Development of Modulus and Fatigue Test Protocol for Fine Aggregate Matrix for Axial Direction of Loading

摘要

The testing of fine aggregate matrix (FAM) is rapidly gaining attention in the pavement research community because of its notable similarities with asphalt concrete (AC) and the increased testing efficiency that it affords. In most of the existing studies, FAM tests are used for characterization of relative material performance in the presence of phenomenon like moisture damage and healing. However, to better understand the fundamental properties of FAM and to establish the mechanistic connection between its properties and those of AC, proper fabrication and testing protocols need to be established. The focus of this research is to develop such standard testing protocols for both dynamic modulus and uniaxial fatigue testing. In the current effort, two FAM materials are prepared with the same gradation but two different asphalt cements (PG 64-22 and PG 76-16). Pilot studies to support the development of sample fabrication protocols are explained. Both FAM materials are tested for modulus and uniaxial fatigue, and during testing both on-specimen and machine actuator displacement are recorded. Material parameters were separately calculated using these two deformation measurements and compared to uncover the errors resulting from machine-based measurements of FAM. The percentage error in measuring dynamic modulus of FAM specimens using actuator strain ranged from 5 % to 79 %. After correcting actuator strain with a constant machine compliance factor, the percentage error changed to 10 %-32 %, which is still high. In addition, variation in time dependency and fatigue damage characterization was observed using the corrected actuator data to on-specimen data. To overcome all of the above issues and measure reliable test data for FAM, it is concluded that protocols must include measurement of on-specimen deformation.