Experimental Study On Direct-shear Strength Of Slag-fly Ash Based Geopolymer Concrete

Geopolymer is a cementitious material formed by aluminosilicate material under the action of alkali activator.Because the preparation process of geopolymer cementitious material does not go through high-temperature calcination,it can save a lot of energy consumption;Moreover,the main raw material of geopolymer is industrial waste,which also reduces a lot of waste pollution.The application of geopolymer concrete in construction engineering can promote the green cycle of industrial waste,reduce the waste of energy and resources and environmental pollution.In this thesis,the shear strength of reinforced concrete based on the size of reinforcement and fly ash is studied as follows:(1)For geopolymer concrete direct-shear specimens,with the increase of concrete strength and transverse reinforcement ratio,the shear stiffness and shear strength of geopolymer concrete are significantly improved.When the reinforcement ratio is 1.31% and 1.88%,the increase of concrete strength has a great impact on the shear strength.Increasing the reinforcement ratio of shear reinforcement is conducive to restrain the development of shear cracks,and the residual shear strength is also improved.Changing the width of the shear plane has little effect on the shear strength of geopolymer concrete,and changing the height of the shear plane has a significant effect on the shear strength of geopolymer concrete,which is shown as increasing the height of the shear plane and decreasing the shear stress.(2)The crack development mode,failure mode and shear stress slip relationship curve of geopolymer concrete shear specimens are basically the same as those of ordinary silicate concrete,and the shear strength of geopolymer concrete is slightly higher than that of ordinary silicate concrete.(3)The test value is compared with the theoretical calculation value of the calculation formula specified in the existing specifications and the commonly used empirical formula.The results show that the test value of all specimens is greater than the calculated value,indicating that the calculation formula of shear capacity in the existing ACI,PCI and CSA specifications can be used to safely calculate the shear strength of polymer concrete.In this thesis,the nonlinear and linear prediction model formulas for calculating the shear strength of geopolymer concrete are fitted according to the ultimate shear strength obtained from the test.(4)Using ABAQUS finite element software,through the nonlinear simulation analysis of the shear test of geopolymer concrete,it is obtained that the shear stress slip curve of geopolymer concrete under shear load is divided into linear elastic section,nonlinear deformation section,descending section and residual stage,which is consistent with the shape of the shear stress-strain relationship curve of the test results.The concrete damage nephogram shows that after the failure of the specimen,the concrete on the left and right sides has obvious vertical sliding,the cracks run through the shear plane,and there are many inclined cracks near the shear plane and concrete failure occurs.