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Epoxy coatings are currently the most popular corrosion protection mechanism for steel reinforcement in structural concrete. However, these coatings are easily damaged on worksites, negating their intended purpose. This study investigates self-healing coatings for steel reinforcement to introduce an autonomous healing mechanism for damaged coatings. Coatings were applied to steel coupons, intentionally damaged, and introduced to a corrosive environment via aerated salt-water tanks. Performance of the experimental coatings was evaluated qualitatively and quantitatively. Adhesion strength and effects of coating thickness were also studied. Results from coated steel coupons subjected to damage and submerged in salt-water aeration tanks exhibited improved corrosion resistance performance with self-healing coatings. However, self-healing coatings have comparable poor adhesion to the substrate as do conventional coatings. This paper shows preliminary results demonstrating the potential benefits of self-healing coatings for steel reinforcement and identifies numerous avenues for future research.

In the Australian Standard, AS 3600-2001, the neutral axis parameter Ku is used as a convenient, but approximate, parameter to design for moment redistribution in building frames. The research work reported herein was conducted to obtain complete information regarding moment redistribution of beams and one-way slabs using 500 MPa steel reinforcement.A computer based iterative numerical method was developed to analyse reinforced two-span continuous concrete beams and one-way slabs. The method takes into account the material and geometrical non-linearities in the calculations. The deflected shape of the beam and one-way slab was calculated by dividing the span length into a number of rigid segments. The program also calculates the failure load and extent of moment redistribution. The analytical method was verified against the test results reported in the literature. The analytical results for load-deflection graphs and moment redistribution showed a good agreement with the test results.A parametric study was conducted using analytical method. The results of this study showed that moment redistribution depends not only on the neutral axis parameter (Ku) but also on the ratio of neutral axis parameter (Ku-/Ku+), ultimate steel strain (ªsu) and concrete compressive strength (fc).

This thesis presents two separate applications of ionising radiation in Civil Engineering. The first is an investigation to determine the cement content of concrete using gamma-rays from the naturally occurring isotopes 238U, 232Th and their decay chains as well as 40K. Two sets of equations are derived and discussed. Spectra from cement, aggregate and concrete samples were made and the useful full energy peaks from the above sources identified. Two concrete samples were prepared using the same cement, but, containing two different aggregates: a granite based aggregate and a flint based aggregate. A third concrete sample was then prepared where the cement content was not initially known. Data from the first two tests was then used to determine the mass of cement used in the blind test. A great deal of valuable information has also been accrued concerning the interaction of statistical errors in the equations for the prediction of cement content. Spectra from four different cements were collected at regular intervals over a 24 month period and the variation in the activity of each cement over this period is discussed. The second section of this work presents an imaging technique that uses pair production annihilation photons to examine the state of steel reinforcement in concrete structures. Computer simulations along with experimental work have been used. The experimental work used a 226Ra needle as a photon source as it provided a range of gamma-rays with energies over the pair production threshold of 1022keV. A 31mm rebar with 30mm of concrete cover was successfully located during the experimental work. The data collected from the computer simulations has shown that the geometry and the material between the photon source, rebar and detector is of great importance.

