JPH1112010A - Concrete admixture, concrete composition and concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an admixture having both excellent slump improving effects (cement dispersibility) and slump loss preventing effects (cement dispersion retention), comprising a copolymer as an essential component prepared by polymerizing monomers composed of each specific amount of an α,β-unsaturated carboxylic acid (salt), a (meth)acrylic acid ester and a (meth)acrylic acid hydroxyalkyl ester. SOLUTION: This admixture comprises a copolymer as an essential component obtained by monomers comprising 40-83 pts.wt. of an α,β unsaturated carboxylic acid (salt) (e.g. methacrylic acid), 10-30 pts. wt. of a (meth)acrylic acid ester which is preferably an acrylic acid ester of a 1-4C alkyl alcohol and 7-50 pts. wt. (the total of the components is 100 pts.wt.) of a (meth)acrylic acid hydroxyalkyl ester containing preferably a 2-4C alkyl group. A hardened material of concrete obtained by using the admixture has excellent compression strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete admixture, a concrete composition and a concrete structure which are excellent in concrete fluidity (referred to as slump), fluid retention (referred to as slump loss prevention), and concrete strength. About.

[0002]

2. Description of the Related Art Conventionally, concrete admixtures have been blended with concrete for various purposes. However, in response to the recent increase in the number of layers and high durability of structures and changes in aggregate conditions, the use of admixtures has been increasing. At present, high performance is required. Add stable air entrainment to concrete,
There have been demands for securing a water reduction rate for high durability and high strength and for preventing slump loss for stabilizing concrete quality.The situation remains the same today, and increasingly advanced levels are targeted. Is coming. Currently used admixtures include lignin sulfonate, naphthalene sulfonate folimarin condensate, melamine sulfonate formalin condensate, amino sulfonate, and polycarboxylate. , Each has its own strengths and weaknesses and is not universal. In recent years, expectations for polycarboxylic acids have been increasing, particularly from the viewpoint of high water reduction and slump loss prevention. Attention has been paid to (co) polymers of vinyl monomers such as acrylic monomers having a carboxylic acid, sulfonic acid or ether structure among polycarboxylic acids.

An example of the disclosed technology is disclosed in
In Japanese Patent Application Laid-Open No. 2-2122252, a slump of concrete with little change with time in dispersibility is obtained by using a monomer containing a sulfone group and a monomer containing a carboxylic acid group as hydrophilic constituent units and further containing a specific amount of a hydrophobic monomer as a hydrophobic constituent unit. It says that the loss has been improved.

In Japanese Patent Application Laid-Open No. Hei 5-213544, slumps and admixtures which are characteristic for preventing slump loss are produced by using an alkylene oxide-added monomer and a carboxylic acid-based monomer. It is said to be useful for improvement and concrete durability.

JP-A-59-162161 discloses a copolymer comprising a monomer having a hydroxyl group such as a monoester of an unsaturated monocarboxylic acid and a glycol and a monomer having a carboxyl group, or a salt thereof. However, it is disclosed that even a very small addition gives excellent concrete fluidity and does not delay the setting of the cement at all.

[0006] The applicant has previously disclosed in Japanese Patent Application Laid-Open No. 63-162563.
As a publication, (meth) acrylic acid esters of α, β-unsaturated carboxylic acids and / or salts thereof and alkyl alcohols having 1 to 4 carbon atoms and, if necessary, other copolymerizable unsaturated monomers A cement dispersant comprising a copolymer of the formula (1) as an essential component has been proposed, and this is also said to have an effect of improving slump and slump loss when added in a small amount.

However, these materials are not sufficiently satisfactory in preventing slump and slump loss. In particular, these additives require an admixture having a high water reduction rate in view of recent social needs and a high level of anti-slump loss effect, and none have been satisfactory.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a concrete admixture, a concrete composition and a concrete structure having a high effect of improving slump and a high effect of preventing slump loss on concrete.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that these problems can be solved by using a copolymer having a specific composition. The present invention has been completed.

