Study On Mechanical Characteristics And Crack Resistance Factors Of Cement Stabilized Crushed Stone Reclaimed Base Under Dynamic Load

With the gradual improvement of infrastructure in our country,transportation facilities have gradually shifted from the previous stage of construction oriented development to a stage of simultaneous development of construction and maintenance.According to the 2021 Statistical Bulletin on the Development of the Transportation Industry,the proportion of highway maintenance mileage to the total highway mileage is 99.4%.In the future,a large amount of old road materials will be produced.If these materials cannot be reasonably utilized,it will cause environmental pollution and resource waste,Reasonable secondary or multiple uses can effectively solve these problems.Although recycled materials have good application prospects,the shortcomings in their related properties are also very obvious.Therefore,this article takes cement stabilized crushed stone recycled base as the research object,analyzes the mechanical properties of asphalt mixture recycled asphalt pavement(RAP)and base inorganic recycled aggregate(Reclaimed Aggregate or Reclaimed Inorganic Binder Stabilized Aggregate(RAI)mixture,and provides a theoretical basis for the application of cement stabilized crushed stone recycled base.First of all,this paper conducts raw material performance tests on mixing water,cement and RAP aggregate,and designs and optimizes the mix proportion of recycled base mixture through screening and compaction tests;Secondly,the compressive resilience modulus test of recycled base mixture provides parameters for numerical simulation,and fracture mechanics provides theoretical basis for crack expansion of cement stabilized crushed stone recycled base,and establishes the road structure model of cement stabilized crushed stone recycled base;Finally,the influence of the crack propagation and mechanical properties at the crack tip of the cement-stabilized crushed stone recycled base under the action of vehicle axle load,different base thickness and different vehicle speed is simulated and analyzed.The conclusions are as follows:(1)Mixing water and Composite portland cement meet the requirements of the specification.RAP aggregate and RAI aggregate are tested for raw materials and compared with natural aggregate.It is found that the surface of recycled aggregate is bound by asphalt or cement mortar,and the crushing value,water absorption and other indicators of recycled aggregate are at a disadvantage compared with natural aggregate,and there are many fine aggregates due to milling,so coarse aggregate needs to be added for optimization during grading design,Then provide parameters for numerical simulation through compaction test and compressive modulus of resilience test.(2)Based on fracture mechanics,the calculation method of stress intensity factor at the crack tip is analyzed,and then the model of cement stabilized crushed stone recycled base road structure is established using ABAQUS software.The vehicle dynamic load is 108km/h standard axle load(except where described in this paper),and the Mises stress,vertical stress,shear stress and horizontal stress of recycled base are analyzed,It is found that the change of cement content has little effect on Mises stress.The horizontal stress of recycled base gradually changes from horizontal compressive stress to horizontal tensile stress with the increase of base depth.When the cement content is 4%,the recycled base has good mechanical properties when the maximum value of vertical stress,shear stress and horizontal stress is small under the action of vehicle dynamic load.(3)Through numerical simulation,the effects of vehicle axle load,vehicle speed,recycled base thickness,and cement content on the mechanical properties and cracks of cement stabilized crushed stone recycled base were analyzed.It was found that vehicle axle load had a significant impact on the mechanical properties and crack propagation at the crack tip of the recycled base;The impact of vehicle driving speed on different recycled base layers is different.Comprehensive analysis shows that RAP: RAI of 1:1 and 1:2 recycled base layers is suitable for roads with faster vehicle speeds,and RAP: RAI of 1:4 recycled base layers is suitable for roads with slower vehicle speeds;Under vehicle dynamic load,the increase in the thickness of recycled base has an impact on the crack resistance and mechanical properties of the base.When the thickness of the base is 50 cm,the recycled base has a good crack propagation resistance;Changing the cement content under different vehicle speeds and recycled base thickness can have an impact on the mechanical properties and crack resistance of the recycled base.However,RAP: RAI ratios of 1:1,1:2,and 1:4 vary with the change in cement content of the recycled base.Therefore,in road engineering,it is necessary to analyze the mechanical properties and crack resistance of the recycled base with different cement content based on actual conditions.