JP5278245B2 - Life evaluation method and apparatus for reinforced concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for evaluating the life of reinforced concrete, simply calculating a corrosion quantity at the time of production of a crack and easily calculating the corrosion quantity at the time of production of the crack even with respect to the reinforced concrete different in shape or structure. <P>SOLUTION: The FEM analysis of the reinforced concrete is executed and the virtual temperature simulating the corrosion of a reinforcing rod is applied to the reinforcing rod of the reinforced concrete to execute the FEM analysis of the reinforced concrete when the reinforcing rod is virtually expanded not only to calculate the virtual temperature when the crack occurs in the concrete surface of the reinforced concrete but also to operate the corrosion quantity at the time of occurrence of the crack on the basis of the calculated virtual temperature. The crack occurrence period of the reinforced concrete is estimated on the basis of the obtained corrosion quantity at the time of occurrence of the crack, the corrosion start period of the reinforcing rod, and the corrosion speed after the production of corrosion. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention predicts the crack initiation time of reinforced concrete on the basis of the corrosion start time of the reinforcing bars, the corrosion rate after the occurrence of corrosion, and the amount of corrosion at the time of crack occurrence, which is the amount of corrosion of the reinforcing bars when cracks occur on the concrete surface. The present invention relates to a life evaluation method and apparatus for reinforced concrete.

  The mechanism of deterioration of reinforced concrete due to salt damage is that chloride ions that have penetrated from the surface reach the surface of the reinforcing bar, and after corrosion of the reinforcing bar occurs, cracks occur on the surface of the concrete, resulting in peeling of the concrete. It is considered.

  As shown in FIG. 10, the mechanism of such deterioration can be organized by a deterioration curve of time and corrosion amount (see, for example, Patent Document 1).

  The deterioration curve shown in FIG. 10 shows the corrosion start time of the reinforcing bar indicating the time when the chloride ions gradually penetrate the concrete and reach the reinforcing bar, and the reinforcing bar is corroded, and the amount of corrosion after the reinforcing bar is corroded. It can be obtained by determining both the corrosion rate after the occurrence of corrosion showing the rate of increase.

  The corrosion start time of the reinforcing bars can be determined using the Fick diffusion formula, the natural potential method, the polarization resistance method, the concrete resistance method, and the like. On the other hand, the corrosion rate after the occurrence of corrosion can be determined using the polarization resistance method.

  By using the deterioration curve of FIG. 10, it is possible to predict the time (time) at which the reinforcing bar reaches a certain corrosion amount. Therefore, if the amount of corrosion of the rebar when cracks occur on the concrete surface (hereinafter referred to as the amount of corrosion at the time of cracking) is calculated, the time it takes for the reinforcing bar to reach the amount of corrosion at the time of cracking, that is, the crack occurrence time of the reinforced concrete ( It is possible to predict the life of reinforced concrete.

Conventionally, the amount of corrosion at the time of cracking has been defined to be constant at 10 mg / cm ² regardless of the compressive strength and fogging of the reinforced concrete (distance from the concrete surface to the reinforcing bar) (Non-patent Document 1).

JP 2008-8249A JP 2002-90230 A JP 2007-264840 A Japanese Patent Laid-Open No. 9-165839

Japan Society of Civil Engineers, Standard Specification for Concrete [Maintenance], 2007, p. 95

However, when the present inventors actually conducted experiments to examine the amount of corrosion at the time of cracking, the amount of corrosion at the time of cracking was found to vary greatly depending on the compressive strength of the reinforced concrete and the size of the cover. . Therefore, when the amount of corrosion at the time of crack occurrence is constant at 10 mg / cm ² as described above, the crack occurrence time of reinforced concrete cannot be accurately predicted.

  In other words, in order to accurately predict the crack generation time of reinforced concrete, it is necessary to accurately determine the amount of corrosion at the time of crack generation of the reinforced concrete to be evaluated.

  As a method for obtaining the amount of corrosion at the time of crack occurrence, a method is conceivable in which a reinforced concrete specimen is prepared to forcibly corrode the reinforcing bar, and the amount of corrosion when the concrete surface is actually cracked is measured.

  However, this method has a problem that it takes a very long time because it is necessary to actually conduct experiments and measure the amount of corrosion when cracks occur. In particular, when the concrete cover is large, cracks may not occur on the concrete surface unless the experiment is conducted for several years, which is not realistic.

  Also, in the method of experimentally determining the amount of corrosion when cracks occur, in order to determine the amount of corrosion when cracks occur in reinforced concrete with different shapes and structures, experiments must be performed for each shape and structure of reinforced concrete, There is also a problem of cost and time.

