JPS6247830B2 - - 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, the present invention relates to an expandable cement composition that exhibits excellent expandability by controlling the reactivity of alkali-reactive metal powder in cement, which has conventionally been difficult to control in terms of expansion properties or amount of expansion.

In recent years, grouting materials that have been given expandability using various methods have been used for grouting purposes such as fixing anchor bolts in bridges, pouring concrete, and installing various types of machine pedestals.

It is also necessary to reduce volume changes in secondary products such as pre-packed concrete.
Metal powders that react in alkali and have a foaming effect are often used as expansion materials that impart these expandability properties, and in particular, aluminum powders are often used.

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 is that the cement composition undergoes slight expansion continuously until the heat generation 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 ends in a short period of time, and the foaming action almost ends before the cement solidifies, leading to the expansion peak. This caused recontraction from time to time. Due to this re-shrinkage, it is currently impossible to expect true non-receivable properties.

In addition to the difficulty of controlling the reaction time of the foaming action, it is also difficult to control the amount of expansion because these metal powders are highly active, so even a small amount added has a large effect on the amount of expansion, and the reaction Since the properties are greatly influenced by the amount of calcium hydroxide produced during the hydration process of cement, one type of highly active metal powder has to be greatly affected by the hydration rate of the cement.

For these reasons, when using these alkali-reactive metals or alloys 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 cannot 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 and provides a cement composition for expandable grout that controls the reaction of alkali-reactive metals in cement, causes a stable and continuous reaction, and has ideal expansion properties. It provides:

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 expansion reaction process of grout. This can be achieved by using two or more types of metal powders with different values in combination to control gas generation due to reaction and provide stable expansion properties.

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

This makes it possible to prevent so-called initial shrinkage during cement nourishment and re-shrinkage due to thermal factors after cement heat generation.

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 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, it may cause a decrease in strength or breakage. Metal powders with different degrees of activity are appropriately combined.

The metal powders having alkali reactivity used in the present invention include aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys, nickel, nickel alloys, silicon, and silicon alloys, among which highly active ones are selected. Low activity drugs can be selected and used together.

However, among these materials that can be used as metal powders with low activity and alkali reactivity, it is relatively difficult to control the amount of addition and expansion, or it is economically disadvantageous to add large amounts. .

In consideration of these points, the present invention uses a metal powder that allows easy control of reactivity and provides good expansion properties.

That is, by using a metal powder having a low activity and alkali reactivity, the surface of which has been treated to make the metal powder low in activity, is used, thereby making it possible to carry out the expansion reaction more stably over a long period of time.

Low-activated metal powder or alloy powder can be obtained by surface-treating ordinary metal powder or alloy powder with hydrogen peroxide solution. In this treatment with hydrogen peroxide solution, the desired degree of activation can be easily adjusted by appropriately selecting treatment conditions such as treatment time and treatment temperature. This is an advantage that cannot be obtained when metal or alloy powder is coated with a polymeric substance or the like.

A suitable treatment solution is a 0.1 _to 10% _H2O2 aqueous solution; _below 0.1% _H2O2 , surface oxidation is difficult to occur and low activation is _difficult , and above 10% _H2O2 the processing time is It is difficult to control the degree of surface oxidation, making it difficult to obtain stable properties.

Further, the amount of each of the various metal powders used in the present invention can be adjusted as appropriate depending on their activity and reaction properties. It is preferably in the range of 0.0001 to 0.1 part by weight; below this range, no expansion effect due to gas generation can be obtained, and above this range, strength deterioration and appearance deterioration occur due to rapid gas generation.

Regarding low activity or suppressed activity, the amount is preferably in the range of 0.001 to 10 parts by weight per 100 parts by weight of the cement composition for grout, and below this range, re-shrinkage during curing is prevented. It is ineffective, and if it exceeds 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.

In addition, in the inorganic composition which is the main component of these hydraulic cements, 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 1 100 parts by weight of the above cement mixture for grout was treated with stearic acid to give a specific surface area of 4000 to 6000 cm ² /
g of aluminum powder, 0.001 parts by weight and 3%
Specific surface area 200-300 treated with _{H2O2 aqueous} solution
Adding 0.05 parts by weight of aluminum powder of cm ² /g,
The case in which 18 parts by weight of water was added is shown in the solid line a in the attached figure.

Comparative Example In the attached figure, the broken line b indicates the case of conventional expandable cement, and is included for comparison with the effect of the thermally expandable cement according to 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.
These are the results of the same tests as in each example, in which 0.001 part by weight of aluminum powder of ~5000 cm ² /g was added and 18 parts by weight of water were added and mixed to form a slurry.

[Brief explanation of the drawing]

The attached drawings are diagrams showing the effects of the present invention in comparison with a conventional example, where a and b show the embodiment of the present invention, and b shows the conventional example.

Claims (1)

[Claims] 1. Metal powders or alloy powders that have high activity and alkali reactivity in cement compositions, and metal powders or alloy powders that are made low in activity by treating these metal powders or alloy powders with hydrogen peroxide solution. An expandable cement composition characterized by adding a combination of one or more of the following. 2. The metal powder or alloy powder having alkali reactivity according to claim 1 is one selected from aluminum, aluminum alloy, zinc, zinc alloy, magnesium, magnesium alloy, nickel, nickel alloy, silicon, and silicon alloy; An expandable cement composition comprising two or more types.