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Strong ultraviolet light and low-temperature are the typical environmental characteristics in high-altitude areas. The performance of SBS-modified asphalt in the above environmental characteristics needs further study. To improve the resistance ultraviolet (UV) ageing and low-temperature performance of copolymer- (SBS-) modified asphalt, an SBS-modified asphalt containing nano-ZnO and nano-TiO2 is proposed. In this paper, nano-ZnO, nano-TiO2, and SBS were used as modifiers with the silane coupling agent (KH-560) as the nanomaterial surface modification. The orthogonal test table was used to analyse the effects of the three modifiers on the physical properties of modified asphalt at different dosages. On this basis, the physical properties, low-temperature properties, and ageing indices (carbonyl index and sulfoxide index) were studied for base asphalt, SBS-modified asphalt, nano-ZnO/SBS-modified asphalt, and nano-ZnO/nano-TiO2/SBS composite-modified asphalt before and after photoaging. The content changes of characteristic elements (Zn and Ti) in the nano-ZnO/nano-TiO2/SBS composite-modified asphalt before and after ageing were studied by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), and the UV ageing mechanism was revealed. The results indicate that two nanoparticles show the best compatibility with asphalt after surface modification and can improve the binding ability between SBS and base asphalt. The orthogonal test analysis shows that nano-ZnO has a highly significant effect on the low- and high-temperature performance of the nano-ZnO/nano-TiO2/SBS composite-modified asphalt, and nano-TiO2 has a significant effect on the high-temperature performance. Three optimal composite-modified systems for base asphalt including 4% nano-ZnO/1.5% nano-TiO2/3.2% SBS were proposed and had the best antiaging ability. Compared with the sulfoxide index, the carbonyl index changed most obviously before and after ageing. Additionally, the results reveal that nano-TiO2 has a good absorption effect at a wavelength of 365 nm (ultraviolet light), while nano-ZnO is liable to photolysis, and its activity decreases at this wavelength.

Mortar has an important influence on the viscosity and durability of a mixture. The effects of the amount of mineral powder in asphalt mortar on the ultraviolet (UV) aging properties of asphalt were investigated by a Fourier transform infrared spectrum (FTIR), gel permeation chromatography (GPC), and dynamic shear rheometer (DSR). The FTIR results show that the UV-resistant aging ability of asphalt mortar was superior to asphalt and that the carbonyl indices of the SBS- (styrene-butadiene-styrene-) asphalt mortar and matrix asphalt mortar were more significant. The GPC results show that the molecular weight distribution coefficient (Mw/Mn) of the SBS-asphalt-filler mastic is 1.0 and that of the matrix asphalt-filler mastic is 1.2, which is the largest. The macro-property is the most stable. The DSR results show that the matrix asphalt-filler mastic ranging from 1.0 to 1.2 and the SBS-modified asphalt-filler mastic ranging from 0.8 to 1.0 show the best UV aging resistance. Therefore, the effects of the amount of mineral powder cannot be ignored, suggesting that the best mass ratio of the matrix asphalt mortar is 1.2 and that of the SBS-modified asphalt mortar is 1.0 during the UV aging process.

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The strength-formation mechanism for industrial-construction residue cement stabilization of crushed aggregate (IRCSCA) is not clear. To expand the application range for recycled micro-powders in road engineering, the dosages of eco-friendly hybrid recycled powders (HRPs) with different proportions of RBP and RCP affecting the strengths of cement-fly ash mortar at different ages, and the strength-formation mechanism, were studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the early strength of the mortar was 2.62 times higher than that of the reference specimen when a 3/2 mass ratio of brick powder and concrete powder was mixed to form the HRP and replace some of the cement. With increasing HRP content substituted for fly ash, the strength of the cement mortar first increased and then decreased. When the HRP content was 35%, the compressive strength of the mortar was 1.56 times higher than that of the reference specimen, and the flexural strength was 1.51 times higher; XRD and SEM studies of the hydrated cement mixed with HRP showed that the amount of CH in the cement paste was reduced by the pozzolanic reaction of HRP at later hydration ages, and it was very useful in improving the compactness of the mortar. The XRD spectrum of the cement paste made with HRP indicated that the CH crystal plane orientation index R, with a diffraction angle peak of approximately 34.0, was consistent with the cement slurry strength evolution law, and this research provides a reference for the application of HRP to produce IRCSCA.

