4 edition of Influence of cracks on chloride ingress into concrete found in the catalog.
Influence of cracks on chloride ingress into concrete
Olga Garces Rodriguez
Thesis (M.A.Sc.) -- University of Toronto, 2001.
|Series||Canadian theses = -- Thèses canadiennes|
|The Physical Object|
|Pagination||3 microfiches : negative.|
The accelerated chloride diffusion test on uncracked and cracked concrete showed the big influence of a µm wide crack on the chloride ingress in concrete. Close to the exposed surface, the influence was rather limited, but increased nearly exponentially in depth. After 15 years exposure it was concluded inches of cover was insufficient to prevent rusting of steel reinforcement and cracking of concrete . Preventing ingress of chloride in reinforced concrete is not simple. Fundamentally only crack-free, good-quality, un-carbonated, concrete . 4. Conclusions Based on the results discussed above, some conclusions are drawn. (1)The use of calcium stearate in concrete can decrease the compressive strength of concrete. The amount that can be added safely is no more than % of the weight of the cement.(2)The higher the amount of calcium stearate added to the concrete, the lower the chloride ion infiltration.
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Autorisation. infiuence of Cracks on Chioride Ingress into Concrete Olga Garces Rodriguez, Master of Applied Science, 1. Department of Civil Engineering, University of Toronto Exposure of concrete to chloride ions is considered to be the main cause of premature corrosion of steel by: Cracks have been found to locally promote both chloride ingress as well as carbonation   , resulting in much faster ingress of chlorides and the carbonation front in the concrete.
Title: Influence of Cracks on Chloride Ingress into Concrete. Author(s): Olga Garces Rodriguez and R. Doug Hooton. Publication: Materials Journal. Volume: Issue: 2. Appears on pages(s): Keywords: concrete; crack; scanning electron microscope. Date: 3/1/ Abstract:Cited by: If cracks, caused by early drying, thermal effects, shrinkage movements or overstress, are present in the concrete, the penetration of chlorides is much faster than in uncracked concrete.
In this way, the corrosion process is initiated earlier and the service life is decreased drastically. combined with dynamic loading which resulted in an increased chloride ingress into concrete.
It can be concluded that preferably variable loading conditions have to be simulated during laboratory testing, rather than static or unloaded, as more similar to reality. Influence of cracks. In this chapter, the effect of cyclic wet-dry in the salt-fog condition which mimics the atmospheric zone environment on the chloride ingress into concrete is discussed.
Also, the influence of carbonation on the chloride penetration in concrete under service load is discussed. As mentioned above, the DZ has a pronounced influence on chloride diffusivity in cracked concrete, and in order to effectively distinguish this influence, three magnitudes of D DZ /D cp, i.e., 10, 20 are selected to investigate the influence of the D DZ on chloride diffusivity in cracked concrete, as presented in Fig.
It is apparent that for cracks under 80 μm the results show a transition period and a steady-state period characterised by a constant rate of chloride increase with time. The transition period was dependent on the crack width and on the concrete mixes.
A higher crack width produced a shorter transition period and an increase in the slope. Recently, some laboratory studies conducted accelerated tests using alternating schemes of carbonation-chloride ingress to address the combined actions in both senses.
The chlorides were found to transport further into concrete under such combined actions while the quantitative aspect depends much on the alternating schemes [11, ]. Download Citation | Impacts of reinforcement ratio and fatigue load level on the chloride ingress and service life estimating of fatigue loaded reinforced concrete (RC) beams | High-cycle fatigue.
Garces Rodriques (), “Influence of Cracks on Chloride Ingress into Concrete” P. Zacarias (), “Effects of Fly Ash on Delayed Ettringite Formation” (with M. Thomas) Gustavo Julio-Betancourt (), “Effects of Testing Conditions on Chloride Diffusion Measurements” A.
