Frontiers in Materials

Integrated formwork removal decision framework for concrete slabs using FBG sensors and machine learning

2026-03-27

Hyoung-Jun Park, Yubin Choe, Dae-Gil Kim, Inkyu Rhee

Accurate prediction of early-age concrete strength is critical for ensuring construction safety and optimizing formwork removal schedules. This study presents an integrated decision-making framework for curing quality management, employing Fiber Bragg Grating (FBG) sensors to monitor internal temperature and drying shrinkage for 28 days. To validate hydration kinetics, a thermo-mechanical coupled analysis was conducted, and a machine learning framework using Gradient Boosting was explored to predict compressive strength. The results indicated that a literature-based dataset limited to 55 points led to an R2 approaching 1, revealing inherent overfitting due to reliance on ambient rather than internal core temperatures. These observed deviations highlight the necessity of in-situ monitoring. The study concludes that enhancing predictive robustness requires larger datasets synchronized with internal hydration heat records to mitigate overfitting in field applications.

Effect of steel slag contents on road performance of rubber-modified permeable asphalt mixtures

2026-03-26

Shanshan Wang, Guangyong Wang, Fangzhou Liu, Zhengchao Zhang, Xiaomeng Zhang, Yanzhu Wang, Xufeng Wang

Based on laboratory test results, this study provides a comprehensive evaluation of the mechanical properties, durability, microstructural characteristics, and functional properties of steel slag rubber permeable asphalt mixtures with different steel slag contents, leading to the following conclusions: Incorporating steel slag into the mixture effectively enhances its skeleton strength and high-temperature stability. When the steel slag content reaches 60%, the dynamic stability (DS) of the mixture increases to 7,852 cycles/mm. Although the low-temperature failure strain of the steel slag mixture decreases to 2,820 με, the addition of rubber modifiers ensures that the mixture meets winter road performance requirements. Due to the alkalinity of steel slag which enhances bonding between aggregates and asphalt, the soaked residual stability of the mixture increases to a maximum of 91.2%, and the freeze-thaw splitting strength ratio peaks at 88.6% when the steel slag content is 50%. The addition of steel slag effectively regulates the internal void structure of the mixture, creating more interconnected voids. At a 60% steel slag content, the water permeability coefficient of the mixture significantly increases to 5,581 mL/min. Although the porous surface structure of steel slag causes aggregates to adhere to a thicker asphalt film, resulting in an initial pendulum value stabilizing around 62, the texture depth of the mixture significantly increases to 2.48, which benefits road traffic safety. The optimal steel slag incorporation ratio is ultimately determined to be 50%–60%. This study concludes that steel slag rubber permeable asphalt mixture is a highly promising sustainable material that not only alleviates the shortage of high-quality natural aggregates but also enables high-value utilization of industrial solid waste.

Research on the development and application of dope-modified, environmentally friendly composite thin spray materials

2026-03-25

Jingang Li, Ming Zheng, Hao Li

The current underground roadway spraying materials face challenges such as low flexibility, poor adhesion, high rebound rate, easy cracking, and complicated construction procedures. In response to these issues, this study developed a new composite slurry material using white silicate cement (P·W) and fast-hardening sulfoaluminate cement (SAC) as base materials, with the addition of clay and fly ash as admixtures, along with xanthan gum, cellulose ether, naphthalene water reducing agent, and coagulant to enhance performance. The material’s properties and microstructure were evaluated through mechanical tests, setting time and flowability measurements, dry shrinkage tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM), followed by field application to verify spraying effectiveness. The results demonstrated that the material possesses good flowability, adjustable setting time, rapid hardening, early strength, low dry shrinkage, and a large water contact angle. Field tests confirmed excellent flexible support performance, with the 100-mair leakage value reduced to 2.8 m3/min. Additionally, the material is environmentally friendly and promotes resource recycling. These findings provide a valuable reference for future slurry spraying construction and support the application of flexible support materials in underground engineering.

Editorial: Biodegradable polymers for biomedical applications - Volume IV

2026-03-25

Dan Li, Liqun Yang

Study on mechanical properties and mesostructure of subgrade silty sand under freeze-thaw cycles

