Research On Adhesion Of Aggregate-asphalt And Performance Of Warm-mixing Recycled Asphalt Mixture Pavement

Warm-mixing recycled asphalt mixture is a new environment-friendly pavement material based on the development of warm-mixing and hot-mixed regenerated technology,and it can enhance the proportion of recycled asphalt pavement mixtures,and make the mixing and compaction at low temperatures,thus achieve the purpose of recycling the asphalt mixture and reducing carbonate exhaustion and saving energy.In this paper,the author carry out the relative research depending on Chongqing traffic science and technology projects "Chongqing expressway asphalt pavement warm mix recycled key technology and application research".Through the evaluation of old asphalt material performance,the analysis of recycled aggregate morphology and the mechanism research of the aggregate-asphalt adhesion,the impact of the warm mix additive on the performance of warm-mixing recycled asphalt mixture is analyzed and then the mechanism of warm mix agent in warm-mixing recycled asphalt mixture is explored.First,by analyzing the asphalt content and gradation variability,RAP needs squashing,sifting and categorizing before the recycling in order to decrease the variation of asphalt content and gradation.Through the analysis of the grey correlations between asphalt indexes as well as comparing simulated aging and natural aging,the needle penetration,viscosity and rutting factor are selected as evaluation factors for the anti-aging performance of asphalt.In order to overcome problems in previous four-group asphalt experiment,a new four-group asphalt device is invented which can adjust’ the solvent flow rate by controlling the nitrogen pressure and effectively reduce the oxidation of the lightweight component in the washing process.Second,two indexes-the ellipticity and shape factor-was proposed to characterize the two-dimensional morphology structure of recycled coarse aggregate.For the same size of aggregate,with the increase of old material dosage,the ellipticity and shape factor of aggregate shows a downward trends.Through the dynamic particle image analyzer,three indexes-roughness,sphericity and convex degree-are selected to evaluate the angularity characteristic of the old and new aggregate.Through the analysis of angularity and texture characteristics of recycled materials,limestone,granite,there has a certain relationship between aggregate angularity and particle size,and the greater the particle size,the weaker the angularity.Third,through applying the surface free energy theory,the change laws of surface energy of recycled asphalt and asphalt recycled with warm mix method are investigated,meanwhile,the adhesion between aggregate and recycled asphalt with warm mix technology is analyzed.Besides,the models of adhesion between asphalt and aggregate when with water or not are both derived,which helps to lay a theoretical basis for investigating the water stability of warm-mixing recycled asphalt mixture.The results shows that warm mix additive changes the polarity components of recycled asphalt and Lewis acid-base reaction parameters,enhanced the surface energy of asphalt and cohesiveness,thus increased the adhesion between asphalt and aggregate.Fourth,through laboratory test,the mix design of warm mix asphalt with RAP is studied,an addition method for mix design with recycled asphalt mixture is proposed.Through investigating the compaction characteristics of warm-mixing recycled asphalt mixture by using volumetric parameters,the optimum temperatures for mixing and compaction is determined,which is 120-135℃ for compaction,and 125-140℃ for mixing.Through the research on high temperature stability,low temperature crack resistance,and water stability of AC-13 and AC-20 WMA with RAP,the author conclude that WMA with RAP could increase the proportion of recycled asphalt mixture,and also has good road performance.By comparing the aging degree between warm-mixing recycled asphalt mixture and hot recycled asphalt mixture during the construction process,the aging degree can be effectively reduced by using the warm-mixing technology,and it is helpful for the durability of asphalt pavement.Based on the grey correlation analysis of factors affecting recycled asphalt mixture,the RAP content,aggregate morphology have a closely correlation with the high temperature performance of warm-mixing recycled asphalt mixture,the surface free energy of asphalt and aggregate closely associate with water stability and the correlation between aggregate morphology structure and low temperature performance is also close.Finally,based on the test road,each indexes of warm-mixing recycled asphalt mixture meet the requirement about pavement performance,such as high temperature performance,water stability and porosity.Through the economic and environmental comparison between warm-mixing recycled asphalt mixture,hot mix mixture and hot mix recycled asphalt mixture,warm-mixing recycled technology can improve the utilization of old materials,save the cost and reduce the hazardous gas emission to relieve atmospheric pollution,and has good economic benefits.