JP2020139909A - Method of estimating drying shrinkage strain - Google Patents

Abstract

To provide a method of estimating values of drying strain during a six-month period of drying at an early stage.SOLUTION: A drying shrinkage strain estimation method is provided, involving estimating a drying shrinkage strain value in a six-month drying period, as measured in compliance with JIS A 1129-1, JIS A 1129-2, or JIS A 1129-3, as a value obtained by multiplying an ultimate value of drying shrinkage strain acquired through a specimen mounting step and an ultimate drying shrinkage strain acquisition step by a coefficient selected according to a cement type.SELECTED DRAWING: Figure 4

Description

The present invention relates to a hardened cement paste, concrete, and mortar (hereinafter referred to as "hardened cementum"), JIS A 1129-1, JIS A 1129-2, or JIS A 1129-3 (hereinafter "JIS A 1129"). It relates to a method for estimating dry shrinkage strain, which estimates the value of dry shrinkage strain at an early stage when the drying period is 6 months, which is measured according to (-1 to 3).

Conventionally, the method of measuring the drying shrinkage strain of a cementum hardened product is a method using a comparator specified in JIS A 1129-1, a method using a contact gauge specified in JIS A 1129-2, and a method using JIS A 1129-3. There is a method using a specified dial gauge. However, in each of these methods, it takes a long period of 6 months to obtain the value of the drying shrinkage strain when the drying period is 6 months, and the specimen of 10 cm × 10 cm × 40 cm is obtained every predetermined period. The length of the (cementum hardened body) had to be measured, which took time and effort.

Therefore, Patent Document 1 proposes a method for early evaluation of the drying shrinkage strain of concrete. The method is a relational expression between the measured value of the drying shrinkage strain at a temperature of 80 ° C. on the 28th day of the drying period and the final drying shrinkage strain value at a temperature of 20 ° C., or the final drying shrinkage strain value at a temperature of 80 ° C. and the temperature. This is a method for early evaluation of the dry shrinkage strain of concrete at an arbitrary long-term age by using relational expressions that approximate the relationship with the final dry shrinkage strain value at 20 ° C. by linear equations. However, with this method, it takes time to obtain the relational expression, and if the relationship between the final drying shrinkage strain value at a temperature of 80 ° C. and the final drying shrinkage strain value at a temperature of 20 ° C. is not linear, the evaluation accuracy is high. descend.

Japanese Unexamined Patent Publication No. 2014-20866

Therefore, an object of the present invention is to provide a method for estimating dry shrinkage strain, which is measured according to JIS A 1129-1 to 3 and which estimates the value of dry shrinkage strain at a drying period of 6 months at an early stage. To do.

As a result of diligently studying a method for estimating dry shrinkage strain that meets the above object, the present inventor obtains the above object by multiplying the final value of dry shrinkage strain measured using a specific dry shrinkage strain measuring device by a specific coefficient. The present invention was completed by finding that the above can be achieved.
That is, the present invention is a method for estimating dry shrinkage strain having the following constitution.

