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Asphalt in damp-heat and saline-alkali areas is prone to damage, which resulting in fatigue failure of the mixture. However, the aging damage of asphalt in these areas has not been paid enough attention, and there is a lack of effective evaluation method for asphalt's fatigue performance. In this paper, the base asphalt and SBS-modified asphalt were immersed in several solutions (water, NaCl and Na2CO3) to simulate aging conditions and the frequency sweep test was employed to determine the viscoelasticity properties of the asphalt. And the fatigue properties of the asphalt were analysed by the simplified viscoelastic continuum damage model. The microstructural and chemical evolution of asphalt was investigated by SEM, FTIR, the pH value and total organic carbon tests. After being immersed, the anti-deformation properties of two asphalts were strengthened. The solution erosion led to an increased loss rate of the integrity factor C*, and resulting in weakened fatigue properties of asphalt. The oxygen-containing functional group gradually increased with the extension of immersion. There were chemical interactions in addition to physical interface disruption during the immersion process. Moreover, the influence of Na2CO3 solution on asphalt ranked first due to the highest molar concentration of Na+ and the OH− produced by hydrolysis of ${\rm CO}_3^{2-}$ C O 3 2 − . [ABSTRACT FROM AUTHOR]

High-temperature rutting is one of the common forms of pavement damage. To further improve the high temperature performance of crumb rubber modified asphalt (CRMA) pavement, heavy calcium carbonate (HCC) modified by sodium pyrophosphate was combined with crumb rubber to prepare composite modified asphalt binder. Their physical properties, viscoelastic properties and chemical composition were investigated through conventional physical tests, DSR, FTIR and fluorescence microscopes. The results show that with the increase of HCC content, the mixing and compaction temperatures of composite modified asphalt binders continued to increase. Further, the high temperature performance and fatigue resistance of binders were better than the original CRMA, due to the enhanced lipophilicity of HCC after modification. It can be found from the FTIR spectrum that the addition of HCC only existed in physical action. However, excessive HCC would cause agglomeration of the asphalt matrix, so the optimum dosage of HCC was determined to be 4%. [ABSTRACT FROM AUTHOR]

To reduce vehicle exhaust gas pollution in transport-intensive roadways and tunnels, six types of photocatalytic asphalt binders were designed using graphite-phase carbon nitride (g-C3N4) and nanoscale titanium dioxide (nano-TiO2) particles. In this paper, the rheological behaviors and fatigue life of the nano-TiO2-modified asphalt binder (TiO2-MA) and g-C3N4-modified asphalt binder (C3N4-MA) were investigated. NO degradation capacity of six types of photocatalytic asphalt binders was characterized under visible light conditions. The results showed that TiO2-MA had more excellent rheological behaviors and rutting resistance than C3N4-MA. In addition, 4 wt% nano-TiO2 markedly improved the rheological behaviors and rutting resistance of MA compared to other dosages. TiO2-MA exhibited higher fatigue resistance. The fatigue life of TiO2-MA with 4 wt% nano-TiO2 was increased to 234.1% at 2.5% strain and 242.5% at 5% strain, respectively, compared to base asphalt binder (BA). C3N4-MA had better NO degradation capacity than TiO2-MA. Meanwhile, the NO degradation efficiency of C3N4-MA reached 17.8% with 5 wt% g-C3N4. [ABSTRACT FROM AUTHOR]

