JP2019173473A - Manufacturing method for precast member - Google Patents

Abstract

To provide a precast member which can stably obtain compactness of the upper layer part during use.SOLUTION: A manufacturing method for a precast member 1 in which the precast member 1 has a an ordinary layer 11 made of ordinary concrete, and a dense layer 13 made of a denser material than ordinary concrete, comprises: a dense layer forming step of forming the dense layer 13 in a vertically inverted posture with respect to when provisioned for use; and an ordinary layer forming step of forming the ordinary layer 11 by placing and hardening ordinary concrete so as to cover the dense layer 13, formed in the dense layer forming step, from above. Thus, the precast member 1 is formed in a vertically inverted posture with respect to when provisioned for use.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a precast member.

  As a conventional precast member, Patent Document 1 discloses a precast concrete floor slab for a road bridge. In patent document 1, the precast concrete floor slab formed in the road width is arranged in the bridge axis direction, and is installed on the girder. These precast concrete slabs are prestressed by a post-tension method and integrated to form a road slab.

Japanese Patent Publication No.7-113203

  For this type of slab, chloride ions and water are degradation factors. And the above deterioration factors penetrate | infiltrate from the upper surface mainly of the floor slab at the time of service, and penetrate | invade into a floor slab. In addition, wear and the like are likely to occur particularly in the upper layer portion of the floor slab due to the traffic load. Therefore, it is desired to make the upper layer part of the floor slab as dense as possible from the viewpoint of suppressing the penetration of deterioration factors, wear, and the like. This type of precast member is not limited to a road slab, and in particular, the denseness of the upper layer portion may be required during service. However, since this type of precast member is mainly manufactured by flat-casting concrete on a mold, its finished surface corresponds to the upper layer portion of the member. And the quality of the said upper layer part tends to be influenced by factors, such as bleeding at the time of manufacture, latency, and a dry crack. Therefore, the quality of the upper layer portion of the precast member tends to be difficult to ensure stably.

  In view of such problems, an object of the present invention is to provide a precast member that can stably obtain the denseness of the upper layer portion during service.

  In the method for producing a precast member of the present invention, the precast member has a normal layer made of a predetermined concrete material and a dense layer made of a material denser than the concrete material, and a posture in which the precast member is turned upside down with respect to service. A dense layer forming step for forming a dense layer, and a normal layer forming step for forming a normal layer by placing and curing a concrete material so as to cover the dense layer formed in the dense layer forming step from above. The precast member is formed in an upside down posture with respect to the service.

  According to this manufacturing method, the precast member in the in-service posture has a structure in which a dense layer made of a material denser than the ordinary layer is present on the ordinary layer. Therefore, a relatively high density can be obtained in the upper layer portion of the precast member during service due to the presence of the dense layer. At the time of manufacture, the precast member is formed in an upside down posture with respect to the service, so that the upper layer part at the time of service is not a finished surface of concrete placement. Therefore, the denseness of the upper layer part at the time of service of a precast member is ensured stably.

  In the dense layer forming process, a dense layer member prepared in advance is placed in a concrete mold in an upside down orientation with respect to in-service, to form a dense layer. In the normal layer forming process, concrete material is placed in the concrete mold. It may be cast and cured.

  In the dense layer forming step, the dense layer member prepared in advance is used as a dense layer, and in the normal layer forming step, the concrete material is contained in a concrete formwork that includes the dense layer member in an upside down orientation as in use as an embedded formwork. May be placed and cured.

  In addition, the material of the dense layer has higher compressive strength, higher cracking strength, higher tensile strength, higher Young's modulus, lower water permeability, lower chloride ion diffusion coefficient than ordinary layer concrete material. It may have at least one characteristic of low, high freeze-thaw resistance, or low wear coefficient.

  Further, the material of the dense layer may be a material containing ultra high strength fiber reinforced concrete or high strength fiber reinforced mortar.

  Further, the method for producing a precast member of the present invention further includes an adhesive application step of applying an adhesive to a surface of the dense layer that becomes a boundary with the normal layer between the dense layer formation step and the normal layer formation step. You may prepare. According to this configuration, the adhesion between the dense layer and the normal layer is improved by the presence of the adhesive.

  Moreover, the manufacturing method of the precast member of this invention may further comprise the reinforcing bar arrangement | positioning process which arrange | positions the reinforcing bar embed | buried in a normal layer between a dense layer formation process and a normal layer formation process. According to this configuration, the reinforcing bars are embedded in the normal layer.

