JP2003192403A - Portland cement for concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide cement for concrete in which a waste material of a gypsum board is used as at least a portion of the gypsum component, and which can be obtained by a simple treatment and in which the blending amount of an AE agent (air-entraining agent) to be used, or the like can be reduced when it is used in concrete. <P>SOLUTION: Recovered gypsum recovered from the waste material of the gypsum board can be reused in cement by a simple treatment by producing the cement by incorporating, as a gypsum component, the recovered gypsum which is obtained by removing paper from the waste material of the gypsum board by dry crushing. In this case, it is preferable to remove the paper so that the content of the residual paper becomes ≤5 wt.%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Portland cement for concrete (hereinafter,
Also referred to as cement). Specifically, it is a cement that uses waste gypsum board as at least a part of the gypsum component, and can be obtained by a simple treatment,
Moreover, when used for concrete, use A
The present invention provides a cement for concrete, which can reduce the blending amount of E agent (air entraining agent) and the like.

[0002]

2. Description of the Related Art Annual amount of waste gypsum board is about 150
It is 10,000 tons, of which about 500,000 tons are scraps from production and new interior work, and are recycled by gypsum board makers. However, the remaining 1 million tons is discharged by renovation and dismantling work, and almost all of it is landfilled. The amount of waste gypsum board waste tends to increase year by year, and recycling of gypsum board waste is required from the viewpoint of landfill shortage and environmental conservation.

As one aspect of the above recycling, utilization of waste gypsum board as a gypsum component of cement has been studied.

However, a gypsum board is mixed with a surface active agent for volume adjustment at the time of production, and in a cement strength test for evaluating the performance of the cement, the composition of the test composition is determined by the bubble action of the surface active agent. It has been pointed out that it is not practical because the unit volume weight of concrete decreases and the strength of cement decreases.

Therefore, conventionally, there has been adopted a method in which such a gypsum board waste material is subjected to a treatment for removing such a surfactant and then used as a gypsum for cement. As the removal treatment, for example, a method of washing a gypsum board waste material with water to remove the surfactant, and a gypsum board waste material of 600 to 1100
A method in which the paper and the surfactant in the waste material are burned and removed by heating to ℃ to obtain type II anhydrous gypsum (JP-A-10-36).
149), a method of adding sulfuric acid to a waste gypsum board material and heating (JP-A-10-45446), and a method of adding an adsorbent that adsorbs a surfactant to the waste gypsum board material (JP-A-1).
0-45442) and the like have been proposed.

[0006]

However, the method of removing the surfactant from the gypsum board waste material requires a lot of work as described above and is costly, and in recycling the gypsum board waste material into cement, It was a big wall.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, the surfactant in the waste gypsum board, which was conventionally thought to be the cause of the strength reduction in the cement test, exhibits the same function as the AE agent used when making the concrete composition in the construction on site. I got the knowledge to do. That is, by using the gypsum board waste material as a part of the gypsum component of the cement without removing the surfactant, a complex treatment for removing the surfactant is not required, and the concrete preparation It has been found that the amount of AE agent added at that time can be reduced.

Furthermore, in order to effectively reduce the amount of the AE agent used when using the gypsum board waste material containing the above-mentioned surfactant, paper such as board base paper adhered to the gypsum board waste material should be used. They have found that they need to be removed, and have completed the present invention.

That is, the present invention is an aggregate-containing Portland cement for concrete, which contains recovered gypsum obtained by removing paper from a gypsum board waste material by dry crushing as at least a part of the gypsum component.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The gypsum board waste material to be treated according to the present invention includes all gypsum board end materials at the time of gypsum board production and new interior construction work, and gypsum board discarded at renovation and dismantling work. .

In the present invention, it is important that the recovered gypsum is obtained by removing paper from the above-mentioned gypsum board waste material by dry crushing. That is, when the waste gypsum board is used as a gypsum component in cement, when paper is contained, the chemical admixture is added to the paper in concrete using the chemical admixture such as AE agent, superplasticizer, and high performance water reducing agent. Since it is adsorbed, the effect of the addition of such an agent cannot be sufficiently exerted, and the amount of addition increases.

Therefore, by removing the paper mainly composed of the gypsum board base paper, it becomes possible to reduce the amount of the AE agent used and to obtain a cement which gives concrete having stable fluidity. You can

The removal of the paper is preferably carried out so that the residual amount of the paper in the recovered gypsum is 5% by weight or less, particularly 2% by weight or less.

