Effects of Different Antioxidant Intercalated Layered Double Hydroxides on Anti-Aging Properties of Asphalt Binders

This research aims to prepare different antioxidant intercalated layered double hydroxides (LDHs) and compare the thermal oxidation and ultraviolet (UV) aging resistances of different modified asphalts. The ion exchange technique was used to intercalate three different antioxidants: 3-(3,5-di-tert-butyl-4-carboxyphenyl) propionic acid, antioxidant 1222, and sodium dibutyl dithiocarbamate (rubber accelerator TP) into the interlayer of LDHs. The morphology, structures, UV blocking, and free radical scavenging properties of different antioxidant intercalated LDHs were characterized, respectively. The effects of the anti-aging agents on the physical properties (penetration, softening point, ductility, and viscosity); rheological behaviors (complex modulus and phase angle); and functional groups (C=O and S=O) of asphalt both before and after thermal oxidation aging and UV aging were systematically investigated. The results of the crystal structure and functional group analysis show that the three different antioxidants can be successfully inserted into the interlayer of LDHs without destroying their layered structures. Antioxidant intercalated LDHs exhibit a remarkable capacity for absorbing UV rays, coupled with a moderate ability to reflect UV light. Moreover, the inclusion of antioxidants into the interlayers of LDHs confers upon them the ability to scavenge free radicals. After 2 h of reaction, the free radical scavenging rates of LDHs-3, LDHs-1222, and LDHs-TP were 57.7%, 35.6%, and 17.1%, respectively. With an increase in the content of the antioxidant intercalated LDHs, the performance of the modified asphalt varies, and 4% is the optimal content of the anti-aging agents. Asphalts with the three antioxidant intercalated LDHs all had favorable storage stability, and their physical and rheological properties were improved after aging compared to LDHs-modified asphalt. The LDHs-3-modified asphalt showed the best anti-ultraviolet aging effect, while LDHs-1222-modified asphalt showed the best anti-thermal oxidation aging effect. This research lays the foundation for developing aging-resistant asphalt and improving the durability of asphalt pavement

An Energy-Based Anisotropic Vector Hysteresis Model for Rotational Electromagnetic Core Loss

In this article, a model that describes the anisotropic behavior and core loss of electrical steel sheets over a wide range of rotational excitation is developed. Based on the definition of the effective field, the macroscopic anisotropy field is deduced from a weighted average of the magnetocrystalline energy of a single crystal. An anisotropic vector hysteresis model is then proposed by applying the effective field to the energy-based model. Experimental measurements are used to fit and validate the model. Either alternating or rotational measurements with a maximum magnetic flux density 1.55 T under 10 Hz are employed to fit the model parameters and the remaining set of measurements is used for validating the model accuracy. The results show that the model can naturally account for the drop in the rotational losses at high flux densities regardless of whether it is identified from alternating or rotational measurement data. The generality of the model is demonstrated through continuous angle results and modeling of another material.Peer reviewe

A systematic review on the strategies of reducing asphalt pavement temperature

Under the action of repeated load of vehicles, asphalt pavement tends to suffer rutting and other failures at high temperatures, which shortens the service life of the pavement. Meanwhile, asphalt pavement aggravates the urban heat island (UHI) effect, reducing the livability of the city. Research shows that lower road temperatures can mitigate the UHI effect. For this reason, researchers have launched lots of studies to cool asphalt pavement under high temperatures, such as reflective pavement and phase change pavement, etc. Although these technologies are effective at reducing the temperature of asphalt pavement, there are still some limitations. This paper mainly discusses the latest development of asphalt pavement temperature reduction strategies, classifies them according to different action mechanisms, and discusses the advantages and limitations of each strategy in detail. Suggestions for future research are given to address the limitations of each strategy, such as passive radiation technology can provide new ideas for reflective pavement, planting trees should consider plant physiological parameters and spatial distribution of planting, and phase change materials can be encapsulated by high thermal conductivity materials, etc. This study can provide a guidance for further development of asphalt pavement cooling technologies

Performance Evaluation of Asphalt Modified with Steel Slag Powder and Waste Tire Rubber Compounds

