Study On Performance Of Cement Concrete Regenerated By Course Reclaimed Asphalt Pavement

During the "Twelfth Five-Year Plan" period,the proportion of maj or and medium repairs of my country’s highway network increased from about 12%to 17%.According to estimates,only 160 million tons of asphalt pavement materials are generated every year in the major and medium repair projects of arterial highways.However,the current recycling rate of road pavement materials in my country is less than 30%.In order to open up a new way of using asphalt pavement waste material coarse aggregate(Course Reclaimed Asphalt Pavement),the waste asphalt pavement material is applied to recycled low-grade cement concrete as part of the coarse aggregate.On the one hand,it improves the utilization of asphalt pavement materials,and on the other hand,it provides a new idea for the selection of waste materials for cement concrete recycling.In order to obtain the low-grade recycled cement concrete based on the reasonable blending method of CRAP and the best water-binder ratio sand ratio,the maximum CRAP content of the designed strength grade and the durability performance and improvement measures of the recycled cement concrete with high content of CRAP are carried out.Performance test to ensure that new materials and recycled old materials meet the recycling requirements;the C30 cement concrete is subjected to three-factor three-level orthogonal test of aggregate mixing method,water-binder ratio,and sand ratio,and it is concluded that the aggregate mixing method has an effect on the strength The influence range of CF is much smaller than the water-binder ratio.Therefore,it is determined that the CRAP mixing method for low-grade concrete recycling is a continuous gradation starting at 4.75mm;then cubes with different CRAP content of strength grades C15,C20,and C25 are made.Compressive strength test,the maximum CRAP content of C15,C20,C25 conforming to the design strength grade determined by the experimental regression equation is 25.48%,14.9%,7.85%;the water-binder ratio,sand ratio,and aggregate adjusted by orthogonal test Incorporation method,strength test,electric flux test,freeze-thaw cycle test and meso-structure observation were carried out on recycled cement concrete with 30%,40%,50%,60%CRAP content of C30.The results showed that waste asphalt pavement Material coarse aggregate is mixed as the coarse aggregate of recycled cement concrete,which increases the pore diameter of recycled cement concrete.For every 10%increase in CRAP content,the pore diameter increases between 10 and 25 microns,and the electric flux increases by approximately 6%;microscopic observation results show that the texture of the high-volume CRAP-cement concrete cement paste is loose and the amount of ettringite is small,indicating that the degree of hydration reaction is low,and the early strength of CRAP-cement concrete can only reach the design strength.60%～70%of the test results are consistent;the introduction of air-entraining agent and early strength agent can effectively improve the strength performance of CRAP-cement concrete.When 0.08%triterpene saponin solid air-entraining agent is added,C30 concrete meets the maximum strength The content of CRAP can reach 18.3%.