Thickness Design Procedure for Portland Cement Concrete Pavements

Past experience in Kentucky indicated that thickness designs using portland cement concrete best agreed with criterion used in the Portland Cement Association\u27s design method for 2 or 3 million EAL\u27s or less. For EAL\u27s greater than 3 million, past experience best agreed with criterion developed from the AASHO Road Test. Research reported herein indicates the two criteria become asymptotic at approximately 2.5 million EAL\u27s. The merger of the criteria is presented, and the combined criterion is coupled with the principal of equal work as defined in classical physics to produce thickness design curves for portland cement concrete pavements. Research has indicated that a general conic equation can be used to satisfactorily estimate the work, as calculated by the Chevron N-layered program, at the bottom of the portland cement concrete slab under an 18-kip single axleload. The transition from a tensile strain to a work criterion is presented. The thickness of portland cement concrete varied up to a maximum of approximately 0.15 inch for the same CBR and design EAL when the thickness of crushed-stone base was varied from 3 to 6 inches. Therefore, the design thickness of the portland cement concrete slab is relatively insensitive to changes in thickness of the crushed-stone base. Resulting thickness design curves are presented for a concrete elastic modulus of 4.2 million psi (typical of Kentucky conditions)