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21 Pavement sections with some delamination problems in four states were selected for uncontrolled field testing of the two nondestructive testing (NDT) techniques. However, because of some delays in equipment improvement, uncontrolled field testing did not begin until winter 2010 for the ground- penetrating (GPR) technique and until spring 2011 for the mechanical wave technique. Weather conditions were not suit- able for field testing in Maine and Washington State. Therefore, the two NDT techniques were evaluated only on pavement sections in Florida and Kansas. In Kansas, a westbound pavement section between Milepost (MP) 412 and MP 425.5 on US-400 was selected for high- speed GPR testing. Results of the high-speed GPR testing were then reviewed, and a pavement section of approximately 3,500 ft starting from MP 417.1 was selected for low-speed GPR testing. On the basis of core data provided by the Kansas Department of Transportation (KDOT), the pavement thick- ness of the long section varied from 13.5 to 19 in., and the pave- ment thickness of the short section was approximately 13.5 in. This section was a full-depth asphalt pavement. In 1988, an 8-in. dense-graded asphalt base layer was built on top of sub- grade and then surfaced with a 2-in. asphalt layer. In 1991, this section was overlaid with an asphalt layer 1 to 1.5 in. thick. Another surface layer approximately 2-in. thick was placed on top of this section in 1999. The data also showed that all the cores cut from the short section broke at a depth of between 1.75 and 4.75 in. from the surface, and the base layer had a severe stripping problem. After reviewing the GPR test results and other information provided by KDOT, the research team decided to conduct field testing of the mechanical wave technology on the same 3,500-ft section starting from MP 417.1. Locations where anomalies were identified in the GPR results were selected for lightweight deflectometer testing and cutting cores to ver- ify the delamination condition. This chapter discusses the selection of coring locations and the results from testing cores in the laboratory. Table 4.1 shows the locations where anomalies were found in the GPR results and where cores were extracted in the 3,500-ft pavement site starting from MP 417.1. Figures 4.1 and 4.2 show the anomalies and the locations of the first six cores in conjunction with the NDT test results. All the cores cut from the short section broke at a depth of between 1.75 and 4.75 in. from the surface, and the base layer had a severe stripping problem. Figure 4.3 shows that Core 6 broke during coring and had severe stripping problems in the lower layers. C h a p t e r 4 Kansas Cores Analysis: Coring Locations and Results for US-400 Pavement Site Table 4.1. Locations of Anomalies and Cores for US-400 Pavement Site Core Distance (ft) from South Deck Joint Offset GPR Observation Core Condition 1 1,080.8 CL Anomaly Stripped 2 1,694.2 RWP Anomaly Stripped 3 2,271.5 CL Anomaly Stripped 4 2,996.3 RWP Anomaly Stripped 5 3,022.6 LWP Anomaly Stripped 6 3,224.6 RWP Anomaly Stripped 7 288.8 CL Anomaly Stripped 8 427.9 CL No anomaly Stripped Note: CL = centerline.
22 1 2 3 Figure 4.1. Locations of Cores 1, 2, and 3.
23 4 5 6 Figure 4.2. Locations of Cores 4, 5, and 6. Figure 4.3. Severe stripping problems in Core 6.
