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• Calculation of the crack propagation rate due to hydrogen embrittlement

  J. Sánchez, Á. Ridruejo, E. Muñoz, C. Andrade, J. Fullea, P. Andrés

  Hormigón y Acero (2016). Vol. 67 (280), pp. 325-332

  
  

  Abstract

  The durability of high strength steels in aggressive media is determined by the presence of hydrogen, in particular hydrogen embrittlement processes. Hydrogen embrittlement is present in many of the failures of structures made with steel components. The effect of interstitial hydrogen within the network of iron has been investigated in previous studies at the atomic level. It is concluded that the main role of hydrogen is not to establish chemical bonds with iron atoms, but to introduce internal stresses that weaken the interactions between iron atoms and decrease fracture toughness. In this work, the spread of a crack has been stimulated inside a matrix of iron in the presence of hydrogen. Hydrogen transport, stress distributions, and the evolution of fracture toughness were analysed together in a multi-physics finite element model. The behaviour in the fracture was simulated using two different models for the cohesive law, one lineal and the other polynomial. Results show that the choice for the cohesive law influences the crack propagation rate and the hydrogen concentration profiles.

  Abstract
  The durability of high strength steels in aggressive media is determined by the presence of hydrogen, in particular hydrogen embrittlement processes. Hydrogen embrittlement [...]

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• Some historical notes on the research in corrosion of reinforcement

  C. Andrade

  Hormigón y Acero (2018). Vol. 69 (S1), pp. 21-28

  
  

  Abstract

  A brief exercise is made on reporting some achievements in the history of reinforcement corrosion. It is a difficult task to try to summarize because there are numerous protagonists in the history then choices were made from a personal point of view. In the decade 1960–1970, reinforcement corrosion was a subject only of marginal interest because the number of built environment was limited. The use of electrochemical techniques was a milestone which enabled from the decade of the 1970 to study the effect of each variable with much more rigor. The studies on service life started in the decade of 1980, although they were not of general interest until next decade. From 1990 Rilem Committees and the Iberoamerican Program on Corrosion of CYTED extended the knowledge so widely that in the XXI century the subject attracts much research interest.

  Abstract
  A brief exercise is made on reporting some achievements in the history of reinforcement corrosion. It is a difficult task to try to summarize because there are numerous protagonists [...]

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• Test methods for on-site corrosion rate measurement of steel reinforcement in concrete by means of the polarization resistance method

  C. Andrade, C. Alonso

  Materials and Structures (2004). Vol. 37, pp. 623-643

  
  

  Abstract

    This recommendation covers the description of non-destructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous corrosion current densiti, icor, expressed in gA/cm2, by means of the so called Polarization Resistance technique, Rp, in order to asses the condition of embedded Steel reinforcement related to its corrosion. The values of icor, can be used to assess the rate of degradation of concrete structures affected by reinforcement corrosión. However, the cannot give information on the actual loss in steel cross section which, at present, only can be assessed by means of direct visual observation.   Values of the free corrosión potential or half-cell potential, Ecorr [V], of the embedded reinforcing Steel and of the electrical concrete resistance, Re [f)], are obtained as preliminary steps of the Rp measurements. Values of the concrete resistivity, P [~m], can be calculated from Re values providing the geometrical arrangement of the electrodes enables this calculation. Both parameters, Ecorr and Re (or P) may be used to complement the reliability of the ico~r measurements.

  Abstract
    This recommendation covers the description of non-destructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous [...]

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• Revisión sobre el comportamiento de las armaduras galvanizadas en el hormigón

  J. González, R. Vargas, C. Andrade

  Hormigón y Acero (1977). Vol. 28 (124), pp. 113-131

  
  

  Abstract

  Esta comunicación pretende ofrecer una panorámica de las ventajas e inconvenientes derivados del empleo de las armaduras de acero galvanizados en el hormigón. Se resumen las causas que pueden provocar la corrosión de las armaduras embebidas en el hormigón y se analiza la protección suplementaria que el galvanizado puede conferir a dichas armaduras en condiciones especialmente agresivas. Se mencionan los datos publicados sobre los límites tolerables de cloruros para las armaduras normales, punto en el que se echa en falta la existencia de datos cuantitativos similares para las armaduras galvanizadas y se examina, asimismo, las repercusiones sobre ellas de la carbonatación del hormigón y de la presencia de pilas de aireación diferencial, así como la influencia sobre la adherencia hormigón-armaduras, y el peligro de fragilización de estas, por el hidrógeno desprendido en el curso del fraguado. Finalmente se nombran algunas de las obras donde se han empleado armaduras galvanizadas. 

  Abstract
  Esta comunicación pretende ofrecer una panorámica de las ventajas e inconvenientes derivados del empleo de las armaduras de acero galvanizados en el hormigón. Se [...]

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• Electrochemical Behavior of Galvanized Steel in a Calcium Hydroxide-Saturated Solution. A Quantitative Assessment of Corrosion Rate.

  C. Andrade, A. Vazquez, J. González

  Revista de Metalurgia (1978). Vol. 13, pp. 142-145

  
  

  Abstract

  An electrochemical study has been carried out involving immersion of galvanized steel in a Ca(OH)//2-saturated solution with and without chloride additions. Results show that galvanized steel corrodes steadily during the first few days; after approximately a week, however, it becomes passive, the passivity being perfectly stable both in the presence and absence of chlorides for the entire test period which lasted for more than 60 days' exposure.

  Abstract
  An electrochemical study has been carried out involving immersion of galvanized steel in a Ca(OH)//2-saturated solution with and without chloride additions. Results show that [...]

