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46 moisture escaping from aggregate pores during mixing with of the workability data was finding a single torque value to use binder may cause the asphalt film to foam and significantly as a reference point for comparing the binders. In the tempera- expand, which would enhance the coating process. Although ture range that the workability tests span, typically from about steam was evident during the mixing, foaming of the asphalt 180C to 120C, the results for all binders did not cross any was not observed during the tests with the incompletely dried given torque value, which required an extrapolation for some aggregates. results beyond the experimental range. 10 N-m was selected as a reasonable reference torque value because it was close to the average equiviscous midpoint torque and required Workability Tests small extrapolations. Therefore, using the temperature-torque The raw torque data from each workability test was processed regressions, the temperatures at which the binder-sand mix- and a least-squares regression was used to fit a quadratic ture reached 10 N-m of torque were determined. These results equation to the processed torque versus temperature data. also are summarized in Table 23. It can be seen that for over The temperature-torque regressions for each replicate sample half of the binders tested, the difference between replicates was are shown in Table 23. Initially, a reference torque based on the more than 25F. Some samples had very shallow temperature- midpoints between the equiviscous mixing and compaction torque relationships, which meant that the torque only temperatures of the unmodified binders was considered. This changed by a relatively small amount over a wide temperature yielded a reference torque value of 9.7 N-m. However, results range. Replicate results that had similar but shallow and nearly with some modified binders did not quite reach this value even parallel temperature-torque regressions had large differences at the highest temperature. One of the challenges with analysis between the temperatures to reach the reference torque value. Table 23. Workability experiment -- temperatures to yield equivalent torque. ID Run Regression Equation R2 C F F Avg. 1 y = 0.0035x2 - 1.2027x + 111.88 0.67 152 305 M 328 2 y = 0.0045x2 - 1.5717x + 147.32 0.80 177 351 1 y = 0.0044x2 - 1.4866x + 135.3 0.63 177 351 N 347 2 y = 0.0032x2 - 1.1296x + 110.27 0.50 173 343 1* y = 0.0135x2 - 4.2228x + 339.19 0.39 134 272 G 2 289 2 y = 0.0046x -1.554x + 139.94 0.89 152 306 1 y = 0.002x2 - 0.834x + 95.567 0.89 182 360 H 358 2 y = 0.0041x2 - 1.5494x + 158.01 0.96 180 356 1 y= 0.0021x2 - 0.8114x + 88.106 0.61 181 358 C 352 2 y = 0.0012x2 - 0.5356x + 67.004 0.56 175 347 1 y = 0.0039x2 - 1.3958x + 136.84 0.74 180 356 I 361 2 y = 0.0029x2 - 1.1313x + 120.13 0.75 186 367 1 y = 0.0018x2 - 0.6268x + 62.533 0.23 141 285 B 2 307 2 y = 0.0011x - 0.3908x + 44.778 0.19 165 328 1 y = 0.0019x2 - 0.6247x + 60.037 0.59 138 280 F 295 2 y = 0.002x2 - 0.7276x + 74.616 0.59 154 309 1 y = 0.0027x2 - 0.8801x + 78.499 0.51 129 263 O 251 2 y = 0.0021x2 - 0.6556x + 57.564 0.15 115 238 1 y = 0.001x2 - 0.3593x + 37.633 0.39 112 233 K 257 2 y = 0.0013x2 - 0.4528x + 47.712 0.56 138 280 1 y = 0.0028x2 - 0.927x + 82.634 0.64 128 262 J 2 257 2 y = 0.0016x - 0.5354x + 51.654 0.47 123 253 1 y = 0.0001x2 - 0.1246x + 25.015 0.42 135 275 E 294 2 y = 0.002x2 - 0.7656x + 80.762 0.78 156 313 1 y = 0.001x2 - 0.4073x + 47.171 0.47 138 280 D 305 2 y = 0.002x2 - 0.6858x + 68.707 0.46 165 329 * Incomplete data set.