JP2000264694A - Expandable powder composition for cement admixing use and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having a combination of respective functions of expanding material and shrinkage reducer, therefore having long- term shrinkage-reducing effect while suppressing the excessive expansion of mortar or concrete in its early stage of hardening, thereby enabling hard-to- crack, high-quality mortar or concrete molded forms to be manufactured, and to provide a method for producing the above composition. SOLUTION: This composition is obtained by sprinkling the surface of inorganic expanding powder with an organic shrinkage reducer to form the aimed powdery single-pack composition dry as a whole; more precisely, this composition is produced by the following process: the surface of a powdery or lumpy inorganic expanding material stock weighted and then conveyed on a belt conveyor 11 is sprinkled with a liquid organic shrinkage reducer instead of a conventional dispersion auxiliary using a spraying device 15, and the resulting stock, together with other feedstock(s), is fed, via a hopper 19, to a pulverizer 7 where these feedstocks are mixed and pulverized until they become dry and powdery as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an inorganic expanding material used as a cement admixture for preventing shrinkage cracking by providing shrinkage compensation from the initial stage or for giving a chemical prestress, and for reducing shrinkage cracking in the medium to long term. The present invention relates to an expandable powder composition for cement admixture, which has both functions of an organic shrinkage reducing agent used as a cement admixture for preventing and can maintain a shrinkage reducing effect for a long period of time, and a method for producing the same.

[0002]

2. Description of the Prior Art Concrete hardens slightly during hardening, and after hardening, it shrinks dry when exposed to the open air, causing cracks due to the shrinkage.

[0003] For the purpose of compensating for such shrinkage and reducing the occurrence of cracks due to shrinkage, powdery inorganic expanders and liquid organic shrinkage reducing agents have been mainly used.

[0004] The expanding material contains, for example, lime, sulfuric acid and alumina, and is mixed with cement in an appropriate amount to produce mortar or concrete. When mortar or concrete is produced, ettringite (3CaO.Al ₂ O ₃ .3CaSO ₄・ 32H
Needle-shaped crystals called ₂ O) and calcium hydroxide (Ca
Some (OH) ₂ ) generate a large amount of crystals and expand the mortar or concrete by the power of the crystals.

[0005] In addition, calcium hydroxide (Ca (OH) ₂ ) mainly containing free calcium oxide (expandable CaO), and also containing calcium silicate and a vitreous phase, formed by hydration of expansive CaO. And the use of crystal pressure and crystal pressure as expansion sources.

[0006] These are all powdery, and stable performance as an expanding material is exhibited by proper particle size adjustment. The amount of use is 20-40kg /
m ^{3, and} about 30-60 kg / m ³ for civil engineering. If the amount is too large, the compressive strength decreases due to excessive expansion.

As the organic shrinkage reducing agent, for example, there are those containing an alkylene oxide adduct of a lower alcohol as a component. The compound is put into a mixer together with other materials and kneaded, or the mixture is added to an agitator car at a construction site. It may be used in addition. In any case, an amount of about 4 to 8 kg / m ³ is often used as a part of the kneading water.

Further, as a conventional method for producing an inorganic expanding material, a gypsum-based material, a lime-based material, a cement-based material, a calcium sulfoaluminate-based material, and the like are mixed and pulverized to obtain a powdery expanding material. In production, for example, diethylene glycol or the like is added as a grinding aid to prevent the powders from agglomerating in the grinding step, thereby reducing the grinding efficiency.

[0009]

When mortar or concrete is cast, generally when the above-mentioned chemicals are not added,
As shown by the dotted line C in FIG. 2, it expands slightly in the initial stage, and gradually shrinks as the material age advances, causing cracks as described above.

On the other hand, when a mortar or concrete is made by mixing an inorganic expanding material, as shown by the solid line A in FIG. The initial expansion compensates for the contraction. However, also in this case, although the amount of shrinkage is smaller than that in the case where the expanding material is not added, the material gradually shrinks as the material age advances.

As a method of suppressing the amount of shrinkage, it is conceivable to increase the amount of the expanding material. One of the methods is to increase the initial amount of the expanding material. It has an adverse effect. Also,
Pop-out phenomenon easily occurs.

For this reason, various attempts have been made to reduce the amount of shrinkage over a long period of time while suppressing the initial amount of expansion by using an organic shrinkage reducing agent in addition to the inorganic expandable material. It is known that a curve closer to the ideal as shown by a broken line B can be obtained by adjusting the mixing ratio.

[0013] However, it is troublesome to simultaneously mix two types of powdery expanding material as an admixture and a liquid organic shrinkage reducing agent as an admixture to be used as a medicament at the site. There is a problem that the operation becomes complicated.

For example, if a powdery inorganic expander and an organic shrinkage reducing agent are mixed and used before mixing with cement or the like, lumps are formed, and when kneading mortar or concrete with a mixer, both are used. Are difficult to disperse uniformly in cement.

