JPH01131042A - Electrically conductive cement - Google Patents

Abstract

PURPOSE:To obtain electrically conductive cement providing a set cement material having excellent electrical conductivity by using a small amount of carbon fiber, having excellent dispersibility of carbon fiber, comprising carbon fiber, so aluminate and a hydraulic composition. CONSTITUTION:(A) Carbon fibers are blended with (B) an aluminate (e.g. sodium aluminate or magnesium aluminate) and (C) a hydraulic composition (e.g., ordinary Portland cement) by a mixer to produce electrically conductive cement. When the electrically conductive cement is kneaded with a proper amount of water, the carbon fibers are uniformly dispersed into the cement since the aluminate is added. Consequently, a set cement material having excellent electrical conductivity can be produced with a small amount of carbon fibers used. The prepared electrically conductive cement is preferably used in the field of an agent to reduce earthing resistance, electrical radiation absorbing material, etc., requiring electrical conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cement used in fields requiring electrical conductivity, such as grounding resistance reducers and radio wave absorbers.

[Conventional technology and its problems]

To impart conductivity to cement, conductive powders such as carbon black and conductive fibers such as carbon fibers or steel fibers are added to the cement.

Among these, carbon fibers are preferable because they improve conductivity when added in small amounts, but they are elongated and high-strength, so it is difficult to mix and disperse them in cement. There was a drawback that it was difficult to obtain a cured cement product (Japanese Patent Publication No. 45142/1982).

In view of the above-mentioned drawbacks, the present invention was made with the object of obtaining a hardened cement body in which carbon fibers are uniformly dispersed and has good electrical conductivity.

[Means for solving problems]

The present invention is a conductive cement characterized by comprising carbon fiber, an aluminate, and a hydraulic composition.

The present invention will be explained in detail below.

The length and diameter of the carbon fibers referred to in the present invention are not particularly limited, but as the length of the fibers becomes shorter, the conductivity tends to decrease, and conversely, when the length of the fibers becomes longer, the dispersibility tends to decrease. The length is preferably 3 to 100 mm. Further, as the fiber diameter becomes larger, the dispersion density becomes coarser with the same amount added, making it difficult to conduct uniformly, and it becomes necessary to add a large amount, so the fiber diameter is preferably 50 μm or less.

Aluminate refers to sodium aluminate, potassium aluminate, magnesium aluminate, calcium aluminate, etc. The above aluminates may be used alone or in combination of two or more. .

Hydraulic compositions include Portland cements such as ordinary Portland cement, moderate heat Portland cement, early strength Portland cement, ultra early strength Portland cement, or sulfate-resistant Portland cement, blast furnace cement, silica cement, or fly ash cement. Special cements such as mixed cements, alumina cements, white cements, ultra-fast hardening cements, or expansive cements, or hydraulic substances such as gypsum trihydrate and gypsum hemihydrate are the main components.

To prepare a conductive cement, the carbon fibers, aluminate and hydraulic composition may be premixed in various mixers, or may be mixed simultaneously when used as cement paste, mortar or concrete.

The mixing ratio is preferably 6% by weight or less of carbon fiber and 30% by weight or less of aluminate based on the hydraulic composition.

If carbon fiber is added in a proportion exceeding 6% by weight, the fibers will become lump-like and no improvement in electrical conductivity can be expected. Since aluminate has the effect of accelerating coagulation and hardening, if it is added in a proportion exceeding 30% by weight, it will coagulate immediately after pouring water, resulting in poor fiber dispersibility.

As a mixer, for example, a Nauta Mixer 1 blender, a ball mill, a tilting mixer, or a product manufactured by Chiyoda Giken Kogyo Co., Ltd. under the trade name "Omni Mixer" can be used for uniform mixing.

When using the conductive cement mixed by the above method, it may be kneaded with water and used as a paste, or this conductive cement and fine aggregate may be mixed and used as mortar. Moreover, this conductive cement, fine aggregate, and coarse aggregate may be mixed and used as concrete.

In this case, the kneading machine may be a general one such as a tilting mixer, a mortar mixer, a hand mixer, or a forced mixer.

Furthermore, for the purpose of preventing cracks and the like due to drying shrinkage of the hardened cement product, hydrated inert powder such as quartz, calcium carbonate, silicon carbide, alumina or talc may be added.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Ordinary Portland cement (manufactured by Andes Cement) 1
00 parts by weight, fiber length 25n, fiber diameter 15μm
2 parts by weight of carbon fiber (manufactured by Kureha Kagaku Kogyo Co., Ltd.) and 1 part by weight of sodium aluminate (manufactured by Denki Kagaku Kogyo Co., Ltd.) were mixed for 3 minutes using an omnimixer.

To this, 80 parts by weight of water was added and kneaded for 5 minutes using a hand mixer. The paste was not lump-like and the fibers were sufficiently dispersed.

In order to use this paste as a grounding resistance reducer, we dug a hole 50 x 50 am in length and width and 70 cm in height and poured it into the place where the copper earth rod was embedded. After 5 minutes, it hardened and could be backfilled. Met.

Table 1 shows the measurement results of specific resistance before treatment, 7 days after treatment, 6 months after treatment, and 1 year after treatment.

As shown in Table 1, the specific resistance of the cured product was improved, and no change was observed even after 1 year.

Table 1 Example 2 To 100 parts by weight of ordinary Portland cement, 2 parts by weight of carbon fibers with a fiber length of 25 mm and a fiber diameter of 15 μm and 1 part by weight of sodium aluminate (manufactured by Denki Kagaku Kogyo Co., Ltd.) were added.
(2) Mixed for 5 minutes using a blender. 80 parts by weight of water was added to this, and the mixture was kneaded for 5 minutes using a mortar mixer.

For comparison, a similar test was conducted without the addition of sthorium aluminate.

In the case where sodium aluminate was added, the fibers were sufficiently dispersed without forming a dumpling-like shape, but in the case of the case without the addition, the fibers were intertwined with each other, resulting in a ball-like shape.

These pastes were placed in a 4 x 4 x 15 cm mold, and placed at a temperature of 20° C. and a relative humidity of 60%. Seven days after casting, the specific resistance of the cured product was measured, and Table 2 was obtained.

If sodium aluminate is not added, cement 10
Even when 6 parts by weight of carbon fiber was added to 0 parts by weight, the specific resistance of the cured product was not improved.

Table 2 Example 3 In Example 2, potassium aluminate and calcium aluminate were used in place of sodium aluminate in a weight ratio of 1:1.
A similar test was carried out by adding 1 part by weight of the mixture of 1 and 2, and Table 3 was obtained.

〔Effect of the invention〕

By using the conductive cement of the present invention, the following effects can be obtained.

(1) Carbon fibers can be uniformly dispersed in the cement hardened body.

(2) By mixing a small amount of carbon fiber, the cement hardened body can obtain high conductivity.

Patent applicant: Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] A conductive cement comprising carbon fiber, an aluminate, and a hydraulic composition.