JPH04349160A - Cement admixture - Google Patents

Abstract

PURPOSE:To provide a cement dispersant, especially a water reducing agent, and a slump loss preventive agent. CONSTITUTION:Phenol or its derivative charaterized by using an amino terminator as the essential component and one or >=2 kinds of compds. selected from melamine, its derivative and urea, as required, are copolycondensed with formaldehyde to obtain a cement admixture with the condensate as the essential component. CONSTITUTION:Since the workability of concrete is kept for a long time by this invention, the cement dispersant is used for various purposes. This dispersant is used when the pumping of concrete is suspended or used as the cement milk or mortar grouting assistant. The dispersant is also effectively used to prevent separation of materials and to keep the flowability of the cement formulation placed by a tremie, underwater concrete, concrete in the continuous underground wall, shotcrete, centrifugally formed concrete, vibrated and compacted concrete, etc.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention 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.

0002

[Prior Art] Various types of cement dispersants are known, but a typical one is β-naphthalenesulfonic acid formaldehyde condensate (hereinafter referred to as β-NSF).
(hereinafter abbreviated as LS) salts, melamine sulfonic acid formaldehyde condensate salts, oxycarboxylic acid salts, polycarboxylic acid salts, and lignin sulfonic acid (hereinafter abbreviated as LS) salts are 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, chemical and physical aggregation of cement particles progresses over time after mixing, gradually losing fluidity and causing problems in workability during construction. In particular, concrete to which a high-performance water reducer such as β-NSF has been added is difficult to use when concrete admixtures are not used, or when AE (air entrainment) agents, water reducers, and AE
Compared to when conventional admixtures such as water reducing agents are used, the water reduction rate is high and the slump loss is significant.

[0004] When such a slump loss occurs, for example, when a cement composition is being pumped at a factory for concrete secondary products (piles, balls, fume pipes, etc.), the pumping is temporarily interrupted due to trouble, etc. When the pumping is then resumed, the pumping pressure may suddenly increase or the pump may become blocked, which may lead to accidents. Furthermore, if compaction or other shaping is delayed for some reason after the cement composition is poured into the mold, problems such as non-filling may occur.

[0005] With regard to ready-mixed concrete, slump loss occurs during transportation from the concrete manufacturing plant to the pouring site using an agitator truck (ready-mixed concrete mixer truck), resulting in a significant decrease in work efficiency, blockage of pumps, and problems during construction. This may cause problems such as not filling the tank properly.

The cause of such slump loss is not clear, but cement particles in the cement paste may coagulate due to a chemical hydration reaction after coming into contact with water, and/or
It is speculated that this is because physical aggregation due to interparticle attraction progresses, and 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.

The following methods have been discovered as countermeasures against slump loss based on this concept.

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

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

0010

[Problem to be solved by the invention] However, the above (1)
Although the chemical aggregation of cement particles is suppressed to some extent in the above method, the effect is not sufficient. Furthermore, if the amount added is increased in order to increase the effect, the initial slump loss will become too large, and there is a risk of causing aggregate separation, and the setting time will also increase, which will seriously impede breathing and initial strength. Furthermore, although the method (2) above has a sufficient effect of preventing slump loss, the cement dispersant remains locally in the cement mixture even after the purpose of maintaining slump has been completed, resulting in localized bleeding. occurrence of
As a result, negative effects such as a decrease in strength remain.

[0011] As described above, each method has its own drawbacks and poses practical problems.

0012

[Means for Solving the Problems] The present inventors have proposed a method in which the curing retarder is not added as in the above-mentioned method, and the dispersant is not a solid substance such as powder or granules, but a concrete in a normal form. As a result of research into a method for preventing slump loss using admixtures, the product of the present invention was completed.

That is, the present invention requires phenol or a derivative thereof, and optionally one or more compounds selected from the group consisting of melamine or a derivative thereof and urea, in the presence of an amino polymerization terminator. The following relates to a cement admixture containing a condensate condensed or co-condensed with formaldehyde as an essential component.

