JP6550241B2 - Super rapid hardening type high toughness fiber reinforced concrete - Google Patents

Description

  The present invention relates to a super rapid hardening type high toughness fiber reinforced concrete composition. Specifically, it is a concrete composition which gives a concrete having high toughness, excellent in workability, excellent in workability, capable of thin layer construction and high toughness, while having super rapid hardness and causing no sag on a road having a slope About.

It is necessary to complete and restore the construction of road slabs in a short time except in special cases such as intensive work.
Conventionally, ultra rapid hardening steel fiber reinforced concrete (SFRC) or the like is used, but since the slump is about 5 cm, a large finisher is required. As 25 mm is common for coarse aggregate, the standard installation thickness is 40 mm or more.
Fiber reinforced concrete compositions are proposed in U.S. Pat.

Patent Document 1 proposes a method of mixing and designing concrete containing short fibers excellent in workability. Patent Document 2 proposes a fiber-reinforced concrete composite material having a slump of 16 to 21 cm capable of imparting bending toughness. Patent Document 3 proposes a highly fluid fiber-reinforced mortar or concrete composition in which fibers are mixed and the slump flow is 500 mm or more.
However, in the above-mentioned patent documents, since the slump flow is 250 or more and less than or equal to 550 mm or 500 mm or more and the slump has a relatively high fluidity of 16 to 21 cm, a slope like a road floor slab in service is When applied to a place where there is repeated vibration due to traffic, there is a risk of sagging at least downward.

JP 2001-302310 A Unexamined-Japanese-Patent No. 2010-053014 JP 2007-126317 A

An object of the present invention is to provide a concrete having super rapid hardness, good sagging property without causing sagging on a road with slopes, good fillability to the back of a reinforcing bar, excellent workability, thin layer construction possible and high toughness. It is in providing a concrete composition.
Other objects and advantages of the present invention will become apparent from the following description.

According to the invention, the above objects and advantages of the invention are, first of all:
From 100 parts by weight of cement, 120 to 210 parts by weight of coarse aggregate, 105 to 280 parts by weight of fine aggregate having an absolute dry specific gravity of 2.3 or more, and 3.2 to 7.0 parts by weight of organic fiber of 18 to 24 mm in length And a fine aggregate ratio of 44.0-57.0%. The fine aggregate ratio is the volume percentage of fine aggregate to the total volume of coarse aggregate and fine aggregate.

The above objects and advantages of the present invention are secondly:
This is achieved by using the above-described organic fiber-containing lightweight concrete composition of the present invention for repairing a road surface.

The organic fiber-containing lightweight concrete composition of the present invention has excellent super-hardening property, for example, a compressive strength after 3 hours of 24 N / mm ² or more, and has good workability. It provides a concrete with a good slump value, eg 12.0 ± 2.5, and high toughness capable of thin layer construction, eg maximum coarse aggregate diameter 13 mm, eg excellent bending and flex-hardening properties.
The fiber-reinforced concrete composition of the present invention is suitable as a road surface repair material, and is suitably used, for example, as a repair material for floor slabs, particularly concrete floor slabs for bridges.

FIG. 1 is a load-deflection curve for the concrete composition of Example 1.

  Hereinafter, each component which the fiber reinforced concrete composition (it may only be mentioned a concrete composition hereafter) of this invention contains is demonstrated.

<Cement>
The cement contained in the concrete composition of the present invention includes, for example, ordinary portland cement, early strength portland cement, ultra early strength portland cement, moderate heat portland cement, low heat portland cement, sulfate resistant portland cement, ecocement, super rapid hardening A cement, an alumina cement, etc. can be mentioned, 1 or more types selected from these can be used.
When the concrete composition of the present invention is used for road surface repair, fast-hardening is important, so use either early-strength Portland cement, ultra-early-strength Portland cement, super-fast-hardening cement or alumina cement as cement or alumina cement and other It is preferable to use a mixture consisting of cement, and it is further preferable to use super rapid-hardening cement.

<Coarse aggregate>
Examples of the coarse aggregate contained in the concrete composition of the present invention include gravel, crushed stone, regenerated coarse aggregate and the like, and one or more selected from these can be used.
The particle diameter of the coarse aggregate is preferably 5 to 20 mm, more preferably 5 to 13 mm;
The density is preferably 2.5 to 3.0, and more preferably 2.5 to 2.7, as absolute dry specific gravity.
The content ratio of the coarse aggregate in the concrete composition of the present invention is preferably 120 to 210 parts by weight, and more preferably 130 to 200 parts by weight with respect to 100 parts by weight of the cement.

