JP2003222622A - Deterioration prediction method of concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To predict the advance of compound deterioration due to salt damage and carbonation in a technique for predicting deterioration in a concrete structure. <P>SOLUTION: The deterioration prediction method of a concrete structure predicts the advance of deterioration due to the salt damage and carbonation of the concrete structure by analyzing various kinds of deterioration factors using a finite element method. The progress of compound deterioration is expressed by a chemical reaction expression including a hydration product in concrete and carbon dioxide in the atmosphere at one side and calcium carbonate at the other side, and a reversible chemical expression containing calcium carbonate, an aluminum acid, and chloride at one side, and Friedel salt and a carbon dioxide gas at the other side. The progress is predicted by analyzing diffusion equations (1) and (2) by finite element method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for predicting deterioration of a concrete structure, and more particularly, in a realistic case where deterioration due to salt damage and deterioration due to carbonation of concrete proceed in combination. The present invention relates to a method for predicting deterioration of a concrete structure.

[0002]

2. Description of the Related Art In recent years, early deterioration of concrete structures has become a problem. In addition to the fact that the environmental conditions in which concrete structures are placed have become more severe on average than before, this is due to changes in the materials used for concrete, manufacturing methods, and construction methods. The deterioration of concrete mainly includes deterioration due to salt damage and deterioration due to neutralization. The salt damage of the concrete means that steel materials (rebar, P, etc.) are produced by the action of chloride ions existing in the concrete.
C steel, etc. ) Corrodes and damages concrete structures.

The neutralization of concrete means that, as shown in the following chemical reaction formula (1), the cement hydration product in the strong alkali present in the concrete structure is converted to carbon dioxide in the atmosphere. The reaction is to produce calcium carbonate.

[Chemical 1]

When the concrete is neutralized, the protective function of the reinforcing bar is lost, the reinforcing bar is corroded, and its expansion causes cracks in the cover concrete. Water, oxygen, carbon dioxide gas, etc., enter from these cracks, promote corrosion, and cause deterioration such as floating and peeling of the cover concrete.

Regarding the deterioration prediction after repairing an existing concrete structure, the present inventors proposed in Japanese Patent Application No. 2001-142969 a method of predicting deterioration due to salt damage, and predicting deterioration due to neutralization. The method was proposed in Japanese Patent Application No. 2001-188429.

[0006]

However, since the actual deterioration of the concrete structure is a combination of deterioration due to salt damage and deterioration due to neutralization, the deterioration can be predicted with higher accuracy. Therefore, the proposal of the prediction method considering the combined deterioration of salt damage and neutralization was awaited. Normally, the concentration distribution of chloride ions going from the surface to the back of a concrete structure is considered to be the highest at the surface and decrease toward the back (deeper), but the actual concrete structure In the chloride ion concentration distribution in a substance, there is a phenomenon that the chloride ion concentration inside is higher than at the surface. Since such a phenomenon cannot be expressed by a method of individually analyzing deterioration due to salt damage and deterioration due to neutralization, a method for predicting complex deterioration due to salt damage and neutralization has been awaited.

The reversible chemical reaction formula (2) below is a formula for analyzing complex deterioration in consideration of both salt damage and neutralization.

[Chemical 2] In the above equation, the first term on the right side is a fixed salt content called Friedel's salt and does not directly contribute to deterioration of concrete. In the peripheral part of the concrete, when the initial chloride ion concentration is high, the reaction toward the right side in the formula (2) proceeds, and chlorine is fixed as Friedel's salt. At this time, since carbon dioxide gas is generated, neutralization proceeds due to the reaction of the formula (1), and the pH is lowered. When the pH drops,

In the equation (2), the reaction toward the left side progresses, chlorine ions are generated, and salt damage progresses.

Therefore, in the present invention, in order to predict the progress of complex deterioration due to salt damage and neutralization, the reactions represented by the above equations (1) and (2) are analyzed by the finite element method. It is intended to provide a method for predicting deterioration of concrete.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is directed to various effects of salt damage of concrete structures and progress of deterioration due to neutralization. Is a method for predicting deterioration of a concrete structure by predicting the deterioration factor of by using the finite element method, wherein one side contains cement hydration products in concrete and carbon dioxide in the atmosphere, and the other side , A chemical reaction formula containing calcium carbonate and a reversible chemical reaction formula containing calcium carbonate, aluminate and chloride on one side and Friedel's salt and carbon dioxide gas on the other side. , The diffusion equation,

[Equation 2] Was analyzed and predicted by the finite element method.

