JPH1045442A - Cement composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the degradation in the strength of mortar, to eliminate a foaming effect and to obtain the strength equivalent to the strength of cement formed by using stack gas desulfurization gypsum by mixing cement clinker, the gypsum recovered from waste gypsum board materials and an adsorbent and pulverizing the mixture. SOLUTION: The waste gypsum board materials are supplied between roll crushers provided with ruggedness on the circumferences of their surfaces and compressive, tensile and shearing forces are acted thereon to separate and disintegrate these materials to raw paper for boards and gypsum and to obtain the recovered gypsum contg. the raw paper for boards at <=2wt.%. Cement clinker, the recovered gypsum described above and the adsorbent of the surfactants contained in the recovered gypsum of >=10wt.% of the weight of the recovered gypsum are mixed and the mixture is pulverized and is then subjected to viscosity adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement composition using gypsum recovered from waste gypsum board and a method for producing the same.

[0002]

2. Description of the Related Art The amount of waste gypsum board is 1.2 million tons / year in 1993 and 1.5 million tons / year in 1995, and tends to increase year by year. Currently, most gypsum board waste is disposed of for landfill use. However, the enactment of the "Law Concerning the Promotion of Use of Recycled Resources" (Recycling Law) and the review of the "Law on Waste Treatment and Cleaning" The need to reuse industrial waste, including gypsum board waste, has been clearly stipulated by law.

As a method of recycling gypsum board waste material, a gypsum portion and a board base paper (pulp portion) are separated from the board waste material, and the recovered gypsum is mixed and used as a part of a raw material for gypsum board production. The proportion of the virgin raw material is at most about 5% by weight, and usually only 2-3% by weight is recycled, which is far from effective utilization.

Under such circumstances, as a means for treating a large amount of gypsum board waste material, utilization as gypsum for cement is expected. Currently, flue gas desulfurization gypsum is mainly used for cement gypsum, but if all or part of flue gas desulfurization gypsum can be replaced with gypsum recovered from gypsum board waste, gypsum board as a recycled resource This can greatly contribute to the effective use of waste materials. However,
In the gypsum recovered from the gypsum board waste material, the surfactant used for adjusting the board weight during board production remains, and when this recovered gypsum is reused as cement gypsum, the surfactant contained in the gypsum is included. Since the foaming action causes a decrease in the unit weight of the mortar or concrete and the resulting decrease in the strength of the mortar or concrete, waste gypsum board cannot be reused as gypsum for cement.

[0005]

Therefore, the present invention provides
Solving the above problems, gypsum recovered from gypsum board waste material can be effectively used for cement, has no foaming action at the time of kneading mortar and concrete, and has the same strength as cement using flue gas desulfurization gypsum. It is an object to provide a cement composition having the same and a method for producing the same.

[0006]

According to the present invention, there is provided a cement composition comprising gypsum recovered from waste gypsum board and an adsorbent for a surfactant contained in the gypsum. (Claim 1), and the adsorbent is at least one selected from coal ash, heavy oil ash, and activated carbon (claim 2).

Further, according to the method for producing a cement composition of the present invention, when gypsum recovered from gypsum board waste is used as gypsum for cement, a surfactant contained in the gypsum is adsorbed to an adsorbent ( Claim 3) mixing and grinding the gypsum and the adsorbent recovered from the cement clinker and the gypsum board waste material, or mixing the gypsum recovered from the gypsum board waste material by mixing and grinding or adjusting the particle size. After pulverization or mixing after pulverization, an adsorbent is added (claim 5), and the adsorbent is at least one selected from coal ash, heavy oil ash, and activated carbon having a methylene blue adsorption amount of 0.5 mg / g or more. (Claim 6), the amount of the adsorbent added is 10% by weight or more, preferably 30 to 120% by weight, based on the amount of recovered gypsum ( Motomeko 7), characterized by. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The first feature of the present invention is that gypsum recovered from waste gypsum board is used as gypsum for cement, but the waste gypsum board is obtained by adding base paper for board to gypsum used as a core material. It is a composite material that has adhered, and the gypsum to be collected from now on will be mixed with board base paper,
When the content is large, there is an adverse effect such as a decrease in mortar flow value when used as gypsum for cement. Therefore, the amount of board base paper in the recovered gypsum is desirably 2% by weight or less, preferably 0.3% by weight or less. As an example of the means for separating gypsum and board base paper for this purpose, the “composite crushing method and crushing apparatus” proposed by the applicant as Japanese Patent Application No. 7-245578 can be suitably used. This is to supply gypsum board waste material between rolls with irregularities on the surface circumference of the roll crusher and compress, pull, and apply shear stress to the waste material, effectively separating board base paper and gypsum It crushes, but is not necessarily limited to this.

[0009] Further, as described above, an organic surfactant remains in gypsum recovered from gypsum board waste material, and when the recovered gypsum is used as a gypsum for cement, there is a case where gypsum is used as a waste plaster. In comparison, the strength of mortar and concrete is significantly reduced due to the decrease in unit weight of mortar and concrete. In order to remove the surfactant in the gypsum board waste material, it is conceivable to decompose and remove the surfactant by firing the waste material at a high temperature of 500 ° C. or more. Is uneconomical in terms of heat and equipment, and is not a preferable means. INDUSTRIAL APPLICABILITY The present invention allows a surfactant to be adsorbed by an adsorbent to be used as gypsum for cement.

