Understanding fracture mechanism and behaviour of ultra-high strength concrete using mesoscale modelling
Introduction
UHSC has become an integral aspect in the construction industry due to its enhanced performance characteristics [1]. Ultra-high compressive strength, higher stiffness, low porosity, increased durability characteristics and reduced deformations are some of the vital characteristics which increase the usage of UHSC in structures [2], [3], [4].
Mechanical behavior of the UHSC is significantly different from the behavior of the NSC. UHSC is a remarkably brittle material compared with the NSC and hence the fracture behavior of the UHSC is also comparatively different [5]. Even though these brittle fractures are visible in the macro scale, fracture and damage behavior depends on the material composition and the interactions of the constituent phases in mesoscale. It is very difficult to understand this complex fracture behavior of UHSC and how the constituent phases affect this behavior considering all the parameters using conventional macro/micro experimental testing methods. Hence, to investigate the brittle fracture initiation, propagation and to investigate the contribution of the constituent phases to this process, a mesoscale model was developed and analyzed capturing all these complex phenomena.
Mesoscale modelling of concrete consists of modelling the concrete as a three-phase material including aggregates, mortar and the ITZ-thin weak boundary layer between mortar and aggregate. 3D finite element analysis was used to simulate the composite behavior of the material and step by step procedure was followed to create the mesoscale model, analyze it and investigate the fracture behavior of the material. Damage initiation of UHSC due to the formation of microcracks, coalescence of these microcracks to form macro crack networks and how damage progresses through the concrete specimens due to the external loading were investigated using the 3D mesoscale model developed in this study. This paper covers comprehensive modelling of mesoscale UHSC with accurate mesoscale geometries, correct material models including the behavior of ITZ which captures the accurate failure and damage propagation as seen in the experimental observations and reasons for this complex behavior, which have been not addressed properly in previous studies.
Section snippets
Mesoscale modelling of concrete
Macroscale modelling of concrete is carried out assuming that concrete is a homogeneous material. This assumption of homogeneity of concrete neglects some of the key aspects such as particle size distribution, aggregate shape, interface in between aggregates etc. which significantly affect the way in which concrete behaves in the macro scale. Hence, concrete needs to be considered as a composite material as shown in Fig. 1 to understand how heterogeneities affects the macro properties. This
Geometry generation for the mesoscale model
Mesostructure of concrete consists of aggregates, ITZ and mortar. Aggregates were the first to be generated and distributed uniformly in a cylinder and then the mortar geometry was generated. In this paper, three aggregate shapes were used to represent the aggregates.
When placing these three types of aggregates inside the cylinder following criteria were satisfied [41].
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Placed aggregates should be completely inside the cylinder
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There should not be any overlaps between aggregate particles
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There
Material models and parameters for mortar
For UHSC mixes, a very low water/binder ratio is used. Hence, the resulting mortar has a very high strength (>100 MPa). Very high strength mortar is significantly brittle compared with the normal strength mortar and hence it is difficult to obtain the complete stress strain behavior with softening under uniaxial compression. In this study the compressive stress strain model proposed by Cusson and Paultre [59] was used.
Concrete Damage Plasticity Model (CDPM) was used as the constitutive law for
Numerical analysis
Tetrahedral meshing was used to mesh the constituent phases of the model. Proper meshing of the model is very important to ensure the transfer of stresses between the constituent phases through the contacts. Also, it is important to generate a good quality mesh to avoid numerical problems after the post peak behavior of the concrete. In this scenario, Hypermesh was used to preprocess the mesh before analyzing the model using Abaqus. This significantly enhanced the quality of the mesh compared
Studies on the fracture behavior of UHSC
Typical stress strain curve of a cylindrical specimen under uniaxial loading obtained using the numerical mesoscale model is shown in Fig. 13. Ascending branch of the stress strain curve is depended on the elastic modulus of the concrete. UHSC has a higher elastic modulus compared with the NSC. From the stress strain curve, it is evident that UHSC behaves elastically to a great degree up to the peak stress. Elastic portion can be up to 80–90% of the peak stress [89]. This behavior differs from
Conclusions and recommendations
3D mesoscale modelling is a powerful tool which can be used to understand the nonlinear behavior of UHSC concrete under various loading conditions. In this study 3d mesoscale models were developed with the aim of investigating the fracture and damage behavior of UHSC under uniaxial compression. For future research, fracture and failure studies of UHSC by inserting cohesive elements between all the mesh lines using a simple cohesive law [74], [76], [98] are recommended.
Following are some of the
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
P.S.M Thilakarathna would like to thank The University of Melbourne, Australia for providing Melbourne Graduate Research Scholarship Award.
References (99)
- et al.
Understanding failure and stress-strain behavior of very-high strength concrete (>100 MPa) confined by lateral reinforcement
Constr. Build. Mater.
(2018) - et al.
Meso-scale studies in fracture of concrete: A numerical simulation
Comput. Struct.
(2011) - et al.
Fracture simulations of concrete using lattice models: Computational aspects
Eng. Fract. Mech.
(1997) - et al.
Damage distribution and size effect in numerical concrete from lattice analyses
Cem. Concr. Compos.
