Mechanistic approach for construction quality management of compacted geomaterials

Earthwork and unbound aggregates, are among the most critical components of the construction of transportation infrastructures. Their structural performance can only be assured with appropriate quality management to ensure the materials used are similar to the ones selected in design stage, proper processing of the material to ensure that the materials are uniformly mixed and contain appropriate amount of moisture before compaction, and proper compaction equipment to ensure adequate density and stiffness. The primary tool for quality management is currently a density gauge to ensure that proper density, and in some instances moisture content, are achieved during construction. However, in-situ nondestructive testing (NDT) devices that estimate the stiffness parameters of constructed pavement layers have been emerging over the past decades. Such stiffness parameters are more representative of the structural performance, predicted during the mechanistic-empirical based design process. This paper summarizes a series of laboratory and small-scale evaluations to establish a mechanistic approach for quality management of compacted geomaterials. A synthesis of current state of practice is followed by the evaluation of two nondestructive testing devices during controlled laboratory conditions. The small-scale results were interpreted to represent the moisture and stiffness variations in the field. Based on the results of a range of geomaterials, a mechanistic-based quality management framework was developed.