Numerical simulation of the through-thickness cracking of concrete cover due to steel reinforcing bars corrosion

2015 ◽  
pp. 37-43
Author(s):  
M Mirzaee ◽  
F Alaee ◽  
M Hajsadeghi ◽  
C Chin
Keyword(s):  
Numerical Simulation ◽  
Concrete Cover ◽  
Reinforcing Bars

scholarly journals Updating Carbon Storage Capacity of Spanish Cements

2018 ◽  
Vol 10 (12) ◽  
pp. 4806 ◽  
Author(s):  
Carmen Andrade ◽  
Miguel Sanjuán
Keyword(s):  
Carbon Storage ◽  
Storage Capacity ◽  
Concrete Cover ◽  
Raw Material ◽  
Cement Clinker ◽  
Reinforcing Bars ◽  
Concrete Element ◽  
Length Of Service ◽  
Carbonation Reaction ◽  
Carbon Dioxide Uptake

The fabrication of cement clinker releases CO2 due to the calcination of the limestone used as raw material, which contributes to the greenhouse effect. The industry is involved in a process of reducing this amount liberated to the atmosphere by mainly lowering the amount of clinker in the cements. The cement-based materials, such as concrete and mortars, combine part of this CO2 by a process called “carbonation”. Carbonation has been studied lately mainly due to the fact that it induces the corrosion of steel reinforcement when bringing the CO2 front to the surface of the reinforcing bars. Thus, the “rate of carbonation” of the concrete cover is characterized by and linked to the length of service life of concrete structures. The studies on how much CO2 is fixed by the hydrated phases are scarce and even less has been studied the influence of the type of cement. In present work, 15 cements were used to fabricate paste and concrete specimens withwater/cement (w/c) ratios of 0.6 and 0.45 which reproduce typical concretes for buildings and infrastructures. The amount of carbon dioxide uptake was measured through thermal gravimetry. The degree of carbonation, (DoC) is defined as the CO2 fixed with respect to the total theoretical maximum and the carbon storage capacity (CSC) as the carbonation uptake by a concrete element, a family or the whole inventory of a region or country. The results in the pastes where analyzed with respect to the uptake by concretes and indicated that: (a) the humidity of the pores is a critical parameter that favours the carbonation reaction as higher is the humidity (within the normal atmospheric values), (b) all types of cement uptake CO2 in function of the CaO of the clinker except the binders having slags, which can uptake additional CO2 giving aDoC near or above 100%. The CSC of Spain has been updated with respect to a previous publication resulting in proportions of 10.8–11.2% of the calcination emissions, through considering a ratio of “surface exposed/volume of the element” of 3 as an average of the whole Spanish asset of building and infrastructures.

Effect of Chloride-Induced Steel Corrosion on Working Life of Concrete Structures

2018 ◽  
Vol 272 ◽  
pp. 226-231 ◽  
Author(s):  
Ivan Hollý ◽  
Juraj Bilčík
Keyword(s):  
Pore Solution ◽  
Concrete Structures ◽  
Steel Corrosion ◽  
Radial Pressure ◽  
Concrete Cover ◽  
Transport Infrastructure ◽  
Reinforcing Bars ◽  
Volume Increase ◽  
Volumetric Expansion ◽  
High Alkalinity

The reinforcing steel embedded in concrete is generally protected against corrosion by the high alkalinity (pH = 12.5 to 13.5) of the concrete pore solution. The structural degradation of concrete structures due to reinforcement’s corrosion has an impact on the safety, serviceability and durability of the structure. The corrosion of reinforcements in the construction of a transport infrastructure (especially bridges), parking areas, etc., is primarily initiated by chlorides from de-icing salts. When corrosion is initiated, active corrosion results in a volumetric expansion of the corrosion products around the reinforcing bars against the surrounding concrete. Reinforcement corrosion causes a volume increase due to the oxidation of metallic iron, which is mainly responsible for exerting the expansive radial pressure at the steel–concrete interface and development of hoop tensile stresses in the surrounding concrete. When this tensile stress exceeds the tensile strength of the concrete, cracks are generated. Higher corrosion rates can lead to the cracking and spalling of the concrete cover. Continued corrosion of reinforcement causes a reduction of total loss of bond between concrete and reinforcement.

