Test Methods and Specification Criteria for Mineral Filler Used in Hot-Mix Asphalt (2011)

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pare coarse- and fine-graded mixtures for HMA performance testing. Mixtures were tested to char- acterize their workability and their resistance to rutting, fatigue damage, low-temperature cracking, and moisture damage using the performance-related methods in Table 3. The mastic and mixture test re- sults were then statistically correlated to the filler test results to identify possible relationships among filler properties, mastic properties, and mixture per- formance, and models to estimate mastic perfor- mance in terms of filler and binder properties were developed. Finally, the practicality and repeatabil- ity of the filler test methods to capture the critical filler properties were assessed. The assessment in- cluded testing of six fillers by multiple laboratories and operators using the selected filler test methods. FINDINGS Table 4 presents (1) the primary filler character- istics experimentally identified as critical for defin- ing the influence of fillers on mixture performance and (2) test methods for measuring these proper- ties. The test methods are well established—most as AASHTO, ASTM, or European standards—and so would be suitable in the future as a basis for filler spec- ifications. However, some proposed testing equipment are not yet available in the North American market (e.g., that specified in EN 1097-4 to measure Rigden Voids, RV) or are relatively costly (e.g., the X-ray fluorescence spectrometer needed to measure calcium content). The test results in Table 1 for the initial set of 32 fillers indicate that mineral fillers currently used in HMA production in the United States vary sig- nificantly in the physical and chemical properties measured by the selected test methods. In general, manufactured fillers show a more extreme range of properties compared to natural fillers and their ef- fects on mastic and mixture performance indicators 3 Table 2 Mastic testing program. Mastic Characteristic Response Variable Test Method Aging 1. Workability Viscosity RotationalViscosity (RV) Unaged Accumulated Strain 2. Rutting Resistance Non Recoverable Compliance Dynamic Shear Rheometer (DSR)/Multiple Stress Creep and Recovery (MSCR) 25 mm PP Unaged Fatigue Life Time Sweep3. Fatigue Resistance G*sin DSR Unaged and PAV only 4. Thermal Cracking Resistance S and m Bending Beam Rheometer (BBR) PAV only Water Sensitivity EN 1744-4 5. Moisture Damage Resistance Bond Strength PATTI/or DSR Unaged Table 3 Mixture testing program. Mixture Characteristic Measured Response Test Method Workability Gyrations to 92%Gmm Superpave Gyratory Compactor Dynamic Modulus (E*) Asphalt Mixture Performance Test (AMPT) Permanent Deformation Flow Number (FN) AMPT Fatigue Resistance Cycles to 45% Drop in E* Indirect Tension Test (IDT) Thermal Cracking Fracture IDT Moisture Damage Rut Depth Hamburg Wheel Test