JP4160773B2 - Method for suppressing warpage deformation of precast concrete plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for suppressing warpage deformation of a precast concrete plate having a surface decorative material on its surface.
[0002]
[Prior art]
Precast concrete plates are often integrated into a concrete panel by placing surface decorative materials such as tiles, porcelain plates, stones, and metal plates on the surface side.
By the way, after the concrete is hardened, the capillary water inside is dissipated by drying, so that drying shrinkage occurs. At this time, when the surface decorative material is driven into the precast concrete plate, drying on the front surface side is suppressed, whereas drying on the back surface side freely proceeds. As a result, a difference occurs in the drying speed between the front and back surfaces, and the shrinkage of the back surface proceeds, causing warpage deformation such that the front side becomes a convex surface as shown in FIG.
[0003]
Therefore, conventionally, the following means are used to correct such warpage.
(1) In order to increase the out-of-plane rigidity of the precast concrete slab, reinforcing ribs are placed on the back to constrain panel deformation, and the position of the support point relative to the precast concrete slab at the stock stage such as flat stacking is considered. By doing so, warpage is suppressed by the weight of the plate.
(2) (Method to warp the formwork in advance in anticipation of warping deformation)
The amount of warpage deformation due to shrinkage is predicted from the actual results, and the mold is warped in the opposite direction, and the deformation is brought close to 0 by shrinkage.
(3) (JP-A-5-229862)
A high-performance water reducing agent and an ultrafine powder admixture having a pozzolanic activity such as silica fume are added to a mortar material having a water cement ratio of 25% or less and a sand cement ratio of 1 or more by weight. The mortar material thus prepared is kneaded to prepare a mortar. After the mortar is placed on a mold, it is cured to obtain a precast concrete plate. Thus, by increasing the sand cement ratio as much as possible and increasing the proportion of sand, the proportion of cement hydrate causing drying shrinkage in the mortar can be reduced, and precast concrete accompanying dry shrinkage. Prevent warping of the plate.
(4) (JP-A-8-175883)
Surface decorative materials such as stones, tiles, metal plates, etc. are placed on the mold surface of the formwork, and on the surface decorative material, napped cotton is laid on one side with the raised parts facing upward, and then concrete is placed in the formwork. To cast. Thereafter, at least after the disappearing stage of the breathing water, an acrylic resin emulsion (polymer emulsion) is applied to the concrete surface, and the concrete surface is covered with an acrylic resin film by dry curing. Furthermore, a vinylidene chloride resin emulsion (polymer emulsion) is applied to the upper surface of the acrylic resin film, and a layer of the vinylidene chloride resin film is formed on the acrylic resin film by drying and curing. After the required strength is developed, the mold is removed from the mold to obtain a precast concrete plate in which the surface decorative material is integrated on the surface. Thereby, the drying rate and the shrinkage rate associated therewith are the same on the front and back due to the covering curing effect by the film, thereby preventing warpage.
(5) (JP 2001-71318 A)
A surface decorative material is arranged in the mold, and after placing mesh streaks and hardware, the concrete is placed. After 2-3 hours of placing the concrete, a drying inhibitor is sprayed onto the concrete surface and steam curing is performed.
[0004]
[Problems to be solved by the invention]
Each of the above means (1) to (5) has the following problems.
[0005]
Problem of Means (1) Precast concrete due to the combination of several factors such as seasonal environmental factors such as temperature and humidity, difference in moisture permeability of surface cosmetics, and panel shape It was difficult to completely suppress this because the warpage deformation occurred more or less in the plate.
[0006]
Problem of means (2): The deformation amount expected due to changes in the conditions (weather, temperature, humidity, etc.) of the member and the variation in the concrete may not match the deformation amount of the actual member. However, there is a problem that warpage deformation occurs or warpage in the opposite direction remains.
[0007]
Problem of Means (3) Since mortar with W / C of 25% or less is cured at a high temperature of 60 ° C. to 90 ° C., concrete cracks are likely to occur. Moreover, it is limited to special preparation and curing conditions, and lacks versatility.
