Resilient modulus of two recycled base course materials consisting of recycled pavement material (RPM) and road surface gravel (RSG), alone and with fly ash stabilization, were investigated using a large-scale model experiment (LSME). A natural limestone aggregate, Class 5, was tested as a reference material. The LSME allows evaluating the deflection behavior of a prototype-scale pavement under cyclic loading, which replicates field conditions and accounts for scale effects. Standard specimen resilient modulus tests were performed on the compacted specimens. Summary resilient moduli from the LSME and the specimen resilient modulus tests indicate that RSG has the lowest modulus, RPM the highest, and Class 5 gravel in between.Stabilization of RPM and RSG with 10% by weight of cementitious fly ash considerably increased the resilient modulus. The resilient moduli from the LSME and the standard laboratory specimen tests were different due to a variety of factors, such as the scale effect and different strain amplitude, with the additional factor of differences in mixing and curing in the case of fly ash stabilized materials. LSME modulus, unlike the modulus obtained from the standard specimen test, varies with layer thickness due to differences in strain amplitude for granular materials. The moduli obtained from the LSME were used to develop an equivalency based design for the recycled materials with and without fly ash. Stabilization of recycled materials reduces the thickness of the base course up to 30%.
Abstract