  Therefore, the object of the present invention is to solve the above-mentioned problems and to easily determine the amount of corrosion when cracks occur, and to easily determine the amount of corrosion when cracks occur even in reinforced concrete with different shapes and structures. The object is to provide a method and an apparatus for evaluating the life of reinforced concrete.

  The present invention has been devised to achieve the above-described object, and is the time when cracking occurs, which is the corrosion start time of the reinforcing bar, the corrosion rate after the occurrence of corrosion, and the amount of corrosion of the reinforcing bar when cracking occurs on the concrete surface. A method for evaluating the life of a reinforced concrete that predicts the occurrence of cracks in a reinforced concrete based on the amount of corrosion. The FEM analysis of the reinforced concrete is performed, and a virtual temperature that simulates the corrosion of the reinforced concrete is applied to the reinforced concrete reinforcing bar. Then, FEM analysis of the reinforced concrete when the reinforcing bar is virtually expanded is performed to determine a virtual temperature when a crack occurs on the concrete surface of the reinforced concrete, and based on the calculated virtual temperature Calculate the amount of corrosion at the time of crack occurrence, and the obtained corrosion amount at the time of crack occurrence and at the start of corrosion of the rebar , Based on the corrosion rate after the corrosion occurs, a life evaluation method of reinforced concrete for predicting crack generation timing of the reinforced concrete.

The calculation of the amount of corrosion at the time of the occurrence of cracks is based on the hypothetical temperature Δt when cracks occur on the concrete surface, the radius r before corrosion of the reinforcing bars, and the linear expansion coefficient a of the reinforcing bars. (1)
r _d = a × r × Δt + r (1)
A result, the seek radius r _d rebar inflated virtually, the following equation (2)
β = (πr _d ² −πr ² ) / πr ² × 100 (2)
Thus, the reinforcing bar expansion coefficient β is obtained, and based on the obtained reinforcing bar expansion coefficient β and the preset volume expansion coefficient α, the following equation (3)
Δx = {(1 + β / 100) ^1/2 −1} / (α ^1/3 −1) (3)
Thus, the corrosion depth Δx is obtained, and based on the obtained corrosion depth Δx and the density ρ of the reinforcing bar, the following equation (4)
W _cr = Δx × ρ (4)
Thus, the amount of corrosion W _cr when a crack is generated may be obtained.

  A corrosion area ratio that is a ratio of the area of the corrosion portion to the total surface area of the reinforcing bars is set in advance, and only a part of the reinforcing bars corresponding to the corrosion area ratio is virtually expanded to perform the FEM analysis. You may make it do.

  The corrosion rate after the corrosion may be obtained by a polarization resistance method.

  In addition, the present invention is based on the corrosion start time of the reinforcing bars, the corrosion rate after the occurrence of corrosion, and the amount of corrosion at the time of cracking, which is the amount of corrosion of the reinforcing steel when cracks occur on the concrete surface. The reinforced concrete life evaluation apparatus predicts the FRC analysis of the reinforced concrete, and the reinforced concrete rebar is virtually expanded by giving a virtual temperature simulating the corrosion of the rebar to the reinforced concrete rebar. FEM analysis of the reinforced concrete at the time, an imaginary temperature when a crack occurs on the concrete surface of the reinforced concrete is obtained, and an analysis unit that calculates the amount of corrosion at the time of the crack occurrence based on the obtained imaginary temperature And the amount of corrosion at the time of occurrence of cracks obtained by the analysis section, the corrosion start time of the rebar, and the corrosion after the occurrence of corrosion. Based on the speed, a lifetime estimation device reinforced concrete and a lifetime prediction unit for predicting a crack generation timing of the reinforced concrete.

  According to the present invention, it is possible to easily determine the amount of corrosion at the time of occurrence of cracks, and it is possible to easily determine the amount of corrosion at the time of occurrence of cracks even if the reinforced concrete has a different shape and structure. And a device can be provided.

It is a functional block diagram of the lifetime evaluation apparatus of the reinforced concrete which concerns on one embodiment of this invention. It is explanatory drawing explaining the principle of the life evaluation method of the reinforced concrete which concerns on one embodiment of this invention. (A)-(c) is explanatory drawing explaining a corrosion area rate in this invention. It is a flowchart of the life evaluation method of the reinforced concrete which concerns on one embodiment of this invention. In this invention, it is a flowchart at the time of estimating the crack generation time by the corrosion amount at the time of the crack generation of a solid reinforced concrete. In this invention, it is explanatory drawing explaining that a crack generate | occur | produces in the interface of concrete and repair material in repaired reinforced concrete. In this invention, it is a flowchart at the time of estimating the crack generation time by the corrosion amount at the time of the crack generation of repaired reinforced concrete. In this invention, it is explanatory drawing explaining an electrophoresis method. In this invention, it is an expanded view of a reinforcing bar when the reinforcing bar corroded by the electrophoresis method is taken out. It is a figure which shows the deterioration curve of time and the amount of corrosion.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, a reinforced concrete life evaluation apparatus used in the reinforced concrete life evaluation method according to the present embodiment will be described.

