Performance Evaluation of Bakelite and Nano-Clay Modified Asphalt Concrete Mixtures

Abstract

Utilizing polymers complemented with nanomaterials has received great attention to balance the antagonistic effects of polymers while enhancing the performance of the asphalt concrete mixtures. This study investigates the impact of Bakelite polymer and Nano-clay (NC) as an additive on various mechanical properties such as resilient modulus, rutting propensity, and moisture susceptibility of asphalt concrete mixes. The modified asphalt concrete mix was prepared by a wet process that involved the direct mixing of bitumen (60/70 penetration grade) with Bakelite and Nano-clay at high temperature (160 ̊C-165 ̊C), followed by adding aggregates (Babozai aggregate) during the mixing process. NHA Class B gradation was employed to find optimum bitumen content (OBC) using Marshall mix design. The modified asphalt concrete specimens were prepared with the Nano-clay percentages (2%,4%,6%, and 8%) with fixed 6% Bakelite. Both modified and unmodified (controlled) samples were fabricated for a series of performance tests, including Resilient Modulus (MR)/ Indirect Tensile Strength Test (ITS), Moisture Susceptibility/ Tensile Strength Ratio (TSR), were performed using Universal Testing Machine UTM-25. In contrast, the rutting test was also performed using Hamburg Wheel Tracking Test (HWTT). Results indicated that the addition of Bakelite and NC improved the HMA mechanical properties such as enhancing MR, stability, stiffness and increased resistance against rut susceptibility and moisture damage. In addition, it has been observed that 6% Bakelite with 4% NC content by weight of bitumen in asphalt mixtures outperformed other Bakelite and NC percentages. Results showed that adding this combination of modifiers has enhanced the MR by 1.6 times that of the controlled mix whereas the rutting test also found that adding 6% Bakelite and 4%Nano-clay could reduce the rutting up to 28.9 % compared to the controlled mix. The findings also indicate that 6% Bakelite and 4% NC content performed the best with a 17.98% increase in TSR compared to the controlled mix. The experimental investigation of these conditions and their interaction were analyzed by the Analysis of Variance (ANOVA) experiment with Tukey's Analysis. The statistical analyses showed that Bakelite and NC content was the most significant factor influencing the resilient modulus and ultimately, the strength of the asphalt concrete mix.