The Modification Mechanism, Evaluation Method, and Construction Technology of Direct-to-Plant SBS Modifiers in Asphalt Mixture: A Review

To further promote the development of research on direct-to-plant SBS-modified asphalt, this article analyzes the development of direct-to-plant SBS modifiers. Starting from the material composition and mechanism of action, common direct-to-plant SBS modifiers were analyzed and classified into four categories based on their mechanism of action, including the instant dissolution principle, intramolecular lubrication principle, non-granulation principle, and vulcanization principle. From the evaluation of the modification effect, the method of studying the performance of direct-to-plant SBS-modified asphalt is summarized, including fluorescence microscopy, AFM technology, and molecular dynamics simulation technology. From the perspective of practical application, the construction process of direct-to-plant SBS-modified asphalt was discussed, including the design stage, raw material preparation stage, mix design stage, and on-site construction stage. The results show that common direct-to-plant SBS modifiers are primarily SBS with a small particle size (less than 200 mesh) or specific model, supplemented by additives (EVA, naphthenic oil, sulfur, petroleum resin, etc.), which improve melting efficiency and lubricity or make it undergo vulcanization reaction, change the proportion of asphalt components, and improve stability. In the evaluation of the modification effect of direct-to-plant SBS-modified asphalt, the disparity of the direct-to-plant SBS modifier is determined by observing the particle residue after dry mixing. Macroscopic indexes of modified asphalt and modified asphalt mixture are used to determine the cross-linking effect of direct-to-plant SBS modifier and asphalt, and the modification mechanism and modification effect of wet SBS modifier are evaluated at the microscopic level. The development of direct-to-plant SBS-modified asphalt should combine the characteristics of direct-to-plant SBS modifiers and the attributes of field application, targeted research, and the development of high-performance direct-to-plant SBS modifiers and complete production technologies applicable to different regions, strengthen the improvement of modification effect evaluation, and form a complete theoretical system.