[0008]
Problem of Means (4) A film is formed to prevent premature evaporation of moisture in the concrete, but there is a drawback that the performance deteriorates due to peeling off or scratching. In addition, when a vinylidene chloride resin emulsion is applied to the upper surface of an acrylic resin film to form a double film, it is necessary to apply twice, and since it will be applied at the stage where the breathing water has disappeared, as a whole There is a disadvantage that the working time of the process increases. In addition, there is a disadvantage that the cost increases due to the addition of two steps of laying napped cotton on the surface decorative material and applying an acrylic resin film and a vinylidene chloride resin emulsion on the back of the panel.
[0009]
Problem of Means (5) When construction is carried out 2 to 3 hours after placing concrete, the drying inhibitor is an organic substance such as glycol ether, amino alcohol, ethylene oxide, etc., so the hardening of concrete is delayed and the surface becomes rough. There is a case. Further, since the drying inhibitor can reduce the shrinkage amount but cannot reduce it to 0, there is a case where sufficient measures cannot be taken for long and thin panels.
An object of the present invention is to provide a method for suppressing warp deformation of a precast concrete plate, which is simple and can be optimally flattened corresponding to a warped state, without the above-described problems.
[0010]
[Means for Solving the Problems]
As a reference invention, In a precast concrete plate with a surface decorative material on the surface, in the concrete layer, a linear steel material such as a steel bar or a steel stranded wire is placed along the surface direction at a position eccentric to the surface side from the center position of the thickness. After the concrete layer is hardened, by applying tensile stress to both ends of the linear steel material and fixing both ends to the precast concrete plate, the surface of the precast concrete plate is made convex by its restoring shrinkage force. A method for suppressing warp deformation of a precast concrete slab characterized by correcting warpage deformation is proposed.
[0011]
Such a method, by applying tension (extension stress) to the linear steel material inserted in a position eccentric from the center of the member to the surface side provided with the surface decorative material, due to the action of its restoring contraction force, The warp deformation caused by drying shrinkage of the concrete is canceled by the warping force in the reverse direction of the precast concrete plate, and the precast concrete plate is flattened.
[0012]
That is, after the concrete is hardened, the capillary water inside is dissipated by drying, and thus shrinkage occurs. At this time, when the surface decorative material is driven into the precast concrete plate, drying on the front surface side is suppressed, whereas drying on the back surface side freely proceeds. As a result, a difference occurs in the drying speed between the front and back surfaces, and the shrinkage of the back surface proceeds, causing warpage deformation such that the front side becomes a convex surface as shown in FIG. Therefore, tension (extension stress) is applied to the linear steel material inserted at a position eccentric to the surface side where the surface decorative material is provided, and the linear steel material is fixed at the end face of the precast concrete plate. , Hold tension. Thereby, as shown in the figure (b), the restoring contraction force acts on the surface side on which the surface decorative material is provided, and the deformation force acts such that the surface side becomes concave. Then, due to this deformation force, the warpage of FIG. 1A is eliminated, and the state of FIG. Here, FIG. 1 (b) shows the warp deformation due to the tension force f. In practice, the state shown in FIG. 1 is obtained after drying, and the state shown in FIG.
[0013]
Here, as a means for applying prestress, in such a configuration, a method (post-tension method) in which a linear steel material is tensioned after the concrete is hardened and a tension force is introduced into the concrete is used. In such means, the tension force can be adjusted according to the amount of warping of the plate, and therefore, an optimal flattening corresponding to the warping state is possible. In addition, the adjustment can be performed even when the concrete panel is used for the outer wall of the building.
[0014]
In addition, since the tension | tensile_strength to a linear steel material is a big thing of 5t-12t, what is necessary is just to add the correction (for example, less than 1/1000 of full length) to the extent of allowable curvature amount, and tension | tensile_strength and curvature amount. It is not necessary to correct until it is flattened while keeping the harmony, and it becomes a completely flat surface.
