| According to the dispersion theory, filler as a dispersed phase in the dispersion, forming the "stiffening effect" that enhance the modulus of asphalt mastic. Without changed temperature sensitivity, while adding fillers to improve the performance of asphalt mastic in high-temperature, low temperature performance will be damaged. The success of SBS polymer modified asphalt, illustrating the internal structure optimization of asphalt is the key to improve the high temperature and low temperature performance of asphalt mastic. To do this, select the fly ash has rich pore structure in order to improve the internal structure of the asphalt mastic as a starting point, do the following study.Frist, I achieve the basic performance test of fly ash to judge feasibility that fly ash Instead of mineral powder. Compared to Mineral Powder, fly ash has a low density, rich pore structure, high activity, and other advantages; because of the different combustion conditions, the recovery process, fly ash in aspect of particle size, specific surface area and chemical composition fluctuated greatly. The average particle size less than 2μm ultrafine ash agglomerate that conducive to micro aggregate effect of fly ash.Secondly, considering the high and low temperature performance of modified asphalt mastic by fly ash to determine Powder-binder ratio of 1.0.In this Powder-binder ratio, Comparing modified asphalt mastic by fly ash and mineral powder road performance(rutting factor, creep compliance, creep stiffness, etc.) to determine asphalt mastic by fly ash is better or worse than asphalt mastic modified by mineral powder. Tests showed that asphalt mastic modified by fly ash improve its high temperature stability at the expense of damaging its low temperature cracking resistance under ultimate stress.Then, based on physical and chemical properties of fly ash, analyzes relation of the basic properties of filler and the performance of asphalt mastic. By hydrophilic coefficient, specific surface area, pore volume multiple nonlinear analysis, we can see that the hydrophilic factor shows inverse function with rutting factor and creep stiffness, specific surface area and pore volume shows linear function with rutting factor and creep stiffness. The hydrophilic factors influence high temperature properties of asphalt mortar most, While pore volume of asphalt mastic influence low temperature performance most.Furthermore, in order to take into account the high temperature and low temperature performance of asphalt mastic. Based on theory of chemical bond, a modification method of using silane coupling agent and Na OH composite modified fly ash surface is proposed. On this basis, the principle of coupling agent use in asphalt mastic is proposed. Composite Modified solved ultrafine ash agglomeration. Compared to single modified by fly ash,compound modified while improving the high and low temperature performance of asphalt mastic; compared to asphalt mastic by mineral powder, Composite modified of asphalt mastic by ultrafine Fly Ash asphalt achieve the goal of improve both high temperature performance and low temperature performance.Finally, by IR test, XRD tests and road performance of modified asphalt mastic by fly ash clarify the mechanism of Composite modified method. The results showed that the inorganic group of silane coupling agent does dehydration condensation reaction with the filler, organic group twine with SBS polymers or asphalt polymer that form "anchor" structure. Because of dissolution of Na OH aqueous in the filler surface, increasing the fillers pore structure and surface area, enhancing the fly- physical adsorption of asphalt-filler surface.Studies included all have shown that fly ash has rich pore structure, large specific surface area, which has good to high-temperature stability for asphalt mastic. By complex modification method, optimizing the internal structure of asphalt mastic, while maintaining the high temperature stability of asphalt mastic, significantly improves the low temperature cracking resistance. It is indicating that modified asphalt cement with fly ash to a certain applicatio n value and significance. |
