| Due to its excellent viscous-elastic properties,bitumen has been widely used in the construction of asphalt pavement all over the world.It can make the pavement skid-resistance better,more comfortable and low noise.The performance of bitumen is the key factor to determine the quality and service life of asphalt pavement.However,present polymer modified bitumens(such as SBS,SBR etc.)are very expensive and easy to segregate because of the poor compatibility.Therefore,seeking new modifiers is an important way to improve the performance of modified bitumens.The biological polymer materials have a good thickening properties.In the field of infrastructure construction,they have been mainly used in cement mortar to control bleeding,and to prevent segregation and sedimentation,because the cement system can show a better rheological properties with addition of them.However,the application of the biopolymer in the field of bitumen is still relatively rare.Based on that,this paper studied the effect of biopolymer materials on the rheological property,storage stability and aging property of bitumen by using the welan gum,xanthan gum and gellen gum as the modifiers.First of all,the biopolymer modified bitumens were prepared with four contents(0.2wt.%,0.5wt.%,1.0wt.% and 3.0wt.%)by melt blending.In order to evaluate the influence of biopolymer on the rheological properties of bitumen,the dynamic shear rheometer(DSR)was adopted to conduct the temperature sweep test,frequency sweep test,shear creep test and viscosity test.The results indicated that the rutting factor at high temperature and the total strain as well as permanent strain at low temperature were both increased.Meanwhile,the addition of welan gum increased the zero shear viscosity values of base bitumen by several orders of magnitude at 135°C and 160°C.However,the improvement to the rheological properties of bitumen was not always in direct proportion to the content of biopolymer.The optimum dosage range was between 0.5 wt.% and 1.0 wt.%.Secondly,four kinds of bitumens modified by different inorganic modifiers,namely the montmorillonite(MMT),Layered double hydroxides(LDHs),graphite and mine powder,were all composite modified by 0.5wt.% welan gum,respectively.Meanwhile,the styrene-butadiene-styrene(SBS)bitumen was modified with different dosages of welan gum.At last,all modified bitumens were investigated by segregation test to figure out the influence of biopolymer on the storage stability of modified bitumens.The storage stability was characterized by the difference in the softening point,complex modulus(G*)and the phase angle(?)of bitumen sampled from the top and bottom layer of the storage tube(i.e.the |?T|,|?G*| and |??|).The resulted indicated that the |?T| had a tendency to decrease,and the values of |?G*| and |??| were significantly reduced with addition of welan gum.Based on the results,this paper can conclude that the biopolymer materials can apparently improve the storage stability of the modified bitumens.Finally,the bitumens modified with 0.5wt.% biopolymer were investigated by the thin film oven test(TFOT)and the pressure aging vessel(PAV)test.Then,the dynamic shear rheometer and Fourier Transform Infrared Spectroscopy(FTIR)were adopted to analysis the changes of the rheological parameters,molecular structure and chemical composition.The results implied that the rutting factor ratio at high temperature,aging indexes,carbonyl index and sulphoxide index of base bitumen were all bigger than that of the biopolymer modified bitumens,which meant that the addition of biopolymer improved the ability of bitumen to resist TFOT aging and PAV aging. |
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