COLLECTIONS

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• Tendencias actuales en la investigación sobre corrosión de armaduras

  C. Andrade

  Informes de la Construcción (2012). Vol. 40 (398), pp. 7-14

  
  

  Abstract

  During the last 20 years, the corrosion of concrete rebars is increasily being considered a major problem due the high costs spent by some Governments on repair and of civil concrete structures. In the present paper, a brief description on the causes of this type of corrosion is offered together with some references to the costs of repairing of bridge decks published by USA researchs. Finally, the main lines of research which, in opinion of the authors have priority, are commented.

  Abstract
  During the last 20 years, the corrosion of concrete rebars is increasily being considered a major problem due the high costs spent by some Governments on repair and of civil [...]

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• Análisis de las condiciones de fisuración en las estructuras de hormigón armado y su relación con la probabilidad de corrosión de las armaduras

  J. Rodríguez, C. Andrade

  Informes de la Construcción (2012). Vol. 36 (366), pp. 37-52

  
  

  Abstract

  Cracks appears in reinforced concrete structures as something inherent to the material they are composed. Causes of diverse kind advise to control this cracking, considering it can not be prevented. The durability of reinforcements is, till now, the reason that has determined, in most structures, the study and the control of this cracking. In this report, the information contained in certain standards in force (CP-110; ACI-318-83; B.A.E.L. 80; MODEL CODE AND EH-82) about the characteristics the concrete must have and about the cracking in pieces of reinforced concrete under pliability attempts, are analysed and resumed, trying to judge later its connection with the corrosion phenomenon in reinforcements

  Abstract
  Cracks appears in reinforced concrete structures as something inherent to the material they are composed. Causes of diverse kind advise to control this cracking, considering [...]

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• Testing and modelling chloride penetration into concrete

  M. Prieto, P. Tanner, C. Andrade, F. Tavares, R. D'Andrea

  Construction and Building Materials (2013). Vol. 39, pp. 9-18

  
  

  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 establishment of verification of durability in categories. Three categories have been identified: (I) it would be the prescriptive method already given in present codes based on “deemed-to-satisfy” rules, (II) this is based in the testing through “durability indicators” 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, (III) it is the category in which the calculation of aggressive ingress through models having explicit the time is made including probabilistic treatments. In the paper in addition to the comment on the most common methods of calculation of the chloride ingress and their limitations it is illustrated how 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. Finally the paper comments on the tests methods used for the measurement of the diffusion coefficient and of resistivity

  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. [...]

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• Linking fresh and durability properties of paste to SCC mortar

  H. Figueiras, S. Nunes, J. Coutinho, C. Andrade

  Cement and Concrete Research (2014). Vol. 45, pp. 209-226

  
  

  Abstract

  In the last years many approaches to design SCC have been developed, but it remains a very complex process since it is necessary to manipulate several variables and understand their effects on concrete behaviour (fresh and hardened state). The prediction of concrete or mortar behaviour based on paste properties will be a significant contribution to simplify SCC design. With this purpose, two statistical experimental designs were carried out, one at paste level and the other at mortar level, to mathematically model the influence of mixture parameters on fresh and durability properties. The derived numerical models were used to define an area, labelled by self-compacting zone at paste level (SCZ), where fresh properties of the paste enable the design of SCC mortar. Furthermore, in order to extend this link to durability properties, the effect of including aggregate in cement paste was evaluated by means of the electrical resistivity test.

  Abstract
  In the last years many approaches to design SCC have been developed, but it remains a very complex process since it is necessary to manipulate several variables and understand [...]

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• The Eurocode 2 and the assessment of concrete structures with corroded reinforcement

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

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

  
  

  Abstract

  The reinforcement corrosion is one of the major problems with relevant economic impact in the life cycle of concrete structures and that is why it is necessary to optimize the repair strategies in corroded structures. However, almost no international codes are available for structural evaluation and some criteria will be included in the revision of Eurocode 2 to evaluate existing deteriorated structures. A summary of Contecvet project funded EC is presented in this paper as well as some more recent developments. A first step in the evaluation of existing structures is to identify if the aggressive has reached the reinforcement and how much has affected to the structural performance. As soon as the corrosion rate has been calculated from the data taken in the structure, it is possible to estimate the rate of the structural deterioration process through the developed models and the remaining service life. Some models and expressions are summarized to estimate the residual bearing capacity of concrete structures with corroded reinforcement to be considered when drafting the new Eurocode 2.

  Abstract
  The reinforcement corrosion is one of the major problems with relevant economic impact in the life cycle of concrete structures and that is why it is necessary to optimize [...]

