JPH10102623A - Sound absorbing concrete panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorbing concrete panel having a sound absorbing factor of not less than 0.8 for the sound in a frequency range of 400 to 4,000Hz. SOLUTION: A sound absorbing concrete board comprises a porous concrete panel having an irregular shape on the surface and an ordinary concrete panel on which the rear surface of the porous concrete panel is superimposed, and a partial air storing space is formed between the porous concrete panel and the ordinary concrete panel. In this case, the continuous void ratio of the porous concrete panel is 20 to 40%, the average void radius is 2 to 5mm, the thickness of the porous concrete panel is about 50 to 80% of that of the sound absorbing concrete panel, and the area of the stored space projected to the sound absorbing area is more than 10% relative to the sound absorbing area of the sound absorbing concrete panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound-absorbing concrete plate which is installed along a highway or a railway to absorb or block noise generated from an automobile or a train.

[0002]

2. Description of the Related Art With the recent increase in traffic volume, noise countermeasures along highways and railways have become a major social problem, and it is necessary to reduce noise in the frequency range of 400 to 4,000 Hz. Have been. The target value is 0.8
That is all. Generally, a metal sound absorbing plate is used along a highway or a railway. However, when a metal sound absorbing plate is used, a sound in a specific frequency range (400 to 1,50) is used.
0 Hz), a sound absorption coefficient of 0.8 or more can be obtained. Also, a sound absorbing plate in which a normal concrete plate is attached to a porous concrete plate is used. Such a sound absorbing plate is configured such that a porous concrete plate has a sound absorbing effect of absorbing sound, and a normal concrete plate has a sound insulating effect. However, since the continuous porosity of the porous concrete plate used therein is as small as about 10%, the sound in a specific frequency region (1,400 to 2,000) is used.
Hz), a sound absorption coefficient of 0.8 or more can be obtained.

[0003] Therefore, a normal concrete plate is attached to the back of a porous concrete plate having an uneven surface,
In addition, a sound absorbing plate in which an air storage space is provided between a porous concrete plate and a normal concrete plate has been proposed. However, in this sound absorbing plate, the frequency range in which a sound absorbing coefficient of 0.8 or more can be obtained can only be expanded to 400 to 2,000 Hz, and the higher frequency range of 2,000 to 4,
At 000 Hz, a sound absorption coefficient of 0.8 or more cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention provides a sound of a wider frequency range (400 to 4.0, 4.0) than a conventional sound absorbing plate.
It is an object of the present invention to provide a sound-absorbing concrete plate exhibiting a high sound absorption coefficient of at least 0.8 with respect to 00 Hz.

[0005]

Means for Solving the Problems The inventors of the present invention provide a sound absorbing concrete plate in which a normal concrete plate is attached to a porous concrete plate and an air storage space is provided therein, and further, a void structure of the porous concrete plate is specified. As a result, it has been found that a sound absorbing concrete plate having a sound absorbing coefficient of 0.8 or more can be obtained even in the frequency range of 2,000 to 4,000 Hz, and the present invention has been completed. That is, the sound absorbing concrete plate of the present invention is:
It is composed of a porous concrete plate having an irregular shape on the surface and a normal concrete plate superimposed on the back surface of the porous concrete plate, and an air storage space is partially formed between the porous concrete plate and the normal concrete plate. (1) the continuous porosity of the porous concrete plate is 20 to 40%, the average pore diameter is 2 to 5 mm, and (2) the thickness of the porous concrete plate is 50% of the thickness of the sound absorbing concrete plate. (3) The projected area of the air storage space to the sound absorbing surface with respect to the sound absorbing surface area of the sound absorbing concrete plate is 10% or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The continuous porosity of the porous concrete plate used in the present invention is 20 to 40%, preferably 22 to 35%. Here, the continuous porosity refers to a ratio of the volume of voids continuously formed from the surface of the porous concrete plate to the volume of voids in the entire porous concrete plate. In other words, it refers to the proportion of the volume of the voids in the porous concrete that can be attenuated due to sound intrusion into the interior. If the continuous porosity is less than 20%, the sound absorption of sound in the frequency range of 2,000 to 4,000 Hz is less than 0.8, and if it exceeds 40%, the strength of the porous concrete plate is 3.5 N / mm. Less than ² ,
Demolding is difficult and not practical.

