Mode I Fracture Behaviors between Cement Concrete and Asphalt Concrete Layer

Asphalt overlay or concrete overlay on existing pavements is a common strategy for pavement maintenance. Interlayer bonding performance between asphalt and concrete layers is a critical concern in achieving optimal long-term structural performance due to the possible cracking along the interface. In this study, bonding behaviors of asphalt concrete interface were characterized by employing mode I fracture tests conducted at −10 and 25°C, respectively. Two typical interface conditions were manually prepared. A tack coat material was applied on the interface with four distinct rates: 0.1, 0.2, 0.3, and 0.4 L/m2. Parameters including fracture strength, stress intensity factor (KIC), facture energy (GF), and energy release rate (J integral) were selected to evaluate the fracture performance. Results showed that optimum tack coat rates were 0.1 and 0.3 L/m2 for specimens with unmilled and milled surfaces. At the optimum tack coat rates, KIC and GF increased with the increase of interface roughness at −10°C, while, at 25°C, J integral of specimens with unmilled interface was larger than that of specimens with milled interface at the optimum tack coat rates. Analysis of variance (ANOVA) was conducted to evaluate the significance of the factors on the fracture loads and found that surface roughness is significant at −10°C and becomes nonsignificant at 25°C. Temperature and tack coat rate were significant factors considering a given interface.