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Evaluation of repair materials for functional improvement of slabs and beams with corroded reinforcement
Abstract
The effectiveness of epoxy resins and cementitious repair materials, including silica fume cement, in improving the functional performance of beams and slabs with corroded reinforcement was evaluated. Reinforcement corrosion in the beams and slabs was accelerated by application of a direct current for various periods of time. The deteriorated specimens were repaired and tested for flexural strength. The results indicate that not all the repair materials are able to restore the original strength of the components. The improvement in the load-carrying capacity was related to the increase in the bond between the parent concrete and the repair material, inter alia, the steel reinforcement for an effective load transfer. One of the epoxy resin mortars investigated, as well as silica fume cement concrete, to some extent, were able to restore the original strength of the component. Furthermore, the improvement in the functional performance of the repair materials, vis-à-vis, epoxy resin mortar, was observed to be dependent on the degree of reinforcement corrosion. The repair using this material was only effective when the degree of reinforcement corrosion was less than 10%.
... Authors also presented the average corrosion penetration, x, estimated from gravimetric metal loss, and the measured crack-width values. Almusallam et al. (1996Almusallam et al. ( , 1997 [9,10] during 1990-1997 tested 24 beams (15 3153100 cm), 54 prisms (3136371 cm) for pullout bond tests, and eight small slabs (3136371 cm). The 28 day concrete strengths were between 30 and 45 MPa. ...
... Authors also presented the average corrosion penetration, x, estimated from gravimetric metal loss, and the measured crack-width values. Almusallam et al. (1996Almusallam et al. ( , 1997 [9,10] during 1990-1997 tested 24 beams (15 3153100 cm), 54 prisms (3136371 cm) for pullout bond tests, and eight small slabs (3136371 cm). The 28 day concrete strengths were between 30 and 45 MPa. ...
... The results showed trends similar to Almusallam et al. (1997). When the percentage of mass loss was smaller than 2%, bond strength or moment capacity increased almost 20%. ...
Structures, approaching the end of their service life, show serious level of deterioration. Hence in this scenario, assessment of service life of structural materials and components is very significant aspect to look upon. Keeping in mind about the importance of residual useful service life (RUSL) of structures, different techniques have been developed through the last decade, to predict the RUSL. This situation has a significant economic impact on society by means of finding the amount of deterioration in material and structure, helping us to take a step for timely diagnosis and prognosis of structure. Significant amount of investigations have been done throughout the decade in this area with development of
several methodologies for evaluating and finding residual life of concrete structures. Many work have been done on concrete structures residual life but very few are available
for steel structures. This study compiles some of the existing and important methodologies developed by investigators in the past on this area for better understanding of the current situation of the prospect in this field and thus for better
advancement of further research. Hence there is a large scope for research in prognosis (evolution of damage, residual life, etc.) of steel structures.
... 1 Ten investigations conducted between 1990 and 1999 were discussed previously. [1][2][3][4][5][6][7][8][9][10] All studied the effect when corrosion was generalized (all the reinforcing steel was corroding uniformly). Table 1 shows the most important corrosion parameters used and obtained from such investigations. ...
... Table 1 shows the most important corrosion parameters used and obtained from such investigations. [2][3][4][5][6][7][8][9][10] Nine were performed using an accelerated corrosion technique. The anodic current densities applied ranged between 0.3 mA/cm 2 and 3 mA/cm 2 . ...
... The previously presented investigations experimentally determined the structural capacity for differ-ent loading cases (fl exure, axial compression, bond) and different degrees of corrosion degradation. [2][3][4][5][6][7][8][9][10] Some simplifi cations were presented to establish possible trends between metal loss, the load capacity (or strength) loss, and the maximum crack width, W C (measured at the concrete surface), due to corrosion of the embedded steel. 1 Estimations of radius loss on the order of 10% could produce loss in strength of 50% to the reinforced concrete element. 1 As a fi rst part of this investigation, the results of an experimental program to determine the fl exure load capacity changes of localized corroded concrete simple-supported beams were presented. 11 The results obtained showed a marginal decrease (10% in the fl exure load capacity) for a 14% rebar radius loss due to localized corrosion, as compared to 40% decrease of fl exure load capacity for generalized corrosion specimens, 7 with similar radius loss. ...
This work presents an experimental investigation that correlates the stiffness changes of reinforced concrete beams with the amount of steel cross section loss and concrete cover-cracking morphology due to localized corrosion of the embedded steel. Ten concrete beams (100 by 150 by 1,500 mm) with the central portion contaminated by chlorides placed during mixing of the concrete were used in this investigation. In addition, two beams without chloride contamination were used as controls. Corrosion was further accelerated in the chloride-contaminated beam by impressing an anodic current to the single no. 3 steel reinforcement bar (10 mm diameter). During corrosion acceleration, the beams were tested under flexure by a cyclic loading-unloading procedure. The changes on the stiffness (slope of the force-displacement diagram) and crack morphology of the concrete cover were recorded periodically while the specimens were corroded. The results obtained showed a decrease in the flexure stiffness as much as 32% for a 14% reduction in the rebar radius.
