JP2005049217A - Rusting time estimating method, reinforcing steel corrosion rate estimating method and reinforcing steel corrosion estimating method of reinforcing steel in reinforced concrete, and durability diagnosing method of reinforced concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accurately estimating reinforcing steel corrosion in reinforced concrete on various environmental conditions such as an underground structure and a method for diagnosing durability of the reinforced concrete based on the reinforcing steel corrosion in comparison with an existing method for estimating a corroded area on a surface of the reinforcing steel in the reinforced concrete at a location such as an aboveground structure easily examined. <P>SOLUTION: In an experiment, the reinforcing steel is discovered to rust at high humidity even although neutralization of the concrete does not proceed. A method for calculating a rusting time of the reinforcing steel is discovered by determining a difference α between a neutralization depth of the concrete rusted by the humidity and a covering depth determined from the experiment. A method for estimating a loss rate in weight by the rust after a start of the rust is found by determining the fact that a reinforcing steel corrosion rate is high if the humidity is high and determining the corrosion rate from the experiment. The method diagnoses the durability of the reinforcing concrete based on the loss rate in weight by the rust in the concrete determined from the result. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to corrosion evaluation of reinforcing steel in reinforced concrete, and more particularly to durability evaluation of reinforced concrete based on the corrosion weight loss ratio.

  There has been a method for evaluating the durability of reinforced concrete.

  Measure the neutralization depth and corrosion rate at a certain time, or measure the corrosion rate at two times, and apply an estimated time constant to the corrosion amount time calendar function in advance to determine an unknown constant. A function is obtained and estimation is performed. (For example, Patent Document 1) However, in order to determine the time calendar function of the corrosion amount, there is only a method of actually measuring the neutralization depth and the corrosion rate after the reinforcing bar starts to rust, and there are great restrictions on application. It is not possible to evaluate the phenomenon in which the corrosion rate of the reinforcing bars is increased and the corrosion rate is increased after moisture and oxygen are easily supplied after cracks are generated. The corrosion rate varies depending on the site, and the impact of the entire building cannot be evaluated. Although the amount of corrosion is estimated, the durability has not been evaluated.

  Estimate the degree of corrosion of reinforcing bars by using formulas obtained from actual measurements using parameters such as concrete cover depth, neutralization depth, total chloride content, cracks, temperature, annual precipitation, and humidity. There is an evaluation method to do. (For example, Patent Document 2) Since a neural network is used, accuracy cannot be ensured unless a large number of actual measurement data is collected, and no coefficient for estimation is shown. In other words, it is a method of estimating with statistical data, but the life of reinforced concrete is very long from 50 to 200 years, and it is difficult to collect statistical data on existing buildings itself, so it should be implemented immediately I can't.

  There are methods and diagnostic devices for evaluating the corrosion degree of reinforcing bars from the natural potential, the salt content, the moisture content, and the carbonation depth of concrete. Although the amount of corrosion can be measured (for example, Patent Document 3), it is impossible to estimate the future corrosion rate or the life of reinforced concrete.

  In order to investigate the corrosion rate of reinforcing steel in concrete due to neutralization, two types of water-cement ratio specimens were produced, and the accelerated neutralization test and the watering accelerated neutralization test were conducted to examine the amount of corrosion of the reinforcing bar. The progress of rebar corrosion with the progress of neutralization is predicted by building a model of rebar corrosion due to neutralization and combining the method for predicting the progress of neutralization. (For example, Non-Patent Document 1) It has been experimentally known that the neutralization rate of concrete becomes slower as the moisture content of the concrete increases. As for the corrosion rate, the size of the specimen was too small, so the conditions with the structure did not match, and the corrosion model could not be applied to a general structure.

