JP6987010B2 - Manufacturing method of precast members - Google Patents

Description

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

As a conventional precast member, Patent Document 1 discloses a precast concrete deck of a road bridge. In Patent Document 1, precast concrete decks formed in the width of the road are arranged in the direction of the bridge axis and installed on the girder. Then, prestress by the post-tension method is applied to these precast concrete decks and integrated to construct a road deck.

Tokuhei 7-13203 Gazette

Chloride ions and water are deteriorating factors for this type of deck. Then, the deterioration factors as described above permeate mainly from the upper surface of the deck during operation and invade into the deck. In addition, due to the traffic load, the upper layer of the floor slab is particularly prone to wear. Therefore, from the viewpoint of suppressing the intrusion and wear of deterioration factors, it is desired to make the upper layer of the deck as dense as possible. Not limited to road decks, this type of precast member may be required to be particularly dense in the upper layer during operation. However, since this type of precast member is mainly manufactured by flattening concrete on a formwork, its finished surface corresponds to the upper layer portion of the member. The quality of the upper layer is likely to be affected by factors such as bleeding, latency, and dry cracking during manufacturing. Therefore, it tends to be difficult to stably secure the quality of the upper layer of the precast member.

In view of such problems, it is an object of the present invention to provide a precast member capable of stably obtaining the denseness of the upper layer portion at the time of operation.

In the method for manufacturing 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 more dense than the concrete material, and the precast member has an upside down posture with respect to the time of operation. It is provided with a dense layer forming step of forming a dense layer and a normal layer forming step of placing and hardening 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 time of operation.

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 exists on the ordinary layer. Therefore, relatively high density can be obtained in the upper layer of the precast member during operation 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 time of operation, so that the upper layer portion at the time of operation is not the finished surface for concrete placement. Therefore, the denseness of the upper layer portion during operation of the precast member is stably ensured.

Further, 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 time of operation to form a dense layer, and in the normal layer forming step, the concrete material is placed in the concrete formwork. It may be cast and cured.

Further, in the dense layer forming step, the dense layer member prepared in advance is used as a dense layer, and in the ordinary layer forming step, the concrete material is contained in the concrete formwork including the dense layer member having an upside down posture with respect to the in-service formwork. May be placed and cured.

In addition, the material of the dense layer has higher compressive strength, higher crack generation strength, higher tensile strength, higher Young's modulus, smaller water permeability coefficient, and chloride ion diffusion coefficient than the concrete material of the ordinary layer. It may have at least one of the following properties: small, high freeze-thaw resistance, or low wear factor.

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, in the method for manufacturing a precast member of the present invention, an adhesive application step of applying an adhesive to a surface of the dense layer which is a boundary between the dense layer and the ordinary layer is further performed between the dense layer forming step and the ordinary layer forming step. You may prepare. According to this configuration, the presence of the adhesive improves the adhesion between the dense layer and the ordinary layer.

Further, the method for manufacturing a precast member of the present invention may further include a reinforcing bar arranging step for arranging reinforcing bars embedded in the ordinary layer between the dense layer forming step and the ordinary layer forming step. According to this configuration, reinforcing bars are embedded in the ordinary layer.

Further, the precast member has 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.

Further, the precast member may be a member including a deck of a road bridge. In the floor slabs of road bridges, intrusion of deterioration factors from the upper layer due to rainwater and fatigue due to repeated traffic loads are concerns, and it is highly necessary to make the upper layer dense, as described above. Configuration may be particularly preferably applied.

According to the present invention, it is an object of the present invention to provide a precast member capable of stably obtaining the denseness of the upper layer portion during operation.

It is an exploded perspective view of the road bridge to which the precast member which concerns on embodiment is applied. It is sectional drawing of the precast member of FIG. (A) and (b) are sectional views which show the manufacturing method of the precast member which concerns on 1st Embodiment in order. (A) and (b) are sectional views which show the manufacturing method of the precast member in order following FIG. (A) and (b) are sectional views which show the manufacturing method of the precast member in order following FIG. (A)-(c) are sectional views which show the manufacturing method of the precast member which concerns on 2nd Embodiment in order. (A)-(c) are sectional views which show a part of the manufacturing method of the precast member which concerns on 3rd Embodiment in order. (A) to (c) are cross-sectional views showing a part of the manufacturing method of the precast member which concerns on the modification. It is a perspective view of the waterway to which the precast member which concerns on a modification is applied.

