Method and program for predicting the useful life of existing buildings

Abstract

The present invention provides a versatile and simple method for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete, based on the neutralization of concrete. [Solution] A method for predicting the service life of existing reinforced concrete and steel-reinforced concrete buildings based on the carbonation of concrete includes steps (1) to (3). Step (1): Neutralization depth values ​​at multiple survey locations obtained from a concrete survey of an existing building are arranged in ascending order, and a representative value Cr of the carbonation depth is identified from the 50th to 100th percentile range. Step (2): The representative value Cr of the carbonation depth and the number of years elapsed from completion of construction to the concrete survey, t, are substituted into the formula Ar=Cr / √t to calculate a representative value Ar of the carbonation rate coefficient. Step (3): The representative value Ar of the carbonation rate coefficient and the concrete cover thickness D over the reinforcing bars are calculated using the formula T=D 2 / Ar 2 and calculate the useful life T from completion.

Description

[Technical field]

[0001] The present disclosure relates to a method and program for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete based on the neutralization of concrete. [Background technology]

[0002] Concrete reacts with carbon dioxide in the air and gradually neutralizes from the surface exposed to the air toward the inside. When the carbonation of concrete reaches the reinforcing bars, the rust-preventive effect of the reinforcing bars is lost, and they may corrode. Therefore, predicting the time it takes for the carbonation of concrete to reach the outermost reinforcing bars can be used to predict the service life of existing reinforced concrete and steel-reinforced concrete buildings.

[0003] It is known that the progress of carbonation of concrete starting from the surface in contact with air is proportional to the square root of time, and is called the "√t law." The carbonation depth of concrete when following the √t law is expressed by the formula C=A√t (where C is carbonation depth (mm), A is carbonation rate coefficient (mm / √year), and t is elapsed time (years)).

[0004] If we rearrange the above equation for carbonation depth with respect to the elapsed time t, we get the carbonation rate equation t=C 2 / A 2 By substituting the concrete cover thickness for the rebar into "C" in this formula and an appropriate value into "A," the time "t" required for the carbonation of the concrete to reach the outermost rebar can be calculated. The challenge here is to determine an appropriate value for the carbonation rate coefficient "A."

[0005] The carbonation rate coefficient is determined by the materials and mix of concrete, as well as the environmental conditions to which concrete is exposed. To date, attempts have been made to estimate the carbonation rate coefficient with high accuracy, and various carbonation rate equations have been proposed. For example, the Kishitani formula and the Hakusan formula, which are representative examples of carbonation rate equations, are shown below.

[0006] Kishitani style: t=0.3(1.15+3Wc) / R 2 (Wc-0.25) 2 C 2 Wc ≥ 0.6 t=7.2 / R 2 (4.6Wc-1.76) 2 C 2 Wc≦0.6 t: time (years), C: carbonation depth (cm), Wc: water-cement ratio, R: carbonation ratio

[0007] Hakusan style: t=αβγδε·5000 / (Wc-38) 2 C 2 t: time elapsed (years), C: carbonation depth (cm), Wc: water-cement ratio (%), α: coefficient due to aggregate and admixture, β: coefficient due to cement, γ: coefficient due to degree of construction, δ: coefficient due to finish, ε: coefficient due to indoor and outdoor

[0008] In the Kishitani or Hakusan formula, by substituting the thickness of concrete covering the reinforcing bars for "C" and substituting appropriate values ​​for the variables and coefficients in the formula, the time "t" required for the carbonation of the concrete to reach the outermost reinforcing bars can be calculated. However, the variables and coefficients that make up the Kishitani or Hakusan formulas are difficult to know unless the building is designed or detailed architectural records are available. Therefore, the Kishitani and Hakusan formulas are difficult to apply to existing buildings that have been constructed for a long time.

[0009] Attempts are also being made to develop methods for predicting the service life of existing buildings from the carbonation depth of concrete. For example, Patent Document 1 discloses a "method for predicting the remaining service life of an existing building." Patent Document 2 discloses a "method for predicting the remaining service life of an existing reinforced concrete structure." [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2020-012710 A [Patent Document 2] Patent Publication No. 2022-092975 Summary of the Invention [Problem to be solved by the invention]

[0011] The "method of predicting the remaining lifespan of an existing building" disclosed in Patent Document 1 is targeted at existing buildings that have decorative building material finishing surfaces, and the existing buildings to which it can be applied are limited. The "method of predicting the remaining useful life of an existing reinforced concrete structure" disclosed in Patent Document 2 calculates the remaining useful life of each of multiple survey locations, and predicts the minimum value of these as the remaining useful life of the existing reinforced concrete structure. In doing so, it is necessary to distinguish the multiple survey locations into shallow neutralized locations and deep neutralized locations, and apply separate equations to the former and the latter to calculate the remaining useful life for each. As such, the "method of predicting the remaining useful life of an existing reinforced concrete structure" disclosed in Patent Document 2 is a complicated prediction method.

