Study on the Effect of Low‐Temperature Modified Additives on the Performance of Asphalt and Asphalt Mixture

By testing the basic performance of asphalt before and after adding low‐temperature modified additives, the changes in high‐temperature performance, low‐temperature ductility, viscosity and other indicators of low‐temperature modified asphalt were evaluated, and the optimal dosage of additives for road petroleum asphalt and SBS modified asphalt was determined. And through Fourier transform infrared spectroscopy experiments, the effect of USP on asphalt functional groups was analyzed, and the modification mechanism of asphalt was clarified. Based on mechanism analysis and composition, a method for Marshall testing of low‐temperature modified asphalt mixtures was proposed. Furthermore, the effect of low‐temperature modified additives on the pavement performance of asphalt mixtures was evaluated through high‐temperature rutting tests, low‐temperature bending tests, immersion Marshall tests, and four point bending repeated loading fatigue tests under 15°C conditions. The results showed that after blending USP with base asphalt, the USP additive was evenly distributed in the asphalt, forming a stable slurry structure without generating new functional groups. The modification process was mainly physical blending without significant chemical reactions. The active additives in low‐temperature modified additive reduced the intermolecular attraction of asphalt, and the surface tension of asphalt decreased. With the increase of the low‐temperature modification additive dosage, the penetration degree of asphalt increased, the softening point decreased, and the 5°C ductility first increased and then decreased. The Marshall compaction method for low‐temperature modified asphalt mixture was proposed, which involves 50 rounds of compaction followed by 48 h of high‐temperature curing and 25 rounds of secondary compaction. After 48 h of high‐temperature curing, the dynamic stability of low‐temperature modified asphalt mixture increased by 70% and 47%, respectively, compared to before curing, and increased by 43% and 18%, respectively, compared to the base asphalt mixture and SBS‐modified asphalt mixture before modification. The failure strain of low‐temperature bending test is increased by 1.6% and 4.2%, respectively. The residual stability, namely water stability, is slightly improved. The fatigue sensitivity of low‐temperature modified asphalt mixture increases, the dissipated energy slightly increases, and the fatigue cracking resistance decreases slightly.