JPH0657617B2 - High strength cement hardened product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a high-strength cement hardened product containing alumina cement as a main component and obtained by cast molding and having high bending strength.

<Conventional technology and problems> Alumina cement has been used as a refractory or cement for emergency work, but it is used as a structure or molded body because its strength decreases significantly due to conversion of hydrated alumina cement. It has not been. On the other hand, a high-strength cement that has a low water cement ratio and can be cast is known (Japanese Patent Laid-Open No. 60-59182), but it has the drawback of low hardness and bending strength.

On the other hand, as a cement hardened product having a high bending strength, macrodefect-free cement (MDF cement), which is a composite material of a large amount of polyvinyl alcohol and alumina cement, is known (JP-A-59-43431).
However, they have drawbacks such as the need for a special method such as the use of twin rolls for kneading and the inability to produce irregularly shaped products.

The present inventors have made various studies to improve the bending strength and hardness of the cured product obtained by the casting method, and alumina cement, ultrafine powder, high-performance water reducing agent, curing modifier and conventionally used. In a cured product obtained by subjecting a kneaded product obtained by using a smaller amount of water as a main component to a vacuum defoaming treatment and by casting, finding that bending strength and hardness are improved, the present invention is completed. Arrived.

<Means for solving the problem> That is, the present invention, in the alumina cement, ultrafine powder, high-performance water reducing agent, and the curing modifier, 30 parts by weight, relative to the total 100 parts by weight of alumina cement and ultrafine powder Mix the following water,
It is a high-strength cement hardened product with air bubbles removed by vacuum defoaming treatment.

The object of the present invention is to knead a mixture containing alumina cement, ultrafine powder, a high-performance water reducing agent, a curing modifier and water as a main component,
It is an object of the present invention to provide a high-strength cement hardened product which is improved in bending strength and hardness by vacuum defoaming treatment during molding, particularly casting molding and hardening, and has no strength decrease due to conversion.

The present invention will be described in more detail below.

The alumina cement used in the present invention means CaO as C, Al ₂
When O ₃ is A, the cement is a hydraulic cement containing at least one of calcium aluminates represented by CA, CA ₂ , C ₁₂ A _7, etc. as a main component. Inorganic materials such as Al ₂ O ₃ and SiO _{2 that} do not have hydration activity may also be those that contain trace amounts of SiO ₂ , Fe ₂ O ₃ , and TiO ₂ as minor components in the composition mineral. It may include the. As commercially available products of these, "Denka Alumina Cement No. 1", "Denka Alumina Cement No. 2", "Denka High Alumina Cement No. 2" (all manufactured by Denki Kagaku Kogyo Co., Ltd., trade name), "Asano Alumina Cement" ( Asahi Hongju (trade name, manufactured by Asahi Glass Co., Ltd.) manufactured by Nippon Cement Co., Ltd.

The ultrafine powder in the present invention has an average particle size smaller than the average particle size of alumina cement by at least one order, preferably two orders, and is 1 μm or less, preferably 0.5 μm or less. Specifically, silica dust, which is a by-product of the production of ferrosilicon or metallic silicon, or crushed and classified blast furnace slag, fly ash, alumina cement, alumina and silica, gas phase method, liquid phase precipitation method, etc. Inorganic ultrafine powder produced by.

The amount of ultrafine powder used is about 5 to 50 parts by weight with respect to 100 parts by weight of alumina cement. If it is less than 5 parts by weight, the fluidity of the kneaded product becomes dilatantic, and exceeds 50 parts by weight. Therefore, it is difficult to obtain fluidity, and in any case, it is difficult to obtain a molded product having a beautiful surface by casting.

The high-performance water-reducing agent in the present invention is a formalin condensate of naphthalene or an alkylnaphthalene sulfonic acid or a salt thereof or a melamine resin sulfonic acid or a salt thereof, and the addition amount is 100 parts by weight of alumina cement and ultrafine powder in total. 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight. If it is less than 1 part by weight, it is difficult to obtain fluidity, and if it exceeds 5 parts by weight, the hydration reaction is significantly delayed.

Further, the curing modifier is necessary for maintaining the fluidity of the mortar or concrete which has been fluidized by the high performance water reducing agent. In particular, in the present invention, it is necessary to carry out a vacuum defoaming treatment, which will be described later, so as to carry out curing adjustment so that a curing reaction does not occur during that period. As a curing modifier, inorganic acids such as sulfuric acid, alkali metal sulfates and carbonates,
Examples thereof include bicarbonates, organic acids such as citric acid, and phosphoric acid esters. The amount used is 30 parts by weight or less, and preferably 25 parts by weight or less, with respect to 100 parts by weight of the total of alumina cement and ultrafine powder (hereinafter referred to as a binder).