Conventionally, there has been a method for evaluating the life using the corrosion probability of reinforcing steel in reinforced concrete. (For example, Non-Patent Document 2) From the survey of the building, the cover thickness and neutralization depth when the average value of the rust rating of the reinforcing bar is 3 (corrosion grade III, equivalent to the surface rusting of the reinforcing bar) To understand the relationship between indoors and outdoors. Cover thickness and neutralization depth can be regarded as normal distributions, so obtain the normal distribution of these differences and integrate from minus infinity to the difference between the cover thickness and neutralization depth at which the rust rating of the reinforcing bar is 3. The corrosion probability is obtained and the durability is evaluated. This method is based on extensive survey results of ground structures, and is highly relevant for ground structures, but the cover thickness and neutralization depth at the time of rusting under environmental conditions such as wet parts of underground structures. If the relationship (rusting conditions) and the corrosion rate differ, a large error will be produced. Furthermore, since the corrosion is captured by the corrosion probability, that is, the corrosion area, the corrosion amount of the reinforcing bars cannot be evaluated.
Conventionally, rusting in reinforced concrete was supposed to occur when neutralization progressed to the cover depth. However, there is a case where the difference in neutralization depth is 10 mm as a calculation standard. (For example, Non-Patent Document 3) The reason for setting the neutralization residue to 10 mm was that there were almost no examples of serious corrosion that would cause the structure to lose its function even if it was corroded. It was found that it did not rust up to 5mm depending on the conditions. However, since the cover thickness and the neutralization depth vary, at sites where the cover thickness is smaller than the average and the neutralization depth is greater than the average value, rusting occurs early and the corrosion rate is determined by the environmental conditions. Corrosion progresses more and more. If the corrosion rate is high, the amount of corrosion becomes considerable and the risk side is evaluated.
Research results of making a specimen with a 70% water cement ratio, which is more likely to rust than general concrete, and comparing the corrosion limit of rebar due to neutralization with the neutralization depth measured by the phenolphthalein method Also exist. (For example, Non-Patent Document 4)
Some studies have conducted experiments on the corrosion rate of reinforcing steel in concrete containing chlorides, and derived an equation for estimating the corrosion rate. (For example, Non-Patent Document 5) Although the corrosion rate of reinforcing steel bars due to chloride occurs at a high stage, an estimation formula for the corrosion rate of reinforcing steel bars due to the neutralization of concrete that occurs in a general environment is not obtained.
Some studies have investigated the reinforced concrete structures in the marine environment regarding the corrosion of reinforcing steel bars caused by salinity, and derived the life prediction formula. (For example, Non-Patent Document 6) Concrete life prediction is not performed for reinforcing steel corrosion due to neutralization of concrete that occurs in a normal place other than the marine environment.

  In order to evaluate the effects of corrosion of reinforcing bars on the durability and water tightness of RC structures, there are cases where the corrosion of reinforcing bars was promoted by an electric corrosion test to study the relationship between the amount of corrosion and the hydraulic conductivity. . (For example, Non-Patent Document 7) As a result, the cracking limit corrosion amount has been investigated.

There are also examples in which neutralization, which is one of the factors that promote reinforcement corrosion in concrete, is conducted under various environmental conditions. (For example, Non-Patent Document 8) Although detailed experiments have been conducted on the neutralization of concrete, no experiments have been conducted on rebar corrosion.
Japanese Patent Laid-Open No. 2002-98660 JP-A-10-21211 JP-A-9-329568 Saeki, “Quantitative evaluation of rebar corrosion in mortar by neutralization”, Journal of Japan Society of Civil Engineers, No.532 / V-30, February 1996, p.55-66 Izumi et al., "Study on durability improvement technology by reliability design of rebar cover thickness, part 1-part 3," Architectural Institute of Japan Annual Meeting Summary, January 1984 Japan Society of Civil Engineers Established in 2002 "Concrete Standard Specification [Construction]" Kishitani et al., "Study on corrosion of reinforcing steel in concrete," Architectural Institute of Japan Proceedings, September 1979, p.11-15 Hamada et al., “Experiment on Rebar Corrosion Rate in Concrete Containing Chloride”, Architectural Institute of Japan, 435 May 1992, p.19-27 Morinaga et al., “Life prediction of reinforced concrete structures due to corrosion”, Proceedings of Concrete Engineering, Vol. 1, No. 1, January 1990, p.177-188 Sakaguchi et al., “Corrosion and Permeability of Reinforcing Bars by Electrical Tests”, 50th Annual Conference of Japan Society of Civil Engineers, V-139, September 1995, p.278-279 Abe et al., "Study on evaluation of accelerated neutralization test method for concrete", Architectural Institute of Japan Structural Papers, No.409, March 1990, p.1-10

