JP6893451B2 - How to predict the ultimate value of drying shrinkage strain of concrete - Google Patents

Description

The present invention relates to a method for easily and accurately predicting the ultimate value of the drying shrinkage strain of concrete in a short period of time.

Since concrete has low tensile strength, cracks (shrink cracks) may occur due to the shrinkage of concrete. This shrinkage crack not only spoils the aesthetic appearance of the concrete structure, but also causes a decrease in the durability of the structure such as deterioration of watertightness and airtightness of concrete and corrosion of reinforcing bars. Therefore, in order to ensure the durability of concrete, it is necessary to control shrinkage cracks.
The main cause of this shrinkage crack is the drying shrinkage strain of concrete. The strain includes a strain caused by external restraint of concrete and a strain caused by internal restraint. Therefore, in order to control shrinkage cracks in concrete, it is necessary to grasp the drying shrinkage strain, which is the main cause, in advance.

Conventionally, the drying shrinkage strain of concrete has been measured in accordance with JIS A 1129-1 to 3 “Method for measuring length change of mortar and concrete” (hereinafter referred to as “JIS method”).
In addition, without measuring the drying shrinkage strain, a formula containing parameters such as concrete volume, surface area in contact with the outside air, volume surface area ratio, and relative humidity is multiplied by a formula containing a correction coefficient representing the influence of a type such as cement. The following proposed formula (prediction formula) is presented (Non-Patent Document 1).

However, according to the JIS method, it takes one year or more to obtain the final value of the drying shrinkage strain of concrete (see FIG. 8). Further, in the above-mentioned proposed formula, as shown in the figure of the proposed formula in Attached FIG. 2.4 of Non-Patent Document 1 (see the upper left figure of FIG. 1 of Patent Document 1), the prediction accuracy is not always sufficient. Absent.
Therefore, the applicant of the present application is a measuring device for the drying shrinkage strain of concrete, in which almost the same value as the final value of the drying shrinkage strain of concrete obtained by using the JIS method can be obtained in a short period of 50 days or less. And proposed a measurement method.
Further, if the ultimate value of the drying shrinkage strain of the concrete used for the concrete structure is known earlier, cracks in the concrete structure can be predicted at an early stage, which is preferable for taking measures to prevent cracks.

"Shrink crack control design / construction guideline (draft) / commentary for reinforced concrete buildings", edited by Architectural Institute of Japan, p. 182 (proposal formula), p. 185 (Appended Figure 2.4), published in February 2006.

Japanese Unexamined Patent Publication No. 2012-251965

Therefore, an object of the present invention is to provide a method for easily and accurately predicting the ultimate value of the drying shrinkage strain of concrete in a short period of time.

As a result of examining a prediction method that meets the above object, the present inventor can easily measure the dry shrinkage strain of concrete in a short period of time by using a specific dry shrinkage strain measuring device using a laser, and can also easily measure the dry shrinkage strain of cement. The present invention has been completed by finding that the value obtained by multiplying the coefficient selected according to the type and the drying period of concrete by the drying strain has high prediction accuracy as the ultimate value of the drying shrinkage strain.
That is, the present invention is a method for predicting the ultimate value of the drying shrinkage strain of concrete having the following constitution.

[1] Dry shrinkage strain of concrete with a drying period of 7, 10, or 14 days measured using the following dry shrinkage strain measuring device (E ₁ ) or dry shrinkage strain measuring device (E _{2), and} The value obtained by multiplying the coefficient shown in Table 1 selected according to the type of cement used for the concrete by the drying shrinkage strain is predicted as the final value of the drying shrinkage strain of the concrete. A method for predicting the ultimate value of dry shrinkage strain.
<Dry shrinkage strain measuring device (E ₁ )>
Drying shrinkage strain measuring device <Drying shrinkage strain measuring device (dry shrinkage strain measuring device) including at least one laser displacement meter, a pedestal for mounting a specimen for measuring drying shrinkage strain, and a positioning jig for the specimen. E ₂ )>
Dry shrinkage strain including at least two laser displacement meters, three or more support members for supporting a specimen for measuring dry shrinkage strain, and a pedestal formed by embedding a part of the support member. measuring device

The method for predicting the ultimate value of the dry shrinkage strain of concrete of the present invention uses the dry shrinkage strain of concrete measured in a short period of time using a dry shrinkage strain measuring device using a laser to obtain the ultimate value of the dry shrinkage strain. It can be predicted easily and accurately.

