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Hot in-place recycling (HIR) is a sustainable pavement rehabilitation method. However, it is susceptible to aging processes that can compromise its mechanical properties and long-term performance. This study investigates the effects of thermo-oxidative (TO) and ultraviolet (UV) aging on HIR mixtures. Basic performance tests were conducted on the aggregate gradation, moisture content, and asphalt content of the reclaimed asphalt pavement (RAP) to assess the aging level. Simulations of long-term and short-term oxidative aging of the HIR mixture, along with 12 months of UV irradiation, were performed to evaluate its high-temperature stability, low-temperature crack resistance, and water stability. The Verhulst model was employed to establish a predictive equation for performance attenuation under UV aging. To quantify the photoaging effect, indicators for UV aging degree were proposed to characterize the road performance of the HIR mixture, including the aging rate and the aging residual index. Results indicate that the improvement in high-temperature performance after aging is limited, but cracking resistance decreases substantially. Notably, the flexural tensile strain was reduced by 129.25 με for 10 years of TO aging compared to 12 months of UV exposure, underscoring the importance of considering environmental factors in performance predictions. This study emphasizes the need for enhanced aging mitigation strategies to improve the sustainability and reliability of HIR mixtures in practical applications. [ABSTRACT FROM AUTHOR]

This research aims at systematically evaluating the properties of SMA-13 asphalt mixture reinforced by several fiber additives including flocculent lignin fiber (FLF), granular lignin fiber (GLF), chopped basalt fiber (CBF), and flocculent basalt fiber (FBF). Firstly, the thermal stability, moisture absorption, and oil absorption property of these fiber additives were analyzed. Secondly, the property of SMA-13 reinforced using four types of single fibers and two kinds of composite fibers (FLF + CBF and FLF + FBF) was comprehensively analyzed. Specifically, the high-temperature performance was evaluated using the uniaxial penetration test and the rutting test, the medium-temperature anticracking property was evaluated using the IDEAL-CT test, the low-temperature property was analyzed using the beam bending test, and the water stability was studied by the freeze–thaw splitting test. Thirdly, the dynamic mechanical response of different-fibers-modified SMA-13 was evaluated using the uniaxial compression dynamic modulus test. Finally, correlation analysis between the results of dynamic modulus and the high-, medium-, and low-temperature mechanical performance was carried out. The research results reveal that the stability of CBF and FBF under thermal action is better than that of GLF and FLF, and FBF shows the best thermal stability. The oil absorption property of FLF is better than that of GLF, followed by FBF and CBF. The comprehensive mechanical properties of CBF- and FBF-reinforced SMA-13 are better than those of FLF- and GLF-modified SMA-13. CBF can better reinforce the mechanical property of SMA-13 under low and medium temperature, while FBF can better reinforce the performance of SMA-13 at high temperature. FLF/CBF- and FLF/FBF-composite-modified SMA-13 show better high-temperature mechanical performance than that of the single-fiber-reinforced mixture, and FLF has some negative impact on the properties of FLF/FBF-composite-modified SMA-13 at low temperature. Fibers have no significant influence on the water stability of the mixtures. Meanwhile, the linear correlation between the mechanical performance of all the fiber-reinforced SMA-13 and the dynamic modulus result is good. [ABSTRACT FROM AUTHOR]

The first aging process for 70# asphalt and SBS modified asphalt was performed. The recycled old asphalt was obtained from RAP by extraction test. Then, the corresponding rejuvenated asphalts were prepared by adding rejuvenating agent into three types of firstly aged asphalts. The properties of the three major indicators of rejuvenated asphalt were researched. The results show that the adding rejuvenating agent at optimal dosage (6%) can effectively recover not only the penetration, softening point and viscosity of firstly aged asphalts, but also the high temperature and low temperature rheological properties. After the secondary aging process, the penetration values of the secondly aged asphalts decrease, while the softening point and rotational viscosity values increase. Besides, high temperature rheological properties improve as well as low temperature rheological properties deteriorate. [ABSTRACT FROM AUTHOR]

