JPH08217504A - Cement admixture - Google Patents

Abstract

PURPOSE: To prevent the lowering of fluidity with the lapse of time and to improve the water reducing property by using the copolymer of three kinds of specified monomers as the main components. CONSTITUTION: 30-90mol% monomer shown by formula I [R<1> is H or methyl, and M is H, alkali (earth) metal, -NH4 or amino compds., 10-70mol% monomer shown by formular II and 0.01-10mol% monomer shown by formula III ((n) is 2 to 6, and X is an alcohol residue having >=2 hydroxyls) are radical- copolymerized in solvent at 0-100 deg.C in the presence of a polymerization initiator and a chain transfer agent to obtain a cement admixture consisting of the copolymer having 1,000-200,000 mol.wt. This cement admixture is used by 0.01-2 pts.wt. for 100 pts.wt. of cement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture which is added to cement compounds such as cement, mortar and concrete to enhance water reducing property and prevent deterioration of fluidity with time.

[0002]

2. Description of the Related Art Conventionally, in the fields of civil engineering and construction,
A large amount of cement, mortar, concrete, etc. are used. Admixtures called dispersants, water reducing agents, superplasticizers, etc. are usually added to these for the purpose of improving workability.

Further, in recent years, with the increase in the number of structures and the lengthening of bridges, concrete moldings having high strength have been demanded. In order to meet such demands, a high-performance water reducing agent that reduces the water-cement ratio is required. On the other hand, when working with concrete, etc., from the viewpoint of workability, in order to reduce labor and improve efficiency,
After being prepared in the ready-mixed plant, it is often transported to the construction site by a mixer truck and placed as it is. Therefore, there is a need for a cement admixture having an effect of preventing slump loss that retains sufficient fluidity of the preparation during transportation without lowering its fluidity.

[0004] In order to satisfy the requirements for the improvement of water reduction and the effect of preventing slump loss, many studies have been made in the past. For example, an amide 95 of an α, β-unsaturated monocarboxylic acid and a sulfonic acid containing a primary or secondary amino group
~ 5 mol% and α, β-unsaturated monocarboxylic acid 5-95
Addition copolymers or salts thereof composed of mol% have been proposed. (JP-A-60-171256) A copolymer of acrylamidopropanesulfonic acid, (meth) acrylic acid and (meth) acrylic acid ester has been proposed.
(JP-A-62-30648)

[0005]

[Problems to be Solved by the Invention] However, the above 2
While some classes of agents show effective potency, they still have deficiencies in their overall properties as cement admixtures. Specifically, although the above-mentioned agents are excellent in terms of the effect of improving the water-reducing property, they are insufficient for the prevention of slump loss, and the above-mentioned agents are effective for preventing the loss, but the water-reducing property is low. Is not sufficient to improve. As described above, the fact is that a drug having both the effects of improving water reduction and preventing slump loss has not yet been obtained.

The present invention has been made in view of such circumstances, and an object thereof is to provide a cement admixture excellent in both improvement of water reduction and prevention of slump loss.

[0007]

In order to achieve the above object, the cement admixture of the present invention comprises the following (A) to (A):
A cement admixture containing, as a main component, a copolymer having a component (C) as a main raw material, wherein the molecular structure of the copolymer is a structural unit derived from the component (A), ) The ratio of structural units derived from the component is (A) /
(B) = 30 to 90 mol% / 10 to 70 mol%,
The structural unit derived from the component (C) is 0.01 to 10 mol% based on 1 mol of the total amount of the components (A) and (B).
Of the copolymer, and the molecular weight of the copolymer is set in the range of 1,000 to 200,000.

(A) A monomer represented by the following general formula (1).

[0009]

[Chemical 4]

(B) A monomer represented by the following general formula (2).

[0011]

Embedded image

(C) A monomer represented by the following general formula (3).

[0013]

[Chemical 6]

That is, the inventors of the present invention conducted a series of studies to obtain a drug which is excellent in both improvement of water reduction and prevention of slump loss, which has never been achieved. As a result, when a copolymer prepared by copolymerizing the monomers consisting of the components (A) to (C) in a specific ratio is added to the cement mixture, the water reducing property is improved and the fluidity is decreased with time. The inventors have found that it is possible to prevent (prevent slump loss) and have reached the present invention. The cement in the cement admixture of the present invention includes not only ordinary hydraulic cement but also hydraulic materials other than cement such as gypsum.

Next, the present invention will be described in detail. The cement admixture of the present invention comprises three types of monomers A to C.
The main component is a terpolymer obtained by using the components. In the present invention, the term “main component” is intended to include a case where the main component is included.

The component (A) is a monomer represented by the general formula (1), and specifically, acrylamidomethanesulfonic acid, acrylamidoethanesulfonic acid, acrylamidopropanesulfonic acid, 2-acrylamido-2-methyl. There are propane sulfonic acid, methacrylamide methane sulfonic acid, methacrylamide ethane sulfonic acid and salts thereof. Examples of the salt include alkali metal salts such as potassium and sodium, alkaline earth metal salts such as calcium and magnesium, ammonium salts, amine salts such as methylamine and ethanolamine.

