JP2008038360A - Inducing joint structure and construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crack inducing joint structure and a construction method, having no problem in design and structural bearing force. <P>SOLUTION: According to this construction method of the crack inducing joint structure, in the concrete crack inducing joint structure 1 where a part to generate a crack inducing joint 5 is filled with mortar and a concrete placing work 7, a mortar filling space part is provided by a lath frame 8, and after a part outside of the mortar filling space part is filled with concrete 4, mortar 5 flows into the mortar filling space part from the concrete 4 so that the mortar filling space part is filled with mortar 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crack-inducing joint structure for concrete and a method for its construction.

  As the demands on the durability and design of concrete structures increase, crack-inducing joints are provided for the purpose of concentrating the places where concrete cracks occur in order to cope with the cracks in concrete that occur after the construction of concrete structures.

  However, while the decorative joint joint has a joint depth of about 1 cm, a general crack-inducing joint joint is required to have a concrete cross-section missing 20% or more of its thickness. Society: Crack prevention measures for reinforced concrete structures (design / construction guidelines / explanation), if there is no concrete cross-section thickness, such as a house foundation, it will not function as an effective crack-inducing joint at a joint depth of about 1 cm. In addition, if a necessary concrete cross-sectional defect is taken, there is a problem in terms of design and structural strength.

JP 2000-314182 A JP 2006-90039 A

  An object of the present invention is to provide a concrete crack-inducing joint structure and a construction method that have no problem in terms of structural strength in terms of design.

  As a result of research and investigation, the present inventor has paid attention to the fact that the drying shrinkage rate of mortar is larger than the drying shrinkage rate of concrete. It has been found that it occurs faster than cracking due to shrinkage. The present invention has been completed by such investigation.

  The above-mentioned problems are solved by a concrete crack-inducing joint structure characterized in that a part that generates a crack-inducing joint is made of mortar in a concrete structure such as a foundation, a wall, or a floor.

  Since the drying shrinkage rate of mortar is higher than the drying shrinkage rate of concrete, cracks concentrate in the mortar part due to the difference in drying shrinkage rate even if there is no cross-sectional defect as a crack-inducing joint in concrete. Even if there is no cross-sectional defect as a part, it is possible to provide an induced joint part for concentrating cracks, and it is possible to make a concrete structure having no problem in design and structural strength.

  In addition, in the construction of concrete structures such as foundations, walls, and floors, the above-mentioned problem is that a mortar filling space is provided by a grid-like partition plate in a concrete casting mold, and other than the mortar filling space. After the concrete is filled, the mortar content flows from the concrete into the mortar filling space portion, so that the mortar filling space portion is filled with the mortar.

  A concrete structure is obtained by providing a mortar filling space portion with a grid-like partition plate in a concrete casting formwork, filling concrete in a space other than the mortar filling space portion, and then wrapping mortar from concrete into the mortar filling space portion. There is a concrete part and a mortar part in the object, and it is easy to construct the induced joint part to concentrate cracks without separately providing concrete and mortar without providing a cross-sectional defect as the induced joint part in the concrete part. It can be realized by the method.

  Since the present invention is as described above, even if there is no cross-sectional defect as a crack-inducing joint in concrete, cracks are concentrated in the mortar part due to the difference in drying shrinkage rate. It is possible to provide an inductive joint that concentrates the structure, and it is possible to make a concrete structure that is free from problems in design and structural strength.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  In the embodiment shown in FIG. 1, 1 is a concrete foundation, 2 is a crack-inducing joint, 3 is a decorative joint, 4 is concrete, 5 is mortar, and 6 is a reinforcing bar.

  The concrete foundation 1 is composed of reinforcing bars 6 arranged at predetermined intervals and concrete 6 surrounding the reinforcing bars 6. Grooves are formed in the longitudinal direction of the concrete foundation 1 as the decorative joints 3 at predetermined intervals in the longitudinal direction of the concrete foundation rising portion.

  Usually, the drying shrinkage rate of mortar is about twice the shrinkage rate of concrete. Therefore, when the drying shrinkage of concrete progresses, the mortar portion having a high drying shrinkage rate is cracked first. Therefore, even if there is no cross-sectional defect on the concrete surface due to the occurrence of induced joints, the location where cracks occur by concentrating the mortar portion in the concrete concentrates and induces cracks in the concrete foundation at appropriate locations be able to.

  That is, in the concrete foundation 1, even if there is no cross-sectional defect as a crack-inducing joint, cracks concentrate in the mortar part due to the difference in drying shrinkage between the concrete 4 and the mortar 5, so there is no cross-sectional defect in the concrete part. The crack-inducing joint 2 for concentrating cracks can be provided, and a concrete structure free from problems in design and structural strength can be produced.