Smith (), “Sulphate Resistance of Ternary Systems”. The results indicate that chloride transport in relatively small cracks can be influenced by the mixture composition (w/c and aggregate size) because this influences the tortuosity of the crack.
However, as the width of the crack increases the crack begins to behave as a free surface and the influence of w/c is much less important.
However, the influence of chloride ions attack on concrete mostly occurs at the larger crack widths, when crack widths decrease to a critical value along the direction parallel to crack segments, the influence of the crack can be neglected.
Synopsis of OPC Results with Different Reinforcement. • Chloride levels were 3 to 4 times higher at the crack than away from the cracks at the top reinforcing bar level ( inches). • Chloride levels at the bottom rebar level were approximately two times higher in the region of the crack versus away from the crack.
Cracking of the reinforced concrete structural members alters the local transport properties of the concrete cover, and allows rapid ingress of chloride ions and onset of corrosion. In the past two decades, several studies have focused on the influence of cracks on chloride ingress in concrete.
It has been shown that water movement at a crack is very sensitive to its saturation level and chloride ions ingress is also significantly affected by the presence of cracks.
Empirical equations for the determination of chloride ions diffusion coefficients have also been proposed for a wide range of w/c ratios based on a comprehensive database and sample design nomographs for concrete cover shown.
This book summarizes the latest advances in understanding chloride ingress and steel corrosion in concrete under service loads. Unlike the existing literature, it focuses specifically on the effect of service loads on chloride-induced durability issues in reinforced concrete structures.
An experimental study of the influence of autogeneous healing on chloride ingress in cracked concrete is presented. In the study, two concrete mixtures (a Portland cement mix and a blast furnace slag mix), two healing regimes (submerged and fog room regime), two cracking ages (14 and 28 days), and multiple crack widths are used as parameters.
Influence of cracks on Chloride-induced corrosion in concrete structures chloride ingress. Reinforcement corrosion can be divided into two periods. In the initiation period, carbon dioxide and/or chloride ions are transported through the concrete cover, eventually reach and break down the protective layer of the steel.
While existing models consider a variety of concrete material and environmental factors, at varying levels of complexity, in predicting the time until the onset of chloride-induced corrosion of the steel reinforcement, the influence of cracking is generally beyond their current scope.
Chloride-induced corrosion of a steel bar in concrete has become one of the leading causes of the deterioration of concrete reinforcement structures exposed to a saline environment .Corrosion not only leads to the loss of the steel bar cross-section but may also decrease the bonding between the bar and the surrounding concrete, thereby promoting cracks and spalling of the concrete cover.
Cracks are always present in reinforced concrete structures. In the presented research, influence of mechanical cracks on chloride ingress is studied. A compact reinforced concrete specimen was. The purpose was to get a quantitative measure of how different exposure conditions influence the durability of reinforced concrete, measured in terms of chloride ingress into the concrete.
Influence of multiple ions on sulfate attack on concrete was studied by measuring the mass change and elasticity modulus (E rd) change and observing cracks at different scale.X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermo gravimetric analysis (TGA) were used to study the evolution of microstructure of concrete during the process of sulfate attack.
This study evaluated the influence of crack opening size on the corrosion initiation and propagation of reinforcing steel bars in precracked concrete as a result of chloride ingress.
Uncracked (reference) and transversely cracked reinforced concrete beam specimens were prepared for laboratory experiments. Specimens were fabricated with crack mouth opening widths of, and mm. The chloride-induced corrosion of steel is a serious problem affecting the durability of reinforced concrete structures.
Cracks may facilitate the ingress of chlorides into concrete and thus accelerate the corrosion process. However, different opinions on the effect of cracks on corrosion of steel were found in the literature. A “crack” above and parallel to the top bar was created in the cover by inserting a mm ( in) thick stainless steel shim into the formwork before placing the concrete.
