KR102479756B1 - Predictive method of steel corrosion of reinforced concrete structures exposed to high pressure immersion environment - Google Patents

Abstract

The present invention relates to a method for predicting corrosion of reinforcing bars of a reinforced concrete structure, and more particularly, to a method for evaluating the soundness and durability of a structure to be installed in the deep sea in the future, and more particularly, to a corrosion factor of reinforcing bars due to high water pressure, which is a major characteristic of deep sea. It is about a method for predicting the corrosion tendency of reinforcing bars based on finite elements considering the penetration of
A method for predicting reinforcement corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention includes a modeling and lattice forming step of determining modeling of a reinforced concrete structure and forming a lattice for finite element analysis; By applying the penetration equation for each corrosion factor affecting the corrosion of the reinforced concrete structure to the modeled reinforced concrete structure and performing numerical analysis of the finite element method, the penetration tendency due to the penetration of the corrosion factor into concrete in a high-pressure immersion environment. Analyze, Penetration trend analysis step of corrosion factors; and a corrosion rate and rust generation amount calculation step of determining the degree of corrosion of the reinforcing bar through finite element numerical analysis based on the analyzed penetration tendency and calculating the amount of rust generated due to the corrosion of the reinforcing bar.

Description

Method for predicting corrosion of reinforced concrete structures exposed to high pressure immersion environment

The present invention relates to a method for predicting corrosion of reinforcing bars of a reinforced concrete structure, and more particularly, to a method for evaluating the soundness and durability of a structure to be installed in the deep sea in the future, and more particularly, to a corrosion factor of reinforcing bars due to high water pressure, which is a major characteristic of deep sea. It is about a method for predicting the corrosion tendency of reinforcing bars based on finite elements considering the penetration of

Various factors such as structural design technology, construction technology, energy supply technology, mobility technology, and safety maintenance technology should be considered for the realization of structures installed in the future subsea space. Among them, safety maintenance management is important in terms of ensuring the safety of users in extreme environments.

One of the most important areas of safety maintenance of structures exposed to the marine environment is the corrosion of rebars embedded in reinforced concrete structures. Reinforced concrete structures exposed to the marine environment experience corrosion of steel bars due to penetration of corrosion factors such as chloride, oxygen, and water. When corrosion occurs in the reinforcing bars inside the concrete, rust corresponding to two to four times the original volume is formed. Under the influence of the rebar expansion pressure, cracks and peeling phenomena occur in concrete, causing structural problems.

Conventional inventions related to the development of corrosion models for reinforcing bars in concrete structures have focused on corrosion of reinforcing bars caused by carbonation due to carbon dioxide in the atmosphere or corrosion of reinforcing bars caused by chloride penetration in tidal zones or orogenic zones where wet and dry environments are repeated. .

In the invention disclosed in Patent Document 1, corrosion of reinforcing bars due to neutralization of concrete, which occurs due to infiltration with carbon dioxide, was predicted using the BIM technique. The purpose of Patent Document 1 is to provide a corrosion prediction method for buildings using modeling that can prepare countermeasures against cracks and corrosion of buildings by modeling buildings with BIM models and substituting various conditions.

The invention disclosed in Patent Document 2 relates to a model for predicting useful life of reinforced concrete due to corrosion in consideration of mixing element information, crack information, and climate change information. Patent Document 2 is proposed based on the formula of the Monte Carlo method.

The invention disclosed in Patent Document 3 proposes a corrosion model for reinforcing bars by simultaneously considering the penetration of chloride ions into the bridge structure and the cracks and defects caused by the repeated load of the vehicle passing through the bridge. The method for predicting the life of a reinforced concrete bridge under the action of corrosion and fatigue bonding disclosed in Patent Document 3 defines the life of a reinforced concrete bridge in three stages: corrosion start-net fatigue crack development stage, corrosion hole and fatigue crack competition development stage, and structural failure stage. Divide into stages.

The invention disclosed in Patent Document 4 relates to the configuration of an expert system that predicts the life of an offshore structure due to corrosion online. In the case of durability design required in the process of designing marine structures, corrosion by chloride is considered first, and the system of Patent Document 4 is used to calculate the optimal material or coating thickness constituting the structure, thereby increasing the service life. Patent Document 4 utilized a permeation model based on the diffusion of chloride as a major factor in reinforcing bar corrosion.

Non-Patent Document 1 has conducted a study on the carbonation resistance of concrete and the diffusion coefficient of carbon dioxide according to the composition of concrete and the surrounding environment; Non-Patent Document 2 has conducted a simulation study on the carbonation depth of reinforced concrete with cracks and non-cracked reinforced concrete. As in the above case, many models for early prediction of corrosion of reinforcing steel have been proposed. However, most of them deal with the part related to diffusion caused by the concentration difference of carbon dioxide and chloride, which are corrosion factors, so research on the corrosion of reinforced concrete structures exposed to high-pressure deep-sea environments is insignificant.

Non-Patent Document 3 has conducted experimental research to propose coefficients and related formulas related to moisture diffusion in consideration of deformation of concrete in a high-pressure environment. Non-Patent Document 4 has conducted a study on the permeability of concrete in a high-pressure environment for the use of anti-rust materials. Non-Patent Document 4 conducted a study to verify the theory related to water penetration in a previously proposed high-pressure environment by comparing it with experimental results. However, the above studies only dealt with the concrete permeability in a high-pressure environment and did not conduct detailed studies considering the corrosion mechanism of reinforcing bars.

As such, referring to conventional patent documents and non-patent documents, although many previous studies have been conducted in relation to corrosion of reinforcing bars in reinforced concrete structures, corrosion factors of reinforcing bars in reinforced concrete structures considering the high-pressure water pressure environment, which is a characteristic of the underwater environment There are no predicted cases of penetration and corrosion.

Considering these points, it is necessary to study the corrosion of reinforced concrete exposed to the high-pressure deep-sea environment in consideration of the importance of the future seabed space described above.

KR 10-2018-0075887 A KR 10-2020-0093221 A KR 10-2020-0026877 A KR 20-2008-0003165 A

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Car, S. (2003). Influence of aggregates on chloride diffusion coefficient into mortar. Cement and Concrete Research, 33(7), 1021-1028. Byfors, K. (1987). Influence of silica fume and flyash on chloride diffusion and pH values in cement paste. Cement and Concrete research, 17(1), 115-130. Nokken, M., Boddy, A., Hooton, R. D., & Thomas, M. D. A. (2006). Time dependent diffusion in concrete―three laboratory studies. Cement and Concrete Research, 36(1), 200-207. Thomas, M. D., & Bamforth, P. B. (1999). Modelling chloride diffusion in concrete: effect of fly ash and slag. Cement and concrete research, 29(4), 487-495. Saeki, T., Sasaki, K., & Shinada, K. (2006). Estimation of chloride diffusion coefficent of concrete using mineral admixtures. Journal of Advanced Concrete Technology, 4(3), 385-394. Thomas, M. D. A., & Bentz, E. C. (2002). Computer program for predicting the service life and life-cycle costs of reinforced concrete exposed to chlorides. Life365 Manual, SFA, 12-56. Stanish, K. (2000). Predicting the diffusion coefficient of concrete from mix parameters. University of Toronto Report. Saetta, A. V., Scotta, R. V., & Vitaliani, R. V. (1993). Analysis of chloride diffusion into partially saturated concrete. Materials Journal, 90(5), 441-451. Leng, F., Feng, N., & Lu, X. (2000). An experimental study on the properties of resistance to diffusion of chloride ions of fly ash and blast furnace slag concrete. Cement and Concrete Research, 30(6), 989-992. Luping, T., & Gulikers, J. (2007). On the mathematics of time-dependent apparent chloride diffusion coefficient in concrete. Cement and concrete research, 37(4), 589-595. Bamforth, P. B. (1998). Spreadsheet model for reinforcement corrosion in structures exposed to chlorides. Concrete under severe conditions, 2, 64-75. Mangat, P. S., & Molloy, B. T. (1994). Prediction of long term chloride concentration in concrete. Materials and structures, 27(6), 338. Isgor, O. B., & Razaqpur, A. G. (2006). Modelling steel corrosion in concrete structures. Materials and Structures, 39(3), 291-302. Papadakis, VG, Vayenas, CG, & Fardis, MN (1991). Physical and chemical characteristics affecting the durability of concrete. Materials Journal, 88(2), 186-196. Song, HW, & Kwon, SJ (2007). Permeability characteristics of carbonated concrete considering capillary pore structure. Cement and Concrete Research, 37(6), 909-915. Murata J, Ogihara Y, Koshikawa S, Itoh Y. Study on watertightness of concrete. ACI Mater J 2004;2:107-16. Yoo, JH, Lee, HS, & Ismail, MA (2011). An analytical study on the water penetration and diffusion into concrete under water pressure. Construction and Building Materials, 25(1), 99-108. Luping, T., & Nilsson, L.O. (1993). Chloride binding capacity and binding isotherms of OPC pastes and mortars. Cement and concrete research, 23(2), 247-253. Han, SH (2007). Influence of diffusion coefficient on chloride ion penetration of concrete structure. Construction and Building Materials, 21(2), 370-378. Glass, GK, Hassanein, NM, & Buenfeld, NR (1997). Neural network modeling of chloride binding. Magazine of Concrete Research, 49(181), 323-335. Glass, GK, Reddy, B., & Buenfeld, N. R. (2000). The participation of bound chloride in passive film breakdown on steel in concrete. Corrosion Science, 42(11), 2013-2021. Suryavanshi, AK, & Swamy, RN (1996). Stability of Friedel's salt in carbonated concrete structural elements. Cement and Concrete Research, 26(5), 729-741. Gouda, V. K. (1970). Corrosion and corrosion inhibition of reinforcing steel: I. Immersed in alkaline solutions. British Corrosion Journal, 5(5), 198-203. Hausmann, DA (1969). Criteria for cathodic protection of steel in concrete structures. Materials Protection. Dhir, RK, Jones, MR, Ahmed, HEH, & Seneviratne, AMG (1990). Rapid estimation of chloride diffusion coefficient in concrete. Magazine of Concrete Research, 42(152), 177-185. Luping, T., & Nilsson, L.O. (1993). Rapid determination of the chloride diffusivity in concrete by applying an electric field. Materials Journal, 89(1), 49-53. Andrade, C. (1993). Calculation of chloride diffusion coefficients in concrete from ionic migration measurements. Cement and concrete research, 23(3), 724-742.

