JPH11322391A - Cement dispersant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement dispersant capable of providing the same or higher effects as or than those attained in the addition of a large amount of a cement dispersant as in a conventional case and reducing the change of flow value with time by further raising the water reducing effects of a high-performance cement water-reducing agent and adding a small amount of the water-reducing agent. SOLUTION: This cement dispersant is obtained by mixing a polysulfonate- based cement water-reducing agent which is a polycondensate of a monomer of a sulfonic acid or its salt such as a naphthalenesulfonic acid-formaldehyde condensate or its salt, an alkylnaphthalenesulfonate formaldehyde condensate or its salt, a melamine sulfonic acid formaldehyde condensate or its salt, etc., with a polyalkylene oxide containing a functional group to be adsorbed on cement and having <4,000 weight-average molecular weight, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cement dispersion which further enhances the water-reducing effect of a high-performance cement water-reducing agent, and achieves the same or better effect by using a smaller amount thereof, and reduces the aging of the flow value. Agent.

[0002]

2. Description of the Related Art Conventionally, the strength of concrete is said to depend on the water / cement ratio. In the production of high-strength concrete, a high-performance cement water reducing agent is used to lower the water / cement ratio. High-performance cement water reducing agents are roughly classified into naphthalenesulfonic acid-based condensates, triazine derivative-based condensates, and polycarboxylic acids based on their chemical structural formulas. All of them exhibit high dispersing power and have a low water / cement ratio, but can be kneaded with concrete excellent in workability, and high-strength concrete can be obtained.
However, in view of the price of the water reducing agent and various performances on the product, naphthalene sulfonic acid-based condensates and triazine derivative-based condensates are still used in many cases, and the mortar and concrete before casting obtained by adding these water reducing agents are fluidized. There is a drawback that the conversion loss is large.

[0003] Japanese Patent Publication No. 1-59986 discloses a high-performance cement water reducing agent comprising a mixture of these high-performance cement water reducing agent, polyethylene oxide and oxycarboxylic acid or a salt thereof. However, this technique is a technique for reducing slump loss as a result of the delay effect of oxycarboxylic acid or a salt thereof, and polyethylene oxide has an average molecular weight of 1.1 million or less, preferably 4
The molecular weight range of polyoxyethylene is from 4,000 to 80,000 as estimated from the examples, and the average molecular weight is about 40,000. Used
In addition, the invention pursues a slump loss prevention effect.

[0004] JP-A-5-246744 discloses a concrete composition containing a cement water reducing agent and polyethylene glycol and having excellent filling properties and separation resistance. However, this technology expects concrete filling properties and separation resistance due to the viscosity of polyethylene glycol, so that the weight average molecular weight of the polyethylene glycol used is 6,000 or more. Thus, the prior art uses polyethylene oxide for the purpose of increasing the viscosity of mortar or concrete and reducing slump loss, and as a result, polyethylene oxide having a high degree of polymerization is used.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a polysulfonic acid-based high-performance water reducing agent which is further improved in performance and can achieve high water-reducing performance with a small amount of use. It is an object of the present invention to provide a cement dispersant that has an effect and suppresses a fluidity loss such as a decrease in slump.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. The present invention comprises a formaldehyde condensate of naphthalenesulfonic acid or a salt thereof, a formaldehyde condensate of alkylnaphthalenesulfonic acid or a salt thereof, and melaminesulfonic acid. Polysulfonic acid-based cement water reducing agent, which is a polycondensate of a sulfonic acid such as formaldehyde condensate or a salt thereof, or a polycondensate of a monomer thereof, has a functional group adsorbed on cement, and has a weight average molecular weight of less than 4000, such as polyethylene glycol. Wherein the polyalkylene oxide is blended.

That is, the present inventors have further improved the performance of a cement water reducing agent by blending a low polymerization degree polyalkylene oxide having a weight average molecular weight of less than 4000, and the same or less than the conventional water reducing agent by adding a smaller amount of water reducing agent. The fact that more water reducing effect is exhibited was found. In order to further improve the performance of the polyalkylene oxide, unlike a conventional fluidization loss reduction effect, a low-polymerized product is preferable, and a high-polymerized product reduces the water-reducing effect.

