Project number: MT-11-21

Funding source: Caltrans

Total cost: $89,976

Performance period: August 2010 to July 2011

Project description

Fatigue cracking is a primary distress in asphalt concrete due to repetitive stresses and strains caused by both traffic loading and environmental factors. The fatigue resistance of AC has been investigated by a number of fatigue tests. The main objective of this study is to investigate the use of the semi-circular bend (SCB) test as a quality assurance/quality control (QA/QC) measure for field construction. SCB test parameters were determined using two methods, the first of which was cross-head movement, and the second was non-contact camera. Comparison of fracture properties of seven AC mixtures from the SCB CHM method and the beam-fatigue test (BFT) is made. The Jc and K1c values for the seven mixtures were determined. BFT was performed on the same mixtures and initial stiffness, Nf and PV were determined. The coefficient of variation (CV) ranged from 0 to 38% for Jc and from 0 to 35% for K1c. The coefficient of variation (CV) ranged from 10 to 93% for the initial stiffness, 2 to 83% for Nf, and 8 to 167% for PV. The SCB Jc and BFT Nf and PV indicated lower fracture properties for PG64-10RAP (LIME), AN-HMA and WMA-ADVERA mixtures than those of other mixtures. The BFT Nf and PV achieved similar ranking for all mixtures. There is good correlation between Nf and PV with Jc, and poor correlation between initial stiffness with Jc, Nf and PV. This has indicated that the initial stiffness is not a good representative of the fracture properties of AC while Jc, Nf and PV are better indicators. In addition, a comparison of the results of two method of measuring SCB test parameters on six AC mixtures indicated that there is good relation between the two SCB test methods. The results of this study indicate that the SCB test has great potential as a QA/QC test of fracture properties of asphalt mixtures.