Dimensionner les structures en beton arme du point de vue de leur durabilite a l'aide d'a... more Dimensionner les structures en beton arme du point de vue de leur durabilite a l'aide d'approche probabiliste est a la mode dans les bureaux d'etudes et les entreprises. Neanmoins, une approche probabiliste necessite une parfaite connaissance des modeles mathematiques utilises et des informations statistiques detaillees sur les parametres de ces modeles. Dans ce papier les fondements mathematiques de l'approche probabiliste sont presentes ainsi que les implications de cette modelisation sur l'initiation de la corrosion des armatures due a la penetration de chlorures. Pour le maitre d'ouvrage, le choix des valeurs des parametres et l'interpretation des resultats n'est pas sans ambiguite. En consequence une approche plus pratique et transparente a ete developpee. Elle permet l'obtention de criteres controlables de performance en terme d'enrobage et de coefficient de migration. (A). (Voir fiche generale du congres : F101134).
This paper will address the relevance of chloride measurements in practice for durability conditi... more This paper will address the relevance of chloride measurements in practice for durability condition assessment and a description of the working principle of LIBS will be given. Examples of chloride profiles obtained by the common wet chemical analysis will be shown and compared with results from LIBS measurements as to demonstrate the accuracy of the LIBS-technique. The latter will be supported by clear graphs. In addition examples on the extra information resulting from measurements performed with LIBS for improvement of condition assessment and prediction will be shown.
This paper describes a concrete corrosion cell, which has been developed to investigate the mutua... more This paper describes a concrete corrosion cell, which has been developed to investigate the mutual influence on corrosion processes of rebars in carbonated concrete and rebars embedded in repair mortar. It analyses the influence qualitatively, and presents preliminary test results. A concrete corrosion cell consists of a solid concrete specimen, which contains electrodes (steel rebars) at carefully specified positions. A specially developed measuring system is set up to determine the very small corrosion currents. Each electrical circuit consists of two electrodes which are continuously interconnected by a copper wire through a resistor. Graphs show the test measurements of corrosion currents over time for the first three weeks after repair for two different climate conditions and three types of repair mortar. The climatic conditions were: (1) three weeks at 80% relative humidity; and (2) two periods of 50% relative humidity, with a long period of 100% relative humidity between them...
On the windward side of an existing box girder bridge exposed to aerosol and incidentally spray c... more On the windward side of an existing box girder bridge exposed to aerosol and incidentally spray chloride profiles were determined at an age of 18 and 32 years as to obtain data on the development of chloride ingress over time and to predict the time to onset of reinforcement corrosion. According to the chloride contents determined at the level of the reinforcing steel for an age of 18 years corrosion was likely to be present, however neither visual inspections nor large scale potential mapping revealed any spots suspect of corrosion. Chloride profiling performed at an age of 32 years indicated that chloride ingress was much slower than was anticipated. A full probabilistic approach was adopted to predict the development of chloride ingress over time and onset of reinforcement corrosion using updated values for the so-called ageing factor and the critical chloride content. However, the results obtained with these predictions proved to be far more pessimistic than is shown by the actu...
There is an increasing demand from asset owners for service life prediction of existing reinforce... more There is an increasing demand from asset owners for service life prediction of existing reinforced concrete structures. This requires assessment of the current condition and modelling to allow for a prediction. This paper critically discusses a number of subjects relevant for service life prediction with respect to durability related to chloride-induced reinforcement corrosion. The subjects include the physical meaning and variability of the end-of-service-life criterion, the validity of the deterioration models, the availability, variability and reality level of input values for some model parameters, as well as some practical issues concerning site investigations. The findings are exemplified by calculation examples using both a deterministic as well as a full probabilistic approach. It is anticipated that in the future a full probabilistic approach will be adopted which makes service life predictions more prone to manipulation of input values, as literature provides a wide spectr...
ABSTRACT In recent European research within the “DuraCrete” [1] and “Darts” [2] projects modified... more ABSTRACT In recent European research within the “DuraCrete” [1] and “Darts” [2] projects modified mathematical expressions for chloride ingress into concrete structures have been used which are based on the well known second law of Fick. While the discussion between scientists and practitioners is still going on about the impact of these modified formulas, there is an urgent practical need to quantify the detrimental influences of chloride ingress on the performance of concrete structures.One of the major drwabacks of the current formulas for chloride ingress into concrete is that these formulas do not take into account the obstructive effect of embedded of reinforcement steel. In addition to the thickness of the concrete cover to a reinforcing bar and the diffusion coefficient of the uncracked concrete, the diameter of the reinforcement bar and the in-between distance between two neighbouring reinforcement bars present essential parameters with respect to the spatial distribution of chloride ingress over time.Today, it is possible to analyse chloride transport by a numerical simulation. Dependancy of time and temperature in the chloride diffusion coefficient of the concrete can be included in the analysis, as well as the above mentioned essential geometrical parameters. This information allows to quatify the probability of initiation of reinforcement corrosion. Consequently, the influence of a wide range in parameter values can be supplied to the design engineer.Based on the chloride concentration at the steel-concrete interfaceand the rate of attack, the residual load bearing capacity of a structure can be predicted. The interfacial chloride concentration can be coupled to the bonding behaviour material property. An impression of the time –dependent development of the load-bearing capacity of a structure affected by chloride-induced reinforcement corrosion can thus be given.
