Study on the optimization design of mixing moisture content in foamed asphalt mix

Abstract

This research discussed the rational mixing moisture content (MMC) in foamed asphalt (FA) mix design. Sieve analysis was firstly used to study the bitumen dispersion and bitumen-aggregate coating and bonding action in FA mixes with three levels of MMC. Then, through variance analysis, the impacts of MMC, bitumen content and their interaction effect on the mechanical properties of FA mixes were studied. Indirect tensile strength test and dry density determination were carried out on FA mixes consisting of different gradings and material types to explore the rational MMC. On base of that, monotonic triaxial test was performed on two types FA mixes with various filler contents to further investigate the rational MMC for FA mix. The research results indicated that improper MMC led to bitumen clots and affected cohesion of FA mix. MMC and bitumen content had important impacts on mechanical properties of FA mix, while their interaction effect could be ignored in mix design. Optimal MMC increased to a certain extent with the increase of fine aggregates content, especially filler content in the grading. 70–80% of the optimum moisture content (OMC) was recommended as rational range of MMC for FA mix with 5–15% filler content and 75–85% of OMC for mix with 15–20% filler content, which offered a reference for easy and simplified MMC design for FA mix.