The shims were removed after the concrete had hardened, leaving an artificial “crack” between the ponding well and the top bar for easy ingress of the chlorides. Li et al.  modeled chloride ingress into cracks based on viscous flow and find the diffusion coefficient proportional to the square of the crack width, Park et al.
 modeled chloride. Crack Width Chloride Diffusion Chloride Penetration Chloride Ingress Chloride Migration These keywords were added by machine and not by the authors.
This process is experimental and the keywords may be updated as the learning algorithm improves. Thus, there is increasing focus on the need for modeling the ingress of chloride into cracked concrete. Present models quantify chloride ingress in static cracks only, although several structural applications display dynamic loading conditions in an environment containing chlorides, e.g.
It is generally recognized that cracks provide easy access to ingress of chlorides in concrete and hence, the initiation of corrosion of steel in cracked concrete occurs at early stage. However, wide variety of results on the effect of crack widths on corrosion of steel in concrete are reported in many studies.
Apart from crack width, the crack depths, cracking frequency and healing of cracks. Influence of Traversing Crack on Chloride Diffusion Into Concrete This study examined the effects of traversing cracks of concrete on chloride diffusion. Three different concretes were tested: 1 ordinary concrete (OC) and 2 high performance concretes with 2 different mix designs (HPC and HPCSF, with silica fume) to show the influence of the.
Part of the RILEM State-of-the-Art Reports book series (RILEM State Art 2nd International RILEM Workshop on Testing and Modelling the Chloride Ingress into Concrete, 11–12 SeptemberParis, France, Bonnet S, Khelidj A, Baroghel-Bouny V. Influence of traversing crack on chloride diffusion into concrete.
Cem Concr Res. In the current work, the transport coefficients of water and chloride through a single crack are developed by treating it as a parallel-plate configuration. The physical migration models coupled with capillary absorption and convection-diffusion are utilized to predict water penetration and chloride ingress into cracked concrete.
Chloride binding capacity for instance may affect the resistivity of the concrete through limiting the chloride ingress and thereby influencing the subsequent rate of corrosion. Regarding SCMs, the presence of sulphides in the pore solution of GGBS concretes is of concern.
and the ingress front of chloride ions was detected by spraying the surface with silver nitrate. Comparisons of the cracking and ingress behaviors indicate only a portion of the crack length readily allows ingress of water. A portion of the crack, near the crack tip, restricts ingress of water.
chloride ingress. In the case of cores drilled from existing structures, the outer 10 mm of concrete should be cut off. This is done in order to measure the chloride ingress resistance corresponding to the bulk concrete and to avoid any effect of the paste enriched surface layer.
In. Influence of cracks on chloride ingress into concrete. ACI Materials Journal ((2)): ISI, Google Scholar. Schießl P, Raupach M. Prediction of chloride ingress is very important for the durability of reinforced concrete structures in chloride-laden environments, especially for concrete with cracks.
It is expected that the chloride diffusion coefficient of a crack is much higher than that of the uncracked part in concrete. A single crack in concrete can be a shortcut for. Protection from Chloride & Water Ingress on Cracked Reinforced Concrete Bridge Columns Background.
On this section of State Route 8, the supporting columns had previously been repaired with Shotcrete to replace unsound, chloride contaminated concrete. reducing the rate of chloride ingress into the concrete by reducing concrete permeability and increasing the transport length (increased concrete cover) .
A change in the chloride threshold can have a much larger effect on the lifetime of RC than do the transport properties of the concrete or the cover Crete thickness.
Thus, for.• The model of chloride ingress into cracked concrete under combination of cyclic flexural load and tidal zone 2 2 2 2 Experiment program The influence of crack depth Finding the coefficient (a) of equation (5): x L cr un= +.
1).a x Generate the single crack by using the center - point flexural test of beam (xx). The. CHLORIDE INGRESS INTO CONCRETE Chloride ion is one of the greatest threats to steel reinforcement.
May enter concrete from the external environment via various mass transport process. These are introduced as a contaminant of the constituent materials or as calcium chloride used as an accelerating admixture.
This chloride is no longer.