Experimental Study On Road Performance Of Hot Recycled Asphalt Mixture And Blending Effect Of New And Old Asphalt

Since the "Thirteenth Five-Year Plan",more and more attention has been paid to the establishment of resource-saving,energy-saving and emission-reducing transportation.The application of recycled asphalt mixture generated during the maintenance of asphalt pavements has become more widespread.However,there are still many problems in the current research on hot mix plant recycled asphalt pavement,such as low content of old materials and poor road performance of recycled asphalt mixtures.In current asphalt pavement regeneration specifications,it is assumed that the new and old asphalt are completely blending.In fact,when the recycled asphalt pavement content is relatively high,the new and old asphalt are not completely blending.Therefore,it is important to study the influence of the content of recycled asphalt pavement on the road performance and the blending effect of the new and old asphalt.Firstly,based on the marshall design method,four ratios of recycled asphalt pavement(15%,30%,45%,60%)of the plant-mixed hot-recycled asphalt mixture and the common hot-mixed asphalt mixture were designed to verify its high temperature stability,low temperature stability,water stability and other road performance.The results show that with the increase of the amount of recycled asphalt pavement,the low-temperature stability and water stability of the recycled asphalt mixture gradually decreased,and the high-temperature stability first increased and then decreased.It shows that when the amount of recycled asphalt pavement reaches a certain high ratio,the road performance of recycled asphalt mixture is worse than ordinary asphalt mixture.From the perspective of recycled asphalt performance,the rheological properties of recycled asphalt in different raito of recycled asphalt pavement were tested using linear amplitude scanning test,dynamic shear rheological test,multi-stress creep recovery test and bending beam rheological test.The research shows that with the increase of the amount of recycled asphalt pavement,the content of old asphalt increases,the fatigue performance of recycled asphalt,the ability to resist deformation at high temperatures increases,the ability to recover from deformation and stress sensitivity increase,and the low temperature crack resistance decreases.The atomic force microscope,fourier transform infrared spectroscopy,and gel permeation chromatography were used to study the micro-physical and chemical properties of the recycled asphalt.The results show that after the old asphalt in the recycled asphalt pavement is mixed with the new asphalt,the original component equilibrium state of the asphalt is changed,and the surface roughness of the asphalt is reduced.,the large molecular amount increases.The micro physical and chemical properties of asphalt have a good correlation with the rheological properties of asphalt,which shows that the change of the microstructure and molecular layer of asphalt will directly lead to the change of the rheological properties of asphalt.Finally,a gel permeation chromatography experiment was used to design a quantitative method for determining the blending effect of new and old asphalt by adding tracer to the mixture and using the percentage of large molecular size as index.The results show that with the increase of the content of the recycled asphalt pavement,the blending effect of the new asphalt and old asphalt decreases gradually.And the blending effect of new and old asphalt has a good correlation with the performance of asphalt and asphalt mixture.The lower the blending effect,the worse the road performance of the mixture.