The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Göran Fagerlund - One of the best experts on this subject based on the ideXlab platform.
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Residual strength of the Frost-damaged reinforced concrete beams
III European Conference on Computational Mechanics, 2020Co-Authors: Manouchehr Hassanzadeh, Göran FagerlundAbstract:The most severe types of destruction mechanisms are those causing internal cracking and thereby loss of cohesion of the concrete, i.e. internal expansive Attacks. The internal Frost damage belongs to this category of destructive mechanisms. The Frost Attack causes a random system of cracks in the heart of the concrete together with cracks parallel to the surface of the concrete. In many cases there are also extended cracks parallel to joints and edges of the concrete, or emanating from corners. The amount of damage can vary from place to place in the same structure. Therefore, in most cases, series of data from many different places are required. Only in special cases data taken from one place can be used for the entire structure.
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Synergetic effects of combined destructive action on concrete
2020Co-Authors: Göran FagerlundAbstract:The effect of a certain aggressive action is often aggravated if another aggressive action takes place at the same time. Examples of mechanisms with synergy are (i) salt-Frost scaling and reinforcement corrosion, (ii) alkali silica reaction (ASR) and internal Frost damage, (iii) leaching of lime and internal Frost Attack, (iv) leaching of lime and reinforcement corrosion, (v) internal Frost and leaching, (vi) ASR and leaching. There are also other destruction mechanisms involved in synergy, such as different types of chemical Attack. Synergetic effects should be considered in service life calculations of structures to be built. They should also be considered in connection with assessments of the residual service life of existing structures. In the paper some of these synergetic effects and their importance are discussed theoretically. The aim of the paper is merely to indicate the importance of considering synergy and not to treat this in great detail. (Less)
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Repair of Concrete Balcony Slabs
Advances in Concrete Slab Technology, 2014Co-Authors: Ove Svensson, Göran Fagerlund, Nils PetersonsAbstract:ABSTRACT More than 200000 concrete balconies in Sweden are badly damaged by Frost Attack and corrosion of the reinforcement. Moreover, although many of these balconies have been repaired, the repair work, which normally consists of applying various types of plastic coating, has often failed within a few years. This paper describes a research project in which the durability of different repairing systems is being studied in the laboratory and in the field. The laboratory studies investigated the Frost resistance, the thermal gradient sensitivity and the diffusivity of the repairs, while the field studies were directed at understanding the general behaviour of different repairing systems. In addition, the moisture state in the structural concrete slab beneath different repairs is being studied. Some preliminary results are given indicating that it is very doubtful if any repairing system can protect a low grade concrete slab from continued damage.
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service life with regard to Frost Attack a probabalistic approach
Report TVBM (Intern 7000-rapport); 7137 (1998), 1998Co-Authors: Göran FagerlundAbstract:Significant Frost damage will not occur until a certain critical moisture level is transgressed over a sufficiently big portion of the structure. The critical moisture level is a “fracture value” which can be compared with the load carrying capacity in structural design. It is a materials property that seems to be rather uninfluenced by normal variations in environmental properties, such as number of freeze-thaw cycles and minimum freezing temperature. The moisture content inside the structure depends on the outer moisture conditions; the more moist the environment, the larger the inner moisture content, and the larger the risk of Frost damage. The actual moisture content in the structure can be compared with the actual load in structural design. The risk of Frost damage can be calculated when the frequency functions of the two parameters, critical moisture content and actual moisture content are known. Some hypothetical cases are treated in the paper showing that the probability of Frost damage might actually decrease with increasing exposure time in moderately moist environments, but that it normally increases with increasing exposure time in continuously moist environments where the structure has no possibility to dry.
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Influence of environmental factors on the Frost resistance of concrete : a contribution to the BRITE/EURAM project BREU-CT92-0591 "The Residual Service Life of Concrete Structures"
Report TVBM, 1994Co-Authors: Göran FagerlundAbstract:This report investigates how the ability of a concrete to withstand Frost Attack depends not only of the concrete itself but also on the internal and external climatic factors. All those internal and external factors and their interaction are discussed.
Kookjae Shin - One of the best experts on this subject based on the ideXlab platform.