Near the coast of China, a large amount of sediment is produced during construction work. In order to mitigate the environmental damage caused by sediment and enhance the performance of rubber-modified asphalt effectively, solidified silt material and waste rubber were prepared to modify asphalt, and its macroscopic properties, such as viscosity and chemical composition, were determined via a routine physical test, DSR, Fourier Transform Infrared Spectroscopy (FTIR), and Fluorescence Microscopy (FM). The results show that, with the increase in powder particles and the addition of a certain amount of hardened mud, the mixing and compaction temperature of modified asphalt can be significantly increased—still reaching the design standard. In addition, the high thermal stability and fatigue resistance of the modified asphalt were clearly better than those of the ordinary asphalt. From the FTIR analysis, rubber particles and hardened silt only exhibited mechanical agitation with the asphalt. Considering that excessive silt might result in the aggregation of matrix asphalt, the addition of an appropriate amount of hardened solidified silt material can eliminate the aggregation. Therefore, the performance of modified asphalt was optimum when solidified silt was added. Our research can provide an effective theoretical basis and reference values for the practical application of compound-modified asphalt. Therefore, 6%HCS(6:4)-CRMA have better performance. Compared to ordinary rubber-modified asphalt, the composite-modified asphalt binder has better physical properties and a more suitable construction temperature. The composite-modified asphalt uses discarded rubber and silt as raw materials, which can effectively protect the environment. Meanwhile, the modified asphalt has excellent rheological properties and fatigue resistance. [ABSTRACT FROM AUTHOR]

Cow dung waste has caused severe environmental pollution and public health issues in China. In this study, the cow dung residues were used as a cheap renewable fiber to modify asphalt binder, providing a new solution for the proper disposal of cow dung waste. Three cow dung fibers with two lengths were prepared using different treatments, including original cow dung fiber (CDF), surface treatments of cow dung fiber (STCDF) and alkali treatments of cow dung fiber (ATCDF). The physicochemical properties of CDF, STCDF and ATCDF were analyzed by scanning electron microscope (SEM) and thermogravimetry (TG). The viscidity, rheological properties and fatigue characteristics of CDF modified asphalt binders (CDFMA) were evaluated using Brookfield viscometer and dynamic shear rheometer. The results showed that the rough surfaces of STCDF and ATCDF improved their thermal stability. STCDF and ATCDF enhanced the resistance to permanent deformation under high temperature conditions of modified asphalt binder. STCDF modified asphalt binders exhibited the best viscosity and rheological performance. The increase of fiber length was positively correlated with the high temperature deformation resistance of CDFMA. CDF, STCDF and ATCDF inhibited fatigue cracking of modified asphalt binders compared to base asphalt binders. ATCDF modified asphalt binders exhibited higher fatigue life and smaller crack under the same cyclic loading. The increase in fiber length had a slight improvement on the fatigue resistance of modified asphalt binders. [ABSTRACT FROM AUTHOR]

Waterborne epoxy-resin-emulsified asphalt (WEREA) has excellent adhesion and can be used as a good waterproofing tack coat; however, there are some problems such as the poor compatibility between the waterborne epoxy and the emulsified asphalt, and the brittleness of the cured material. In the present work, oxidized furfural extract oil was used as a compatibilizer to prepare the waterborne epoxy emulsion and waterborne epoxy-resin-emulsified asphalt, and their modification effects were studied. The extraction oil was oxidized with potassium permanganate. The effects of oxidized extraction oil on the waterborne epoxy-resin-emulsified asphalt performance were investigated through experiments on viscosity, mechanical properties, and aging resistance. Combined with infrared spectroscopy and fluorescence microscopy, the compatibility and microstructure of the oxidized extraction oil modified WEREA were observed and analyzed. The result showed that the carboxyl group was introduced into the chemical structure of the extraction oil after oxidation. Oxidized extraction oil (OEO) and waterborne epoxy resin (WER) had good compatibility. When the content of OEO in the WER is 21%, the elongation at break of the WER can reach up to a maximum of 91.5%, and has a significant increase of 33.2%. OEO can significantly improve the elongation at the break and aging resistance of WEREA, especially when the mix ratio of oxidized extraction oil and epoxy resin was 6:5, when the breaking elongation of WEREA can be increased by 69%, and the compatibility between the epoxy resin and emulsified asphalt was the best. Moreover, the loss in elongation at the break of aged WEREA decreased from 13.7% to 4.9%. [ABSTRACT FROM AUTHOR]

