JPH09255383A - Production of super lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of super lightweight aggregate capable of firing a pellet after granulating as in hydrated state and stably obtaining a super lightweight aggregate having the specific gravity of <=0.8 in absolute dry condition and >=80kgf collapse strength. SOLUTION: The super lightweight aggregate is produced by adjusting the particle size of the pellet, which is obtained by granulating a rhyolite based vitreous mineral, a foaming agent and a sodium silicate aq, solution, and firing as in hydrated state. (1) The ryholite based vitreous mineral has 10-40μm average particle diameter, (2) in the sodium silicate, the molar ratio (SiO2 /Na2 O) of silicon dioxide to sodium oxide is 1.0-2.5, (3) the composition of the pellet is 0.1-2.0 pts.wt. foaming agent and the quantity of the sodium silicate equivalent to >=2.0 pts.wt. Na2 O in the sodium silicate per 100 pts.wt. ryholife based vitreous mineral and (4) the firing temp. is 900-1300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ultralight aggregate that can be applied as an aggregate for lightweight concrete used for concrete products such as curtain walls and concrete structures.

[0002]

2. Description of the Related Art With the recent increase in the structure of super high-rise structures and the increase in the size of curtain wall plates for mass-produced houses, the air-dry specific gravity is 1.0 to 1.4 and the compressive strength is 300 kgf / cm ² or more. Concrete is desired. In order to realize such lightweight concrete, it is necessary to use an ultralight aggregate having an absolute dry specific gravity of 0.8 or less and a crush strength of 80 kgf or more.

Conventionally, as a method for producing an ultralight aggregate,
After adding a foaming agent and an adhesive to the powder of volcanic glassy minerals such as anti-firestone and rhyolite, and granulating the granulated material, and drying the granulated material,
A manufacturing method of firing and foaming at 1000 to 1300 ° C. is known. For example, Japanese Examined Patent Publication No. 62-12186 discloses a volcanic glassy mineral such as anti-firestone and rhyolite at 20 μm.
Disclosed is a method for producing an ultralight aggregate in which the following particles form a fine powder of 70% or more, and a foaming material and an adhesive material are added to the mixture to granulate it, followed by firing and foaming at 1000 to 1300 ° C.

[0004]

DISCLOSURE OF THE INVENTION In a conventional method for producing an ultralight aggregate, granules composed of powders of volcanic glassy minerals such as anti-firestone and rhyolite, a foaming agent, and an adhesive material are in a water-containing state. If it is baked as it is, cracks and sporing will occur, so it cannot be baked in a water-containing state, and it must be dried before baking. Since drying of the granulated product had to be performed at 100 to 200 ° C. for a long time, it took time and labor. Furthermore, in the conventional method for manufacturing ultra-light aggregate, the absolute dry specific gravity required for realizing lightweight concrete is 0.8 or less, and the crush strength is 8
It was difficult to obtain an ultralight aggregate of 0 kgf or more. Also in the method for producing an ultralight aggregate described in Japanese Patent Publication No. 62-12186, volcanic glassy minerals such as anti-firestones and rhyolites are formed into 70% or more fine powders having a particle size of 20 μm or less. The granulated product obtained by adding the foaming material and the adhesive material to the granules must be dried before firing, which requires time and labor. In addition, the ultra-light aggregate produced by this method for producing ultra-light aggregate has a specific gravity of 0.4 to 0.85, and it is possible to reduce the weight of concrete by using this, but it is structurally lightweight. Crush strength required to realize concrete is 80k
It is difficult to obtain an ultralight aggregate of gf or more, and even if it is obtained, it is necessary to strictly control the firing temperature, which is not practical.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
It is possible to bake the granulated pellets in the water-containing state.
And the absolute dry density is 0.8 or less, and the crush strength is 80 kg.
Manufacture of ultra-light aggregate that can stably obtain ultra-light aggregate of f or more
As a result of diligent research on the construction method, rhyolite glassy ore
Adjusting the average particle size of the product, silicic acid content and sodium content
Molar ratio of (SiO _Two/ Na_TwoO) is a specific range
Using an aqueous solution of sodium acidate, and
Completed the present invention with the knowledge that the raw material blend should be specified
did.