That is, the present invention relates to (a) 40 to 83 parts by weight of α, β-unsaturated carboxylic acid and / or its salts in terms of α, β-unsaturated carboxylic acid, and (b) (meth) acrylic acid. 10 to 30 parts by weight of an acid ester, and (c) (meth)
Concrete containing, as an essential component, a copolymer obtained by polymerizing a monomer composed of 7 to 50 parts by weight of a hydroxyalkyl ester of acrylic acid (the total of (a), (b), and (c) is 100 parts by weight). The admixture, preferably the alkyl group of the hydroxyalkyl ester of (meth) acrylic acid (c) has 2 to 4 carbon atoms, preferably the (meth) acrylic acid ester (b) has 1 to 4 carbon atoms. The present invention provides a concrete composition characterized by being an acrylate of an alkyl alcohol and containing these concrete admixtures, and a concrete structure obtained by curing the composition.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. The above-mentioned (a) α, β- used in the present invention.
Examples of the unsaturated carboxylic acid include unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; unsaturated dicarboxylic acids such as itaconic acid, fumaric acid, maleic acid, mesaconic acid, and citraconic acid; and half esters thereof. There is. The salts include alkali metal ions, alkaline earth metal ions, and salts of ammonia and organic amine ions. One or more of these are used and used in an amount of 40 to 83 parts by weight in terms of α, β-unsaturated carboxylic acid. If the amount is less than 40 parts by weight, the effect of preventing slump loss will be poor, and if it exceeds 83 parts, air entrainment to concrete will be poor, which is not preferable.

The (meth) acrylate (b) is preferably an alkyl alcohol having 1 to 4 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, n- (meth) acrylate. -Butyl, iso-butyl (meth) acrylate, t- (meth) acrylate
tert-butyl and the like.
Mixtures of more than one species are used. Its usage is 10-30
Parts by weight. If the amount is less than 10 parts, the effect of improving the slump is poor, and if it exceeds 30 parts, the hydrophilicity of the admixture is impaired and the miscibility with the cement is lacking.

The hydroxyalkyl ester of (meth) acrylic acid (c) preferably has an alkyl group having 2 to 4 carbon atoms, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl ( (Meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-
Chloro-2-hydroxypropyl (meth) acrylate and the like are used, and one or a mixture of two or more thereof is used. The amount used is 7 to 50 parts by weight. If the amount is less than 7 parts by weight, the wettability of the admixture to the cement is poor and the cement dispersibility is poor. If the amount exceeds 50 parts by weight, the effect of preventing slump loss is deteriorated and abnormal air entrainment is not preferred.

As a method for preparing the essential copolymer constituting the concrete admixture of the present invention from the above-mentioned monomers, a radical polymerization method is generally used, and among them, a solution polymerization method is preferable. It is preferable to use water as the polymerization reaction solvent. Solvents other than water are not preferred in terms of harm and danger.

Examples of the radical polymerization initiator include peroxides such as benzoyl peroxide and tert-butylperoxybenzoyl, azo compounds represented by azobisisobutyronitrile, and ammonium persulfate.
It can be appropriately selected depending on the kind of the monomer such as persulfate such as potassium persulfate and sodium persulfate, and the polymerization reaction temperature is usually 50 to 150 ° C. under normal pressure or under pressure. It is preferably carried out at 50 to 100 ° C. under normal pressure.

The concrete admixture containing the copolymer thus obtained as an essential component can be used as it is, but if necessary, part or all of the unneutralized acid groups are further neutralized with an alkaline substance. However, it can be used as an alkali metal salt, an alkaline earth metal salt, or a salt of ammonia or an organic amine.

The concrete admixture of the present invention can be used as a solid or powder, but is usually used as an aqueous solution or dispersion.

