Volume 40, Issue 7 (December 2012)
Effects of Type and Content of Mineral Fillers on the Consistency Properties of Asphalt Mastic
Although commercial mineral fillers have become mandatory for use in asphalt concrete mixtures by many highway agencies, the consequences of such additives have shown a great effect on the consistency properties of asphalt mastic as compared to the neat asphalt binders. A detailed 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. Laboratory experiments were conducted to investigate the effects of type and content of mineral fillers on the consistency properties of asphalt mastic to the neat asphalt binder designed to meet the JTG F40-2004 specification of China. Three different mineral fillers, namely hydrated lime, pulverized limestone, and Portland cement were separately dry mixed with neat asphalt binder at dust to binder ratios ranging from 0.0 to 1.5 in ratio increments of 0.3 % by weight of asphalt. Analysis of test results shows that asphalt mastic consistency properties are well-defined linear functions of mineral filler content. Hydrated lime mastics showed significant effects on the consistency properties of the neat binder as compared to Portland cement and limestone additives tested at the same mineral filler content. Penetration and ductility of the neat binder showed a linear reduction at increased hydrated lime content estimated at 4.8(0.1 mm) and 8.2 cm per 0.1 % of hydrated lime increment respectively while softening point and apparent viscosity increased at the rate of 4.7°C and 0.1 centipoises per 0.1 % of hydrated lime increment respectively. Asphalt mixtures mixing and compaction temperatures determined from equiviscous lines of 0.17±0.02 Pa·s and 0.280±0.03 Pa·s using hydrated lime mastics show a linear increment of 7.7°C and 7.9°C per 0.1 % increment of hydrated lime respectively.