JP2012140269A - Admixture and cement composition for plastering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an admixture which can improve applicability of a cement composition such as cement paste and mortar, by markedly reducing troweling marks on a surface upon plastering without affecting hardening properties of the cement composition, and itself directly functions as an efflorescence inhibitor, and a cement composition for plastering, which hardly shows efflorescence and is excellent in appearance after application.SOLUTION: The admixture comprises an alkali metal phosphate and/or an alkali metal hydrogenphosphate as an active ingredient. Alternatively, the admixture further comprises at least one chosen from diatomaceous earth, fly ash and lime stone powder. The cement composition for plastering comprises one of the admixtures and cement.

Description

  [Technical Field] The present invention relates to an admixture for preventing generation of white flower in mortar and concrete, and particularly to an admixture for preventing white flower generated in plastering work, and a plastering cement composition using the admixture.

  In cement-based compositions such as cement paste, mortar, and concrete, calcium ions eluted from the cement surface on the surface of the construction, and easily react with carbon dioxide in the atmosphere. This is an aesthetic problem. In order to prevent white flower, a method of mixing a substance that reacts with calcium ions to form an insoluble compound (see, for example, Patent Document 1) into white mortar or concrete as a white flower inhibitor, or has a water absorption preventive property to a cured body. There is known a method of giving (see, for example, Patent Document 2).

  Even when such conventional white-white prevention measures are taken, particularly when the uncured construction surface is finished with a plastering method such as wrinkles, many white-white generations are seen along the traces, making it difficult to improve aesthetics. was there. It has been known that when a clay mineral mainly composed of needle-like crystals is blended with mortar or the like as a method for improving workability in which traces do not easily remain, a good smooth surface can be obtained. However, since the clay mineral itself does not have a function to suppress white flower directly, this measure has a limit in reducing white flower. In addition, the possibility of changes in the color of the construction due to the color developed by the clay mineral and the necessity of handling considerations such as safety as a needle-like crystalline material cannot be ignored, leading to a realistic aesthetic improvement measure. Not in.

Japanese Patent Laid-Open No. 11-60301 Japanese Patent Application Laid-Open No. 11-76797

  In view of the above situation regarding measures against white flower, the present invention is an improvement in workability that can remarkably reduce the remains of surface dredging work on plastering without affecting hardened properties in cement compositions such as cement paste and mortar. It is an object of the present invention to provide an admixture that has an action and has a function of directly suppressing the generation of white flower and a plastering cement composition that hardly generates white flower.

  The present inventor, when the material used is constant, the degree of white bloom is affected by the plastering workability of the cement composition such as mortar. Therefore, a material that can greatly improve the finish workability for obtaining smoothness and suppress the elution and floating of calcium ions from the inside of the work to the surface. As a result of repeated studies to solve the above-mentioned problems by using the mixture, the following invention has been made regarding the material.

That is, the present invention is an admixture represented by the following [1] to [4] and a plastering cement composition represented by [5].
[1] An admixture containing an alkali metal phosphate and / or an alkali metal hydrogen phosphate as an active ingredient.
[2] The admixture according to [1], further comprising diatomaceous earth.
[3] The admixture according to [1] or [2], further comprising fly ash.
[4] The admixture according to any one of [1] to [3], further comprising limestone powder.
[5] A plastering cement composition comprising the admixture of any one of [1] to [4] and cement.

  The admixture of the present invention, when mixed with a cement composition such as mortar, suppresses the elution and floating of calcium ions in the composition that causes whiteness without affecting the physical properties of the cured product. In addition, since workability such as fray cutting, wrinkle elongation, and smooth finish in the plastering method can be greatly improved, it is possible to sufficiently prevent white bloom that is likely to occur particularly in the remaining part of the construction mark.

The admixture of the present invention contains an alkali metal phosphate and / or an alkali metal hydrogen phosphate as an active ingredient, and is used for cement paste, mortar, concrete, or the like containing a hydraulic inorganic substance such as cement. It is an admixture that is mixed to express a predetermined property. By using an alkali metal phosphate and / or alkali metal hydrogen phosphate as an active ingredient, it is considered to have an action of insolubilizing calcium ions that are easily eluted when cemented, especially aqueous slurry, and becomes a white flower source. The floating of calcium ions to the cement composition surface can be greatly suppressed. Furthermore, since the alkali metal phosphate and / or alkali metal hydrogen phosphate has a strong water-holding power, it gives a uniform moisture to the cement composition, and drastically slips and breaks during construction are greatly improved. A good smooth surface can be easily obtained even by applying the glazing once. Examples of the alkali metal phosphate that can be used in the present invention include K ₃ PO ₄ or Na ₃ PO ₄ , and two or more of them may be used in combination. Preferably, K ₃ PO ₄ is used because of its high water solubility. The alkali metal hydrogen phosphate usable in the present invention is any one of Li ₂ HPO ₄ , K ₂ HPO ₄ , Na ₂ HPO ₄ , LiH ₂ PO ₄ , KH ₂ PO ₄ , and NaH ₂ PO ₄ . Two or more kinds may be used in combination. Preferably, it is either KH ₂ PO ₄ or K ₂ HPO ₄ because of its high water solubility. Moreover, you may contain together alkali metal phosphate and alkali metal hydrogenphosphate, and the content rate in both in that case is not restrict | limited. Preferably, alkali metal hydrogen phosphates 1 to 10 with respect to the alkali metal phosphate 1 in weight ratio are good in terms of the effect of improving finishing workability. Further, only one of alkali metal phosphate and alkali metal hydrogen phosphate may be contained as an active ingredient. Preferably, those containing an alkali metal hydrogen phosphate are preferable because the workability is improved. As the most preferable admixture, one containing K ₂ HPO ₄ as an active ingredient is recommended. Further, the content of the alkali metal phosphate and the alkali metal hydrogen phosphate in the admixture of the present invention (when either one is not contained, the content is included) is white flower. And 3% by mass or more is desirable for stably expressing desired properties relating to workability.

