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Layer Coefficients for NHDOT Pavement Materials.
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
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In 1992, the New Hampshire Department of Transportation NHDOT experimented with the use of reclaimed asphalt concrete as a base course material, dentified by NHDOT as reclaimed stabilized base RSB. The RSB and a control test section were placed on Interstate 93 between exits 18 and 19. The RSB test section was designed to the same structural number SN as the control. To evaluate the structural capacity of these test sections, the U.S. Army Cold Regions Research and Engineering Laboratory CRREL conducted deflection tests using a Dynatest 8000 falling weight deflectometer FWD. Preliminary analysis of the results by NHDOT personnel showed higher deflection in the reclaimed asphalt concrete test sections. The explanation was that the layer coefficient used for the RSB layer in the design was probably incorrect. A total of 10 test sections constituting the base course materials used by NHDOT were built near Bow 0 ew Hampshire. CRREL evaluated and estimated 000000 0e layer coefficients of the base course materials. The test program was developed to characterize the material in more than one way. Tests were conducted with the heavy weight deflectometer HWD, dynamic cone penetrometer DCP and the Clegg hammer. In situ California bearing ratio CBR tests were also conducted. The deflection from the HWD were used with the WESDEF back calculation program to determine the layer moduli. The moduli were than used with the AASHTO Design Guide to calculate the layer coefficients. The layer coefficients were also determined with the method proposed by Rohde. The CBR values from the Clegg hammer, in situ CBR and DCP tests were also used in the relationships in the HDM model to determine the layer coefficients.
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