[0015]
Here, at the time of concrete placement, the sheath tube is embedded in the surface direction in a position eccentric to the surface side from the center in the thickness direction, and after the concrete layer is hardened, the linear steel material is inserted into the sheath tube. A method (Claim 2) is proposed in which tensile stress is applied to both ends and both ends are fixed to a precast concrete plate. In such a configuration, in the process of applying tension, the elongation does not cause cracks in the surrounding concrete.
[0016]
In addition, the linear steel material is coated with a resin coating with good wear resistance and slipperiness such as polyethylene coating, and when the concrete is cast, the linear steel material is driven and then the concrete layer is hardened and then stretched at both ends. A method is proposed in which stress is applied and both ends are fixed to a precast concrete plate (claim 3). In such a configuration, when the linear steel material is pulled from both sides to cause elongation, the resin coating causes slipping with respect to the concrete and can be expanded without applying a large load.
[0017]
Another means is a precast concrete plate provided with a surface decorative material on the surface, in a state in which a tensile stress is applied in advance to a position eccentric to the surface side from the center position of the thickness of the concrete layer, Proposed a warp deformation suppression method in which linear steel materials such as steel stranded wires are arranged along the surface direction, and the warping deformation with the surface of the precast concrete plate being convex is corrected by the restoring shrinkage force of the linear steel material Is done.
[0018]
This is a method (pretension system) for applying prestress as a method of introducing tension to concrete by tensioning the linear steel material before placing the concrete and releasing the tension after the concrete is hardened. .
[0019]
That is, as shown in FIG. 7 (a), tension (extension stress) is applied to both ends of the linear steel material to fix the linear steel material in the mold. Then, after the concrete has hardened, the tension is released. As a result, as shown in FIG. 7 (b), the restoring shrinkage force of the linear steel material acts on the surface side where the surface decorative material is provided, and the tension force f that makes the surface side concave serves. This tension force f is corrected in balance with the warp deformation and becomes flat.
[0020]
The present invention is a deformed precast concrete plate provided with a surface decorative material on the surface and having a center of gravity located outside the plate, such as a steel bar or a steel stranded wire at a position outside the plate eccentric to the surface side of the center of gravity. By arranging the linear steel material along the surface direction and applying a tensile stress to both ends of the linear steel material after the concrete layer has hardened or dried, and fixing the both ends to the precast concrete plate The method of suppressing warp deformation of a precast concrete plate characterized by correcting warp deformation in which the surface of the precast concrete plate has a convex surface by the restoring shrinkage force . As the deformed precast concrete slab having such a configuration, a configuration having a U-shaped cross-sectional structure is provided.
[0021]
Even in such a method, by applying a tension force (extension stress) to the linear steel material held outside the plate, the warp deformation caused by the drying shrinkage of the concrete due to the action of the restoring shrinkage force is canceled, Precast concrete plate can be straightened.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the method for suppressing warpage deformation of the precast concrete plate 1 of the present invention will be described.
2 and 3 show an example of the precast concrete slab 1 of the present invention, the dimensions of which are 6,000 × 600 × 97 mm in a test example described later, and a tile is driven as a surface decorative material 2 on the surface. Fig. 3 is a longitudinal cross-sectional view thereof, in which the unbonded PC steel rod (C type-φ13mm) 6 which is a linear steel material is placed in the concrete layer 3 at a position 30mm from the surface side, and the mesh reinforcement (D6 @ 100 ) 5 is placed within the plate thickness. Here, although the steel rod 6 is used as a linear steel material, linear steel materials, such as a steel strand wire, can also be applied.
[0023]
Such manufacturing means will be described.
As shown in FIG. 3, the precast concrete plate 1 can be manufactured by sequentially executing the following manufacturing steps (a) to (f).
Manufacturing process (1) The surface decorative material 2 (tile) is laid on the bottom surface 11 of the case-shaped steel mold 10 with the top surface open.
Manufacturing Process The romesh bars 5 and the steel rod 6 are passed in parallel along the bottom surface and held by the side walls 12 of the mold 10. In this case, the delivery position of the steel rod 6 is a position eccentric to the surface side from the center position of the thickness.
Manufacturing process C After kneading the stainless fiber reinforced concrete (SFRC) 3, it is placed in the mold 10 and the concrete layer is compacted.
