| The wide production of construction & demolition waste(C&D W)and its illegal deposition are serioius current peoblems in China.The components includes: bricks,concrete,mortar,waste soil,steel,plastic,wood,etc.In the other hand,the natural aggregates for constrctction are becoming shortage.Therefore,the comprehensive utilization of construction & demolition waste is an effective way to provid the aggragates as well as benefis for environment protection.The research forcus on the high efficient separarion technology,reinforcement of recycled aggregates quality,key tenology and equipment.The conclusion and some recommendations about processing and using of C&D W in road consction are also presented.The storage area distribution,annual production and environment problems of C&D W were investigated in Xi’an city,China.The compostions,technical indicators,gradations,microstructures as well as the mineral compoaitions were studied.Results showed that the bricks take up a large proportion that decreases the pavement properties.The C&D W processing technology,chemical reinforcement and physical reinforcement methods were studied.By coating with high-reflectivity polymers,the recycled aggregates were scaned in a black box.The strengthen methods were optimized by using the ratio of needle-like and roundness of aggregate.The loss ratio of sideline and mortar were characterized by Rw and Rm,which were proposed by images process.Results showed that the strength and adhension ability with bitumen were well enhanced by soaked in lime solution.By rotated 70 circles,the ratio of needle-like was decreased by 5%~10% as well as the roundness was decreased by 50%.Rw and Rm were decreased with rotated circles;recycled concrete with lower strength grade obtained a better reinforcement result.The first gerenation of separation technique was designed based on the cuboid shape of bricks.The second gerenation of separation technique was studied based on the apparent density.The separation technology was studied by new method of separation,mechanism design,theoretical calculation of boundary conditions,macrocode operation,detail design,etc.The third generation of separation technique was researched based on the apparent density,roundness of aggreagtes,internal friction angle and suspended velocity.The aggregate shape and wind speed were considered by simulate the particles movement and airflow(EDEM-CFD).The above theory was verified by the machines designed and applied in the pavement construction.Results show that the concrete in the rececled aggregate were take up 70%,90% and 90%,the production efficiency can be achieved to 60t/h,4t/h and 12t/h.Processing technology of C&D W for pavemen engineering was studied,the economical and multipurpose processing technologies were proposed for the subgrade and pavement engineering.The result show that the processing technology,machine and quality control method suitbale for the roadbed,subbase,foundation treatment and high environment benefit.The mechanical and fatigue properties were studied by testing the cement stabilized mixture with different recycled aggregate content and constituents.Result showed that the proportion and constituents were the main factors for the pavement performance.The asphalt mixture design methods of Marshall and Superpave were compared for asphalt mixture with C&D W.Based on the properties of recycled aggregate,Superpave mixture design,thickness of asphalt film,flow number and fracture energy index,the asphalt mixture design method for C&D W was proposed.Results indicate that the additional asphalt played an important role in rutting and cracking property.The better pavement performance could obtain by add extra asphalt and reduce the gyration number.Moreover,the void content,void in the mineral aggregate and gradyation should change to adjust the mixture design. |
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