Friedmann, H., Amiri, O., At-Mokhtar, A., & Dumargue, P. (2004). A direct method for determining chloride diffusion coefficient by using migration test. Cement and Concrete Research, 34(11), 1967-1973. Polder, RB, & Peelen, WH (2002). Characterization of chloride transport and reinforcement corrosion in concrete under cyclic wetting and drying by electrical resistivity. Cement and Concrete Composites, 24(5), 427-435.

Sbarta, ZM, Laurens, S., Rhazi, J., Balayssac, JP, & Arliguie, G. (2007). Using radar direct wave for concrete condition assessment: Correlation with electrical resistivity. Journal of applied geophysics, 62(4), 361-374. Hope, BB, Ip, AK, & Manning, DG (1985). Corrosion and electrical impedance in concrete. Cement and concrete research, 15(3), 525-534. Saleem, M., Shameem, M., Hussain, SE, & Maslehuddin, M. (1996). Effect of moisture, chloride and sulphate contamination on the electrical resistivity of Portland cement concrete. Construction and building Materials, 10(3), 209-214. Lopez, W., & Gonzalez, J. A. (1993). Influence of the degree of pore saturation on the resistivity of concrete and the corrosion rate of steel reinforcement. Cement and concrete research, 23(2), 368-376. Enevoldsen, J.N., Hansson, C.M., & Hope, B.B. (1994). The influence of internal relative humidity on the rate of corrosion of steel embedded in concrete and mortar. Cement and concrete research, 24(7), 1373-1382. Pruckner, F., & Gjørv, OE (2004). Effect of CaCl2 and NaCl additions on concrete corrosivity. Cement and Concrete Research, 34(7), 1209-1217. Whittington, HW, McCarter, J., & Forde, MC (1981). The conduction of electricity through concrete. Magazine of concrete research, 33(114), 48-60. Oh, BH, & Jang, SY (2004). Prediction of diffusivity of concrete based on simple analytic equations. Cement and Concrete Research, 34(3), 463-480. Garboczi, EJ, & Bentz, DP (1992). Computer simulation of the diffusivity of cement-based materials. Journal of materials science, 27(8), 2083-2092. Luciano, J., & Miltenberger, M. (1999). Predicting chloride diffusion coefficients from concrete mixture proportions. Materials Journal, 96(6), 698-702.

Car, S. (2003). Influence of aggregates on chloride diffusion coefficient into mortar. Cement and Concrete Research, 33(7), 1021-1028. Byfors, K. (1987). Influence of silica fume and flyash on chloride diffusion and pH values in cement paste. Cement and Concrete research, 17(1), 115-130. Nokken, M., Boddy, A., Hooton, RD, & Thomas, MDA (2006). Time dependent diffusion in concrete—three laboratory studies. Cement and Concrete Research, 36(1), 200-207. Thomas, MD, & Bamforth, PB (1999). Modeling chloride diffusion in concrete: effect of fly ash and slag. Cement and concrete research, 29(4), 487-495. Saeki, T., Sasaki, K., & Shinada, K. (2006). Estimation of chloride diffusion coefficent of concrete using mineral admixtures. Journal of Advanced Concrete Technology, 4(3), 385-394. Thomas, MDA, & Bentz, EC (2002). Computer program for predicting the service life and life-cycle costs of reinforced concrete exposed to chlorides. Life365 Manual, SFA, 12-56. Stanish, K. (2000). Predicting the diffusion coefficient of concrete from mix parameters. University of Toronto Report. Saetta, AV, Scotta, RV, & Vitaliani, RV (1993). Analysis of chloride diffusion into partially saturated concrete. Materials Journal, 90(5), 441-451. Leng, F., Feng, N., & Lu, X. (2000). An experimental study on the properties of resistance to diffusion of chloride ions of fly ash and blast furnace slag concrete. Cement and Concrete Research, 30(6), 989-992. Luping, T., & Gulikers, J. (2007). On the mathematics of time-dependent apparent chloride diffusion coefficient in concrete. Cement and concrete research, 37(4), 589-595. Bamforth, P.B. (1998). Spreadsheet model for reinforcement corrosion in structures exposed to chlorides. Concrete under severe conditions, 2, 64-75. Mangat, PS, & Molloy, BT (1994). Prediction of long term chloride concentration in concrete. Materials and structures, 27(6), 338. Isgor, OB, & Razaqpur, AG (2006). Modeling steel corrosion in concrete structures. Materials and Structures, 39(3), 291-302.

The problem to be solved by the present invention is to develop a finite element-based rebar corrosion prediction model using a mathematical model that reflects the penetration tendency of corrosion factors in concrete in a high-pressure immersion environment, and the rebar corrosion tendency of reinforced concrete structures existing in a deep sea environment. And / or a method for predicting steel corrosion of reinforced concrete structures capable of predicting the timing is provided. Although the high-pressure immersion environment, which is the target environment of the present invention, is judged to have a low corrosion rate due to low dissolved oxygen in water, the present invention is significant in terms of predicting the long-term life of a structure.

A method for predicting reinforcement corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention includes a modeling and lattice forming step of determining modeling of a reinforced concrete structure and forming a lattice for finite element analysis; By applying the penetration equation for each corrosion factor affecting the corrosion of the reinforced concrete structure to the modeled reinforced concrete structure and performing numerical analysis of the finite element method, the penetration tendency due to the penetration of the corrosion factor into concrete in a high-pressure immersion environment. Analyze, Penetration trend analysis step of corrosion factors; and a corrosion rate and rust generation amount calculation step of determining the degree of corrosion of the reinforcing bar through finite element numerical analysis based on the analyzed penetration tendency and calculating the amount of rust generated due to the corrosion of the reinforcing bar.

Using the reinforcement corrosion prediction method of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention, the tendency and timing of reinforcement corrosion, which has a decisive effect on the integrity of a reinforced concrete structure to be built in a future deep-sea environment, can be detected at an early stage. There are predictable benefits.

In addition, there is an advantage that it can be used as a basic source technology for the design and safety maintenance of offshore structures to be built in the future.

1 is a flowchart of a method for predicting corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention.
FIG. 2 is a flowchart embodying steps 100 shown in FIG. 1 .
FIG. 3 is a flowchart embodying step 300 shown in FIG. 1 .
Figure 4 is a graph showing the analysis results for the penetration depth of water over time in a water pressure 1.5MPa environment.
5 is a diagram schematically illustrating a process of analyzing a corrosion rate of reinforcing bars and an amount of rust generation.
6 is a graph showing the electrical resistance of concrete according to the degree of saturation in the pores.
7 is a graph showing the electrical resistance of concrete according to the chloride concentration in the pores.
8 is a graph showing the electrical resistance of concrete according to temperature.
9 is a flowchart illustrating a procedure for analyzing corrosion potential distribution and corrosion current values using the substitution method.
10 is a graph showing the results of analysis of corrosion density of reinforcing bars over time in a water pressure of 1.5 MPa environment by way of example.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Among the components of the present invention, specific descriptions of those that can be clearly understood and easily reproduced by those skilled in the art according to the prior art will be omitted in order not to obscure the gist of the present invention. The method for predicting corrosion of reinforced concrete structures exposed to a high-pressure immersion environment according to the present invention is based on a finite element technique as an analysis method for determining the corrosion tendency of steel bars in a high-pressure hydrostatic immersion environment. In order to solve the problem of the present invention, the method for predicting corrosion of reinforced concrete structures exposed to a high-pressure immersion environment of the present invention may suggest the following solutions.

(1) In order to understand the permeation of corrosion factors considering the effect of high pressure, the present invention provides 'permeation diffusion' obtained by adding the fact that water and concrete cause physical elastic deformation by pressure during the permeation process of moisture to Darcy's law. Apply the 'Ryu Equation'. Using this solution, it is possible to determine how much the corrosion factor penetrates into the concrete over time in a high-pressure environment.

(2) The concrete distribution of the corrosion factor due to the penetration of the corrosion factor and the corresponding function related to the calculation of the corrosion rate of the reinforcing bar are all time functions, and the penetrating tendency and corrosion rate according to time are calculated through finite element-based numerical analysis. The finite element based function approximates the overall corrosion factor distribution and corrosion rate through the relevant governing equations and specific boundary conditions.

Hereinafter, a method for predicting reinforcement corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a method for predicting corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention.

Referring to FIG. 1, a method for predicting reinforcement corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment according to an embodiment of the present invention includes modeling and lattice formation of the reinforced concrete structure (100), and corrosion through finite element numerical analysis. Factor penetration tendency analysis step (300); and calculating the corrosion rate and rust generation amount of the reinforcing bar through finite element numerical analysis (500).

The step 100 of modeling and forming a grid of a reinforced concrete structure is a step of modeling and generating a grid of a target reinforced concrete structure for finite element analysis in a three-dimensional form. This step is to determine the shape and size of the target reinforced concrete structure by modeling in order to obtain an approximate result of the penetration and corrosion of the reinforcing steel corrosion factor, and to determine the physical properties of each element by dividing it into a finite number of small elements.

Corrosion factor penetration trend analysis step 300 through finite element numerical analysis performs numerical analysis of the finite element method by applying the penetration equation of corrosion factors that affect reinforcing steel corrosion to the target reinforced concrete structure set in step 100. As a step, calculate the distribution due to the penetration of corrosion factors into concrete in a high-pressure environment. For example, the penetration depth of moisture, chloride, and oxygen over time and the concentration of corrosion factors present in the void are identified and the time point at which reinforcing steel corrosion occurs is analyzed.