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Frost Attack resistance and steel bar corrosion of antiwashout underwater concrete containing mineral admixtures
Construction and Building Materials, 2007Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims to evaluate Frost durability and steel-bar corrosion in antiwashout-underwater concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-underwater concrete specimens. The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on Frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-underwater admixture. Slight improvement of Frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%. Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.
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Freezing and Thawing Resistance and fundamental Properties of Antiwashout Underwater Concrete Containing Mineral Admixtures
Journal of The Korea Concrete Institute, 2005Co-Authors: Hanyoung Moon, Kookjae Shin, Yong-kyu SongAbstract:Today the application of antiwashout underwater concrete to the construction sites is increasing steadily, while its reliability is in issue. Particularly, antiwashout underwater concrete is known to have very weak durability on Frost Attack, and hence Japan society of civil engineers(JSCE) regulated that not to use of antiwashout underwater concrete where the freezing and thawing is suspected. This study aims the improvement of the freezing and thawing resistance for antiwashout underwater concrete. From the results of fundamental test, FA20 and SG50 showed good performance in fluidity and long term compressive strength than control concrete. Meanwhile, MK10 marked the highest compressive strength through the whole curing age but a defect on fluidity was discovered. The results from the repeated freezing and thawing test show that the large volumes of air entrapped by cellulose based antiwashout underwater admixture gave bad effects to Frost durability and hence not much benefits were confirmed from the use of mineral admixtures. However there were some increasing effects on Frost durability of MK10 and SG50 by securing of entraining air. In the meantime, there was a increasing tendency of Frost durability by increasing blame's fineness of ground granulated blast furnace slag.
Luping Tang - One of the best experts on this subject based on the ideXlab platform.
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Validation of models and test methods for assessment of durability of concrete structures in the road environment
2017Co-Authors: Luping Tang, Peter Utgenannt, Anders Lindvall, Dimitrios BoubitsasAbstract:This report presents the results from validation of models and test methods for assessment of durability of concrete structures exposed in Swedish road environment. In the past years a number of models for durability design of concrete structures have been suggested by relevant organisations or international committees. It is necessary to validate these models against long-term field data for their applicability with respect to exposure climate in order to satisfactorily use the models in the durability design and redesign of concrete structures. In this study, various potential models for concrete resistance to chloride ingress, carbonation and Frost Attack were compiled and the sensitive input parameters that affect the modelling results were mathematically analyzed. Three models including the simple ERFC, the DuraCrete and the ClinConc, for prediction of chloride ingress were evaluated using the infield data collected from both the field exposure site after over 10 years exposure and the real road bridges of 25-30 years old. A physicochemical model for prediction of carbonation depth was evaluated using the infield data collected from the field exposure site after 11 years exposure and the limited data from the real structures with the age of 7-13 years. The results from different standard test methods including the newly standardised prEN/TS 12390-11 for chloride diffusivity were compared. For the modelling of Frost Attack, some test procedures for measurement of critical saturation degree and water absorption curves including the pump effect were suggested. Based on the results, recommendations as guidelines for practical application of test methods and models in durability design of concrete structures were suggested.
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durability and service life prediction of reinforced concrete structures
Journal of the Chinese Ceramic Society, 2015Co-Authors: Luping Tang, Peter Utgenannt, Dimitrios BoubitsasAbstract:This paper presents some durability and service life models for reinforced concrete structures with regard to chloride ingress, carbonation and Frost Attack. In the past years a number of models for durability design of concrete structures have been suggested by relevant organisations or international committees. It is necessary to validate these models against long-term field data for their applicability with respect to exposure climate in order to satisfactorily use the models in the durability design and redesign of concrete structures. In this study, various potential models for concrete resistance to chloride ingress, carbonation and Frost Attack were briefly reviewed. Three models including the simple ERFC, the DuraCrete and the ClinConc, for prediction of chloride ingress were evaluated using the infield data collected from both the field exposure site after over 20 years exposure and the real road bridges of about 30 years old. A physicochemical model for prediction of carbonation depth was evaluated using the infield data collected from the field exposure site after 11 years exposure and the limited data from the real structures with the age of 7-13 years. For the modelling of Frost Attack, some problems in measurement of critical saturation degree and actual degree of saturation are discussed. According to the comparison results, the simple ERFC overestimates whilst the DuraCrete model underestimate the chloride ingress in most cases. The ClinConc model on the other hand gives reasonable good prediction for both the short-term (one year) and the long-term (21 years) exposure. The Papadakis model for carbonation also gives fairly good prediction of carbonation depth when compared with the Norwegian infield data classified as exposure class XC3, but underestimates the carbonation depths when compared with the infield data from Norwegian structures in exposure class XC4. For the Frost Attack, it is premature to apply the models to the service life prediction so far.