  As shown in FIG. 1, the reinforced concrete life evaluation apparatus 1 includes a physical property value (compressive strength, tensile strength, elastic modulus) of a reinforced concrete to be evaluated, a cover size, and a predetermined corrosion area ratio (total rebar strength). The ratio of the area of the corroded portion to the surface area; details will be described later), and the analysis to calculate the amount of corrosion at the time of cracking based on the input value input in the reinforced concrete property input unit 2 Obtained by the analysis unit 3, the storage unit 4 for storing the analysis results in the analysis unit 3, the corrosion characteristic input unit 5 for inputting the corrosion start time of the reinforced concrete reinforcement, and the corrosion rate after the occurrence of corrosion Crack generation time of reinforced concrete based on the amount of corrosion at the time of crack occurrence, the corrosion start time of the rebar entered in the corrosion characteristics input section 5, and the corrosion rate after the occurrence of corrosion A lifetime prediction unit 6 that predicts, and an output unit 7 for outputting the cracking occurrence timing of reinforced concrete predicted by the lifetime prediction unit 6 to display such as a display.

  The reinforced concrete property input unit 2, the analysis unit 3, the storage unit 4, the corrosion property input unit 5, the life prediction unit 6, and the output unit 7 are realized by appropriately combining an interface, a memory, a CPU, software, and the like.

  The analysis unit 3 performs an FEM (Finite Element Method) analysis of the reinforced concrete based on the input value input by the reinforced concrete property input unit 2, and a virtual temperature that simulates the corrosion of the reinforcing bar on the reinforced concrete reinforcing bar. FEM analysis of the reinforced concrete when the reinforcing bar is virtually expanded to obtain a virtual temperature when a crack occurs on the concrete surface of the reinforced concrete and crack based on the calculated virtual temperature The amount of corrosion at the time of occurrence is calculated.

  In addition, the life prediction unit 6 calculates the corrosion rate of the reinforced concrete based on the corrosion amount obtained when the crack is generated obtained by the analysis unit 3, the corrosion start time of the reinforcing bar input by the corrosion characteristic input unit 5, and the corrosion rate after the corrosion occurs. It is made to predict when cracks will occur.

  Next, a method for evaluating the life of reinforced concrete according to the present embodiment will be described.

  First, the principle of the reinforced concrete life evaluation method according to the present embodiment will be described with reference to FIG.

As shown in FIG. 2, when the reinforcing bar corrodes, the reinforcing bar containing the corrosion product (corroded reinforcing bar) expands compared to the reinforcing bar before corrosion. That is, the radius r _d of the reinforcing bar containing the corrosion product is larger than the radius r of the reinforcing bar before corrosion.

  Moreover, when a reinforcing bar corrodes, the healthy reinforcing bar after corrosion will become small compared with the reinforcing bar before corrosion. A value obtained by subtracting the radius of a healthy reinforcing bar after corrosion from the radius r of the reinforcing bar before corrosion is called a corrosion depth Δx.

  In the present embodiment, the expansion of the reinforcing bars due to such corrosion is simulated by the expansion when a virtual temperature is applied to the reinforcing bars. In other words, a virtual temperature imitating the corrosion of a reinforcing bar is given to the reinforcing steel of the reinforced concrete, the reinforcing bar is virtually expanded, and the effect of the expansion is analyzed by FEM, so that the virtual surface when cracks occur on the concrete surface The temperature is calculated. By obtaining a hypothetical temperature when cracks occur on the concrete surface, it is possible to obtain the corrosion amount of the reinforcing bars corresponding to this, that is, the corrosion amount when cracks occur.

  More specifically, FEM analysis is performed while gradually increasing the virtual temperature applied to the reinforcing bar to about 0 to 300 ° C., and the virtual temperature Δt when the crack occurs is obtained. By gradually raising the virtual temperature, it is possible to simulate the fact that corrosion has progressed virtually. The virtual temperature here is not an absolute temperature but a temperature relative to the environmental temperature.

The radius of the reinforcing bar when the fictive temperature Δt when cracking occurs is equivalent to the radius r _{d of the} reinforcing bar containing corrosion products when cracking occurs, and the linear expansion coefficient of the reinforcing bar is a. The following formula (1)
r _d = a × r × Δt + r (1)
Can be expressed as In the present embodiment, the linear expansion coefficient of the reinforcing ^bar is set to a = 1.2 × 10 ⁻⁵ .

