Composition optimization of mastic in recycled asphalt mixtures based on pavement performance

Area of Science:

• Civil Engineering
• Materials Science
• Sustainable Construction

Background:

• Natural aggregate depletion and environmental regulations drive the use of recycled asphalt pavement (RAP) in highway construction.
• Asphalt mastic performance, crucial for RAP mixtures, depends on fine RAP (FRAP), fine aggregates, mineral filler, and binder interactions.
• Current understanding of these interactions, including fine aggregate gradation (K value), mineral filler-binder ratio, and FRAP-fine aggregate ratio, is limited for informed asphalt mastic design.

Purpose of the Study:

• To investigate the compositional characteristics of asphalt mastic.
• To propose an optimized gradation for asphalt mastic suitable for engineering applications.
• To evaluate the impact of various compositional parameters on mastic performance.

Main Methods:

• Investigated the influence of mineral filler-binder ratio, FRAP-fine aggregate ratio, and K value on asphalt mastic performance.
• Utilized analysis of variance (ANOVA) to determine the significance of each factor.
• Evaluated the effect of coarse aggregate-to-asphalt mastic ratio on overall mixture performance.

Main Results:

• An optimal asphalt mastic composition was identified with a mineral filler-binder ratio of 1.4, a FRAP-fine aggregate ratio of 50:50, and a K value of 0.65.
• The mineral filler-binder ratio was the most significant factor (p < 0.001), followed by the FRAP-fine aggregate ratio (p < 0.01).
• A coarse aggregate-to-asphalt mastic ratio of 75:25 provided the most balanced mixture performance, leading to a 35% increase in dynamic stability and a 28% increase in fracture toughness compared to standard gradations.

Conclusions:

• The study successfully identified optimal parameters for asphalt mastic design using recycled materials.
• The optimized mastic composition significantly improves the mechanical performance and durability of asphalt mixtures, enhancing resistance to rutting and cracking.
• The findings provide a basis for informed engineering applications of RAP in sustainable highway construction.