As two kinds of solid wastes, waste tires and steel slag have caused serious threats to the environment. Both waste tire rubber (WTR) and steel slag powder (SSP) can improve the performance of asphalt, while the performance indexes and modification mechanism of modified asphalt are not clear. In this paper, asphalt modified with SSP and WTR was prepared, and its performance was evaluated. The physical properties of asphalt modified with SSP and WTR, including penetration, the softening point, and viscosity, were investigated. Furthermore, high-temperature performance, fatigue resistance, low-temperature performance, and blending mechanism of asphalt modified with SSP and WTR were tested with a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and Fourier transform infrared spectrometer (FTIR). The results showed that with the same content of WTR and SSP, WTR reveals a more significant modification effect on physical properties, fatigue, and low-temperature performance of base asphalt than SSP. The anti-rutting performance of SSP-modified asphalt is better than that of WTR-modified asphalt at 30~42 °C, and the anti-rutting performance of WTR-modified asphalt is better than that of SSP-modified asphalt at 42~80 °C. When the total content of WTR and SSP is the same, the physical properties, high-temperature resistance, fatigue resistance, and low-temperature performance of the asphalt modified with WTR and SSP decrease with the decrease in the ratio of WTR and SSP, and their performance is between WTR-modified asphalt and SSP-modified asphalt. Infrared spectrum results verified that the preparation of WTR- and SSP-modified asphalt is mainly a physical blending process. Overall, this research is conducive to promoting the application of modified asphalt with WTR and SSP in the construction of high-standard pavement

Recent advances in calcium alginate hydrogels encapsulating rejuvenator for asphalt self-healing

Summary: The inherent self-healing ability of asphalt is insufficient and fails to timely repair the cracks due to the combined effect of temperature variation, air oxidation, ultraviolet exposure and traffic loading. Rejuvenator encapsulation based on self-healing asphalt is a green sustainable preventive maintenance technology for asphalt pavement. During the last decade, rejuvenator encapsulation for asphalt self-healing has been a research hotspot and calcium alginate hydrogels encapsulating rejuvenator is a promising self-healing technology. Hence, this review sheds light on the recent advances of calcium alginate hydrogels encapsulating asphalt rejuvenator including self-healing capsules and fibers. The synthesis methods of calcium alginate capsules and fibers containing rejuvenator were elaborately introduced, and their surface morphology, interior structure, mechanical strength, thermal stability, rejuvenator content, distribution and survival in asphalt materials were systematically analyzed. Besides, the effect of capsules and fiber on the mechanical property and pavement performance of asphalt concrete were explored. Additionally, a comprehensive review about the effect of calcium alginate capsules and fibers on self-healing ability of asphalt materials were presented, and the rejuvenator release mechanism and release ratio of them in asphalt mixtures were expounded. In a nutshell, this review aims at highlighting the current research achievements on alginate capsules and fibers containing rejuvenator in asphalt materials, and inspiring enhanced self-healing methods for smart and sustainable maintenance of asphalt pavement

An implementation method of incorporating hysteretic material models into electromagnetic FEA

Hysteresis, as most important and intrinsic property of magnetic materials, however, is usually neglected in numerical analysis of electrical equipment due to its complicated history-dependent multi-valued nonlinearity, which will lead to inaccurate predictions of magnetic fields distribution and core loss. In this paper, an efficient implementation method of incorporating hysteretic material models into electromagnetic analysis is presented resorting to a commercial FEA package. This method is characterized by strong universality, and can be easily applied to other complex magnetic property models regarding anisotropy or hysteresis

Performance Evaluation of Asphalt Modified with Steel Slag Powder and Waste Tire Rubber Compounds

As two kinds of solid wastes, waste tires and steel slag have caused serious threats to the environment. Both waste tire rubber (WTR) and steel slag powder (SSP) can improve the performance of asphalt, while the performance indexes and modification mechanism of modified asphalt are not clear. In this paper, asphalt modified with SSP and WTR was prepared, and its performance was evaluated. The physical properties of asphalt modified with SSP and WTR, including penetration, the softening point, and viscosity, were investigated. Furthermore, high-temperature performance, fatigue resistance, low-temperature performance, and blending mechanism of asphalt modified with SSP and WTR were tested with a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and Fourier transform infrared spectrometer (FTIR). The results showed that with the same content of WTR and SSP, WTR reveals a more significant modification effect on physical properties, fatigue, and low-temperature performance of base asphalt than SSP. The anti-rutting performance of SSP-modified asphalt is better than that of WTR-modified asphalt at 30~42 °C, and the anti-rutting performance of WTR-modified asphalt is better than that of SSP-modified asphalt at 42~80 °C. When the total content of WTR and SSP is the same, the physical properties, high-temperature resistance, fatigue resistance, and low-temperature performance of the asphalt modified with WTR and SSP decrease with the decrease in the ratio of WTR and SSP, and their performance is between WTR-modified asphalt and SSP-modified asphalt. Infrared spectrum results verified that the preparation of WTR- and SSP-modified asphalt is mainly a physical blending process. Overall, this research is conducive to promoting the application of modified asphalt with WTR and SSP in the construction of high-standard pavement