JP2009298624A - Ultra-high-strength concrete composition and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultra-high-strength concrete composition which has high strength and excellent workability and effectively suppresses hardening retardation. <P>SOLUTION: The ultra-high-strength concrete composition contains cement containing silica fume and an aqueous solution containing a maleic acid-based surfactant of 0.2-3.5 pts.mass in terms of the solid content based on 100 pts.mass of the cement containing silica fume and calcium nitrite of 20-40% in mass ratio to the solid content of the maleic acid-based surfactant. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an ultra-high-strength concrete composition and a method for producing the same, in particular, high strength (for example, ultra-high strength having a strength of 100 N / mm ² or more), excellent workability, and effective curing delay. The present invention relates to an ultrahigh strength concrete composition suppressed to a low temperature and a method for producing the same.

  Ultra high strength concrete in which cement mixed with dry mixing of silica fume with a particle size of 1 μm or less is mixed with water at a mass ratio of 10 to 25% for the purpose of remarkably reducing the member cross section of a reinforced concrete structure, and Steel fiber reinforced ultra high strength concrete in which steel fibers having a diameter of 1 mm or less are mixed is known. In the concrete, i) the amount of the surfactant used to obtain a homogeneous dispersibility in the constituent materials of cement and water required for ensuring workability and product quality is increased, and ii) delay in hardening of the cement Iii) In order to promote final hydration, special curing such as heating, pressurization, and humidification is required.

In addition, the time required for kneading is short, the decrease in fluidity with time (slump loss) is small, the viscosity is low, the self-shrinkage of the resulting cured product is small, and the resulting cured product has a desired high Examples of using the following surfactants are shown for the purpose of simultaneously satisfying a plurality of performances of developing strength. As the surfactant, a radical copolymerization reaction of a non-aqueous radically polymerizable monomer mixture containing maleic anhydride and a specific allyl ether monomer in a predetermined ratio, with a polymerization conversion rate of 50 to 90% This is a method using a surfactant that is partially or completely neutralized from the reaction mixture containing the produced copolymer and the remaining monomer, which is stopped in the middle of the reaction (see, for example, Patent Document 1).
However, there is no ultra-high-strength concrete composition that has high strength, excellent workability, and effectively suppresses the delay in curing, and further improvement is desired. It was.
JP 2005-132670 A

  An object of the present invention is to provide an ultra-high-strength concrete composition that has high strength, is excellent in workability, and effectively suppresses a delay in curing, and a method for producing the same.

The above problems are solved by the present invention described below.
That is, the configuration of the present invention is as follows.
<1> A cement containing silica fume and a maleic acid surfactant are contained in an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of the cement containing silica fume, and calcium nitrite is added to the maleic acid. An ultrahigh strength concrete composition comprising: an aqueous solution containing 20 to 40% by mass ratio with respect to the solid content of the acid surfactant.

<2> The ultra-high-strength concrete composition according to <1>, wherein the water cement ratio is 10 to 25% by mass.

<3> A cement containing silica fume and a maleic acid surfactant are contained in an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of the cement containing silica fume, and calcium nitrite is added to the maleic acid. An aqueous solution containing 20 to 40% by mass of the solid content of the acid surfactant, and a method for producing an ultrahigh strength concrete composition comprising the calcium nitrite and the maleic acid surfactant And a first step of preparing a mixed solution by mixing caustic soda in an amount necessary for complete neutralization of maleic acid in the maleic surfactant, and a mixed solution obtained in the first step, A second step of mixing water and cement containing the silica fume, and a method for producing an ultra-high-strength concrete composition.

  According to the present invention, it is possible to provide an ultra-high-strength concrete composition that has high strength, is excellent in workability, and effectively suppresses a delay in curing, and a method for producing the same.

The ultra high strength concrete composition of the present invention contains a cement containing silica fume and a maleic acid surfactant in an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of the cement containing silica fume. And an aqueous solution containing calcium nitrite (Ca (NO ₂ ) ₂ ) in a mass ratio of 20 to 40% based on the solid content of the maleic acid surfactant.

  Further, the method for producing the ultrahigh strength concrete composition of the present invention is a method for producing the ultrahigh strength concrete composition of the present invention, wherein the calcium nitrite, the maleic acid-based surfactant, A first step of preparing a mixed solution by mixing an amount of caustic soda required for complete neutralization of maleic acid in the maleic surfactant, the mixed solution obtained in the first step, water, and And a second step of mixing cement containing the silica fume.

Here, although the effect | action of this invention is not necessarily clear, it estimates as follows.
By adding calcium nitrite to the maleic acid surfactant, calcium ions are selectively adsorbed on the sulfate ions contained in the cement, reducing the sulfate ion concentration in the cement paste, and the maleic acid surfactant is effective. In particular, the dispersibility of cement is improved by adsorbing to cement. It is surmised that the improvement of dispersibility improves the fluidity of the concrete composition and improves the workability such as the ease of placing the concrete.

