JP2003012353A - Activated powder, method for producing the same and method for producing inorganic cured body using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an activated powder having high reactive activity with carbon dioxide, its production method and an inorganic cured body having high mechanical strength and excellent in thermal resistance using the powder. SOLUTION: This activated powder is an amorphous calcium silicate powder with Ca/Si mol ratio of 0.8 to 1.5 and substantially containing no water. When the amorphous calcium silicate powder is mixed with water at the weight ratio of 2:3, eluted amount of siliceous component after 90 min at 23 deg.C is >=1 ppm per 1 (m<2> /g) specific surface area of the powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an active powder having a high reaction activity with carbon dioxide, a method for producing the same, and a method for producing an inorganic cured product using the same.

[0002]

2. Description of the Related Art Conventionally, as a method of improving the strength of a hardened cement product, a method of bringing a cement material into contact with carbon dioxide has been known. For example, there has been proposed a method of performing curing in a carbon dioxide gas atmosphere during a specific period when curing a hardened cement (Japanese Patent Laid-Open No. 6-263562).

However, the above-mentioned method has a problem that it requires a long time for curing in a carbon dioxide gas atmosphere and the productivity is not good. In addition, depending on the amount of water contained in the material, the presence of water may be carbonic acid. There remains a problem that gas diffusion is hindered and carbonation does not proceed to the inside of the cured body.

When unreacted material remains inside the carbonized cement hardened product, it is expected to cause deterioration of the material for a long period of time.

In order to solve such problems, there has been proposed a method for producing a carbonation-cured product which carbonates the interior of a molded product by causing a mechanochemical reaction in a granular material in which calcareous and silicate coexist. (Japanese Patent Laid-Open No. 2001-12265
3 gazette).

In the above method, a mechanochemical reaction is caused in a granular material in which calcareous and silicate coexist to produce an energy-unstable amorphous calcium silicate hydrate in the granular material. To do. For this reason, Ca ²⁺ is easily eluted by carbon dioxide curing, and calcium carbonate is promptly deposited. As a result, the carbonation reaction proceeds not only to the surface layer of the molded product but also to the inside of the molded product. To do.

That is, in the above manufacturing method,
It is necessary to produce amorphous calcium silicate hydrate by mechanochemical reaction. That is, it is essential that the powder and granules always contain water. However, the cured product obtained by carbonating calcium silicate hydrate is
There is a problem that a cured product having sufficient strength cannot be obtained.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an active powder having a high reaction activity with carbon dioxide gas, a method for producing the same, and mechanical strength using the same. It is an object of the present invention to provide an inorganic cured product that is high and has excellent heat resistance.

[0009]

The active powder of the present invention comprises C
An amorphous calcium silicate powder having an a / Si molar ratio of 0.8 to 1.5 and containing substantially no water,
When the amorphous calcium silicate powder and water were mixed at a weight ratio of 2: 3, the elution amount of the silicon component after 90 minutes at 23 ° C. was about 1 (m ² / g) of the powder specific surface area. 1
It is characterized by being above ppm.

Amorphous calcium silicate powder means that n / m represented by the composition formula nCaO.mSiO ₂ is 0.8 to
It is a powder whose main component is the compound of 1.5. When n / m is smaller than 0.8 or larger than 1.5, the strength of the cured product obtained by carbonation becomes low. When a hardened body is obtained by carbonating the active powder of the present invention, a hardened body having excellent mechanical properties can be obtained due to volume expansion when the calcium component is carbonated.

When n / m is less than 0.8, the expansion effect at the time of carbonation is small and the strength of the obtained cured product is small. Further, when n / m is more than 1.5, the hydration activity of the powder becomes large, and a large amount of calcium silicate hydrate gel is generated when water is added to shape. When the structure is formed in the calcium silicate hydrate gel, the volume expansion cannot be expected by the carbonation of the gel itself, so that the strength of the obtained hardened body becomes small and the diffusion is inhibited when the carbon dioxide gas acts, The uncarbonated structure remains inside the cured body,
The heat resistance of the cured product will be poor.

[0012] The amorphous powder is a powder having a structure having no clear peak in X-ray diffraction measurement, and substantially not containing water means that when mechanical energy described later is applied, It means that it does not form an amorphous calcium silicate hydrate, and the amount of water is preferably 1% by weight or less in the total amorphous calcium silicate powder.

The active powder of the present invention is the above-mentioned amorphous calcium silicate powder, and when the powder and water are mixed in a weight ratio of 2: 3, the active ingredient powder of the silicon component after 90 minutes at 23 ° C. Elution amount is 1 per 1 (m ² / g) of the powder specific surface area
ppm or more.