... But few investigations have dealt with corrosion propagation, T 2 , and even less with residual life, T RL , predictions which are also needed for durability forecasting. From those investigations dealing with T 2 and T RL periods, quite a few have dealt with the concept of remaining structural capacity of concrete elements due to corrosion of the embedded steel [1][2][3][4][5][6][7][8][9][10][11][12] and are discussed in detail in Ref. [13]. Fig. 2 presents a summary of such results obtained from Ref. [2][3][4][5][6][7][8][9], where different structural elements (beams, columns, slabs) were corroded and tested up to failure. ...
... From those investigations dealing with T 2 and T RL periods, quite a few have dealt with the concept of remaining structural capacity of concrete elements due to corrosion of the embedded steel [1][2][3][4][5][6][7][8][9][10][11][12] and are discussed in detail in Ref. [13]. Fig. 2 presents a summary of such results obtained from Ref. [2][3][4][5][6][7][8][9], where different structural elements (beams, columns, slabs) were corroded and tested up to failure. The horizontal axis in Fig. 2 represent the corrosion-induced rebar radius loss, which is presented as a ratio between the average corrosion penetration, x AVER , and the initial radius of the rebar, r 0 . ...
... The horizontal axis in Fig. 2 represent the corrosion-induced rebar radius loss, which is presented as a ratio between the average corrosion penetration, x AVER , and the initial radius of the rebar, r 0 . The experimental load capacity values from these investigations [2][3][4][5][6][7][8][9] were used to estimate the Load Capacity ratio, LC COR , regardless of the type of loading (flexure for beams and slabs, compression for columns). The LC COR values were calculated by dividing the capacity for corroded elements by the capacity for the non-corroded (control) specimens. ...
This work presents results from an experimental investigation which correlated flexure capacity loss with steel cross-section loss due to generalized corrosion of the embedded steel in a humid environment. Concrete beams (100×150×1500 mm) cast with chlorides were used in this investigation. Further acceleration of the corrosion process was achieved by applying a nominal 80 μA/cm2 constant anodic current for approximately 50–180 days. The specimens were subsequently tested in flexure under three-point loading. The average corrosion penetration, xAVER, the maximum concrete surface crack width, CWMAX, and the maximum rebar pit depth, PITMAX, were estimated for each corroded beam using gravimetric metal loss procedure. The results obtained showed: (1) the corrosion-induced concrete crack propagation was enhanced if dry rather than wet environment is used during the accelerated corrosion stage; (2) wet environment during corrosion acceleration enhanced pit formation at the rebar surface; (3) a decrease of as much as 60% in the flexure load capacity values was observed with only 10% of xAVER/r0, where r0=rebar radius; and (4) PITMAX, not the xAVER/r0 ratio, was the most important parameter affecting flexural load capacity reduction in corroded beams.
... Almusallam et al. [3] investigated the effectiveness of repair materials in improving the functional performance of beams and slabs with corroded reinforcement. In that study [3] reinforcement corrosion in the beams and slabs was accelerated by the application of a direct current for various periods of time. ...
... Almusallam et al. [3] investigated the effectiveness of repair materials in improving the functional performance of beams and slabs with corroded reinforcement. In that study [3] reinforcement corrosion in the beams and slabs was accelerated by the application of a direct current for various periods of time. The deteriorated specimens were repaired and tested for flexural strength. ...
... One of the epoxy resin mortars investigated, as well as silica fume cement concrete, to some extent, were able to restore the original strength of the component. Furthermore, the improvement in the functional performance of the repaired structure due to the application of epoxy resin mortar was noted to be dependent on the degree of reinforcement corrosion [3]. ...
This paper presents result of a study conducted to evaluate the effect of two rebar cleaning procedures and repair materials on reinforcement corrosion and flexural strength of repaired concrete beams. The steel bars in the reinforced concrete beams were corroded to varying degrees to simulate field situations and then repaired utilizing two different cleaning techniques and two repair materials. The repaired beams were then tested in flexure to evaluate the effect of cleaning method and repair materials on the corrosion-resistance and flexural capacity of repaired beams. The electrochemical behavior of cleaned and corroded steel bars was evaluated by conducting a DC potentiodynamic scan. The data indicated an insignificant change in the flexural strength of repaired beams regardless of the cleaning techniques or the repair materials. The accelerated corrosion data indicated lowest corrosion rate in the concrete specimens repaired with polymer-modified cement mortar after cleaning the bars by sand blasting (SB). The DC polarization data indicated the formation of a stable passive film on the steel bars cleaned by SB compared to uncleaned bars and those cleaned by wire brush.
