Experimental Study On The Eccentric Compression Performance Of Geopolymer Concrete Columns

As a kind of green concrete material,Geopolymer Concrete(GC)can not only realize the recycling of a large number of industrial wastes(such as fly ash and slag,etc.),but also significantly reduce the amount of cement-based materials,thus greatly reducing the CO2 emission in the concrete production process.The results show that geopolymer concrete has excellent mechanical properties,corrosion resistance,durability and high temperature resistance,and its large-scale application in civil and hydraulic engineering can save resources and protect the environment.Therefore,the preparation,performance and application of geopolymer concrete have become the focus of current research.At present,the research on the mechanical properties of geopolymer concrete members is still in its infancy at home and abroad,and the relevant research mainly focuses on the flexural and shear properties of geopolymer concrete beam members,while the research on the bias properties of geopolymer concrete columns is not sufficient and there are few literature reports.Therefore,supported by the National Natural Science Foundation of China "Basic Research of Green and Low-carbon Geopolymer Concrete Materials and Structural Design" project(Project Approval No.51638008),this paper conducted a systematic experimental study and theoretical analysis on the eccentric compression performance of geopolymer concrete columns.The main contents of the study are as follows:(1)Taking concrete strength,reinforcement ratio,stirrup ratio,slenderness ratio and eccentricity as experimental parameters,16 eccentric columns of geopolymer concrete were prepared,and 7 eccentric columns of ordinary concrete(PC)were set as control group.The failure modes and mechanical properties of geopolymer concrete columns under eccentric loading were studied,and the influences of various parameters on eccentric loading properties of geopolymer concrete columns were analyzed.By comparing the test results of eccentric compression performance of geopolymer concrete columns with those of ordinary concrete columns,it is found that the failure mode and crack development mode of geopolymer concrete columns under eccentric compression are the same as those of ordinary concrete columns,and all of them are destroyed by concrete crushing.The destruction forms are divided into large and small eccentric destruction.The cracking load of GC column under eccentric pressure is smaller than that of PC column,the crack development is slower than that of PC column,the distribution of cracks is denser and the number of cracks is larger.The bearing capacity of geopolymer concrete columns under eccentric loading is similar to that of PC columns,and the bearing capacity of GC columns is only 5.3% smaller than that of PC columns.(2)Compared with ordinary concrete columns,the compressive strain of geopolymer concrete columns at the edge of compression and the overall lateral deflection of columns develop faster during loading.Compared with PC columns,the ultimate compressive strain of GC columns increased by 21.8% and the ultimate deflection increased by 9.4%.Under the ultimate load,the flexural rigidity of geopolymer concrete column is smaller than that of ordinary concrete column,and the reduction is larger under the condition of large eccentricity.(3)The calculation and analysis of geopolymer concrete columns are carried out by using the calculation method of eccentric compression of columns in China’s current concrete code,Code for Design of Concrete Structures(GB 50010-2010)and Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG 3362-2018).The results show that the calculated values of the bearing capacity of geopolymer concrete columns and the eccentricity increasing coefficient of the secondorder effect are in good agreement with the experimental values,and the formula for calculating the bearing capacity of eccentric columns in existing codes can be used for geopolymer concrete columns.Using the crack calculation formula given in the specification GB 50010-2010 to check the crack spacing and width of the GC eccentric compression column,it is found that the crack spacing value measured by the test is smaller than the calculated value.Combined with the measured results,a crack calculation formula suitable for geopolymer concrete eccentric compression columns is proposed.(4)Using the appropriate constitutive relation of geopolymer concrete material,the nonlinear analysis program of geopolymer concrete eccentric columns is compiled by MATLAB software,and the whole process of the failure of geopolymer concrete eccentric columns is analyzed and calculated.The calculated bearing capacity and ultimate deflection value of the program are in good agreement with the experimental values.And the eccentric compression column of geopolymer concrete is completed by this program.Based on the parameter analysis,81 eccentric compression columns of geopolymer concrete were designed with concrete strength,eccentricity,reinforcement ratio and slenderness ratio as parameters,and the influence law of each parameter on the second-order effect was analyzed.According to the code GB 50010-2010 and JTG3362-2018,it was calculated that the ratio average value of eccentric compression coefficient of 81 eccentric compression columns of geopolymer concrete was 1.05 and1.01 respectively,and the standard deviation was 1.01.