Effect of marshal and gyratory compaction methods on cracking characteristics of hot mix asphalt concrete materials under all three basic modes of fracture

Abstract

Asphalt mixtures in the laboratory scale studies are often compacted and manufactured using two well-known methods namely gyratory and marshal methods. Due to differences in compaction procedure, employing any of these methods can affect the overall strength and mechanical properties (such as the fracture toughness and cracking resistance) of hot mix asphalt (HMA) materials. Understanding the effect of compaction method on cracking behavior of asphalt mixtures can provide good insights for estimating the long-term performance of pavements and roads. Therefore, in this research the effect of HMA compaction method is studied experimentally on modes I, II and III cracking behavior and fracture toughness values using the edge notch disc bend (ENDB) specimen. In addition, the effect of adding recycled asphalt pavement (RAP) material is also studied on the fracture behavior. Accordingly several HMA mixtures compacted with both marshal and gyratory methods and containing 0 and 50 % RAP material are tested at a fixed low temperature of −25 °C and the corresponding values of KIc, KIIc and KIIIc as well as the work of fracture values under all three basic modes of loading are obtained. The experimental results show the noticeable effects of loading mode, RAP content and compaction method on the fracture behavior of tested HMA materials. In general, adding RAP material reduces the fracture toughness values for all loading modes. However, compaction method has different effects on the fracture toughness values. While the KIc value obtained from gyratory compaction method is higher than the sample made of marshal method, opposite trends are seen for the shear type fracture modes (i.e. KIIc and KIIIc). The tensile mode over shear type mode fracture toughness ratios (KIIc/ KIc and KIIIc/KIc) as well as the effective fracture toughness and effective work of fracture values for the tested HMA mixtures are also presented and analyzed.