Simulation of Chloride Diffusivity for Cracked Concrete Based on RBSM and Truss Network Model

For concrete structures exposed to salt environment, the microstructure and cracks play a crucial role in the ingress of chloride ions into concrete. In this study, concrete is simulated on the meso scale as a three-phase composite, i.e., aggregate particles, mortar and the interfacial transition zone (ITZ). Because of the advantages in predicting cracks behavior in concrete, Rigid Body Spring Model (RBSM) is employed to carry out the mechanical analysis to simulate the distribution and width of microcracks. And then, the truss network model is adopted to evaluate the chloride diffusivity of the cracked concrete. On the basis of the statistics analysis of diffusion coefficients of concrete and mortar determined experimentally, the diffusivity of ITZ is analytically clarified. The range of diffusion coefficient of ITZ estimated in this paper is approximately 3-16 times of that of mortar depending on the different assumed thickness, which agrees well with that of the previous experimental results. With the aim to validate the effect of microcracks on the diffusivity of concrete, a series of the chloride ions penetrating analysis is numerically carried out on the concrete specimen under different stress levels. The axial compressive and tensile loading conditions are investigated respectively and the effects of stress level on chloride diffusivity of cracked concrete are examined. Results indicate that the chloride diffusivity is significantly dependent on the stress level, but only considering the effect of cracks predicted by RBSM is not sufficient. So an empirical equation which can account for the microstructure variation of concrete under loading is proposed. With it, a reasonable estimation for chloride diffusivity of cracked concrete is achieved.

[1]  E. Samson,et al.  Prediction of diffusion coefficients in cement-based materials on the basis of migration experiments , 1996 .

[2]  Michael D.A. Thomas,et al.  A study of the effect of chloride binding on service life predictions , 2000 .

[3]  Stefano Berton,et al.  Simulation of shrinkage induced cracking in cement composite overlays , 2004 .

[4]  John E. Bolander,et al.  Modeling crack development in reinforced concrete structures under service loading , 1999 .

[5]  H. Ishimori,et al.  Chloride permeability of concrete under static and repeated compressive loading , 1995 .

[6]  K. T. Chau,et al.  Estimation of air void and aggregate spatial distributions in concrete under uniaxial compression using computer tomography scanning , 2005 .

[7]  Kohei Nagai,et al.  Mesoscopic Simulation of Failure of Mortar and Concrete by 2D RBSM , 2004 .

[8]  N. Gowripalan,et al.  Microcracking and chloride permeability of concrete under uniaxial compression , 2000 .

[9]  N. Banthia,et al.  PREDICTION OF CHLORIDE IONS INGRESS IN UNCRACKED AND CRACKED CONCRETE , 2003 .

[10]  E. Hervé,et al.  Application of a n-Phase Model to the Diffusion Coefficient of Chloride in Mortar , 2004 .

[11]  He Shi-qin Influence of Flexural Loading on Permeability of Chloride Ion in Concrete , 2005 .

[12]  Kenneth C. Hover,et al.  Influence of microcracking on the mass transport properties of concrete , 1992 .

[13]  Theodore W. Bremner,et al.  Effect of Stress on Gas Permeabilityin Concrete , 1996 .

[14]  A. K. Nickerson,et al.  The diffusion of ions through water-saturated cement , 1984 .

[15]  V. Sirivivatnanon,et al.  Chloride diffusivity of concrete cracked in flexure , 2000 .

[16]  Tadahiko Kawai,et al.  New discrete models and their application to seismic response analysis of structures , 1978 .

[17]  Minoru Kunieda,et al.  Time-Dependent Structural Analysis Considering Mass Transfer to Evaluate Deterioration Process of RC Structures , 2006 .

[18]  J. Beaudoin,et al.  Flat aggregate-portland cement paste interfaces, I. Electrical conductivity models , 1991 .

[19]  C. C. Yang,et al.  Effect of the interfacial transition zone on the transport and the elastic properties of mortar , 2003 .

[20]  Koji Takewaka,et al.  Simulation Model for Deterioration of Concrete Structures due to Chloride Attack , 2003 .

[21]  M. Miltenberger,et al.  Predicting Chloride Diffusion Coefficients from Concrete Mixture Proportions , 1999 .

[22]  Michel Pigeon,et al.  Influence of the interfacial zone on the chloride diffusivity of mortars , 1997 .

[23]  N. Otsuki,et al.  NEW TEST METHODS FOR MEASURING STRENGTH AND CHLORIDE ION DIFFUSION COEFFICIENT OF MINUTE REGIONS IN CONCRETE , 2004 .

[24]  Surendra P. Shah,et al.  Effect of Cracking on Water and Chloride Permeability of Concrete , 1999 .

[25]  Kohei Nagai,et al.  Mesoscopic Simulation of Failure of Mortar and Concrete by 3D RBSM , 2005 .

[26]  B. Oh,et al.  PREDICTION OF DIFFUSIVITY OF CONCRETE BASED ON SIMPLE ANALYTIC EQUATIONS , 2004 .

[27]  Edward J. Garboczi,et al.  Effect of the Interfacial Transition Zone on the Conductivity of Portland Cement Mortars , 2004 .

[28]  Tarek Uddin Mohammed,et al.  Relationship between free chloride and total chloride contents in concrete , 2003 .

[29]  S. Caré Influence of aggregates on chloride diffusion coefficient into mortar , 2003 .

[30]  D. W. Hobbs,et al.  Aggregate influence on chloride ion diffusion into concrete , 1999 .

[31]  J. Bolander,et al.  Fracture analyses using spring networks with random geometry , 1998 .

[32]  Erick Ringot,et al.  Modelling of the transition zone porosity , 1995 .

[33]  Taketo Uomoto,et al.  Modeling of Effective Diffusion Coefficient of Substances in Concrete Considering Spatial Properties of Composite Materials , 2005 .

[34]  Raoul François,et al.  Effect of crack opening on the local diffusion of chloride in inert materials , 2004 .

[35]  Surendra P. Shah,et al.  Permeability study of cracked concrete , 1997 .