Resilient modulus for EPS geofoam

Most of the current design methods for geofoam used in pavement structures adopt the allowable working stress concept. These design methods do not fit rationally in conventional pavement design practice such as the AASHTO pavement design guide. To design flexible pavement structures according to AASHTO, the resilient modulus, M_r, for EPS geofoam would need to be estimated. The standard test method for estimating resilient modulus is not suitable for geofoam. Reinforced concrete slab is commonly poured over geofoam subgrades and below the pavement structure. The beneficial contribution of the concrete slab to improving the performance of the geofoam subgrade is not quantified in current design practice. Modified tests were performed to determine resilient modulus values for geofoam. Equivalent resilient modulus estimates were obtained considering the combined response of geofoam subgrade and concrete slab. The estimates were derived from finite element models, reported back calculations from FWD surveys and by correlations. The resilient modulus values obtained for the combination of geofoam and concrete slab are in a range that enables use of conventional pavement design by AASHTO methods. Copyright ASCE 2007.