［２］前記供試体の位置決め治具が２本のピンであり、レーザー変位計と位置決め治具が、図１または図２に示す位置に設置されている乾燥収縮ひずみ測定装置を用いる、前記［１］に記載の乾燥収縮ひずみの推定方法。
［３］円板状の供試体を、時計回りまたは反時計回りに回転して、該供試体の周囲の側面が位置決め治具と接触した状態で、レーザー変位計と該供試体の周囲の側面の間の距離を複数回測定し、これらの距離の平均値を求め、該平均値と乾燥直前におけるレーザー変位計と該供試体の周囲の側面の間の距離との差を、乾燥直前における該供試体の直径で除した値を、該供試体の乾燥収縮ひずみとして求める、前記［１］または［２］に記載の乾燥収縮ひずみの推定方法。
［４］前記供試体の厚さが５〜２０ｍｍである、前記［１］〜［３］のいずれかに記載の乾燥収縮ひずみの推定方法。
［５］所定の乾燥期間が経過する度に、供試体を台座上に載置して、レーザー変位計と該供試体の周囲の側面の間の距離を測定する、前記［１］〜［４］のいずれかに記載の乾燥収縮ひずみの推定方法。
［６］乾燥前の供試体と同じ形状および寸法を有する金属板（基長板）を台座上に載置して、レーザー変位計と該金属板の側面の間の距離（Ｌ_１）を測定した後、該金属板に代えて前記供試体を台座上に載置して、レーザー変位計と供試体の側面の間の距離（Ｌ_２）を測定し、Ｌ_１とＬ_２の差（Ｌ_１−Ｌ_２）を金属板（基長板）の長さ（Ｌ）で除した値（（Ｌ_１−Ｌ_２）/Ｌ）を乾燥収縮ひずみとして求める、前記［１］〜［５］のいずれかに記載の乾燥収縮ひずみの推定方法。
［７］乾燥前の供試体と同じ形状および寸法を有する金属板（基長板）を台座上に載置して、レーザー変位計と該金属板の側面の間の距離を測定し、該距離（の表示）をゼロに設定した後、該金属板に代えて前記供試体を台座上に載置して、レーザー変位計と供試体の側面の間の距離を測定して、該距離を金属板（基長板）の長さ（Ｌ）で除した値を乾燥収縮ひずみとして求める、前記［１］〜［６］のいずれかに記載の乾燥収縮ひずみの推定方法。 [1] JIS A 1129 is the value obtained by multiplying the final value of the drying shrinkage strain obtained through the steps (A) and (B) below by a coefficient selected according to the type of cement shown in Table 1. A method for estimating drying shrinkage strain, which is estimated as a value of drying strain in a drying period of 6 months, measured according to -1 to 3.
(A) On a pedestal of a drying shrinkage strain measuring device equipped with at least one laser displacement meter, a pedestal for mounting a specimen for measuring drying shrinkage strain, and a positioning jig for the specimen. A disk-shaped or square plate-shaped specimen is placed on the specimen so that the side surface around the specimen is in contact with the positioning jig. (B) A side surface around the specimen. The distance between the laser displacement meter and the peripheral side surface of the specimen is measured by irradiating a laser from the laser displacement meter, and the drying shrinkage strain of the specimen when the distance reaches a certain value is determined by the specimen. Step of acquiring the ultimate value of the drying shrinkage strain, which is acquired as the ultimate value of the drying shrinkage strain [Table 1]

[2] The drying shrinkage strain measuring device is used in which the positioning jig of the specimen is two pins and the laser displacement meter and the positioning jig are installed at the positions shown in FIGS. 1 or 2. 1] The method for estimating dry shrinkage strain.
[3] Rotate the disk-shaped specimen clockwise or counterclockwise, and with the peripheral side surface of the specimen in contact with the positioning jig, the laser displacement meter and the peripheral side surface of the specimen. The distance between the two was measured multiple times, the average value of these distances was calculated, and the difference between the average value and the distance between the laser displacement meter immediately before drying and the side surface around the specimen was determined by the difference immediately before drying. The method for estimating dry shrinkage strain according to the above [1] or [2], wherein a value divided by the diameter of the specimen is obtained as the dry shrinkage strain of the specimen.
[4] The method for estimating dry shrinkage strain according to any one of [1] to [3] above, wherein the specimen has a thickness of 5 to 20 mm.
[5] Each time a predetermined drying period elapses, the specimen is placed on a pedestal, and the distance between the laser displacement meter and the side surface around the specimen is measured. ]. The method for estimating dry shrinkage strain according to any one of.
[6] A metal plate (base length plate) having the same shape and dimensions as the specimen before drying is placed on a pedestal, and the distance (L ₁ ) between the laser displacement meter and the side surface of the metal plate is measured. After that, the specimen was placed on a pedestal instead of the metal plate, the distance (L ₂ ) between the laser displacement meter and the side surface of the specimen was measured, and the difference between L ₁ and L ₂ (L). _The value ((L _1- L ₂ ) / L) obtained by dividing _1- L ₂ ) by the length (L) of the metal plate (base length plate) is obtained as the drying shrinkage strain of the above [1] to [5]. The method for estimating dry shrinkage strain according to any one.
[7] A metal plate (base length plate) having the same shape and dimensions as the specimen before drying is placed on a pedestal, and the distance between the laser displacement meter and the side surface of the metal plate is measured, and the distance is measured. After setting (indication) to zero, the specimen is placed on a pedestal in place of the metal plate, the distance between the laser displacement meter and the side surface of the specimen is measured, and the distance is set to metal. The method for estimating dry shrinkage strain according to any one of [1] to [6] above, wherein the value divided by the length (L) of the plate (base length plate) is obtained as the dry shrinkage strain.