The reactivity of the polymerization terminator varies depending on the type and number of functional groups. Suitable types of functional groups include sulfone groups, carboxyl groups, hydroxyl groups, and methoxy groups, with sulfone groups and carboxyl groups being particularly preferred. Furthermore, in consideration of solubility, a sulfone group is most suitable. As for the number of functional groups, one or more usually exhibits a polymerization termination effect, but it is preferable to have one to two in the case of a sulfone group, and two or more in the case of other functional groups.

The mechanism of polymerization termination action is pH 3 to 1.
In the reaction medium of 2, a compound having only an amino group becomes an amino resin, but if the molecule has a functional group such as a sulfone group, carboxyl group, hydroxyl group, or methoxy group, the electron of the nitrogen atom of the amino group This leads to a decrease in density, and the addition reaction of formalin can be suppressed at the stage of the monomethylolation reaction. In the present invention, it is presumed that the polymerization termination effect is exerted due to the reaction selectivity of the above-mentioned amino polymerization terminator.

The amino polymerization terminator is preferably a compound having a sulfonic group such as N-methylsulfonated urea, N,N-dimethylsulfonated urea, sulfamic acid, or an alkali metal salt thereof. Sodium, potassium, lithium, etc. can be used as the alkali metal salt.

[0017]

[Math 1]

The present invention is aimed at controlling the polymerization rate and controlling the Mw/molecular weight distribution of compositions having a weight average molecular weight of 1,000 or more.
An amino polymerization terminator is used as an agent to control Mn to 3.0 or less.

The pH range for producing the formaldehyde condensate or co-condensate of the present invention is from pH 3 to p
A pH range of 12 is suitable, with a pH of 7 to 9 being particularly preferred. Further, in the pH range of 3 to 6, N,N-dimethylsulfonated urea and N-methylsulfonated urea are particularly excellent. If the pH is below 3, the condensation rate of the monomer becomes extremely high, making it difficult to exhibit a polymerization termination effect. On the other hand, p
Since the condensation rate of the monomer is low at H12 or higher, a long time is required to condense the monomer to a predetermined molecular weight.

The weight average molecular weight of the formaldehyde condensate or cocondensate of the present invention is 1,000 to 5.
If it is 0,000, it has sufficient dispersion performance as a dispersant for cement composition, but desirably 3,000 to 2
0,000 is good. Naturally, even if the molecular weight is outside this range, the performance as a dispersant is much better than when the molecular weight is outside the range of 1,000 to 50,000.

The weight average molecular weight (Mw) and number average molecular weight (Mn
) ratio (Mw/Mn) is preferably 3.0 or less. Mw/
If Mn is 3.0 or more, the molecular weight distribution will be too wide and the amount of active ingredient suitable for dispersion will decrease. As a result, the dispersibility deteriorates and the curing time of concrete is delayed.

The amount of formaldehyde used in the production of the condensate or co-condensate is 0.7 to 5.0 moles, preferably 0.9 to 2.0 moles, relative to the total amount of monomers.
5 times the mole is better.

[0023] Regarding the co-condensation of phenol and an amino compound, the method disclosed in JP-A-1-113419 uses an aromatic amino compound, and the method of the present invention is
Compared to N-methylsulfonated urea, N,N-dimethylsulfonated urea and sulfamic acid, the molecular weight per mole is very large, so the present invention is clearly advantageous in terms of the amount of charge per unit weight. Become. As a result, there is a significant difference in terms of dispersibility and dispersion retention.

Regarding the synthesis of formalin condensate using sulfamic acid, it is a co-condensation with melamine and urea, and the amount of charge of the produced condensate is large in the case of the present invention, so it is significantly improved in terms of dispersibility and dispersion retention. There is a difference.

The formaldehyde condensate or cocondensate produced in the present invention can be used as a dispersant as an acid, but it is generally preferable to use it in the form of a salt. Cations formed include sodium, potassium, calcium, ammonium, alkanolamine,
Examples include N-alkyl substituted polyamine, ethylene diamine, polyethylene polyamine, and alkylene oxide adducts thereof.

When the formaldehyde condensate or co-condensate of the present invention is used as a concrete dispersant, the amount added is 0.1 to 2.5% by weight of the solid content based on the cement of the cement composition. good. 0.1
If it is less than %, sufficient dispersion effect for cement particles cannot be obtained. Moreover, if it 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.

