Detecting the Variation of Flow Number (FN) Through the Durability Assessment of Asphalt Concrete (AC)

To monitor the rutting potential of AC mixture throughout its service life, the FN plays a critical parameter which should be considered. The FN is the number of load cycles at which permanent deformation initiates in the flexible pavement and increases significantly under dynamic loading. The influence of long-term ageing and moisture damage on the FN of AC mixture were evaluated in the present durability assessment. Beam specimens of roller compacted AC mixtures were investigated for their resistance to fatigue under dynamic flexural stresses and constant strain level of 400 microstrain before and after practicing the moisture damage and long-term ageing processes. The testing of the beams for flexure was conducted at 20° C environment. It was observed that the FN increased after practicing long-term ageing by (16.6, and 66.6) % for AC mixtures prepared with (4.3, and 4.8) % binder respectively. At the same time, it declined by (33.3, and 178) % for AC mixtures prepared with (5.3, and 4.3) % binder, respectively after practicing the moisture damage process as compared with the control mixtures. The permanent deformation of AC mixture declined after practicing the long-term ageing process by (0.8, and 12.4) % for AC mixtures prepared with (4.3, and 4.8) % binder, respectively. However, the permanent deformation of AC mixture increased after practicing the moisture damage process by (5, and 11.1) % for AC mixtures prepared with (4.3, and 4.8) % binder respectively.