JPH03257053A - Cement dispersant - Google Patents

Abstract

PURPOSE:To enhance the slump loss-preventive properties of cement composition by utilizing the oxidative copolymer of both naphthalenesulfonic acid (salt), alkyl naphthalenesulfonic acid (salt) and an aromatic compd. contg. a hydrophilic group as the essential component of a cement dispersant. CONSTITUTION:(a) Naphthalenesulfonic acid, alkyl naphthalenesulfonic acid, formalin condensate thereof or salts thereof arc allowed to react with (b) an aromatic compd. having a hydrophilic group by oxidative polymerization. A slump loss-prevention type cement dispersant is produced by incorporating the obtained oxidative copolymer as an essential component. As the component (b), a benzene derivative and a naphthalene derivative are shown which have one or more kinds of hydrophilic group such as hydroxyl group, carboxyl group, amino group and sulfo group. The oxidative copolymer is obtained by oxidative polymerization reaction due to metallic oxide such as e.g. permanganate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cement dispersant, and more particularly to a water reducing agent and a slump loss inhibitor used in cement compositions such as cement paste, mortar, and concrete. It is.

[Conventional technology]

Various types of cement dispersants are known, but representative ones include β-naphthalenesulfonic acid formaldehyde condensate (hereinafter abbreviated as β-NSF) salt, melamine sulfonic acid formaldehyde condensate salt, and Carboxylate, polycarboxylate, ligninsulfonic acid (
Hereinafter abbreviated as LS) salt is known. These are used when kneading cement compositions, thereby reducing the amount of water used and improving workability.

However, it is known that all of these known dispersants have a common drawback of a significant decrease in fluidity over time (hereinafter referred to as slump loss).

In general, in hydraulic cement compositions, after mixing, chemical and physical aggregation of cement particles progresses over time, gradually losing fluidity and causing workability problems during construction. In particular, concrete to which a high-performance water reducer such as β-NSF has been added is compared to when no concrete admixture is used or when conventional admixtures such as AB agent, water reducer, and AP water reducer are used. , the slump loss is significant due to the high rate of water reduction.

When such a slump loss occurs, for example, when pumping cement composition at a factory for concrete 2-collapsed products (piles, balls, humid pipes, etc.), pumping may be temporarily interrupted due to trouble, and then pumping may be restarted. When the pump is restarted, the pumping pressure may suddenly increase or the pump may become blocked, leading to accidents. Furthermore, if compaction and other forms are delayed due to reasons such as the cement composition being poured into the formwork, problems such as non-filling may occur.

Ready-mixed concrete also suffers from slump loss while being transported from the concrete manufacturing plant to the pouring site by agitator trucks (ready-mix concrete mixer trucks), which can significantly reduce work efficiency, cause blockage of pumps, and cause problems during construction. This may cause problems such as unfilling.

The cause of such slump loss is not clear, but after the cement particles in the cement paste come into contact with water, they agglomerate due to a chemical hydration reaction and/or physical agglomerate due to interparticle attraction. This is presumed to be due to the fact that the fluidity of the cement paste and, by extension, the hydraulic cement composition decreases over time. Therefore, if a water reducing agent that disperses cement particles can be continuously supplied in some way, the cement particles can always be dispersed in the form of primary particles, and slump loss of the hydraulic cement composition can be prevented. It seems possible.

Based on this idea, the following methods have been compared as countermeasures against slump loss.

(1) A method of adding a hardening retarder such as oxycarboxylate or genin sulfonate for the purpose of preventing chemical agglomeration of cement.

(2) A method in which a high-performance water reducing agent or fluidizing agent is added in granular form to prevent physical agglomeration of cement particles.

[Problem to be solved by the invention]

However, in method (1), although chemical aggregation of cement particles is suppressed to some extent, the effect is not sufficient. Furthermore, if a large amount is added to the highly effective mulberry, the initial slump will become too large, which may cause aggregate separation, and will also increase the setting time, which will seriously impede breathing and initial strength. Although the method (2) has a sufficient effect of preventing slump loss, the cement dispersant remains locally in the cement mixture even after the purpose of maintaining slump is completed, causing local bleeding and As a result, negative effects such as a decrease in strength remain.

As described above, each method has its own drawbacks and poses practical problems.

[Means to solve the problem]

The present inventors did not use the method of adding a hardening retarder as in the above method, nor did the dispersant use a solid substance such as powder or granules, but instead used a conventional concrete admixture to prevent slump loss. As a result of research on the method, the present invention was completed.

That is, the present invention consists of a copolymer obtained by oxidative polymerization reaction of (a) naphthalene sulfonic acid, alkylnaphthalene sulfonic acid, or a formalin condensate thereof, or a salt thereof, and (b) an aromatic compound having a hydrophilic group. The present invention provides a slump loss preventing cement dispersant characterized by the following.

Naphthalene sulfonic acid and alkylnaphthalene sulfonic acid, which are raw materials for component (a) of the present invention, include taleosote oil, naphthalene oil, components such as pitch generated in the process of coking coal, or liquefied coal oil containing these components. Sulfonated products such as the following can also be used. Further, a partially unsulfonated compound may be included as naphthalenesulfonic acid or alkylnaphthalenesulfonic acid.