The paper is removed from the waste gypsum board by dry crushing in order to allow the surfactant to remain positively. As a method for separating the paper from the gypsum board waste material by the dry crushing, a known method is adopted without particular limitation. Specifically, as shown in JP-A-10-286553, gypsum board waste material is crushed and a relatively large paper is removed by combining a sieve having a predetermined mesh size,
A method of removing fine paper by blowing it with a predetermined amount of air and blowing it away. As shown in Japanese Patent Laid-Open No. 2000-254531, a gypsum board waste material is passed through a roll-type breaking machine with a ridge, and a brittle gypsum substrate There is a method of crushing only the paper and removing the gypsum from the paper to remove the paper.

When the waste gypsum board material is reused as a gypsum component of cement, according to the present invention, the treatment is completed by simply removing the paper by dry crushing as described above, and conventionally, the surfactant is removed. It is possible to simplify the step of recycling the waste gypsum without requiring complicated steps such as washing-> drying, use of chemicals->washing-> drying, combustion-> hydration, etc.

The cement of the present invention contains recovered gypsum recovered without removing the surfactant contained in the above-mentioned waste gypsum board as at least a part of the gypsum component. That is, as the gypsum component of cement, flue gas desulfurization gypsum, gypsum phosphate, gypsum dihydrate substantially free of other added components such as natural gypsum is usually used, in the present invention, such gypsum component Cement is constructed by substituting a part or all of the recovered gypsum.

In this case, the recovered gypsum is pulverized, if necessary, into a particle size for incorporation into cement as a gypsum component. Such crushing can be performed using a known crushing device. For example, a ball mill and a vertical mill are common. Further, the crushing may be performed with the recovered gypsum alone, with other gypsum components, and further with cement clinker. However, since the recovered gypsum is easily crushed, other components, for example, when crushing with other gypsum components or cement clinker,
In order to prevent over-pulverization, it is preferable to adjust the pulverization time to be shorter by delaying the time for charging the pulverization device to the other components.

The crushing degree of the recovered gypsum by the above method is
The range of particle size of the gypsum component conventionally used in cement is suitably adopted. Specifically, it is preferable to grind so that the Blaine specific surface area is about 2000 to 10000 cm ² / g.

As the clinker composition for constituting the cement of the present invention, known clinker compositions for obtaining ordinary Portland cement, low heat Portland cement, early strength Portland cement and the like are adopted without particular limitation.

In the cement of the present invention, the gypsum component is generally 1 to 10% by weight. If the replacement ratio of the recovered gypsum in the gypsum component is too small, the recycling effect is poor. Therefore, the recovered gypsum is used so that the replacement ratio of the recovered gypsum is 5% by weight or more, preferably 10% by weight or more. It is preferable.

The cement of the present invention may be used alone or by mixing it with a cement having a normal composition, a blast furnace slag fine powder, a fly ash or the like as a cement admixture to be used for the preparation of concrete. It has been confirmed by the present inventors that the amount of the agent can be reduced, and in some cases, it can be zero, and there is no problem in the workability of the obtained concrete, the strength after hardening, and the like. .

The concrete composition obtained by using the cement of the present invention is not particularly limited, but it is suitable for the concrete composition for a structure containing an aggregate. As the aggregate, fine aggregate such as sand and coarse aggregate such as gravel are used. As the concrete composition, a known composition is adopted without particular limitation. For example, the ratio of water to cement (water / cement) is generally 20 to 70% by weight.

In the present invention, since the amount of the surfactant contained in the recovered gypsum is generally larger than the amount of the AE agent used in the preparation of concrete, when the cement of the present invention is used in concrete, It is preferable to adjust the amount of the surfactant. This adjustment employs a mode in which when the cement of the present invention is used alone to prepare concrete, the recovered gypsum is used as a part of the gypsum component to adjust the ratio of the surfactant in the concrete. Further, when the cement of the present invention is used as a mixture with normal cement, an aspect of adjusting the ratio of the surfactant in the concrete by using the recovered gypsum as a part of the gypsum component, and other, all of the gypsum component As the recovered gypsum, a mode in which the ratio of the surfactant in the concrete is adjusted by adjusting the mixing ratio of the obtained cement and normal cement can be adopted.

The preparation of concrete using the cement of the present invention is carried out by appropriately adjusting the amounts of the above-mentioned recovered gypsum-derived surfactant and the AE agent and AE auxiliary agent to be added, if desired. It is common to do so that As a suitable amount of air, in structural concrete,
It is 2 to 8%, preferably 3 to 6%.