... If the formation of early-age cracks in concrete during the manufacturing stage is not prevented, repair of cracks can be adopted as a solution to effectively protect the internal steel rebars from harmful ingredients [21][22][23]. Issa and Debs [21] repaired cracks in concrete using epoxy resins (sikadur-52) and discovered that the tensile and compressive strengths across cracks increased. Almusallam et al. [22] examined the flexural strength of concrete beams, including corroded steel rebars, according to various repairing materials, and noted that the epoxy resins as a repair material are better than the commercial cementitious repair material and silica fume (SF) cement concrete. ...
... Issa and Debs [21] repaired cracks in concrete using epoxy resins (sikadur-52) and discovered that the tensile and compressive strengths across cracks increased. Almusallam et al. [22] examined the flexural strength of concrete beams, including corroded steel rebars, according to various repairing materials, and noted that the epoxy resins as a repair material are better than the commercial cementitious repair material and silica fume (SF) cement concrete. Calder and Thompson [24] also reported several important findings: 1) approximately 80% of all corrosion sites are associated with cracks; 2) the epoxy resin penetrates the cracks more deeply than the polyester or methyl methacrylate resins; 3) repair with the resins decreases the carbonation depth to be less than the cover; and 4) crack repair reduces the total number of corrosion sites by approximately half, but does not prevent chloride penetration through concrete. ...
This study aims to investigate the influences of the pullout state and pre-crack width on steel fiber corrosion in ultra-high-performance concrete (UHPC) and its implication on the interfacial bond and tensile performances. For this, two pullout states, that is, partial and full debonding, and five pre-crack widths, ranging from 0.02 to 0.5 mm, were considered. An epoxy-based crack repair process was also proposed, and its benefits on limiting steel fiber corrosion were evaluated. The average bond strength of steel fiber from UHPC could be improved by 54%–59% after exposure to a corrosive environment for 4 weeks, mainly due to partial surface corrosion. The debonding region was the main passage of the NaCl solution and led to the growth of ferric oxide. The crack width of ultra-high-performance fiber-reinforced concrete (UHPFRC) clearly affected the degree of steel fiber corrosion and the tensile performance. The tensile behavior of the micro-cracked UHPFRC with a small crack width below 0.15 mm was insignificantly influenced by the 4 week corrosion; whereas, the 0.3-mm cracked UHPFRC provided 10%–14% higher tensile strength and maintained higher stress levels in the softening region because of the moderately corroded fiber surface. Given the wider pre-crack condition (0.5 mm), no increase in the tensile strength was detected by partial ruptures of steel fibers. The steel fiber corrosion in cracked UHPFRC could be effectively prevented by the crack repair process, and no change in tensile behavior was thus obtained after exposure to a corrosive environment for 4 weeks.
... Some studies related to the residual life stage of concrete structures, have been made where accelerated corrosion was performed by applying an anodic current to the rebars [1][2][3][4][5] . After a period of time after applying such anodic currents to the rebar, reduction of the structural capacity was correlated with corrosion parameters such as gravimetric metal loss and corrosion-induced concrete cracking 4,6,7 . ...
... Some studies related to the residual life stage of concrete structures, have been made where accelerated corrosion was performed by applying an anodic current to the rebars [1][2][3][4][5] . After a period of time after applying such anodic currents to the rebar, reduction of the structural capacity was correlated with corrosion parameters such as gravimetric metal loss and corrosion-induced concrete cracking 4,6,7 . Torres Acosta et al. 7,8 have conducted several studies related to this subject, but under natural conditions. ...
Relación entre la velocidad de corrosión de la armadura y el ancho de fisuras en vigas de concreto armado expuestas a ambientes que simulan el medio marino
RESUMEN
Esta investigación presenta una relación empírica entre la velocidad de corrosión de la armadura y la velocidad de ensanchamiento de fisuras por corrosión del recubrimiento de concreto en vigas, con o sin aplicación de carga. Se evaluaron vigas de concreto armado, expuestas a un proceso de corrosión natural mediante el rociado con solución salina al 3,5 %p/p de NaCl, para acelerar el proceso corrosivo de la armadura, mediante ensayos electroquímicos. El ancho de fisuras se evaluó mensualmente para estimar la relación existente entre éste y la pérdida de sección de la armadura. Los resultados demuestran que existe una relación directa entre la propagación del ancho de fisuras y la velocidad de corrosión, observando fisuras de mayor ancho en vigas cargadas.
Palabras clave: corrosion; concreto armado; vigas cargadas; ancho de fisuras.
