JP2753267B2 - Carbonation curing method for compacts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for curing carbon dioxide in molded articles. More particularly, the present invention relates to a method for improving carbonation of a molded article using a binder which is cured by carbonation.

(Prior art) Conventionally, a technique of carbonizing and hardening a molded product using slaked lime, magnesium hydroxide, calcium silicate or the like as a binder has been widely studied. The present applicant has also previously described the carbonation curing method for molded articles using gamma-type dicalcium silicate as a binder, as disclosed in Japanese Patent Application Nos.
No. 70 is proposed.

When carbonizing a molded body using a binder that cures by carbonation, it is known that the amount of water contained in the molded body has a large effect on carbonation, and that there is an optimal amount of water for carbonation. ing. The following three methods have been considered as methods for adjusting a molded body using a binder that is cured by carbonation to a water content suitable for carbonation.

The first is a method in which materials are mixed in advance with an optimum amount of water to form a molded body. According to this, the naturally obtained molded body can be made into a molded body having an optimum water content.

The second method is a method in which a molded body is prepared using a large amount of water suitable for molding, and then the molded body is subjected to drying in a low-humidity environment or by heating or the like to reduce the amount of water to an optimal amount.

The third method is a method in which a molded body is prepared using a large amount of water suitable for molding as in the second method, and then the molded body is subjected to vacuum dehydration to adjust the water content.

However, these conventional methods for adjusting moisture all have problems.

That is, the first method of forming a molded body using water having a water content suitable for carbonation has a problem that the fluidity of the material during molding is poor and it is difficult to make the density of the molded body uniform. Further, in the method of drying after the second molding, uniform drying is difficult, and especially when dried in a short time, unevenness of the water content between the surface and the inside inevitably occurs. To avoid this, drying may be carried out for a long time, but this significantly reduces productivity. In the method of performing vacuum dehydration after the third molding, cracks occur due to shrinkage during dehydration, and it was difficult to adjust the whole to a uniform water content or density.

Due to the non-uniformity of the water content and the density of the molded article whose water content has been adjusted by the above methods 1 to 3, the subsequent carbonation cannot be uniformly carbonated even if various carbonation methods are devised. It was difficult to obtain a good cured product.

On the other hand, when carbonation is performed by supplying carbon dioxide to the molded body from the outside, the carbonation naturally proceeds while proceeding from the outside to the inside of the molded body. Then, since carbonation is an expansion reaction, when carbonation is performed, the voids in that portion are reduced, so that the permeation of carbon dioxide gas into the interior is suppressed thereafter. Due to such a phenomenon, it has been conventionally difficult to uniformly carbonate the inside of the molded body in a short time. In order to solve this, the following proposals have already been made as an efficient carbonation method.

That is, after preparing a molded body in which the necessary water content has been adjusted in advance, a method of permeating carbon dioxide gas into the molded body by utilizing the pressure difference of gas (Japanese Patent Application No. 50-12572), and fibers were put in the molded body. The molded body is subjected to moisture adjustment in advance in the same manner as described above, then loaded and consolidated, then unloaded in a carbon dioxide gas environment, and forcibly carbonated into the molded body using the rebound of fibers in the molded body. This is a method of infiltrating gas (Japanese Patent Application No. 61-174180).

However, if the water content of the molded article is still adjusted by the former method, not only does it take a long time to produce the molded article, but also because of its non-uniform water content, a uniform cured product cannot be obtained. There was a problem. Further, even if the carbonation step is improved by this method, there is a problem that if the adjustment of the water content of the molded body before that is the same as before, the entire curing step of the molded body is not efficient. In the latter method using fiber rebound, the amount of carbon dioxide gas that penetrates due to volume expansion is not sufficient to harden by carbonation, and the actual strength development depends on the subsequent hydration reaction. It is.

As described above, there is a technique in which uniform adjustment of the water content of a molded body can be easily performed, and a carbonation step can be performed in a short time to easily obtain a carbonated cured body having uniform and practical strength. The fact is that it has not been established yet.