On the other hand, the rebar expansion coefficient β is expressed by the ratio of the amount of change in the cross section of the rebar before and after corrosion and the cross section of the rebar before corrosion.
β = (πr _d ² −πr ² ) / πr ² × 100 (2)
It is represented by Determined by Equation (1), the radius r _d rebar containing corrosion products by substituting the equation (2), rebar expansion rate β at the time of crack occurrence can be obtained.

In addition, the following formula (3) proposed by JCI (Japan Concrete Institute)
Δx = {(1 + β / 100) ^1/2 −1} / (α ^1/3 −1) (3)
The corrosion depth Δx at the time of occurrence of cracking can be obtained by substituting the rebar expansion coefficient β obtained by the equation (2) for. In equation (3), α is a volume expansion coefficient (= volume of corrosion product / volume lost due to corrosion of reinforcing bars), and in this embodiment, the volume expansion coefficient is assumed to be α = 3.2.

Further, the corrosion depth Δx obtained by the equation (3) is expressed by the following equation (4)
W _cr = Δx × ρ (4)
By substituting into, the amount of corrosion W _cr when a crack is generated can be obtained. In the equation (4), ρ is the density of the reinforcing bar, and here, the density of the iron (ρ = 7.86 g / cm ³ ) was used as the density of the reinforcing bar.

Thus, by simulating the expansion of the reinforcing bar due to corrosion by the expansion when a virtual temperature is applied to the reinforcing bar, it is possible to obtain the corrosion amount W _cr at the time of crack occurrence by FEM analysis.

  Next, the corrosion area rate will be described.

  In the life evaluation method for reinforced concrete according to the present embodiment, a corrosion area rate that is a ratio of the area of the corroded portion to the total surface area of the reinforcing bar is set in advance, and only a part of the reinforcing bar corresponding to the set corrosion area rate is set. The FEM analysis is performed by virtually expanding.

  As shown in FIG. 3 (a), the reinforcing bar 31 expands in all directions at a corrosion area rate of 100%, and as shown in FIG. 3 (b), half of the reinforcing bar 31 (the cover is small) at a corrosion area rate of 50%. Only half of the side) will expand. Similarly, as shown in FIG. 3C, when the corrosion area ratio is 33%, only 1/3 of the reinforcing bar 31 (1/3 on the side with the smaller cover) expands. Thus, the influence given to the concrete 32 around the reinforcing bar 31 can be arbitrarily set by appropriately setting the corrosion area rate.

  The reason why only a part of the reinforcing bar is virtually expanded is that in the actual corrosion of the reinforcing bar, the entire surface of the reinforcing bar hardly corrodes, and only a part of the reinforcing bar surface, that is, the covering of the reinforcing bar is This is because in most cases only the small side corrodes. As a result of experiments conducted by the present inventors, the actual corrosion area ratio is often about 40 to 50%. Therefore, in this embodiment, the corrosion area ratio is set to about 40 to 50%.

  Next, the procedure of the reinforced concrete life evaluation method according to the present embodiment will be described in detail with reference to FIGS.

  Here, a case where the reinforced concrete to be evaluated is a so-called solid reinforced concrete that has not been repaired will be described.

  As shown in FIG. 4, in the method for evaluating the life of reinforced concrete according to the present embodiment, first, electrochemical measurement of reinforced concrete to be evaluated is performed using a natural potential method or a polarization resistance method (step S1). Then, it is determined whether or not corrosion has occurred in the reinforced concrete reinforcing bars (step S2). Since the natural potential method and the polarization resistance method belong to the prior art, description thereof is omitted.

  If it is determined that there is corrosion in step S2, the salinity concentration (surface salinity) on the concrete surface of the reinforced concrete is measured (step S3), and the corrosion of the rebar is calculated using the Fick diffusion formula based on the obtained surface salinity. The start time is predicted (step S4). Here, since corrosion has already occurred in the reinforcing bar, in step S4, it is estimated how many years ago the corrosion occurred at the time of measurement.

  Thereafter, the corrosion rate after the occurrence of corrosion of the reinforcing bars is measured by the polarization resistance method (step S5). Since the method for measuring the corrosion rate of the reinforcing bars belongs to the prior art, description thereof is omitted here.

After obtaining the corrosion start time of the reinforcing bar and the corrosion rate after the occurrence of the corrosion, the crack generation time is predicted based on the corrosion amount W _cr at the time of the crack generation using the life evaluation device 1 of the reinforced concrete (step S6). ). The procedure in step S6 is shown in detail in FIG.

As shown in FIG. 5, when the crack generation time is predicted based on the corrosion amount W _cr when the crack is generated, first, the concrete property value (compressive strength) is input to the concrete property input unit 2 of the reinforced concrete life evaluation apparatus 1. , Tensile strength, elastic modulus) are input (step S11), and the size of the cover and a preset corrosion area ratio are input (steps S12 and S13). After inputting each value in steps S11 to S13, an FEM analysis model of reinforced concrete to be evaluated is created (step S14).

