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To interpret the diffusion behavior of oxygen in epoxy asphalt with different cross‐linking degrees, epoxy asphalt‐oxygen diffusion layer models were constructed. The effect of temperature on oxygen diffusion and the number of oxygen molecules penetrating the epoxy asphalt was quantitatively analyzed. Fick's second law was used to determine the oxygen diffusion coefficient. The Mean square displacement (MSD) was extracted to analyze the effect of cross‐linking degree on the molecular motion of the base asphalt. The results show that as the cross‐linking degree increases, the number of oxygen in the epoxy asphalt decreases, accompanied by a reduction in the oxygen diffusion coefficient. Temperature significantly affects the rate of oxygen diffusion, with higher temperatures leading to greater diffusion depths over the same simulation time. The oxygen diffusion coefficient of epoxy asphalt ranges from 4.60 × 10−11 to 2.20 × 10−10 m2/s at temperatures of 298–373 K. The epoxy system markedly restricts the movement of base asphalt molecules, with saturate being most affected by cross‐linking degree and asphaltene the least. A high cross‐linking network impedes the asphalt‐oxygen contact oxidation, enhancing epoxy asphalt's anti‐aging capacity. These findings provide support for optimizing epoxy asphalt formulations and guiding the development of anti‐oxidant epoxy asphalt. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To study the effects of curing agent ratio, asphalt content, and crosslinking degree on the properties and distribution of epoxy asphalt with a compound system of dicarboxylic acid and acid anhydride, epoxy asphalt molecular models with two asphalt contents of 25% and 65% and three curing agent ratios of 10:1, 5:1 and 1:1 were constructed by Materials Studio. Various epoxy resin crosslinking degrees were further realised by Perl language crosslinking script. Glass transition temperatures were calculated to characterise low temperature flexibility. Energy systems and interaction energy were simulated to characterise the compatibility of epoxy asphalt. The radial distribution function (RDF) was calculated to observe the composition distribution of epoxy asphalt. The results show that the raise of the crosslinking degree and the proportion of anhydride curing agent increased the Tg of epoxy asphalt, impairing the low temperature performance. The increase in asphalt content was beneficial to the stability of the epoxy asphalt. Resin-based epoxy asphalt had stronger interaction between epoxy resin phase and asphalt phase, and the interaction energies both reached the maximum values at crosslinking degree of around 25%. Resin-based and asphalt-based epoxy asphalt had the most notable composition difference in the distribution of asphaltenes and acid anhydrides. [ABSTRACT FROM AUTHOR]

This research focused on the stabilisation of anhydride-cured epoxy asphalt (EA) over thermal-oxidative aging. EA binders with graduated Irganox 1010 antioxidant contents at 0, 0.3, 0.6, 0.9, and 1.2 wt% were prepared and then subjected to accelerated oven-conditioning aging at 85 and 100°C. The thermal stability, viscosity, mechanical parameters, and chemical structure of EA containing Irganox 1010 were evaluated during aging. The results showed that Irganox 1010 contributed to enhanced thermal stability, higher initial viscosity, and longer allowable construction time for EA. The 0.3–0.9 wt% Irganox 1010 had good compatibility with EA without weakening performance. During aging, Irganox 1010 effectively restrained degradation of the EA binder's mechanical properties and the EA mixture's low-temperature deformation. The variations of functional groups indicate that Irganox 1010 prominently restrained the oxidation of the asphalt phase and lightly affected the post-curing of the resin phase. There was a strong correlation between decreasing rate of bending strain of the mixture and increasing rate of sulfoxide in the binder. The mutual synergistic effect of resin and antioxidant improves the oxidation resistance of asphalt. Considering the aging improvement and economic cost, it is recommended to use 0.6 wt% Irganox 1010 as an antioxidant for anhydride-cured EA. Highlights Epoxy asphalt (EA) binder and mixtures incorporating antioxidant Irganox 1010 were analysed. Irganox 1010 plays a crucial role in aging protection effect of EA binder and mixture. Irganox 1010 antioxidant prominently restrains the oxidation of the asphalt phase and lightly affects the post-curing of the resin phase. There was a strong correlation between the bending strain of mixture and sulfoxide of binder. Addition of 0.6 wt% Irganox 1010 is recommended as an antioxidant for EA materials. [ABSTRACT FROM AUTHOR]

