JP5578543B2 - Cement-based hardened body crack control structure - Google Patents

Description

  The present invention relates to a cement-based cured body crack suppressing structure.

  Methods for dealing with cracks in a hardened cementitious body can be broadly divided into a technique for preventing the occurrence of cracks itself and a technique for controlling (suppressing) the crack width in which cracks are dispersed.

  To prevent the former from cracking, for example, when it is necessary to ensure water tightness and air tightness only with concrete, or when there is a risk of seriously deteriorating the aesthetics and value of concrete structures, it is necessary to take appropriate measures. It becomes. This may be technically possible, for example by the use of low heat cement, expansion materials, shrinkage reducing agents and the like. However, it can be fully expected that the degree of freedom of the composition of the concrete composition is extremely small and that the cost will increase due to other reasons. In other words, it is impossible to prevent cracks from occurring due to the characteristics of the opening (shape) in the hardened cementitious body that has an opening (window part of a building or a part around a column). It is also said that.

  The latter control (inhibition) of crack width can be said to be substantially free from the problem of strength reduction in a cemented hardened body if cracks are small if the problem of landscape deterioration is placed sideways. And unlike the former, since it does not eliminate a crack, it is very advantageous in terms of cost. In this technique, there are known a method of applying a crack induction joint and concentrating the crack at the joint location, and a method of dispersing the crack using a reinforcing reinforcing bar (a method of controlling the crack width).

  The former method of concentrating cracks by applying induction joints has not yet reached the stage of practical use because the control technology using induction joints is not yet complete and the accumulation of technology is small.

  On the other hand, the latter method of controlling the crack width allows the generation of cracks. However, with appropriate management, it is possible to specify the crack site and reduce the crack width. In other words, by making the crack within an appropriate range, the cracked part can be easily identified, repaired easily, and a fatal crack to the structure (the crack width that requires repair is 0.05 mm or more) ) Is suppressed. Therefore, it is very economical. And it is generally performed to install a reinforcing bar for the purpose of controlling the crack width.

  For example, in Japanese Patent Application Laid-Open No. 8-246603, a reinforcing crimp is installed on the outer periphery of at least a corner portion of an opening frame fitted in an opening of a building so as to wrap the opening frame. There has been proposed a reinforcing structure around the opening frame of a building, characterized in that mortar is applied to the outside of the crimp.

  Japanese Patent Application Laid-Open No. 2002-266468 discloses a crack suppressing method for suppressing cracks at the corners of an opening formed in a concrete frame, and deforms the outside of the opening of the concrete frame to be constructed. After that, a rod-shaped shape memory member having the ability to restore the original shape by performing a predetermined process is provided so that its axis is inclined with respect to both edges of the opening that forms the corner portion, and The shape memory member is left in an extended state, and then a predetermined portion of the shape memory member is fixed in the concrete by placing concrete in a portion where the concrete frame is to be constructed. A method for suppressing cracking has been proposed, in which the predetermined processing is performed on the shape memory member after curing.

  Japanese Patent Application Laid-Open No. 2002-339487 discloses an opening reinforcing member that reinforces a concrete wall that is disposed between corners sandwiched between two sides of an opening of a concrete wall, and that extends along two sides of the opening. A reinforcing member body arranged in an angled shape with two fixed pieces and substantially embedded in the concrete wall along the thickness direction of the concrete wall at the corner, and the opening from the reinforcing member body There has been proposed an opening reinforcing member comprising a plurality of extending members extending to the opposite side and embedded in a concrete wall.

JP-A-8-246603 JP 2002-266468 A JP 2002-339487 A JP 2009-126730 A

  However, it has been found that the techniques of Patent Documents 1, 2, and 3 are not necessarily effective in suppressing cracks.

  For example, the technique of Patent Document 1 requires a special structural material having a special shape called a crimp, the handling property of the crimp is poor, and further, the effect of suppressing cracking is not enough. The technique of Patent Document 2 requires a member (shape memory member) such as a shape memory alloy, and attempts to use the characteristics of the shape memory member, so its workability is very poor. And it was not that the cracking suppression effect was excellent enough to cover such problems. The technique of Patent Document 3 has poor installation workability, and there is a problem with the filling property of the concrete composition, there is a problem with the integrity with the concrete, and there is a problem with the strength of the structure itself.

