JP2000281401A - Lightweight fine aggregate for concrete and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain lightweight fine aggregates which comprise plural closed type foam balloons having smooth surfaces, by forming foams having a specific absolute dry specific gravity, a specific water absorption and a specific isotropic strength from the ground product of perlite-based rock containing perlite. SOLUTION: Perlite-based rock containing perlite is crushed into a particle size of 10.0 μm to 3.5 mm and then adjusted to a water content of 0.5 to 20 wt.%. A mixture gas of air and a fuel gas is blown into a medium heated at a higher temperature than the ignition point of the used fuel (LP gas or the like) to fluidise the fuel and the medium and simultaneously form the flowing layer having a uniform temperature distribution of 900 to 1,050 deg.C. The raw material powder is charged into the flowing layer together with the mixture gas to approximately momentarily foam the rock powder, thus producing the foams. Thereby, the excellent lightweight fine aggregates which are useful for concrete, have an absolutely dried specific gravity of <=0.6 to 1.0, a sufficient low water absorption of <=3 wt.% and an isotropic physical strength of >=10 N/mm2 are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight fine aggregate for concrete and a method for producing the same, and more particularly to a concrete made of a foam of a crushed perlite rock material having low water absorption and excellent physical strength. It is intended to provide a lightweight fine aggregate.

[0002]

2. Description of the Related Art As a fine aggregate for concrete, a foam such as hard pearlite obtained by foaming a natural glass material is used. Further, a foam obtained by firing perlite or obsidian contains a large number of air bubbles and has good heat insulating performance, so that it is also used as a heat insulating material.

[0003] However, since the perlite and obsidian foams have a porous surface and a high water absorption, water enters the interior when kneaded with other concrete materials such as cement, resulting in deterioration of the concrete. And shrinkage. Further, the conventional hard pearlite has a problem that it is difficult to control the foaming rate and the specific gravity varies.

As a solution to the above problem, a vitreous foam having a coating layer made of crystalline ceramic powder on its surface has been proposed (JP-A-10-45450).
issue). Also, a method for producing low-shrinkage concrete by mixing blast furnace slag fine powder, silica stone powder, a foaming agent and a water reducing agent with a Portland cement composition together with an inorganic foam such as obsidian-based pearlite, and curing the mixture in an autoclave. (JP-A-5-310454)
issue).

Further, as an aggregate having higher strength than conventional hard pearlite, an average particle size of 10 μm to 50 μm,
In addition, a glassy raw material having a SiO ₂ network structure having a total structural water content of 2% by weight or more is fired and foamed at a temperature of 850 ° C. to 1000 ° C. to obtain an average particle size of 100 μm.
m has been proposed (Japanese Patent Application Laid-Open No. 10-25139).

[0006] On the other hand, in the production of aggregate, a technique of firing a raw material using a fluidized furnace (Japanese Patent Application Laid-Open No. 58-55363 and Japanese Patent Application Laid-Open No. 53-12807), or a mixed gas of air and fuel gas and a sand medium are used. There is known a technique for producing a foam by introducing an expandable inorganic raw material powder into a fluidized bed used (Japanese Patent Publication No. 51-22922). However, it is not known that the raw material of the pearlite rock whose moisture content is adjusted is fired and foamed in a fluidized-bed furnace.

[0007]

Although the water absorption of aggregate and the strength of concrete are improved to some extent by the above-mentioned technology, the manufacturing process is complicated and there is room for improvement in water absorption.

The present invention has been made from the above viewpoint, and has a low specific gravity as low as 0.6 to 1.0 of absolute dry specific gravity. It is an object to provide a lightweight fine aggregate.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a foam made from a crushed material of perlite has a sintering temperature and a sintering temperature during sintering. By adjusting the residence time of the raw material at that temperature, it is possible to control the water absorption, specific gravity and strength.Thus, while increasing the wall thickness constituting the foam cells of the foam, the pores on the foam surface are removed. It has been found that water absorption can be suppressed by reducing as much as possible, and that foam particles having high strength can be obtained. This led to the finding that a lightweight fine aggregate suitable for concrete made of foam having low water absorption and excellent physical properties could be obtained, and completed the present invention.

[0010] That is, the present invention is a non-granulated lightweight fine aggregate made of a crushed perlite rock including perlite, and has a bone-dry specific gravity of 0.6 to 1.0, and The gist of the present invention is a lightweight fine aggregate for concrete having a water absorption of 3% by weight or less and a strength at an isotropic pressure of 10 N / mm ² or more.

[0011] The present invention also provides a lightweight fine aggregate for concrete, comprising a closed-type multi-cell balloon having a smooth surface. Further, the present invention provides a fine aggregate in which the lightweight fine aggregate for concrete is fired by a medium fluidized bed firing furnace.