Furthermore, in most cases, aggregates are usually used together. Aggregates generally used in the case of mixing concrete in the field of civil engineering are good, but harder ones, specifically, Mohs hardness of 6 or more, preferably 7 or more, or Knoop indenter hardness of 700 kg / mm ² It is preferable to use one selected on the basis of any of the above criteria, preferably 800 kg / mm ² or more, because the strength can be remarkably improved. Examples that meet this criterion include quartzite, emery, pyrite, magnetite, yellow jade, lawsonite, corundum, fenasite, spinel, beryl, anemite, tourmaline, granite, beryl, lithite, zircon, Examples include calcined bauxite, heavily burned shale, boron carbide, tungsten carbide, ferrosilicon nitride, silicon nitride, fused silica, fused magnesia, silicon carbide, and cubic boron nitride. In addition, metal such as machinable iron powder, stainless powder and ferromanganese powder is also useful. In particular, iron powder, austenitic stainless steel powder and ferromanganese powder are preferable from the viewpoint of improving bending strength. The reason for this is not clear, but it is thought that it is due to its high strength and its excellent adhesion to cement matrix.

The amount of aggregate used is usually selected and used within 5 times the weight of the binder. However, this is not the case for special molding methods such as pre-packed and post-packed construction methods.

In addition to the above blending, blending of various fibers and nets is also possible.
As the fibers, fibers by chatter cutting method of cast iron, metal fibers such as steel fibers and stainless fibers, and various natural or synthetic mineral fibers such as asbestos and alumina fibers, carbon fibers, glass fibers, further polypropylene, vinylon,
Examples thereof include natural or synthetic organic fibers such as acrylonitrile and cellulose. Further, it is possible to use steel rods, FRP rods and the like which have been conventionally used as a reinforcing material, and these reinforcing materials are indispensable especially for large-sized ones. From the viewpoint of not impairing the fluidity, short metal fibers having a length of about 3 mm and whiskers shorter than that are preferable.

The method of kneading the materials is not particularly limited, but it is preferable to sufficiently knead them. In the present invention, further vacuum defoaming treatment is required. Specifically, a vacuum casting device (Takagi Seisakusho Co., Ltd.), a vacuum omni mixer (Chiyo Giken Kogyo Co., Ltd.), a vacuum mixer (Sanei Seisakusho Co., Ltd.), etc. can be used to form a thin film. There is also a method of defoaming by means of the like, and it is preferable to reduce the rotation speed at the time of defoaming. In particular, the method of forming a thin film and defoaming has a fast defoaming rate and is significantly effective. The defoaming condition is a vacuum degree of about 50 to 70 mmHg, which is suitable in consideration of evaporation of water. The defoaming time is not particularly limited, but is usually preferably about 5 to 30 minutes.

It is preferable that the amount of air measured according to ASTM C-185-59 becomes about 1 to 2% or less by the vacuum defoaming treatment,
It is more preferable that the amount is about 1% or less.

A product that has been subjected to the defoaming treatment as described above can be cast to obtain a molded product.

It is also possible to combine defoaming treatment while applying vibration during casting. This method can also provide a high-strength cement hardened body having high defoaming efficiency and higher bending strength.

Curing of the molded article molded as described above can be carried out by various curing methods, and any of normal temperature curing, normal pressure steam curing, high temperature and high pressure curing and high temperature curing can be adopted. By combining them, a high-strength cement hardened product can be obtained. Further, since the high-strength cement hardened material of the present invention can prevent the leakage of radiation, it can be used for solidification of radioactive waste.

<Example> The present invention will be further described based on the following examples.

Example 1 Using the formulations shown in Table-1, knead with a 30 vacuum omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) for 10 minutes.
Vacuum defoaming was performed at 0 mmHg for a predetermined time, and a 4 × 4 × 16 cm specimen was prepared by casting, sealed with polyethylene, and cured at 50 ° C. for 7 days. Then JIS R
Bending and compressive strength tests were conducted according to -5201, and Rockwell and Mohs hardness were measured. The results are also shown in Table-1.

(Material) White cement: Chichibu Cement Co., Ltd. Alumina cement: "Denka High Alumina Cement"
(Manufactured by Denki Kagaku Kogyo Co., Ltd.) Ultrafine powder: Silica Hume (manufactured by Nippon Heavy Chemical Industry Co., Ltd.) High-performance water reducing agent: β-naphthalene sulfonate formaldehyde condensate system (trade name "Selflo-110P" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) ) Aggregate: Reduced iron powder “metallet” under 0.15 mm (manufactured by Nippon Magnetic Line) Fiber: SUS430, φ50 μm x length 2.5 mm by chatter cutting method (manufactured by Tokyo Steel Co., Ltd.) Hardening modifier: Na ₂ SO ₄ (reagent) Example Using the formulations shown in Table-2, kneading was carried out in the same manner as in Example 1, stainless steel fibers were further mixed in, and then vibration was applied on the vibrator also during molding,
Vacuum deaeration was performed to carefully prepare a 4 × 4 × 16 cm specimen. The test piece was sealed with a polyethylene bag at 50 ° C. for 7 days for curing, and a strength test was performed.

<Effects of the Invention> According to the present invention, it is possible to provide a high-strength cement hardened body having improved hardness and bending strength.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C04B 24:06 A 2102-4G 24:22 A 2102-4G 24:30) B 2102-4G

Claims (1)

[Claims] 1. Vacuum defoaming treatment by mixing 30 parts by weight or less of water with respect to a total of 100 parts by weight of alumina cement, ultrafine powder, a high-performance water reducing agent, and a curing modifier, and 100 parts by weight of alumina cement and ultrafine powder. A high-strength cement hardened product from which air bubbles have been removed.