Comparison of Rutting Resistance of Plant Produced Asphalt Mixes Using Hamburg Wheel Tracker and Surrogate Simple Performance Tests: IDEAL-RT and HT-IDT

The recent emphasis on adopting the balanced mix design (BMD) concept has encouraged highway agencies and practitioners to explore simple performance tests to capture the rutting performance of asphalt mixes. Though many researchers have adopted the Hamburg wheel tracking test (HWTT) to evaluate rutting resistance, certain limitations, such as using this test method during quality control/quality assurance (QC/QA) are challenging. Therefore, researchers are exploring ways to implement surrogate simple performance tests, namely the ideal shear asphalt rutting test (IDEAL-RT) and the high-temperature indirect tensile strength test (HT-IDT) to support QC/QA of asphalt mixes. However, establishing limiting threshold values of rutting parameters based on such simple performance tests is still in the research stage. Eight mixes with different types of aggregates, binders [unmodified, polymer-modified binder (PMB), and crumb rubber–modified binder (CRMB)] and gradations having different nominal aggregate sizes (NMAS) were collected from various plants. HWTT, IDEA-RT, and HT-IDT were conducted on samples compacted at $7\%\pm 0.5\%$ air voids using the Superpave gyratory compactor. The data analysis showed that the rutting resistance index (RRI) parameter derived from HWTT are promising and advantageous compared with final rut depth, as it incorporates the combined effect of rut depth and number of passes. The study presented correlations of different rutting parameters (shear strength, ${\mathrm{RT}}_{\mathrm{Index}}$, and HT-IDT strength) derived from IDEAL-RT and HT-IDT with the HWTT RRI parameter. Moreover, to ascertain the pass/fail criteria of asphalt mixes, critical threshold values were proposed and recommended for shear strength, ${\mathrm{RT}}_{\mathrm{Index}}$, and HT-IDT strength as 1.0 MPa and 65 and 135 kPa, respectively. IDEAL-RT followed by HT-IDT are the most suitable potential surrogate simple performance tests for HWT to screen better and worse rutting performance.