Residual Slurry Stripping Of Recycled Fine Aggregate And Its Quality Improvement

The aggregate produced by the crushing of waste concrete has a large amount of residual slurry adhered to the surface,resulting in high water absorption,low apparent density and high crushing index of recycled fine aggregate,which limits its application and makes it difficult to realize effective resources.For chemical utilization,it is necessary to study and propose corresponding methods to remove residual slurry on the surface of regenerated fine aggregates.In response to this problem,this paper firstly defines the residual slurry stripping rate of recycled fine aggregate,and studies the effect of the load size,load duration and material layer thickness on the residual slurry of recycled fine aggregate in waste concrete under the action of load in the laboratory.The influence of the slurry stripping rate;secondly,the influence of the process parameters of the pilot equipment(roller pressure,grinding disc speed,feeding amount)on the basic properties of the recycled fine aggregate was studied;finally,the 100% mixing of the recycled fine aggregate The effect of process parameters on the working and mechanical properties of recycled mortar and recycled fine aggregate concrete,and the improvement of the performance of recycled mortar and recycled fine aggregate concrete under the optimal parameter combination.The obtained research results have important theoretical and practical guiding significance for the application of recycled mortar and recycled concrete.The main conclusions of the paper are as follows:(1)As the load gradually increases,the peeling rate of the residual slurry of recycled fine aggregates will also increase;the increase in the thickness of the material layer will reduce the peeling rate;and the load duration will not.affect the peeling rate.Through the analysis of the full factor experiment,it is concluded that the load size and the thickness of the material layer have a significant effect,and the effect of the load size is greater than that of the material layer thickness,while the load duration and the interaction between the three factors are not significant.With the increase of the residual slurry stripping rate,the apparent density of the recycled fine aggregate gradually increased,the crushing index and the water absorption rate gradually decreased,and the basic performance was improved.(2)Under the premise that other parameters remain unchanged,the increase of grinding roller pressure and grinding disc speed can significantly improve the basic performance of recycled fine aggregate.When the parameters are controlled at 6MPa and700r/min respectively,the apparent density of recycled fine aggregates in different particle size ranges can reach the highest,and the residual slurry content,crushing index and water absorption can reach the lowest.However,the increase of feeding amount cannot improve the basic properties of recycled fine aggregate,and even negatively affects its properties.Therefore,the best combination of process parameters for the "experimental system for the preparation of waste concrete sand powder" is: "roller pressure 6MPa + grinding disc rotation speed 700r/min + feeding amount 0.3t/h".(3)The increase of grinding roller pressure and grinding disc speed can effectively improve the fluidity of recycled mortar and the rheological properties of recycled fine aggregate concrete.The flexural and compressive strengths of the regenerated mortar increased rapidly in the first 7 days,and after the curing age of more than 7 days,the growth rates of the two gradually slowed down.Similarly,the early strength development of recycled concrete is slow,the strength value is low,and the strength gradually increases with the increase of age.In addition,under the optimal parameter combination,the 28 d flexural and compressive strengths of recycled mortar reached 10 MPa and 29.8MPa,respectively,about 80% of that of natural mortar;the 28 d splitting tensile and compressive strengths of recycled fine aggregate concrete were respectively Up to3.19 MPa,29.5MPa,about 85% of natural concrete.