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• Quantitative measurements of corrosion rate of reinforcing steels embedded in concrete using polarization resistance measurement

  C. Andrade, J. González

  Materials and Corrosion (1978). Vol. 29 (8), pp. 515-519

  
  

  Abstract

  Up to this time all the methods to measure the corrosion rate of reinforcing steels embedded in hardened concrete have been of the destructive type, which requires much time and materials and makes the full scale study of the phenomenon difficult. The authors have applied the polarization resistance method to bars embedded in hardened mortar and immersed in Ca(OH)2‐saturated solution, and have found an acceptable agreement between the gravimetric and the electrochemical weight loss data.

  Abstract
  Up to this time all the methods to measure the corrosion rate of reinforcing steels embedded in hardened concrete have been of the destructive type, which requires much time [...]

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• Valores del potencial de corrosión y de a resistencia de polarización de armaduras galvanizadas embebidas en hormigón

  C. Andrade, J. González

  Materiales de Construcción (1978). Vol. 28 (172), pp. 71-80

  
  

  Abstract

  Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después de periodos muy prolongados de servicio. Ello es debido a que en el hormigón el electrolito está constituido por la fase líquida que rellena sus poros y que es, fundamentalmente, una disolución saturada de CA(OH)2, con un pH alrededor de 13. A este elevado pH y a los potenciales de corrosión Ecorr, que presentan las armaduras, el acero se encuentra en la zona de pasividad descrita por Pourbaix, permaneciendo protegido indefinidamente mientras no cambien las condiciones del medio. Este cambio en las condiciones de servicio del hormigón capaz de introducir en la zona de corrosión al acero de las armaduras, se puede producir con relativa frecuencia. Así, la carbonatación del cemento disminuye el pH del hormigón y provoca una corrosión generalizada, la presencia de iones despasivantes o de fisura conduce a corrosión localizada y, finalmente, la acción simultánea de tensiones mecánicas y factores agresivos puede ser la causa de corrosión bajo tensiones. Así pues, es aconsejable recurrir a una protección suplementaria de los aceros cuando se prevean situaciones que puedas provocar la corrosión de las armaduras. Entre los varios métodos de protección que se utilizan se viene ensayando desde hace varios lustros, con resultados muy contradictorios, la galvanización en caliente de los redondos.

  Abstract
  Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después de periodos muy prolongados de servicio. Ello es debido [...]

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• Corrosion of Reinforcing Bars in Carbonated Concrete

  J. González, J. Algaba, C. Andrade

  British Corrosion Journal (1980). Vol. 15 (3), pp. 135-139

  
  

  Abstract

  In all published studies of cement carbonation there has been general agreement that it must be considered as a cause of generalised corrosion in reinforcements, but quantitative data have been provided in very few cases. In the present work the intensity of attack has been modified by means of the accelerated carbonation of mortar specimens without additives, with 2% CaCl2, and with 3% NaNO2 It has been shown that a critical level of atmospheric moisture must also be present for considerable attack to occur. The measurement of polarisation resistance (Rp) has been used to evaluate the intensity of corrosion of the reinforcements. This method has already been usefully applied by the authors to investigations of corrosion of steel bars in hardened concrete specimens.

  Abstract
  In all published studies of cement carbonation there has been general agreement that it must be considered as a cause of generalised corrosion in reinforcements, but quantitative [...]

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• Influencia de la dosificación en cemento sobre la corrosión de armaduras, negras y galvanizadas provocado por lo penetración de Cl- en el mortero

  C. Andrade, G. Jauregui, J. González

  Materiales de Construcción (1981). Vol. 31 (183), pp. 45-52

  
  

  Abstract

  En el presente trabajo se aborda el estudio de la corrosión de armaduras, tanto desnudas como galvanizadas, producida por la penetración de agua de mar en nueve calidades (dosificaciones y por lo tanto porosidades) diferentes de mortero de cemento portland en el que se embebieron redondos a tres profundidades (0,5-1,5-2,5 cm). Las probeta de 7 X 7 X 7 cm se conservaron sumergidas durante 1 año. Para la evaluación de la velocidad de corrosión se ha utilizado la Resistencia de Polarización, técnica que permite el seguimiento continuo de la despasivación progresiva que provocan los Cl^- al llegar a la armadura. Se aportan resultados sobre la penetración de Cl^-, discutiéndose las relaciones encontradas entre: corrosión, % de Cl^-, porosidad y dosificación de cemento. Finalmente se compara el comportamiento frente a la corrosión de las armaduras de acero desnudo respecto de las galvanizadas.

  Abstract
  En el presente trabajo se aborda el estudio de la corrosión de armaduras, tanto desnudas como galvanizadas, producida por la penetración de agua de mar en nueve [...]

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• Effect of Carbonation, Chlorides and Relative Ambient Humidity on the Corrosion of Galvanized Rebars Embedded in Concrete

  J. Gozález, C. Andrade

  British Corrosion Journal (1982). Vol. 17 (1), pp. 21-28

  
  

  Abstract

  The variation with time of the corrosion rates of galvanized steel and bare steel rebars has been studied as a function of the relative ambient humidity, mortar carbonation and the presence or absence of chloride ions. Corrosion rates are estimated from Rp measurements with electronic compensation for the ohmic drop between the working imd reference electrodes. It is shown that a normal galvanized coating with a continuous layer of practically pure zinc in contact with mortar gives effective protection to the steel reinforcing bars against the aggressive action of carbonation and chlorides. The protective effect of this galvanized coating is much greater under partial immersion conditions of the mortar than in very humid atmospheres, although in the latter case the corrosion rate decreases with time

  Abstract
  The variation with time of the corrosion rates of galvanized steel and bare steel rebars has been studied as a function of the relative ambient humidity, mortar carbonation [...]

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