Light Weight Deflectometer Testing in Proctor Molds to Establish Resilient Modulus Properties of Fine-Grained Soils

Recently, the use of light weight deflectometers (LWDs) for in-situ measurement of soil/aggregate layer moduli has gained significant popularity. A recent study sponsored by the Idaho Transportation Department (ITD) involved extensive laboratory characterization of eight different subgrade soil materials to establish a database of inputs to be used during mechanistic-empirical (M-E) pavement design. Along with commonly used soil index and strength tests, as well as resilient modulus tests, this study also performed LWD testing in Proctor molds to establish $E_{\mathrm{LWD},\mathrm{MOLD}}$ as a representative soil modulus value. The objective was to evaluate the suitability of LWD testing of soils in the laboratory to establish representative resilient modulus values for use during M-E pavement design. The $E_{\mathrm{LWD},\mathrm{MOLD}}$ value exhibited very strong correlations with the summary resilient modulus value [defined by the National Cooperative Highway Research Program (NCHRP) 1-28A] at three different moisture contents. This approach of LWD testing inside Proctor molds deserves further exploration as it can potentially enable highway agencies to predict soil resilient modulus values without the need to perform cumbersome and resource-intensive repeated load triaxial testing.