Sensitivity of Viscoelastic Properties of Asphalt Concrete to the Variation in Binder Content

The variation of asphalt binder content from that of the job mix formula usually influence the viscoelastic properties of asphalt concrete mixture. In the present investigation, asphalt concrete mixtures for wearing course are prepared at ± 0.5 % of the optimum binder content. Asphalt concrete slab samples were prepared using roller compaction. Beam specimens were obtained from the slab samples and tested for viscoelastic properties after practicing long term ageing and moisture damage. The phase angle, and cumulative dissipated energy as a major viscoelastic properties were evaluated with the aid of four-points bending beam test at 20 ºC environment and under constant microstrain level of 750. It was noticed that the specimens prepared with lower than optimum binder content exhibit the higher phase angle after practicing moisture damage or long term ageing. The phase angle decline to a range of (35-15) ° and (10-26) ° for moisture damaged mixture and long term aged mixture at 5.3 % binder content. The phase angle increases to an optimum value of (46 and 54) ° for mixtures prepared with (4.3 and 5.3) % binder respectively. It was concluded that the viscoelastic properties of asphalt concrete in terms of phase angle, and cumulative dissipated energy, are greatly sensitive to the variation in binder content. It was recommended that a stringent control of binder content should be implemented in the field to enhance the viscoelastic properties of asphalt concrete throughout its service life.