  Although there was a method for estimating the surface corrosion area of reinforced concrete in reinforced concrete in places where surveys are relatively easy to perform, such as underground buildings, the amount of reinforced corrosion in reinforced concrete under various environmental conditions such as underground structures is accurate. There was no method to estimate well and to make a durability diagnosis of reinforced concrete based on the amount of corrosion of reinforcing bars.

In the present invention, after accelerating the neutralization of reinforced concrete, which actually takes time, the three factors of "temperature", "humidity" and "reinforced concrete cover depth" are important factors for the life of reinforced concrete. The experiment was conducted. From this experiment, we found that the rebar in the concrete rusts even when the concrete is not neutralized as the humidity increases, and the difference in the neutralization depth of the rusted concrete due to the humidity is parameter α. We found out a method to calculate the rusting time of reinforcing steel in reinforced concrete obtained from experiments. Furthermore, it was discovered that the higher the relative humidity at the reinforcing bar position in the concrete, the faster the corrosion rate of the reinforcing bar in the reinforced concrete, and the corrosion rate due to the relative humidity at the reinforcing bar position in the concrete was determined by experiment. I found a way to calculate the corrosion weight loss ratio.
The present invention is a method for diagnosing the durability of reinforced concrete based on the estimation of the rebar corrosion weight loss ratio over time after completion based on this result.

  By using the present invention, it becomes possible to estimate the amount of corrosion of reinforcing steel in the concrete and the durability diagnosis of reinforced concrete from the concrete cover depth obtained from design data and the humidity estimation data in the concrete without performing measurement as in the past, Even in places where detailed measurements from the outside of concrete such as underground structures are difficult, it is possible to estimate the amount of corrosion of reinforcing steel in the concrete and diagnose the durability of reinforced concrete.

Since the neutralization rate of concrete due to humidity has already been shown in Non-Patent Document 1, an acceleration test was conducted on the neutralization of concrete in order to shorten the experimental period. The concrete mix was the same as that of general structures (60% water cement ratio). The shape and dimensions of the specimen are shown in FIG. The shape of the specimen is 15 × 13.5 × 50 cm, and the polished steel bar Φ12 mm is embedded in the concrete with a concrete cover depth of 5 to 35 mm in 5 mm increments. The test specimens were placed in a neutralization promotion chamber at 20 ° C, 60% RH, CO ₂ 5% after air-drying curing, and neutralization was promoted to a neutralization depth of 25 mm.

  After completion of the neutralization promotion test, the specimen is removed from the neutralization promotion chamber, and 10 ° C / 30% RH assuming winter, 20 ° C / 60% RH assuming spring / autumn, and 35 ° C assuming summer Exposure was performed under four environmental conditions of 80% RH and 20 ° C. and 100% RH (immersion in water) assuming a wet part. Exposure is carried out for 12 months, before neutralization, neutralization 12mm, neutralization 25mm, 3 months after exposure, 12 months after exposure, neutrality of concrete by phenolphthalein method of JIS A 1152 (2002) We measured the rate of weight loss after removing the rust of the reinforcing bars with chemicals. The test specimen was provided with pores as shown in FIG. 2, and a sensor was inserted to measure the relative humidity at the position of the reinforcing bar in the concrete. The result of the weight loss rate is shown in the graph of FIG. The relationship between the relative humidity at the position of the reinforcing bar in the concrete and the corrosion area ratio of the reinforcing bar is the same as the neutralization depth of the concrete, but the corrosion of the reinforcing bar in the concrete rusts when the humidity increases. It was discovered that Next, the environmental humidity was exposed at 85, 90, and 95%, and the effects on the relative humidity at the position of the reinforcing bar in the concrete and the rusting depth of the reinforcing bar were investigated. As a result, the environmental humidity and the relative humidity at the position of the reinforcing bar in the concrete are almost the same, and at a relative humidity of 85% and 90% at the reinforcing bar position in the concrete, the reinforcing bar 5mm deep from the neutralization depth is corroded. However, it was found that the reinforcing bar 10 mm deeper than the neutralization depth was rusted at 95% relative humidity at the reinforcing bar position in the concrete.

