Search Results (355)

To address the lack of systematic quantitative studies on waterborne epoxy resin (WER)-modified emulsified asphalt regarding its rheological optimization and engineering applicability, this study fills the gap by preparing WER-modified emulsified asphalt via a two-step process. New findings reveal that 20% WER content significantly enhances elastic components, creep–recovery, fatigue life, and fracture energy. The main objective is to establish a theoretical basis for high-performance pavement materials. Modified emulsified asphalt specimens with different waterborne epoxy resin contents were prepared using a two-step method of “emulsification followed by compounding”. The stability of the emulsions was quantitatively evaluated by zeta potential, storage stability, particle size distribution, and demulsification time. Their rheological parameters, multi-stress creep–recovery characteristics, fatigue life, and low-temperature crack resistance were systematically tested across the full temperature range using a dynamic shear rheometer and a bending beam rheometer. In addition, the bonding performance, strength development behavior, and water resistance durability were comprehensively assessed through pull-out tests, Marshall stability and splitting strength tests, as well as freeze–thaw cycle tests. These properties were compared with those of unmodified emulsified asphalt (UEA-0) and SBR-modified emulsified asphalt (SBR-EA). With an increase in waterborne epoxy resin content, the elastic component of the modified asphalt improved significantly, and the phase angle continuously decreased. The specimen with 20% waterborne epoxy resin content (WER-EA-20) exhibited the best performance: its phase angle was lower than those of the other groups under high-, medium-, and low-temperature conditions. After seven creep–recovery cycles, its creep–recovery rate remained at 33%, substantially higher than the 8% observed for the unmodified specimen. The fatigue life reached 15,000 cycles under a shear stress of 2.1 MPa. At −10 °C, the fracture strength was 0.92 MPa, and the fracture energy reached 21.4 J. Furthermore, the pull-out strength of WER-EA-20 was 0.86 MPa, with the failure mode identified as asphalt cohesive failure. After 37 days of curing, the Marshall stability reached 22.5 kN, and the splitting strength was 1.36 MPa. After 40 freeze–thaw cycles, the freeze–thaw splitting strength ratio (TSR) of WER-EA-20 remained above 75%, representing an improvement of more than 110% compared to the unmodified UEA-0 (TSR ≈ 35.5%), which highlights the significant enhancement in water resistance imparted by the waterborne epoxy resin. Compared to SBR-EA, WER-EA-20 has a higher softening point, a lower suitable mixing temperature, and better anti-aging properties. Waterborne epoxy resin can effectively improve the viscoelastic properties and overall road performance of emulsified asphalt, and the modification effect increases with increasing dosage. Full article

Additive manufacturing using laser powder bed fusion (LPBF) has been widely used to produce nickel-based superalloy components with complex shapes for high-temperature applications requiring creep resistance. In this research, the creep behavior of LPBF Inconel 718 under solution and double-aging heat treatments, performed at 590–650 °C under stresses of 450–550 MPa, is studied. The characterization included optical microscopy, scanning electron microscopy (SEM), porosity analysis, Vickers microhardness tests, and fracture surface examination. The findings revealed that even after heat treatment, the material maintained a mainly directional, columnar microstructure, with an average porosity below 1%, which was unevenly distributed and contained critical defects related to lack-of-fusion (LOF) and trapped powder. Fracture after creep presents regions of ductile failure alongside facets indicative of quasi-cleavage. Kinetic analysis revealed a high stress exponent (n = 18.26) and an activation energy (Qc = 410–538 kJ/mol), indicating that the deformation operates within the power-law breakdown (PLB) regime, where dislocation–precipitate interactions govern the creep rate in this precipitation-strengthened superalloy. Overall, the results highlight that the directional microstructure and residual defects typical of LPBF can reduce the creep resistance of Inconel 718, underscoring the importance of post-processing methods and internal defect control specifically tailored for additively manufactured materials. Full article