In addition, as the aromatic compound having a parent wood group which is component (ra) of the present invention, benzene derivatives and naphthalene derivatives having one or more types of parent wood groups such as hydroxyl group, carboxyl group, amino group, sulfone group, etc. etc.

The oxidized copolymer in the present invention can be obtained by a known method. For example, oxidative polymerization reactions using metal oxides such as permanganates, oxidative polymerization reactions using oxygen or air using transition metals or metal salts or metal complexes such as vanadium compounds and palladium compounds as catalysts, and oxygen or air polymerization reactions using alkaline catalysts. Examples include oxidative polymerization using air, and oxidative polymerization using hydrogen peroxide or water-soluble peroxides such as persulfates such as ammonium persulfate.

In the oxidative polymerization reaction using a water-soluble peroxide, it is preferable to use metal ions in combination. The reaction conditions are as follows: 100 parts by weight of a mixture of a polymer and an aromatic compound, which are reaction raw materials, and 100 parts by weight of a solvent.
~2000 parts by weight, 0.1 to 20 parts by weight of metal ions are added within a range from room temperature to below the boiling point temperature, and further 5 to 100 parts by weight of peroxide is added dropwise. Although the pH at this time is not particularly limited, it is generally preferred to be on the acidic side.

Through these oxidative polymerization reactions, it is possible to obtain an oxidized copolymer having arbitrary amounts of hydrophilic groups such as hydroxyl groups, carboxyl groups, amino groups, and sulfone groups, which are effective in improving the dispersibility of cement. However, according to the findings of the present inventors, the dispersion effect of the oxidized copolymer into cement changes mainly depending on the amount of hydrophilic groups of the component (a) and the molar ratio of the component (a) to the component (ra) is 9.
It is noticeable in the range of 5=5 to 30:70.

Naturally, even if it is outside this range, the performance as a dispersant is (a)
It has a much superior effect compared to the case of each component alone.

The oxidative polymerization reaction in the present invention is disclosed in Japanese Patent Application Laid-open No. 60-3323 in that two or more types of compounds can be copolymerized.
This is clearly different from the oxidation reactions disclosed in Publication No. 9 and Japanese Unexamined Patent Publication No. 62-202850.

The reason why the oxidized copolymer of the present invention is extremely effective as a slump loss preventing cement dispersant is surmised as follows.

That is, it is known that formalin condensates or formalin copolymers of naphthalene sulfonic acid and/or alkylnaphthalene sulfonic acids, which are constituent components of the oxidized copolymer of the present invention, exhibit high dispersibility. Hydrophilic groups such as hydroxyl groups, carboxyl groups, and amino groups contained in the copolymer are effectively adsorbed onto cement particles, and the sulfone groups present in the oxidized copolymer are aligned outward, providing a high charge to the cement particles. This is thought to prevent slump loss due to charge storage due to the hydration reaction of cement.

Although the cement dispersant of the present invention can be used as an acid, it is preferably used in the form of a salt for boat fishing. Examples of cations that form salts include sodium, potassium, calcium, ammonium, alkanolamines, N-alkyl-substituted polyamines, ethylenediamine, polyethylenepolyamines, and alkylene oxide adducts thereof.

The amount of the cement dispersant of the present invention added is 0.1% by weight of solid content based on the cement in the hydraulic cement composition.
~2.5% is good. If the amount added is less than 0.1%, sufficient dispersion effect and slump loss prevention effect on cement particles cannot be obtained.

Moreover, if the amount added exceeds 2.5%, it may be economically disadvantageous, or the dispersion of cement particles may become excessive, causing breathing or paste separation, or the setting time may increase, resulting in a decrease in initial strength.

The cement dispersant according to the present invention can be added to a cement mixture in the form of an aqueous solution or a powder, and the time of addition is determined by tri-blending with cement, dissolving in mixing water, or at the start of mixing of the cement mixture, i.e. It is also possible to add it at the same time as water is poured into the cement, or immediately after the water is poured into the cement until the mixing of the cement mixture is completed, and it is also possible to add it to the cement mixture that has already been kneaded.

Further, the dispersant of the present invention can be added in its entirety at once, or it can be added in several portions.

In addition, when using a water reducing agent together, add a water reducing agent such as naphthalene sulfonic acid formalin condensate or its salt, lignin sulfonic acid or its salt, melamine sulfonic acid formalin condensate or its salt, or polycarboxylic acid or its salt in advance. They may be mixed together, or one may be blended into the cement or cement mixture, or one may be blended into the cement or cement blend and kneaded before the other is blended.

In addition, other cement additives (materials), such as A8 water reducer, superplasticizer, high performance water reducer, retarder, early strength agent, accelerator,
Foaming agents, foaming agents, antifoaming agents, water retention agents, thickeners, self-leveling agents, waterproofing agents, rust prevention agents, coloring agents, antifungal agents, crack reducing agents, polymer emulsions, other surfactants, water-soluble It is also possible to use it in combination with polymers, expanding agents (materials), glass fiber, fly ash, cylinder ash, clinker ash, husk ash, blast furnace slag, silica fume, silica powder, etc.

