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27 (a) (b) Figure 20. Description of the coring procedure. Prior to testing, cored samples were cut to a height of a new pull-off test device--the Louisiana Tack Coat Quality 6.0 in, avoiding disturbances to the interface and the top Tester (LTCQT)--was developed. Details of the development layer. Because water was used as a coring lubricant, the sam- of this test device are presented in Section 4 of this report. ples were placed in an oven at 40C to dry for a minimum of The efficiency of this device was evaluated in the field, and 24 hours. The dried samples were placed in a conditioning a consistent and reliable test procedure was developed. Sub chamber at 25C for a minimum of 4 hours. This conditioning sequent to the application of the tack coat materials described period was adequate as determined through experimentation. in the previous section, tack coat material quality testing was A hole was drilled through a dummy core to its interface in conducted using the LTCQT device. The sections tested were which a temperature probe was inserted. The core was heated those of high cleanliness with no water present. The materials to 40C and then placed inside the conditioning chamber at tested for tack coat quality were SS-1h, CRS-1, and trackless. 25C to determine how long it would take the core to reach The sections for which tack coat quality was measured are pre- 40C at the center. After conditioning the sample for a mini- sented in Table 6. A minimum of three locations were tested mum of 4 hours, the sample was ready for interface shear for each section. strength testing. Table 6. LTCQT test sections. 3.3Experiment Plan I: Development of a Test Device to Evaluate the Quality of the Bond Strength Material Residual Application Rate (gal/yd2) of Tack Coat Spray Application in the Field 0.031 SS-1h 50 % Coverage 0.155 The objective of Experiment I was to develop a consistent 0.031 and reliable test method to evaluate the bonding characteris- tics of tack coat spray application in the field. Developing a SS-1h 100 % Coverage 0.062 consistent and reliable test method to evaluate the bonding 0.155 characteristics of tack coat in the field was achieved in three 0.031 main phases. In the first phase, a comprehensive review of Trackless 0.062 current interface bond strength test devices was conducted 0.155 (see Task 1). After careful evaluation of these test methods, a 0.031 test method known as the ATackerTM, was selected for further CRS-1 0.062 evaluation and possible improvement (37). After several mod- 0.155 ifications were introduced to the original ATacker test setup,