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• Proposed amendment of concrete durability criteria in Eurocode 2

  C. Andrade, R. Martínez, M. Sanjuán

  Hormigón y Acero (2014). Vol. 65 (272), pp. 133-140

  
  

  Abstract

  The CEN/TC 250/SC2 and TC104/SC1 Committees have established a Joint Working Group, JWG TC250/TC104, in order to review all the durability aspects related to durability in Eurocode 2 “concrete structures” and EN 206-1 “concrete” standard. This JWG has studied the possibility of classifying concrete, not only by mechanical strength, but also by durability. This JWG has proposed that this classification be based on a direct test of carbonation or chloride resistance, which would oblige to make these types of tests routine in the future. As an alternative, the Spanish Mirror group has proposed to make this classification first by concrete mix proportioning as it is currently made and, in order to advance to a performance-based approach, by an indirect test (Durability Indicator). In present paper, the Spanish proposal is described and compared to that presented in the JWG. Advantages and disadvantages of both proposals are discussed and two Tables are presented that summarize what has been submitted by the AENOR CTN-140/SC2 for the revision of Chapter 4 of the Eurocode 2

  Abstract
  The CEN/TC 250/SC2 and TC104/SC1 Committees have established a Joint Working Group, JWG TC250/TC104, in order to review all the durability aspects related to durability in [...]

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• Modelling the concrete‐real environment interaction to predict service life

  C. Andrade

  Structural Concrete (2015). Vol. 16 (2), pp. 1-2

  
  

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• Recent durability studies on concrete structure

  S. Tang, Y. Yao, C. Andrade, Z. Li

  Cement and Concrete Research (2015). Vol. 78 (Part A), pp. 143-154

  
  

  Abstract

  The durability of concrete has attracted significant attention over the past several decades and is still a research hotspot until now. This paper reviews and discusses recent research activities on the durability of concrete, including: 1) major durability problems such as alkali aggregate reaction, sulfate attack, steel corrosion and freeze–thaw; 2) durability of concrete in marine environment; and 3) coupling effects of mechanical load and environmental factors on durability of concrete. Moreover, the consideration of durability in concrete structure design (DuraCrete and performance-based specifications) is also briefly reviewed.

  Abstract
  The durability of concrete has attracted significant attention over the past several decades and is still a research hotspot until now. This paper reviews and discusses [...]

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• Influence of Crack Width on Long Term Degradation of Concrete Structures

  J. Torres, C. Andrade

  (2014). Durability of Reinforced Concrete from Composition to Protection. Springer, Cham

  
  

  Abstract

  The study of the influence of concrete crack width on corrosion of steel reinforcement due to exposure to aggressive environments is very important for durability design. Premature failure of structures may eventually occur during their service life. Since cracks in the concrete cover are inevitable due to the stress structures are subjected to, penetration of aggressive substances will occur more rapidly in cracked areas than in areas without cracking. This study addresses the corrosion effects on the reinforcement in cracked areas. Reinforced beams 2 m long and cracked at half-length with widths up to 1 mm were prepared 20 years ago, exposed to carbonation and chlorides and kept outdoors sheltered from rain until present. After 20 years, the carbonation depth in the faces of the cracks, and the reinforcement at the crack region have been examined. The results indicated that flexural cracks in high quality carbonated concrete present only a small additional risk of corrosion which, however, is significant in the presence of chlorides

  Abstract
  The study of the influence of concrete crack width on corrosion of steel reinforcement due to exposure to aggressive environments is very important for durability design. [...]

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• Multiple linear regression model for the assessment of bond strength in corroded and non-corroded steel bars in structural concrete

  M. Prieto, P. Tanner, C. Andrade

  Materials and Structures (2016). Vol. 49, pp. 4749-4763

  
  

  Abstract

  With the growth and ageing of the stock of existing structures, structural assessment and retrofitting are fast acquiring a significant role in the construction industry. The benefits of upgrading existing reinforced concrete (RC) structures or extending their service life and of ensuring greater durability in designs for de novo construction have led to a need to include deterioration as a factor in structural safety models. Bond between reinforcing steel and concrete is of cardinal importance in this respect. The present paper proposes a unified formulation for assessing bond strength in corroded and non-corroded steel bars, and an associated model to accommodate the effect of transverse pressure where appropriate. The formulation is the result of applying multiple linear regression analysis to a database built from the findings of over 650 bond tests on corroded and non-corroded reinforcing steel reported in the literature. The data collected include a wide range of variables affecting bond strength, such as bar diameter, concrete compressive strength, concrete cover, anchorage length, confinement ratio and cross-sectional loss. A number of statistical criteria are used to compare the proposed formulation to the other bond strength assessment models, including the fib Model Code 2010 proposal for corroded steel bars. Further to the statistical tests conducted, the model proposed can be usefully applied to assess the structural safety of corroded RC members.

  Abstract
  With the growth and ageing of the stock of existing structures, structural assessment and retrofitting are fast acquiring a significant role in the construction industry. [...]

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