If the amount of the above surfactant does not reach the target amount of air in the concrete, the amount of the AE agent to be mixed may be adjusted.

In the present invention, it is possible to add other additives to the concrete as long as the effects of the present invention are not significantly impaired. For example, fluidizing agents,
Examples include additives such as high-performance water reducing agents.

As a shipping form of the cement of the present invention, a form in which the content of the contained surfactant is displayed in advance in a packaging bag is preferable because concrete can be prepared more accurately.

[0028]

EXAMPLES Examples will be shown below to more specifically describe the present invention, but the present invention is not limited to these examples.

Various tests in Examples and Comparative Examples were carried out by the following methods. (1) Slump Measured according to JIS A 1101. (2) Air amount Measured according to JIS A 1118. (3) Compressive strength Measured according to JIS A 1108.

Example 1 Gypsum board waste material was dry crushed with a crusher and a disk mill and sieved with a 2 mm mesh to obtain recovered gypsum with the amount of base paper in the gypsum being 1.2% by weight. Next, as the gypsum component, 10% by weight of the recovered gypsum and flue gas desulfurization gypsum 9
These were used in an amount of 0% by weight, and these were mixed and ground in a ball mill together with ordinary Portland cement clinker to produce a cement having a Blaine specific surface area of about 3220 cm ² / g.

Concrete was prepared with the concrete composition shown in Table 1 using the cement obtained by the above method. In this case, the addition amount of the AE agent was determined so that the air amount of the obtained concrete had the values shown in Table 2.

Slump and compressive strength of the obtained concrete were measured, and the results are shown in Table 2.

Example 2 In Example 1, 25% by weight of recovered gypsum as a gypsum component
Ordinary Portland cement was produced in the same manner except that the flue gas desulfurization gypsum was used at a ratio of 75% by weight and the Blaine specific surface area after pulverization was 3280 cm ² / g.

Concrete was prepared with the concrete composition shown in Table 1 using the cement obtained by the above method. In this case, since the air content of the concrete in such a composition was the value shown in Table 2, the AE agent was not added.

Slump and compressive strength of the obtained concrete were measured, and the results are shown in Table 2.

Example 3 The same as Example 1 except that 5% by weight of recovered gypsum and 95% by weight of flue gas desulfurization gypsum were used as gypsum components, and the Blaine specific surface area after pulverization was 3170 cm ² / g. Manufactured ordinary Portland cement.

Using the cement obtained by the above method, concrete was prepared with the concrete composition shown in Table 1. In this case, the addition amount of the AE agent was determined so that the air amount of the obtained concrete had the values shown in Table 2.

Slump and compressive strength of the obtained concrete were measured, and the results are shown in Table 2.

Comparative Example 1 A normal Portland cement was produced in the same manner as in Example 1 except that the raw paper was not removed from the gypsum board waste material.

Concrete was prepared with the concrete composition shown in Table 1 by using the cement obtained by the above method. In this case, the addition amount of the AE agent was determined so that the air amount of the obtained concrete had the values shown in Table 2.

Slump and compressive strength of the obtained concrete were measured, and the results are shown in Table 2.

Reference Example 1 Blaine specific surface area of 3200 cm ² / g was obtained in the same manner except that waste gas of gypsum board was not used and only flue gas desulfurization gypsum was used.
Manufactured ordinary Portland cement.

Concrete was prepared with the concrete composition shown in Table 1 using the cement obtained by the above method. In this case, the addition amount of the AE agent was determined so that the air amount of the obtained concrete had the values shown in Table 2.

Slump and compressive strength of the obtained concrete were measured, and the results are shown in Table 2.

[0045]

[Table 1]

[Table 2]

As can be understood from the above description, according to the present invention, gypsum treated without complicated treatment such as washing or firing of gypsum board waste material is used as at least a part of the gypsum component. A cement for concrete, which is a cement obtained as described above and is capable of reducing the compounding amount of an AE agent (air entraining agent) and the like used when used for concrete.

Therefore, it is possible to industrially advantageously reuse the gypsum board waste material as gypsum for cement, and it can be said that its industrial value is extremely high.

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Claims (2)

[Claims] 1. A portland cement for concrete, comprising recovered gypsum obtained by removing paper from a waste material of gypsum board by dry crushing as at least a part of a gypsum component. 2. The portland cement for concrete according to claim 1, wherein the residual amount of paper in the recovered gypsum is 5% by weight or less.