JP5336909B2 - Concrete expansion prediction method - Google Patents

Description

  The present invention relates to a concrete expansion prediction method.

  The alkali aggregate reaction is a phenomenon in which the aggregate expands due to the reaction between the aggregate in the concrete and the alkali component in the cement, and cracks are gradually generated in the concrete structure over a long period of time.

  Predicting the progress of deterioration of a concrete structure is important in terms of maintenance and management of the concrete structure.

  Therefore, in order to predict the future expansion of a concrete structure that has undergone an alkali-aggregate reaction, an accelerated expansion test is performed on a concrete core sampled from this concrete structure to determine the amount of residual expansion (future expansion). A method of measuring (quantity) is generally performed.

  Patent Document 1 discloses alkali silica according to the correlation between the expansion rate of concrete obtained by measuring a concrete core collected from a concrete structure and the alkali hydroxide concentration in the pore solution of the concrete core. A method for predicting the progress of future deterioration of a concrete structure deteriorated by reaction is disclosed.

  Furthermore, Patent Document 2 discloses a method for determining the progress of an alkali-aggregate reaction from the propagation velocity of longitudinal acoustic waves in a concrete core.

JP 2001-99833 A JP 2008-128846 A

  However, in the conventional prediction method, only the presence or absence of future expansion can be determined, and it has not been possible to grasp the progress of deterioration from the construction of the structure to the point of investigation. Moreover, since the data is calculated by the accelerated test, it is difficult to predict the progress of deterioration in the service environment based on this data.

Moreover, since the prediction method described in Patent Document 1 uses a special device that is used to extract the pore solution from the concrete core, the capital investment is expensive and expensive.
Although it is possible to determine whether or not the deterioration of the concrete structure will proceed in the future, it is not possible to grasp the progress of the deterioration between the construction of the concrete structure and the time of the survey. It was not possible to judge the degree of expansion at any time.

Furthermore, in the prediction method described in Patent Document 2, an apparatus used for generating and receiving an elastic wave is expensive.
Although it is possible to determine whether concrete structures have deteriorated or whether future deterioration will proceed, it is not possible to grasp the progress of deterioration from the time the concrete structure is constructed until the time of the survey. It was not possible to judge the progress of future deterioration.

  The present invention aims to solve the above-mentioned problems, and predicts the current expansion amount and the progress of expansion at any future time for a structure deteriorated by an alkali-aggregate reaction. It is an object to propose a method for predicting the expansion of concrete that can be carried out easily and inexpensively.

  In order to solve the above problems, the method for predicting expansion of concrete according to the present invention collects at least one first concrete specimen from a sound part of a concrete structure, and secondly extracts from a deteriorated part of the concrete structure. A test specimen collecting step for collecting at least one concrete specimen, an accelerated expansion test for each of the first concrete specimen and the second concrete specimen, and an accelerated expansion rate over time for each concrete specimen. Obtained by a test step for obtaining changes, an expansion curve creation step for approximating a time-dependent change in the accelerated expansion rate for the first concrete specimen, and an accelerated expansion test for the second concrete specimen. And a fitting process for correcting the test data and fitting to the S-shaped function. The amount of correction of the second concrete specimen was considered as the expansion rate in the accelerated environment at the time of the survey, and the amount of correction of the accelerated material age was considered as the age of the second concrete specimen in the accelerated environment at the time of the survey. The future expansion rate is predicted.

According to the concrete expansion prediction method, the expansion amount at the time of the survey can be grasped, and the final expansion amount can also be grasped. Further, the expansion amount at an arbitrary time in the future can be predicted from the expansion amount and the final expansion amount at the time of these investigations.
Furthermore, since it can be predicted with high accuracy without requiring special equipment and facilities, it is inexpensive.

  Further, in the method for predicting the expansion of the concrete, the acceleration factor is calculated by dividing the service period of the concrete structure by the correction amount of the accelerator material age, and the accelerator material age is determined under the service environment using the acceleration factor. It may be converted into the age of the material.

  According to the method for predicting the expansion of concrete, it is possible to easily predict the expansion rate after the elapse of an arbitrary period or the period until an arbitrary expansion rate in the service environment by using the calculated acceleration magnification. It becomes.

  Further, in the concrete expansion prediction method, an asymptotic value of the expansion curve may be used as an ultimate expansion coefficient, and may be used for prediction of an expansion amount after construction of a structure.

