JPS605052A - Cement dispersant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION 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.

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 lignin. Sulfone #/, [hereinafter abbreviated as L8] salt is known.

These are used when kneading cement compositions.

This reduces the amount of water used and improves 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 problems in workability during construction. In particular, concrete added with a tube performance water reducer such as β-NSF is significantly lower than when concrete admixtures are not used or when conventional admixtures such as Ag agents, water reducers, and AE water reducers are used. , the slump loss is significant because the water reduction rate is a factor.

If such a slump loss occurs, 1. For example, when pumping cement composition at a concrete factory, etc., the pumping is temporarily interrupted due to a lunch break or trouble, and then when the pumping is resumed, the pumping pressure suddenly increases. This can lead to accidents such as the pump closing, and if compaction or other forming is delayed for any reason after the cement A compound is poured into the formwork, problems such as sagging can occur. arise.

For ready-mixed concrete, slump loss occurs during the process from the concrete manufacturing plant to the pouring site, resulting in a significant decrease in work efficiency, blockage of pumps, and
This may cause problems such as non-filling during molding. Although the cause of such slump loss is not clear,
After the cement particles in the cement paste come into contact with water, - coagulation due to chemical water-phase reactions and/or physical aggregation due to interparticle attraction occurs, which increases the hardness of the cement paste and thus the hydraulic cement composition. This is thought to be due to a decrease over time, especially when a concrete water reducer (cement dispersant) such as β-NSF4'LS is added.

The water reducing agent adsorbs to the cement particles, increases the zeta potential of the cement particles, and its electrical repulsion can disperse the cement particles and improve the fluidity of the hydraulic cement composition. , Concrete Engineering, Vol. 14, No. 6, pp. 12-19%, March 1976 issue). Over time, the water reducing agent is stored in the precipitated minerals in the aqueous phase of cement, and its electrical repulsion cannot be expected (and the fluidity Therefore, if water reducing agent that disperses cement particles can be continuously supplied in some way,
It is considered that the cement particles can always be dispersed in the form of primary particles, and slump loss of the hydraulic cement composition can be prevented.

The following methods have been discovered as countermeasures against slump loss based on this idea. Namely, 1) the concrete admixture is made into powder or granules, or encapsulated in a carrier, and the active ingredient is gradually released into the system to maintain its effect (for example, JP-A-54-139929).

H) Repeatedly adding concrete admixtures to hydraulic cement compositions by mechanical force (e.g. Japanese Patent Publication No. 51-1
585<S Publication).

etc.

However, in case 1), although the effect of preventing slump loss is well recognized, the cement dispersant remains locally in the cement mixture even after the purpose of maintaining slump has ended, causing local bleeding. generation, and even leave negative effects such as a decrease in strength. Although the effect of preventing slump loss is observed in case U], it is difficult to add concrete admixtures if the concrete after being discharged from the mixer is in the pressure-feeding piping or formwork. In addition, as a measure to prevent slump loss, to suppress chemical coagulation of cement particles,
A method of delaying the initial aqueous phase reaction of cement by adding or combining substances such as oxycarboxylate or genin sulfonate (for example, Japanese Patent Publication No. 52-24533, Japanese Patent Publication No. 52-15855, Japanese Unexamined Patent Application Publication No. 1982-1982) -17918
It has also been found that chemical coagulation of cement particles can be suppressed to some extent by this method, but the effect is not sufficient. Also, in order to increase the effect, the amount added is increased (if this happens, the initial slump will become too large and there is a risk of causing aggregate separation, causing an increase in setting time and causing a major problem in breathing and initial strength.

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

The present inventors have discovered that the dispersant is not in a solid state such as a powder or granules as in method 1) above, and that the dispersant is not mixed by K43A mechanical force as in method I), but in a conventional form. The present invention has been completed by developing a method for preventing slump loss using a chemical agent.

That is, the present invention has as an essential component a compound obtained by polymerizing a formalin cocondensate of components (a) and (b) shown below.
The present invention provides a cement dispersant that prevents slump loss.

(a) One or more compounds selected from the following compounds (1), (2) and (3).

(1) 7talenesulfonic acid or alkylnaphthalenesulfonic acid.

(2) A formalin condensate or co-condensate of one or more of the above (1).

(3) The salt of (1) or (2) above.

