JPH0625007B2 - Cement admixture and cement composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement admixture, particularly a cement admixture and a cement composition used in the fields where early and long-term strength is required.

[Conventional technology]

It has been conventionally known to mix calcium aluminate such as alumina cement, gypsum and a coagulation adjusting agent with Portland cement to prepare a rapid hardening cement. Mortar and concrete using this cement,
Since it shows rapid hardening, it can be used several hours after the casting.

However, in this rapid hardening cement, 3CaO.SiO ₂ (hereinafter referred to as C ₃ S), which is the main component of Portland cement, is hardly hydrated until the age of 7 days,
Also, it tended to be difficult to hydrate even in the long term. Accordingly, the strength of the conventional rapid hardening cement is largely due to ettringite _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H 2 O) produced by the reaction of calcium aluminate and gypsum. This ettringite is approximately 46% water of crystallization, as evidenced by stoichiometric calculations. Generally, the durability of concrete can be determined by, for example, a freeze-thaw resistance test. However, since water in ettringite has a relatively small binding force, water flows in and out violently, leading to a long-term decrease in strength and deterioration in durability.

The reason why C ₃ S in Portland cement is not sufficiently hydrated is not clear, but it is presumed that alumina gel [Al (OH) ₃ ] by-produced by the reaction of the following formula covers the surface of C ₃ S particles. It

3CA _n ＋ 3CaSO ₄ ＋ (9n + 29) H ₂ O → 3CaO ・ Al ₂ O ₃ / 3CaSO ₄・ 32H ₂ O ＋ (6n-2) ・ Al (OH) ₃ However, CA _n is CaO / Al ₂ O ₃ Means a calcium aluminate whose molar ratio is n.

[Problems to be Solved by the Invention]

For the above reasons, the conventional rapid hardening cement not only cannot be expected to have long-term strength elongation, but also has a problem in durability.

An object of the present invention is to provide a cement admixture that solves the above problems and a cement composition containing the same.

[Means for Solving the Problems]

Briefly describing the present invention, the first invention of the present invention is an invention relating to a cement admixture, which is 300 parts by weight or less of gypsum and 100 parts by weight of calcium aluminosilicate glass, and a settling agent 0.1-. 20 parts by weight is an essential component.

A second invention of the present invention is an invention relating to a cement composition, which is characterized in that the cement admixture of the first invention and cement are the main components.

The present invention will be described in detail below.

Calcium aluminosilicate glass (hereinafter C
AS glass) has a compositional area Is preferred, and more preferably Is. When CaO is less than 30% by weight or Al ₂ O ₃ exceeds 60% by weight, rapid hardening is poor, and conversely, when CaO exceeds 60% by weight or Al ₂ O ₃ is less than 20% by weight,
Even if a large amount of the coagulation modifier is added, it will momentarily set, which is not preferable from the viewpoint of workability. On the other hand, if the SiO ₂ content is less than 5% by weight, the hydration of C ₃ S in Portland cement will be extremely delayed, so long-term strength extension cannot be expected, and conversely 25
If it exceeds 5% by weight, the initial strength is low. Incidentally, general industrial raw materials naturally contain impurities such as MgO, Fe ₂ O ₃ , TiO ₂ , K ₂ O and Na ₂ O, and these impurities are CaO-Al ₂ O.
_{Since the 3-} SiO ₂ -based vitrification region is expanded, the presence of less than 10% by weight is preferable, and problems such as rapid hardening, workability, and elongation of long-term strength do not occur. It is preferable to add alkali nitrates (NaNO ₃ , KNO _3, etc.), calcium fluoride (CaF ₂ ), borax, etc., which are general glass fusing agents, because the melting point of the glass is lowered.

The term "glass" as used herein is generally used in the field of glass, that is, "glass that exhibits a glass transition point". All do not have to be glass, and the vitrification rate is 5
There is no problem if it is 0% by weight or more. It is more preferably 70% by weight or more, still more preferably 80% by weight or more. Fifty
If it is less than wt%, there is a problem in terms of early strength.

