Abstract
Concrete is a porous material containing aggregate of different sizes, hardened cement matrix with air pores, microcracks and water. Concrete internal structure is different from that of other engineering materials. Furthermore concrete is described as quazi-brittle material. Fracture processes in it form in a way that does not fit within classical theories. Therefore, to describe failure of concrete structures nonlinear fracture mechanics is often applied with success. Basic concrete parameters, like compressive and tensile strength, and modulus of elasticity, are not enough to analyze fracture processes in concrete structures. Additional fracture properties should be tested, among them fracture energy, complete diagram of stress-deformation under axial tension and the width of fracture process zone. Recognizing and testing fracture parameters is of paramount importance when analysing fracture process in concrete structures. The correct data of material’s properties and the adequate fracture model applied in numerical simulations influence final results. In the paper the findings reported in the professional literature are summarized and obtained results of the own numerical simulation are reported in order to give a deeper knowledge on the role of aggregate on fracture properties of concrete.
Highlights
Concrete is a porous material containing aggregates, hardened cement paste and water
In the paper the findings reported in the professional literature are summarized and obtained results of the own numerical simulation are reported in order to give a deeper knowledge on the role of aggregate on fracture properties of concrete
T o analyze how the choice of the width of the fracture process zone influences the results of numerical calculations in the case of concrete beams, the numerical simulation has been performed using the commercial program ALGOR, which is based on Finite Element Method (FEM)
Summary
Concrete is a porous material containing aggregates, hardened cement paste and water. In order to obtain the basic characteristic of concrete as a constructional material the following parameters should be known: - compressive strength of the concrete (fc ), - tensile strength of the concrete (fct ), - modulus of elasticity (Ecm ), - Poisson’s ratio, - coefficient of thermal expansion These parameters are not enough to deeper analyze failure in concrete structures. In a crack bend model additional concrete fracture parameters should be determined These parameters are: - uniaxial tensile strength limit (fct ), - fracture energy (GF ), - the shape of the stress-deformation diagram ( ). The stress-deformation properties of concrete are given by two curves: stress-strain ( ) and stress-crack opening curve The width of the active microcracking band, which is called the width of fracture process zone (wc), is the additional parameter taken into account when fracture in concrete is modelled as a smeared crack band
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