JP2013002195A - Method for preventing cracking generated around opening - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing cracking generated around an opening which can suppress or reduce the cracking of mortar due to the movement of a skeleton, regarding the cracking generated around the opening of a building.SOLUTION: In a method for preventing cracking generated around an opening, at the time of constructing mortar around the opening of a building, a reinforcement lath is laid at least in the mortar located outside the corners of the opening.

Description

  The present invention relates to a crack generated around an opening of a building, and more particularly to a method for preventing a crack generated around an opening that suppresses or reduces a crack of a mortar caused by the behavior of a frame.

Cracks generated around the opening of a building are classified into those caused by distortion of the material accompanying the deformation of the structural frame, and those caused by water absorption / drying shrinkage distortion of the material and distortion caused by the hot / cold movement.
When the area around the opening is constructed with a wet material, depending on the material properties, such as reduction of the drying shrinkage rate, reduction of Young's modulus due to the mixing of short fibers, lightweight aggregates, and resin, and tensile reinforcement or elasticity of the wet material Correspondence and countermeasures by tensile reinforcement by fiber net sag on the wet material surface are made. It is effective to dispose the fiber net on the surface of the wet material as much as possible. If the fiber net is embedded in the wet material, cracks may occur in the wet material outside the fiber net. On the other hand, in the case of dry materials, it is managed by factory production.
The above-mentioned fiber net sag is effective against cracks in the wet material that occur around such openings, but it is still insufficient for the movement of the structure, and even higher tensile strength. Even if a fiber net having a thickness is used, the strength balance with the mortar is poor, and the fiber net is turned up. Moreover, in the fiber net, the effect which restrains the crack generated unavoidably and makes the width | variety small cannot be expected.
In addition, the fiber net is relatively expensive, and the net may appear on the surface of the wet material after construction.
Conventionally, there is a method of fixing the flat lath No. 1 to the base with staples at the corners of the opening, but the crack prevention effect has never been quantitatively evaluated.

With regard to material properties, pre-prepared materials in which binders, aggregates, various admixtures, etc. are dry-mixed are sold by manufacturers of wet materials, rather than on-site preparation as before, and cracks are unlikely to occur. Maintains stable quality.
However, it is difficult to completely prevent cracks caused by water-absorbing drying shrinkage strains and hot / cold movements of materials constituting wet materials, and cracks caused by deformation of the structural body are still likely to occur.

Therefore, the present applicant has proposed Patent Document 1 for the purpose of preventing cracks generated around the corners of the opening of a building that suppresses or reduces cracks in the mortar caused by the behavior of the frame.
The construction method proposed in Patent Document 1 is to form a space part with the outer corner part of the opening as a center, and to form the periphery of the opening part and the outer corner part corresponding to the space part with different materials. is there.
In this construction method, there is no source of cracks, and no corners where stress tends to concentrate are formed. Therefore, cracks are unlikely to occur, and even if they occur, the cracks are minor. Therefore, it is possible to effectively prevent cracks resulting from deformation of the wet material that is linked to the behavior of the housing, and cracks resulting from deformation due to drying shrinkage or hot / cold movement of the wet material.

JP 2011-42980 A

However, when the construction method of Patent Document 1 is carried out by a wet construction method, two types of materials, ie, a coating composition, that is, a material for forming the space portion and a material for forming the other portion are used. Therefore, the management and construction were troublesome.
Moreover, as a formation method of a space part, you may form beforehand, for example using a detachable frame-shaped partition (division material) etc., for example, in anticipation of the state where the coated material lost fluidity It may be formed later by removing a part or the like, but in any case, it takes time and labor to do so.

  Therefore, the present inventors proposed a construction method that can be easily carried out using a single mortar material (coating composition) and has excellent workability, and in particular, suppresses cracking of the mortar caused by the behavior of the casing. The purpose is to reduce.

  The present invention has been proposed in view of the above, and has an opening characterized in that a reinforcing lath is concealed at least inside the mortar located outside the corner of the opening in the mortar construction around the opening of the building. The present invention relates to a method for preventing cracks generated around the part.

  Further, in the above method, a crack generated around the opening is characterized in that a reinforcing lath having a predetermined width is depressed from each corner of the opening in a direction inclined by 45 degrees with respect to two sides forming the corner. We propose a prevention method.

Also proposed is a method for preventing cracks generated around the opening, characterized in that a reinforcing lath having a mass greater than 0.45 kg / m ² is used.

Furthermore, in the above construction method, a method for preventing cracks generated around the opening is also proposed, characterized in that the fiber net is further buried in the surface layer portion of the mortar where the reinforcing lath is buried.
As the fiber net, a glass fiber net is preferable.

In the present invention, at the time of mortar construction around the opening of the building, since the reinforcing lath is laid down at least inside the mortar located outside the corner of the opening, cracks are unlikely to occur, and even if they occur, It becomes minor.
By fixing the reinforcement lath to the ground and lying down in the mortar, the strain linked to the behavior of the frame can be cut off.
Therefore, this invention can prevent effectively the crack resulting from the deformation | transformation of the wet material linked with the behavior of a housing | casing, and the deformation | transformation by the drying shrinkage | contraction of a wet material, or a warm / cool movement.

  In addition, when a reinforcing lath having a predetermined width is depressed from each corner of the opening in a direction inclined by 45 degrees with respect to the two sides forming the corner, since the range of use of the reinforcing lath is narrow, cracking is more inexpensive. Reduction suppression is achieved.

In addition, when a reinforcing lath having a mass greater than 0.45 kg / m ² , for example, flat lath No. 4, is used, the cracking suppression and prevention effects are higher than when a reinforcing lath having a low mass, for example, flat lath No. 1 is used. can get.

  Furthermore, when a fiber net, for example, a glass fiber net, is further laid down on the surface layer portion of the mortar with the reinforcing lath concealed, the effect of suppressing and preventing cracking by the reinforcing lath and the fiber net is exerted both in the mortar and on the surface layer portion. Cracks are effectively prevented. In other words, as described above, the sag of the fiber net is not sufficient for preventing cracks in the movement of the structure, and it was not expected to turn up or constrain the cracks and reduce the width. This disadvantage can be eliminated by the sag of the reinforcing lath.

It is a top view which shows the axis group figure of the test case used for the implementation test. It is a top view which shows the allocation figure of the structural plywood used for the implementation test. (A) It is a top view which shows arrangement | positioning of the reinforcement lath with respect to the opening part in an implementation test, and is a top view which shows the state which enclosed the circumference | surroundings of the opening part in the shape of a belt | band | zone, (b) It installs in C shape outside the opening part corner part. It is a top view which shows the state which carried out. It is sectional drawing which shows the depression position (depth) of the reinforcement lath in an implementation test. It is a graph which shows the measurement result of a crack width. It is a graph which shows the measurement result of the displacement amount by a pi type displacement meter.

The reinforcing lath used in the present invention is preferably a flat lath, but is not particularly limited. In view of the gist of the present invention that the reinforcement lath as a tensile reinforcement material is laid down at the corner of the opening to prevent cracking, if the mass is 0.45 kg / m ² or more, it is not necessary to be a flat lath. It may be a lath welded bone vertically and horizontally into a stitch shape.

1. Test purpose Of the cracks that occur on the outer wall of the lath mortar, the aim is to prevent cracks that occur at the end of the opening. It was verified by testing.

2. Crack prevention method Reinforce the reinforcing lath (flat lath) in the undercoat mortar around the opening.

3. Test method A column base fixed type in-plane shear test was conducted using a horizontal force tester.
After the specimen was deformed for each deformation angle, the cracks in the state where the casing was returned to the original displacement (displacement 0) were observed. A π-type displacement meter was used for strain measurement at the end of the opening.
π-type displacement meter: distance between gauge points 150 mm Attached to the end of the opening at an angle of 45 degrees.
An in-plane shear test was performed to observe cracks generated at the end of the opening.
Assuming an outer wall surface of a lath mortar having an opening, a test body having an opening having a height of 780 mm and a width of 865 mm at the center of a shaft assembly housing having a height of 2730 mm and a width of 1,820 mm was used. The test specimen specification was a direct coating method using a structural plywood as a base.
Table 1 shows the specifications and common items of the test case. FIG. 1 shows a shaft assembly diagram, and FIG. 2 shows an allocation diagram of the structural plywood.

4). Method for arranging reinforcing lath The lath reinforcement was tested with a total of 11 types of specifications including a blank (no reinforcing lath). Table 2 shows the specifications of the reinforcing lath, and FIGS. 3A and 3B show the arrangement of the reinforcing lath.

図４に示すようにモルタルを下塗り後、下地から１０ｍｍの位置に補強ラスを伏せ込み、上塗りを行った。 Specifications of test specimens (Nos. 2 to 9 and 11 are examples, Nos. 1 and 10 are comparative examples)

As shown in FIG. 4, after the mortar was undercoated, the reinforcing lath was laid down at a position of 10 mm from the base, and the overcoating was performed.