<Fine aggregate>
The concrete composition of the present invention contains, as a fine aggregate, a fine aggregate (usually fine aggregate) having a bone dry specific gravity of 2.3 or more. Ordinary fine aggregate refers to fine aggregate having a bone dry specific gravity of 2.3 or more. The bone dry specific gravity is preferably 2.5 to 3.0, more preferably 2.5 to 2.8. As such ordinary fine aggregate, for example, one or more selected from river sand, mountain sand, sea sand, crushed sand, blast furnace slag fine aggregate and the like can be used.
The particle size of the fine aggregate is preferably 0.1 to 5.0 mm, more preferably 0.15 to 2.5 mm.
The content of the ordinary fine aggregate in the concrete composition of the present invention is preferably 105 to 280 parts by weight, and more preferably 105 to 270 parts by weight with respect to 100 parts by weight of the cement.

<Fine aggregate rate>
In the concrete composition of the present invention, the fine aggregate ratio is 44.0 to 57.0%. The fine aggregate rate is the volume percentage of fine aggregate to the total volume of coarse aggregate and fine aggregate, and specifically,
Fine aggregate rate (%) = fine aggregate volume ÷ (coarse aggregate volume + fine aggregate volume) × 100
It is indicated by. If the percentage of fine aggregate in the concrete composition of the present invention is out of the above range, the slump value of the concrete after mixing can not be obtained, or if it is attempted to obtain it forcibly, material separation may occur to make it difficult to repair the road surface. Become. The percentage of fine aggregate in the concrete composition of the present invention is more preferably 49.0 to 56.0%.

<Organic fiber>
The organic fibers contained in the concrete composition of the present invention have a fiber length (average fiber length) of 18 to 24 mm.
As this organic fiber, it is preferable to use, for example, one or more selected from the group consisting of polyolefin fiber, polyvinyl alcohol fiber, polyester fiber, aramid fiber and nylon fiber. As a specific example of the said polyolefin fiber, a polyethylene fiber, a polypropylene fiber etc. can be mentioned, for example.
The diameter of the organic fiber in the concrete composition of the present invention is preferably 100 to 1,000 μm, and more preferably 300 to 800 μm. With the use of organic fibers of smaller diameter, it is difficult to obtain the desired toughness.
For example, polypropylene fibers of 500 to 4000 dtex can be exemplified as particularly preferred organic fibers.
Commercially available products of such organic fibers include, for example, Ballink (polypropylene fiber, manufactured by Sugahara Kogyo Co., Ltd.), Balchip (polypropylene fiber, manufactured by Sugahara Kogyo Co., Ltd.), Amylantaff binder (nylon fiber, Toray Amtex) (Manufactured by Co., Ltd.), Unitikabinirone ABI (Vinylone fiber, manufactured by Unitika Co., Ltd.), and the like.

The content ratio of the organic fiber in the concrete composition of the present invention is 3.2 to 7.0 parts by weight, preferably 3.4 to 6.8 parts by weight with respect to 100 parts by weight of the cement. .
When the concrete composition of the organic fiber is out of the above range, it becomes difficult to obtain the desired toughness.
The concrete composition of the present invention preferably contains substantially no aggregate, generally known as lightweight fine aggregate. Here, the lightweight fine aggregate refers to a fine aggregate having an absolute dry specific gravity of less than 1.2, such as a urethane foam, a polystyrene foam, a natural lightweight fine aggregate, an artificial lightweight fine aggregate, and the like.
When the concrete composition of the present invention "does not substantially contain light-weight fine aggregate" as described above, the content ratio of the light-weight fine aggregate is, for example, 5% by weight or less based on the total amount of fine aggregate, It is preferably 3% by weight or less, and most preferably not containing it at all.

<Other ingredients>
The concrete composition of the present invention may contain other components in addition to the above components, as long as the effects of the present invention are not impaired. Examples of such other components include water reducing agents, setting retarders, expanding agents, antifoaming agents, gypsum, hydrated lime, calcium carbonate, silica fume and the like.

