Experimental Study On The Axial Pressure Of Column Of Recycled Brick Concrete Aggregate Concrete With Lepidolite Lithium Slag

With the proposal of strategic objectives such as carbo n emissions and carbon neutrality,and the continuous expansion of emerging industries such as new energy.lepidolite lithium slag and construction waste occupy a lot of land,causing environmental pollution and resource waste.The application of lepidolite lithium slag（LLS）and recycled brick concrete aggregate（RBCA）in concrete structures is conducive to promoting the green and low-carbon transformation and development of the construction industry.Lepidolite lithium slag is a waste slag produced by indust rial production of lithium carbonate,which has potential pozzolanic activity.In this paper,the pretreatment process of LLS is firstly determined,and the material properties of RBCA,LLS,water reducing agent and steel bar are preliminariously studied.The mechanical properties of LLS-RBCA concrete were tested on 54 cubes and 27 prisms.and the conversion formulas of splitting tensile strength,axial compressive strength and cube compressive strength of LLS-RBCA concrete are established.Considering LLS content,RBCA substitution rate,longitudinal reinforcement diameter,spiral stirrups spacing.The axial compression performance of 38 columns of LLS-RBAC concrete confined by spiral stirrups was studied.The influences of various variables on the load-displacement,concrete strain,reinforcement strain,ductility and ultimate bearing capacity of the specimen column were studied.The lateral constraint coefficient and binding force of spiral stirrup were analyzed.Based on the peak strength,peak strain and constitutive relationship,the constitutive relationship model suitable for columns of LLS-RBAC concrete confined by spiral stirrups was established.In addition,finite element analysis was carried out on 38 columns of LLS-RBAC concrete confined by spiral stirrups.The main conclusions are as follows:（1）LLS is an acid slag,mostly irregular polygonal block crystals and granular crystals.The activity index is 81.8%at 28d,and the stability is qualified when the LLS content is less than 40%.In RBCA,t he ratio of recycled brick aggregate to concrete coarse aggregate is about 4:6.Compared with natural aggregate,RBCA has lower density,easy water absorption and high crushing index.（2）The cubic compressive strength,split tensile strength and axial com pressive strength of LLS-RBCA concrete all increase first and then decrease with the increase of LLS content,and decrease with the increase of RBCA substitution rate.When LLS content is 10%,the mechanical properties of concrete are optimal.The strength conversion formulas of f_cuand f_ts、f_cuand f_c are suggested to refer tof_ts=0.241 f_cu^0.694and f_c=0.577 f_cu+0.912.（3）The failure process and failure morphology of different LLS-RBCA columns are basically similar,and the principle of d eformation coordination is satisfied among all materials.LLS content,RBCA substitution rate,spiral stirrup spacing and longitudinal reinforcement diameter have different degrees of influence on the failure degree,peak displacement,ductility and bearin g capacity of the the specimens.The Chinese code can be directly applied to the calculation of the bearing capacity of spiral stirrup confined LS-RBCA concrete columns.（4）The peak stress model of spiral stirrup confined LS-RBCA column is based on Cusson model.The peak strain calculation model is based on Legeron model,and LLS and RBCA substitution rate are introduced as important parameters.The ascending section of the constitutive curve is based on the Khaloo model,and the descending section is based on the Guozhenhai-Zhang Xiuqin model.The parameters of the ascending section and descending section are determined according to the boundary conditions,control points,test variables and other factors.Finally,the columns of LLS-RBAC concrete confined by spiral stirrups constitutive model is proposed.（5）It is feasible to analyze the axial compression performance of columns of LLS-RBAC concrete confined by spiral stirrups based on ABAQUS,which is embodied in ABAQUS simulation of failure mode of speci men column,plastic deformation of concrete,stress distribution of concrete in the middle of specimen column,stress distribution of reinforcement,displacement curve and ultimate bearing capacity.