Cement admixtures, cement compositions

Abstract

Provided is a cement admixture containing: a pozzolanic fine powder; gypsum; and one or more kinds of water-soluble calcium salts of an inorganic acid or an organic acid, excluding gypsum.

Description

[Technical Field]

[0001] The present invention relates to a cement admixture and a cement composition. [Background technology]

[0002] The strength of cement and concrete is largely dependent on the water / cement ratio, and it is now common practice to use water-reducing agents and high-performance water-reducing agents to keep the water / cement ratio as low as possible.

[0003] In this context, the water reduction rate of polycarboxylate-based water reducers has improved dramatically in recent years. As a result, by combining appropriate amounts of silica fume generated during the production of silicon alloys and silicon metal in electric furnaces, fly ash by-product from pulverized coal-fired thermal power plants, classified fly ash classified to 20 μm or 10 μm or less, coal gasification fly ash by-product from thermal power plants that burn gasified coal, and other spherical pozzolanic fine powders, it has become possible to reduce the water-to-binder ratio to the minimum, and achieve a design standard strength of 100 to 150 N / mm. 2 It has become easier to manufacture and construct architectural columns and beams using high-flow concrete. Furthermore, piles, which are high-strength concrete products, have a design strength of 80 to 85 N / mm. 2 105~123N / mm 2 Centrifugal molding specimens have been developed and have been approved by the Building Center of Japan (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 63-008248 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-19527 Summary of the Invention [Problem to be solved by the invention]

[0005] However, cement or cement containing pozzolanic fine powder as a binder can significantly change the fluidity of mortar or concrete to which a polycarboxylate-based water-reducing agent has been added, or the particles can be insufficiently dispersed, resulting in a decrease in reaction rate and a decrease in strength.

[0006] Similarly, when trying to increase the strength or speed up the hardening of concrete, a common method is to reduce the water-to-cement ratio, but this increases viscosity and makes the concrete less workable. Therefore, water-reducing agents or high-performance water-reducing agents may be used, but if used in large quantities, the hydration of cement is inhibited and strength development is poor. Another method is to use salts such as calcium formate or calcium chloride to accelerate the hydration reaction of cement, but this results in large slump loss and makes it difficult to ensure sufficient working time.

[0007] In view of the above, an object of the present invention is to provide a cement admixture that can exhibit good fluidity while maintaining strength development, even when the water / cement ratio is low, without using a large amount of a water-reducing agent or a high-performance water-reducing agent. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the present inventors have come up with the following invention and found that the above problems can be solved.

[0009] [1] A cement admixture containing pozzolanic fine powder, gypsum, and one or more water-soluble calcium salts of inorganic or organic acids other than gypsum. [2] The cement admixture according to [1], further comprising one or more water-soluble sodium salts of inorganic or organic acids. [3] The cement admixture according to [1] or [2], wherein the water-soluble calcium salt of an inorganic acid or an organic acid is calcium acetate. [4] The cement admixture according to [3], wherein the calcium acetate has an average particle size of 5 to 100 μm. [5] The cement admixture according to any one of [2] to [4], wherein the water-soluble sodium salt of an inorganic acid or an organic acid is sodium sulfate and / or sodium gluconate. [6] The cement admixture according to any one of [3] to [5], wherein the calcium acetate is 1 to 10 parts by mass per 100 parts by mass of the cement admixture. [7] The cement admixture according to any one of [2] to [6], wherein the total amount of water-soluble sodium salts is 0.6 parts by mass or less per 100 parts by mass of the cement admixture. [8] A cement composition comprising cement containing the cement admixture according to any one of [1] to [7]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a cement admixture that can exhibit good fluidity while maintaining strength development, even when the water / cement ratio is low, without using a large amount of a water-reducing agent or a high-performance water-reducing agent. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described below. [Cement admixture] The cement admixture according to this embodiment contains pozzolanic fine powder, gypsum, and one or more water-soluble calcium salts of inorganic or organic acids other than gypsum (hereinafter, sometimes referred to as "water-soluble calcium salts"). The pozzolanic fine powder and gypsum provide strength development, and the presence of the water-soluble calcium salts provides good fluidity. In the present invention, these components are blended to achieve both strength development and fluidity.

[0012] (pozzolanic fine powder) Examples of pozzolanic fine powders include silica fume generated during the production of silicon alloys and silicon metal in electric furnaces, silica fume derived from zirconia, classified fly ash obtained by classifying fly ash produced as a by-product in pulverized coal-fired thermal power plants, coal gasification fly ash produced as a by-product in thermal power plants that combust gasified coal, fused silica fine powder, and synthetic aerosil, and one or more of these can be used.