  Regarding the rusting condition of reinforcing bars, in Non-Patent Document 4, when rusting of reinforcing bars is determined by neutralization, the portion 6 to 8 mm deeper than the neutralization depth by the phenolphthalein method is the rusting limit of reinforcing bars. In Non-Patent Document 1, the corrosion status of the reinforcing bar in the test specimen neutralized while in the air and watering was investigated, and when neutralization progressed to 5 mm before the cover thickness under any conditions. Rust has been reported. As described above, it is a well-known fact that corrosion of a reinforcing bar starts before the neutralization depth reaches the reinforcing bar position. However, when the relative humidity at the rebar position in concrete is as high as 95% or more, it was found by experiments that the position of the rebar that rusts becomes deeper than when the humidity is less than 95%. Fig. 4 shows an example. Even when the neutralization depth is the same, when the humidity is 100%, it rusts to deeper reinforcing bars than when the humidity is 80%, 60%, and 30%. It is necessary to determine the rusting condition of the reinforcing bar in consideration of the relative humidity at the reinforcing bar position in the concrete in addition to the relationship between the neutralization depth and the covering thickness of the reinforcing bar.

  Regarding the progress of neutralization of concrete, the calculation formula for the neutralization rate in the dry section is Cd = A√Td, where Cd is the neutralization depth, A is the neutralization rate coefficient, and Td is the duration. . A is called the neutralization rate coefficient, and in general, the progress of neutralization is often confirmed by field surveys, so the age T at the time of survey and the average value C of the measured neutralization depth are And can be obtained by A = C / √T. When the field survey is not conducted, various prediction formulas are shown, which can be used for estimation.

  However, it is necessary to reduce the neutralization rate coefficient in consideration of the fact that neutralization does not proceed easily when the environmental humidity and the moisture content of concrete are high. If the coefficient is β (0 <β <1), the neutralization depth Cw and the period Tw are as follows.

Aを中性化速度係数と呼び、一般的な乾燥条件（温度15〜25℃、湿度50〜70%）で様々な実験により、岸谷式、和泉式等の予測式が示されている。

A is called the neutralization rate coefficient, and various experiments under typical drying conditions (temperature of 15 to 25 ° C. and humidity of 50 to 70%) have shown prediction formulas such as Kishitani and Izumi formulas.

  The value of the coefficient β has the following various report examples, and should be set based on the state of the structure and actual measurement data. According to Non-Patent Document 1, when the water is continuously wet and dry for 3 hours a day, β = 0.3 to 0.5 is reported. In the case of single-sided drying, β = 0.5 to 0.7 is obtained by experiments.

  According to Non-Patent Document 2, if the outdoor exposure to wind and rain is 1.0, 1.7 indoors (0.51 indoors if indoors 1) is obtained.

  The influence coefficient that the environmental humidity has on the neutralization rate coefficient is also shown in Non-Patent Document 8, where the neutralization rate coefficient of 60% humidity is used as a reference, and the ratio β is β = Hu (100 -Hu) (140-Hu) / 192000. Β = 0.5 at 80% environmental humidity. When extrapolating the environmental humidity 90,95% (experiment range is humidity 40-80%), β = 0.23 and 0.11.

