COLLECTIONS

Documents published in Scipedia

• Estimating corrosion attack in reinforced concrete by means of crack opening

  C. Andrade, A. Cesetti, G. Mancini, F. Tondolo

  Structural Concrete (2016). Vol. 17 (4), pp. 533-540

  
  

  Abstract

  The corrosion of reinforcement in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion generally crack due to the expansive nature of oxides. One very important task is estimating the corrosion level using a non‐destructive method in order to establish both the actual safety of the structure and a priority intervention plan. Many researchers have studied the relationship between the corrosion phenomenon and the corresponding crack openings and their evolution; several statistical analyses, based on test data from experimental campaigns under a wide range of test conditions, are available. The present work attempts to contribute to finding a relationship between the crack opening and the amount of corrosion induced in the reinforcing bars. The result of the analysis is that only a reduced number of tests can be used to establish an empirical model based on a reliable set of test data. A simple relationship between crack opening and corrosion penetration is not recommended, due to the different parameters that are able to influence this correlation. Therefore, two fundamental parameters, the ratio of the concrete cover to the rebar diameter and the concrete strength, have also been considered. The considerations made regarding these parameter test results have been rearranged and the result is a formulation that shows reduced scatter

  Abstract
  The corrosion of reinforcement in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion [...]

  • 3
  •  read

• Indicator of carbonation front in concrete as substitute to phenolphthalein

  S. Chinchón-Payá, C. Andrade, S. Chinchón-Yepes

  Cement and Concrete Research (2016). Vol. 82, pp. 87-91

  
  

  Abstract

  A method to substitute the recognized toxic phenolphthalein in mortars and concretes is proposed. It comprises putting a portland cement sample in contact with an innocuous solution, curcumin-based, which acts as an indicator yielding a red color in areas where there is alkaline reserve (pH ~ 12) and yellow in carbonate zones (pH ≤ 9). Solutions containing curcumin extracted from commercial turmeric powder and from the rhizomes of the turmeric plant were prepared by using ethanol as a solvent. Subsequently it has been experienced with solutions in which curcumin has been used with a purity of over 95%. The dissolution of curcumin can be used with the same reliability as phenolphthalein in the carbonation process with the advantage that it is safe and presents no health risks.

  Abstract
  A method to substitute the recognized toxic phenolphthalein in mortars and concretes is proposed. It comprises putting a portland cement sample in contact with an innocuous [...]

  • 28
  •  read

• Review of the Current State of Knowledge on the Effects of Radiation on Concrete

  T. Rosseel, I. Maruyama, Y. Pape, O. Kontani, A. Giorla, I. Remec, J. Wall, M. Sircar, C. Andrade, M. Ordoñez

  Journal of Advanced Concrete Technology (2016). Vol. 14 (7), pp. 368-383

  
  

  Abstract

  A review of the current state of knowledge on the effects of radiation on concrete in nuclear power production applications is presented. Emphasis is placed on the effects of radiation damage, as reflected by changes in engineering properties of concrete, in the evaluation of the long-term operation and for plant life or aging management of nuclear power plants (NPPs) in Japan, Spain, and the United States. National issues and concerns are described for Japan and the United States followed by a discussion of the fundamental understanding of the effects of radiation on concrete. Specifically, the effects of temperature, moisture content, and irradiation on ordinary Portland cement paste and the role of temperature and neutron energy spectra on radiation-induced volumetric expansion (RIVE) of aggregate-forming minerals are described. This is followed by a discussion of the bounding conditions for extended operation; the significance of accelerated irradiation conditions; the role of temperature and creep; and how these issues are being incorporated into numerical and meso-scale models. From these insights on radiation damage, analyses of these effects on concrete structures are reviewed, and the current status of work in Japan and the United States is described. Also discussed is the recent formation of a new international scientific and technical organization, the International Committee on Irradiated Concrete, to provide a forum for timely information exchanges among organizations pursuing the identification, quantification, and modeling of the effects of radiation on concrete in commercial nuclear applications. The paper concludes with a discussion of research gaps, including (1) interpreting test-reactor data, (2) evaluating service-irradiated concrete for aging management and to inform radiation damage models with the Zorita NPP (Spain) serving as the first comprehensive test case, (3) irradiated-assisted alkali-silica reactions, and (4) RIVE under constrained conditions.

  Abstract
  A review of the current state of knowledge on the effects of radiation on concrete in nuclear power production applications is presented. Emphasis is placed on the effects [...]