In step 500 of calculating the corrosion rate and rust generation amount through finite element numerical analysis, based on the penetration result of the corrosion factor performed in step 300, the degree of corrosion of the reinforcing bar is determined through finite element numerical analysis, and the rust generation amount due to corrosion is determined. This is the final calculation step. The governing equations and boundary conditions related to penetration of corrosion factors and corrosion of reinforcing bars are modeled in mathematical expressions, and approximate solutions are calculated by calculating the size of the basis function expressed as a combination of interpolation functions. Through the calculated approximate solution, it is possible to grasp the corrosion rate of reinforcing steel and the amount of rust generated from it.

Each of the above steps 100, 300, and 500 may be performed in an apparatus for predicting steel corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment. Here, the apparatus for predicting reinforcing steel corrosion of a reinforced concrete structure exposed to the high-pressure immersion environment may include configurations in which each of the steps 100, 300, and 500 are performed, for example, modeling that performs step 100. and a grid forming unit, a penetration tendency analysis unit performing step 300, and a corrosion rate and rust generation amount calculating unit performing step 500.

In addition, each of the steps 100, 300, and 500 may be implemented in a computer-readable recording medium. Such a computer-readable recording medium may have a program recorded thereon to execute steps 100, 300, and 500 above. Here, the computer-readable recording medium includes hard disks, floppy disks, magnetic recording media, and optical recording media.

Hereinafter, each of the steps 100, 300, and 500 shown in FIG. 1 will be described in more detail with reference to the drawings.

FIG. 2 is a flowchart embodying steps 100 shown in FIG. 1 .

Referring to FIG. 2, the modeling and grid formation step 100 of the reinforced concrete structure of FIG. 1 includes inputting parameter and material information of the target reinforced concrete structure 110; and forming element and node information (130).

The step of modeling the reinforced concrete structure and forming the grid (100) is a step of determining the size and shape of the target reinforced concrete structure in consideration of corrosion of the reinforced concrete structure through modeling, and forming a grid for finite element analysis. Modeling of the target reinforced concrete structure and grid formation may be performed using the MIDAS CIVIL program, and coordinate value information of each element and the nodes of each element may be obtained through modeling and grid formation of the formed reinforced concrete structure. In addition, it is possible to enter the material properties of the concrete constituting the target reinforced concrete structure (ratio of water to cement, porosity, silica fume/fly ash/blast furnace slag replacement rate, etc.), and in the case of lattice formation, various types of lattice can form

In the embodiment of the present invention, the target reinforced concrete structure is formed with a lattice composed of minute elements in the shape of a hexahedron.

FIG. 3 is a flowchart embodying step 300 shown in FIG. 1 .

In general, the concrete deterioration process by corrosion of reinforcing bars can be considered in two stages. The first stage is the initial stage, when reinforcement corrosion begins due to penetration of corrosive factors, and the second stage is the stage in which the reinforced concrete structure cracks and the performance of the joint deteriorates after the reinforcement corrosion begins. Step 300 shown in FIG. 1 was performed focusing on the first step described above.

Referring to FIG. 3, step 300 shown in FIG. 1 is a step of figuring out the penetrating tendency of corrosion factors affecting corrosion of reinforcing bars through numerical analysis. More specifically, in step 300 shown in FIG. 1, finite element analysis using the Calakin method is performed by reflecting the related equilibrium equation to determine the corrosion factors (moisture, oxygen, chloride) to analyze the infiltration tendency.

As is generally known, the main factor determining the time of the first step is the permeation of moisture, oxygen and chloride ions reaching the reinforcing bar and the resulting change in the surrounding conditions of the reinforcing bar. The criterion for determining the condition around the rebar is generally identified as the pH value of the pore solution.

The permeation equation applied for each corrosion factor (moisture, oxygen, chloride) in step 300 shown in FIG. 3 is as follows.

I. Reinforcement corrosion factor concrete penetration equation

(1) Moisture penetration in concrete subjected to water pressure

Moisture penetration into concrete in a pressurized environment must be considered, depending on the degree of pressure. In general, in the case of moisture penetrating into concrete, it can be identified differently according to the difference between low pressure and high pressure. In the case of a low-pressure water pressure environment, Darcy's law can be used to determine the depth of penetration over time. On the other hand, in the case of high pressure, it can be identified through permeation and diffusion flow analysis that simultaneously considers the deformation of concrete and internal moisture caused by the pressure.

When low-pressure water pressure is applied (below 0.15Mpa, 1.5atm), Darcy's law is applied. The water pressure acts on the concrete surface to determine the penetration depth over time. The penetration rate is assumed to be constant. The related expression is as shown in Equation 1 below.

는 콘크리트에 작용하는 수압이며,

은 수분의 평균 침투 깊이,

는 시간,

는 투수 계수,

는 대상 콘크리트의 특성으로 인해 결정되는 계수이다. 위 <수학식 1>에 의해, 시간에 따른 수분의 침투 깊이를 파악할 수 있으며, 이때 침투 깊이까지의 공극 속 용액의 포화도는 100%로 가정한다. 다만, 위 <수학식 1>은 0.15MPa 이하의 압력에 대해 적용 가능한 방식으로서, 수중 구조물이 설치되는 비교적 높은 압력이 작용하는 환경에서는 실질적인 적용이 어렵다.here,

is the water pressure acting on the concrete,

is the average depth of penetration of silver water,

time,

is the pitching coefficient,

is a coefficient determined due to the characteristics of the target concrete. According to the above <Equation 1>, it is possible to determine the penetration depth of moisture over time, and at this time, it is assumed that the saturation of the solution in the pores up to the penetration depth is 100%. However, the above <Equation 1> is a method applicable to a pressure of 0.15 MPa or less, and is difficult to apply in practice in an environment where a relatively high pressure acts in which an underwater structure is installed.

인 콘크리트의 한면에 압력

를 가하고 나머지 면을 수밀하게 유지한 상태에서 수압을 가한 면에서 일정 간격

에서 미소 거리

라 하였을 때,

를 경계로 존재하는 단면 a 및 b에 유입된 수량(Q_a, Q_b)은 다음의 <수학식 2> 및 <수학식 3>과 같다.On the other hand, when high-pressure water pressure is applied (over 0.15 MPa, 1.5 atm), the penetration diffusion equation obtained by adding the point that water and concrete cause physical elastic deformation by pressure during the water penetration process to Darcy's law apply cross section

pressure on one side of the concrete

is applied and the water pressure is applied at a certain interval while the rest of the surface is kept watertight.

smile on the street

When said

The water flows (Q _a , Q _b ) flowing into cross sections a and b existing on the boundary of Equation 2 and Equation 3 are as follows.

에 존재하는 유량(

)은 다음의 <수학식 4>와 같다.here, smile

The flow rate present in (

) is equal to the following <Equation 4>.

)를 고려하여, a, b 사이의 압력 변화

는 아래의 <수학식 5>와 같다.flux

), the pressure change between a and b

Is equal to the following <Equation 5>.

는 물과 콘크리트를 하나의 물질로 가정한 경우의 체적 탄성 계수이다.

는 아래의 <수학식 6>으로 표현이 가능하다.here,

is the bulk modulus of elasticity when water and concrete are assumed to be one material.

can be expressed by Equation 6 below.

는 콘크리트의 체적 탄성 계수이며,

는 물의 체적 탄성 계수이다.

는 물 대비 콘크리트의 체적 비율이다.앞서 설명한 다르시의 법칙을 살펴보면, 아래의 <수학식 7>과 같은데,here,

is the bulk modulus of elasticity of concrete,

is the bulk modulus of elasticity of water.

is the volume ratio of concrete to water. Looking at Darcy's law described above, it is the same as the following <Equation 7>,

When <Equation 7> is substituted into <Equation 5>, the following <Equation 8> is derived

을 콘크리트의 침투 확산 계수로 정한다. 위 <수학식 8>은 특정 초기 조건(

) 및 경계 조건(

,

)에서 아래의 <수학식 9>와 같이, 역 오차 함수 형태의 방정식으로 변환할 수 있다. The above <Equation 8> is a basic equation for pressure in one dimension, which is referred to as a permeation diffusion equation. Since it is a differential equation in a form similar to the case of the diffusion equation due to the general concentration difference,

is determined as the penetration diffusion coefficient of concrete. The above <Equation 8> is a specific initial condition (

) and boundary conditions (

,

) can be converted into an equation in the form of an inverse error function, as shown in Equation 9 below.

를 가하였을 때, 일정 시간

가 지난 후 물의 침투 깊이를

라 하였을 때, 침투 깊이에서의 압력(

)를 해로 가지는 방정식이다. 콘크리트의 특성에 따라 시간 경과에 따른 침투되는 물의 깊이가 달라지며, 침투 지점에서의 압력 값(

)을 통해 침투 확산 계수(

)를 구할 수 있다.The above <Equation 8> is the pressure on the surface

When applied, a certain time

After , the water penetration depth

When , the pressure at the penetration depth (

) as a solution. Depending on the characteristics of concrete, the depth of water penetration over time varies, and the pressure value at the penetration point (

) via the permeation diffusion coefficient (

) can be obtained.

)은 일반적으로 다르시의 법칙을 활용하는 저압 환경에서의 침투 방정식 적용이 가능한 최대 압력 값(

을 실험을 통해 파악하고, 압력의 감소가 미미하여 압력 구배가 거의 일정 해지는 시점의 압력을

로 정하여 결정한다(

). 저압 환경의 경우, 수분 침투량의 차이가 미미하기 때문에,

는 대상 콘크리트의 압력 별 수분 침투에 따른 물-공극 공간 비율(Water-to-pore space ratio)의 차이가 거의 없는 최대 압력 값을 실험을 통해 파악하여 결정한다.

와

를 구하면

를 구할 수 있으며, 시간에 따른 침투 깊이를 실험을 통해 파악하여 침투 확산 계수(

)를 구할 수 있다. 관련 선행연구에서는 공극 속에 침투한 물과 콘크리트 속 미세 입자의 용해로 인한 탄성 계수 값의 변화로 인해 이론 값과 미세한 차이가 있을 수 있다고 밝혔으며 이를 고려한 보정 값을 추가로 반영하여 침투 확산 계수를 아래의 <수학식 10>과 같이 최종적으로 제안하고 있다.The pressure value at the penetration point (

) is the maximum pressure value that can be applied to the seepage equation in a low pressure environment using Darcy's law (

is identified through experimentation, and the pressure at the point where the pressure gradient becomes almost constant due to the insignificant decrease in pressure

Determined by (

). In the case of a low pressure environment, since the difference in water permeation is insignificant,

The maximum pressure value with little difference in water-to-pore space ratio according to water penetration by pressure of the target concrete is determined through experimentation.