It is a schematic diagram showing an example of a state in which a specimen is placed on a drying shrinkage strain measuring device (E ₁ ) having one laser displacement meter, and the left figure is a plan view of the measuring device, and the right is a plan view of the measuring device. Is a side view of the measuring device. It is a schematic diagram showing an example of a state in which a specimen is placed on a drying shrinkage strain measuring device (E ₁ ) having two laser displacement meters, and the left figure is a plan view of the measuring device and the right is a plan view of the measuring device. Is a side view of the measuring device. Some of the lower portion of the support member, on a support member formed by installing a state embedded in the pedestal drying shrinkage strain measurement device (E _1), a a schematic view showing an example of a state of mounting the specimen The left figure is a plan view of the measuring device, and the right figure is a side view of the measuring device. However, in FIG. 3, the description of the laser displacement meter is omitted. _{It is a schematic diagram showing an example of a drying shrinkage strain measuring device (E 2} ) in which two laser displacement meters are arranged so as to face each other. The left figure is a plan view of the measuring device, and the right figure is the said. It is a side view of the measuring device. It is a schematic diagram which shows an example of _{the drying shrinkage strain measuring apparatus (E 2} ) which arranges two laser displacement meters so that the lasers radiated from the laser displacement meters intersect at an angle of 90 °. The left figure is a plan view of the measuring device, and the right figure is a side view of the measuring device. However, the description of the laser displacement meter located behind the paper is omitted. Four laser displacement meter, a laser irradiated from the laser displacement meter is arranged so as to intersect at an angle of 90 °, a schematic diagram showing an example of a drying shrinkage strain measurement device (E ₂₎ The left figure is a plan view of the measuring device, and the right figure is a side view of the measuring device. However, the laser displacement meters located in front of and behind the paper are omitted. The drying shrinkage strain measurement device (E _2), is a photograph showing a state of mounting the specimen. The pin at the center of the pedestal (A) is not a support member but a screw for fixing the pedestal. It is a figure which shows the time-dependent change of the drying shrinkage strain of the specimen made using various cements, (A) is ordinary Portland cement, (B) is blast furnace cement type B, (C) is moderate heat Portland cement, and (D) shows the drying shrinkage strain of the specimen using low heat Portland cement. The curve shown by "the present invention" in the figure is a curve of the drying shrinkage strain measured _{by using the drying shrinkage strain measuring device (E 1} ), and the curve shown by the "JIS method" in the figure is JIS A. It is a curve of the drying shrinkage strain measured using 1129-2 "Measurement method for length change of mortar and concrete Part 2: Contact gauge method".

According to the present invention, as described above, the drying shrinkage strain _{of concrete measured using the drying shrinkage strain measuring device (E 1} ) or the drying shrinkage strain measuring device (E ₂ ) has a drying period of 7, 10, or 14 days. , And the value obtained by multiplying the coefficient shown in Table 1 selected according to the type of cement used for the concrete by the drying shrinkage strain is predicted as the final value of the drying shrinkage strain of the concrete. The method.
Hereinafter, the present invention will be described in detail separately for a drying shrinkage strain measuring device, a drying shrinkage strain measuring method, and a drying shrinkage strain prediction method.

1. 1. Dry shrinkage strain measuring device (E ₁ )
As illustrated in FIGS. 1 to 3, the drying shrinkage strain measuring device (E ₁ ) includes one or more laser displacement meters 4, a pedestal 2 for mounting a specimen for measuring drying shrinkage strain, and the same. It is an apparatus including at least the positioning jig 3 of the specimen 1.
The laser displacement meter is not particularly limited, and examples thereof include commercially available laser displacement meters such as a reflection type and a transmission type. In the present invention, if the number of laser displacement meters is increased, the number of data is increased, and the measurement accuracy is improved accordingly, but the cost of the apparatus is high. Therefore, the number of laser displacement meters is preferably 1 to 4. The number is preferably 2-4. The laser displacement meter is installed so that the laser can be irradiated toward the center of the disk-shaped or square plate-shaped specimen placed on the pedestal. Examples of the installation position of the laser displacement meter include the positions shown in FIGS. 1 and 2.

