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

Abstract

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.

Keywords: asphalt; construction technology; direct-to-plant SBS; evaluation method; material composition; modifier.

Figure 1

Distribution diagram of dry SBS-T modifier test road.

Figure 2

The mechanism of direct injection SBS modifier [18], (a) represents a mixed solution stage, (b) represents a viscous flow stage, and (c) represents a swelling crosslinking stage.

Figure 3

Schematic diagram of dispersion and swelling process direct-to-plants modifier in asphalt [24].

Figure 4

Fluorescence micrograph of SBS-C9 asphalt [41], (a) Represents the fluorescence microscopic image of C9 petroleum resin not added, and (b) represents the fluorescence microscopic image of C9 petroleum resin added.

Figure 5

Sulfur crosslinking reaction mechanism.

Figure 6

Experimental and simulation methods for the microstructural composition of bitumen [70].

Figure 7

Fluorescence micrographs of direct-to-plant SBS-modified bitumen [24], (a) is the fluorescence microscopy RGB image, (b) is the binary image, and (c) is the skeletonized image [24].

Figure 8

RGB schematic diagram and AFM schematic diagram, (a) represents the RGB image, (b) represents the AFM three dimensional morphology diagram, and (c) represents the AFM two dimensional morphology diagrams.

Figure 9

Asphalt molecular model, SBS molecular model, and SBS-modified asphalt mixture model [116].

Figure 10

Modification process of direct-to-plant SBS modifier, (a) represents the direct casting SBS modifier and dry mixing of aggregates, (b) represents the wet mixing of sprayed asphalt, and (c) represents the formation of a modified asphalt coating.

Figure 11

Production diagram of direct-to-plant SBS-modified asphalt mixture.