Electrochemical assessment of the condition of the steel reinforced concrete structures is being carried out increasingly and more regularly, both in the laboratory and in the field. It is important to have enough information about the factors that may affect these measurements. In this way, results obtained from different tests can be interpreted in more reliable manner and the condition of the embedded reinforcing steel bars in concrete structures can be evaluated with more confidence. The main goals of this project were: • to determine the causes of the errors in electrochemical measurements that may mislead the researchers, • to determine factors that may affect the measurements, • to attempt to manifest better interpretation of the results, • to avoid the problematic pitfalls and overcome them as much as possible. To this end, two types of concrete specimens were prepared for performing gravimetric and electrochemical tests: beams with four pre-weighed sections of rebars, and prisms with a single rebar and with different variables (cracked in two directions, carbonated and different cover depth). These have been exposed to de-icing salt for more than 2.5 years. The condition of the rebar in the beams and prisms was evaluated over this period by (i) half-cell potential measurements, (ii) galvanostatic pulse measurements (using the GalvaPulse™ and the potentiostat), (iii) potentiostatic linear polarisation resistance measurements (LPR), (iv) electrochemical impedance spectroscopy (EIS) and (v) potentiodynamic cyclic polarisation. Also, specimens were prepared to determine the amount of required time for steel to passivate itself in pore solution and mortar. Results from corrosion measurements in the laboratory show that: • Steel bar in mortar and pore solution needs time for passivation: about 7 days for steel embedded in mortar and about 3 days for steel in simulated pore solution. • Data from gravimetric tests were compared with the values calculated from electrochemical tests and results show that, in the laboratory condition, values obtained from potentiostatic LPR technique are more realistic and closer the actual mass loss than those obtained by galvanostatic techniques. • It was observed that, in most cases, when the steel bars were corroding actively, the half-cell potential values were more negative than -350 mV vs. CSE, in agreement with ASTM guidelines. • When performing the half-cell potential measurements, it was found that it is essential provide sufficient time after wetting the surface to allow the potential to stabilise. A minimum of about 15-20 minutes was found to be required. • One of the most informative electrochemical tests is the cyclic polarisation technique. The half-cell potential, corrosion rate, susceptibility to pitting, severity of corrosion, protecting potential, concentration limitations and, with appropriate procedures, Tafel constants, can be obtained by this technique. However, it is essential to choose the appropriate scan rate for the particular system, otherwise the achieved data mislead the researcher. The appropriate scan rate can be determined by using the Bode plot obtained from the EIS experiment. • To measure the concrete resistance, the galvanostatic pulse technique and EIS are suggested. Wenner four probe technique measures only the surface resistance and is, therefore, very dependant on the surface condition and is not recommended. • The guard ring in the GalvaPulse™ instrument which is designed to limit the polarised area was found to be working in reverse and, in fact, it polarises the steel even more than when it is not used. It is recommended that the guard ring electrode not be used during the measurements. • Another limitation of the GalvaPulse™ is its lack of capability to measure the high corrosion rates. • It was found that the GalvaPulse™ pulse generator unit must be calibrated every month, or before each measurement, which ever is longer period. In addition to the experiments in the laboratory, four locations were chosen for field measurements in collaboration with the Ministry of Transportation of Ontario. These measurements show that: • The half-cell potential of galvanised steel in much more negative than that in the black steel. This emphasises the importance that the ASTM C876 recommended guideline should not be used for other types of reinforcing bars. • It is recommended that half-cell potential contour map rather than the absolute values of potential be used for condition analysis. However, it is found that these maps are not constant varying with time and ambient conditions. Based on this experience, it is recommended that half-cell potential measurements be made exactly at the same time and date in different years. The results might be closer and more readily interpretable. • The measured half cell potential is a function, not only of the state of corrosion, but also of environmental factors. The temperature and relative humidity of both the atmosphere and inside the concrete play a role. The permittivity of concrete is dependent on all these factors and needs to be taken into account. • To measure the corrosion current density in the field, galvanostatic and galvanodynamic LPR and galvanodynamic polarisation can be used. The potentiostatic LPR, potentiodynamic LPR and EIS techniques appear to be limited by the size of full-scale structures and are also very sensitive to extraneous electrical noise. Consequently, they cannot be performed in the field.

