Correlation Analysis Between Mesostructure And Mechanical Characteristics Of Concrete Based On Random Aggregate Model

In the construction of hydraulic engineering,the application field of concrete has become more and more extensive,and its mechanical properties have been greatly improved with the requirements of complex engineering background.As a multi-phase composite material,the generation,development and extension of internal cracks in the process of failure have always been difficult and important points that cannot be solved by macroscopic research,especially related to the weak link of concrete,the interface transition between aggregate and mortar.In the section,conventional testing methods cannot directly measure the mechanical properties of the zone,nor can it explore its influence on the mechanical behavior of concrete,involving the influence of mesostructure on the mechanical characteristics of concrete,the indoor test can not make a reasonable answer.In order to explore the correlation between meso-structure and mechanical characteristics of concrete,the particle discrete element method is used as the research method.Through the combination of laboratory test and numerical simulation,the mesoscopic model of concrete under random aggregate is established and the composition is composed.The mechanical properties of the materials were studied to analyze the influence degree of the mesostructure on the mechanical behavior of concrete.It provides a theoretical basis for considering the influence of mesostructure on the mechanical characteristics of concrete in the future concrete numerical test.The main research contents and results of this paper are as follows:(1)Through the laboratory test,the mechanical properties and crack evolution of concrete components: aggregate,cement mortar and concrete were obtained,the compressive strength of the interface transition zone was calculated,which provided a macroscopic parameter basis for the establishment of subsequent numerical models.(2)The contact model in PFC2 D software under the particle discrete element method is introduced,and through the statistical test method,the parallel bond model(PB)and the straight joint model(FJ)are used to characterize the difference and stability of the concrete material properties.The results show that the PB model is selected as a mesoscopic constitutive model for the subsequent study of the macroscopic mechanical results and the stability of the failure mode.(3)Establishing a suitable two-dimensional aggregate model is the basic premise for studying the numerical model of concrete.In this paper,an algorithm for a random convex polygon aggregate model with a circular aggregate model as the aggregate base and a random point distribution on the circle is proposed,the concrete aggregate model was established by the application software PFC2 D,which verified the feasibility of the algorithm and greatly facilitated the establishment and calculation of the numerical model of concrete materials.(4)Based on the above research,the trial and error method is used to calibrate the mesoscopic parameters of cement mortar and interface transition zone.The concrete mechanical parameters and stress-strain curves are used as macroscopic responses,and the influence of interface transition zone on the mechanical characteristics of concrete is explored,the macroscopic mechanical parameters of the interface transition zone are inversely simulated,which is close to the numerical value calculated by the fitting curve obtained by the predecessors,which verifies the correctness of the numerical model.(5)Based on the mesoscopic parameters of the above studies,the effects of different random aggregate models on the mechanical properties of concrete were investigated.The results show that when the shape of the aggregate is better(regular and round),the strength of the interface transition zone will be improved,and the mechanical properties of the concrete will be improved.At this time,the change of the mesostructure is the root cause of the change of the mechanical characteristics of the concrete.