Preparation And Properties Of TLA Modified Asphalt

Trinidad Lake Asphalt (TLA) modified asphalt has been widely used in airport runway, bridge deck pavement and superhighway due to its good pavement performance. However, more attention of the researchers has been paid to the physical properties of asphalt and pavement performance of TLA modified asphalt mixture. There were relatively few reports on the rheological properties and aging properties of TLA modified asphalt, which is closely related to its service performance and durability. Furthermore, very little previous research involves to the mechanism of TLA modified asphalt. In this paper, the effect of TLA on the physical, rheological and aging properties of different pristine asphalts (TZ-70 and SK-90) was investigated. The mechanism of TLA modified asphalt was studied by Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM). The results obtained are as follows:The softening point and viscosity of two asphalts were increased, while the penetration and ductility were decreased with the introduction of TLA. After TLA modification, the softening point and viscosity increments of TZ-70 were obviously higher than that of the SK-90, which was further enhanced with the increasing of TLA content. The good compatibility was found between the TLA and the two pristine asphalts. Compared with SK-90, the better compatibility was shown between TLA and TZ-70, which was in accordance with the better improved properties of TZ-70 in comparison with the SK-90.The rheological properties of asphalt were remarkably affected by TLA. Complex modulus of asphalt was increased, while phase angle was decreased with the addition of TLA as well as the increasing of rutting factor. Per 10% increase of the TLA would add one grade high temperature PG grades of asphalt, which contributed to the increasing of the high temperature stability and the rutting resistance ability of asphalt.Furthermore, the aging properties of asphalt were also improved by TLA. Compared with unmodified asphalt, the softening point rate and viscosity aging index of TLA modified asphalt were decreased remarkably, while the penetration retention rate was increased obviously after thin-film oven test, pressure ageing vessel aging and ultraviolet aging, indicating the good aging resistance of TLA modified asphalt to thermo-oxidative and UV radiation.No new absorption peaks appeared in TLA modified asphalt according to FTIR, indicating the main physical modification of pristine asphalts by TLA. AFM observation showed that after TLA modification, the topographic image of asphalt was more smoothly than that of the pristine asphalt. The dimension of the 'bee-like' structures was decreased obviously and its dispersion in the system was more homogeneous. Considering the appearance of 'bee-like'structures could be attributed to the existence of asphaltenes in pristine asphalt, it is reasonable to assume that the interaction between asphaltenes and other components was changed with the addition of TLA, which contributed to a new stable system of asphalt. Moreover, the dispersed phases taking the asphaltenes as core components in the asphalt showed an obvious association action, which contributed to the stiffer of the asphalt. As a result, the properties of asphalts, such as softening point, viscosity, were improved remarkably.