Hereinafter, embodiments of the method for manufacturing 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 according to the description may be exaggerated as appropriate, and the dimensional ratios of the components do not always match the actual ones, 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 shown in FIG. 1, the precast member 1 according to the present embodiment is made of a concrete material 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 as a replacement for a floor slab of an existing road bridge. The road bridge 100 shown in FIG. 1 includes a plurality of steel girders 102 extending in the direction of the bridge axis. 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, applying prestress 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 deck and a balustrade portion 5 constituting a balustrade. That is, the precast member 1 has a flat plate-shaped floor slab portion 3 that exhibits a long rectangle in the direction perpendicular to the bridge axis in a plan view, and a balustrade portion 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-sectional shape when viewed from the direction of the bridge axis. Further, 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 the pavement layer of the road or the like on the upper surface of the deck portion 3.

Chloride ions and water are deterioration factors for the deck of the road bridge 100. Then, the deterioration factors as described above permeate mainly from the upper surface of the deck during operation and invade into the deck. In addition, the floor slab is prone to fatigue deterioration due to repeated traffic loads. Therefore, from the viewpoint of suppressing the invasion of deterioration factors and reinforcing against fatigue, it is desired to make the upper layer portion (particularly, the cover portion) of the deck as dense as possible.

Therefore, as shown in FIG. 2, in the precast member 1, the upper layer portion of the deck portion 3 is formed as a dense layer 13 which is denser than the other portions. Specifically, the floor slab portion 3 is mainly composed of two layers, and the floor slab portion 3 is composed of an ordinary layer 11 made of ordinary concrete and a material more dense than ordinary concrete, and has an upper surface of the ordinary layer 11. It has a dense layer 13 to cover. The ordinary layer 11 and the dense layer 13 extend integrally not only to the deck portion 3 but also to the balustrade portion 5. In the balustrade portion 5, the ordinary layer 11 exists on the outside, and the dense layer 13 is the ordinary layer 11. It covers the inner surface of the.

The dense layer 13 has an upper layer portion of the floor slab portion 3 integrally connected and an inner portion of the left and right balustrade portions 5. The cross section of the dense layer 13 has a slightly small U-shape along the inner edge of the U-shaped cross section of the precast member 1, and is formed on the upper surface of the deck portion 3 of the precast member 1 and the inner surface of the balustrade portion 5. Positioned to be exposed. The dense layer 13 also includes a haunch portion 4. An adhesive layer with an adhesive 15 is provided on the boundary surface between the ordinary layer 11 and the dense layer 13, but this adhesive layer may be omitted. Further, although the reinforcing bar 17 is embedded in the ordinary layer 11, the reinforcing bar 17 may be omitted. Further, the reinforcing bar may be embedded in the dense layer 13.

Here, the above-mentioned "dense" means high compressive strength, high crack generation strength, high tensile strength, high Young's modulus, small water permeability coefficient, small chloride ion diffusion coefficient, and freeze-thaw resistance. Has a characteristic of at least one of high or low wear factor. That is, the material of the dense layer 13 has higher compressive strength, higher crack generation strength, higher tensile strength, higher Young's modulus, lower water permeability coefficient, and chloride than the material of the ordinary layer 11 (ordinary concrete). It has at least one of the following characteristics: a small ion diffusion coefficient, a high freeze-thaw resistance, or a small wear coefficient.