[0012] It is against the above background that the present disclosure has been made. An objective of the present disclosure is to provide a versatile and simple method for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete, based on the neutralization of concrete. [Means for solving the problem]

[0013] In order to predict the service life of existing buildings from information on the carbonation depth obtained by concrete surveys, the inventors have studied how to estimate the carbonation rate coefficient that constitutes the carbonation rate equation under the assumption that concrete carbonation follows the √t law. While measuring the carbonation depth of concrete in many existing buildings, the inventors have faced the difficulty of estimating the carbonation rate coefficient by theoretically or empirically accumulating factors involved in the carbonation of concrete in buildings that have been in operation for several decades. For example, there are cases where it is assumed that the thickness of the base mortar contributes to suppressing carbonation (see Building A in the example described below, left diagram in Figure 2), while there are cases where it is assumed that the thickness of the base mortar is not related to the degree of carbonation (Building F, left diagram in Figure 10). For example, it is generally recognized that tiles are more effective at suppressing carbonation than finishing coating materials, but there were also cases where the carbonation depth was the opposite of what would be predicted from the finishing material material (tile surface and finishing coating surface of Building C, see Tables 6 and 7). For example, there was a case where the economics of construction influenced the quality of the concrete, and that quality was thought to have had a significant impact on carbonation (Building E). If the background, history and current state of each existing building were carefully considered individually, it would be possible to identify factors that contribute to the carbonation of concrete (see the discussion in paragraph 0102), but such factors would be unique to each existing building and would lack general applicability. In addition, among the factors that can be identified, there are some that are difficult to quantify as coefficients that make up the carbonation rate equation.

[0014] As a result of continuing the above-mentioned investigations, the present inventors came to a change of perspective. The carbonation rate coefficient of concrete in existing buildings can be derived by those who wish to predict the service life of existing buildings from the results of actual concrete surveys, depending on the event they wish to predict. For example, if you want to predict the number of years it will take for the area where concrete is currently most neutralized to neutralize down to the rebar, you can use the value of the neutralization depth at that area (i.e., the 100th percentile of the neutralization depth values ​​of multiple surveyed areas, sorted in order from smallest to largest) and calculate the neutralization rate coefficient using the √t law formula. For example, if one wishes to predict the number of years required for 5% of an existing building's structure to be neutralized down to the steel bars, one can use the value of the neutralization depth of the top 5 percent of structures (i.e., the 95th percentile, calculated by arranging the neutralization depth values ​​of multiple survey locations in order from smallest to largest) and calculate the neutralization rate coefficient using the √t law formula.

[0015] Based on the above idea, the present disclosure provides a novel method for predicting useful life that solves the above problems. Specific means for solving the above problems include the following aspects.

[0016] <1> A method for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete based on the neutralization of concrete, comprising the following steps (1) to (3). Step (1): The values ​​of the carbonation depth at multiple survey locations obtained through concrete surveys of existing buildings are arranged in ascending order, and a representative value of the carbonation depth, Cr, is identified from the 50th to 100th percentile range. Step (2): The representative value of the carbonation depth Cr and the number of years elapsed from completion to the concrete inspection t are substituted into the equation Ar = Cr / √t to calculate the representative value of the carbonation rate coefficient Ar. Step (3): The representative value of the carbonation rate coefficient Ar and the concrete cover thickness D of the reinforcing bar are calculated using the formula T = D 2 / Ar 2 and calculate the useful life T from completion. <2> Further, the method includes the following step (4), which includes predicting a service life from a concrete survey, <1> A method for predicting the useful life of an existing building as described above. Step (4): Subtract the number of years elapsed between completion of construction and the concrete inspection, t, from the service life from completion of construction, T, to calculate the service life from the concrete inspection (Tt). <3> Further, the method includes the following steps (5) to (6), which include predicting the neutralization depth at the time when the useful life from completion has elapsed for each of the plurality of survey locations, <1> or <2> A method for predicting the useful life of an existing building as described above. Step (5): Substitute the carbonation depth Cn of each of the multiple investigation locations and the number of years elapsed from completion to the concrete investigation t into the equation An = Cn / √t to calculate the carbonation rate coefficient An for each of the multiple investigation locations. Step (6): Substitute the carbonation rate coefficient An and the service life T from completion into the equation Cnf = An√T, and calculate the carbonation depth Cnf for each of the multiple survey locations at the point when the service life T from completion has elapsed. <4> <1> ~ <3> A program for causing a computer to execute any one of the methods for predicting the useful life of an existing building described above. Effect of the Invention