Wow

If you get

can be obtained, and the permeation diffusion coefficient (

) can be obtained. Related previous studies revealed that there may be slight differences from the theoretical value due to changes in the elastic modulus value due to the dissolution of water penetrating into the pores and fine particles in the concrete. As shown in Equation 10, it is finally proposed.

: 초기 침투 확산 계수,

or

: Initial penetration diffusion coefficient,

or

: 초기 침투 확산 계수,

: Initial penetration diffusion coefficient,

: 수분 침투 시간,

: Moisture penetration time,

: 침투 시간에 따른 보정 계수(

),

or

: Correction coefficient according to penetration time (

),

or

: 수압에 의한 계수(

: Coefficient by water pressure (

를 0.15MPa으로 정하고 48시간을 기준으로 정하고, 수분의 침투 깊이를 파악하여 특정 압력 값에서의

를 파악하였다. 본 발명의 실시 형태에서 또한 측정 시간을 48시간으로 정하고 그에 따른 측정 깊이를 파악하여 침투 확산 계수를 파악한다. 아래의 <표 1>은

일 때 계수(

) 정보를 나타낸다.In the case of previous studies applying this theory, the water-to-pore space ratio value according to the pressure was identified for general concrete specimens with W/C 0.55% and 0.7%,

is set at 0.15MPa and set on the basis of 48 hours, and the depth of penetration of moisture is determined at a specific pressure value

figured out. In the embodiment of the present invention, the measurement time is also set to 48 hours, and the measurement depth is determined accordingly to determine the permeation diffusion coefficient. <Table 1> below

When the coefficient (

) indicates information.

(2) Chloride penetration of concrete subjected to hydraulic pressure

In a pressurized environment, chlorides dissolved in water migrate with the water. Therefore, it is basically assumed that chloride permeation in concrete under water pressure is equal to water permeation. However, in the process of water infiltration, the concentration of chloride in the moisture decreases due to physical and chemical reactions of some chloride dissolved in the concrete and moisture in the pore surface. Free chloride in water, except for chloride ions bound to concrete, has a substantial effect on steel corrosion. The bonding strength of concrete and chloride has a significant effect on the corrosion of concrete reinforcement. The bonding strength of concrete and chlorides depends mainly on the amount and type of cement. Among them, the bond of tricalcium-aluminate (C3A) in concrete is higher than that of other components, so the C3A is mainly considered. The degree of bonding between concrete and chloride is expressed by isothermal adsorption, and is expressed as the relationship between the concentrations of bound chloride and free chloride. In an embodiment of the present invention, a Freundlich isothermal adsorption method was utilized. The Freundlich isothermal adsorption equation is shown in Equation 11 below.

와

는

농도에 큰 영향을 받으며, 아래의 <수학식 12> 및 <수학식 13>과 같이 나타낸다.where constant

Wow

Is

It is greatly influenced by the concentration, and is represented as in <Equation 12> and <Equation 13> below.

: 단위 시멘트 량,

: Unit cement amount,

: 시멘트 속 Tricalcium - aluminate 구성비,

: Composition ratio of Tricalcium - aluminate in cement,

이상일 때 적용하는 것으로 정한다. 일부 연구에서 결합된 염화물이 콘크리트 탄산화로 인해 물 속으로 다시 방출된다는 연구 결과가 있으나, 침지 환경에서는 콘크리트 탄산화가 거의 않으므로 생략한다. 이러한 과정으로 결정된 물 속 염화물 농도를 통해 철근의 부식 환경을 파악할 수 있다. In the case of the above <Equation 11>, the chloride concentration in the water is 0.355

It is decided to apply when it is abnormal. Some studies have reported that the combined chloride is released back into the water due to concrete carbonation, but it is omitted because concrete carbonation is almost non-existent in the immersion environment. The corrosion environment of the rebar can be identified through the chloride concentration in the water determined by this process.

의 농도 비가 중요하다. 일반적으로 염화물이 없는 콘크리트 속의 안전한 부동태가 달성된 pH 값은 11.5이상이다. 하지만 용액 속에 염화물이 존재하게 되면 철근 부식이 발생하는 한계 pH값이 결정되며 용액 속의 염화물 농도의 증가와 함께 증대된다. 한계 pH값과 염화물 농도의 관계는 아래의 <수학식 14>와 같다.In general, moisture in the pores of concrete exists as a solution containing a foamed calcium hydroxide solution and a small amount of sodium hydroxide and potassium hydroxide, which creates a strong alkaline environment of about PH 12.5 around the rebar. In an alkaline environment, a passivation film is formed around the reinforcing bar, and the migration of chlorides adsorbs on the passivation film and locally destroys the film, causing corrosion of the reinforcing bar. Whether the passivation film of rebar is destroyed in an alkaline environment

The concentration ratio of is important. In general, the pH value above 11.5 at which safe passivation in chloride-free concrete is achieved. However, when chloride is present in the solution, the limit pH value at which steel corrosion occurs is determined and increases with the increase of the chloride concentration in the solution. The relationship between the limiting pH value and the chloride concentration is shown in Equation 14 below.

: 한계 염화물 농도

:

이온 농도

: limit chloride concentration

:

ion concentration

: 정수

: essence

이하의

이온 농도에서 강은 부동태 영역이 있지만, 이상의 염화물 농도에서는 농도의 증가와 함께 부식이 발생하게 된다. 본 발명의 실시 형태에서는 철근 부식을 일으키지 않는 염화물의 이온의 허용 농도는 0.02M(700ppm)으로 정한다.By reflecting the above <Equation 14>, the chloride concentration value that affects the corrosion of the reinforcing bar can be obtained. Typically 0.02 for solutions in pores formed in Portland cement.

below

At the ion concentration, steel has a passivation region, but at a higher chloride concentration, corrosion occurs with an increase in concentration. In the embodiment of the present invention, the permissible concentration of chloride ions that do not cause corrosion of reinforcing bars is set at 0.02M (700 ppm).

(3) Oxygen diffusion penetration

와

의 분자량을 나타낸다.In the case of oxygen diffusion, which has a direct effect on reinforcing steel corrosion, it can permeate into the concrete through various mechanisms. Analysis is performed based on oxygen. However, while the chloride-dissolved water reaches the reinforcing bar for the first time and completely penetrates the entire reinforcing bar, the molecular weight of oxygen is high due to the influence of oxygen in the gas present in the void, and is divided into three stages as shown in <Table 2> below. to determine the amount of oxygen required for corrosion. The following <Table 2> shows the voids around the reinforcing bars according to water penetration.

Wow

represents the molecular weight of

The time for which step 300 shown in FIG. 1 is applied is determined by calculating the penetration depth of water per hour at the depth where the reinforcing bar is located through the water penetration equation of the concrete subjected to water pressure, and permeating as much as the total height of the reinforcing bar. In step 300 shown in FIG. 1, the solubility of the gas in the pores according to the pressure is omitted. After that, the analysis is performed by applying in step 500.

II. Finite element-based rebar corrosion factor penetration analysis

By applying the penetration equation for each corrosion factor organized in I. above, a finite element-based analysis model is created and the analysis is performed to calculate the concrete tendency of the corrosion factor. In an embodiment of the present invention, water penetration in a high-pressure environment is identified through finite element-based numerical analysis, and the molecular weight of the total corrosion factor is determined based on the oxygen and chloride values dissolved in the water in consideration of the immersion environment.

(1) Analysis of water penetration in a high-pressure immersion environment

In an embodiment of the present invention, a three-dimensional equilibrium equation may be created using the permeation diffusion coefficient determined through the permeation diffusion equation determined in step 310. Reflecting the above <Equation 8>, the equilibrium equation in a three-dimensional form can be expressed as the following <Equation 15>.

: 초기 침투 확산 계수,

or

: 작용 압력,

은 라플라시안(Laplacian) 연산자로서 3차원 미분 방정식에 활용된다. 시간 t에서의 콘크리트 안의 압력을(

) 유한 요소 해석을 위한 형상 함수(

)와 시간 t에서의 유한 요소의 각 노드에서의 압력(

)의 곱으로 나타낼 수 있다.

: Initial penetration diffusion coefficient,

or

: working pressure,

is a Laplacian operator and is used in three-dimensional differential equations. The pressure in the concrete at time t (

) shape function for finite element analysis (

) and the pressure at each node of the finite element at time t (

) can be expressed as a product of

In addition, if Galerkin's method is applied to <Equation 15>, a finite element equation such as <Equation 16> below can be obtained.

:

:

:

:

:

:

에서 콘크리트 표면에 작용하는 경계 조건을 아래의 <수학식 17>과 같이 표현할 수 있다.Numerical equation of <Equation 16>

The boundary condition acting on the concrete surface in can be expressed as in Equation 17 below.

: 압력 전달에 대한 표면 계수,

: Surface coefficient for pressure transfer,

: 외부 환경에서의 수압

: Water pressure in the external environment

: 콘크리트 표면에서의 수압

: water pressure on the concrete surface

값과 다음의 <수학식 19>와 같은

값을 얻을 수 있다.When <Equation 17> is substituted into <Equation 16>, the following <Equation 18> is finally obtained.

value and the following <Equation 19>

value can be obtained.

After constructing <Equation 16> applied to each element reflecting <Equation 18> and <Equation 19>, a general finite element equation applied to the entire structure can be combined as shown in <Equation 20> below. there is.

:

,

:

,

:

,

:

:

,

:

,

:

,

:

In an embodiment of the present invention, the pressure distribution and the depth of moisture penetration over time may be determined by utilizing the finite element equation of Equation 20. In the case of a one-dimensional analysis according to convenience, the penetration depth may be calculated using the equation of Equation 9. In the embodiment of the present invention, after determining the penetration depth over time through analysis, it is assumed that all water has penetrated into the pores at the penetration depth, and the pore saturation is set to 100%. This analysis proceeds by assuming laminar flow rather than turbulent flow according to the flow of the fluid.

