COLLECTIONS

Documents published in Scipedia

• Mechanisms of corrosion of steel in concrete

  A. Rosenberg, C. Hansson, C. Andrade

  (1990). Corrosion Rates of Steel in Concrete, ed. N. Berke, V. Chaker, and D. Whiting (West Conshohocken, PA: ASTM International), 174-188.

  
  

  Abstract

  The corrosion of metals in concrete is a multibillion dollar problem which affects the construction, transportation, and many other industries. While much has been written about the problem, and numerous reports have appeared which discuss how this corrosion can be controlled, little has appeared on the mechanism whereby this corrosion occurs. It is well known that highway structures corrode, for the most part, due to the influence of deicing salts or marine environments. Relatively little has appeared about the equally severe corrosion problems which occur in buildings and other nonhighway structures. Most of these structures are not exposed to the salts present in highway structures, yet they still corrode. This paper discusses how all forms of concrete and similar cementitious environments protect embedded metals. It discusses the three protection mechanisms—passive film formation, changes in the conductivity of the electrolyte, and mineral scales—that have been used to explain how corrosion in concrete occurs. It also presents evidence to explain how, and why, corrosion occurs in these structures, even in the absence of deicing salts, marine environments, or other salt sources. Examples are discussed including buildings, marine piers, foundations, and highway structures.

  Abstract
  The corrosion of metals in concrete is a multibillion dollar problem which affects the construction, transportation, and many other industries. While much has been written [...]

  • 40
  •  read

• Concrete durability of the new Panama Canal: Background and aspects of testing

  C. Andrade, N. Rebolledo, F. Tavares, R. Pérez, M. Baz

  (2016). Marine Concrete Structures: Design, Durability and Performance, Chapter 15, pp. 429-458

  
  

  Abstract

  The Panama Canal, vital to international trade, connects the Pacific Ocean and the Caribbean Sea, through the Gatun inland lake (which is almost entirely freshwater). The canal is now 100 years old. Since 2011, new lanes and locks have been or are being built, which will greatly enhance capacity and accommodate vessels with a much deeper draft. This is being done under the Panama Canal Authority (ACP) by a consortium named Grupo Unidos por el Canal, (GUPC), whose engineering division is headed by the firm Sacyr, S.A. Although the concrete on the earlier existing canal is not reinforced, the design for the new canal structures calls for reinforcing steel as an anti-seismic precaution. In its specifications, the ACP requires a 100-year service life for the concrete in all members, which is defined to mean conformity with the 1000-C electrical charge requirement of ASTM C1202, and an application of a reliable method for calculating service life. This chapter describes the tests performed on cores drilled from the old canal and the working program developed with GUPC for demonstrating the requirements, together with complementary test methods. The main tests were the measurement of concrete resistivity, as well as natural chloride diffusion found by ponding. The model used was the LIFEPRED numerical model, using the natural diffusion coefficients. The ageing of the diffusion coefficient was also measured through the resistivity evolution with time. The relationship between electrical charge and resistivity values is shown, along with the variation in these parameters over time. Also given are the chloride diffusion values obtained in four concrete mixes used as examples and their ‘age factor’, which proved to have an even more critical effect on predictions than the diffusion coefficient itself.

  Abstract
  The Panama Canal, vital to international trade, connects the Pacific Ocean and the Caribbean Sea, through the Gatun inland lake (which is almost entirely freshwater). The [...]

  • 17
  •  read

• Reinforcement corrosion in chloride environment of different concentrations

  C. Andrade, S. García, L. Toro, M. Alonso, M. Castellote

  (2006). International RILEM-JCI Seminar on Concrete Durability and Service Life Planning: Curing, Crack Control, Performance in Harsh Environments

  
  

  Abstract

  Steel reinforcement remains passive until a certain amount of chlorides entry in contact with them. The corrosion develops in local areas and extends around depending on the level of chloride concentration. The further evolution of the corrosion depends on the total amount of chlorides although there is a maximum in the expected values of the corrosion rate. In present paper results are given on several tests that have been performed to establish the corrosion rates in chloride environments of different concentrations. First, the chloride threshold for depassivation will be commented on and its dependence of the Cl- /OH- ratio as well as on the electrical potential exhibited by the reinforcement will be discussed. The depassivation occurs for Cl- amounts between 0.2 and 1 % by cement weight for corrosion potentials more noble positive than -200 mVsce. Concerning the values of the corrosion rate, they increase when increasing the chloride concentration until around 1M NaCl, but above this concentration, the corrosion rate does not increase more likely due the decreasing oxygen content in the pore solution. Certain unexpected results are presented to illustrate that the corrosion rate is the result of some counterbalance phenomena, not always taken into account.

  Abstract
  Steel reinforcement remains passive until a certain amount of chlorides entry in contact with them. The corrosion develops in local areas and extends around depending on the [...]