The method for estimating the drying shrinkage strain of the present invention can accurately estimate the drying shrinkage strain of a cementum-hardened product at a drying period of 6 months, which is measured according to JIS A 1129-1 to 3. Further, the specimen used in the present invention is smaller than the specimen used in JIS A 1129-1 to 3, and the work such as moving the specimen is easy, so that the labor for measuring the drying shrinkage strain can be significantly reduced. ..

A schematic view showing an example of a state in which a specimen is placed on a drying shrinkage strain measuring device of the present invention having one laser displacement meter, the left figure is a plan view of the measuring device, and the right is a plan view of the measuring device. The figure 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 of the present invention having two laser displacement meters, and the left figure is a plan view of the measuring device and the right side. The figure is a side view of the measuring device. A schematic view showing an example of a state in which a specimen is placed on a support member which is installed with a part of the lower part of the support member embedded in a pedestal, and the figure on the left is a schematic view of the measuring device. The plan view and the right view are side views of the measuring device. However, in FIG. 3, the description of the laser displacement meter is omitted. It is a figure which shows the time-dependent change of the drying shrinkage strain of each concrete specimen of an Example, (N) is ordinary Portland cement, (BB) is blast furnace cement type B, (M) is moderate heat Portland cement, (L) is Low heat Portland cement, (EX) is expansion material-containing cement, (FA30) is dry shrinkage strain of concrete specimens using fly ash cement type C, and (SR) is dry shrinkage strain of concrete specimens containing shrinkage reducing agent. , Is shown.

In the present invention, JIS A is obtained by multiplying the final value of the drying shrinkage strain obtained through the steps (A) and (B) by a coefficient selected according to the type of cement shown in Table 1. This is a method for estimating dry shrinkage strain, which is estimated as a value of dry strain in a drying period of 6 months, measured according to 1129-1 to 3.
Hereinafter, the present invention will be described in detail separately for a drying shrinkage strain measuring device, a drying shrinkage strain measurement, an acquisition of a final value of the dry shrinkage strain, and a method for estimating the dry shrinkage strain.

1. 1. Drying Shrink Strain Measuring Device (A) Laser Displacement Meter The laser displacement meter 4 used in the present invention 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 1 or 2.
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 1 placed on the pedestal. Examples of the installation position of the laser displacement meter include the positions shown in FIGS. 1 and 2.

(B) Pedestal The pedestal 2 used in the present invention is used to mount 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 for measuring the drying shrinkage strain. When the support member is installed, the heat transfer between the specimen for measuring the drying shrinkage strain 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, it is preferable that the upper portion is hemispherical.
It is preferable that the number of support members is 3 or more because the specimen can be stably placed, but if the number of support members is increased, it takes time and effort to manufacture the device. Therefore, the number of support members is preferably 3 to 4. 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.

(C) Positioning Jig The positioning jig 3 used in the present invention is used to determine and fix the placement position of the specimen when measuring the drying shrinkage strain of the specimen. For example, FIG. As shown in FIG. 2, examples thereof include two pins installed on a pedestal in an inverted state. In FIGS. 1 and 2, when the disc-shaped specimen is placed on the pedestal when the drying period is 0 (zero) days, the center of the disc-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, in the drying shrinkage strain measuring device of the present invention, it is preferable that the laser displacement meter, the pedestal, and the positioning jig are integrated by using a base. In this case, the base used for installing the laser displacement meter, the pedestal, and the positioning jig is preferably manufactured using Invar steel material in order to prevent deformation due to heat or impact.

