JP2008162842A - High-strength admixture for mortar or concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength admixture drastically increasing dispersibility of fine silica fume that strongly affects strengthening of mortar or concrete and sufficiently imparting high strength development to mortar or concrete with a low water content without reducing its flow property. <P>SOLUTION: The high-strength admixture for mortar or concrete comprises 100 pts.mass silica fume and 100-600 pts.mass water-insoluble inorganic powder having specific gravity of 2.2-2.7 and substantially no hydration reactivity. Preferably, the high-strength admixture for mortar or concrete comprises silica stone powder as the water-insoluble inorganic powder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-strength admixture used for enhancing the strength of mortar or concrete.

In order to obtain mortar and concrete having high strength, the strength increases as the blending amount of water in the cement is lowered. However, the decrease in the blending amount of water brings about a decrease in fluidity, making construction and molding difficult. When water reducing agents are mixed, the decrease in fluidity is alleviated, but the mortar and concrete binder phase is formed by the hydration reaction of cement, so there is a limit to the decrease in the amount of water added. If silica fume is mixed with mortar or concrete, high strength can be achieved by the microfiller effect without reducing the amount of blended water to the limit. In order to increase the strength, a sufficient effect cannot be obtained unless fine silica fume having a high reaction activity, for example, about 0.1 μm is used. Even if such fine powder is not mixed, it is easy to agglomerate, and even when mixed with mortar or concrete, it is very difficult to disperse. For this reason, for example, silica fume is mixed and pulverized with cement clinker (for example, see Patent Document 1), blast furnace slag (for example, see Patent Document 2) or limestone (for example, see Patent Document 3), and around the silica fume particles. It is known that if such particles are brought into contact with each other and mixed with mortar or concrete, the agglomeration of silica fume during mixing can be suppressed, and the dispersibility of the silica fume fine powder is improved.
JP-A-8-91885 JP-A-5-147984 JP 2000-128616 A

  However, the dispersibility of silica fume in mortar and concrete is still insufficient in the measures using the mixed pulverized material with cement clinker, blast furnace slag or limestone. This is because the silica fume once dispersed in the mortar and concrete is fine, so the cement clinker particles, etc. that were in close contact with the silica fume particles were separated during the mortar-concrete kneading after pouring, and the kneading was completed. Later, silica fume reaggregation was likely to occur. As a result, it is difficult to obtain mortar and concrete having a uniform composition, and strength development is not so high as expected. This situation becomes more prominent as the blending amount of the kneaded water becomes lower. Therefore, the present invention dramatically increases the dispersibility of fine silica fume, which has a strong effect on increasing the strength of mortar and concrete, and has high strength without reducing fluidity even when used in mortar and concrete containing low water content. The present invention provides a high-strength admixture that can impart sufficient expression.

  As a result of intensive studies to solve the problem, the present inventor has a relatively good miscibility with silica fume among inorganic powders that do not perform hydration reaction activity that does not affect the setting properties of mortar and concrete. In addition, by selecting a water-insoluble inorganic powder having a specific gravity close to that of both and mixing it with silica fume, mortar or concrete is mixed, so that the silica fume can be mixed even after mixing with a relatively low amount of water. The knowledge that a high dispersion state is secured and mortar and concrete having a sufficiently high strength can be easily obtained has been obtained, and the present invention has been completed.

  That is, the present invention is a high-strength admixture for mortar or concrete represented by the following (1) to (2). (1) High strength blending for mortar or concrete comprising 100 parts by mass of silica fume and 100 to 600 parts by mass of a water-insoluble inorganic powder having a specific gravity of 2.2 to 2.7 and having substantially no hydration reaction activity Agent. (2) The high-strength admixture for mortar or concrete according to (1), wherein the inorganic powder is silica powder.

  According to the present invention, high strength of mortar and concrete can be sufficiently achieved, and the amount of water blended in mortar and concrete can be considerably reduced, so that higher strength development can be easily obtained.

  The silica fume used for the high-strength admixture for mortar or concrete of the present invention is not particularly limited in terms of ingredients and production sources. The particle size recommended and exemplified because it is easy to obtain desired fluidity and high strength developability is suitably about 0.1 to 0.5 μm in average particle size, but finer particles may be used.

