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[Display omitted] • The R (–NCO/–OH) has a significant effect on the properties of PUMA. • High-temperature performance: MOCA > BDO, low-temperature performance: BDO > MOCA. • The performance of PUMA increased significantly within 5 h at 105 °C. • PU was successfully synthesized in-situ in asphalt. • Chain extenders can help PU form long chains in asphalt. To improve the performance of ordinary road asphalt, and overcome the problems of poor thermal storage stability, easy segregation, and high preparation temperature of polymer-modified asphalt such as SBS (styrene–butadienestyrene block copolymer) or rubber powder. Polyurethane-modified asphalt (PUMA) was synthesized in-situ by the one-shot process with varying dosages of polyurethane (PU) raw materials (2.86 wt% ∼ 11.94 wt%) and isocyanate index R (–NCO/–OH) values (2, 3, 5, and 7) for a total of 12 samples, in this study. The material composition, development time, and modification mechanism of PUMA were analyzed using the approach of "macro performance + micro mechanism". Firstly, the conventional properties, rotational viscosity, and rheological properties of PUMA samples were evaluated and compared to virgin asphalt. Secondly, under the optimal material composition scheme, the conventional performance and thermal storage stability differences between MOCA (3, 3′ -dichloro-4,4′ -diamino diphenyl methane) and BDO (1,4-butanediol) were compared. Comparing the performance of PUMA during the development times of 0 to 12 h, the oven temperature is 105 °C. Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were used to analyze the chemical structure and spatial structure of PU in asphalt. The results indicate that: 1) the higher the R (–NCO/–OH), the higher the asphalt's high-temperature performance, elastic recovery performance, and viscosity, but the lower its low-temperature performance. 2) Under the same R (–NCO/–OH) condition, the increase in PU has little effect on the preceding performance. 3) MOCA is marginally superior to BDO in terms of high-temperature performance, whereas BDO has greater advantages in terms of low-temperature performance; compatibility is comparable. 4) At 105 °C, the performance continued to improve for 0 to 5 h, but after 5 to 12 h, the improvement was no longer noticeable. 5) Due to the reaction of the isocyanate group with the polyol and the active group in the asphalt, functional groups such as carbamate and urea are directly synthesized in the asphalt, allowing the PU molecular chain to expand and form a network structure within the asphalt. This procedure modifies the performance of the virgin asphalt. These findings not only improve our understanding of the effect of optimal material composition and development time on the properties of PUMA, but they also provide direction for future research. [ABSTRACT FROM AUTHOR]

[Display omitted] It has been reported that a novel multi-component styrene-butadienestyrene composite (SBSC) modifier composed of the SBS as the main content and additional components including ethyl-vinyl-acetate (EVA), maleic anhydride grafted with ethyl-vinyl-acetate (MAH-g-EVA), naphthenic oil, and antioxidant can be produced by melt blending. This SBSC modifier can be directly mixed with bitumen and aggregate to prepare bitumen mixture, thus thoroughly addressing inferior thermal storage stability of SBS-modified bitumen. However, it is necessary to explore the efficient utilization of the SBSC modifier due to its inadequate engineering application and poor dispersion when the SBSC modifier was added directly to the bitumen mixture. The objective of this research was to investigate the feasibility of using the SBSC modifier to obtain modified bitumen with acceptable thermal storage stability and other enhanced properties. Modified bitumens (SBSC-modified bitumens with 3, 4, 5, 6, 7 % SBSC modifier content, SBS-modified bitumen with 4.5 % SBS modifier content as the control sample) were prepared. The thermal storage stability of modified bitumen was investigated by the segregation test. Besides, the basic physical properties of modified bitumen were tested, including penetration, softening point, and ductility. The rheological properties were evaluated by temperature sweep test, multiple stress creep recovery (MSCR) test, rotational viscosity (RV) test and bending beam rheometer (BBR) test, respectively. Meanwhile, fluorescence microscopy and Fourier transform infrared (FTIR) spectrometer were also applied to characterize the microproperties of the modified bitumen. Results show that the difference in softening point of SBSC-modified bitumens with modifier contents ranging from 3 % to 7 % is less than 2.5 °C after 72 h of high temperature storage at 163 °C. The softening point and ductility of SBSC-modified bitumen increase considerably with the addition of the SBSC modifier but the decrements of penetration are not significant. Besides, with the increasing addition of the SBSC modifier, complex modulus, average percent recovery, and viscosity of modified bitumen all improve. Meanwhile, phase angle, non-recoverable creep compliance of modified bitumen decrease. The flexural creep stiffness also decreases with the increasing content of the SBS modifier. When the SBS content is the same, the SBSC-modified bitumen gets better thermal storage stability, high and low temperature properties than the SBS-modified bitumen. The microproperties show that the SBSC modifier can be uniformly dispersed in base bitumen and physically mixed with the base bitumen. The SBSC-modified bitumen obtains preferable thermal storage stability. The high and low temperature properties of the bitumen are also enhanced by the addition of the SBSC modifier. Meanwhile, the melt blending method does not restrict the role of the additional components in the SBSC modifier to improve the performance of bitumen. Based on the above findings, it can be considered that the use of SBSC modifier to prepare modified bitumen with enhanced performance is a promising practice. This research may shed light on the application of SBSC modifier to bitumen pavements. [ABSTRACT FROM AUTHOR]

• CRM with and without diesel pre-swelling was radiated by microwave. • Composition of compound activated CRM were different from untreated sample. • Binders modified with compound activated CRM showed improving performance. • Microwave radiation could improve thermal storage stability of CRM modified binders. Some novel methods are introduced to improve thermal storage stability and pavement performance of crumb rubber modified binder. In this paper, the objective was to investigate the effects of compound activation on the molecular structure and physical properties of crumb rubber, as well as rheological properties and thermal storage stability of crumb rubber modified binders. Two activation methods, with and without diesel pre-swelling, and six microwave radiation intensities were designed in this study. Fourier transform infrared spectroscopy (FTIR) test, swelling equilibrium test and dynamic mechanical thermal analyzer (DMA) test were performed to evaluate the characteristic functional groups and physical properties of crumb rubbers before and after activation. Additionally, rheological properties test at various service temperatures and thermal storage stability test were carried out on the crumb rubber modified binders. The results show that certain microwave radiation intensity would break the C-S and C=S bonds and reduces the cross-linking density of crumb rubber. Activation mode was the main factor affecting high temperature stability, fatigue life and low temperature relaxation property rather than microwave radiation intensity compared with control one. In addition, thermal storage stabilities of activated crumb rubber modified binders were better than control one. The more radiation intensity, the improvement effect of thermal storage stability is. Synthesizes each kind of property, diesel pre-swelling and microwave radiation intensity of 1.2 kJ/g was a preferable combination in this study. [ABSTRACT FROM AUTHOR]