  Further, the precast member may have a U-shaped cross-sectional shape, and in the dense layer forming step, the dense layer may be formed in a U shape along the inner edge of the U shape.

  The precast member may be a member including a floor slab of a road bridge. In road bridge slabs, ingress of deterioration factors from the upper layer due to rainwater and fatigue due to repeated traffic loads are a concern, and it is highly necessary to make the upper layer dense. Such a configuration can be applied particularly preferably.

  According to the present invention, an object is to provide a precast member that can stably obtain the denseness of the upper layer portion during service.

It is a disassembled perspective view of the road bridge to which the precast member concerning an embodiment is applied. It is sectional drawing of the precast member of FIG. (A), (b) is sectional drawing which shows the manufacturing method of the precast member which concerns on 1st Embodiment in order. (A), (b) is sectional drawing which shows the manufacturing method of a precast member in order following FIG. (A), (b) is sectional drawing which shows the manufacturing method of a precast member in order following FIG. (A)-(c) is sectional drawing which shows the manufacturing method of the precast member which concerns on 2nd Embodiment in order. (A)-(c) is sectional drawing which shows a part of manufacturing method of the precast member which concerns on 3rd Embodiment in order. (A)-(c) is sectional drawing which shows a part of manufacturing method of the precast member which concerns on a modification, respectively. It is a perspective view of the water channel where the precast member concerning a modification is applied.

  Hereinafter, embodiments of a method for producing a precast member according to the present invention will be described in detail with reference to the drawings. In each drawing, the features of the parts related to the description may be exaggerated as appropriate, and the dimensional ratios of the components do not necessarily match the actual objects, and do not necessarily match between the drawings. FIG. 1 is an exploded perspective view of a road bridge 100 to which the precast member 1 according to the present embodiment is applied, and FIG. 2 is a cross-sectional view of the precast member 1.

(First embodiment)
As FIG. 1 shows, the precast member 1 which concerns on this embodiment consists of concrete materials, and is used for a road bridge. The precast member 1 may be used at the time of construction of a road bridge, or may be used for replacement of a floor slab of an existing road bridge. A road bridge 100 shown in FIG. 1 includes a plurality of steel girders 102 extending in the bridge axis direction. A plurality of precast members 1 are installed on the steel girder 102, the precast members 1 are arranged in the direction of the bridge axis, and are connected by, for example, prestressing to construct a road structure.

  As shown in FIG. 2, the precast member 1 is formed by integrally forming a floor slab portion 3 constituting a road floor slab and a balustrade portion 5 constituting a rail. That is, the precast member 1 has a flat floor slab portion 3 that has a rectangular shape that is long in the direction perpendicular to the bridge axis in a plan view, and a rail section 5 that rises upward from both ends of the floor slab portion 3 in the direction perpendicular to the bridge axis. However, it has a U-shaped cross section when viewed from the bridge axis direction. In addition, a haunch portion 4 is provided at the joint between the floor slab portion 3 and the balustrade portion 5. The road of the road bridge 100 is formed by providing a road pavement layer or the like on the upper surface of the floor slab portion 3.

  For the floor slab of the road bridge 100, chloride ions and water are degradation factors. And the above deterioration factors penetrate | infiltrate from the upper surface mainly of the floor slab at the time of service, and penetrate | invade into a floor slab. In addition, the floor slab tends to deteriorate due to repeated traffic loads. Therefore, it is desired to make the upper layer part (particularly, the cover part) of the floor slab as dense as possible from the viewpoint of suppressing deterioration factors and reinforcing fatigue.

  Therefore, as shown in FIG. 2, in the precast member 1, the upper layer portion of the floor slab portion 3 is formed as a dense layer 13 that is denser than other portions. Specifically, the floor slab portion 3 is mainly composed of two layers. The floor slab portion 3 is composed of an ordinary layer 11 made of ordinary concrete and an upper surface of the ordinary layer 11 made of a material denser than ordinary concrete. And a dense layer 13 for covering. The normal layer 11 and the dense layer 13 extend integrally not only to the floor slab portion 3 but also to the high rail portion 5. In the high rail portion 5, the normal layer 11 exists outside, and the dense layer 13 is the normal layer 11. It covers the inside surface.