Further, in order to effectively disperse calcium nitrite in the concrete, it is mixed as an aqueous solution as described above. However, it is stored in the atmosphere for a long time in a single solution with a maleic acid surfactant, and the pH of the aqueous solution is When it is less than 7, harmful nitrogen oxides (NO _x ) are generated from calcium nitrite. Therefore, it is preferable to add caustic soda in an amount necessary for complete neutralization of maleic acid in the maleic surfactant. . The amount of caustic soda required for complete neutralization of maleic acid and long-term stable storage is recommended to be twice the number of moles of maleic acid.
In general, when caustic soda is added, the rate of decrease in workability when uncured is increased. Therefore, the action of the present invention in improving workability can be obtained more effectively by using a surfactant having a small number of moles or a surfactant having a low content for obtaining a predetermined plasticity. is there.

  However, when the compounding quantity of calcium nitrite exceeds 40% by mass ratio with respect to the maleic acid-based surfactant, the fluidity of the high-strength concrete composition is lowered and the workability is lowered. In addition, when the blending amount of calcium nitrite is less than 20% by mass ratio with respect to the maleic acid-based surfactant, due to the influence of the quality fluctuation of the concrete composition, the smaller the amount of surfactant used, the more significant in concrete engineering. The difference is not recognized.

  In addition, calcium nitrite reduces the pH of fresh concrete by ion exchange between calcium ions and sodium ions in the gel, and promotes calcium hydroxide elution from cement. It is presumed that this promotes early hydration. Acceleration of hydration suppresses the delay in curing, shortening the work period for construction in low-temperature environments, continuous construction of tower structures, construction in precast concrete factories with a short time span from casting to demolding, etc. Construction is streamlined.

In particular, an ultra-high-strength concrete composition (for example, a concrete composition exhibiting a compressive strength of 100 N / mm ² or more) having a water cement ratio of 10 to 25% by mass is a uniaxial compressive strength (JIS A 1132 and 1108), compressive strength of about 90% of the long-term material age is developed at one week of material age. Therefore, when an optimal amount of calcium nitrite that promotes initial hydration is mixed, the long-term strength does not necessarily decrease, but rather increases.

Furthermore, the ultrahigh-strength concrete composition of the present invention can provide a preferable effect even when steel fibers are mixed.
In concrete compositions containing steel fibers, the surface layer is generally covered with mortar, but the adhesion between the mortar and concrete is incomplete and the service life is short, and the mortar may float, peel or peel off. On the other hand, by containing calcium nitrite, calcium nitrite acts as a rust preventive agent even at a site where mortar float or the like occurs, and rusting can be prevented.

<Ultra high strength concrete composition>
Subsequently, each material which comprises the ultra-high-strength concrete composition of this invention is demonstrated in detail.

・ Calcium nitrite (Ca (NO ₂ ) ₂ )
The ultra-high strength concrete composition of the present invention contains an aqueous solution containing a maleic acid surfactant and calcium nitrite.
In addition, when content with respect to solid content of surfactant exceeds 40% by mass ratio, calcium nitrite will reduce the fluidity | liquidity of a high-strength concrete composition and will reduce workability. On the other hand, when the amount is less than 20%, due to the influence of the quality variation of the concrete composition, a significant difference is not recognized in concrete engineering especially as the amount of the surfactant used is reduced.
Note that the optimum blending amount of calcium nitrite with respect to the surfactant varies depending on other factors such as the water cement ratio and the atmospheric temperature. For example, at an atmospheric temperature of 2 ° C., the water cement ratio is 14% by mass. When the mass ratio is approximately 20%, the water cement ratio is approximately 40% when the mass ratio is 20 mass%. In addition, if the ambient temperature becomes higher, the blending amount of calcium nitrite may be reduced. It is desirable to define.

-Maleic acid type surfactant The maleic acid type surfactant is an essential requirement to use an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of cement containing silica fume described later. And In addition, it is more preferable that the said usage-amount is 1.0-2.5 mass parts further.
When the amount of the maleic surfactant used is less than the above lower limit, (1) the necessary plasticity is not obtained, the workability when uncured is inferior, the quality after curing is reduced, ( 2) All the materials containing calcium nitrite have disadvantages such as that necessary stirring and mixing cannot be performed and uniform quality cannot be ensured. On the other hand, if the above upper limit is exceeded, (1) material separation resistance is not obtained, workability at the time of uncured is inferior, quality after curing is lowered, (2) in order to induce delay in setting of cement There are disadvantages such as an increase in the amount of calcium nitrite mixed to obtain a predetermined performance.

  The maleic acid surfactants are classified as polycarboxylic acid surfactants that are most frequently used in the production of ultra high strength concrete.

Among them, the specific maleic acid type surfactant has a high carboxyl group content and a long side chain length, so it is not easily affected by sulfate ions, specializing in dispersibility and minimizing the amount of calcium nitrite used. It is preferably used from the viewpoint that it can be suppressed to the limit.
The composition of the maleic acid-based surfactant that is suitably used below and an outline of the production process of the surfactant are shown.

1) Reaction mixture (surfactant) obtained through the following step (A) and step (B)
2) Further, one or two or more kinds selected from 1) and 2) of a part of the reaction mixture obtained through the following step (C) or a completely neutralized product.

