Research On Design Method And Performance Of Micro-surfacing Based On Long-term Performance

At present,our country’s roads and municipal roads have entered a large number of maintenance period,and micro surfacing,as a commonly used preventive maintenance technology,has been widely used at home and abroad,but also exposed some problems,including the normal technical indicators such as the wet wheel wear value and width deformation rate in the design of indoor mix proportion of micro surfacing,which meet the specification requirements,but are polished rapidly after construction There are ruts,peeling and other problems.This is due to the strong empirical design of the indoor mix proportion of the micro surfacing,and the long-term performance has not been verified.In order to prolong the service life of micro surface and solve many problems after the construction of micro surface,this paper summarizes and analyzes the evaluation methods of domestic and foreign experts and scholars on the long-term skid resistance and rut resistance of asphalt mixture on the basis of the existing mix design methods of micro surface,uses accelerated load test and long-term high temperature test to evaluate the long-term performance of micro surface,and puts forward the basis In this paper,the influence of gradation,modified emulsified asphalt and rubber powder on the micro surface performance is studied,and the shear resistance of the micro surface mixture is also studied through the new oblique shear test.This paper first summarizes and analyzes the research results of experts and scholars on micro surface grading,and studies the working performance,road performance and long-term performance of four kinds of MS-3 micro surface with different 7mm mesh passing rate by using SBR modified emulsified asphalt,and selects a wear-resistant grading.It is found that under the same conditions,the MS-3 micro surface can be mixed with the reduction of 7mm mesh passing rate With the increase of time and consistency,the cohesion becomes smaller;the wear resistance and water damage resistance increase,but the rutting resistance decreases;the long-term sliding resistance and long-term wear resistance increase,but the long-term high-temperature performance decreases.In order to make the micro surface matching have good wear resistance and rutting resistance,it is recommended that the passing rate of 7mm sieve should be in the range of 80% ～ 95%.On the basis of optimizing the gradation,this paper uses SBR modified emulsified asphalt,SBS modified emulsified asphalt and water epoxy modified emulsified asphalt to carry out a comparative study on the road performance and long-term performance of the micro surface.It is found that the comprehensive performance of water epoxy modified emulsified asphalt is better.In this paper,the micro surface of 60 mesh rubber powder with 0%,2%,3% and 4%rubber powder was studied on the basis of the existing research on the micro surface of rubber powder.It was found that under the same conditions,the addition of rubber powder in the micro surface mixture will reduce its wear resistance,water damage resistance,long-term high temperature performance,long-term sliding resistance and long-term wear resistance,and the higher the content,the lower the performance Therefore,it is suggested that rubber powder should not be added alone to reduce noise at micro surface.Based on the comparative analysis of accelerated loading and long-term high temperature test results of micro surfacing mixtures with different gradations,modified emulsified asphalt and rubber powder,this paper recommends that the long-term anti sliding performance of micro surfacing should be controlled according to the swing value not less than 55 and the structure depth not less than0.45 mm after 50000 times of accelerated loading,and the long-term anti sliding performance of micro surfacing should be controlled according to the long-term anti sliding performance of mass loss not more than 1.0% It can control the long-term high-temperature performance of micro surface according to the rut depth not more than 5mm after 5000 times of load.At the end of this paper,a new type of oblique shear test is used to study the shear resistance of the mixture at the micro surface.It is found that the shear failure at the micro surface is mainly interlaminar shear failure at low temperature,and the shear failure at the micro surface is mainly self shear failure at high temperature.When the surface of the original pavement is rough and has a large friction coefficient,the spreading of tack coat oil has little contribution to the increase of the interlaminar shear strength,while when the original pavement has soil pollution,it will affect the adhesion of the micro surface and the original pavement,thus reducing the interlaminar shear strength of the micro surface,and the immersion of water will also reduce the interlaminar shear strength of the micro surface.