[Water reducing agent]
The concrete composition of the present invention can contain a water reducing agent.
Examples of the water reducing agent include polycarboxylic acid, naphthalene sulfonic acid formaldehyde condensate, melamine sulfonic acid formaldehyde condensate, lignin sulfonic acid and the like, and one or more selected from these may be used. it can. Among these, it is preferable to use one or more selected from the group consisting of polycarboxylic acid, naphthalenesulfonic acid-formaldehyde condensate and melamine sulfonic acid-formaldehyde condensate.
Examples of commercially available water reducing agents include Mighty 21 HF (methacrylic acid based polymer, manufactured by Kao Corporation), Merment F 4000 (melamine sulfonic acid, manufactured by SKW corporation), Mighty 100, Mighty 150 (naphthalenesulfonic acid) And Kao Co., Ltd.).
The content ratio of the water reducing agent in the concrete composition of the present invention is preferably 3.0 parts by weight or less, and more preferably 0.05 to 2.5 parts by weight with respect to 100 parts by weight of the cement. And preferably 0.1 to 2.0 parts by weight.

[Settlement retarder]
The concrete composition of the present invention can contain a setting retarder.
Examples of the above-mentioned setting retarder include sodium salts of inorganic acids, sodium salts of organic acids, oxycarboxylic acids, anhydrides of oxycarboxylic acids, oxycarboxylic acid salts, etc. More than a species can be used.
Examples of sodium salts of the above inorganic acids include sodium sulfate, sodium bicarbonate and the like;
Examples of sodium salts of the organic acids include sodium L-tartrate, sodium DL-tartrate, sodium hydrogen tartrate, sodium malate, sodium citrate, sodium gluconate and the like.

Examples of the above-mentioned oxycarboxylic acids include aliphatic oxy acids and aromatic oxy acids. Specific examples thereof include, as aliphatic oxy acids, for example, citric acid, gluconic acid, tartaric acid, glycolic acid, lactic acid, Hydroacrylic acid, α-oxybutyric acid, glyceric acid, tartronic acid, malic acid etc .;
As an aromatic oxy acid, a salicylic acid, m-oxybenzoic acid, p-oxybenzoic acid, gallic acid, mandelic acid, tropic acid etc. can be mentioned, for example.
As the above-mentioned oxycarboxylic acid anhydride, for example, anhydrides of the above-mentioned exemplified oxycarboxylic acids;
Examples of the oxycarboxylic acid salts include alkali metal salts and alkaline earth metal salts of oxycarboxylic acids exemplified above. Examples of the alkali metal include sodium and potassium;
As said alkaline-earth metal, magnesium, calcium, barium etc. can be mentioned, for example.
The content ratio of the setting retarder in the concrete composition of the present invention is preferably 1.0 parts by weight or less, and more preferably 0.15 to 0.95 parts by weight with respect to 100 parts by weight of the cement. The content is preferably 0.2 to 0.9 parts by weight.

[Expander]
The concrete composition of the present invention may further contain an expanding agent.
As the expansion agent in the present invention, a lime-based expansion agent can be preferably used, and specific examples thereof include, for example, quick lime, quick lime-gypsum mixed system, quick lime-calcium sulfoaluminate mixed system, calcined dolomite, etc. One or more selected from these can be used.
The content ratio of the expanding agent in the concrete composition of the present invention is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less, with respect to 100 parts by weight of the cement.

<Method of Preparing Concrete Composition>
The concrete composition of the present invention can be prepared by appropriately mixing each essential component such as cement as described above, as well as the other components as required, and water.
In the present invention, water is preferably used in an amount of 35 to 43 parts by weight, more preferably 36 to 42 parts by weight, based on 100 parts by weight of the cement.
In order to ensure the uniformity of the dispersion of each component and to prevent the scattering of the organic fiber, the organic fiber first prepares a precursor slurry formed by dispersing or dissolving each component other than the organic fiber in water. It is preferable to use the method of adding the organic fiber to the precursor slurry.