Further, the present invention provides a method of crushing perlite rock containing perlite, which has been crushed to a predetermined particle size and having a water content of 0.5 to 2.0% by weight, in a medium fluidized bed calcining furnace.
Provided is a method for producing a lightweight fine aggregate for concrete which is fired and foamed at 0 to 1050 ° C.

Further, the present invention provides the above method for producing a lightweight fine aggregate for concrete, wherein the calcination of perlite rock including perlite by a medium fluidized bed calcination furnace is instantaneously increased from a room temperature to a calcination temperature range. A method characterized in that the method comprises:

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention relates to a non-granulated lightweight fine aggregate made of crushed perlite rock including perlite and having a bone-dry specific gravity of 0.
It is a lightweight fine aggregate for concrete having a water absorption of 6 to 1.0, a water absorption of 3% by weight or less, and an isotropic pressure strength of 10 N / mm ² or more.

In the present invention, "pearlite-based rocks containing perlite" are preferably perlite in view of the physical properties of the fine aggregate obtained and the ease of production, but the obsidian (malecanite. Even if it is a pearlite containing (called a ball). Further, the “crushed material” in the present invention is obtained by crushing perlite rock including perlite, which is a raw material.

The "non-granulated material type" in the present invention means that the raw material is crushed and then fired without granulation. The term “absolute specific gravity” in the present invention refers to an absolute dry state of an aggregate (dried to a constant mass at a temperature of 100 to 110 ° C.,
This is a value obtained by dividing the mass of water (in a state in which water contained in the aggregate particles is removed) by the mass of the same volume of water. In the present invention, the absolute dry specific gravity can be measured by a constant volume gas replacement method.

The term "water absorption" in the present invention refers to an aggregate in a surface dry state (a state in which the aggregate has no surface water and the voids inside the aggregate are filled with water). It is a percentage of the total water content relative to the absolute dry mass of the aggregate. Here, “surface water” is water on the surface of the aggregate, and is obtained by subtracting the water inside the aggregate grain from all the water contained in the aggregate. In the present invention, the water absorption is
It can be measured according to JIS A 1134 “Test method for specific gravity and water absorption of lightweight fine aggregate for structure” 4.2 “Water absorption”.

The term “strength at isotropic pressure” in the present invention means:
Aggregates in mortar and concrete will be subjected to an isotropic load as well as solids in the liquid medium, especially during pumping, but this is specified, for example, using a mercury intrusion porosimeter. The pressure when the volume reduction reaches 50% can be evaluated as strength.

If the absolute dry specific gravity of the lightweight fine aggregate for concrete exceeds 1.0, the lightness of the concrete using it becomes insufficient, and if the absolute dry specific gravity is less than 0.6, the water absorption and the strength are good. No concrete can be obtained.

Further, the water absorption rate of the lightweight lightweight aggregate for concrete exceeds 3% by weight, and the strength at isostatic pressure is 10 N / m.
If it is less than m ² , it becomes difficult to obtain good lightweight concrete.

Another feature of the lightweight fine aggregate for concrete of the present invention is that it comprises a closed-type multi-cell balloon having a smooth surface.

In the present invention, "smooth surface" means that the finger has a smooth touch and there are no large holes or irregularities when the surface is observed with the naked eye. "Balloon" in the present invention,
It is a substantially spherical foam of closed cells. Further, the fine aggregate is a closed-type multi-bubble balloon having a smooth surface, so that the water absorption is suppressed and high strength is obtained.

The lightweight lightweight aggregate for concrete of the present invention is fired by a medium fluidized bed firing furnace. The present invention has been achieved by a combination of specific raw materials and firing in a medium fluidized bed firing furnace.

Further, the lightweight fine aggregate for concrete of the present invention is crushed to a predetermined particle size and has a water content of 0.5 to 2.0.
The crushed material of perlite rock containing perlite adjusted to the weight% can be manufactured by firing at 900 to 1050 ° C. in a medium fluidized bed firing furnace. In particular,
For example, pearlite is crushed to 10.0 μm to 3.5 mm,
After adjusting the water content to 0.5 to 2.0% by weight, baking is performed under the above conditions.

In the present invention, the particle size of the raw material is adjusted by JI
It can be carried out according to SA 1102 “Aggregate sieving test method”. The “water content” in the present invention is a percentage of the total amount of water contained in the voids inside the aggregate grains with respect to the mass of the aggregate in an absolutely dry state.

