Study On The Pavement Performance Of Large Stone Porous Asphalt Mixes With Rubber Pitch

With the increase of freeway mileage and the extension of service time, the early construction freeway has gradually appear different sorts of diseases. One of the most serious diseases is crack, and the pavement cracks are closely related with the grass-roots cracks. The treatment of grass-roots cracks, now the reasonable solution with good application effects is milling asphalt surface course and the cement stabilized gravel base, paving large stone porous asphalt mixes base and asphalt layer again,by large stone porous asphalt mixes base instead of cement stabilized gravel base. Most of the pavement engineering after maintenance is still fracture structure.This paper based on the Anhui freeway asphalt pavement maintenance engineering, Based on crack resistance, research the design method and the road performance of large stone asphalt mixes. The content of this research topic:(1)Analyze the mechanics performance of asphalt pavement maintenance engineering. Contrastively analyze the law of stress and strain of pavement structure with good condition (no cracks at the grass-roots level) and with cracks (containing the cracks at the grass-roots level). (2) Properties and selection of raw material, putting forward the index system applied to the rubber asphalt, and contrastively analyze the performance of rubber asphalt and SBS modified asphalt. (3) The mix proportion design of large stone porous asphalt mixes (LSPM), mixture design of large stone porous asphalt mixes according to the test-empirical method. (4) By performance test of large stone asphalt mixes road, Test Marshall stability, water stability, high temperature stability, the compressive modulus of large size asphalt macadam with different asphalt cement. (5) The crack resistance research of large stone rubber asphalt mixes base material, use low temperature test to evaluate low temperature crack resistance of large diameter asphalt mixture. Exploring low temperature crack resistance of large stone asphalt mixes with different cements and different distributions, analyze the improvement effect of low temperature anti-cracking performance of large stone asphalt mixes under basalt fiber. Improve technical measures of crack resistance of large size asphalt mixture.Conclusions of this research topic:(1) The maximum tensile stress appears in the surface layer of 20-30 cm, when the grass-roots level of asphalt pavement with the cracks under the load. For large size asphalt macadam base position here, hence the crack resistance of large stone asphalt mixes is very important to pavement structure. (2) Index evaluation of rubber asphalt include:recovery of elasticity, rotary viscosity of 135℃, dynamic viscosity of 60℃, penetration and softening point of 25℃ and ductility of 5℃. It’s elastic recovery is slightly lower than the SBS modified asphalt, dynamic viscosity of 60℃ improved 162.42% than SBS modified asphalt. (3) The best asphalt content of large diameter rubber asphalt macadam is 3.7%, suggest the thickness of asphalt film is greater than 12μm. (4) dynamic stability, residual stability index of large size asphalt rubber asphalt macadam are higher than the SBS modified asphalt, Modulus of resilience is also greater than the SBS modified asphalt. (5) Void fraction dramatically affects crack resistance of the large stone asphalt mixes. The bending Tensile strain of large stone asphalt mixes increases by 14.29% than large stone porous asphalt mixes, bending and tension strength increases by 370.69%, critical strain energy density increases by 251.31%. Basalt fibers can obviously improve the flexural strength and strain energy density of large stone porous asphalt mixes, flexural strength increases by 118.97%, strain energy density increases by 74.91%.(6) Reducing the air voids of large stone asphalt mixes, adding mineral fibre, can both improve the crack resistance of materials.