Date of this Version
Nsengiyumva, G.M., Kommidi, S.R., Kim, Y-R., Xu, H., and Yang, Y. (2018). "New Mixture Additives for Sustainable Bituminous Pavements", NDOT Research Report SPR-P1(17) M055.
In an effort to improve mechanical properties of asphalt concrete, an exploratory research using mixture additives was attempted. Two different types of additives on two material scales were used: asphalt concrete (AC) level and binder level. At the start of this study, the effect of natural cornhusk fibers on the resistance of two types of AC mixtures on cracking were tested for hot-mix asphalt (HMA) and cold-mix asphalt (CMA). The results showed slight improvements in cracking resistance in cornhusk reinforced HMA, and in the case of the CMA, marshal flow. Overall, based on the test results, cornhusk-reinforced HMA and CMA may not significantly improve critical mechanical properties given the added cost of fibers. In addition, cornhusk fibers proved difficult to properly disperse in HMA and CMA when mixed in laboratory. However, when fibers were mixed in an asphalt production plant, the fibers appeared to become more distributed. The second part of this study, two different types of carbon nano-fillers (F1 and F2) with different surface properties and sizes were added to two different asphalt binders: the base binder and the polymer modified binder. Also, mastic samples were prepared by replacing parts of the limestone filler by the carbon nano-fillers. It was observed that the nanoscale additives interacted with the binder quite differently. Additive F1 did not show a drastic improvement in the mechanical properties, fatigue resistance, and rutting resistance of the base and polymer modified binder at the mastic and the binder scale; however, additive F2 improved all the above- mentioned properties. From the experimental investigation, it can be inferred that part of the polymer modification can be replaced by additive F2. Although additive F1 showed a minimal change, it could be useful in improving the secondary application of the pavement, such as the electrical conductivity, thermal conductivity, and absorption of radiation for energy storage, which was not the scope of this study but appears worthy to investigate.