Impact of Spatial Variability of Material Properties Compacted Geomaterials on Acceptance

Proper compaction of unbound materials in the pavement structure is a key component towards achieving the desired performance of a well-designed pavement. Transportation agencies commonly use the nuclear density gauge as a part of their quality management program to ensure the desired compaction density is achieved. Because the mechanistic-empirical pavement structural design process makes use of modulus to characterize geomaterials, transportation agencies are seeking to transition to modulus-based methods for quality management. This paper presents the findings of a comprehensive study aimed at understanding the impact of in situ variability in stiffness, moisture content, and density of compacted geomaterials on construction quality acceptance. To conduct this study, a dataset was compiled from test sections selected from various pavement construction sites throughout the United States. A grid pattern of spot test locations was established along the test section where modulus-based testing using lightweight deflectometer alongside moisture and density measurements was systematically conducted. The study revealed instances where sites that met density requirements failed to meet acceptance when using a modulus criterion. Thus, achieving density is necessary but not sufficient, as the density and modulus are not directly related.