JPWO2019093099A1 - Expandable cement admixture, expandable cement admixture slurry, expandable cement concrete using it, and its manufacturing method. - Google Patents

Abstract

An expandable cement admixture containing an expansive material, a setting retarder having an oxycarboxylic acid group, and an alkali metal salt.

Description

The present invention relates to an expandable cement admixture mainly used in the civil engineering and construction industry, an expansive cement admixture slurry, an expandable cement concrete using the same, and a method for producing the same.

Cement is an excellent material that is inexpensive and can form large concrete structures in any shape. Further, by using a cement admixture together, it is possible to improve the strength, durability and aesthetics of the structure. Many cement admixtures have been proposed so far, but the most used admixture for the purpose of reducing cracks in cement concrete and improving bending strength is a cement expander that imparts expandability to concrete.

Examples of the cement admixture that imparts expandability to the concrete structure include free lime-auin-anhydrous gypsum-based expansion material (Patent Document 1) and free lime-calcium silicate-anhydrous gypsum-based expansion material (Patent Document 2). There is. In addition, high-performance expansion materials that can reduce cracks in concrete with a smaller amount of addition than before have also been developed (Patent Documents 3 to 6).

On the other hand, in the ready-mixed concrete factory (ready-mixed concrete plant), the work of adding the expansion material is mainly done manually, and it takes a lot of labor and labor to unload and dismantle, and it is difficult to ship finely. was there. In addition, when the expansion material made of powder is put into the mixer at the ready-mixed plant or directly into the agitator car, the expansion material adheres to the mixer or solidifies, and the expansion material of the powder is sufficient. There is a problem that a pop-up phenomenon occurs in which the particles are not dispersed, lumps are formed, and the particles are partially expanded and broken during curing.

To solve this problem, for example, in Patent Documents 7 and 8, a powder expansion material is used together with water and a dispersant, or water and starch to prepare an expansion material slurry that secures a predetermined workability, and the performance is stable. It has been reported that expanded concrete can be easily obtained.

In Patent Documents 9 to 12, long-term kneading is possible by slurrying the expansion material with a non-aqueous liquid such as a shrinkage reducing agent, no dust is generated, and excellent expansion performance and shrinkage even after kneading. It has been reported that a cement composition showing a reducing effect can be obtained.

In Patent Document 13, by preparing the slurry with the expanding material and the non-aqueous solution to a predetermined viscosity, the expanding material slurry can be directly put into the agitator vehicle and mixed, and the quality is stabilized at the place required at the construction site. It is reported that the expanded and low shrinkage cement concrete can be placed freely.

Special Publication No. 42-21840 Special Publication No. 53-31170 Japanese Unexamined Patent Publication No. 07-232944 JP-A-2002-226243 Japanese Unexamined Patent Publication No. 2005-162564 Japanese Unexamined Patent Publication No. 2008-239392 Japanese Unexamined Patent Publication No. 2004-216739 Japanese Unexamined Patent Publication No. 7-97248 JP-A-2002-348158 JP-A-2002-356355 Japanese Unexamined Patent Publication No. 2003-12351 Japanese Unexamined Patent Publication No. 2003-12352 Japanese Unexamined Patent Publication No. 2016-2655

However, Patent Document 7 describes that in order to obtain concrete having high expandability, it is necessary to add it to concrete that has not hardened within 60 minutes after the step of preparing the expansive material slurry. Therefore, it is necessary to discard the prepared slurry when a trouble occurs. Further, the expansion amount is about 70% when the expansion material slurry is used as compared with the expansion amount when the conventional mixing method is used. Therefore, in order to obtain a predetermined expansion amount, it is necessary to increase the amount of the expansion material used as compared with the current formulation.
Patent Document 8 reports that by using a specific starch, workability can be maintained for several hours even when a slurry is prepared using water. However, regarding the physical properties of the cured product, only the results regarding the presence or absence of pop-out and the effect on the compressive strength are described, and there is no specific description on the effect on the amount of expansion.
In addition, when a hydraulic expansive material is mixed with water, it is clear that the working time retention that retains sufficient working time using the slurry decreases when the ambient temperature rises, but the temperature There is no specific description of the effect of.

