Fracture Resistance of HMA Mixtures Modified with Nanoclay and Nano-Al2O3

In recent years, the use of nanoparticles as a binder modifier has increased because of their unique properties. This article investigates the effect of nanoclay and nano-aluminum oxide (Al2O3) particles on mixed mode I/II fracture behavior of hot mix asphalt (HMA) mixtures. In this study, two types of modified HMA mixtures were prepared for conducting the fracture experiments using cracked semicircular bend specimens. These modified HMA mixtures contained five different percentages (i.e., 2, 2.5, 3, 3.5, and 4 %) of nanoclay and four different percentages (i.e., 0.1, 0.4, 0.8, and 1.2 %) of nano-Al2O3. The fracture experiments demonstrated that both the nanoclay and nano-Al2O3 particles improve the fracture resistance of HMA mixtures significantly, such that nanoclay particles with percentages of 2, 2.5, 3, 3.5, and 4 % increase the fracture resistance by 2, 8, 14, 19, and 31 %, respectively. As such, improvement in the fracture resistance that was achieved by the use of 0.1, 0.4, 0.8, and 1.2 % nano-Al2O3 was on average 6, 15, 21, and 27 %, respectively. Furthermore, the improvement effect of nanoclay and nano-Al2O3 was more pronounced when the HMA mixtures were loaded under high shear deformation modes.