[0017] According to the present disclosure, there is provided a versatile and simple method for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete, based on the neutralization of concrete. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram illustrating the hardware configuration of a computer. [Diagram 2] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building A, Survey location: Outdoors. [Diagram 3] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building A, Survey location: Indoors. [Figure 4] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building B, Survey location: Outdoors, tile surface. [Diagram 5] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building B, Survey location: Outdoors, coating surface. [Figure 6] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building C, Survey location: Outdoors, tile surface. [Figure 7] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building C, Survey location: Outdoors, coating surface. [Figure 8] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building D, Survey location: Outdoors. [Figure 9] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building E, Survey location: Outdoors. [Figure 10] A scatter plot showing the relationship between mortar thickness and carbonation depth, and a graph showing percentiles of carbonation depth. Target building: Building F, Survey location: Outdoors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

[0020] In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value exemplified in the embodiment or a value shown in the example.

[0021] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, it may be only B, or it may be a combination of A and B.

[0022] In the present disclosure, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0023] <Method of predicting the useful life of existing buildings> The prediction method disclosed herein targets existing buildings made of reinforced concrete and steel-reinforced concrete, and predicts their service life based on the neutralization of concrete, which is one of the causes of deterioration of buildings. In this disclosure, “service life” means the number of years required for the neutralization of concrete in an existing building to reach the outermost reinforcing bars, and more specifically, the number of years until the neutralization of the “concrete cover thickness D over the reinforcing bars” in step (3) is complete. According to the prediction method disclosed herein, the “useful life” is calculated from the completion of the existing building (i.e., the “useful life T” in step (3)) and the “useful life Tt” in step (4) calculated from the concrete survey.

[0024] The prediction method of the present disclosure uses the results of an investigation into the carbonation depth of concrete in an existing building (referred to as a "concrete investigation" in this disclosure) to predict the service life. The investigation results may be the results of a new concrete investigation conducted for use in the prediction method of the present disclosure, or may be the results of a concrete investigation conducted in the past.

[0025] The prediction method disclosed herein targets existing buildings made of reinforced concrete and steel-reinforced concrete, and includes the following steps (1) to (3) to predict the useful life of an existing building from completion.

[0026] Step (1): The values ​​of the carbonation depth at multiple survey locations obtained through concrete surveys of existing buildings are arranged in ascending order, and a representative value of the carbonation depth, Cr, is identified from the 50th to 100th percentile range. Step (2): The representative value of the carbonation depth Cr and the number of years elapsed from completion to the concrete inspection t are substituted into the equation Ar = Cr / √t to calculate the representative value of the carbonation rate coefficient Ar. Step (3): The representative value of the carbonation rate coefficient Ar and the concrete cover thickness D of the reinforcing bar are calculated using the formula T = D 2 / Ar 2and calculate the useful life T from completion.

[0027] An example of an embodiment of the prediction method of the present disclosure further includes the following step (4), which includes predicting the service life from a concrete survey.

[0028] Step (4): Subtract the number of years elapsed between completion of construction and the concrete inspection, t, from the service life from completion of construction, T, to calculate the service life from the concrete inspection (Tt).

[0029] An example of an embodiment of the prediction method disclosed herein further includes the following steps (5) to (6), and includes predicting the neutralization depth for each of a plurality of survey locations at the time when the useful life from completion has elapsed.

[0030] Step (5): Substitute the carbonation depth Cn of each of the multiple investigation locations and the number of years elapsed from completion to the concrete investigation t into the equation An = Cn / √t to calculate the carbonation rate coefficient An for each of the multiple investigation locations. Step (6): Substitute the carbonation rate coefficient An and the service life T from completion into the equation Cnf = An√T, and calculate the carbonation depth Cnf for each of the multiple survey locations at the point when the service life T from completion has elapsed.

[0031] The prediction method disclosed herein does not require determining each of the concrete coefficients, finishing coefficients, construction method coefficients, environmental coefficients, etc. that make up the carbonation rate formula. The prediction method disclosed herein does not classify or limit the target existing buildings, but applies a simple calculation formula to all target existing buildings. The prediction method disclosed herein makes it possible to predict the service life of an existing building if survey results are available for the depth of concrete neutralization and the number of years that have elapsed since completion of construction until the concrete survey are known. Therefore, the prediction method of the present disclosure is versatile and simple.

[0032] The target building and concrete inspection, and steps (1) to (6) will be described in detail below.

[0033] [Target building, concrete survey] The buildings targeted by the prediction method of the present disclosure are existing buildings made of reinforced concrete and steel-reinforced concrete. There are no restrictions on the number of years since the completion of the existing buildings. There are no restrictions on the structure, size, purpose of use, construction site, etc. of the existing buildings.