[0013] Other pozzolanic materials that can be used to increase strength include fine powders of heat-treated clay minerals such as white clay and metakaolin, ash from silicified wood containing amorphous SiO2 as the main component, diatomaceous earth, and opalescent silica powder. Of the pozzolanic materials, silica fume is the most preferred, as it improves both fluidity and strength.

[0014] Classified fly ash, coal gasification fly ash, and fused silica fine powder can be expected to improve fluidity, but they cannot be expected to have the strength-improving effects that silica fume does. However, the combined use of small amounts of silica fume and spherical pozzolanic fine powder such as classified fly ash or fused silica not only further promotes fluidity but also synergistically increases strength, making it particularly preferable.

[0015] The mass mixing ratio (silica fume / non-silica fume pozzolanic fine powder) of silica fume to at least one non-silica fume pozzolanic fine powder of classified fly ash, coal gasification fly ash, and fused silica fine powder is preferably 1 / 1 to 5 / 1, and more preferably 2 / 1 to 4 / 1. A ratio of 1 / 1 to 5 / 1 can improve fluidity and strength.

[0016] (plaster) As gypsum, any of anhydrous gypsum, dihydrate gypsum, and hemihydrate gypsum can be used, but anhydrous gypsum is preferred from the viewpoint of obtaining high strength. The particle size of the gypsum is 3,000 cm in Blaine value from the viewpoint of obtaining good strength. 2 / g or more is preferable, and 4,000 to 8,000 cm 2 / g is more preferred.

[0017] (Water-soluble calcium salts of inorganic or organic acids, excluding gypsum) The water-soluble calcium salt of an inorganic or organic acid other than gypsum may be any salt that is water-soluble enough to dissolve in water and generate calcium ions, and examples thereof include calcium salts of acetic acid, nitric acid, nitrous acid, thiocyanic acid, cyanic acid, formic acid, etc. Specific examples include calcium acetate, calcium formate, and calcium nitrate, with calcium acetate being preferred from the viewpoints of solubility in water and maintaining the fluidity of mortar and concrete.

[0018] The average particle size (median diameter) of the water-soluble calcium salt is preferably 5 to 100 μm, more preferably 10 to 80 μm, from the viewpoints of solubility and ease of handling. The average particle size can be measured using a laser diffraction particle size distribution analyzer.

[0019] From the viewpoints of strength development and fluidity, the amount of pozzolanic fine powder is more preferably 50 to 90 parts by mass per 100 parts by mass of the cement admixture. From the viewpoint of strength development, the amount of gypsum is preferably 1 to 30 parts by mass, and more preferably 5 to 25 parts by mass. The amount of the water-soluble calcium salt is preferably 1 to 10 parts by mass, more preferably 3 to 7 parts by mass, from the viewpoint of imparting fluidity. From the viewpoint of fully exerting the combined effect of the above three components, the total amount of the pozzolanic fine powder, gypsum, and water-soluble calcium salt per 100 parts by mass of the cement admixture is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 99.4 parts by mass or more.

[0020] (Water-soluble sodium salts of inorganic or organic acids) In this embodiment, from the viewpoint of moldability in centrifugal molding, a water-soluble sodium salt of an inorganic acid or an organic acid (hereinafter sometimes referred to as "water-soluble sodium salt") may be contained.

[0021] The water-soluble sodium salt may be any salt that is water-soluble and dissolves in water to produce sodium ions. Examples include inorganic acid sodium salts such as sodium carbonate, sodium sulfate, sodium chloride, sodium bicarbonate, sodium nitrate, and sodium nitrite, and organic acid sodium salts such as sodium tartrates (monosodium tartrate, disodium tartrate), sodium malate, sodium citrates, and sodium gluconate. From the viewpoint of dehydration and compaction properties during centrifugal molding of concrete, sodium sulfate and / or sodium gluconate are preferred.

[0022] In terms of the total alkali content of concrete and its effect on setting, the total amount of water-soluble sodium salts in 100 parts by mass of the cement admixture is preferably 0.6 parts by mass or less, and more preferably 0.1 to 0.4 parts by mass.

[0023] [Cement composition] The cement composition of the present embodiment comprises cement containing the cement admixture of the present embodiment.

[0024] Examples of cement include various types of Portland cement, such as ordinary, early-strength, and extra-early-strength Portland cement, various blended cements in which blast furnace slag or fly ash is mixed with these Portland cements, moderate-heat Portland cement, and bilite cement.

[0025] In terms of strength development, the cement admixture of this embodiment is preferably contained in an amount of 1 to 30 parts by mass, more preferably 4 to 20 parts by mass, per 100 parts by mass of the cement composition of this embodiment.

[0026] The cement composition of this embodiment may further contain one or more of aggregates such as sand and gravel, setting accelerators, air-enhancing agents, thickeners, cement rapid hardening agents, cement expansion agents, rust inhibitors, antifreeze agents, polymer emulsions, clay minerals such as bentonite and montmorillonite, ion exchangers such as zeolite, hydrotalcite and hydrocalumite, inorganic phosphates, and boric acid, to the extent that the object of the present invention is not substantially impaired.