(Problems to be Solved by the Invention) The present invention is intended to efficiently obtain a good cured product which is uniformly carbonated, and therefore, it is necessary to uniformly adjust the water content of the molded product and perform carbonation in a short time. And try to do it.

(Means for Solving the Problems) In the present invention, when a molded body of a mixture containing a binder which is cured by carbonation is carbonated and cured, the molded body is squeezed and dewatered with a pressurized gas, and simultaneously or simultaneously. A carbonation curing method for a molded body, characterized in that a gas containing carbon dioxide gas is allowed to permeate the molded body. Hereinafter, the present invention will be further described.

The binder used in the present invention is not particularly limited as long as it is cured by carbonation. For example, in addition to calcium silicate hydrates such as zonotolite, tobermorite and cement hydrate, calcium silicate such as slaked lime, magnesium hydroxide, Portland cement and the like are used. In the examples shown below, γ-2CaO · SiO ₂ (hereinafter γ-C ₂ S
Disilicate and ordinary cement. These binders that are hardened by carbonation are kneaded with water alone or together with fine aggregate such as sand, poured into a mold and molded. The water used here is the material used 10
The ratio is set to 15 or more with respect to 0 so that the fluidity of the material is improved so that a molded article having a uniform density can be obtained. The kneaded material is poured into a mold, but the mold used here is a closed mold, and carbon dioxide gas and / or other pressurized gas is introduced from one of the molds.
After passing through the inside of the formed body and carbonizing it, it is configured to be discharged to the outside through the opposite side of the formed body. This example will be described with reference to the drawings.

The figure shows a molding die composed of a lower die 1 and an upper die 2. The lower mold 1 has a (b) part forming a chamber and a bolt 3 thereon.
And a kneaded material storage section 4 fixed at 3. At the upper end of the lower mold, there is formed a filtration unit 5 composed of punched metal, mesh, and filter paper. Further, the lower mold is provided with a carbon dioxide gas introduction pipe and a discharge pipe through which water squeezed out of the molded body is discharged, as shown in the figure. The upper die is airtightly fitted to the lower die via the packing 6. The upper mold is provided with a vacant space (a) at the upper part thereof, and a lower end thereof is provided with a filtering section 5 'similar to that attached to the lower mold. Further, a carbon dioxide gas introducing pipe is also attached to the upper mold by a branch together with the discharge pipe as shown in the figure. Note that valves are attached to the pipes mounted on the upper and lower molds, respectively, as shown in the figure. Such a mold has a structure in which the mold is pressed from above and below by a press (not shown) as shown by arrows, or is fixed after pressing.

The kneaded material poured into the above-mentioned mold is formed into a predetermined thickness by operating a press or the like. By this pressurizing operation, a part of water is discharged from the molded body. The discharged water falls into the lower chamber (b) and is discharged outside through a discharge pipe at the lower end thereof. When the molded body has reached the predetermined thickness,
The operation of the press or the like is stopped, and the molded body is squeezed and dewatered with a pressurized gas as it is or transferred to another fixture. Referring to the drawing, first, the valve of the lower carbon dioxide gas introduction pipe is closed, and the valve of the discharge pipe is opened to open the (b) chamber. Next, the valve of one discharge pipe of the pipe serving as the upper mold branch is closed, and the valve of the other carbon dioxide gas introduction pipe is opened to introduce carbon dioxide into the chamber (a). In this case, carbon dioxide gas is introduced in a pressurized state. The introduced gas pressurizes the molded body, penetrates through the inside of the molded body from the filtration unit, reaches the chamber (b), and is discharged from the discharge pipe provided at the lower part of the chamber (b). Thereby, the molded body is first dehydrated. By pressurizing the molded body with the pressurized carbon dioxide gas, countless air holes are formed in the molded body, and the entire molded body including the central portion is uniformly dehydrated through the vents. In addition, by adjusting the pressure, the water content of the molded article after dehydration can be appropriately adjusted. The moisture adjustment by pressurized dehydration of the molded article by gas is proposed for the first time by the present invention. However, when this method is employed, the dehydration can be performed in a short time, and even the central part of the molded article can be uniformly dehydrated. It is a feature. In the above description, carbon dioxide gas is used as the pressurized gas. However, the pressurized dehydration of the molded body is not limited to carbon dioxide gas, but may be air. In this case, a gas other than carbon dioxide may be introduced from the other one of the branches of the gas introduction pipe shown in the figure. However, if carbon dioxide gas is used for dehydration, there is an advantage in production that the molded product is carbonated following or simultaneously with the dehydration of the molded product.