[0034] The concrete survey investigates the depth of neutralization of concrete in the existing building that is the subject of the prediction method disclosed herein.

[0035] The method for investigating the depth of neutralization of concrete may be any of the following methods: chipping method, core method, small diameter core method, drill method, etc.

[0036] Concrete surveys should be conducted at two or more locations. From the viewpoint of increasing the accuracy of service life predictions, the more locations surveyed, the better. From the viewpoint of shortening the survey period or reducing survey costs, the fewer locations surveyed, the better.

[0037] The location of the survey is outdoors and / or indoors. Since the carbon dioxide gas concentration differs between outdoors and indoors, the method of the present disclosure for predicting the service life based on the carbonation depth of concrete is preferably carried out by dividing the survey location into outdoors and indoors. The survey locations are typically outdoors, where the steel bars are exposed to rain and prone to corrosion. An example of the embodiment of the investigation location is an indoor location. For example, if the target building has a humid environment indoors where water constantly acts, the indoor location of the humid environment is set as the investigation location.

[0038] When it is desired to predict the overall service life of the entire target building, it is preferable that the survey locations include all four directions, north, south, east and west, in order to provide diversity to the environment to which the concrete will be exposed. If you wish to predict the service life of a building for a specific orientation, limit the survey locations to that specific orientation.

[0039] When it is desired to predict the overall service life of the entire building, it is preferable to survey multiple floors in order to provide variety in the timing of concrete pouring. For example, the survey areas may include the bottom floor, middle floors, and top floor. If you wish to predict the useful life of a specific floor of a target building, limit the survey to that specific floor.

[0040] The investigation points may be structural or non-structural components as long as the carbonation depth of concrete can be measured. Inspection areas include, for example, load-bearing walls, non-structural walls, columns, beams, floor slabs, roof slabs, and slab foundations.

[0041] The survey area may be finished in any of the following forms: (a) Fair-faced concrete. (b) Concrete with a mortar finish, where mortar is applied over the concrete. (c) Concrete with a finish coating applied over it. (d) Concrete with mortar applied over it and then a finishing coating applied over it. (e) Concrete with a finishing material applied via mortar. Examples of finishing materials include tiles, stone, wood, insulation, wallpaper, and combinations of these.

[0042] The useful life may be predicted from the results of a survey that combines (a) to (e), or the useful life may be predicted for each of the results of a survey that separates (a) to (e).

[0043] In this disclosure, the number of survey locations is represented by "n." In this disclosure, the neutralization depth of concrete at each investigation point during concrete investigation is represented as "Cn".

[0044] [Process (1)] Step (1) is a step of sorting the values ​​of the carbonation depth at multiple survey locations obtained through a concrete survey of an existing building in ascending order and identifying a representative value of the carbonation depth Cr (mm) from the 50th to 100th percentile range.

[0045] That is, in step (1), n ​​values ​​of the neutralization depth Cn are sorted in ascending order, and one representative value Cr of the neutralization depth is identified from the interval between the 50th percentile and the 100th percentile. Alternatively, the n values ​​of the neutralization depth Cn may be arranged in descending order, and one representative value Cr of the neutralization depth may be specified from the 0th percentile to the 50th percentile. Generally, percentiles are indices in which data is arranged in ascending order, so in this disclosure, a form in which data is arranged in ascending order will be described. The method of calculating percentiles may differ depending on the instruction manual and calculation software, but it does not matter which calculation method is used, so any calculation method can be used.

[0046] Since the prediction method disclosed herein is a method for predicting the service life based on the carbonation of concrete, a representative value Cr of carbonation depth is identified from the top half of the group in which carbonation depth is progressing, i.e., the section above the 50th percentile.

[0047] Examples of the form in which the representative value Cr of the neutralization depth is specified from the interval between the 50th percentile and the 100th percentile are as follows: These forms are set by the person who carries out the prediction method of the present disclosure.

[0048] We want to predict the number of years required for the most carbonatable location out of n survey locations to carbonate down to the outermost rebar, and specify the 100th percentile carbonation depth as the representative value Cr. Since the upper 5 percentile (or, for example, the upper 3 percentile) of the n neutralization depths Cn may be outliers, the upper 5 percentile (or, for example, the upper 3 percentile) is excluded, and a more conservative prediction is considered to be more useful than a more conservative prediction, so the 95th percentile (or, for example, the 97th percentile) neutralization depth is specified as the representative value Cr. - The structural safety of the target building is considered to be maintained even if X% of the structure is neutralized up to the outermost rebar, and the 100-X percentile neutralization depth is specified as the representative value Cr. Here, X% takes into consideration the importance of the target building (e.g., purpose of use, public nature, etc.) and is set, for example, to 3% (97th percentile) for particularly important buildings, 5% (95th percentile) for important buildings, and 10% (90th percentile) for other buildings. You want to predict the number of years it will take for 50% (or, for example, 40%, 30%, 25%, 20%, 15%) of the structure to be neutralized down to the outermost rebars, and you specify the 50th percentile (or, for example, 60th percentile, 70th percentile, 75th percentile, 80th percentile, 85th percentile) of the neutralization depth as the representative value Cr.

