Past experience indicates that thickness designs using portland cement concrete best agree with criterion used in the Portland Cement Association's design method for 18-kip EAL of 2 to 3 million or less. For EALs greater than 2 to 3 million, past experience best agrees with criterion developed from the AASHO Road Test. Research herein indicates the two criterion become asymptotic to each other at approximately 2.5 million EAL. For a variation in thickness and elastic moduli in portland cement concrete, dense-graded aggregate, and sub grade elastic modulus, research indicates that a general conic equation (included herein) very closely duplicates the work at the bottom of the portland cement concrete caused by an 18-kip single axle load. The transition from a tensile strain to a work criterion is presented. Decreasing the thickness of dense-graded aggregate base caused a maximum increase of 0.15 inches in the thickness of portland cement concrete. Thus, the thicknesses of the portland cement concrete were averaged. The resulting thickness design curves are presented for a concrete elastic modulus of 4.2 million psi (Kentucky concrete strength).

Report Date


Report Number


Digital Object Identifier



The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky nor of the Kentucky Department of Highways. This report does not constitute a standard, specification, or regulation.