The invention of claim 2 is a method of predicting the progress of deterioration of a concrete structure after repairing an existing concrete structure using a repair material, by the method of claim 1. In addition, the boundary conditions of the existing concrete structure after repair and the characteristic data of the repair material used for repair are added to the new factor of deterioration prediction by the finite element method to determine the progress of deterioration of the concrete structure after repair. I tried to predict.

According to the third aspect of the invention, the characteristic data of the repair material further includes the initial chloride ion concentration of the repair material and the diffusion coefficient of chloride ion of the repair material. In the invention of claim 4, the characteristic data of the repair material further includes the initial calcium hydroxide ion concentration of the repair material and the diffusion coefficient of carbon dioxide gas of the repair material. In this way, after the repair, as the characteristic data of the repair material, the initial chloride ion concentration of the repair material, the chloride ion diffusion coefficient of the repair material, the initial calcium hydroxide ion concentration of the repair material, the repair material It is possible to analyze by adding at least one data of the diffusion coefficient of carbon dioxide.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A composite deterioration phenomenon due to salt damage and neutralization of a concrete structure will be described below.

1 Explanation of Phenomena Related to Composite Deterioration The following explanations are given in "Durability Diagnosis Series of Concrete Structures, Early Degradation and Durability Diagnosis of Concrete Structures" (Kazusuke Kobayashi) Morikita Publishing, and "Concrete Research Committee Report on Long-Term Durability "(Japan Concrete Institute).

1.1 Properties of hardened concrete 1) Two-phase multi-structure aggregate: 70-80% Cement-based hardened structure: 25-30% 2) Presence of voids Usually 10% or more of these voids It is filled with Na ⁺ and K ⁺ and maintains a high pH.・ Capillary pores and gel voids that are irreversibly generated from the hardening mechanism of cement ・ Material separation ・ Insufficient compaction ・ Small closed air bubbles introduced by using a surfactant These pores serve as mass transfer routes. Mass transfer modeled by diffusion equation

1.2 Main compounds of Portland cement

[Chemical 3]

[0017]

[Chemical 4]

1.3 Reaction of Carbon Dioxide in Air with Hydration Product By hydration reaction of cement, sulfate ion in concrete is taken in and ettringite and chloride ion are taken in to form a double salt of Friedel's salt. Sulfate ions and chloride ions are liberated by the reaction of these double salts with carbon dioxide. Carbon dioxide gas and sulfate ions and chloride ions influence each other. It has become necessary to model deterioration with consideration of these interactions.

[0019]

[Chemical 5]

The chloride ions introduced into the concrete from sea sand and the admixture are fixed as Friedel's salt in an amount corresponding to about 0.4% of the cement weight. Sulfate ions eluted from the alkali sulfate in cement and gypsum added for controlling the setting react with tricalcium aluminate (C ₃ A) to react with ettringite + CO ₂ to release sulfate ions. With the progress of carbonation, the liberated ions move to the non-carbonated portion and form Friedel's salt or ettringite. Occurrence of concentration and release phenomena of chloride and sulfide.

[0021]

[Chemical 6]

1.4 Mass transfer in concrete Fig. 1
Will be described with reference to. Inside, the movement of salt, sulfur, and alkali is active. Mechanism of reduction of alkali concentration in the surface layer ・ The alkali concentration in the surface layer decreases due to moisture supplied from the surface ・ Internal alkali content diffuses toward the surface ・ Alkali carbonate reacts with carbon dioxide on the surface When the progress of carbonation becomes remarkable after 10 to 20 years,
Reversal of alkali concentration due to internal alkali concentration lower than the surface layer

CO ₂ in the atmosphere is

[Chemical 7]

Therefore, the amount of alkali metal increases in the carbonation region. Invasion of carbon dioxide Friedel's salt and ettringite are decomposed to release chloride ion and sulfate ion.

1.5 Carbonation (Neutralization) Carbon dioxide is present in air at 0.035%. (This triggers early deterioration.) Relationship between calcium carbonate and carbon dioxide in cement production 1 tonf cement 1.2 tonf limestone 45 WT% carbon dioxide is released C _a O 0.3 tonf clay C _a O reacts with air This is the phenomenon of returning to calcium carbonate, which can be said to be the same phenomenon as the phenomenon of iron rusting.

By hydration reaction with cement

[Chemical 8] When these hydrates react with carbon dioxide,

[Chemical 9] Reacts with.

In concrete structures, the above 2)
The phenomenon of is progressing rapidly. And the above 3), 4)
The reaction of the formula concentrates chloride and sulfur compounds inside the concrete structure, so that the reinforcing bar corrodes.

