Mechanism Of Diatomite-Cellulose Composite Fiber Modified Asphalt

Transportation plays a leader role in economic development and highway construction is the most important in transportation construction, which is closely related with the people’s livelihood. However, as the influence of natural factors and load of traveling, some pavement diseases have come into being. The service quality and lifespan of the pavement have been reduced because of these diseases and the safety of traffic has been threatened as well. Modified bituminous technology has provided impactful means to lessen or prevent pavement disease and enhance the paving performance for using.Diatomite and cellulose fiber are both used to strengthen asphalt’s performance, but there is no report about diatomite-cellulose composite fiber (DCCF) modified asphalt. DCCF was used to modify asphalt in this thesis, and the road properties of the modified bitumen and reinforced mechanism were researched. The major objective of this research was to enhance service function of the road, to reduce road surface disease and to increase pavement life.In the thesis, variety of advanced analytical instruments and methods, such as FT-IR, SEM, DSR, DSC and so on, were carried out to investigate the mechanism of DCCF modified asphalt. The road performance of modified asphalt was evaluated by indexes of penetration and softening point.The modified asphalt was prepared by mechanical stirring method, using three kinds of cellulose fibers. The technical properties of modified asphalt were evaluated from the following three aspects, high temperature performance, low temperature performance and temperature susceptibility. Thereinto, equivalent softening point T800was used to evaluate high temperature performance, equivalent breaking point T1.2was selected to appraise low temperature property and temperature susceptibility was estimated by penetration index P1. The results showed that these performances of the modified asphalt were all improved obviously and significantly associated with content of cellulose fiber. These three kinds of cellulose fibers had the same changing regularity when used to strengthen asphalt’s properties, and all would be the best if the modifier dosage was0.5%. There was obvious difference in the performance of each fiber modified asphalt, and H-2DCCF was the best.The modified mechanism was deeply discussed from the points of interfacial adsorption behavior, interfacial microstructure, interfacial interaction intensity and congeries state change, by means of FT-IR, SEM, DSR, DSC and so on. The results indicated that there was no chemical reaction between cellulose fiber and asphalt matrix. The fibers selectively adsorbed light composition of asphalt, became cylindrical from flat ribbon because of swelling, and discontinuously dispersed in the asphalt as dispersion structure. The fibers made the colloform texture of asphalt retuned, the form and quantity of some components in asphalt changed. These changes altered the microstructure of asphalt and decreased amount of the congeries state. Thus cellulose fiber modifying asphalt was a physical enchase blending process, during which the microstructure of asphalt was improved. Interface structure took shape between the asphalt and fiber. Due to the surface microstructure difference of these three kinds of fibers, their interfacial configuration was significantly different, and the interface between asphalt and H-2DCCF was the best. The interfacial interaction strength could be characterized using the parameter F. The interfacial bonding was obvious difference among these interfaces, the interface between asphalt and H-2DCCF was the strongest. The changing regularity of congeries state, interface structure and interfacial strength of these three kinds of cellulose fiber modified asphalt was consistent with their road properties. The formation process of interface between asphalt and fiber could be divided into three steps, namely, contacting and wetting of asphalt matrix and fiber, fiber absorbing light composition of asphalt, interface curing. The microstructure of DCCF modified asphalt could be visually signified through three micro-physical models, which were adsorbing and swelling model, distribution model and interface model.The mechanism of DCCF modified asphalt included the following three aspects:①the large number of pores, cracks and adherent diatomite on DCCF surface would selectively adsorb saturates and aromatics in asphalt, by which the content and existential state of these components was converted.②In the asphalt, DCCF distributed randomly in the three-dimensional space, these crisscross DCCF kept the asphalt adsorbed on the surface, and structure-asphalt nets was formed.③There had favourable infiltration between the asphalt and DCCF, so they would fully integrate, and good bond and consecutive transition interface structure was formed.The research by this paper can enrich the theory about improving road properties of asphalt, which has some significance for preparation of modified asphalt and improving the performance of asphalt.