  • 2
  •  read

• Advances in modeling of RILEM TC 178-TMC "Testing and modelling chloride penetration in concrete"

  C. Andrade, J. Gulikers

  (2006). 2nd International RILEM Symposium on Advances in Concrete through Science and Engineering, Publisher by RILEM Publications SARL

  
  

  Abstract

  Reinforced concrete structures may prove to be very durable; however their gradual degradation over time impairing both serviceability and structural safety is still a matter of great practical concern in view of the economical consequences related to assessment, maintenance, and repair. Corrosion of embedded steel reinforcement is considered the most detrimental process responsible for structural deterioration and numerous researches are in progress to try to find a comprehensive engineering approach for the initiation as well as the propagation period. The importance of concrete permeability for the durability of concrete itself or the steel in reinforced concrete was recognized more than a decade ago by Rilem members. A technical committee TC-116-Permeability of concrete as a criterion for its durability was set up and its results were published (Rilem, 1999). This TC-116 promoted an important amount of research and contributed to the advance of understanding the relation between concrete permeability and durability. At the time of the initiation of the work of TC-116 durability was a dealt with on a broad and comprehensive perspective. At the end of the work, the need to study specifically chloride penetration into concrete in more depth was identified, since chloride attack represents the most severe corrosion damage on reinforced concrete structures with tremendous economical consequences. At the same time gaps in understanding many of the individual mechanisms controlling the attack still existed. This was the justification for the formation of a separate Rilem TC on chloride attack and its objectives in the description of the specific deterioration mechanism.

  Abstract
  Reinforced concrete structures may prove to be very durable; however their gradual degradation over time impairing both serviceability and structural safety is still a matter [...]

  • 0
  •  read

• Types of Models of Service Life of Reinforcement: The Case of the Resistivity

  C. Andrade

  Concrete Research Letters (2010). Vol. 1 (2), pp. 73-80

  
  

  Abstract

  The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. A similar approach should also be followed in the case of durability design regarding reinforcement corrosion. This type of consideration enables the definition of a four level methodology for design against reinforcement corrosion in parallel with that followed for strength design. Levels from I to IV are proposed: a] level I would be the prescriptive method already given in present codes based on "deemed-to-satisfy" rules, b] level I is that where still not quantification of the time to reach a limit state is explicit but the minimum life time is assured through performance based tests, c] level III would be the level in which the calculation of aggressive ingress through models having explicit the time is made and d] level IV includes the verification that the resistance of the cover thickness against the penetration of aggressive substances is higher than the environmental action effect including probabilistic treatments. For level II and III the measurement of the electrical resistivity results a very suitable proposal due to this parameter can be measured in a non destructive test and serves to quality control. It is not only a performance test [level II] but it can be included in models of both the initiation and propagation periods. For the time to corrosion onset, the electrical resistivity represents the porosity and its connectivity and therefore can be used to model transport processes. It also results very suitable for measuring concrete aging and then accounting for the reduction of the diffusion coefficient with time. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a certain relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law.

  Abstract
  The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. [...]

  • 1
  •  read

• Nanotecnologia en el hormigón y hormigones autocompactantes

  C. Andrade, P. Borralleras, H. Corres, S. Shah, P. Monteiro, J. Navarro

  (2009). Nanotecnología en el hormigón y hormigones autocompactantes, Universitat Politècnica de Catalunya. Departament d'Enginyeria de la Construcció (EC),

  
  

  Abstract

  Dentro de las jornadas técnicas de la Cátedra de Innovación en Tecnología del Hormigón patrocinada por BASF, MOLINS y BEKAERT (Cátedra BMB-UPC), en la presente ocasión se ha querido plantear dos temas de gran vigencia como son: la nanotecnología en el mundo del hormigón y la visión estructural de los hormigones autocompactantes. Respecto a la nanotecnología cabe señalar que si bien tiene un desarrollo reciente ya está bien introducida en distintos sectores de la ciencia, tecnología y ingeniería. La nanotecnología puede mejorar nuestro entendimiento de los origines de las características básicas de materiales muy comunes, de estructuras y de procesos de fabricación. Permite de tener una caracterización adelantada, hasta una predicción y control, de las características de los materiales. Su potencial de desarrollo es tal que se lo considera ya como la revolución industrial del siglo 21. En cuanto a los hormigones autocompactantes, hay que señalar que si bien llevan tiempo en el mercado, existen barreras importantes en su aplicación in situ, donde alcanzan cotas inferiores al 2%, en contraposición del 50 al 60 % en los prefabricados. Entre estas barreras, puede situarse la falta de documentos normativos, hasta la reciente aparición del anejo de la EHE08, o bien la falta de un planteamiento estructural de este hormigón. Este es el punto de vista que se quiere hacer énfasis en el desarrollo de la jornada desde diferentes puntos de vista, tanto desde el proyecto, como la construcción como el material. 

