Performance of Aged Asphalt Mastic Combining Active and Inert Filler Materials in Terms of Creep Recovery

ABSTRACT
Mastic is the main component of an asphalt structure that deforms when stress is applied. Substantial research has been done on the deformation and creep and recovery characteristics of asphalt mastic with varying filler proportions to develop a rheological parameter. Few research, however, has examined the combined impact of active and inert fillers. This study compares the creep recovery performance of asphalt mastics fabricated with the combination of different active and inert fillers containing modifier and anti-stripping agent. To understand the creep recovery characteristics of aged asphalt mastic, an experimental campaign of Multiple Stress Creep Recovery (MSCR) tests following AASHTO T 350 was performed using the Dynamic Shear Rheometer (DSR). This investigation used Styrene-Butadiene-Styrene (SBS) as modifiers to modify the neat PG 58-28 binder and Zycotherm as liquid anti-stripping agent. For fabricating the mastics, different proportions (10%,20%,30% by the weight of base binder) of Hydrated lime (HL) and Fly ash (FA) were selected as active fillers, whereas different proportions (70%,60%,50% by the weight of base binder) of Limestone (LS), Dolomite (DM) and Basalt (Ba) were selected as inert filler materials. The active and inert fillers were added in such a way that the Filler-Binder (F/B) ratio remains 0.8. Rolling Thin-Film Oven (RTFO) protocol was applied to simulate construction and laying time oxidative aging. The performance of these mastics was compared using non-recoverable creep compliance, stress sensitivity analysis, and percent recovery analysis. AASHTO M 332 specifications have been used to classify all the mastics based on the Jnr value at 3.2 kPa and stress sensitivity. In addition, polymer method MSCR curve specified by the Asphalt Institute (AI) were employed to interpret the test results. Based on the analysis of experimental data, active filler HL produced better creep recovery performance compared to FA, and when combined with inert filler LS, it showed the best performance. The combined effect of 10%HL and 70%LS modified with SBS containing Zycotherm was predominant and satisfied all the creep recovery performance requirements.

Keywords: Asphalt mastic, Multiple Stress Creep Recovery, Active filler, Inert filler, Combined effect