  Therefore, the problem to be solved by the present invention is to solve the above problems. That is, the present invention is to provide a technique that is excellent in workability for suppressing cracks, can be easily implemented at low cost, and is excellent in suppressing cracks.

The above issues are
A cement-based hardened body crack suppressing structure in which cracking at the corner corresponding portion of the opening (the opening edge length of the opening is 2x) having a corner in the cement-based hardened body,
The cement-based cured body is provided with a net body (the length of the net body in the longitudinal direction is Y),
The net body is
The length Y in the longitudinal direction of the net body is a length that satisfies the following formula [II] with respect to the opening edge length 2x of the opening,
The problem is solved by a cement-based hardened body crack suppressing structure characterized in that the intersection angle between the line in the longitudinal direction of the net body and the line that bisects the inner angle at the corner is 80 to 100 °.
Y ≧ 0.16x−0.24 Formula [II]

In particular, the cement-based hardened body crack suppressing structure in which cracks at the corner corresponding portions of the opening (opening edge length of the opening is 2x) having a corner in the cement-based hardened body,
The cement-based cured body is provided with a net body (the length of the net body in the longitudinal direction is Y),
The net body is
The length Y in the longitudinal direction of the net body is a length satisfying the following formula [I] with respect to the opening edge length 2x of the opening,
The problem is solved by a cement-based hardened body crack suppressing structure characterized in that the intersection angle between the line in the longitudinal direction of the net body and the line that bisects the inner angle at the corner is 80 to 100 °.
Y ≧ 0.16x−0.05 Formula [I]

  Further, the above-mentioned cement-based hardened body crack suppressing structure is preferably arranged so that an intermediate position in the longitudinal direction of the net body is substantially present on a line that bisects the inner angle at the corner of the opening. This is solved by a structure for suppressing cracks in a hardened cementitious body, which is characterized by comprising:

  Moreover, it is said cement-type hardened body crack suppression structure, Comprising: Preferably, the said net | network body is 10-50 cm (more preferably 10-30 cm) in the width | variety (length in a transversal direction). It is solved by the characteristic cement-based hardened body crack control structure.

  In the above-mentioned cement-based hardened body crack suppressing structure, preferably, the net body is formed by combining a first thread and a second thread having a shorter length than the first thread in a net shape. This is solved by the cement-based hardened body crack suppressing structure, wherein (tensile stiffness of the first yarn) / (tensile stiffness of the second yarn) is 1.5 to 30.

  Further, in the above-mentioned cement-based hardened body crack suppressing structure, preferably, the net body is (total area of the opening having a size of 10 mm or more in the opening and 10 mm or more in the opening in the net) / This is solved by a cement-based hardened body crack suppressing structure characterized in that the total area of the net body is 0.2 to 0.9.

  The crack of the cementitious hardened body with the opening could be effectively suppressed. In addition, the workability for suppressing cracks is good and can be carried out easily and at low cost.

Perspective view of hardened cementitious body Explanatory drawing of net body arrangement Top view of net body Explanatory drawing showing the features of the present invention

  The present invention is a cement-based cured body crack suppressing structure. In particular, the cement-based cured body cracks in which cracks at the corner-corresponding portions of the openings having corners in the cement-based cured body (the opening edge length of the opening (periphery length of the opening) is 2x) are suppressed. It is a suppression structure. The structure has a net body. That is, a net body (the length in the longitudinal direction of the net body is Y) is disposed in the cement-based cured body. The net body is arranged such that an intersection angle between a line in the longitudinal direction of the net body and a line that bisects an inner angle at a corner of the opening is 80 to 100 °. In particular, they are arranged to be orthogonal (substantially orthogonal). The net body to be disposed has a regulation in the length in the longitudinal direction. That is, the relationship between the length Y in the longitudinal direction of the net body and the opening edge length 2x of the opening needs to satisfy Y ≧ 0.16x−0.24. Preferably, Y ≧ 0.16x−0.05. There is no particular restriction on the upper limit of Y. That is, there is no problem in suppressing cracking even if Y is too long for x. The problem of Y being too long is the cost. Or, it is in terms of workability. Therefore, a preferable upper limit value of Y is 4x / 10 (more preferably 2x / 10: 2x is the circumference of the opening). The width of the net body is preferably 10 to 50 cm. More preferably, it is 10-30 cm.