  The dense layer 13 includes an upper layer portion of the floor slab portion 3 and inner portions of the left and right handrail portions 5 that are integrally connected. The cross section of the dense layer 13 has a slightly smaller U shape along the inner edge of the U-shaped cross section of the precast member 1, and the upper surface of the floor slab portion 3 of the precast member 1 and the inner surface of the rail section 5 Located so as to be exposed. The dense layer 13 also includes the haunch portion 4. An adhesive layer made of an adhesive 15 is provided on the boundary surface between the normal layer 11 and the dense layer 13, but this adhesive layer may be omitted. Moreover, although the reinforcing bar 17 is embed | buried under the normal layer 11, this reinforcing bar 17 may be abbreviate | omitted. Further, reinforcing bars may be embedded in the dense layer 13.

  Here, the above "dense" means high compressive strength, high cracking strength, high tensile strength, high Young's modulus, low water permeability, low chloride ion diffusion coefficient, freeze-thaw resistance Having at least one characteristic of high or low wear coefficient. That is, the material of the dense layer 13 is higher in compressive strength, higher in cracking strength, higher in tensile strength, higher in Young's modulus, lower in water permeability, lower in chloride than the material in the normal layer 11 (ordinary concrete). It has at least one characteristic of a low product ion diffusion coefficient, a high freeze-thaw resistance, or a low wear coefficient.

  The “compressive strength” is a value measured by a test method defined in JIS A 1108 “Test method for compressive strength of concrete”. The “cracking strength” is, for example, a value measured by a test method defined in JIS A 1113 “Testing method for split tensile strength of concrete”. “Tensile strength” is, for example, a value calculated from a tensile softening curve obtained by inverse analysis of a value measured by a test method specified in JSCE-G552 “Bending strength and bending toughness test method of steel fiber reinforced concrete”. is there. The “Young's modulus” is a value measured by a test method defined in JISA 1149 “Testing Method for Static Elastic Modulus of Concrete”. The “water permeability coefficient” is, for example, a value converted from a gas permeability coefficient calculated from a test method defined in RILM TC116-PCD “Permeability, of concrete as acriterion of its durability”. “Chloride ion diffusion coefficient” is a value measured by the test method specified in JSCE-G572 “Apparent diffusion coefficient test method for chloride ions in concrete by immersion (draft). The “ability” is a value (durability index) measured by a test method defined in JISA 1148 (Method A) “Freeze-Thaw Test Method for Concrete”. “Abrasion coefficient” is a value measured by a test method stipulated in the O-type (Okuda-type) abrasion test devised by the Central Research Institute of Electric Power.

  In the present embodiment, in view of the characteristics desired for the upper layer portion of the floor slab portion 3 of the road bridge, the material of the dense layer 13 is at least higher in compressive strength than the material of the ordinary layer 11 (ordinary concrete). A material having a small water permeability coefficient and a small chloride ion diffusion coefficient is employed. As the material of the dense layer 13 having such characteristics, for example, ultra high strength fiber reinforced concrete (UFC) or high strength fiber reinforced mortar is preferably employed.

  An example of the properties of ultra-high strength fiber reinforced concrete that can be employed as the material of the dense layer 13 will be described below. This ultra-high-strength fiber reinforced concrete is obtained, for example, by curing a mixture containing cement, aggregate, kneading water, concrete chemical admixture, and reinforcing fibers. The cement is, for example, ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, or low heat Portland cement.

As an example, the above-mentioned aggregate has a particle size of 2.5 mm or less, an absolute dry density of 2.5 g / cm ³ or more, a water absorption of 3.0% or less, a clay lump amount of 1.0% or less, and a fine particle amount of 2.0%. Hereinafter, the aggregate has an NaCl content of 0.02% or less. This aggregate is one in which the organic impurity test result of the fine aggregate organic impurity test method specified in JISA 1105 is “light”. Further, this aggregate has a stability of 10% or less according to the stability test method of the aggregate with sodium sulfate defined in JIS A 1122, and further has an alkali silica reactivity defined in Appendix 1 of JIS A 5308. It is an aggregate whose division by is division A.

The aforementioned mixing water is, for example, mixing water other than the recovered water defined in JSCE-B 101-2005. The aforementioned chemical admixture for concrete is a high-performance water reducing agent defined in JISA 6204. The reinforcing fiber is a fiber having a diameter of 0.1 to 0.25 mm, a length of 10 to 24 mm, and a tensile strength of 2 × 10 ³ N / mm ² or more. The reinforcing fibers described above may be, for example, steel fibers, high-strength aramid fibers, high-density polyethylene fibers, or carbon fibers.

