To explore the influence of surfactant on performance of diluted asphalt and its mixture, the mixture of heavy oil viscosity reducer AMS and Span80 is added to diluted asphalt, the influences of surfactant on the mixing and compaction of diluted asphalt mixture are investigated through the tests of viscosity-temperature relationship, surface contact angle, mixing adhesion rate and compaction characteristics. The experimental result shows that (1) The mixed oil-soluble surfactant can significantly reduce the surface tension of asphalt-aggregate interface and reduce the viscosity of the diluted asphalt, in which the influence on interface is dominant. The addition of the mixed surfactant can ensure the mixing effect of the mixture under the condition of reducing the diesel consumption. (2) The addition of the mixed surfactant can reduce the viscosity of diluted asphalt, and has significant effect on improving the construction workability of diluted asphalt. It can significantly change the liquid-solid interfacial tension between asphalt and aggregate, and make the asphalt mixture still achieve good construction performance under the condition of reducing the content of diluent. (3) The addition of the mixed surfactant can make asphalt spread better on aggregate surface, reduce resistance and is easier for paving. (4) During the compaction process, the addition of the mixed surfactant can play lubricating effect between asphalt and aggregate, make the final compactness of the diluted asphalt mixture greater, improve the wetting and paving ability of asphalt on the aggregate surface, improve the mixing uniformity of the mixture and make it easier for paving and compaction. (5) At the surfactant dosage of 1.0%-1.5%, the improvement of the paving and compaction characteristics of the diluted asphalt mixture can achieve the effect of adding 4%-6% diesel oil, the 1.0%-1.5% mixed surfactant can replace 4%-6% diesel diluent, so that the mixture can achieve the same mixing uniformity and compacting performance.

To study the influence factors of low-temperature performance of semi-flexible pavement materials, a freezing test was conducted, and the cracking temperature was used as the evaluation index to study the influence of asphalt type (90 matrix asphalt, SBS-modified asphalt, TPS high-viscosity modified asphalt), cement-based grout material types (ordinary grout, rubber powder grout, emulsified asphalt grout), and skeleton void ratio (20%, 24%, 28%, 32%) on the low-temperature performance of semi-flexible pavement materials. Results indicate that the freezing test can effectively distinguish the low-temperature crack resistance improvement benefits of semi-flexible pavement materials with different asphalt, cement-based grouting materials, and skeleton void ratios. Cracking temperature can effectively evaluate the low-temperature performance of semi-flexible pavement materials. The substrate void ratio is in the range of 20%-32%, and the cracking temperature changes with the increase in the substrate void ratio, decreasing initially and then rising. When the void ratio is around 24%, the best low-temperature performance of semi-flexible materials is achieved. The improvement effect of the elasticity of grout on the low-temperature crack resistance of semi-flexible pavement materials is obvious; the improvement effect of emulsified asphalt grout on the low-temperature performance of semi-flexible pavement materials is better than that of rubber powder grout. After the modified asphalt is used in the substrate, the cracking temperature is reduced by 31.4%-38.3%, which is much greater than the effect of grouting. At the same time, the elasticity of the base asphalt is more effective than the viscosity increase in improving the low-temperature crack resistance of semi-flexible materials.