Reasearch On Diffusion Of Recycled Bitumen And RAP Dispersion Characteristics In Hot Central Plant Recycled Mixture

As the service period of the expressway asphalt pavement built in China was completed one by one,the national expressway industry began to gradually enter the small-scale maintenance and maintenance period."Low-carbon environmental protection and resource recycling" became the main theme of China's transportation facilities construction industry at present.In order to actively respond to policies and explore the road construction technology of high efficiency,environmental protection and economy in line with the development of the times,the plant regenerative regeneration technology with the characteristics of resource reuse and performance not inferior to conventional mixed materials has become one of the researcher's technical key points.The current "Technical Specification for Road Asphalt Pavement Recycling" is based on the theory of complete mixing of new and old asphalt,and through a large number of actual engineering feedback and laboratory research results,it has been proved that it is difficult to achieve complete mixing of new and old asphalt through the use of the specified mixing process.Dissolved state,so it is necessary to make in-depth exploration of the regeneration behavior of the recycled mixture in the actual production process to propose construction improvement recommendations.Based on summarization and analysis of previous research results,this thesis conducts experimental design research on the regeneration characteristics of both asphalt and mixture.The specific contents and results of the research on asphalt reclaiming are as follows:comparative analysis of the new and old asphalt diffusion test methods and evaluation index indicators,and a new DSR asphalt diffusion research test plan and evaluation index,and different DSR test scanning modes are proposed.The influences of DSR parameters,new and old asphalt types,storage temperature and time,and old asphalt aging degree on the diffusion rate and degree of new and old asphalt were discussed.Finally,the applicability and factors of the evaluation indicators were significantly discussed.The results show that:(1)Based on the Pearson correlation analysis in SPSS,it is found that the fitting logarithm coefficient has a good correlation with the relative complex modulus index proposed by the predecessors,and the fitting logarithmic coefficient does not need to measure the comparison group data,so it is recommended.Using the fitted logarithmic coefficient to evaluate the diffusion degree and diffusion rate of new and old asphalt;(2)Setting different DSR scanning frequency and scanning strain have significant influence on the diffusion characteristics of new and old asphalt.High scanning frequency and high strain level will speed up the diffusion process of new and old asphalt.In order to reduce the impact of DSR on new and old asphalt diffusion,it is recommended to scan at 10 rad/s.The frequency and 1%strain level were used as test setting parameters.And the new and old asphalt types also have a significant impact on the diffusion characteristics,indicating that the high-viscosity aged asphalt should be selected for low-viscosity new asphalt for regeneration in actual engineering;(3)After SPSS one-way ANOVA,the factors affecting the primary and secondary factors are:aging time>Construction stage temperature-time>Asphalt type>Aging time×Asphalt type,all have significant influences.It is recommended that in the actual construction process,RAP materials with lower age and matrix asphalt type should be used first to build recycled asphalt pavement.If the RAP material with a deeper aging is used under the objective reasons,it is necessary to increase the temperature during the construction period and extend the construction time.Based on the image method RAP dispersion uniformity,the results of the research on the dispersion uniformity of asphalt mixture based on image method are summarized.The static distance dispersion method,sector scanning method,distributed eigenvalue method and double threshold method are realized on matlab platform.Based on the analysis of the advantages and disadvantages of each method and the applicability,two evaluation indexes of centroid distance and expansion clustering suitable for evaluating the uniformity of RAP dispersion in recycled asphalt mixture were proposed.Finally,the correlation between the performance of indoor mix and the evaluation index is analyzed.The results show that:(1)Compared with the RAP content and dry mix time,the one-way variance of six evaluation indicators is significant,and the RAP content is different from the centroid distance.The significance of the five indicators was higher than the dry mixing time,and all of them were significant effects,while the dry mixing time only had a significant effect on the centroid distance.This is due to the different evaluation index principles.Therefore,it is recommended to use the centroid distance method after in-depth analysis.The RAP position dispersion uniformity in the recycled asphalt mixture under the same RAP content,and the double threshold method and the expansion cluster method are suitable for analyzing the degree of RAP agglomeration in the recycled asphalt mixture under different RAP contents;(2)Extending the dry mix time can effectively reduce the void ratio of the recycled mixture and can improve Asphalt mixture water stability,high and low temperature performance;and the dry mixing time from lmin to 2min is effective in reducing the agglomeration ratio,thus recommending plant heat Raw asphalt mixing chamber lmin on prolonged regeneration current specification.