JP3203505B2 - Method for improving fluidity, admixture thereof and cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the fluidity of cement paste, mortar or concrete (hereinafter referred to as a cement composition), an admixture thereof and a cement composition. The method and the admixture of the present invention are applied to the production of concrete and concrete products in general civil engineering and building structures.

[0002]

2. Description of the Related Art In recent years, with the diversification of needs for building structures, high-strength concrete and high-fluidity concrete have been actively used. In such concrete, it is necessary to balance both fluidity and material separation resistance at a high level. Generally, the material separation resistance is adjusted by the water cement ratio or the water powder ratio, and the fluidity is adjusted by the addition amount of an organic admixture such as a high performance water reducing agent or a high performance AE water reducing agent. . However, depending on the type and amount of the organic admixture and the quality of the cement, there is a problem that the slump (flow) loss at which the fluidity decreases with time increases. Recently, high-performance AE water reducing agents, which are mainly used, have a function of retaining slump of concrete. Therefore, although the degree of slump loss is smaller than that of concrete using a superplasticizer, a decrease in fluidity is still unavoidable. . Even if the initial fluidity is good, if the fluidity is significantly reduced within one hour, the time required for the construction cannot be secured, which is not suitable for practical use. Therefore,
It is required that the slump loss is as small as possible.

[0003] In addition to high-performance water reducing agents and high-performance AE water reducing agents, the addition of mineral powder such as fly ash and blast furnace slag has also increased the fluidity. Limestone powder has also been used. However, when a mineral powder such as limestone powder is added, the fluidity immediately after kneading is improved, but the problem of slump loss is still not solved. Fluctuations in fluidity over time are largely due to the complex interaction between cement or powder and an organic admixture such as a high-performance AE water reducer, and simply blending an inorganic admixture such as fly ash into a slump. It is difficult to reduce losses effectively.

[0004]

SUMMARY OF THE INVENTION The present invention solves the conventional problems of fluidity of cement compositions such as mortar and concrete, and a method of improving fluidity for effectively suppressing slump loss. And its admixture and cement composition.

That is, the present invention relates to the following method for improving fluidity of a cement composition. (1) To the cement, together with the mineral powder, the total SO _{3 in the} powder
A method for improving fluidity, characterized by increasing the fluidity of a cement composition and reducing slump loss by adding hemihydrate gypsum or soluble anhydrite in an amount of 1.5 to 3.5% by weight. (2) The mineral powder is limestone powder, and the cement 100
The fluidity improving method according to (1), wherein 5 to 150 parts by weight of limestone powder and 0.02 to 40 parts by weight of gypsum hemihydrate or soluble anhydrite are added to parts by weight. (3) and limestone powder with a specific surface area of 2000~30000cm ² / g, the use of the hemihydrate gypsum or soluble anhydrite having a specific surface area 3000~12000cm ² / g (1) or (2) flow improvers methods described. (4) The method according to any of the above (1) to (3), wherein the hemihydrate gypsum or the soluble anhydrous gypsum and the mineral substance powder are individually or preliminarily mixed and added during or before kneading of the cement composition. How to improve liquidity.

The present invention also relates to the following admixture for cement. (5) An admixture for cement, which comprises hemihydrate gypsum or soluble anhydrite as a main component together with mineral powder, and improves the fluidity and slump loss of a cement composition. (6) The mineral powder is limestone powder, and limestone powder 10
0.5 parts by weight of hemihydrate gypsum or soluble anhydrous gypsum 0.5
The admixture for cement according to the above (5), containing up to 25 parts by weight. (7) and limestone powder with a specific surface area of 2000~30000cm ² / g, using hemihydrate gypsum or soluble anhydrite having a specific surface area 3000~12000cm ² / g cement admixture as described above (6).

Further, the present invention relates to the following cement composition. (8) To the cement, together with the mineral powder, the total SO _{3 in the} powder
A cement composition characterized by improving flowability and slump loss by adding hemihydrate gypsum or soluble anhydrite in an amount of 1.5 to 3.5% by weight. (9) Limestone powder 5 to 100 parts by weight of cement
The cement composition according to the above (8), comprising 150 parts by weight and 0.02 to 40 parts by weight of hemihydrate gypsum or soluble anhydrite. (10) A cement composition comprising a cement and the admixture for cement described in any of (5), (6) or (7) above.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to examples. The fluidity improving method, the cement composition, and the cement admixture according to the present invention suppress a decrease in fluidity due to a temporal change of the cement composition by using gypsum together with a mineral powder. The type of cement to which the present invention is applied is not limited, and any general-purpose cement such as ordinary Portland cement or mixed cement can be used. As gypsum, hemihydrate gypsum or soluble anhydrous gypsum (type III anhydrous gypsum, hereinafter simply referred to as soluble anhydrous gypsum) having a high dissolution rate is suitable, and hemihydrate gypsum and soluble anhydrous gypsum may be used in combination. In the present invention, hemihydrate gypsum or soluble anhydrous gypsum includes a case where it is used alone and a case where it is used in combination. Fly ash or limestone powder can be used as the mineral powder. Among them, fly ash tends to reduce air entrainment, but limestone powder does not have such disadvantages, and has very low reactivity with cement, which impairs fluidity by reaction with cement components. Is particularly preferred because of its low content. By the presence of mineral fine powder of moderate particle size in the cement, a more preferable particle size distribution as a powder is obtained,
The fluidity of concrete and the like is improved.

