4.1 This test method covers the determination of stiffness or modulus of unbound materials based on acquiring deflection measurements on laboratory compaction samples at varying moisture content. The target values are determined by acquiring LWD measurements on laboratory compaction samples (referred to as proctor tests) of the unbound materials. This method covers determining these target moduli by comparing the compaction moisture density characteristics from standard laboratory compaction measurements in order to optimize the uniformity of compaction and strength condition of the unbound layers.

4.2 This standard provides a modulus calculation that accounts for the constrained conditions (in the compaction mold) of the test sample. The intent is to be able to compare the results from the molded sample analysis to that of similar material in the field and at a similar stress level.

4.3 The target modulus or deflections may be either correlated directly to pavement or structure performance or used to determine in situ material characteristics of the pavement or structure foundation layers. Some uses of the data include quality control and quality assurance of compacted layers, and for structural evaluation of load carrying capacity. It should be noted that the modulus obtained in this manner on laboratory samples should not be used for design or pavement evaluation.

4.4 Overall the LWD, and by extension this procedure, is intended to be used as a tool to ensure optimal compaction of unbound materials. Optimizing the soil compaction of infrastructure projects will maximize load capacity and stability of the soil, decrease permeability (which will minimize seepage, erosion, and other unwanted conditions), and prevent or reduce the settlement and differential settlement of supported pavements and structures. The target modulus or deflections are used primarily employed to establish QC/QA criteria for LWD data acquired on similar material at similar stress levels.