That is, the present invention is a method for producing an ultralight aggregate in which pellets obtained by granulating a rhyolite glassy mineral, a foaming agent and an aqueous sodium silicate solution are subjected to particle size adjustment and fired in a water-containing state. Therefore, (1) rhyolite glassy mineral has an average particle size of 10 to 40 μm, and (2) sodium silicate has a molar ratio of silicon dioxide and sodium oxide (SiO ₂ / Na ₂ O). 1.0-2.5, (3)
The pellets are compounded with 0.1 to 2.0 parts by weight of a foaming agent and 2.0 parts by weight or more of Na ₂ O in sodium silicate based on 100 parts by weight of rhyolite glassy mineral. And (4) firing temperature is 900 to 13
The method for producing an ultralight aggregate is characterized in that the temperature is 00 ° C.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

Examples of the rhyolite glassy mineral used in the present invention include malecanite containing pearlite and obsidian, and anti-firestone. As the rhyolite-based glassy mineral, a powder obtained by drying the rhyolite-based glassy mineral lump and then crushing it so that the average particle diameter becomes 10 to 40 μm, preferably 15 to 30 μm, or a powder whose particle size is adjusted after crushing is used. . If the average particle size of the rhyolite glassy mineral is less than 10 μm, it becomes difficult to pulverize, and since the pellet is highly dense, when foaming during firing,
Internal cracks easily occur, and the crush strength of the ultralight aggregate becomes less than 80 kgf. Also, if the average particle size of the rhyolite glassy mineral exceeds 40 μm, it becomes difficult to granulate the pellets, and since the pellets are not dense, internal bubbles expand during foaming during firing. It becomes voids as internal defects, and the crush strength of the ultralight aggregate becomes less than 80 kgf.
The rhyolite glassy mineral may be crushed using a crusher such as a roll mill or a ball mill. When adjusting the particle size, a classifier may be used. Furthermore, the average particle size of the rhyolite glassy mineral may be measured using a particle size distribution measuring device such as a laser diffraction type particle size distribution measuring device.

Examples of the foaming agent include SiC, Si ₃ N _{4 and the} like, but SiC is particularly preferable. The foaming agent is 0.1 to 2.0 with respect to 100 parts by weight of rhyolite glassy mineral.
Add by weight. If the amount of the foaming agent added is less than 0.1 part by weight with respect to 100 parts by weight of the rhyolite glassy mineral, the ultralight specific gravity of the ultralight aggregate exceeds 0.8. Further, the amount of the foaming agent added is 2.0 with respect to 100 parts by weight of the rhyolite glassy mineral.
If it exceeds the weight part, the crushing strength of the ultralight aggregate is 80kgf.
Less than.

Sodium silicate has a molar ratio of silicon dioxide to sodium oxide (SiO ₂ / Na ₂ O) of 1.0 to.
An aqueous solution of sodium silicate of 2.5 is used. Pellets using an aqueous solution of sodium silicate in which the molar ratio of silicon dioxide and sodium oxide is less than 1.0 cause cracks and spalling when fired in a water-containing state. Also,
Pellets using an aqueous solution of sodium silicate in which the molar ratio of silicon dioxide and sodium oxide exceeds 2.5 also cause cracks and spalling when fired in a water-containing state.
On the other hand, in the case of powdery sodium silicate, the crush strength of the ultralight aggregate is less than 80 kgf.

Sodium silicate is Na _{2 in} sodium silicate based on 100 parts by weight of rhyolite glassy mineral.
O is added in an amount of 2.0 parts by weight or more, preferably 2.0 to 4.0 parts by weight. Rhyolite glassy mineral 100
2.0 parts by weight of Na ₂ O in sodium silicate relative to parts by weight
If the amount of sodium silicate added is less than 1 part by weight, the crush strength of the ultralight aggregate is less than 80 kgf. Further, if the amount of sodium silicate added exceeds 4.0 parts by weight of Na ₂ O in the sodium silicate to 100 parts by weight of rhyolite-based glassy minerals, fusion will easily occur during firing, and thus fusion prevention will occur. It is not preferable because an agent is required.

The concentration of the sodium silicate aqueous solution is preferably 30% by weight or more. When the concentration of the aqueous sodium silicate solution is less than 30% by weight, aggregated particles of adjacent pellets are likely to occur during granulation of pellets, which is not preferable. The mixing ratio of Na ₂ O in sodium silicate to the rhyolite glassy mineral can be changed by adjusting the concentration of the sodium silicate aqueous solution and the water content of the pellet during granulation.

Pellet granulation is carried out, for example, by putting the rhyolitic glassy mineral, a foaming agent and an aqueous solution of sodium silicate in a granulator such as a pan pelletizer or an extrusion granulator such as a disk pelleter, The pellets are granulated with or without addition of water so that the water content of the pellets is preferably 15 to 25% by weight. If the water content of the pellets is less than 15% by weight, granulation becomes difficult, which is not preferable. Also,
If the water content of the pellets exceeds 25% by weight, aggregates of adjacent pellets are likely to occur, which is not preferable.