[0027] The formaldehyde condensate or co-condensate of the present invention can be added to the cement mixture in the form of an aqueous solution or powder, and the addition timing can be determined by dry blending with cement, dissolving in kneading water, or It is possible to add it at the same time as the start of mixing of the cement mixture, that is, when water is poured into the cement, or immediately after the water injection until the end of the mixing of the cement mixture, and it is also possible to add it to the cement mixture once it has been kneaded. . It is also possible to add the entire amount at once or to add it in several parts.

When a water reducing agent is used in combination, naphthalene sulfonic acid formalin condensate or its salt, lignin sulfonic acid or its salt, melamine sulfonic acid formalin condensate or its salt, polycarboxylic acid or its salt, polyalkyl carbon anhydride It may be mixed in advance with a water reducing agent such as an acid or its salt, or it may be mixed with a water reducing agent such as an acid or its salt, or it may be mixed with a water reducing agent such as an acid or its salt, or it may be mixed with a water reducing agent such as an acid or a salt thereof, or it may be mixed with a water reducing agent such as an acid or its salt, or after blending one with a cement or a cement blend, or after blending one with a cement or a cement blend and kneading the other. May be combined.

Other cement additives such as sustained release dispersants, AE (air entrainment) water reducers, superplasticizers, superplasticizers, retarders, early strength agents, accelerators, foaming agents, foaming agents, etc. agent, antifoaming agent, water retention agent, thickener, self-leveling agent, waterproofing agent, rust preventive agent, coloring agent, antifungal agent, crack reducing agent, polymer emulsion, other surfactants, water-soluble polymer, swelling It is also possible to use it in combination with glass fiber.

The weight average molecular weight of the cement dispersant used in the present invention is a value measured by gel permeation chromatography using polystyrene sulfonic acid sodium salt as a reference material.

[0031]

[Effects of the Invention] By using the cement admixture of the present invention, it has become possible to maintain the workability of concrete for a long period of time, and this cement admixture is specifically used as a dispersant in various applications.

[0032] For example, cement mixtures used as concrete pumping aids are often placed by pumping, but as mentioned above, temporary suspension of pumping due to work lunch breaks, changeovers, or mechanical failures may occur. When an interruption is made, if the interruption time is prolonged, the workability of the concrete in the pressure-feeding piping decreases, causing problems such as a sudden increase in the pumping pressure when the pressure-feeding is restarted, or 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 an increase in pressure when restarting pumping after pumping is interrupted can be prevented. This makes it possible to significantly increase 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, shotcrete, centrifugally formed concrete, vibratory compaction. It is also effective for maintaining the fluidity of hardened concrete and preventing material separation.

[0035]

[Examples] The present invention will be explained below with reference to production examples and examples, but the present invention is not limited to these examples.

Production Example 1 1.0 mol of phenol and 0.9 mol of sulfamic acid were placed in a reaction vessel equipped with a stirrer, and this solution was adjusted to pH 6.2 by adding 40% sodium hydroxide solution and water.
In addition, the solid content concentration was adjusted to 35% by weight. next,
This prepared solution was heated to 90°C and heated to 37°C while stirring.
% formalin are added and the reaction mixture is stirred under reflux for 8 hours. Thereafter, it is cooled to room temperature, the pH is adjusted to 9 by adding a 40% aqueous sodium hydroxide solution, and water is added to adjust the solid content concentration to 25% by weight to obtain a formaldehyde cocondensate.

Table 1 below shows the contents of a condensate produced in the same manner as in this example except that the raw materials (molar ratio) were changed as shown in Table 1.

[0038]

[Table 1]

Production Example 2 1.0 mol of phenol, 0.3 mol of melamine and 1.3 mol of sulfamic acid were placed in a reaction vessel equipped with a stirrer, and this solution was mixed by adding a 40% aqueous sodium hydroxide solution and water. pH to 8.6 and solids concentration to 3.
Adjust to 5% by weight. Next, this prepared solution is heated to 95° C., 2.6 mol of 37% formalin is added while stirring, and the reaction mixture is stirred under reflux for 7 hours. Then, cool to room temperature and
pH 9 by adding 0% sodium hydroxide aqueous solution
Then, water is added to adjust the solid content concentration to 25% by weight to obtain a formaldehyde cocondensate.