After the dehydration of the molded body and the completion of the moisture adjustment, subsequently, carbon dioxide gas is introduced from the introduction pipe in a pressurized state. The introduced carbon dioxide gas uniformly penetrates the molded body to the center thereof while penetrating the molded body, reaches the opposite surface of the molded body, exits into the (b) chamber, and discharges it from the discharge pipe to the atmosphere. Is done. The dehydration by the pressurized gas and the subsequent carbonation are completed in about 5 minutes in total, depending on the thickness of the compact. Next, in order to perform carbonation more efficiently and surely, a carbon dioxide gas is blown from a lower mold. To do this, for example, close the valve of the lower mold discharge pipe, the valve of the upper mold carbon dioxide introduction pipe, open the valve of the lower mold carbon dioxide introduction pipe, the valve of the upper mold discharge pipe, The carbon dioxide gas is sent from the carbon dioxide gas introduction pipe to the lower (b) chamber in a pressurized state. The carbon dioxide gas passes through the inside of the molded body while carbonating the inside of the molded body, passes through the upper mold (a), and exits into the atmosphere through the exhaust pipe. In addition,
The blowing of the carbon dioxide gas from the lower mold is performed as needed and is not always essential. The time for feeding the carbon dioxide gas from the lower mold may be almost the same as the time for blowing the gas from the upper mold. By blowing gas into such a compact, the compact is carbonated in a short time. After the molded body is carbonated and hardened, the mold is removed from the press and removed from the mold to obtain a product. In the present invention, when γ-C ₂ S is used as a binder that cures by carbonation, water is not generated by carbonation, so that pores through which gas permeates during carbonation are not closed, and carbonation of the molded body is advantageously performed. Can be performed.

Various composite materials can be added to the raw material mixture. For example, if fibers having pores such as pulp are mixed, it is advantageous for permeation of carbon dioxide gas. When a reinforcing fiber such as glass, vinylon, carbon, and aramid fiber is mixed, a cured product having excellent toughness can be obtained. Further, by adding a thickening agent such as methyl cellulose to the kneading water, the dehydration time can be adjusted and the thickness of the water film adhered to the material particles can be controlled, whereby carbonation can be performed efficiently.

Carbon dioxide used in the present invention is a carbon dioxide dilution gas,
Waste gas containing carbon dioxide gas such as combustion exhaust gas may be used.Although it depends on the pressure, gas composition, and thickness of the molded product, approximately 2k
g / cm ² range ~25kg / cm ² is preferred. If it is less than the lower limit of this range, the penetration of carbon dioxide into the molded product is not sufficient,
It is not usually necessary to exceed the upper limit. Hereinafter, the present invention will be further described with reference to experimental examples.

Experimental example 1. A carbonated cured product was produced using different water content adjustment and carbonation methods, the bending strength of the resulting cured product was measured, and the average value, maximum value, minimum value, and coefficient of variation were compared. did.

The raw materials used were γ-C ₂ S and ordinary cement.
The size of the cured product to be molded is 32 x 32 x 2 (cm),
This was cut out into 16 pieces of 4 cm × 16 cm × 2 cm, and the bending strength was measured for each piece.

A to C depending on the raw materials used and the mixing water
Was divided into two parts, as shown in Table 1.

Adjustment of water content and carbonation of each molded product were performed as follows.