In the above explanation of carbonation,

[Chemical 10] The composition of the concrete pore solution is OH- in equilibrium with Na ⁺ and K ^+, and Ca ²⁺ is negligible. The pH in concrete is governed by this hydroxide ion.

Solubility of calcium hydroxide

[Chemical 11] The reaction proceeds to form calcium carbonate and precipitate. There is no change in pH until the calcium hydroxide near the pores disappears.

1.6 Transfer and concentration of salt will be described with reference to FIG. The higher the pH of the pore solution, the higher the rate of carbonation in concrete. 1) The concentration of hydroxyl ions increases with increasing amount of sodium chloride. 2) Sodium chloride dissociates into Na ⁺ and Cl- 3) Alumina in cement Acid tricalcium

[Chemical 12] Up to 0.4% of the cement weight is combined with Cl- to form Friedel's salt. 4) Decrease in chloride ion Anion corresponding to this is required, and calcium hydroxide existing in the solid phase is eluted

The facts in the investigation of the migration / concentration of chloride and sulfur compounds by carbonation and the corrosion deterioration of rebar are as follows. 1) The chloride content is low near the concrete surface, but rather high inside. 2) Corresponding cases of corrosive internal reinforcement 3) Concrete carbonation is abnormally fast

1.7 The mechanism of carbonation (neutralization) will be described with reference to FIG. Carbon dioxide in the air not only transforms calcium hydroxide into calcium carbonate, but also reacts with ettringite and Friedel's salts to form water-soluble chloride and sulfur compounds. These ions move inside the concrete due to concentration diffusion and are concentrated. Sodium chloride in concrete increases the pH of the pore solution, which significantly accelerates carbonation. Carbon dioxide in the air not only transforms calcium hydroxide into calcium carbonate, but also reacts with ettringite and Friedel's salts to form water-soluble chloride and sulfur compounds. These ions move inside the concrete due to concentration diffusion and are concentrated. Sodium chloride in concrete increases the pH of the pore solution, which significantly accelerates carbonation.

2 Modeling of composite deterioration 2.1 Mass transfer inside concrete It is assumed that mass transfer inside concrete is a diffusion phenomenon. In addition, carbon dioxide, chloride, and hydroxide ion are used as substances exhibiting the diffusion phenomenon. Also, it is assumed that Friedel's salt, calcium carbonate, and aluminate, which are related to the concentration and release of chloride by Friedel's salt, are fixed.

[0034]

[Chemical 13]

2.2 Concentration of hydroxide ion Alkali metals (Na ⁺ , K ⁺ , C) on the concrete surface
With the outflow of a ²⁺ ), a concentration gradient of the alkali metal near the inside and outside occurs. This concentration gradient causes the alkali metal to move to the surface layer along with the hydroxide ion.

2.3 Chloride Concentration Chloride in concrete is the sum of the amount of chloride contained in the concrete from the beginning and the amount of chloride due to the diffusion phenomenon from the outside. Chloride may be fixed or released as Friedel's salt depending on the concentration of calcium hydroxide.

Condition Concentration of calcium hydroxide> threshold: Friedel's salt> 0.4% The concentration is determined by the diffusion phenomenon of chloride from the outside. Friedel's salt <0.4% Chloride is fixed by the diffusion phenomenon until Friedel's salt reaches 0.4%. Friedel's salt and chloride reaction rate constants are required. When the concentration of calcium hydroxide is less than the threshold value, Friedel's salt releases chloride by reaction with carbon dioxide. The liberated chloride spreads into the concrete due to the diffusion phenomenon. The reaction rate constant of carbon dioxide and Friedel's salt is required. Therefore, the chloride concentration is the total of chloride ions generated by the reaction of chloride ions and Friedel's salt due to diffusion from the outside.

2.4 Carbon dioxide concentration is calculated by the diffusion phenomenon from the outside. It is also absorbed in concrete by the reaction with calcium hydroxide. When chloride ions are fixed as Friedel's salt, carbon dioxide gas is generated. Therefore, the carbon dioxide concentration is the sum of both.

2.5 Concentration of Calcium Hydroxide The concentration of calcium hydroxide is determined by the reaction between calcium hydroxide and carbon dioxide gas. Therefore, the concentration distribution of carbon dioxide is obtained, and as a result, the concentration of calcium hydroxide is determined. Therefore, the concentration of calcium hydroxide is calculated by the reaction with carbon dioxide.

2.6 Concentration of Friedel's salt The concentration of Friedel's salt is calculated as follows according to the concentration of calcium hydroxide. When the concentration of calcium hydroxide is greater than the threshold value of 0.4%, chloride is fixed and increased. At 0.4% or more, there is no chloride fixation and no increase or decrease due to the reaction. Concentration of calcium hydroxide <threshold Friedel's salt reacts with carbon dioxide to release chloride and reduce it.

