Experimental evaluation of asphalt mixtures with emerging additives against cracking and moisture damage

Abstract

The objective of this study was to evaluate and recommend an asphalt mixture design with emerging additive technologies that would provide superior performance against asphalt concrete (AC) stripping and cracking. To achieve this objective, a laboratory test program was developed to evaluate the use of nanomaterials (nanoclay and graphene nanoplatelet), an emerging anti-stripping agent (adhere), and warm-mix asphalt technologies (ZycoTherm, Sasobit, and EvoTherm). Two mix types were evaluated, which were a stone-matrix asphalt (SMA) and a dense-graded binder mix. In addition, the modified Lottman test (AASHTO T 283) and the indirect tensile asphalt cracking test (IDEAL-CT) test were used as performance indicators of moisture damage resistance and cracking susceptibility. Results were analyzed statistically to identify and quantify the effects of the design variables and selected additives on the performance, moisture damage resistance, and durability of asphalt mixes. Based on the cracking test results, a superior cracking resistance performance was observed with ZycoTherm, irrespective of the mix type. Adhere had the lowest average cracking indices for both mix types, which suggest that it would not perform as well as the other additives in terms of cracking resistance. Overall, SMA mixes displayed greater cracking resistance than the dense-graded mixtures, which may have been the result of the reclaimed asphalt pavement (RAP) material used in the dense-graded mix and its lower asphalt binder content. In terms of moisture resistance, both nanomaterials (graphene nanoplatelet and nanoclay) did not perform well as they did not meet the minimum required tensile strength ratio (TSR) criterion (>0.80). In addition, nanomaterials showed the lowest TSR values in both mix types suggesting that their effectiveness against moisture-induced damage may not be as good as warm-mix additives. On the other hand, warm-mix additives were expected to show enhanced performance in terms of moisture resistance as compared to the other additives evaluated in this study.