The “compressive strength” is a value measured by the test method specified in JIS A 1108 “Compressive strength test method for concrete”. The “crack generation strength” is, for example, a value measured by the test method specified in JIS A 1113 “Split tensile strength test method for concrete”. The "tensile strength" is, for example, a value calculated from a tensile softening curve by inverse analysis of a value measured by the test method specified in JSCE-G552 "Bending strength and bending toughness test method of steel fiber reinforced concrete". be. The "Young modulus" is a value measured by the test method specified in JIS A 1149 "Test method for static elastic modulus of concrete". The "water permeability coefficient" is, for example, a value converted from the air permeability coefficient calculated from the test method specified in RILM TC116-PCD "Permeability, of concrete as acriterion of its durability". The "chloride ion diffusion coefficient" is a value measured by the test method specified in JSCE-G572 "Apparent diffusion coefficient test method (draft) of chloride ions in concrete by immersion". "Performance" is a value (durability index) measured by the test method specified in JIS A 1148 (Method A) "Freeze-thaw test method for concrete". The "wearing coefficient" is a value measured by the test method specified in the O-type (Okuda-type) wear-out test devised by the Central Research Institute of Electric Power Industry.

In the present embodiment, in view of the characteristics desired for the upper layer of the deck portion 3 of the road bridge, the material of the dense layer 13 has at least a higher compressive strength than the material of the ordinary layer 11 (ordinary concrete). Moreover, a material having a small water permeability coefficient and a small chloride ion diffusion coefficient is adopted. 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 adopted.

An example of the properties of the ultra-high-strength fiber-reinforced concrete that can be used as the material of the dense layer 13 will be described below. This ultra-high-strength fiber-reinforced concrete is obtained by hardening a mixture containing, for example, cement, aggregate, kneading water, a chemical admixture for concrete, and reinforcing fibers. The above-mentioned cement is, for example, ordinary Portland cement, early-strength Portland cement, moderate heat 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 rate of 3.0% or less, a clay mass of 1.0% or less, and a fine particle content of 2.0%. Hereinafter, it is an aggregate having a NaCl content of 0.02% or less. In this aggregate, the test result of the organic impurity by the organic impurity test method of the fine aggregate specified in JIS A 1105 is "pale". Further, this aggregate has a stability of 10% or less according to the stability test method of the aggregate with sodium sulfate specified in JIS A 1122, and further has alkali silica reactivity specified in Annex 1 of JIS A 5308. It is an aggregate whose classification according to is Category A.

The above-mentioned kneading water is, for example, kneading water other than the recovered water specified in JSCE-B 101-2005. The above-mentioned chemical admixture for concrete is a high-performance water reducing agent specified in JIS A 6204. The reinforcing fibers described above are fibers 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 above-mentioned reinforcing fibers 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 has, for example, a binder composed of Portland cement, pozzolan material, and ettrin guide-forming material, aggregate having a particle size of 2.5 mm or less, water, and water reduction. It is composed of agents. The reinforcing fibers are steel fibers having a diameter of 0.2 mm, a length of 15 mm (manufacturing error less than ± 2 mm), and a tensile strength of 2 × 10 ³ N / mm ² or more, and a diameter of 0.2 mm and a length of 22 mm (manufactured). An error of less than ± 2 mm) and a ^{mixture of steel fibers with a tensile strength of 2 × 10 3} N / mm ² or more are mixed with 1.75 vol. % May be mixed. The characteristic values of ultra-high-strength fiber reinforced concrete after hardening are 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, and water permeability coefficient 1 × 10 ^-11 cm /. It is preferably less than s, a chloride ion diffusion coefficient of ^{less than 0.14 cm 2} / year, and a wear coefficient of less than 240 mm ³ / cm ^2.

In addition, the standard specification formulation of ultra-high-strength fiber reinforced concrete forming the dense layer 13 has a flow value of 250 ± 20 mm, a ratio of kneaded water to the binder of 15%, an air volume of 2.0%, and kneaded 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.%} ).