  Next, the construction method of a crack induction joint structure will be described.

  As shown in FIG. 2 (a), the reinforcing bars 6 are arranged and the surroundings are surrounded by a concrete casting mold 7, and then the lath frame 8 processed into a box shown in FIG. While installing vertically so as to be orthogonal to the longitudinal direction of the frame 7, a joint material 9 for forming a decorative joint is provided on the surface side of the mold 7. Here, as shown in FIG. 2B, the lath frame 8 is formed by bending the lath into a box shape, and the four sides of the lath are surrounded by the lath frame, and the upper and lower surfaces are open. The lateral dimension of the side of the lath frame is equal to the joint width of the crack-inducing joint 2, for example, about 1 cm, and the longitudinal dimension is adjusted to the dimension obtained by subtracting the joint joint width from the concrete foundation width. The dimensions are matched to the rising dimensions of the concrete foundation. Although not shown, the lath frame 8 is provided with a hole or a notch so that the reinforcing bar 6 can be installed.

  The shape of the lattice of the lath frame 8 is required to be a shape that allows only the mortar in the concrete to pass through without passing the crushed stone in the concrete.

  As shown in FIG. 3A, the concrete 4 is not placed in the range surrounded by the lath frame 8 in the mold 7 where the lath frame 8 is installed. Concrete 4 is placed. After placing the concrete, as shown in FIG. 3 (b), when vibration is applied by the vibrator 11 and the concrete is compacted, only the mortar in the concrete 6 flows through the lattice of the lath frame 8, and FIG. The lath frame 8 is filled with only the mortar 5 as shown in FIG.

  After the concrete is cured, when the mold 8 is removed, the concrete foundation 1 having a crack-inducing joint having a portion made only of mortar is completed.

  Usually, the drying shrinkage rate of mortar is about twice the shrinkage rate of concrete. Therefore, when the drying shrinkage of concrete progresses, the mortar portion having a high drying shrinkage rate is cracked first. Therefore, as shown in FIG. 4, even if there is no cross-sectional defect on the concrete surface due to the occurrence of induced joints, the location where cracks 10 occur is concentrated by providing a portion made of mortar in the concrete, and the concrete foundation 1 Can be triggered at appropriate points.

  Further, due to the difference between the drying shrinkage rate of the mortar and the drying shrinkage rate of the concrete, cracks may occur in a form in which the interface between the concrete 4 and the mortar 5 deviates. In any case, even if there is no cross-sectional defect on the concrete surface due to the occurrence of induced joints, by providing a part made of mortar in the concrete, the places where cracks 10 occur are concentrated, and the concrete foundation 1 is properly cracked. Can be triggered at any point.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention. For example, in the present embodiment, a box made of a lath frame is used in the mold, but it is not limited to a lath, and the main point is that it is a lattice from which only mortar flows out from concrete. In addition, the lath frame 8 is cut in order to dodge the reinforcement 6 installed in the mold 8, but other methods may be used.

  In the above embodiment, the lath frame 8 separates the mortar-filled portion from the portion that is not, but it goes without saying that the method may be performed by other methods.

The figure is a perspective view showing an induced joint structure according to an embodiment of the present invention. Fig. (A) is a front view showing a construction method of the induced joint structure, and Fig. (B) is a perspective view showing a lath frame. FIGS. 1A to 1C are cross-sectional side views sequentially showing a construction method of the induced joint structure. The figure is a front view showing a situation where cracks are generated in the induced joint structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Concrete foundation 2 ... Crack induction joint 3 ... Makeup joint 4 ... Concrete 5 ... Mortar 6 ... Reinforcement 7 ... Formwork 8 ... Lath frame (partition board)

Claims (3)

  In concrete structures such as foundations, walls, and floors, a crack-inducing joint structure for concrete, characterized in that the part that generates crack-inducing joints consists of mortar.   In the construction of concrete crack-inducing joints in concrete structures such as foundations, walls, and floors, a mortar filling space is provided in the concrete placement formwork by a grid-like partition plate, and in addition to the mortar filling space A method of constructing a crack-induced joint structure in concrete in which mortar is filled into the mortar filling space by filling the mortar with the mortar after the concrete is filled.   The method for constructing a crack-inducing joint structure in concrete according to claim 2, wherein the lattice of the lattice-shaped partition plate is smaller than the coarse aggregate diameter of the concrete to be placed.

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