Comparison of moisture and fracture damage resistance of hot and warm asphalt mixes containing reclaimed pavement materials

Abstract

The present study evaluates moisture and fracture resistance performance of Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA) containing different percentages of Reclaimed Asphalt Pavement (RAP) materials. The HMA and WMA mixes with different percentages of RAP (i.e., 0%, 10%, 20%, 30% and 40%) were designed using Marshall mix design. The warm mixes were prepared by adding 2% wax. Overall, 10 mixes (five HMA-RAP mixes, and five WMA-RAP mixes) were prepared in the laboratory. The moisture damage potential of different mixes was determined using Tensile Strength Ratio (TSR) test. Furthermore, fracture resistance of HMA-RAP and WMA-RAP mixes were evaluated using a Semi Circular Bending (SCB) test based on fracture mechanics principles. The analyses of results showed that addition of RAP increased TSR value of the mix, indicating that RAP may help in enhancing moisture damage potential of a mix. The TSR value of HMA-RAP mixes was found to be higher compared to WMA-RAP mixes for all RAP percentages, showing that WMA mixes are more prone to moisture damage compared to HMA mixes. The fracture resistance was found to be increasing with increase in RAP content in this research work. However, it is to be noted that improvement in fracture property with increase in RAP content may not be theoretically correct due to increase in stiffness characteristics. Such trend in the present research work may be attributed to absence of relaxation time in SCB testing protocol, unaccountability of post peak behaviour in the present research work and variability in material properties. Therefore, further investigation is needed in this direction to develop more understanding for such change before making further recommendation. Furthermore, the fracture resistance of HMA-RAP mixes was found to be better compared to WMA-RAP mixes. Overall moisture and fracture resistance performance of HMA-RAP mixes were observed to be better compared to WMA-RAP mixes. Moreover, Literature showed that asphaltic mixture containing RAP and WMA additive is highly influenced by amount of RAP and WMA added to HMA, type of WMA additive, source and nature of collected RAP etc. Therefore considering finding of current research work and reported literature in this area, inclusion of RAP in WMA mixes should be evaluated carefully before making further recommendation.