  The admixture of the present invention preferably further contains diatomaceous earth. Diatomaceous earth is composed of fossil deposits of diatom shell, and is a porous body mainly composed of silicon dioxide and generally having open pores that communicate with most of the pores. In the present invention, any diatomaceous earth that is generally commercially available for use as, for example, a filtering agent or building material can be used, and is not particularly limited. In use, it is preferably pulverized to have a particle size of about 5 to 30 μm. When such particle size adjustment is performed, the mixing property at the time of mixing becomes better. The content of diatomaceous earth is preferably the total content of the alkali metal phosphate and alkali metal hydrogen phosphate (if either one is not contained, the content is only the content of the one contained. ) Diatomaceous earth is 3000 parts by mass or less (excluding 0 parts by mass) with respect to 100 parts by mass. More preferably, it is an admixture containing 50 to 2000 parts by mass of diatomaceous earth because good strength development is easily obtained. If the content of diatomaceous earth exceeds 3000 parts by mass, the strength of the composition after mixing is not suitable. By containing diatomaceous earth, the workability of construction centering on the growth of dredging is dramatically improved. Moreover, the cement composition containing diatomaceous earth promotes the disappearance of color spots and the like of the cement composition by the moisture and color tone adjusting action of diatomaceous earth, and contributes to the improvement of aesthetics.

The admixture of the present invention is preferably an admixture further containing fly ash. The inclusion of fly ash can improve the plastering workability centering on the elongation and breakage of the kite. In addition, when used in combination with diatomaceous earth, these workability properties are greatly improved, smoothness is easily obtained, and scars are hardly left, thereby reducing the generation of white flower. The fly ash to be contained is not particularly limited, but a fly ash having a high reaction activity and a specific surface area of 2500 cm ² / g of brane is preferably used. As an example, fly ash corresponding to type I or type II specified in JIS A 6201 is recommended. The content of fly ash is 100 parts by mass of the total content of the alkali metal phosphate and the alkali metal hydrogen phosphate (when either one is not contained, the content is only the content of one). The amount is preferably 200 to 3000 parts by mass. If the amount is less than 200 parts by mass, the blending effect may not be obtained in some cases, so that it is not appropriate, and if it exceeds 3000 parts by mass, the early strength development tends to be reduced, and therefore not appropriate.

The admixture of the present invention is preferably an admixture further containing limestone powder. As the limestone powder, a powder having a brain specific surface area of 3500 cm ² / g or more can be preferably used. Those having a brain specific surface area of less than 3500 cm ² / g are not suitable because they are difficult to uniformly disperse in the cement composition. Limestone powder promotes the carbonation of calcium ions generated in the cement composition when it is made into an aqueous slurry, and has an action of fixing inside the composition. From this, the calcium ions floating on the cement composition surface along with the water evaporation process can be drastically reduced, and the white flower phenomenon can be prevented. This action complements the white flower source production suppressing action by the alkali metal phosphate or alkali metal hydrogen phosphate, and can prevent white flower more strongly. The content of the limestone powder is preferably the total content of the alkali metal phosphate and the alkali metal hydrogen phosphate (if either one is not contained, the content is only the content of the contained one. ) 200-3000 parts by mass with respect to 100 parts by mass. If the amount is less than 200 parts by mass, the blending effect may not be substantially obtained, so that it is not appropriate. If the amount exceeds 3000 parts by mass, the early strength development tends to decrease, which is not appropriate.