[0027] The cement composition of the present embodiment may contain a water-reducing agent such as a water-reducing agent, an air-entraining water-reducing agent, a high-performance water-reducing agent, or a high-performance air-entraining water-reducing agent, but the content thereof is preferably 6 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the cement composition of the present embodiment. Since the cement composition of the present embodiment contains the cement admixture of the present embodiment, the amount of water-reducing agent used can be reduced.

[0028] Any existing mixing device can be used as a mixing device when producing the cement admixture and cement composition of this embodiment, such as a tilting mixer, an omni mixer, a V-type mixer, a Henschel mixer, a Nauta mixer, etc. Furthermore, the materials may be mixed at the time of application, or some or all of them may be mixed in advance.

[0029] When the cement composition of this embodiment is used as mortar or concrete, the water / cement ratio is preferably 30% by mass or less, and more preferably 15 to 25% by mass. Since the cement composition contains the cement admixture of this embodiment, it can be used at such a low water / cement ratio. [Example]

[0030] Cement admixtures were prepared by mixing pozzolanic fine powder, gypsum, water-soluble calcium salt, and water-soluble sodium salt in the mass proportions shown in Table 1. A cement composition was prepared by mixing 13 parts by mass of the prepared cement admixture, 87 parts by mass of cement, 1.0 part by mass of water-reducing agent, and 150 parts by mass of fine aggregate, and water was added to achieve a water / cement ratio of 30% by mass, and various measurements were performed.

[0031] <Materials used> Pozzolanic fine powder: Silica fume (Elkem, granular, density 2.44 g / cm 3 ) and classified fly ash (classified to 20 μm or less, density 2.44 g / cm 3 ) in a mass ratio of 3:1 Gypsum: anhydrous gypsum, blaine 5,000 cm 2 / g, natural gypsum Water-soluble calcium salt Water-soluble calcium salt A: Calcium acetate monohydrate (reagent) Median diameter: 50 μm Water-soluble calcium salt B: Calcium acetate monohydrate (reagent) Median diameter: 3 μm Water-soluble calcium salt C: Calcium acetate monohydrate (reagent) Median diameter: 10 μm Water-soluble calcium salt D: Calcium acetate monohydrate (reagent) Median diameter: 90 μm Water-soluble calcium salt E: Calcium acetate monohydrate (reagent) Median diameter: 110 μm Water-soluble calcium salt F: Calcium formate (reagent) Water-soluble calcium salt G: Calcium chloride (reagent) Water-soluble sodium salt Water-soluble sodium salt A: Sodium sulfate (reagent) Water-soluble sodium salt B: Sodium gluconate (reagent) Water-soluble sodium salt C: Sodium chloride (reagent) Cement: Ordinary Portland cement (commercially available) Water reducing agent: Polycarboxylic acid water reducing agent Fine aggregate: river sand Water: Tap water

[0032] <Measurement method> The following measurements were carried out, and the results are shown in Table 1. Mortar flow: The flow value was measured when the cone was removed in accordance with JIS R5201. However, a 50 x 50 x 2 cm acrylic glass plate was placed on the flow table, and the measurement was performed without subjecting it to dropping vibration. The measurement was taken 3 minutes after the flow cone was removed. Compressive strength: Based on JSCE-G505. The specimen dimensions were φ5 x 10 cm, and after steam curing at 85°C for 5 hours, the compressive strength was measured after 1 day.

[0033] [Table 1] [Industrial Applicability]

[0034] The cement admixture of the present invention can be suitably used in the fields of civil engineering and construction, particularly when a small water / cement ratio is desired.

Claims

1. A cement admixture comprising a pozzolanic fine powder, gypsum, and one or more water-soluble calcium salts of inorganic or organic acids other than gypsum, the water-soluble calcium salt of an inorganic or organic acid is calcium acetate; The cement admixture contains 5 to 10 parts by mass of calcium acetate per 100 parts by mass of the cement admixture.

2. 2. The cement admixture according to claim 1, further comprising one or more water-soluble sodium salts of inorganic or organic acids.

3. 2. The cement admixture according to claim 1, wherein the calcium acetate has an average particle size of 5 to 100 μm.

4. 3. The cement admixture according to claim 2, wherein the water-soluble sodium salt of an inorganic or organic acid is sodium sulfate and / or sodium gluconate.

5. 3. The cement admixture according to claim 2, wherein the total amount of the water-soluble sodium salts of the inorganic or organic acids is 0.6 parts by mass or less per 100 parts by mass of the cement admixture.

6. A cement composition comprising cement containing the cement admixture according to any one of claims 1 to 5.

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