The ultra-high-strength fiber reinforced concrete forming the dense layer 13 is, for example, a binder whose matrix is made of Portland cement, pozzolanic material, and ethrin guide generating material, aggregate having a particle size of 2.5 mm or less, water, and water reduction It is composed of an agent. The reinforcing fiber has a diameter of 0.2 mm, a length of 15 mm (manufacturing error less than ± 2 mm), a steel fiber having a tensile strength of 2 × 10 ³ N / mm ² or more, a diameter of 0.2 mm, and a length of 22 mm (manufacturing). Error of less than ± 2 mm), and a mixture of steel fibers having a tensile strength of 2 × 10 ³ N / mm ² or more is 1.75 vol. % May be mixed. Moreover, the characteristic values after curing of the ultra high strength fiber reinforced concrete are as follows: compressive strength 150 N / mm ² or more, crack generation strength 4 N / mm ² or more, tensile strength 5 N / mm ² or more, water permeability 1 × 10 ⁻¹¹ cm / Preferably, it is less than s, chloride ion diffusion coefficient is less than 0.14 cm ² / year, and wear coefficient is less than 240 mm ³ / cm ² .

The standard composition of ultra high strength fiber reinforced concrete forming the dense layer 13 has a flow value of 250 ± 20 mm, a ratio of the mixing water to the binder of 15%, an air amount of 2.0%, and a mixing water of 195 kg / m. ^3, binder 1287kg / ^{m 3,} it is possible to aggregate 905 kg / ^{m 3,} superplasticizer 32.2kg / ^{m 3,} and the reinforcing fibers ^{137.4kg / m 3 (1.75vol.%} ).

  An example of the properties of the high-strength fiber reinforced mortar that can be employed as the material of the dense layer 13 will be described below. This high-strength fiber reinforced mortar is formed by curing a mixture containing cement, aggregate, kneading water, a chemical admixture for concrete, and reinforcing fibers, for example. The cement is, for example, ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, or low heat Portland cement.

As an example, the above-mentioned aggregate has a particle size of 2.5 mm or less, an absolute dry density of 2.5 g / cm ³ or more, a water absorption of 3.0% or less, a clay lump amount of 1.0% or less, and a fine particle amount of 2.0%. Hereinafter, the aggregate has an NaCl content of 0.02% or less. This aggregate is one in which the organic impurity test result of the fine aggregate organic impurity test method specified in JISA 1105 is “light”. Further, this aggregate has a stability of 10% or less according to the stability test method of the aggregate with sodium sulfate defined in JIS A 1122, and further has an alkali silica reactivity defined in Appendix 1 of JIS A 5308. It is an aggregate whose division by is division A.

The aforementioned mixing water is, for example, mixing water other than the recovered water defined in JSCE-B 101-2005. The aforementioned chemical admixture for concrete is a high-performance water reducing agent defined in JISA 6204. The reinforcing fiber is a fiber having a diameter of 0.1 to 0.25 mm, a length of 10 to 30 mm, and a tensile strength of 400 N / mm ² or more. The reinforcing fibers described above may be, for example, steel fibers, high-strength aramid fibers, high-density polyethylene fibers, polypropylene fibers, vinylon fibers, or carbon fibers.

The high-strength fiber reinforced mortar forming the dense layer 13 is, for example, a binder whose matrix is made of Portland cement, pozzolanic material, and ethrin guide generating material, aggregate having a particle size of 2.5 mm or less, water, and water reducing agent. It is constituted by. Further, the reinforcing fiber is a polypropylene fiber having a diameter of 0.5 mm, a length of 20 mm (a manufacturing error of less than ± 2 mm), and a tensile strength of 400 N / mm ² or more. % May be mixed. The characteristic values after curing of the high-strength fiber reinforced mortar are as follows: compressive strength of 100 N / mm ² or more, crack generation strength of 4 N / mm ² or more, tensile strength of 5 N / mm ² or more, and water permeability of 1 × 10 ⁻¹¹ cm / s. Is less than 0.14 cm ² / year, and the wear coefficient is less than 240 mm ³ / cm ² .

The standard composition of the high-strength fiber reinforced mortar forming the dense layer 13 has a flow value of 220 ± 20 mm, a ratio of the mixing water to the binder of 18%, an air amount of 3.0%, and a mixing water of 200 kg / m ^3. , binder 1111kg / ^{m 3,} it is possible to aggregate 1075kg / ^{m 3,} superplasticizer 22.8 kg / ^{m 3,} and the reinforcing fibers ^{18.2kg / m 3 (2.0vol.%} ).