[0009] These limestone powders and gypsum are not limited in their origin, mineral type and production method. Gypsum hemihydrate may be preliminarily used as gypsum hemihydrate or soluble anhydrite, or gypsum is used, and after mixing, or during mixing and pulverization, or after pulverization, this is hemihydrated or soluble dehydrated. It may be something. Further, the limestone powder and the gypsum may be individually pulverized into powder, or may be preliminarily mixed and pulverized with limestone and gypsum.

When the gypsum and limestone powder are added to cement to improve the flowability of the cement composition, the mixing method is not limited. Gypsum and limestone powder may be individually added to cement, or gypsum and limestone powder may be mixed in advance and added to cement. The timing of addition to the cement is not limited, and may be added at the time of kneading the cement composition or may be added before kneading. When gypsum and limestone powder are mixed and used, a cement admixture obtained by mixing these in advance may be used.

[0011] Limestone powder may have a particle size of a specific surface area 2000~30000cm ² / g, preferably about 3000~12000cm ² / g.
The gypsum preferably has a specific surface area of about 3000 to 12000 cm ² / g. The admixture of the present invention contains the above-mentioned limestone powder and gypsum as main components.
2000~30000cm ² / g is the appropriate, preferably 3000 to 1200
About 0cm ² / g is good. If the specific surface area of the admixture is less than 2000 cm ² / g, the number of coarse particles as small as fine aggregate increases, which is not preferable.
On the other hand, if the particle size exceeds 30,000 cm ² / g, the effect of increasing the fluidity of mortar or concrete cannot be sufficiently obtained. By using limestone powder having an appropriate particle size range, the fluidity during kneading can be increased.

Gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum)
Is suitably used in such an amount that the total amount of SO ₃ becomes 1.5 to 3.5% by weight in the powder of the cement composition (total of cement and admixture). If the amount of gypsum is less than this, the effect of reducing slump loss is small. On the other hand, if the amount of gypsum is larger than this, the fluidity immediately after kneading is greatly reduced, and the slump flow becomes too small, which is not suitable for practical use. In addition, in order to set the total SO ₃ amount of the cement composition powder to which the amount of gypsum and limestone powder is added to the above range, the amount of hemihydrate gypsum or soluble anhydrous gypsum is considered in consideration of the amount of gypsum previously contained in cement. The usage amount can be adjusted.

The amount of limestone powder used is preferably 5 to 60% by weight in the cement composition, that is, 5 to 150 parts by weight based on 100 parts by weight of cement. Although less than 5 parts by weight of limestone powder can be used, the effect of increasing the fluidity of the limestone powder is reduced. On the other hand, limestone powder is 6
Even if it exceeds 0% by weight, it can be used, but if it is too much, the amount of cement in the powder becomes too small, curing is delayed, strength is too low, etc., so that it is not suitable for practical use.

In order to adjust the contents of gypsum and limestone powder in the cement composition to each of the above ranges by using an admixture composed of limestone powder and gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum), Plaster for 100 parts by weight
An admixture containing 0.5 to 25 parts by weight (mainly hemihydrate gypsum or soluble anhydrous gypsum) is preferred. If the amount of the gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum) is less than 0.5 part by weight, it is difficult to obtain a desired slump loss reduction effect. If a large amount of such an admixture is used until the required amount of gypsum is obtained, the amount of limestone powder added becomes excessive, and the amount of cement becomes relatively small, which is not practical. In addition, plaster amount is 2
The admixture in excess of 5 parts by weight is the total SO in the cement composition.
_When used in a range not exceeding ₃ amounts, the amount of limestone powder is reduced, and a sufficient fluidity improving effect cannot be obtained.