The pellets having a particle size of 5 to 15 mm are selected. The selection method is not particularly limited, but it is performed by sieving using, for example, 5 mm and 15 mm sieves conforming to the JIS standard. Pellets other than 5 to 15 mm may be pulverized to have an average particle size of 10 to 40 μm and then returned to the mixing step to be used as a raw material.

The pellets of the present invention can be fired in a water-containing state after granulation. That is, 1 after granulation
The pellets having a water content of 5 to 25% by weight are 900 to 13
At 00 ° C., preferably, Na ₂ O in sodium silicate is 2.0 to 100 parts by weight with respect to the rhyolite glassy mineral.
1100-1 for the pellets which are 3.0 parts by weight
At 300 ° C., the pellets having Na ₂ O in sodium silicate of 3.0 to 4.0 parts by weight with respect to 100 parts by weight of rhyolite glassy mineral are fired at 900 to 1100 ° C. Is good. If the firing temperature is less than 900 ° C, sufficient foaming does not occur and the ultralight specific gravity of the ultralight aggregate exceeds 0.8. If the firing temperature exceeds 1300 ° C., the crush strength of the ultralight aggregate becomes less than 80 kgf. The firing time is preferably 5 to 15 minutes in any case.

If necessary, an anti-fusion agent may be added and the mixture may be fired. Examples of the fusion preventing agent include aluminum hydroxide and aluminum oxide.

The firing may be carried out using a conventional firing device such as a rotary kiln.

[0018]

EXAMPLES Examples of the present invention will be described below together with comparative examples.
The present invention will be described in more detail.

1. Materials used The materials used are shown below. Rhyolite glassy minerals; Malekanite from Okushiri Foaming agent; SiC (manufactured by Pacific Random Co., Ltd.) Sodium silicate; a: Sodium metasilicate (manufactured by Nippon Chemical Industry Co., Ltd.) SiO ₂ / Na ₂ O (moles) Ratio) = 1.0 b: Sodium silicate No. 1 (manufactured by Nippon Kagaku Kogyo Co., Ltd.) SiO ₂ / Na ₂ O (molar ratio) = 2.0 c: Sodium silicate No. 2 (Nippon Kagaku Kogyo Co., Ltd.) SiO ₂ / Na ₂ O (molar ratio) = 2.5 d: sodium sesquisilicate (manufactured by Nippon Kagaku Kogyo Co., Ltd.) SiO ₂ / Na ₂ O (molar ratio) = 0.67 e: sodium silicate No. 3 (manufactured by Nippon Kagaku Kogyo Co., Ltd.) SiO ₂ / Na ₂ O (molar ratio) = 3.0 Okushiri produced malecanite was crushed using a ball mill.
Table 1 shows the average particle size of the malecanite produced in Okushiri. In addition,
The average particle size is measured by SKLASER manufactured by Seishin Enterprise Co., Ltd.
MICRON SIZER was used.

2. Mixing and granulation The above-mentioned materials are put in a bread type pelletizer manufactured by Fuji Paudal Co., Ltd. at a mixing ratio shown in Table 1, and pellets are formed at a rotation speed of 8.5 rpm while spraying water so that the water content shown in Table 1 is obtained. Was granulated. A part of the ingredients was extruded and granulated using a disk pelleter (F-20 type) manufactured by Fuji Paudal Co. The obtained pellets have a particle size of 5 to 15 m using a 5 mm and 15 mm sieve that conforms to JIS standards.
It screened so that it might become m.

3. Properties of Firing and Lightweight Aggregate The pellets having the formulations shown in Table 1 were fired at 880 to 1320 ° C. using a rotary kiln. The ultra-dry specific gravity of the obtained ultralight aggregate was measured according to "JIS A 1135 (Testing method for specific gravity and water absorption of lightweight coarse aggregate for structure)". In addition, the crush strength was measured using a material testing machine manufactured by Orientec. The crushing strength was an average value of 50 aggregates having a particle size of 14 mm. The results are shown in Table 1.

[0022]

[Table 1]

Examples 1 to 3 were evaluated by changing the firing temperature, and 900 to 130 specified in the present invention.
In the range of 0 ° C., an ultralight aggregate having an absolute dry specific gravity of 0.8 or less and a crush strength of 80 kgf or more was obtained. on the other hand,
As shown in Comparative Example 1, the one having a low firing temperature of 880 ° C. had an absolute dry specific gravity of more than 0.8. Further, as shown in Comparative Example 2, the one having a high firing temperature of 1320 ° C. had a crushing strength of less than 80 kgf.