  • 1
  •  read

• Substantial global carbon uptake by cement carbonation

  F. Xi, S. Davis, P. Ciais, D. Crawford-Brown, D. Guan, C. Pade, T. Shi, M. Syddall, J. Lv, L. Ji, L. Bing, J. Wang, . Wei, K. Yang, B. Lagerblad, I. Galan, C. Andrade, Y. Zhang, Z. Liu

  Nature Geoscience (2016). Vol. 9, pp. 880-883

  
  

  Abstract

  Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 20131,2. Considerable attention has been paid to quantifying these industrial process emissions from cement production2,3, but the natural reversal of the process—carbonation—has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr−1 in 1998 to 0.25 GtC yr−1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.

  Abstract
  Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 20131,2. [...]

  • 7
  •  read

• Future trends in research on reinforcement corrosion

  C. Andrade

  (2016). Corrosion of Steel in Concrete Structures, pp.269-288

  
  

  Abstract

  The concept of service life in the science in reinforcement corrosion has evolved from a basic description of phenomena to a more detailed engineering perspective in which quantification of processes is of vital importance. This chapter treats the following subjects: (1) causes of reinforcement corrosion – carbonation, chloride ingress and stress corrosion cracking, (2) corrosion onset and chloride threshold, (3) corrosion propagation period, (4) modelling of service life, (5) additional preventive methods, (6) repair materials and techniques and (7) corrosion measurement techniques. The paper does not develop the known aspects of these different subjects, but rather identifies those aspects still needing further research work. In this exercise, the modelling of processes and their incorporation into structural and engineering calculations is identified as the most important subject needing to be improved and further developed in the near future.

  Abstract
  The concept of service life in the science in reinforcement corrosion has evolved from a basic description of phenomena to a more detailed engineering perspective [...]

  • 6
  •  read

• Corrosion induced cracking: Effect of different corrosion rates on crack width evolution

  F. Pedrosa, C. Andrade

  Construction and Building Materials (2017). Vol. 133, pp. 525-533

  
  

  Abstract

  Reinforcement corrosion leads to several damage types that influence the structure service lifetime, among which can be mentioned the cracking of concrete cover due to the increase in volume of the oxides with respect to the original volume of the parent steel. The relation between crack width and corrosion level has been studied by some authors while its analytical or numerical modelling is attracting increasing interest. In the modelling attempts, it has not been found the consideration of the corrosion rate effect, which, on the other hand was experimentally demonstrated more than 20 years ago. In the present paper the impact of different corrosion rates on the crack width development of reinforced concrete (RC) was studied. Identical RC prisms were subjected to accelerated corrosion in galvanostatic conditions with distinct electrical currents each, in order to monitor the superficial crack width growth of every specimen. Crack width growth with steel attack penetration is analysed as a two stage bilinear process where the crack width grows faster in the first stage. An empirical relation is found between the ratio crack width/steel attack and the corrosion rate applied for the first stage of cracking. With the new-found relation, a formula relating crack width evolution through time with the corrosion rate is presented. This study shows that it is crucial to take into account the strong influence of the corrosion rate on the crack width/steel attack ratio variation in order to successfully predict corrosion induced cracking

  Abstract
  Reinforcement corrosion leads to several damage types that influence the structure service lifetime, among which can be mentioned the cracking of concrete cover due to the [...]

  • 2
  •  read

• Contactless safety evaluation of damaged structures through energetic criteria

  L. Saucedo-Mora, C. Andrade, C. López, J. Sánchez, A. Zamora

  Structural Control and Health Monitoring (2017). Vol. 25 (1), pp. 1-11

  
  

  Abstract

  The reinforced concrete structures need to be monitored to ensure their structural integrity, but sometimes those measurements are very local, and the instrument is complex to locate physically in the structure and may interfere on it. Digital Image Correlation is a noncontact and nondestructive experimental technique capable to measure the displacement field in a big region of a structure with a great accuracy. This allows extracting valuable information from the fracture processes of reinforced concrete structures, critical for the evaluation of the structural integrity. The measurement of the energy dissipated by the structure is essential for the identification of the strength mechanisms that are failing in the structure and to identify a proper repair. Also, using fracture mechanics, other valuable information are extracted from the fracture processes of the reinforced concrete beam, such as the Modes I and II fracture energy released at each loading step, which is essential to evaluate the elastic energy that the structure can accumulate before collapse. The examples enable to anticipate the importance of Digital Image Correlation for future large scale studies of fracture in concrete and other materials related to construction.

  Abstract
  The reinforced concrete structures need to be monitored to ensure their structural integrity, but sometimes those measurements are very local, and the instrument is complex [...]