• The compaction process of asphalt mixture was simulated in the laboratory. • The migration and rotation characteristics of aggregate particle was analyzed during asphalt mixture compaction. • The development of surface texture was explored during asphalt mixture compaction. • The compaction mechanism of asphalt mixture was discussed in combination with the Stribeck curve. Pavement performance is not only affected by materials and production but also by compaction quality. This paper investigates the migration and rotation law of coarse aggregate during asphalt mixture compaction using the statistical means based on 2D image analysis. The variation of surface texture during compaction was extracted by laser scanner, and its anti-sliding performance was tested. The compaction mechanism was then discussed in combination with the Stribeck curve. The results show that mixtures with different gradations required different compaction energy during compaction, the AC-13 mixture was easier to compacted than the SMA-13. The aggregate contact developed rapidly in the early compaction stage in the horizontal direction but increased gradually in the vertical direction. With the compaction, the radial angle of the aggregate tended to be consistent in the horizontal direction and the major axis of the aggregate approached to the horizontal axis in the vertical direction. At the same time, the aggregates on the surface of the mixture were embedded with each other with compaction, and the surface structure gradually decreased. Combined with the aggregate contact, asphalt mortar viscosity and the Stribeck curve theory, the compaction process of asphalt mixture could be divided into pre-mixed lubrication dominated by asphalt lubrication and post-mixed lubrication dominated by aggregate contact. The research results offer a reliable basis for studying the compaction mechanism and improving the construction quality control of the asphalt pavement. [ABSTRACT FROM AUTHOR]

For the preventive maintenance engineering of special pavements such as ultra-thin friction courses and bridge deck pavements, the performance requirements of the utilized high-viscosity asphalt, including the resistance to permanent deformation, cracking ability, durability, and recyclability, are becoming increasingly stringent. In this study, based on the click reaction principle of carbon-carbon double (C C) bond, hydroxyl-terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) were selected as the raw materials to synthesize thermoplastic polyurethane (TPU), and then 4,4'-disulfanediyldiphenol (DSDDP) was introduced as the chain extender to design a high-viscosity thermoplastic polyurethane modified asphalt (PUA). Subsequently, the mechanical and rheological properties of PUA under different types of chain extenders and polyurethane (PU) contents were tested, and the microstructure and modification mechanism were investigated at multiple scales. The results indicated that after the introduction of DSDDP, the basic physical properties and viscosity of PUA were greatly enhanced, the fluidity was significantly reduced, and excellent deformation and cracking resistance were achieved at various temperatures. The microscopic tests revealed that the viscosity enhancement effect mainly originated from the click reaction between the disulfide (S-S) bonds in DSDDP and the C C bonds on the soft segments of PU, which can further crosslink the linear PU molecular chain and form a dense spatial network structure to restrict the flow of macromolecules. The dynamic exchange of some S-S bonds facilitates the repetitive opening of the PUA network structure at high temperatures, so the PUA still exhibits thermoplasticity at high temperatures, which verifies the feasibility of the proposed design. Moreover, the addition of DSDDP reduced the degree of microphase separation of PUA, so the designed PUA can effectively adapt to various temperature environments. Overall, the findings of this study can boost the application of this novel PUA in the thin surface layers of high-performance pavements. [Display omitted] • The click reaction principle is applied to polyurethane modified asphalt (PUA) system. • Formed carbon-sulfur bonds provide PUA with high viscosity and excellent mechanical properties. • The PUA has a thermoplastic three-dimensional network structure that is partially reversible. • The designed PUA is a suitable material for high-performance pavement surface thin layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A CR/polyurethane modified asphalt sealant was prepared by the in-situ polymerization method. • The high and low temperature rheological properties of sealant were all excellent. • The PU phase was uniformly dispersed in asphalt quantified by fluorescence images. • The sealant has achieved great effects in the treatment of pavement cracks on site. Under the long-term effect of loads and climate conditions, various diseases can appear on the surface of asphalt pavement, causing deterioration in its performance. To address the pavement surface cracks during service, the present study developed a crumb rubber/polyurethane (CR/PU) compound as the modified asphalt sealant with excellent properties. The optimal material proportion, ensuring the best asphalt compatibility was selected to meet the requirements of standard hot-poured sealants for pavement. Additionally, the fineness and content of CR were determined. The research investigated rheological properties, aging performance, microstructure, and modification mechanism of the CR/PU sealant was then applied in an engineering project to evaluate its effectiveness in treating pavement cracks, and suitable construction techniques were summarized. The results revealed that the in-situ polymerization method is an appropriate approach for preparing the CR/PU sealant, demonstrating good high-temperature deformation resistance and low-temperature crack resistance, indicating synergistic interactions between CR and PU. Among various compositions, the sealant with 30 %PU and 15 %CR content exhibited the best thermal oxygen and UV aging properties. Microscopic tests indicated that CR was physically blended with asphalt, while PU underwent chemical modification and formed a cross-linked network structure with asphalt, resulting in CR dispersion around it, enhancing the thermal stability of the system. Furthermore, the test section displayed an ideal crack treatment effect, demonstrating the sealant's excellent sealing, durability, and watertight capacity. [ABSTRACT FROM AUTHOR]

