Effect of filler gradation on creep response of asphalt mix

Abstract

Smaller fractions of aggregates in asphalt mix are known as fillers. Although substantial literature dealing with, (i) the response of asphalt mastic due to load and (ii) estimation of optimal quantity of filler for different types of fillers, is available, literature on the effect of gradation of filler (derived from same natural source) on the response of asphalt mix is rather scanty. This issue has been explored in the present work. In this study, granite stone dust is used as filler. Three different gradations of filler (G1, G2 and G3) are prepared from natural filler (G0) by varying the size proportions of the filler particles. Indirect tensile strength (IDT) and creep tests are conducted on filler–binder mix and also on asphalt mix. The results show that gradation of filler affects the creep response of the filler–binder mix as well as that of the asphalt mix. It is observed that the IDT value varies from about 555 to 665 kPa across the four fillers (G0, G1, G2 and G3) for 5.5% of asphalt content. Likewise, the deformation value in the creep test (with 500N creep loading for 120s) varies from about 0.26–1.09 mm across the four fillers. The average inter-particle distance between the filler particles is hypothesised as a possible indicator so as to explain the variations observed in the test results.