JP2899036B2 - Cement admixture for fiber reinforcement and cement composition for fiber reinforcement - Google Patents

Description

The present invention relates to a cement admixture for fiber reinforcement and a cement composition for fiber reinforcement, which are used mainly in the field of civil engineering and construction and have excellent strength development and dimensional stability. About.

The concrete in the present invention is a general term for mortar or concrete.

(Conventional technology and its problems) Fiber reinforced concrete is superior to ordinary concrete in bending strength, tensile strength, toughness, etc.
It is widely used for floors, cast-in-place, and structures.

As cement for these fiber-reinforced concretes, ordinary or early-strength Portland cement is used, but when these cements are used, there are problems such as poor initial strength expression and large dry shrinkage. . In particular, in the case of OA floors, the warpage of panels has occurred, and in the case of cast-in-place, cracks or problems have become a problem.

The present inventors have conducted various studies in order to solve the above-described problems, and as a result, by using a specific cement admixture and a cement composition, a fiber-reinforced concrete having high initial strength expression and excellent dimensional stability has been obtained. The present invention has been completed based on knowledge that can be manufactured.

(Means for Solving the Problems) That is, the present invention relates to a fiber-reinforcing cement admixture containing 4,000 to 8,000 cm ² / g of calcium fluoroaluminate and an inorganic sulfate as main components. sulfonate is _{xCaO · yAl 2 O 3 · zCaF} 2 ( however, x / y / z =
1 / 0.65 to 2 / 0.01 to 1), which is a cement admixture for fiber reinforcement, which is a cement composition for fiber reinforcement mainly comprising cement and the cement admixture for fiber reinforcement.

 Hereinafter, the present invention will be described in detail.

Calcium fluoroaluminate in the present invention is a calcareous material, an alumina material and a raw material mainly composed of fluoride, the molar ratio of CaO, Al ₂ O ₃ and CaF _{2 in} the product, CaO
Is set to 1, it is obtained by blending Al ₂ O _{3 so as to} be 0.65 to ₂ and CaF ₂ so as to be 0.01 to 1 and firing at 1,200 ° C. or more.

Fineness of calcium fluoroaluminate is 4,000 ~
8,000 cm ² / g.

The molar ratio of CaO, Al ₂ O ₃ and CaF ₂ needs to be within the above-mentioned range, and if it is out of this range, it is not preferable from the viewpoint of initial development or poor dimensional stability.

The method for producing calcium fluoroaluminate is not particularly limited, and examples thereof include a method of melting in an electric furnace and a method of firing in a rotary kiln.

The method of cooling the product is not particularly limited, either.
For example, any method such as rapid cooling by water or high-pressure air or slow cooling by standing can be used.

As the form of calcium fluoroaluminate, any of crystalline, amorphous and coexisting materials thereof can be used, but the use of amorphous is more preferable. In addition, the presence of other components and impurities in these production processes is not particularly limited, but particularly when industrialized, mixing of other components such as SiO ₂ , Fe ₂ O ₃ , TiO _2, and MgO from the raw material. However, the content of these is usually less than 10% by weight, and does not impair the properties of the calcium fluoroaluminate of the present invention.

The inorganic sulfate in the present invention is a sulfate of an alkali metal or an alkaline earth metal, and among them, anhydrous calcium sulfate, hemihydrate and dihydrate are preferable. Among them, use of hardly soluble or insoluble calcium sulfate such as type II anhydrous gypsum is particularly preferred.

The fineness of the inorganic sulfate is preferably 2,000 cm ² / g or more, more preferably 3,000 to 10,000 cm ² / g.

The proportion of calcium fluoroaluminate and inorganic sulfate in the cement admixture for fiber reinforcement is such that the inorganic sulfate is 75 to 25 to 70 parts by weight of calcium fluoroaluminate.
-30 parts by weight are preferred. Outside this range, the initial strength of the fiber-reinforced concrete is reduced, or the amount of shrinkage or expansion is increased, and the dimensional stability is unfavorably deteriorated.

