KR20120131006A - Experimental Device and Method of restrained shrinkage of Concrete - Google Patents

Abstract

PURPOSE: A device and a method for testing the restrained shrinkage of concrete are provided to reduce the thickness of a concrete specimen to a radial direction and vertical direction and to increase the restraint intensity of the dry shrinkage of the concrete. CONSTITUTION: A device for testing the restrained shrinkage of concrete comprises a base plate, an inner ring member(200), an outer ring member, a strain gauge, and a shielding member(500). The inner ring member is joined to a top surface of the base plate. The concrete is place between the inner and outer ring members so that a ring-shaped concrete specimen is cured for reference time. The strain gauge measures a strain of the inner ring member by being mounted in the inner circumference of the inner ring member. The shielding member is mounted to be touched to the outer circumference of the concrete specimen, thereby preventing the concrete specimen to be exposed to outside.

Description

Experimental Device and Method of restrained shrinkage of Concrete

The present invention relates to a concrete restraint shrinkage test apparatus and method. More specifically, by increasing the degree of restraint on the drying shrinkage of the concrete to induce the initial crack during the dry shrinkage process, and evenly induces dry shrinkage during the dry shrinkage process of the concrete, not only for general concrete but also fiber reinforced concrete (FRC) Test and evaluation of restraint shrinkage behavior can be more easily and smoothly performed, and the stress concentration caused by the thickness difference can be concentrated by forming and shrinking the concrete specimens differently through the eccentric arrangement of the inner and outer ring members. Phenomenon can be used to increase the degree of restraint and induce an initial crack, and due to the difference in thickness, it is possible to form various restraints in one concrete specimen. Therefore, the restraint shrinkage behavior of various restraints can be evaluated through one concrete specimen. A concrete concrete restraint shrinkage testing apparatus and method are disclosed.

Concrete exhibits superior economics compared to other construction materials, and has excellent mechanical performance and durability. However, it has several problems such as low strength to weight and brittle fracture.In order to overcome these limitations, fiber reinforced concrete (FRC: Fiber Reinforced) is obtained by incorporating a plurality of fibers into concrete to improve tensile strength. Research on the development and commercialization of concrete has been actively conducted at home and abroad. In particular, recently developed ultra-high performance concrete (UHPC) exhibits excellent compressive strength and toughness of 200MPa compressive strength and 35MPa flexural tensile strength.

However, ultra-high-performance concrete has a low water-binding ratio (W / B) and uses high-molecular mixed materials, resulting in large initial self-shrinkage, and initial shrinkage without sufficient strength development results in cracking of the structure. To reduce the durability and structural performance. Therefore, in order to apply ultra high performance concrete to actual structures, it is necessary to understand and evaluate the restraint shrinkage behavior.

The behavior that appears when the shrinkage of concrete is constrained is complicated by the speed and magnitude of contraction, the degree of restraint, the strength expression, and the relaxation of stress. Therefore, there is a limit to the evaluation of cracking behavior only through free shrinkage (self shrinkage, dry shrinkage, temperature shrinkage, etc.) experiments in which strength expression and creep characteristics of concrete cannot be considered.

In the case of foreign countries, this problem has been recognized, and since the late 1980s, an experimental study on restraint shrinkage of general concrete and high-strength concrete has been performed. On the other hand, studies on restraint contraction are still insufficient in Korea. In particular, high-strength concrete with a low water-binding ratio (W / B) has to undergo an experimental study on restraint shrinkage, because self-shrinkage and brittle fracture behavior are shown before the development of sufficient strength. .

  Currently, the restraint shrinkage test methods generally performed at home and abroad include a ring-test proposed by AASHTO and ASTM, and a dry shrinkage crack test proposed by KS and JIS. However, these test methods are suitable for normal concrete (NC), and there is a problem that the initial crack induction is difficult when applied to fiber reinforced concrete with improved tensile strength.

