JPS6247829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an expandable cement composition particularly suitable as a grout material.

More specifically, it is an expansible cement that exhibits excellent expansibility by controlling the reactivity of alkali-reactive metal or alloy powder in cement, for which it has been difficult to control expansivity or expansion amount. Regarding the composition.

In recent years, anchor bolt fixing for bridges, etc.
For grouting at places where concrete is poured in reverse or when installing various types of machine pedestals,
Grout materials that have been given expandability by various methods are used. It is also necessary to reduce volume changes in secondary products such as pre-packed concrete, and metal powders, which have a foaming effect when reacted in alkali, are often used as the expanding agent to impart expandability to these products. aluminum powder is used in many cases.

However, all of these metal powders, typified by aluminum powder, are extremely active, and bubble generation ends within a short time after addition and kneading, making it extremely difficult to apply their effects. .

The ideal expansion property of such a cement composition is that slight expansion is performed continuously until the exothermic and solidification reaction of the cement composition is completed.

However, with the usual addition of aluminum powder alone, when water is added and kneaded, the reaction completes in a short time, and the foaming action ends before the cement solidifies, resulting in the expansion reaching its peak. This caused re-shrinkage. Due to this re-shrinkage, it was not currently possible to expect true non-shrinkage properties.

In addition to the difficulty in controlling the reaction time of the foaming action, in addition to the difficulty in controlling the amount of expansion, due to the high activity, even a small amount added has a large effect on the amount of expansion, and the reactivity of these metal powders. Since it is greatly influenced by the amount of calcium hydroxide produced during the hydration process of cement, when one type of highly active metal powder is used, it cannot help but be greatly influenced by the hydration rate of cement.

For this reason, when these metals or alloys having alkali reactivity are used as cement expansion materials, it has been extremely difficult to control the expansion amount and expansion properties.

In recent years, various methods have been used to control the amount of expansion, but it is still difficult to control the expansion properties.
Re-shrinkage from the expansion peak could not be prevented. This re-shrinkage causes cracking and destruction of the grout material, and improvements in this respect are needed.

The present invention solves these problems, controls the reaction of alkali-reactive metals or alloys in cement, produces stable and continuous reactions, and provides an expandable grouting cement with ideal expansion properties. A composition is provided.

The purpose of the present invention is to provide re-expansion properties to correct the re-shrinkage after the completion of the initial expansion reaction in the expansible reaction process of grout. This can be achieved by using two or more types of metal or alloy powders that react at different times in combination to control the gas generation caused by the reaction and provide stable expansion properties.

In other words, among the metals or alloy powders used, which differ in reactivity depending on specific surface area, particle size, activity, etc., those with high activity and a fast reaction rate give initial expansion properties, whereas those with a slow reaction rate give long-term expansion properties. Use things together. By preparing and using several kinds of metal or alloy powders in this way, the gas generation by the reaction of these metal powders is continuously continued little by little, thereby providing stable expansion properties over a long period of time.

This makes it possible to prevent so-called initial shrinkage during cement curing and re-shrinkage due to thermal factors after cement heats up.

Further, by continuously generating a small amount of gas for a long period of time in this manner, fine bubbles can be uniformly dispersed in the cured product, and there is no possibility of a decrease in strength due to concentration of bubbles.

When adjusting the gas generation time depending on the activity of the metal or alloy powder, if the reaction is too fast, gas generation will end in a short time, causing re-shrinkage, and if the reaction is too slow and the reaction is large for a long period of time, the strength may decrease. May cause destruction.

Highly active alkali-reactive metals or alloys used in the present invention include flaky aluminum, aluminum alloys, magnesium, and magnesium alloys having a specific surface area of 4000 to 6000 cm ² /g. On the other hand,
Examples of low-activity alkali-reactive metals or alloys include atomized aluminum, aluminum alloys, nickel, nickel alloys, zinc, zinc alloys, silicon, silicon alloys, etc., each having a specific surface area of 200 to 300 cm ² /g.

The amount of highly active metal or alloy powder to be added is preferably in the range of 0.0001 to 0.1 parts by weight per 100 parts by weight of the cement composition for grouting; below this range, expansion effects due to gas generation cannot be obtained. Moreover, if it exceeds this, the strength will deteriorate due to rapid gas generation and the appearance will deteriorate.

In addition, the amount of low activity or suppressed activity is preferably in the range of 0.0001 to 10 parts by weight per 100 parts by weight of the cement composition for grout, and below this range, the effect of preventing re-shrinkage during curing is If the temperature is higher than this, the expansion effect after the material hardens will be large, causing cracks and destruction.

Hydraulic cements used in the present invention include ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, medium heat Portland cement, blast furnace cement, silica cement, fly ash cement, white cement, sulfate resistant cement, etc. Either is fine.

Furthermore, in these inorganic compositions containing hydraulic cement as a main component, cement admixtures such as dispersants, water reducing agents, and AE agents can be used in combination, if necessary.

In particular, as a cement composition for grout, it is essential that it has free flow properties and that there is no breathing, and these properties can be solved by applying a dispersant or the like.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 50 parts by weight of dry silica sand, 50 parts by weight of ordinary Portland cement, and 0.5 parts by weight of sodium polyalkylaryl sulfonate are mixed in advance so as to be homogeneous to prepare a cement mixture for grouting. 100 parts by weight of this cement mixture for grouting, 0.001 part by weight of aluminum powder treated with stearic acid and having a specific surface area of 4000 to 5000 cm ² /g, and a specific surface area of 200 to 5000 cm 2 /g.
Adding 0.01 part by weight of nickel powder of 300 cm ² /g,
A slurry of 18 parts by weight of water was poured into a metal frame with a diameter of 50 mm and a height of 100 mm, and the expansion of the material surface was measured. The measurement results are shown in the solid line a in the attached figure.
It is shown by.

In the figure, a broken line b indicates an example of a conventional expandable cement for comparison with the effects of the present invention.

50 parts by weight of dry silica sand and 50 parts by weight of ordinary Portland cement were mixed in advance to make it homogeneous, and this was treated with stearic acid to give a specific surface area of 4000.
0.001 part by weight of aluminum powder of ~5000 cm ² /g was added, 18 parts by weight of water was added, mixed to form a slurry, and tested in the same manner as in the example.

[Brief explanation of the drawing]

The attached drawings are diagrams showing the effects of the expandable cement of the present invention in comparison with conventional expandable cement.

Claims (1)

[Claims] 1 An inorganic composition whose main component is hydraulic cement, and a highly active alkali-reactive metal or alloy consisting of particles with a specific surface area of 4000 to 6000 cm ² /g and particles with a specific surface area of 200 to 300 cm ² /g. An expandable cement composition comprising a combination of one or more metals or alloys having low activity and alkali reactivity.