Further, an example of the properties of the high-strength fiber-reinforced mortar that can be used as the material of the dense layer 13 will be described below. This high-strength fiber-reinforced mortar is obtained by curing a mixture containing, for example, cement, aggregate, kneading water, a chemical admixture for concrete, and reinforcing fibers. The above-mentioned cement is, for example, ordinary Portland cement, early-strength Portland cement, moderate heat 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 rate of 3.0% or less, a clay mass of 1.0% or less, and a fine particle content of 2.0%. Hereinafter, it is an aggregate having a NaCl content of 0.02% or less. In this aggregate, the test result of the organic impurity by the organic impurity test method of the fine aggregate specified in JIS A 1105 is "pale". Further, this aggregate has a stability of 10% or less according to the stability test method of the aggregate with sodium sulfate specified in JIS A 1122, and further has alkali silica reactivity specified in Annex 1 of JIS A 5308. It is an aggregate whose classification according to is Category A.

The above-mentioned kneading water is, for example, kneading water other than the recovered water specified in JSCE-B 101-2005. The above-mentioned chemical admixture for concrete is a high-performance water reducing agent specified in JIS A 6204. The reinforcing fiber described above 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 above-mentioned reinforcing fibers 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, pozzolan material, and ettrin guide-forming material, aggregate having a particle size of 2.5 mm or less, water, and a water reducing agent. It is composed of. As the reinforcing fiber, polypropylene fiber having a diameter of 0.5 mm, a length of 20 mm (manufacturing error less than ± 2 mm), and a tensile strength of 400 N / mm ² or more is used in 2.0 vol. % May be mixed. The characteristic values of the high-strength fiber reinforced mortar after curing are compressive strength 100 N / mm ² or more, crack generation strength 4 N / mm ² or more, tensile strength 5 N / mm ² or more, and water permeability coefficient 1 × 10 ^-11 cm / s. It is preferably less than, chloride ion diffusion coefficient ^{less than 0.14 cm 2} / year, and wear coefficient less than 240 mm ³ / cm ^2.

In addition, the standard specification formulation of the high-strength fiber reinforced mortar forming the dense layer 13 has a flow value of 220 ± 20 mm, a ratio of kneaded water to the binder of 18%, an air volume of 3.0%, and kneaded 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.%} ).

Further, an example of the properties of "ordinary concrete" that can be adopted as the material of the ordinary layer 11 will be described below. This ordinary concrete is obtained by hardening a mixture containing, for example, cement, aggregate, mixed water, and a chemical admixture for concrete. The above cement is, for example, ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, fly ash cement, blast furnace cement or low heat Portland cement. Regarding the characteristic values of this ordinary concrete after hardening, the compressive strength value is smaller and the water permeability coefficient value is smaller than the characteristic values of the ultra-high-strength fiber-reinforced concrete and high-strength fiber-reinforced mortar as described above. It is large and the value of the chloride ion diffusion coefficient is large. The general ordinary concrete corresponds to the nominal strength of 18 to 60 in JIS A 5308 "ready-mixed concrete", and the ratio of the mixing water to the binder is 65% to 30%.

The above-mentioned ultra-high-strength fiber-reinforced concrete and high-strength fiber-reinforced mortar have higher compressive strength, lower water permeability coefficient, and lower chloride ion diffusion coefficient than ordinary concrete as described above. In addition to the characteristics such as, the crack generation strength is high, the tensile strength is high, the Young's modulus is high, the freeze-thaw resistance is high, and the wear coefficient is small.

Subsequently, a method for manufacturing the precast member 1 as described above will be described.

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 balustrade portion 5 extends upward from both ends of the floor slab portion 3, and the floor slab portion 3 Has a positional relationship such that the dense layer 13 is located on the ordinary layer 11. On the other hand, in the method of manufacturing the precast member 1, the precast member 1 is formed in a posture that is upside down with respect to the posture at the time of operation as described above. In the following description, the posture of the precast member 1 during operation is referred to as "in-service posture", and the posture inverted upside down with respect to the in-service posture is referred to as "inverted posture". The method for manufacturing the precast member 1 according to the present embodiment includes a dense layer forming step, an adhesive coating step, a reinforcing bar arranging step, and a normal layer forming step described below.

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

Separately, a prefabricated member 23 (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 formed into the same shape as the dense layer 13. That is, the dense layer member 23 has a flat plate portion 23a corresponding to the upper layer portion of the floor slab portion 3 and a side wall portion 23b erected at both ends of the flat plate portion 23a and corresponding to the inner portions of the left and right balustrade portions 5. The cross section of the dense layer member 23 has a small U-shape 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 reinforcing bars to be embedded.

