JP2013019120A - Construction method of wall-like structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of a wall-like structure, capable of facilitating construction without generating cracks on a wall part, and reducing costs further, when erecting the wall part on a bottom slab and forming the wall-like structure.SOLUTION: A wall part 20 is constructed by constructing a wall base part 21 by installing a precast burial mold form 30 to be the wall base part 21 on a bottom slab 10 and driving concrete to which a retarder is added to the precast burial mold form 30, and constructing a wall body part 22 by driving concrete to which the retarder is not added to an upper part of the wall base part 21.

Description

  The present invention relates to a method for constructing a wall-like structure, and more particularly, to a technique relating to a method for constructing a wall-like structure that is formed by standing a wall portion on a bottom plate.

Conventionally, in order to construct wall-like structures such as hard walls of wall-type abutments, side walls of box culverts, ground cover and railings of bridge superstructure, existing concrete (bottom slab) such as footing, bottom slab and floor slab is constructed, Wall concrete is driven onto this bottom plate. At this time, the bottom slab acts as a restraint to restrain the volume change of the wall concrete, so that a temperature crack occurs in the wall. That is, in mass concrete, the heat of hydration of cement is accumulated in the cross section, so that the volume change of expansion and contraction occurs at the initial age. In these volume changes, if shrinkage deformation is constrained, cracks are likely to occur. Such cracks often penetrate the cross section and increase in width, often leading to reduced usability and durability such as water leakage.

  In order to avoid such an inconvenience, a construction method has been developed in which a leading wall body portion with a small constraint is formed on the upper portion of the bottom plate, and concrete that becomes a wall portion is driven into the upper portion of the preceding wall body portion (see Patent Document 1). . In the technique described in Patent Document 1, a ridge portion (preceding wall body portion) having a thickness corresponding to a wall portion is formed upward on the upper surface of the bottom plate, and concrete is driven onto the ridge portion. Thus, an upper wall body (wall portion) is formed.

JP 2008-291494 A

  The technique described in Patent Document 1 described above is less cracked because the restraint from the bottom plate is weakened and the generated temperature stress is reduced compared to the case where the wall portion is constructed by directly injecting concrete onto the bottom plate. It has the outstanding effect that generation | occurrence | production of is suppressed. However, this technology has a feature in the preceding wall body part at the top of the bottom plate, but the construction (formation) of the preceding wall body part requires a floating formwork or divided driving of the wall part. In order to reduce the construction cost, further ingenuity has been demanded.

  The present invention has been proposed in view of the above-mentioned circumstances, and when a wall portion is erected on a bottom plate to form a wall-like structure, the wall portion is not cracked and construction is easy. And it aims at providing the construction method of the wall-shaped structure which can further reduce cost.

  The construction method for a wall-like structure of the present invention has the following characteristics in order to achieve the above-described object. That is, the construction method of the wall-like structure of the present invention is a construction method of the wall-like structure for constructing the wall portion on the bottom plate, and the precast embedded formwork that becomes the wall base portion is installed on the bottom plate, and The wall base is constructed by placing concrete with setting retarder added into the precast embedding formwork, and the wall body is constructed by placing concrete with no setting retarder added to the top of the wall base. To do.

  In the method of constructing a wall-like structure consisting of such processes, the bottom plate is driven by placing concrete with a setting retarder added to the bottom and concrete with no setting retarder added to the top. Delays the setting of concrete at the base of the wall that touches the wall. In addition, in the part where the setting retarding concrete is driven, a precast embedded formwork is installed inside the normal formwork, and the surrounding concrete is restrained by the upper concrete and the precast embedded formwork at the initial age, so that the wall base Keep the concrete in a stable state even before strength is developed.

  Moreover, in the construction method of this wall-like structure, it is desirable to delay the strength expression by the setting retarder for 2 days or more. In the construction method of the wall-like structure composed of such steps, it is possible to sufficiently ensure the concrete delay effect at the wall base.

  According to the construction method of the wall-like structure of the present invention, when constructing the wall portion on the bottom slab, the concrete is added with a setting retarder to the wall base portion (lower wall portion), so that at the initial age, the wall Even if the volume change of expansion and contraction occurs at the base, since the restraint from the bottom plate is weakened and the generated temperature stress is reduced, the generation of cracks is suppressed. In addition, since the wall base and the wall main body continuous to the upper portion can be constructed at a stretch, not only the construction is easy, but also the work time is shortened, so that the construction cost can be reduced.

  In addition, by appropriately managing the strength expression due to the setting retarder at the wall base, it is possible to reduce the rate of increase in compressive stress at the time of temperature rise and tensile stress at the time of temperature drop, thereby improving the construction quality. It becomes possible.

The cross-sectional schematic diagram of the thickness direction of the wall-shaped structure using the construction method which concerns on embodiment of this invention. The cross-sectional schematic diagram of the length direction of the wall-shaped structure using the construction method which concerns on embodiment of this invention.

