Zhaohui Min

High-modulus asphalt mixtures (HMAMs) achieve high stiffness but exhibit insufficient resistance to low-temperature cracking. To balance high- and low-temperature performance, HMAMs containing 0.3%, 0.6%, and 1.0% high-modulus modifier (HMM) were toughened with a styrene–butadiene-based polymer (SBP) through a dry process. The toughening behavior and mechanisms were investigated at different SBP dosages (0.2%, 0.4%, and 0.6%) and conditioning times using mixture tests, binder rheological characterization, individual and co-swelling tests, and molecular dynamics simulations. Increasing HMM content substantially improved dynamic modulus and rutting resistance but continuously reduced low-temperature bending strain. At 0.4%, SBP provided favorable strength–deformation compatibility, increasing bending strain by 76.1%, 75.3%, and 63.2% in the three HMM systems, respectively. The optimal conditioning time extended from 30 min (0.3% HMM) to 60 min (0.6% and 1.0% HMM). The 0.6% HMM–0.4% SBP combination exhibited the most balanced overall performance. Rheological results showed that HMM enhanced high-temperature elasticity, whereas SBP reduced low-temperature creep stiffness and improved stress relaxation. With limited availability of light fractions, increasing HMM from 0.3% to 1.0% reduced the swelling ratio of SBP from 114.87% to 62.30%. Molecular simulations further showed that HMM–light fraction interactions increased, whereas the magnitude of the SBP–light fraction interaction energy decreased by 13.2%. These findings suggest that competition for limited light fractions may contribute to the HMM-dependent toughening response, providing a basis for further investigation of material composition and conditioning requirements.

The high- and low-temperature performance of asphalt-based seamless expansion joints seriously affects road performance. The purpose of this paper is to explore the application of thermosetting epoxy asphalt-based materials in bridge expansion joints. The composite modification of asphalt was performed using Styrene–Butadiene rubber (SBR) and Styrene–Butadiene–Styrene (SBS) copolymer. The study then investigates the impact of five different dosages of SBR/SBS-modified asphalt on the performance of epoxy asphalt. The results of the cone penetration test, tensile test, and stress relaxation test of SBR/SBS-modified epoxy asphalt (SSEA) and BJ200 (a commercial Seamless expansion joint material) were comparatively analyzed. The Marshall test, rutting test, three-point bending test, and freeze–thaw split test were used to evaluate the road performance of SSEA mixtures. The test results show that with the increase in asphalt content, the shear resistance and tensile strength of SSEA decrease, and the low-temperature relaxation ability and elongation at break increase. The content of SBR/SBS-modified asphalt has a positive effect on the low-temperature performance of SSEA mixtures, and the residual stability in water and freeze–thaw splitting strength ratio (TSR) are higher than that of BJ200. Based on the requirement of balancing high and low-temperature performance, SSEA-3 has the best overall performance, and the dosage of SBR and SBS modifier is 12% and 2.5%, respectively. The ratio of epoxy resin, SBR/SBS-modified asphalt, and the curing agent is 1:4:1.6, and its use is recommended in areas with slight temperature differences.

This paper investigated the cross‐linking network structure of epoxy asphalt (EA) with the different ratio of composite curing agents, and further determined the effect of photooxidation aging on the tensile and interfacial adhesion behavior of EA with different cross‐linking network structures through molecular simulation. Based on the molecular models of EA and the interface model between EA and aggregate, the crosslinking network structural characteristics and tensile mechanical behavior were determined. The interfacial adhesion behavior and the mechanization were further studied. The results indicate that 20‐EA and 6‐EA have an epoxy resin cross‐linked network with uniform pore structure and phase distribution. 2‐EA showed a denser cross‐linking network and uneven aggregation phenomenon. Photooxidative aging alleviated the aggregation phenomenon. A dense cross‐linking network improved the tensile strength and the ability of tensile performance to resist photooxidation aging. The interface of EA‐quartz exhibited higher adhesion strength than EA‐calcite due to the closer distance and stronger nonbonding interactions between EA and quartz. The low anhydride content and photooxidation aging made EA approach to the aggregate interface, increasing nonbonding interaction and interfacial adhesion strength. In addition, quartz aggregates were more suitable for application in EA mixtures due to the higher interfacial adhesion strength and lower water sensitivity.

To study the influence of the cross‐linking network on the thermal oxygen aging performance of the epoxy asphalt, the laser copolymerization microscopy, Fourier transform infrared spectroscopy and element analysis tests were used to characterize the changes in chemical components of epoxy asphalt with composite curing system during thermal oxygen aging. According to the changes in chemical components, the epoxy asphalt molecular models were constructed. The diffusion behavior of oxygen atoms was analyzed, the aging degree was determined. Moreover, the T_g and radial distribution function were calculated to determine the effect of aging on the low‐temperature performance and component distribution of epoxy asphalt. The results show that a proper proportion of curing agent helped to uniform distribution of the asphalt phase. The rise in anhydride curing agent content increased the density of crosslinking network, limited the diffusion of oxygen atoms, and contributed to the resistance of epoxy asphalt chemical components to thermal oxygen aging. However, the high proportion of anhydride aggravated the oxidation reaction of the asphalt phase due to the uneven coating of the asphalt phase. After thermal oxygen aging, the distribution of asphaltene and epoxy resin phase showed a concomitant phenomenon due to polarity adsorption.

This research investigated the effect of ultraviolet absorber (UV‐531) on the properties of epoxy asphalt (EA) binders. EA binders were modified by adding UV‐531 absorber at contents of 0, 0.3, 0.6, 0.9, and 1.2 wt%, and composites were then subjected to ultraviolet (UV)‐based aging, including UV, oxygen, and heat treatment. Laboratory tests were conducted to assess UV absorption, viscosity, mechanical parameters, contact angle, microstructure, and chemical functional groups of absorber‐modified EA composites before and after aging. The results showed that the addition of UV‐531 resulted in enhanced UV absorption capacity, lower initial viscosity, and longer allowable application time for EA composites. The UV‐531 absorber has good compatibility with EA binders and does not weaken the performance of EA binders. From anti‐aging perspective, UV‐531 absorber effectively delayed the degradation of the physical, mechanical, and chemical structures of EA composites. The breakage of alkyl and ester groups of EA composites containing absorber was significantly reduced under aging conditions. Overall, the presence of UV‐531 retarded severe performance deterioration in EA composite. Considering aging improvement and economic cost, it is recommended to use a content of 0.9 wt% UV‐531 absorber as an anti‐aging agent for EA composites.