(2) Oxygen and chloride permeation

In the case of oxygen permeation, as described in step 310, water permeation is divided into a total of three steps (3 steps), and oxygen permeation and molecular weight are determined for each step. After setting the molecular weight according to each step, set the conditions suitable for corrosion of the reinforcing bars to calculate the corrosion potential and current density. Although the high-pressure immersion environment, which is the target environment of the embodiment of the present invention, is judged to have a low corrosion rate due to low dissolved oxygen in water, it is meaningful in terms of predicting the long-term life of a structure.

In the case of chloride penetration, in the embodiment of the present invention, the analysis is performed by assuming that the depth of water penetrated by high pressure and the penetration depth are the same, and the analysis is performed by selecting the amount of free chloride set in Equation 11.

(3) Direct integration in the time domain

)에 관계없이 안정적으로 활용할 수 있는 뉴마크 베타법(Newmark-

method)를 활용하여 시간에 따른 압력 분포를 계산하였다(330). Newmark-

method를 활용한 직접 적분 방식은 다음과 같다.The above <Equation 20> is a function of time, and the internal pressure of concrete transmitted over time together with moisture penetration can be obtained by integrating <Equation 20> using a numerical step procedure. In the embodiment of the present invention, the time interval (Time step =

), the Newmark beta method (Newmark-

method) was used to calculate the pressure distribution over time (330). Newmark-

The direct integration method using method is as follows.

Initial calculation setup steps :

1. Set the initial distribution of pressure, the rate of pressure transfer, and the acceleration.

)를 계산2. Integral constant (

) to calculate

,

,

,

,

-1,

,

,

,

,

-One,

,

,

,

,

와

는 적분 정확도와 안정성을 결정하는 매개 변수이다. 시간에 따른 압력 전달 해석을 위해

,

를 정하였다.here

Wow

is a parameter that determines integration accuracy and stability. For analysis of pressure transmission over time

,

was determined.

3. A stiffness matrix for physical quantity analysis according to time interval is configured as shown in Equation 21 below.

Integral implementation steps taking into account each time interval:

에서 유효 압력 전달량을 계산한다.1. As shown in Equation 22 below, time

Calculate the effective pressure transfer from

에서 압력을 산정한다.2. Using <Equation 21> and <Equation 22>, as shown in <Equation 23> below, time

Calculate the pressure at

에서 압력 변화의 가속도와 속도를 계산한다.3. Time as shown in <Equation 24> and <Equation 25> below

Calculate the acceleration and rate of pressure change in

4. Repeat the above method.

Using the method 1.-4. above, it is possible to determine the distribution of the target corrosion factor per hour by calculating the change in the target physical quantity per time interval. 4 shows the analysis results for the penetration depth of water over time.

Referring back to FIG. 1, in step 500 of analyzing the corrosion rate and amount of rust through finite element-based numerical analysis, the corrosion rate and amount of rust are calculated based on the penetration tendency and distribution of corrosion factors over time identified in step 300. This is the step of figuring it out. In detail, FIG. 5 schematically illustrates the process of analyzing the corrosion rate of reinforcing steel and the amount of rust produced. It will be described in detail below.

I. Rebar corrosion related equations

(1) Calculation of electrical resistance of concrete

Since the water containing chloride that has penetrated into the concrete is a conductive solution, when an electric potential, which is the driving force for the electrical movement of the electrolyte, is applied, charged ions move in the solution in the pores, allowing electrons to move through the concrete. In the electric field region formed through the potential, the movement speed of ions in the solution in the pores of the concrete is inversely proportional to the electrical resistance of the concrete.

Since concrete resistivity is closely related to the movement of ions in concrete, and the time required for estimating concrete resistivity is shorter than that required for diffusion estimation, many studies have been conducted to determine the direct relationship between concrete resistivity and theoretical diffusion. In addition, electrical resistance is closely related to the corrosion rate of steel reinforcement in concrete, especially in the case of macrocell corrosion where the anode and cathode are quite far apart from each other (several centimeters to several meters). According to related studies, concrete resistance depends on the concrete mixing ratio, ionic diffusivity, water content, concrete temperature, and ionic concentration (chloride ion concentration) of the pore solution. For reinforcing steel corrosion analysis, equations related to ion diffusion, concrete moisture content, chloride ion concentration, and temperature were formulated through various studies.

Since concrete is a porous material containing a conductive solution, electrons in the solution can move through the concrete due to the movement of charged ions in the pores due to the electrical driving force. In the electric field region formed through potential, the speed of ion movement inside concrete is inversely proportional to the electrical resistance of concrete. The electrical resistance of concrete is as shown in Equation 26 below.

: 콘크리트 전기 저항(

)

: Concrete electrical resistance (

)

: 염화물 침투 관련 보정계수

: Correction factor related to chloride permeation

: 각 영향 인자에 대한 보정 계수(

: 확산성,

: 공극률, ,

: 염화물 농도, ,

: 온도)

: Correction coefficient for each influencing factor (

: diffusive,

: porosity, ,

: Chloride concentration, ,

: Temperature)

와 관련한 식을 아래의 <수학식 27> 및 <수학식 28>에 나타내었다.

Expressions related to are shown in <Equation 27> and <Equation 28> below.

는 물 바인더 비,

는 시간이다. 콘크리트 전기 저항에 영향을 미치는 공극 속 염화물의 확산은 염화물에 노출된 시간에 크게 의존하며 콘크리트 혼합 비율에 의해 결정되는 지수를 활용한 거듭 제곱 법에 의해 표현된다.

은 콘크리트에 첨가된 미네랄 혼합물과 관련한 상수 값으로서 아래의 <수학식 29>와 같다.here,

is the water binder ratio,

is the time Diffusion of chlorides in the voids, which affect the electrical resistance of concrete, is highly dependent on the time exposed to chlorides and is expressed by a power method using an exponent determined by the concrete mixing ratio.

is a constant value related to the mineral mixture added to concrete and is expressed in Equation 29 below.

: 대상 콘크리트 내부 플라이애쉬 치환율(%)

: Fly ash replacement rate inside target concrete (%)

: 대상 콘크리트 내부 슬래그 치환율(%)

: Target concrete internal slag replacement rate (%)

와 관련한 식을 아래의 <수학식 30> 내지 <수학식 33>에 나타내었다. 일반적으로 콘크리트 전기 저항과 염화물 이온의 겉보기 확산도는 다음과 같은 선형관계가 있다. 선형 관계의 기울기 범위는 약

의 범위를 가지며 본 발명의 실시 형태에서는

를 선택하여 해석을 진행하였다. 아래의 <수학식 30>에 염화물 확산과 관련한 콘크리트 전기 저항 보정 계수 관련식을 나타내었다.

Expressions related to are shown in <Equation 30> to <Equation 33> below. In general, the electrical resistance of concrete and the apparent diffusivity of chloride ions have the following linear relationship. The slope range for a linear relationship is about

Has a range of, and in the embodiment of the present invention

was selected to proceed with the analysis. In <Equation 30> below, an expression related to a concrete electrical resistance correction factor related to chloride diffusion is shown.

Assuming that the pore structure of concrete is similar to that of rock, Archie's law can be used to consider the following relationship in which the electrical resistance of concrete depends on the degree of pore saturation. In <Equation 31> below, an expression related to a concrete electrical resistance correction factor related to saturation of pores is shown.

의 저항으로 정규화된 상대 저항 값을 나타내었다. 모델 방정식은 수분 함량의 콘크리트 전기 저항의 영향을 상당히 합리적으로 재현한다.또한, 콘크리트 전기 저항은 기공 용액의 염화물 이온 농도에 크게 영향을 받는다. 콘크리트 전기 저항은 공극 속 염화물 이온 농도가 증가함에 따라 감소한다. 아래의 <수학식 32>에 염화물 이온 농도와 관련한 콘크리트 전기 저항 보정 계수 관련 식을 나타내었다. 도 7에 <수학식 32>와 실험을 통해 얻은

의 저항으로 정규화 된 상대 저항 값을 나타내었다. <수학식 32>는 실제 범위의 염화물 이온 농도에 대한 저항 감소 추세를 효과적으로 보여준다.6 obtained through the above <Equation 31> and the experiment

Relative resistance values normalized to the resistance of The model equation reproduces the influence of the water content on the electrical resistance of concrete quite reasonably. In addition, the electrical resistance of concrete is strongly influenced by the chloride ion concentration of the pore solution. The electrical resistance of concrete decreases as the chloride ion concentration in the pores increases. In <Equation 32> below, an expression related to a concrete electrical resistance correction factor related to a chloride ion concentration is shown. 7 obtained through <Equation 32> and the experiment

Relative resistance values normalized to the resistance of Equation 32 effectively shows the trend of decreasing resistance for a real range of chloride ion concentrations.

The reciprocal form of the Arrhenius equation is used for the relationship between concrete electrical resistance and temperature. In <Equation 33> below, an expression related to a concrete electrical resistance correction factor related to temperature is shown.

: 이온 이동을 위한 활성화 에너지 (25350

) [18]도 8에 <수학식 33>과 실험을 통해 얻은 콘크리트 상대 저항 값을 나타내었다. 실험은 10~25

의 영역에서 진행되었지만, 다양한 온도에서 적용이 가능하다. <수학식 33>은 실제 범위의 온도에 대한 저항 감소 추세를 효과적으로 보여준다.

: Activation energy for ion movement (25350

) [18] Figure 8 shows the concrete relative resistance value obtained through <Equation 33> and the experiment. Experiments 10 to 25

However, it can be applied at various temperatures. <Equation 33> effectively shows the trend of decreasing resistance for a real range of temperatures.