(2011) - et al.
Discrete element modelling of concrete submitted to dynamic loading at high strain rates
Comput. Struct.
(2004) - et al.
Fracture analyses using spring networks with random geometry
Eng. Fract. Mech.
(1998) - et al.
Influence of aggregate deformation and contact behaviour on discrete particle modelling of fracture of concrete
Eng. Fract. Mech.
(2008) New discrete models and their application to seismic response analysis of structures
Nucl. Eng. Des.
(1978)- et al.
The effects of three-dimensional multi-particle arrangements on the mechanical behavior and damage initiation of particle-reinforced MMCs
Compos. Sci. Technol.
(2001) - et al.
Influence of the meso-structure in dynamic fracture simulation of concrete under tensile loading
Cem. Concr. Res.
(2011)
Computational model of mesoscopic structure of concrete for simulation of fracture processes
Comput. Struct.
Mesoscale modelling of fibre reinforced concrete material under compressive impact loading
Constr. Build. Mater.
Mesoscopic modeling and simulation of the dynamic tensile behavior of concrete
Cem. Concr. Res.
Fracture modeling of fiber reinforced concrete in a multiscale approach
Compos. Part B Eng.
Multi-scale modeling of fracture in concrete composites
Compos. Part B Eng.
Meso-scale computational modeling of the plastic-damage response of cementitious composites
Cem. Concr. Res.
Monte Carlo simulations of mesoscale fracture of concrete with random aggregates and pores: a size effect study
Constr. Build. Mater.
Mesoscale modeling of concrete: Geometry and numerics
Comput. Struct.
Mesoscale models for concrete: Homogenisation and damage behaviour
Finite Elem. Anal. Des.
3D mesoscale finite element modelling of concrete
Comput. Struct.
Monte Carlo simulations of meso-scale dynamic compressive behavior of concrete based on X-ray computed tomography images
Int. J. Impact Eng.
Modelling the diffusivity of mortar and concrete using a three-dimensional mesostructure with several aggregate shapes
Comput. Mater. Sci.
Development and validation of a 3D computational tool to describe concrete behaviour at mesoscale. Application to the alkali-silica reaction
Comput. Mater. Sci.
Stochastic multiscale modeling and simulation framework for concrete
Cem. Concr. Compos.
Computer simulation of fracture processes of concrete using mesolevel models of lattice structures
Cem. Concr. Res.
Mesoscale finite element prediction of concrete failure
Comput. Mater. Sci.
Simulation and analysis of composite structures
Mater. Sci. Eng.
Three-dimensional mesoscale modelling of concrete composites by using random walking algorithm
Compos. Sci. Technol.
Realistic 3D modeling of concrete composites with randomly distributed aggregates by using aggregate expansion method
Constr. Build. Mater.
Mesoscopic study of concrete I: generation of random aggregate structure and finite element mesh
Comput. Struct.
Aggregate shape effect on the diffusivity of mortar: A 3D numerical investigation by random packing models of ellipsoidal particles and of convex polyhedral particles
Comput. Struct.
Mesostructural characterization of particulate composites via a contact detection algorithm of ellipsoidal particles
Powder Technol.
Numerical investigations on the effect of reinforcement on penetration resistance of concrete slabs using a 3D meso-scale method
Constr. Build. Mater.
An advanced 3D modeling method for concrete-like particle-reinforced composites with high volume fraction of randomly distributed particles
Compos. Sci. Technol.
Mesoscopic analysis of concrete under excessively high strain rate compression and implications on interpretation of test data
Int. J. Impact Eng.
Effects of interfacial transition zones on the stress-strain behavior of modeled recycled aggregate concrete
Cem. Concr. Res.
A plastic-damage model for concrete
Int. J. Solids Struct.
The effect of the bond between the matrix and the aggregates on the cracking mechanism and fracture parameters of concrete
Cem. Concr. Res.
Toughening cement-based materials through the control of interfacial bonding
Cem. Concr. Res.
Assessing the ITZ microcracking via scanning electron microscope and its effect on the failure behavior of concrete
Cem. Concr. Res.
Behavior of meso-scale heterogeneous concrete under uniaxial tensile and compressive loadings
Constr. Build. Mater.
A mesoscale interface approach to modelling fractures in concrete for material investigation
Constr. Build. Mater.
A three-dimensional meso-scale modelling of concrete fracture, based on cohesive elements and X-ray μCT images
Eng. Fract. Mech.
Mesoscopic simulation of the dynamic tensile behaviour of concrete based on a rate-dependent cohesive model
Int. J. Impact Eng.
Monte Carlo simulation of complex cohesive fracture in random heterogeneous quasi-brittle materials: A 3D study
Int. J. Solids Struct.
A mesoscale fracture model for concrete
Cem. Concr. Res.
On the mechanics of mother-of-pearl: A key feature in the material hierarchical structure
J. Mech. Phys. Solids.
Discontinuous crack-bridging model for fracture toughness analysis of nacre
J. Mech. Phys. Solids.
The relation between crack growth resistance and fracture process parameters in elastic-plastic solids
J. Mech. Phys. Solids.
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