Study On Axial Compression Behavior Of Geopolymer Recycled Concrete Columns With Tungsten Tailings

The building materials industry is one of the industries with large energy and resource consumption and high carbon emission.Under the background of green sustainable development,the realization of the"carbon peak and carbon neutral"goal of the whole industry should be considered from the aspects of comprehensive utilization of resources,reducing production energy consumption and carbon emissions.At present,the demand for sand aggregate is huge,but long-term mining and consumption have led to a shortage of sand resources.Due to high energy consumption and high carbon emission,the cement industry has become the focus of energy conservation and emission reduction.Replacing natural sand aggregate with recycled aggregate made from construction waste and replacing cement with geopolymer made from industrial tailings can make up for the huge demand gap of sand aggregate,reduce cement consumption and absorb a large amount of solid waste,thus alleviating the contradiction between engineering construction and green sustainable development.The resource utilization of tailings with large reserves in local areas should be studied urgently,such as Hunan scheelite tailings.Scheelite tailings have fine particles and high content of silicon and aluminum oxide,which are suitable for use as the raw material of geoppolymer.The geopolymer with strong cementation ability can be tightly wrapped in aggregate surface,and tailings particles can also be filled into the micro-cracks of aggregate.Recycled aggregate itself can also provide a certain alkaline excitation environment.The mixed use of them can make up for the defects of recycled aggregate.Therefore,the basic mechanical properties of geopolymer recycled aggregate concrete with tungsten tailings（GRAC-TT）were studied in this paper.And the tungsten tailings replacement rate,recycled coarse aggregate（RCA）replacement rate and tungsten tailings particle size as experimental variables.Furthermore,the axial compression performances of GRAC-TT columns were studied with tungsten tailings replacement rate,recycled coarse aggregate replacement rate,reinforcement ratio and stirrup spacing as variables,and the theoretical model research and finite element numerical analysis were carried out.The main conclusions are as follows:（1）With the increase in the substitution rate of tungsten tailings and RCA,the cube compressive strength(f_cu),prism compressive strength（f_c）and cube splitting tensile strength(f_ts)of GRAC-TT showed a gradual downward trend.The mechanical properties of GRAC-TT were slightly improved after grinding the tailings,and the 3d compressive strength was 70%-86%of that of 28d.The f_c,f_tsand f_cuwere roughly linear.（2）With the increase of tungsten tailings and RCA replacement rate,the axial compression bearing capacity of GRAC-TT columns decreased gradually,but the peak displacement and strain increased,which were more affected by the change of RCA content.The smaller stirrup spacing and larger reinforcement ratio have enhanced the bearing capacity and deformation capacity of the specimens,and the improvement effect on the specimens with high RCA replacement rate were more obvious.The design value of GRAC-TT column axial compression bearing capacity calculated by Chinese code was more reasonable,while the European and American codes were conservative.（3）Based on the classical theoretical models of concrete confined by stirrups and considering the effects of tungsten tailings replacement rate,recycled coarse aggregate replacement rate,reinforcement rate and volumetric stirrup ratio,the calculation models of peak strength and strain and constitutive relation model proposed in this paper were suitable for GRAC-TT confined by stirrups.（4）In this paper,the axial compression simulation results of the GRAC-TT column finite element model established by ABAQUS were basically close to the experimental results.Through parameter analysis,it can be seen that the constraint effect on concrete can be effectively enhanced by using uniform arrangement of longitudinal reinforcement along the surrounding and the use of rhombic composite stirrup,and the use of high-strength steel bars can save materials.