Thereafter, based on the input value input to the concrete property input unit 2 in steps S11 to S13 and the FEM analysis model set in step S14, the analysis unit 3 performs FEM analysis (step S15). The analysis unit 3 performs FEM analysis while gradually changing the virtual temperature applied to the reinforcing bar to obtain a virtual temperature Δt at the time of crack occurrence, and at the time of crack occurrence using the above formulas (1) to (4) _Is calculated (step S16). The analysis result in the analysis unit 3 is stored in the storage unit 4.

  Thereafter, the corrosion start time obtained in step S4 and the corrosion rate after the corrosion of the reinforcing bar obtained in step S5 are input to the corrosion characteristic input unit 5 (step S17).

The life prediction unit 6 determines the crack generation time of the reinforcing bar based on the corrosion amount W _cr when the crack is generated obtained in step S16 and the corrosion start time of the reinforcing bar input in step S17 and the corrosion rate after the corrosion occurs. Obtained (step S18). The life prediction unit 6 outputs the obtained crack generation time of the reinforcing bars to a display or the like via the output unit 7.

  Returning to FIG. 4, when it is determined that there is no corrosion in step S2, the salinity concentration (surface salinity) on the concrete surface of the reinforced concrete is measured (step S7), and based on the obtained surface salinity, the Fick diffusion formula is It is used to predict the corrosion start time of the reinforcing bars (step S8). Here, since corrosion does not occur in the reinforcing bars, in step S8, it is estimated how many years later the corrosion will occur from the time of measurement.

  If there is no corrosion in the reinforcing bars, the corrosion rate after the corrosion of the reinforcing bars cannot be measured from the reinforced concrete to be evaluated, but for example, a test body having the same shape and structure as the reinforced concrete to be evaluated must be created. Thus, the corrosion rate after the occurrence of corrosion of the reinforcing bars can be measured using the specimen. If the corrosion rate after the occurrence of corrosion of the reinforcing bar is obtained, the crack generation time of the reinforced concrete can be predicted by the same procedure as in FIG.

As described above, in the method for evaluating the life of reinforced concrete according to the present embodiment, FEM analysis of reinforced concrete is performed when a virtual temperature imitating the corrosion of reinforcing steel is given to the reinforcing steel of the reinforced concrete and the reinforcing steel is virtually expanded. To calculate the virtual temperature Δt when cracks occur on the concrete surface of reinforced concrete, calculate the amount of corrosion W _cr at the time of crack generation based on the calculated virtual temperature Δt, and generate the cracks obtained The crack generation time of the reinforced concrete is predicted based on the corrosion amount W _cr at the time, the corrosion start time of the rebar, and the corrosion rate after the corrosion occurs.

Thereby, it becomes possible to obtain the corrosion amount W _cr at the time of crack occurrence by FEM analysis, and it is possible to obtain the corrosion amount W _cr at the time of crack occurrence only by simulation without _performing an experiment. Therefore, the amount of corrosion W _cr at the time of crack occurrence can be obtained easily and in a short time, and the cost for the experiment can be reduced.

Further, in this embodiment, since the corrosion amount W _cr at the time of occurrence of cracks is obtained by FEM analysis, even if the reinforced concrete has a different shape and structure, the corrosion amount W at the time of occurrence of cracks can be obtained only by changing the FEM analysis model. _cr can be easily obtained.

Furthermore, in this embodiment, since the corrosion amount W _cr at the time of occurrence of cracking is obtained by FEM analysis, for example, when the concrete cover is large, if the experiment is not conducted over several years, the concrete surface will not crack. Even if it exists, the corrosion amount _Wcr at the time of a crack generation can be _{calculated |} required easily.

Furthermore, in the present embodiment, since the corrosion area rate is set in advance and only a part of the reinforcing bar corresponding to the corrosion area rate is virtually expanded, the FEM analysis is performed. The amount of corrosion W _cr when a crack is generated can be accurately obtained.

  In the above embodiment, the case where solid reinforced concrete that has not been repaired is used as the reinforced concrete to be evaluated has been described, but the present invention is reinforced concrete that has been repaired using a repair material (hereinafter referred to as repaired reinforced concrete). ) Is also applicable.

  As shown in FIG. 6, in the repaired reinforced concrete 71, when the reinforcing bar 72 expands due to corrosion, peeling occurs at the interface 75 between the concrete 73 and the repair material 74, and cracking occurs when the peeling reaches the surface of the repaired reinforced concrete 71. Will occur.

