In recent years, the American Association of State Highway Transportation Officials (AASHTO) has recommended the use of resilient modulus for characterizing highway materials for pavement design. This recommendation evolved as result of a trend in pavement design of using mechanistic models. Although much progress has been made in recent years in developing mathematical, mechanistic pavement design models, results obtained from those models are only as good as the material parameters used in the models. Resilient modulus of aggregate bases is an important parameter in the mechanistic models. The main goal of this study was to establish a simple and efficient means of predicting the resilient modulus of different types of Kentucky crushed stone aggregate bases. To accomplish this purpose, resilient modulus tests were performed on several different types of aggregate bases commonly used in pavements in Kentucky. Specimens were remolded to simulate compaction conditions typically encountered in the field. Tests were performed on wet and dry specimens. The compacted specimens were 6 inches in diameter and 12 inches in height Crushed limestone base materials included Dense Graded Aggregate (DGA), and Crushed Stone Base (CSB). Number 57s, crushed river gravel, recycled concrete, and asphalt drainage blanket samples were submitted for testing by engineers of the Kentucky Transportation Cabinet.

A new mathematical resilient modulus model, developed in a previous study by researchers of the University of Kentucky Transportation Center (UKTC), was used to relate resilient modulus to any selected, or calculated, principal stresses in the aggregate base. This model improves the means of obtaining best data “fits” between resilient modulus and stresses. Furthermore, the resilient modulus can be predicted, using the UKTC resilient modulus model, when the stress condition and type of Kentucky base aggregate are known. Multiple regression analysis is used to obtain model coefficients, k1, k2, and k3, of the relationships between resilient modulus and confining and deviator stresses used in the testing procedure. Also, multiple regression analysis was performed using other models developed by the National Cooperative Highway Research Program (NCHRP Project 1-37A, 2001) and Uzan (1985) to obtain the model coefficient, k1, k2, and k3.

The resilient modulus data and the UKTC model, as well as models developed by NCHRP and Uzan, are readily available to design personnel of the Kentucky Transportation Cabinet. Computer software was developed in a client/server and Windows environment. This program is embedded in the Kentucky Geotechnical Database, which resides on a Cabinet server in Frankfort, Kentucky.

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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, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.