은 내부강재 링의 구속 변형률,

과, 콘크리트의 탄성 변형률,

과, 구속 응력에 의한 콘크리트의 크리프,

에 대한 합과 같다.The cracking behavior by the restraint of concrete shrinkage is closely related to the restraint. Therefore, it is possible to evaluate the degree of restraint that causes tensile cracking by the restraint restraint by calculating the degree of restraint by the restraint shrinkage test method. In general, based on the ring-test crack test method, assuming that the concrete ring is relatively small in thickness and shrinkage occurs evenly, the shrinkage of the concrete,

Is the constraint strain of the inner steel ring,

And elastic strain of concrete,

And creep of concrete due to restraint stress,

Is equal to the sum for.

은 다음과 같이 나타낼 수 있다.If it is assumed that concrete is completely constrained by the internal steel ring,

Can be written as

Therefore, the constraint degree Ψ can be defined as the constraint strain divided by the total dry shrinkage.

This constraint must be maintained above a certain degree to be applied to the ring-test and dry shrinkage crack test to evaluate the cracking behavior due to shrinkage restraint. In the case of the conventional ring-test and the dry shrink crack test, it is difficult to induce the initial crack due to the lack of restraint, and therefore, the restraint shrinkage test cannot be performed.

In addition, the conventional constrained shrinkage test method is limited in the test method in that it is impossible to evaluate various restraints, and due to the relatively thick thickness of concrete, unequal dry shrinkage occurs, and the tensile stress for each age is calculated in consideration of this. In order to measure the relative humidity by thickness and the prediction equation becomes very complicated, the test process is very difficult and complicated.

The present invention has been invented to solve the problems of the prior art, an object of the present invention is to increase the degree of restraint to dry shrinkage of concrete to induce an initial crack in the dry shrinkage process, even drying shrinkage in the dry shrinkage process of concrete In order to provide a concrete restraint shrinkage test apparatus and method that can more easily and smoothly test and evaluate the restraint shrinkage behavior for not only ordinary concrete but also fiber reinforced concrete such as UHPC. .

Another object of the present invention is to form a different thickness of the concrete specimen through the eccentric arrangement of the inner and outer ring members to dry shrinkage, to increase the degree of restraint through the stress concentration phenomenon caused by the thickness difference to induce the initial crack In addition, it is possible to form a variety of constraints in one concrete specimen due to the thickness difference, and to provide a concrete restraint shrinkage test apparatus and method capable of evaluating restraint shrinkage behavior for a variety of restraint through one concrete specimen.

The present invention, the base plate; An inner ring member formed in a ring shape and coupled to an upper surface of the base plate; A ring-shaped outer ring member coupled to an upper surface of the base plate to be spaced apart from an outer circumferential surface of the inner ring member to pour concrete between the inner ring member and to cure the concrete specimen in a ring shape for a reference time; A strain gauge mounted on an inner circumferential surface of the inner ring member to measure a strain of the inner ring member; And a blocking member mounted to contact the outer circumferential surface of the concrete specimen to block external exposure to the outer circumferential surface of the concrete specimen, wherein the base plate and the outer ring member are formed to be separated and separated from the concrete specimen. The concrete specimen provides a concrete restraint shrinkage test apparatus characterized in that the upper and lower surfaces are formed to be exposed to the outside.

At this time, the base plate may be combined with a separate anti-friction sheet on the upper surface to reduce the friction with the concrete specimen.

In addition, the outer ring member may be formed separately from the first and second members are arranged symmetrically to each other about the axis of the radial direction.

In addition, the concrete for the production of the concrete specimen may be applied as fiber reinforced concrete (FRC).

In addition, the inner ring member may be applied to steel.

Meanwhile, the inner ring member and the outer ring member may be eccentrically positioned so that their centers do not coincide with each other.

In this case, the strain gauge may be mounted on an inner circumferential surface of the inner ring member having a shortest distance from the outer ring member.

In addition, a plurality of strain gauges may be mounted on the inner circumferential surface of the inner ring member along the circumferential direction.

