Influence Of Coarse Aggregate Of Recycled Coal Gangue Brick On Strength And Bearing Capacity Of Cement Stabilized Recycled Mixture

In 2017,the output of construction waste in 35 pilot cities（districts）in China has reached about 1.09 billion tons.Among the construction waste generated,the content of waste bricks accounts for more than 50%.Due to the low strength,high porosity and high water absorption of waste bricks,it is not easy to reuse them in the field of building materials.Searching for efficient recycling of waste bricks is the key to reducing the stock and increment of construction waste.Based on this purpose,this paper uses recycled coal gangue brick（RCGB）coarse aggregate to replace part of natural coarse aggregate to prepare cement-stabilized recycled mixture.By evaluating the changes of its unconfined compressive strength and bearing ratio,the feasibility of using it as a cement-stabilized bonding layer in the pavement base was studied.Before the laboratory test,the basic physical and mechanical indexes of RCGB coarse aggregate were tested,the volume replacement method of RCGB coarse aggregate was proposed,and the preparation,maintenance and demoulding standards of cement-stabilized recycled mixture were discussed.Then,the unconfined compressive strength（UCS）and California Bearing Ratio（CBR）of the cement-stabilized recycled mixture were studied by designing the mix ratio scheme.The following main conclusions are drawn:（1）Considering the apparent density difference between RCGB coarse aggregate and natural coarse aggregate,in order to ensure the size of the specimen,the height control standard of the cement-stabilized recycled mixture specimen after demoulding is150_-1⁺².（2）The local fluctuation of the gradation of the coarse aggregate has no significant influence on UCS and CBR of the cement-stabilized recycled mixture,but has a certain influence on the discrete type of the test data.（3）The variation of sand ratio has a significant effect on UCS and CBR of the cement-stabilized recycled mixture,but the effect of sand ratio on UCS and CBR is not consistent.The sand rate increased from 30%to 40%to 50%,and UCS of the cement-stabilized recycled mixture increased from 3.0 MPa to 3.7 MPa,and then decreased to2.5 MPa.When the sand ratio is 30%,CBR is the largest;When the sand rate is 50%,CBR is the smallest;when the sand ratio is 40%,the value of CBR is between the two,but not much different from CBR when the sand ratio is 30%.（4）The values of UCS and CBR of the cement-stabilized recycled mixture both increase with the increase of cement content.（5）Whether the recycled coal gangue brick coarse aggregate replaces the single particle size range of 4.75 mm-9.5 mm of coarse aggregate or the whole particle size range of 4.75mm-26.5 mm,UCS and CBR value of cement stabilized recycled mixture prepared at the same cement content decrease with the increase of recycled coal gangue brick aggregate replacement rate.（6）When 4.75-9.5mm coarse aggregate is replaced by 50%RCGB coarse aggregate and cement content is 7%,the cement stabilized recycled mixture can meet the strength requirements of pavement base under any traffic grade of all highways.when the cement content is 4%and 5%,it can meet the strength requirements of the secondary and lower secondary highway base under heavy traffic conditions,the strength requirements of the middle and light traffic pavement base of the highway and the first grade highway,and the strength requirements of the bottom base of all highways.When the cement content is 7%,UCS can reach 2 MPa when the replacement ratio of coarse aggregate of recycled coal gangue brick in the particle size range of 4.75 mm–26.5 mm is less than 69%,which can meet the strength requirements of the secondary and lower secondary highways under medium and light traffic conditions.