As shown in FIG. 3B, the dense layer member 23 is installed in the inverted posture in the portion corresponding to the dense layer 13 in the lumen portion of the formwork 25. The dense layer member 23 forms an inverted U-shape, and the inner surface of the U-shape comes into contact with the wall surface of the corresponding formwork 25. By installing the dense layer member 23 in this way, the dense layer 13 is first formed in the mold 25. The dense layer member 23 does not necessarily have to be integrated, and the parts of the dense layer member 23 divided into a plurality of parts may be appropriately spread in the mold 25 to form the dense layer 13.

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

(Reinforcing bar placement process)
Next, as shown in FIG. 4B, the reinforcing bar 17 is arranged on the dense layer 13. The reinforcing bar 17 is arranged in the lumen portion of the formwork 25 excluding the dense layer 13, and is embedded in the ordinary layer 11 after the precast member 1 is completed.

(Ordinary layer forming process)
Next, as shown in FIG. 5A, ordinary concrete 19 is placed in the lumen portion of the mold 25 except for the dense layer 13. Here, ordinary concrete 19 is placed so as to cover the dense layer 13 formed in the above-mentioned dense layer forming step from above. It should be noted that concrete may be spliced between the portion corresponding to the balustrade portion 5 and the portion corresponding to the floor slab portion 3. After that, the ordinary layer 11 is formed by hardening the ordinary concrete 19. After that, as shown in FIG. 5B, the formwork 25 is demolded to complete the precast member 1 in the inverted posture.

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

The operation and effect of the manufacturing method of the precast member 1 as described above will be described. According to the above manufacturing method, the precast member 1 in the in-service posture has a structure in which a dense layer 13 made of a material denser than the ordinary layer 11 exists on the ordinary layer 11. Therefore, relatively high density can be obtained in the upper layer portion (particularly, the cover portion) of the precast member 1 during operation due to the presence of the dense layer 13. As a result, since the upper layer portion of the road deck in which the dense layer 13 of the precast member 1 is present has a relatively high compressive strength, fatigue deterioration of the road deck due to repeated traffic loads can be suppressed. In addition, since the upper layer of the road deck has a relatively small water permeability coefficient and a relatively small chloride ion diffusion coefficient, deterioration factors such as rainwater and chloride ions from the upper surface side of the road deck are inside the road deck. Invasion of the road deck is suppressed, and deterioration of the road deck is suppressed. As a result, the service life of road decks is improved and life cycle costs are reduced.

Further, since the precast member 1 is formed in an inverted posture at the time of manufacturing, the upper layer portion of the precast member 1 at the time of operation is not a finished surface for concrete placement. Therefore, the denseness of the upper layer portion of the precast member 1 during operation is stably ensured. Further, if the precast member 1 is formed in the 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, since air bubbles are likely to accumulate on the lower surface of the dense layer member 23 during filling with ordinary concrete, the adhesiveness between the dense layer 13 and the ordinary layer 11 may decrease at the time of completion. On the other hand, according to the method in which ordinary concrete is cast 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 precast member 1 is formed in the in-service posture by adhering the dense layer member 23 to the upper surface of the previously formed ordinary layer 11 is also conceivable. However, in this manufacturing method, the hardened concrete members are bonded to each other, so that the normal layer 11 and the dense layer 13 may not be sufficiently integrated. 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.

Generally, when a road deck is constructed of cast-in-place concrete, a deck portion may be formed first, and then a balustrade portion may be formed by being spliced to the upper surfaces of both ends of the deck portion. In this case, the upper surface of the floor slab may not be of sufficient quality due to the effects of dry cracks, bleeding water, and latency layer. Therefore, when the balustrade portion is joined to the upper surface, the seam between the deck portion and the balustrade portion tends to become a water path. Then, deterioration factors such as rainwater and chloride ions invade from the upper surface of the deck portion via the above-mentioned water path, and easily deteriorate the boundary portion between the deck portion and the balustrade portion. 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 deck portion 3 and the inner side surface of the balustrade portion 5 so as to be integrally connected. Therefore, the boundary portion between the floor slab portion 3 and the balustrade portion 5 is closed by the dense layer 13, so that the above problem is avoided.