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 Tg 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Anhydride-cured epoxy asphalt (AC-EA) is an asphalt/resin two-phase system, the properties of which are affected by the asphalt and resin contents. This study aims to investigate the effect of asphalt content on the tensile properties, hardness, dynamic mechanical parameters, chemical components, and microscopic structure of AC-EA through experimental methods. Thermal aging resistance and mechanism of AC-EA with the asphalt content of 25%, 35%, 45%, 55%, and 65% were also investigated. The results show that as the asphalt content increased from 25% to 65%, the tensile strength and hardness of AC-EA binder increased first and then decreased, the elongation decreased, the glass transition temperature (Tg) rose, and the carbonyl absorption band changed from a single peak to double peak. The absorption bands of aromatic ether and sulfoxide in AC-EA binder overlapped with each other. The carbonyl ester index (CEI) and sulfoxide index (SI) showed a good linear correlation with the asphalt content. Besides, phase inversion occurred in the AC-EA system when the asphalt content was between 45% and 55%. AC-EA binder with an asphalt content less than 45% is a resin-based composite, and that with the asphalt content higher than 45% is an asphalt-based composite. At the thermal aging process, AC-EA binders with asphalt content higher than 45% were more likely to cause significant changes in the tensile parameters, hardness, and modulus than those with asphalt content less than 45%, indicating that the existence of the resin network can reduce the sensitivity of AC-EA to oxidation. After aging, Tg of resin-based composites increased, whereas that of asphalt-based composites decreased. The Fourier transform infrared (FTIR) and scanning electron microscope (SEM) analyses indicated that the AC-EA binder had both postcuring and oxidative degradation during thermal aging. The postcuring was dominant in the resin-based AC-EA composite, whereas the oxidative degradation was dominant in the asphalt-based composite. [ABSTRACT FROM AUTHOR]

In order to explore the effect of composite curing agent ratio on the photooxidative aging behavior of epoxy asphalt with an acidic composite curing system, three curing agent ratios of epoxy asphalt were prepared to obtain different cross-linking network densities. The prepared epoxy asphalt was subjected to photooxidation aging for 240 h at 60 ℃. Fourier transform infrared (FTIR) and elemental analysis tests were conducted to determine the evolution of chemical components during photooxidative aging. Based on the chemical components before and after aging, molecular models of photooxidation aged epoxy asphalt with different curing agent ratios were constructed. The mean square displacement (MSD) of oxygen atoms and the oxygen uptake of each component were calculated to study the diffusion behavior of oxygen atoms and the oxidation degree of each component under various cross-linking networks. Glass transition temperature (Tg) and interaction energy were determined to characterize the thermodynamic properties and interaction between asphalt phase and epoxy resin phase of epoxy asphalt before and after aging. The radial distribution function (RDF) was determined to simulate the distribution of asphaltene and epoxy resin crosslinked networks in different cross-linking networks. The results show that the formation of carbonyl groups, alcohol hydroxyl groups, and the fracture of methylene groups was observed during the photooxidative aging process of epoxy asphalt. The rise in the proportion of anhydride curing agents improved the stability of the chemical components in epoxy asphalt under photooxidation aging. High cross-linking density and methylene fracture weakened the diffusion ability of oxygen atoms in epoxy asphalt due to a reduction in free volume. In addition, photooxidation aging had a negative impact on the low-temperature performance and interaction between asphalt phase and epoxy resin phase of epoxy asphalt. However, a high content of acid anhydride alleviated the damage of photooxidation aging to low-temperature performance. Photooxidation aging developed the polar functional groups of epoxy asphalt, promoting the stacking of asphaltene under a high content of dicarboxylic acid curing agent, while breaking the stacking of asphaltene under a high content of acid anhydride curing agent. • High content of anhydride improved the stability of chemical components during aging. • The photooxidative aging process of epoxy asphalt was successfully simulated. • A dense cross-linked network resisted the diffusion of oxygen atoms effectively. • A dense cross-linking network benefited aging resistance of epoxy asphalt. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation technology was introduced into the characterization of epoxy asphalt performance, to display the reaction process between the epoxy resin and curing agent in epoxy asphalt clearly and explore the influence of epoxy resin content and conversion rate on the epoxy asphalt performance containing thermodynamic, compatibility, component distribution and diffusion. The reaction between the epoxy resin and curing agent was realized through Perl script, and epoxy asphalt molecular dynamics models with different resin content (25%, 45%, and 65%), and various conversion rates were prepared. Results demonstrated that the addition of epoxy resin enhanced the low-temperature performance of epoxy asphalt, but the increase in conversion rate played a negative impact on low-temperature performance. The CED and solubility parameter were synergistically affected by the epoxy resin content and conversion rate. Furthermore, the raise in the content of epoxy resin was the main reason for enhancing the compatibility between epoxy resin and asphalt. Therefore, the reasonable control of the resin content and conversion rate was beneficial to enhance the stability of the epoxy asphalt system and improve the compatibility between the resin phase and the asphalt phase. 25%-EA and 45%-EA were considered as asphalt phase materials. Aggregation behaviors exhibited between asphaltenes, and adsorption behaviors presented between epoxy resin and asphaltene. With the increase of conversion rate, the adsorption behavior gradually disappeared. 65%-EA belonged to the resin phase material, and the aggregation between asphaltenes was diminished. In addition, the epoxy resin without conversion reaction had the smooth diffusion behavior in epoxy asphalt. [ABSTRACT FROM AUTHOR]

Selecting an epoxy asphalt (EA) material with excellent low-temperature performance is a challenging task due to that the traditional test methods and indicators for thermoplastic asphalt may not be appropriate for thermosetting EA, and the binders' low-temperature performance does not always match that of mixtures. The primary purpose of this study is to determine the appropriate low-temperature evaluation methods and indexes of EA materials and the correlation between the low-temperature performance of EA binder and EA mixture (EAM). First, the low-temperature performance of four EA binders was analyzed using tensile, bending beam rheometer (BBR), and dynamic mechanical analysis (DMA) tests. Then, the low-temperature cracking resistance of the EAMs was evaluated through beam bending and semi-circular bend (SCB) tests. Finally, Pearson correlation analysis was performed separately on the low-temperature indicators of EA binders and EAMs. Moreover, the Grey correlation analysis was employed to determine the correlation between the low-temperature properties of the two. The results showed that the correlation between fracture elongation (ε) and other test indicators was not significant. The multiple indicators of the BBR, such as viscoelastic parameters, viscous deformation ratio (J R), along with the glass transition temperature (T g) of the DMA, showed consistent evaluation results for the low-temperature performance of the four EA binders. However, the correlation of these indicators with the cracking resistance of the EAM was notably different. The flexural strain energy density of the beam bending test and SCB fracture energies demonstrated excellent correlation. The grey correlation analysis results of these two indicators as reference series were highly similar. Specifically, the novel J R in this study and the T g exhibited a better correlation with the low-temperature cracking resistance of EAM. These two indicators were preferentially recommended for the evaluation of the low-temperature performance of EA and the prediction of the low-temperature cracking resistance of EAM. • The low-temperature performance of four types of epoxy asphalt binders and their mixtures is analyzed. • The Pearson correlation analysis is performed separately on the low-temperature indicators of EA binders and EAMs. • The Grey correlation analysis is employed to analyzed the low-temperature performance of epoxy asphalt binders. • A feasible novel indicator, the viscous deformation ratio (J R) obtained from the BBR test, is proposed. [ABSTRACT FROM AUTHOR]