As the adsorbent, at least one selected from coal ash, heavy oil ash, and activated carbon can be suitably used. In particular, coal ash and heavy oil ash are industrial wastes generated in thermal power plants and the like, and can contribute to the recycling of these industrial wastes. Unburned carbon contained in the adsorbent is It adsorbs a surfactant having a foaming action and can prevent a decrease in unit weight of mortar and concrete. The adsorbent such as coal ash desirably has an adsorbed amount of methylene blue (Cement Association method) of 0.5 mg / g or more from the viewpoint of the adsorption ability of the surfactant. The amount of methylene blue adsorbed is measured by adding a sample to a methylene blue solution, stirring the solution, and measuring the amount of adsorbed methylene blue by a colorimetric method (absorption spectrophotometer). It can be suitably used as an indirect guide. When the amount of methylene blue adsorbed is 0.5 mg / g or more, the surfactant has an excellent ability to adsorb the surfactant, the bubble action of the surfactant remaining in the recovered gypsum disappears, and the gypsum for cement can be suitably used. .
In addition, the use of a classified product in which the average particle size of the adsorbent, particularly coal ash, is adjusted to 10 μm or less is excellent in the ability to adsorb a surfactant and is suitable.

The amount of adsorbent added is 1 to the amount of gypsum recovered.
0% by weight or more, preferably 30 to 120% by weight.
If the amount is less than 10% by weight, the adsorbing ability of the surfactant is insufficient, and even if it exceeds 120% by weight, the adsorbing ability of the surfactant reaches a plateau and the increase of the adsorbent is not increased. Economy.

Next, the addition of the adsorbent may be performed at the time of ordinary cement production or at the time of using cement. That is, at the time of cement production, the cement clinker and the gypsum and the adsorbent recovered from the gypsum board waste material are mixed and crushed, or these materials are crushed or adjusted in particle size and mixed, or the cement clinker and the gypsum board waste material Mixed and crushed plaster collected from
Alternatively, an adsorbent can be separately added after pulverization and mixing. When the adsorbent is separately added, it may be added at the time of on-site use or at the time of preparing mortar or concrete. Furthermore, the cement composition of the present invention is obtained by adding gypsum and adsorbent recovered from gypsum board waste material to Portland cement and mixed cement in the same manner as ordinary gypsum is used as various additives. You can also.

The amount of the recovered gypsum can be used in place of the total amount of gypsum added to the cement. It is desirable to use. In this case, the recovered gypsum is particularly preferably 20 to 70% by weight based on the total amount of gypsum in order to effectively use the recovered gypsum and maintain the quality of mortar and concrete. Hereinafter, the present invention will be further described with reference to examples.

[0014]

EXAMPLES 9 g / m gypsum board waste generated as construction waste was crushed by a roll crusher, and then the pulp portion and the gypsum portion were separated by a vibrating sieve to recover gypsum. The recovered gypsum, the waste gypsum, and the adsorbent shown in Table 1 were added to ordinary Portland cement clinker so that the amount of gypsum in the cement was 2.0% by weight as SO ₃ , and the resulting mixture had a Blaine specific surface area of 3300 cm ² / g of the cement composition was obtained. Next, a JIS mortar was prepared, and the mortar unit weight and the compressive strength were measured. Table 2 shows the results.

[0015]

[Table 1]

[0016]

[Table 2]

As shown in Table 2, by adding a surfactant adsorbent to the mortar, a decrease in the unit weight of the mortar can be prevented, and the compressive strength is inferior to that of the conventional waste plaster. There was nothing.

[0018]

According to the present invention, the surfactant contained in the waste gypsum board is adsorbed by using coal ash, heavy oil ash and activated carbon, whereby a decrease in mortar strength is suppressed, and the gypsum board is recovered from the waste gypsum board. The recycled gypsum can be very easily and easily reused as cement gypsum.
In addition, recycling gypsum board waste, coal ash, and heavy oil ash, which are industrial wastes, greatly contributes to society.

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Claims (7)

[Claims] 1. A cement composition comprising gypsum recovered from gypsum board waste and an adsorbent for a surfactant contained in the gypsum. 2. The cement according to claim 1, wherein the adsorbent is at least one selected from coal ash, heavy oil ash, and activated carbon. 3. A method for producing cement, wherein a gypsum recovered from gypsum board waste is used as a gypsum for cement, wherein a surfactant contained in the gypsum is adsorbed to an adsorbent. 4. The method for producing cement according to claim 3, wherein the cement clinker, the gypsum recovered from the gypsum board waste material and the adsorbent are mixed and crushed, or crushed or adjusted in particle size and mixed. 5. The method for producing cement according to claim 3, wherein the cement clinker and the gypsum recovered from the waste gypsum board are mixed and pulverized or mixed after the pulverization, and then an adsorbent is added. 6. The adsorbent has a methylene blue adsorption amount of 0.5 m.
4. At least one selected from coal ash, heavy oil ash, and activated carbon having a g / g or more.
A method for producing a cement according to any one of claims 1 to 5. 7. The amount of adsorbent added is 1 to the amount of recovered gypsum.
The method for producing cement according to any one of claims 3 to 6, wherein the amount is 0% by weight or more, preferably 30 to 120% by weight.