Performance and Reinforcement Mechanism of Modified Asphalt Binders with Nano-Particles, Whiskers, and Fibers

Effects of Polyethylene Glycol/Porous Silica Form-Stabilized Phase Change Materials on the Performance of Asphalt Binders

The road performance and temperature-regulating properties of asphalt binders modified with novel polyethylene glycol (PEG)/porous silica (PS) form-stabilized phase-change materials (PEG/PS-fs-PCMs) were studied. PS and PEG were used as the supporting substance and PCMs. The results showed that PEG/PS-fs-PCMs could maintain a maximum weight percentage of 70% without leakage, at temperatures as high as 90 °C. The PEG/PS-fs-PCMs exhibited stable chemical structures, excellent thermal stability, high heat storage density, and suitable phase-change temperature. Based on conventional physical tests, the addition of PEG/PS-fs-PCMs can increase the viscosity and the degree of hardness of asphalt binders; thus, achieving an excellent comprehensive performance of the modified asphalt binder depends on determining the optimal dosage of PEG/PS-fs-PCMs. Additionally, incorporating PEG/PS-fs-PCM particles into the asphalt binder can enhance its ability to withstand permanent deformation at elevated temperatures, while PEG/PS-fs-PCMs mainly act as a filler, weakening the cohesive force of the asphalt molecules, and preventing the ductility of asphalt from expansion, according to DSR and BBR tests. Moreover, the use of PEG/PS-fs-PCMs can enhance the heat transfer properties of the asphalt binders, resulting in an improved temperature regulation performance. However, the accumulation of PEG/PS-fs-PCM particles on asphalt binders can negatively impact the storage stability of the modified asphalt binders, because of the difference in density between the two materials.

Applications of Synthetic, Natural, and Waste Fibers in Asphalt Mixtures: A Citation-Based Review

The utilization of synthetic, natural, and waste fibers in asphalt mixtures is constantly increasing due to the capability of fibers to improve the mechanical performance of asphalt mixes. The combination of fibers in asphalt mixes contributes to ecological sustainability and cost benefits. The objective of this paper is to introduce a citation-based review on the incorporation of synthetic, natural, and waste fibers in bitumen, dense-graded asphalt mix, stone mastic asphalt, and porous asphalt mix. Additionally, this article aims to identify research gaps and provide recommendations for further work. The outputs of this article demonstrated that there has recently been a growing interest in the use of natural and waste fibers in asphalt mixtures. However, more future studies are needed to investigate the performance of fiber-modified stone mastic asphalt and porous asphalt mix in terms of resistance to aging and low-temperature cracking. Furthermore, the period of natural fibers' biodegradability in asphalt mixtures should be investigated.

Laboratory Characterization of Porous Asphalt Mixtures with Aramid Fibers

Recent studies have shown that fibers improve the performance of porous asphalt mixtures. In this study, the influence of four different fibers, (a) regular aramid fiber (RegAR), (b) aramid fiber with latex coating (ARLat), (c) aramid fiber with polyurethane coating (ARPoly), (d) aramid fiber of length 12 mm (AR12) was evaluated on abrasion resistance and toughness of the mixtures. The functional performance was estimated using permeability tests and the mechanical performance was evaluated using the Cantabro test and indirect tensile strength tests. The parameters such as fracture energy, post cracking energy, and toughness were obtained through stress-strain plots. Based on the analysis of results, it was concluded that the addition of ARLat fibers enhanced the abrasion resistance of the mixtures. In terms of ITS, ARPoly and RegAR have positively influenced mixtures under dry conditions. However, the mixtures with all aramid fibers were found to have adverse effects on the ITS under wet conditions and energy parameters of porous asphalt mixtures with the traditional percentages of bitumen in the mixture used in Spain (i.e., approximately 4.5%).