  An example of the properties of “ordinary concrete” that can be employed as the material for the ordinary layer 11 will be described below. For example, this ordinary concrete is obtained by curing a mixture containing cement, aggregate, mixing water, and a chemical admixture for concrete. The cement is, for example, ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, fly ash cement, blast furnace cement, or low heat Portland cement. About the characteristic value after hardening of this ordinary concrete, the value of the compressive strength is small and the value of the hydraulic conductivity is smaller than each characteristic value of the ultra high strength fiber reinforced concrete and the high strength fiber reinforced mortar as described above. Large and the value of chloride ion diffusion coefficient is large. General ordinary concrete corresponds to the nominal strength of 18 to 60 in JISA 5308 “Ready mixed concrete”, and the ratio of the mixing water to the binder is 65% to 30%.

  The ultra-high-strength fiber reinforced concrete and the high-strength fiber reinforced mortar as described above have a high compressive strength, a small water permeability coefficient, and a small chloride ion diffusion coefficient compared to the above-described ordinary concrete. In addition to the above properties, the material has such properties as high cracking strength, high tensile strength, high Young's modulus, high freeze-thaw resistance, and low wear coefficient.

  Then, the manufacturing method of the above precast members 1 is demonstrated.

  Here, in the posture of the precast member 1 when the road bridge 100 is in service, as shown in FIGS. 1 and 2, the rail section 5 extends upward from both ends of the floor slab part 3, and the floor slab part 3 Are in a positional relationship such that the dense layer 13 is positioned on the normal layer 11. On the other hand, in the manufacturing method of the precast member 1, the precast member 1 is formed with the attitude | position reversed up and down with respect to the attitude | position at the time of the above use. In the following description, the posture of the precast member 1 in service is referred to as “service posture”, and the posture inverted up and down with respect to the service posture is referred to as “reverse posture”. The manufacturing method of the precast member 1 according to the present embodiment includes a dense layer forming step, an adhesive applying step, a reinforcing bar arranging step, and a normal layer forming step, which will be described below.

(Dense layer forming process)
As shown in FIG. 3A, a mold 25 having a shape corresponding to the precast member 1 is prepared. The lumen portion of the mold 25 has a shape corresponding to the precast member 1 in an inverted posture. That is, from both ends of the flat plate-shaped lumen corresponding to the floor slab portion 3, the lumen corresponding to the rail portion 5 extends downward.

  Separately, a member 23 prepared in advance (hereinafter referred to as “dense layer member 23”) is prepared as a component constituting the dense layer 13. The dense layer member 23 is a precast member made of ultra high strength fiber reinforced concrete or high strength fiber reinforced mortar, and is molded in the same shape as the dense layer 13. That is, the dense layer member 23 includes a flat plate portion 23 a corresponding to the upper layer portion of the floor slab portion 3, and side wall portions 23 b erected at both ends of the flat plate portion 23 a and corresponding to the inner portions of the left and right rail sections 5. The dense layer member 23 has a small U-shaped cross section along the inner edge of the U-shaped cross section of the entire precast member 1. Reinforcing bars may be embedded in the dense layer member 23, or there may be no embedded reinforcing bars.

  As shown in FIG. 3B, the dense layer member 23 is installed in a portion corresponding to the dense layer 13 in the lumen of the mold 25 in an inverted posture. The dense layer member 23 has an inverted U-shaped posture, and the inner surface of the U-shape contacts the wall surface of the corresponding mold 25. By providing the dense layer member 23 as described above, the dense layer 13 is first formed in the mold 25. The dense layer member 23 is not necessarily integral, and the dense layer 13 may be formed by appropriately laying parts of the dense layer member 23 divided into a plurality of parts in the mold 25.

(Adhesive application process)
Next, as shown in FIG. 4A, an adhesive 15 is applied to the dense layer 13 formed as described above. The surface to which the adhesive 15 is applied is a surface that becomes a boundary with the normal layer 11 in the dense layer 13, and specifically, the upper surface of the flat plate portion 23a of the dense layer member 23 and the both side wall portions 23b. Adhesive 15 is applied to the outer surface. As the adhesive 15, for example, a dedicated adhesive based on an epoxy adhesive is used. As the above-mentioned epoxy adhesive, for example, a fresh concrete joining adhesive “KS Bond Series” (manufactured by KRL Co., Ltd.) or the like is used.

(Rebar placement process)
Next, as shown in FIG. 4B, the reinforcing bar 17 is disposed on the dense layer 13. The reinforcing bar 17 is disposed in the lumen of the mold 25 excluding the dense layer 13 and is embedded in the normal layer 11 after the precast member 1 is completed.

