JP2014181920A - Manufacturing method of sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a sample capable of displaying progression of deterioration as a model expression while being along an actual environment.SOLUTION: Concrete is solidified in a state in which a recess part 1a, having a shape according to the outer periphery of a reinforcement bar, of a spacer 1 contacts with the reinforcement bar. Consequently, a crack can be formed, where the cross-sectional shape from the surface of a sample to the reinforcement bar becomes even and a predetermined part of the reinforcement bar can contact with ambient air. As the result, a sample capable of displaying progression of deterioration as a model expression while being along an actual environment can be manufactured.

Description

  The present invention relates to a method for producing a concrete or mortar specimen used for testing deterioration of concrete.

  For example, reinforced concrete is used as a member of a building or the like. This reinforced concrete is a composite material of reinforcing steel and concrete, in which reinforcing steel is embedded in order to supplement the strength of concrete that is vulnerable to tension. Reinforced concrete is used as a construction material or civil engineering material because the thermal expansion coefficient of concrete and rebar are almost equal, the combination of concrete that can withstand compression and rebar that can withstand tension is advantageous in terms of mechanical properties, and the raw materials are inexpensive. Widely used. In such a reinforced concrete, the buried reinforcing bar is easily rusted in a natural environment, but since it is covered with alkaline concrete, it is difficult to corrode.

  However, if the neutralization of concrete with acid gases such as carbon dioxide progresses for many years, the steel bars may corrode. In addition, when concrete cracks due to aging, etc., and this crack reaches the rebar, the outside air can come into contact with the rebar, especially when it is affected by acid gas or salt, the rebar is more likely to rust. .

  Therefore, it is important to grasp the deterioration of concrete and reinforcing bars. Therefore, various tests are performed to grasp such deterioration. In this test, a specimen made of concrete or mortar that simulates the actual structure is used instead of the actual structure of reinforced concrete. In addition, a simulated crack (crack) consisting of a continuous gap from the surface of the specimen to the reinforcing bar is formed in this specimen in order to simulate deterioration and to consider the rust of the reinforcing bar ( For example, refer nonpatent literatures 1 and 2.). Currently, as a method for forming a simulated crack in a concrete specimen and a mortar specimen, a method using a spacer and a method of applying a load are representative. These will be described below.

  In the case of a method using a spacer, first, as shown in FIG. 8, a spacer 100 made of a rectangular flat plate is prepared. Then, as shown in FIGS. 9 and 10, after reinforcing bars are placed inside the mold 200 and concrete (or mortar) 300 is poured, the spacer 100 is inserted into the mold 200. At this time, the spacer 100 is in contact with a reinforcing bar arranged inside the mold 200. When the concrete 300 is solidified, the spacers 100 embedded in the concrete 300 are extracted as shown in FIG. As a result, as shown in FIGS. 12 and 13, a specimen 500 in which a linear simulated crack 501 communicating from the concrete surface to the reinforcing bar 400 is formed. Here, since the spacer 100 is in contact with the reinforcing bar 400 at one location, the crack 501 exposes only one location to the outside.

  As shown in FIG. 14, the spacer 600 may be formed with a hole 601 through which the reinforcing bar 400 is inserted. In this case, as shown in FIG. 15, the spacer 600 is arranged inside the mold frame 200 with the reinforcing bar 400 fitted in the hole 601. Then, as shown in FIGS. 16 and 17, a specimen 700 having a linear simulated crack 701 communicating from the concrete surface to the reinforcing bar 400 is produced. Here, since the spacer 600 is in contact with the entire periphery of the reinforcing bar 400 through the hole 601, the crack 701 exposes the entire periphery to the outside. In this case, since it is necessary to remove the spacer 600 through which the reinforcing bar 400 is inserted, the spacer 600 is made of a cuttable material such as resin.

  In the case of the method of applying a load, first, as shown in FIG. 18, a rectangular parallelepiped specimen 700 in which reinforcing bars are embedded is prepared, and both end portions of one side surface (lower surface) of the specimen 700 are connected to the ground. The both ends of the specimen 700 in the longitudinal direction are placed on the convex fulcrums 801 and 802 arranged on a flat surface. Further, convex contact points 803 and 804 are arranged at positions sandwiching the central portion of the upper surface of the specimen 700, a plate-like member 805 is placed on these, and the member 805 is pressed toward the specimen 700. To do. As a result, a simulated crack 701 communicating from the concrete surface to the reinforcing bar is formed at a position between the contact points 803 and 804. The crack 701 formed in this way usually exposes one half of the reinforcing bar.

Yasuhiro Iizuka, Tsuguo Nishimura, Kento Uomoto “Study on Crack Followability of Surface Coating Materials for Concrete” Proceedings of the 55th Annual Scientific Lecture Meeting of Japan Society of Civil Engineers V-404, September 2000 Yasuhiro Iizuka, Tsuguo Nishimura, Kento Uomoto “Million times and 10 million fatigue tests of surface protective material applied to cracked concrete”, Japan Concrete Institute Annual Report, Vol23, No.1, 2001 P427.