Generally, the usable amount of the admixture is several percent.
From about 60% by weight. 70-80% by weight in cases such as concrete mix where the unit powder amount is extremely large
May also be used. When the amount of the admixture used is as small as 5 to 10% by weight of the total powder, the admixture preferably contains about 15 to 25 parts by weight of hemihydrate gypsum or soluble anhydrous gypsum. Is about 10 to 20% by weight, it is suitable to contain about 2 to 10 parts by weight of hemihydrate gypsum or soluble anhydrous gypsum. When the amount of the admixture is larger than this, for example, when it is 30% by weight or more, it is suitable to contain 10 parts by weight or less of hemihydrate gypsum or soluble anhydrous gypsum.

[0016]

By adding limestone powder to the cement composition, the fluidity of mortar, concrete, etc. is improved. Therefore, it is possible to reduce the amount of water and the use of admixtures such as a high-performance AE water reducing agent in these compositions. it can. Here, simply reducing the amount of water increases the amount of powder per unit volume of concrete and increases the cost, so if there is no problem in strength or properties, it is more appropriate to adjust the amount of the high-performance AE water reducing agent than the amount of water. preferable. However, since the high-performance AE water reducing agent has a function of retaining a slump of concrete, a slump loss increases when the amount used decreases.

Therefore, the present invention provides a method for improving the fluidity immediately after kneading by adding limestone powder by using gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum) together with limestone powder to improve the slump loss. Solved the problem of increasing The use of hemihydrate gypsum or soluble anhydrite for such a purpose has not been known at all. Usually, when hemihydrate gypsum or soluble anhydrous gypsum is present in cement, hemihydrate gypsum or soluble anhydrous gypsum hydrates immediately after water injection and dihydrate gypsum rapidly precipitates, resulting in reduced fluidity. It is known to lead to false setting. For this reason, conventionally, in the cement production process, it has been common practice to keep the temperature in the mill at the time of finish grinding as low as possible, and to suppress as much as possible the dehydration of the dihydrate gypsum and the hemihydrate or soluble dehydration in the mill. It is.

However, when a high-performance water reducing agent or a high-performance AE water reducing agent is used, if gypsum hemihydrate or soluble anhydrous gypsum is present as shown in the present invention, gypsum dihydrate is formed immediately after mixing. Although it precipitates and lowers the fluidity, the adsorption of the high-performance water-reducing agent and high-performance AE water-reducing agent is also suppressed by SO ₄ ^2- ions eluted from the gypsum. Since it lasts without being lost, the fluidity after kneading is maintained, and thus slump loss is reduced.

The high-performance naphthalene sulfonate-based water reducing agent has a competitive adsorption relationship with the SO ₄ ²⁻ ion eluted from the gypsum, and the adsorption of this water reducing agent under a high SO ₄ ²⁻ ion concentration. It has recently been known that the tendency is to be suppressed, but it has not heretofore been known that the slump loss can be reduced. In addition, as described above, hemihydrate gypsum and soluble anhydrous gypsum having a high dissolution rate produce dihydrate gypsum and have a remarkable effect of rapidly decreasing fluidity.Therefore, it has also been conventionally possible to reduce slump loss by adding gypsum. Not tried. The present inventors have newly found that the slump loss can be reduced with the use of the water reducing agent by actively using hemihydrate gypsum or soluble anhydrous gypsum with respect to such a conventional technique.

As described above, in the present invention, the flowability of the cement composition is improved by using limestone powder (mineral powder), and gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum) is used together with limestone powder. By doing so, slump loss is suppressed. Note that gypsum (mainly hemihydrate gypsum or soluble anhydrous gypsum) exhibits an effect of suppressing slump loss, but tends to slightly reduce fluidity immediately after kneading due to precipitation of gypsum. The present invention uses a limestone powder having an effect of increasing fluidity in combination with gypsum,
As a result, good fluidity can be obtained for a long time including immediately after kneading, and a temporal decrease (slump loss) of fluidity can be effectively suppressed.

[0021]

EXAMPLES Examples and Comparative Examples Limestone powder (specific surface area: 9000 cm ² / g), hemihydrate gypsum and soluble anhydrite (exhausted dihydrate gypsum having a specific surface area of 7000 cm ² / g is hemihydrated or dehydrated) And hemihydrate gypsum or soluble anhydrous gypsum was added to this limestone powder to prepare admixtures having different amounts of gypsum. On the other hand, using low-heat Portland cement (made by Chichibu Onoda), sand (land sand from Ogasa), and a high-performance AE water reducing agent (Mayty 2000WHZ made by Kao Corporation), powder consisting of cement and admixture (powder = cement + Admixture / powder = 0.3, water / powder = 0.3, sand / powder = 1.5, addition amount of high-performance AE water reducing agent to powder 1.0 wt. %, And the flow of the mortar was measured according to Japanese Industrial Standards (JIS R5201-1992). However, the flow measurement was performed without vertically moving the flow table. The results are shown in Table 1. In the table, samples No. 1 and No. 2 are samples to which no admixture was added, and sample No. 3 was a sample to which an admixture containing only limestone powder without containing gypsum,
Samples No. 5, No. 9, and No. 12 are samples using soluble anhydrite instead of hemihydrate gypsum.

