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[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]

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]