  The net body is preferably formed by combining a first yarn and a second yarn having a shorter length than the first yarn in a net shape, and (the tensile rigidity of the first yarn) / (the first yarn). The tensile rigidity of the second yarn) is 1.5-30. The net body is a thread that exists in at least two directions (simply referred to as a thread, but this is a fiber itself, a plurality of fibers twisted, or a plurality of fibers twisted. The twisted one is a twisted one, or a string or a narrow sheet-like one). The shape surrounded by this intersection (intersection) (opening shape: window shape) is, for example, a square, a rhombus, or a rectangle. Of course, not only the quadrangle as described above, but also other polygons may be used. However, if a net having a shape other than the quadrangle is to be manufactured, the cost increases. It is a net body of quadrilateral (square or rectangular, in particular rectangular). Yarns present in the first direction (first yarn) and yarns present in the second direction (second yarn: second yarn shorter in length than the first yarn) ) Preferably has the following relationship: The two directions are, for example, a vertical direction and a horizontal direction. When it is going to produce a net body, generally the thread | yarn of a longitudinal direction is a warp, and the thread | yarn of a transversal direction is a weft. (Tensile stiffness of first yarn (for example, longitudinal yarn: warp)) / (Tension stiffness of second yarn (for example, lateral yarn: weft)) = 1.5-30. More preferably, the value is 1.8 or more. More preferably, the value is 5 or more. More preferably, the value is 25 or less. More preferably, the value is 20 or less. That is, the effect of suppressing cracking of the hardened cement body by the net body configured such that (tensile stiffness of the first yarn) / (tensile stiffness of the second yarn) becomes the above value is large. Moreover, the yarn amount can be reduced. The tensile rigidity of the yarn can be obtained by (yarn elastic modulus) × (yarn cross-sectional area). When several fibers are twisted to form a thread, if the cross section is taken, there is a gap between the fibers in the cross section. However, in the case of (tensile stiffness of warp) / (tensile stiffness of weft), there is almost no problem even if the gap is neglected in the cross-sectional area of the yarn. Therefore, the cross-sectional area of the yarn is an area determined by the outer shape in the cross-section. This is the value obtained in. In order to configure the net body so that (the tensile stiffness of the first yarn) / (the tensile stiffness of the second yarn) is the above value, each of the yarns having the tensile stiffness ratio that is the above value is selected. However, in the case where an equivalent yarn is used, this can be achieved by considering the width of the yarn and the number of yarns. For example, when substantially the same yarn is used, this can be achieved by using a plurality of first yarns. That is, it can be achieved by knitting the net with a ratio of N (N is an integer of 2 or more) of the first yarn to one second yarn.

From the viewpoint of the effect of suppressing cracks, the net body preferably has (the total area of the opening having a size of 10 mm or more and 10 mm or more in the opening in the net body) / (total area of the net body) of 0. .2 to 0.9. More preferably, the value is 0.4 or more. The value is 0.8 or less. Also, the size of the transverse 10mm or more openings in the longitudinal 10mm or more (rectangular conversion area), and preferably 100mm ² ~10000mm ^2. In particular, when converted into a rectangular shape, the long side is preferably 10 mm or more. And it is 400 mm or less. More preferably, it is 15 mm or more. And it is 300 mm or less. Especially preferably, it is 20 mm or more. And it is 200 mm or less. From the viewpoint of the effect of suppressing cracking, the net body is preferably a net body having four or more intersections between the first yarn and the second yarn per 10 cm square. More preferably, it is 20 or more. And it is 500 or less. Especially preferably, it is 40 or more. And it is 300 or less. This is because when the opening is as described above, it is difficult to adversely affect the filling of concrete or the like. Preferably, the yarn has a width of about 0.1 to 30 mm. More preferably, it is 1 mm or more. And it is 10 mm or less. That is, the strength of the yarn that is too small is poor, and conversely, in the case of the yarn that is too large, the integrity of the cemented cured body located on both sides of the crack suppressing material is so poor. Dimensional width yarns were preferred. Since the second yarn (weft yarn) having a short length is waved at the intersection point and positioned above and below the first yarn (warp yarn) having a long length, the first yarn (warp yarn) is also provided. It is preferable to make the thickness of the first yarn (warp yarn) thicker than the thickness of the second yarn (weft yarn). Further, it is preferable that the width of the first yarn (warp yarn) is wider than the width of the second yarn (weft yarn).