  • 3
  •  read

• Corrosion-induced brittle failure in reinforcing steel

  J. Sánchez, J. Fullea, C. Andrade

  Theoretical and Applied Fracture Mechanics (2017). Vol. 92, pp. 229-232

  
  

  Abstract

  Steel rebar corrosion is the main cause of reinforced concrete structure deterioration and shortened service life. A number of corrosion mechanisms induce geometric flaws in rebar, reducing its mechanical strength. Interstitial hydrogen, which lowers steel toughness, may also prompt embrittlement.This paper discusses the effect of local, pitting and corrosion stress on steel rebar performance. The findings show that rebar bearing strength depends on corrosion morphology and weight loss, which would explain the scatter in experimental results when the latter is the sole parameter studied.

  Abstract
  Steel rebar corrosion is the main cause of reinforced concrete structure deterioration and shortened service life. A number of corrosion mechanisms induce geometric flaws [...]

  • 0
  •  read

• The effect of two types of modified Mg-Al hydrotalcites on reinforcement corrosion in cement mortar

  Z. Yang, R. Polder, J. Col, C. Andrade

  Cement and Concrete Research (2017). Vol. 100, pp. 186-202

  
  

  Abstract

  Two modified Mg-Al hydrotalcites (MHTs), (MHT-pAB and MHT-NO2) were incorporated into mortar (with different w/c ratios) in two different ways: (1) as one of the mixing components in bulk mortar; (2) as part of cement paste coating of the reinforcing steel. Accelerated chloride migration, cyclic wetting-drying and diffusion tests were performed to investigate their effect on reinforcement corrosion. The results indicated that MHTs could be promising alternatives for preventing chloride-induced corrosion when an appropriate dosage is adopted and applied in a proper way, particularly, replacing 5% mass of cement by MHT-pAB in bulk mortar or as a coating of reinforcing steel (MHT-pAB/MHT-NO2 to replace 20% mass of cement). The effect of MHT-pAB on time-to-corrosion initiation (TTC) of reinforcing steel was estimated using the DuraCrete model. It was found that the incorporation of 5% MHT-pAB in bulk mortar led to a more than double TTC relative to reference mortar without MHTs.

  Abstract
  Two modified Mg-Al hydrotalcites (MHTs), (MHT-pAB and MHT-NO2) were incorporated into mortar (with different w/c ratios) in two different ways: (1) as one of the [...]

  • 2
  •  read

• Reliability analysis of corrosion onset: initiation limit state

  C. Andrade

  Journal of Structural Integrity and Maintenance (2017). Vol. 2 (4), pp. 200-208

  
  

  Abstract

  The relatively premature failure of structures by steel corrosion has increased interest in incorporating to the standards calculation of the time to corrosion. These models in general identify the end of service life with the starting of bar corrosion, either by chlorides or by carbonation. Additionally, from the publications of the project Duracrete, funded by the EU, probabilistic treatments have been applied to steel depassivation which is associated with a serviceability limit state (SLS). Thus, fib Model Code (MC2010) recommends a probability of failure of 10% for calculation of the time to corrosion. However, this recommendation leads to uncertainties because, on the one hand, the chloride threshold is not a fixed value and the carbonation front affects first the external face of the bar, developing progressive perimetral damage and, on the other hand, the consideration of the limit state as an SLS, with so low a fixed failure probability, introduces some degree of contradiction with the classical definition of the SLS. This is because, while the SLS is defined as a failure to fulfil the design prescriptions, any structural design performance changes just at the moment of steel depassivation. Additionally, no treatment on how to consider the damaged section or corrosion propagation model is usually given in the MC2010 or other standard and how to verify the classical SLS and ultimate limit state (ULS) is undefined. The present work introduces new perspectives on the subject from a probabilistic point of view by, (1) treating statistically the depassivation step, (2) by introducing a corrosion propagation model and quantifying the corrosion limit states and (3) by calculation of the depassivation probability which is dependent on the rate of the deterioration process itself. The whole exercise stresses the need to not consider a fixed value (10%) associated with a SLS as the probability of corrosion, but to consider it a limit state of “corrosion initiation” following ISO 2394. The value of the adequate probability of corrosion would be dependent on the consequences of the failure and on the rates of chloride ingress, of carbonation or of steel corrosion.

  Abstract
  The relatively premature failure of structures by steel corrosion has increased interest in incorporating to the standards calculation of the time to corrosion. These models [...]

  • 4
  •  read