Further, in the medium fluidized bed type sintering furnace as the sintering furnace in the present invention, since the material to be heated and the combustion gas are intensely fluidized and mixed, the temperature inside the furnace is substantially uniform everywhere and newly supplied. The rate of temperature rise of the raw material is extremely high. Compared to kiln firing furnaces, the residence time during firing is shorter,
When the vitreous material becomes semi-melted at a high temperature without diffusion of water for foaming, the water-containing material can be vaporized at a stretch to form a balloon.

As described above, the particle size and the water content of the perlite rock containing perlite used as a raw material are adjusted by adjusting the expansion ratio and expansion state, in other words, of the lightweight fine aggregate to be manufactured. This is because it affects specific gravity, strength, and water absorption. In particular, in the case of perlite, it is easy to control the water absorption, specific gravity, and strength by adjusting the burning temperature and the residence time during firing, in addition to the above firing. That is, by increasing the thickness of the wall constituting the air bubbles and reducing the number of pores on the surface as much as possible, it is possible to suppress the water absorption rate and obtain foam particles having high strength.

The particle size adjustment in the present invention can be continuously performed by, for example, a dry automatic vibrating sieve classifier. The reason for setting the water content to 0.5 to 2% by weight is to make the non-uniformity of water in the raw material almost uniform at the time of adjusting the water content, to make the foaming state uniform at the time of firing, and to suppress the degree of foaming. Since the melting point increases when the water content decreases, 0.5% by weight
If it is less than this, unfoamed ones tend to increase. If the content is more than 2.0% by weight, foam control becomes difficult, and the desired performance cannot be obtained, or the unevenness of the water content in the raw material is not sufficiently uniformized during the water content adjustment, so that the quality may vary. . The water content of the raw material in the present invention can be calculated from the ignition loss obtained after calcining (350 ° C. × 2 to 4 hours) in an electric furnace and the ignition loss of the unadjusted raw material.

The firing in the present invention is preferably carried out by firing a perlite rock including perlite in a medium fluidized bed firing furnace from room temperature to a firing temperature range instantaneously.
The instant may vary depending on the particle size distribution and water content of the raw material, but is preferably usually within 1 second. A suitable heating rate can be easily set by conducting preliminary experiments on the raw materials and examining the physical properties of the obtained foam.

According to the firing method of the present invention, a mixed gas of air and fuel gas is blown into a medium which has been heated to a flash point of the used fuel in advance, and the fuel and the medium are fluidized. It is possible to form a fluidized bed having a uniform temperature distribution of 1050 ° C., introduce foamable inorganic raw material powder into the fluidized bed together with the above-mentioned mixed gas, and foam the foam almost instantaneously to produce a foam. it can.

The firing temperature is preferably 900 to 1050 ° C. If the firing temperature is too low, it is difficult for softening to occur in the crushed product of the perlite rock of the present invention, and if the firing temperature is too high, the produced foam will be overfoamed and the water absorption will increase. As a result, the strength of the aggregate cannot be ensured, so that a high-strength lightweight fine aggregate for concrete cannot be obtained.

As the fuel gas, natural gas, LP
Any gaseous fuel such as gas, coal gas, and water gas can be used, and the amount of use is not particularly limited because it depends on the size of the firing furnace. The air flow rate is also not particularly limited since it varies depending on the scale of the firing furnace as in the case of the combustion gas. In addition, as a medium of the fluidized bed type medium firing furnace used in the present invention,
Examples include silica sand and ceramic balls.

[0033]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples. Using the raw materials having the water content shown in Table 1, sintering and foaming were performed in the sintering furnace shown in Table 1 set at the sintering temperature shown in Table 1.

In all of the examples and comparative examples of the present invention, the particle size of the raw materials was adjusted by a dry automatic classifier. In Examples 1 to 5 and Comparative Example 6, the water content of the raw material is calculated from the ignition loss obtained after calcining (350 ° C. × 2 to 4 hours) in an electric furnace and the ignition loss of the unconditioned raw material. This was adjusted.

The “ballooning rate” in Table 1 is
It is a measure of the ratio of foamed particles in all the raw material particles, and is also one of the indicators of the shape. It is considered that the higher the figure, the higher the proportion of the foam, and the larger the number of foams as a whole.

FIG. 1 is a schematic diagram of a fluidized bed furnace which can be used in the present invention. The diameter of the firing furnace 1 is 500 mm, the aperture ratio of the dispersion plate 3 is 2.2%, and the hole diameter is 2.0 m.
m. The fluid medium 2 is silica sand, and the static thickness of the fluid medium 2 is 100 mm.

The room where the magnetic balls 4 under the dispersion plate 3 are placed is at room temperature. In Examples and Comparative Examples of the present invention, the amount of air blown into the medium is 2500
４4500 L / min, the fuel gas is LPG,
Its usage is 45-55 L / min. The raw material supply amount is
15 to 40 kg / hour. By using the present fluidized bed, the raw material is instantaneously heated from the room temperature to the firing temperature range.