[0049] [Process (2)] Step (2) is the process of substituting the representative value Cr (mm) of the carbonation depth determined in step (1) and the number of years t (years) that have elapsed since completion of construction until the concrete inspection into the equation Ar = Cr / √t to calculate the representative value Ar (mm / √years) of the carbonation rate coefficient.

[0050] The representative value Ar of the carbonation rate coefficient is the solution of a three-element equation, "Ar=Cr / √t." The coefficients of the various factors involved in the carbonation of concrete in existing buildings are integrated into one, called "Ar," and Ar is calculated from the representative value Cr based on the population of actual carbonation depths Cn and the actual number of years since construction t.

[0051] [Process (3)] In step (3), the representative value of the carbonation rate coefficient Ar (mm / √year) calculated in step (2) and the concrete cover thickness D (mm) are calculated using the formula T = D 2 / Ar 2 This is the process of substituting this value into the calculation of the useful life T (years) from completion.

[0052] The service life T is the number of years calculated from the completion of the existing building. The service life T is the number of years predicted to be required for the concrete of thickness D in the target building to complete neutralization.

[0053] Formula T=D 2 / Ar 2 As specific values ​​of the covering thickness D to be substituted into, for example, the following can be mentioned. Any one of the following (1) to (3) can be selected according to the type of structure whose service life is to be predicted.

[0054] (1) The minimum value of 20 mm as stated in Article 79, Paragraph 1 of the Enforcement Order of the Building Standards Act, which states "for walls or floors other than load-bearing walls, the thickness must be at least 2 centimeters." (2) The minimum value of 30 mm as defined in Article 79, Paragraph 1 of the Enforcement Order of the Building Standards Act, which states "3 centimeters or more for load-bearing walls, pillars or beams." (3) The minimum value of 40 mm is set forth in Article 79, Paragraph 1 of the Enforcement Order of the Building Standards Act, which states "4 centimeters or more for the rising parts of walls, pillars, floors, beams, or slabs that are in direct contact with the soil."

[0055] Formula T=D 2 / Ar 2 Specific values ​​of the cover thickness D to be substituted include the average, median, or mode of the actual cover thickness. If the actual cover thickness of the target building can be known, the form in question can be adopted.

[0056] In the prediction method of the present disclosure, the value of the representative value Cr of the carbonation depth of concrete may be changed, and steps (1) to (3) may be repeated multiple times to calculate the service life T multiple times. For example, steps (1) to (3) are performed for the 95th percentile carbonation depth, the 90th percentile carbonation depth, and the 85th percentile carbonation depth, respectively, to predict three useful lives T.

[0057] In the prediction method of the present disclosure, step (3) may be repeated multiple times while changing the value of the concrete covering thickness D over the reinforcing bar, thereby calculating multiple service lives T. For example, step (3) is performed for cover thicknesses of 20 mm, 30 mm, and 40 mm, and three service lives T are predicted.

[0058] [Process (4)] Step (4) is a step of subtracting the number of years t (years) elapsed from the completion of construction to the concrete inspection from the useful life T (years) from the completion of construction calculated in step (3) to calculate the useful life from the concrete inspection (Tt) (years). In this disclosure, the useful life (Tt) is sometimes referred to as the "remaining useful life."

[0059] In the prediction method of the present disclosure, the value of the representative value Cr of the carbonation depth of concrete may be changed and steps (1) to (4) may be repeated multiple times to calculate the remaining useful life (Tt) multiple times. For example, steps (1) to (4) are performed for the 95th percentile carbonation depth, the 90th percentile carbonation depth, and the 85th percentile carbonation depth, respectively, to predict three remaining useful lives (Tt).

[0060] In the prediction method of the present disclosure, steps (3) and (4) may be repeated multiple times while changing the value of the concrete covering thickness D over the reinforcing bar, to calculate the remaining useful life (Tt) multiple times. For example, steps (3) and (4) are performed for cover thicknesses of 20 mm, 30 mm, and 40 mm, respectively, and three remaining useful lives (Tt) are predicted.

[0061] [Process (5)] Step (5) is a step of substituting the concrete neutralization depth Cn (mm) at each of the multiple survey locations and the number of years t (years) that have elapsed since completion of construction until the concrete survey into the equation An = Cn / √t, and calculating the neutralization rate coefficient An (mm / √years) at each of the multiple survey locations.

