detailed analysis of soil particle displacement and the evolution of force chain. Furthermore, the study explores the stress distribution and porosity changes of soil particles during penetration from a microscopic perspective, further illuminating the mechanical response of the soil at various stages of penetration. This study not only enriches the theoretical framework of pile penetration behavior but also provides critical theoretical and practical guidance for the design and optimization of offshore wind turbine pile foundations.

Ecological river slope protection techniques have received considerable attention for sustainable development. This study focuses on a newly developed material called cast-in-situ vegetation concrete (CVC), which incorporates vegetation and punched holes. A series of anti-scouring tests were conducted to optimize its construction parameters. Wave scouring tests on bare slopes and rainfall scouring tests on vegetated slopes were carried out to evaluate the effects of flow velocity, rainfall intensity, slope gradient, punched hole parameters, and construction thickness on underlying soil erosion. Additionally, high-flow scouring tests were conducted to examine the overall survival status of vegetation after scouring under different construction thicknesses and perforation parameters. The results indicate that flow velocity, rainfall intensity, and slope gradient are positively correlated with soil erosion. Among these, Perforation Group A (4.5 cm in depth, 2.5 cm in diameter, 2.8 cm in spacing) demonstrated superior performance to Perforation Group B (4.0 cm in depth, 1.0 cm in diameter, 3.5 cm in spacing), exhibiting lower erosion volume and better vegetation-reinforced slope protection effects. In terms of promoting stable vegetation survival, construction thicknesses of 6 cm or 10 cm were found to be preferable to 15 cm. Therefore, the parameters of Perforation Group A with a thickness of 6 cm or 10 cm are recommended. These findings offer practical guidance for the application of Cast-in-place Vegetation Concrete (CVC) technology in ecological slope protection.

Oscillatory instabilities of dynamic fractures arise under mode-I loading as the crack velocity approaches or exceeds the Rayleigh wave speed, c_{R}. Anomalously, at velocities far below c_{R}, experiments reveal a distinct quasistatic oscillatory instability in fluid-driven fracturing of porous materials, formed by continuous bifurcations of "daughter cracks." This phenomenon falls outside the applicability of existing fracture theories. Our asymptotic stability analysis of wave-shaped cracks reveals that oscillations originate from the competition between the stabilizing effect of cohesive force in the process zone and the destabilizing effect of shear perturbations along the crack sides. We further derive the characteristic oscillation wavelength and demonstrate that it is jointly governed by the fracture process and fluid invasion. The findings broaden the physical basis of competing mechanisms governing oscillatory fracture instabilities.

Industrial solid wastes are increasingly used as alternative feedstocks for synthesising sulfoaluminate cement (SAC). However, their complexity in compositions leads to unstable performance. To optimise production, machine learning (ML) models are developed to predict the compressive strength of SAC pastes based on a dataset of 707 datapoints from literature. Distinct from traditional mineral-based approaches, this model incorporates multi-source factors including feedstock composition, clinker calcination temperature and duration time, gypsum type and content, specimen preparation conditions, and curing time. Single and ensemble ML approaches, including Random Forests (RF), Supporting Vector Regression (SVR), and Neural Network (NN) algorithms, are employed. The ensemble RF + NN model demonstrates higher accuracy (testing R2 = 0.87) than the single models. Model-based interpretation reveals that feedstock composition is the foremost input feature group that accounts for 34.9 % importance, thereby validating the composition-driven prediction strategy. Moreover, the correlations of each input feature with compressive strength have been analysed. The ensemble ML model is validated through 14 independent experiments on SAC paste samples prepared exclusively from hazardous waste, with all prediction errors well below 10.82 %. This work provides a precise, data-driven tool for rapid feedstock screening and process optimisation, offering a labour-saving and cost-effective pathway to accelerate sustainable SAC production.

Superhydrophobic surfaces have attracted significant attention due to their ability to enhance the durability of concrete by preventing water and aggressive agent penetration. However, traditional superhydrophobic materials have limitations, being poorly durable and prone to wear. In this study, we propose a novel design for robust superhydrophobic cementitious composites: nano-CaCO3 is grown ex-situ on fly ash particles to ensure the complete leaching of Ca2+ from carbide slag during carbonation, which also allows nano-CaCO3 to be uniformly introduced into the composite through a carrier effect of carbonated fly ash. In addition, fluoroalkylsilane was incorporated into the carbon-sequestered composite to further reduce surface energy and achieve superhydrophobicity. The results demonstrate that the hydrophobicity of the composites is closely tied to the carbonation process, with a contact angle of 163.0 degrees which signifies a superhydrophobic condition. This study provides valuable insights into the innovative design and production of carbon-sequestered, robust superhydrophobic cement-based materials.

