Micro-Foamed-Based Viscosity Reduction of SBS-Modified Asphalt and Its Physical and Rheological Properties

Area of Science:

• Materials Science
• Civil Engineering
• Chemical Engineering

Background:

• Traditional asphalt foaming methods (mechanical, water-based) have limitations including specialized equipment needs, strict parameter control, performance variability, and safety risks.
• Developing efficient, low-carbon pavement construction techniques is crucial for sustainability in road infrastructure.
• Polymer-modified asphalt requires viscosity reduction for effective pavement construction and maintenance.

Purpose of the Study:

• To investigate the feasibility of using crystalline hydrates with high water of crystallization for creating micro-foamed asphalt.
• To evaluate the impact of this micro-foaming technique on the physical, chemical, and rheological properties of SBS-modified asphalt.
• To assess the performance improvements, including viscosity reduction, adhesion, compatibility, rutting resistance, fatigue life, and aging resistance.

Main Methods:

• Preparation of micro-foamed SBS-modified asphalt (MFPA) using three types of crystalline hydrates (Na₂SO₄·10H₂O, Na₂HPO₄·12H₂O, Na₂CO₃·10H₂O).
• Comprehensive testing including physical property tests, foaming characteristics, viscosity-temperature analysis, FTIR, adhesion tests, SEM, fluorescence microscopy, DSR, BBR, and fatigue life modeling.
• Analysis of bubble evolution behavior and rheological properties under various conditions, including aging.

Main Results:

• Micro-foaming using crystalline hydrates is a short-term, reversible physical viscosity reduction process, releasing H₂O and CO₂.
• MFPA achieved a maximum expansion ratio (ERmax) of 8-10, a stable half-life (HL) of ~180 s, and a foaming index (FI) peak of ~1160.
• Construction temperature was reduced by 10-15%, viscosity reduction was stable for 60 min, compatibility increased by ~65%, rutting resistance by ~32%, and fatigue life by ~30%, with a 18% decrease in low-temperature performance.
• MFPA demonstrated superior aging resistance, with rutting resistance increasing by 37% and fatigue resistance by 30% compared to aged SBS-modified asphalt.

Conclusions:

• Crystalline hydrates offer a viable method for micro-foaming SBS-modified asphalt, providing significant viscosity reduction and improved performance characteristics.
• The micro-foaming process enhances key pavement properties such as compatibility, rutting resistance, and fatigue life, while also improving aging resistance.
• This technology presents a promising approach for low-carbon pavement construction and maintenance, balancing performance trade-offs, particularly concerning low-temperature behavior.