Difference in neutralization depth of rusting due to relative humidity at the location of reinforcing bars in concrete is less than 95% humidity by this experiment: Neutralization depth + 5 mm
Humidity 95% or more: Neutralization depth + 10mm
It can be expressed. Therefore, the rusting time of the reinforcing bars in the concrete is

となる。

It becomes.

  As for the corrosion rate of the reinforcing bar, it was found from experiments that the higher the relative humidity RH at the reinforcing bar position in the concrete, the higher the rate, which is inversely proportional to the cover thickness C and proportional to the reinforcing bar diameter φ. The results of multiple regression analysis with the corrosion rate v as the objective variable and the explanatory variables as φ / C, RH, and the interaction φ / C × RH between φ / C and RH are shown in FIG. As explanatory variables, φ / C and φ / C × RH were selected, and from the multiple regression equation, the following equation was obtained indicating that the higher the humidity and the smaller the cover thickness, the higher the corrosion rate.

(2)式は一般的な塩化物量の範囲で実験した結果得られた式であるため、塩化物量が非常に多い場合は正しく推定できない場合がある。

Since equation (2) is an equation obtained as a result of experiments in a general chloride content range, it may not be able to be estimated correctly when the chloride content is very large.

  Regarding the influence coefficient γ of temperature, material, and blending for the reference concrete, when the water cement ratio is other than 60%, use the Morinaga formula to calculate the corrosion rate ratio for the water cement ratio of 60% (2 It is good to reflect by multiplying the formula. When the temperature is particularly high, it is better to calculate the reaction rate constant ratio with respect to the reference temperature (about 20 ° C) by the Arrhenius equation and to reflect the influence of the temperature in the equation (2).

  The method of calculating the amount of corrosion using statistics will be shown.

となる。中性化深さのばらつきは正規分布であると考えられるので、材齢tの中性化深さの正規分布は

It becomes. Since the variation in neutralization depth is considered to be a normal distribution, the normal distribution of the neutralization depth of the age t is

で表される。同様に鉄筋のかぶり深さの正規分布は

It is represented by Similarly, the normal distribution of rebar cover depth is

で表される。従って鉄筋のかぶり深さと中性化深さの差の分布も正規分布となり

It is represented by Therefore, the distribution of the difference between the cover depth and the neutralization depth of the reinforcing bar is also a normal distribution.

で表される。よって鉄筋のかぶり深さと中性化深さの差の正規分布は

It is represented by Therefore, the normal distribution of the difference between the cover depth and the neutralization depth is

と表される。発錆する条件は(1)式のαと同じで鉄筋のかぶり深さと中性化深さの差がα以下になった部分が発錆することになる。従って分布関数のα以下の面積が鉄筋腐食確率P(t)となるので、

It is expressed. The conditions for rusting are the same as α in the equation (1), and the portion where the difference between the cover depth of the reinforcing bar and the neutralization depth is less than α is rusted. Therefore, the area below α in the distribution function is the reinforcing bar corrosion probability P (t).

と表される。
図6は経年により中性化が進行してゆくときの(3)式で求められる腐食確率の変化を示したもので、腐食面積の面から評価すると中性化が進行しやすい乾燥部は湿潤部より腐食確率はかなり大きくなる。
図7に腐食確率と腐食減量比の関係を示す。腐食を腐食減量で評価するには以下のように考えると良い。ある時刻t_iから時間増分Δtの間に新たにΔP_iだけ発錆し、この発錆した部位は経年とともに腐食速度v_iで腐食してゆく。時刻T_Aある時間増分の腐食量は

It is expressed.
Fig. 6 shows the change in the probability of corrosion obtained by equation (3) when neutralization progresses over time, and the dry part where neutralization is likely to progress is wet when evaluated from the aspect of the corrosion area. Corrosion probability is considerably larger than the part.
Figure 7 shows the relationship between the corrosion probability and the corrosion weight loss ratio. To evaluate corrosion by corrosion weight loss, the following should be considered. Rust is newly rusted by ΔP _i during a time increment Δt from a certain time t _i , and the rusted portion corrodes at a corrosion rate v _i with the passage of time. Corrosion of the time T _A is the time increment

で表される。各時間増分を総和することにより、全体の腐食減量比Q(T_A)が求められる。

It is represented by The total corrosion weight loss ratio Q (T _A ) is obtained by summing up each time increment.