On the other hand, Patent Documents 9 to 13 report that it is possible to prepare an expansion material slurry using a non-aqueous solution, and that it exhibits excellent expansion and shrinkage reduction effect. However, non-aqueous solutions are more expensive than water, and there is a problem in terms of price when applied to existing expansion material applications.

From the above, it is an object of the present invention to provide an expandable cement admixture that is excellent in holding time even in a high temperature environment when mixed with water and can produce an inexpensive expandable cement admixture slurry. And. Another object of the present invention is to provide an inexpensive expandable cement admixture slurry having excellent work time retention even in a high temperature environment. Another object of the present invention is to provide an expandable cement concrete containing the expandable cement admixture slurry and a method for producing the same.

As a result of various studies in view of the above circumstances, the present inventors have found that the above problems can be solved when the following expandable cement admixture slurry of the present invention is used together with water to prepare an expandable cement admixture slurry. The present invention was completed. That is, the present invention is as follows.

[1] An expandable cement admixture containing an expansive material, a setting retarder having an oxycarboxylic acid group, and an alkali metal salt.
[2] The expandable cement admixture according to [1], which further contains dextrin.
[3] An expandable cement admixture slurry containing the expansive cement admixture according to [1] or [2] and water.
[4] An expandable cement concrete containing the expandable cement admixture slurry according to [3].
[5] Production of expandable cement concrete in which the expandable cement admixture slurry and the base concrete are mixed and stirred before the viscosity of the expandable cement admixture slurry according to [3] exceeds 9.0 Pa · s. Method.

According to the present invention, it is possible to provide an expandable cement admixture that is excellent in holding time even in a high temperature environment when mixed with water and can produce an inexpensive expandable cement admixture slurry. In addition, it is possible to provide an inexpensive expandable cement admixture slurry having excellent work time retention even in a high temperature environment. Further, it is possible to provide an expandable cement concrete containing the expandable cement admixture slurry and a method for producing the same.
In addition, it becomes possible to freely manufacture expandable cement concrete, which exhibits performance equal to or higher than that of expandable cement concrete obtained by a conventional manufacturing method, only at a place desired to be used at a construction site.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In addition, "part" and "%" in this specification are based on mass unless otherwise specified. In addition, "cement concrete" is a general term for cement paste, mortar, and concrete.

[1. Expandable cement admixture]
The expandable cement admixture of the present embodiment contains an expansion material, a setting retarder having an oxycarboxylic acid group, and an alkali metal salt as essential components, and further contains dextrin and the like. The details will be described below.

(Expansion material)
The expansion material is not particularly limited, and a commercially available product can be used. When kneaded with cement and water, ettringite, calcium hydroxide, etc. are generated by a hydration reaction to expand concrete or mortar. A certain admixture material.

Types of expansion materials include ettringite type, which positively produces ettringite to impart swelling property, lime type, which imparts swelling property by generation of calcium hydroxide, and ettringite / lime type, which is a composite type of both. Can be mentioned. In normal concrete, when using the shrinkage compensation purposes, a standard amount of the unit amount of 20 kg / m ³ lime and ettringite-lime system is divided into expandable member 20 inch in JISA 6202 are preferred, ettringite- Lime-based is more preferred.

The content of the expansive material is not particularly limited because it varies depending on the composition of the concrete, but is usually preferably 3 to 12 parts out of 100 parts of the expansive cement composition composed of the cement and the expansive material, and 5 to 9 parts. More preferred. When the number of parts is 3 or more, sufficient expansion performance can be obtained, and when the number is 12 or less, it is possible to prevent overexpansion and expansion cracks in concrete.
Fineness of expanding material from the surface to obtain a proper slurry viscosity and expansion performance, preferably 2000~6000cm ² / g in Blaine specific surface area, preferably from ^{2500~4500cm 2 / g, 2600~4000cm 2 /} g and more Of these, 2800 to 3600 cm ² / g is more preferable.
The specific surface area of the brain is measured in accordance with "JIS R 5201: 2015 (physical test method for cement)".

