Yuanzhao Chen

In order to promote the sustainable development of road engineering, this study used waste tire rubber powder (RP) and surface organic layered double hydroxide (SOM-LDHs) to modify 70# matrix asphalt. The Box–Behnken design response surface method with three factors (rubber powder content, surface organic layered double hydroxide content, shear temperature) and three responses (penetration, ductility, softening point) was used to optimize the preparation parameters. The optimum formula was determined to be 21.7% rubber powder content, 4.8% surface organic layered double hydroxide content, and 160 °C shear temperature. The effect of the modifier on the surface morphology was analyzed using a rotating film oven test and ultraviolet aging test. The high and low temperature rheological properties of asphalt were evaluated by dynamic shear rheometer (DSR), bending beam rheometer (BBR), and the multi-stress creep recovery test (MSCR). The microstructure was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aging mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The results show that after aging, the complex shear modulus of rubber powder/surface organic layered double hydroxide composite modified asphalt is the highest, which is 27.35% higher than that of matrix asphalt. The rutting factor reaches 79.86 kPa at 46 °C, the phase angle decreases by 11.83% after UV aging, and the high temperature plastic deformation resistance is the best. In the low temperature range of −18 °C to −24 °C, the creep stiffness of the composite modified asphalt is about 30% lower than that of the matrix asphalt, while the m value is increased by about 15%, and the low temperature stress relaxation performance is significantly improved. The strain recovery rate of composite modified asphalt under 3.2 kPa stress reaches 78.5%, and the unrecoverable creep compliance is as low as 0.18 kPa⁻¹, which is better than that of matrix asphalt and single rubber powder modified asphalt.

Styrene-butadiene-styrene (SBS) modifier can enhance the resistance of asphalt mixtures to load-induced deformation and fatigue cracking by constructing a three-dimensional physical gel network. However, a rigorous mechanical characterization of this mechanism remains lacking. This study elucidates the nonlinear fatigue damage evolution of SBS-modified asphalt mixtures with physical gel structures based on residual strain response analysis. Indirect tensile fatigue tests were conducted to characterize the residual strain response of SBS-modified asphalt mixtures. A damage-informed residual strain model was established, and a relative residual strain change rate was defined to analyze the correlation between fatigue cracking and residual strain response. Furthermore, the nonlinear fatigue damage evolution of SBS-modified asphalt mixtures was investigated based on the fatigue damage theory. The results demonstrate a strong correlation between fatigue cracking and a viscoplastic strain in the SBS-modified asphalt mixtures. The proposed residual strain model accurately describes the nonlinear fatigue damage evolution and residual strain response. The relative residual strain change rate serves as a rational indicator of the material’s resistance to fatigue cracking and residual strain accumulation. The SBS modifier enhances resistance to residual strain and fatigue cracking by forming a complex polymer network that establishes a three-dimensional physical gel structure.

Waste sweet potato vine fiber (WSVF) effectively extends asphalt service life by enhancing cracking resistance in gel-like base asphalt matrices, yet its crack-resistant mechanism lacks mechanical characterization. This study proposes an analytical method for evaluating WSVF-modified asphalt’s crack-resistant behavior based on the principle of mechanical energy balance. First, alkali-treated WSVF with a mass fraction of 1% was added into 70# gel-like base asphalt to prepare WSVF-modified asphalt. Lignin fiber (LF)-modified asphalt and 70# gel-like base asphalt were selected as control groups, and three types of time sweep and scanning electron microscopy tests were conducted. Then, the three-dimensional cracking volume model and damage kinetics model were established for analyzing the cracking response behavior, defining the asphalt damage variable and determining the cracking damage activation energy (E_acd). Finally, the E_acd was used to quantify the difficulty of the cracking damage process for the WSVF-modified asphalt. The reinforcement and cracking resistance mechanisms of WSVF in asphalt were analyzed by the E_acd and asphalt microstructure. The results show that the cracking volume response of WSVF-modified asphalt under cyclic loading presents three-stage nonlinear behaviors. The established fatigue damage kinetics model can accurately describe the fatigue damage evolution process of alkali-treated WSVF-modified asphalt. The E_acd values of WSVF-modified asphalt, LF-modified asphalt, and 70# gel-like base asphalt are 10.60 kJ·mol⁻¹, 21.83 kJ·mol⁻¹, and 29.74 kJ·mol⁻¹, respectively. After alkali treatment, the WSVF surface exhibits grooves, demonstrating superior adsorption and storage capacity for asphalt. The WSVF can cross link through the bonding effect of asphalt and form a three-dimensional network framework structure, which can significantly increase the E_acd and provide strengthening and toughening effects on gel-like base asphalt. In summary, E_acd values are used as a mechanical indicator to quantitatively evaluate the fatigue cracking resistance of WSVF-modified asphalt.

