Effect Of Vibration Mixing On Attrition And Cleavage Of Recycled Aggregate And Performance Of Recycled Aggregate Concrete

Recycled aggregate surface hardened cement mortar has high porosity,strong water absorption,low strength,and weak interface transition zone,which causes performance defects in recycled concrete.Attrition and cleavage occur during the pretreatment of the recycled aggregate in the mixer,and particles of different particle sizes are produced.Different mixing methods and parameters have different attrition and cleavage effects,so the particle size distribution and quantity of the attrition and cleavage particles are different,and these particles will inevitably affect the performance of recycled concrete.In this paper,the effect of mixing on the attrition and cleavage of recycled aggregates was studied.The particle size distribution of the particles was analyzed.The effects of the particles on the working performance and mechanical properties of recycled.In this paper,three rounds of tests were designed.In the first round of experiments,a total of 15 working conditions were designed.The recycled aggregates were mixed under two mixing machines,two mixing speeds and four mixing processes to determine the particle size distribution and range.The second round of tests is based on the performance test of recycled aggregate concrete in the first round of tests.The test consists of a total of 20 working conditions,including four types of coarse aggregates and four levels of recycled aggregates,The recycled concrete was prepared in a manner of vibration mixing and ordinary mixing,and its slump,gas content and compressive strength were tested.In the third round of experiments,the two-stage mixing method of recycled concrete based on the vibration mixing pretreatment of recycled aggregate was designed to optimize the performance of the recycled aggregate concreteThe test results show that the cleavage phenomenon of the recycled aggregate in the double-shaft mixer is the most obvious,the vibration mixing method is the second,the planetary mixing is the least obvious in the planetary mixer;the attrition is the most obvious under the vibration mixing mode,the common forced mixing Secondly,the planetary mixing attrition is minimal.The twin-shaft mixer has high power,mixing blades and mixing arms.When the particles move,the friction collides with these rotating firmware,and there is a gap between the blades and the mixer liner,resulting in partial regeneration of the bone.The phenomenon of jamming of the material causes the attrition and cleavage of the recycled aggregate to increase.The vibration mixing reduces the friction between the aggregates,so that the aggregate particles,the blades and the shaft are in the state of flutter,which increases the frictional collision of the aggregate particles.The frequency increases the attrition phenomenon,but as the friction decreases,the degree of fragmentation of the recycled aggregate decreases.The larger the mixing speed,the longer the mixing time,the more obvious the attrition and cleavage phenomenon,and with the increase of the mixing time,the particles that have been attrited and cleaved will suffer secondary attrition and cleavage;Water addition can increase attrition,reduce cleavage,and reduce the total value of attrition and cleavage.Attrited particles can cause the slump of recycled concrete to decrease,affecting the working performance only in the vibration mixing.The broken particles can increase the compressive strength and slump of the concrete.On this basis,combined with the actual production application,the two-stage mixing method of recycled concrete based on the recycled aggregate pre-treatment of vibration mixing was determined.