Effects of mineral fillers on rheological properties of asphalt binders

Abstract

Asphalt binders during mixing, construction or in-service of asphalt mixtures do not exist alone, but are admixed with mineral matter varying immensely in mineralogical and physical properties. Mineral filler or dust suspensions in asphalt binders form asphalt mastics which act as a matrix for coating the larger mineral aggregates. Since asphalt binder specifications for material grading, acceptance and construction control practices for asphalt mixtures are based on engineering properties of the neat binder, an analysis as to whether neat asphalt binders or asphalt mastic should provide pertinent information for material characterization and construction indices for asphalt mixtures is presented. Analysis of the effects of type and content of mineral fillers on the rheological properties of asphalt mastic to the No. 70 (Pen Grade) neat asphalt binder designed to meet the JTG F40-2004 specification of China is demonstrated. Three different mineral fillers, or dust were separately dry mixed at dust to binder ratios ranging from 0.0 to 1.5 in ratio increments of 0.3% by measuring the weight of asphalt to get the desired binder content. Analysis of test results show that asphalt mastic consistency properties are well-defined linear functions of mineral filler type and content. Hydrated lime mastics showed more significant effects than those for Portland cement and limestone tested at the same mineral filler content. Penetration and ductility shows a linear reduction at increased hydrated lime content of 4.8 (0.1 mm) and 8.2 cm per 0.1% of hydrated lime increment respectively while softening point increases at the rate of 4.7°C. The asphalt mixtures mixing and compaction temperatures determined from hydrated lime mastics increases at the rate of 7.7°C and 7.9°C per 0.1% of dust increment respectively from those determined from neat binders.