On the other hand, the present invention, preparing a base plate; The inner ring member and the outer ring member are disposed on the upper surface of the base plate so that the outer ring member is spaced along the outer circumference of the inner ring member with respect to the ring-shaped inner ring member and the outer ring member having different diameters. Joining members to join; A gauge mounting step of mounting a strain gauge on an inner circumferential surface of the inner ring member; A curing step of placing concrete in a space between the inner ring member and the outer ring member and curing for a reference time to produce a ring-shaped concrete specimen; After the curing step, the base plate and the outer ring member are separated and separated from the concrete specimen, the upper and lower surfaces of the concrete specimen are exposed to the outside and the outer peripheral surface of the concrete specimen so that the outer circumferential surface of the blocking member on the outer circumferential surface Blocking step for mounting; And after the blocking step, provides a concrete restraint shrinkage test method comprising the step of calculating the information on the restraint shrinkage behavior of the concrete specimen through the measured value of the strain gauge.

In this case, the preparation step may include a sheet bonding step of coupling a separate anti-friction sheet on the upper surface of the base plate so that the friction between the base plate and the concrete specimen is reduced.

In addition, the concrete for the production of the concrete specimen may be applied as fiber reinforced concrete (FRC).

In addition, in the member coupling step, the inner ring member and the outer ring member may be arranged to be eccentric with each other such that their centers do not coincide with each other.

In addition, in the gauge mounting step, the strain gauge may be mounted on an inner circumferential surface of the inner ring member having a shortest distance from the outer ring member.

In addition, in the gauge mounting step, a plurality of strain gauges may be mounted on the inner circumferential surface of the inner ring member along the circumferential direction.

According to the present invention, by reducing the radial thickness and the vertical thickness of the concrete specimen, by blocking the outer peripheral surface of the concrete specimen to the external exposure and to expose the upper and lower surfaces to the outside, by increasing the degree of restraint to dry shrinkage of the concrete to dry By inducing initial cracking during shrinkage process and evenly drying shrinkage during dry shrinkage process of concrete, it is easier to test and evaluate the restraint shrinkage behavior for not only ordinary concrete but also fiber reinforced concrete such as ultra high performance concrete (UHPC). It has the effect of doing it smoothly.

In addition, through the eccentric arrangement of the inner and outer ring members to form a different thickness of the concrete specimen to shrink and dry, it is possible to induce the initial crack by increasing the degree of restraint through the stress concentration phenomenon caused by the thickness difference, Due to the difference in thickness, it is possible to form various restraints in one concrete specimen, and thus, it is possible to evaluate restraint shrinkage behavior for various restraints through one concrete specimen.

1 is a perspective view schematically showing the configuration of the concrete restraint shrinkage test apparatus according to an embodiment of the present invention,
Figure 2 is a perspective view schematically showing a test operation state through the concrete restraint shrinkage test apparatus according to an embodiment of the present invention,
3 is a view conceptually showing a test operation principle through the concrete restraint shrinkage test apparatus according to an embodiment of the present invention;
Figure 4 is a plan view schematically showing the configuration of a concrete restraint shrinkage test apparatus according to another embodiment of the present invention,
FIG. 5 conceptually illustrates a test operation state through the concrete restraint shrinkage test apparatus illustrated in FIG. 4;
6 is a flowchart illustrating a step-by-step operation flow for the concrete restraint shrinkage test method according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a perspective view schematically showing the configuration of the concrete restraint shrinkage test apparatus according to an embodiment of the present invention, Figure 2 is a schematic diagram showing a test operation state through the concrete restraint shrinkage test apparatus according to an embodiment of the present invention Figure 3 is a perspective view, Figure 3 is a diagram conceptually showing the test operation principle through the concrete restraint shrinkage test apparatus according to an embodiment of the present invention.

Concrete restraint shrinkage test apparatus according to an embodiment of the present invention is a device capable of restraint shrinkage test for fiber reinforced concrete by improving the degree of restraint against concrete shrinkage, the base plate 100, the inner ring member 200, the outer It is configured to include a ring member 300, strain gauge 400 and blocking member 500.