In Examples 4 and 5, the evaluation was conducted by changing the mixing ratio of SiC, but 0.1 to 2.0 parts by weight of 100 parts by weight of Okushiri-made malecanite specified in the present invention was used. In the range, an ultralight aggregate having an absolute dry specific gravity of 0.8 or less and a crushing strength of 80 kgf or more was obtained. On the other hand, as shown in Comparative Example 3, the one having a small compounding ratio of 0.08 parts by weight had an absolute dry specific gravity of more than 0.8. Further, as shown in Comparative Example 4, the crushing strength of 2.1 parts by weight with a large mixing ratio was less than 80 kgf.

In Examples 6 and 7, the evaluation was carried out by changing the mixing ratio of Na ₂ O in sodium silicate with respect to the malekanite produced in Okushiri. In 100 parts by weight of malecanite produced in Okushiri, sodium silicate was used. When the Na ₂ O content is 2 parts by weight or more, the absolute dry specific gravity is 0.8 or less and the crush strength is 80 k.
An ultralight aggregate of gf or more was obtained. On the other hand, as shown in Comparative Example 5, 1.9 parts by weight of Na ₂ O in sodium silicate having a small compounding ratio had a crushing strength of less than 80 kgf.

In Examples 8 and 9, the evaluation was conducted using aqueous solutions of sodium silicate having different molar ratios (SiO ₂ / Na ₂ O) of silicon dioxide and sodium oxide as raw materials. In the aqueous solution of sodium silicate whose molar ratio (SiO ₂ / Na ₂ O) between silicon dioxide and sodium oxide is 1.0 to 2.5, the absolute dry specific gravity is 0.8 or less and crushing is performed. An ultralight aggregate having a strength of 80 kgf or more was obtained. On the other hand, as shown in Comparative Example 6, cracks and spalling occurred in an aqueous solution of sodium silicate having a small molar ratio (SiO ₂ / Na ₂ O) of silicon dioxide and sodium oxide of 0.67. In addition, as shown in Comparative Example 7, the molar ratio of silicon dioxide and sodium oxide (SiO ₂ / Na ₂ O)
In an aqueous solution of sodium silicate having a large value of 3.0, cracks and spalling occurred.

In Examples 10 and 11, the evaluation was performed by changing the average particle size of Okushiri-produced malecanite, but in the range of 10 to 40 μm specified in the present invention, the absolute dry specific gravity is 0.1.
An ultralight aggregate of 8 or less and a crush strength of 80 kgf or more was obtained. On the other hand, as shown in Comparative Example 8, the maleukanite produced in Okushiri having a small average particle diameter of 8 μm had a crushing strength of less than 80 kgf. Further, as shown in Comparative Example 9, the maleukanite produced in Okushiri having a large average particle diameter of 43 μm had a crushing strength of less than 80 kgf.

Examples 12 to 14 were evaluated by changing the concentration of the sodium silicate No. 1 aqueous solution, but the ultra-dry specific gravity was 0.8 or less and the crush strength was 80 kgf or more. Aggregate was obtained. On the other hand, as shown in Comparative Example 10, powdered sodium silicate No. 1 had a crushing strength of less than 80 kgf.

In Examples 15 and 16, pellets having different water contents were fired, and an ultralight aggregate having an absolute dry specific gravity of 0.8 or less and a crushing strength of 80 kgf or more was obtained. .

In Examples 17 and 18, the pellets prepared by extrusion granulation were evaluated, and an ultralight aggregate having an absolute dry specific gravity of 0.8 or less and a crush strength of 80 kgf or more was obtained. Was obtained.

[0031]

According to the method for producing an ultralight aggregate of the present invention, pellets after granulation can be fired in a water-containing state.
Also, the air-dry specific gravity is 1.0 to 1.4 and the compressive strength is 300k.
Applicable as aggregate for lightweight concrete with gf / cm ² or more, absolute dry specific gravity of 0.8 or less, crushing strength of 80 kgf
The above ultralight aggregate can be stably obtained.

Claims (1)

[Claims] 1. A method for producing an ultra-lightweight aggregate in which pellets obtained by granulating a rhyolitic glassy mineral, a foaming agent and an aqueous sodium silicate solution are subjected to particle size adjustment and fired in a water-containing state, (1) Rhyolite glassy mineral has an average particle size of 10 to 40 μm, and (2) sodium silicate is
The molar ratio of silicon dioxide and sodium oxide (SiO ₂ / N
a ₂ O) is 1.0 to 2.5, and (3) the pellets are mixed in such a manner that the blowing agent is 0.1 to 2.0 parts by weight and the silica is added to 100 parts by weight of the rhyolite glassy mineral. The method for producing an ultralight aggregate, characterized in that sodium acid is in an amount such that Na ₂ O in sodium silicate is 2.0 parts by weight or more, and (4) the firing temperature is 900 to 1300 ° C.