Hamburg Wheel-Track Test Equipment Requirements and Improvements to AASHTO T 324 (2016)

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82 10. APPENDIX D Figure 46 Locations of the embedded RTDs Table 16. Sensor labelling convention Side Specimen Sensor position Sensor ID 1 Left Front Top LFT 2 Left Front Bottom LFB 3 Left Back Top LBT 4 Left Back Bottom LBB 5 Right Front Top RFT 6 Right Front Bottom RFB 7 Right Back Top RBT 8 Right Back Bottom RBB

83 Specimen preparation for temperature verification Cylindrical HMA specimens were fabricated in the laboratory and a table saw was used to cut grooves 0.25-inch wide x 0.25-inch deep, for installation of the RTDs and lead wires. Next, the RTDs were placed in the grooves and centered with respect to the width of the specimen. Finally, plumber’s putty was used to seal the grooves and keep the RTDs in place. Each of these steps is shown in Error! Reference source not found.. It should be noted that through-holes for the bottom RTDs were drilled at an angle of 45° to avoid sharp bends of the lead wire. (a) Grooves cut and holes drilled (b) Drill press used for holes for bottom RTDs (c) Plumber’s putty used to seal grooves after RTD placement (d) Instrumented specimens in machine Figure 47 Instrumented specimen preparation

84 RTD and signal conditioner specifications The RTDs were purchased after evaluating the temperature range and accuracy requirements. Model HSRTD (class A) RTDs from Omega Engineering, Inc. were found suitable for this application. Next, signal conditioners to interface these RTDs with data acquisition equipment were selected and acquired. The signal conditioners excite and amplify 100-ohm platinum, 4- wire RTDs that are based on the 0.00385 ohm/ohm/°C curve. The RTDs and the data acquisition system were calibrated by using a NIST-traceable thermometer and a ±0.01°C bath circulator. Figure 44 presents the details of the calibration setup. All the RTDs were calibrated to be within ±0.1°C.

85 (a) Top view of RTDs in bath (b) Neslab model RTE 17 Bath circulator (c) Overall setup Figure 48 RTD calibration setup