| In the dissertation, a new stabilization method, equal-density method was adopted to prepare modified asphalts with storage stability at high temperature. In this method, a compound was prepared by premixing polymer and filler, and the compound was mixed with asphalt to prepare Polymer-Modified Asphalt (PMA) by changing the ratio of polymer and filler. The asphalts with good storage stability were formed with the addition of filler, by regulating the density difference between polymer and asphalt. With identifying the effect of composition factor and the technique conditions on mechanical properties of polymer/filler compound and the molecular distribution of the polymer, identifying the effect of composition factor and the technique conditions on the properties and structure of polymer/filler modified asphalt, Styrene-Butadiene-Styrene copolymer (SBS), Low Density PolyEthylene (LDPE), Styrene-Ethylene-Butadiene-Styrene block copolymer (SEBS) modified asphalts with good storage stability and performance were prepared. Rheological method, gel content analysis and swelling measurement were adopted to elucidate the interaction between the polymer and filler. Filler reduced the difference between the polymer and asphalt with the premixing technique, which led to the improvement of the storage stability of the modified asphalts. The thermo-oxidative aging process of base asphalt and PMA were studied and the effect of antioxidant additives on the base asphalt and PMA were analyzed.Some disadvantages occur in simple blending and reactive blending methods to make PMAs. The asphalt is common unstable using simple blending method, which is an obstacle to road pavement. For reactive blending, the problem of storage stability also existed in preparing high-viscosity asphalt. Meanwhile, cost, pollution and selectivity to reactive additives were concerned. Adopting equal density method to prepare PMA, it is not need to add reactive additives and the problem of pollution and selectivity to reactive additives avoided. Adopting the method, the asphalts modified by polymers, including SBS, LDPE, SEBS were easily prepared with storage stability at high temperature and cost less.With the method of equal density, high performance and good storage-stability of SBS modified-asphalts were prepared by premixing SBS and kaolinite or diatomite clay. Applying the technique, some products can be obtained, which reached the standards of Heavy Traffic Modified Asphalt and High Viscosity Asphalt for Drainage Pavement. The effect of technique conditions, including temperature and time, on the mechanical properties of SBS/kaoline compounds and the molecular distribution of SBS were studied. The result of the research showed that the temperature was 140℃and the time 10 min in preparing the compound of SBS and kaoline. When the temperature was too high, the compound was not easy to be dispersed in asphalt. When it was too low, then the kaoline was not mixed homogenously with SBS, giving rise to need more time and decreasing process efficiency. Premixing technique was vital to prepare modified asphalts with storage stability at high temperature, which was not obtained using simple blending method. The ratio of SBS and the filler in the compound had a great effect on the storage stability of the modified asphalt. When the filler amount was too high or low, the SBS modified asphalts with storage stability at high temperature were not obtained. When the amount of SBS was 4%, the modified asphalt with good stability was obtained with the SBS/kaolinite ratio of 100/30, the amount of SBS 6%, the ratio of 100/40. When the ratio of SBS/diatomite clay compound was 100/30, the modified asphalts with good storage stability were obtained after adding different amount SBS. With increasing the SBS amount, the softening point, viscosity and dynamic mechanical properties of the modified asphalts increased much. Meanwhile, the filler, including kaolinite and diatomite clay, had little effect on the properties of the modified asphalts.Double bond is absent in saturated polymer, therefore, it is difficult to prepare good storage stability asphalts by adopting reactive blending method, which is always a big problem of putting saturated PMA into application in road pavement. Using equal density method, the asphalts modified by saturated polymer, including LDPE and SEBS, with good storage stability at high temperature, were prepared. When the ratio of SEBS and kaoline was 100/50, the modified asphalts with good storage stability were obtained after adding SEBS with the amount of from 3% to 6%. When the SEBS content was 4%, the kaoline had little effect on the mechanical, morphological and rheological properties of the asphalts. However, the content increased to 5% or 6%, the clay worsened the properties of the asphalts. The worsening properties might be attributed to the introduction of the kaoline, which hindered the forming of SEBS continuous phase. When the ratio of LDPE and silica was 100/60, the modified asphalts with good storage stability were obtained after adding LDPE with the amount of from 3% to 5%. The silica had little effect on the other properties of the modified asphalts. With the wide application of polyethylene-modified asphalt into road pavement, the equal density method to prepare LDPE-modified asphalt has a good future.The structures and storage mechanism of polymer/filler-modified asphalts were studied by using rheological method, gel test and swelling measurement. Basic asphalt was Simple Newtonian fluid in the range of tested temperatures while the polymer/filler-modified asphalt was Non-Newtonian fluid, which showed a transformation from Newtonian fluid to Non-Newtonian fluid in a given shear rate. For LDPE modified asphalt, a simple shear-thinning existed, while SBS and SEBS modified asphalts showed two shear-thinning regions, and the filler made it more obvious. Two Mode Carrueau Viscosity model showed that polymer and filler had a strong effect on structure orientation, demonstrating that the interaction between polymer and filler in premixing them existed, and the interaction made the polymer and the filler gather in blending the polymer/filler compound with asphalt. Then, by altering the ratio of polymer and filler, the compounds with different density were formed. Therefore, the density difference between polymer and asphalt was decreased by changing the filler amount. In a given filler amount, the stable modified-asphalt was obtained.Unsaturated PMA showed a short longevity in road service because it contained double bond, which increased the maintaining cost. The aging properties of base asphalt and polymer modified-asphalt were studied using conventional and InfroRed spectrum analysis method. Some anti-aging base asphalt and polymer modified-asphalt were prepared by addition of some antioxidant additives. An increase of the viscosities and softening points, decrease of the penetration and ductility were observed in both base asphalt and PMA after aging. As introduction of the additives: naphthenoid oil, ZDBC, ZDDP, the physical properties of the asphalt and PMA were improved to some extent. The improvement extent of the properties increased in the order: oil, ZDBC, ZDDP. By adopting heating- and ATR- FTIR techniques, the spectra of both asphalt and PMA were quantitatively studied. The occurrence of carbonyl groups and the decrease of intensity of the 965 cm-1 (the characteristic peak of SBS) were the aging results in oxidation of the PMA. The changes in the spectra of the base asphalt and PMA before and after TFOT aging were in accordance with the changes of the physical properties. Antioxidants, ZDDP or ZDBC modified PMA were resistant to the formation of carbonyl to some extent, indicating the improvement of aging resistance of the PMA by the addition of the antioxidants. ZDDP and ZDBC as antioxidants could retard the oxidation of the PMA through the inhibition of peroxides and radical scavenging. Furthermore, ZDDP in a state of liquid at room temperature acted as plasticizer, giving rise to a good ductility of PMA.
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