Step (A): In a non-aqueous system, maleic anhydride and a monomer represented by the following general formula (I) are contained in a total amount of 97 mol% or more in the presence of a non-aqueous radical polymerization initiator, and maleic anhydride A step of initiating a radical copolymerization reaction of a radical polymerizable monomer mixture containing acid / monomer represented by the following general formula (I) = 50/50 to 70/30 (molar ratio).

Step (B): The radical copolymerization reaction started in step (A) is stopped by adding water to the reaction system in the course of the reaction in which the polymerization conversion rate represented by the following formula (i) is 50 to 90%. And a step of obtaining a reaction mixture (surfactant) containing the produced copolymer and the remaining monomer.

Step (C): The reaction mixture obtained in Step (B) is partially or completely neutralized with one or more selected from alkali metal hydroxides, alkaline earth metal hydroxides and amines. Obtaining a part of the reaction mixture or a completely neutralized product.

Formula (I)
_{CH 2 = CH-CH 2 -O} -A-O-R

In general formula (I):
R: a methyl group, an acetyl group or a hydrogen atom A: having a (poly) oxyalkylene group composed of 1 to 150 oxyethylene units or a total of 2 to 150 oxyethylene units and oxypropylene units (poly) Residues obtained by removing all hydroxyl groups from alkylene glycol

Formula (i)
Polymerization conversion rate: {(TM-UM) / TM} × 100

In formula (i),
TM: Total mass of radical polymerizable monomer mixture when starting radical copolymerization reaction in step (A) UM: Total mass of remaining monomer when radical copolymerization reaction is stopped in step (B)

  Step (A) is a step of starting a radical copolymerization reaction of a radical polymerizable monomer mixture in the presence of a non-aqueous radical polymerization initiator in a non-aqueous system. As the radical polymerizable monomer mixture, maleic anhydride and the monomer represented by the general formula (I) are contained in a total of 97 mol% or more, preferably 100 mol%, and maleic anhydride / general formula (I ) = 50/50 to 70/30 (molar ratio), preferably 55/45 to 65/35 (molar ratio).

  In the monomer represented by the general formula (I), examples of R in the general formula (I) include a methyl group, an acetyl group, and a hydrogen atom. Among them, a methyl group and an acetyl group are preferable.

  In the monomer represented by the general formula (I), A in the general formula (I) is 1) (poly) ethylene having a (poly) oxyethylene group composed only of oxyethylene units in the molecule. Residues obtained by removing all hydroxyl groups from glycol 2) (Poly) ethylene (poly) propylene glycol having (poly) oxyethylene (poly) oxypropylene groups composed of oxyethylene units and oxypropylene units in the molecule In the case of 1), a residue in which all hydroxyl groups are removed is preferable. In the case of 2), the bond mode between the oxyethylene unit and the oxypropylene unit may be either a random bond or a block bond, but a random bond is preferred. The number of repeating oxyalkylene units such as oxyethylene units constituting A is 1 to 150, but 15 to 90 is preferable.

  Accordingly, the monomer represented by the general formula (I) includes a polyoxy group in which R in the general formula (I) is a methyl group or an acetyl group, and A is composed of 15 to 90 oxyethylene units. More preferred is a residue obtained by removing all hydroxyl groups from polyethylene glycol having an ethylene group.

  Specific examples of the monomer represented by the general formula (I) described above include 1) α-allyl-ω-methoxy- (poly) oxyethylene, 2) α-allyl-ω-methoxy- (poly) oxy. Ethylene (poly) oxypropylene, 3) α-allyl-ω-acetyl- (poly) oxyethylene, 4) α-allyl-ω-acetyl- (poly) oxyethylene (poly) oxypropylene, 5) α-allyl- ω-hydroxy- (poly) oxyethylene, 6) α-allyl-ω-hydroxy- (poly) oxyethylene (poly) oxypropylene.

  The radical polymerizable monomer mixture used in step (A) contains maleic anhydride and the monomer represented by the general formula (I) in a total of 97 mol% or more, preferably 100 mol%, In other words, other radical polymerizable monomers can be contained within a range of 3 mol% or less. Examples of such other radically polymerizable monomers include styrene, vinyl acetate, acrylic acid, acrylate, alkyl acrylate, (meth) allyl sulfonic acid, (meth) allyl sulfonate, and the like.

  Step (A) is a step of starting a radical copolymerization reaction in a non-aqueous system by adding a non-aqueous radical polymerization initiator to the radical polymerizable monomer mixture described above. Non-aqueous methods for initiating radical copolymerization reaction include 1) a method for initiating radical copolymerization reaction of a radical polymerizable monomer mixture without using a solvent, and 2) benzene, toluene, xylene, methyl isobutyl. A method of starting a radical copolymerization reaction by dissolving a radical polymerizable monomer mixture in such a non-aqueous solvent using a non-aqueous solvent such as ketone or dioxane is preferable, but the method of 1) is preferable. In the method 1), for example, a radical polymerizable monomer mixture is charged into a reaction vessel, and a non-aqueous radical polymerization initiator is added to the reactor in a nitrogen atmosphere, followed by heating to 40 to 60 ° C. to initiate a radical copolymerization reaction. Let Examples of the non-aqueous radical polymerization initiator used in the step (A) include azo initiators such as azobisisobutyronitrile, 2,2′-azobis (4-methoxy2,4-dimethylvaleronitrile), and benzoyl peroxide. , Lauroyl peroxide, cumene hydroperoxide and the like.

