Preparation Of Polyurethane/organic Montmorillonite Composite Modified Asphalt And Performance Studies

The ordinary road bitumen has the characteristics of high temperature flow and low temperature brittleness,which will reduce the service quality of the asphalt pavement.Therefore,it is necessary to modify the bitumen.This paper proposes to use polyurethane(PU)and organic montmorillonite(OMMT)as modifiers to prepare PU/OMMT/bitumen composites to verifying its road performance.(1)Na-MMT was modified by eighteen alkyl two methyl benzyl ammonium chloride(1827),and the OMMT with larger interlayer spacing and stronger lipophilicity was prepared under the best preparation process.The microstructure and modification mechanism of OMMT were studied by XRD,FTIR,and SEM,and the hydrophilicity coefficient was used as one of the indexes for evaluating the compatibility of OMMT and bitumen.(2)Using the best preparation process to prepare polyurethane/OMMT composite modified bitumen with different modifier ratios,and study its conventional road performance.The results show that the best amount of polyurethane is 9%,and the best amount of OMMT is 1%.(3)The individual OMMT sheets dispersed in the bitumen matrix have a barrier effect on oxygen and can reduce the volatility of the light components and enhance the heat resistance of the polyurethane.When OMMT content is 1% and polyurethane content is 9%,the area difference of C=O and S=O absorption peaks before and after aging of composite modified asphalt is reduced to 0.060 and 0.012,respectively,and the aging resistance is significantly improved.(4)All asphalts are flowing at the end of the DSR test temperature range.This is a common feature of viscous reactions.The addition of modifiers does not change the viscoelastic behavior of bitumen,but it significantly increased the viscosity and elastic modulus of the bitumen.There was a bigger rate of increase amplitude of modulus,if the test temperature is higher.OMMT forms a clay-based network structure in the bitumen matrix,which enhances the elastic properties and fatigue resistance of the bitumen at high temperatures,especially when the asphalt begins to soften,with the most significant enhancement.BBR test results show that the addition of OMMT has a decreasing effect on the low temperature crack resistance of bitumen.The addition of polyurethane enhances the flexibility of the bitumen and lowers the limit temperature of asphalt binder from-28°C to-34°C.(5)The modification mechanism and microstructure of the composite modified bitumen were studied by XRD,FTIR,AFM and other test methods.The results show that the bitumen and polyurethane molecular chains are inserted into the OMMT interlayer,and the composite modified bitumen forms an exfoliated structure,and chemical reaction occurs in the system.