  Accordingly, not only the physical property values of the concrete 73 but also the physical property values of the repair material 74 (compressive strength, tensile strength, elastic modulus) and repair conditions (the length d of the interface 75, the thickness of the repair material 74, and the adhesion strength) are considered. Therefore, it is necessary to perform FEM analysis.

Therefore, as shown in FIG. 7, the procedure for obtaining the corrosion amount W _cr when cracks occur in the repaired reinforced concrete 71 is the procedure for obtaining the corrosion amount W _cr when cracks occur in the solid concrete described in FIG. In step S21 for inputting the physical property value of the concrete 73 and step S12 for inputting the cover size, step S21 for inputting the physical property value (compressive strength, tensile strength, elastic modulus) of the repair material, Step S22 for inputting repair conditions (length d of interface 75, thickness of repair material 74, adhesion strength) is added. By performing the FEM analysis in consideration of the input values input in steps S21 and S22, it becomes possible to obtain the corrosion amount W _cr when the repaired reinforced concrete 71 is cracked.

  Note that the corrosion area rate input in step S13 may be determined in consideration of the fact that corrosion is unlikely to occur in the reinforcing bars 72 covered with the repair material 74. Specifically, for example, when the repair material 74 covers more than half of the surface area of the reinforcing bar 72, the ratio of the surface area of the reinforcing bar 72 exposed from the repair material 74 may be the corrosion area ratio. Moreover, what is necessary is just to set it as about 15 to 20%, for example, about the corrosion area rate when the repair material 74 has covered the whole rebar 72 (or when substantially the whole rebar 72 is covered).

  In the above embodiment, the corrosion start time of the reinforcing bar is predicted using the Fick diffusion formula, but the method of predicting the corrosion start time of the reinforcing bar is not limited to this. For example, the natural potential method, the polarization resistance method, the concrete You may obtain | require using arbitrary methods, such as a resistance method.

  In the above embodiment, the corrosion rate after the corrosion of the reinforcing bar is measured by the polarization resistance method, but the method of measuring the corrosion rate after the corrosion of the reinforcing bar is not limited to this.

  Examples of the present invention will be described below.

  Table 1 shows a list of materials used for concrete. Table 2 shows the concrete composition.

  A 200 mm × 200 mm × 100 mm reinforced concrete test specimen was prepared using the concrete blends shown in Table 2. Reinforced concrete test specimens were prepared with the number of reinforcing bars (polished steel bar φ16 mm, blast furnace product) being 1, 2 (in the case of two, 50 mm and 100 mm reinforcing bar pitch) and the cover being 30 mm.

The physical property values of the prepared reinforced concrete specimens were as follows.
Compressive strength: 24.05 N / mm ² (material age 7 days), 32.55 N / mm ² (material age 28 days) Static elastic modulus: 26.46 kN / mm ² (material age 28 days)

  Moreover, the repaired reinforced concrete test body was created using the repair material which has the physical property shown in Table 3.

  In Table 3, a primer is an adhesive applied between concrete and a repair material. The repaired reinforced concrete specimen has one rebar, the cover is 30 mm, the interface length between the concrete and the repair material is 20,40 mm, the thickness of the repair material is to the center of the rebar, or to the top of the rebar, with a primer, Created under each condition. The size of the repaired reinforced concrete test specimen was 100 mm × 70 mm × 56 mm for an interface length of 20 mm, and 100 mm × 70 mm × 96 mm for an interface length of 40 mm.

The physical property values of the prepared repaired reinforced concrete specimens were as follows.
Compressive strength: 21.25 N / mm ² (material age 7 days), 31.24 N / mm ² (material age 28 days) Static elastic modulus: 27.71 kN / mm ² (material age 28 days)

  5 surfaces of each test specimen, excluding the surface infiltrated with chloride, are coated with an epoxy resin coating that satisfies the solvent-free epoxy resin paint standards for waterworks (JWWAK157 Japan Waterworks Association standards), and corrosion by electrophoresis Promoted. In addition, about the repaired reinforced concrete test body, the surface of concrete was made into the surface which permeate | transmits a chloride.

  In the electrophoresis method, as shown in FIG. 8, a test body (here, a reinforced concrete test body) 92 is accommodated in a water tank 91 filled with an aqueous chloride ion solution S having a concentration of 3%. The test body 92 is arranged on an installation table 93 installed on the bottom surface of the water tank 91 with the surface that allows the chloride to penetrate (the surface that is not covered with the epoxy resin coating).

  The installation base 93 is provided with a titanium mesh 94 serving as a cathode, and a titanium mesh 96 serving as an anode is provided near the reinforcing bar 95 of the test body 92 (on the side opposite to the surface infiltrating chloride). . This titanium mesh 96 is provided in advance at the time of preparing the test body. A plastic mesh (not shown) is disposed between the titanium mesh 96 and the reinforcing bar 95 so as not to contact each other. The short circuit is prevented.

