The Preparation And Characterization Of Photocatalytic Self-healing Materials For Asphalt

In the effect of the external environment and the repeated vehicle load,cracks,loose and other diseases appear inevitably in asphalt pavement.As the damage worsens over time,the quality of vehicle traffic will be seriously affected.In this study,a trithiocarbonate(TTC)cross-linked polymer were used as a self-repairing material to achieve cracks repairation in the early stage of fracture development through reshuffling reaction of trithiocarbonate units under ultraviolet light excitation,which effectively inhibit the further expansion of cracks.The main conclusions are as follows:(1)Self-repairing mechanism of self-repairing agent(cross-linked polymers of trithiocarbonate units)is that under the excitation of ultraviolet light,the energy of C=S in the trithiocarbonate units of the self-repairing agent is transferred to C-S to break it into sulfur radical and carbon free radical.The two kinds of radicals between the different molecules are reconnected,resulting in reshuffling reactions.Molecular chains staggered to form a network structure to achieve the repair of cracks.The mechanism of the repair was confirmed by the reaction of the trithiocarbonic dicarboxylic acid with the trithiocarbonic dibasic acid ester.(2)The self-repairing materials were characterized by Fourier transform infrared spectroscopy,nuclear magnetic resonance analysis and thermogravimetric analysis.Infrared spectroscopy and nuclear magnetic resonance analysis were used to characterize the molecular structure of the self-repairing materials.The thermogravimetric analysis of the cross-linked polymers of trithiocarbonate units shows that the thermal stability is good and can be well adapted to the road application environment.(3)Considering the effect of the size and shape of asphalt cracks on the self-repairing rate of asphalt cracks,a self-repairing evaluation index is proposed.Using the asphalt cracks with similar shape and area(the coefficient of variation of the size of the asphalt crack area in the same control group is less than 5%)is used as a comparative test.The self-healing effect of the restorative agent was evaluated by the rate of change of the area of the asphalt crack before and after the repair.And the further optimization of the synthesis conditions of the cross-linked polymers of trithiocarbonate units was studied.Azodiisobutyronitrile(AIBN)-induced,UV-induced and 100°C-induced of these three methods,AIBN-induced is the best initiation method;The optimum amount of AIBN is AIBN/TTC crosslinker(mol/mol)= 0.7;Among the three polymer monomers such as n-butyl acrylate,methyl methacrylate and styrene,n-butyl acrylate is the best polymer monomer;The optimum amount of n-butyl acrylate is n-butyl acrylate/TTC crosslinker(mol/mol)= 19.(4)The synthesized trithiocarbonate cross-linked polymer improved the low temperature performance,construction performance and anti-aging properties of asphalt,whereas the high temperature performance was slightly weakened.