The base plate 100 is formed in a simple flat shape and may be manufactured using wood. An inner ring member 200 and an outer ring member 300 are coupled to an upper surface of the base plate 100, and an upper surface of the base plate 100 through a space between the inner ring member 200 and the outer ring member 300. As concrete is poured and cured for a reference time, concrete specimen (P) is produced. Accordingly, the base plate 100 functions as a kind of formwork together with the inner ring member 200 and the outer ring member 300, whereby restrained by friction is prevented against concrete placed on the upper surface of the base plate 100. It is preferable that a separate anti-friction sheet 110 is coupled to the upper surface of the base plate 100 so as to be possible.

For example, the anti-friction sheet 110 may be a Teflon sheet having a low coefficient of friction, thereby reducing friction between the base plate 100 and the concrete specimen P, thereby reducing friction in the concrete restraint shrinkage test. Minimization of restraint allows for more accurate restraint shrinkage testing.

The inner ring member 200 and the outer ring member 300 are both formed in a ring shape and coupled to an upper surface of the base plate 100, wherein the diameter of the outer ring member 300 is larger than the diameter of the inner ring member 200. The outer ring member 300 is formed to be large so as to surround the outer circumference of the inner ring member 200. That is, the inner circumferential surface of the outer ring member 300 is spaced apart from the outer circumferential surface of the inner ring member 200 so that the concrete for manufacturing a ring-shaped concrete specimen P can be poured into the space therebetween.

Concrete poured into the space between the inner ring member 200 and the outer ring member 300 is made of concrete specimen P that is cured for a reference time, for example, about 24 hours, and has a certain degree of strength. At this time, the concrete poured for the production of concrete specimens may be applied as general concrete, but fiber reinforced concrete (FRC) may be applied according to an embodiment of the present invention, the present invention is a restrained shrinkage test for such fiber reinforced concrete It can be done correctly.

At this time, while the concrete is cured for a reference time and the concrete specimen (P) is made, the concrete specimen (P) is bonded and cured with the inner ring member 200, and after curing for the reference time after the outer ring member 300 is separated and removed from the concrete specimen (P). Accordingly, the inner ring member 200 is integrally formed with one member having a simple ring shape as shown in FIG. 1, but the outer ring member 300 can be separated and removed from the ring shaped concrete specimen P. It is preferable that the semicircular first and second members 301 and 302 are arranged to be symmetrically arranged and coupled to each other about an axis in the radial direction.

Since the first and second members 301 and 302 constituting the outer ring member 300 are formed in a semicircular shape, the outer ring member 300 is a ring-shaped concrete specimen P as shown in FIG. 2. Can be easily separated and removed from the concrete specimen (P) without damage. In addition, flanges 301a and 302a are formed at both side ends of the first and second members 301 and 302 so as to correspond to each other and to be coupled to each other, and the flanges 301a and 302a are coupled to the coupling bolt T. By coupling through, the first and second members 301 and 302 may be configured to be coupled in a ring shape.

At this time, the inner ring member 200 and the outer ring member 300 are made of the same material as that of the actual site in consideration of the fact that steel is used as a material such as formwork and reinforcement, which is a factor constraining the shrinkage of concrete in an actual building site. It is preferred to be applied as steel. However, although the inner ring member 200 is cured by being combined with concrete according to an embodiment of the present invention, since the outer ring member 300 is separated and removed after curing for a reference time, it is largely a factor that restrains shrinkage of concrete. It doesn't work. Therefore, the inner ring member 200 is applied to the steel as in the actual building site, the outer ring member 300 is easily manufactured using steel, etc. to be used many times, but the thickness is thin so that it can be easily removed It is preferable.

On the other hand, the inner ring member 200 is equipped with a separate coupler 210 on the inner circumferential surface and the base in such a way to couple the coupler 210 to the upper surface of the base plate 100 through a separate coupling bolt (T) The outer ring member 300 may be coupled to the plate 100, and separate coupling holes 310 may be mounted at lower ends of the outer circumferential surfaces of the first and second members 301 and 302, respectively. It can be coupled to the base plate 100 in a manner that is coupled to the upper surface of the base plate 100 through the coupling bolt (T) of. Therefore, when the poured concrete is cured for a reference time and manufactured as the concrete specimen P, by decoupling the coupling bolt T, the inner ring member 200 and the outer ring member 300 are removed from the base plate 100. It can be separated and separated, and thus the concrete specimen (P) coupled to the inner ring member 200 can be maintained in the exposed state of the lower surface is separated from the base plate 100, of course, in this case the concrete specimen ( The upper surface of P) may be always kept in an externally exposed state regardless of whether it is coupled with the base plate 100.