3 Derivation of basic equations regarding composite deterioration The basic equations of the phenomenon described in Section 2 are derived. The substances that move in concrete due to the diffusion phenomenon are hydroxide ion, chloride and carbon dioxide gas. Also assume that calcium hydroxide, aluminate and Friedel's salt are fixed in the concrete. In addition, the modeling only deals with the interaction between chloride and neutralization, and does not deal with phenomena related to sulfide, carbon dioxide and ettringite. Equation-3.1 shows the concentration diffusion of hydroxide ion (alkali metal).
In Equation-3.1, the boundary condition in contact with air is the Neumann type condition, and alkali metal is allowed to flow out from concrete.

[0042]

[Equation 3]

The chemical reaction formulas for carbon dioxide, chloride and aluminate are shown in Formula-3.2. Friedel's salt is produced by the reaction of aluminate and chloride (concentration of chloride)

[Chemical 14]

Friedel's salt reacts with carbon dioxide to form chloride (release of chloride) The reaction formula of Formula-3.2 is the reaction direction due to the interaction of chloride, carbon dioxide, aluminate and Friedel's salt. Is determined. The direction of the reaction is determined by the concentrations of calcium hydroxide, chloride ions and carbon dioxide. Equation-3.3 and equation-3.4 show the diffusion equations of carbon dioxide and chloride in consideration of the reaction of equation-3.2.

Further, it is assumed that the reaction rate follows the Arrhenius equation.

[Equation 4]

Here

[Chemical 15]

The first term on the right side of the equation-3.3 is the term relating to the concentration diffusion of carbon dioxide gas flowing from the outside, the second term is the term showing the amount of reduction of carbon dioxide gas due to the reaction between calcium hydroxide and carbon dioxide gas, and the third term. Is a term for producing carbon dioxide by reacting aluminate with chloride. That is, the third term in Equation-3.2 is
In the reaction formula shown in, the increase of carbon dioxide gas generated when chloride is fixed in concrete as Friedel's salt is shown. In addition, the diffusion coefficient is determined depending on the hydroxide ion.

The first term on the right-hand side of the equation-3.4 is the concentration diffusion of chloride flowing in from the outside, the second term is carbon dioxide gas and Friedel's salt react to release chloride, and the third term is aluminate. And chloride reacts, indicating fixation of chloride. Formula-3.3 and Formula-3.4 are formulas that calculate the amount of substances (carbon dioxide, chloride) that move without being fixed in concrete. Calculate calcium hydroxide, Friedel's and aluminate which are separately fixed in concrete. An expression is required. The formulas for obtaining these quantities are shown in Formula-3.5, Formula-3.6, and Formula-3.7. Equation-3.5 is the equation for calculating calcium hydroxide, and it is assumed that the amount of calcium hydroxide is determined by the reaction with carbon dioxide. Expression-
It is assumed that the reaction of 3.5 is only one way in which calcium hydroxide reacts with carbon dioxide to form calcium carbonate.
Therefore, the reaction of the following formula is a reaction in the right direction only.

[0049]

[Chemical 16]

Further, the amounts of Friedel's salt and aluminate are calculated from the equations -3.6 and -3.7. The first term on the right side of formula -3.7 is the amount of reduction of aluminate when chloride reacts with aluminate to form Friedel's salt, and the second term releases chloride by the reaction of Friedel's salt and carbon dioxide gas. It shows the amount of decrease of aluminate in the case. Equation-3.7 is the inverse reaction of equation-3.6 to obtain the amount of Friedel's salt. Therefore, the amount of Friedel's salt is obtained in the form of the interaction of carbon dioxide with chloride and aluminate. Reaction of calcium hydroxide with carbon dioxide

[0051]

[Equation 5]

Here

[Chemical 17]

The reaction (1) is a one-way reaction if calcium hydroxide is present in the concrete. Also, the formula-3.6,
The reaction of Equation-3.7 is assumed as follows.

[0054]

[Equation 6] The reduction described above is schematically shown in FIG.

4 Formulation on composite deterioration 4.1 Formulation of diffusion equation Formulations of -3.1 to -3.8 are performed. The Galerkin method is applied to the formulation. Formula-3.1 is a special form of Formula-3.2, so Formula
The formulation of -3.2 is shown below.

[0056]

[Equation 7]

The analysis target is divided into a finite number of elements, and the concentration distribution in element e is expressed as in equation -4.2.