[0015] In addition, the powdery inorganic expander is kneaded with cement, and the liquid organic shrinkage reducing agent is sometimes mixed with the compounding water. However, it is troublesome and the work on site becomes complicated. .

In addition, the inorganic intumescent material itself is more susceptible to moisture than cement or the like, and the organic shrinkage reducing agent cannot be stored in large quantities due to the restrictions of the Fire Service Law because of its components. Therefore, development of a single powder or liquid having both functions of an expanding material and a shrinkage reducing agent has been desired.

The present invention has been made in view of the above background, and a single powder has both functions of an expanding material and a shrinkage reducing agent, and is caused by uneven mixing and the like. By eliminating the drawbacks caused by both pop-out phenomenon, partial strength reduction, abnormal setting and hardening,
The purpose is to provide a long-term shrinkage reduction effect while suppressing excessive expansion of mortar and concrete during the initial stage of hardening, and to enable the formation of high-quality mortar or concrete moldings that are less likely to cause shrinkage cracking by simpler construction than before. It is what it was.

[0018]

The expandable powder composition for admixing cement according to claim 1 of the present invention is obtained by adding a liquid organic shrinkable powder to an inorganic hydrated expansible powder or an inorganic expandable raw material for admixing cement. It is made into one powder by spraying a reducing agent.

Further, the expandable powder composition for cement admixture according to the second aspect of the present invention is provided on the surface of at least a part of the powder of the inorganic hydrated expandable powder or the raw material powder of the inorganic expandable material for cement admixture. Adhere organic shrinkage reducing agent
It is a powdered agent.

The inorganic hydrated expandable powder mentioned here includes lime-based, calcium sulfoaluminate-based, and gypsum-based (as the gypsum-based, sulfates such as sodium sulfate) as described in the section of the prior art. Not limited to commercially available inorganic expanding materials such as MgO-based materials, powders corresponding to the raw materials thereof, and other powders which expand similarly by reacting with water to function as an expanding material or a part thereof. Point to. In addition, the inorganic expanding material raw material,
The meaning is not necessarily limited to powder, but includes particles and lumps before pulverization.

Examples of the liquid organic shrinkage reducing agent include, in addition to alkylene oxide adducts of lower alcohols described in the section of the prior art, shrinkage of cement such as amide compounds, modified amide compounds, and various other surfactants. Examples of the agent include a reducing agent and a commercially available organic shrinkage reducing agent.

The state in which the inorganic hydration expandable powder or the raw material of the inorganic expandable material according to claim 1 is dusted with a liquid organic shrinkage reducing agent is defined as the inorganic hydrate expandable powder or the inorganic hydrate expandable powder. The group on the surface of the inorganic expander raw material and the group in the organic shrinkage reducing agent partially react with each other, and the organic shrinkage reducing agent adheres to the surface, and suppresses agglomeration of powders due to static electricity. Refers to a state in which a smooth powder is generated.

Also, a liquid organic shrinkage-reducing agent is adhered to at least a part of the powder surface of the inorganic hydration expandable powder or the raw material powder of the inorganic expandable material according to claim 2 to form a powder. This is because the groups on the surface of the powder react with some of the groups in the organic shrinkage reducing agent, and the organic shrinkage reducing agent adheres, causing the powder to coagulate as if the surface were coated. It refers to a state in which the powder is produced as a whole, for example, and the raw material of the expansive material is intended only for the case of powder. However, it partially overlaps with claim 1.

The expandable powder composition for admixing cement according to claim 3 of the present application is obtained by mixing at least a part of the raw material of the inorganic expandable material containing the raw material of hydrated expandable material and the liquid organic shrinkage reducing agent. The whole is mixed and pulverized to form a single powder.

Claim 3 is a case where, as opposed to claim 2, the raw material and the like are not limited to powder, and the whole becomes a powder through pulverization of mixed raw materials including granular or massive raw materials. This can be understood as a concept partially overlapping with the items 1 and 2.

[0026] Claim 4 restricts the case where the content ratio of the organic shrinkage reducing agent or its main component in the expandable powder composition for cement admixture according to claim 1, 2 or 3 is 10 to 20%. It is.

Originally, the inorganic expander and the organic shrinkage reducing agent are mixed and designed according to the purpose, required strength of the mortar or concrete, cement amount, aggregate amount, other admixtures and admixtures. The test is performed to determine the amount of admixture, but as the most general range, as for the inorganic expandable material, 20 to 4
0 kg / m ³ approximately, in civil engineering about 30~60kg / m ³ is considered a suitable amount in the range, functions as an expansion material and too small than this is insufficient, which when from too much initial expansion amount is large In some cases, the strength and quality may be reduced. However, when chemical stress is applied by using reinforcing bars or other constraints, a larger amount of expanding material is used.

