Resilient Moduli of Typical Missouri Soils and Unbound Granular Base Materials

Abstract

The objective of this project was to determine the resilient moduli (M sub r) for common Missouri subgrade soils and typical unbound granular base materials in accordance with the AASHTO T 307 test method. The results allow Missouri Department of Transportation (MoDOT) pavement engineers to calibrate software included with the National Cooperative Highway Research Program Project 1-37A Mechanistic-Empirical Pavement Design Guide according to Missouri’s conditions and materials. The test results included M sub r data from 27 common subgrade soils out of the 99 Missouri soil associations and from 5 unbound granular base materials. The subgrade soils, selected and provided by MoDOT, were tested at their optimum water content [as determined from AASHTO T 99 testing (AASHTO, 2001)] and at an elevated water content. The 5 unbound granular base materials, again selected and provided by MoDOT and representing a typical range in geologic source, were tested at 2 different gradations (typical as-delivered percent minus #200 sieve size and at an elevated amount of fines). All testing included 3 replications for all materials. Data are provided in the form of tables and graphs. As a part of the granular base material M sub r specimen preparation deliberation, maximum dry density (MDD) and optimum moisture content (OMC) were determined for each of the 10 material/gradation combinations. The M sub r testing program results indicate that both the material source and fines content are highly significant in the level of attained M sub r. In regard to material source, the range between the highest and lowest M sub r values was more than two-fold. Also, 2 of the 5 aggregate sources suffered a 15 to 20% loss in M sub r with the addition of 5% fines.