The method for measuring the vitrification ratio is as follows:
After heating at 000 ° C. for 2 hours (h), it was gradually cooled at a cooling rate of 5 ° C./min (m), and the area S ₀ of the main peak of the crystalline mineral was determined by the powder X-ray diffraction method to determine the crystals in the glass of the present invention. The vitrification rate x was determined from the main peak area S of.

The above CAS glass is completely different from the composition of granulated blast furnace slag, which is a by-product in metallurgy or metal smelting, and the present invention is not derived from the composition of granulated blast furnace slag. By the way, the average chemical composition of granulated blast furnace slag is as follows: CaO: 40-43% by weight, MgO: 5-8% by weight, Al ₂ O ₃ : 13-15% by weight, and SiO ₂ : 31-35%.
% By weight.

Furthermore, the CAS glass of the present invention comprises alumina cement,
It's not a derivative. That is, the SiO ₂ content of ordinary alumina cement is less than 5% by weight [Junichi Kasai, Concrete Engineering, Vol. 22, No. 8, p. 67 (198).
4)], and the vitrification rate does not exceed 25% [1964, Academic Press, Inc., London City, Limited, HFW Taylor (HFWTaylor), The Chemistry of Cement, No. 2] Volume 16
page〕.

As the raw material for the CAS glass according to the present invention, as the CaO-based raw material, quick lime (CaO), slaked lime [Ca (OH) ₂ ], limestone (CaCO ₃ ), and the like can be used, and Al ₂ O ₃ -based raw material is alumina. , bauxite, diaspore, feldspar, it can be used clay or the like, as SiO ₂ feedstocks, silica sand, clay,
Diatomaceous earth or the like can be used. Alternatively, it can be achieved by supplementing relatively inexpensive blast furnace slag with CaO-based raw material and Al ₂ O ₃ -based raw material.

After mixing the above CaO-based raw materials, Al ₂ O ₃ -based raw materials, and SiO ₂ -based raw materials in the prescribed proportions, they are melted using a direct current melting furnace or high-frequency furnace, and the resulting melt is compressed with air or high pressure. It is manufactured by a method of blowing off with water or a method of pouring into water. Alternatively, the CAS glass can also be produced by melting in a rotary kiln and quenching.

If the particle size of the CAS glass is small, the reactivity is improved, which is preferable, and the Blaine specific surface area is particularly preferably 3000 cm ² / g or more.

Gypsum according to the present invention refers to dihydrate, semi-water, type II anhydrous and type III anhydrous gypsum, natural ones, chemical gypsum such as phosphoric acid, drainage and hydrofluoric acid gypsum, or heat treatment of these. The obtained product can be used, and is not affected by the type and amount of impurities normally contained. From the viewpoints of initial strength development and workability, type II anhydrous gypsum is particularly excellent and usually does not leave unreacted matter. Therefore, it is preferable to use one pulverized to have a Blaine specific surface area of 3000 cm ² / g or more.

Furthermore, since type II anhydrous gypsum is produced as a large amount as a by-product from the hydrofluoric acid generation step, use it as it is or neutralize the free H ₂ SO ₄ content with CaCO ₃ , Ca (OH) ₂ , and CaO. Is most convenient.

The blending ratio of gypsum is 300 parts by weight or less, more preferably 20 parts by weight or more and 200 parts by weight or less, and further preferably 50 parts by weight or more with respect to 100 parts by weight of CAS glass.
It is preferably 50 parts by weight or less. If it exceeds 300 parts by weight,
Due to the expansion of the unreacted gypsum due to the reaction, a decrease in strength occurs in the long term.

