Study On Compound Mineral Fillers Modified Asphalt And Its Mixtures Paving Performance

The demands of polymer modified asphalts with high-property and low-cost is increasing with the development of modern traffic and of high-level highway. Polymer modified asphalts possessing high-temperature rigidity and low-temperature flexibility is focused on by many researchers. However, their applications are limited by high-temperature storage unstability and high-cost. In this dissertation, using melted mixing method and seed emulsion grafting technology, the elastomers and their composites modifiers such as SBR/MMT and SBR/MMT composites as well as core-shell PB-g-PS and PB-g-PS/Asphalt particles were prepared, respectively. SBR/MMT modified asphalts, SBR/MMT modified asphalts, PB-g-PS modified asphalts and PB-g-PS/Asphalt cooperated with SBR modified asphalts were prepared using high-speed shearing technology. The properties of these modified asphalts including physical properties, phase structure, high temperature storage stability and rheological properties were systematically studied. The modified mechanisms were also disscussed.Firstly, Styrene-butadiene-rubber/Montmorillonite (SBR/MMT) composite modifiers were prepared by melted mixing method and SBR/MMT modified asphalts were prepared by by high-speed shearing technology. The properties of SBS/MMT modified asphalts such as physical properties, phase structure, high temperature storage stability and rheological properties were investigated. XRD and TEM results show that SBR/MMT composites may form intercalated or exfoliated structures. The structures and properties of modified asphalts with different SBR/MMT mass ratios were investigated. The results indicate that the modified asphalts with 3/5 SBR/MMT mass ratios possess best properties and the exfoliated strcture SBR/MMT is better modifier. The morphologies of the samples have been characterized by fluorescent microscopy. The results indicate that SBR/MMT modifier micro spheres dispersed in continuous phase of asphalt. High-temperature storage stability tests indicated that the modified asphalts are very stable in some SRB/MMT content range and the difference in the softening points between top and bottom sections was lower than 2.5℃.Especially, the modified asphalts exhibited higher complex modulus (G*) and lower damping factor (Tan8). It implies that SBR/MMT displays improved viscoelastic properties, resulting in enhancing its resistance to rutting at high temperature.Secondly, the high-properties SBS/MMT modified asphalts with stability were prepared by melted mixing method. XRD and TEM results show that SBS/MMT composites may form an exfoliated structure at 5/1 SBS/MMT mass ratio and intercalated structure at others mass ratios in SBS/MMT modified asphalts. The different SBS/MMT mass ratios influencing the properties of modified asphalts were investigated. The structures and properties of SBS modified asphalts, composite SBS/MMT modified asphalt and separated SBS,MMT modified asphalt were compared. The results show that SBS/MMT composites have best modified effect in improving physical properties and high temperature storage stability. High-temperature storage stability tests indicated that the modified asphalt is the most stable in 5/5 SRB/MMT mass ratio and the difference in the softening points between top and bottom sections was only 0.4℃.The fluorescent microscopy results show that SBS/MMT composites may form stable structure in SBS/MMT modified asphalts and no sediments particles were found after high temperature storage. The rheological tests indicate that the SBS/MMT modified asphalts exhibited higher complex modulus (G*) and lower damping factor (Tan8).It implied that SBR/MMT modified asphalts displaying improved viscoelastic properties.Thirdly, Core-shell PB-g-PS polymer latex particles and novel sub-micron core-shell rubber PB-g-PS/Asphalt particles were synthesized by the seed emulsion grafting technology. The comparation was taken between PB-g-PS modified asphalts and PB-g-PS/Asphalt modified asphalts in physical properties and high temperature storage stability. The morphologies and thermal properties of the samples have been characterized by SEM and DSC.The results showed that the high-temperature properties were increased obviously but the low-temperature properties were improved unobviously by Core-shell polymer latex particles. At 30/70 S/B mass ratio, Core-shell PB-g-PS polymer latex particles have best modified effect to asphalts. The high temperature storage stability of PB-g-PS/Asphalt modified asphalts is better than one of PB-g-PS modified asphalts.This indicates that the compatibility between PB-g-PS modifier and asphalt was improved by introducing asphalt into PB-g-PS.Finally, in order to obtain a kind of modified asphalt with good high and low temperature properties, the PB-g-PS/Asphalt cooperated with SBR modified asphalts were synthesized. The physical properties, phase structure and high temperature storage stability of the modified asphalts were studied. The results showed that as compatibility agent PB-g-PS/Asphalt has obvious effect. It changed phase structure of modified asphalt and resulted in SBR absorbing small molecule and increasing motive chance to gel and asphaltene in asphalt. This improves all properties of modified asphalts.