〔Effect of the invention〕

Since the present invention makes it possible to maintain the workability of concrete for a long time, the cement dispersant according to the present invention can be used for various purposes.

For example, it is used as a concrete pumping aid. Cement mixtures are often placed by pumping, but as mentioned above, if pumping is temporarily interrupted due to work stoppages, setup changes, or mechanical failures, if the interruption is prolonged, the pumping piping will be damaged. The workability of the concrete inside has decreased, causing problems such as a sudden increase in pumping pressure when pumping is restarted, and blockage.

However, when the cement dispersant according to the present invention is added, the workability of concrete is kept constant, a decrease in fluidity is prevented, and it is possible to prevent a rise in pressure when pumping is resumed after pumping is interrupted. This makes it possible to significantly improve the effectiveness of the pumping operation.

Further examples include grouting aids in cement milk or mortar, cement mixtures cast by tremie tubes, underwater concrete, concrete for continuous underground walls, sprayed concrete, centrifugally formed concrete, vibratory compaction. It is also effective in maintaining the fluidity of concrete and other materials and preventing material separation.

〔Example〕

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

The concrete formulations and materials used in the Examples and Comparative Examples are shown in Table 1 below.

Cement (C): Ordinary Portland cement (specific gravity 3,
17> Fine aggregate (S): Kinoyo sand (specific gravity 2.58. FM2
．． 91) Coarse aggregate (G): Crushed stone from Takarazuka (specific gravity 2.61.
FM6.98) Water (v4) AE agent: Mighty AE-03 (manufactured by Kao ■, trade name) *AE agent was used as necessary.

Method for mixing concrete - 1) Various cement dispersants obtained in the production examples described below were mixed in advance, dissolved in water, and mixed with 50 liters of concrete for 2 minutes using a 100 liter tilting mixer at 20°C. After kneading, the slump and air amount were measured at predetermined times while stirring at a low speed of 4 rpm. Slump test is JIS A
1101, air volume test JIS A 1128, and compression test 1t Jrs A 11081.

(Method-2) Except for adding the cement dispersant separately from the mixing water,
It was carried out in the same manner as method-1.

Production example Naphthalenesulfonic acid (208g), methylnaphthalenesulfonic acid (45g), 98% concentrated sulfuric acid (Log),
Water (50 g) was placed in a 500-flask and heated to 80°C. Next, 37% formalin (14%
0g) was added dropwise over 0.5 hours, and then reacted at 90 to 100°C for 8 hours to obtain a cocondensate. After that, it was made weakly acidic with sulfuric acid, oxybenzoic acid (83g) and ferrous sulfate (8g) were added, and 35% hydrogen peroxide solution (500g) was added at 60°C.
g) was added dropwise over a period of 6 hours, and then aged at 60°C for 30 minutes. After aging, the mixture was neutralized to be slightly alkaline with IJ hydroxide to obtain copolymer 9.

Table 2 shows the composition of the copolymer obtained in the same manner.

The average molecular weights of the cement dispersants in Table 2 are measured by gel permeation chromatography using polystyrene sulfonic acid sodium salt as a reference material.

Examples 1 to 12 and Comparative Example 1.2 A mixing test in concrete was conducted using the copolymers shown in Table 2 as dispersants. Table 3 shows the dispersant, its amount added and the kneading method, and Tables 4 and 5 show the test results.

1) Wt% of cement (solid content) Table 3) Standard curing Table 2) Slump residual rate = (slump value after a certain period of time) / (
Slump value during kneading) . The combination conditions are shown in Table 6, and the test results are shown in Tables 7 and 8.

The kneading was carried out in accordance with Method-1.

4) Sodium lignin sulfonate salt 5) Sodium melamine sulfonate salt From the results in Tables 4, 5, 7, and 8, the cement dispersant of the present invention has a high slump retention rate (slump retention) and initial strength. It is clear that it provides extremely excellent effects in terms of.

Claims (1)

[Scope of Claims] 1. A cement dispersant for preventing slump loss, which contains as an essential component an oxidized copolymer obtained by subjecting a mixture of components (a) and (b) shown below to an oxidative polymerization reaction. (a) Naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, formalin condensate thereof, or salt thereof. (b) Aromatic compound having a hydrophilic group. 2 The hydrophilic group of the aromatic compound is a hydroxyl group, a carboxyl group,
The slump loss preventing cement dispersant according to claim 1, which is one or more functional groups selected from amino groups and sulfone groups. 3. The slump loss preventing cement dispersant according to claim 1, wherein the oxidative polymerization reaction is a reaction using a metal oxide. 4. The slump loss preventing cement dispersant according to claim 1, wherein the oxidative polymerization reaction is a reaction using oxygen or air using a metal or a metal salt as a catalyst. 5. The slump loss preventing cement dispersant according to claim 1, wherein the oxidative polymerization reaction is a reaction using hydrogen peroxide or a water-soluble peroxide. 6. The slump loss preventing cement dispersant according to claim 1, wherein the aromatic compound is benzene or a derivative thereof, or naphthalene or a derivative thereof.