• Quantitative determination for SBS content of aged modified asphalt by FTIR and potentiometric titration tests. • The rheological properties were investigated after TFOT and long-term aging of modified asphalt. • The actual SBS content versus the rheological indexes of aged modified asphalt can be well-fitted. The content of styrene–butadiene–styrene (SBS) modifier has a significant influence on the physical and chemical characteristics of asphalt. However, determining the SBS content in SBS modified asphalt (SBS MA) after aging remains a challenge. To facilitate the understanding of the relationship between physical properties and SBS content, the Fourier transform infrared (FTIR) and potentiometric titration test were utilized to detect SBS content of aged binders. In this paper, radial and linear SBS were incorporated into asphalt binders at three levels, and their rheological properties were investigated after thin film oven aging (TFOT) and long-term aging. Furthermore, the actual SBS content versus the rheological index at different aging stages was investigated. The results showed that both I C=C and Na 2 S 2 O 3 titration volume highly correlated with SBS content (R2 > 0.99), and there was only a slight difference between the actual content of SBS determined by the two methods. The fatigue resistance, high-temperature elastic, and low-temperature cracking characteristics of asphalt were weakened after aging, due to SBS degradation, especially in the early stage. In addition, the resistance to deformation, elastic recovery, anti-fatigue properties of radial SBS MA were superior to that of linear SBS MA at the same SBS content, while the low-temperature cracking performance demonstrated an opposite trend. The actual SBS content versus the rheological indexes after aging can be well-fitted by a nonlinear equation. Therefore, FTIR and potentiometric titration tests can effectively predict SBS content and analyze the aging degree of SBS MA. [ABSTRACT FROM AUTHOR]

• CN pcf promotes the majority of coarse aggregates to form a well-embedded skeleton. • Optimum contents of dominant structure and disturbing aggregates were determined. • Correlation of CN pcf with contact zones (CZ) can describe internal structural features. • Mann-Whitney U test verified stability of the dominant skeleton with the appropriate level of CN pcf for resisting permanent rutting. Optimizing asphalt mix design at the indoor stage is of significant importance for enhancing the rutting resistance of asphalt mixture, which is affected by its structural characteristics. In this work, the coordination number of particle contact force (CN pcf) was proposed as an indicator to represent contact characteristics of skeleton structure aggregates in asphalt mixture. Nine asphalt mixtures with different gradations were designed, and the relationship of CN pcf with the number of aggregate contact zones (CZ) was established by combining rutting tests and digital image processing technique (DIP). The Mann-Whitney U test was implemented to analyze the distribution properties of inter-particle contacts before and after the rutting test. In addition, the resistance to the further expansion of rutting was analyzed. The results revealed a significant positive correlation (PCCs = 0.843, R 2 = 0.711) between CN pcf and CZ. The content of coarse aggregates in the dominant structure did not exhibit monotonic related to anti-rutting performance of the asphalt mixture. Therefore, an optimum aggregate content of 57% was utilized. The Mann-Whitney U test revealed that the mesoscale skeleton structure of the asphalt mixes before and after rutting exhibited excellent stability. This study further indicated the applicability of combining CN pcf to adjust the mix design to enhance the rutting resistance of asphalt mixture and to prevent rutting expansion in flexible pavement. [ABSTRACT FROM AUTHOR]