2. 2. Measurement of Dry Shrink Strain and Acquisition of Ultimate Value of Dry Shrink Strain In the present invention, the measurement of dry shrink strain is performed by first placing a disk-shaped or square plate-shaped specimen on the pedestal of the dry shrink strain measuring device. The specimen is placed so that the side surface around the specimen comes into contact with the positioning jig (step of placing the specimen).
In the present invention, (1) a method of placing a specimen dried in another place on a pedestal at a predetermined drying period and measuring the drying shrinkage strain, and (2) placing the specimen on the pedestal. It is possible to measure the drying shrinkage strain of a large number of specimens in parallel by drying the specimen while it is still placed and measuring the drying shrinkage strain at predetermined drying periods. Therefore, the method (1) described above is preferable.
In the present invention, when the specimen is in the shape of a disk 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 length of one side is 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 of the present invention, the side surface around the disk-shaped or square plate-shaped specimen is in contact with the positioning jig on the support member. The specimen is placed in the space.

In the measurement of drying shrinkage strain in the present invention, a laser displacement meter is used to irradiate the peripheral side surface of the specimen with a laser, and the distance between the laser displacement meter and the peripheral side surface of the specimen is measured. Measure the drying shrinkage strain of the specimen. Then, the drying shrinkage strain of the specimen at the time when the distance between the laser displacement meter and the side surface around the specimen reaches a certain value is acquired as the ultimate value of the drying shrinkage strain of the specimen (the ultimate drying shrinkage strain). Value acquisition process). Here, the time when the distance between the laser displacement meter and the side surface around the specimen reaches a constant means the time when the amount of change in the distance in 7 days becomes 0.001 mm or less.
In the present invention, in order to improve the measurement accuracy of the drying shrinkage strain, the specimen is preferably in the shape of a disk, and the specimen is rotated clockwise or counterclockwise so that the peripheral side surface of the specimen is formed. In contact with the positioning jig, measure the distance between the laser displacement meter and the peripheral side surface of the specimen a plurality of times, preferably 3 to 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 was calculated, and the difference between the average value and the distance between the laser displacement meter immediately before drying and the side surface around the specimen was divided by the diameter of the specimen immediately before drying to obtain the drying shrinkage strain. Ask as.
In the measurement of the drying shrinkage strain in the present invention, the measurement interval of the drying shrinkage strain is arbitrary, but in order to obtain the final value of the drying shrinkage strain at an early stage and to reduce the labor of measurement, the drying period 1 is preferable. Every 10 to 10 days, more preferably every 1 to 7 days of drying period.

Further, in the measurement of the drying shrinkage strain in 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 the pedestal. After measuring the distance (L ₁ ) between the laser displacement meter and the side surface of the metal plate, the specimen is placed on a pedestal in place of the metal plate, and the laser displacement meter and the side surface of the specimen are placed. The distance between (L ₂ ) is measured, and the difference between L ₁ and L ₂ (L _1- L ₂ ) is divided by the length (L) of the metal plate (base length plate) ((L _1- L). ₂ ) / L) is defined as the drying shrinkage strain.
Further, when the measuring device in which the measured distance is displayed on the screen is used, the measurement of the drying shrinkage strain in the present invention uses a metal plate (base length plate) having the same shape and dimensions as the specimen before drying. Place it on top, 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. After mounting, the distance between the laser displacement meter and the side surface of the specimen is measured, and the value obtained by dividing the distance by the length (L) of the metal plate (base length plate) is defined as 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 more preferably Invar in order to prevent deformation due to heat or impact. It is a steel material.