The amount of free lime in the expansion material is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40 to 60% by mass. When the amount of free lime is 30% by mass or more, sufficient expansion performance can be obtained with a small amount of addition. The amount of free lime can be determined in accordance with "Cement Association Standard Test Method JCAS I01 (Method for Quantifying Free Calcium Oxide)".

(Caking retardant with oxycarboxylic acid group)
The setting retarder may be any one that delays the setting of cement and has an oxycarboxylic acid group. Examples of the setting retarder having an oxycarboxylic acid group include tartaric acid, citric acid, gluconic acid, malic acid and salts thereof.

The content of the setting retarder is preferably 0.05 to 2.5 parts, more preferably 0.1 to 2.0 parts, still more preferably 0.5 to 1.5 parts with respect to 100 parts of the expanding material. .. By setting the amount to 0.1 parts or more, the working time retention of the expandable cement admixture slurry can be improved, and by setting the amount to 2.0 parts or less, the performance fluctuation of the cement concrete containing the slurry can be changed. Can be prevented.

(Alkaline metal salt)
The alkali metal salt is an alkali metal salt other than the above-mentioned setting retarder having an oxycarboxylic acid group, and those used as a setting adjusting agent for cement can be used. Examples of metal salts of alkali metal salts include hydroxides, carbonates, bicarbonates, nitrates, nitrites, silicates, phosphates, sulfates, sulfites, bicarbonates, thiosulfates, and thiosian acids. Examples include salt. Among these, carbonates or bicarbonates are more preferable from the viewpoint of maintaining workability of the slurry in a high temperature environment. Further, as the alkali metal, sodium and potassium are preferable.

The content of the alkali metal salt is preferably 0.1 to 6.0 parts, more preferably 0.3 to 3.0 parts, still more preferably 0.5 to 1.5 parts with respect to 100 parts of the expanding material. .. In particular, the working time retention of the expandable cement admixture slurry can be improved by setting the amount to 0.3 parts or more, and in particular, the performance fluctuation of the cement concrete containing the slurry is set to 3.0 parts or less. Can be prevented.

(dextrin)
Dextrin, also commonly referred to as modified starch, is usually obtained by hydrolyzing starch. Among them, acid roasted dextrin obtained by adding dilute acid and decomposing it is the most common. However, those obtained by the acid immersion method, maltodextrin obtained by enzymatic decomposition of starch, British gum obtained by acid-free roasting, or starch mixed with water can be heated, or alkaline or concentrated salts can be used. It is possible to use one or more of the pregelatinized starch and the like obtained by rapidly dehydrating and drying the pregelatinized product by adding a solution, as long as the object of the present invention is not substantially impaired. is there.

As the roasted dextrin, there are types such as white dextrin, yellow dextrin obtained by further hydrolyzing white dextrin, and British gum. In this embodiment, white dextrin is preferred. The white dextrin preferably has many branches in the dextrin. When there are many branches, the strength is likely to be developed.

The cold water-soluble content of dextrin at 20 ° C. is preferably 5 to 100%, more preferably 20 to 100%, still more preferably 40 to 100%. By setting the soluble content of dextrin in cold water at 20 ° C. to 5% or more, the working time retention of the expandable cement admixture slurry can be improved.
The cold water-soluble component of dextrin means the amount of dextrin dissolved in distilled water at 20 ° C. Specifically, 10 g of sample dextrin is placed in a 200 ml measuring flask and 150 ml of distilled water at 20 ° C. is placed. The dextrin obtained by adding water, keeping the temperature at 20 ± 1 ° C. for 1 hour without stirring, filtering, and evaporating and drying the filtrate is shown in terms of mass ratio to sample dextrin.

The content of dextrin is preferably 0.2 to 5 parts, more preferably 0.2 to 2.0 parts, and even more preferably 0.5 to 2.5 parts with respect to 100 parts of the expanding material. When the amount is 0.2 parts or more, the workability of the expansion material slurry can be maintained, and when the amount is 5 parts or less, the performance fluctuation of the cement concrete containing the expansion material slurry can be prevented.