Improvements of Developed Graphite Based Composite Anti-Aging Agent on Thermal Aging Properties of Asphalt

To reduce the thermal-oxidative aging of asphalt and the release amount of harmful volatiles during the construction of asphalt pavement, a new composite anti-aging agent was developed. Since the volatiles were mainly released from saturates and aromatics during the thermal-oxidative aging of asphalt, expanded graphite (EG) was selected as a stabilizing agent to load magnesium hydroxide (MH) and calcium carbonate (CaCO₃) nanoparticles for preparing the anti-aging agents of saturates and aromatics, respectively. Thermal stability and volatile constituents released from saturates and aromatics before and after the thermal-oxidative aging were characterized using the isothermal Thermogravimetry/Differential Scanning Calorimetry-Fourier Transform Infrared Spectrometer test (TG/DSC-FTIR test). Test results indicate that anti-aging agents of EG/MH and EG/CaCO₃ effectively inhibit the volatilization of light components in asphalt and improve the thermal stability of saturates and aromatics. Then, the proportions of EG, MH, and CaCO₃ added in the developed composite anti-aging agent of EG/MH/CaCO₃ are 2:1:3 by weight. EG/MH/CaCO₃ plays a synergetic effect on inhibiting the thermal-oxidative aging of asphalt, and reduces the release amount of harmful volatiles during the thermal-oxidative aging after EG/MH/CaCO₃ is added into asphalt at the proposed content of 10 wt.%. EG plays a synergistic role with MH and CaCO₃ nanoparticles to prevent the chain reactions, inhibiting the thermal-oxidative aging of asphalt.

Investigating the pavement performance and aging resistance of modified bio-asphalt with nano-particles

Bio-asphalt binders have been proposed as replacements for traditional asphalt binders, owing to advantages such as environmental protection, low costs, and abundant resources. However, a limitation of bio-asphalt binders is that their high-temperature performance is not suitable for pavement construction. In recent years, nano-particles have been widely used to improve the pavement performance of asphalt binders, particularly the high-temperature performance. Thus, the nano-particles might also provide a positive modified effect on the high-temperature performance of bio-asphalt binders. Based on this, five types of nano-particles including SiO2, CaCO3, TiO2, Fe2O3, and ZnO are selected for the preparation of modified bio-asphalt binders, using different dosages of nano-particles and bio-oil. The high- and low-temperature performances, aging resistance, workable performance, and water stability of the nano-modified bio-asphalt binders and mixtures are investigated. The results reveal that, the high-temperature performance and aging resistance of the nano-modified bio-asphalt binders and mixtures are improved at increased nano-particle dosages, whereas their low-temperature performance is slightly weakened. The effects of the nano-particles on the workable performance and water stability are insignificant.

On the Numerical Analysis of Unsteady MHD Boundary Layer Flow of Williamson Fluid Over a Stretching Sheet and Heat and Mass Transfers

A thorough and detailed investigation of an unsteady free convection boundary layer flow of an incompressible electrically conducting Williamson fluid over a stretching sheet saturated with a porous medium has been numerically carried out. The partial governing equations are transferred into a system of non-linear dimensionless ordinary differential equations by employing suitable similarity transformations. The resultant equations are then numerically solved using the spectral quasi-linearization method. Numerical solutions are obtained in terms of the velocity, temperature and concentration profiles, as well as the skin friction, heat and mass transfers. These numerical results are presented graphically and in tabular forms. From the results, it is found out that the Weissenberg number, local electric parameter, the unsteadiness parameter, the magnetic, porosity and the buoyancy parameters have significant effects on the flow properties.

Structure and properties of particles/rubber composites applied on functionally graded lapping and polishing plate

To obtain uniform and controllable material removal on hard and brittle materials, a novel processing technology with functionally graded lapping and polishing plate (FG-LPP) was proposed. Taking application of particles/rubber composites and adjustable contact stress of workpiece as key point, the abrasive particles and rubber were mixed with different mass ratios; then the FG-LPP was formed with characteristics of required quasi-continuous distribution of Young’s modulus in the radial direction by two-step processing technique. The properties of Young’s modulus, loss factor, and glass transition temperature of different particles/rubber composites were tested and calculated. Through comparison and analysis, silicon carbide (SiC)/chloroprene rubber (CR) composites are the suitable application object of FG-LPP. Moreover, by laser particle size analyzer, scanning electron microscope, and X-ray diffraction, the size distribution of abrasive particles, micromorphology of particles/rubber composites and their phase composition were tested respectively to better reveal the structure and properties. The test results indicate that under the action of ZnO and MgO, CR undergoes a vulcanization reaction gently and forms a spatial three-dimensional structure. Thus, it helps to increase the intermolecular distance and weaken the intermolecular forces because the NO is easy to enter the CR molecules, which improves the intermiscibility between SiC and CR.