Numerical Interpretation of Bond Between Steel and Concrete in Presence of Corrosion and Cyclic Action

2009 ◽  
Vol 417-418 ◽  
pp. 349-352 ◽  
Author(s):  
Luca Giordano ◽  
Giuseppe Mancini ◽  
Francesco Tondolo
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Stress Transfer ◽  
Experimental Tests ◽  
Radial Pressure ◽  
Mechanical Action ◽  
Concrete Cover ◽  
Reinforcing Bars ◽  
Cyclic Action ◽  
Bond Slip

Bond between steel and concrete in reinforced concrete structures plays a fundamental role. The stress transfer mechanism depends on the condition of the contact surface between the two materials, the mechanical characteristics of concrete near the rebar and on the available level of confinement. Corrosion of reinforcing bars in concrete structures modifies those three factors. Because of corrosion, on the rebar surface a granular oxide layer is present and with its expansion it generates a significant radial pressure; consequently tensile stresses grow till cracking of the concrete cover with a subsequent reduction of the confinement effect. Moreover the presence of a mechanical action modifies the resisting mechanism producing an increasing damage. In this study, a model is presented for the numerical simulation of experimental tests on r.c. ties subjected to mechanical action; furthermore some considerations on reinforced concrete ties subjected also to corrosion effect are reported. From those analyses it is possible to estimate a modified bond-slip law between the reinforcing bars and the concrete, in order to take into account the level of damage.

scholarly journals Diagnóstico patológico y propuesta de intervención de los cimientos y de los muros de contención de derrames de dos tanques de almacenamiento de ácido sulfúrico para usos industriales

2013 ◽  
Vol 3 (3) ◽  
pp. 177-187 ◽  
Author(s):  
M.Y. Dikdan ◽  
R. M. De Corrales ◽  
D. Avon
Keyword(s):  
Concrete Cover ◽  
The Other ◽  
Reinforcing Bars ◽  
Industrial Facility ◽  
Concrete Walls ◽  
Floor Slab ◽  
Structural Capacity ◽  
Epoxy Material ◽  
Concrete Tank ◽  
Cover Thickness

RESUMENEn los muros y la losa de piso de una piscina de contención de derrames de tanques metálicos de ácido sulfúrico se evidenciaron sintomatologías de fallas. Se observó desagregación en las bases de los tanques y en la losa de piso. En la parte inferior de los muros se evidenció pérdida de conexión con la losa de piso. Mediante la extracción de núcleos al concreto se determinó: carbonatación, porosidad, penetración de sulfatos y resistencia a compresión. Al acero se le midió: espesor de recubrimiento, diámetro, potenciales y velocidad de corrosión. Se determinó la capacidad remanente del muro mediante cálculo estructural. Como conclusión la estructura se apreció muy afectada. Se recomienda el diseño especial de concreto con revestimiento antiácido y dos acciones, una inmediata mediante la construcción de tacos que garanticen apoyo y estabilidad a los tanques, y otra definitiva, reubicación del sistema de los tanques y la piscina.Palabras clave: Tanques; Ácido sulfúrico; Desagregación; Corrosión; Muros.ABSTRACTIn an industrial facility, several failure symptoms were found on walls, floor slab, and foundations of concrete tanks designed to contain eventual spilling from two metallic containers of sulfur acid (one at 11% concentration, and the other at 98%). Loss of connection between lateral walls and floor slab was observed. Interior wall areas and foundations of tanks were covered with epoxy material which was mostly peeled off. By extraction of concrete nucleus samples, the following parameters were determined: carbonation, porosity, sulfate penetration, and compressive strength. Reinforcing bars were tested for: concrete cover thickness, diameter, potential measurements (Cu/SO4Cu), and corrosion rate. Remaining structural capacity of concrete walls was calculated, concluding that the structure is severely affected by sulfur acid. Two actions are suggested: a provisional one by constructing big reinforced concrete cubes around the tank to make it stable; the other, a final solution, replacing the sulfur acid containers and the concrete tank for possible sulfur infiltration to the ground underneath them.Keywords: Tanks; Sulfur acid; disaggregation; corrosion; walls.

scholarly journals New warning sensors to detect corrosion risk in reinforced concrete