一般的な構造物をモデルとして本発明を用いて腐食減量比を求め、腐食減量比による鉄筋コンクリートの劣化度評価を以下のように設定した（実施例１、２参照）。コンクリート中の鉄筋の腐食減量比が0.1％以上0.5％未満の時は、鉄筋の腐食減量としては比較的少なく、目視点検または簡易な点検により健全性の確認を行えばよい状況で「軽微」な劣化と判定できる。腐食減量比が0.5以上2%未満となると、鉄筋の腐食が進んでいるため、ひびが発生している可能性が高く鉄筋コンクリートへの延命処置が必要となるので、詳細な調査に基づいて延命処置を行うことが望ましい段階となる。この時点を劣化度評価「中」とした。腐食減量比が2％以上になった場合強度上重大な影響を及ぼすため補強策が必要になる。この時点を劣化度評価「大」すなわち鉄筋コンクリートの寿命とした。

The corrosion weight loss ratio was determined using the present invention using a general structure as a model, and the deterioration evaluation of reinforced concrete based on the corrosion weight loss ratio was set as follows (see Examples 1 and 2). When the corrosion weight loss ratio of the reinforcing steel in the concrete is 0.1% or more and less than 0.5%, the corrosion weight loss of the reinforcing steel is relatively small. It can be determined as degradation. If the corrosion weight loss ratio is 0.5 or more and less than 2%, the corrosion of the reinforcing bars is progressing, so there is a possibility that cracks are likely to occur, and it is necessary to extend the life of the reinforced concrete. It is a desirable stage to perform. This point in time was evaluated as “medium”. If the corrosion weight loss ratio is 2% or more, it will have a significant effect on strength, so reinforcement measures will be required. This time point was regarded as the deterioration degree evaluation “large”, that is, the life of the reinforced concrete.

  For general concrete (60% water cement ratio) and the humidity in the concrete is 60 to 100%, the corrosion amount of the reinforcing bars is estimated.

Neutralization rate coefficient A at 60% RH, average value 4.0 mm√year,
Coefficient of variation 30%, cover thickness average value 40mm, standard deviation 10mm,

鉄筋径12mm、αはコンクリート中の湿度95%未満5mm、95%以上10mm、βは既往のデータを参考に安全側の値として湿度60% RHを基準として、80%RHでβ=0.7、90%RHでβ=0.5、100%RHでβ=0.4として腐食量を推定する。

Reinforcing bar diameter 12mm, α is less than 95% humidity in concrete 5mm, 95% to 10mm, β is a safe value with reference to past data, humidity is 60% RH, 80% RH, β = 0.7, 90 Estimate the amount of corrosion with β = 0.5 at% RH and β = 0.4 at 100% RH.

  Assuming that neutralization proceeds according to the √T rule over time, the corrosion probability is determined in time steps using equation (3), and the result is shown in FIG. 8-A.

  Multiply the corrosion probability increment ΔPi of each time step by the number of years, and then multiply by the corrosion rate obtained sequentially from the average cover thickness of the newly rusted reinforcing bar. Can be requested. The result is shown in Figure 8-B.

  At a humidity of 100%, the progress of neutralization is slow and the corrosion probability (corrosion area rate) is small, but the corrosion weight loss ratio is the maximum, and it can be estimated that the partial rebar has a large defect. At each time step, the average corrosion weight loss of the corroded part is obtained by dividing the corrosion weight loss ratio by the corrosion probability, and the horizontal axis shows the corrosion probability. It can be clearly seen that the weight loss varies greatly. That is, the durability evaluation is difficult only by the corrosion probability, and it is necessary to evaluate the progress of corrosion of the reinforcing bars, that is, the corrosion weight loss. According to the present invention, it is possible to directly evaluate the durability of the structure by accurately estimating the corrosion weight loss. Table 2 shows the estimated years of the results of calculations for durability evaluation.