  In the step (B), the radical copolymerization reaction started in the step (A) is stopped by adding water to the reaction system in the course of the reaction in which the polymerization conversion represented by the formula (i) is 50 to 90%. In this step, a reaction mixture containing the produced copolymer and the remaining monomer is obtained. In the step (B), the radical copolymerization reaction started in the step (A) is stopped during the reaction in which the polymerization conversion rate represented by the formula (i) is 50 to 90%, preferably 65 to 85%. As a method of stopping the radical copolymerization reaction in the middle of the reaction in which the polymerization conversion represented by the formula (i) is 50 to 90%, preferably 65 to 85%, 1) A part of the reaction mixture from the reaction system Collected at regular intervals, calculated the ratio of copolymer and residual monomer produced by rapid analysis methods such as GPC and high performance liquid chromatography, and calculated the polymerization conversion rate using the obtained numerical value, A method for determining the time for stopping the copolymerization reaction, 2) The relationship between the torque of the stirrer used in the reaction system and the polymerization conversion rate is obtained in advance, and the torque corresponding to the desired polymerization conversion rate is obtained based on this relationship A method for stopping the radical copolymerization reaction over time, 3) A relationship between the radical copolymerization reaction time and the polymerization conversion rate is obtained in advance, and a radical corresponding to a desired polymerization conversion rate is obtained based on the relationship. Stop copolymerization reaction That a method and the like, a method of the 3) degrees of freedom and simplicity of the apparatus is preferred. By using, as a surfactant, a radical copolymerization reaction stopped in the middle of the reaction in which the polymerization conversion represented by the formula (i) is in the range of 50 to 90%, a plurality of performances as described above are simultaneously satisfied. An ultra-high strength concrete composition can be prepared more efficiently.

  The temperature at which the radical copolymerization reaction is started in the step (A) and the temperature at which the radical copolymerization reaction is continued until stopped in the process (B) are not particularly limited, but should be 60 to 90 ° C. Is preferred. In the step (B), the amount of water added to stop the radical copolymerization reaction is not particularly limited, but it is preferably 2 to 10 moles per mole of maleic anhydride as a raw material.

  Thus, in the step (B), a reaction mixture containing the produced copolymer and the remaining monomer is obtained. The formed copolymer contained in the reaction mixture is composed of at least maleic anhydride in the molecule, based on the radical polymerizable monomer mixture subjected to the radical copolymerization reaction in step (A). In order to stop the radical copolymerization reaction by adding water in the course of the reaction in step (B), the unit and the structural unit formed from the monomer represented by the general formula (I). As a result, the structural unit formed from maleic anhydride becomes the structural unit formed from the hydrolyzed form of maleic acid. Similarly, the remaining monomer contained in the reaction mixture is at least maleic anhydride and / or a general formula as long as it is a radical polymerizable monomer mixture subjected to the radical copolymerization reaction in step (A). Although it contains the monomer represented by (I), since the radical copolymerization reaction is stopped by adding water during the reaction in step (B), as a result, maleic anhydride is hydrolyzed. It becomes the decomposed form of maleic acid.

  In the step (B), the molecular weight of the copolymer contained in the reaction mixture is not particularly limited, but the weight average molecular weight by gel permeation chromatography (hereinafter referred to as GPC) is not limited. In the measurement, it is preferable that the weight average molecular weight in terms of peak top pullulan (hereinafter simply referred to as a weight average molecular weight) is in the range of 30000 to 45000. The weight average molecular weight is adjusted by adjusting the type and amount of the non-aqueous radical polymerization initiator used in step (A), and the type and use of the radical chain transfer agent added as necessary in step (A) or step (B). It can be achieved by appropriately selecting the amount, and the temperature and time during the radical copolymerization reaction in steps (A) to (B).

  Step (C) is a step of partially or completely neutralizing the reaction mixture obtained in step (B) with a basic compound to obtain a part of the reaction mixture or a completely neutralized product. Examples of such basic compounds are 1) alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, 2) alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, 3) ammonia, triethanolamine. Amines such as alkali metal hydroxides are preferred.

Among these, the following admixtures (A-1) (A-2) (A-3) obtained through the following steps are preferably used.
Admixture (A-1): A reaction mixture obtained through the following first step and second step.
First step: maleic anhydride and α-allyl-ω-methyl-poly (number of moles of oxyethylene unit: 33, hereinafter n) in the presence of azobisisobutyronitrile in a non-aqueous system without using a solvent Radical polymerization monomer mixture comprising oxyethylene and containing maleic anhydride / α-allyl-ω-methyl-poly (n = 33) oxyethylene = 60/40 (molar ratio) Starting the radical copolymerization reaction.
Second step: The radical copolymerization reaction started in the first step was stopped by adding water to the reaction system in the course of the reaction in which the polymerization conversion rate represented by formula (i) was 83%, and the weight average produced. A step of obtaining a reaction mixture containing a copolymer having a molecular weight of 38000 and maleic acid and α-allyl-ω-methyl-poly (n = 33) oxyethylene as remaining monomers.