(2) Calculation of electrode potential

이 철 이온(

)으로 이온화되어 철근에 음전하가 생기는 양극 반응이고, 두번째는 같은 환경에서 철근에 존재하는 음전하와 산소의 그리고 물이 반응하여 수산화 이온(

)을 형성하는 음극 반응이다. 부식 발생으로 인해 전자는 강철 내부를 통해 양극에서 음극으로 이동하며 이온화된 철 이온은 기공 용액을 통해 양극에서 음극으로 이동한다. 금속 내부의 전극 전위(

)와 금속 표면의 인접한 공극 속 용액의 전위(

)는 매우 가깝게 위치하지만 하전된 입자와 물의 쌍극자로 배열된 전기 이중층이 사이에 존재하여 각 지점의 전위 값이 다르다. 일반적으로 양극과 음극에서의

와

의 차이(

)를 전극 전위(

)라고 한다. 부식 반응으로 인한 전자와 양이온의 이동으로부터 다음의 <수학식 34> 및 <수학식 35>를 알 수 있다.Corrosion of rebar inside concrete is an electrochemical reaction consisting of a reaction of two electrodes. The first is the iron of the rebar (

This iron ion (

) is ionized to create a negative charge on the reinforcing bar, and the second is the reaction of the negative charge present in the reinforcing bar with oxygen and water in the same environment to form hydroxide ions (

) is a cathodic reaction that forms Due to corrosion, electrons move from anode to cathode through the steel interior, and ionized iron ions move from anode to cathode through the pore solution. Electrode potential inside the metal (

) and the potential of the solution in the adjacent pores of the metal surface (

) are located very close together, but the electric double layer arranged with the charged particles and water dipoles exists between them, so the potential value at each point is different. usually at the anode and cathode

Wow

difference of (

) to the electrode potential (

) is called From the movement of electrons and cations due to the corrosion reaction, the following <Equation 34> and <Equation 35> can be found.

: 양극 및 음극에서의 발생 전위

: Potential generated at positive and negative electrodes

,

: 양극 및 음극에서의 전극 전위

,

: Electrode potential at the anode and cathode

)은 아래의 <수학식 36>으로 정의할 수 있다.The electrode potential difference between the local anode and cathode depends on the resistance of the electrolyte in the pores (i.e., the resistance of the concrete to the corrosion of the reinforcing steel) and the distance between each electrode. Since the absolute value of the electrode potential is uncertain, the standard electrode potential measured by defining the reference electrode potential as the zero point is generally used. The potential value of the electrode (reference electrode) in the reference half-cell has a relatively constant potential value regardless of the use environment. Reference electrodes mainly utilize standard hydrogen electrode (SHE), copper sulfate electrode (CSE) and saturated calomel electrode (SCE). However, since most environments are not environments for measuring a standard electrode potential, a potential value considering a specific environment is determined by considering a change in Gibbs free energy reflecting thermodynamic characteristics. Change in Gibbs free energy in a constant pressure and temperature environment (

) can be defined by the following <Equation 36>.

: 생성 물질과 반응 물질의 활동도 적

: Activity of products and reactants

: 기체 상수(8.3114

)

: gas constant (8.3114

)

: 절대 온도

: absolute temperature

When the above <Equation 36> is expressed in an electrochemical manner, it is equivalent to <Equation 37> and <Equation 38>.

: 특정 환경을 고려한 전극 전위 (

)

: Electrode potential considering a specific environment (

)

: 표준 전극 전위 (

)

: standard electrode potential (

)

The above <Equation 37> and <Equation 38> are called Nernst equations, and by using them, the electrode potential of each half-cell can be calculated considering the surrounding environment of the reinforcing bar to be currently identified. The electrode potential of each half-cell considering the environment around the reinforcing bar inside the concrete is as shown in <Equation 39> and <Equation 40> below.

: 양극 반응인 철의 산화 반응에서의 전극 전위(철 이온 형성)

: Electrode potential in the anodic reaction of iron oxidation (iron ion formation)

: 음극 반응인 산소의 환원 반응에서의 전극 전위(수산화 이온 형성)

: Electrode potential in the reduction reaction of oxygen, which is a cathode reaction (hydroxide ion formation)

,

: 철과 산소의 표준 전극 전위

,

: Standard electrode potential for iron and oxygen

,

: 철과 수산화 이온의 활동도(농도)

,

: Activity (concentration) of iron and hydroxide ions

: 산소의 퓨개시티(산소 농도 분압으로 간략화)

: Fugacity of Oxygen (Simplified as Oxygen Concentration Partial Pressure)

: 패러데이 상수(

)

: Faraday constant (

)

The resultant value above is the potential in the equilibrium state generated at the two electrodes according to the concentration of the ion. The equilibrium state refers to a state in which the oxidation-reduction rate in the half-cell is the same and no reaction occurs.

(3) Calculation of corrosion rate through polarization and current density

Calculation of corrosion rate : The corrosion rate of concrete reinforcement is an important factor in determining the life of a reinforced concrete structure. The corrosion rate is determined by the electrochemical reaction that occurs on the metal surface or electrode. Therefore, understanding the fundamental principles governing the kinetics of electrochemical reactions is very important in determining the degree of corrosion.

)이 면적

(

)인 전극에서 t초 동안 산화 반응을 통해 m

의

와 z개의 전자가 생산되었다고 가정하자(

계 반응). 여기서 발생하는 부식 속도 관련 식은 아래의 <수학식 41>과 같다.Since the corrosion reaction occurring on the surface of a metal or electrode involves the production and consumption of electrons, the corrosion rate can be quantitatively measured by measuring the current, that is, the flow of electrons going out or coming in from the electrode. certain metals (

) is the area

(

) through the oxidation reaction for t seconds at the electrode m

of

Assume that and z electrons are produced (

system reaction). The equation related to the corrosion rate generated here is as shown in Equation 41 below.

: 패러데이 상수(

)

: Faraday constant (

)

: 시간당 면적에서 생성된 이온 수(

)

: The number of ions generated in the area per hour (

)

: 산화 반응을 통한 전류 밀도(

)

: Current density through oxidation reaction (

)

의 전하량에 의하여 전극의 전류밀도와 반응 속도를 서로 전환할 수 있다. 부식 반응에 생성되는 전류 밀도를 계산함으로서 부식 속도 값을 파악할 수 있다. 일반적으로

계가 동적 평형 상태일 때, 산화 환원 반응 속도가 동일하며 이때, 전극 전위는 <수학식 38>의 네른스트 방정식을 활용하여 구한 평형 전극 전위(

)이다. 평형 전극에서 산화 반응 전류 밀도(

)와 환원 반응 전류 밀도(

)는 동일하며 이를 교환 전류 밀도(

)라고 부른다. 반응 속도론에 따르면 교환전류밀도는 아래의 <수학식 42>와 같다.The above <Equation 41> is called Faraday's law, and according to this law

The current density and reaction rate of the electrode can be converted to each other by the amount of charge. By calculating the current density produced by the corrosion reaction, the value of the corrosion rate can be determined. Generally

When the system is in dynamic equilibrium, the redox reaction rates are the same, and at this time, the electrode potential is the equilibrium electrode potential (calculated by using the Nernst equation of Equation 38) (

)to be. Oxidation current density at the balanced electrode (

) and reduction reaction current density (

) is equal to the exchange current density (

) is called. According to the reaction kinetics, the exchange current density is as shown in Equation 42 below.

: 화학종에 따른 상수

: constant according to chemical species

: 전기 화학적 활성화 에너지

: Electrochemical activation energy

)는 아래의 <수학식 43>과 같이 0이다. Activation polarization : Since the oxidation-reduction reaction is the same at the equilibrium electrode potential, the current density flowing through the wire outside the electrode (

) is 0 as shown in Equation 43 below.

)로부터

로 전위가 상승하면

는 상승하고

는 감소한다. 이때 발생하는

는

의 함수이며 아래의 <수학식 44>와 같이 표현 가능하다.When the potential value increases due to the electrochemical reaction at the equilibrium electrode potential, the potential difference with the equilibrium electrode potential becomes a driving force, and an oxidation reaction occurs beyond the activation energy. On the other hand, when the potential value is lowered, a reduction reaction occurs on the contrary. Due to the electrochemical reaction, the equilibrium electrode potential (

)from

If the potential rises to

is rising

decreases. occurring at this time

Is

It is a function of and can be expressed as in Equation 44 below.

) 과전압(overvoltage)이라고 부른다.

이면 애노드 과전압(

)이라 부르며,

이면 캐소드 과전압(

)이라 부른다. 분극에 의한 반쪽 전지의 반응 속도는 전하 전달 과정의 활성화 에너지의 크기에 의하여 결정되며, 이를 활성화 분극(activation polarization)이라 한다. 산화 분극의 경우, 전극 전위를

로부터

로 올리면 금속 상의 금속 M 1

에 대하여 전기화학적 자유에너지가

만큼 증가한다. 산화 분극에서의 산화 반응의 활성화 에너지와 환원 반응의 활성화 에너지는 아래의 <수학식 45> 및 <수학식 46>과 같다.This change in the equilibrium electrode potential through a specific electrochemical reaction is called polarization, and the amount of potential change is (

) is called overvoltage.

If the anode overvoltage (

) is called,

If the cathode overvoltage (

) is called The reaction rate of the half-cell by polarization is determined by the magnitude of the activation energy of the charge transfer process, and this is called activation polarization. For oxidative polarization, the electrode potential is

from

Raised by , metal on metal M 1

The electrochemical free energy for

increase as much as The activation energy of the oxidation reaction and the activation energy of the reduction reaction in the oxidation polarization are as follows <Equation 45> and <Equation 46>.

Current densities for each activation energy are shown in <Equation 47> and <Equation 48> below.

The current measured through the external wire due to the oxidation polarization can be expressed as the following <Equation 49> using the above <Equation 47> and <Equation 48>, which is called the Volmer-Butler equation. .

이라 가정하면 아래의 <수학식 50>으로 수식을 간략화할 수 있다.In the above <Equation 49>,

Assuming that , the equation can be simplified to Equation 50 below.

From the above <Equation 50>, the relationship between the anode overvoltage and the current density due to the oxidation polarization can be expressed as the following <Equation 51>.

