JPH01145357A - Low shrinkage cement composition - Google Patents

Abstract

PURPOSE:To obtain cement composition with dimensional change reduced by adding an active silica powder and a shrinkage-reducing agent to cement. CONSTITUTION:The subject composition is obtained by adding an activated silica powder and a shrinkage reducing agent to cement. The activated silica powder is suitably amorphous silica, especially amorphous silica fine powder which is produced as a by-product in the production of metal silicon or ferrosilicon. The amount of the silicon powder is generally 5-40wt.% based on the cement. The shrinkage-reducing agent is preferably lower alcohol alkylene oxide or glycol ester. The amount of the shrinkage-reducing agent is generally 0.5-6wt.%. The cement composition can be combine with any additives such as aggregate, sand and coloring materials, as long as their objects are inhibited.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a low shrinkage cement composition, particularly a cement composition suitable for producing cement reinforced with reinforcing materials such as alkali-resistant glass fibers (GRC). This is related.

[Conventional technology] GRC is a cement product that is inherently high in strength but heavy, but instead of a cement product, a reinforcing material such as alkali-resistant glass fiber is mixed into the cement, making it stronger than the original strength of cement. At the same time, it is intended to significantly reduce its weight, and it is being used as a variety of building materials.

The cement composition used for such GRC is conventionally composed of cement, sand, water, water reducing agent, etc., and in order to achieve high strength, the amount of cement used is considerably higher than that of ordinary concrete products. ing.

[Problems to be solved by the invention] However, it is well known that cement shrinks during the hydration reaction process, and that the cured product undergoes dimensional changes due to wetting and drying, and the amount of these changes is The larger the amount of 7-ment, the bigger the effect.

For this reason, when manufacturing GRC, the design must take these dimensional changes into account, and the drawback is that precise dimensions are required, and considerable restrictions are required for manufacturing tiled panels and large panels. was there.

Of course, attempts have been made to add shrinkage reducing agents for the purpose of dealing with these dimensional changes, but none of these have resulted in very effective improvements.

[Means for Solving the Problems] In view of these circumstances, the present inventor conducted various studies and examinations with the aim of reducing dimensional changes in cement compositions as much as possible. It has been found that the above object can be achieved by adding .

Thus, the present invention provides a low-shrinkage cement composition characterized in that activated silica powder and a shrinkage-reducing agent are added to the cement.

The amount of activated silica powder used in the present invention is generally about 5 to 40% by weight based on cement.

If the amount used is less than the above range, it will be difficult to effectively reduce the dimensional change of the hardened cement together with the shrinkage reducing agent.
On the other hand, if it exceeds the above range, curing will be insufficient and the effect of suppressing shrinkage may not be expected, so it is not preferable. When this method is adopted, it is particularly preferable because it is possible to obtain a cement hardened body with high strength and minimal change in pore size.

Various types of activated silica powder can be used, but amorphous silica, particularly amorphous fine silica powder obtained as a by-product during the production of metal silicon or ferrosilicon, is suitable.

On the other hand, the amount of the shrinkage reducing agent used in the present invention is generally about 0.5 to 6% by weight based on the cement. If the amount used is less than the above range, it will be difficult to effectively reduce the dimensional changes and changes in the hardened cement product.On the other hand, if it exceeds the above range, curing will be insufficient and an effect of suppressing shrinkage may not be expected. None of these are preferable because there is a risk that the cement will disappear.
It is particularly preferable to use % by weight because it is possible to obtain a hardened cement with high strength and minimal change in pore size.

Various types of shrinkage reducing agents can be used, but shrinkage reducing agents such as lower alcohol alkylene oxide type and glycol ester type are particularly effective.

The cement composition according to the present invention is particularly suitable for GRC, but is not limited thereto, and can be appropriately used for ordinary concrete products or concrete products requiring low shrinkage such as mortar compositions.

In addition, the cement composition according to the present invention may contain not only the above-mentioned composition, but also suitable additives, such as suitable aggregates, sand, and colorants, as long as they do not substantially impede the purpose of the present invention. .

In addition, when used for GR (:), as reinforcing materials, for example, alkali-resistant glass fibers, steel fibers, carbon fibers, aramid fibers, vinylon fibers, etc. are used in an appropriate form such as chopped strands, rovings, mats, etc. The amount used is not particularly limited.

Further, the cement used in the present invention is not particularly limited, and various cements including ordinary Portland cement can be appropriately employed.

[Example] 200 mix 2 was prepared by mixing the composition as shown in Table 1, mixing chopped strands of alkali-resistant glass fiber as a reinforcing material, and using a normal direct spray method.
Table 1 shows the results of wet-dry shrinkage measurements for samples of 0 G mm x 10 m, and FIG. 1 shows the dry shrinkage results.

Table 1 and FIG. 1 also show the measurement results of samples obtained as comparative examples having the compositions shown in Table 1 in the same manner as in the Examples.

The activated silica powders used were those with average particle diameters o, ts, and t, which were generated as a by-product during the production of ferrosilicon, and the shrinkage reducing agent was a lower alcohol alkylene oxide based product called Tetragat manufactured by Nippon Cement Co., Ltd. Using.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the drying shrinkage of a low-shrinkage cement composition according to an example of the present invention and that of a comparative example.

Claims (1)

[Claims] 1. A low-shrinkage cement composition characterized in that activated silica powder and a shrinkage reducing agent are added to cement. 2. The amount of activated silica powder added is 5 to 40% of cement.
% by weight of the cement composition of claim (1). 3. The cement composition according to claim 1 or 2, wherein the activated silica powder is amorphous silica fine powder. 4. The amount of shrinkage reducing agent added is 0.5 to 6 to cement.
% by weight of the cement composition of claim (1). 5. The cement composition according to claim 1 or 4, wherein the shrinkage reducing agent is a lower alcohol alkylene oxide shrinkage reducing agent or a glycol ester shrinkage reducing agent.