During the aging process, the desulfurization and degradation process of crumb rubber modified asphalt binders (CRMA) consistently occurs. In this paper, a toluene insoluble test, an electrochemical titration method, viscosity, FTIR and GPC were developed to determine the effective crumb rubber content of CRMA after exposure to various aging conditions. Centering on efficiency and accuracy, these five methods were compared with the Pearson coefficient method. The results show that when the degree of aging was severe, the desulfurization and degradation of rubber were aggravated, causing the C C bond in the rubber to break and an increase in the large molecular weight of the asphalt binder. The effective rubber content in the aged CRMA was 7.7–14.2% less than the unaged CRMA. At the same time, the correlation coefficients among the five methods were all above 0.90, but the electrochemical titration and FTIR had priority over the other methods. • Aging will accelerate the degradation of rubber in modified asphalt binder. • The effective rubber content using electrochemical titration and FTIR are quantitative evaluated. • GPC and mass methods have certain man-made errors. • The Pearson correlation coefficients of methods are all over 0.9. [ABSTRACT FROM AUTHOR]

• The freeze-thaw cycle caused the complex modulus of asphalt binders to decrease and the phase angle to increase. • The influence of freeze-thaw cycles on SBS modified asphalt binder was more obvious than that of base asphalt binder. • The creep recovery rate of SBS modified asphalt binder was reduced, opposite to that of base asphalt binder. Perennial freeze-thaw cycles have caused frequent disasters on asphalt pavements. To investigate the effect of four types of freeze-thaw cycles on asphalt binders, the DSR and FTIR test results of #70 Jinlin base asphalt binder (J binder) and SBS modified asphalt binder (S binder) were studied. The rutting factor, creep compliance and fatigue life of binders after freeze-thaw cycles were evaluated first, and then the chemical composition was analyzed. The results show that multiple freeze-thaw cycles lead to a growth in the complex modulus of asphalt binders, but the phase angle of S binder did not decrease significantly. The attenuation of fatigue life of S binder was significantly higher than that of J binder, and there was a certain dependency on fatigue parameters and freeze-thaw damage based on the S-VECD model. Furthermore, after the freeze-thaw cycle, the creep recovery of S binder decreased, while that of J binder increased, due to the increased elasticity by the oxidation of J binder. Carbonyl index (CI) and sulfoxide index (SI) of binders gradually grew with the number of freeze-thaw cycles, and butadiene index (BI) of S binder also slightly decreased. In general, during repeated freezing and thawing, low temperature had a certain adverse influence on the binders, but it is lower than that caused by high temperature. [ABSTRACT FROM AUTHOR]

The utilization of processed waste materials in road construction is of utmost significance from the environmental and economic viewpoints. In this paper, waste cooking oil (WCO) and ground tire rubber (GTR) were applied to modify the asphalt binder. Based on the optimal content of both modifiers, sixteen asphalt samples with different combinations of the two wastes were designed. Relevant tests including basic properties along with rheological behavior and chemical characterization were carried out on the modified asphalt. The results indicated that the modified asphalt with 20 wt % GTR and 2.5 wt %-5 wt. % WCO exhibited satisfactory high temperature resistance and low temperature rheological properties. The Fourier transform infrared spectroscopic investigation revealed that the presence of GTR increased the concentration of styrene and butadiene while the addition of WCO introduced fatty acids and esters to modified asphalt. Overall, the road performance studies demonstrate that modified asphalt mixture with 5 wt % WCO and 20 wt % GTR displayed a markedly improved anti-rutting properties, water stability and superior low-temperature performance compared to normal asphalt mixture. • The molecular structures of WTO/GTR-modified asphalt were analyzed. • Asphalt modified with an appropriate amount of GTR and WCO exhibited optimum properties. • GTR increased the concentration of functional groups in modified asphalt binder. • WCO introduced fatty acids and esters to modified asphalt binder. • WTO/GTR-modified asphalt mixtures showed a promising application in road industry. [ABSTRACT FROM AUTHOR]