Fluctuation of the Viscoelastic Properties of Asphalt Concrete under Variable Strain Level

Abstract

The viscoelastic properties of asphalt pavement usually practices variable microstrain levels due to the mixed traffic loading throughout its service life. In the present assessment, asphalt concrete mixtures were prepared in the laboratory at optimum binder content, and compacted in a slab mold using the roller compaction. Beam specimens of 5.6 Cm depth, 6.2 Cm width, and 40 Cm length; have been extracted from the slab samples and subjected to repeated flexural stresses at 20℃ using the constant strain mode of loading. Seven various levels of constant microstrain have been implemented as a target amplitude, (20, 200, 250, 400, 700, 750, and 1000) microstrain while a loading frequency of 5 Hz was implemented. Test results regarding the viscoelastic properties were analysed and compared. It was observed that the phase angle increases by (7, 8.5, 5.5, 17.5, 12.5, and 16) folds and the flexural stiffness declines by (87.5, 87, 85, 97, 75, and 37) % when the strain level changes from 250 to 1000, 750, 700, 400, 200, and 20 respectively. However, the cumulative dissipated energy declines by (125, 53, 62, 93.7, and 95) folds when the strain level declines from 1000 to 750, 700, 400, 250, and 20 respectively. The permanent deformation increases by (8, 14, 18, 30, 33, and 44) folds when the strain level increases from 20 to 200, 250, 400, 700, 750, and 1000 respectively. Moderate strain level of 250 exhibits the highest flexural stiffness as compared with higher or lower strain levels.