Further, the pedestal 2 is used for placing a specimen for measuring drying shrinkage strain. The shape of the pedestal is not particularly limited, and is, for example, a square plate shape or a disk shape shown in FIGS. 1 and 2. Further, in order to improve the measurement accuracy, it is preferable that the pedestal is kept horizontal.
Further, the pedestal is preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact. Further, the pedestal may be provided with a support member 5 for supporting the specimen. By installing the support member, the heat transfer between the specimen and the pedestal can be reduced, so that the measurement accuracy of the drying shrinkage strain is improved.
The shape of the support member is not particularly limited, and examples thereof include a spherical shape as shown in FIG. 3 (in FIG. 3, a part of the lower portion of the support member is embedded in the pedestal), a columnar shape, and the like. When the support member is columnar, the surface of the support member in contact with the specimen is preferably hemispherical so as to make point contact with the specimen.
The number of support members is preferably 3 or more because the specimen can be stably placed. It should be noted that the number of support members is more preferably 3 to 4, because it takes time and effort to manufacture the device when the number of support members is increased. Further, the support member is preferably installed so as to form an equilateral triangle or a square in order to stably place the specimen. FIG. 3 shows an example in which the support members are installed so as to form a square. Further, the support member is preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact.

The positioning jig 3 is used to determine and fix the placement position of the specimen when measuring the drying shrinkage strain of the specimen. For example, as shown in FIGS. 1 and 2, the positioning jig 3 is placed on a pedestal. Examples include two pins installed in an inverted state. In FIGS. 1 and 2, when the disk-shaped specimen is placed on the pedestal when the drying period is 0 (zero) days, the center of the disk-shaped specimen and the center of the pedestal coincide with each other. The positioning jig is installed at a position where it comes into contact with the side surface around the disk-shaped specimen. The positioning jig may be installed outside the pedestal in addition to the pedestal. Further, the positioning jig is preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact.
Further, the drying shrinkage strain measuring device (E ₁ ) preferably includes a laser displacement meter, a pedestal, and a positioning jig integrally by using a base. The laser displacement meter, pedestal, positioning jig, and the substrate used to install them are preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact.

2. Method for measuring dry shrinkage strain using a dry shrinkage strain measuring device (E ₁ ) The measuring method is to place a disk-shaped or square plate-shaped specimen on the pedestal of the dry shrinkage strain measuring device (E _1). After placing the specimen so that the peripheral side surface of the specimen is in contact with the positioning jig, the laser displacement meter is used to irradiate the peripheral side surface of the specimen with a laser to obtain the laser displacement meter and the peripheral side surface of the specimen. This is a method of measuring the drying shrinkage strain of a specimen by measuring the distance between them.
When the specimen has a disk shape and the diameter of the specimen is 10 to 30 cm, it is preferable that the specimen is easy to manufacture and the specimen dries quickly. The diameter of the specimen is more preferably 10 to 20 cm. Further, if the thickness of the specimen is 5 to 20 mm, the specimen is not easily cracked and the specimen dries even faster, which is preferable. The thickness of the specimen is more preferably 6 to 18 mm, further preferably 7 to 15 mm, and particularly preferably 8 to 12 mm.
When the specimen is in the shape of a square plate, the length of one side of the square plate is preferably 10 to 30 cm, more preferably 10 to 20 cm, and even more preferably 10 to 30 cm on one side. A square, particularly preferably a square with a side length of 10 to 20 cm. If the square has a side length of 10 to 30 cm, the specimen can be easily manufactured and the specimen can be dried quickly. The thickness of the square plate-shaped specimen is preferably 5 to 20 mm, more preferably 6 to 18 mm, still more preferably 7 to 15 mm, and particularly preferably 8 to 12 mm. If the thickness of the specimen is 5 to 20 mm, the specimen is hard to crack and the specimen dries even faster.
When a support member is installed on the pedestal of the drying shrinkage strain measuring device (E ₁ ), the peripheral side surface of the disk-shaped or square plate-shaped specimen comes into contact with the positioning jig on the support member. As such, the specimen is placed.