FIG. 2 is a schematic diagram of the equipment of an externally heated kiln firing furnace according to a comparative example of the present invention. Kiln firing zone length x kiln diameter is
It is 1.2 mx 0.15 m. In the comparative example of the present invention, the peripheral speed is 0.086 m / sec. The inclination of the kiln firing furnace is 2.5%. Raw material supply amount is 1.0 ~
3.0 kg / hour. Table 1 shows the physical properties of the fired products obtained from the examples and the comparative examples.

[0039]

[Table 1]

In Examples 1 to 5, specific gravity, strength and water absorption were specified to predetermined values, and as a result of observation with a transmission optical microscope, the obtained foam was a closed balloon, It was confirmed that it consisted of bubbles.
Further, the shape is substantially spherical, and there is no noticeable unevenness in the contour of the surface, and the surface is a smooth surface with few defects.

On the other hand, in Comparative Examples 1 and 2, perlite raw materials were fired using an externally heated kiln in a firing furnace. As a result of observation with a transmission optical microscope, it was confirmed that the surface had many irregularities and was porous.

In Comparative Example 3, sinter was used as a raw material, and firing was performed using a fluidized medium layer. As a result of observation with a transmission optical microscope, it was found that the surface was a smooth surface without any irregularities in the contour line, but there were portions that seemed to be holes in some places.

In Comparative Examples 4 and 5, obsidian was used as a raw material, and firing and foaming were performed by an externally heated kiln. As a result of observation with a transmission optical microscope, contour-shaped breaks which seemed to be holes were found at various places on the surface.

In Comparative Example 6, obsidian was used as a raw material, and firing and foaming were performed using an externally heated kiln. As a result of observation with a transmission optical microscope, 70% or more could be judged to be unfoamed particles by visual observation. Each of the foams of Comparative Examples 1 to 6 has a water absorption of 4
% By weight.

In Comparative Example 7, obsidian was used as a raw material.
Although calcination was performed in a fluidized bed furnace, most of the input raw materials were deposited in the medium and did not foam, and the test was stopped.

[0046]

As described above, according to the present invention,
Lightweight concrete for crushing perlite rock containing perlite to a specified particle size, adjusting the water content to 0.5 to 2.0% by weight, and sintering and foaming at 900 to 1050 ° C in a medium fluidized bed sintering furnace A fine aggregate and a method for producing the same. as a result,
According to the present invention, even if the absolute specific gravity is as low as 0.6 to 1.0, the water absorption is as low as 3% by weight or less, and the physical strength is equal to that required for obtaining lightweight two-class concrete. It is possible to provide a lightweight fine aggregate for concrete having an excellent direct pressure of 10 N / mm ² or more and a high ballooning ratio as an index of the shape.

[Brief description of the drawings]

FIG. 1 is an outline of equipment of a fluidized bed reactor used in an embodiment of the present invention.

FIG. 2 is an outline of equipment of an externally heated kiln firing furnace used in a comparative example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace main body 2 Medium (silica sand) 3 Dispersion plate 4 Magnetic ball

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeshi Mochinaga 1-2-23 Kiyosumi Research Institute, Koto-ku, Tokyo (72) Inventor Yoshiji Nishi 1-2-23 Kiyosumi, Koto-ku, Tokyo Taiheiyo Cement Co., Ltd.

Claims (5)

[Claims] 1. A non-granulated lightweight fine aggregate made of a foam of a crushed product of perlite, including perlite, having a bone-dry specific gravity of 0.6 to 1.0 and water absorption. A lightweight fine aggregate for concrete having a ratio of 3% by weight or less and a strength at isotropic pressure of 10 N / mm ² or more. 2. The lightweight fine aggregate for concrete according to claim 1, wherein the lightweight fine aggregate is a closed-type multi-cell balloon having a smooth surface. 3. The lightweight fine aggregate for concrete according to claim 1, wherein the lightweight fine aggregate is fired by a medium fluidized bed firing furnace. 4. A crushed powder having a predetermined particle size and a water content of 0.5
A method for producing a lightweight fine aggregate for concrete, in which perlite rock containing perlite adjusted to ~ 2.0% by weight is fired and foamed at 900 to 1050 ° C in a medium fluidized bed firing furnace. 5. The lightweight concrete for use according to claim 4, wherein the calcination of the perlite rock including the pearlite in the medium fluidized bed calcination furnace is instantaneously raised from a room temperature to a calcination temperature range. Manufacturing method of fine aggregate.