The strain gauge 400 is mounted on the inner circumferential surface of the inner ring member 200 to measure the strain of the inner ring member 200. That is, since the concrete specimen (P) is combined with the inner ring member 200 and cured, the load is applied to the inner ring member 200 by the contraction phenomenon of the concrete specimen (P) according to the curing period, and deformation occurs. The strain gauge 400 is mounted on the inner circumferential surface of the inner ring member 200 to measure the strain of the inner ring member 200.

As described above, the blocking member 500 is mounted to contact the outer circumferential surface of the concrete specimen P after the outer ring member 300 is separated and removed from the cured concrete specimen P during the reference time as described above. By the blocking member 500, the outer circumferential surface of the concrete specimen P is maintained in a state where external exposure is blocked. The blocking member 500 is to block the external exposure of the concrete specimen (P) to block the movement of water from the concrete specimen (P) through the outer peripheral surface, it can be manufactured using silicon and aluminum tape.

According to this structure, the concrete restraint shrinkage test apparatus according to an embodiment of the present invention refers to the concrete specimen P in the form of a ring through the base plate 100, the inner ring member 200, and the outer ring member 300. After curing for a period of time, the base plate 100 and the outer ring member 300 is separated from the concrete specimen (P) and separated, and by mounting the blocking member 500 on the outer peripheral surface of the concrete specimen (P), the concrete specimen (P The restraint shrinkage test is performed on the concrete specimen (P) in such a way that the top and bottom of the c) are exposed outside.

In general, shrinkage of fiber reinforced concrete is constrained by formwork, reinforcing bars, etc., as described in the prior art, causing cracks in structures, thereby deteriorating durability life and structural performance. Therefore, in order to prevent shrinkage cracking of concrete and apply it to the actual structure, the cracking behavior at various constraints is evaluated based on the constraint shrinkage test, and the restraint shrinkage test is performed by calculating the minimum constraint that causes cracking. This is done. Since the evaluation and analysis methods are performed in various ways through the general concrete restraint shrinkage test method, detailed description thereof will be omitted.

Concrete restraint shrinkage test apparatus according to an embodiment of the present invention, as shown in Figure 3 by allowing the water movement to the outside only through the upper and lower surfaces of the concrete specimen (P), radial direction of the concrete specimen (P) Moisture is prevented from being moved to a relatively even dry shrinkage, and also, because the concrete specimen (P) is kept in the state coupled only to the inner ring member 200, as shown in the stress distribution curve of Figure 3 The maximum tensile stress of the concrete specimen (P) is generated at the contact surface between the 200 and the concrete specimen (P). In this case, the strain strain of the inner ring member 200 may be measured through the strain gauge 400 mounted on the inner circumferential surface of the inner ring member 200, and the constraint degree may be calculated through the strain gauge 400.

On the other hand, in this case, it is preferable to make the height of the inner ring member 200 relatively small. That is, since the concrete specimen (P) is exposed to the outside of the upper and lower surfaces to dry shrinkage, it is preferable that the thickness in the vertical direction is formed relatively thin to induce even dry shrinkage, for example, the inner ring member 200 ) And the concrete specimen (P) through it is preferable to be less than 70mm. Through this structure, the tensile stress can be predicted through a relatively simple equation, and it will be possible to predict and evaluate the crack initiation point in comparison with the results of the separate strength test.

In addition, in the conventional concrete restraint shrinkage test apparatus according to the prior art, the restraint of the fiber reinforced concrete (FRC) is not large enough to induce an initial crack, and thus could not perform an exact restraint shrinkage test. Concrete restraint shrinkage test apparatus according to the embodiment is induced so that the maximum stress occurs in the contact surface between the inner ring member 200 and the concrete specimen (P) according to the structure that the upper and lower surfaces of the concrete specimen (P) is exposed to the outside, the tensile stress prediction This facilitates faster and more constrained shrinkage tests while ensuring reliability.