  In tests using simulated cracked concrete specimens and mortar specimens, the deterioration progressed by placing the specimens in the actual environment or in the degradation accelerator for a certain period of time, and then the difference between the physical quantities before and after this and the elapsed time. The degree of deterioration of concrete and rebar will be considered. At this time, the deterioration that occurs in the specimen progresses from the concrete surface toward the reinforcing bar and from the crack surface to the inside of the concrete. The progress of such deterioration can be more easily expressed by a model formula when the cross-sectional shape perpendicular to the crack traveling direction is uniform from the concrete surface to the reinforcing bar. Moreover, the crack which arises in a real environment is the state which the half circumference (concrete surface side) of a column-shaped reinforcement touches air normally. For this reason, in the specimen that can be expressed in a model formula along with the actual environment, the cross-sectional shape is uniform, and a crack that allows the half circumference of the reinforcing bar to come into contact with air is formed. It is desirable.

  However, it is difficult to form such a crack by the conventional method described above. The reason is as follows.

  First, in the method using a spacer, it is possible to form a crack with a uniform cross-sectional shape in the direction of travel from the concrete surface to the reinforcing bar, but only a crack with a shape where the entire circumference or one part of the reinforcing bar is in contact with air is formed. I couldn't.

  In addition, in the method using loading, the half circumference of the reinforcing bar is in a state where it can be exposed to the air. However, since the crack enters by avoiding the aggregate, it is difficult to form a crack with a uniform cross-sectional shape. It was.

  Then, an object of this invention is to provide the preparation method of the specimen which can represent progress of deterioration along with a real environment as a model formula.

  In order to solve the problems as described above, a method for producing a specimen according to the present invention includes a step of pouring concrete or mortar into a mold of a specimen in which a reinforcing bar is disposed, and an outer periphery of the reinforcing bar at one end. Solidifying concrete or mortar in a state where the concave portion of the shape corresponding to the outer periphery of the reinforcing bar formed on one end of the spacer having a concave shape with a longer overall length than the cover thickness of the reinforcing rod is in contact with the reinforcing bar, and solidification And a step of extracting the spacer from the concrete or mortar.

  In the above-described specimen manufacturing method, the reinforcing bar is made of a rod-like member having a substantially circular cross section perpendicular to the axis, the spacer is made of a rectangular plate, and the concave portion has a substantially semicircular shape in the planar direction. You may do it.

  According to the present invention, by solidifying the concrete or mortar in a state where the concave portion of the spacer according to the outer periphery of the reinforcing bar is in contact with the reinforcing bar, the cross-sectional shape from the surface of the specimen to the reinforcing bar is uniform, and Since a simulated crack in which a predetermined portion of the reinforcing bar can come into contact with the outside air can be formed, it is possible to produce a specimen that can be expressed as a model equation along the actual environment and the progress of deterioration.

FIG. 1 is a flowchart showing a method for producing a specimen according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing the configuration of the spacer. FIG. 3 is a diagram for schematically explaining a method for producing a specimen according to the embodiment of the present invention. FIG. 4 is a diagram for schematically explaining a method for producing a specimen according to the embodiment of the present invention. FIG. 5 is a diagram for schematically explaining a method for producing a specimen according to the embodiment of the present invention. FIG. 6 is a perspective view schematically showing a configuration of a specimen manufactured by the specimen manufacturing method according to the embodiment of the present invention. FIG. 7 is a plan view schematically showing the configuration of a specimen manufactured by the specimen manufacturing method according to the embodiment of the present invention. FIG. 8 is a plan view schematically showing a configuration of a conventional spacer. FIG. 9 is a diagram for schematically explaining a method for producing a specimen using a conventional spacer. FIG. 10 is a diagram for schematically explaining a method for producing a specimen using a conventional spacer. FIG. 11 is a diagram for schematically explaining a method for producing a specimen using a conventional spacer. FIG. 12 is a perspective view schematically showing a configuration of a specimen manufactured using a conventional spacer. FIG. 13 is a front view schematically showing a configuration of a specimen manufactured using a conventional spacer. FIG. 14 is a plan view schematically showing a configuration of a conventional spacer. FIG. 15 is a diagram for schematically explaining a method for producing a specimen using a conventional spacer. FIG. 16 is a perspective view schematically showing a configuration of a specimen manufactured using a conventional spacer. FIG. 17 is a front view schematically showing a configuration of a specimen manufactured using a conventional spacer. FIG. 18 is a diagram for schematically explaining a method for producing a specimen using a conventional load.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a flowchart showing a method for producing a specimen according to the present embodiment. In the following, the case of a method for producing a concrete specimen will be described as an example. However, by changing the concrete to mortar, a method for producing a mortar specimen can be obtained.

First, as shown in FIG. 2, the spacer 1 is prepared (step S1). The spacer 1 corresponds to the shape of a simulated crack to be formed, and in the present embodiment, the spacer 1 is composed of a flat plate having a substantially rectangular shape in plan view. On one short side, a recess 1a corresponding to the shape of the outer peripheral surface of the reinforcing bar embedded in the specimen is formed. In the present embodiment, the reinforcing bar has a columnar shape, that is, a cross section perpendicular to the axis is formed in a substantially circular shape. Therefore, the recess 1a is formed in a substantially semicircle in a plan view. The total length of the spacer 1, that is, the length of the long side, is longer than the cover thickness of the reinforcing bar embedded in the specimen, that is, the distance from the reinforcing bar to the specimen surface.
As a material of such a spacer 1, various materials can be used as long as the shape does not change even when embedded in concrete or mortar, such as metal or resin.