Ultra High-Performance Concrete (UHPC) is a cement-based composite material with great strength and durability. Fibers can effectively increase the ductility, strength, and fracture energy of UHPC. This work describes the impacts of individual or hybrid doping of basalt fiber (BF) and steel fiber (SF) on the mechanical properties and microstructure of UHPC. We found that under individual doping, the effect of BF on fluidity was stronger than that of SF. Moreover, the compressive, flexural, and splitting tensile strength of UHPC first increased and then decreased with increasing BF dosage. The optimal dosage of BF was 1%. At a low content of fiber, UHPC reinforced by BF demonstrated greater flexural strength than that reinforced by SF. SF significantly improved the toughness of UHPC. However, a high SF dosage did not increase the strength of UHPC and reduced the splitting tensile strength. Secondly, under hybrid doping, BF was partially substituted for SF to improve the mechanical properties of hybrid fiber UHPC. Consequently, when the BF replacement rate increased, the compressive strength of UHPC gradually decreased; on the other hand, there was an initial increase in the fracture energy, splitting tensile strength, and flexural strength. The ideal mixture was 0.5% BF + 1.5% SF. The fluidity of UHPC with 1.5% BF + 0.5% SF became the lowest with a constant total volume of 2%. The microstructure of hydration products in the hybrid fiber UHPC became denser, whereas the interface of the fiber matrix improved. [ABSTRACT FROM AUTHOR]

Reflection cracks are one of the most common problems in semi-rigid base pavement. Setting a stress absorption layer can effectively delay the occurrence of reflection cracks, but further improvement is still needed in its interlayer bonding performance and anti-reflection crack performance. Considering the excellent crack resistance of basalt fibers and the good elastic recovery ability of rubber asphalt, it is considered worthwhile to incorporate them into traditional stress absorption layers to improve performance. To simulate the actual pavement layer effect, composite specimens consisting of a cement-stabilized macadam base + basalt fiber rubber asphalt stress-absorbing layer + AC-20 asphalt mixture surface layer were prepared to evaluate their performance through interlayer direct shear tests, interlayer tensile tests, three-point bending tests, and overlay tests (OTs). To determine the optimal fiber blending combination, four fiber lengths (3 cm, 6 cm, 9 cm, 12 cm) and four fiber proportions (120 g/m2, 140 g/m2, 160 g/m2, 180 g/m2) were selected respectively. The specific effects of basalt fibers with different lengths and dosages were analyzed. The results show that compared with the absence of fibers, the improvement of interlayer bonding performance of rubber asphalt with basalt fibers is not significant, and it has certain limitations; however, the improvement of anti-reflective crack performance is significant, with an increase of up to 305.5%. This indicates that the network structure formed by basalt fibers and rubber asphalt stress absorption layer can effectively absorb and disperse external loads, causing an excellent crack resistance effect. Meanwhile, the results indicate that the main factor affecting its interlayer bonding strength and anti-reflective crack performance is the fiber content. Based on the comprehensive analysis of the performance and economy of the stress absorption layer of basalt fiber rubber asphalt, the optimal fiber parameter combination recommended is as fiber length 9 cm and fiber content 160 g/m2. These results can provide a reference for the design and performance evaluation of basalt fiber rubber asphalt stress absorption layer, and have certain application value. [ABSTRACT FROM AUTHOR]

In order to study the effects of composite fiber on the performance of cold-mixed mixture of epoxy and SMA-10 asphalt, basalt fiber (BF) and polyester fiber (PF) codoping were carried out to analyze the effects of various composite fiber ratios on the high temperature performance, low temperature crack resistance, water stability, fatigue resistance, and aging resistance. A two-dimensional numerical model of asphalt mixture was constructed by digital image processing and discrete element simulation technology. The skeleton characteristic parameters of discrete element model were extracted to determine the optimal fiber blending length. The fiber contents were 0. 3%PF, 0. 2%PF+0. 1%BF, 0. 2%BF+0. 1%PF, and 0. 3%BF. The results show that the road performance, anti-fatigue performance and anti-aging performance of 0. 3% basalt fiber are better than that of 0. 3% polyester fiber. Among them, 0. 2%BF+0. 1%PF has the best performance improvement. Compared with single-doped polyester fiber and basalt fiber, the dynamic stability of 0. 2%BF+0. 1%PF increases from 37 058 timesµmm-1 and 42 000 timesµmm-1 to 45 000 timesµmm-1, an increase of 21. 4% and 7. 1%. The flexural tensile strength increases from 29. 01 MPa and 30. 53 MPa to 32. 08 MPa, an increase of 10. 6% and 5. 1%. The fatigue life under 650 strain condition increases from 1. 63 million times and 1. 83 million times to 1. 97 million times, indicating a increase by 20. 9% and 7. 7%, respectively. The codoping of mixed fiber in the cold mix epoxy SMA-10 asphalt mixture can improve its road performance, and the mixed effect of basalt fiber and polyester fiber is better than that of single fiber. [ABSTRACT FROM AUTHOR]