[0008] The polyalkylene oxide is further improved in performance because the polyalkylene oxide having a functional group adsorbed on the cement is adsorbed on the cement prior to or simultaneously with the polysulfonic acid-based cement water reducing agent. It is considered that the reason is that the adsorption to the cement is delayed, and these water reducing agents are deactivated without being effectively utilized in the initial hydration reaction with the cement. Based on this consideration, by adding a polyalkylene oxide containing a functional group capable of reacting with cement at the terminal or in the structure, a polysulfonic acid-based cement water reducing agent having an effective cement water reducing performance in mortar water immediately after mixing. The condensate is left, and the polysulfonic acid-based water reducing agent deactivated by the initial hydration reaction with the cement is reduced to effectively contribute to the water reducing action.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polysulfonic acid-based cement water reducing agent in the present invention is a polycondensate of a monomer comprising sulfonic acid or a salt thereof. That is, a condensate of naphthalenesulfonic acid formaldehyde or a salt thereof, a condensate of alkylnaphthalenesulfonic acid formaldehyde or a salt thereof, a polycondensate of a monomer having a sulfonic acid group such as a condensate of melaminesulfonic acid formaldehyde or a salt thereof, or a salt thereof. Can be mentioned. Specifically, as trade names, Mighty 150 (manufactured by Kao Corporation), Paul Fine 51
0-AN (manufactured by Takemoto Yushi Co., Ltd.), Sunflow PS (manufactured by Sanyo Kokusaku Pulp Co., Ltd.), Denka FT-500 (manufactured by Denki Kagaku Kogyo Co., Ltd.), Leo Build NL-1440 (manufactured by NMB Co., Ltd.), Seacare S, and the like. The brand name of the melamine sulfonic acid type water reducing agent is Rheobuild NL-400.
0, Denka FT-3S, Sekament FF, Neoactor MS and the like.

Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, polybutylene oxide and the like, and polyethylene oxide is generally used. A copolymer of ethylene oxide and propylene oxide is also used, but the oxyethylene group accounts for 50 mol% or more, preferably 70 mol% or more of all oxyalkylene groups so as not to impair hydrophilicity. The polyalkylene oxide used in the present invention has a weight average molecular weight of 106 or more and less than 4000, preferably 150 or more and 3000 or less. Weight average molecular weight of 4
If it exceeds 000, the water reducing effect of the cement water reducing agent is not sufficiently exhibited.

[0011] The functional group for the cement means that if one or both terminals of the polyalkylene oxide remain -OH group, the polyalkylene oxide is adsorbed to the cement which still has activity. -O
The H group may be in the middle rather than at the end. Further, the object of the present invention is achieved even with a functional group other than -OH group such as an amino group and a carboxyl group.

The ratio of polyalkylene oxide to water reducing agent is 1:99 to 50:50, preferably 3:97 to 40:
60. 1: 9 polyalkylene oxide ratio
If it is less than 9, the effect of adding the polyalkylene oxide is not obtained, and if it exceeds 50:50, the water reducing effect of the water reducing agent is reduced, and the flow value is greatly reduced with time. The amount of the water reducing agent used is 0.1 to 2.0%, preferably 0.5 to 1.5% based on the cement. The addition amount of the polyalkylene oxide is 0.02 to 0.2% based on the cement.

In general, it is known that the post-addition of the cement water reducing agent has a greater water reducing effect than the simultaneous addition. Simultaneous addition is to knead a mortar or concrete by mixing and mixing a water reducing agent in water. Post-addition is a method of adding a cement water reducing agent during kneading of mortar or concrete with mixing water. As a method for adding the condensate of sulfonic acid or a salt thereof and the polyalkylene oxide, there are a method of mixing both and adding them simultaneously or afterward, and a method of adding them separately. In the method of separately adding, the effect of the present invention can be obtained by adding the polyalkylene oxide before the condensate of sulfonic acid or a salt thereof.

[0014]

Examples 1 to 9 and Comparative Examples 1 to 8 (1) Mortar Mixing and Materials Used Water / cement ratio = 35%, fine aggregate cement ratio = 1.7 cement: Chichibu Onoda Portland cement fine aggregate: Oikawa product A component: Polyethylene glycol having hydroxyl groups at both ends. The number after-after A is a value indicating the weight average molecular weight. Component B: A 40% by weight aqueous solution of sodium naphthalenesulfonate formaldehyde condensate was used, and the indication was converted to a solid content.

(2) Test Conditions A mixer was used at 20 ° C. as a mixer to be used, using a kneader described in JIS R 5201 Cement Physical Test Method. The surface dry fine aggregate and the cement were mixed at a low speed for 10 seconds, the whole amount of kneading water in which the cement dispersant was dissolved was added, and the mixture was kneaded at a low speed for 30 seconds. The kneading was stopped for 30 seconds, and scraping was performed during that time. The mixture was again mixed at a low speed for 150 seconds.

