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

Abstract

Warm-mix asphalt (WMA) was produced using a two-phase mixing process without additives, with bitumen–emulsion-coated aggregates and with bitumen at different mixing temperatures (MTs). The asphalt samples were prepared with 8% ground granulated blast-furnace slag fillers determined from hot-mix asphalt (HMA) analysis, with different bitumen-to-emulsion ratios and different MTs. 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 WMA prepared at 120°C with a bitumen-to-emulsion ratio of 80:20 performed best, with indirect tensile strength, tensile strength ratio, retained stability, rutting tests and ravelling loss values all meeting the standard code limits. Compared with HMA, the chosen WMA had a 37% lower ravelling loss.