Waterborne epoxy resin emulsified asphalt (WEA) is often used as a preventive maintenance material for asphalt pavement due to its excellent mechanical properties and high-temperature stability. However, its relatively poor toughness and low-temperature crack resistance limit its broader application. To address this issue, a PPG-IPDI-based waterborne polyurethane/epoxy resin (WER/PU) emulsion was synthesized via the prepolymer dispersion method using polypropylene glycol (PPG), isophorone diisocyanate (IPDI), 2,2-bis(hydroxymethyl)propionic acid (DMPA), and epoxy resin (E-44) as the main raw materials. Fourier transform infrared (FT-IR) spectroscopy confirmed that flexible polyurethane segments were successfully grafted onto the epoxy resin. This WER/PU emulsion was then incorporated as a modifier into emulsified asphalt to prepare waterborne polyurethane/epoxy resin composite-modified emulsified asphalt (WER/PU-CMEA). A series of laboratory tests were conducted to compare the compatibility, conventional properties, mechanical performance, high temperature rheological properties, low-temperature crack resistance and aging resistance of ordinary emulsified asphalt (OEA), WEA, and WER/PU-CMEA. Scanning electron microscopy (SEM) was employed to analyze the modification mechanism of WEA by WPU. The results show that WER/PU exhibits good compatibility with emulsified asphalt, and the synergistic effect of WER/PU significantly enhances the overall performance of the emulsified asphalt. Compared with WEA, WER/PU-CMEA shows a slight decrease in tensile strength and high-temperature stability, but it notably improves material compatibility, flexibility, bond strength, elongation at break, high-temperature creep-recovery performance, and low-temperature crack resistance. This study provides a promising approach for developing high-performance emulsified asphalt materials, which have strong application potential in pavement maintenance, waterproof coatings, and tack coats. Full article

Under intensive farming conditions, a decline in feed intake after weaning in suckling piglets often results in reduced body weight or diarrhea. We hypothesized that a sow–piglet co-feeding strategy during the suckling period—in which piglets participate in the sow’s feeding process and consume both lactating sow feed and creep feed—could alleviate certain aspects of weaning stress. To test this hypothesis, 102 newborn piglets (Large White × Duroc × Min Pig) were selected and divided into a co-feeding group (CF) and a non-co-feeding group (NCF), based on whether they had access to the sow’s feed during lactation. The study investigated the effects of the two feeding strategies on piglet growth performance, diarrhea incidence, behavior, and post-weaning immune status, intestinal morphology, and antioxidant capacity. The results showed that the CF group had significantly higher body weight at the end of the nursery period (p < 0.05) and a significantly lower post-weaning observed fecal staining rate (p < 0.05). At 16–17 days post-weaning, piglets in the CF group exhibited a significant increase in feeding behavior (p < 0.05). Compared with the NCF group, the CF group showed highly significant reductions in serum levels of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ) (p < 0.01), as well as significantly increased intestinal superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities (p < 0.05) and significantly reduced malondialdehyde (MDA) content (p < 0.05). In terms of intestinal morphology, the CF group had a highly significant increase in the villus-to-crypt ratio in the jejunum (p < 0.01) and a highly significant reduction in crypt depth (p < 0.05), while villus length did not differ significantly between groups (p > 0.05). Overall, in the present study, sow–piglet co-feeding during the suckling period effectively alleviated weaning stress and reduced the incidence of diarrhea. These beneficial effects appear to be associated with reduced inflammatory responses, enhanced antioxidant capacity, and improved intestinal morphology. It should be noted that the relatively late weaning age used in this study likely facilitated the piglets’ ability to efficiently utilize solid feed and derive benefits from the co-feeding strategy. Therefore, caution should be exercised when extrapolating these findings to earlier weaning ages, at which the digestive tract is less mature. Full article

The degradation of styrene-butadiene-styrene (SBS) modified asphalt under thermal-oxidative aging can reduce pavement service life. Lignin is a renewable material with active phenolic hydroxyl groups. Incorporating lignin into SBS modified asphalt may provide a potential bio-based auxiliary modification route. To investigate the antioxidative effect and rheological properties of SBS modified asphalt after adding lignin, a molecular dynamics test and experimental tests were employed. The molecular simulation results suggested that lignin preferentially associated with asphaltene and resin molecules and changed the molecular mobility of asphalt components in a component-dependent manner. The SBS/lignin composite modified asphalt was evaluated by temperature sweep (TS), Multiple Stress Creep and Recovery (MSCR), Linear Amplitude Sweep (LAS) and Fourier transform infrared spectroscopy (FTIR). Rheological tests showed that lignin increased the complex shear modulus and rutting factor. LAS results showed that lignin reduced the fatigue life of SBS-modified asphalt in the unaged state due to increased stiffness and embrittlement. However, after long-term aging, the lignin-containing binders retained higher fatigue resistance than the SBS-only control, which may be related to the slower evolution of oxidation-related functional groups and SBS-related spectral indices. FTIR analysis provided semi-quantitative evidence that lignin addition reduced the growth of sulfoxide-related bands and helped maintain the polybutadiene-related index during aging. Overall, lignin may serve as a potential auxiliary antioxidant modifier for SBS modified asphalt, while its exact source-specific molecular mechanism requires further verification. Full article