Electrochemical assessment of the condition of the steel reinforced concrete structures is being carried out increasingly and more regularly, both in the laboratory and in the field. It is important to have enough information about the factors that may affect these measurements. In this way, results obtained from different tests can be interpreted in more reliable manner and the condition of the embedded reinforcing steel bars in concrete structures can be evaluated with more confidence. The main goals of this project were: • to determine the causes of the errors in electrochemical measurements that may mislead the researchers, • to determine factors that may affect the measurements, • to attempt to manifest better interpretation of the results, • to avoid the problematic pitfalls and overcome them as much as possible. To this end, two types of concrete specimens were prepared for performing gravimetric and electrochemical tests: beams with four pre-weighed sections of rebars, and prisms with a single rebar and with different variables (cracked in two directions, carbonated and different cover depth). These have been exposed to de-icing salt for more than 2.5 years. The condition of the rebar in the beams and prisms was evaluated over this period by (i) half-cell potential measurements, (ii) galvanostatic pulse measurements (using the GalvaPulse™ and the potentiostat), (iii) potentiostatic linear polarisation resistance measurements (LPR), (iv) electrochemical impedance spectroscopy (EIS) and (v) potentiodynamic cyclic polarisation. Also, specimens were prepared to determine the amount of required time for steel to passivate itself in pore solution and mortar. Results from corrosion measurements in the laboratory show that: • Steel bar in mortar and pore solution needs time for passivation: about 7 days for steel embedded in mortar and about 3 days for steel in simulated pore solution. • Data from gravimetric tests were compared with the values calculated from electrochemical tests and results show that, in the laboratory condition, values obtained from potentiostatic LPR technique are more realistic and closer the actual mass loss than those obtained by galvanostatic techniques. • It was observed that, in most cases, when the steel bars were corroding actively, the half-cell potential values were more negative than -350 mV vs. CSE, in agreement with ASTM guidelines. • When performing the half-cell potential measurements, it was found that it is essential provide sufficient time after wetting the surface to allow the potential to stabilise. A minimum of about 15-20 minutes was found to be required. • One of the most informative electrochemical tests is the cyclic polarisation technique. The half-cell potential, corrosion rate, susceptibility to pitting, severity of corrosion, protecting potential, concentration limitations and, with appropriate procedures, Tafel constants, can be obtained by this technique. However, it is essential to choose the appropriate scan rate for the particular system, otherwise the achieved data mislead the researcher. The appropriate scan rate can be determined by using the Bode plot obtained from the EIS experiment. • To measure the concrete resistance, the galvanostatic pulse technique and EIS are suggested. Wenner four probe technique measures only the surface resistance and is, therefore, very dependant on the surface condition and is not recommended. • The guard ring in the GalvaPulse™ instrument which is designed to limit the polarised area was found to be working in reverse and, in fact, it polarises the steel even more than when it is not used. It is recommended that the guard ring electrode not be used during the measurements. • Another limitation of the GalvaPulse™ is its lack of capability to measure the high corrosion rates. • It was found that the GalvaPulse™ pulse generator unit must be calibrated every month, or before each measurement, which ever is longer period. In addition to the experiments in the laboratory, four locations were chosen for field measurements in collaboration with the Ministry of Transportation of Ontario. These measurements show that: • The half-cell potential of galvanised steel in much more negative than that in the black steel. This emphasises the importance that the ASTM C876 recommended guideline should not be used for other types of reinforcing bars. • It is recommended that half-cell potential contour map rather than the absolute values of potential be used for condition analysis. However, it is found that these maps are not constant varying with time and ambient conditions. Based on this experience, it is recommended that half-cell potential measurements be made exactly at the same time and date in different years. The results might be closer and more readily interpretable. • The measured half cell potential is a function, not only of the state of corrosion, but also of environmental factors. The temperature and relative humidity of both the atmosphere and inside the concrete play a role. The permittivity of concrete is dependent on all these factors and needs to be taken into account. • To measure the corrosion current density in the field, galvanostatic and galvanodynamic LPR and galvanodynamic polarisation can be used. The potentiostatic LPR, potentiodynamic LPR and EIS techniques appear to be limited by the size of full-scale structures and are also very sensitive to extraneous electrical noise. Consequently, they cannot be performed in the field.

No description available.

No description available.

<p>Bridge deck deterioration due to chloride-induced pitting corrosion of steel reinforcement is a common occurrence. Because rust decreases the cross-sectional area of reinforcing bars, corrosion of bridge deck reinforcement directly reduces the structural capacity of the bridge deck. A typical NDT method for assessing the possibility of corrosion at the top reinforcement level is ground-penetrating radar (GPR). The goal of the study is to investigate the effect of reducing the cross-sectional area of the reinforcing bar on deck strength due to corrosion. Flexural and shear failure were considered in the analysis. In conclusion, typical corrosion of reinforcement was not found to cause a bridge deck to collapse after testing the flexure with the yield line method, the one-way and two-way shears with AASHTO LRFD Bridge Design Specifications (2020), and the one-way shear with ACI 318 (2019). </p>