[0058]

[Equation 8]

Here, the shape function of the one-dimensional element is

[Equation 9]

Since the same function as the shape function is applied as the weighting function in the Galerkin method, equation-4.5 is obtained by weighting equation-4.1 and integrating within the element.

[0061]

[Equation 10]

Since the second differential term with respect to the density C is included in the equation-4.5, the partial integration based on the Gauss-Green theorem results in the equation-4.6.

[0063]

[Equation 11]

Substituting equation-4.3 and equation-4.4 into equation-4.6 and rewriting it yields equation-4.7.

[Equation 12]

The chloride diffusion equation of Equation-3.5 is formulated in a similar manner. Equation-3.5 has the same shape as the case where the third term on the right side of Equation-3.2 does not exist, and is therefore Equation-4.9.

[0066]

[Equation 13]

Applying the same method to equations-3.6 and 3.7, equations-4.10 and-4.11.

[Equation 14]

4.2 Differentiation with respect to time The basic formula derived in Section 4.1 is differentiated with respect to time. Equation-4.12 and equation-4.13 are the diffusion equations for carbon dioxide and chloride.
Shown in.

[0069]

[Equation 15]

When the expressions -4.14 and -4.15 are differentiated with respect to time, finally the expressions -4.16 and -4.17 are solved.

[0071]

[Equation 16]

Forward difference here Crank-Nicholson method Regression difference

[0073]

[Equation 17]

When formula-4.16 and formula-4.17 are rearranged, formula-4.18,
Formula becomes 4.19.

[0075]

[Equation 18]

When the respective terms of Expression-4.18 and Expression-4.19 are set as follows, Expression-4.18 and Expression-4.19 are finally summarized in the form of Expression-4.20.

[0077]

[Formula 19]

Formula-4.16 is a form summarizing the interaction between carbon dioxide and chloride. By solving Formula-4.16, the concentration distribution can be obtained in a form that takes into account the interaction between the two.
Next, the time difference of Formula-3.3, Formula-3.6, and Formula-3.7 for calculating calcium hydroxide, aluminate, and Friedel's salt is performed. The Galerkin display of Formula-3.6 and Formula-3.7 is Formula-4.1
0, already shown in Equation-4.11. The formula is shown below. Also,
The formula for calculating calcium hydroxide in formula 3.3 is as shown in formula 4.20 because it has no interaction.

[0079]

[Equation 20]

When equation −4.21, equation −4.22, and equation −4.23 are differentiated with respect to time, equation −4.24, equation −4.25, and equation −4.26 are obtained.

[0081]

[Equation 21]

When the respective terms of equations -4.24 and -4.25 are set as follows, equation -4.27 is obtained. Also, since the equation for calculating calcium hydroxide is a one-way reaction with carbon dioxide, equation -4.26 is solved.

[0083]

[Equation 22]

[0084]

[Embodiment 1] Hereinafter, a specific example of a composite deterioration prediction result of a concrete structure by the deterioration prediction method of the present invention will be described. Figure 5 shows the actual concrete structure
3 shows a chloride ion concentration distribution curve A after 30 years predicted by the method of the present invention and a measured chloride ion concentration distribution curve B after 30 years. In addition, the example of FIG. 5 is an example when the repair of the concrete structure is not performed for 30 years. As is obvious in the distribution curve B in FIG. 5, the actual chloride ion concentration distribution has a peak in the concentration distribution inside (about 2.5 cm in depth) from the surface. Similar peaks are also expressed in the distribution curve predicted by the present invention, and the concentration distribution in the deeper part is very close to the measured value.

Further, in FIG. 7A, 100 years after 100 years
The calculation results of chloride ion concentration up to a year later are shown. Then, FIG. 7B shows the calculation result of the calcium hydroxide concentration from 5 years to 100 years.

From the above, according to the method of the present invention, it is possible to properly calculate the chloride ion concentration distribution which can grasp the progress of complex deterioration due to salt damage and neutralization.

Next, a method of predicting deterioration when a concrete structure is repaired on the way will be described. When repairs are performed on the way as described above, depending on the type of the repair method, the boundary conditions of the existing concrete structure after repair and the characteristic data of the repair material used for repair are added to the deterioration prediction factors. Predict the progress of deterioration of the concrete structure after repair.

As for the type of repair of the existing concrete structure, a surface protector for covering the concrete surface (see (a) of FIG. 6) and a concrete surface layer are removed and then a repair material such as a hardening material is used for removal. There are a cross-section restoration work (see (b) of FIG. 6) for repairing the damaged portion and a repair method (see (c) of FIG. 6) using both the surface protection work and the cross-section restoration work.