Water is used as a solvent for measuring the elution amount of the silicon component. As the water, it is preferable to use ion-exchanged water. The method of mixing the powder and water is not particularly limited. For example, after the powder and water are put in a container, the mixture is stirred with a magnetic stirrer for 1 hour, and then 30 minutes.
The method of leaving still for minutes is mentioned.

The elution amount of the above-mentioned silicon component is the concentration of silicon atoms contained in silicate ions and the like present in the solution, and is measured by a conventionally known method using an inductively coupled plasma emission analysis (ICP emission analysis) device or the like. To be done.

If the amount of the silicon component eluted is too small, the reaction activity on the powder surface is low, the desired reactivity with carbon dioxide cannot be obtained, and the mechanical properties of the cured product obtained by carbonation are also reduced. Therefore, the specific surface area of the powder is limited to 1 ppm or more per 1 (m ² / g), and usually 10,000 ppm
It is the following.

The specific surface area of the powder is measured by, for example, the BET method using nitrogen gas adsorption.

The method for producing an active powder according to the present invention is the method for producing an active powder according to claim 1, wherein the Ca / Si molar ratio is 0.8 to 1.5 and the water is substantially water. 0.01 to 30k in amorphous calcium silicate powder not containing
The mechanical energy of Wh / kg is applied.

The average particle size of the amorphous calcium silicate powder on which mechanical energy is applied is not particularly limited, but it is 0.1 to 100 μm for more effective application of mechanical energy. Preferably there is.

The mechanical energy is not particularly limited, and for example, compressive force, shearing force, impact force,
Examples of energy include frictional energy.

The method of applying the mechanical energy is not particularly limited, and for example, it can be carried out by using a crushing device generally used for the purpose of crushing.
For example, a ball mill, a vibration mill, a planetary mill, a pulverizer that combines a compressive force, a shearing force, an impact force, a frictional force, etc.
A ball medium mill such as a medium stirring mill; a roller mill; a mortar and the like. In addition, as a device mainly for impact, friction, etc., there is a jet crushing device. Of these, a ball medium type mill is preferable in order to effectively impart mechanical energy to the amorphous calcium silicate powder.

If the mechanical energy to be applied is too small, the structural change of the obtained powder is small and the reaction activity (the easiness of carbonation of the powder) becomes small, and if it is too large, an excessive load on the crushing device, the medium As a result, there are disadvantages such as contamination to the treated powder due to severe abrasion of the balls and containers, coarsening of the particles due to agglomeration of the treated powder, and disadvantages in productivity such as cost. kg
And preferably 0.1 to 5 kWh / kg.

The mechanical energy is calculated from the total amount of electric power consumed by the crushing device when the amorphous calcium silicate powder and the crushing medium are put into the crushing device and actually operated. It is a value obtained by dividing the value obtained by subtracting the amount of power consumed when the engine is idled under the conditions by the mass (kg) of the amorphous calcium silicate powder subjected to the treatment.

The method for producing an inorganic hardened material of the present invention comprises mixing active powder according to claim 1 with water and then carbonating.

In the method for producing an inorganic hardened material of the present invention, the amount of water mixed with the active powder is not particularly limited, and the specific surface area, shape, other kinds of additives and the amount of the active powder are not particularly limited. Although it is appropriately determined by the above, when the amount is too small, the reaction with the carbon dioxide gas does not sufficiently occur, and the shapeability is lowered, and when the amount is too large, it becomes difficult for the carbon dioxide gas to reach the powder surface. Since the efficiency decreases, when only the active powder and water are used, 10 to 100 parts by weight is preferable to 100 parts by weight of the active powder.

The water mixed with the active powder may be supplied as water vapor. In addition, when the water content during compounding is too large, the water content can be adjusted to an appropriate amount by applying pressure or suction during shaping.

In the method for producing a cured inorganic material of the present invention, the above-mentioned active powder, water, and, if necessary, other cement materials, aggregates, reinforcing fibers, etc. are mixed and then, if desired, desired. Carbonate after shaping into shape.

In the above shaping, any conventionally known method such as compression molding method such as dewatering press, extrusion molding method and the like can be used.

Examples of the carbonation method include a method of treating in a carbon dioxide atmosphere. The concentration of carbon dioxide gas is not particularly limited, but it is efficient to treat at a concentration close to 100%. If necessary, the treatment may be performed in an atmosphere of carbon dioxide in a supercritical state.

The temperature for carbonation is not particularly limited, but if it is too low, it takes a long time for the carbonation reaction to sufficiently occur, and if it is too high, the carbonation reaction is rapid but a large amount of energy is required. Is required, and when an organic reinforcing fiber or the like is used as the reinforcing fiber, there is a risk that the fiber or the like is likely to be deteriorated by heat, so 30 to 200 ° C. is preferable.

