Moisture Effect Analysis on Bituminous Mix Containing Reclaimed Asphalt Pavement Material by Durability Index

This paper reports moisture damage analyses of recycled asphalt pavement (RAP) aggregate-enriched bituminous concrete (BC). This investigation determines the effective RAP aggregate percentage for producing a moisture-resistive 19-mm nominal-sized aggregate-enriched BC mix. To execute such a study, virgin aggregate (VA) has been replaced by 0%, 10%, 20%, 30%, 40%, 50%, 60%, 75%, and 100% RAP aggregate a on random selection basis at laboratory scale to explore the effect of each sample in BC mix. After calculating the optimum bitumen contents (OBCs) for the aforementioned BC mixes via the Marshall mix design, a moisture damage analysis was conducted using a modified Marshall immersion test. Experimental results show that 50% RAP aggregate-enriched BC mix may be used in low-volume roads in colder regions containing 0.07% less OBC than conventional BC mix. That mix may have 83.71% moisture damage resistive potency up to a 7-day immersion period. This improvement is due to the presence of a sufficient amount of carbonyl compound in the binder. Quantifying such compounds in the bitumen has been done by Fourier transform infrared analysis of the bitumen, as reported in the literature (Karmakar et al. 2018; Karmakar and Roy 2021). The moisture resistive potency of the 50% RAP aggregate-enriched BC mixes has also been confirmed by the indirect tensile strength (ITS) test, energy loss ratio test, and boiling water test. The results of those tests revealed that the presence of carbonyl compound in the binder of 50% RAP-enriched BC mix elevates the mix's flexural resistance against moisture damage for a 4-day immersion period due to having 1.15% more coating ability than a virgin binder.