The measuring method is a method of measuring the drying shrinkage strain by placing the specimen on a pedestal every predetermined drying period. Then, in order to improve the measurement accuracy of the drying shrinkage strain, preferably, the specimen has a disk shape, and the specimen is rotated clockwise or counterclockwise so that the peripheral side surface of the specimen is positioned. In contact with the tool, measure the distance between the laser displacement meter and the peripheral side surface of the specimen at least twice, preferably 3-5 times. For example, after measuring the point a of the specimen shown in FIG. 1, the specimen is rotated 90 ° clockwise to measure the point b, and further rotated 90 ° clockwise to measure the point c. The average value of the points is calculated as the drying shrinkage strain.
In the measuring method of the present invention, the measurement interval of the drying shrinkage strain is arbitrary, but the measurement interval of the drying shrinkage strain is preferable in order to obtain the final value of the drying shrinkage strain at an early stage and to reduce the time and effort for measurement. The drying period is every 1 to 10 days, more preferably every 1 to 7 days.

Further, in the measuring method of the present invention, in order to measure the drying shrinkage strain more accurately, a metal plate (base length plate) having the same shape and dimensions as the specimen before drying is placed on a pedestal and a laser is used. _{After measuring the distance (L 1} ) between the displacement meter and the side surface of the metal plate, the specimen is placed on a pedestal in place of the metal plate, and between the laser displacement meter and the side surface of the specimen. This is a method _{of measuring the distance (L 2} ) and determining the drying shrinkage strain based on the difference between _{L 1} and L _{2 (L 1 −} L _2).
Further, when using a measuring device in which the measured distance is displayed on the screen, the measuring method of the present invention mounts a metal plate (base length plate) having the same shape and dimensions as the specimen before drying on the pedestal. Place, measure the distance between the laser displacement meter and the side surface of the metal plate, set the distance (indication) to zero, and then place the specimen on the pedestal in place of the metal plate. This is a method of measuring the distance between the laser displacement meter and the side surface of the specimen to determine the drying shrinkage strain.
The metal plate (base length plate) is preferably a metal of the same material as the pedestal so that the change in length due to a change in temperature is the same, and is more preferably Invar in order to prevent deformation due to heat or impact. It is a steel material.

3. 3. Dry shrinkage strain measuring device (E ₂ )
As illustrated in FIGS. 4 to 7, the drying shrinkage strain measuring device (E ₂ ) includes two or more laser displacement meters 4, and three or more supporting members 5 for supporting the specimen for measuring the drying shrinkage strain. , And a device including at least a pedestal 2 formed by embedding a part of the support member.
The laser displacement meter is the same as the laser displacement meter of the drying shrinkage strain measuring device (E ₁ ). Further, in order to improve the measurement accuracy of the drying shrinkage strain, two or more laser displacement meters are installed. With one laser displacement meter, the measurement accuracy of drying shrinkage strain may decrease. Further, if the number of laser displacement meters is increased, the number of data is increased, and the measurement accuracy is further improved by that amount, but the cost of the device is increased. Therefore, 2 to 6 laser displacement meters are preferably installed, and 2 to 4 laser displacement meters are more preferably installed.
Since the laser displacement meter improves the measurement accuracy of drying shrinkage strain and makes it easy to place the specimen, it is preferable to irradiate the laser at positions equilaterally spaced from the center of the equilateral triangle or square formed by the support member. Install with the surface facing the center. Further, in order to further improve the measurement accuracy of the drying shrinkage strain, more preferably, 2 to 6 of the laser displacement meters are crossed so that the lasers emitted from the laser displacement meters intersect at an angle of 60 to 300 °. Deploy.
In the mode of installing the laser displacement meter, when two laser displacement meters are installed, for example, the laser displacement meters are installed facing each other as shown in FIG. 4, or the laser is 90 ° as shown in FIG. When four laser displacement meters are installed so as to intersect at the angle of the above, two sets of laser displacement meters are installed facing each other as shown in FIG.

In the drying shrinkage strain measuring device (E ₂ ), the support member is an indispensable jig and is used to separate the specimen from the pedestal and provide a space between the specimen and the pedestal. By providing this space, the specimen dries homogeneously and early, so that the ultimate value of the drying shrinkage strain can be measured early.
The shape, number, arrangement shape (position shape), and material of the support members are the same as those of the drying shrinkage strain measuring device (E ₁ ).

The pedestal is formed by burying and fixing a part (lower part) of the support member. Incidentally, the pedestals shown in FIGS. 4 to 6 have a square plate shape, and the pedestals shown in FIG. 7 have a disk shape. Incidentally, the pedestal is preferably being kept horizontal, the material it Invar steel is preferable is the same as the drying shrinkage strain measurement device (E _1).

