Optimization Of RAP Material Refinement Treatment Process Based On Coarse Aggregate Morphology

At present,China’s high-grade highways have changed from a large-scale construction period to a period of construction and maintenance,and a large amount of waste asphalt mixture(RAP)is produced every year.However,under the conventional recycling process,the agglomeration phenomenon of RAP material is serious,and the asphalt film coated on the surface of the aggregate cannot be effectively regenerated,resulting in a generally low RAP content.In order to improve the regeneration content of RAP,the researchers proposed a refined treatment technology for RAP,which can effectively reduce the particle size variability of RAP materials and achieve "oil-stone separation",but the influence of the fine treatment process on the particle morphology and performance of the mixture has not yet been paid attention to,so it is difficult to determine the optimal treatment process.In order to solve the above problems,this paper proposes the fine treatment and screening technology of RAP material based on "shot blasting and grinding",establishes a multi-scale evaluation system for the particle morphology of recycled coarse aggregate by using 3D scanning technology and AIMS system,and analyzes the influence of RAP material fine treatment technology on the particle morphology of coarse aggregate.At the same time,a threedimensional uniaxial penetration numerical model was established to analyze the correlation between the shear resistance of recycled asphalt mixture and the particle morphological characteristics of coarse aggregate,and then after comprehensively considering the influence of RAP "oil-stone separation" effect and coarse aggregate morphology,the fine treatment process of RAP material was optimized,and the RAP content was analyzed.Under the determined optimal treatment process,the comprehensive road performance evaluation of recycled asphalt mixture with a content of 75%was carried out,and the main conclusions were as follows:(1)The refined treatment and screening technology of RAP material based on "shot blasting and blasting" has realized "oil and stone separation",and the aging asphalt content of RAP material after treatment is less than 1.5%.At the same time,the multi-scale evaluation system established can effectively characterize the macro-fine-micro morphological characteristics of coarse aggregates,and the measurement method adopted is simple to operate and has high data accuracy.(2)The comparison results of recycled coarse aggregate morphology under different treatment processes show that the fine treatment process of RAP material has a significant impact on the gradient angularity and texture index of recycled coarse aggregate.After treatment,the square differences of the four morphological indicators of RAP material are significantly reduced compared to RAP material,effectively improving the variability of RAP material morphological characteristics.(3)The real morphological reconstruction of coarse aggregate is realized by using 3D scanning technology and Template template,and a uniaxial penetration test model of recycled asphalt mixture with a RAP content of 75%is constructed,and the meso-parameters are determined by combining the DSR test,and the results show that the numerical model is highly consistent with the actual specimen in terms of volume characteristics and force characteristics.(4)The relationship between the morphology of recycled aggregate and the shear performance of the mixture was studied by using a uniaxial penetration numerical model,and it was found that the influence order of four morphological indexes was:comprehensive angularity>comprehensive texture index>comprehensive sphericity>Based on the needle sheet index and the effect of "oil-stone separation",the treatment process is optimized to have a spindle speed of 40rad/min and a treatment time of 30min,and the RAP content should not exceed 75%.(5)Under the optimal treatment process,the design and research of recycled asphalt mixture with high RAP content(75%)was carried out,and all indicators of the mixture after adding regent reached the requirements of asphalt pavement,which verified the optimal treatment process of RAP material proposed in this paper.In this paper,the fine treatment process of RAP material is proposed,its effects on the particle morphology of recycled coarse aggregate and recycled asphalt mixture are analyzed,and the optimization of the fine treatment process of RAP material is finally determined by combining the effect of "oil stone separation",and the comprehensive road performance of recycled asphalt mixture with high content of 75%is verified.The research in this paper is of great significance for the realization of RAP high content recycling,which can effectively improve the road performance of recycled asphalt mixture,and has good economic,environmental and social benefits.