influence of filler fractional voids on mastic and mixture performance

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9 GRQ2 Gravel Quartzite (2) 10 GS1 S<strong>of</strong>t Granite (1) 11 GS2 S<strong>of</strong>t Granite (2) 12 LH1 Hard Limestone (1) 13 LS2 S<strong>of</strong>t Limestone (2) Two base binders were used from two sources with the same performance grade (PG64- 22), One binder has high asphaltene content (heavy). The other binder has low asphaltene content (light). The heavy asphalt is modified with SBS and PPA to obtain two additional binders <strong>of</strong> PG 76 grade. The four binders (two modified, and two unmodified) are blended with the 13 <strong>filler</strong>s at one <strong>filler</strong> to binder (F/B) ratio, which was kept at the mass ratio <strong>of</strong> 1.0 for a total <strong>of</strong> 52 mastics. Based on the distribution <strong>of</strong> the mastic population, 12 mastics are selected to be used to construct mixture specimens for two gradations (fine, course). The selected mastics cover the range <strong>of</strong> data observed and balance between the binders such that all four binders are equally present in the selection. The following sequential diagram represents the sequence <strong>of</strong> work in this study. Table 3 lists the mastic characteristics measured and the associated test methods. 13 <strong>filler</strong>s 52 Mastics: Combine 13 <strong>filler</strong>s with 4 binders 24 mixtures: 12 mastics selected combined with two gradations TABLE 3 Mastic Testing Program Mastic Response Test Method Temperature Aging Characteristic Variable 1. Constructability Viscosity Rotational Viscosity 135°C Un-aged Accumulated Dynamic Shear Strain Rheometer 2. Rutting Resistance Non Recoverable (DSR)/ Multiple Stress Creep and Recovery 64°C Un-aged Compliance (MSCR) 25 mm PP Constructability To evaluate the effect <strong>of</strong> <strong>filler</strong> on mastic workability, viscosity was measured at 135°C using a Brookfield Rotational Viscometer. Viscosity testing was conducted using a size 27 spindle. In the procedure, the spindle is rotated at 20rpm for 600sec after 40 minutes <strong>of</strong> thermal TRB 2012 Annual Meeting Paper revised from original submittal. 4
equilibration. Viscosity measurements over the last 300sec <strong>of</strong> testing are averaged as the apparent viscosity. It should be mentioned that several experiments were conducted to evaluate the effect <strong>of</strong> shear rate on viscosity <strong>of</strong> mastics. Although the mastics were found to be shear dependent, the relative ranking <strong>of</strong> mastics did not change as a function <strong>of</strong> the shear rates covered in the testing. It was therefore determined most appropriate to use the results at only one shear rate. The shear rate <strong>of</strong> 20rpm was used because it is currently the most frequently used shear rate in binder testing. Mixture constructability was measured as the number <strong>of</strong> gyrations to 92% maximum density in the Superpave Gyratory Compactor. The number <strong>of</strong> gyrations to 92% is used as an indicator for workability since it is the typical target density for field projects. Permanent Deformation Mastic and binder rutting resistance was evaluated using the Multiple Stress Creep and Recovery (MSCR) test in accordance with ASTM D7405. Testing included three stresses (0.1kPa, 3.2kPa, and 10kPa) and two temperatures (58°C and 64°C). The non-recoverable creep compliance, (Jnr), and percent recovery, at a stress level <strong>of</strong> 3.2 kPa and 58°C, were chosen as the indicators <strong>of</strong> rutting resistance. These test conditions are chosen since changing the temperature to 64°C and the stress level to 10kPa led to the same ranking <strong>of</strong> mastics. Flow number testing was used to determine mixture rutting resistance according to procedures recommended in the NCHRP 9-19 project report with target air <strong>voids</strong> in the mixture equal to 7%. According to NCHRP 9-19, the deviator stress level used in the flow number test should be within the range <strong>of</strong> 70 to 210kPa for unconfined tests. In this study, the flow number tests were conducted using uniaxial compression loads without confinement at 58°C. A loading stress level <strong>of</strong> 200kPa was selected to attain tertiary flow in a reasonable number <strong>of</strong> cycles for various mixtures with different binders, gradations, and mineral <strong>filler</strong>s. The mixtures were tested with 0.1sec <strong>of</strong> creep loading and 0.9sec <strong>of</strong> recovery per cycle. Flow number, which represents the number <strong>of</strong> cycles <strong>of</strong> repeated creep at which the mixture enters a tertiary creep flow region, was used as the indicator <strong>of</strong> rutting resistance (25). FILLER TEST RESULTS The Rigden <strong>voids</strong> results collected in this study are shown in Figure 1. The results show a wide range <strong>of</strong> values (29.4 % - 47.1%) for the tested <strong>filler</strong>s. There appears to be no trend in Rigden Voids values with source or mineralogy <strong>of</strong> natural <strong>filler</strong>s. TRB 2012 Annual Meeting Paper revised from original submittal. 5
Page 1 and 2: INFLUENCE OF FILLER FRACTIONAL VOID
Page 3: Table 1. Comparison of</str
Page 7 and 8: The regression analysis indicates t
Page 9 and 10: Mixture Flow Number Mixture Flow Nu
Page 11 and 12: Permanent Deformation To derive <st
Page 13 and 14: characteristics) vary significantly
Page 15: 23. Anderson, D. A., and W. H. Goet

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