Admixture (A-2): A reaction mixture obtained through the following first step and second step.
First step: consisting of maleic anhydride and α-allyl-ω-methyl-poly (n = 68) oxyethylene in the presence of azobisisobutyronitrile in the non-aqueous system without using a solvent and A step of starting a radical copolymerization reaction of a radical polymerizable monomer mixture containing maleic anhydride / α-allyl-ω-methyl-poly (n = 68) oxyethylene = 60/40 (molar ratio).
Second step: The radical copolymerization reaction started in the first step was stopped by adding water to the reaction system in the course of the reaction in which the polymerization conversion rate represented by formula (i) was 78%, and the generated weight average A step of obtaining a reaction mixture containing a copolymer having a molecular weight of 40300 and maleic acid and α-allyl-ω-methyl-poly (n = 68) oxyethylene as remaining monomers.

Admixture (A-3): A reaction mixture obtained through the following first step and second step.
First step: maleic anhydride and α-allyl-ω-methyl-poly (n = 80) oxyethylene-poly (oxy) in the presence of azobisisobutyronitrile in a non-aqueous system without using a solvent. And 5 maleic anhydride / α-allyl-ω-methyl-poly (n = 80) oxyethylene-poly (m = 5) oxypropylene = 55 A step of starting radical copolymerization reaction of a radical polymerizable monomer mixture contained at a ratio of / 45 (molar ratio).
Second step: The radical copolymerization reaction started in the first step was stopped by adding water to the reaction system in the course of the reaction in which the polymerization conversion represented by formula (i) was 68%, and the weight average produced. A reaction mixture containing a copolymer with a molecular weight of 34000 and maleic acid and α-allyl-ω-methyl-poly (n = 80) oxyethylene-poly (m = 5) oxypropylene as the remaining monomers is obtained. Process.

-Silica fume The super-high-strength concrete composition of this invention contains the cement containing a silica fume.
The silica fume used preferably can be used in either powder or granular form. The silica fume preferably contains 80% or more of silicon dioxide by mass and has a specific surface area of 15 to 25 m ² / g by the BET method.
If the content of silicon dioxide is less than 80% by mass, the pozzolanic reactivity is lowered and the strength expression may be inferior. On the other hand, if the specific surface area is out of the above range, the fluidity and kneadability may be lowered regardless of the increase or decrease. Therefore, the material composition suitable for obtaining the predetermined physical properties, particularly the required amount of the surfactant is changed, and a concrete composition suitable for practical use cannot always be obtained.

-Cement As the cement, a cement obtained by mixing the above silica fume with a low heat Portland cement in a dry manner (as a specific example of the product, for example, silica fume cement (manufactured by Mitsubishi Materials Corporation)) is preferable.
Also, (1) extending the stirring and mixing time, (2) increasing the amount of the surfactant used, (3) 5 to 25 parts by mass of the silica fume with respect to 75 to 95 parts by mass (that is, cement and An amount of 100 parts by mass after mixing) Low heat Portland cement can also be used, provided that it is wet mixed in the mixer.
However, since the material composition suitable for obtaining the specified physical properties, particularly the required amount of the surfactant, changes and a concrete composition suitable for practical use cannot always be obtained, the former silica fume is dried with low heat Portland cement. More preferred is a cement mixed in

-Mixing As a method of mixing silica fume with cement, a conventionally well-known method can be used suitably, for example, can be performed based on the method of Unexamined-Japanese-Patent No. 8-91885.

-Water cement ratio Water cement ratio represents the ratio of the total amount of water to the total amount of cement added in the ultra-high strength concrete composition. Here, the silica fume is treated as being contained in the mass part of the cement.
In the ultra high strength concrete composition of the present invention, the water cement ratio is preferably 10 to 25% by mass ratio, and more preferably 10 to 15%. When the water cement ratio is 10% or more by mass ratio, an advantage is obtained that the dispersibility of each constituent material is maintained at the time of stirring for concrete production. On the other hand, when it is 25% or less, there are advantages that the case where curing delay becomes a problem at the time of practical use increases, and the merit of blending calcium nitrite is realized.

Other constituent materials Examples of other constituent materials that can be added to the ultra-high-strength concrete composition of the present invention include steel fibers, fine aggregates, coarse aggregates, antifoaming agents, and organic fibers.

In the ultra high strength concrete composition of the present invention, steel fibers can be mixed. In addition, in concrete mixed with steel fibers, there is a concern that rusting due to the steel fibers may occur, but in the ultrahigh strength concrete composition of the present invention containing calcium nitrite, the rusting can be suitably prevented. it can.
As the steel fibers, for example, steel fibers described in JP-A-5-262544 are suitably used.