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Intense ultraviolet irradiation is an important environmental factor affecting the service performance of asphalt mixtures in high-altitude areas, and the asphalt mortar is the main factor affecting the durability of asphalt mixtures. It is of great theoretical significance and engineering value to study the performance of the asphalt mortar at medium and low temperatures under ultraviolet irradiation. Therefore, this paper focuses on the evolution of the effect of the filler content on the rheological properties of different asphalt materials at low and medium temperatures under quantitative UV irradiation. Taking the average amount of UV irradiation observed annually in Northwest China as the indoor aging condition, the matrix asphalt mortar and modified asphalt mortar with different mass ratios of asphalt mortar are selected for indoor aging tests. Physical property tests, low-temperature performance tests, and dynamic shear rheological tests are carried out. The effects of the UV irradiation intensity and mineral powder content on the low temperature performance of the asphalt mortar are studied by variance analysis method, and the reasonable mass ratio range of the asphalt mortar under UV irradiation is proposed based on the standard residual square sum (STRSS) method. The results show that the temperature sensibility and low-temperature deformation energy significantly decrease with the increase in the filler content, while the values of the softening point, fatigue factor (G*sin δ), and creep stiffness modulus of the asphalt mortar increase. In addition, the variance analysis of the creep stiffness modulus aging index (SAI) shows that the ultraviolet radiation intensity has a significant impact on the performance of the asphalt mortar. When the mineral powder content is less than 40%. When the filler content is greater than 40%, the filler content effects the performance of the asphalt mortar. According to the standard residual square sum (STRSS) method, the best mass ratio of the base asphalt mortar is 1.096, and the best mass ratio of the modified asphalt mortar is 0.9091.

To expand the application range of modified asphalt and mixtures and effectively reduce the aggregation of nanomaterials in asphalt, nanocarbon/styrene butadiene styrene (SBS)/rubber powder composite-modified asphalt is proposed. This paper presents a laboratory study on the performance of nanocarbon/copolymer SBS/rubber powder composite-modified asphalt, and nanocarbon particles modified by titanate coupling agents as modifiers are selected. The nanocarbon/copolymer SBS/rubber powder composite-modified asphalt was prepared by a high-speed shearing method. The physical properties and rheological performance were assessed using ductility tests, softening point tests, penetration tests, dynamic shear rheometer (DSR) tests, and bending beam rheometer (BBR) tests. Furthermore, the mixture properties, including the high-temperature stability, low-temperature cracking resistance, moisture stability, and freeze-thaw splitting, were evaluated in the laboratory. The micromorphology of the base asphalt and composite-modified asphalt was examined by scanning electron microscopy (SEM), and the reactions between the modifiers and AH-70 base asphalt were studied by Fourier transform infrared spectroscopy (FTIR). The results reveal that the surface-modified nanocarbon and rubber powder additives substantially increased the softening point and penetration index of the base asphalt, with little obvious influence on the low-temperature performance. In addition, when nanocarbon/copolymer SBS/rubber powder composite-modified asphalt was used, the high-temperature stability and low-temperature cracking resistance of the nanocarbon/copolymer SBS/rubber powder composite-modified asphalt mixture were approximately 1.3 times those of the nanocarbon/rubber powder asphalt mixture. In terms of the micromorphology and reaction, the addition of the nanocarbon can increase the compatibility between the base asphalt and rubber powder, and then the addition of copolymer SBS can improve the structure of nanocarbon (after surface modification)/rubber powder-modified asphalt to form a stable network. Moreover, the physical reaction plays the dominant role in the modification process for the rubber powder and base asphalt, and chemical reactions occur in the modification process for the surface-modified nanocarbon and base asphalt.