(1) After pouring the compounding material of A into the device shown in the figure
Press pressure was performed at 25 kg / cm ² . In this state, the chamber (b) was opened, carbon dioxide gas was supplied to the chamber (a) at a pressure of 9.9 kg / cm ² , and dehydration of the molded body and carbonation were performed for 5 minutes.
Thereafter, the chamber (a) was opened, and carbon dioxide gas was supplied to the chamber (b) at a pressure of 9.9 kg / cm ² , followed by carbonation for 5 minutes.
…… The present invention (2) After the compounding material of A is poured into the apparatus shown in the figure, press-molding is performed at 25 kg / cm ² , then demolded, and dried at 105 ° C. with dry air to form the entire molded body. Was dried until the water content became 8% based on the weight of the molded body. This was put into the apparatus shown in the figure again, and the same gas operation as in (1) was performed.

(3) After the compounding material of A was poured into the apparatus shown in the figure, the pressure in the chamber (b) was reduced by a vacuum pump, and vacuum dehydration was performed until the water content of the entire molded body became 8% based on the weight of the molded body. Thereafter, the same gas operation as in (1) was performed.

(4) Spread the compounding material of B evenly on the equipment shown in the figure, press it at 25 kg / cm ² , and in that state, fill the chambers (a) and (b) with carbon dioxide and unload. Then 10
Carbonated for minutes.

(5) Spread the compounding material of C evenly on the equipment shown in the figure, press it at 25 kg / cm ² , press the carbon dioxide gas in chambers (a) and (b) and then unload. Then 10
Carburize for a minute.

 Table 2 shows the experimental results of (1) to (5).

Experimental Example 2 A mixture of γ-C ₂ S100 and water at a weight ratio of 50 was poured into the apparatus shown in the figure, and pressed at 25 kg / cm ² to 2 cm. In this state, the room (b) is opened, the room (a) is pressurized with carbon dioxide for 3 minutes, and then the room (a) is opened and the room (b) is pressurized with carbon dioxide for 3 minutes. Gas pressure in this case is 2,5,10,20kg
/ cm ² and cured, and the flexural strength was measured. For those having a gas pressure of 20 kg / cm ² , 0.5% of methylcellulose based on water was added. Further, to those having a gas pressure of 2 kg / cm ² , 5% of pulp was added to γ-C ₂ S. The results were as shown in Table 3.

Example 1. A mixture of γ-C ₂ S100, aggregate (river sand) 75, water 50, and 0.5% of methylcellulose with respect to water in a weight ratio was poured into the apparatus shown in the drawing, and press-pressed at 25 kg / cm ^2. , 2 cm. In that state, open the room (b) and open the room (a) at 9.9kg / cm.
^It was pressurized with air at a pressure of ² for 5 minutes. After that, the room (a) was pressurized with a mixture of 15% carbon dioxide at a pressure of 9.9 kg / cm ² for 20 minutes, and then the room (a) was opened and the room (b) was filled with 15% carbon dioxide. Was pressurized at a pressure of 9.9 kg / cm ² for 20 minutes. The one obtained here has a bending strength of 142 kg / cm
^2. The cured product had a coefficient of variation of 6.3%.

Example 2. Mortar was kneaded with γ-C ₂ S100, river sand 75, and water 60 by weight ratio. The glass fiber (3.5 cm in length) was sprayed onto a mold having a size of 90 × 180 (cm) having a size similar to that shown in FIG. This was pressed at 40 kg / cm ² , and in this state, the lower gap side was opened to the atmospheric pressure, and pressurized and ventilated with carbon dioxide gas at a pressure of 7.5 kg / cm ² from the upper surface for 5 minutes. Thereafter, the gas flow was changed, and pressurization and ventilation were performed for an additional 3 minutes, and pressurization and ventilation were performed for an additional 3 minutes. In this way, 90 × 180 × 2 (cm) exterior plates were produced at 4 sheets / hour. The wallboard was a uniform building material with a bending strength of 280 kg / cm ² and no unevenness on the surface to the inside.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a molding die used for carrying out the present invention. 1 lower mold 2 upper mold 4 kneaded material storage section 5,5 '
... Filtering section.

Claims (1)

(57) [Claims] When a carbonized hardening of a mixture of a mixture containing a binder which is hardened by carbonation is performed, the formed body is squeezed and dewatered with a pressurized gas, and simultaneously or successively, carbon dioxide gas is added to the formed body. A carbonation curing method for a molded article, characterized by allowing a gas containing nitrogen to pass therethrough.