Manufacturing process D Steam curing is performed as necessary.
The next day of the manufacturing process, the mold is removed from the mold, and after reversing, the surface is washed with water.
After curing to a predetermined age in the manufacturing process (14 days in the test), a tension force f was applied to the steel bar 6. Here, it is considered that the introduction time of the tension force f may be after the concrete strength has been developed to some extent, so that the age is 7 days or more, preferably 14 days or more.
[0024]
FIG. 4 shows a means for applying a tension force f to the steel bar 6.
Here, steel bars 6 protrude from both end faces of the precast concrete plate 1. A male screw 8 is formed at the end of the steel rod 6. An anchor plate 15 is fitted on the end of the steel rod 6, and a tightening nut 16 is screwed onto the male screw 8. Further, a U-shaped gantry 17 is disposed so as to straddle the steel rod 6. A hydraulic jack 19 is disposed on a base portion 18 orthogonal to the steel rod 6 of the gantry 17, and a movable pipe 22 having an end screwed to the male screw 8 of the steel rod 6 is inserted in the center thereof. When the nut 23 screwed to the movable pipe 22 is brought into contact with the movable surface 20 of the hydraulic jack 19 and a pressurized fluid is supplied to the hydraulic mug 19 from the hydraulic pump, the movable surface 20 is brought into contact with the precast concrete plate 1. The steel bar 6 is pulled outward at both ends via the movable pipe 22 that moves in a direction away from the end face and is engaged with the movable face 20 by the nut 23, and a tension force f is applied. In this state, the tightening nut 16 is tightened to maintain the tensioned state.
[0025]
Thereby, since the steel bar 6 is arrange | positioned in the position which shifted | deviated from the thickness center of the concrete layer 3 of the precast concrete plate 1 to the surface side, by the restoring contractive force as a reaction by extensional stress (tensile force f) The precast concrete slab 1 is given a warping force with a concave surface (see FIG. 1 (b)). For this reason, after the concrete layer 3 is cured, the precast concrete plate 1 is warped and deformed so that the surface side becomes convex as shown in FIG. Such warpage deformation is corrected by the warping force. In this correction, the hydraulic jack is driven while observing the state of the precast concrete plate 1 to confirm that it is flat, the drive is stopped, the tightening nut 16 is tightened, and the tension state is reached. Therefore, flattening of the precast concrete plate 1 can be easily achieved. Further, such a configuration can be adjusted even when the concrete panel is used for the building outer wall or the like.
[0026]
Here, the steel rod 6 is disposed at a position where the tension force f is smaller as the eccentric distance from the center is larger. However, in the case of a concrete product, as shown in FIG. It is desirable to arrange at a position where the cover thickness can be secured. Here, the cover thickness refers to the distance from the surface to the reinforcing bar (steel material). That is, if the reinforcing bar is close to the surface side, it is easily oxidized by air and liquid from the surface side, whereby the reinforcing bar expands, cracks in the concrete layer 3 and the strength decreases. For this reason, it is usually required to secure a cover thickness of 20 mm or more from the surface decorative material. Therefore, even with the steel rod 6, the same cover thickness is ensured.
[0027]
2 shows an example in the case of single reinforcement, but in the case of large reinforcement and double reinforcement (see FIG. 3), the mesh reinforcement on the surface side or the cover thickness of the PC steel bar should be 20 mm or more. It is desirable to do. In addition, when the unbonded steel rod 6 having a polyethylene film on the surface is applied, the cover thickness can be reduced. When the cover thickness is reduced and the eccentric distance from the center is increased, the warping force with the surface being concave is increased, and the tension force f can be reduced.
[0028]
Here, when the steel rod 6 is pulled, as shown in FIG. 4, the sheath tube 30 is embedded in advance along the surface direction at a position eccentric to the surface side from the center in the thickness direction when placing concrete. After the concrete layer is hardened, a means is proposed in which a steel rod 6 is inserted into the sheath tube 30 and tensile stress is applied to both ends thereof by means as shown in FIG. In such a means, in the process of applying the tension force f, the surrounding concrete layer 3 is not cracked due to its elongation.
