JPH0753594B2 - Cement composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement composition, not to mention the field in which ordinary cement is used, and also as a repair material, grout material, floor material, etc. The present invention relates to a cement composition which can be used and is particularly effective in applications where heat resistance is particularly required such as a repair material around a furnace.

2. Description of the Related Art Cement hardens only by kneading with water, increases strength over a long period of time, and is inexpensive, so it is indispensable as an amorphous material, especially in the field of civil engineering and construction.

However, its physical properties have many drawbacks such as low tensile strength, large shrinkage, and poor heat resistance.

Conventionally, in order to overcome these drawbacks, mechanical improvement methods such as reinforcing bar, composite with steel frame, prestressing, fiber mixing, coating etc., or reduction of shrinkage by addition of expansion material as strength improvement, strengthening Increase the strength by reducing the water-cement ratio by adding materials or water-reducing materials, or by adding pozzolanic materials or siliceous materials
Improvements such as Ca (OH) ₂ reduction have been proposed and implemented.

Problems to be Solved by the Invention The matrix-forming backbone of a hardened cement is a C--S--H gel bond, and since the reaction is a liquid phase reaction, excess water above the theoretical amount of water is required, and Deterioration and disintegration due to dehydration, deviation are unavoidable, and the drawbacks of hardened cement products are largely due to these two problems.

Means for Solving the Problems In order to solve the above problems, the composition of the present invention is 100 parts by weight of cement, and alumina sol and / or powder type colloidal alumina is converted into alumina solid content of 0.
It is a cement composition containing 2 to 5 parts by weight.

Examples of the above-mentioned cement include ordinary Portland cement, early-hardening cement, ultra-fast-hardening cement, blast furnace cement, alumina cement, fly ash cement, white cement, jet cement, moderate heat cement and the like.

The content of the alumina sol and / or the powdery colloidal alumina is 0.2 to 5 parts by weight, preferably 0.2 to 1 part by weight, based on 100 parts by weight of cement, in terms of alumina solid content. If it is less than 0.2 parts by weight, the desired effect cannot be obtained, and if it exceeds 5 parts by weight, not only the strength generation is hindered but also the cost becomes high, which is not economical.

The powder-type colloidal alumina includes rod-shaped, feather-shaped,
Fibrous elongated particles are not included.

In this cement composition, additives / materials such as a water reducing agent, a thickening agent, a hardening accelerator, a hardening retarder, a defoaming agent, a foaming agent, a strength accelerating material and an expanding material can be appropriately used.

Action The action of adding alumina sol and / or powder type colloidal alumina is that the stable region is in the low pH region, whereas the cement slurry is in the high pH region,
When they coexist, the gelation of alumina is promoted, which contributes to the formation of a hardened cementitious matrix and acts to increase the strength.

Further, in a high temperature atmosphere where the C—S—H gel bond (cement matrix) is significantly deteriorated and disintegrated, the polymerization and crystallization of alumina are promoted, and as a result, the deterioration and disintegration of the cement matrix is prevented or the matrix of the matrix is prevented. It is considered that as a result of reinforcing the strength, it has an action of macroscopically strengthening the cured body.

Hereinafter, a specific description will be given with reference to examples.

Examples Hereinafter, the amounts (%) of the respective components described in Examples and Comparative Examples are all weight%.

Example 1 The materials having the compositions shown in Table 1 below were mixed in a Hobart mixer 3 times.
A 4 × 4 × 6 cm specimen was prepared using mortar that had been kneaded for minutes, and was subjected to wet air curing at 20 ° C. until a prescribed age.

The results of the compressive strength test of the above specimens are shown in Table 2 below.

Example 2 Specimens of 4 × 4 × 16 cm were prepared from a paste prepared by kneading the raw materials having the compositions shown in Table 3 below with a Hobart mixer for 3 minutes.

A compressive strength test was conducted on the above-mentioned test piece that had been cured at 20 ° C. in wet air for 7 days and then further heated at 250 ° C. for 24 hours. The results are shown in Table 4 below.

Example 3 When a hardened cement product is heated, free water and hydration-bonded water are dehydrated and deviated, the structure of the hardened product is changed, and especially the bending strength is significantly reduced.

Ordinary Portland cement paste hardened product estimated to have a hydration rate of 90% or more, and the paste hardened product of the present invention (4 x
4 × 16 cm) was heated at 100 ° C., 200 ° C. and 300 ° C. for 24 hours, and the bending strengths were compared.

Table 5 shows the composition of the raw materials and the preparation conditions of the specimen.

Table 6 shows the test pieces and the results after subjecting them to a predetermined heating test.

EFFECTS OF THE INVENTION As described above, the cement composition of the present invention can be handled in the same manner as ordinary cement, has a higher strength than neat cement when the water-cement ratio is the same, and C-S -H The weakness of the cement hardened product due to the deterioration and the collapse of the gel bond can be greatly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyuki Tokumaru 3-6-20 Ibori, Kokurakita-ku, Kitakyushu City, Fukuoka (56) References Japanese Patent Publication No. 44-2219 (JP, B1)

Claims (1)

[Claims] 1. A cement composition comprising 0.2 to 5 parts by weight of alumina sol and / or powder type colloidal alumina in terms of alumina solid content based on 100 parts by weight of cement.