[0062] The carbonation rate coefficient An is the solution of a three-element equation: An = Cn / √t. The coefficients of the various factors involved in the carbonation of concrete in existing buildings are combined into one, called An, and An is calculated from the actual carbonation depth Cn and the number of years since construction t.

[0063] The timing of performing step (5) is not limited. Step (5) may be performed before step (1), in parallel with step (2), or after step (3).

[0064] [Process (6)] Step (6) is a step of substituting the carbonation rate coefficient An (mm / √year) calculated in step (5) and the useful life T (years) from completion calculated in step (3) into the equation Cnf = An√T to calculate the carbonation depth Cnf for each of the multiple survey locations at the point when the useful life T from completion has elapsed.

[0065] The calculation results in step (6) are shown in tables and / or graphs, such as Tables 12 to 20 and / or FIGS. 2 to 10 described below.

[0066] The prediction method of the present disclosure may involve performing steps (1) to (3) and steps (5) to (6) multiple times by changing the value of the representative value Cr of the carbonation depth of concrete, and calculating multiple values ​​of the carbonation depth Cnf at each of the investigation locations. For example, steps (1) to (3) and steps (5) to (6) are performed for the 95th percentile neutralization depth, the 90th percentile neutralization depth, and the 85th percentile neutralization depth, respectively, and three neutralization depths Cnf are predicted for each survey site.

[0067] The prediction method of the present disclosure may involve performing steps (3) and (6) multiple times by changing the value of the concrete cover thickness D over the reinforcing bar, and calculating multiple values ​​of the neutralization depth Cnf for each investigation location. For example, steps (3) and (6) are performed at cover thicknesses of 20 mm, 30 mm, and 40 mm, respectively, and three carbonation depths Cnf are predicted for each investigation site.

[0068] <Program> The present disclosure provides a program for predicting the useful life of an existing building. The program of the present disclosure is a program for causing a computer to execute the prediction method of the present disclosure, i.e., the program of the present disclosure is a program for causing a computer to execute steps (1) to (3), steps (1) to (4), steps (1) to (3) and steps (5) to (6), or steps (1) to (6).

[0069] The present disclosure provides a computer operated with a program for predicting the useful life of an existing building. The computer of the present disclosure is a computer operated by a program for causing a computer to execute the prediction method of the present disclosure. That is, the computer of the present disclosure is a computer operated by a program for causing a computer to execute steps (1) to (3), steps (1) to (4), steps (1) to (3) and steps (5) to (6), or steps (1) to (6).

[0070] The program of the present disclosure is realized, for example, by the operation of a computer 100 (an example of a computer of the present disclosure) shown in FIG.

[0071] 1, the computer 100 includes a central processing unit (CPU) 101, a read only memory (ROM) 102, a random access memory (RAM) 103, and a storage 104. Each component is connected to each other via a bus 109 so as to be able to communicate with each other.

[0072] The CPU 101 is a central processing unit that executes various programs and controls each part. That is, the CPU 101 reads a program from the ROM 102 or the storage 104, and executes the program using the RAM 103 as a working area. The CPU 101 executes the program recorded in the ROM 102 or the storage 104, and controls each stage and performs various calculation processes.

[0073] The ROM 102 stores various programs and various data. The RAM 103 temporarily stores programs or data as a working area. The storage 104 is configured with a hard disk drive (HDD), a solid state drive (SSD) or a flash memory, and stores various programs including an operating system and various data.

[0074] In the computer 100, the CPU 101 executes steps (1) to (3) to calculate the useful life T of an existing building from the completion of its construction. In the computer 100, the CPU 101 executes steps (1) to (4) to calculate the useful life T from the completion of the existing building and the useful life (Tt) from a concrete inspection of the existing building. In computer 100, CPU 101 executes steps (1) to (3) and steps (5) to (6) to calculate the service life T from the completion of the existing building and the neutralization depth Cnf of each of the multiple survey locations at the time when the service life T has elapsed. In computer 100, CPU 101 executes steps (1) to (6) to calculate the service life T from the completion of the existing building, the service life (Tt) from the concrete inspection of the existing building, and the neutralization depth Cnf of each of the multiple inspection locations at the time when the service life T has elapsed. EXAMPLES

[0075] The prediction method of the present disclosure will be described more specifically below with reference to examples. The target buildings, survey locations, survey methods, calculation procedures, chart formats, etc. shown in the following examples can be changed as appropriate without departing from the spirit of this disclosure. Therefore, the scope of the prediction method of this disclosure should not be interpreted as being limited by the specific examples shown below.

[0076] [1] Overview of the target buildings We present six examples of applying the prediction method disclosed in this paper to actual existing buildings. Table 1 shows an overview of the six buildings.