를 산화 분극에 대한 타펠(Tafel)의 상수라 한다. 위 과정을 캐소드 과전압이 발생하는 환원 분극에 동일하게 적용할 수 있으며 환원 분극에 따라 발생하는 캐소드 과전압과 전류 밀도의 관계식은 아래의 <수학식 52> 및 <수학식 53>와 같다.The above equation is called Tafel's equation,

is called Tafel's constant for the oxidative polarization. The above process can be equally applied to the reduction polarization where the cathode overvoltage occurs, and the relational expression between the cathode overvoltage and the current density generated according to the reduction polarization is shown in Equation 52 and Equation 53 below.

The above <Equation 52> and <Equation 53> show the relationship between the overvoltage and the current density caused by the activation polarization. In the embodiment of the present invention, the degree of corrosion is predicted by calculating the potential difference due to the activation polarization and the current density corresponding thereto, using Equation 51 and Equation 53 above.

)이 활발하게 이뤄지면 전극에 근접한 용액에서 반응 금속 이온의 농도(

)가 용액의 농도(

)보다 감소하는 층이 형성되는데 이를 네른스트 층이라고 부른다. 아래의 <수학식 54>는 용액 속의 농도 (

)를 고려한 평형 전위이다. Concentration polarization : In the Volmer-Butler equation, the concentration of the solution in the vicinity of the electrode is assumed to be uniform. However, the reduction reaction (

) is active, the concentration of reactive metal ions in the solution close to the electrode (

) is the concentration of the solution (

) is formed, which is called the Nernst layer. <Equation 54> below is the concentration in the solution (

) is the equilibrium potential considering

)를 고려한 평형 전위는 아래의 <수학식 55>와 같다.Concentration of the solution around the electrode surface reduced due to the reduction reaction (

) The equilibrium potential considering ) is as shown in Equation 55 below.

A voltage difference caused by a difference in concentration is called a concentration overvoltage, and is expressed in Equation 56 below.

의 확산속도는 환원 반응 속도와 동일하므로, 아래의 <수학식 57>과 같이 나타낼 수 있다.Based on Fick's law of diffusion, in the Nernst layer

Since the diffusion rate of is the same as the reduction reaction rate, it can be expressed as in Equation 57 below.

:

의 확산계수

:

Diffusion coefficient of

: 네른스트 층의 두께(0.1

)

: Thickness of the Nernst layer (0.1

)

Therefore, the current density generated by the decrease in concentration across the Nernst layer is expressed by Equation 58 below.

가 0이 되면

는 한계전류밀도(limiting current density,

)D에 도달한다. 용액 속의 농도에 영향을 받는 한계 전류 밀도는 아래의 <수학식 59>와 같다.The reduction reaction rate is further increased

becomes 0

is the limiting current density,

)D is reached. The limiting current density affected by the concentration in the solution is as shown in Equation 59 below.

Substituting the above <Equation 59> into <Equation 58> can be expressed as <Equation 60> below, and substituting <Equation 60> below into <Equation 56> finally gives the concentration overvoltage Can be expressed as in Equation 61 below.

에 다가갔을 때 음의 값으로 크게 증가한다. 한계전류밀도는 용액의 유속을 증가시켜 네른스트 층의 두께를 줄이거나, 용액의 온도를 높여 확산 계수를 증가시키거나 농도를 증가시키면 증가한다. 다른 반쪽 전지인 산화 반응에서는 농도 분극을 무시할 수 있는데 이는 반응 물질인 금속이 무제한으로 공급되기 때문이다.The concentration polarization converges to zero as the current density increases, then

increases significantly to a negative value when approaching . The limiting current density increases when the thickness of the Nernst layer is reduced by increasing the flow rate of the solution, or when the diffusion coefficient is increased or the concentration is increased by increasing the temperature of the solution. In the other half-cell, the oxidation reaction, the concentration polarization is negligible because the reactant, metal, is supplied indefinitely.

)에서의 전위는 아래의 <수학식 62>와 같으며 환원 극(

)에서의 전위는 아래의 <수학식 63>과 같다. 아래 식을 통해 파악한 전위 값과 전류 밀도 값을 토해 부식 속도를 산정할 수 있다. Calculation of corrosion rate through polarization and current density : Corrosion potential value due to corrosion of reinforcing steel can be calculated by reflecting the relationship between equilibrium potential, polarization and current density discussed above. In an embodiment of the present invention, the equilibrium potential of the half-cell is obtained using the above <Equation 28> and <Equation 29> reflecting the Nernst equation, and the activation polarization using the above <Equation 40> to <Equation 42> In consideration of the concentration polarization using the above <Equation 50>, the corrosion potential generated by corrosion of the reinforcing bar and the corresponding corrosion current density are calculated. Oxidation pole (

The potential at ) is as shown in Equation 62 below, and the reducing pole (

The potential at ) is as shown in Equation 63 below. The corrosion rate can be calculated using the potential value and current density value obtained through the equation below.

: 산화 극에서의 전위(

)

: Potential at the oxidation pole (

)

: 철근 부식 환경을 고려한 산화 극의 평형 전극 전위(

)

: Equilibrium electrode potential of the anode considering the corrosive environment of the steel bar (

)

: 산화 반응을 반영한 활성화 분극(

)

: Activation polarization reflecting the oxidation reaction (

)

: 산화 반응을 반영한 Tafel의 상수(

)

: Tafel's constant reflecting the oxidation reaction (

)

: 산화 극에서의 교환 전류 밀도(

)

: Exchange current density at the oxidizing pole (

)

: 산화 반응으로 인한 전류 밀도(

)

: Current density due to oxidation reaction (

)

: 환원 극에서의 전위(

)

: Potential at the reducing pole (

)

: 철근 부식 환경을 고려한 환원 극의 평형 전극 전위(

)

: Balanced electrode potential of the reducing pole considering the corrosive environment of the reinforcing bar (

)

: 환원 반응을 반영한 활성화 분극과 농도 분극의 합(

)

: Sum of activation polarization and concentration polarization reflecting the reduction reaction (

)

: 환원 반응을 반영한 Tafel의 상수(

)

: Tafel's constant reflecting the reduction reaction (

)

: 환원 극에서의 교환 전류 밀도(

)

: Exchange current density at the reducing pole (

)

: 한계 전류 밀도(

)

: Limiting current density (

)

: 환원 반응으로 인한 전류 밀도(

)

: Current density due to reduction reaction (

)

)을 알고 있는 경우 해당 지점에서 양극 및 음극 반응에 대한 부식 전류 밀도는 위 <수학식 51> 및 <수학식 52>에서의

,

를

로 대체하여 계산할 수 있다. 양극 전류 밀도는 위 <수학식 51>을 통해 바로 구할 수 있지만 음극 전류 밀도의 경우, 한계 전류 밀도로 인해

와

사이에 비선형 관계가 형성되기 때문에 치환법에 의한 수치해석을 실시하여 찾아내어야 한다.The above values depend on the pH around the reinforcing steel, the fugacity of oxygen and the ionic activity of the iron, but for simplicity in the corrosion analysis, it is assumed to remain constant during the corrosion process. Potential value at a specific point on the steel surface due to corrosion (

) is known, the corrosion current density for the anodic and cathodic reactions at that point is

,

cast

can be calculated by substituting The anode current density can be obtained directly through Equation 51 above, but in the case of the cathode current density, due to the limiting current density

Wow

Since a non-linear relationship is formed between them, it must be found by performing numerical analysis by the substitution method.

)는 아래의 <수학식 64>와 같이 결정될 수 있다(전류 밀도에 대한 부호 규칙은

를 양수로,

를 음수로 정한다). Calculation of the macrocell current through the formation of boundary conditions on the surface of the rebar : The macrocell current is defined as the net current flowing from the electrode to be measured, that is, the apparent movement speed of charge at the electrode. The macrocell current density obtained through the anode and cathode current densities obtained from <Equation 51> and <Equation 52> above (

) can be determined as shown in Equation 64 below (the sign rule for the current density is

as a positive number,

is set as a negative number).

According to Ohm's law, the gradient of the potential on the surface of the reinforcing bar is proportional to the macrocell current as shown in Equation 65 below.

: 철근 표면과 수직인 방향

: direction perpendicular to the rebar surface

: 콘크리트 비저항(

)

: Concrete resistivity (

)

: 매크로 셀 전위

: macro cell potential

The above <Equation 65> serves as a boundary condition for the equilibrium equation related to corrosion analysis that finally obtains the corrosion potential and the corrosion current density on the surface of the reinforcing bar.

(4) Finite element-based rebar corrosion numerical analysis

Create a finite element-based analysis model and conduct analysis to determine the corrosion potential and current density according to the corrosion of the reinforcing bar and to determine the amount of rust formed on the surface of the reinforcing bar.

(5) Calculation of corrosion potential and corrosion current density through analysis

In order to determine the corrosion rate of reinforcing steel, it is necessary to calculate the corrosion potential distribution on the surface of the reinforcing steel. Assuming that the electrical resistance of the concrete identified in the above <Equation 15> is isotropic, the potential distribution of the corroded electrode is determined by the Laplace equation as shown in the following <Equation 66>.

)를 형상 함수(

)와 각 유한 요소 노드에서의 전위 값(

)의 곱으로 나타내고, 위 <수학식 66>에 캘러킨 방식을 적용하면 아래의 <수학식 67>과 같은 유한요소 방정식을 구할 수 있다.Corrosion potential at time t (

) to the shape function (

) and the potential value at each finite element node (

), and applying the Calakin method to the above <Equation 66>, a finite element equation such as <Equation 67> below can be obtained.

:

:

:

:

The construction procedure of the above finite element equation can be applied to all elements similarly to the water permeation analysis to obtain the finite element equation, and is shown in Equation 68 below.

:

,

:

,

:

:

,

:

,

:

In order to obtain the potential distribution of concrete, it is necessary to find the solution of the general finite element equation with the above <Equation 53> as the boundary condition. However, since both sides of Equation 53 above depend on the potential distribution, this equation cannot be solved explicitly. In addition, since a specific solution to the above equation cannot be obtained with only natural boundary conditions, essential boundary conditions must be additionally considered. For this reason, the solution for obtaining the potential value proposed in the embodiment of the present invention is as follows, and a flowchart is shown in FIG. 9.

