Effects Of Type And Content Of Mineral Fillers On Engineering Properties Of Asphalt Mastic

Asphalt mastic consists of asphalt binder and mineral filler, and is an important component in asphalt mixture for paving roads. However, adding different type and content of mineral fillers to asphalt binders could result in considerable changes in the engineering properties of asphalt mastic. In this thesis, the effects of type and content of mineral fillers on the engineering properties of asphalt mastic are investigated. Laboratory experiments were conducted by using No. 70 petroleum asphalt binder to mix with each of the three different types of mineral fillers, namely, limestone, Portland cement, and hydrated lime to form asphalt mastic specimens whose dust to binder ratio ranged from 0 up to 1.5 in ratio increaments of 0.3. In a similar manner, separate SBS I-D asphalt binder with limestone filler asphalt mastic specimens were prepared for testing. Engineering properties of the asphalt mastic such as penetration, penetration index, softening point, ductility, and viscosity were observed as a function of type and content of mineral filler used.Experimental results indicated that all mineral fillers used in the study reduced the penetration of the asphalt mastic with increasing filler content. For the No. 70 petroleum asphalt binder, the decrease in penetration was more significant for hydrated lime asphalt mastic estimated at 50dmm (dmm = 0.1mm) over 0 to 1.2 dust to binder ratio, than limestone and Portland cement asphalt mastics, about 25dmm over 0 to 1.2 dust to binder ratio at 25℃. The limestone and SBS I-D also showed a penetration reduction of about 25dmm over the same range of dust to binder ratio at the same test temperature. Penetration index values for hydrated lime and Portland cement with No. 70 petroleum asphalt mastics, increased with increasing filler content up to an optimum dust to binder ratio, whilst limestone with the same binder, exhibited the reverse. For the limestone and SBS I-D asphalt mastic, the penetration index values also showed an optimum dust to binder ratio but with higher values than other mastics. Softening point and viscosity values in all the mastics increased with increasing filler content, while ductility in all the mastics reduced with increasing filler content.Hydrated lime filler in all the asphalt mastics showed more significant changes to the engineering properties of the asphalt mastics than other fillers at the same dust to binder ratio. However, engineering properties for hydrated lime asphalt mastics at 1.5 dust to binder ratio, couldn't be tested because the specimens were too stiff to mix at this ratio.