  The plastering cement composition of the present invention comprises at least the admixture according to the present invention, cement and water. Any cement can be used. Specifically, for example, various ordinary portland cements such as normal, early strength, super early strength, moderate heat, low heat, various mixed cements such as blast furnace cement and fly ash cement, white cement, Special cements such as eco-cement or alumina cement can be used, and two or more kinds may be used in combination. The amount of each constituent material is not particularly limited. Preferably, 0.1 to 30 parts by mass of the admixture according to the present invention and 20 to 100 parts by mass of water are contained per 100 parts by mass of cement. If the admixture is less than 0.1 part by mass, it may not be adequate because a sufficient whitening prevention effect may not be obtained. On the other hand, if it exceeds 30 parts by mass, it is difficult to obtain good strength. . Also, if the amount of water is less than 20 parts by mass, the workability by the plastering method tends to be lowered, so that it is not appropriate. If the amount exceeds 100 parts by mass, the strength may be lowered. The plastering cement composition of the present invention contains each component containing water, for example, a water repellent, a water retention agent, a pozzolanic reactive material, an extender, and the like within a range not losing the effect of the present invention. Also good.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples shown here.

Using materials selected from the following A1 to D2, the mixture was placed in a small powder mixer so as to achieve the blending amounts shown in Table 1, and mixed at room temperature for 60 seconds to prepare an admixture.
A1: Dipotassium hydrogen phosphate (food additive, commercial product)
A2: Sodium phosphate (reagent)
B: Freshwater diatomaceous earth (commercially pulverized product, bulk density 0.45 g / cm ³ , average particle size 12 μm)
C1: Fly ash (Blaine specific surface area 4500 cm ² / g)
C2: Limestone powder (CaCO ₃ content> 95%, Blaine specific surface area 4000 cm ² / g)
D1: Sepiolite (needle crystal having a diameter of about 0.1 μm and a length of about 5 μm)
D2: Silicone (Asahi Kasei Wacker Silicone, trade name: SILRES BS POWDER)

Next, using the admixture, materials selected from the following E to H, and water, the mixture was put into a Hobart mixer so as to have the blending amounts shown in Table 2, and mixed at room temperature for 2 minutes to prepare a mortar.
E: Normal Portland cement (manufactured by Taiheiyo Cement Co., Ltd.)
F: Fine aggregate (Yamagata quartz sand, FM = 2.5)
G: Methyl cellulose thickener (Matsumoto Yushi Co., Ltd., trade name: Marporose 90MP-4T)
H: Naphthalenesulfonic acid-based high-performance water reducing agent (“Mighty-100” manufactured by Kao Corporation)

The following (1) to (5) were evaluated for this mortar. The results are shown in Table 3.
(1) Evaluation of workability by plasterer to cocoon elongation: under the conditions of temperature 20 ° C and humidity 70%, mortar is applied to the surface (600 x 600mm) of a concrete flat plate installed horizontally on the ground. In doing so, the mortar accumulated in the cocoon was applied to the length of 300 mm without any unpainted part by one glazing, and the heel mortar was evaluated as good ○ elongation (○), and other conditions were obtained. The product was evaluated as having poor heel elongation (x).
(2) Evaluation of workability by plasterer to cutting ability: In the same manner as above, the mortar accumulated on the heel is stretched to a length of 300 mm by a single glazing, and visually observed. Those having almost no mortar adhered to the ridges were evaluated as having good chopping properties (◯), and those having other conditions were evaluated as having poor chopping properties (×).
(3) Evaluation of workability by plasterer to smoothness: Over the entire surface of the mortar coated with a thickness of 10 cm over the entire surface of the concrete flat plate as a result of visual observation in the same coating as above. Those that were finished to a state where no traces were left and no irregularities were observed were evaluated as good smoothness (◯), and those other than that were evaluated as poor smoothness (×).
(4) White flower prevention, etc .: A mortar was applied to the top surface of a concrete flat plate so as to have a thickness of 10 cm, and left standing indoors at a temperature of 10 ° C. and a humidity of 70% for 7 days. Immediately after being left, the occurrence of white flower on the mortar surface was observed. If the presence of white flower was not clearly confirmed by observation with the naked eye, it was judged that white flower was not generated, and it was evaluated that white flower could be prevented (◯). In addition, white flowers were not clearly recognized, but those in which color unevenness could be visually confirmed were regarded as aesthetic improvement (Δ). The thing other than these was evaluated as having not been able to prevent white flower (x).
(5) Compressive strength; The compressive strength was measured by the method according to JISR5201 with respect to the 28-day-old test body (dimension 40x40x160mm) of the produced mortar.

  From the results shown in Table 3, the mortars using the admixture of the present invention were all excellent in plastering work with a flaw, and could be made into a good smooth surface construction. Further, the mortar using the admixture of the present invention did not show white flower and exhibited an excellent aesthetic appearance. Moreover, it can be seen that the mortar according to the present invention in which such an effect is obtained does not hinder the physical properties of the cured body including strength development.

Claims (5)

An admixture containing an alkali metal phosphate and / or an alkali metal hydrogen phosphate as an active ingredient. The admixture according to claim 1, further comprising diatomaceous earth. The admixture according to claim 1 or 2, further comprising fly ash. Furthermore, the admixture in any one of Claims 1-3 formed by containing limestone powder. A plastering cement composition comprising the admixture according to any one of claims 1 to 4 and cement.