[2. Expandable cement admixture slurry]
The expandable cement admixture slurry of the present embodiment contains the expansive cement admixture of the present invention and water.
The amount of water mixed is preferably 30 to 200 parts, more preferably 40 to 100 parts, with respect to 100 parts of the expandable cement admixture. When the number is 30 parts or more, an expandable cement admixture slurry having low viscosity and good handling can be obtained, and when the number is 200 parts or less, an expandable cement admixture slurry in which material separation is suppressed can be obtained. ..

The viscosity of the expandable cement admixture slurry in the present invention is preferably 0.2 to 9.0 Pa · s, more preferably 0.5 to 3.0 Pa · s, from the viewpoint of dispersibility in cement concrete. By setting the viscosity of the expandable cement admixture slurry to 0.2 Pa · s or more, it is possible to prevent input errors due to material separation, and by setting it to 9.0 Pa · s or less, the expandable cement admixture slurry is dispersed. Expandable cement concrete can be obtained.
It is possible to adjust the viscosity of the expandable cement admixture slurry by using a fluidizing agent or a thickener within a range that does not substantially impede the object of the present invention.

Any existing device can be used as a mixing device for mixing the expandable cement admixture and water, for example, a proshare mixer, a radige mixer, a tilting mixer, an omni mixer, a henschel mixer, and a V-type mixer. , And a Nauta mixer, etc. can be used.

[3. Expandable cement concrete and its manufacturing method]
(Expandable cement concrete)
The expandable cement concrete of the present embodiment contains the expandable cement admixture slurry of the present invention.

Expandable cement Examples of cement used in concrete include various Portland cements such as ordinary, early-strength, ultra-fast-strength, low-heat, and moderate-heat, and various mixed cements in which blast furnace slag, fly ash, or silica is mixed with these Portland cements. , Filler cement mixed with limestone powder, blast furnace slow cooling slag fine powder, etc., Portland cement such as environment-friendly cement (eco-cement) manufactured from municipal waste incineration ash and sewage sludge incineration ash. One or more of these can be used.

The expandable cement admixture slurry is mixed with cement or the like so as to be preferably 4 to 18 parts, more preferably 6 to 13 parts with respect to 100 parts of cement. Sufficient expansion performance can be obtained by using 4 or more parts of the expandable cement admixture slurry. Further, when the number of parts is 18 or less, it is possible to prevent overexpansion and expansion cracks in the concrete.

In the present embodiment, in addition to cement, expansive cement admixture slurry, fine aggregate such as sand, and coarse aggregate such as gravel, a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, and slag are used. Foaming agent, thickener, conventional rust preventive, antifreeze, shrinkage reducing agent, coagulation adjuster, clay mineral such as bentonite, anion exchanger such as hydrotalcite, blast furnace granulated slag fine powder, blast furnace slow cooling slag It is possible to use one or more selected from the group consisting of slag such as fine powder and an admixture material such as limestone fine powder in combination within a range that does not substantially impair the object of the present invention.

(Manufacturing method of expandable cement concrete)
In the method for producing expandable cement concrete of the present embodiment, the expandable cement admixture slurry and the base concrete are mixed and stirred before the viscosity of the expandable cement admixture slurry of the present invention exceeds 9.0 Pa · s. To do.
Cement concrete is produced by mixing and stirring the expandable cement admixture slurry and the base concrete. In the present embodiment, before the viscosity of the expandable cement admixture slurry of the present invention exceeds 9.0 Pa · s. , These are mixed and stirred. Mixing after the viscosity exceeds 9.0 Pa · s may cause poor dispersion of the expandable cement admixture slurry. The mixing timing is preferably before the viscosity of the expandable cement admixture slurry exceeds 9.0 Pa · s, and more preferably before it exceeds 3.0 Pa · s.
The viscosity can be measured with a B-type viscometer or the like. Further, in the present specification, the “base concrete” refers to uncured concrete kneaded with water, cement, fine aggregate, coarse aggregate, and a water reducing agent.

