Simple technique for tracking chloride penetration in. World academy of science, engineering and technology journals. In the work, the increasing diffusion coefficient from the total cracked. This test method assesses the coefficient of chloride migration, which is a measure of the resistance of the tested material to chloride penetration.
The different mechanisms of chloride penetration are presented, followed by a further elaboration of the chloride diffusion theory. Influence of crack depth on chloride transport of cracked. The present paper adopts a nonsteady state diffu sion test to study the chloride transport in concrete samples with different crack densities prepared by the nondestructive notch method. Azad impact on corrosion of reinforcement chloride. From a physical and mechanical point of view, concrete cracking is hard to avoid. Advances in materials science and engineering 2018 article. Aacm concrete and conventional concrete specimens of similar strength, developed for structural applications, were exposed to a 5% nacl solution. The chloride penetration into the concrete was realised with a non steady state migration test and modelled with the finite element method cosmosffe thermal software. This test takes less time and is less complicated than the steady state electrophoretic. Chloride migration coefficient from nonsteadystate migration experiments 38. The precise calculation of steady state chloride diffusion coefficients is laborious, expensive, and time consuming due to the fact that it is necessary to take liquid samples for the chlorides to be analysed. In this analysis the nonsteady state of the chloride diffusivity is considered. Effect of transverse crack on chloride penetration into concrete subjected to dryingwetting cycles. These tests include the rapid chloride penetrability test, astm c1202, the non steady state migration experiment, nt build 492, and numerous other methods.
Testing chloride penetration resistance of concrete. Concrete cracks, caused by mechanical loading, thermal stresses, shrinkage etc. However, the long term methods are often not preferred in practice because they are. The squared values represent the spectral energy densities of diffuse wave. Park, kwon, and jung 2012 evaluated the crack effect on chloride diffusion in splitting cylinder concrete by nonsteadystate migration test and proposed an analytical. In order to investigate chloride migration in cracked concrete, considering the mesoscopic heterogeneity of concrete, concrete modeled here is treated as a fourphase composite consisting aggregate, mortar, crack, and interfacial transition zone itz. The durability of the studied compositions was evaluated by the absorption of water into concrete under capillary and under immersion action, the non steady state chloride migration tests and fourpoint electrode resistivity measurements. The present study investigates nonsteady state chloride diffusion in concrete. Diffusion coefficient from nonsteady state condition is very vulnerable to crack width since it reflects the local chloride penetration depth in the crack width, so that the enlarged diffusion coefficient reaches to 160 times for normal condition park et al. However the non steady state, dns, is expressed by volume of concrete or mass of cement and therefore refers to the total amount of chlorides in the sample. Ma, nonsteady state chloride diffusion in concrete with different crack densities, materials and structures, vol. So, it is meaningful to study the influence of crack depths on chloride transport in cracked selfcompacting concrete. The gain in mass per unit area over the density of water is plotted versus the square root.
Therefore, the aim of this study is to analyze the possibility of determination of the chloride diffusion coefficient in accelerated chloride migration test for various concretes and whether the applied blended. Bound chloride concentrations water and acid soluble were determined up to 270 days of chloride exposure. A phasefield model is proposed to describe cracking and its coupling with diffusion. The different mechanisms of chloride penetration are presented. However, a non steady state electrophoretic test, nt bilud 492 of nordtest, has been proposed. Bound chloride ingress in alkali activated concrete. From the chloride penetration profiles on 117 concrete cores, the influence of the crack width, measured on the concrete surface exposed to chlorides, on the. Testing chloride penetration resistance of concrete fhwa.
Prediction of chloride ion penetration of recycled. Modeling the effect of damage on diffusive behavior in a. Lattice modeling of chloride diffusion in sound and cracked concrete. The combining of sodium chloride and calcium chloride by a number of different hardened cement pastes, cement and concrete research, vol. Permeability plays an important role in governing the durability of concrete in deleterious environments. Simulation of chloride diffusion in cracked concrete with different.
The present paper investigates the chloride binding of selfcompacting concrete with different crack lengths using non steady state migration test. Applicability of diffuse ultrasound to evaluation of the water. The chloride diffusivity in cracked zone is expressed as functions of crack width. The results showed that the proposed multiscale model gave a little higher chloride diffusivity of uhpc than experiment results. The method uses nonlinear chisquare and newtons ncsn method to determine the diffusion coefficient. Baroghelbounyinfluence of traversing crack on chloride diffusion into concrete. Chloride penetration resistance properties of concrete. Measurement of the steady and nonsteadystate chloride. In this paper, the concentration of chlorides is monitored by measuring the conductivity of the anolyte which initially is distilled water. Many researchers have also developed test methods to measure the chloride diffusion coefficient under steady state and nonsteady state conditions page 1981. Electrical migration tests have gained in popularity as a quicker method of measuring transport properties. The influence of basic properties of concrete on its chloride penetrability is also discussed.
