JPS5852942B2 - Anti-breathing additive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an additive for preventing breathing in chillers containing cement.

Specifically, a mixture of hydroxyethyl cellulose and aluminum sulfate is added to a watery chiller containing cement to provide an additive that effectively prevents breathing.

Generally, when a solid material such as cement is mixed with water and left to stand still, the difference in specific gravity between the solid material and water causes the solid material to settle and water to rise to the top, causing a so-called breathing phenomenon.

Traditionally, most of the forms in which cement has been used have been in the form of concrete or mortar, with the remaining very small amount being in the form of paste or milk.

Breathing in ordinary concrete and mortar can be indirectly reduced or improved by various admixtures used to improve other physical properties, so there was little need to specifically address the prevention of breathing as an issue.

In addition, at the paste and milk stage, the degree of breathing was small and the amount used was small, so this did not pose a problem.

However, in recent years, with the active and effective use of ocean space, the deep cement mixing method (De
ep Cement Mixing Method),
Because grouting methods, pre-packed methods, etc. use cement slurry with a large amount of water, and it is necessary to process large quantities using large machines, the issue of breathing has become a completely new issue that cannot be managed using conventional thinking. .

The cement slurry used in this construction method uses a cement slurry with a larger amount of water than the cement slurry used in general cement factories, ready-mixed concrete factories, etc.

However, when transferring cement slurry with a large amount of water through a pipe, operation may be temporarily stopped at S while the cement slurry is still present in the pipe due to process reasons or mechanical trouble.

At that time, the cement slurry caused a breathing phenomenon, and solid materials separated from water were deposited in the pipes, causing problems such as clogging of the pipes when restarting operations.

As a result of intensive research based on this background, the present inventors discovered that a synergistic anti-bleeding effect can be achieved by adding hydroxyethyl cellulose and aluminum sulfate to cement slurry. It has been completed.

The present invention is an additive for preventing breathing of a moment slurry consisting of 3 to 90 parts by weight of aluminum sulfate to 1 part by weight of hydroxyethyl cellulose and 60 to 150 parts by weight of water to 100 parts by weight of cement.

As the hydroxyethylcellulose used in the present invention, a conventional hydroxyethylcellulose produced by reacting cellulose and ethylene oxide in the presence of an alkali can be used.

The breathing effect of hydroxyethyl cellulose varies depending on the number of moles of ethylene oxide reacted per cellulose molecule unit (hereinafter abbreviated as MS), and the larger the MS, the more effective it is, and preferably hydroxyethyl cellulose has an MS of 2.6 to 5. is used.

Moreover, the aluminum sulfate used in the present invention is in the range of 3 to 90 parts by weight, preferably 7 to 30 parts by weight, per 1 part by weight of hydroxyethyl cellulose.

If the amount is less than 3 parts by weight or more than 90 parts by weight, a desirable synergistic effect cannot be exhibited.

The aluminum sulfate is not particularly limited, and in general, aluminum sulfate, potassium light bread, sodium light bread, etc. are preferably used.

The additive consisting of hydroxyethyl cellulose and aluminum sulfate of the present invention is generally added in an amount of 0.3 to 5 parts by weight, preferably 0.5 to 3 parts by weight, based on the cement components in the cement slurry.

If the amount added is less than 0.3 parts by weight, the anti-breathing effect will be small, and if it is added in excess of 5 parts by weight, no significant difference will be observed, which is also economically disadvantageous.

The manner in which the additive of the present invention is mixed into the cement slurry is not particularly limited.

In general, it is preferable to mix additives into cement components in advance, before adding water to the cement components to form a slurry.

As the cement component of the cement slurry, Portland cement such as ordinary Portland cement and early strength Portland cement, mixed cement such as blast furnace cement, silica cement, fly ash cement, etc. are used.

Furthermore, it contains aggregates such as sand and gravel and other admixtures such as setting regulators, if necessary.

Therefore, the term "cement slurry" in the present invention is a broader concept than the so-called "cement slurry" in which water is added to cement alone, and includes, for example, highly fluid mortar.

That is, the cement slurry used in the present invention contains 60 to 150 parts by weight of water based on 100 parts by weight of cement.

When the amount is less than 60 parts by weight, the degree of the breathing phenomenon is small, and there are few problems caused by temporary stoppage of operation due to normal process circumstances or mechanical troubles.

On the other hand, if the amount of water exceeds 60 parts by weight, the breathing phenomenon becomes noticeable, and if the amount increases further to 150 parts by weight or more, it may be difficult to expect practical breathing prevention even by the method of the present invention. In such cases, the strength after construction is difficult to put into practical use.

The present invention is characterized in that bleeding is synergistically prevented by using hydroxyethyl cellulose and aluminum sulfate together in such a cement slurry.

The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

Example 1 Cement (Portland cement: manufactured by Tokuyama Soda) 10
A slurry was prepared by adding and mixing a predetermined amount of hydroxyethyl cellulose (MS2.8) and sulfuric acid band to 0 parts by weight into 100 parts by weight of water with stirring, and thoroughly kneading the slurry, which was then subjected to a breathing test.

The test method was based on the Japan Society of Civil Engineers standard I-3 method for testing the breathing rate and expansion rate of prepacked concrete pouring mortar.

The temperature is 20°C.

Figure 1 shows the relationship between the breathing rate and the rate of addition of additives to cement.

In addition, the breathing rate without additives is 31.8
%Met.

Example 2 The same procedure as in Example 1 was carried out except that 0.15 parts by weight of hydroxyethyl cellulose having an MS of 3.2 and 1.5 parts by weight of sulfuric acid were used based on 100 parts by weight of cement.

As a result, the breathing rate was 2, which is indicated by a mark ◎ in Figure 1.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amounts of hydroxyethylcellulose and sulfate added and the breathing rate.

Claims (1)

[Claims] 1. Cement 10 consisting of 3 to 90 parts by weight of aluminum sulfate per 1 part by weight of hydroxyethyl cellulose.
An additive for preventing breathing that is added to cement slurry in an amount of 60 to 150 parts by weight per 0 parts by weight. 2 The number of moles of ethylene oxide bonded per cellulose molecule unit of hydroxyethylcellulose is 2.6 to 5
The additive according to claim 1.