[0007] The average void diameter of the voids in the porous concrete plate is 2 to 5 mm, preferably 2.5 to 4.6 mm. Here, the average pore diameter is determined by an image analyzer or the like.
The average area is calculated by measuring the area of each void and converting it to a circle equivalent diameter. If the average void diameter is less than 2 mm,
It is difficult to increase the continuous porosity of the porous concrete plate to 20% or more.
The sound absorption coefficient of the sound in the frequency region of z is less than 0.8. When the average gap diameter exceeds 5 mm, 1,500 to 4,000H
The sound absorption coefficient in the high frequency region of z is less than 0.8.

In the present invention, by providing the surface of the porous concrete plate with irregularities, the frequency range in which sound can be absorbed can be widened. If the uneven shape is not provided, only in the low frequency region of about 400 to 700 Hz,
A sound absorption coefficient of 0.8 or more cannot be obtained. As the uneven shape provided on the surface of the porous concrete plate, for example, a mountain shape, a depression shape, a concave shape, and the like can be given. A specific example is shown in FIG. FIG. 1A shows an example of a mountain shape.
(B) is an example of a depression type, and (c) is an example of a depression type.
The mountain shape means a porous concrete plate whose surface is formed from a large number of grooves (peaks and valleys). The cross-section of the groove may be curvilinear or cut out of several straight lines. The bottom and top of the cross-section of the groove may be straight, curved or pointed with a certain width. The depression type is a porous concrete plate in which a number of depressions are formed on the surface. As shown in FIG. 1B, the rows of the depressed portions may be shifted from each other on the left and right. The depressed portion may have a curved surface or a shape cut out from a flat surface. The shape of the bottom of the recessed part is a plane,
It is arbitrary such as a curved surface or a point. The height of the unevenness of the uneven shape is preferably 20 to 50% of the thickness of the porous concrete plate.

The ordinary concrete plate provided on the back of the porous concrete plate reflects or blocks sound transmitted through the porous concrete plate. The ordinary concrete plate is, for example, a water / cement ratio of 40 to 60%,
Fine aggregate ratio 40-50%, water reducing agent / cement ratio 0.5-
2.0% concrete (slump 8-18cm)
Degree) is obtained by curing.

[0010] The thickness of the porous concrete plate is 50 to 80% of the thickness of the sound absorbing concrete plate. If it is less than 50%, the sound absorbing effect of the porous concrete plate is reduced, and the sound absorption of sound in the frequency range of 400 to 4,000 Hz becomes less than 0.8. On the other hand, if it exceeds 80%, the effect of reflecting or blocking sound by the ordinary concrete plate is reduced, and the sound transmitted through the sound absorbing concrete plate increases, so that the sound absorption coefficient of sound in the frequency range of 400 to 4,000 Hz is 0. Less than 8.

The projected area of the storage space on the sound absorbing surface relative to the area of the sound absorbing surface of the sound absorbing concrete plate is 10% or more, preferably 15 to 60%. 10% of projected area
If it is less than 400, the sound absorption coefficient of the sound in the low frequency region of 400 to 800 Hz is less than 0.8, and if it exceeds 60%, the adhesion between the porous concrete and the ordinary concrete decreases, and the strength or durability of the sound absorbing concrete plate decreases. So
Not preferred. The storage space is particularly low frequency (400
〜800 Hz) to effectively absorb sound by resonance. Examples of the shape of the air storage space include a rectangular parallelepiped, a cube, and the like.

From the viewpoint of the strength of the sound absorbing concrete plate, the distance between the storage space and the outer surface of the porous concrete and the distance between the storage space and the outer surface of the ordinary concrete are both 2.5.
cm or more. The dimensions of the sound absorbing concrete plate are preferably 50 to 100 cm in length, 100 to 200 cm in width, and 15 to 25 cm in thickness from the viewpoint of ease of construction.

The sound-absorbing concrete plate is formed by molding a porous concrete plate having an uneven surface on its surface, and then opening a container made of wood, plastic, or synthetic resin which is open on one side so as to obtain a predetermined storage space. It can be manufactured by fixing the open surface at a predetermined position facing the porous concrete molded body, then pouring ordinary concrete, curing and hardening. Alternatively, a porous concrete plate having an uneven surface and a normal concrete plate may be fixed with an anchor or the like. In this case, the air storage space can be formed by providing a concave portion serving as a predetermined air storage space on the back surface of the porous concrete plate and / or the ordinary concrete plate.

