Evaluating the influence of volumetric properties on back-calculated asphalt layer moduli using falling weight deflectometer data

Abstract

The back-calculation process performed in pavement systems is the numerical analysis of captured deflections for estimating layer stiffness parameters. The prediction of fatigue performance in terms of back-calculated asphalt layer moduli by using a falling weight deflectometer (FWD) has specific challenges in terms of testing protocol, skillset, and complex back-calculation analysis. The performance of the asphalt layer is primarily governed by extrinsic parameters such as temperature, vehicular transient loading characteristics, moisture content, and intrinsic parameters such as binder properties and aggregate mix properties. The role of volumetric properties of asphalt mixes contributes significantly to the back-calculated asphalt layer moduli in terms of the overall life of the structure. The asphalt layer moduli are dependent on the traditional volumetric properties of asphalt mixes such as air voids in the mix (AVIM), voids in mineral aggregate (VMA), the percentage of bitumen content (PBM), and voids filled with asphalt (VFA). In this study, a total of 60 in-service pavement sections are identified from three different categories of roads to perform FWD tests and collection of asphalt layer core samples. A detailed laboratory investigation is carried out to estimate the volumetric properties of different core samples. This study uses field investigations to determine the degree of interdependency between the volumetric characteristics of asphalt mixtures and temperature on the back-calculated layer moduli. Furthermore, the findings from this study are utilized to establish several correlations at the aggregate level, demonstrating strong relationships with R² values ranging from 0.84 to 0.875. The developed model is validated and depicted in good agreement with the actual values.