Reinforcement corrosion rate and crack width relationship in concrete beams exposed to simulated marine environment
ABSTRACT
This investigation presents an empirical correlation between the rebar corrosion rate and the corrosion-induced crack width propagation rate produced on beam's concrete cover, with or without load application to these beams. Reinforced concrete beams were evaluated, exposed to a natural corrosion process by spraying with 3.5 %w/w NaCl solution, to accelerate the rebar corrosion process, was performed with electrochemical tests. The beams corrosion-cracking evaluation was performed once every month, to determine the relation between crack width and the rebar corrosion loss. The results showed a direct relation between crack width propagation and rebar corrosion rate, showing wider cracks in the loaded beams.
Keywords: corrosion; reinforced concrete; loaded beams; crack widths.
Relação entre a velocidade de corrosão da armadura e a largura das fissuras em vigas de concreto armado expostas a ambientes que simulam o ambiente marinho
RESUMO
Esta pesquisa apresenta uma relação empírica entre a taxa de corrosão da armadura e a abertura de fissuras por efeito da corrosão da armadura em vigas de concreto, com ou sem aplicação de carga. Foram avaliadas vigas de concreto armado, expostas a um processo de corrosão natural por pulverização com solução salina a concentração de 3,5% de NaCl, para acelerar o processo de corrosão da armadura, mediante ensaios eletroquímicos. A abertura das fissuras foi avaliada mensalmente para estimar a relação entre ela e a perda de seção da armadura. Os resultados mostram que existe uma relação direta entre a propagação da abertura da fissura e a taxa de corrosão, observando a ocorrência de fissuras de maior abertura nas vigas sob carga.
Palavras-chave: corrosão; vigas de concreto armado sob carga; abertura de fissuras.
... Some studies related to the residual life stage of concrete structures, have been made where accelerated corrosion was performed by applying an anodic current to the rebars [1][2][3][4][5] . After a period of time after applying such anodic currents to the rebar, reduction of the structural capacity was correlated with corrosion parameters such as gravimetric metal loss and corrosion-induced concrete cracking 4,6,7 . ...
... Some studies related to the residual life stage of concrete structures, have been made where accelerated corrosion was performed by applying an anodic current to the rebars [1][2][3][4][5] . After a period of time after applying such anodic currents to the rebar, reduction of the structural capacity was correlated with corrosion parameters such as gravimetric metal loss and corrosion-induced concrete cracking 4,6,7 . Torres Acosta et al. 7,8 have conducted several studies related to this subject, but under natural conditions. ...
This study aims to evaluate the correlation between crack width and apparent corrosion rate in reinforced concrete specimens exposed to a tropical marine environment of very high aggressiveness. Specimens from DURACON project (prismatic 15x15x60 cm), with 0.65 and 0.45 w/c ratios were monitored in this investigation for more than a 6-year period. Six of them have six reinforcing steel bars (rebars) placed at three different depths (two each at 15, #y20 and 30 mm) for electrochemical tests, and six specimens without reinforcement were used for concrete destructive testing. These specimens were exposed for more than 6 years at the station La Voz, Venezuela.Each day, the meteorochemical parameters (relative humidity, temperature, precipitation, wind speed and Cl-) were monitored. Also, once a month, the electrochemical parameters (corrosion potential and corrosion rate) were measured. This paper presents the results obtained with the0.65 w/c ratioconcrete specimens, which were the only ones that presentedcorrosion-induced surface cracks. Results obtained shown excellent linear correlation between mean maximum crack width and rebar cross section loss, depending also on the rebar's concrete cover.
... Long-term performance is a much-recognized but less-addressed issue in the field of reinforced concrete structures strengthened with externally bonded fiber reinforced polymer system (Almusallam et al. 1997(Almusallam et al. , 2006. The structure may show increased deflections and crack widths over time and may also fall short of the safety margin against the ultimate collapse state when subjected to weathering effects in addition to sustained loading. ...
... Muchas investigaciones realizadas se basan en el estudio de la durabilidad durante la vida útil de dichas estructuras pero en realidad muy pocas son las que se han enfocado hacia la predicción de durabilidad del concreto armado durante su vida residual. Existen varios estudios (Tachibana, et.al., 1990;Huang and Yang, 1997;Rodriguez et.al., 1997;Almusallam, et.al., (1997); Cabrera, 1996) donde, con corrosión acelerada mediante la aplicación de una corriente anódica a la armadura, se evaluó la disminución de la resistencia a la compresión por este efecto; así como la pérdida metálica gravimétrica y los valores ancho-fisura (Almusallam, 1997;Mangat and Elgarf, 1999;Torres-Acosta, 1999), encontrando correlaciones sobre el particular. Se han efectuado varias investigaciones relacionadas con este tema en condiciones de corrosión natural Revista ALCONPAT, 8 (3), 2018: 318 -333 Correlación entre ancho de grietas y velocidad de corrosión en la durabilidad de concreto reforzado en un ambiente marino tropical altamente agresivo O. Troconis de Rincón, V. Milano, A. A. Torres-Acosta, Y. Hernández-López 320 (Torres-Acosta y Martínez-Madrid, 2003;Torres-Acosta and Castro-Borges, 2013;Cabrera-Madrid et al, 2014), reportando resultados acerca de la degradación de la vida residual. ...