The component (B) is a monomer represented by the general formula (2), and specific examples thereof include acrylic acid, methacrylic acid and salts thereof. As the salt, the same salts as those used for the monomer (1) can be mentioned.

The component (C) is a monomer represented by the general formula (3), specifically, an ester of a polyhydric alcohol having 2 to 6 hydroxyl groups and acrylic acid or methacrylic acid. As the polyhydric alcohol having 2 to 6 hydroxyl groups, for example, ethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, polyglycerin, pentaerythritol, sorbitol, sucrose, diethanolamine, Examples include triethanolamine, trimethylolpropane, and oxyethylene adducts and oxypropylene adducts thereof. Ethylenediamine, polyethylene polyamine oxyethylene or oxypropylene adducts, and alkylphenol forma Oxyethylene or oxypropylene adduct of emission condensate may also be mentioned. Of these, those having 2 to 4 hydroxyl groups are preferable.

In the polyhydric alcohol, in the case of an oxyethylene / oxypropylene adduct, the number of moles added is an integer of 1 to 50 per 1 active hydrogen in each case.

The above components (A) and (B) are (A) /
It is necessary to copolymerize (B) = 30 to 90 mol% / 10 to 70 mol%. If it deviates from this range, the water-reducing property will be inferior.

The component (C) must be copolymerized in a proportion of 0.01 to 10 mol% based on 1 mol of the total amount of (A) and (B). If it is less than 0.01 mol%, the slump loss will occur. The prevention effect is weak, and if it exceeds 10 mol%, gelation occurs.

The terpolymer which is the main component of the admixture of the present invention is obtained by polymerizing the above three components (A) to (C) by a known method, and is generally synthesized by radical polymerization. To be done. That is, it is usually obtained by polymerizing in a solvent using the above three components, a polymerization initiator and a chain transfer agent.

Examples of the solvent include water, lower alcohols such as methanol, ethanol and isopropyl alcohol,
Examples thereof include ketones such as acetone and methyl ethyl ketone, hydrocarbons such as benzene, toluene, xylene, n-hexane and cyclohexane, and ethyl acetate. Among them, water or lower alcohol is preferably used from the viewpoint of solubility of the monomer and the copolymer.

The above-mentioned polymerization initiator is not particularly limited and conventionally known ones, alkali or ammonium persulfates, azo compounds such as azobisisobutyronitrile, hydrogen peroxide, benzoyl peroxide and lauroyl. Examples thereof include peroxides such as peroxides, and a polymerization initiator suitable for the above reaction system may be appropriately selected.

The reaction temperature in the above-mentioned polymerization reaction step is appropriately set depending on the kind of the polymerization initiator, the solvent, etc.
Usually, it is performed in the range of 0 to 100 ° C.

The terpolymer thus obtained is
It is necessary to set the molecular weight in the range of 1,000 to 200,000.
From the viewpoint of water reduction, the molecular weight is preferably 5,000 to 70,000. That is, when the molecular weight is out of the above range, the dispersibility is lowered, and the required water reducing property and fluidity cannot be obtained. In order to adjust the setting to the above-mentioned specific molecular weight, it is possible to carry out by adjusting the concentration or reaction temperature of the reaction system, but generally, the molecular weight is specified by using a chain transfer agent such as mercaptans or sodium hypophosphite. Control within range. Further, in the cement admixture which is the above terpolymer, each of A to
The polymerization form of the C component may be alternating polymerization, block polymerization, random polymerization, or any polymerization form.

The molecular structure of the terpolymer thus obtained is such that its constitution is derived from the raw materials (A) to (C), and each of the derived structural units is The ratio is the same as the above-mentioned mixing ratio (weight ratio) of each component in the copolymer.

In the cement admixture of the present invention, the above terpolymer can be used alone. However, other than this copolymer, other conventionally known cement admixtures can be appropriately used in combination as required. May be. Examples of the conventionally known cement admixture include naphthalene sulfonic acid formalin condensate, sulfonated melamine resin, lignin sulfonic acid, sulfanilic acid formalin condensate and the like. Furthermore, AE
Agents (air entraining agents), air amount regulators, setting retarders, setting accelerators, etc. These may be used alone or in combination of two or more.

The cement admixture of the present invention can be used not only in hydraulic cements such as Portland cement, alumina cement, blast furnace cement, fly ash cement, silica cement and silica fume cement, but also in water other than cement such as gypsum. It can also be used for hard materials and the like.

The cement admixture of the present invention can exert its effect even if it is mixed in a relatively small amount.
With a compounding amount of 0.01 to 2 parts, preferably about 0.1 to 1.5 parts, relative to 100 parts by weight of cement (hereinafter abbreviated as “part”), improvement of water reduction and slump loss can be prevented. Preventive effect is exhibited. Therefore, a concrete product having a high strength can be obtained by improving the water reduction property.

Although it is not clear why the admixture of the present invention exerts excellent water-reducing property in a small amount and at the same time exerts an excellent effect in preventing slump loss, the water-reducing property of the admixture is the same as the component (A). The component (B) mainly plays its role,
It is considered that the slump loss prevention is effective by crosslinking these structures with the component (C).
The component (C) has an ester bond in its structure, which gradually hydrolyzes in concrete,
The structure is suitable, and the apparent amount of the admixture is gradually increased. Therefore, it is considered that the dispersion effect also increases with time and slump loss can be prevented.