Both titanium meshes 94 and 96 are connected to a DC power source 97. Here, a voltage of 18 V is applied from the DC power source 97 and a current of 0.07 to 0.1 A is passed between the titanium meshes 94 and 96 to cause chloride ions (Cl ⁻ ) to enter from the concrete 98 surface. The internal rebar was corroded.

  Then, cracks along the reinforcing bars occurred about 14 days after the start of electrophoresis. FIG. 9 shows an appearance of the reinforcing bar 95 taken out from the test body 92 after the occurrence of the crack and etched. As shown in FIG. 9, it was confirmed that corrosion occurred only on the surface side of the reinforcing bar 95 where the chloride penetrates.

  The corrosion of the removed reinforcing bar 95 was evaluated by the corrosion rate of weight change (hereinafter referred to as the corrosion rate), the corrosion amount (per unit reinforcing bar area), and the corrosion area rate. In addition, regarding the corrosion area ratio, as shown in FIG. 9, the corroded portion and the non-corroded portion were divided into black and white, and numerical values were calculated by image analysis. Table 4 shows the evaluation results for the reinforced concrete specimens, and Table 5 shows the evaluation results for the repaired reinforced concrete specimens.

  In the repaired reinforced concrete specimens, unlike the solid reinforced concrete specimens (reinforced concrete specimens), cracks did not occur on the surface infiltrated with chloride, but cracks occurred on the epoxy resin coating surface that is the side of the specimen. This is thought to be because the expansion pressure generated on the concrete side caused interfacial delamination between the concrete and the repair material, and cracks occurred on the epoxy resin coating surface.

  When the repaired reinforced concrete specimen was cracked after cracking, rust due to rebar corrosion was seen at the interface, and it was confirmed that corrosion occurred significantly. Moreover, when the corrosion position on the surface of the reinforcing bar was confirmed, it was confirmed that no corrosion occurred on the repair material side, and corrosion occurred only on the concrete side. In other words, in this test, it was possible to simulate the re-degradation of reinforced concrete, in which chloride ions penetrate from the concrete side and corrode the reinforcing bars.

On the other hand, FEM analysis was performed by inputting the physical property values of the prepared specimens, and the amount of corrosion W _cr when cracking occurred was obtained. At this time, for the reinforced concrete specimen and the repaired reinforced concrete specimen with the repair material thickness up to the center of the reinforcing bar, the corrosion area rate was 50%, and the repaired reinforced concrete specimen with the repair material thickness up to the top of the reinforcing bar was The corrosion area ratio was 16.7%.

Moreover, when carrying out the FEM analysis of the repaired reinforced concrete specimen, the analysis was performed in consideration of the physical properties of the epoxy resin coating provided on the side surface where the crack occurred. The physical properties of the epoxy resin coating were set as follows.
Static elastic modulus E: 4.0 kN / mm ²
Tensile strength f _t: 10N / mm ²
Coating thickness: 1.0mm

Furthermore, the physical properties of the interface between the concrete and the repair material were obtained from two molding circles of compressive strength and tensile strength. The physical properties of the interface between the obtained concrete and the repair material are shown below.
Viscosity coefficient C: 4.52 N / mm ²
Friction coefficient tanφ: 1.67

  The analysis values obtained by the FEM analysis are also shown in Tables 4 and 5.

As shown in Table 4, the analysis value in the reinforced concrete specimen was in good agreement with the experimental value, and it was found that the analysis value was closer to the actual measurement value than the conventionally used numerical value (10 mg / cm ² ). Further, when the influence of the reinforcing bar pitch was examined, the corrosion amount of the analysis value was 22.3 mg / cm ² , and it was found that the corrosion amount was not affected when the reinforcing bar pitch was about 50 mm. Therefore, it was confirmed that the prediction accuracy of the amount of corrosion at the time of cracking was improved by obtaining the amount of corrosion at the time of cracking by using FEM analysis.

  On the other hand, as shown in Table 5, in the repaired reinforced concrete specimen, the experimental value and the analytical value showed relatively good agreement for the specimen with the interface length of 20 mm and the repair material thickness up to the center of the reinforcing bar. For the specimen with an interface length of 20 mm and the thickness of the repair material up to the top of the reinforcing bar, the analytical value of the corrosion rate and the corrosion amount was about twice as large. This is thought to be because the corrosion area ratio increased in the experiment, corrosion occurred in a wide range, and the expansion pressure due to corrosion was widely dispersed. Therefore, when the FEM analysis is performed, if the corrosion area ratio is set high according to the actual phenomenon, the experimental value and the analysis value are considered to be close to each other.

