JP6550245B2 - Fiber reinforced lightweight concrete composition - Google Patents

Description

  The present invention relates to organic fiber reinforced lightweight concrete compositions. More specifically, while having ultra-rapid hardness, the organic fiber reinforcement gives concrete having high fluidity, high fluidity, excellent workability, and no dripping and an excessively large static elastic modulus after 28 days of hardening. It relates to a lightweight concrete composition.

If the existing concrete is damaged, only the damaged part (including punching damage) is peeled off and filled, the surface of the existing concrete is scraped off temporarily and thick concrete is added for reinforcement. It is necessary to maintain the integrity with the existing concrete after the repair reinforced concrete construction.
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. The concrete has a compressive strength exceeding 50 N / mm ² at 28 days of age due to the property of exhibiting strength in a short period of time, and the static elastic modulus rises to 40 KN / mm ² . Since the static modulus of the existing concrete is 30 KN / mm ² , after repeated repairs, repeated loading of the vehicle causes a stress difference between the repaired portion and the existing concrete boundary, and there is a high risk of re-deterioration.
A highly fluid mortar or concrete mixed with fibers is disclosed in US Pat.
Several high toughness lightweight concrete compositions for reducing the static modulus of elasticity have been proposed to date.
Patent Document 2 proposes a cement culture (remediation concrete composition) containing ultra rapid-hardening cement, coarse aggregate, ultra-lightweight fine aggregate, and foam at a predetermined ratio. In addition, Patent Document 3 proposes a method of repairing a road slab that essentially uses a resin material, a high toughness FRP material, and the like.
However, Patent Document 2 has insufficient strength of the obtained cured product. Patent Document 3 is expensive as a road repair material, and is not practical in consideration of repair costs.

JP 2007-126317 A JP 2000-239075 A JP, 2013-91982, A

It is an object of the present invention to have super-fast-hardening properties, but with an excessively large static modulus after 28 days of hardening, no dripping, medium fluidity, good workability, low cost, and high toughness. An object of the present invention is to provide an organic fiber-containing lightweight concrete composition which gives concrete.
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:
100 parts by weight of cement, 120 to 210 parts by weight of coarse aggregate, 93 to 255 parts by weight of fine aggregate having an absolute dry specific gravity of 2.3 or more, 12 to 25 parts by weight of inorganic hollow balloon and organic fibers of 18 to 30 mm in length 3. This is achieved by an organic fiber-containing lightweight concrete composition comprising 2 to 7.0 parts by weight.

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 can be repaired because the static elasticity coefficient after 28 days of hardening remains equivalent to that of the existing concrete while having super rapid hardening, for example, compressive strength after 3 hours of 24 N / mm ² or more. There is no concentration of stress at the location and boundary of existing concrete, good workability, for example no sag on road with slope and good filling property to the back of the rebar with medium fluidity, thin layer construction eg maximum coarse bone A material diameter of 13 mm gives a lightweight concrete with high toughness, eg excellent bending and flex-hardening properties.
The organic fiber-containing lightweight 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 organic fiber containing lightweight 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.
Mixing amount of ultra-rapid-cement, concrete 1 m ³ per, 300Kg～450kg are preferred. If it is less than 300 kg, the compressive strength after 3 hours does not reach 24 N / mm ² and it will take time to open the traffic after repairing the floor slab. If there are restrictions on the lane regulation period, there is also the concern that it will not be possible to open in time. If it exceeds 450 kg, the fluid retention time required for construction may not be secured, or the occurrence of rapid strength may cause problems in repair work. In addition, the amount of heat generated by hydration increases to cause temperature cracking.

<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.
If the particle size of the coarse aggregate is less than 5 mm, the unit water content will be increased, so the water content for cement will increase, and the compressive strength after 3 hours will not exceed 24 N / mm ² or the dimensional change after hardening Becomes large and causes cracks.
If it exceeds 20 mm, the filling property to the back of the reinforcing bar will deteriorate, and the minimum construction thickness will exceed 40 mm, so if it is necessary to scrape the existing concrete excessively to the thickness of the floor plate damage, construction time And waste will increase.
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.
If the amount of coarse aggregate mixed is less than 120 parts by weight, the amount of fine aggregate mixed will be increased, resulting in horizontal flowability to make it impossible to obtain a predetermined slump value, or drying after curing. Shrinkage increases and cracks may occur. On the other hand, if it exceeds 210 parts by weight, the mixing amount of the fine aggregate will be reduced, and material separation may occur due to the lack of mortar (total amount of cement and fine aggregate), and uniform concrete can not be obtained.