(Normal layer forming process)
Next, as shown in FIG. 5A, ordinary concrete 19 is placed in the inner cavity of the mold 25 excluding the dense layer 13. Here, the ordinary concrete 19 is placed so as to cover the dense layer 13 formed in the dense layer forming step from above. In addition, the joining of concrete may generate | occur | produce between the part corresponding to the railing part 5, and the part corresponding to the floor slab part 3. FIG. Thereafter, the ordinary layer 11 is formed by curing the ordinary concrete 19. Thereafter, as shown in FIG. 5B, the mold 25 is removed from the mold, whereby the precast member 1 in the inverted posture is completed.

  The completed precast member 1 is transported to the construction site of the road bridge 100 and installed on the steel girder 102 in a service posture as shown in FIG.

  The effect by the manufacturing method of the above precast members 1 is demonstrated. According to the above manufacturing method, the precast member 1 in the in-service posture has a configuration in which the dense layer 13 made of a material denser than the ordinary layer 11 is present on the ordinary layer 11. Therefore, a relatively high density can be obtained in the upper layer part (particularly, the cover part) of the precast member 1 in service due to the presence of the dense layer 13. As a result, the upper layer portion of the road floor slab in which the dense layer 13 of the precast member 1 is present has a relatively high compressive strength, so that fatigue deterioration of the road floor slab due to repeated traffic loads can be suppressed. In addition, the upper part of the road slab has a relatively low permeability coefficient and a relatively low chloride ion diffusion coefficient, so that deterioration factors such as rainwater and chloride ions from the upper side of the road slab are inside the road slab. Intrusion into the road is suppressed and deterioration of the road deck is suppressed. As a result, the service life of the road deck is improved and the life cycle cost is reduced.

  Moreover, since the precast member 1 is formed in an inverted posture at the time of manufacture, the upper layer portion of the precast member 1 at the time of service is not a finished surface of concrete placement. Therefore, the denseness of the upper layer part at the time of service of the precast member 1 is ensured stably. Further, if the precast member 1 is formed in an in-service posture, it is necessary to fill the space below the dense layer member 23 with ordinary concrete in the ordinary layer forming step. In this case, air bubbles tend to accumulate on the lower surface of the dense layer member 23 when filling with the ordinary concrete, so that the adhesion between the dense layer 13 and the ordinary layer 11 may be reduced upon completion. On the other hand, according to the method in which ordinary concrete is placed on the dense layer member 23 and the precast member 1 is formed in an inverted posture, the above problem is avoided.

  As another manufacturing method, a manufacturing method in which the dense cast member 23 is bonded to the upper surface of the previously formed normal layer 11 to form the precast member 1 in an in-service posture is also conceivable. However, in this manufacturing method, since the hardened concrete members are bonded together, the integrity of the normal layer 11 and the dense layer 13 may not be sufficient. On the other hand, in the manufacturing method of the above-described embodiment, since the ordinary concrete is placed on the already hardened dense layer 13, sufficient integrity is ensured.

  In general, when a road floor slab is constructed of cast-in-place concrete, a floor slab portion is first formed, and then a railing is formed on the upper surfaces of both ends of the floor slab portion. In this case, the upper surface of the floor slab portion may not have sufficient quality due to the effects of dry cracks, bleeding water, and the latency layer. Therefore, when the handrail part is joined to the upper surface, the joint line between the floor slab part and the handrail part tends to become water. If it does so, deterioration factors, such as rainwater and a chloride ion, will invade from the upper surface of a floor slab part via the above-mentioned water path, and will tend to deteriorate the boundary part of a floor slab part and a railing part. On the other hand, in the precast member 1, the dense layer 13 is formed so as to seamlessly cover the upper surface of the floor slab portion 3 and the inner side surface of the balustrade portion 5 so as to be integrally connected. Therefore, the above-mentioned problem is avoided by closing the boundary between the floor slab portion 3 and the railing portion 5 with the dense layer 13.

  Further, since the adhesive 15 is present at the boundary surface between the dense layer 13 and the ordinary layer 11 by the adhesive application process, the adhesion between the dense layer 13 and the ordinary layer 11 is improved. Therefore, the possibility that the integrity of the normal layer 11 and the dense layer 13 is reduced due to repeated fatigue of the traffic load is reduced.

(Second Embodiment)
Then, 2nd Embodiment of the manufacturing method of the precast member 1 is described, referring FIG. The concrete mold 45 used in the manufacturing method of the present embodiment is different from the mold 25 of the first embodiment in that the dense layer member 23 is included as an embedded mold. In the following, differences from the first embodiment in the manufacturing method of the present embodiment will be mainly described, and other configurations are the same as those in the first embodiment, and therefore the same or equivalent components are denoted by the same reference numerals. Therefore, duplicate explanations are omitted.