  The water-insoluble inorganic powder used together with silica fume in the high-strength admixture for mortar or concrete of the present invention is an inorganic substance having substantially no hydration reaction activity and having a specific gravity of 2.2 to 2.7. If there is, it is not particularly limited as long as it can be contained in mortar or concrete. Preferably, among the inorganic powders having such properties, it is preferable to use silica powder because it has little influence on the setting properties and curability, has good miscibility with silica fume, and is easily available. A water-soluble inorganic powder is not preferable because it dissolves after water injection of mortar or concrete and has no barrier action against agglomeration of silica fume. Further, if the inorganic powder has hydration reaction activity, it is not preferable because silica fume particles are easily taken into the hydration reaction product after water injection, the microfiller effect is reduced, and the strength is difficult to improve. Furthermore, when the inorganic powder has a specific gravity of less than 2.2 or more than 2.7, it tends to separate from the silica fume in the mortar / concrete slurry after water injection due to the difference in specific gravity with the silica fume, and as a result, in the slurry. A portion where a large amount of silica fume is present is formed, reaggregation is likely to occur, and a uniform dispersion state is hardly obtained, which is not preferable. In addition, the particle size of the water-insoluble inorganic powder is not limited, but preferably, when the average particle size is approximately 5 to 25 μm, the contact area with the silica fume particles is increased and aggregation can be efficiently prevented.

  The amount of the water-insoluble inorganic powder used in the high-strength admixture for mortar or concrete of the present invention is 100 to 600 parts by mass of the water-insoluble inorganic powder with respect to 100 parts by mass of silica fume. Less than 100 parts by weight of the water-insoluble inorganic powder is not preferable because the inorganic powder that becomes a barrier to the aggregation of the silica fume is insufficient and the dispersibility is lowered, and when it exceeds 600 parts by weight, the dispersibility of the silica fume is hardly improved. Moreover, since the ratio of the binder phase forming component in mortar or concrete is insufficient and high strength cannot be achieved sufficiently, it is not preferable.

  The high-strength admixture for mortar or concrete of the present invention contains a mixture of the silica fume and a water-insoluble inorganic powder. By using the mixed particles, the state in which the water-insoluble inorganic powder is in contact with the silica fume particles is increased, the aggregation of the silica fume can be prevented, and the dispersibility is dramatically improved. The mixing method is not particularly limited. As a suitable example, a predetermined amount of silica fume and a non-water-soluble inorganic substance such as dried silica stone may be put into a ball mill or a rod mill and pulverized and mixed in a dry manner. Not particularly necessary.

  Moreover, the high intensity | strength admixture for mortar or concrete of this invention can contain components other than the said silica fume and water-insoluble inorganic powder, as long as the effect of this invention is not lost.

[Preparation of admixture]
Using materials selected from the following A1 to A4 and silica fume (B), they are charged all at once into a ball mill (internal volume 100 liters, iron pulverized ball usage 200 kg) so as to achieve the blending amount shown in Table 1. 75 minutes The mixture was pulverized and mixed dry to obtain a mixture of about 20 kg per batch. This mixture was used as an admixture.

A1: Normal Portland cement (manufactured by Taiheiyo Cement Co., specific gravity 3.2)
A2: Limestone powder (manufactured by Taiheiyo Materials Co., Ltd., specific gravity 2.8)
A3: Silica (manufactured by Taiheiyo Materials Co., Ltd., specific gravity 2.6, maximum particle size 0.8mm)
A4: Fly ash (commercially available product, specific gravity 2.2, brain specific surface area 3400 cm ² / g)
B: Silica fume (commercially available product, specific gravity 2.4, BET specific surface area 19 m ² / g)

[Preparation of concrete specimen]
Admixtures made above, ordinary Portland cement (manufactured by Taiheiyo Cement), high-performance water reducing agent (trade name “Pacific Core Flow”, Taiheiyo Materials Co., Ltd.), fine aggregate (mountain sand from Kikugawa City, Shizuoka Prefecture), coarse aggregate The crushed stone from Sakuragawa City, Ibaraki Prefecture) and water were mixed in a biaxial forced kneading mixer so that the blending amounts shown in Table 2 were obtained, and a kneaded product was obtained. Next, this kneaded product was poured and filled into a cylindrical mold having an inner diameter of 10 cm and a height of 20 cm. In addition, the fluidity | liquidity of the grade which can be poured into a mold form without resistance of any kneaded material was ensured. The filling in the mold was removed after 24 hours in the atmosphere at 20 ° C., and further cured in water at 20 ° C. for 27 days to prepare a concrete specimen.

[Concrete strength properties]
The compressive strength of a 28-day-old concrete specimen prepared as described above was measured by a method based on JIS A 1108. The results are shown in Table 2.

  From the results in Table 2, it can be seen that the concrete using the admixture of the present invention exhibited significantly higher strength than the concrete obtained by the prior art.

Claims (2)

A high-strength admixture for mortar or concrete comprising 100 parts by mass of silica fume and 100 to 600 parts by mass of a water-insoluble inorganic powder having a specific gravity of 2.2 to 2.7 and having substantially no hydration reaction activity. The high-strength admixture for mortar or concrete according to claim 1, wherein the inorganic powder is quartzite powder.