  Abstract
  Dentro de las jornadas técnicas de la Cátedra de Innovación en Tecnología del Hormigón patrocinada por BASF, MOLINS y BEKAERT (Cátedra [...]

  • 2
  •  read

• Condition control and assessment of reinforced concrete structures

  C. Gehlen, C. Andrade, M. Bartholemew, F. Papworth

  (2011). International Federation for Structural Concrete (fib) Bulletin; Vol. 59

  
  

  Abstract

  For the ongoing condition assessment of concrete structures, it is necessary to identify the extent, nature, cause and prognosis of any deterioration using a range of tools and methods, including prediction models. Combined with the original design and construction details, this gives a vast amount of information over a long time period. A framework concept is therefore needed to process the entirety of the information in order to make sound investment decisions on future maintenance management.

  Abstract
  For the ongoing condition assessment of concrete structures, it is necessary to identify the extent, nature, cause and prognosis of any deterioration using a range of tools [...]

  • 5
  •  read

• Impact of surface roughness on the debonding mechanism in concrete repairs

  J. Mier, G. Ruiz, C. Andrade, R. Yu, X. Zhang, M. Lukovic, E. Schlangen, G. Ye, B. Savija

  FranMCoS-8 (2013).

  
  

  Abstract

  Surface roughness of the existing concrete substrate was considered to have the greatest impact on the bond strength in repair systems. However, the influence of this parameter has been subject for debates in recent years. The effect of concrete surface roughness is not quite clear, nor there exist a clear relation between the surface roughness and the adhesion in multilayer systems. In order to understand and explain this relation, simple numerical experimentation is used. Repair systems with different roughness parameters are simulated in order to get load displacement diagrams and crack debonding propagation. The influence of roughness on the composite response in simulated direct tension, shear and three point bending test using a lattice model, is studied. Results indicate that roughness has different influence on tensile and shear bond strength. In addition, although it seems to have negligible influence on load bearing capacity of the composite system in bending, it enables more monolithic response and slower debonding propagation.

  Abstract
  Surface roughness of the existing concrete substrate was considered to have the greatest impact on the bond strength in repair systems. However, the influence of this parameter [...]

  • 7
  •  read

• Experimental and Numerical Study of Bond Response in Structural Concrete with Corroded Steel Bars

  M. Prieto, P. Tanner, C. Andrade, M. Ruiz

  IABSE Symposium Report (2013). Vol. 99

  
  

  Abstract

  Corrosion can affect the bond between reinforcing bars and concrete and hence the transfer of longitudinal stresses. Although a number of experimental studies on bond failure have been conducted in recent years, the findings have diverged rather widely, due primarily to differing test conditions.The present paper reports on an experimental programme consisting of eccentric pull-out tests run on corroded steel bars in specimens subjected to accelerated or natural corrosion [1]. An axisymmetric bi-dimensional FE model with finite deformations initially developed to study bond mechanics with sound steel bars [2], has been enhanced to consider bond effects in corroded steel bars. The model simulation is compared to some of the experimental results for corroded and sound bars and the findings are analysed.

  Abstract
  Corrosion can affect the bond between reinforcing bars and concrete and hence the transfer of longitudinal stresses. Although a number of experimental studies on bond failure [...]

  • 1
  •  read

• El Eurocódigo 2 y la evaluación de estructuras de hormigón armado con armaduras corroídas

  J. Rodríguez, C. Andrade, D. Izquierdo, P. Tanner

  Hormigón y Acero (2014). Vol. 65 (272), pp. 123-132

  
  

  Abstract

  La corrosión de la armadura es uno de los problemas de mayor impacto económico en el ciclo de vida de las estructuras de hormigón por lo que es necesario optimizar las estrategias de reparación de estructuras corroídas. Sin embargo, a nivel internacional no hay códigos que permitan una evaluación por lo que se incluirán criterios en la revisión del Eurocódigo 2 para la evaluación de estructuras existentes y deterioradas. En el presente artículo se resumen el trabajo realizado en el proyecto Contecvet, financiado por la Comisión Europea, y los avances realizados desde entonces. En las estructuras existentes, una primera precisión consiste en determinar si el deterioro ha alcanzado a la armadura, y en ese caso, cuánto se ha afectado al comportamiento estructural. Calculada la velocidad de corrosión a partir de los datos tomados en la propia estructura es posible estimar la velocidad de avance del deterioro mediante los modelos desarrollados y la vida residual remanente. Se resumen los modelos y expresiones para estimar la capacidad resistente de estructuras con armaduras corroídas a considerar en la elaboración del nuevo Eurocódigo 2.

  Abstract
  La corrosión de la armadura es uno de los problemas de mayor impacto económico en el ciclo de vida de las estructuras de hormigón por lo que es necesario [...]

  • 0
  •  read