[0032]

As described above, the cement admixture of the present invention contains, as a main component, a copolymer obtained by copolymerizing the monomers consisting of the components (A) to (C) in a specific ratio. It is a thing. Therefore, when this is added to the cement mixture, the water reducing property is improved, and further, the deterioration of the fluidity over time can be prevented (slump loss prevention). Therefore,
When the concrete admixture of the present invention is used to produce a concrete product from a concrete raw material, labor is reduced, work efficiency is improved, and a high-strength concrete product can be obtained.

[0033]

EXAMPLES Next, examples will be described together with comparative examples. However, the present invention is not limited to the embodiments.

Example 1 A glass reaction vessel equipped with a thermometer, a stirrer, a nitrogen introducing tube and a reflux cooling tube was charged with 2-acrylamido-2-methylpropanesulfonic acid 103.
5 parts (0.5 mol), methacrylic acid 43 parts (0.5 mol), polyethylene glycol (MW200) diacrylate 3 parts (0.01 mol) and water 180 parts were charged and completely dissolved, and the system was filled with nitrogen. Replaced. System at 50 ℃
Heat to 4.5 and add β-mercaptopropionic acid to 4.5.
(3 wt% relative to the monomer), an aqueous solution of 0.9 part of azobisamidinopropane hydrochloride dissolved in 5 parts of water was charged, and the mixture was reacted for 6 hours under a nitrogen stream. 40% N after reaction
Neutralization was performed with 100 parts of an aOH aqueous solution to obtain a desired terpolymer.

[Examples 2 to 12] and [Comparative Examples 1 to 3]
Table 1 shows the types of the components A to C which are the respective monomers, the compositions of these three components, and the amount of β-mercaptopropionic acid. A copolymer was obtained in the same manner as in Example 1 except these.

A 40% NaOH aqueous solution is added in an amount equivalent to the acid component of the monomer, and azobisamidinopropane hydrochloride is 0.2% of the total amount, and the water content is 40% in the solid content. I set it appropriately and prepared it.

[Conventional Example 1] 20/60/20 of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, methacrylic acid sodium salt, and methyl acrylate
(Parts by weight) A copolymer (MW1000) was used as an admixture.

[0038]

[Table 1]

Using each of the examples, comparative examples and conventional examples thus obtained as a cement admixture,
A concrete raw material was prepared. The material of the concrete raw material is shown below, and the mixing ratio thereof is shown in Table 2 below.

Cement: Normal Portland cement (manufactured by Nippon Cement Co., Ltd.) Fine aggregate: Aichigawa, specific gravity 2.65, coarse grain ratio 2.96 Coarse aggregate: Aichigawa, specific gravity 2.70, coarse grain ratio 6 .77

[0041]

[Table 2]

Then, the above cement admixture and concrete raw material were weighed so that the mixing amount was 50 liters, and all materials were put into a forced kneading mixer.
Then, the mixture was immediately kneaded for 2 minutes (19 rpm), the whole amount was discharged from the mixer, and the slump and the air amount were measured. This value is the value immediately after kneading. Then, the entire amount of concrete is returned to the tilting mixer, and low speed (4-5 r
pm) and agitated for a predetermined time, and then subjected to a slump measurement test. The results are shown in Tables 3 and 4 below. The elapsed time was based on the point after kneading for 2 minutes.
Further, the compressive strength and setting time of the product obtained from this concrete raw material, the addition amount of the cement admixture and the concrete temperature are also shown in Tables 3 and 4 below.

The slump, the amount of air, the compressive strength, the concrete temperature and the setting time were measured and tested according to the following methods.

Slump: According to JIS A1101. Air volume: According to JIS A1128. Compressive strength: The test piece was manufactured according to JIS A1132.
The measurement test conformed to JIS A1108. Concrete temperature: Measured with an alcohol thermometer. Setting time: According to ASTM C403-79T.

[0045]

[Table 3]

[0046]

[Table 4]

From the results shown in Tables 3 and 4, it can be seen that the products of all Examples are superior in compressive strength and slump loss prevention effect to the conventional examples and comparative examples. From these facts, it is understood that the example products exhibit excellent effects both in terms of water reduction and prevention of slump loss.

Claims (1)

[Claims] 1. A cement admixture containing as a main component a copolymer comprising the following components (A) to (C) as main raw materials, wherein the molecular structure of the copolymer is the component (A). The ratio of the structural unit derived from (A) / (B) = 30 to 90 mol% / 1
It is 0 to 70 mol%, and the structural unit derived from the component (C) is set to occupy 0.01 to 10 mol% with respect to 1 mol of the total amount of the components (A) and (B), In addition, a cement admixture characterized in that the molecular weight of the above copolymer is set in the range of 1,000 to 200,000. (A)
A monomer represented by the following general formula (1). Embedded image (B) A monomer represented by the following general formula (2). Embedded image (C) A monomer represented by the following general formula (3). Embedded image