Implementation of Semi-Circular Bend (SCB) Test for QC/QA of Asphalt Mixtures

The objective of this study is to develop a specification for the implementation of the semi-circular bend (SCB) test in the field quality control/quality assurance (QC/QA) phases of production and construction of asphalt mixtures. A scaling factor will be developed to predict the LTA SCB Jc values from plant-produced unconditioned SCB Jc. In this process, the research team expects to explore and obtain a scaling model for Jc, a relationship between Jc and the aging state of the mixture that is traced by a set of rheological and chemical aging indices. To achieve the objective of this study, a minimum of 15 field projects throughout the State with a good plant record of mixture consistency will be identified and selected. The selected projects are expected to encompass a range of material types (virgin and recycled; modified and unmodified asphalt binders, limestone and gravel, etc.) and volumetrics. The plant-produced loose mixtures as well as extracted cores from field compacted layers will be collected and evaluated in this study. The Laboratory Compacted (LC) and Field Compacted (FC) samples will be conditioned to obtain a series of progressive aging intensities and then evaluated using the SCB test; Table 1. For each mixture (both LC and FC) with each aging condition, the asphalt binder will be extracted and evaluated with respect to its rheological and chemical characteristics. The rheological binder testing under consideration includes performance grading, frequency sweep at multiple temperatures, Multiple Stress Creep and Recovery (MSCR), and Linear Amplitude Sweep (LAS) tests. The chemical evaluation is aimed to examine the shift of molecular components because of progressive aging using Gel Permeation Chromatography (GPC) and Saturate, Aromatic, Resin and Asphaltene (SARA) analysis, and changes in the functional group through Fourrier Transform Infrared (FTIR) spectroscopy technique. Table 1 presents the candidate-testing matrix for each mixture and extracted binder.