Sustainability 2017, 9, 282 3 of 14 sustainability 2017, 9, 282 3 of 14 figure 1. Many researchers have also developed test methods to measure the chloride diffusion coefficient under steady state and non steady state conditions page 1981. Nonsteady state chloride diffusion in concrete with different crack. Yang and wang found that there is a linear relationship between the nonsteady state diffusion coefficient obtained from the accelerated chloride. These methods monitor the current passed through a sample submerged in a solution. Chloride ions penetrated into concrete cause rebar corrosion. The model is formulated in gurtins framework and first applied to a twodimensional plate subject to mechanical and. Chloride diffusion in the steadystate condition through cracked concrete. However the nonsteadystate, dns, is expressed by volume of concrete or mass of cement and therefore refers to the total amount of chlorides in the sample. Diffusion coefficient from non steady state condition is very vulnerable to crack width since it reflects the local chloride penetration depth in the crack width, so that the enlarged diffusion coefficient reaches to 160 times for normal condition park et al.
The other method is the nordtest method nt build 492. Any cracks or other imperfections on the surface open up additional routes for. Determination of the concrete chloride diffusion coefficient. Nonsteady state chloride diffusion in concrete with different crack densities. Carbonation, freezethaw cycles, and chloride penetration of concrete are the important factors for reinforced concrete rc structures. As freeair diffusion coefficients are compound dependent, ranging from 2. In these cases, we can define a fickian diffusivity property d by uid. Usually, the socalled steady state diffusion coefficient, ds, refers to the pore solution concentration and therefore expresses the movement of water soluble chlorides.
A chloride ion is a key factor affecting durability of reinforced concrete rc structures. Lattice modeling of chloride diffusion in sound and. In his study, mu, 20 adopted a nonsteady state diffusion test to investigate the relationship between the diffusion coefficient and crack density. Ion diffusion in a liquid usually could be treated as a movement of an ion cluster in a viscous media. Microstructural refinements of concrete due to fiber.
Salt ponding 2 and bulk diffusion 3 are examples of non steady state chloride diffusion tests where the apparent diffusion coefficient is determined by fitting profiles of the acid soluble chloride concentration to ficks second law of diffusion 4. Simple technique for tracking chloride penetration in concrete. Crack geometry characteristics, such as crack width, crack depth, crack shape parallel crack and tapered crack, and crack spacing, are considered. Park, kwon, and jung 2012 evaluated the crack effect on chloride diffusion in splitting cylinder concrete by non steady state migration test and proposed an analytical. Other crack characteristics, such as chloride depth, crack shape equalwidth crack or tapered crack, crack density, and spacing, are not studied in detail. Secondly, the influential zone caused by the crack is limited to a distance of 10 mm at both sides from the crack.
Kailas mems 10 nonsteadystate diffusion 1 most interesting industrial applications are nonsteadystate diffusion in nature. Diffusion through liquids is considerably more rapid than diffusion in the solid state, so that processes of this kind can transport salts deep into the interior of, for example, concrete structures. Using the steadystate chloride migration test to evaluate. While our specific interest is on diffusion of chloride ions in hardened cement paste, the proposed model has more general applicability to any porous material potentially developing cracks. The steadystate chloride diffusion coefficient was evaluated using the. Concrete is not inert relative to the chlorides in the pore solution. In this thesis, microstructural refinement and corrosion resistivity performance of fiber reinforced concrete frc were. Therefore, this study proposes a test method to evaluate the selfhealing capacity of cementbased materials in. Pdf nonsteady state chloride diffusion in concrete with. The contour of free chloride concentration and chloride penetration depth at 8 weeks and 20 weeks. Assuming a steadystate condition, the equivalent flux jt for the rev can be calculated using equation 3 based on the flux and the crosssectional area.
The results show that the influence of crack depth on chloride concentration of concrete is significant for the concrete zone deeper than 20 mm from the surface. The correlation of chloride diffusion coefficient and. These tests include the rapid chloride penetrability test, astm c1202, the nonsteadystate migration experiment, nt build 492, and numerous other methods. However, a nonsteady state electrophoretic test, nt bilud 492 of nordtest, has been proposed. The model is formulated in gurtins framework and first applied to a twodimensional. This model is used to derive the corrosion current density and corrosion.
In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. The cracked zone and sound zone of concrete are given individual diffusion coefficients. Chloride diffusion in three different position of aggregate after 20 weeks the halfcell potential values of each bar of the steel bars in each sample figure 4. Nevertheless, in real concrete structures, multiple cracks instead of a single crack are most commonly observed. However, the proposed model is still helpful for the durability design of uhpc structure in chloride environments. Characteristics of concrete cracks and their influence on. Materials free fulltext using the steadystate chloride. The timedependent chloride diffusion model was established based on the. Time and crack effect on chloride diffusion for concrete with. Nonsteady chloride diffusion tests were performed to validate the proposed model.