Dimensionner les structures en beton arme du point de vue de leur durabilite a l'aide d'a... more Dimensionner les structures en beton arme du point de vue de leur durabilite a l'aide d'approche probabiliste est a la mode dans les bureaux d'etudes et les entreprises. Neanmoins, une approche probabiliste necessite une parfaite connaissance des modeles mathematiques utilises et des informations statistiques detaillees sur les parametres de ces modeles. Dans ce papier les fondements mathematiques de l'approche probabiliste sont presentes ainsi que les implications de cette modelisation sur l'initiation de la corrosion des armatures due a la penetration de chlorures. Pour le maitre d'ouvrage, le choix des valeurs des parametres et l'interpretation des resultats n'est pas sans ambiguite. En consequence une approche plus pratique et transparente a ete developpee. Elle permet l'obtention de criteres controlables de performance en terme d'enrobage et de coefficient de migration. (A). (Voir fiche generale du congres : F101134).
This paper will address the relevance of chloride measurements in practice for durability conditi... more This paper will address the relevance of chloride measurements in practice for durability condition assessment and a description of the working principle of LIBS will be given. Examples of chloride profiles obtained by the common wet chemical analysis will be shown and compared with results from LIBS measurements as to demonstrate the accuracy of the LIBS-technique. The latter will be supported by clear graphs. In addition examples on the extra information resulting from measurements performed with LIBS for improvement of condition assessment and prediction will be shown.
This paper describes a concrete corrosion cell, which has been developed to investigate the mutua... more This paper describes a concrete corrosion cell, which has been developed to investigate the mutual influence on corrosion processes of rebars in carbonated concrete and rebars embedded in repair mortar. It analyses the influence qualitatively, and presents preliminary test results. A concrete corrosion cell consists of a solid concrete specimen, which contains electrodes (steel rebars) at carefully specified positions. A specially developed measuring system is set up to determine the very small corrosion currents. Each electrical circuit consists of two electrodes which are continuously interconnected by a copper wire through a resistor. Graphs show the test measurements of corrosion currents over time for the first three weeks after repair for two different climate conditions and three types of repair mortar. The climatic conditions were: (1) three weeks at 80% relative humidity; and (2) two periods of 50% relative humidity, with a long period of 100% relative humidity between them...
On the windward side of an existing box girder bridge exposed to aerosol and incidentally spray c... more On the windward side of an existing box girder bridge exposed to aerosol and incidentally spray chloride profiles were determined at an age of 18 and 32 years as to obtain data on the development of chloride ingress over time and to predict the time to onset of reinforcement corrosion. According to the chloride contents determined at the level of the reinforcing steel for an age of 18 years corrosion was likely to be present, however neither visual inspections nor large scale potential mapping revealed any spots suspect of corrosion. Chloride profiling performed at an age of 32 years indicated that chloride ingress was much slower than was anticipated. A full probabilistic approach was adopted to predict the development of chloride ingress over time and onset of reinforcement corrosion using updated values for the so-called ageing factor and the critical chloride content. However, the results obtained with these predictions proved to be far more pessimistic than is shown by the actu...
There is an increasing demand from asset owners for service life prediction of existing reinforce... more There is an increasing demand from asset owners for service life prediction of existing reinforced concrete structures. This requires assessment of the current condition and modelling to allow for a prediction. This paper critically discusses a number of subjects relevant for service life prediction with respect to durability related to chloride-induced reinforcement corrosion. The subjects include the physical meaning and variability of the end-of-service-life criterion, the validity of the deterioration models, the availability, variability and reality level of input values for some model parameters, as well as some practical issues concerning site investigations. The findings are exemplified by calculation examples using both a deterministic as well as a full probabilistic approach. It is anticipated that in the future a full probabilistic approach will be adopted which makes service life predictions more prone to manipulation of input values, as literature provides a wide spectr...
ABSTRACT In recent European research within the “DuraCrete” [1] and “Darts” [2] projects modified... more ABSTRACT In recent European research within the “DuraCrete” [1] and “Darts” [2] projects modified mathematical expressions for chloride ingress into concrete structures have been used which are based on the well known second law of Fick. While the discussion between scientists and practitioners is still going on about the impact of these modified formulas, there is an urgent practical need to quantify the detrimental influences of chloride ingress on the performance of concrete structures.One of the major drwabacks of the current formulas for chloride ingress into concrete is that these formulas do not take into account the obstructive effect of embedded of reinforcement steel. In addition to the thickness of the concrete cover to a reinforcing bar and the diffusion coefficient of the uncracked concrete, the diameter of the reinforcement bar and the in-between distance between two neighbouring reinforcement bars present essential parameters with respect to the spatial distribution of chloride ingress over time.Today, it is possible to analyse chloride transport by a numerical simulation. Dependancy of time and temperature in the chloride diffusion coefficient of the concrete can be included in the analysis, as well as the above mentioned essential geometrical parameters. This information allows to quatify the probability of initiation of reinforcement corrosion. Consequently, the influence of a wide range in parameter values can be supplied to the design engineer.Based on the chloride concentration at the steel-concrete interfaceand the rate of attack, the residual load bearing capacity of a structure can be predicted. The interfacial chloride concentration can be coupled to the bonding behaviour material property. An impression of the time –dependent development of the load-bearing capacity of a structure affected by chloride-induced reinforcement corrosion can thus be given.
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