<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.
When the particle size of the fine aggregate exceeds the range of 0.1 to 5.0 mm, a decrease in fluidity, an increase in unit water content, and a decrease in compressive strength after curing occur.
The content of the ordinary fine aggregate in the concrete composition of the present invention is preferably 93 to 255 parts by weight, and more preferably 95 to 245 parts by weight with respect to 100 parts by weight of the cement.
When the proportion of fine aggregate is less than 93 parts by weight, the volume for filling the voids of the coarse aggregate is insufficient, so material separation occurs, and the compressive strength after curing decreases and 24 N / mm ² is obtained in 3 hours. It disappears. If it exceeds 255 parts by weight, the unit water content increases to obtain a predetermined slump, so that the dimensional change after curing becomes large and cracks occur.

<Inorganic hollow balloon>
The inorganic hollow balloon contained in the concrete composition of the present invention is preferably composed of a particulate inorganic component, and it is possible to adjust the density (absolute dry specific gravity) to a small value by including air bubbles in the particles. Say. The inorganic hollow balloon may be a balloon-like hollow body having only one air bubble in a shell made of an inorganic component, or may be an embodiment having a plurality of air bubbles in a shell made of an inorganic component, or It may consist of a porous inorganic component. Among them, it is preferable to have only one air bubble in the shell or to have a plurality of air bubbles in the shell, and more preferable to have only one air bubble in the shell.
As an inorganic component which comprises the shell of an inorganic hollow balloon, an inorganic oxide can be illustrated preferably, for example. Specifically, for example, glass, silica, alumina, zirconia, titania, ceria and the like, and composites composed of a plurality of these can be mentioned. The complex may be any of complex oxides and mixtures. As the inorganic oxide complex, a silica-alumina complex oxide is preferable.

As the inorganic component constituting the shell of the inorganic hollow balloon in the present invention, particularly preferred are glass, silica, alumina and a silica-alumina composite oxide, and it is particularly preferable to use glass.
The density of the inorganic hollow balloon is preferably 1.1 or less, more preferably 0.7 to 1.0, as the absolute dry specific gravity.
The particle diameter of the inorganic hollow balloon is preferably 3.0 mm or less as a median diameter, more preferably 0.1 to 2.5 mm, and still more preferably 0.15 to 2.0 mm.
When the particle size of the inorganic hollow balloon includes those having a particle size of more than 3.0 mm, the particle size composition of the entire fine aggregate changes because the particle size composition with the fine aggregate usually changes significantly. For this reason, the fluidity of concrete is affected, and a predetermined slump can not be obtained.

As a commercial item of the inorganic hollow balloon suitably used in the concrete composition of the present invention, for example, Rex (recycled glass balloon, manufactured by Sakai Industry Co., Ltd.), senolite (fly ash balloon, manufactured by Sakai Industry Co., Ltd.), etc. Can be mentioned.
The content ratio of the inorganic hollow balloon in the concrete composition of the present invention is preferably 12 to 25 parts by weight, and more preferably 14 to 23 parts by weight with respect to 100 parts by weight of the cement.
When the content ratio of the inorganic hollow balloon is less than 12 parts by weight, the lowering effect of the static elasticity coefficient can not be obtained, and when it exceeds 25 parts by weight, the compressive strength over 3 hours of 24 N / mm ² can be obtained It will not be possible.
The total volume of the inorganic hollow balloon and the ordinary aggregate in the concrete composition of the present invention is the total aggregate volume (hereinafter referred to as the fine aggregate percentage) from the viewpoint that good slump value can be obtained after mixing and mixing. The ratio is preferably 44.0 to 57.0%, 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 30 mm. The average fiber length is preferably 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. Polyolefin fibers can be particularly suitably used in the present invention because the specific gravity of the polyolefin is as small as about 0.85 to 1.0 g / cm ³ . Among them, polypropylene fiber is suitable in that it is easy to obtain strength, has appropriate rigidity, and is excellent in creep resistance.
The diameter (average diameter of the cross section perpendicular to the longitudinal direction of the fiber) 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.
In order to obtain desired toughness, the fineness is preferably in the range of 100 to 7,500 dtex, and in the case of polypropylene fiber, preferably 500 to 4,000 dtex.
Commercial products of such organic fibers include, for example, Baltip (polypropylene fiber, manufactured by Sugahara Kogyo Co., Ltd.), an Amirantafu binder (nylon fiber, manufactured by Toray Amtex Co., Ltd.), Unitikabinilon ABI (vinylon fiber, Unitika Co., Ltd. product etc. can be mentioned.
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.
It is preferable that the concrete composition of the present invention does not substantially contain an aggregate generally known as a light-weight fine aggregate (but excluding the above-mentioned inorganic hollow balloon). 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 with respect to 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. As such other components, there can be mentioned, for example, water reducing agents, setting retarders, fibers, swelling agents, antifoaming agents, gypsum, calcium hydroxide, 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.

