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Comprehensive Performances of Hybrid-Modified Asphalt Mixtures with Nano-ZnO and Styrene-Butadiene-Styrene (SBS) Modifiers

An effort was made to improve the separation issue of styrene-butadiene-styrene modifiers in styrene-butadiene-styrene-modified asphalt binders and to further enhance their performance by adding nano-ZnO to the styrene-butadiene-styrene-modified asphalt binder to prepare compound modified binder. First, the optimum nano-ZnO dosage was determined based on conventional tests, i.e., penetration, ring and ball softening point, and ductility at a fixed styrene-butadiene-styrene dosage; then, dynamic shear rheometer, bending beam rheometer, and fluorescence microscopy tests were conducted to evaluate the properties of the nano-ZnO/styrene-butadiene-styrene hybrid-modified asphalt binders. Finally, the rutting test, trabecular bending test, submerged Marshall test, and the freeze-thaw splitting test was conducted to evaluate the properties of the asphalt mixtures produced with the hybrid-modified binders. The main results showed that: the optimum nano-ZnO dosage, which was 4% by weight to the asphalt binder, and an improvement of the separation issue of the styrene-butadiene-styrene, and the flexural tensile strength and the maximum bending tensile strain of the hybrid-modified asphalt mixtures increased by 13.4% and 16.4%, respectively. In addition, the residual stability and the tensile strength ratio also increased by 4.3% and 4.8%, respectively, compared to the styrene-butadiene-styrene-modified asphalt mixtures. In conclusion, nano-ZnO improves the low-temperature and water stability performances of the styrene-butadiene-styrene-modified asphalt mixture.