The net body is made of synthetic fibers such as aramid fibers, carbon fibers, glass fibers, and the like. That is, it is preferably configured using a fiber having a high elastic modulus. In view of affinity with cement and cost, a net body formed using glass fiber yarn is preferable. Among them, a net body made of alkali-resistant glass fiber (for example, glass fiber containing 14% by mass or more of zirconium oxide (ZrO ₂ )) is preferable.

  The cement-based hardened body is a hardened body of a cement-based composition such as mortar, concrete, cement paste, etc. using a hydraulic substance such as cement or blast furnace slag as a binder. The net body is provided integrally. Here, being provided integrally means, for example, a form in which a kneaded product of an uncured cement composition is placed and integrated in a mold frame in which a net body is disposed, particularly a mold in which a net body is bound to a reinforcing bar and disposed. The form in which the uncured cement composition kneaded material is placed and integrated in the frame, the net body is disposed on the surface where the cement composition kneaded material is integrated, and then the cement composition is kneaded again. Various forms such as a form in which objects are cast and integrated are conceivable. Of course, it is not restricted to the said form. However, the net body is preferably embedded in the cement-based cured body.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 is a perspective view of a cement-based cured body for explaining the present invention. That is, in order to explain the crack-inhibiting effect of the cement-based cured body in which cracks at the corner-corresponding portions of the opening having corners in the cement-based cured body (the opening edge length of the opening is 2x) are suppressed. It is a perspective view of the cementitious hardened body used for. In FIG. 1, 1 is a cement-type hardened body. The cement-based cured body 1 is a rectangular parallelepiped. That is, it is a cement-type hardened body having a rectangular parallelepiped shape of length (height: H), width (width: B), and depth (L). Reference numeral 2 denotes an opening (window) provided at the center of the cement-based cured body 1. The opening 2 has a square cross section. Therefore, the opening 2 has a corner. That is, the shape is vertical (height: h), horizontal (width: b), and depth (L). Although not shown in the drawing, reinforcing bars are arranged. In other words, the reinforcing bars are arranged so as to form a 100 mm × 100 mm grid with two-stage bar arrangement in the depth direction and a cover of 25 mm. The reinforcing steel used is D-10.

  FIG. 2 explains the arrangement of the net body with respect to the cement-based hardened body. That is, the net body 3 is arranged as shown in FIG. For example, the net body 3 is arranged so that the line in the longitudinal direction of the net body 3 is orthogonal to the line (indicated by the one-dot chain line in FIG. 2) that bisects the internal angle (90 °) at the corner of the opening 2. Has been. However, the orthogonality of the lines is the most preferable form, and if it is within a range of about ± 10 °, no significant difference was observed in the crack suppression effect even if it is slightly inclined. The edge of the net body 3 is in contact with the corner of the opening 2. This point is also the most preferable form, and the net body 3 may be slightly separated from the corner of the opening 2 (for example, about 2 cm). The end of the net body 3 is tied to the reinforcing bar with a binding wire. That is, the net body 3 is tied to the reinforcing bar with an interval of 100 to 300 mm.

