Effects of Type and Content of Mineral Filler on Viscosity of Asphalt Mastic and Mixing and Compaction Temperatures of Asphalt Mixture

Abstract

The mineral filler suspends in asphalt binder and forms asphalt mastic, which coats coarser aggregate particles in asphalt mixture. There are reasons to believe that the viscosity of the asphalt mastic, rather than that of the asphalt binder, should provide pertinent information on the mixing and compaction temperatures of asphalt mixture. Apparent viscosities were tested according to the procedure in ASTM D4402 on various types of asphalt mastics. Analyses of test results show that mastic viscosity is a well-defined linear function of temperature in the coordinates defined in ASTM D2493. The binder type, filler type, and dust-to-binder ratio have significant effects on the relationship between temperature and viscosity. A four-parameters model is appropriate to describe the variation of viscosity with temperature and mineral filler content. With the mastic equiviscous concept, the viscosity ranges are 0.576 ± 0.071 Pa-s and 0.968 ± 0.107 Pa-s for mixing and compaction, respectively, for asphalt mastic of unmodified binder, while for asphalt mastic of modified binder, the ranges are binder specific. The type and content of mineral filler have significant effects on the mixing and compaction temperatures. The dust-to-binder ratio of 0.9 for pulverized limestone is equivalent to 0.75 for portland cement and 0.4 for hydrated lime. For a change of 0.1 in dust-to-binder ratio, the mixing and compaction temperatures vary 3.5°C for pulverized limestone mastics, 4.8°C for portland cement mastic, and 9.3°C for hydrated lime mastic. The modified binder does not exhibit any extraordinary behavior in determining the temperatures using mastic viscosity.