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.

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.

Layered double hydroxides (LDHs) can shield polymeric materials from UV light, which allows reducing material aging and erosion damage of bituminous pavement under physical and chemical action. In this study, the physicochemical properties, aging resistance, and erosion resistance to the aqueous solution of LDHs modified bitumen mastic (BM) were characterized by Fourier-transform infrared spectroscopy, basic physical tests, viscosity tests, a dynamic shear rheometer, and a bending beam rheometer. The results show that few chemical reactions occurred between LDHs and BM, indicating that a physical mechanism underlay the modification of BM by LDHs. Moreover, LDHs could increase the flow activation energy of BM by 0.12%, increase the high failure temperature from 69.07 °C to 71.07 °C, and decrease the low failure temperature from −10.50 °C to −12.39 °C. Therefore, LDHs could slightly reduce the temperature sensitivity of BM, while slightly enhancing the high and low-temperature rheological properties of BM. Compared with short-term aging and long-term aging, LDHs could significantly improve the UV aging resistance of BM. The above results are consistent with previous studies of LDHs-modified bitumen. Furthermore, water and pH 3 acidic solutions had the greatest degree of erosion to BM, and LDHs could improve the resistance to aqueous solutions. Overall, this study can help to investigate the effects of various environmental factors on the performance of LDHs modified bitumen pavements during long-term use.

Flexible thin-film sensors exhibit considerable application potential in the structural health monitoring of bridges under complex traffic scenarios, owing to their capability of rapidly responding to dynamic loads, static loads, and dynamic-static coupled loads. In this study, following the evaporation crystallization method, ZnO/PVA was deposited on the substrate to form a 10-µm-thick film by adjusting the material ratio (m(ZnO):m(PVA) = 4:1) and solution environment (pH = 12). After cutting and packaging, the flexible piezoelectric film sensor was obtained. The sensing characteristics of the ZnO/PVA film sensor under quasi-static, vibratory, and coupled-force loads were analyzed using a dynamic data acquisition system, revealing excellent response feedback in detecting these three stress states. the sensitivity, linearity, and electrical output response time (at 25°C) were 1.33, 0.38, and 14.44 mV/N; 2.1, 5.1, and 5.3%; and 50, 5, and 8 ms, respectively. Temperature-dependent tests (10–60°C) demonstrated significant signal stability after implementing a curve-fitting compensation algorithm (R²=0.998). This temperature correction mechanism addresses the critical challenge of environmental fluctuations in practical bridge monitoring scenarios where static stresses and dynamic vibrations coexist.