Inverstigation Of Silica Fume As An Asphalt Aging Modifier

A contrastive approach was adopted in this thesis to study the aging resistance ofsilica fume modified asphalt. Referring to the good anti-ageing properties ofpolyphosphoric acid, various amount of silica fume and polyphosphoric acid wereadded into asphalt respectively to make corresponding modified asphalt. Their agingprocess were simulated by short-term aging test in rolling thin film oven (RTFOT). Thechanges in the basic physical properties and rheological properties before and afterageing of both modified and base asphalts were investigated. In addition, infraredspectrum analysis and scanning electron microscope (SEM) were used to analyze themicrostructure before and after ageing of both modified and base asphalts.The results show that, adding silica fume changed the physical properties of theasphalt: softening point of asphalt increased, softening point’s difference value ofageing asphalt decreased, penetration ratio and ductility retention increased; Addingsilica fume also changed the rheological properties of the asphalt: the rutting factor andcomplex shear modulus of asphalt increased, the phase angle reduced. The silica fumemodified asphalt has the lower composite modulus of aging index. These effects ofsilica fume on the physical properties and rheological properties of asphalt show that,the addition of silica fume improved the anti-ageing properties of asphalt. Comparedwith polyphosphoric acid modified asphalt, silica fume can be used as a asphaltmodifier at cheaper cost to achieve the same anti-aging properties.The analytical results of the infrared spectrogram and scanning electron microscoperevealed the mechanism of silica fume improved the performance of asphalt: Addingsilica fume reduced the carbonyl index of aging asphalt and the silica fume can bedispersed into asphalt uniformly to achieve a better improve effectiveness.