The irregular shape on the surface of the porous concrete plate is formed by using a mold having the irregular shape. The porous concrete plate has, for example, a particle size of 2.
For a coarse aggregate of 5 to 7.5 mm, a powder mixture containing cement or cement and a particle size of 1.0 mm such that a weight ratio to the cement or powder mixture containing cement becomes 0 to 150%. A fine aggregate having a weight ratio of 0.5 to 4.0% to the cement or the powder mixture; and a weight ratio of 10 to 25% to the cement or the powder mixture containing the cement. And a mortar containing the kneading water of the above are charged into a mixer so that the volume ratio is 25 to 30% with respect to 100% of the coarse aggregate, kneaded and granulated, and the coarse aggregate is added to the coarse aggregate. Independent granules coated with a paste or mortar made of a material other than the material, and the obtained granules are put into a predetermined mold, and then subjected to an external vibration having a vibration frequency of 3,000 to 8,000 vpm. After vibration molding with It can be produced by curing form.

The powder mixture containing cement refers to a powder mixture composed of cement and other powder materials added as needed. Examples of other powder materials added as necessary include fly ash, blast furnace slag powder, silica fume, limestone powder, and inorganic powder such as silica stone powder. The proportion of the volume of these optional materials in the powder mixture is from 0 to 60.
%.

[0016]

The present invention will be described below by way of examples. 1. Production of Sound Absorbing Concrete Plate (1) Materials Used The following materials were used as materials for porous concrete. Cement: Portland cement manufactured by Nippon Cement Co., Ltd .; Blast furnace slag powder: Fine cement 10A (trade name) manufactured by Daiichi Cement Co .; High performance water reducing agent: Mighty 150 (trade name) manufactured by Kao Corporation; Fine aggregate : Silica sand No. 7 manufactured by Nichetsu Co., Ltd. Coarse aggregate: Crushed stone No. 7 from Ome (particle size 2.5 to 5 m)
m) (used in Examples 1 to 8 and Comparative Examples 1 and 3 to 7) and crushed stone No. 5 from Ome (particle size: 13 to 20 mm) (used in Comparative Example 2)

The following materials were used as ordinary concrete materials. Cement: Portland cement manufactured by Nippon Cement Co., Ltd .; High performance water reducing agent: Mighty 150 (trade name) manufactured by Kao Corporation; Fine aggregate: crushed sand from Ome (particle size of 5 mm or less); Coarse aggregate: crushed stone from Ome 2005 (Particle size 5-20m
m)

(2) Mixing and mixing of porous concrete
The materials shown above were put together in a pan-type mixer (0.1 m ³ ) at the compounding ratio shown in Table 1 and kneaded for 3 minutes. After that, 90 grooves (4 having a width of 10 cm and a depth of 4 cm) were prepared. It was put into a mold having a size of 50 × 20 cm in a direction having a concave-convex shape in a cross section, and compacted by external vibration of 6,000 vpm. The thickness of the porous concrete plate is basically 14cm,
For some of the compacts, the thickness of the porous concrete plate was changed as shown in Table 2. FIG. 2 shows the shape of the porous concrete compact. The width of the porous concrete molded body is 90 cm, the length is 50 cm, and the width of the groove is 10 c.
m, the depth of the groove is 4 cm. In Comparative Example 4, 9
Using a mold frame of 0 × 50 × 20 cm, a porous concrete flat plate having a thickness of 14 cm was formed.

[0019]

[Table 1]

[0020]

[Table 2] * 1 The ratio of the area of the air storage space to the area of the sound absorbing concrete board (90 × 50 cm).

(3) Placing and storage of ordinary concrete
Using materials shown in the formation of the space, water / cement ratio of 50%, fine aggregate ratio of 45%, with water reducing agent / cement ratio 1.25% condition,
Concrete with a slump of 15 cm was prepared and cast on a porous concrete plate to produce a sound-absorbing concrete plate having a compaction thickness of 20 cm. The air storage space was made up of six 17 × 17 × 3.5 cm plastic containers, one of which was open, and the open surface of which was made of a porous concrete molding (90).
× 50cm) and fixed to the position shown in FIG.
It was formed by casting concrete. For some molded products, 7 × 7 × 3.5 cm, 10.5 × 10.5 ×
The area of the air storage space was changed by using a 3.5 cm, 20 × 20 × 3.5 cm plastic container. In Comparative Example 6, a plastic container of 17 × 17 × 0.5 cm was used.

(4) Pre-curing 3 hours, heating rate: 20 ° C./hour, holding at 65 ° C. for 3 hours, steam curing under natural cooling conditions to produce a sound absorbing concrete plate.