Examples of the fine aggregate include river sand, land sand, mountain sand, sea sand, crushed sand, silica sand, and a mixture of two or more kinds of lightweight aggregates. Coarse aggregates include river gravel, gravel. , Crushed stone, and one or two or more mixed products among lightweight aggregates.
In order to obtain high-strength concrete more effectively, it is necessary to select crushed sand and crushed stone optimized for rock type, particle size, particle size, linear expansion coefficient, absolute dry density, water absorption rate, and reactivity.
Especially when the aggregate is not carefully selected, the material composition for obtaining the specified compressive strength changes, so there is a possibility that curing may be delayed, and even when curing delay is improved, significance is recognized in the actual process. May not be possible.

  Examples of the antifoaming agent include aliphatic polyether antifoaming agents, polyether-modified silicone antifoaming agents, etc. Among them, aliphatic polyethers that are inexpensive and have a defoaming effect with a small amount of use. System antifoaming agents are preferred. Examples of the aliphatic polyether antifoaming agent include polyoxyalkylene glycol monoalkyl (or alkenyl) ether obtained by adding ethylene oxide or propylene oxide to an aliphatic alcohol having 16 to 20 carbon atoms.

  Examples of the organic fibers include synthetic fibers such as polypropylene and vinylon. The shape is short fibers such as flat yarn, chopped, strand, and monofilament, and the dimensions are selected within a range of 12 to 200 μm in diameter and 5 to 20 mm in length.

<Method for producing ultra-high strength concrete composition>
Next, the method for producing the ultrahigh strength concrete composition of the present invention, which is suitable as a method for producing the ultrahigh strength concrete composition of the present invention, will be described in more detail.

(First step)
First, in the first step, a mixture is prepared by mixing calcium nitrite, a maleic acid-based surfactant, and caustic soda in an amount necessary to completely neutralize maleic acid in the maleic acid-based surfactant. To do.
The calcium nitrite used in the first step is used in an amount of 20 to 40% by mass ratio with respect to the maleic surfactant. The amount of the maleic surfactant used in the first step is 0.2 to 3.5 parts by mass with respect to 100 parts by mass of the cement containing silica fume mixed in the second step.

Caustic soda In the first step, caustic soda is mixed from the viewpoint of effectively suppressing generation of harmful nitrogen oxides (NO _x ) due to calcium nitrite. The amount of caustic soda required for complete neutralization of maleic acid and long-term stable storage is recommended to be twice the number of moles of maleic acid.

(Second step)
Next, in the second step, the obtained mixed solution is diluted with water, and the cement containing silica fume and other constituent materials are added and mixed to obtain the ultrahigh strength concrete composition of the present invention.
In the above production method, it is preferable to adjust the amount of water added so that the amount satisfies the above-mentioned range of “water cement ratio”. Here, the “amount of water added” in the above production method refers to the amount of water (W1) added for diluting the maleic surfactant when the maleic surfactant is mixed in the first step. This represents the sum of the amount and the amount of the water (W2) added in the second step.

  The other constituent materials described above can be added in the second step. In addition, it is not always necessary to mix in the second step, for example, a concrete composition obtained by mixing and stirring a surfactant containing calcium nitrite and caustic soda, water, cement, fine aggregate, and coarse aggregate, It can be mixed separately after being discharged into a mobile mixer or the like. However, it is preferable to confirm in advance the time during which the plasticity of the concrete composition lasts.

<Manufacture of concrete members using ultra high strength concrete composition>
By using the above-described ultrahigh strength concrete composition of the present invention, an ultrahigh strength reinforced concrete member can be produced by a conventionally known method. Although it does not specifically limit as a method to manufacture a reinforced concrete member, For example, it can apply suitably for manufacture of a precast reinforced concrete member.

As a method for producing a precast reinforced concrete member, for example, a method shown in “Building Construction Standard Specification / Explanation JASS10 Precast Reinforced Concrete Work 2003 (Architectural Institute of Japan)” or the like is preferably applied.
In the method for manufacturing a precast reinforced concrete member, for example, the reinforced concrete member is manufactured by the following procedure.
(1) Manufacture or assembly of formwork for manufacturing parts. Formwork for manufacturing parts by assembling concrete is assembled.

(2) Reinforcing bar installation Reinforcing bars / steel materials, welded wire nets, etc. are installed, and if there is a pre-attached part, the part is attached.
(3) Concrete placement The ultra-high strength concrete composition of the present invention is placed in a mold. In addition, it is important to drive into the mold uniformly and densely, and using a vibrator or the like, it is performed so as not to damage the attached parts.
If necessary, the driven-in surface can be finished by a method such as a brushing finish, a metal iron or a wooden iron presser.

(4) Curing During the period from when the concrete is kneaded until the required strength is reached, keep it at a suitable temperature and humidity, and protect it from harmful vibrations and shocks.
(5) Demolding and lifting The mold is removed so that it is not cracked or damaged, and then the member is lifted by a lifting jig or the like. Then, a concrete member is manufactured through product inspection etc. as needed.
(6) Formwork cleaning and application of release agent Thoroughly clean in order to divert the formwork from which the concrete member has been removed, and apply a release agent on the contact surface between the formwork and the concrete member for smooth removal. Apply.