(Dense layer forming process)
As shown in FIG. 6A, in the dense layer forming step of the present embodiment, the dense layer 13 is formed by preparing the dense layer member 23 in an inverted posture. Next, the formwork plate 27 for the rail section 5 is attached to both ends of the dense layer member 23 in the prepared reverse orientation. Further, the wife-side formwork plate 28 is attached, and the concrete formwork 45 including the dense layer member 23 in the inverted posture is assembled. In this case, the dense layer member 23 forms a part of the concrete mold 45 and functions as an embedded mold, and finally remains as the dense layer 13 that is a part of the precast member 1. Although omitted in the example of FIG. 6, thereafter, the adhesive 15 is applied to the dense layer member 23 (adhesive application step) and the reinforcing bar 17 is arranged (rebar arranging step) as in the first embodiment. Also good.

(Normal layer forming process)
In the subsequent ordinary layer forming step, as shown in FIG. 6B, ordinary concrete 19 is placed in the concrete mold 45 and hardened to form the ordinary layer 11. Thereafter, as shown in FIG. 6C, the mold plate 27 and the mold plate 28 are removed, whereby the precast member 1 in an inverted posture is completed.

(Third embodiment)
Then, 3rd Embodiment of the manufacturing method of the precast member 1 is described, referring FIG. In the manufacturing method of this embodiment, the formation method of the dense layer 13 is different from that of the first embodiment. In the following, differences from the first embodiment in the manufacturing method of the present embodiment will be mainly described, and other configurations are the same as those in the first embodiment, and therefore the same or equivalent components are denoted by the same reference numerals. Therefore, a duplicate description is omitted.

(Dense layer forming process)
As shown in FIG. 7A, in the dense layer forming process of the present embodiment, a dense layer mold 29 is assembled in the lumen of the mold 25. Then, as shown in FIG. 7B, ultra high strength fiber reinforced concrete or high strength fiber reinforced mortar is placed in the mold 29 for the dense layer. At this time, the reinforcing bars embedded in the dense layer 13 may be disposed in the mold 29 in advance prior to the placement. The cast ultra-high-strength fiber reinforced concrete or high-strength fiber reinforced mortar forms the dense layer 13 in the mold 29. After the ultra high strength fiber reinforced concrete or the high strength fiber reinforced mortar is cured, the mold 29 is removed and the dense layer 13 is completed as shown in FIG. Thereafter, an adhesive application step and a reinforcing bar arrangement step are performed as necessary, and a normal layer forming step is further performed, whereby the precast member 1 in an inverted posture is completed.

  The present invention can be implemented in various forms including various modifications and improvements based on the knowledge of those skilled in the art including the above-described embodiments. Moreover, it is also possible to configure a modified example using the technical matters described in the above-described embodiment. You may use combining suitably the structure of each embodiment and a modification.

  For example, the adhesive application step and the reinforcing bar placement step in each embodiment are not essential steps and may be executed as necessary. Moreover, although embodiment demonstrated the case where the material of the dense layer 13 was ultra high strength fiber reinforced concrete or high strength fiber reinforced mortar, it is not limited to this. That is, as the material of the dense layer 13, another material denser than the normal layer 11 may be selected as appropriate.

  Although each embodiment described the example which manufactures the U-shaped cross-section precast member 1, this invention is applicable also to the manufacturing method of the flat-shaped precast member 51, as FIG. 8 (a) shows. . In the example of FIG. 8A, first, a dense layer 13 made of ultra-high-strength fiber reinforced concrete or high-strength fiber reinforced mortar is formed in the lower layer of the mold 25, and ordinary concrete is covered so as to cover the dense layer 13 from above. The normal layer 11 is formed by casting, and the precast member 51 is formed in an inverted posture. Further, as shown in FIG. 8B, the present invention can also be applied to a method of manufacturing a precast member 53 having an L-shaped cross section. In the example of FIG. 8B, first, a dense layer 13 made of ultrahigh strength fiber reinforced concrete or high strength fiber reinforced mortar is formed in a portion corresponding to the inside of the inverted L-shape in the mold 25, and the dense layer 13 Ordinary concrete is cast so as to cover from above, the ordinary layer 11 is formed, and the precast member 53 is formed in an inverted posture. As shown in FIG. 8 (c), a road bridge component comprising a floor slab portion 3 and a balustrade portion 5 by appropriately combining the above-described plate-like precast member 51 and L-shaped precast member 53. May be configured.