(3) Test method and test results The flow value is determined by using the flow table described in the physical test method of cement in JIS R 5201, and the direction in which the spread of the mortar when the mortar is packed and pulled up vertically is recognized as the maximum. And the direction perpendicular thereto, and expressed as an average value. The time-dependent flow value was measured by covering with a compress and leaving it to stand for a predetermined time, and then turning over. The air volume is JIS A 117
4 was measured. 2.4 to 2.8 immediately after mixing
%, And 2.2 to 2.6% after 60 minutes. Compressive strength: 4 × 4 × 16 cm specimen, mortar stuffed with a stick,
It was measured according to IS R5201. The results are shown in Table 1. From Table 1, it can be seen that the flow value was remarkably increased according to the present example, the decrease was small even after a lapse of time, and good results were obtained without adversely affecting the compressive strength.

[0017]

[Table 1]

Examples 10 to 12 and Comparative Examples 9 to 11 Experiments were carried out in the same manner as in Example 4 except that the water / cement ratio was 30%. The addition method of the polyethylene glycol and the water reducing agent was simultaneously added and post-added, and the concentration of the water reducing agent dissolved in the mortar solution was measured. The results are shown in Table 2. Simultaneous addition is a method in which a cement dispersant component is kneaded and dissolved in water and added, and post addition is kneaded with 90% kneading water, leaving 10% of the kneading water as secondary addition water. After 90 seconds, the cement dispersant component was dissolved.
% Of secondary added water is mixed and measured. Method for measuring component A: The concentration of polyethylene glycol having a weight average molecular weight of 2,000 dissolved in a mortar solution is measured by LC / MS (APCI method). And the residual amount% was determined with the concentration added and dissolved in the kneading water being 100%. Method for measuring component B: The water reducing agent component, sodium naphthalenesulfonate formaldehyde condensate, was set to a concentration of 100% dissolved in mixing water, and the concentration dissolved in the mortar solution was measured at a wavelength of 228 nm using a spectrophotometer. It measured, and calculated | required the water reducing agent residual amount%.

The component B, that is, sodium naphthalenesulfonate formaldehyde condensate has a water-reducing effect by adsorbing on cement at a rate of 80%, and the other is a simple or low-condensate of sodium naphthalenesulfonate which is not adsorbed on cement (Ando) Et al., Cement concrete, 430,
30, 1982). Therefore, the remaining amount of the cement water reducing agent 2
0% indicates that the substance having a water reducing action in the mortar solution has been completely consumed. According to Table 2, in the present invention, about half of the component A is adsorbed on the cement, and the remaining amount of the water reducing agent composed of the sodium component of the naphthalene sulfonate condensate of the component B is larger immediately after mixing than in the comparative example. It is supposed that the water reducing effect is increased by suppressing the adsorption, and the remaining water reducing agent in the mortar liquid has the same effect as the effect of re-adding the water reducing agent, and it is supposed that the deterioration with time of the fluidity is suppressed.

[0020]

[Table 2]

Examples 13 to 16 and Comparative Examples 12 to 13 Tests were carried out in the same manner as in Examples 1 to 5 except that sodium melamine sulfonate formaldehyde condensate was used as the component B. Table 3 shows the results. As is clear from Table 3, even when a sodium melamine sulfonate formaldehyde condensate is used as the water reducing agent, the flow value increases, the flow value decreases little with time, and the compressive strength is not adversely affected. The result was obtained.

[0022]

[Table 3]

[0023]

According to the present invention, the effect of increasing the water reducing effect of the cement water reducing agent can be obtained by adding a small amount of the water reducing agent to the same effect as when a large amount of the water reducing agent is added. Can be done.

Claims (4)

[Claims] A polysulfonic acid cement water reducing agent which is a polycondensate of a monomer comprising sulfonic acid or a salt thereof,
It has a functional group that adsorbs to cement and has a weight average molecular weight of 4
A cement dispersant comprising less than 000 polyalkylene oxide. 2. The polysulfonic acid-based cement water reducing agent is a naphthalene sulfonic acid formaldehyde condensate, a salt of naphthalene sulfonic acid formaldehyde, an alkyl naphthalene sulfonic acid formaldehyde condensate, a salt of an alkyl naphthalene sulfonic acid formaldehyde condensate, or a melamine sulfonic acid formaldehyde condensate 2. The cement dispersant according to claim 1, wherein the dispersant is at least one member selected from the group consisting of a product and a melaminesulfonic acid formaldehyde condensate. 3. The cement dispersant according to claim 1, wherein the polyalkylene oxide is polyoxyethylene oxide. 4. A polysulfonic acid cement water reducing agent which is a polycondensate of a monomer comprising sulfonic acid or a salt thereof,
It has a functional group that adsorbs to cement and has a weight average molecular weight of 4
A cement dispersant mixed with a polyalkylene oxide of less than 000 is added with or after mixing with kneading water, or has a functional group adsorbed on cement before adding a polysulfonic acid-based cement water reducing agent, and has a weight average molecular weight. Is 40
Use of a cement dispersant characterized by adding less than 00 polyalkylene oxide.