The aim of this investigation was to evaluate the correlation between crack width and apparent corrosion rate in reinforced concrete specimens exposed for more than six years to a tropical marine environment, at the natural test site La Voz, Venezuela. Six specimens from DURACON Project (prismatic 15x15x60 cm, with 0.65 w/c ratio) were monitored; each specimen having six reinforcing steel bars placed at three different depths (two each at 15, 20, and 30 mm) for electrochemical tests (corrosion potential and corrosion rate). An empirical correlation between surface crack propagation rate and iCORR was established, which may help iCORR estimation indirectly if values of maximum surface crack widths due to reinforcement corrosion are obtained in at least one-year period of monitoring.
... Cabrera ͑1996͒ also reported the measured values of the average crack width for each specimen tested. The results by Cabrera showed trends similar to those of Almusallam et al. ͑1997͒. When the percent of mass loss was smaller than 2%, bond strength or moment capacity increased almost 20%. ...
Investigations have been conducted during the last three decades regarding chloride penetration and prediction of corrosion initiation. However, few investigations have dealt with corrosion propagation and/or residual life predictions, which are also needed for durability forecasting. Therefore, the aim of this investigation is to discuss, based on experimental information from previous investigations, the possibility of linking the degree of degradation (from a load-capacity reduction point of view) to the surface distress (for example, crack width opening) of a corroding reinforced concrete element in a marine environment. An empirical relationship between the residual load capacity of a reinforced-concrete element and the degree of reinforcement radius loss by corrosion was estimated, and a second empirical relationship between the surface crack width and the reinforcement radius loss was established based on available experimental data. Finally, data between the average corrosion penetration and the maximum pit depth were used to propose an empirical relationship that may be applicable to the performance of corroding prestressed-concrete elements.
... This kind of corrosion can come from sea water, salt spray particles or deicing salts used on road bridges. Recently, both experimental (Almusallam, Al-Gahtani, Aziz, Dakhil, & Rasheeduzzafar, 1996a; Almusallam, Al-Gahtani, Aziz, & Rasheeduzzafar, 1996b; Almusallam, Al-Gahtani, Maslehuddin, Khan, & Aziz, 1997; Almusallam, 2001; Cabrera, 1996; Castel, François, & Arliguie, 2000a, 2000b Rodriguez, Ortega, & Garcia, 1994; Rodriguez, Ortega, & Casal, 1995; Rodriguez, Ortega, Casal, & Diez, 1996; Rodriguez, Ortega, & Casal, 1997) and modeling (Lundgren, 1999Lundgren, , 2005aLundgren, , 2005b Coronelli & Gambarova, 2004; Dekoster, Buyle-Bodin, Maurel, & Delmas, 2003; Lee, Noguchi, & Tomosawa, 2002; Spacone and Limkatanyu, 2000; Liu, 2004, 2006; Berto, Simioni, & Saetta, 2008; Saether & Sand, 2009) approaches have been carried out to provide a better understanding of the corrosion phenomenon. But the time and spatial evolution of steel rebar corrosion in concrete is not yet completely understood. ...
One of major causes responsible for the performance loss of reinforced concrete structures is the corrosion phenomenon. Thereby, taking into account the local effects of the steel/concrete interface is of primary importance to predict properly the response of corroded reinforced concrete structures. A multifiber-based model including the steel/concrete interface is proposed. This interface model allows taking into consideration the bond strength variation due to corrosion. Such an approach leads to reasonable computational costs which a powerful feature of the model. A numerical study of beams already studied in the French project « benchmark des poutres de la Rance » is proposed in order to show the efficiency and reliability of the proposed model:Une des causes majeures pouvant conduire à une perte de performance est due au phénomène de corrosion. De ce fait, considérer le comportement de l’interface acier/béton est de première importance pour prédire la réponse de structures en béton armé corrodées. Un modèle simplifié incluant les effets locaux de l’interface acier/béton est proposé. Ce modèle permet de prendre en compte la variation d’adhérence due à la corrosion. Une telle approche conduit à des coûts de calcul raisonnables ce qui est un des points forts du modèle. Pour ce faire, une étude numérique de poutres issues du projet de recherche « Benchmark des poutres de la Rance » est proposée dans le but de montrer l’efficacité et fiabilité de la méthode proposée.
... It is usually associated with carbonation or chloride penetration, which generally induces uniform or pitting corrosion. Recently, both experimental (Almusallam et al., 1996a(Almusallam et al., , 1997Almusallam, 2001;Cabrera, 1996;Castel et al., 2000a,b;Rodriguez et al., 1997) and modeling (Coronelli and Gambarova, 2004;Dekoster et al., 2003;Lee et al., 2002;Spacone and Limkatanyu, 2000;Liu, 2004, 2006) approaches have been carried out to provide a better understanding of the corrosion phenomenon. The assessment of the structural performance of civil engineering structures requires on one hand an efficient and reliable constitutive model which is able to represent the particular behavior of the steel/concrete interface in presence of corrosion, and on the other hand a robust numerical framework with reasonable computational costs. ...