<How to repair bridge decks>
The concrete composition of the present invention as described above can be suitably used as a floor slab repair concrete composition in repairing a road surface on a bridge.
To repair the road surface, remove the asphalt in advance if necessary, then lay and harden the concrete composition of the present invention in the recessed portion created by cutting and grinding the damaged existing concrete. Can be done by After that, further asphalt laying may be performed if necessary.
Use concrete composition repaired floor plate of the present invention, at 3 hours after laying, for example, 24N / mm ² or more, because preferably capable of expressing the 27N / mm ² or more strength, repairs The closing time for the train can be extremely short.
In addition, the concrete composition of the present invention preferably has a slump of 12.0 ± 2.5 cm, so that a wide range of repair can be smoothly performed including the thickening of the upper surface of the floor slab, and the workability is extremely excellent. ing.

The details of the components used in the following examples and comparative examples are as follows. Examples 4 and 5 are reference examples.

Cement: Super jet cement, manufactured by Pacific Cement Co., Ltd. Coarse aggregate: crushed stone 1305, density 2.69
Fine aggregate;
Ordinary fine aggregate: Silica sand (mixed sand of No. 4 silica sand and No. 5 silica sand, density 2.60)
Swelling agent: Pacific Dipcal Pacific Material Co., Ltd. silica fume: Ferrosilicon Co., Ltd. BASF Pozzolith Anhyd. Gypsum: anhydrous hydrofluoric acid gypsum Co., Ltd. Asahi Glass Co., Ltd. ))
Setting retarder: Citric anhydride anhydride Fiber: polypropylene fiber, density = 0.91 g / cm ³ ,
(1) fineness = 2000 dtex, length = 18 mm
(2) fineness = 2000 dtex, length = 24 mm
(3) fineness = 2000 dtex, length = 30 mm
(4) fineness = 13 dtex, length = 13 mm
(5) fineness = 13 dtex, length = 24 mm
The polypropylene fiber of (2) above is obtained from Kuwahara Kogyo Co., Ltd. product.

Examples 1 to 5 and Comparative Examples 1 to 4
(1) Preparation of concrete composition Each component except coarse aggregate, fibers and water was weighed so as to become the ratio described in Table 1, and mixed by an omnimixer to prepare a powder mixture.
The coarse aggregate and the powder mixture are added to a fiber mixer (manufactured by Yodo Seikenki Co., Ltd.) and air-kneaded for 30 seconds. Subsequently, a predetermined amount of water was added to the mixer and mixed for 90 seconds, and then fibers were added and the mixture was further mixed for 120 seconds to prepare each concrete composition.
In addition, the ratio of each component shown in Table 1 is the compounding quantity (unit: weight part) of fresh concrete. "-" Of the component column shows that the component applicable to the said column was not used.

(2) Evaluation method The slump of the concrete composition was measured according to JIS A1101 after mixing.
The compressive strength and static modulus of elasticity of the concrete composition were measured in accordance with JIS A1108 and JIS A1149, respectively, using samples after 3 hours, 7 days and 28 days after immediately after mixing.
The flexural toughness coefficient of the concrete composition was measured in accordance with JSCE-G 552-2010.
In addition, the presence or absence of bending / flexure-hardening characteristics was determined from the load-deflection curve of the sample in accordance with the "Multiple fine cracked fiber-reinforced cement composite material design and construction guidelines (draft)" edited by the Japan Society of Civil Engineers. The measurement was performed 3 times with the same concrete composition. The figure is the result of the load-deflection curve in Example 1. The three curves in the figure are the results of three measurements.
The evaluation results are shown in Table 2.

Claims (6)

From 100 parts by weight of cement, 120 to 210 parts by weight of coarse aggregate, 105 to 280 parts by weight of fine aggregate having an absolute dry specific gravity of 2.3 or more, and 3.2 to 7.0 parts by weight of organic fiber having a fiber length of 18 to 24 mm A fiber-reinforced concrete composition having a fine aggregate percentage of 44.0 to 57.0%.   The fiber reinforced concrete composition according to claim 1, wherein the cement is super rapid hardening cement. The fiber reinforced concrete composition according to claim 1, wherein the organic fiber having a fiber length of 18 to 24 mm is a polypropylene fiber of 500 to 4,000 dtex.   The fiber reinforced concrete composition according to claim 1, wherein the slump is 12.0 ± 2.5 cm.   A method of repairing a bridge floor slab characterized by using the fiber reinforced concrete composition according to any one of claims 1 to 4 for repairing a bridge floor slab.   The method for repairing a bridge floor slab according to claim 5, wherein the bridge floor slab is concrete.

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