Optimization of Nanocomposite HMA Containing Nanoalumina and SBS Based on Microscale Homogeneity Coefficient and Balanced Mechanical Properties

Extensive research has been done on using nanoadditives in hot mix asphalt (HMA). However, significant knowledge gaps still persist in this research field. An evaluation of the temperature characteristics of HMA containing polymer nanocomposites was undertaken. Nanoalumina and styrene butadiene styrene (SBS) polymer were used separately and together as modifiers for the base binder. The nanoadditive dosage was varied from 2% to 5% by weight of bitumen, with increments of 1%. Additionally, two SBS contents were utilized at rates of 2.5% and 5% by weight of bitumen. The laboratory component of this research was conducted in two phases: on bitumen; and on HMA. The studied bituminous binders comprised polymer-modified bitumen (PMB) specimens incorporating the aforementioned SBS dosages and nanocomposite-modified bitumen (NCMB) specimens containing the previously mentioned nanoalumina dosages in conjunction with 2.5% SBS. Following preliminary examinations, the microscale homogeneity and storage stability of PMBs and NCMBs were assessed using energy-dispersive X-ray spectroscopy by defining a novel homogeneity coefficient (HC). The mechanical performance of HMA incorporating PMB and NCMB across a spectrum of low, intermediate, and high service temperatures was studied. A dynamic modulus test was done to analyze the behavior at different performance temperatures. Also, an indirect tension asphalt cracking test was performed to study the fracture behavior. Microstructural analysis using the HC revealed an enhancement in the storage stability of PMB upon the addition of nanoalumina up to a concentration of 4%. HMA formulations incorporating NCMB with 2.5% SBS and up to 4% nanoalumina exhibited superior mechanical performance compared to HMA formulations utilizing PMB with either 2.5% or 5% SBS.