The expandable cement-concrete kneading device used to stir the mixed paper is not particularly limited, but a concrete agitator car that can transport concrete to the construction site and mix it at the construction site should be used. Is preferable.

When the expandable cement admixture slurry of the present invention is put into an agitator wheel loaded with cement concrete and stirred at high speed for mixing, the stirring speed is preferably 1 to 60 rpm, more preferably 3 to 30 rpm. Within such a range, an expandable cement admixture slurry in which the expandable cement admixture slurry is sufficiently dispersed can be obtained.

The stirring time in the agitator car is preferably 60 to 180 seconds. By setting the stirring time to 60 to 180 seconds and setting it to 60 seconds or more, cement concrete in which the expansion material slurry is uniformly dispersed can be obtained. Even if it exceeds 180 seconds, no further effect can be expected, which is not preferable from the viewpoint of the load on the agitator vehicle.

Hereinafter, the present invention will be described in detail with reference to Examples.
<Material used>
Water: Tap water cement: Ordinary Portland cement, density 3.16 g / cm ³ , commercially available expansion material A: Denka power-CSA type S, manufactured by Denka, ettringite / lime type, brain specific surface area value 3440 cm ² / g, free lime 49.8% by mass
Expansion material B: Hyperexpan, manufactured by Pacific Materials Co., Ltd., lime-based, brain specific surface area value 3450 cm ² / g, free lime 50.0 mass%
Expansion material C: Denka CSA # 20, manufactured by Denka, ettringite type, brain specific surface area value 2930 cm ² / g, free lime 20% by mass
Fine aggregate: River sand from Himekawa, Niigata Prefecture, particle size: 5 mm below sieve, coarse grain ratio 2.82, specific gravity 2.64
Coarse aggregate: Crushed stone from Himekawa, Niigata Prefecture, maximum grain size 25 mm, coarse grain ratio 6.98, specific gravity 2.62
Caking retarder a: citric acid, commercially available caking retarder b: sodium citrate, commercially available caking retarder c: sodium gluconate, commercially available caking retarder d: tartrate acid, commercially available alkali metal salt I: sodium carbonate, commercially available Product Alkali metal salt II: Sodium bicarbonate, Commercial product Alkali metal salt III: Potassium carbonate, Commercial product Alkali metal salt IV: Sodium nitrate, Commercial product Alkali metal salt V: Sodium sulfate, Commercial product Dextrin i: White dextrin, cold water available Dissolution 81.2%
Water reducing agent: Polycarboxylic acid-based high-performance AE water reducing agent

<Test method>
(1) Working time retention of expandable cement admixture slurry Work the viscosity until the slurry viscosity reaches 9.0 Pa · s in each environment of 20 ° C and 30 ° C by measuring the viscosity using a B-type viscometer. It was evaluated as time retention.
(2) Slump test The concrete slump immediately after kneading was measured in accordance with JIS A1101 "Concrete slump test method".
(3) Compressive strength test The compressive strength of concrete was measured in accordance with JIS A1108 “Concrete compressive strength test method”.
(4) Restraint expansion test (length change rate: ^10-6 )
According to the B method shown in Annex 2 of JIS A6202 "Expansion material for concrete", the rate of change in length at 14 days of underwater curing was measured by a restraint expansion test of concrete.

(Example 1)
<Expandable cement admixture and expandable cement admixture slurry>
A setting retarder, an alkali metal salt, and dextrin were mixed with 100 parts of the expanding material A in the formulation shown in Table 1 below to prepare an expanding cement admixture.
20 parts of the above-mentioned expandable cement admixture and 11 parts of water were mixed in each room at 20 ° C. and 30 ° C. to prepare an expandable cement admixture slurry, and the working time retention of the slurry was evaluated. The results are shown in Table 1.

<Expandable cement concrete>
31 parts of the above-mentioned expandable cement admixture slurry prepared in a room at 20 ° C. was added to 2265.08 parts of base concrete prepared in a room at 20 ° C. and kneaded for 15 minutes, and kneaded again to obtain expandable cement concrete. It was prepared and the slump, compression strength and length change rate were measured. The results are shown in Table 1.
The composition of the base concrete was 288 parts of cement, 158 parts of water, 848 parts of fine aggregate, 968 parts of coarse aggregate, and 3.08 parts of water reducing agent.