[0077] [Table 1]

[0078] [2] Survey items and methods The concrete surveys carried out on buildings A to F are as follows: Core sampling: Concrete cores including the finishing materials were sampled. Carbonation depth: Measured according to JIS A 1152 "Method of measurement of carbonation depth of concrete." The core split surface was used as the measurement surface. -Type of finishing material: Confirmed visually. - Thickness of base mortar: The thickness of the concrete core was measured using a scale. Compressive strength: Measured in accordance with JIS A 1107 "Methods for extracting cores from concrete and testing for compressive strength."

[0079] [3] Survey results The survey results for Buildings A to F are shown in Tables 2 to 10. In Tables 2 to 10, the survey locations are arranged in ascending order of the concrete neutralization depth Cn.

[0080] [Table 2]

[0081] [Table 3]

[0082] [Table 4]

[0083] [Table 5]

[0084] [Table 6]

[0085] [Table 7]

[0086] [Table 8]

[0087] [Table 9-1]

[0088] [Table 9-2]

[0089] [Table 10]

[0090] [4] Calculation results Steps (1) to (6) will be explained below using the outdoors of Building A as an example.

[0091] -Process (1)- From the data range of the carbonation depth Cn at 11 locations shown in Table 2, the 95th percentile carbonation depth was specified as the representative value Cr. The reason for using the 95th percentile is that it is believed that the structural safety of the building will be maintained even if 5% of the structure is carbonated up to the outermost rebar. The value of the representative value Cr is shown in Table 11.

[0092] -Process (2)- The representative value Cr determined in step (1) and the number of years that have elapsed since the completion of Building A until the concrete inspection (t = 89) were substituted into the formula Ar = Cr / √t to calculate the representative value Ar of the carbonation rate coefficient. The values ​​of the representative value Ar are shown in Table 11.

[0093] -Process (3)- The representative value Ar calculated in step (2) and the concrete cover thickness D=30 for the reinforcing bar are calculated using the formula T=D 2 / Ar 2 The useful life T from completion was calculated by substituting the above. Here, the value of D was the minimum value of 30 mm specified in Article 79, Paragraph 1 of the Enforcement Order of the Building Standards Act, which states "For load-bearing walls, columns or beams, the minimum is 3 centimeters." As a result, the outdoor service life T of Building A was determined to be 66 years.

[0094] -Process (4)- The remaining service life (Tt) was calculated by subtracting the number of years that had elapsed between the completion of construction and the concrete inspection (t = 89) from the service life T = 66. As a result, the remaining service life (Tt) of the exterior of Building A was -23 years.

[0095] -Process (5)- For each of the outdoor survey locations in Building A, the carbonation depth of concrete Cn and the number of years that have passed since the completion of Building A until the concrete survey (t = 89) were substituted into the formula An = Cn / √t to calculate the carbonation rate coefficient An for each survey location. The values ​​of the carbonation rate coefficient An are shown in Table 12.

[0096] -Process (6)- The carbonation rate coefficient An calculated in step (5) and the service life from completion T = 66 were substituted into the equation Cnf = An√T to calculate the carbonation depth Cnf for each surveyed location after the service life T had elapsed. The values ​​of carbonation depth Cnf are shown in Table 12.

[0097] For the interior of Building A and for each of Buildings B to F, the 95th percentile neutralization depth was specified as the representative value Cr, and the concrete cover thickness over the reinforcing bars was set at D = 30, and steps (1) to (6) were performed.

[0098] Table 11 shows the calculation results for steps (1) to (4), and Tables 12 to 20 show the calculation results for steps (5) to (6).

[0099] [Table 11]

[0100] The negative values ​​of the remaining service life (Tt) shown in Table 11 indicate that the calculated service life had expired before the concrete survey was conducted.

[0101] The useful life T and remaining useful life (Tt) shown in Table 11 can be evaluated as appropriate years in light of the background, history and current status of each building, from Building A to Building F. Details are as follows.

[0102] · Building A: It is reasonable that the service life T is shorter indoors than outdoors, where the carbon dioxide concentration is higher. Building B: Generally, tiles are less permeable to carbon dioxide than coating materials, so it is reasonable that the service life T of the tile surface is longer than the service life T of the finishing coating material surface. Building C: Since lifting and peeling of tiles were observed, it is reasonable that the service life T of the tile surface is shorter than the service life T of the finishing coating material surface. Building D: There is no mortar applied to the base, the finishing coating has deteriorated with age, and the building has not been repainted, so it is reasonable that the service life T is short at 53 years. Building E: This building was built during a time of inflation known as "crazy prices." The short service life T of 34 years may be due to the quality of the concrete. · Building F: There is little relationship between mortar thickness and carbonation depth, and carbonation is generally suppressed. This is presumably because the mortar contained an admixture with carbonation-suppressing ingredients, or the carbonation-suppressing effect of the finishing coating material applied on top of the mortar was large. Therefore, it is reasonable that the service life T is long.

