Assessing Compaction Quality Using Light Weight Deflectometer: Laboratory versus Field Conditions

This study was conducted to investigate the behavior of highway subgrade and subbase materials (2A, 2RC, and A-6) under varying compaction and moisture conditions using the light weight deflectometer (LWD). LWD tests were conducted across three testing scales: small-scale laboratory testing using Proctor molds, large-scale testing in a test pit, and full-scale field testing. Results demonstrate that LWD test response, for deflection and modulus, is highly sensitive to moisture content, increasing to an optimum point and then declining. Deflection measurements increased from laboratory to pit to field conditions, reflecting the influence of support stiffness and boundary conditions. Two correction factors ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ≈ 1.65 for laboratory-to-pit and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ≈ 2.7 for laboratory-to-field) were developed and proposed to convert the laboratory LWD test results to the LWD deflection response in field applications. The study highlights the importance of scale effects, moisture variability, and soil behavior under impact loading, providing practical insights for using LWD as a compaction quality control tool in pavement construction. Because of the limited number of data points in this study, these preliminary correction factors <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> are proposed as exploratory values to bridge the gap between laboratory and field LWD measurements. These findings support improved interpretation of LWD data and its implementation in performance-based quality assurance practices.