Residual Structural Capacity of a Cement-Treated Base Layer Constructed Using Full-Depth Reclamation on Interstate 84 in Northern Utah

Abstract

The purpose of this research was to assess the residual structural capacity of the cement-treated base (CTB) layer on Interstate 84 in Weber Canyon following premature fatigue cracking of the overlying asphalt layer. Field testing included falling-weight deflectometer (FWD) testing by Utah Department of Transportation personnel and portable falling-weight deflectometer (PFWD) testing, dynamic cone penetrometer (DCP) testing, and coring by research personnel. The results of the testing indicated that the average modulus and unconfined compressive strength (UCS) values measured in the wheel path were consistently lower than the corresponding values measured between the wheel paths; reductions in structural capacity in the wheel path probably occurred as a result of asphalt cracking, water ingress, freeze-thaw cycling, and continued trafficking of the pavement in these conditions. Despite these effects, the average CTB modulus, California bearing ratio (CBR), and UCS values were still considerably higher than those of typical unbound granular base materials. Specifically, the average CTB modulus values measured during the spring using the FWD in the eastbound and westbound lanes were determined to be 1699 and 852 MPa (246.4 and 123.6 ksi), respectively, while the average CTB modulus values measured during the fall using the PFWD in the eastbound lane were 2609 and 3378 MPa (378.5 and 490.0 ksi) in the wheel paths and between the wheel paths, respectively. Furthermore, based on DCP testing, the average CBR value in the wheel path of the eastbound lanes was determined to be 198. Finally, the average UCS values were determined to be within or just above the range of 2070 to 2760 kPa (300 to 400 psi) recommended by the Portland Cement Association for the 7-day design strength of CTB.