[0103] [Table 12]

[0104] [Table 13]

[0105] [Table 14]

[0106] [Table 15]

[0107] [Table 16]

[0108] [Table 17]

[0109] [Table 18]

[0110] [Table 19-1]

[0111] [Table 19-2]

[0112] [Table 20]

[0113] Furthermore, Figures 2 to 10 show the survey results and calculation results for each of Buildings A to F. The left figures in Figures 2 to 10 are scatter plots showing the relationship between mortar thickness and carbonation depth at the survey sites. The right diagrams of Figures 2 to 10 are graphs in which the horizontal axis represents neutralization depth and the vertical axis represents percentile. The ● marks and solid lines on the right side of Figures 2 to 10 are graphs in which the neutralization depths Cn (i.e., actual measured values ​​from surveys) shown in Tables 2 to 10 are plotted at the corresponding percentile positions and connected by straight lines. The ■ marks and dashed lines on the right side of Figures 2 to 10 are graphs in which the carbonation depth Cnf (i.e., the carbonation depth after the useful life T) shown in Tables 12 to 20 is plotted at the corresponding percentile positions and connected by straight lines. Since this embodiment specifies the 95th percentile carbonation depth as the representative value Cr and sets the cover thickness D = 30 mm, the ■ marks and dashed line graphs pass through the intersection of the horizontal axis 30 mm and the vertical axis 95th percentile.

[0114] In the right diagram of Figure 2 (outdoors of Building A), the right diagram of Figure 3 (indoors of Building A), and the right diagram of Figure 9 (Building E), the ■ marks and dashed lines (graphs in which the carbonation depth after the useful life T has elapsed is plotted at the corresponding percentile positions and connected by straight lines) are located to the left (closer to the origin) of the ● marks and solid lines (graphs in which the actual measured values ​​from the survey are plotted at the corresponding percentile positions and connected by straight lines). This means that the calculation results show that the useful life had expired before the concrete survey was conducted.

[0115] The above are the results of applying the prediction method disclosed herein to Buildings A to F. As described above, the useful life T and remaining useful life (Tt) of each of Buildings A to F predicted using the prediction method disclosed herein can be evaluated as appropriate in light of the background, history, and current status of each building.

[0116] The prediction method of the present disclosure does not require classification or limitation of the target existing building, and does not require determination of each of the concrete coefficients, finishing coefficients, construction method coefficients, environmental coefficients, etc. that constitute the carbonation rate equation. Therefore, the prediction method of the present disclosure is versatile and simple. [Explanation of symbols]

[0117] 100 Computers 101 CPU 102 ROM 103 RAM 104 Storage 109 Bus

Claims

1. A method for predicting the service life of existing buildings made of reinforced concrete and steel-reinforced concrete based on the neutralization of concrete, comprising the following steps (1) to (3): Step (1): The values ​​of the carbonation depth at multiple survey points obtained through a concrete survey of an existing building are arranged in ascending order, and a representative value Cr of the carbonation depth is identified from the 50th percentile to 100th percentile range. Step (2): The representative value Cr of the neutralization depth and the number of years elapsed from completion to the concrete inspection t are substituted into the equation Ar = Cr / √t to calculate the representative value Ar of the neutralization rate coefficient. Step (3): The representative value Ar of the carbonation rate coefficient and the concrete cover thickness D of the reinforcing bar are calculated using the formula T = D ２ / Ar ２ and calculate the useful life T from completion.

2. The method for predicting the service life of an existing building according to claim 1, further comprising the following step (4): predicting the service life from a concrete survey. Step (4): Subtract the number of years elapsed from completion of construction to the concrete inspection, t, from the service life from completion of construction, T, to calculate the service life from the concrete inspection (T-t).

3. The method for predicting the useful life of an existing building as described in claim 1, further comprising the following steps (5) to (6), and including predicting the neutralization depth for each of the multiple survey locations at the point when the useful life from completion has elapsed. Step (5): Substitute the carbonation depth Cn of each of the multiple investigation locations and the number of years t elapsed from completion to the concrete investigation into the equation An = Cn / √t to calculate the carbonation rate coefficient An for each of the multiple investigation locations. Step (6): Substitute the carbonation rate coefficient An and the useful life T from completion into the equation Cnf = An√T, and calculate the carbonation depth Cnf of each of the multiple survey locations at the point in time when the useful life T from completion has elapsed.

4. A program for causing a computer to execute the method for predicting the useful life of an existing building according to any one of claims 1 to 3.

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