[0089]

[Embodiment 2] FIG. 8A shows the results of prediction of deterioration of a concrete structure when surface coating was performed. In this case, the amount of carbon dioxide gas supplied from the surface is reduced, and the chloride ion fixed as Friedel's salt is not separated as soluble salt, which means that the maximum chloride ion concentration does not increase. There is.

[0090]

[Embodiment 3] Next, FIG. 9A shows the result of prediction of deterioration of a concrete structure when repairing a section up to 4 cm by a cross section restoration work. In this case, 4 cm from the surface
Since it becomes a new concrete up to now, it represents a phenomenon that the concentration of chloride ion, which was distributed in the depth direction where the soluble salt content in the concrete is fixed as Friedel's salt, becomes small.

[0091]

[Embodiment 4] Next, FIG. 10A shows the result of prediction of deterioration of the concrete structure when both the surface coating work and the cross-section repair work were carried out. In this case, the phenomenon of the second embodiment and the phenomenon of the third embodiment are added and appear.

Next, the prediction results when the prediction of deterioration due to neutralization is evaluated by the decrease amount of calcium hydroxide are shown in FIGS. 8 (b) to 10 (b). 8B shows the case of the surface coating, and FIG. 9B shows the case of the cross-section restoration.
(B) shows the case where the surface coating work and the cross-section repair work are performed. In addition, the result of summarizing these is shown in FIG.
1, shown in FIG.

The outline of the procedure for carrying out the prediction method of the present invention using a computer will be described below. FIG. 6A
Shows a cross section of the concrete structure Z after repair when the surface of the concrete is covered with the repair material D1 using the above surface protection work. In this case, in the method for predicting deterioration of a concrete structure of the present invention, the boundary condition of the boundary layer of the concrete surface of the existing concrete structure Z is changed to the boundary condition of the concrete surface after being repaired by being covered with the repair material D1. Change to predict the progress of deterioration of the concrete structure Z after repair.

FIG. 6B shows a repair material D2 after the surface layer of the concrete structure is removed by using a cross-section restoration work.
The cross section of the concrete structure Z after repairing which repaired the part removed in FIG. In this case, in the method for predicting deterioration of a concrete structure according to the present invention, the chloride ion concentration, the calcium hydroxide concentration and the carbon dioxide diffusion coefficient of the portion repaired with the repair material D2 are calculated as the initial chloride ion of the repair material D2. Change the concentration, calcium hydroxide concentration, and carbon dioxide diffusion coefficient.

The core was sampled from the existing concrete structure Z to measure the chloride ion concentration, and the carbon dioxide diffusion equation was obtained from the measured neutralization depth obtained using the phenolphthalein solution. The diffusion coefficient is obtained by inverse analysis using, the diffusion coefficient of the existing concrete deeper than the repaired part is changed to this value, and the boundary condition of the concrete structure repaired by the repair material D2 is changed,
From these data, the progress of deterioration of the concrete structure Z is predicted by the finite element method.

FIG. 6 (c) shows that the surface protection work and the cross-section repair work are used together to remove the surface layer portion of the concrete structure, and then the removed portion is repaired with the repair material D2. The cross section of the concrete structure Z after the repair which covered the repair material D1 on the surface is shown. In this case, in the deterioration prediction method of the concrete structure of the present invention,
The boundary conditions of the concrete surface after being covered with the repair material D1 and repaired are changed, and the chloride ion concentration, the calcium hydroxide concentration, and the carbon dioxide diffusion coefficient of the portion repaired with the repair material D2 are respectively calculated after the repair. The boundary conditions of the concrete surface, the initial chloride ion concentration and the initial calcium hydroxide concentration of the repair material D2, and the diffusion coefficient of carbon dioxide are changed. Furthermore, from the measured values of chloride ion concentration and neutralization depth obtained by sampling the core from the existing concrete structure Z, the diffusion coefficient was obtained by inverse analysis using the diffusion equation of carbon dioxide, and these data were obtained. From this, the progress of deterioration of the concrete structure Z is predicted by the finite element method.

Next, a concrete procedure of the method for predicting deterioration of the concrete structure will be described with reference to the flowchart shown in FIG. Here, since each procedure of the deterioration prediction method of the present invention is realized by software, in the following description, an operation procedure of hardware for executing the above-mentioned software will be described.

The above hardware includes an input device, a storage device, a computing device, and a display device (all not shown). In the following description, necessary data is input from the input device. However, by processing this data in accordance with each step of the program stored in the storage device by the processing device, the prediction result of deterioration of the concrete structure after repair can be displayed on the display device. .