The concrete admixture of the present invention may optionally contain the following additional components. Known air entrainers such as alkylbenzene sulfonates, sulfates of higher fatty acid alkylene oxide adducts, and vinsol; lignin sulfonates, polyalkylene glycols, styrene sulfonic acid polymers, styrene sulfonic acids and monoethylenic monomers Copolymer, oxycarboxylate, polyethylene sulfonate, copolymer of α, β-unsaturated carboxylic acid and linear olefin, heavy aromatic hydrocarbon sulfonate, or formalin condensate thereof Publicly known concrete admixtures such as known dispersants, naphthalenesulfonic acid formalin condensate and melaminesulfonic acid formalin condensate; calcium chloride, sodium chloride,
Known cement hardening accelerators such as sodium sulfate, sodium carbonate, potassium carbonate, sodium thiosulfate, and alkanolamine: ligninsulfonic acid, gluconic acid, citric acid,
Known cement setting retarders such as tartaric acid and polyphosphoric acid:
Various agents such as known pastes such as polyvinyl alcohol, starch, methylcellulose and hydroxymethylcellulose; known rust preventives such as sodium nitrite and calcium nitrite can be mentioned.

The concrete admixture of the present invention can be used as a hydraulic cement to form a concrete composition. At that time, the amount of concrete admixture
The admixture of the present invention can be generally added to cement in an amount of from 0.01 to 2% based on the solid content of the copolymer which is an essential component, although it can be varied depending on the use of the concrete and the required performance.
0% by weight, preferably 0.1 to 1.0% by weight, and more preferably 0.1 to 0.7% by weight. If the amount added is less than 0.01% by weight, the dispersibility of the cement is insufficient, and if the amount exceeds 2.0% by weight, the effect level out and the effect is disadvantageous from the viewpoint of economy. .

The hydraulic cement includes, for example, white, early-strength or ordinary Portland cement, alumina cement, various mixed cements and the like. Preferably, it is ordinary Portland cement.

The addition time of the concrete admixture of the present invention may be determined by mixing and dissolving the mixture at the time of kneading water, adding it at the same time as adding the kneading water, or adding to the kneaded concrete composition. An embodiment is possible, and a split addition method in which the mixture is further added once or more may be used.

The concrete composition contains at least cement, fine aggregate and / or coarse aggregate, water and the concrete admixture according to the present invention. In that case, it is preferable that the concrete composition has a water / cement ratio (W / C, a value obtained by dividing the amount of water by the amount of cement) of 55% or less. If it is greater than 55%, the effect of improving slump and slump loss of the present invention will be small.

The concrete structure is not particularly limited as long as it is a structure hardened by using at least the concrete composition. For example, a concrete building, a concrete floor, a bridge, a roadbed, a pile, a fume made of such a composition are exemplified. Tubes and the like.

[0024]

EXAMPLES Hereinafter, the concrete admixture of the present invention will be described in more detail with reference to Reference Examples, Comparative Examples, and Examples. Of course, the present invention is not limited to these examples. In the examples,% is% by weight unless otherwise specified.
And parts are by weight.

Reference Example 1 In a stainless steel reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen gas inlet tube and a reflux condenser, water was used as a polymerization reaction solvent under a radical polymerization initiator.
β-unsaturated carboxylic acid and / or salts thereof were copolymerized with various (meth) acrylic esters and further, hydroxyalkyl esters of (meth) acrylic acid at various ratios shown in Table 1.

The concrete admixture of the present invention is obtained by converting the copolymer thus prepared into a sodium salt.
Table 1 shows the copolymer compositions of the product of the present invention and the comparative product, and Comparative Samples 17 and 18 of the applicant's earlier application (JP-A-63-16 / 1988).
2563) is also shown.

[0027]

[Table 1]

Here, * 1: MAA is methacrylic acid * 2: MMA is methyl methacrylate * 3: HEMA is 2-hydroxyethyl methacrylate.

In the comparative reference examples, BMA means butyl methacrylate, and AA means MA acrylate means methyl acrylate. In addition, No. 16 was not subjected to the subsequent tests due to poor solubility in water.