In precast factories, there are many cases in which the steps (1) to (6) above are repeated on the same production line, and in this case, the curing period until demolding after placing concrete is reduced. Thus, the productivity per unit area of the equipment is improved.
However, in concrete of general strength, in the curing process of (4) above, on the premise of adopting curing accelerated curing by heating, it reaches the strength that can be demolded in a few hours after placing, so there is a delay in curing. There are few cases to be problematic.
On the other hand, in ultra-high-strength concrete, firstly, a large amount of surfactant is used to significantly delay curing, and secondly, long-term strength is significantly reduced when heated initially, so curing by heating is accelerated. Since the curing cannot be adopted, a case where the predetermined strength is reached during the daytime working day the next day occurs, and the above-described productivity improvement effect becomes obvious.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by a following example.

[Example 1]
(Preparation of surfactant 1)
As surfactant 1, the above-mentioned admixture A-1 was prepared.

(Preparation of calcium nitrite-containing surfactant 2)
In addition, calcium nitrite having a ratio relative to the surfactant 1 described in Table 1 below and caustic soda having a mole number twice the moles of maleic acid in the surfactant 1 were made into an aqueous solution. To obtain a surfactant 2.
The content of the surfactant was measured by determining an amount by which a predetermined plasticity was obtained after mixing all the constituent materials of ultra high strength concrete. The predetermined plasticity was defined as a range in which the slump flow obtained by JIS A 1150 was 65 ± 10 cm.

・ Silica fume premix cement (Product name: Silica fume cement, manufactured by Mitsubishi Materials Corporation)
・ Aggregate (crushed stone 2005 and crushed sand, manufactured by Oizumi Crushed Stone Co., Ltd.)
(In addition, the mass of the aggregate shown in Table 1 below is the mass in the surface dry and saturated state defined in JIS A 0203)
Organic fiber (trade name: Daiwabo Polypro (17 dtex, L = 10 mm), manufactured by Daiwabo Polytech Co., Ltd.)

The above materials were mixed in an aqueous solution containing the surfactant shown in Table 1 in the amounts shown in Table 1 to obtain a concrete composition. Table 1 below shows “water cement ratio, calcium nitrite content, surfactant content, air content, and content of each material”.
The sample was produced using a forced biaxial test mixer having a capacity of 100 l in a test room in which the ambient temperature was adjusted assuming winter construction conditions. The stirring time for the water cement ratio of 14% by mass shown in Table 1 below is “30 seconds for empty kneading, 150 seconds for mortar, 90 seconds after feeding coarse aggregate, 60 seconds after feeding fiber”. In addition, the water cement ratio of 20% by mass shown in Table 1 below is “30 seconds for emptying, 90 seconds for mortar, 90 seconds after feeding coarse aggregate, 60 seconds after feeding fiber”.

[Examples 2-5, Comparative Examples 1-2]
In Example 1, “water cement ratio, calcium nitrite content, surfactant type, surfactant content, air content, content of each material” is as shown in Table 1 below. Except for the change, a concrete composition was obtained by the method described in Example 1.

-Evaluation method-
・ Slump flow (Xave)
In accordance with JIS A 1150, the slump flow was measured.
・ 50cm flow arrival time (t50)
Based on JIS A 1150, 50 cm flow arrival time was measured.

In the experimental results described in Table 1, the slump flow is within a range of 65 ± 10 cm in all Examples and Comparative Examples, and the surfactant content in Examples 1 and 2 is Comparative Example. It can be seen that 0.1 to 0.15 parts by mass less than 1, and the surfactant content in Examples 3 to 5 is 0.1 to 0.2 parts by mass less than Comparative Example 2.
In general, in this strength region, the addition of 0.1 part by mass of surfactant corresponds to the required amount for increasing the slump flow by about 10 cm. According to this rule of thumb, the interface in Examples 1 and 2 The content of the activator is a content at which a slump flow smaller than Comparative Example 1 by about 10 to 15 cm is obtained. Similarly, the contents of the surfactants in Examples 3 to 5 are contents that provide a slump flow that is about 10 to 20 cm smaller than that of Comparative Example 2, respectively.
However, even when the surfactant content is 0.1 to 0.2 parts by mass, an equivalent slump flow is obtained, and the calcium nitrite content is 100 parts by mass with respect to the solid content of the surfactant. Although it is paradoxical, it is obvious that the workability is improved even when the amount is blended in a wide range of 20 to 40 parts by mass.

Example 6
・ Silica fume premix cement (Product name: Silica fume cement, manufactured by Mitsubishi Materials Corporation)
・ Aggregate (crushed stone 2005 and crushed sand, manufactured by Oizumi Crushed Stone Co., Ltd.)
(In addition, the mass of the aggregate shown in Table 2 below is the mass in the surface dry saturated water state defined in JIS A0203)
Organic fiber (trade name: Daiwabo Polypro (17 dtex, L = 10 mm), manufactured by Daiwabo Polytech Co., Ltd.)