On the other hand, the admixing amount of a commercially available liquid organic shrinkage reducing agent is usually about 4 to 8 kg / m ^{3. If the} amount is too small, the effect is insufficient, and if it is too large, it is uneconomical. In some cases, the quality of the mortar or concrete is reduced.

Further, in order to make the whole into a smooth powder while maintaining the functions of both, the amount of the organic shrinkage reducing agent used is limited. From these, the expandable powder composition for cement admixture of the present invention is used. It is considered that the content ratio of the organic shrinkage-reducing agent or the main agent therein is suitably from 10 to 20%.

A fifth aspect of the present invention is a method for producing an expandable powder composition for cement admixture according to the first, second, third or fourth aspect, wherein aggregation of the powder to be ground is suppressed and grinding efficiency is improved. In the step of pulverizing an inorganic expander material for cement admixture, a liquid organic shrinkage reducing agent or its main component is added as a material having a role of a grinding aid added for raising the inorganic expander material. Are mixed and pulverized to produce an expandable powder composition containing an organic shrinkage reducing agent.

The pulverizing step in the present invention refers to a transportation step to a pulverizer and a pulverization process in the pulverizer. As described in the section of the prior art, in the production of a conventional inorganic expanding material, when a raw material is mixed and pulverized to produce a powdery expanding material, diethylene glycol or the like is used as a pulverizing aid, and the pulverizing process is performed. Although the powders are prevented from agglomerating in the present invention, in the present invention, the organic shrinkage reducing agent itself, which is a component of the expandable powder composition for cement admixture, is used by having a role as a grinding aid. In this way, it is possible to produce an intumescent powder composition in which the whole becomes a smooth powder without any waste.

In addition, the conventional equipment for producing an inorganic expansion material can be used almost as it is, which is economical.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a production flow in one embodiment of a method for producing an expandable powder composition for cement admixture of the present invention.

The present embodiment utilizes a conventional process for producing an expanding material using lime, sulfuric acid, alumina and the like as raw materials. As a general flow in the production of an ordinary expanding material, for example, calcium sulfoaluminate, gypsum and cement as the raw materials of an inorganic expanding material are C
The raw material is supplied to the SA tank 1, the gypsum tank 2, and the cement tank 3, and the raw materials are collectively supplied to the crusher (rod mill) 7 through the measuring devices 4, 5, and 6, and the crushed material is classified. 8 or passed through a vibrating sieve or the like.

More specifically, the cement passed through the measuring device 6 (measuring belt feeder) from the cement tank 3 is supplied to the belt conveyor 11, and the screw conveyor 12 and the gypsum extracting rotary feeder 13 are similarly supplied from the gypsum tank 2. , Measuring device 5 (measuring belt feeder)
Is supplied to the belt conveyor 11.

On this belt conveyor 11, the drum 1
The liquid organic shrinkage reducing agent containing a lower alcohol alkylene oxide adduct as a main component is uniformly sprayed on the cement and the gypsum conveyed on the belt conveyor 11 by the spray device 15. Regarding the control of the addition amount, the necessary spray amount is automatically calculated based on the amount of the raw material that is measured and conveyed on the belt conveyor,
The amount of jet from the spray device 15 is automatically controlled in consideration of the amount of scatter and the like. However, the method of adding the organic shrinkage reducing agent in the present invention is not limited to this.

In the ordinary production process of an inorganic expanding material, a grinding aid such as diethylene glycol is sprayed on these materials from a spray device 15 to suppress agglomeration of the powders in the grinding process. Producing powder.

In the present invention, it can be considered that an organic shrinkage-reducing agent that has been sprinkled in place of diethylene glycol or the like plays a role of this grinding aid. As such an organic shrinkage reducing agent, for example, a liquid organic shrinkage reducing agent such as commercially available Tetra Guard AS ₂₁ (manufactured by Sanyo Chemical Industries, Ltd.) can be used. The type of the liquid organic shrinkage reducing agent is not particularly limited as long as it functions as a pulverization aid, such as suppressing crushing.

The cement and the gypsum dusted with the organic shrinkage reducing agent are supplied to the screw conveyor 17. The screw conveyor 17 has a measuring device 4 from the CSA tank 1.
(Measurement belt feeder), CSA that has passed through the belt conveyor 16 is also supplied, is transported upward by a bucket elevator 18, and is collectively supplied to the hopper 19 before the mill.

Subsequently, these raw materials are sent to the crusher 7 through the belt feeder 20 and the screw conveyor 21, where the raw materials are mixed and pulverized. The expanding material containing the organic shrinking agent component which has been uniformly powdered in the mixing and pulverizing step is sent to the classifier 8 through the bucket elevator 22 or the like (a vibrating screen or the like can be used instead of the classifier 8). ), The smooth powder having a predetermined fineness or less is sent to a product transport process and a shipping process.