  FIG. 3 is a plan view of the net body 3. The net body 3 has a length in the short direction of 10 to 30 cm, for example, about 15 cm. Different lengths in the longitudinal direction were prepared depending on the size of the opening 2. As can be seen from FIG. 3, the net body 3 is made of three hardened glass fibers (alkaline resistant glass fibers) in the longitudinal direction (vertical direction in FIG. 3). Threads (thread width: about 3 mm, thread thickness: about 0.7 mm) are provided with an interval of about 17 to 19 mm (interval of about 17 to 19 mm in the left-right direction in FIG. 3). The three yarns that are provided tightly may be in contact with each other. Therefore, instead of using three yarns having a yarn width of about 3 mm, a yarn having a yarn width of 9 mm may be used. However, in this embodiment, as can be seen from FIG. 3, since three yarns having a yarn width of about 3 mm are used, although the three yarns are solidified, in reality, between the warp yarns, A slight gap, for example, a gap of about 1 mm is provided. And it is preferable from the viewpoint of cracking suppression that such a slight gap has a gap as the cement compositions on both sides of the crack suppression material are integrated through the gap. In FIG. 3, the first, second and third yarns from the left side are solidified and provided in the vertical direction, and the fourth yarn is provided in the vertical direction with an interval of about 17 to 19 mm from the third yarn, and The fourth, fifth, and sixth yarns are similarly set in the longitudinal direction, and the seventh yarn is provided in the longitudinal direction with an interval of about 17 to 19 mm from the sixth yarn. The seventh, eighth, and ninth yarns are similarly set in the vertical direction, and the tenth yarn is provided in the vertical direction with an interval of about 17 to 19 mm from the ninth yarn. The tenth, eleventh and twelfth yarns are also set in the vertical direction in the same manner, and the thirteenth yarn is provided in the vertical direction with an interval of about 17 to 19 mm from the twelfth yarn. The thirteenth, fourteenth and fifteenth yarns are also set in the longitudinal direction in the same manner. In the lateral direction (left-right direction in FIG. 3), one glass fiber (alkali-resistant glass fiber) yarn (yarn width: about 2.3 mm, yarn thickness: about 0.5 mm, yarn length: about 155 mm) Is provided with an interval of about 30 to 32 mm (in FIG. 3, an interval of about 30 to 32 mm in the vertical direction). The lateral yarns are arranged so as to be the back and front in order with respect to the longitudinal yarns (three yarns). That is, if weft is arranged on the first, second and third warps from the left (on the surface), the weft is arranged under the fourth, fifth and sixth warps from the left (under the back), Then, the weft is arranged on the seventh, eighth and ninth warps from the left (on the surface), the weft is arranged under the tenth, eleventh and twelfth warps (below the back), and the next 13, This is a form in which wefts are arranged on the 14th and 15th warp yarns (on the surface). Also, the weft adjacent to the above-mentioned weft is assumed to be above the first, second, third warp from the left (under the back), and above the fourth, fifth, sixth warp from the left ( Weft yarn is arranged on the top surface, and the weft yarn is arranged below the seventh, eighth and ninth warp yarns from the left (bottom of the back surface), and the weft yarn is arranged on the next tenth, eleventh and twelfth warp yarns (on the surface). Is arranged, and the weft is arranged under the next 13, 14, 15th warp yarn (under the back surface). Of course, this vertical relationship may be such that the three yarns are not one lump but one by one alternately. The warp and weft are made of a plurality of fibers. Therefore, at the intersection of the warp and the weft, the weft can be removed between the warps. That is, the warp and the weft are knitted so that the weft can be removed between the fibers of the warp. The intersection of the warp and the weft is impregnated with resin, and the warp and the weft are bonded to each other so that no deviation occurs at the intersection. Since the warp and weft are knitted as described above, the shape of the opening (window) formed by the four intersections of the warp and weft is substantially rectangular (longitudinal dimension: 30 to 30). 32 mm, short direction dimension: about 17 to 19 mm).

  Now, since the cracks after the lapse of 6 months were evaluated by visual observation for the cement-based cured body (B = 4 m, H = 3 m, L = 0.5 m), the results are shown in FIG. In FIG. 4, half the opening edge length 2x (= 2b + 2h) of the opening, that is, (b + h (b = 0.5 m to 3.5 m, h = 0.5 m to 3.5 m)) is plotted on the horizontal axis (X The longitudinal length Y of the net body is taken on the vertical axis (Y axis), and the degree of cracks occurring at that time is plotted in the xy coordinate system. In this coordinate system, a circle mark indicates that no cracks were observed, and a triangle mark indicates that the crack width was within 0.05 mm (though cracks were recognized but no repair was required). Is a case where the crack width exceeds 0.05 mm and a crack requiring repair is observed.