[0029]
Further, as shown in FIG. 5, the steel rod 6 is coated with a resin coating 35 having good wear resistance and slipperiness such as polyethylene coating, and the steel rod 6 is driven when the concrete layer 3 is placed. After the concrete layer 3 is hardened, a method is proposed in which tensile stress is applied to both ends thereof by means similar to those described above (the same reference numerals are used and description thereof is omitted). In such a configuration, when the steel rod 6 is pulled from both sides to cause elongation, the resin coating 35 causes the concrete layer 3 to slip and can be stretched without applying a large load. Become. Such a configuration has the advantage that the number of parts is small and the structure is simple.
[0030]
Here, in order to confirm the effect | action of this invention, the some test body was created by the above-mentioned means, and one body did not introduce the tension | tensile_strength f, and gave tension | tensile_strength f to others. As a result, in the case where the tension force f was not applied, there was a warpage of about 9 mm in the case of the total length of 6000 mm in FIG. In addition, since this tension | tensile_strength f gives a big load to the precast concrete plate 1, it is not necessarily flattened completely, and if it is flattening of the extent which leaves the curvature of about 4 mm, it can use for practical use. It is. That is, since the tension force to the steel bar 6 is a large one of 5t to 12t, it is only necessary to add correction (e.g., within 1/1000 of the total length) within the allowable warpage amount. It is not necessary to correct until it is flattened while keeping the harmony, and it becomes a completely flat surface.
[0031]
Depending on the precast concrete plate 1 ′, as shown in FIG. 6, there is a U-shaped section having a surface decorative material 2 on the surface and a center of gravity located outside the plate. In such a configuration, it is also possible to correct the warp by introducing a tension force f outside the precast concrete plate 1 ′.
[0032]
That is, in the deformed precast concrete plate 1 ′ having such a configuration, a linear steel material such as a steel bar or a steel stranded wire is disposed along the surface direction at a position outside the plate that is eccentric to the surface side of the center of gravity. The bearings 30 and 30 are supported on the back surface of the deformed precast concrete plate 1 ′. Then, after the concrete layer 3 is cured, tensile stress is applied to both ends thereof by the same means as in FIG. 4, and both ends are held by the fastening nuts 16 and 16. Thereby, the warp deformation in which the surface of the precast concrete plate 1 ′ is convex is corrected by the restoring shrinkage force inside the center of gravity.
FIG. 7 shows another method of the present invention, a method (pretension system) for introducing tension to concrete by releasing the tension after the concrete is hardened.
[0033]
That is, as shown in FIG. 7A, a tensile force (extension stress) is applied to both ends of the linear steel material 6 by jigs 40 and 40, and the linear steel material 6 is formed into a molding thickness of the concrete layer 3. Is held in the mold 10 so that the positional relationship is returned from the center to the front side. After that, the concrete is driven. And after the concrete has hardened, when the tension force is released, as shown in FIG. 7 (b), on the surface side where the surface decorative material 2 is provided, the restoring shrinkage force of the linear steel material 6 acts, A tension force f having a concave surface is applied. This tension force f is corrected in balance with the warp deformation and becomes flat. This means can also be used for forming the precast concrete slab 1 'shown in FIG.
[0034]
【The invention's effect】
In a precast concrete plate provided with a surface decorative material on the surface, a linear steel material such as a steel bar or a steel stranded wire is arranged along the surface direction at a position eccentric to the surface side from the center position of the thickness, and concrete after the layer is cured, by applying a tensile stress to both ends, by fixing the both ends precast concrete panel, by its restoring contraction force, apparatus having to correct warp deformation of the surface of the precast concrete plate and the convex surface Thus, the tension force f can be adjusted according to the amount of warpage of the plate, and flattening can be performed easily and appropriately by tensioning the linear steel material while confirming the degree of warpage. In addition, the adjustment can be performed even when the concrete panel is used for the outer wall of the building.