The setting regulator according to the present invention is necessary to secure the required working time and further improve the initial strength enhancing property. Examples of the coagulation modifier include chlorides such as calcium chloride, ferric chloride and aluminum chloride, aluminates such as sodium aluminate and potassium aluminate, carbonates such as sodium carbonate and potassium carbonate, sodium hydroxide and hydroxide. Hydroxides such as calcium, zinc silicofluoride, magnesium silicofluoride, inorganic salts such as silicofluoride such as sodium silicofluoride, and further citric acid, gluconic acid, tartaric acid, or their calcium salts, sodium salts,
There are organic acid compounds such as potassium salts, which may be added alone or in combination of two or more. Among the above-mentioned setting regulators, the combined use of alkali carbonate and organic acid compounds is
Most preferable because it shows a rapid curing reaction.

The mixing ratio of the coagulation modifier is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of CAS glass. If it is less than 0.1 part by weight, workability is poor, and if it exceeds 20 parts by weight, initial strength development is not preferable.

The cement admixture of the present invention includes various types of Portland cement such as normal, early strength, super early strength, moderate heat, silica, etc.
It can be used as a mixture with various mixed cements in which blast furnace slag and fly ash are mixed.

The mixing amount of the cement admixture is preferably 5 to 50 parts by weight based on 100 parts by weight of the total amount of cement and the cement admixture.
When the amount is less than 5 parts by weight, strength development is low, and on the other hand, 5
If the amount exceeds 0 parts by weight, both are not preferable from the viewpoint of workability.

Various additives other than the above may be used in combination with the cement admixture and the cement composition of the present invention.

For example, silica sand, aggregates such as natural sand and gravel, fibrous substances such as glass fiber, carbon fiber and steel fiber, polymer emulsion (latex), colorant (pigment),
AE agents, water reducing agents, AE water reducing agents, superplasticizers, rust preventives, water inseparable admixtures such as methyl cellulose, thickeners, water retention agents, waterproofing agents such as calcium chloride and sodium silicate, foaming agents, One or more of foaming agents, calcium-containing compounds such as calcium hydroxide, and antifreezing agents can be used together in an amount that does not substantially impair the object of the present invention.

As the mixing device used in producing each composition of the present invention, any existing stirring device can be used,
For example, a tilting barrel mixer, an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.), a V-type mixer, a Henschel mixer, a Nauta mixer and the like can be used. Further, the mixing may be carried out by mixing the respective materials at the time of construction, or by mixing a part or all of them in advance.

Regarding the actual construction method of the cement composition of the present invention,
It suffices to comply with the conventional method of construction of conventional mortar or concrete, and by using the composition of the present invention,
It does not adversely affect the workability (workability).

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 (Comparative Example) Commercially available special grade reagents CaCO ₃ , Al ₂ O ₃ and SiO ₂ were mixed and mixed together.
Place 00g in a carbon crucible and use a high frequency furnace for about 2000
After heating and melting at 0 ° C., it was put into water and rapidly cooled to synthesize 14 kinds of glasses of A to N shown in Table 1. As shown in the remarks column, A, B, H, J, K, and N are CaO-Al ₂ O ₃ -Si.
Since it is not within the O ₂ -based vitrification region, 1% by weight of CaF ₂ was added by external splitting, and the glass was vitrified by quenching after melting. L, M, and N are comparative examples other than the present invention. These C
AS glass was ground until each becomes Blaine 4000cm ² / g, II type anhydrous gypsum (Blaine 4500cm ² / g
) [Sankei Gypsum Co., Ltd.] and a setting modifier to form an admixture, and ordinary Portland cement [Electrochemical Industry]
Co., Ltd.] 20 parts by weight of admixture was mixed with 100 parts by weight.

A 1: 2 mortar was produced from this by the method of JIS-R-5201, and a test piece of 4 × 4 × 16 cm was molded.

The curing was performed at 20 ° C. and 80 RH. The results are second
Shown in the table.