Taking into account the specific behavior of the steel/concrete interface is of primary importance to predict properly the structural response of RC structures. Several constitutive models have been proposed in the literature within the framework of nonlinear finite element method (2D and 3D). Such approaches usually lead to high computational costs due to the large number of degrees of freedom. In the present paper, a multifiber-based model including the steel/concrete interface behavior is proposed. Despite the fact that the kinematics of the multi-fiber approach is based on the theory of beams, this simplified strategy accounts for local phenomena such as the relative sliding between concrete and steel. Furthermore, this steel/concrete interface constitutive model can be extended to model the loss of bond properties due to corrosion. The numerical implementation aspects are described and local responses at the Gauss point level are exposed in the cases of monotonic loadings with and without corrosion. The efficiency and the reliability of the proposed approach are tested on structural case studies which highlight a good agreement between numerical and experimental results. This multifiber-based model provides a pertinent tool for the engineers concerns with the structural assessment of degraded reinforced concrete structures.
This study aims to evaluate the correlation between crack width and apparent corrosion rate in reinforced concrete specimens exposed to a tropical marine environment of very high aggressiveness. Specimens from DURACON project (prismatic 15x15x60 cm), with 0.65 and 0.45 w/c ratios were monitored in this investigation for more than a 6-year period. Six of them have six reinforcing steel bars (rebars) placed at three different depths (two each at 15, 20 and 30 mm) for electrochemical tests, and six specimens without reinforcement were used for concrete destructive testing. These specimens were exposed for more than 6 years at the station La Voz, Venezuela. Each day, the meteorochemical parameters (relative humidity, temperature, precipitation, wind speed and Cl−) were monitored. Also, once a month, the electrochemical parameters (corrosion potential and corrosion rate) were measured. This paper presents the results obtained with the0.65 w/c ratio concrete specimens, which were the only ones that presented corrosion-induced surface cracks. Results obtained shown excellent linear correlation between mean maximum crack width and rebar cross section loss, depending also on the rebar's concrete cover.
Chloride-induced corrosion and its effect on structural and seismic performance of reinforced concrete (RC) structures have been the topic of several research projects in past decades. This literature review summarizes the state of the art by presenting a brief description of chloride-induced corrosion, its main characteristics and influencing factors, a summary of experimental published data, and existing corrosion-induced deterioration models together with numerical and experimental methods used to evaluate corroded RC bridge pier. This literature review highlights the need for reliable deterioration models for RC structures and appropriate analysis methods are needed for design of new structures or assessment of existing civil engineering structures especially in seismic areas.
Buildings with cast-in-situ reinforced concrete shear walls are widespread in many earthquake-prone countries and regions, such as Canada, Chile, Romania, Iran, Turkey, Colombia, the republics of the former Soviet Union, etc. This type of construction has been practiced since the 1960s in urban regions for medium- to high-rise buildings (4 to 35 stories high). Shear wall buildings are usually regular in plan and in elevation. However, in some buildings, lower floors are used for commercial purposes and the buildings are characterized with larger plan dimensions at those floors. In other cases, there are setbacks at higher floor levels. Shear wall buildings are commonly used for residential purposes and can house from 100 to 500 inhabitants per building. This type of construction has been described in the WHE reports from Chile (Report 4), Kyrgyzstan (Report 40), Canada (Report 79), Iran (Reports 78 and 87), Turkey (Report 101), and Colombia (Report 109).
Drying shrinkage may be a significant cause of deterioration of thin concrete repairs. Shrinkage induced stresses can at least partially be relieved by tensile creep. Hydration effects and interface properties may have significant influence on concrete repair behaviour. An important experimental study was undertaken
to understand the overall behaviour and to feed a numerical analysis tool. Different repair materials and setting techniques were studied. Long term and short term flexural tests were performed. Drying shrinkage and creep was found to be a very significant phenomenon for crack development. The used materials and setting techniques are shown to be very satisfying to restore structural capacity. The numerical formulation is presented in
this thesis. Both humidity effects and non-linear mechanical behaviour of the constitutive materials are taken into account. Phenomenological laws are used to describe mechanical damage and drying shrinkage. Moisture migration is described using a single diffusion equation. The aim of this numerical model is to obtain an analysis tool to complete experimental tests. Experimental results obtained on small lab specimens permit to calibrate numerical coefficients. Numerical results show close agreement with
experimental data.