In this case, in order to increase the degree of restraint, it is preferable to relatively reduce the distance between the inner ring member 200 and the outer ring member 300, that is, the radial thickness of the concrete specimen P. However, the distance between the inner ring member 200 and the outer ring member 300 in a range larger than the maximum dimension of the coarse aggregate and the length of the fiber in consideration of the maximum dimension of the coarse aggregate, the length of the fiber in accordance with the type of concrete to be poured. It is desirable to adjust the distance. For example, when applying fiber reinforced concrete such as UHPC, 13 mm long steel fibers are mixed. Therefore, the separation distance between the inner ring member 200 and the outer ring member 300 is greater than the length of the fiber. It is preferable to set it as about 40 mm or less which can induce an initial shrinkage crack.

As such, as the distance between the inner ring member 200 and the outer ring member 300 is reduced, the degree of restraint on concrete shrinkage increases, thereby not only inducing an initial crack but also increasing the maximum tension for each age. The prediction equation of the stress can be simplified, which can be easily calculated by measuring the strain of the inner ring member 200 through the strain gauge 400. This prediction equation is expressed as follows.

,

는 각각 내부 링 부재(200)와 콘크리트 시편(P)의 내부 반경이며,

,

는 각각 내부 링 부재(200)의 구속 변형률 및 탄성 계수를 나타낸다.
here,

,

Are the inner radii of the inner ring member 200 and the concrete specimen P, respectively,

,

Denote the restraint strain and elastic modulus of the inner ring member 200, respectively.

Figure 4 is a plan view schematically showing the configuration of the concrete restraint shrinkage test apparatus according to another embodiment of the present invention, Figure 5 conceptually shows a test operation state through the concrete restraint shrinkage test apparatus shown in FIG. One drawing.

In the concrete restraint shrinkage test apparatus according to another embodiment of the present invention, the inner ring member 200 and the outer ring member 300 may be eccentrically disposed so that their centers do not coincide with each other, as shown in FIG. 4. have.

That is, since the center C1 of the inner ring member 200 and the center C2 of the outer ring member 300 are eccentrically positioned with each other by an e distance, the space between the inner ring member 200 and the outer ring member 300 is separated. The distance d is formed differently at every point. Therefore, the concrete specimen P formed by the arrangement of the inner ring member 200 and the outer ring member 300 is formed in a radial thickness different from each other as shown in FIG.

As such, the concrete specimen P formed according to the eccentric arrangement of the inner ring member 200 and the outer ring member 300 has a stress concentration phenomenon in a portion having a relatively thin cross section due to the radial thickness difference. As a result, the degree of restraint may be increased to induce an initial crack. At this time, the strain gauge 400 is preferably located at the point where the stress concentration phenomenon occurs to the maximum. That is, as shown in FIG. 4, it is preferable to be mounted on the inner circumferential surface of the inner ring member 200 having the shortest distance from the outer ring member 300.

Therefore, the concrete restraint shrinkage test apparatus according to an embodiment of the present invention, unlike the prior art by generating a stress concentration phenomenon by such an eccentric arrangement, it can increase the restraint to dry shrinkage of the concrete to induce the initial crack In addition, it is possible to smoothly evaluate the cracking behavior of the fiber reinforced concrete (FRC).

On the other hand, according to the eccentric arrangement of the inner ring member 200 and the outer ring member 300, the thickness of the concrete specimen (P) is formed differently along the circumference, and thus the thickness of the concrete specimen (P) according to the point Because they are all different, the stress concentration at each point is different and the resulting constraints are all different. Therefore, as shown in FIG. 5, a plurality of strain gauges 400 may be mounted along the circumferential direction of the inner ring member 200, and evaluation of various constraints different from each other may be performed at each point.

That is, as shown in FIG. 5, the strain gauges 400 are mounted at positions corresponding to the points d1 to d8, respectively, and their respective constraints are calculated differently because the thicknesses are different at each point. The resulting cracking behavior can be evaluated separately at each point. Therefore, the concrete restraint shrinkage test apparatus according to an embodiment of the present invention can simultaneously perform evaluation of various restraints through a single device, so that the restraint shrinkage test on concrete can be more easily performed.

