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"Coupled model of initiation and propagation of corrosion in reinforced concrete"^^ .
"Corrosion of reinforcing steel in concrete due to chloride ingress is one of the\r\nmain causes of the deterioration of reinforced concrete structures. Structures\r\nmost affected by such a corrosion are marine zone buildings and structures\r\nexposed to de-icing salts like highways and bridges. Such process is\r\naccompanied by an increase in volume of the corrosión products on the rebarsconcrete\r\ninterface. Depending on the level of oxidation, iron can expand as\r\nmuch as six times its original volume. This increase in volume exerts tensile\r\nstresses in the surrounding concrete which result in cracking and spalling of the\r\nconcrete cover if the concrete tensile strength is exceeded.\r\nThe mechanism by which steel embedded in concrete corrodes in presence of\r\nchloride is the local breakdown of the passive layer formed in the highly alkaline\r\ncondition of the concrete. It is assumed that corrosion initiates when a critical\r\nchloride content reaches the rebar surface. The mathematical formulation\r\nidealized the corrosion sequence as a two-stage process: an initiation stage,\r\nduring which chloride ions penetrate to the reinforcing steel surface and\r\ndepassivate it, and a propagation stage, in which active corrosion takes place\r\nuntil cracking of the concrete cover has occurred.\r\nThe aim of this research is to develop computer tools to evaluate the duration of\r\nthe service life of reinforced concrete structures, considering both the initiation\r\nand propagation periods. Such tools must offer a friendly interface to facilitate\r\nits use by the researchers even though their background is not in numerical\r\nsimulation.\r\nFor the evaluation of the initiation period different tools have been\r\ndeveloped:\r\nProgram TavProbabilidade: provides means to carry out a probability analysis\r\nof a chloride ingress model. Such a tool is necessary due to the lack of data and\r\ngeneral uncertainties associated with the phenomenon of the chloride diffusion.\r\nIt differs from the deterministic approach because it computes not just a chloride\r\nprofile at a certain age, but a range of chloride profiles for each probability or occurrence.\r\nProgram TavProbabilidade_Fiabilidade: carries out reliability analyses of the\r\ninitiation period. It takes into account the critical value of the chloride\r\nconcentration on the steel that causes breakdown of the passive layer and the\r\nbeginning of the propagation stage. It differs from the deterministic analysis in\r\nthat it does not predict if the corrosion is going to begin or not, but to quantifies\r\nthe probability of corrosion initiation.\r\nProgram TavDif_1D: was created to do a one dimension deterministic analysis\r\nof the chloride diffusion process by the finite element method (FEM) which\r\nnumerically solves Fick’second Law.\r\nDespite of the different FEM solver already developed in one dimension, the\r\ndecision to create a new code (TavDif_1D) was taken because of the need to\r\nhave a solver with friendly interface for pre- and post-process according to the\r\nneed of IETCC.\r\nAn innovative tool was also developed with a systematic method devised to\r\ncompare the ability of the different 1D models to predict the actual evolution of\r\nchloride ingress based on experimental measurements, and also to quantify the\r\ndegree of agreement of the models with each others.\r\nFor the evaluation of the entire service life of the structure: a computer\r\nprogram has been developed using finite elements method to do the coupling of\r\nboth service life periods: initiation and propagation.\r\nThe program for 2D (TavDif_2D) allows the complementary use of two external\r\nprograms in a unique friendly interface:\r\n• GMSH - an finite element mesh generator and post-processing viewer\r\n• OOFEM – a finite element solver.\r\nThis program (TavDif_2D) is responsible to decide in each time step when and\r\nwhere to start applying the boundary conditions of fracture mechanics module in\r\nfunction of the amount of chloride concentration and corrosion parameters\r\n(Icorr, etc). This program is also responsible to verify the presence and the\r\ndegree of fracture in each element to send the Information of diffusion\r\ncoefficient variation with the crack width.\r\n• GMSH - an finite element mesh generator and post-processing viewer • OOFEM – a finite element solver.\r\nThe advantages of the FEM with the interface provided by the tool are:\r\n• the flexibility to input the data such as material property and boundary\r\nconditions as time dependent function.\r\n• the flexibility to predict the chloride concentration profile for different\r\ngeometries.\r\n• the possibility to couple chloride diffusion (initiation stage) with chemical\r\nand mechanical behavior (propagation stage).\r\nThe OOFEM code had to be modified to accept temperature, humidity and the\r\ntime dependent values for the material properties, which is necessary to\r\nadequately describe the environmental variations.\r\nA 3-D simulation has been performed to simulate the behavior of the beam on\r\nboth, action of the external load and the internal load caused by the corrosion\r\nproducts, using elements of imbedded fracture in order to plot the curve of the\r\ndeflection of the central region of the beam versus the external load to compare\r\nwith the experimental data."^^ .
"2013" .
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"Caminos"^^ .
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"Ciencia_Materiales, Caminos"^^ .
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"Rena Chengxiang"^^ .
"Yu"^^ .
"Rena Chengxiang Yu"^^ .
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"Fabiano"^^ .
"Tavares Bejar"^^ .
"Fabiano Tavares Bejar"^^ .
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"María del Carmen"^^ .
"Andrade Perdrix"^^ .
"María del Carmen Andrade Perdrix"^^ .
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"Coupled model of initiation and propagation of corrosion in reinforced concrete (PDF)"^^ .
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"Fabiano_Tavares.pdf"^^ .
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"Coupled model of initiation and propagation of corrosion in reinforced concrete (Other)"^^ .
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"Coupled model of initiation and propagation of corrosion in reinforced concrete (Other)"^^ .
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"Coupled model of initiation and propagation of corrosion in reinforced concrete (Other)"^^ .
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"Coupled model of initiation and propagation of corrosion in reinforced concrete (Other)"^^ .
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