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 step, the adhesiveness between the dense layer 13 and the ordinary layer 11 is improved. Therefore, the possibility that the integralness of the normal layer 11 and the dense layer 13 is lowered due to the repeated fatigue of the traffic load is reduced.

(Second Embodiment)
Subsequently, a second embodiment of the method for manufacturing the precast member 1 will be described with reference to FIG. The concrete formwork 45 used in the manufacturing method of the present embodiment is different from the formwork 25 of the first embodiment in that the dense layer member 23 is included as an embedded formwork. Hereinafter, the differences from the first embodiment in the manufacturing method of the present embodiment will be mainly described, and since the other configurations are the same as those of the first embodiment, the same or equivalent components are designated by the same reference numerals. The duplicate explanation will be 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 the inverted posture. Next, the formwork plates 27 for the balustrade portion 5 are attached to both ends of the prepared dense layer member 23 in the inverted posture. Further, the formwork plate 28 on the gable side 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 formwork 45 and functions as an embedded formwork, and finally remains as the dense layer 13 which is a part of the precast member 1. Although omitted in the example of FIG. 6, after that, the adhesive 15 is applied to the dense layer member 23 (adhesive application step) and the reinforcing bars 17 are arranged (reinforcing bar placement step) as in the first embodiment. May be good.

(Ordinary layer forming process)
In the subsequent ordinary layer forming step, as shown in FIG. 6B, ordinary concrete 19 is placed in the concrete formwork and hardened to form the ordinary layer 11. After that, as shown in FIG. 6C, the formwork plate 27 and the formwork plate 28 are removed to complete the precast member 1 in the inverted posture.

(Third Embodiment)
Subsequently, a third embodiment of the method for manufacturing the precast member 1 will be described with reference to FIG. 7. In the manufacturing method of the present embodiment, the method of forming the dense layer 13 is different from that of the first embodiment. Hereinafter, the differences from the first embodiment in the manufacturing method of the present embodiment will be mainly described, and since the other configurations are the same as those of the first embodiment, the same or equivalent components are designated by the same reference numerals. And the duplicate explanation is omitted.

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

The present invention can be carried out in various forms having various changes and improvements based on the knowledge of those skilled in the art, including the above-mentioned embodiment. It is also possible to construct a modified example by utilizing the technical matters described in the above-described embodiment. The configurations of the respective embodiments and the modifications may be appropriately combined and used.

For example, the adhesive coating step and the reinforcing bar arranging step in each embodiment are not essential steps and may be performed as needed. Further, in the embodiment, the case where the material of the dense layer 13 is ultra-high-strength fiber-reinforced concrete or high-strength fiber-reinforced mortar has been described, but the present invention is not limited thereto. That is, as the material of the dense layer 13, another material that is denser than the ordinary layer 11 may be appropriately selected.

In each embodiment, an example of manufacturing a precast member 1 having a U-shaped cross section has been described, but the present invention can also be applied to a method of manufacturing a flat plate-shaped precast member 51 as shown in FIG. 8A. .. 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 formwork 25, and ordinary concrete is formed so as to cover the dense layer 13 from above. The ordinary 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 for manufacturing a precast member 53 having an L-shaped cross section. In the example of FIG. 8B, first, a dense layer 13 made of ultra-high-strength fiber-reinforced concrete or high-strength fiber-reinforced mortar is formed in a portion of the formwork 25 corresponding to the inside of the inverted L-shape, and the dense layer 13 is formed. Ordinary concrete is cast so as to cover the 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 provided with a deck portion 3 and a balustrade portion 5 by appropriately combining a flat plate-shaped precast member 51 and a precast member 53 having an L-shaped cross section as described above. May be configured.