As shown in FIG. 13, in the method of predicting deterioration of a concrete structure according to the present invention, steps S101 to S101 for inputting characteristic data relating to the structural conditions of the concrete structure.
S109, Steps S201 to S203 for inputting boundary conditions of the existing concrete structure when repaired and characteristic data of the repair material used for repair, and prediction of deterioration progress of the concrete structure from each input data It is composed of a calculation step S301.

First, in step S101, characteristic data relating to the structural conditions of the concrete structure to be repaired,
For example, the cover of the concrete structure, the member thickness, the main bar diameter, etc. are input. Next, in step S102, the boundary conditions of this concrete structure are set. For this boundary condition, for example, the chloride ion absorption rate of the boundary layer, the carbon dioxide gas absorption rate, the thickness of the boundary layer, the chloride ion outflow rate from the boundary layer, the carbon dioxide outflow rate coefficient, and the like are input. Then, in step S103, it is selected whether this concrete structure is a new structure or an existing structure.

Next, when the existing concrete structure is selected in step S103, step S1
Proceed to 04 to select whether or not to measure the progress of deterioration of the existing concrete structure so far. here,
When “Measure progress of deterioration of concrete structure” is selected, in step S105, measurement data obtained by sampling the core of the existing concrete structure, that is, measured values of chloride ion concentration and neutralization depth. Enter.

In step S106, the above step S1
The diffusion coefficient of this existing concrete structure is calculated by performing an inverse analysis using the diffusion equation of carbon dioxide from the measurement data of the chloride ion concentration and the neutralization depth input in 05. If the progress of deterioration of the existing concrete structure is not measured in step S104, the process proceeds to step S107 to set the carbon dioxide diffusion coefficient of the existing concrete structure. For the diffusion coefficient of carbon dioxide gas, the diffusion coefficient for each type of concrete described in the standard specifications for concrete is used.

Next, in step S201, it is selected whether or not to repair the existing concrete structure. Here, if "repair" is selected, in step S202,
Select a repair method. Specifically, on the repair method selection screen (not shown), the selection items of the above-mentioned surface protection work, cross-section repair work and repair method using both surface protection work and cross-section repair work are prepared. The repair method is selected from.

When the repairing method is selected in step S202, the boundary conditions of the repaired portion, the carbon dioxide diffusion coefficient and the initial chloride ion concentration are selected in step S203 according to the selected repairing method. Set the initial calcium hydroxide concentration. Further, the boundary condition is set by inputting necessary data for each item displayed on the screen (not shown) for inputting the boundary condition when the surface protection work is selected as the repair method.

When the cross-section protector is selected on the above selection screen, the initial chloride ion concentration and the initial calcium hydroxide concentration and the carbon dioxide diffusion coefficient of the portion repaired with the repair material are input, and If you select a repair method that uses both surface protection and cross-section repair as the repair method,
The setting is performed by reading the boundary conditions, the chloride ion concentration, the calcium hydroxide concentration and the diffusion coefficient from a preset database. Note that the above step S
When “No repair” is selected in 201, the diffusion coefficient calculated by the inverse analysis in step S106 is used.

When the case where the concrete structure is newly constructed is selected in step S103, the calculation conditions such as the cement type and the water cement ratio are input in step S108, and the carbon dioxide diffusion coefficient is calculated in step S109. .

As described above, when all the data necessary for predicting the deterioration of the concrete structure due to salt damage and neutralization are input, the process proceeds to step S301, and the combined deterioration of salt damage and neutralization is performed based on the finite element method. The deterioration prediction calculation of the concrete structure is executed by and the calculation result is displayed on the display device.
7 to 10 show output results when the above calculation results are output in a graph format.

As is clear from the above prediction results, according to the deterioration prediction method of the present invention, it is possible to predict the composite deterioration of the concrete structure without repairing, and when repairing, depending on the type of the repairing method. , In order to predict the progress of deterioration of the concrete structure after repair by adding the boundary condition of the existing concrete structure after repair and the characteristic data of the repair material used for repair to the new factor of deterioration prediction, Compared with the deterioration prediction method, there is an effect that the deterioration of the concrete structure after repair can be predicted more accurately.

[0109]

According to the invention of claim 1 of the present invention, one side contains a cement hydration product in concrete and carbon dioxide in the atmosphere, and the other side contains calcium carbonate. A complex represented by a chemical reaction formula and a reversible chemical reaction formula containing calcium carbonate, aluminate and chloride on one side and Friedel's salt and carbon dioxide gas on the other side. Since the progress of deterioration is analyzed by the finite element method using the diffusion equation, it is possible to predict the progress of deterioration due to salt damage and neutralization of the concrete structure.