  Moreover, although each embodiment demonstrated the example which manufactures the precast member 1 used for a road bridge, as shown in FIG. 9, this invention is the precast for waterways for constructing the waterway 60 of a U-shaped cross section. The method for manufacturing the member 57 can also be applied. Of this type of water channel 60, the inner wall portion that contacts the water W is less likely to penetrate the water W, wear caused by the water flow and wear caused by the gravel carried along with the water W are reduced. It is required as a characteristic to secure a predetermined water flow for a long time by securing the roughness coefficient of the water for a long time. Therefore, the dense layer 13 is provided so as to cover the upper layer portion and the inner wall portion side of the precast member 57. As the material of the dense layer 13, a material having a smaller water permeability coefficient and a smaller wear coefficient than that of ordinary concrete that is the material of the ordinary layer 11 is employed. As the material for the dense layer 13 having the above-described characteristics, it is preferable to employ ultrahigh strength fiber reinforced concrete or high strength fiber reinforced mortar. Such a precast member 57 for a water channel is also manufactured by the same manufacturing method as in the above-described embodiment.

  Further, in the precast member 1 of the embodiment, the material of the dense layer 13 is (1) higher compressive strength and (2) higher cracking strength and (3) tensile than the material of the ordinary layer 11. High strength, (4) high Young's modulus, (5) low water permeability, (5) low chloride ion diffusion coefficient, (6) high freeze-thaw resistance, and (7) wear Although it has the characteristic that a coefficient is small, the relationship of the characteristic of the material of the dense layer 13 and the material of the normal layer 11 is not limited to said relationship. That is, it is not essential that the material of the dense layer 13 has all of the above characteristics (1) to (7) as compared to the material of the ordinary layer 11, and among the above characteristics (1) to (7) It is sufficient that the relationship has at least one characteristic.

  DESCRIPTION OF SYMBOLS 1,51,53,57 ... Precast member, 11 ... Normal layer, 13 ... Dense layer, 15 ... Adhesive, 17 ... Reinforcing bar, 23 ... Dense layer member, 100 ... Road bridge.

Claims (9)

A method of manufacturing a precast member,
The precast member has a normal layer made of a predetermined concrete material and a dense layer made of a material denser than the concrete material,
A dense layer forming step of forming the dense layer in an upside down orientation with respect to service;
A normal layer forming step of forming the normal layer by placing and curing the concrete material so as to cover the dense layer formed in the dense layer forming step from above,
The manufacturing method of the precast member by which the said precast member is formed with the attitude | position inverted upside down with respect to the said service time. In the dense layer forming step, the dense layer member prepared in advance is installed in the concrete formwork in an upside down posture with respect to the in-service state to form the dense layer,
The method for producing a precast member according to claim 1, wherein in the normal layer forming step, the concrete material is placed and cured in the concrete formwork. In the dense layer forming step, a dense layer member prepared in advance is used as the dense layer,
2. The production of a precast member according to claim 1, wherein, in the normal layer forming step, the concrete material is placed and cured in a concrete mold that includes the dense layer member in an upside down orientation as an embedded mold in service. Method. The material of the dense layer is compared with the concrete material of the normal layer,
High compression strength, high cracking strength, high tensile strength, high Young's modulus, low water permeability, low chloride ion diffusion coefficient, high freeze-thaw resistance, or low wear coefficient The manufacturing method of the precast member of any one of Claims 1-3 which has at least 1 characteristic of these.   The method for producing a precast member according to any one of claims 1 to 4, wherein the material of the dense layer is a material containing ultra high strength fiber reinforced concrete or high strength fiber reinforced mortar.   The adhesive application process of apply | coating an adhesive agent to the surface used as the boundary with the said normal layer among the said dense layers between the said dense layer formation process and the said normal layer formation process is further provided. The manufacturing method of the precast member of any one of Claims 1.   The precast member according to any one of claims 1 to 6, further comprising a reinforcing bar arrangement step of arranging a reinforcing bar embedded in the normal layer between the dense layer forming step and the normal layer forming step. Production method. The precast member has a U-shaped cross-sectional shape,
The method for producing a precast member according to claim 1, wherein in the dense layer forming step, the dense layer is formed in a U shape along an inner edge of the U shape.   The said precast member is a member containing the floor slab of a road bridge, The manufacturing method of the precast member of any one of Claims 1-8.

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