  According to the method for predicting the expansion of concrete according to the present invention, it is possible to easily and inexpensively predict the current expansion amount and the progress of expansion at an arbitrary time in the future for a concrete structure deteriorated by an alkali-aggregate reaction. It becomes possible.

It is a flowchart figure which shows the procedure of the expansion prediction method of the concrete which concerns on suitable embodiment of this invention. (A)-(c) is a graph which shows each step of the expansion prediction method of the concrete of FIG. (A)-(b) is a graph which shows each step of the expansion prediction method of the concrete of FIG.

A preferred embodiment of a concrete expansion prediction method of the present invention will be described in detail with reference to the drawings.
In the present embodiment, a description will be given of a case where the current amount of expansion of a deteriorated portion and the progress of future expansion are predicted for an existing concrete structure that has deteriorated due to an alkali-aggregate reaction.

  As shown in FIG. 1, the concrete expansion prediction method according to the present embodiment includes a specimen collection step S1, a test step S2, an expansion curve creation step S3, a fitting step S4, and an acceleration magnification calculation step S5. ing.

  The specimen collection step S1 is a process of collecting at least one first concrete specimen from the sound part of the concrete structure and collecting at least one second concrete specimen from the deteriorated part of the concrete structure. .

  The first concrete specimen and the second concrete specimen (hereinafter referred to as “concrete specimen” unless they are distinguished from “first concrete specimen” and “second concrete specimen”) Is a columnar specimen taken by coring a concrete structure. Basically, the first concrete specimen and the second concrete specimen are collected from concrete having the same material and composition, and it is preferable to collect them from the same placing block as much as possible.

  In the present embodiment, the case of collecting one each as the first concrete specimen and the second concrete specimen will be described, but the number of each concrete specimen is not limited and can be set as appropriate. Good. Moreover, what is necessary is just to set suitably according to the accelerated expansion test method performed in test process S2, the core removal method, etc., and the shape (diameter, length, etc.) of each concrete test body is not limited.

  In the test step S2, an accelerated expansion test is performed on each of the first concrete test body and the second concrete test body collected in the test body sampling process S1, and the time-dependent change in the accelerated expansion rate is obtained for each concrete test body. It is a process to do.

In this embodiment, the accelerated condition of the Canadian method (immersion in an 80 ° C.-1 mol / L NaOH solution) is adopted as the accelerated expansion test, the alkali aggregate reaction of each concrete specimen is promoted, and the appropriate accelerated material age Measure accelerated expansion.
The accelerated expansion test method is not limited to the above-described test method, and is appropriately selected from known test methods, for example, extending the test period of the method defined in Danish law or JISA 1804. Just do it.

  As shown in FIG. 2 (a), the results of accelerated expansion test of the first concrete specimen and the second concrete specimen (change in accelerated expansion coefficient with time) are as follows. Plot on the axis coordinates. Here, in FIG. 2 (a), reference numeral 1 represents a change over time in the accelerated expansion coefficient of the first concrete specimen (sound part), and reference numeral 2 represents the accelerated expansion coefficient of the second concrete specimen (deteriorated part). It is a change with time.

The expansion curve creation step S3 is a step of approximating the time-dependent change 1 of the accelerated expansion rate of the first concrete specimen collected in the test step S2 to an S-shaped function.
In the present embodiment, the temporal change 1 is approximated to an S-shaped function, and then displayed on the coordinates as an expansion curve B as shown in FIG.

  The expansion curve B approximates the time-dependent change 1 of the accelerated expansion coefficient of the first concrete specimen to the S-shaped function shown in Equation 1 to obtain optimum values for a to e and t, and is shown in FIG. Thus, it is created by approximating with one S-shaped curve.

  In the test step S2, when an accelerated expansion test is performed on a plurality of first concrete specimens, all test results are collectively plotted on one coordinate and approximated to an S-shaped function. An expansion curve B may be created to express the accelerated expansion behavior.

  The fitting step S4 is a step of correcting (moving) the change over time of the expansion coefficient obtained in the accelerated expansion test for the second concrete specimen and fitting it to an S-shaped function (expansion curve B).

  In this embodiment, as shown in FIG. 2C, fitting is performed by moving the plot group of the change 2 with time of the expansion rate of the second concrete specimen collected in the test step S2 toward the expansion curve B. To do.

The fitting is performed by moving the origin of the plot group with time change 2 so that the plot group with time change 2 approaches the expansion curve B (S-shaped curve).
Since the same concrete has the same expansion curve under the same conditions, the expansion curves of the first concrete specimen and the second concrete specimen almost coincide with each other by shifting the origin.

