Effects of a two-phase mixing process on warm-mix asphalt by factorial analysis

Abstract

Warm-mix asphalt was produced using a two-phase mixing process without additives, with bitumen-emulsion-coated aggregates, and with bitumen at different mixing temperatures. The asphalt samples were made with 8% ground granulated blast furnace slag filler determined from hot-mix asphalt analysis, with different bitumen-to-emulsion ratios and different mixing temperatures. Using the factorial design technique, the effects of the selected factors on Marshall performance parameters were investigated using interaction plots and main effect plots. The analysis from contour plots revealed that warm-mix asphalt made at 120°C with 80:20 bitumen-to-emulsion performed best, with indirect tensile strength, tensile strength ratio, retained stability, rutting tests, and ravelling loss values all meeting the standard code limits. Compared to the hot-mix asphalt, the chosen warm-mix asphalt had a 37% lower ravelling loss.