La détérioration des infrastructures au Canada due à la corrosion des armatures est l'un des défis majeurs de l'industrie de la construction. Les progrès récents dans la technologie des polymères ont conduit au développement d'une nouvelle génération de barres d'armature à base de fibres renforcées de polymères (PRF), (en particulier les fibres de verre). Ces barres, résistant à la corrosion, ont montré un grand potentiel d'utilisation pour mieux protéger les infrastructures en béton armé contre les effets dévastateurs de la corrosion. Avec la publication du nouveau code S807-10 "Spécifications pour les polymères renforcés de fibres" et la production de barres en PRF de très haute qualité, celles-ci représentent une alternative réaliste et rentable par rapport à l'armature en acier pour les structures en béton soumises à de sévères conditions environnementales. La conception des éléments en béton armé de barres en PRF est généralement gouvernée par l'état de service plutôt que l'état ultime. Par conséquent, il est nécessaire d'analyser les performances en flexion et le comportement en service en termes de déflexion et de largeur de fissures des éléments en PRF sous charges de service et de vérifier que ces éléments rencontrent les limites des codes. Aussi, de récents développements dans l'industrie des PRF ont conduit à l'introduction des barres en PRF avec des configurations de surface et des propriétés mécaniques différentes. Ces développements sont susceptibles d'affecter leur performance d'adhérence et, par conséquent, la largeur des fissures dans les éléments en PRF. Cependant, les codes de conception et les guidelines de calcul fournissent une valeur unique pour le coefficient d'adhérence (k[indice inférieur b]) en tenant compte des configurations de surface et en négligeant le type de barre en PRF, le diamètre de la barre, et le type de béton et de sa résistance. En outre, le code canadien S807-10 "Spécifications pour les polymères renforcés de fibres" fournit une étape en classant les barres en PRF par rapport à leur module d'élasticité (E[indices inférieurs frp]). Ces classifications ont été divisées en trois classes : Classe I (E[indices inférieurs frp]<50 GPa), Classe II (50 GPa [plus petit ou égal] E[indices inférieurs frp]< 60 GPa) et Classe III (E[indices inférieurs frp] [plus grand ou égal] 60 GPa). Ce programme de recherche vise à étudier expérimentalement le comportement en flexion des éléments en béton en service armé avec différents paramètres sous charges statiques. Le programme expérimental est basé sous plusieurs paramètres, dont les différents ratios de renforcement, différents types de barres (différentes classes comme classifiées par le CAN/CSA S807-10), le diamètre et la surface de la barre, la configuration ainsi que la résistance du béton. De plus, les recommandations actuelles de design pour les valeurs de k[indice inférieur b] et la vérification de la dépendance des valeurs de k[indice inférieur b] sur le type de barres (verre ou carbone), le diamètre des barres et le type de béton et sa résistance ont été étudiées. Le programme expérimental comprenait la fabrication et les essais sur 33 poutres à grande échelle, simplement appuyées et mesurant 4250 mm de long, 200 mm de large et 400 mm de hauteur. Vingt et sept poutres en béton ont été renforcées avec des barres en PRF à base de verre, quatre poutres en béton ont été renforcées avec des barres de PRF à base de carbone, et deux poutres ont été renforcées avec des barres en acier. Toutes les poutres ont été testées en flexion quatre points sur une portée libre de 3750 mm. Les paramètres d'essai étaient: le type de renforcement, le pourcentage d'armature, le diamètre des barres, configurations de surface et la résistance du béton. Les résultats de ces essais ont été présentés et discutés en termes de résistance du béton, de déflection, de la largeur des fissures, de déformations dans le béton et l'armature, de résistance en flexion et de mode de rupture. Dans les trois articles présentés dans cette thèse, le comportement en flexion et la performance des poutres renforcées de barres en PRFV et fabriquées avec un béton normal et un béton à haute performance ont été investigués, ainsi que les différentes classes de barres en PRFV et leurs configurations de surface. Les conclusions des investigations expérimentales et analytiques contribuent à l'évaluation des équations de prédiction de la déflection et des largeurs de fissures dans les codes de béton armé de PRF, pour prédire l'état de service des éléments en béton renforcés de PRF (déflection et largeur de fissures). En outre, à la lumière des résultats expérimentaux de cette étude, les équations de service (déflection et largeur des fissures) incorporées dans les codes et guidelines de design [ACI 440.1R-06, 2006; ISIS Manual No.3, 2007; CAN/CSA-S6.1S1, 2010; CAN/CSA-S806, 2012] ont été optimisées. En outre, les largeurs de fissures mesurées et les déformations ont été utilisées pour évaluer les valeurs courantes de k[indice inférieur b] fournies par les codes et les guidelines de calcul des PRF. En outre, les conclusions ne prennent pas en charge la valeur unique de k[indice inférieur b] pour les barres en PRF de types différents (carbone et verre) avec des configurations de surface similaires et s'est avéré être dépendant du diamètre de la barre.