  According to this, when the opening part 2 and the net body 3 satisfy | filled Y> = 0.16x-0.05, the crack was not recognized. When 0.16x−0.05> Y ≧ 0.16x−0.24 was satisfied, cracks were observed, but in this case the cracks were within 0.05 mm in width. Therefore, it was not necessary to repair. Therefore, it can be seen that if the net body is arranged as described above, the crack suppressing effect is very remarkable.

  In particular, the above net body effectively suppresses cracks that occur in the direction perpendicular to the longitudinal direction of the net body. In other words, the net body is a uniaxially arranged continuous fiber in the longitudinal direction, has extremely high reinforcement efficiency, and it is possible to greatly reduce the crack width by suppressing cracks by improving tensile resistance and the effect of uniform dispersion of stress. is there. In particular, cracks that occur at the corners are greatly suppressed. Moreover, because it uses a net body, it is easy to install and anyone can easily install. Therefore, it is very economical. Moreover, overcrowded reinforcing bars can be prevented, and excessive design is not required.

  In addition, when the net body 3 was not used, a large crack having a width of 0.15 mm or more was observed. Of course, the crack width increased as the size of the opening 2 increased. For example, when the opening shape is b = 3 m and h = 2.5 m, the crack width is as large as 0.30 mm.

  When two reinforcing bars were similarly arranged instead of the net body 3, a large crack having a width of 0.12 mm or more was recognized. Of course, the crack width increased as the size of the opening 2 increased. For example, when the opening shape is b = 3 m and h = 2.5 m, the crack width is as large as 0.20 mm.

1 Cement-based hardened body 2 Opening 3 Net body

Claims (5)

A cement-based hardened body crack suppressing structure in which cracking at the corner corresponding portion of the opening (the opening edge length of the opening is 2x) having a corner in the cement-based hardened body,
The cement-based cured body is provided with a net body (the length of the net body in the longitudinal direction is Y),
The net body is
The first yarn and the second yarn having a shorter length than the first yarn are combined in a net shape, (tensile rigidity of the first yarn) / (tensile rigidity of the second yarn). Is 1.5-30,
The length Y in the longitudinal direction of the net body is a length satisfying the following formula [I] with respect to the opening edge length 2x of the opening,
The cement-based hardened body crack-suppressing structure, characterized in that an intersection angle between a longitudinal line of the net body and a line that bisects an inner angle at the corner is 80 to 100 °.
Y ≧ 0.16x−0.05 Formula [I] A cement-based hardened body crack suppressing structure in which cracking at the corner corresponding portion of the opening (the opening edge length of the opening is 2x) having a corner in the cement-based hardened body,
The cement-based cured body is provided with a net body (the length of the net body in the longitudinal direction is Y),
The net body is
The first yarn and the second yarn having a shorter length than the first yarn are combined in a net shape, (tensile rigidity of the first yarn) / (tensile rigidity of the second yarn). Is 1.5-30,
The length Y in the longitudinal direction of the net body is a length that satisfies the following formula [II] with respect to the opening edge length 2x of the opening,
The cement-based hardened body crack-suppressing structure, characterized in that an intersection angle between a longitudinal line of the net body and a line that bisects an inner angle at the corner is 80 to 100 °.
Y ≧ 0.16x−0.24 Formula [II] The cement-based hardened body crack according to claim 1 or 2, characterized in that the intermediate position in the longitudinal direction of the net body is disposed so as to substantially exist on a line that bisects the inner angle at the corner of the opening. Suppression structure. The width of the net body is 10 to 50 cm, and the cement-based hardened body crack suppressing structure according to any one of claims 1 to 3. The net body
The total area of the opening having a size of 10 mm or more and 10 mm or more in the opening in the net body / (total area of the net body) is 0.2 to 0.9. The cement-based cured body crack suppressing structure according to any one of claims 1 to 5.

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