[Expanding material]
The concrete composition of the present invention may further contain an expansive agent.
As the expansion material in the present invention, a lime-based expansion material 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 expansive material 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. On the other hand, the static modulus of elasticity at the time of 28 days after laying, for example 25~32kN / mm ^2, because preferably is suppressed to about 29~31kN / mm ^2, the difference in hardness between the slabs of the existing very small. Accordingly, since the degree of stress concentration generated in the boundary area between the existing floor slab and the repaired floor slab at the time of passing the vehicle is small, it is possible to avoid a situation where the repaired portion is afflicted preferentially.
In addition, the concrete composition of the present invention preferably has a medium fluidity of 8 to 12 cm slump, so that a wide range of repair can be smoothly performed including the thickening of the upper surface of the floor slab, and the administration is extremely excellent. ing. Such medium fluidity is preferably such that the ratio of the weight of the fine aggregate to the total aggregate amount, that is, the total weight of the coarse aggregate, the fine aggregate and the inorganic hollow balloon is 0.40 or more, more preferably 0.45 or more. It is advantageously achieved by If this ratio is less than 0.40, it becomes difficult to separate the above-mentioned essential components and to achieve the desired medium fluidity.

The details of the components used in the following examples and comparative examples are as follows.
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)
Inorganic hollow balloon: Rex (trade name, recycled glass balloon, specific gravity 0.86, manufactured by Sakai Industry Co., Ltd.)
Expansive material:
Water reducing agent: Mighty 21 HF (trade name, methacrylic acid polymer, manufactured by Kao Corporation)
Setting retarder: Citric anhydride anhydride Fiber: polypropylene fiber, density = 0.91 g / cm ³ ,
(1) fineness = 2000 dtex, length = 24 mm,
(2) fineness = 13 dtex, length = 12 mm
The above polypropylene fiber is available from Ebara Industries Co., Ltd. product.

Rubber;
(1) B-2.5: trade name, rubber chip, particle size 1.0 to 2.5 mm
(2) P-16: trade name, powder rubber, particle size 1 mm (# 16) under (3) P-100: trade name, powder rubber, particle size 0.15 mm (# 100) under The above rubber is Shinsei Co., Ltd. Obtain rubber products.

Examples 1 to 5 and Comparative Examples 1 to 6
(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.
The ratio of the respective components shown in Table 1 is the amount per fresh concrete 1 m ³ (Unit: kg) is. "-" Of the component column shows that the component applicable to the said column was not used.

(2) Evaluation method The compressive strength and the static modulus of elasticity of the cured product were measured according to JIS A1108 and JIS A1149, using samples after 3 hours, 7 days and 28 days, respectively, immediately after mixing.
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 three times with a cured product of the same composition. FIG. 1 shows the results 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 (5)

  100 parts by weight of cement, 120 to 210 parts by weight of coarse aggregate, 93 to 255 parts by weight of fine aggregate having an absolute dry specific gravity of 2.3 or more, 12 to 25 parts by weight of inorganic hollow balloon and organic fibers of 18 to 30 mm in fiber length An organic fiber-containing lightweight concrete composition comprising 2 to 7.0 parts by weight.   The organic fiber-containing lightweight concrete composition according to claim 1, wherein the cement is ultra rapid-hardening cement.   The organic fiber-containing lightweight concrete composition according to claim 1, wherein the organic fiber having a fiber length of 18 to 30 mm is a polypropylene fiber of 500 to 4,000 dtex.   A method for repairing a bridge floor slab characterized by using the organic fiber-containing lightweight concrete composition according to any one of claims 1 to 3 for repairing a bridge floor slab.   The method for repairing a bridge floor slab according to claim 4, wherein the bridge floor slab is concrete.