2019 ◽  
Vol 289 ◽  
pp. 06002
Author(s):  
Mahdi Khadra ◽  
Elisabeth Marie-Victoire ◽  
Myriam Bouichou ◽  
Christian Crémona ◽  
Stéphanie Vildaer
Keyword(s):  
Reinforced Concrete ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Cultural Value ◽  
Original Material ◽  
Reinforcing Bars ◽  
First Results ◽  
Corrosion Risk ◽  
Deterioration Mechanism ◽  
Different Depths

Corrosion is the most frequent but also the most deleterious deterioration mechanism affecting reinforced concrete. In addition to the economic impact of the repair works, for historical concrete structures, corrosion can generate irreversible losses of original material of great cultural value. If the usual non-destructive electrochemical methods have highlighted their efficiency in evaluating on-going corrosion activity, they also have pointed out their drawbacks for accurate extrapolation and prevention. To prevent the corrosion phenomenon, by detecting the penetration of aggressive agents, a new warning sensor system has been developed. The principle of the technique is to embed thin metallic sheets (called orphan blades) in the concrete cover, at different distances from the surface to the reinforcing bars. Then the corrosion of those very reactive orphan blades is followed during the propagation of the carbonation front and/or the penetration of chloride ions using stimulated infrared thermography. The corrosion of the sensors at different depths is indicative of the ingress speed of the front and can alert about the risk of corrosion of reinforcing bars in the concrete. The purpose of this study is to present this new technique and the first results obtained in the laboratory on corroded and non-corroded sensors.

Behavior of FRP-RC Members during Exposure to Fire

2014 ◽  
Vol 1054 ◽  
pp. 27-32
Author(s):  
David Horak ◽  
Martin Zlámal ◽  
Petr Štěpánek
Keyword(s):  
Fire Effects ◽  
Concrete Cover ◽  
Fiber Reinforced Polymer ◽  
Reinforcing Bars ◽  
Concrete Members ◽  
Reinforced Polymer ◽  
High Durability ◽  
University Of Technology ◽  
Frp Reinforcement ◽  
New Type

New type of fiber reinforced polymer (FRP) reinforcement has been developed in previous years at Brno University of Technology, which can be used for reinforcing, strengthening and prestressing of concrete structures. The main advantage of FRP reinforcement is resistibility against aggressive environment and thus the possibility to use thinner concrete cover. High durability and resistibility are demanded from modern constructions. Some of the influences cover the effects of fire exposure or high temperature in general. Hence the next part of the research is focused on resistibility of FRP reinforced structures under effects of fire. The paper deals with experiments oriented to observing the behaviour of prestressed and non-prestressed FRPRC panels subjected to fire effects as well as behaviour of FRP reinforcement itself. Results of experiments proved resistibility of FRP reinforced panels to fire effects. They also demonstrate the importance of understanding the behaviour of composite reinforcing bars alone and their behaviour along the anchoring zone in concrete members exposed to fire. A sufficient anchorage length (enabling the transfer of load from the reinforcement into the concrete) turned out to be a key feature enabling a structure to withstand over much longer time periods and even under surprisingly high temperatures.

Behavior of Reinforced Concrete Subjected to High Temperatures-A Review

2013 ◽  
Vol 4 (4) ◽  
pp. 281-295 ◽  
Author(s):  
Aijaz Zende ◽  
A. Kulkarni ◽  
Aslam Hutagi
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Concrete Surface ◽  
Concrete Cover ◽  
Mechanical And Thermal Properties ◽  
Reinforcing Bars ◽  
Cover Layer ◽  
Higher Temperature ◽  
Effects Of Temperature

This paper reviews the research carried on effects of fire on the mechanical and thermal properties on concrete. Fire in the structure causes higher temperature at the concrete surface, which causes a reduction in compressive strength, modulus of elasticity of concrete. Though concrete is a poorer conductor than steel, sustained high temperature at the surface leads to progressive heating of the inner layers of concrete. This leads to exposing reinforcing bars to higher temperature; which causes a reduction in the yield stress, ductility and tensile strength of steel. This paper also focuses on the concrete cover, the reinforcement bars in a concrete structure are protected against fire only by the concrete cover layer thus higher is the cover more is the resistance and vice a versa. Effects of temperature on the thermal conductivity of concrete is also discussed in detail.

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