[0035]
Here, at the time of concrete placement, the sheath tube is embedded in the surface direction in a position eccentric to the surface side from the center in the thickness direction, and after the concrete layer is hardened, the linear steel material is inserted into the sheath tube. , by applying a tensile stress at both ends, in the method so as to secure the two ends to the precast concrete plate, in the process of applying a tensioning force f, it is possible to generate cracks in the concrete around by its elongation There is no advantage.
[0036]
In addition, the linear steel material is coated with a resin coating with good wear resistance and slipperiness such as polyethylene coating, and when the concrete is cast, the linear steel material is driven and then the concrete layer is hardened and then stretched at both ends. stress grant, the both ends in the method for fixing the precast concrete panel, in the case that gave rise to elongation and tensile linear steel material from both sides, a resin coating, slip against the concrete It is possible to expand without applying a large load. Such a configuration has the advantage that the number of parts is small and the structure is simple.
Further, at a position eccentric to the surface side than the central position of the thickness of the concrete layer, in advance in a state where the tensile stress was applied, the linear steel material of the steel rod or steel wire strands or the like along surfaces arranged linear In the case where the warp deformation with the surface of the precast concrete plate being convex is corrected by the restoring shrinkage force of the steel material, the tension force f of the linear steel material is corrected in balance with the warp deformation, Become.
[0037]
Even if it is in a deformed precast concrete plate provided with a surface decorative material on the surface and having a center of gravity located outside the plate, a steel rod or a steel stranded wire, etc. The linear steel material is arranged along the surface direction, and after the concrete layer is hardened or dried, it is applied with tensile stress at both ends, and both ends are fixed to the precast concrete plate to restore it. In the method of correcting the warp deformation with the surface of the precast concrete plate as a convex surface by the shrinkage force, by applying tension (extension stress) to the linear steel material held outside the plate, The warp deformation caused by drying shrinkage of the concrete can be canceled by the action of the restoring shrinkage force, and the precast concrete plate can be flattened.
[Brief description of the drawings]
FIG. 1 shows the principle of the first means of the present invention, (A) shows the warp deformation on the surface side occurring in the precast concrete slab 1, (B) shows the tension force f according to the present invention, ) Shows the straightened state of the precast concrete slab 1.
FIG. 2 shows a design example of the precast concrete slab 1 of the present invention, where (A) is a plan view and (B) is a longitudinal side view.
FIG. 3 is an explanatory view showing a manufacturing process of the precast concrete plate 1;
4 is a longitudinal side view showing an example of means for applying a tension force f to the steel rod 6. FIG.
FIG. 5 is a longitudinal side view of the same in a configuration in which a steel rod 6 is provided with a resin coating 35;
6 shows a configuration in which a steel bar 6 is applied to a deformed precast concrete slab 1 ′ having a U-shaped cross section, (A) is a plan view, (B) is a longitudinal side view, and (C) is a front view.
FIG. 7 shows the principle of the second means of the present invention, (A) shows the tension force f according to the present invention, and (B) shows the straightened state of the precast concrete plate 1.
[Explanation of symbols]
1,1 'Precast concrete plate 2 Surface decorative material 3 Concrete layer 6 Steel rod 30 Sheath tube 35 Resin coating

Claims (2)

  In a deformed precast concrete slab with a surface decorative material on the surface and the center of gravity located outside the plate, a linear steel material such as a steel bar or steel strand wire is placed on the outside of the plate that is eccentric to the surface side of the center of gravity. After the concrete layer is hardened or dried, it is stretched along the surface direction and applied to both ends of the linear steel material to fix the both ends to the precast concrete plate, thereby restoring its shrinkage. A method for suppressing warp deformation of a precast concrete plate, wherein the warp deformation in which the surface of the precast concrete plate is convex is corrected by force. A deformed precast concrete slab with a surface decorative material on the surface and a center of gravity located outside the plate, and in a deformed precast concrete slab. 2. A method for suppressing warpage deformation of a precast concrete plate according to claim 1, wherein a linear steel material such as a steel bar or a steel stranded wire is disposed along the surface direction and supported on the back surface of the plate by a bearing.

Images