Those which do not reach the predetermined degree of fineness or less pass through the screw conveyor 23 returned from the classifier 8 and are then returned to the pulverizer 7 together with the newly supplied raw materials by the screw conveyor 17 described above. Will be supplied.

In the embodiment described above, the contact between the calcium sulfoaluminate and the organic shrinkage reducing agent before entering the mixing and pulverizing step is avoided as much as possible, and the hydration reaction causes the calcium sulfoaluminate to function as an expanding material. However, the position where the organic shrinkage reducing agent is introduced is not limited to the above-mentioned belt conveyor 11, and may be, for example, in the vicinity of the hopper 19 before the mill or in the pulverizer 7, or in the calcium sulfo. Depending on the supply form of aluminate, an organic shrinkage reducing agent may be applied to calcium sulfoaluminate, or the organic shrinkage reducing agent may be adhered in such a manner as to coat the powder surface of calcium sulfoaluminate.

Various design changes can be made to the mixing ratio of each raw material according to the performance required as a product, the type and form of the raw material, the production equipment, and the like. In a composition mainly comprising a sulfoaluminate-based raw material and a gypsum-based raw material, as an example, 15 parts by weight of an organic-based shrinkage reducing agent (Tetraguard AS ₂₁ ) is added to 100 parts by weight of these inorganic expanded materials (expansion for cement admixture). When the content ratio of the organic shrinkage reducing agent in the water-soluble powder composition is about 13%), the whole expansible powder composition for cement admixture of the present invention is in the form of a smooth white powdery single agent. Thus, the effect substantially along the line B in FIG. 2 has been confirmed.

[0044]

The expandable powder composition according to the present invention comprises:
Since it can be used in the same way as conventional powdery expanders, such as by mixing it with cement as a powder, the effort of separately mixing the expander and the liquid organic shrinkage reducing agent at the site in the past can be omitted. Workability is good.

Since the expanding material and the shrinkage reducing agent are mixed in advance, there is no variation in dispersibility or the like in the on-site work, the management is easy, and high-quality mortar or concrete can be applied.

Although the initial expansion of the mortar or concrete is equal to that in the case where only the expandable powder composition is mixed, shrinkage cracks are less likely to occur over a long period of time due to less long-term shrinkage.

According to the production method of the present invention, the conventional organic expansion material production equipment can be used almost as it is, because the liquid organic shrinkage reducing agent has a role as a grinding aid in the production of the expansion material. Is economical.

[Brief description of the drawings]

FIG. 1 is a production flowchart of an expandable powder composition for admixing cement in one embodiment of the present invention.

FIG. 2 is a graph conceptually showing the effect of the expandable powder composition for cement admixture of the present invention in comparison with a case where a conventional inorganic expander is mixed and a case where no expander is mixed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CSA tank, 2 ... Gypsum tank, 3 ... Cement tank, 4, 5, 6 ... Measuring device, 7 ... Crusher, 8 ... Classifier, 1
1 ... belt conveyor, 12 ... screw conveyor, 13
... Rotary feeder, 14 ... Drum can, 15 ... Spray device, 16 ... Belt conveyor, 17 ... Screw conveyor, 18 ... Bucket elevator, 19 ... Mill hopper, 20 ... Belt feeder, 21 ... Screw conveyor, 22 ... Bucket elevator, 23 ... Screw conveyor,

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masao Sasashima 3-8-1, Nishikanda, Chiyoda-ku, Tokyo Taiheiyo Cement Co., Ltd. F-term (reference) 4G012 MA00 MA02 MB06 MB12 MB23 MB33

Claims (5)

[Claims] Claims: 1. An expandable powder for cement admixture, wherein a liquid organic shrinkage reducing agent is applied to an inorganic hydrated expansible powder for cement admixture or a raw material of an inorganic expander to form a powdery agent. object. 2. A powdery organic shrinkage reducing agent is adhered to at least a part of the surface of an inorganic hydration expandable powder or a raw material powder of an inorganic expandable material for cement admixture to form a powdery agent. An expanded powder composition for admixing cement. 3. A cement in which at least a part of a raw material of an inorganic expandable material containing a hydrated expandable raw material and a liquid organic shrinkage reducing agent are mixed or mixed and pulverized, so that the whole is made into a powdery single agent. Expandable powder composition for mixing. 4. The expandable powder composition for cement admixture according to claim 1, 2 or 3, wherein the content of the organic shrinkage reducing agent or its main component in the expandable powder composition for cement admixture is 10 to 20%. . 5. In the step of pulverizing the raw material of the inorganic expander for cement mixing, a liquid organic shrinkage reducing agent or a main agent thereof is added, and the raw material of the inorganic expander is mixed and pulverized. A method for producing an expandable powder composition for cement admixture, comprising producing an expandable powder composition containing: