KTC-05-27
SPR 229-01-1F
"Resilient Modulus of Compacted Crushed Stone Aggregate Bases", T.C. Hopkins, T.L. Beckham, C. Sun
ABSTRACT
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.