Research On Optimal Design Method Of Asphalt Mixture Ratio Based On RAP Coarse Material

The recycling of asphalt pavement materials can not only prevent the waste of resources and save costs,but also effectively solve the problems of waste materials polluting the environment and occupying land resources.Therefore,it has been widely valued by road workers for a long time,and some important research has been obtained.Achievements and mature engineering experience.With the continuous development of road construction in our country,the maintenance and repair of existing asphalt pavements have become more frequent,and the significance of asphalt mixture recycling has become more prominent.Regarding the dosage of RAP in the regeneration process,the usual practice is to use regenerating agent to make full use of old materials.However,under the premise of using regenerating agent,the utilization rate is generally up to 50%;in this regard,the use of regenerating agent The use has a certain degree of adverse effects on the performance of the mixture.On the other hand,the utilization of 50%is far from insufficient.For the previous research,more attention is paid to the regeneration of asphalt,and with the shortage of domestic mineral resources,reuse of mineral materials is also valued.In view of this,this research converts the technical idea of the use of old materials.The RAP material is first separated from the coarse and fine,and then only the coarse material is used without the use of regenerating agent;and the skeleton density characteristics of the gradation are considered,so that after the addition of new aggregates,The old coarse aggregate and the new coarse aggregate form a coarse aggregate skeleton embedding structure,and the recycled asphalt mixture forms a skeleton dense asphalt mixture.Through formula derivation and gradation optimization,the method of asphalt mixture mix proportion optimization design is formed.The moisture content,asphalt content and asphalt performance of RAP and RAP coarse material parts are determined through related tests,and the gradation composition of RAP and RAP coarse material parts is determined;Based on the maximum dosage of traditional RAP when the regenerant is not used(the blending rate is generally considered to be 30%),the maximum blending rate of the coarse material content in RAP is analyzed,and the calculation formula for the maximum blending ratio is established through derivation,taking AC20 RAP as Example calculations show that as long as the ratio of the quality of the crude RAP to the quality of the new aggregate is not more than 5 times or the maximum amount of RAP is 8.5 times the mass of the new coarse aggregate,the regenerant can not be used.Refer to the maximum blending rate of the coarse material content in RAP,carry out the gradation design of the skeleton-dense recycled asphalt mixture,and obtain the target skeleton-dense gradation of the recycled asphalt mixture in the theoretical sense;determine the optimal asphalt content through the Marshall test method OAC.Determine whether the relevant performance meets the specification requirements through experiments,and then optimize the gradation on the basis of the skeleton dense gradation in the theoretical sense to obtain the actual skeleton dense gradation.As a further comparison,all new materials were used to debug a gradation curve close to the theoretically dense gradation of the skeleton,and related performance tests were carried out.Compare the results of the two sets of performance experiments and observe their pros and cons.The experimental results show that the performance of the asphalt mixture under RAP blending fully meets the requirements of relevant specifications,and the established gradation optimization design method is feasible.