3. 3. Method for estimating dry shrinkage strain In the method for estimating dry shrinkage strain of the present invention, the final value of the dry shrinkage strain obtained through the steps (A) and (B) is set according to the type of cement shown in Table 1. This is a method for estimating dry shrinkage strain, in which the value obtained by multiplying the selected coefficient is estimated as the value of dry strain in a drying period of 6 months, which is measured according to JIS A 1129-1 to 3.
According to the estimation method of the present invention, as shown in Examples described later, the value of the drying shrinkage strain of the cementum hardened product during the drying period of 6 months measured in accordance with JIS A 1129-1 to 3, especially compression. The value of the drying shrinkage strain of a cementum-hardened product having a strength of 18 N / mm ² or more can be accurately estimated within a short period of 100 days or less.
The type of cemented hardened material to which the method for estimating dry shrinkage strain of the present invention can be applied is not particularly limited, and in addition to ordinary concrete, concrete containing a shrinkage reducing agent or an expanding material (see FIG. 5), and quick-hardening type. It can also be applied to hardened cement materials such as concrete, lightweight concrete, and high-strength concrete.
When the concrete contains a shrinkage reducing agent, the unit amount of the shrinkage reducing agent is preferably 12 kg / m ³ or less, more preferably 9 kg / m ³ or less, still more preferably 6 kg / m ³ or less, and the concrete When the expanding material is included, the unit amount of the expanding material is preferably 30 kg / m ³ or less, more preferably 25 kg / m ³ or less, and further preferably 20 kg / m ³ or less.
When the cement is a blast furnace cement, the cement is preferably a blast furnace cement type A or type B. When the cement contains silica fume, the content of silica fume in the cement is preferably 20% by mass or less.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.
1. 1. Materials used (1) Cement (manufactured by Taiheiyo Cement)
(i) Ordinary Portland cement (abbreviation: NC)
(ii) Blast furnace cement type B (abbreviation: BB)
(iii) Moderate heat Portland cement (abbreviation: MC)
(iv) Low heat Portland cement (abbreviation: LC)
(v) Fly ash cement type C (abbreviation: FA)
Brain specific surface area: 3300 cm ² / g, fly ash content: 30% by mass)
(2) Fine aggregate (abbreviation: S)
Mountain sand (surface dry density 2.56 g / cm ³ )
(3) Coarse aggregate (abbreviation: G)
Sandstone crushed stone (surface dry density 2.61 g / cm ³ )
(4) Water (abbreviation: W)
Tap water (5) AE water reducing agent (abbreviation: LS)
Ligno sulfonic acid-based AE water reducing agent, trade name Pozoris No. 70 [Registered Trademark] (manufactured by BASF)
(6) Air Entrainment Product Name Master Air 404 [Registered Trademark] (manufactured by BASF)
(7) Shrinkage reducing agent (abbreviation: SR)
Product name Tetra Guard AS21 (manufactured by Pacific Materials)
(8) Expansion material (abbreviation: EX)
Pacific Hyper Expand (manufactured by Pacific Materials)

2. 2. Preparation of Specimen for Dry 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 of 10 cm and a height of 10 cm. It was cast into a 20 cm mold 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 dry shrinkage strain having a diameter of 10 cm and a thickness of 10 mm.
The compression strength of JIS A 1108 concrete was measured according to "the concrete compressive strength test" A, D, and F age of 28 days, respectively ^{47N / mm 2, 40N / mm} 2, and 46N / mm It was ² .

3. 3. Measurement of drying shrinkage strain of specimen The measurement of drying shrinkage strain of specimen will be described below with reference to the figure.
The specimen 1 for measuring the drying 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 peripheral side surface of the specimen is placed on the pedestal 2 so as to be in contact with the positioning jig 3 of the drying shrinkage strain measuring device shown in FIG. 1, and then the laser displacement meter 4 is used. The distance between the laser displacement meter and the side surface around the specimen was measured. 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. The average value was calculated, and the difference between this average value and the distance between the laser displacement meter and the side surface around the specimen immediately before drying was divided by the diameter of the specimen immediately before drying to obtain the drying shrinkage strain of the specimen. Further, the drying shrinkage strains (average values) of these three specimens were averaged to calculate the total drying shrinkage strains. The results are shown in FIGS. 4 and 3.
However, the meanings of the numerical values in Table 3 are as follows.
(i) Ultimate value of strain The numerical value in the column of "the present invention" indicates the ultimate value of dry shrinkage strain measured by using the dry shrinkage strain measuring device of FIG.
(ii) The numerical value in the "Ultimate value of strain JIS method" column is described in JIS A 1129-2 "Mortar and concrete length change measurement method Part 2: Contact gauge method" (hereinafter referred to as "JIS method"). The final value of the drying shrinkage strain measured according to the above is shown.
(iii) The numerical value in the "measured value of strain with a drying period of 6 months" indicates the value (measured value) of the drying shrinkage strain with a drying period of 6 months measured in accordance with the JIS method (comparison). Example).
(iv) For the numerical value in the "Estimated value of strain with a drying period of 6 months" column, as an example, the coefficient selected from Table 1 according to the type of cement in the specimen is used as the final value of the drying shrinkage strain. The value (estimated value) obtained by multiplying is shown (Example).