The above materials were stirred and mixed in an amount shown in Table 2 in an aqueous solution containing a surfactant shown in Table 2 to obtain a concrete composition. Table 2 below describes “water cement ratio, calcium nitrite content, surfactant type, surfactant content, air content, and content of each material”.
The sample was produced using a forced biaxial test mixer having a capacity of 100 l in a test room in which the ambient temperature was adjusted assuming winter construction conditions. The stirring time is 30 seconds for empty kneading, 150 seconds for mortar, 90 seconds after feeding coarse aggregates, and 60 seconds after feeding fibers.
The concrete composition is formed into a cylindrical shape having a diameter of 100 mm and a height of 200 mm, and after subjecting it to a simple thermal insulation curing to the age shown in Table 2 in accordance with JASS5T-705-2005, the compression strength is compared. It was used for.

[Examples 7 to 12, Comparative Examples 3 to 9]
Examples 7 to 12 are concrete compositions obtained by the method described in Example 6.
Comparative Examples 3 to 9 are as described in Example 6 except that in Example 6, the “type of surfactant and the content of surfactant” were changed to those shown in Table 2 below. A concrete composition is obtained by the method.

-Evaluation method-
Compressive strength Uniaxial compressive strength was evaluated according to JIS A 1108.
・ Age Age was determined in units of time for each specimen according to the time from the start of mixing of concrete to the start of the strength test. Significant figures are limited to the first decimal place.
(Note that “Maturity” here is the integrated value of the internal temperature of the concrete, and the starting point is −10 ° C.)

  FIG. 1 and FIG. 2 show the correlation between the age, materiality and compressive strength shown in Table 2.

  In any case where a surfactant containing calcium nitrite was used, the compressive strength was higher than that in the case where surfactant 1 was used, and a curing accelerating effect was confirmed.

Example 13
・ Silica fume premix cement (Product name: Silica fume cement, manufactured by Mitsubishi Materials Corporation)
-Aggregate (crushed stone 2005 and crushed sand, manufactured by Sugiyama Contec Co., Ltd.)
(In addition, the mass of the aggregate shown in Table 3 below is the mass in the surface dry and saturated state defined in JIS A 0203)
Organic fiber (trade name: RCP17dtex (l = 10mm), manufactured by Ube Nitto Kasei)
-Steel fiber (trade name: SFR2-0.6-30, manufactured by Shinko Construction Materials Co., Ltd.)

The above materials were stirred and mixed in an amount shown in Table 3 in an aqueous solution containing a surfactant shown in Table 3 to obtain a concrete composition. Table 3 below lists “water cement ratio, calcium nitrite content, surfactant type, surfactant content, air content, and content of each material”.
Samples were prepared in winter and standard periods using a permanent machine in a factory located in the Chubu region. The mixer is a forced biaxial type and has a capacity of 1 m ³ . The stirring time is 90 seconds with mortar, 90 seconds after feeding the coarse aggregate, 60 seconds after feeding the fiber, and the stirring time as concrete is 150 seconds.

  The concrete composition is formed into a cylindrical shape having a diameter of 100 mm and a height of 200 mm, and is subjected to 20 ° C. water curing for 91 days (“Standard” in Table 3) and simple thermal insulation curing for 91 days (Table Compressive strength was compared for “simple heat insulation” in 3). Specifically, in the open air of winter and standard period, when the prepared sample was subjected to water curing at 20 ° C. for 91 days in accordance with JIS A 1132, simple thermal insulation curing was performed in accordance with JASS5T-705-2005. This is the case for 91 days.

[Examples 14 to 16, Comparative Examples 10 to 13]
In Example 13, except that “Environment (winter, standard period), curing method, type of surfactant, content of surfactant” was changed to that shown in Table 3 below, Example 13 was used. A concrete composition was obtained by the method described.

-Evaluation method-
Compressive strength Uniaxial compressive strength was evaluated according to JIS A 1108.

  In the test in the long-term age of samples prepared in the winter and standard periods, higher compressive strength was obtained when calcium nitrite was blended regardless of the curing method.

It is a graph which shows the correlation with the age and compressive strength in an Example. It is a graph which shows the correlation of Maturity and compressive strength in an Example.

Claims (3)

Cement containing silica fume;
The maleic acid surfactant is contained in an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of the cement containing the silica fume, and calcium nitrite is contained in the solid content of the maleic acid surfactant. An aqueous solution containing 20 to 40% by mass,
An ultra-high-strength concrete composition comprising:   The ultra-high-strength concrete composition according to claim 1, wherein the water cement ratio is 10 to 25% by mass ratio. A cement containing silica fume and a maleic acid surfactant are contained in an amount of 0.2 to 3.5 parts by mass in terms of solid content with respect to 100 parts by mass of the cement containing silica fume, and calcium nitrite is contained in the maleic acid interface. An aqueous solution containing 20 to 40% by mass with respect to the solid content of the activator, and a method for producing an ultra-high strength concrete composition comprising:
A first step of preparing a mixed solution by mixing the calcium nitrite, the maleic acid-based surfactant, and caustic soda in an amount necessary to completely neutralize maleic acid in the maleic acid-based surfactant. When,
And a second step of mixing the mixed solution obtained in the first step, water, and the cement containing the silica fume, and a method for producing an ultra-high strength concrete composition.