Waste battery powder (WBP) can effectively enhance the service performance of virgin asphalt with sol–gel structures; however, its toughening mechanism for sol–gel virgin asphalt still lacks rigorous mechanical characterization. Therefore, the objective of this study is to investigate the toughening of WBP-modified asphalt based on the mechanical parameter of cracking area. First, a 12% content of WBP was incorporated into the sol–gel 70# virgin asphalt to prepare WBP-modified asphalt and its fatigue performance was evaluated through linear amplitude, non-damage, and damage time sweep tests. Then, energy–mechanics balance equations were used to establish a cracking area model. Furthermore, the asphalt cracking area was employed to quantify its induced damage and determine the representative rate for the cracking damage process (k_cd). Finally, the activation energy for cracking damage (E_acd) was used to quantify the difficulty of the cracking damage process. The scanning electron microscope test was employed to examine the microstructure of WBP-modified asphalt and the E_acd and microscopic morphology of WBP-modified asphalt were analyzed to reveal the toughening effect of WBP on virgin asphalt. The results showed that WBP-modified asphalt exhibits three nonlinear cracking stages, with a lower cracking rate than virgin asphalt. Its cracking damage generally increases over time, and the damage evolution parameter β serves as k_cd. The micro-grooves and wrinkles of WBP improve bonding to asphalt, increasing the E_acd of sol–gel 70# virgin asphalt from 10.6 to 23.88 kJ·mol⁻¹, thus achieving toughening. In summary, the fatigue damage process of WBP-modified asphalt can be characterized by the kinetic parameters β and E_acd.

To prolong the service life of asphalt pavement and reduce its maintenance cost, a fiber Bragg grating (FBG) sensor encapsulated in carboxylated carbon nanotube (CNT-COOH)-modified gel material suitable for strain monitoring of asphalt pavement was developed. Through tensile and bending tests, the effects of carboxylated carbon nanotubes on the mechanical properties of gel materials under different dosages were evaluated and the optimal dosage of carbon nanotubes was determined. Infrared spectrometer and scanning electron microscopy were used to compare and analyze the infrared spectra and microstructure of carbon nanotubes before and after carboxyl functionalization and modified gel materials. The results show that the incorporation of CNTs-COOH increased the tensile strength, elongation at break, and tensile modulus of the gel material by 36.2%, 47%, and 17.2%, respectively, and increased the flexural strength, flexural modulus, and flexural strain by 89.7%, 7.5%, and 63.8%, respectively. Through infrared spectrum analysis, it was determined that carboxyl (COOH) and hydroxyl (OH) were successfully introduced on the surface of carbon nanotubes. By analyzing the microstructure, it can be seen that the carboxyl functionalization of CNTs improved the agglomeration of carbon nanotubes. The tensile section of the modified gel material is rougher than that of the pure epoxy resin, showing obvious plastic deformation, and the toughness is improved. According to the data from the calibration experiment, the strain and temperature sensitivity coefficients of the packaged sensor are 1.9864 pm/μm and 0.0383 nm/°C, respectively, which are 1.63 times and 3.61 times higher than those of the bare fiber grating. The results of an applicability study show that the internal structure strain of asphalt rutting specimen changed linearly with the external static load, and the fitting sensitivity is 0.0286 με/N. Combined with ANSYS finite element analysis, it is verified that the simulation analysis results are close to the measured data, which verifies the effectiveness and monitoring accuracy of the sensor. The dynamic load test results reflect the internal strain change trend of asphalt mixture under external rutting load, confirming that the encapsulated FBG sensor is suitable for the long-term monitoring of asphalt pavement strain.

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification.

Aiming at the problems of serious pavement temperature diseases, low efficiency and high loss of ice-breaking methods, high occupancy rate of waste tires and the low utilization rate and insufficient durability of rubber particles, this paper aims to improve the service level of roads and ensure the safety of winter pavements. A pavement material with high efficiency, low carbon and environmental friendliness for active snow melting and ice breaking is developed. Firstly, NaOH, NaClO and KH550 were used to optimize the treatment of rubber particles. The hydrophilic properties, surface morphology and phase composition of rubber particles before and after optimization were studied, and the optimal treatment method of rubber particles was determined. Then, the optimized rubber particles were used to replace the natural aggregate in the polyurethane gel mixture by the volume substitution method, and the optimum polyurethane gel dosages and molding and curing processes were determined. Finally, the influence law of the road performance of RPGM was compared and analyzed by means of an indoor test, and the ice-breaking effect of RPGM was explored. The results showed that the contact angles of rubber particles treated with three solutions were reduced by 22.5%, 30.2% and 36.7%, respectively. The surface energy was improved, the element types on the surface of rubber particles were reduced and the surface impurities were effectively removed. Among them, the improvement effect of the KH550 solution was the most significant. With the increase in rubber particle content from 0% to 15%, the dynamic stability of the mixture gradually increases, with a maximum increase of 23.5%. The maximum bending strain increases with the increase in its content. The residual stability increases first and then decreases with the increase in rubber particle content, and the increase ranges are 1.4%, 3.3% and 0.5%, respectively. The anti-scattering performance increases with the increase in rubber content, and an excessive amount will lead to an increase in the scattering loss rate, but it can still be maintained below 5%. The fatigue life of polyurethane gel mixtures with 0%, 5%, 10% and 15% rubber particles is 2.9 times, 3.8 times, 4.3 times and 4.0 times higher than that of the AC-13 asphalt mixture, respectively, showing excellent anti-fatigue performance. The friction coefficient of the mixture increases with an increase in the rubber particle content, which can be increased by 22.3% compared with the ordinary asphalt mixture. RPGM shows better de-icing performance than traditional asphalt mixtures, and with an increase in rubber particle content, the ice-breaking ability is effectively improved. When the thickness of the ice layer exceeds 9 mm, the ice-breaking ability of the mixture is significantly weakened. Mainly through the synergistic effect of stress coupling, thermal effect and interface failure, the bonding performance of the ice–pavement interface is weakened under the action of driving load cycle, and the ice layer is loosened, broken and peeled off, achieving efficient de-icing.