6 is a flowchart illustrating a step-by-step operation flow for the concrete restraint shrinkage test method according to an embodiment of the present invention.

The present invention provides a concrete restraint shrinkage test method capable of smoothly performing restraint shrinkage test for fiber reinforced concrete (FRC) using the concrete restraint shrinkage test apparatus described above, which is prepared as shown in FIG. 6. It comprises a step S1, a member coupling step S2, a gauge mounting step S3, a concrete pouring step S4, a curing step S5, a blocking step S6 and an information calculation step S7. Each step performing method is the same as described in the description of FIGS. 1 to 5, and thus will be briefly described in order to prevent duplication.

Concrete constrained shrinkage test method according to an embodiment of the present invention first starts from the preparatory step (S1) to prepare the base plate 100, at this time, the base plate 100 can be made of wooden boards, the preparation step ( In step S1) further performs a sheet joining step (S1-1) for coupling a separate anti-friction sheet 110 to the upper surface of the base plate 100 so as to reduce the friction between the base plate 100 and the concrete specimen (P). can do.

After the preparation step S1, a member joining step S2 of joining the ring-shaped inner ring member 200 and the outer ring member 300 having different diameters to the upper surface of the base plate 100 is performed. At this time, the outer ring member 300 is coupled so as to be spaced apart along the outer periphery of the inner ring member 200, the general concrete or fiber reinforced concrete (space) to the space between the inner ring member 200 and the outer ring member 300 ( FRC) is cast so that it can be cured for a reference time. At this time, the inner ring member 200 and the outer ring member 300 may be arranged to form concentric circles with each other, as shown in FIG. 1, but as shown in FIG. It may be.

Gauge mounting step (S3) is a step of mounting the strain gauge 400 on the inner peripheral surface of the inner ring member 200, after the member coupling step (S2) for coupling the inner ring member 200 to the base plate 100 It may be performed, or may be performed by mounting the strain gauge 400 in advance before the inner ring member 200 is coupled to the base plate 100. In this case, one or more strain gauges 400 may be mounted. When the inner ring member 200 and the outer ring member 300 are eccentrically arranged as illustrated in FIG. 4, one strain gauge 400 may be mounted. ) Is mounted on the inner circumferential surface of the inner ring member 200 having the shortest distance from the outer ring member 300, or a plurality of strain gauges 400 are arranged along the circumferential direction on the inner circumferential surface of the inner ring member 200. Can also be equipped with a dog.

Concrete pouring step (S4) and curing step (S5) is the inner ring member 200 and the outer ring member 300, the inner ring member 200 and the outer ring member 300, with the inner ring member 300 is coupled to the base plate 100 Placing concrete in the space between the) and curing for a reference time, for example 24 hours to produce a ring-shaped concrete specimen (P).

After the curing step (S5) is separated from the base plate 100 and the outer ring member 300 from the concrete specimen (P), the upper and lower surfaces of the concrete specimen (P) is exposed to the outside and the concrete specimen (P) A blocking step S6 is performed to mount the blocking member 500 on the outer circumferential surface of the concrete specimen P so that the outer circumferential surface is blocked outside.

When the blocking step (S6) is carried out as described above and the upper and lower surfaces of the concrete specimen (P) is maintained in an externally exposed state, the moisture in the concrete specimen (P) continuously shrinks and moves to the outside through the upper and lower surfaces to dry shrinkage. In this dry shrinkage process, the inner ring member 200 is contracted and restrained.