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some questions in modelling of service life of concrete structures with regard to Frost Attack
Proceedings from a Nordic Miniseminar "Freeze-Thaw Testing of Concrete - Input to Revision of CEN Test methods", 2010Co-Authors: Luping TangAbstract:In this paper, the previous work in the study of mechanisms of water uptake and modelling of service life is reviewed and some questions in the modelling of service life are taken out for discussions. The results from a preliminary study of test procedures for determination of the critical degree of saturation and other necessary parameters for modelling of service life are presented. Based on the experience from the preliminary study the practical test procedures are suggested. With these test procedures, all test results can be obtained in a reasonably short period.
Hanyoung Moon - One of the best experts on this subject based on the ideXlab platform.
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Frost Attack resistance and steel bar corrosion of antiwashout underwater concrete containing mineral admixtures
Construction and Building Materials, 2007Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims to evaluate Frost durability and steel-bar corrosion in antiwashout-underwater concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-underwater concrete specimens. The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on Frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-underwater admixture. Slight improvement of Frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%. Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.
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Freezing and Thawing Resistance and fundamental Properties of Antiwashout Underwater Concrete Containing Mineral Admixtures
Journal of The Korea Concrete Institute, 2005Co-Authors: Hanyoung Moon, Kookjae Shin, Yong-kyu SongAbstract:Today the application of antiwashout underwater concrete to the construction sites is increasing steadily, while its reliability is in issue. Particularly, antiwashout underwater concrete is known to have very weak durability on Frost Attack, and hence Japan society of civil engineers(JSCE) regulated that not to use of antiwashout underwater concrete where the freezing and thawing is suspected. This study aims the improvement of the freezing and thawing resistance for antiwashout underwater concrete. From the results of fundamental test, FA20 and SG50 showed good performance in fluidity and long term compressive strength than control concrete. Meanwhile, MK10 marked the highest compressive strength through the whole curing age but a defect on fluidity was discovered. The results from the repeated freezing and thawing test show that the large volumes of air entrapped by cellulose based antiwashout underwater admixture gave bad effects to Frost durability and hence not much benefits were confirmed from the use of mineral admixtures. However there were some increasing effects on Frost durability of MK10 and SG50 by securing of entraining air. In the meantime, there was a increasing tendency of Frost durability by increasing blame's fineness of ground granulated blast furnace slag.
C Alonso - One of the best experts on this subject based on the ideXlab platform.
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relative humidity in the interior of concrete exposed to natural and artificial weathering
Cement and Concrete Research, 1999Co-Authors: C Andrade, J Sarria, C AlonsoAbstract:The moisture content is a crucial parameter for most of the degradation processes suffered by concrete. Thus, a certain water content is needed to develop alkali-silica reaction, Frost Attack, or steel corrosion, while in contrast carbonation can only progress if the concrete is relatively dry. The importance of the concrete moisture state has been studied for many years in the concrete literature, and the internal relative humidity has been addressed mainly by those researchers interested in creep and shrinkage. However, despite the numerous works on the subject, almost no data can be found on the monitoring of the moisture content or of the internal relative humidity in structures subjected to real weathering conditions. In general the extensive studies have been made in the laboratory in well-controlled chambers to examine water isotherms. In addition, modelling has been developed assuming general isothermic conditions. However, natural weathering usually implies irregular changes of temperature and relative humidity, which induce continuous nonsteady-state conditions in the interior of the concrete. In the present paper, values of the internal relative humidity of concretes submitted to natural and artificial weathering are presented. From these, it is possible to deduce that the temperature is the main factor influencing the concrete internal relative humidity in samples sheltered from rain, while rain periods are the main factor in unsheltered samples. In the environment tested, two kinds of temperature cycles are acting: the day-night cycle and the seasonal cycle. The paper discusses the phenomenological features of the observed evolution of the internal relative humidity and presents some interpretations on the mechanisms of water transport induced by the external environment.