Examples 1 to 19, Comparative Examples 1 to 9 Samples 1 to 9 of the present invention obtained in Reference Example 1 and obtained in the same manner as in Reference Example 1 (see Table 1), 19 to 28 (Table 4) and Comparative Samples 10 to 18 (see Table 1).
ISA-6204 (1995) Concrete composition is made based on the standard of chemical admixture for concrete. The water-cement ratio (W / C) of concrete is around 50%,
Slump, concrete slump loss (after 1 hour),
The air volume and the 7-day compressive strength ratio were measured.

As other comparative examples, a lignin sulfonate admixture (commercially available, Table 3, A), a naphthalene sulfonate formalin condensate admixture (commercially available, same as B),
The properties described above were measured for concrete using a polycarboxylate-based admixture (commercially available, C) and concrete without additives. Tables 3 and 5 show the obtained results.

The following materials were used for mixing the concrete.

[0033]

The concrete mixing conditions were as follows. Cement amount: 320 kg / m ³ Slump: 18 cm s / a (fine aggregate ratio): 40 to 50%

Air volume: 2% or less for reference concrete (concrete without admixture) Test concrete (concrete with admixture) + 3% for reference concrete

AE agent: An AE agent was not used for the reference concrete, but an appropriate amount of the AE agent was used for the test concrete, and the amount of air was adjusted.

Admixture: For the product of the present invention and the comparative product,
The amount of the solid content was 0.35 parts by weight based on 100 parts by weight of cement. As for a commercially available product, a commercially available undiluted solution is used for cement 100.
1.0 part by weight was used per part by weight.

Table 2 shows an example (1 m ³ ) of the reference concrete containing no admixture.

[0039]

[Table 2]

As can be seen from the results in Table 3, when the fluidity of the concrete is adjusted to a slump of 18 ± 1 cm, the product of the present invention has a higher water reduction rate than the comparative product, the comparative reference product and the commercial product, and has a slump loss. It turns out that it is small. Furthermore, it was recognized that the compressive strength was also excellent from the 7-day strength ratio (%).

[0041]

[Table 3]

[0042]

[Table 4]

Here, * 1: MAA is methacrylic acid * 2: MMA is methyl methacrylate * 3: HEMA is 2-hydroxyethyl methacrylate * 4: MA is methyl acrylate * 5: HEA is 2 -Hydroxyethyl acrylate * 6: HOP means 2-hydroxypropyl methacrylate * 7: HOB means 2-hydroxybutyl methacrylate * 8: 2-EHA means 2-ethylhexyl acrylate.

[0044]

[Table 5]

[0045]

The admixture of the present invention has an excellent slump improving effect (cement dispersibility) and a slump loss improving effect (cement dispersion maintaining effect) by adjusting the hydrophilic component and the hydrophobic component of the copolymer which is an essential component. ) And excellent compressive strength of the hardened concrete, presumably having a structure that does not extremely hinder the hydration reaction of cement.

Claims (5)

[Claims] (1) α, β-unsaturated carboxylic acid and / or
Or 40 to 83 parts by weight of a salt thereof, (b) 10 to 30 parts by weight of (meth) acrylic acid ester, (c) 7 to 50 parts by weight of hydroxyalkyl ester of (meth) acrylic acid ((a), (b), (A total of 100 parts by weight). A concrete admixture comprising, as an essential component, a copolymer obtained by polymerizing a monomer comprising: 2. The concrete admixture according to claim 1, wherein the alkyl group of the hydroxyalkyl ester of (meth) acrylic acid (c) has 2 to 4 carbon atoms. 3. The (meth) acrylic acid ester (b) is
The concrete admixture according to claim 1, which is an acrylate of an alkyl alcohol having 1 to 4 carbon atoms. 4. A concrete composition comprising the concrete admixture according to claim 1. 5. A concrete structure obtained by curing the concrete composition according to claim 4.