After the blocking step (S6), the calculation step (S7) is performed in the dry shrinkage process of the concrete specimen, and calculates various information about the restrained shrinkage behavior of the concrete specimen (P). For example, the restraint degree can be calculated by measuring the restraint strain of the inner ring member 200 through the measured value of the strain gauge 400 in the drying shrinkage process, and from this, the tensile tension of the concrete specimen P is according to the age. Prediction and evaluation of crack initiation can be made in comparison with stress or strength test results. In addition, when the inner ring member 200 and the outer ring member 300 are eccentrically arranged as shown in FIG. 4, the restraint shrinkage behavior of various restraints may be evaluated through one concrete specimen P formed therethrough.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

100: base plate 110: anti-friction sheet
200: inner ring member 300: outer ring member
400: strain gauge 500: blocking member

Claims (14)

Base plate;
An inner ring member formed in a ring shape and coupled to an upper surface of the base plate;
A ring-shaped outer ring member coupled to an upper surface of the base plate to be spaced apart from an outer circumferential surface of the inner ring member to pour concrete between the inner ring member and to cure the concrete specimen in a ring shape for a reference time;
A strain gauge mounted on an inner circumferential surface of the inner ring member to measure a strain of the inner ring member; And
Blocking member mounted to contact the outer circumferential surface of the concrete specimen to block external exposure to the outer circumferential surface of the concrete specimen
It includes, wherein the base plate and the outer ring member is formed so as to be separated and separated from the concrete specimen, the concrete concrete restraint shrinkage test apparatus, characterized in that the upper and lower surfaces are formed to be exposed to the outside.
The method of claim 1,
The base plate is a concrete restraint shrinkage test device, characterized in that a separate anti-friction sheet is coupled to the upper surface to reduce friction with the concrete specimen.
The method of claim 2,
The outer ring member
Concrete restraint shrinkage test apparatus, characterized in that formed separately from the first and second members are arranged symmetrically arranged with respect to the axis in the radial direction.
The method according to any one of claims 1 to 3,
Concrete restraint shrinkage test device, characterized in that the concrete for the production of the concrete specimen is applied as fiber reinforced concrete (FRC).
The method of claim 4, wherein
Concrete ring restraint test device, characterized in that the inner ring member is applied to the steel.
The method of claim 4, wherein
And the inner ring member and the outer ring member are eccentrically positioned so that their centers do not coincide with each other.
The method according to claim 6,
And the strain gauge is mounted on the inner circumferential surface of the inner ring member having the shortest distance from the outer ring member.
The method according to claim 6,
The strain gage is a concrete restraint shrinkage test apparatus, characterized in that mounted on the inner circumferential surface of the inner ring member in a plurality of circumferential direction.
Preparing a base plate;
The inner ring member and the outer ring member are disposed on the upper surface of the base plate so that the outer ring member is spaced along the outer circumference of the inner ring member with respect to the ring-shaped inner ring member and the outer ring member having different diameters. Joining members to join;
A gauge mounting step of mounting a strain gauge on an inner circumferential surface of the inner ring member;
A curing step of placing concrete in a space between the inner ring member and the outer ring member and curing for a reference time to produce a ring-shaped concrete specimen;
After the curing step, the base plate and the outer ring member are separated and separated from the concrete specimen, the blocking member on the outer peripheral surface of the concrete specimen so that the upper and lower surfaces of the concrete specimen are exposed to the outside and the outer circumferential surface of the concrete specimen is blocked outside. Blocking step for mounting; And
After the blocking step, calculating the information on the restraint shrinkage behavior of the concrete specimen through the measured value of the strain gauge
Concrete restraint shrinkage test method comprising a.
The method of claim 9,
The preparatory step includes a sheet bonding step of coupling a separate anti-friction sheet on the upper surface of the base plate to reduce the friction between the base plate and the concrete specimen.
The method of claim 9,
Concrete confinement shrinkage test method characterized in that the concrete for the production of the concrete specimen is applied as fiber reinforced concrete (FRC).
12. The method according to any one of claims 9 to 11,
The member coupling step is a concrete restraint shrinkage test method, characterized in that the inner ring member and the outer ring member are arranged eccentrically with each other so that their centers do not coincide with each other.
13. The method of claim 12,
The gauge mounting step is a concrete restraint shrinkage test method characterized in that for mounting the strain gauge on the inner circumferential surface of the inner ring member is formed the shortest distance from the outer ring member.
13. The method of claim 12,
The gauge mounting step is a concrete restraint shrinkage test method, characterized in that for mounting the plurality of strain gauges on the inner circumferential surface of the inner ring member in the circumferential direction.

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