  When there are a plurality of plot groups for the second concrete specimen, each plot group is fitted to the expansion curve B. In the present embodiment, the fitting was performed by shifting the position of the plot group of the time-dependent change 2 of the expansion rate of the second concrete specimen on the coordinates. An S-shaped function may be calculated for 2 and the S-shaped function may be matched with the expansion curve B.

When the fitting operation is completed, as shown in FIG. 3A, the movement amount (correction amount) of the origin of the second concrete specimen is obtained for each axis.
Then, the amount of concrete deterioration portion had expanded the moving amount B ₀ of promoting expansion direction up to the time of the survey (in-service) (expansion ratio of the second concrete test body in the time of the survey), promoting material age axis direction of the moving amount T ₁ and converted to time a service period in an environment of accelerated test regarded as (accelerated ages of the second concrete test body in the time of the survey).
Further, an asymptotic value of the expansion curve (S-shaped curve) is defined as the ultimate expansion rate _BE .

In addition, the expansion coefficient B ₀ of the second concrete specimen at the time of the survey can be calculated by Equation 2.

Further, the ultimate expansion rate _BE can be calculated by Equation 3.

  The acceleration magnification calculation step S5 is a step of calculating an acceleration magnification α for replacing the expansion curve B with the service environment.

The acceleration factor α is calculated by dividing the service period of the concrete structure by the movement amount T ₁ in the time axis direction of the origin (see Equation 4).

By using the acceleration magnification α, it is possible to calculate the time until an arbitrary expansion rate in the service environment or the expansion rate at any time in the service environment.
That is, as shown in FIG. 3B, when the accelerated material age at which a concrete specimen having an expansion rate of 0 reaches the accelerated expansion rate B _A at an accelerated material age of 0 is T ₂ , the expansion rate B _{A in the} service environment. time to reach can be calculated from multiplying the promotion magnification α in accelerated test time T _2. Further, the expansion ratio at the time T ₄ under any serviced environment calculates the accelerated ages T _{3 (time} T _{4 /} accelerator ratio alpha) which corresponds to the time T _4, corresponding to the accelerator ages T ₃ It can be determined from the accelerated expansion rate B _B.

  As described above, according to the method for predicting the expansion of concrete according to the present invention, since the correlation between the service environment and the time of the accelerated test environment can be obtained, the accelerated test data can be used when the service environment is replaced. Become.

  Therefore, it becomes possible to grasp the degree of progress (expansion amount) of deterioration at the time of investigation. Moreover, it becomes possible to predict the future expansion amount of the concrete structure at an arbitrary time. Furthermore, the final expansion amount can be obtained.

  By accurately grasping the progress of the future expansion amount, it becomes possible to set an optimal repair time for a concrete structure and to select a repair method.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that the above-described constituent elements can be appropriately changed in design without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the fitting is performed by moving the plot group on the drawing. However, the fitting means is not limited, and may be appropriately performed by a known means, for example, by calculation using a spreadsheet. .

1 Temporal change of expansion coefficient of first concrete specimen 2 Temporal change of expansion coefficient of second concrete specimen B Expansion curve

Claims (3)

Collecting at least one first concrete specimen from a sound part of the concrete structure, and collecting at least one second concrete specimen from the deteriorated part of the concrete structure;
A test step of performing an accelerated expansion test on each of the first concrete specimen and the second concrete specimen, and obtaining a time-dependent change in the accelerated expansion rate for each concrete specimen;
An expansion curve creating step for approximating the time-dependent change in the accelerated expansion rate for the first concrete specimen to an S-shaped function;
A fitting step of correcting the accelerated expansion rate and the accelerated material age obtained in the accelerated expansion test for the second concrete specimen and fitting to the S-shaped function,
The correction amount of the accelerated expansion rate is regarded as the expansion rate in the accelerated environment of the second concrete specimen at the time of the survey, and the corrected amount of the accelerated material age is the age of the second concrete specimen in the accelerated environment at the time of the survey. A concrete expansion prediction method characterized by predicting the future expansion rate.   Calculating the accelerating magnification by dividing the service period of the concrete structure by the correction amount of the accelerating material age, and converting the accelerating material age to the material age in the service environment using the accelerating factor. The method for predicting expansion of concrete according to claim 1. The method for predicting the expansion of concrete according to claim 1, wherein an asymptotic value of the expansion curve is used as an ultimate expansion coefficient.

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