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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]

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]

• 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]

• 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]