Foamed concrete is a lightweight and easily placed material with adjustable strength, which is promising for highway subgrade/backfill application. However, the uniaxial or conventional triaxial test cannot capture its behaviour under complex in-service multiaxial stress states. To this end, this study investigates the response of foamed concrete under true triaxial conditions with wet densities from 600 to 1000 kg/m3 under varied confining pressures. Stress-strain behaviours, energy dissipations, and failure modes were analysed, with an emphasis on the influence of the intermediate and minor principal stresses. Results show that confining pressure enhances the compressive strength, and the extent of the enhancement is determined by the ratio of the von Mises stress and the hydrostatic stress. Air void buckling dominates along the minor principal stress direction, whereas brittle shear failure prevails in both the intermediate and the minor principal stress direction. Finally, Miller's yield criterion is shown to successfully predict the strength of foamed concrete under true triaxial loading. The scaling laws are proposed to correlate the peak stress, elastic strain energy ratio, and Miller's model parameters with porosity. The study contributes to the knowledge of the mechanical behaviour of foamed concrete under a true triaxial stress state.

To quantitatively evaluate the influence of asphalt migration on skid resistance degradation, this study investigated an SBS-modified asphalt SMA-13 mixture under selected temperature-load combinations. Accelerated loading abrasion tests, layered extraction tests, British Pendulum Number (BPN) tests, and Mean Texture Depth (MTD) tests were conducted. The evolution of asphalt migration, BPN, and MTD during abrasion was then characterized. The results show that both temperature and load promoted asphalt migration toward the surface layer. Increasing temperature had a more pronounced effect on asphalt migration and BPN loss. BPN increased during the initial abrasion stage and entered a degradation stage after 5,000 cycles. In contrast, MTD continuously decreased, while asphalt migration continuously increased with abrasion cycles. Taking 5,000 cycles as the baseline, the asphalt migration increment showed strong positive correlations with both BPN loss and MTD loss. Within the tested range, every 0.1% increase in asphalt migration increment corresponded to an average BPN loss of approximately 2.95 and an MTD loss of approximately 0.030 mm. The positive correlation between MTD loss and BPN loss indicates that macro-texture loss is an important pathway linking asphalt migration to skid resistance degradation. Furthermore, the migration-associated loss ratio increased with abrasion cycles. At 50,000 cycles, the average BPN migration-associated loss ratio and MTD migration-associated loss ratio reached 70.7% and 66.8%, respectively. These results indicate that asphalt migration had a stronger explanatory effect on BPN loss and MTD loss in the middle-to-late abrasion stage. These findings provide a reference for improving the skid resistance durability of asphalt pavements by considering asphalt migration and macro-texture degradation.

Sodium carbonate (SC) has emerged as a promising activator for ground granulated blast-furnace slag. However, engineering application of the SC-activated slag is hindered by its sluggish early hydration. This study investigates the effectiveness of triethanolamine (TEA) in accelerating the early hydration of SC-activated slag and the underlying mechanisms. TEA was added to SC-activated slag paste at dosages of 0, 0.5, 1, and 2 wt% of slag, and its effects on hydration kinetics, strength development, phase evolution, and microstructure were systematically characterized. Results demonstrated that TEA can markedly accelerate the early hydration, especially at higher TEA dosage. While the reference paste could not harden within the first 7 d, the addition of 2% TEA advanced the onset of acceleration period from 7 d to 10 h, achieving rapid early strength development without compromising long-term strength. TEA did not fundamentally alter the overall hydration pathway, but accelerated phase evolution, promoted earlier hydrotalcite formation, and increased the Al incorporation and Ca/Si ratio of C-A-S-H at early age. The accelerating effect of TEA originated from its chelating interaction with Al species, which promoted dissolution of Al units and adjacent Si units from the glassy structure. This resulted in a more leached diffusion layer of slag grains, sustaining their fast dissolution. The increased Ca2+ release then rapidly consumed CO32-and raised the pH, thereby triggering earlier main hydration. These findings provide new insight into effective acceleration for early hydration of SC-activated slag.