  Further, for the test body having an interface length of 40 mm and a repair material thickness up to the center of the reinforcing bar, the corrosion rate and the corrosion amount were about 4 times larger in the experimental values. This is thought to be because peeling occurred between the concrete and the repair material, and corrosion products flowed out during that time. In this experiment, the side of the specimen was coated with an epoxy resin coating, and the static elastic modulus of the epoxy resin coating was lower than that of concrete and the tensile strength was higher than that of concrete. It is considered that the amount of corrosion until cracks occur on the surface of the epoxy resin coating is increased. Actually, it can be seen from the FEM analysis results that the separation between the concrete and the repair material occurs even if the amount of corrosion is relatively small.

From the above results, according to the present invention for predicting the amount of corrosion at the time of occurrence of cracks by FEM analysis, the amount of corrosion at the time of occurrence of cracks that is closer to the actual value than the conventionally used value (10 mg / cm ² ) is obtained. It can be seen that the crack occurrence time of reinforced concrete can be accurately predicted.

DESCRIPTION OF SYMBOLS 1 Reinforced concrete life evaluation apparatus 2 Reinforced concrete characteristic input part 3 Analysis part 4 Memory | storage part 5 Corrosion characteristic input part 6 Life prediction part 7 Output part

Claims (5)

Life of reinforced concrete that predicts the crack initiation time of reinforced concrete based on the corrosion initiation time of the reinforcement, the corrosion rate after the occurrence of corrosion, and the amount of corrosion at the time of crack occurrence, which is the amount of corrosion of the reinforcement when cracks occur on the concrete surface An evaluation method,
FEM analysis of the reinforced concrete is performed, a virtual temperature imitating the corrosion of the reinforcing bar is applied to the reinforcing steel of the reinforced concrete, and the FEM analysis of the reinforced concrete is performed when the reinforcing bar is virtually expanded, Calculate the virtual temperature when cracks occur on the concrete surface of the reinforced concrete, and calculate the amount of corrosion when cracks occur based on the calculated virtual temperature,
A method for evaluating the life of a reinforced concrete, comprising predicting the crack occurrence time of the reinforced concrete based on the obtained corrosion amount at the time of crack occurrence, the corrosion start time of the rebar, and the corrosion rate after the corrosion occurs. The calculation of the amount of corrosion at the occurrence of the crack is
Based on the hypothetical temperature Δt when cracks occur on the concrete surface, the radius r before corrosion of the reinforcing bar, and the linear expansion coefficient a of the reinforcing bar, the following formula (1)
r _d = a × r × Δt + r (1)
A result, the seek radius r _d rebar inflated virtually, the following equation (2)
β = (πr _d ² −πr ² ) / πr ² × 100 (2)
Thus, the reinforcing bar expansion coefficient β is obtained, and based on the obtained reinforcing bar expansion coefficient β and the preset volume expansion coefficient α, the following equation (3)
Δx = {(1 + β / 100) ^1/2 −1} / (α ^1/3 −1) (3)
Thus, the corrosion depth Δx is obtained, and based on the obtained corrosion depth Δx and the density ρ of the reinforcing bar, the following equation (4)
W _cr = Δx × ρ (4)
The method for evaluating the life of reinforced concrete according to claim 1, which is carried out by _calculating the corrosion amount W _cr when cracking occurs.   A corrosion area ratio that is a ratio of the area of the corrosion portion to the total surface area of the reinforcing bars is set in advance, and only a part of the reinforcing bars corresponding to the corrosion area ratio is virtually expanded to perform the FEM analysis. The life evaluation method of the reinforced concrete of Claim 1 or 2 made to do.   The corrosion rate after the said corrosion is a lifetime evaluation method of the reinforced concrete in any one of Claims 1-3 calculated | required by the polarization resistance method. Life of reinforced concrete that predicts the crack initiation time of reinforced concrete based on the corrosion initiation time of the reinforcement, the corrosion rate after the occurrence of corrosion, and the amount of corrosion at the time of crack occurrence, which is the amount of corrosion of the reinforcement when cracks occur on the concrete surface An evaluation device,
FEM analysis of the reinforced concrete is performed, a virtual temperature imitating the corrosion of the reinforcing bar is applied to the reinforcing steel of the reinforced concrete, and the FEM analysis of the reinforced concrete is performed when the reinforcing bar is virtually expanded, Obtaining a virtual temperature when cracks occur on the concrete surface of the reinforced concrete, and an analysis unit that calculates the amount of corrosion when cracks occur based on the calculated virtual temperature;
A life prediction unit for predicting the crack occurrence time of the reinforced concrete based on the amount of corrosion at the occurrence of cracks obtained by the analysis unit, the corrosion start time of the rebar, and the corrosion rate after the occurrence of corrosion. Characteristic equipment for evaluating the life of reinforced concrete.

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