The pressure during carbonation is not particularly limited either, but if it is too low, a decompression device is required, which is inefficient in both energy consumption and progress of the carbonation reaction, and if it is too high, a large amount of energy is required. Since it is unsuitable from the standpoint of industrial productivity and enlargement of equipment, normal pressure to 5 MPa
Is preferred. It should be noted that the pressure in this specification indicates a gauge pressure, not an absolute pressure.

The time required for carbonation is not particularly limited either, but if it is too short, carbonation does not proceed sufficiently and the mechanical properties of the resulting cured product deteriorate, and if it is too long, carbonation is sufficient. Although it progresses, the production efficiency of the cured product decreases, so 1
Minutes to 10 hours are preferred.

(Function) The active powder of the present invention is Ca / Si.
Since the amorphous calcium silicate powder has a molar ratio of 0.8 to 1.5 and contains substantially no water, most of it reacts with unhydrated calcium silicate powder during carbonation. Therefore, it is possible to obtain a molded product having a cured product with high strength due to the expansion effect of carbonation.

Generally, carbonation of a calcium silicate material proceeds by binding a calcium component with carbon dioxide to form calcium carbonate, and polymerizing the silicate component to form silica gel. When the amorphous calcium silicate powder and water are mixed at a weight ratio of 2: 3, the active powder of the present invention has a silicon component elution amount after 90 minutes at 23 ° C. of the powder. Since the amorphous calcium silicate powder has a specific surface area of 1 ppm or more per 1 (m ² / g) and a large elution amount of the silicon component, the activity of the silicate component on the powder surface is large and the silicate component is rapidly polymerized. And the progress of carbonation is easy.

The method for producing an active powder according to the present invention is the method for producing an active powder according to claim 1, wherein the Ca / Si molar ratio is 0.8 to 1.5 and the method is substantially water. 0.01 to 30k in amorphous calcium silicate powder not containing
Since the mechanical energy of Wh / kg is applied, active amorphous calcium silicate powder can be efficiently produced.

In the method for producing an inorganic cured product of the present invention, the active powder according to claim 1 is mixed with water and then carbonated, so that the amount of carbonation reaction is large and the resulting inorganic cured product is obtained. The body develops strength by filling the voids between the active powders with volume expansion due to carbonation, so that a cured product having excellent mechanical properties can be obtained. Further, since the inorganic hardened body obtained by the production method of the present invention contains calcium carbonate and silica gel as the main components, it has a chemically stable structure and has excellent mechanical properties and heat resistance.

[0037]

Example (Preparation of Active Powder) Active Powders A to D Amorphous calcium silicate powder (Nacalai Tesque, Ca / Si molar ratio 1) was placed in a vibration mill (pot volume 45).
0 cm ³ , ball medium: 220 zirconia balls of 10 mmφ), vibration frequency 1200 rpm, amplitude 8 mm
Then, the powder was pulverized for a predetermined amount shown in Table 1 for a predetermined time and mechanical energy was applied to obtain active powders A to D. The mechanical energy applied was calculated as follows and shown in Table 1.

Mechanical energy applied (kWh / k
g) = {Power consumption during processing (kWh) -Power consumption during idling (kWh)} / mass of treated powder (kg)

(Preparation of calcium silicate hydrate powder) A 0.085 wt% aqueous solution of calcium hydroxide and a 10 wt% aqueous solution of ethyl silicate were mixed at a weight ratio of 45: 1, and the mixture was stirred with a stirrer for 7 days. Cure and get the precipitate,
The obtained precipitate was degassed and dried for 24 hours to obtain calcium silicate hydrate powder. The Ca / Si molar ratio of the obtained calcium silicate hydrate powder was 1.11 as a result of elemental quantitative analysis by X-ray.

Evaluation of powders (measurement of specific surface area) Obtained active powders A to D, amorphous calcium silicate powders not subjected to mechanical energy (referred to as powder E in Table 1), crystals As normal calcium silicate powder, ordinary Portland cement (referred to as powder G in Table 1) is dried at 166 ° C. for 30 minutes, and
The obtained calcium silicate hydrate powder (referred to as powder F in Table 1) was washed with acetone and dried at 80 ° C. for 2 hours (to prevent thermal decomposition of the hydrate), and then nitrogen gas, respectively. It was measured by the BET 5-point method by adsorption, and the results are shown in Table 1.