As shown in Table 1, by using limestone powder as an admixture, the flow value immediately after kneading is increased as in the case where the amount of the high-performance AE water reducing agent is increased, and the fluidity is improved. (Sample No. 1, No. 2, No. 3). However, when the limestone powder is used, the decrease in the mortar flow over time is larger than that when the amount of the high-performance AE water reducing agent is increased (samples No. 2 and No. 3). On the other hand, when an admixture obtained by adding hemihydrate gypsum and soluble anhydrous gypsum to limestone powder is used, although the flow value immediately after kneading is slightly reduced, the amount of decrease in the flow is small according to the change over time, and the flow loss is small. Improved (Sample Nos. 4-1
2). The flow value and the flow loss immediately after the kneading tend to decrease as the amount of hemihydrate gypsum in the admixture increases. However, when the amount of hemihydrate gypsum was too large, the flow value immediately after kneading became considerably small (Sample No. 13). From these results, the total SO ₃ in the powder was 1.5 to 3.5% by weight.
Was confirmed to be preferable. Similar results were found with soluble anhydrous gypsum.

[0023]

[Table 1]

[0024]

According to the method and the admixture of the present invention, the fluidity of the cement composition is enhanced, and the fluidity of the cement composition changes with time.
(Slump loss) can be effectively suppressed. Further, the cement composition according to the present invention has excellent fluidity and small slump loss.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-259286 (JP, A) JP-A-6-48790 (JP, A) JP-A-9-86976 (JP, A) JP-A-8-86 169736 (JP, A) JP-A-6-199549 (JP, A) Published by the British Standards Institute (BSI) in 1995, "Cement-Composition, Specifications and Compliance Standards" (Japanese translation) (58) Int.Cl. ⁷ , DB name) C04B 2/00-32/02 C04B 40/00-40/06

Claims (10)

(57) [Claims] 1. A cement containing hemihydrate gypsum in an amount such that the total SO ₃ content in the powder together with the mineral powder is 1.5 to 3.5% by weight.
A method for improving fluidity , characterized by increasing the fluidity of a cement composition by adding soluble anhydrite or reducing slump loss . 2. The mineral powder is limestone powder, and 5-150 parts by weight of limestone powder and 0.02% by weight of gypsum hemihydrate or soluble gypsum per 100 parts by weight of cement.
The method for improving fluidity according to claim 1, wherein 40 parts by weight are added. 3. A limestone powder with a specific surface area of 2000~30000cm ² / g, using hemihydrate gypsum or soluble anhydrite having a specific surface area 3000~12000cm ² / g according to claim 1 or
2. The method for improving fluidity described in 2 . 4. The fluid according to claim 1, wherein the hemihydrate gypsum or the soluble anhydrous gypsum and the mineral powder are separately or premixed and added during or before kneading the cement composition. Sex improvement method. 5. Hemihydrate gypsum or soluble with mineral powder
Containing anhydrous gypsum as the main component, fluidity of cement composition
And a cement admixture characterized by improving slump loss . 6. The admixture for cement according to claim 5, wherein the mineral substance powder is limestone powder and contains 0.5 to 25 parts by weight of gypsum hemihydrate or soluble anhydrite based on 100 parts by weight of the limestone powder. 7. A specific surface area 2000~30000cm ² / g
Limestone powder and specific surface area of 3000 to 12000 cm ² / g
The admixture for cement according to claim 6, wherein hemihydrate gypsum or soluble anhydrous gypsum is used . 8. A cement containing hemihydrate gypsum or mineral oxide together with mineral powder in such an amount that the total SO ₃ content in the powder becomes 1.5 to 3.5% by weight.
Is a cement composition characterized by having improved fluidity and slump loss by adding soluble anhydrite . 9. A mixture of 5-150 parts by weight of limestone powder and hemihydrate gypsum or soluble anhydrite with respect to 100 parts by weight of cement.
The cement composition according to claim 8, wherein the plaster is added in an amount of from 0.02 to 40 parts by weight. 10. A cement according to claim 5, 6 or 7 have <br/> deviation or cement composition comprising adding cement admixtures as described in the.