Research On Beneficiation Technique Of High Quality Recycled Concrete Aggregate

With the rapid development of civil engineering,a large number of construction waste generates serious impact on the environment and human life.In order to solve the problem of these construction waste,some ideas recycling waste were put forward.However,the existing technology was imperfect,and the quality of aggregate was poor and the cost of secondary modification was high,which caused the recycled concrete cannot be widely applied.It was urgent to propose a high quality recycled aggregate beneficiation to promote the application of recycled concrete in practical engineering.In this paper,the test study method was used to treat the waste concrete blocks by microwave-assisted mechanical beneficiation.The high quality recycled coarse aggregates were obtained,and their mechanical properties were studied from the macro and micro aspect respectively.Then,the recycled coarse aggregate were used to make recycled concrete,and the compressive properties and failure modes were studied.The main contents and conclusions were shown as follows:(1)From the perspectives of different dielectric constants between coarse aggregate and mortar and the weakening principle of the interface between coarse aggregate and mortar,the principle of microwave-assisted mechanical beneficiation of waste concrete blocks was studied,and finally it was concluded that between the coarse aggregate and mortar was a hypothesis that the cement slurry shrinkage.(2)The best range of irradiation parameters could be obtained by irradiating concrete blocks with different sources of 900W power.Through the thermal imaging tests,the surface and internal temperature distribution of waste concrete blocks were analyzed to explore the influence of temperature on the damage degree of coarse aggregate.The mechanical properties of the regenerated coarse aggregate were compared with that of the natural coarse aggregate and other high-quality recycled coarse aggregate,and the superiority of the microwave-assisted mechanical beneficiation process was illustrated.Through the scanning electron microscope tests,the damage degree of coarse aggregate was studied from the perspective of micro,indicating that the coarse aggregate selected from discarded concrete lumps by microwave-assisted mechanical process was of high quality.(3)The compressive strength and failure mode of ordinary concrete and recycled concrete were studied.From three aspects of test results,damage mechanics and fracture mechanics,it was analyzed and concluded that recycled concrete and ordinary concrete have similar compressive strength and failure modes,which mainly experienced the elastic stage,the micro crack generation stage,the micro crack development stage and the failure stage.The main failure modes were the destruction of the mortar body,accompanying with the destruction of the interface between coarse aggregate and mortar,and the peeling of the surface concrete.