Further, in each embodiment, an example of manufacturing the precast member 1 used for the road bridge has been described. However, as shown in FIG. 9, the present invention is a precast for a waterway for constructing a waterway 60 having a U-shaped cross section. It can also be applied to the manufacturing method of the member 57. In the inner wall portion of this type of water channel 60 that comes into contact with water W, it is difficult for water W to permeate, and wear caused by water flow and wear caused by gravel carried with water W are reduced, and the wall surface of the water channel is reduced. It is required as a characteristic to secure the roughness coefficient of the above for a long period of time and to secure a predetermined water flow for a long period of time. Therefore, the dense layer 13 is provided so as to extend to 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, which is the material of the ordinary layer 11, is adopted. As the material of the dense layer 13 having the above-mentioned characteristics, it is preferable to use ultra-high-strength fiber-reinforced concrete or high-strength fiber-reinforced mortar. The precast member 57 for such a waterway is also manufactured by the same manufacturing method as that of the above-described embodiment.

Further, in the precast member 1 of the embodiment, the material of the dense layer 13 has (1) high compressive strength, (2) high crack generation strength, and (3) tensile strength as compared with the material of the ordinary layer 11. High strength, (4) high Young's modulus, (5) low water permeability coefficient, (5) low chloride ion diffusion coefficient, (6) high freeze-thaw resistance, and (7) wear. Although it had the property of having a small coefficient, the relationship between the properties of the material of the dense layer 13 and the material of the ordinary layer 11 is not limited to the above relationship. That is, it is not essential that the material of the dense layer 13 has all of the above-mentioned properties (1) to (7) as compared with the material of the ordinary layer 11, and among the above-mentioned properties (1) to (7). Any relationship may be used as long as it has at least one characteristic of.

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 (8)

A method for manufacturing a precast member having a U-shaped cross section having a floor slab portion constituting a road slab and a slab portion rising upward from both ends of the deck slab and forming a balustrade of the road.
The precast member includes a common layer formed in the shape of U-shaped cross section over the outer layer of the lower layer and the railing of the deck portion Ri Do from a predetermined concrete material, dense material than the concrete material Tona Ri has a dense layer that is formed integrally with the shape of the U-shaped cross-section across the inner layer of the upper layer and the railing of the deck section,
A dense layer forming step of integrally forming the dense layer having an inverted U-shaped cross section with the posture turned upside down with respect to the time of operation.
An ordinary layer forming step of forming the ordinary layer having an inverted U-shaped cross section on the outside of the dense layer by placing and hardening the concrete material so as to cover the dense layer formed in the dense layer forming step from above. And, with
A method for manufacturing a precast member, wherein the precast member is formed in an upside-down posture with respect to the in-service state. 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 time of operation to form the dense layer.
The method for manufacturing a precast member according to claim 1, wherein in the ordinary layer forming step, the concrete material is placed in the concrete formwork and hardened. In the dense layer forming step, the dense layer member prepared in advance is used as the dense layer.
The production of the precast member according to claim 1, wherein in the ordinary layer forming step, the concrete material is placed and hardened in a concrete formwork including the dense layer member having an upside-down posture with respect to operation as an embedded formwork. Method. The material of the dense layer is compared with the concrete material of the ordinary layer.
Of the following: high compressive strength, high cracking strength, high tensile strength, high Young's modulus, low water permeability coefficient, low chloride ion diffusion coefficient, high freeze-thaw resistance, or low wear coefficient. The method for manufacturing a precast member according to any one of claims 1 to 3, which has at least one characteristic of. The method for manufacturing 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. Claims 1 to 5 further include an adhesive application step of applying an adhesive to a surface of the dense layer that becomes a boundary with the ordinary layer between the dense layer forming step and the ordinary layer forming step. The method for manufacturing a precast member according to any one of the following items. The precast member according to any one of claims 1 to 6, further comprising a reinforcing bar arranging step of arranging a reinforcing bar embedded in the ordinary layer between the dense layer forming step and the ordinary layer forming step. Production method. In the normal layer forming step,
The invention according to any one of claims 1 to 7, wherein the concrete material is spliced between the portion corresponding to the balustrade portion and the portion corresponding to the deck portion of the ordinary layer. How to manufacture precast members.

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