Experimental Study On Strength Size Effect And Triaxial Compression Of Geopolymer Concrete

Geopolymer materials can make full use of solid waste and help reduce CO₂emissions,while having a series of excellent performance.However,the size and shape effects of conventional strength and high strength geopolymer concrete（GPC）,the effect of age on the strength of GPC,and the mechanical properties of GPC under triaxial stress state are less studied,which need to be further studied.Two kinds of strength GPC size effect and shape effect are systematically studied in this paper.The elastic modulus of conventional strength GPC is studied for different shapes of test blocks,and is compared and analyzed with the formulas for predicting elastic modulus proposed by other scholars.The triaxial compression characteristics of two kinds of GPC under 13 confining pressure ratios were studied,and the stress-axial strain curves and stress-lateral strain curves were obtained.Furthermore,three failure criteria were used for fitting analysis and comparison.（1）The difference of size effect between GPC and portland concrete（OPC）at 180days of age is due to the fact that GPC is affected by efflorescence.Moreover,the specimen with large specific surface area is more susceptible to the influence of efflorescence,which weakens the further development of strength of GPC specimen.The prediction equation of elastic modulus of GPC proposed by Lee et al.well predicted the elastic modulus of the standard specimen GPC in this test.（2）Under triaxial compression,the compressive strength and critical strain increase with the increase of confining pressure ratio.Similar to OPC,the ascending slope of the compression meridian of the failure surface of GPC is relatively large under the medium and low horizontal confining pressures,and the failure curve of GPC tends to be stable under the higher confining pressures.The calibrated Power-Law and Willam-Warnke failure criteria are very suitable for the test data.（3）The relationship between critical strain and confining pressure of GPC conforms to the model proposed by Xiao et al for OPC.The relationship between transverse strain and axial strain conforms to the model proposed by Montoya et al.Under deviatoric stress,the volume of GPC is compressed first and then expanded,and the secant strain ratio under different confining pressures is 0.5,which shows the same property as OPC.