5. Test results For only cracks generated from the edge of the opening, the surface of the test body was divided by squares with a constant interval, and the degree of cracking was quantified by the number of squares (crack rate).
Crack rate (%) = number of cells with cracks / total number of cells × 100

平ラス（補強ラス）を使用することにより、ひび割れが少なくなった。また、従来のように下地にステープルで固定したもの（Ｎｏ.８，Ｎｏ.９）より、下塗りモルタルに伏せこんだものの方が、ひび割れが少なくなった。なお、Ｎｏ.７，Ｎｏ.１０，Ｎｏ.１１以外は、せん断ひび割れが発生しているが、Ｎｏ.７、Ｎｏ.１０，Ｎｏ.１１は発生していない。また、モルタル表面に繊維ネットを伏せ込んだＮｏ.１０は、繊維ネットを使用することによりひび割れが少なくなり、剪断ひび割れが発生しなくなったが、依然開口部端部にひび割れは発生し、繊維ネットがめくれることによる浮きが見られた。Ｎｏ.７は平ラス（補強ラス）と繊維ネットを併用することにより、開口部端部のひび割れや繊維ネットの浮き、剪断ひび割れは発生せず、損傷しなかった。Ｎｏ.１１も平ラスと繊維ネットを併用することにより、開口部端部のひび割れや繊維ネットの浮き、剪断ひび割れは発生せず、損傷しなかった。Ｎｏ.１１にて使用した繊維ネットは、前述の通り比較的高価である。 Crack rate

By using a flat lath (reinforcing lath), cracks were reduced. In addition, the cracks were less in the case of the laying in the undercoat mortar than in the conventional case (No. 8, No. 9) fixed to the base with staples. In addition, except for No. 7, No. 10, and No. 11, shear cracks occurred, but No. 7, No. 10, and No. 11 did not occur. In addition, No. 10 with the fiber net lying on the surface of the mortar had less cracks and no shear cracks due to the use of the fiber net, but cracks still occurred at the end of the opening. There was a float caused by turning over. No. 7 was not damaged by using a flat lath (reinforcing lath) and a fiber net together, so that cracks at the end of the opening, fiber net floating, and shear cracks did not occur. No. 11 was not damaged by using a flat lath and a fiber net together without causing cracks at the end of the opening, floating of the fiber net, or shear cracks. The fiber net used in No. 11 is relatively expensive as described above.

FIG. 5 shows the crack width observation result in the state of zero displacement after deformation of the test body.
The crack width is a value measured by a crack gauge, and is an average value at four positions at the open end.
By using a flat lath, the crack width was reduced. In addition, the cracks were smaller in the case where the mortar was laid down than in the conventional case where the mortar was fixed with staples. No. 4, No. 5, No. 6, No. 6 No. 10 had a crack width of 0.1 mm or less and was difficult to see. No. 7, No. 7 No cracks occurred in No. 11.

FIG. 6 shows the measurement result of the displacement amount by the π-type displacement meter.
Each numerical value is an average value of four positions at the open end portion subjected to the tensile force at the time of deformation of 1/120 rad.
Rather than covering the periphery of the opening in a band shape, the strain generated at the corner of the opening becomes smaller when installed obliquely, and the effect can be obtained with less reinforcing lath.

[Construction Example 1]
2011 May 16, Narita, Chiba Prefecture Sanrizuka Steel 433m ² construction
With the staple "V0625R" manufactured by Tachikawa Pin Seisakusho, the lath "Nicken breathable lath" manufactured by Nikken Build Co., Ltd. was fastened and undercoated with the pre-prepared lightweight cement mortar "Lasmol II" manufactured by Fujikawa Construction Materials Co., Ltd. Immediately after undercoating, flattened the flat lath 4 (reinforced lath) manufactured by Nishiyama Ironworks Co., Ltd., which had been cut into dimensions 200 mm x 450 mm, and then prepared the pre-prepared lightweight cement mortar "Lasmol II" manufactured by Fujikawa Construction Materials Co., Ltd. A total of 15 mm thick was applied, and “Alice Glass Fiber Net” from Fujikawa Construction Materials Co., Ltd. was covered.
In terms of workability, workability was good and it was easy to lie down. In addition, the time-lapse change after applying pre-prepared lightweight cement mortar was observed for half a month.

Claims (4)

  A method for preventing cracks generated around an opening, characterized in that, during construction of a mortar around an opening of a building, a reinforcing lath is buried inside at least the outside of the corner of the opening.   2. A crack generated around an opening according to claim 1, wherein a reinforcing lath having a predetermined width is depressed from each corner of the opening in a direction inclined by 45 degrees with respect to two sides forming the corner. Prevention construction method. The method for preventing cracks generated around an opening according to claim 1 or 2, wherein a reinforcing lath having a mass greater than 0.45 kg / m ² is used.   The method for preventing cracks generated around an opening according to any one of claims 1 to 3, wherein the fiber net is further sunk into the surface layer portion of the mortar in which the reinforcing lath is sunk.

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