Assessment of structural behaviour of corrosion affected structures is an important issue, which would help in making certain decisions pertaining to the inspection, repair, strengthening, replacement and demolition of such structures. The paper presents formulations to predict the loss of weight and the loss of cross-sectional area of the reinforcing bar undergoing corrosion based on the earlier study carried out by the present authors (Bhargava et al. 2006). These formulations have further been used to analytically evaluate the ultimate bending moment and ultimate shear force capacity of the corroded concrete beams. Results of the present study indicate that, a considerably good agreement has been observed between the experimental and the analytically predicted values for the weight loss and reduction in radius of the corroded reinforcing bars. A considerably good agreement has also been observed between the experimental and the analytically predicted values of ultimate bending moment and ultimate shear force capacity for the corroded concrete beams.
This work presents a n experimental investigation which correlates the flexure load capacity loss of reinforced concrete beams with the amount of steel cross section loss due to localized corrosion of the em-bedded steel. Concrete beams (1 00x 150x 1500 mm) with the central portion contarninated by chlorides, placed during mixing of the concrete, were used in this investigation. By applying 8 0 pA/cm2 constant an-odic current for approximately 4 8 to 183 days, further acceleration of the corrosion process was achieved. After the corrosion-acceleration period was over. the specimens were tested in flexure under three-point loading. In addition. the average corrosion penetration, XAVER. was estimated for each corroded beam from gravimetric metal loss. The results obtained show a decrease as high a s 40% i n the flexure load capacity values with only 10% of rebar radius loss. But the appearance of deep pits (70% of original radius) on the rebar generated capacity losses a s much as 60%.
The paper deals with the flexural and cracking behavior experimentally observed in the plain concrete beam with a hybrid polyvinyl alcohol (PVA) and polyethylene (PE) fiber reinforced strain-hardening cement composite (SHCC) layer before and after repeated freeze–thaw exposure. The influences of the SHCC layer thickness, SHCC type, and freezing–thawing cycles on the overall flexural performance of SHCC-layered concrete beams are investigated. Concrete beams, which had 100 × 100 mm rectangular cross section and 300 mm span length, were tested in four-point bending. Two kinds of SHCCs were used as layer materials for the tension zone of concrete beam. Beam specimens with two different SHCC layer thicknesses (30 mm and 50 mm) were prepared. Freezing and thawing tests of SHCC materials and SHCC-layered concrete beams followed ASTM C 666 Procedure B and continued until the specimen achieved 300 freeze–thaw cycles. Experimental study shows that when subject to monotonic flexural loading, the SHCC-layered repair system showed 2.5–3.5 times increased load carrying capacity, and mitigated cracking damage of plain concrete beam with a SHCC layer compared with plain concrete beam. The enhancement in the flexural strength and ductility is found to increase with the SHCC’s tensile strain capacity and layer thickness. While the freezing and thawing exposure decreased the deflection at the ultimate flexural strength of SHCC-layered concrete beam, flexural strength of SHCC-layered beam after 300 cycles of freezing and thawing increased up to average 15% compared to that of virgin SHCC-layered concrete beam.
This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members.
The effectiveness of a repair work for the restoration of spalled reinforced concrete (r.c.) structures depends to a great extent, on their ability to restore the structural integrity of the r.c. element, to restore its serviceability and to protect the reinforcements from further deterioration. This paper presents results of a study concocted to investigate the structural performance of eight spalled r.c. beams repaired using two advanced repair materials in various zones for comparison purposes, namely a free flowing self compacting mortar (FFSCM) and a polymer Modified cementitious mortar (PMCM). The repair technique adopted was that for the repair of spalled concrete in which the bond between the concrete and steel was completely lost due to reinforcement corrosion or the effect of fire or impact. The beams used for the experiment were first cast, then hacked at various zones before they were repaired except for the control beam. The beam specimens were then loaded to failure under four point loadings. The structural response of each beam was evaluated in terms of first crack load, cracking behavior, crack pattern, deflection, variation of strains in the concrete and steel, collapse load and the modes of failure. The results of the test showed that, the repair materials applied on the various zones of the beams were able to restore more than 100% of the beams' capacity and that FFSCM gave a better overall performance.
Steel corrosion in reinforced concrete structures leads to severe degradation processes which usually affect both the ultimate and serviceability limit state performance of the whole construction. Numerical modelling of such a behaviour requires effective non linear models able to capture all the main effects of corrosion (i.e. cracking, reduction in bond strength, reduction in steel cross-section, bond degradation, etc.). This paper discusses these topics by focusing on the effects of corrosion on bond behaviour. In particular, a coupled mechanical-environmental damage model is used to simulate the deterioration of concrete (i.e. cover cracking and reduction of mechanical properties), while the effects of corrosion on bond behaviour have been dealt with using two different approaches, one based on a “frictional type” law and the other on a “damage type” law. A comparison between experimental pull-out test data and numerical results verifies that the proposed procedures can effectively simulate the effects of corrosion on bond behaviour, mainly for the “damage type” approach. Finally the numerical simulation of some experimental tests of corroded beam has been carried out.