This study investigates the effects of ultrasonic vibration on the creep-aging tensile behavior of 7055-T6 aluminum alloy through experiments and finite element simulations. Two characteristic parameters—effective softening amplitude (ESA) and recovery amplitude (RA)—are introduced to quantify the competing softening and hardening effects induced by ultrasonic vibration. Experimental results reveal that the maximum ESA (28.1 MPa) occurs at an amplitude of 14.01 μm, whereas optimal plasticity is achieved at 12.53 μm, indicating that maximum softening does not coincide with optimal formability. Intermittent vibration enhances creep plastic strain by up to 6.95% at 12.53 μm, contrasting with the detrimental effect of continuous vibration. A viscoplastic constitutive model incorporating the volumetric effect of ultrasonic vibration is developed and validated via finite element simulations, achieving close agreement with experiments (ESA deviation ≤ 1.9 MPa). These findings provide quantitative guidance for parameter optimization in ultrasonic-assisted creep-aging formation. Full article

To enhance the overall performance of direct coal liquefaction residue (DCLR)-modified asphalt, particularly its low-temperature cracking resistance, SBS and aromatic oil were employed for composite modification. Nine composite-modified asphalt formulations were prepared based on an orthogonal experimental design. High-and low-temperature rheological properties and microstructure of all modified asphalts were systematically evaluated using a dynamic shear rheometer (DSR), a bending beam rheometer (BBR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that composite modification significantly enhanced the high-temperature performance of the asphalt. Modified asphalt labeled as Sample No. 9 (9% DCLR, 4% SBS, and 6% aromatic oil) demonstrated the minimal non-recoverable creep compliance ($J_{nr}$) value of 0.58 kPa⁻¹ at 64 °C, indicating a 78.6% decrease relative to the matrix asphalt. In terms of low-temperature performance, Sample No. 3 satisfied the Superpave cracking resistance criterion, exhibiting a creep rate ($m$-value) of 0.312 at −12 °C. It was revealed by FTIR analysis that the interaction between the composite modifier and the base asphalt was mainly physical blending, and no new functional groups were generated either before or after aging. The improvement in performance was attributed to the physical compatibility and structural reorganization among the components. Microstructural analysis revealed that the uniform dispersion of modifiers in matrix asphalt and the subsequent formation of a dense micelle structure after aging contributed to the enhanced macroscopic performance. This study provides theoretical and technical support for the high-value application of DCLR in asphalt pavements. Full article

Background: Early detection of developmental disorders in infants is an important topic for scientists and clinicians, but above all for children and their families. Early detection of changes in the mechanical properties of muscles is crucial for starting therapeutic processes. This study aims to fill the research gap regarding the use of myotonometry in the infant patient group (aged 0–3 months). The study aimed to evaluate the test–retest repeatability of myotonometric measurements in infants at three time points, with particular attention to potential age-related differences. Methods: The study group consisted of healthy newborns born from physiological pregnancies with an Apgar score of 8–10 points. The studies began on the 1st–3rd day of life and lasted until the 12th week in cycles every 6 weeks. Results: In the study conducted on the 1st–3rd day of life, the repeatability of the studied parameters can be described as moderate (muscle tone, elasticity, relaxation, and creep) or poor (stiffness). Measurements conducted in the 6th week of life show high repeatability of muscle stiffness and elasticity or moderate repeatability of muscle tone, creep, and relaxation time. Measurements in the 12th week of life of the infants may be considered as high repeatability of muscle tone, stiffness, relaxation time, and the creep parameter, and moderate muscle elasticity. Conclusions: The study demonstrated the usefulness of using myotonometric measurement for infants from the 6th and 12th week of age in the studied parameters, confirmed by the high repeatability of measurements. Whereas in the group of newborns aged 1–3 days, the repeatability of all analyzed parameters can be described as moderate or low. Full article

Owing to the pronounced compositional heterogeneity of waste cooking oil (WCO), WCO-rejuvenated asphalt often exhibits unstable performance. To improve the compositional controllability of WCO-based rejuvenators, WCO was fractionated according to molecular weight differences into three characteristic fractions: light, medium, and heavy components. Nine rejuvenator formulations with different component ratios were prepared to investigate the synergistic mechanism among WCO fractions with different molecular weights and to propose an optimal blending range. Thermal stability tests, dynamic shear rheometer (DSR) tests, multiple stress creep recovery (MSCR) tests, and bending beam rheometer (BBR) tests were conducted to evaluate the performance of the rejuvenators and rejuvenated asphalts. Gas chromatography (GC) and gel permeation chromatography (GPC) were further used to analyze the chemical composition and molecular-weight distribution. The results show that increasing the proportions of light and medium WCO components improves the low-temperature performance of rejuvenated asphalt; however, when the combined content of light and medium components exceeds 40%, the high-temperature performance is adversely affected. The heavy component improves the rutting factor, creep recovery capacity, and thermal oxidative aging resistance of rejuvenated asphalt, and the coefficient of determination between the long-term aging CAI and heavy-component content reaches 0.959. Thermal stability tests show that the mass loss rate of the nine rejuvenators after 1.5 h of heating ranges from 2.8% to 4.3%, with greater mass loss for formulations containing higher light-component contents. GPC results show that the Mn and Mw of R-4 (492 g/mol and 641 g/mol) are higher than those of R-8 (463 g/mol and 600 g/mol), indicating that a higher macromolecular fraction contributes to improved thermal stability. Considering high-temperature, low-temperature, and aging performance together, rejuvenated asphalt achieves the closest overall performance to the base binder when the heavy component is controlled at 50–60% and the medium component is approximately 30%. Full article

Due to excellent performance, polytetrafluoroethylene (PTFE), being sealing material, is widely used in chemical engineering, aerospace engineering, mechanical engineering, civil engineering, energy engineering and other sectors. However, due to obvious temperature drops in supplying or storing fluids, the mechanical behavior of PTFE under cryogenic conditions is still unclear. In this study, the creep mechanical performance of PTFE gaskets after cryogenic aging in liquid oxygen is experimentally investigated. The circular PTFE gasket samples are immersed into liquid oxygen for cryogenic aging treatment. The universal testing machine is utilized for material mechanic tests. Three different load levels, including 10 MPa, 15 MPa and 20 MPa, are designed and accounted for. It is found that the creep strain of PTFE exhibits three typical stages, namely the initial rapid increase phase, transition phase with a reducing growth rate, and stable linear growth phase. Moderate cryogenic immersion aging can effectively improve the creep resistance of PTFE, but excessive aging treatments will lead to mechanical property degradation of PTFE. The Burgers life prediction model is improved by introducing a nonlinear correction term, which can accurately predict the creep behavior of PTFE under different aging states. The present study can provide experimental evidence and a theoretical basis for a deep understanding of the mechanical response of PTFE materials under extreme cryogenic intermittent service conditions. Full article

Creep is one of the main failure mechanisms of materials at elevated temperatures, and the creep rate curve is a key descriptor of creep deformation and damage evolution. However, existing creep models are mainly phenomenological or stage-wise, and the physical origin of the bathtub-shaped creep rate curve over the full creep process has not been systematically clarified. In this study, creep damage is treated as an aging failure process of a material system, and a physically interpretable hierarchical model is established based on statistical physics for disordered complex systems. By linking the evolution and interaction of microscopic material units with macroscopic creep behavior, the proposed model provides a unified description of the primary, secondary, and tertiary creep stages and offers a theoretical explanation for the bathtub-shaped creep rate curve. Validation using representative metallic and composite material cases shows that the model can reasonably reproduce the overall three-stage creep rate evolution, with residual sums of squares of 1.3088 and 0.5369, respectively. These results demonstrate the ability of the model to capture full-process creep behavior in different material systems. The main advantage of the proposed approach is its physical interpretability within a unified framework, while its current limitation is that the validation remains limited in scale and broader benchmark comparisons with conventional methods are still needed. This work provides a statistical perspective for creep behavior modeling and for understanding the microscopic mechanisms and interactions underlying creep degradation in structural materials. Full article

This study investigates the synergistic effects of combining polyphosphoric acid (PPA) and styrene–butadiene–styrene (SBS) as modifiers in asphalt binders to enhance their performance. The research focuses on optimizing the concentrations of PPA and SBS to improve the resistance to permanent deformation, cracking at intermediate and low temperatures, and resistance to aging. A series of empirical and rheological tests, including penetration, softening point, elastic recovery, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR), were conducted to evaluate the rheological and engineering properties of the modified binders. The results indicate that PPA can partially replace SBS, offering comparable improvements in high-temperature performance and creep resistance. The MSCR test revealed a statistically significant synergistic effect between PPA and SBS, resulting in improved recovery and reduced non-recoverable compliance. However, PPA alone shows limited effectiveness at low temperatures and in properties that are governed by elastic response. This study highlights the potential for optimizing asphalt modifiers by leveraging the complementary properties of PPA and SBS in hybrid systems, particularly regarding high-temperature properties and dynamic loading. Full article

Oxidative aging drives asphalt pavement degradation, causing critical structural failures. This study evaluated hazelnut (HS) and walnut shell (WS) powders (0–3% w/w; 10–12 μm) as sustainable antioxidants, from valued residues, to mitigate thermo-oxidative aging in CA-24 binders. After evaluating the antioxidant potential (ORAC; Oxygen radical absorbance capacity, and TPC; Total phenolic content), modified binders underwent RTFO (Rolling thin film oven) and PAV (Pressure aging vessel) aging, evaluated by Fraass fragility, Relative Aging Index (RAI), dynamic shear rheometry (G*/sin δ), and Multiple Stress Creep Recovery (MSCR). WS exhibited significantly higher antioxidant capacity (6000 μmol TE g DW⁻¹) and TPC than HS. The 3% treatments demonstrated optimal antioxidant efficacy, reducing long-term RAI by 14% and improving low-temperature flexibility by 3.8 °C (Fraass point −12.3 °C). However, MSCR revealed initial plasticizing effects decreasing elastic recovery (70%) and increasing non-recoverable compliance (Jnr) compromising unaged rutting resistance. Principal component analysis confirmed progressive diversification of aging-induced properties, evidencing complex multivariate trajectories. Ultimately, while nutshell derived phenolic modifiers provide effective concentration-dependent antioxidant protection, practical application requires optimization through targeted phenolic extraction, particle engineering, or elastomeric co-modification. Balancing aging resistance with high temperature stability remains essential for advancing these sustainable biomodification strategies in road infrastructure. Full article

This article compares the analytical results from two models, based on the theory of hereditary creep strain, with experimental results on the rheological properties of lightweight sintered aggregate concrete under cyclically varying loads. In a previous article, the authors analyzed the adequacy of standard models for the same test results. Because the use of standard models is very complex and does not improve the approximation of test results without additional calibration, the authors suggest reconsidering the use of hereditary models for LWAC. The application of four such long-term models was analyzed. Among these models, the Arutiunian theory of hereditary creep with aging and the modified hereditary theory with Bažant aging function yielded quantitatively and qualitatively correct results. The application of hereditary creep theory allowed for the formulation of the total strain as a superposition of strain increments, obtained by an integral equation. This equation was applied to a series of constant stress increments and decrements, as in the case of cyclic loading, and it was mathematically described in segmented form. Knowledge of the properties of LWAC and useful long-term models is essential for the design of prestressed structures made of lightweight aggregate concrete subjected to time-varying loads. Full article

To address the prominent problem of early rutting distress in asphalt pavements under heavy-load traffic in China, this study proposes a composite modifier consisting of direct coal liquefaction residue (DCLR), styrene–butadiene–styrene block copolymer (SBS), and styrene–butadiene rubber (SBR). The preparation process and formula were optimized through single-factor experiments and orthogonal tests. Systematic investigations were conducted on its conventional performance, water damage resistance, aging resistance, fatigue performance, rheological properties, and microscopic mechanism, with comparisons made against base asphalt, single DCLR-modified asphalt, SBS-modified asphalt, and SBS/SBR-modified asphalt. The results indicate that the optimal preparation process for the novel composite high-modulus modified asphalt is as follows: DCLR particle size of 0.3 mm, addition in molten state, shear temperature of 170 °C, shear rate of 5000 r·min⁻¹, shear time of 50 min. The optimal formula is 10% DCLR + 3% SBS + 2% SBR + 3% compatibilizer, with the addition sequence of “DCLR → SBS + compatibilizer → SBR”. This asphalt exhibits a softening point of 77.8 ± 2.1 °C, a Brookfield viscosity at 135 °C of 1.928 ± 0.105 Pa·s, and a grading of 5 for adhesion to aggregates; the rutting factor at 64 °C reaches 10.8 ± 0.9 kPa (6.43 times that of the base asphalt), the creep stiffness at −12 °C is 136 ± 12.5 MPa, and the low-temperature limit temperature is −17 °C; the freeze–thaw splitting strength ratio (TSR) is 94.6 ± 1.8%, and both aging resistance and water damage resistance are significantly superior to those of the control group asphalts (p < 0.05). The novel composite high-modulus modified asphalt showed improved overall laboratory performance and may be suitable for heavy-load traffic and complex climatic conditions, however, field validation is needed. Full article