  When the spacer 1 is prepared, concrete is poured into the mold of the specimen in which the reinforcing bars are arranged (step S2). Here, the inner space of the mold is formed in a shape corresponding to the outer shape of the specimen.

  When the concrete is poured into the mold, as shown in FIG. 3, the spacer 1 is inserted into the mold 2 into which the concrete 3 is poured (step S3). At this time, the spacer 1 is disposed so that the concave portion 1 a of the spacer 1 abuts on a reinforcing bar disposed inside the mold 2. Thereby, the half circumference part in one location of a reinforcing bar will contact | abut with the recessed part 1a. Further, the end of the spacer 1 opposite to the end where the recess 1 a is formed is exposed to the outside of the mold 2.

  As shown in FIG. 4, when the spacer 1 is inserted into the mold 2 in which the concrete 3 is placed, the concrete 3 is solidified (step S4). Solidification of the concrete 3 is performed, for example, by allowing a predetermined time to elapse.

  When the concrete 3 is solidified, the spacer 1 embedded in the solidified concrete 3 is extracted as shown in FIG. 5 (step S5). Further, the solidified concrete 3 is extracted from the mold 2 (step S6). Thereby, as shown in FIGS. 6 and 7, a concrete specimen 10 in which a reinforcing bar 12 is embedded and a simulated crack 11 including a continuous gap from the surface to the reinforcing bar 12 is formed. It will be.

  Here, since the crack 11 formed in the specimen 10 is formed in a plate shape in which the spacer 1 has a uniform cross-sectional shape in the longitudinal direction, the cross-sectional shape perpendicular to the extending direction is from the surface of the specimen 10. It is uniform over the reinforcing bar 12. Further, since the concrete 3 is solidified in a state where the semicircular recess 1a is in contact with the columnar reinforcing bar 12, the contacted part, that is, the half circumference of the reinforcing bar 12, is exposed to the outside by the crack 11. It has become. For this reason, the half circumference part can contact outside air, such as air.

  By placing the specimen 10 having such a crack 11 in a real environment or in a deterioration accelerating device for a certain period of time and waiting for the progress of deterioration, the progress of deterioration can be modeled from the difference in physical quantity before and after this experiment and the time. It can be expressed more easily.

  As described above, according to the present embodiment, the concrete 3 is solidified in a state where the concave portion 1 a of the spacer 1 having the concave portion 1 a having a shape corresponding to the outer periphery of the reinforcing bar 12 is in contact with the reinforcing bar 12. Since the cross-sectional shape is uniform from the surface of the specimen 10 to the rebar 12 and a simulated crack 11 in which a predetermined portion of the rebar 12 can come into contact with the outside air can be formed. In addition, a specimen capable of expressing the progress of deterioration as a model equation can be produced.

  In this embodiment, the case where the spacer 1 is inserted into the mold 2 into which the concrete 3 has been poured has been described as an example. However, the concave portion 1a of the spacer 1 is fitted into the reinforcing bar arranged inside the mold 2. After that, concrete may be poured into the mold 2.

  Moreover, in this Embodiment, although the case where the solidified concrete 3 was extracted after extracting the spacer 1 was demonstrated to the example, you may make it reverse this order.

Further, in the present embodiment, the case where the spacer 1 is formed in a rectangular plate shape has been described as an example. However, the shape of the spacer 1 is not limited to a plate shape, for example, depending on the shape of a crack formed such as a rectangular parallelepiped. Can be set freely.
Similarly, the shape of the concave portion 1a is not limited to a semicircular shape, and the concave portion 1a abuts in a range wider than one point at one location of the reinforcing bar and shorter than the entire circumference, more desirably, at a half circumference at one location of the reinforcing bar. If it exists, it can be set as appropriate according to the cross-sectional shape of the reinforcing steel bar.

  The present invention can be applied to a method for manufacturing a cracked specimen.

  DESCRIPTION OF SYMBOLS 1 ... Spacer, 1a ... Recessed part, 2 ... Formwork, 3 ... Concrete, 10 ... Specimen, 11 ... Crack.

Claims (2)

Pouring concrete or mortar into the mold of the specimen in which the reinforcing bars are placed,
Solidifying the concrete or the mortar in a state in which a recess having a shape corresponding to the outer periphery of the reinforcing bar formed at one end of a spacer having a total length longer than the cover thickness of the reinforcing bar is in contact with the reinforcing bar;
And a step of pulling out the spacer from the solidified concrete or the mortar. In the manufacturing method of the specimen of Claim 1,
The reinforcing bar is made of a rod-shaped member having a substantially circular cross section perpendicular to the axis,
The spacer is a rectangular plate,
The method for producing a specimen, wherein the recess has a substantially semicircular shape in the planar direction of the spacer.

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