This paper presents numerical results obtained from finite element simulations of the time-dependent behaviour of moderately loaded patch-repaired reinforced concrete short columns. Patch repair is a structural concrete repair method in which damaged concrete is replaced with one of a wide range of materials. Relative to the concrete substrate, the patch repair materials used in this study had different properties, such as the elastic modulus, shrinkage and creep. A priori, it would appear that simple theory such as the engineer's theory of bending cannot be used to quantify the behaviour of the patch-repaired member. Experimental evidence needed to clarify such issues remains scarce. The finite element simulations performed in this study indicate that shrinkage and creep cause the progressive shedding of the load carried by the patch repair to the concrete substrate. Finite element results compare favourably with the predictions of the engineer's bending theory. Relative to test results some qualitative agreement is observed though there is significant quantitative deviation.
This work presents an experimental investigation which correlates the flexure load capacity loss of reinforced concrete beams with the amount of steel cross section loss due to localized corrosion of the embedded steel. Concrete beams (100x150x1500 mm) with the central portion contaminated by chlorides, placed during mixing of the concrete, were used in this investigation. By applying a 200 µA/cm2 constant anodic current for approximately 48 to 183 days, further acceleration of the corrosion process was achieved. After the corrosion-acceleration period was over, the specimens were tested in flexure under three-point loading. In addition, the average corrosion penetration, χAVER* estimated for each corroded beam from gravimetric metal loss. The results obtained show a decrease as high as 20% in the flexure load capacity values from the localized corroded specimens with only 14% of re bar radius loss.
Este trabajo presenta una investigación experimental que relaciona la pérdida de capacidad de carga por flexión en vigas de hormigón reforzado y la pérdida de acero debido a la corrosión localizada en el refuerzo. Se utilizaron en esta investigación vigas de hormigón (100x150x1.500 mm) con la parte central contaminada con cloruros, colocados éstos durante la fabricación del hormigón. Durante la etapa experimental se aceleró la corrosión del acero de refuerzo mediante la aplicación de una corriente anódica de 200 µA/cm2 entre 48 y 183 días. Al finalizar el período de corrosión acelerada, las vigas fueron probadas por flexión, utilizando el método de aplicación de la carga en tres puntos. Además, se estimó la pérdida promedio de la penetración χPROM* de la corrosión, utilizando el método gravimétrico. Los resultados obtenidos a la fecha, presentaron una disminución del 20% en la resistencia a la flexión cuando la corrosión localizada obtenida fue de solamente un 14% de pérdida de radio.
In this investigation, the durability performance, namely, resistance to reinforcement corrosion of reinforced concrete beams repaired with ordinary cement mortar, polymer-based cementitious mortar, and ferrocement mortar was evaluated. The effect of temperature fluctuations, representative of the environmental conditions in the arid regions, on the corrosion-resisting characteristics of these repair materials was also evaluated. The performance of these materials was compared with unrepaired concrete beams. Results indicate superior performance by ordinary cement mortar compared to other materials. However, in the structural components subjected to thermal variations, ferrocement mortar was observed to be more beneficial.
SYNOPSIS
Although resins have been used for repairing concrete for many years, there is still a lack of convincing data about their performance in this role. This is largely due to the absence of a suitable test for evaluating the repair techniques. Details are given of a test which realistically appraises the effectiveness of the injection of resin into cracks, the repair of damaged concrete with resin mortars and the use of resin primers with fresh concrete. The test piece is a rectangular prism with either a diagonal repaired crack or a scarf joint between the original concrete and the repair material. It is subjected to compressive test and compared directly with an undamaged concrete prism of similar dimensions. Thus the repair is subjected to a high degree of shear and is appraised in the same simple terms of cube or prism strength with which the engineer assesses the quality of his original concrete.
The repair performance of resinous and cementitious materials exposed to static and fluctuating temperature conditions has been evaluated in this study, which is of importance for the repair of concrete structures in the Arabian Gulf region. Specimens were exposed to a total of 90 thermal cycles between 25°C and 70°C, simulating the temperature variation of concrete surfaces on typical summer days in the Arabian Gulf region. The slant shear bond strengths as well as failure characteristics have been observed at 0, 60, and 90 cycles. The results show that the shear slant bond strength undergoes significant reduction with thermal fluctuations due to the thermal incompatibility between the concrete and the repair materials. It is found that for resinous materials the reduction varied from 9.3-20.47% for 60 cycles, and from 18.98-36.43% for 90 thermal cycles. For the cementitious materials, the corresponding values were 3.2-17.46% for 60 cycles, and 8.07-34.80% for 90 cycles. It is also seen, in general, that the mode of failure of the test specimens changed from crushing of concrete to combined crushing-joint00 failure at 60 cycles, and then to a distinct joint failure at 90 thermal cycles.