Impact on Resilient Modulus Values of the Bituminous Mixture Using Different Standard Methods

The resilient modulus of bituminous mixes is determined by the indirect tension test conducted in accordance with ASTM and EN standards. These two standards differ with respect to each other in terms of loading procedure, loading time, and the rest period. ASTM standard D7369 is based on the controlled stress loading procedure, whereas the EN standard 12697-26, Annex C is based upon the controlled strain loading procedure. Therefore, there is a need for comparing, analyzing, and selecting one standard which would best suit as per Indian conditions. In our study, experiments were carried out on virgin bituminous mixture and the bituminous mix containing 15% RAP at 15℃, 25℃ and 35℃. It was found out from the study that the values of the resilient moduli measured by the EN standard were always less than the resilient moduli values measured by the ASTM standard. At lower temperature, the difference was found to be lower between the resilient moduli values, but with increase in the temperature, the difference increased. At higher temperature, the difference was found to be higher, and the resilient modulus was found to be insignificant when measured through EN standard. The mix containing the RAP material was found to have higher stiffness modulus as compared to the virgin mix. The resilient modulus values by the ASTM standard demonstrated a better correlation with the resilient modulus mentioned in IRC 37. Therefore, this paper recommends the use of the ASTM standard for measuring the resilient modulus of the bituminous mixture for Indian conditions.