The effect of Nano-CaO modified binder on the rutting and fatigue performance of asphalt mixtures

Asphalt pavement is susceptible to various types of damage, including fatigue and rutting, which can be caused by factors such as the quality of materials, frequency of dynamic loads, and weather conditions. These damages can significantly reduce the pavement's bearing capacity and compromise driving safety. Recently, Nano-materials usage is increasing in order to enhance the rutting resistance and fatigue behavior of asphalt pavements. In the present research, the effect of Nano-Calcium Oxide (CaO) on the rutting potential and fatigue life of asphalt binder (AB) and asphalt mixtures (AMs) was investigated. For this purpose, firstly, different contents of Nano-CaO (i.e. 0 %, 0.5 %, 1.0 %, and 1.5 % by weight of the virgin AB) were added to the AB, and AMs were subsequently prepared. The four-point bending beam fatigue (4-PBBF) test at two strain levels of 600 and 1000 microstrain (at 15℃ and 20℃) and wheel track (WT) test (at 40℃ and 50℃) were used to investigate the fatigue and rutting properties of the AMs, respectively. The test results indicated that Nano-CaO usage improved the rheological behavior of the AB and enhanced the fatigue performance and rutting resistance of the AMs. Moreover, the resistance to rutting and fatigue performance of the Asphalt Mixtures (AMs) exhibited a minimum increase of 31 % and 30 % respectively. Additionally, a significant enhancement of 40 % and 56 % was observed, with the optimal Nano-CaO content in the AB identified at 1.5 %. The study investigated the correlation between rutting depth and both G*/Sinδ (R² = 0.98) and J nr3.2 (R² = 0.96), as well as fatigue life and G*.Sinδ at 600 and 1000 microstrain (R² = 0.86 and 0.89, respectively). Finally, in this paper fatigue life models were proposed that higher Nano-CaO percentage resulted in increased fatigue life at each strain level. As the strain level rises from 600 to 1000 microstrain, there is a substantial up to 50 % increase in fatigue life at every Nano-CaO percentage.