JPS59111955A - Expandable cement composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 using a combination of several types of cement having different expansion reaction properties.

In recent years, expandable grouting materials have been used for grouting work such as fixing anchor bolts in bridge sheaths, joints for reverse concrete pouring, and installing various machine pedestals.

In addition, it is necessary to give expandability to secondary products such as pre-packed concrete to reduce volume changes.

As the expanding agent for these hydraulic cements, metal powders, calcium fluoroaluminate systems, high lime content systems, etc., which have a foaming effect by reacting in alkali, have been used alone. Among them, metal powders such as aluminum powder are widely used from an economical standpoint.

The ideal property of these expanding materials is that they continue to undergo minute expansions until the exothermic and solidifying reactions of the cement composition are completed.

In recent years, various methods have been tried to control the amount of expansion, but it is still difficult to control the expansion to give cement such ideal expansion properties, which may cause cracks and destruction of the grout. There was a need for improvements in this respect for the expansion material to prevent re-shrinkage from the expansion peak.

However, it is difficult to obtain ideal expansion properties by using conventional cement expansion materials alone.

there were.

For example, in the case of a single addition of metal powder such as aluminum, when added to a cement composition and then kneaded with water,
Because the reaction ends in a short time and the foaming action ends before the cement solidifies, no expansion action can be expected from the peak of expansion, which causes re-shrinkage when the cement solidifies, resulting in no shrinkage. There was a problem that it was not possible to give gender.

In addition to the difficulty in controlling the reaction time of the foaming action, there is also the problem that because of the high activity, even a small amount added has a large effect on the amount of expansion, making it difficult to control the amount of expansion.

Furthermore, since the reactivity of these metal powders is greatly influenced by the amount of calcium hydroxide produced during the hydration process of cement, adding only highly active metal powders will result in the expansion amount being as low as expected. There was also the problem of not being able to control the situation.

On the other hand, various calcium sulfoaluminate-based and high lime-based expansive materials have been proposed, but they are difficult to adjust to suit the solidification time of the cement composition, and if the reaction until solidification is too slow, However, if the expansion effect is too large or occurs too late, there is a problem that partial cracking or destruction may occur.

The present invention solves the problems caused by the conventional addition of an expanding agent alone.The present invention aims to improve the re-expansion property in order to compensate for the re-shrinkage after the completion of the initial expansion reaction during the expansion reaction process of the grout. The object of the present invention is to provide a cement composition for grout that can obtain the following properties and has stable expansion properties.

The object of the present invention is to combine, in the cement expanding material used, an expanding material that is highly active, has a fast reaction rate, and provides initial expansion properties, with an expanding material that has a slow reaction rate, and provides long-term expansion properties, to form a hydraulic cement. This is achieved by controlling the behavior of expansion due to reaction with

In other words, by preparing several types of cement expansion materials with different expansion properties and using them in combination, the expansion reaction in the cement composition can be continued step by step and continuously, and cement curing can be achieved. It is possible to prevent so-called initial shrinkage and re-shrinkage due to thermal factors caused by the re-lowering of the material temperature after the cement heats up, and it is possible to obtain stable expansion properties over a long period of time during the cement hardening process.

As the cement expansion material used in the present invention, a metal powder that reacts in the presence of an alkaline component in cement to generate gas can be used. Among these metal powders, those with high activity and initial reactivity and those with low activity and long-term reactivity are combined. If a small amount of gas is continuously generated for a long period of time using this combination, fine bubbles can be uniformly dispersed in the cured product, and the concentration of bubbles will not cause a forced drop.

However, when adjusting the gas generation time depending on the activity of the metal or alloy 8) powder, if the reaction is too fast, the 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, This may cause a decrease in strength or breakage, so it is necessary to check the characteristics of the expanding agent with respect to the cement composition before combining it.

The expanding material used in the present invention includes, first of all, a combination of metal powders having alkali reactivity.

Specifically, aluminum and aluminum alloys.

Examples include powders of zinc, zinc alloys, magnesium, magnesium alloys, nickel, nickel alloys, silicon, and silicon alloys. In addition to the above-mentioned metal powders, it is also possible to use expansive components such as calcium sulfoaluminate, calcium aluminate, and lime 1 gypsum, and from these, high-activity and low-activity ones can be used in combination. It is also possible to use it in combination with the above-mentioned metal and alloy powders.

Furthermore, when combining materials, it is possible not only to combine different types of materials, but also to combine the same types of materials by changing their reactivity depending on the particle size and shape of the particles.

Furthermore, regardless of whether the materials are of the same type or different types, it is also possible to perform a surface treatment to condition the expanding material particles and combine them as desired.

The amount of the expanding agent to be added is preferably in the range of 0.0001 to 0.1 part by weight per 100 parts by weight of the cement composition for grouting for those with high initial reactivity; below this range, gas generation may occur. Expansion hardening cannot be obtained due to the amount of gas used, and if the amount exceeds this amount, the strength will deteriorate due to the sudden demand for gas, and the appearance will deteriorate.

In addition, for low-activity materials with long-term reactivity or materials with 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, There is no effect of preventing re-shrinkage during curing, and if it exceeds this, the expansion effect after the material hardens becomes 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, moderate heat Portland cement, blast furnace cement, silica cement, fly ash cement, white cement, sulfate-resistant cement, etc. Both are applicable.

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, it is essential for a cement composition for grout to have free flow properties and to be free from pleating, 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 dried silica sand and 5 parts by weight of ordinary Portland cement
0 parts by weight and 0 parts of sodium polyalkylaryl sulfonate
．． 5 parts by weight 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 grout was treated with stearic acid as a highly active expanding agent with initial reactivity to give a specific surface area of 4,000~
5,000c+a/g aluminum powder at 0.001
parts by weight and specific surface area 20 as a long-term reactive intumescent material.
0.01 part by weight of 0 to 300 cal/g nickel powder was added and mixed into a slurry.

This slurry was poured into a metal frame with a diameter of 50 mm and a height of I 00 +n, and the expansion was measured, and the results are shown by the solid line a in the attached figure.

Moreover, the broken line in the same figure shows a case where aluminum powder is used alone as a conventional expansion material as a comparative example. 50 parts by weight of dry silica sand, 50 parts by weight of ordinary Portland cement
Parts by weight were mixed in advance to make it homogeneous, and this was treated with stearic acid to give a specific surface area of 4,000 to 5,000.
0.001 part by weight of aluminum powder of cnl/g and 18 parts by weight of water were mixed to form a slurry, and the degree of expansion was observed in the same manner as in the example.

The attached figure shows that while the expansion rate of conventional expansion materials decreases after the initial expansion peak, the cement composition according to the present invention maintains a slight continuous expansion over a long solidification period. I know that there is.

[Brief explanation of the drawing]

The attached figure is a diagram showing the expandability of the cement composition of the present invention in comparison with a conventional cement composition. Patent applicant Nippon Steel Corporation Kurosaki Ceramics Co., Ltd. Agent Masu Tebori (2 people)

Claims (1)

[Claims] 1. An expandable cement composition characterized by adding a combination of an expanding agent with high initial reactivity and an expanding agent that maintains long-term reactivity to an inorganic composition whose main component is hydraulic cement.