In the drying shrinkage strain measuring device (E ₂ ), a specimen mounting auxiliary jig may be used in order to facilitate mounting of the specimen on the support member. Examples of the specimen mounting auxiliary jig include two pins installed on the outside of the pedestal as shown in FIG. 7. When, for example, a disk-shaped specimen having a diameter of 10 cm is placed on the support member of the drying shrinkage strain measuring device (E _{2) shown in FIG. 7, the specimen is supported so as to be in contact with the two pins.} When placed on the member, the specimen can be placed so that the center of the specimen and the center of the square formed by the support member coincide with each other.
The specimen mounting auxiliary jig may be installed on the outside of the pedestal as shown in FIG. 7, or may be installed on the pedestal. Further, the specimen mounting auxiliary jig is preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact.

The drying shrinkage strain measuring device (E ₂ ) is also configured by integrating two or more laser displacement meters, a pedestal, and, if necessary, a specimen mounting auxiliary jig, as shown in FIGS. 4 to 7. To do. The material of such pedestal that Invar steel is preferable is the same as the drying shrinkage strain measurement device (E _1).

4. Method of measuring dry shrinkage strain using a dry shrinkage strain measuring device (E ₂ ) In this measuring method, the center of a disk-shaped or square columnar specimen is placed on the support member of the dry shrinkage strain measuring device (E _2). After placing the support member so as to coincide with the center of the regular triangle or square formed by the support member, a laser displacement meter is used to irradiate the side surface around the specimen with a laser to irradiate the side surface around the laser displacement meter and the specimen. This is a method of determining the drying shrinkage strain of a specimen by measuring the distance between the sides of the specimen.
For example, as shown in FIG. 7, a disk-shaped specimen is placed on the support members (four spherical points on the pedestal) of _{the drying shrinkage strain measuring device (E 2), and the center and the support member of the specimen are placed.} After placing the squares to be formed so that the centers of the squares coincide with each other (Fig. 7 (B)), the side surface around the specimen is irradiated with a laser using a laser displacement meter, and the laser displacement meter and the periphery of the specimen are used. The drying shrinkage strain of the specimen is measured by measuring the distance between the sides.
The shape, size, and thickness of the specimen are the same as in the case of the method for measuring the drying shrinkage strain using the drying shrinkage strain _{measuring device (E 1).}

The measurement method is different from (a) a method in which the specimen is dried with the specimen still placed on the support member and the drying shrinkage strain is obtained every predetermined drying period, and (b) another method. Any method of obtaining the drying shrinkage strain by placing the specimen dried in the place on the support member at a predetermined drying period is possible, but the labor of work is reduced and the measurement accuracy is improved. From the point of view, the method (a) is preferable.
The measurement interval of the drying shrinkage strain is the same as that of the method of measuring the drying shrinkage strain using the drying shrinkage strain _{measuring device (E 1).}
As described above, if the drying shrinkage strain measuring device (E ₁ ) or (E ₂ ) is used _{, the} drying shrinkage strain (final value) can be accurately obtained in a short period of time.

5. Method for Predicting Ultimate Value of Drying Shrink Strain The prediction method is a drying period of 7, 10, or 14 days measured using a _{drying shrinkage strain measuring device (E 1} ) or a drying shrinkage strain measuring device (E _2). The value obtained by multiplying the coefficient shown in Table 1 selected according to the dry shrinkage strain of the concrete and the type of cement used for the concrete by the dry shrinkage strain is the dry shrinkage strain of the concrete. It is a method of predicting as the final value of. The coefficients in Table 1 are numerical values obtained by regression analysis using the already obtained data.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.
1. 1. Measurement of dry shrinkage strain of concrete using a dry shrinkage strain measuring device (E ₁ ) (1-1) Materials used (i) Cement (abbreviation: C, all manufactured by Taiheiyo Cement Co., Ltd.)
Ordinary Portland cement (abbreviation: NC)
Blast furnace cement type B (abbreviation: BB)
Moderate heat Portland cement (abbreviation: MC)
Low-grade Portland cement (abbreviation: LC)
(Ii) Fine aggregate (abbreviation: S): Mountain sand (surface dry density 2.56 g / cm ³ )
(Iii) Coarse aggregate (abbreviation: G): Surface dry density 2.61 g / cm ³
(Iv) Water (abbreviation: W): Tap water (v) AE water reducing agent: Ligno sulfonic acid-based AE water reducing agent, trade name Pozoris No. 70 [registered trademark], manufactured by BASF, Ltd.
(Vi) AE agent: Brand name Master Air 404 [registered trademark], manufactured by BASF