The amount of cement admixture for fiber reinforcement used for cement is the sum of cement and cement admixture for fiber reinforcement.
It is 7 to 40 parts by weight, preferably 15 to 30 parts by weight based on 100 parts by weight. If the amount is less than 7 parts by weight, the increase in initial strength cannot be expected, and if it exceeds 40 parts by weight, the dimensional stability tends to deteriorate.

When used as a cement composition for fiber reinforcement,
It is preferable that calcium fluoroaluminate and inorganic sulfate are contained in an amount of 7 to 40 parts by weight, preferably 15 to 30 parts by weight, based on 100 parts by weight of the cement composition for fiber reinforcement.

Further, the whole or a part of the fiber reinforcing cement composition can be produced by a kiln or an electric furnace. When only a part of the fiber reinforcing cement composition is manufactured, the remaining fiber reinforcing cement composition can be mixed and pulverized or pulverized and mixed.

Examples of the cement that can be used in the fiber reinforcing cement composition include various portland cements such as ordinary / early high strength / very early strength / moderate heat, and various mixed cements of blast furnace cement, fly ash cement and silica cement.

Examples of the fiber used in combination with the fiber reinforcing cement admixture or the fiber reinforcing cement composition of the present invention include glass fiber, alkali-resistant glass fiber, alumina fiber, inorganic fiber such as boron fiber and asbestos, polypropylene fiber, nylon fiber, and acrylic fiber. Organic fibers such as fibers, polyethylene fibers, vinylon fibers, amilad fibers and polyacetal fibers, and metal fibers such as steel fibers.

These fibers are used for various purposes depending on the properties of the fibers, such as fiber length, fiber diameter, density, Young's modulus, tensile strength, and aspect ratio, but can be used in any case.

The amount of fiber used is usually 100% by volume of all materials used.
0.05 to 10 parts by volume is preferable, but not particularly limited thereto.

In addition, the cement admixture for fiber reinforcement and the cement composition for fiber reinforcement, if necessary, as other components,
It is possible to use coagulation regulators, thickeners, water reducing agents, pozzolanic substances such as silica fume, fly ash and slag, aggregates and the like in combination.

In the present invention, when kneading the fiber-reinforced cement admixture or the fiber-reinforced cement composition with other substances and water, the setting is fast, and the required working time cannot be taken, or the setting time is too long. It is possible to use a setting regulator to adjust the setting time.

Examples of the setting regulator include organic acids such as citric acid, tartaric acid, gluconic acid, malic acid and succinic acid or salts thereof, alkali carbonate, alkali hydrogen carbonate and phosphoric acid or salts thereof, and further, boric acid, boric acid, and the like. Acid alkali,
Examples thereof include alkali aluminate, calcium oxide, calcium hydroxide, and mixtures thereof.

The amount of setting retarder used is 10
Usually, 5 parts by weight or less is preferable with respect to 0 parts by weight.

In the present invention, when the dispersion of the fibers is insufficient or when breathing occurs during molding, it is preferable to use a thickener to prevent the occurrence.

As the thickener, methyl cellulose, polyvinyl alcohol, polyacrylic acid or a salt thereof, and the like can be used.

The amount of the thickener used is usually preferably 2 parts by weight or less based on 100 parts by weight of the cement composition for fiber reinforcement.

In the present invention, an aggregate can be used if necessary.

As the aggregate, various aggregates such as gravel, sand, quartz sand, quartzite powder and lightweight aggregate can be used, and can be selected according to the purpose of use.

As a method of kneading fiber-reinforced concrete, there are a method of kneading fibers with a mixer, a method of kneading fibers with a spray gun, and the like, but the kneading method is not particularly limited.

The molding method of the fiber reinforced concrete is not particularly limited, and includes, for example, a usual method of casting on site or casting on a form, a method of centrifugal force molding, a method of press molding, a method of spray molding, and an extrusion method. Any method such as a molding method and an injection molding method can be used.

The fiber reinforced concrete of the present invention has practical strength in a short time, and is excellent in durability and dimensional stability.

