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Title: The Mechanism of Modification and Properties of Polymer Modified Asphalts
Author: Jasso, Martin
Advisor: Zanzotto, Ludovit
Bakos, Dusan
Keywords: Chemistry--Polymer;Engineering--Civil
Abstract: In this thesis, several technologies of asphalt modification with polymers and/or PPA were investigated. The impact of modifying materials on the rheological properties of conventional asphalt was studied in both linear (dynamic mechanical analysis, multiple stress creep and recovery, steady shear viscosity) and non-linear viscoelastic region (start-up and interrupted start-up of steady shear experiments). The morphology of brittle fracture of different modified systems was investigated by cryo-SEM. The studied technologies and modifiers in this thesis were: modification of asphalt with thermoplastic elastomer SBS Kraton D1101 with and without use of sulfur as a crosslinking agent, modification of asphalt with reactive elastomeric terpolymer Elvaloy 4170 and modification of asphalt by PPA. The last mentioned modification was also used in combination with Kraton D1101 and Elvaloy 4170 technologies – addition of PPA creating ternary or quaternary modified systems. From the establish patterns of creation of chemical and physicochemical systems in binary, ternary and quaternary asphalt blends it was suggested that the addition of PPA appears to create new asphaltenes and also probably impacts the existing asphaltenes through their dispersion. Further addition of PPA leads to gel-type systems and deterioration of the material. In asphalt blends modified by SBS Kraton D1101, the limiting amount appears to be 3 wt.%. Above this concentration the SBS is sufficiently distributed throughout the blend and passing its elastic properties to whole asphalt blend through the creation of weak polymer network. The properties of these blends significantly improved with addition of sulfur, optimal range was found to be 0.12 – 0.16 wt.%. The quaternary sulfur vulcanized SBS asphalt blends modified by PPA showed that the contribution of PPA is via creating a parallel modified system of asphaltenes rather than by acting jointly with the network of vulcanized SBS. In the last modification, the effect of Elvaloy 4170 with and without use of PPA was studied. The presence of chemical reaction between Elvaloy and asphaltenes was observed, leading to creation of Elvaloy-asphaltene complex. The introduction of PPA in Elvaloy modified asphalt blends showed two independent networks which are acting in synergy.
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