(1-2) Preparation of Specimen for Drying Shrink Strain Measurement According to the formulation shown in Table 2, each of the above materials was put into a pan-type mixer having a capacity of 50 liters, kneaded for 2 minutes, and then the kneaded product had an inner diameter. It was cast into a mold having a height of 10 cm and a height of 20 cm and molded to obtain concrete. Next, the concrete was moist-air-cured at 20 ° C. for 1 day, then demolded, and further water-cured at 20 ° C. for 7 days. After curing in water, the vicinity of the central portion in the height direction of the concrete was cut to prepare three specimens for measuring drying shrinkage strain having a diameter of 10 cm and a thickness of 1 cm.

(1-3) Measurement of Dry Shrinkage Strain of Specimen The test piece 1 for measuring the dry shrinkage strain was dried under the conditions of room temperature 20 ± 2 ° C. and relative humidity 60 ± 5%. Then, every 7 days during the drying period, the specimen for measuring the drying shrinkage strain is brought into contact with the positioning jig 3 of the _{drying shrinkage strain measuring device (E 1) shown in FIG.} After mounting on the pedestal 2, the distance between the laser displacement meter and the side surface around the specimen was measured using the laser displacement meter 4. In this embodiment, the distance between the laser displacement meter and the side surface around the specimen is measured at three points (points a, b, and c in FIG. 1) for one specimen. , This average value was calculated as the drying shrinkage strain of the specimen, and further, the drying shrinkage strain (average value) of these three specimens was averaged to calculate the total drying shrinkage strain. The results are shown in FIGS. 8 and 3 (however, in FIG. 8, a part of the data after the drying period of 56 days is omitted).
For comparison, the drying shrinkage strains of the concretes A to D were measured in accordance with JIS A 1129-2 "Mortar and concrete length change measurement method Part 2: Contact gauge method" (JIS method). .. The results are shown in FIG. 8 and Table 3.
Further, each concrete obtained by multiplying the value of the drying shrinkage strain of concretes A to D measured by using the drying shrinkage strain measuring device shown in FIG. 1 for a drying period of 7 days or 14 days by the coefficient in Table 1 was obtained. Table 4 shows the predicted final values of the drying shrinkage strain.
Further, the value of the drying shrinkage strain having a drying period of 10 days was estimated from the values of the drying shrinkage strain having a drying period of 7 days and 14 days, and the estimated value was multiplied by the coefficient in Table 1 to obtain the drying of each concrete. Table 4 also shows the predicted values of the final values of contraction strain.

As shown in FIG. 8, in any concrete, the final value of the drying shrinkage strain cannot be obtained by the JIS method until the drying period has passed for one year or more.
On the other hand, as shown in Table 4, according to the present invention, the final value of the drying shrinkage strain is obtained by multiplying the value of the drying shrinkage strain having a drying period of 7, 10, or 14 days by the coefficient of Table 1. It can be obtained quickly and accurately.

1 Specimen 2 Pedestal 3 Positioning jig 4 Laser displacement meter (However, the black arrow indicates the laser)
5 Support member

Claims (1)

Dry shrinkage strain of concrete with a drying period of 7, 10, or 14 days measured using the following dry shrinkage strain measuring device (E ₁ ) or dry shrinkage strain measuring device (E _{2), and the concrete.} The value obtained by multiplying the coefficient shown in Table 1 selected according to the type of cement used by the drying shrinkage strain is predicted as the final value of the drying shrinkage strain of concrete. How to predict the final value of.
<Dry shrinkage strain measuring device (E ₁ )>
Drying shrinkage strain measuring device <Drying shrinkage strain measuring device (dry shrinkage strain measuring device) including at least one laser displacement meter, a pedestal for mounting a specimen for measuring drying shrinkage strain, and a positioning jig for the specimen. E ₂ )>
Dry shrinkage strain including at least two laser displacement meters, three or more support members for supporting a specimen for measuring dry shrinkage strain, and a pedestal formed by embedding a part of the support member. measuring device

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