Rheological properties and modification mechanism of PPA modified asphalt

Key words:  rheological properties  polyphosphoric acid  dynamic mechanical analysis  modified asphalt  modification mechanism

Abstract:

With the dynamic mechanical analysis (DMA), dynamic shear test as well as steady state flow measurement which were conducted with dynamic shear rheometer (DSR) and Carreau model were used to study the effect of polyphosphoric acid (PPA) on the rheological properties and modification mechanism of asphalt. And the modification mechanism of PPA on asphalt was investigated by the changes of colloidal structure and infrared spectra. The results show that the storage moduli G′ and the loss moduli G″ increase constantly for all modified asphalts as the increase of frequency at the studied frequency region, which indicates more elastic behavior is enhanced by PPA. Consequently, PPA improves the modulus and rutting resistance of asphalt. Moreover, at the same frequency, G″ shows more pronounced than G′ and the discrepancy between G′ and G″ appears smaller as the increase of PPA content, frequency and decrease of temperature. The critical shear rate,c, decreases drastically with the addition of PPA and this trend is more significant as the increase of PPA, indicating more susceptibility to shear force. Compared to base asphalt, light components decrease in asphalt while the proportions of asphaltene increase as the increase of PPA addition. Infrared spectrum analysis shows that characteristic peak occurs at 1026 cm-1 (the emergence of P-O and P=O) in the PPA modified asphalt, which reveals PPA reacts with base asphalt.