Determination of the Optimum Conditions for Gilsonite and Glass Fiber in HMA under Mixed Mode I/III Loading in Fracture Tests

This study used the Taguchi method to determine optimum conditions for Gilsonite and glass fibers as modifier materials in hot mix asphalt (HMA) by conducting the mixed Mode I/III fracture test. These modifier materials were used under different experimental parameters. The parameters and their levels were angle of fracture ($\alpha =30°$ and 45°), nominal maximum aggregate size (9.5, 12.5, and 19 mm), air void content (4, 7, and 10%), Gilsonite content (6, 12, and 18%, as percentage of binder weight), glass fiber content (0.1, 0.2, and 0.3%, as percentage of aggregate weight), glass fiber length (3, 8, and 12 mm), and experimental temperature ($\Theta =0$, $-15$, and $-30°\mathrm{C}$). The optimum conditions for experimental parameters were fracture angle ($\alpha =45°$), air void content (4%), nominal maximum aggregate size (9.5 mm), Gilsonite content (6%), glass fiber weight (0.3%), glass fiber length (12 mm), and experimental temperature ($\Theta =-15°\mathrm{C}$).