Research On Ultraviolet Ageing Performance And Ageing Dynamic Of Bitumen

In the service period of asphalt pavement,bitumen is easily to be aged because of the temperature,oxygen and ultraviolet（UV）radiation,eventually resulting in changes of its physical properties and chemical properties and the deterioration of its performance.Although UV ageing on bitumen received a lot of attention in recent years,there is still no unified ageing method or standard to stipulate that how to do the indoor simulation experiment of UV ageing on bitumen.Furthermore,the ageing mechanism is still unknown.So the effects of UV and thermal-oxidation and their coupling,as well as sample thicknesses,UV radiation in different wavebands,UV intensity and temperature on bitumen UV aeing were studied.What’s more,the reaction kinetics constant parameters were calculated and the prediction model of the carbonyl index was established.Then,ageing depth and UV penetration depth versus ageing time was studied and bitumen UV ageing model was established.Finally,the relationships between rheological properties parameters and other performance indicators of bitumen were established.What’s more,the basic performance parameters of bitumen in first layer were calculated.The main conclusions were as follows.（1）The effects of different ageing procedures on bitumen UV ageing were studied.The reults showed that after UV ageing,the thinner bitumen film has bigger complex modulus（G*）and carbonyl index(I_C=O).When the thicker bitumen was UV aged,only the surface film of bitumen was affected seriously by UV radiation,which resulting the ageing degree is small.（2）According to the ageing effects of UV radiation in different on bitumen,UV radiation in different wavebands had ageing effects on bitumen and the effects were different.Futhermore,UV radiation from 300nm to 350nm have the strongest ageing effect on bitumen.（3）The ageing depth was found that it increased along with the UV ageing time by peeling the bitumen after different ageing time one layer by one layer.The results of spetum experiment showed that the ozone effect on bitumen was feeble.What’s more,the UV penetration depth was proved increased after being UV aged.However,the increase amplitude of UV penetration depth is small.The main cause of UV ageing depth is that aged bitumen permeate fresh bitumen and fresh bitumen permeate aged bitumen.（4）The ageing kinetics parameters were calculated based on determining IC=O at different temperature and different UV radiation intensity.The I_C=O prediction model was established and the error between computational data and experimental data is small.（5）The rheological properties under different ageing ways are very similar from the comparison results of bitumen rheological properties aged by UV radiation and PAV.The performance parameters could be calculated through the relationship between the rheological properties parameters and other performance parameters in PAV experiment.In conclusion,the performance of bitumen aged by UV radiation is closely related to the ageing procedure and thickness of bitumen sample.Besides,the effects of UV radiation in different wavebands on bitumen are different.What’s more,functional groups of bitumen could be predicted by ageing kinetic models,which provide the basis of characterization of bitumen performance after UV ageing and the judgement of pavement maintenance time.