Meso-scale Modeling And Numerical Investigation Of Concrete With Pores

As common building materials,concretes have the advantages of widely getting,easily constructing and cheaply spending.At present,concretes have been widely used in civil,military and other fields,which play an important role in engineering construction.At the mesoscale level,the concrete is considered as a composite material with strong heterogeneity,which is composed of coarse aggregates,cement mortar matrix,pores and cracks.The microfractures and pores with random distribution and different shapes are the main factors to determine the mechanical properties of the concrete.Studying the distribution of initial pores is a key point in the research of concrete mechanical properties.It has great significance to study the damage evolution of concrete and improve its strength and durability.In this paper,the influence of pore parameters on macroscopic properties is studied based on the numerical concrete model with random initial pores.It can provide a reasonable reference for improving the mechanical properties of concrete.The main research work includes:According to the concrete meso-structure,a high-efficiency stepwise overlap checking method is proposed based on the traditional 2D modeling.Pores are introduced directly into the models,and different concrete meso-structures with pores are generated.Various concrete models with circular,elliptical,polygonal aggregates and circular,elliptical pores are generated,which shows the feasibility of the method.Numerous modeling examples with different area fractions and aggregates shapes are generated which show that the stepwise overlap checking method has high computational efficiency.The generated finite element model can simulate the static mechanical properties of concrete specimens well under uniaxial compression.The damage distribution shows that the pores have a great influence on the failure path of concretes.Based on the comparison of modeling results,the influence of random distribution of concrete composition on both mechanical properties and failure modes of concrete are studied systematically.This paper studies the mechanical properties of concrete samples with circular,elliptic and irregular polygonal aggregates in 2D mesoscopic models.On the premise of ensuring uniform aggregate gradation,particle size and distribution,the microscopic concrete models with different aggregate contents are generated.The influence of aggregate contents on the macroscopic mechanical performance of concrete is studied under uniaxial compression through comparative analysis.The results show that the random distribution and the aggregate shapes have no obvious influence on the macroscopic mechanical properties of concrete,but the failure patterns of numerical concrete are greatly affected.Based on the 3-phase composite concrete composed of mortars,coarse aggregates and initial pores,the influence of initial pores on uniaxial compression strength,crack initiation and propagation and failure modes are studied when the pore shapes,the pore sizes and the porosity change.The research shows that the bearing capacity of concrete is weaker when the shape of pores is closer to narrow.When the porosity is constant,the strength of concrete decreases with the decline of pore size.The increase of porosity causes a significant decrease in the compressive strength of concrete.