Table 2 below shows the contents of the condensate produced in the same manner as in this example except that the raw materials (molar ratio) were changed as shown in Table 2.

[0041]

[Table 2]

Production Example 3 1.2 mol of phenolsulfonic acid, 0.5 mol of catechol and 1.4 mol of N-methylsulfonated urea were placed in a reaction vessel equipped with a stirrer, and 0.1N sulfuric acid and water were added. The solution is adjusted to pH 5.2 and solids concentration to 35% by weight. Next, add this prepared solution to 95%
The temperature is raised to 0.degree. C., 6.2 mol of 37% formalin are added with stirring, and the reaction mixture is stirred under reflux for 12 hours. Thereafter, it was cooled to room temperature, adjusted to pH 9 with a 40% aqueous sodium hydroxide solution, and water was added to bring the solid content concentration to 25% by weight.
A co-condensate with formaldehyde is obtained.

Table 3 below shows the contents of the condensate produced in the same manner as in this example except that the raw materials (molar ratio) were changed as shown in Table 3.

[0044]

[Table 3]

A: Phenolsulfonic acid B: Catechol C: N-methylsulfonated urea Examples and Comparative Examples (Evaluation as a cement admixture) The concrete formulations and materials used in the Examples and Comparative Examples are shown in Table 4 below. It is as follows.

[0046]

[Table 4]

Cement (C): Ordinary Portland cement (specific gravity 3.
17) Fine aggregate (S): Kinokawa sand (specific gravity 2.58,
FM2.91) Coarse aggregate (G): Crushed stone from Takarazuka (specific gravity 2
．． 61, FM6.98) Water (W) Method of mixing concrete Dissolve cement dispersant in mixing water in advance,
After kneading 50 liters of concrete for 3 minutes at 20° C. using a 100 liter tilting mixer, the mixture was rotated 4 times per minute and the slump and air content were measured over time. Slump test is JIS A 1101, air volume test is JIS A112
8.

Table 5 shows the evaluation results obtained.

[0049]

[Table 5]

From the results in Table 5, the cocondensate according to the present invention has a smaller difference in slump value immediately after and after 60 minutes than the conventional dispersant, and has an excellent water reduction effect and a remarkable effect on preventing slump loss. You can see what it shows.

Claims (3)

[Claims] Claim 1: Phenol or its derivatives are essential, and if necessary, one or more compounds selected from the group consisting of melamine or its derivatives and urea are added to formaldehyde in the presence of an amino polymerization terminator. A cement admixture containing a condensate condensed or co-condensed as an essential component. [Claim 2] The amino polymerization terminator has the following general formula (
1 selected from the group of compounds shown in A) and (B)
The cement admixture according to claim 1, which is a compound of more than one species. General formula (A) [Formula 1] Here, Z is hydrogen, an alkyl group having 1 to 3 carbon atoms, -C
selected from H2SO3M, where M means hydrogen or an alkali metal. General formula (B) H2 NSO3 M Here, M means hydrogen or an alkali metal. [Claim 3] The phenol derivative has the following general formula (C
), the melamine derivative has the following general formula (D): The cement admixture according to claim 1. General formula (C) [Formula 2] Here, X3 is selected from the group consisting of hydrogen, an alkyl group having 1 to 3 carbon atoms, a carboxyl group or an alkali metal salt thereof, a sulfone group or an alkali metal salt thereof, a hydroxyl group, and a methoxy group. It will be done. General Formula (D) embedded image Here, X4 is selected from hydrogen, a hydroxyl group, and -CH2SO3M, and M means hydrogen or an alkali metal. X5
is selected from hydrogen, hydroxyl group, -CH2SO3M, and M
means hydrogen or an alkali metal. X6 is selected from hydrogen, hydroxyl group, -CH2SO3M, and M means hydrogen or an alkali metal.