Past experience indicates that thickness designs using portland cement concrete best agree with criterion used in the Portland Cement Association\u27s 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)
