Feasibility of using Mastic for Performance Grading in Place of Extraction using SPS10 Mixtures

Because of the increased use of reclaimed asphalt pavement, reclaimed asphalt shingles, rejuvenators, and other additives, performance of asphalt mixtures can no longer be guaranteed by controlling properties of the binder. To determine the effect of additives on asphalt performance, the current procedure is to extract the binder from the mixture using solvents and recover the binder by removing the solvent. This is a two-step procedure, which can be time consuming and costly and which requires chemicals considered hazardous unless used with special care. Another issue is the quality of the extracted binder, as the process of dissolving the binder and recovering it from chemicals may affect the properties of the extracted binder. In this study, we suggest the use of mastic separated from the mixture, in place of extraction. The fine portion of the mixture (particles less than 0.25 mm) is physically separated from the mixture without use of solvents. This material is called composite mastic since it includes effects from all additives on the binder. The process of preparing composite mastic is significantly faster and less costly than extracting the binder. The separated mastic is tested following the Unified Performance Tests by incremental Method (UPTiM) using a dynamic shear rheometer to determine the high-, low-, and intermediate-temperature performance grades, similar to those of asphalt binder. This study shows strong correlations between properties of composite mastic, extracted asphalt, and asphalt mixture. Therefore, testing mastic could be a reliable alternative to testing extracted binder and compacted mixture.