Time and crack effect on chloride diffusion for concrete. As expected, the discreteness is reduced by taking into account the crack tortuosity, and a linear relationship can be approximately used to relate the chloride diffusivity with the crack density in the concrete. Many different conditions of cracks may occur in concrete structures under. Chloride diffusion assessment in rc structures considering. In section 4, individual test procedures are presented. Lattice modeling of chloride diffusion in sound and cracked. Usually, the socalled steadystate diffusion coefficient, ds, refers to the pore solution concentration and therefore expresses the movement of water soluble chlorides. Prediction of chloride ion penetration of recycled aggregate. The correlation of chloride diffusion coefficient and concrete maturity value within 56 days of curing was investigated by the chemically combined water content method, rapid chloride migration rcm test, and concrete maturity test. Effect of transverse crack on chloride penetration into. However the nonsteady state, dns, is expressed by volume of concrete or mass of cement and therefore refers to the total amount of chlorides in the sample. Therefore, this study proposes a test method to evaluate the selfhealing capacity of cementbased materials in terms of their resistance to.
We find a different behavior for small ions in liquid xenon. Concentration distribution of chloride ion in cracked concrete. Using experimental results of chloride penetration depth, the apparent chloride diffusion coefficient of sound concrete is calibrated as 3. Influence of traversing crack on chloride diffusion into concrete. The experimental results showed that chloride diffusion coefficient of concretes decreased not only with increasing. Behaviour of concrete under severe environment effect of. Solution of ficks second law of diffusion ficks second law of diffusion is given as 265. These models can handle non steadystate conditions and complicated. Interest in selfhealingcrack technologies for cementbased materials has been growing, but research into such materials remains in the early stage of development and standardized methods for evaluating healing capacity have not yet been established. The present study investigates nonsteady state chloride diffusion in concrete samples with different crack densities prepared by a. Influence of cracks and crack width on penetration depth of. In order to investigate chloride migration in cracked concrete, considering the. Chloride migration coefficient from nonsteadystate migration experiments nt build 492 size. The development of nondestructive ultrasonic techniques is thus needed for.
Study on chloride binding of selfcompacting concrete with. As a corrosion process, rust appears on the surface of a rebar, which induces greater volume of the rebar and cracks of concrete cover 1. Based on the experimental and numerical results, a crack influencing factor was determined. Determination of the chloride diffusion coefficient in. Ma 5 the influence of different preparation methods on the aggregation status. Nonsteadystate diffusion is characterized by ficks second law, which can be expressed as where dcdt is the time rate of change of concentration at a particular position, x. The relationship between diffusion coefficient and crack density is discussed. Interest in selfhealing crack technologies for cementbased materials has been growing, but research into such materials remains in the early stage of development and standardized methods for evaluating healing capacity have not yet been established. Dec 01, 2016 a phasefield model is proposed to describe cracking and its coupling with diffusion. Nonsteady state chloride diffusion in concrete with different crack densities, materials and structures, vol. To overcome these drawbacks, nonsteadystate chloride diffusion and migration tests were developed. Following the nt build 492 chloride migration test method, water soluble chloride conetnt, acid soluble chloride content and penetration depth were determined on. Earlier studies indicated that the addition of cellulose fiber is effective in reducing water permeability and thereby making concrete more durable.
The present study investigates non steady state chloride diffusion in concrete samples with different crack densities prepared by a non destructive notch method. However, if the diffusion coefficient is measured after steadystate conditions have. Influence of cracks and crack width on penetration depth. A fuzzy control system for reducing urban stormwater runoff by a stormwater storage tank.
The chloride diffusivity for the nonsteady state condition is about 10 times higher than that the steady state condition. Different physical and chemical transport mechanisms can contribute to chloride ingress, and they depend on the concrete pore structure, micro environmental conditions, temperature, moisture content in concrete, etc. Experimental and simulation study on diffusion behavior of. Calculation of the rate of coagulation of hydrophobic. Nonsteady state chloride diffusion in concrete with.
A phasefield approach to fracture coupled with diffusion. The present study investigates nonsteady state chloride diffusion in concrete samples with different crack densities prepared by a nondestructive notch method. Pdf nonsteady state chloride migration and binding in. C i 0 can be reasonably assumed when the longterm effects are investigated. The precise calculation of steadystate chloride diffusion coefficients is laborious, expensive, and time consuming due to the fact that it is necessary to take liquid samples for the chlorides to be analysed. The effect of crack opening size and repair methods on. Simulation of chloride diffusion in cracked concrete with.
377 744 898 635 1607 330 1681 130 598 1155 4 564 1184 226 1533 938 1534 1684 636 1019 323 935 750 1061 1087 613 417 263 174 838 1483 274 140 732 302 632 216 861