[0023] 2. Evaluation (1) Five areas of 10 cm in diameter were installed on a porous concrete plate having an average void diameter , cores were cut out, and cut at positions of 7 cm and 11 cm from the surface of the porous concrete plate, and an image analysis device (Kawasaki Steel Corporation) Was used to determine the number of voids and the equivalent circle diameter, and the average void diameter was calculated.

(2) Continuous Porosity The continuous porosity was measured in accordance with the porosity test method for porous concrete (draft) (Eco-Concrete Research Committee of the Japan Concrete Institute (JCI)). (3) Sound absorption coefficient The sound absorption coefficient was measured according to "JIS A 1409 (method of measuring sound absorption coefficient in reverberation room method)". Table 2 shows the average pore diameter and the continuous porosity. 4 to 9 show the relationship between the frequency and the sound absorption coefficient.

Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by changing the materials used and the blending. As shown in FIG. 5, in Examples 1 to 4, 400 to 4,000 Hz
The sound absorptivity of the sound in the frequency region is 0.8 or more.
On the other hand, as shown in FIG. 6, in Comparative Example 1 in which the continuous porosity was less than 20%, the sound absorptivity of sound in the frequency range of 2,000 to 4,000 Hz was less than 0.8. Average void diameter is 5m
m, in Comparative Example 2 exceeding 1,500 to 4,000 Hz
Was less than 0.8. In Comparative Example 3 in which the average void diameter was less than 2 mm and the continuous porosity was less than 20%, the sound absorption in the frequency range of 2,000 to 4,000 Hz was less than 0.8.

In Comparative Example 4, the evaluation was carried out without making the surface of the porous concrete plate uneven. FIG.
As shown in Comparative Example 4, the sound absorption coefficient of 0.8 or more could be obtained only for the sound in the frequency range of 400 to 600 Hz. Examples 5 to 6 and Comparative Example 5
The evaluation was performed by changing the projected area of the air storage space.
FIG. 8 shows the result. Comparative Example 5 was a case where the projected area of the air storage space was less than 10%, and the sound absorptivity of sound in a frequency region of 400 to 800 Hz was less than 0.8.

Examples 7 to 8 and Comparative Examples 6 to 7 were evaluated by changing the thickness of the porous concrete plate. FIG. 9 shows the result. In Comparative Example 6, the thickness of the porous concrete plate was 50 times the thickness of the sound absorbing concrete plate.
%, And the sound absorption coefficient of the sound in the frequency range of 400 to 4,000 Hz was less than 0.8. Conversely, Comparative Example 7 is a case where the thickness of the porous concrete plate exceeds 80% of the thickness of the sound absorbing concrete plate,
The sound absorption coefficient of the sound in the frequency range of 000 Hz was less than 0.8.

[0028]

The sound-absorbing concrete plate according to the present invention comprises:
Since the sound absorption coefficient is 0.8 or more with respect to a wide range of sounds in a frequency range of 400 to 4,000 Hz, noise along a highway or a railway can be reduced more effectively than before.

[Brief description of the drawings]

FIG. 1 is a perspective view showing various forms of irregularities on the surface of a porous concrete plate used in the present invention.

FIG. 2 is a perspective view showing an example of a porous concrete molded body.

FIG. 3 is a plan view showing a state in which six plastic containers are fixed to a porous concrete molded body.

FIG. 4 is a perspective view of a sound absorbing concrete plate in the embodiment.

FIG. 5 is a diagram showing the sound absorbing performance of a sound absorbing concrete plate.

FIG. 6 is a diagram showing the sound absorbing performance of a sound absorbing concrete plate.

FIG. 7 is a diagram showing the sound absorbing performance of a sound absorbing concrete plate.

FIG. 8 is a diagram showing the sound absorbing performance of a sound absorbing concrete plate.

FIG. 9 is a diagram showing the sound absorbing performance of a sound absorbing concrete plate.

Continued on the front page (72) Inventor Takuaki Shirosho 213-31-103 Futsubashi-cho, Seya-ku, Yokohama-shi, Kanagawa

Claims (1)

[Claims] 1. A porous concrete plate having an uneven shape on its surface, and a normal concrete plate superimposed on the back surface of the porous concrete plate, and partially storing air between the porous concrete plate and the normal concrete plate. In the sound absorbing concrete plate in which the space is formed, (1) the continuous porosity of the porous concrete plate is 2
(2) the thickness of the porous concrete plate is 50 to 80% of the thickness of the sound absorbing concrete plate, and (3) the thickness of the sound absorbing concrete plate. A sound-absorbing concrete plate, wherein a projected area of the air storage space to the sound-absorbing surface with respect to the sound-absorbing surface area is 10% or more.