(bJ Lignosulfonic acid or its basic invention (a)
As the ingredient 7talenesulfonic acid and alkylnaphthalenesulfonic acid, creosote oil, naphthalene oil, ingredients such as pitch produced in the process of coking coal, or sulfonated products such as coal liquefied oil containing these ingredients can also be used. be done. Further, a partially unsulfonated compound may be included as naphthalene sulfonic acid or alkylnaphthalene sulfonic acid. In addition, (before co-condensing the shun component with formalin, component (a) itself may be subjected to formalin condensation or formalin co-condensation in advance.

As the geninsulfonic acid (bJ acid component) of the present invention, those used as general cement dispersants are used, and among them, those with less air entrainment (and less setting retardation) are preferred.

For this reason, it is preferable to remove sugar content and low molecular weight components by ultrafiltration or the like. These polygenin sulfonic acids include Ohemi cal Admix
turesfor Conoreta(M,R,RIX
OM, E&F, N+5pon Ltd) pages 5-9
Pure lignosulfonate acid with properties similar to the analysis value and molecular weight distribution described on the page is typical. Also, those partially modified by desulfonation may also be used.

A reaction similar to the formalin cocondensation reaction of components (a) and (b) of the present invention is described in Japanese Patent Publication No. 52-24533, and a cocondensate can be obtained by a similar method. However, in Japanese Patent Publication No. 52-24533, desulfonated ligninsulfonic acid obtained by subjecting ligninsulfonic acid to an alkaline treatment such as air oxidation is used as the component (b), but in the present invention, (bJ acid The component genin sulfonic acid or lignin sulfonate can be used without limitation.In particular, when the ratio of component (b) is large, insoluble precipitates are likely to form. It is preferable to remove low molecular weight components by ultrafiltration or the like.The reason for this is that low molecular weight components have many reaction points for the formalin cocondensation reaction and are crosslinked in a five-dimensional manner, resulting in insoluble precipitates. Seem.

The polymerized reaction product of the formalin cocondensation reaction product of components (a) and (b) of the present invention can be obtained by a known method. For example, oxidation reactions using gold bullion oxides such as permanganates under acidic or neutral conditions, oxidation reactions using oxygen or air using transition metals or metal salts or metal complexes such as vanadium compounds or palladium compounds as catalysts, hydrogen peroxide or There are polymerization reactions using water-soluble peroxides such as persulfates such as ammonium persulfate. The structure of these polymerization reaction products is not clear, and various bonds are formed depending on the conditions of the polymerization reaction. The compound of the present invention exhibits an extremely significant slump loss prevention effect by being made into a polymer, so the molecular weight is extremely important. There are various methods for measuring the molecular weight, such as viscosity measurement and gel permeation chromatography, but it is desirable that the viscosity at 20% solids concentration be 25 cmV or more at a temperature of 20C using a B-type rotational viscometer.

The reason why the compound of the present invention is extremely effective as a cement dispersant for preventing slump loss is not clear, but it is thought to be as follows.

That is, it is known that the (aJ acid component) polymeric condensate or formalin cocondensate of the constituent components of the compound of the present invention exhibits high dispersibility, but since the compound of the present invention is polymerized, cement particles It is thought that it effectively adsorbs to cement particles and prevents agglomeration of cement particles due to charge and steric repulsion.Also.

It is thought that the polymerization suppresses charge storage and prevents slump loss.

The ratio of component (a) to component (b) is preferably 957
5-20780, preferably 90/10-25/
It is 75. If this ratio is too large, the polymerization reaction rate will be low, and if this ratio is too small, retardation of coagulation will occur.

Although the cement dispersant of the present invention can be used as an acid, it is generally preferable to use it in the form of a salt. As a cation that forms salt.

Examples of Na include Oa, NH4, alkanolamine, N-alkyl substituted polyamine, ethylenediamine, polyethylenepolyamine, polyethyleneimine, and alkylene oxide adducts thereof.

The amount of 6N added to the cement dispersant of the present invention is 0.2% by weight of solid content with respect to the cement of the hydraulic cement composition.
5 to 2.5 is good. If it is less than 0.25%, sufficient dispersion effect and slump loss prevention effect on cement particles cannot be obtained. Moreover, if it exceeds 2.5%, it may be economically disadvantageous.

Excessive dispersion of cement particles may cause breathing and paste separation.

Although it is most desirable to add the cement dispersant formulation according to the present invention to a hydraulic cement composition in the form of an aqueous solution, the effect of preventing slump loss can also be obtained in the form of a powder or granules. Also, at the time of addition, the compound is mixed and dissolved in water. Add at the same time as kneading water. Cement in powder form added to the kneaded hydraulic cement composition! It is possible to add it to a product, etc. Furthermore, it is also possible to add the dispersant of the present invention in portions at each stage.