From Table 1, by using an expansive cement admixture containing a setting retarder having an oxycarboxylic acid group and an alkali metal salt, the working time retention of the expansive material slurry at 30 ° C. was determined in Experiment No. 1. It increased significantly compared to 1-0 and 1-8. In particular, by setting the content of the alkali metal salt to 0.3 to 3.0 parts, the working time retention of the expansion material slurry is good at 20 ° C and 30 ° C, and the slump (compared to the base concrete) It can be seen that an expandable cement concrete with a small fluctuation in compression strength is obtained.

(Example 2)
<Expandable cement admixture and expandable cement admixture slurry>
An expandable cement admixture was prepared by mixing 0.8 parts of the setting retarder a and 1.0 part of the alkali metal salt I with respect to 100 parts each of the expansion materials A to C shown in Table 2 below. For comparison, only each of the expanding materials A to C was used as an expanding cement admixture.
In each room at 20 ° C. and 30 ° C., 20 parts of the above-mentioned expandable cement admixture and 11 parts of water were mixed to prepare an expandable cement admixture slurry, and the workability retention time of the slurry was evaluated. The results are shown in Table 2.

<Expandable cement concrete>
31 parts of the above-mentioned expandable cement admixture slurry prepared in a room at 20 ° C. was added to the base concrete of Example 1 which was adjusted in a room at 20 ° C. and kneaded for 15 minutes, and kneaded again to obtain the expandable cement concrete. It was prepared and the slump, compression strength and length change rate were measured. The results are shown in Table 2.

From Table 2, regardless of which of the expansion materials A to C is used, the working time retention of the expansion cement admixture slurry is increased by using the expansion cement admixture according to the present invention, and the slump and compression strength are increased. It can be seen that an expandable cement concrete with a small fluctuation in the amount of expansion and showing a good expansion amount is obtained.

(Example 3)
An expandable cement admixture was prepared by mixing 0.8 parts of the setting retarder a and 1.0 part of the alkali metal salt I with 100 parts of the expansion material A. In a room at 20 ° C., 20 parts of the expandable cement admixture and 11 parts of water are mixed to prepare an expandable cement admixture slurry, which is kneaded until the viscosity shown in Table 3 below is reached. The base concrete was loaded and put into an agitator car after 30 minutes had passed.
After adding the slurry, stirring with an agitator car is performed for 120 seconds, and then the first sampling is performed when the discharge amount becomes approximately 1/3 (first half), and then the discharge amount is 2/3 to 3/3 /. A second sampling was performed while the volume was 3 (the latter half), and the slump, compression strength and length change rate were measured.
For comparison, measurements were also performed on the base concrete to which the expandable cement admixture slurry was not added. The results are shown in Table 3.

From Table 3, it can be seen that by using the expandable cement admixture according to the present invention, the expandable material is uniformly dispersed in the base concrete, and the fluctuations in slump and compressive strength are small. In particular, it can be seen that by adding the expandable cement admixture slurry before the viscosity exceeds 9.0 Pa · s, the expandable cement concrete with less slump fluctuation is obtained in the first and second half of the discharge.

The expandable cement admixture, the expandable cement admixture slurry of the present invention, the expandable cement concrete using the same, and the method for producing the same can be suitably used in the fields of civil engineering, construction and the like.

Claims (5)

An expandable cement admixture containing an expansive material, a setting retarder having an oxycarboxylic acid group, and an alkali metal salt. The expandable cement admixture according to claim 1, further comprising dextrin. An expandable cement admixture slurry obtained by mixing the expansive cement admixture according to claim 1 or 2 with water. An expandable cement concrete containing the expandable cement admixture slurry according to claim 3. A method for producing expandable cement concrete, wherein the expandable cement admixture slurry and the base concrete are mixed and stirred before the viscosity of the expandable cement admixture slurry according to claim 3 exceeds 9.0 Pa · s.