)와 필수 경계 조건을 할당하고(910), 초기 전위 분포를 가정한다(920). Referring to Figure 9, select the pivot (Pivot) point and pivot (Pivot) potential (

) and required boundary conditions are assigned (910), and an initial potential distribution is assumed (920).

Then, the macrocell current at the boundary is calculated using Equation 51 to Equation 53 above, and a free boundary condition is set using Equation 54 above (930). Then, the entire potential distribution is calculated by solving the above <Equation 63> from the set boundary conditions (940).

이 허용 한계 값(

)보다 낮아질 때까지, 930 및 940 과정을 반복한다(950). 관련 식은 아래의 <수학식 69>와 같다.Standard values obtained through convergence tests (

This tolerance value (

), steps 930 and 940 are repeated (950). The related expression is shown in <Equation 69> below.

:

번째 노드에서

번 iteration하였을 때 부식 전위 값

:

at the second node

Corrosion potential value when iteration times

: 전제 노드의 수

: number of premise nodes

)를 조정하고 전위의 일반적인 기울기 값으로부터 얻은 부식 전류와 피봇(Pivot) 점에서의 전위 값으로부터 얻은 매크로셀 전류의 차이의 절대값이 허용 값(

)보다 낮을 때까지 910 내지 950과정을 반복한다(960). 관련 내용은 아래의 <수학식 70>과 같다.Next, the pivot potential (

) and the absolute value of the difference between the corrosion current obtained from the general slope value of the potential and the macrocell current obtained from the potential value at the pivot point is the allowable value (

) Repeat steps 910 to 950 until lower than (960). The related information is shown in Equation 70 below.

The corrosion current density analysis result for each time determined in the following way is shown in FIG. 10 . Using the anode current density obtained by the numerical analysis method, the corrosion depth can be estimated by the equation of Equation 71 below.

: 철근의 부식 깊이(

)

: Corrosion depth of rebar (

)

II. Calculation of rust formation of rebar through corrosion current density calculation

)은 페러데이 법칙에 근거한 녹 생성률과 관련이 있다. 산화 반응으로 인한 양극에서의 수산화 제2철(

) 생성률(

)은 아래의 <수학식 72>와 같다.The rate of rust formation at the anode due to the corrosion of the rebar surface (

) is related to the rust formation rate based on Faraday's law. Ferric hydroxide at the anode due to the oxidation reaction (

) generation rate (

) is as shown in Equation 72 below.

: 수산화 제2철 생성률 (

)

: Ferric hydroxide production rate (

)

: 반응 전하 량 (

)

: Reaction charge amount (

)

: 산화 반응으로 인한 전류 밀도(

)

: Current density due to oxidation reaction (

)

) 이 되며 1몰에 해당하는 제2 수산화 철과 제3 수산화 철의 질량 비를 통해서 제3 수산화 철에 의한 녹 생성률(

)을 아래의 <수학식 73>과 같이 구할 수 있다.The produced second iron hydroxide is tertiary iron hydroxide (

), and the rust formation rate by iron tertiary hydroxide (through the mass ratio of iron 2 and 3 hydroxide corresponding to 1 mole)

) can be obtained as shown in Equation 73 below.

: 수산화 제2 철 생성률 (

)

: Ferric hydroxide production rate (

)

In this way, by calculating the current density generated on the surface of the reinforcing bar due to corrosion, the rate of rust formation around the reinforcing bar can be intuitively obtained.

The features, structures, effects, etc. described in the embodiments above are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified with respect to other embodiments by those skilled in the art in the field to which the embodiments belong. Therefore, contents related to these combinations and variations should be construed as being included in the scope of the present invention.

In addition, although the embodiment has been described above, this is only an example and does not limit the present invention, and those skilled in the art to the present invention pertain to the above to the extent that does not deviate from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications not exemplified are possible. That is, each component specifically shown in the embodiment can be implemented by modifying it. And differences related to these modifications and applications should be construed as being included in the scope of the present invention as defined in the appended claims.

Claims (10)

A modeling and lattice forming step of determining the modeling of the reinforced concrete structure and forming a lattice for finite element analysis;
By applying the penetration equation for each corrosion factor affecting the corrosion of the reinforced concrete structure to the modeled reinforced concrete structure and performing numerical analysis of the finite element method, the penetration tendency due to the penetration of the corrosion factor into concrete in a high-pressure immersion environment. Analyze, Penetration trend analysis step of corrosion factors; and
A corrosion rate and rust generation amount calculation step of figuring out the degree of corrosion of the reinforcing bar through numerical analysis of a finite element method based on the analyzed penetration tendency, and calculating the rust generation amount due to the corrosion of the reinforcing bar;
including,
The step of analyzing the penetration tendency of the corrosion factor,
If the corrosion factor is oxygen, in the time taken to penetrate from the concrete surface of the reinforced concrete structure to the surface of the reinforcing bars, in the voids around the reinforcing bars

The molecular weight of is determined by the amount of oxygen required for corrosion, and in the time from reaching the surface of the reinforcing bar for the first time to penetrating into the entire reinforcing bar, the ratio of water and gas in the void is set to 1: 1, and then in the void

Wow

The molecular weight of is determined by the amount of oxygen required for the corrosion, and at the time after penetration of the entire reinforcing bar, based on the amount of dissolved oxygen in the water,

Wow

A method for predicting reinforcement corrosion of a reinforced concrete structure exposed to a high-pressure immersion environment, which determines the molecular weight of as the amount of oxygen required for the corrosion.
According to claim 1,
In the step of analyzing the penetration tendency of the corrosion factor, the penetration depth of the corrosion factor over time and the concentration of the corrosion factor present in the pores of the target reinforced concrete structure due to the penetration depth are calculated, and the To analyze whether corrosion of rebar will occur,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
A modeling and lattice forming step of determining the modeling of the reinforced concrete structure and forming a lattice for finite element analysis;
By applying the penetration equation for each corrosion factor affecting the corrosion of the reinforced concrete structure to the modeled reinforced concrete structure and performing numerical analysis of the finite element method, the penetration tendency due to the penetration of the corrosion factor into concrete in a high-pressure immersion environment. Analyze, Penetration trend analysis step of corrosion factors; and
A corrosion rate and rust generation amount calculation step of figuring out the degree of corrosion of the reinforcing bar through numerical analysis of a finite element method based on the analyzed penetration tendency, and calculating the rust generation amount due to the corrosion of the reinforcing bar;
including,
The step of analyzing the penetration tendency of the corrosion factor,
If the corrosion factor is moisture, penetration into the reinforced concrete structure over time in the high-pressure immersion environment is based on the penetration diffusion flow equation in which moisture and concrete cause physical elastic deformation by pressure to Darcy's law. Analyze the penetration depth of moisture to
The variables of the penetration diffusion flow equation are the time at which pressure is applied to the surface of the reinforced concrete structure and the penetration depth of the moisture,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
The method of claim 3, wherein the step of analyzing the penetration tendency of the corrosion factor,
If the corrosion factor is chloride, the free chloride concentration according to water permeation is calculated based on the Freundlich isothermal adsorption equation, and the chloride concentration value affecting the corrosion of the reinforcing bar is based on the limit pH and chloride concentration relational expression to calculate,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
delete The method of claim 3, wherein the step of analyzing the penetration tendency of the corrosion factor,
Determining the internal pressure distribution of the reinforced concrete structure over time by directly integrating the finite element equation using the Newmark beta method,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
A modeling and lattice forming step of determining the modeling of the reinforced concrete structure and forming a lattice for finite element analysis;
By applying the penetration equation for each corrosion factor affecting the corrosion of the reinforced concrete structure to the modeled reinforced concrete structure and performing numerical analysis of the finite element method, the penetration tendency due to the penetration of the corrosion factor into concrete in a high-pressure immersion environment. Analyze, Penetration trend analysis step of corrosion factors; and
A corrosion rate and rust generation amount calculation step of figuring out the degree of corrosion of the reinforcing bar through numerical analysis of a finite element method based on the analyzed penetration tendency, and calculating the rust generation amount due to the corrosion of the reinforcing bar;
including,
The step of calculating the corrosion rate and the amount of rust production includes the step of calculating the corrosion rate of the reinforcing bar and the step of calculating the rust production amount of the reinforcing bar,
The step of calculating the corrosion rate of the reinforcing bar,
Calculating the electrical resistance of concrete;
Calculating the equilibrium electrode potential of the rebar based on the Nernst equation;
Calculating a corrosion potential generated by corrosion of the reinforcing bar and a corrosion current density according to the corrosion potential based on the activation polarization and the concentration polarization; and
Calculating the corrosion rate of the reinforcing bar based on the corrosion potential and the corrosion current density; including,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
According to claim 7,
Calculating the corrosion potential and the corrosion current density,
A first step of selecting a pivot point and assigning a pivot potential and essential boundary conditions;
a second step of predicting an initial potential distribution;
A third step of calculating a macrocell current at a boundary based on a relational expression between a cathode overvoltage and a current density generated according to reduction polarization and setting a free boundary condition;
a fourth step of calculating an overall potential distribution from the free boundary conditions;
a fifth step of repeating the first to fourth steps until the standard value obtained through the convergence test is lower than the tolerance limit value; and
When the standard value is lower than the allowable limit value, the pivot potential is adjusted, until the absolute value of the difference between the corrosion current and the macrocell current obtained from the potential value at the pivot point is lower than the allowable value. a sixth step of repeating steps 1 to 5;
Rebar corrosion prediction method of reinforced concrete structures exposed to a high-pressure immersion environment comprising a.
According to claim 7,
The step of calculating the rust generation amount of the reinforcing bar calculates the rust generation rate formed around the reinforcing bar based on the corrosion current density,
A method for predicting steel corrosion in reinforced concrete structures exposed to high-pressure immersion environments.
A computer-readable recording medium recording a program for executing the method for predicting corrosion of reinforced concrete structures exposed to a high-pressure immersion environment according to any one of claims 1 to 4 and 6 to 9.

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