Study On The Effect Of Recycled Aggregate Cyclic Utilization On The Strength And Durability Of Recycled Concrete

A lot of waste concrete will be produced in the process of urban construction,human beings is faced with the problem of waste disposal and shortage of natural resources,as an important renewable resource,can be used as recycled concrete.The study on the strength and durability of recycled concrete which focus on the recycled coarse aggregate once broken utilization,Therefore,this paper carried out the study on the strength and durability of the recycled concrete which the recycled coarse aggregate three times broken utilization produces,talking the possible of the recycled coarse aggregate cyclic utilization,the research results as follows:(1)The waste concrete crushing,grading,taking the particle size of 5~31.5mm as the recycled coarse aggregate R1,R1 recycled concrete curing 60 d broken,the group of recycled coarse aggregate R2,according to the circular method to produce recycled coarse aggregate R3,the physical and mechanical properties of recycled coarse aggregate can meet the quality requirements of the coarse aggregate in concrete.(2)Taking the replacement rate of 0%、30%、60%、100% as a variable,the recycled coarse aggregate R1,R2 and R3 were substituted natural coarse aggregate was prepared with ten kinds of C30 recycled concrete,the experimental results show that,with the recycling times of recycled concrete repeated and the replacement rate increase,the slump of concrete mixture decrease.(3)In this paper,we study the strength of R1、R2 and R3 recycled concrete,the experimental results show that,when the R1 substitution rate is 60%,which has the highest compressive strength,more than the ordinary concrete strength;With the cycling time of recycled coarse aggregate increasing,the compressive strength and splitting tensile strength of recycled concrete decreased gradually,C30-R3 series are compared with C30-R1 series strength decreased obviously,the recycling times of the recycled coarse aggregate are the main factors affecting the strength of the concrete.(4)we study on the frost resistance test and drying shrinkage experiment of R1、R2 and R3 recycled concrete,the experimental results show that,the mass loss rate and relative dynamic elastic modulus rate of C30-R1 series concrete and C30-R2-30、C30-R2-60 recycled concrete meet the requirements specification,the frost resistance is better,the frost resistance of C30-R2-100 and C30-R3 series recycled concrete is poorer;With the times of the recycled coarse aggregate cycling and the replacement rate increasing,the mass loss and the lengthchange rate of test pieces increase significantly,the age before 90 days showed a linear increase,after 90 days tends to be stable.