Research on the back analysis and failure mechanism of recycled concrete aggregate meso-parameters based on Box-Behnken Design response surface model

Abstract

To obtain the mesophase material parameters of recycled concrete aggregate and analyze the material failure mechanism, based on the Box-Behnken Design, a non-linear material parameter back analysis model of recycled concrete is proposed, and the failure mechanism of recycled concrete materials is explored. Based on the indoor experiment, the numerical simulation experiment of 25 sets of inversion parameters was constructed with the help of Design-Expert. The response surface relationship between different response variables (inversion parameters) and independent variables (mortar elastic modulus, interface elastic modulus, mortar tensile strength, and interface tensile strength) was obtained, which realized the explicit expression of the implicit relationship between mesophase parameters and macroscopic mechanical properties. The mesophase parameters are obtained by inverse analysis, and the stress-strain curve is obtained by bringing it into the numerical model. The comparison with the test results shows that the peak stress error is only 2.8%, the peak strain error is close to 8%, and the fitting degree is good. Combined with the grey relational degree theory, the material failure mechanism is analyzed from the perspectives of the material area ratio of each phase and the mesophase material parameters: the effect of the mortar phase parameters on the stress-strain process is greater than that of the interface phase. The elastic modulus of the mortar has the greatest influence on the stress of each stage, and the tensile strength of the mortar has the greatest influence on the peak strain. This study provides a theoretical basis for the follow-up research on the mechanical properties of recycled concrete.