In addition to the cement dispersant of the present invention, other cement dispersants, water-soluble polymer compounds, etc. can also be used in combination.

Other cement dispersants include formalin condensates of naphthalene sulfonic acid, lignin sulfonates, formalin condensates of melamine sulfonic acids, and polycarboxylic acid salts.

Among these, polymarine condensates of naphthalenesulfonic acid and ligninsulfonates are particularly preferred. As the lignin sulfonate, Ohemioal Admi
xtures for Ooncrete (M,R,R
IXOM.

Pure lignosulfonate with properties close to the analysis and value 1 molecular weight distribution as described on pages 5 to 9 of ``G&F, N, 5pon Ltd'' is good.

The present invention will be described 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.

Table 1 Cement (0): Ordinary Portland cement (Onoda cement) Fine aggregate (S): Kinokawa me (ratio M 2.58, FM2
．． 91) Coarse aggregate (G): Takarazuka crushed stone (specific gravity 2.61, FM6.9
8) Water (W) (Company) % Mighty Ag-03 (product name manufactured by Kako Soap Co., Ltd.) was added in an appropriate amount, and the method for adding a cement dispersant and the method for mixing concrete were as described in Method 1 and Method 2 below. (It was held at i'J Reka.

Method 1: Mix the cement dispersant in advance, dissolve it in water, and mix it with a tilting mixer at 25C for 40 minutes. Mixed and warmed concrete shown in Table 1 was obtained, and the concrete was further kneaded at a rotational speed of 2 rpm for a predetermined period of time, and changes in slump and air content over time were measured. Measurements of slump, air content, compressive strength, and collection of strength specimens were all carried out in accordance with JIS.Method 2: The same procedure as method 1 was carried out except that the cement dispersant was added at the same time as the mixing water. .

Reference example Naphthalene sulfonic acid (2 oa#), 98% concentrated sulfuric acid (7 oa#)
5#) and water (45g) to 80-90C,
% formalin (155g) into a flask h-180C
Warm to. Next, at 80-90C, 67% formalin (140y) was added dropwise over 0.5 hours, and then reacted at the same temperature for 1 hour, followed by ultrafiltration. A mixture of formalin (85, P) was added in 4 portions at 1 hour intervals until 95-10
The reaction was carried out with stirring at 0C for 18 hours. The formalin cocondensate thus obtained was made into a solution of pf (2) with sodium hydroxide, and polymerized with 60% hydrogen peroxide (15,!i') at 60-70C. The pH was adjusted to 7 with sodium oxide.The viscosity of the resulting product at 20% solids concentration was 260 centiboise (20C
)Met. Table 2 shows the compositions and viscosities of the inventive products and comparative products obtained in the same manner. Examples 1 to 8 and Comparative Examples 1 to 4 A test was conducted on mixing the dispersant into concrete using the dispersant as a dispersant. Test conditions are shown in Table 3.

Tables 4 and 5 show the results of the mixing test for concrete 1.

Table 4 Note Reslump residual rate = (Slump after a certain period of time) / (Initial slump x 1oo (%) Table 5 Note 2) Standard curing (kg / cni2) Tables 4 and 5
From the results shown in the table, it is clear that the product of the present invention has an extremely excellent effect in terms of slump survival rate.

Applicant's agent Kaoru Furutani

Claims (1)

[Scope of Claims] 1. A cement dispersant containing as an essential component a compound obtained by polymerizing a formalin cocondensate of the following components (&) and (b). (aJ) One or more compounds selected from the following compounds (17, (2) and (3). (1) 7talenesulfonic acid or alkylnaphthalenesulfonic acid. (2) One of the above (1) or Two or more types of formalin condensate or co-condensate. (3) Salt of the above (1) or (2). (b) ') Geninsulfonic acid or its salt 2, (a) component and (b The cement dispersant according to claim 1, wherein the polymerization reaction of the cocondensate is an oxidation reaction involving one or more of air, oxygen, or peroxide under acidic or neutral conditions. 5. The cement dispersant according to claim 1, wherein the polymerization reaction of the formalin cocondensate of component (a) and component (b) is a reaction using a metal oxide under acidic or neutral conditions. 4. The cement dispersant according to claim 2, wherein the peroxide is hydrogen peroxide or a water bath peroxide. 5. The viscosity of the polymerized compound at 20% solid content at a temperature of 20C. The cement dispersant according to any one of claims 1 to 4, which has a particle diameter of 25 centivoids or more.6.
The cement dispersant according to claim 1, which is 0/80.