  The amount of corrosion is estimated under the same conditions as in Example 1 for concrete with a water-cement ratio of 55%.

  Regarding the neutralization rate coefficient, if there is an actual measurement value, the neutralization rate coefficient may be obtained from the actual measurement value and used. Here, using the Kishitani formula, which is one of the existing neutralization prediction formulas, the ratio of the neutralization rate coefficient of 55% water cement ratio to 60% water cement ratio is calculated.

となる。

It becomes.

  As for the corrosion rate, γ may be set by using knowledge about the influence of the mixing of conventional concrete on the corrosion rate. For example, if the equation shown in Non-Patent Document 6 is graphed, it is as shown in FIG. It is better to use about 0.8 from the graph of FIG. Multiplying the corrosion rate estimation formula (2) by 0.8,

とし、実施例１と同様に腐食減量比を求めた。腐食確率の経年変化、腐食減量比の経年変化および腐食確率と平均的な腐食量の関係が得られた。計算結果を図10A-Cに示した。

The corrosion weight loss ratio was determined in the same manner as in Example 1. The relationship between the corrosion probability and the corrosion weight loss ratio and the correlation between the corrosion probability and the average corrosion amount was obtained. The calculation results are shown in FIGS. 10A-C.

  Table 3 shows the estimated years of the results of the durability evaluation.

The shape and dimensions of the test body will be described. A method for measuring the internal humidity of the concrete will be described. The experimental result about the time-dependent change of the weight reduction rate of a reinforcing bar is shown. The relationship between the cover thickness and the corrosion rate is shown. The relationship between cover thickness, humidity and corrosion rate is shown. The concept of the secular change of corrosion probability is shown. The concept of the relationship between the corrosion probability and the total corrosion amount is shown. The result of Example 1 is shown. The result of Example 1 is shown. The result of Example 1 is shown. The comparison of the corrosion rate by water cement ratio is shown. The result of Example 2 is shown. The result of Example 2 is shown. The result of Example 2 is shown.

Claims (5)

The parameter α, which indicates the difference between the concrete cover depth that rusts due to the humidity in the concrete and the neutralization depth, is 5 mm when the relative humidity at the rebar position in the concrete is 0% or more and less than 95%, and is 95% or more and 100%. Rusting is characterized by calculating the rusting time of reinforcing steel in reinforced concrete according to the depth of cover from the concrete surface using the following formula (1) using 10mm when% or less Time estimation method.

A method for estimating the corrosion rate of a reinforcing bar, comprising calculating the corrosion rate of the reinforcing bar using Equation (2) using the relative humidity at the position of the reinforcing bar in the concrete, the diameter of the reinforcing bar, and the cover thickness of the reinforcing bar.

Considering the normal distribution of the difference between the steel cover depth and the neutralization depth of the structure, set the rusting time when neutralization proceeds using the parameters α and β according to claim 1, Corrosion weight loss ratio according to time increment is calculated using equation (3) for calculating the probability P (t) of rusting due to the progress of crystallization, and the corrosion rate and elapsed time from the time of rusting in (2). A method for estimating the amount of corrosion of reinforcing steel in reinforced concrete, characterized by calculating using an equation.

A method for diagnosing durability of a reinforced concrete, comprising evaluating the durability of the reinforced concrete based on the number of years until the predetermined corrosion weight loss ratio is obtained based on the corrosion weight loss ratio of the reinforcing bars obtained according to claim 3. In claim 4, when the corrosion weight loss ratio is 0.1% or more and less than 0.5%, it is judged as “a state that is confirmed by visual inspection or simple inspection”, and when it is 0.5% or more and less than 2%, “inspection diagnosis is performed and appropriate Durability of reinforced concrete characterized in that it is judged as “necessary to extend the life” and when it is 2% or more, it is judged as “a state that requires detailed inspection and extensive repairs to extend the life” Diagnosis method.

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