  Hereinafter, with reference to drawings, the embodiment of the construction method of the wall-like structure concerning the present invention is described. 1 and 2 show a wall-like structure using a construction method according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view in the thickness direction, and FIG. 2 is a schematic cross-sectional view in the length direction. is there.

  As shown in FIGS. 1 and 2, the wall-like structure to be constructed using the construction method according to the embodiment of the present invention is formed by forming a wall portion 20 on the upper portion of the bottom plate 10. It consists of a wall base 21 and a wall main body 22 constructed on and connected to the wall base 21. Moreover, the wall base 21 is formed by driving concrete added with a setting retarder, and the wall main body 22 is formed by driving concrete not added with a setting retarder.

  That is, in the present embodiment, a mold for forming the wall portion 20 is installed on the bottom slab 10, and reinforcement is placed in the mold. At this time, the precast embedded form 30 is installed in the portion that becomes the wall base 21. And the wall base 21 is constructed by driving concrete into which the setting retarder is added into the portion where the precast embedded form 30 is installed. Subsequently, the wall main body portion 22 is constructed by driving concrete into which the setting retarder is not added to the upper portion of the wall base portion 21.

  Further, the height of the wall base 21 to be constructed using the concrete to which the setting retarder is added is determined by appropriately changing according to the thickness of the wall 20 and the diameter of the reinforcing bar used. Generally, this height is 200 to 900 mm, only the precast embedded mold 30 is installed on both sides of the wall portion 20, or the precast embedded mold 30 is installed inside the mold, and from the upper surface of the bottom plate 10 to about 400 mm, It is set as the wall base 21 by driving in the concrete which added the setting retarder.

  In experiments conducted by the inventors, it has been confirmed that the temperature stress generated in the wall portion 20 is reduced by 50% or more by delaying the expression of the strength of the concrete by a setting retarder in the wall base portion 21 for about 7 days. Therefore, when constructing the wall base 21, it is desirable to delay by the setting retarder until the age at which the concrete temperature of the wall 20 is reduced to the outside air temperature. For example, it is desirable to delay the strength expression by 5 days or more in a wall body having a thickness of about 500 mm. In general, the occurrence of cracks can be effectively suppressed by delaying strength development for 2 days or more. In addition, the setting retarder to be used is not particularly limited, but it is desirable to use, for example, a gluconic acid based retarder in consideration of strength development after product delay and product quality.

  In addition, when a preliminary analysis was performed assuming that the temperature characteristics and strength development characteristics of the concrete layer to which the setting retarder was added were accurately delayed by 7 days, a specimen of the concrete layer to which the setting retarder was not added (standard specimen) ) And the concrete layer specimen (addition specimen using retarder) to which a setting retarder was added, the analysis results shown in Table 1 below could be obtained. The standard specimen has an implantation temperature of 30.7 ° C., a maximum temperature of 58.6 ° C., and a temperature increase of 27.9 ° C. The retarding agent-use specimen has an implantation temperature of 30.7 ° C., a maximum temperature of 57.9 ° C., The analysis was performed with a temperature increase of 27.2 ° C.

  As is clear from Table 1 above, when the standard specimen and the retarder-use specimen were compared, the probability of occurrence of cracks, which was 80.2% for the standard specimen, was 23.1% for the retarder-use specimen. In addition, it has been found that a remarkable crack-preventing effect can be exhibited in a specimen using a retarder.

  As described above, in the wall-like structure constructed by the construction method according to the embodiment of the present invention, the concrete added with a setting retarder is used when forming the wall base 21 that is in direct contact with the upper surface of the bottom plate 10. As a result, the restraining force by the bottom plate 10 is reduced, so that the rate of increase of the compressive stress when the temperature rises and the tensile stress when the temperature drops are reduced. For this reason, at the initial age, the restraint from the bottom plate 10 with respect to the wall base 21 is weakened, and the occurrence of cracks can be effectively suppressed.

  In the above-described embodiment, an example in which the present invention is applied to construction of a general wall-like structure is described as a model case. However, the present invention is a wall-like structure in which the wall portion 20 is constructed on the bottom plate 10. This is a technique that can be applied to any wall-like structure as long as it is a structure, and can be applied, for example, when building a box culvert.

DESCRIPTION OF SYMBOLS 10 Bottom plate 20 Wall part 21 Wall base 22 Wall main-body part 30 Precast embedding formwork

Claims (2)

It is a construction method of a wall-like structure that builds a wall on the bottom plate,
While installing a precast embedded formwork to be a wall base on the bottom plate, constructing the wall base by driving concrete added with a setting retarder into the precast embedded formwork,
Constructing the wall body by driving concrete to which the setting retarder is not added to the top of the wall base,
The construction method of the wall-shaped structure characterized by this.   The method for constructing a wall-shaped structure according to claim 1, wherein the wall base part delays strength development by the setting retarder for two days or more.

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