Resilient moduli of raw and stabilized aggregate bases and evaluation of layer coefficients for AASHTO flexible pavement design volume I (FHWA-OK-98-05) 2199

Abstract

A comprehensive study involving laboratory testing of resilient moduli (MR) of aggregate materials, determination of layer coefficients, and their application in AASHTO flexible pavement design was conducted. Three coarse aggregates, namely, Richard Spur (RS), Sawyer, and Meridian, that are commonly used as subbase/base of roadway pavements in Oklahoma were selected. Based on the Los Angeles abrasion values, the RS and the Sawyer aggregates are considered good quality aggregates, whereas the Meridian is considered a marginal aggregate. A series of laboratory tests was conducted on the RS and the Sawyer aggregates to investigate the effect of testing procedure, gradation, moisture content, and drainage condition on the MR values. For the marginal (Meridian) aggregate, the effect of stabilization on the MR values was investigated in terms of different amount of stabilizing agents and different curing periods. Three different industrial by-products (Class C fly ash, Fluidized bed ash, and Cement-kiln-dust) were used for comparison. The variation in MR values due to these effects was examined and the material parameters kl and k2 required by the AASHTO design equation were evaluated The AASHTO flexible pavement design methodology uses layer coefficients to relate the structural design of the pavement with its performance. Layer coefficient values (a2) for the base course layer were determined for each combination of three different MR values of asphalt concrete (AC) layer, three different AC layer thicknesses, and four different base layer thicknesses. Furthermore, the effects of gradation, moisture content, drainage condition, and different stabilizing agents on layer coefficients were investigated. Finally, regression equat ions for predicting the layer coefficients of base layers were developed for the selected aggregates and their applications in pavement design were illustrated through design examples.