In the invention of claim 2, when repaired,
Predict the progress of deterioration of the concrete structure after repair by adding the boundary condition of the existing concrete structure after repair and the characteristic data of the repair material used for repair to the new factor of deterioration prediction by the finite element method Therefore, there is an effect that the progress of deterioration due to neutralization of the concrete structure after repair can be more accurately predicted.

According to the third and fourth aspects of the invention, the characteristic data of the repair material includes the initial chloride ion concentration, chloride ion diffusion coefficient, calcium hydroxide ion concentration, carbon dioxide diffusion coefficient of the repair material. Therefore, it is possible to predict the progress of deterioration of the concrete structure after the repair by considering the characteristic data of the repair material, and as a result, the neutralization of the concrete structure after the repair can be performed more accurately. There is an effect that the progress of deterioration can be predicted.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a method for predicting deterioration of a concrete structure according to the present invention.

FIG. 2 is an explanatory diagram illustrating a method for predicting deterioration of a concrete structure according to the present invention.

FIG. 3 is an explanatory diagram illustrating a method for predicting deterioration of a concrete structure according to the present invention.

FIG. 4 is an explanatory view schematically showing a method of predicting deterioration of a concrete structure according to the present invention.

FIG. 5 is an explanatory diagram showing a result of prediction by the method for predicting deterioration of a concrete structure of the present invention, in comparison with an actual measurement result.

FIG. 6 is a cross-sectional view of a concrete structure for explaining a repair method used in the method for predicting deterioration of a concrete structure according to the present invention.

FIG. 7 is a screen configuration diagram showing a case where a prediction result by the deterioration prediction method for a concrete structure of the present invention is output in a graph format.

FIG. 8 is a screen configuration diagram showing a case where a prediction result by the deterioration prediction method for a concrete structure of the present invention is output in a graph format.

FIG. 9 is a screen configuration diagram showing a case where a prediction result by the deterioration prediction method for a concrete structure of the present invention is output in a graph format.

FIG. 10 is a screen configuration diagram showing a case where a prediction result by the deterioration prediction method for a concrete structure of the present invention is output in a graph format.

FIG. 11 is a screen configuration diagram showing a case where a prediction result by the method for predicting deterioration of a concrete structure of the present invention is output in a graph format.

FIG. 12 is a screen configuration diagram showing a case where a prediction result by the method for predicting deterioration of a concrete structure of the present invention is output in a graph format.

FIG. 13 is a flowchart showing each procedure of the method for predicting deterioration of a concrete structure according to the present invention.

FIG. 14 is a table illustrating each variable used in this specification.

[Explanation of symbols]

Z concrete structure X 40mm depth of concrete structure D1 surface repair material D2 Cross section restoration material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kunikazu Higashi             2nd-2nd share, Matsuzaki-cho, Abeno-ku, Osaka-shi             Company Okumura group (72) Inventor Masahiro Kurimoto             2nd-2nd share, Matsuzaki-cho, Abeno-ku, Osaka-shi             Company Okumura group (72) Inventor Hitoshi Masui             2nd-2nd share, Matsuzaki-cho, Abeno-ku, Osaka-shi             Company Okumura group

Claims (4)

[Claims] 1. A method for predicting deterioration of a concrete structure, which comprises predicting the progress of deterioration of a concrete structure due to salt damage and neutralization by analyzing various deterioration factors by a finite element method, the method comprising: Includes a cement hydration product in concrete and carbon dioxide in the atmosphere, a chemical reaction formula containing calcium carbonate on the other side, and calcium carbonate, aluminate, and chloride on one side, and The reversible chemical reaction formula containing Friedel's salt and carbon dioxide is shown on the side, and the progress of complex deterioration represented by A method for predicting deterioration of concrete structures, characterized by analyzing and predicting by the finite element method. 2. A method for predicting the progress of deterioration of a concrete structure after repairing an existing concrete structure using a repair material by the method according to claim 1, The feature is that the boundary condition of the existing concrete structure and the characteristic data of the repair material used for repair are added to the new factor of deterioration prediction by the finite element method to predict the progress of deterioration of the concrete structure after repair. The method for predicting deterioration of a concrete structure according to claim 1. 3. The characteristic data of the repair material includes an initial chloride ion concentration of the repair material and a diffusion coefficient of chloride ion of the repair material. A method for predicting deterioration of a concrete structure described. 4. The characteristic data of the repair material includes an initial calcium hydroxide ion concentration of the repair material and a diffusion coefficient of carbon dioxide gas of the repair material. 3. A method for predicting deterioration of a concrete structure according to item 3.