Further, the strength of the fiber reinforced concrete is adjusted by the ratio of calcium fluoroaluminate and inorganic sulfate and the amount used for cement.

Further, by performing steam curing or the like, it is possible to obtain the strength required for demolding in a shorter time.

In addition, organic fibers and resins having low heat resistance could not be used in the case of heat curing such as autoclave curing or steam curing, but use of the fiber admixture for fiber reinforcement and the cement composition for fiber reinforcement of the present invention was not possible. In this case, it is possible to use it because heating curing is not required.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 A commercially available calcium carbonate as a calcareous material, a commercially available alumina as an alumina material, and a special grade of calcium fluoride, a reagent manufactured by Wako Pure Chemicals, as a fluoride were mixed at 1,700 ° C. in a platinum crucible using an electric furnace. After melting under time conditions,
Dropped in water and quenched. The resulting product was then ground to 5,700 cm ² / g and used. The results of analysis of the products are shown in Table 1.

Next, fiber-reinforced concrete having the composition shown in Table 2 was produced using the materials shown below.

(Water / cement + cement admixture) = 40%, after kneading using an omni mixer manufactured by Chiyoda Giken Kogyo Co., Ltd., 4 × 4 ×
A test specimen of 16 cm is formed, and the bending strength and the compressive strength are measured in accordance with JIS R 5201.
The length change rate according to 29 was measured for each material age.

The curing conditions are 20 ° C and 60% RH. However, when using ordinary Portland cement alone of the comparative example, 65%
Two curings were performed, one that had been steam cured at 4 ° C. for 4 hours and another that had been standard cured at 20 ° C. and 60% RH.

[Materials used]

Cement: ordinary Portland cement, manufactured by Andes Cement Calcium Fluoroaluminate: Table 1 Inorganic sulfate: Type II anhydrous gypsum, manufactured by Shin-Akita Kasei Co., Ltd., Brain 7,000cm ² / g Aggregate: No. 7 silica sand Agent: Citric acid, made by Wako Pure Chemical, first-class reagent Fiber: Vinylon fiber, Kuraray brand name "Kuraron", diameter 14μ, specific gravity 1.3 Example 2 Using calcium fluoroaluminate C of Table 1,
Table 3 also shows the results obtained in the same manner as in Example 1 except that fiber-reinforced concrete having the composition shown in Table 3 was produced.

Example 3 A test was performed in the same manner as in Example 1 except that the types of fibers were changed as described below, and the blends shown in Table 4 were used. In addition,
As a comparative example, when ordinary Portland cement was used alone, steam curing was performed at 65 ° C. for 4 hours.

[Materials used]

Fiber-a: alkali resistant glass fiber, Nippon Electric Glass brand name "ARG fiber", hard type, length 13mm, specific gravity 2.7
8-b: asbestos, chrysotile, specific gravity 2.5 -c: polyethylene fiber, Mitsui Petrochemical's trade name `` Bonfix '', specific gravity 0.96 -d: aramid fiber, Dupont trade name `` Kepler 49 '',
Diameter 12μ, specific gravity 1.45 -e: steel fiber, Kobe Steel trade name `` Shinko Fiber '', length 30mm, diameter 0.5mm, specific gravity 7.8 [Effect of the Invention] By using the cement admixture for fiber reinforcement of the present invention, a fiber-reinforced concrete having high initial strength expression and excellent dimensional stability can be obtained.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 14/38 C04B 16/06 C04B 22/14 C04B 24/06 C04B 28/00-28/36

Claims (3)

(57) [Claims] 1. A fiber admixture for reinforcing fibers comprising 4,000 to 8,000 cm ² / g of calcium fluoroaluminate and an inorganic sulfate as main components. 2. Calcium fluoroaluminate is xCaO.yA
_{2. The} cement admixture for fiber reinforcement according to claim 1, wherein l ₂ O ₃ .zCaF ₂ (x / y / z = 1 / 0.65 to 2 / 0.01 to 1). 3. A fiber reinforcing cement composition comprising a cement and the fiber reinforcing cement admixture according to claim 1 or 2 as a main component.