2026-03-13

Da Xiang, Zhongming He, Zhenhong Yan

IntroductionFreeze–thaw cycles induce frost heave and thaw settlement in subgrades, degrade their service performance, and jeopardize traffic safety, making them primary concerns for transportation infrastructure in seasonally frozen regions. Silty sand is widely distributed in these areas. Investigating its mechanical behavior and mesostructure under repeated freeze–thaw cycling is therefore essential to improve subgrade durability.MethodsTherefore, silty sand was chosen as the study material, and triaxial compression tests together with scanning electron microscopy were performed on silty sand subjected to freeze–thaw cycles to elucidate the correlation between mechanical property evolution and mesostructural change under those cycles.ResultsThe results indicated that the stress–strain behavior of silty sand shifted from strain-softening to strain-hardening as confining pressure, the number of freeze–thaw cycles, and moisture content increased. At freezing temperatures of −10 °C, −20 °C, and −30 °C, the maximum difference in peak strength was less than 6%, indicating only a minor influence of freezing temperature. Peak strength increased with confining pressure and decreased with both freeze–thaw cycles and moisture content. The elastic modulus followed a similar trend to peak strength. Freeze–thaw cycling degraded the silty sand structure, promoting particle breakage and pore development, and higher moisture content exacerbated this damage. The silty sand was dominated by micropores and small pores, and the total pore area grew with increasing freeze–thaw cycles and moisture content. Freeze–thaw cycles and greater moisture content also reduced the average shape parameter. The average fractal dimension of pores increased with additional freeze–thaw cycles, and under the combined influence of high moisture content and freeze–thaw cycling it exhibited an initial decrease followed by an increase. The grey correlation coefficients between macro- and meso-scale parameters lay between 0.6 and 0.8, indicating a strong linkage between the macroscopic mechanical behavior and the mesostructure of silty sand.DiscussionThese findings offer a theoretical basis for the design and maintenance of silty sand subgrades in seasonally frozen regions.

Experimental study on the influence of gradient structure design on the thermal response behavior of composite materials

2026-03-12

Zhihong Han, Yaoqian Wang, Shuyang Liu, Junjie Hu

This study investigates how gradient layer thickness affects the thermal response of CuSn10/316L stainless steel composites fabricated by selective laser melting (SLM). Three gradient architectures with varying layer thicknesses were designed and analyzed through both simulation and experiment. Simulations predicted that increasing interfacial layers would enhance thermal barrier performance. However, experimental results showed the opposite trend: samples with thinner layers and lower porosity (10.03%) exhibited poorer thermal barrier properties, while those with thicker layers and higher porosity (15.42%) performed best. This discrepancy reveals that porosity—governed by layer thickness—is the dominant factor controlling thermal behavior, outweighing the effect of interfacial density. Thicker layers promote heat accumulation and gas entrapment, increasing porosity and thermal resistance. The findings establish a clear pathway from gradient layer thickness to porosity evolution to thermal response, providing practical guidance for designing functionally graded materials with tailored thermal barrier performance.

Smart responsive hydrogels for intervertebral disc regeneration

2026-03-11

Chao Jiang, Li Wang, Chenyang You, Yuan Wei, Yanjun Che

Intervertebral disc degeneration (IVDD) is the leading cause of chronic low back pain (LBP), driven by a pathological microenvironment marked by acidic pH, increased reactive oxygen species (ROS), and elevated matrix metalloproteinase (MMP) activity, which hinder tissue regeneration. Conventional hydrogels, while replicating the hydrophilic environment of the nucleus pulposus and enabling minimally invasive delivery, fail to dynamically adapt to the evolving pathological signals during degeneration due to their static structure. Smart responsive hydrogels overcome this limitation by integrating “sensing-response-output” functionality, achieved through molecular elements such as dynamic covalent/non-covalent bonds, enzyme-substrate peptides, and external field-responsive units, or gene circuits responsive to specific pathological cues, including pH changes, ROS levels, MMP concentrations, and mechanical stress. Recent developments highlight that these materials provide timely mechanical support (e.g., in situ modulus enhancement to mitigate fibrosis) and enable microenvironment-driven sequential therapies, including targeted delivery of anti-inflammatory/pro-regenerative factors, ROS scavenging, inhibition of enzymatic activity, immune microenvironment remodeling, and precise regulation of cell fate via endogenous stem cell recruitment/differentiation and ferroptosis suppression. Advanced fabrication techniques such as microfluidics, 3D bioprinting, and in situ self-assembly further enhance biomimetic structural and functional integration. Despite promising regenerative outcomes in animal models—such as achieving NP cell survival rates reaching 85%, a 3.3-fold increase in COL2 synthesis, and 87% recovery of disc height through spatiotemporally controlled release, ROS scavenging, and immune modulation—significant challenges remain for clinical translation. These include the need for long-term biosafety validation, the stability of delivery systems under physiological conditions, and their adaptability to the complex mechanical environment of the spine. This review systematically explores the design principles, response mechanisms, fabrication innovations, therapeutic applications, and translational challenges of smart responsive hydrogels for IVDD regeneration, providing a roadmap for future development.