Example 2 Using raw materials having the chemical composition shown in Table 3, quicklime,
45:45:10 (wt%) of bauxite and silica
10% of CAS glass was manufactured by mixing in a ratio of 1 to 3, melted in a direct current type melting furnace with a maximum power load of 5000 kVA, flowing the melt, dropping it into water and quenching. The temperature of the melt at the outlet was 1770 ° C.

In the X-ray diffraction result of this CAS glass, no crystal peak was observed and the vitrification rate was 100%. Also this CA
Table 4 shows the chemical analysis values of S glass.

The CAS glass was ground to a Blaine 4000cm ² / g, II type anhydrous gypsum [Sankei gypsum (Ltd.) (Blaine 4500cm ² / g), and reagents citric acid (Wako Pure Chemical)
And reagent potassium carbonate (Wako Pure Chemical Industries), CAS glass 1
100 parts, 2 parts and 10 parts by weight, respectively, were added to 100 parts by weight and mixed to obtain a cement admixture. This admixture was mixed with ordinary Portland cement and Table 5 was obtained.

The kneading method and the curing conditions are the same as in Example 1.

Example 3 Using the raw materials having the chemical compositions shown in Table 3, blast furnace slag [Nippon Steel Corporation], quick lime, and bauxite at 30:
Mixing was carried out at a ratio of 30:40 (% by weight), and 10 tons of CAS glass was manufactured in the same manner as in Example 2. The chemical analysis values are shown in Table 6.

Using this CAS glass, an admixture was mixed in the same composition as in Example 2, and Table 7 was obtained.

Comparative Example 1 CA granulated blast-furnace slag (brain 4500 cm ² / g) having the chemical composition shown in Table 3 and alumina cement (2 types) having the chemical composition and the mineral composition shown in Table 8 were CA respectively.
It is used in place of S glass. For 100 parts by weight of the above blast furnace slag or alumina cement, II type anhydrous gypsum,
Reagent citric acid, reagent potassium carbonate 100, 2,
10 parts by weight were added and mixed to obtain a cement admixture. 25% by weight of this admixture in ordinary Portland cement
It was added and the results shown in Table 9 were obtained.

The kneading method and the curing conditions are the same as in Example 1.

Example 4 (including Comparative Example) Type II anhydrous gypsum, reagent tartaric acid (Wako Pure Chemical Industries, Ltd.), and reagent sodium carbonate were used for 100 parts by weight of each of the CAS glass produced in Example 3 and the alumina cement P used in Comparative Example 1. 100 parts, 2 parts, and 10 parts by weight of (Wako Pure Chemical Industries, Ltd.) were added and mixed to produce two cement admixtures.
These admixtures were mixed in an amount of 25 parts by weight with respect to 100 parts by weight of the ordinary Portland cement and the admixture, and test pieces were prepared with the concrete composition shown in Table 10.

<Materials used> Cement: Normal portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. Water: Groundwater Sand: Niigata Prefecture Himekawa-produced river sand (specific gravity 2.63) Gravel: 〃 Crushed stone (〃 2.66) Regarding the curing, the test piece having a compressive strength of φ10 × 20 cm was demolded the next day, and then cured in water at two temperatures of 5 ° C. and 20 ° C.

Freeze-thaw resistance test conducted to check durability was 10 ×
The test piece of 10 × 40 cm was demolded the next day, cured at 20 ° C. in water for 14 days, and then subjected to ASTM C-290.

Table 11 shows the results of the compressive strength test, and Table 12 shows the results of the freeze-thaw resistance test.

[Effects of the Invention] As described in detail above, (1) pot life can be arbitrarily adjusted by using the cement admixture or composition of the present invention.

(2) Good strength development.

(3) High long-term strength.

(4) Good durability.

(5) Good strength development at low temperature.

The effects such as

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Claims (2)

[Claims] 1. A cement admixture containing 100 parts by weight of calcium aluminosilicate glass and 300 parts by weight or less of gypsum and 0.1 to 20 parts by weight of a setting modifier as essential components. 2. A cement admixture according to claim 1, and a cement composition containing cement as a main component.