(Measurement of Elution Amount of Silicon Component) 12 g of ion-exchanged water was added to 8 g of the obtained active powders A to D and powders E to G, and the mixture was stirred for 1 hour with a magnetic stirrer and allowed to stand for 30 minutes. After filtering, the silicic acid component contained in the filtrate is measured by an ICP emission spectrometer (inductively coupled plasma emission spectrometer),
The results are shown in Table 1.

[0042]

[Table 1]

(Preparation of Inorganic Cured Product) (Examples 1 to 4, Comparative Examples 1 to 3) When the elution amount of the silicon component from the active powders A to D and the powders E to G was measured, it was filtered. For the mixture of the clay-like active powder and water obtained in Example 1, in an autoclave under the conditions shown in Table 2.
Carbonation was carried out by treating in an atmosphere of 00% carbon dioxide gas to obtain an inorganic cured body.

Evaluation of Inorganic Cured Body (Measurement of Compressive Strength) The inorganic cured bodies obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were cut into 10 mm squares, and the compressive strength at a crosshead speed of 0.5 mm / min. Was measured.

(Measurement of calcium ion elution amount) Example 3
And the inorganic cured body obtained in Comparative Example 3 with a particle size of 100 μm
100 g of ion-exchanged water was added to 1 g of the pulverized product, shaken for 5 minutes, and allowed to stand for 24 hours. The calcium ion concentration in the aqueous solution was measured by an ICP emission spectrometer.

(Heat Resistance Test) After heating the inorganic cured bodies obtained in Example 3 and Comparative Example 3 at 600 ° C. for 30 minutes,
The compressive strength was measured at a crosshead speed of 0.5 mm / min. The above results are summarized in Table 2.

[0047]

[Table 2]

As can be seen from Table 2, in Examples 1 to 4,
Since amorphous calcium silicate having an appropriate elution amount of silicon component is used by applying mechanical energy, an inorganic hardened material having good mechanical properties can be obtained at low pressure. On the other hand, in Comparative Example 1, since mechanical energy is not applied, the strength of the cured product is insufficient because the amorphous calcium silicate that does not have an appropriate elution amount of the silicon component is used. It became a thing.
Further, in Comparative Example 2, since calcium silicate hydrate was used, the elution amount of the silicon component was appropriate, but the strength of the cured product was very small.

In Comparative Example 3, the elution amount of the silicon component is sufficient, but since crystalline calcium silicate having a large Ca / Si molar ratio is used, the initial strength is sufficiently expressed, but the elution calcium ion concentration becomes large. There is. The dissolved calcium ion concentration shows the stability of the cured product to water, and the cured product using the active powder of the present invention (Example 3) is very small, indicating that it is stable to water. On the other hand, in Comparative Example 3, since crystalline calcium silicate having a large Ca / Si molar ratio was used, hydration proceeded and carbonation did not proceed to the inside when mixed with water. The elution of calcium exceeding the solubility was observed, and it is considered that the elution of calcium occurred inside the cured product.

Comparing the cured products obtained in Example 3 and Comparative Example 3, the cured product obtained by carbonating the active powder of the present invention shows almost no change in compressive strength after the heat resistance test. On the other hand, in the case of the cured product obtained by carbonating the powder whose hydration has progressed, the compressive strength after the heat resistance test was significantly reduced. It is considered that this is because the hydrate remaining in the hardened body obtained in Comparative Example 3 loses its water content by heating and the structure collapses, causing a decrease in strength.

[0051]

Since the active powder of the present invention is constructed as described above, it has a high reaction with carbon dioxide even under relatively low temperature and low pressure conditions. Since the method for producing the active powder of the present invention has the above-mentioned constitution, the above-mentioned active powder can be obtained with high productivity. Since the method for producing an inorganic cured body of the present invention has the above-mentioned constitution, it is possible to obtain an inorganic cured body having high mechanical strength and excellent heat resistance.

The inorganic hardened material obtained by such a method can be suitably used as a building material such as an outer wall of a house or a roof tile, or a civil engineering construction material.

Claims (3)

[Claims] 1. An amorphous calcium silicate powder having a Ca / Si molar ratio of 0.8 to 1.5 and containing substantially no water, wherein the amorphous calcium silicate powder and water are mixed. When mixed at a weight ratio of 2: 3, the elution amount of the silicon component after 90 minutes at 23 ° C. was such that the specific surface area of the powder was 1 (m
² / g) 1 ppm or more per active powder. 2. A mechanical energy of 0.01 to 30 kWh / kg is applied to an amorphous calcium silicate powder having a Ca / Si molar ratio of 0.8 to 1.5 and containing substantially no water. The method for producing the active powder according to claim 1, wherein 3. A method for producing an inorganic cured product, which comprises mixing the active powder according to claim 1 with water and then carbonating the mixture.