Investigation of In Situ Strength of Various Construction and Widening Methods Utilized on Local Roads

Abstract

The project goal was to develop and verify a low-cost, repeatable, nondestructive methodology to characterize the load-carrying capacity of materials used in road widening and construction when established values are not available, and to establish a range of structural coefficients and moduli for these materials. Ninety-nine test sites were selected from 68 projects in eight counties across Ohio, grouped into five clusters. These sites included 19 different widening treatments. Each site was visited, tests conducted, and specimens gathered using the following techniques: falling weight deflectometer (FWD), portable seismic property analyzer, light weight deflectometer, dynamic cone penetrometer, and coring. The data and specimens collected were used to measure layer thicknesses, moduli, effective structural numbers, and layer coefficients applicable to each treatment. At least seven analysis methods were used to obtain the numbers from the data collected. The results were plotted in box plot and cumulative frequency formats for each material and analysis method. For each material, there was a wide variability of values both within and between sections. There were many sources of variability, however a range of numbers for moduli and layer coefficients were identified for most treatments, which could be utilized by local engineering personnel to design future projects. The procedure based on Section 2.3.5 of the 1993 AASHTO pavement design guide using FWD data provided the best estimate of published layer coefficients. However, using these values in other areas cannot guarantee accuracy; truly accurate layer coefficients result from careful monitoring of test sections under controlled loads.