As shown in Table 3, according to the present invention, the drying period is 6 months, which is measured in accordance with the JIS method by simply multiplying the final value of the drying shrinkage strain by a coefficient according to the type of cement in the specimen. The value of the drying shrinkage strain can be estimated at an early stage without any effort with high accuracy with an error of 3.1% or less. Moreover, since the high estimation accuracy of the present invention does not depend on the type of cement, it is highly versatile.

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

Claims (7)

JIS A 1129-1, a value obtained by multiplying the final value of the drying shrinkage strain obtained through the steps (A) and (B) below by a coefficient selected according to the type of cement shown in Table 1. A method for estimating drying shrinkage strain, which is estimated as a value of drying strain at a drying period of 6 months, measured according to JIS A 1129-2 or JIS A 1129-3.
(A) On a pedestal of a drying shrinkage strain measuring device equipped with at least one laser displacement meter, a pedestal for mounting a specimen for measuring drying shrinkage strain, and a positioning jig for the specimen. A disk-shaped or square plate-shaped specimen is placed on the specimen so that the side surface around the specimen is in contact with the positioning jig. (B) A side surface around the specimen. The distance between the laser displacement meter and the peripheral side surface of the specimen is measured by irradiating a laser from the laser displacement meter, and the drying shrinkage strain of the specimen when the distance reaches a certain value is determined by the specimen. Step of acquiring the ultimate value of the drying shrinkage strain, which is acquired as the ultimate value of the drying shrinkage strain [Table 1]

The first aspect of the present invention, wherein the positioning jig of the specimen is two pins, and the laser displacement meter and the positioning jig use a drying shrinkage strain measuring device installed at the position shown in FIG. 1 or 2. How to estimate the drying shrinkage strain of. Rotate the disk-shaped specimen clockwise or counterclockwise so that the peripheral side surface of the specimen is in contact with the positioning jig, between the laser displacement meter and the peripheral side surface of the specimen. The distances are measured multiple times, the average value of these distances is calculated, and the difference between the average value and the distance between the laser displacement meter immediately before drying and the peripheral side surface of the specimen is determined by that of the specimen immediately before drying. The method for estimating dry shrinkage strain according to claim 1 or 2, wherein the value divided by the diameter is obtained as the dry shrinkage strain of the specimen. The method for estimating dry shrinkage strain according to any one of claims 1 to 3, wherein the specimen has a thickness of 5 to 20 mm. Any one of claims 1 to 4, wherein the specimen is placed on a pedestal and the distance between the laser displacement meter and the peripheral side surface of the specimen is measured each time a predetermined drying period elapses. The method for estimating dry shrinkage strain according to. After placing a metal plate (base length plate) having the same shape and dimensions as the specimen before drying on the pedestal and measuring the distance (L ₁ ) between the laser displacement meter and the side surface of the metal plate, The specimen is placed on a pedestal instead of the metal plate, the distance (L ₂ ) between the laser displacement meter and the side surface of the specimen is measured, and the difference between L ₁ and L ₂ (L _{1 −} L) is measured. _The value ((L _{1 −} L ₂ ) / L) obtained by dividing ₂ ) by the length (L) of the metal plate (base length plate) is obtained as the drying shrinkage strain, according to any one of claims 1 to 5. How to estimate the drying shrinkage strain of. A metal plate (base length plate) having the same shape and dimensions as the specimen before drying is placed on the pedestal, the distance between the laser displacement meter and the side surface of the metal plate is measured, and the distance (display) is measured. ) Is set to zero, the specimen is placed on a pedestal instead of the metal plate, the distance between the laser displacement meter and the side surface of the specimen is measured, and the distance is determined by the metal plate (base). The method for estimating dry shrinkage strain according to any one of claims 1 to 6, wherein the value divided by the length (L) of the long plate) is obtained as the dry shrinkage strain.

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