JPS5825816B2 - Cement concrete porous sound absorbing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound absorbing material made of a cement concrete porous body.

Various sound absorbing materials have been developed so far, but conventional sound absorbing materials do not necessarily have sufficient mechanical strength, fire resistance, or heat resistance, and in some cases, they use expensive materials, resulting in high costs. , have individual drawbacks depending on the type of material used therein.

However, the biggest drawback is that conventional sound-absorbing materials are generally only effective at absorbing sounds in a limited frequency band, and the width of that band is narrow. It is in.

Therefore, in order to ensure sufficient sound absorption for sounds over a wide range of frequency bands, it is necessary to take measures such as combining two or more sound absorbing materials with different sound absorption characteristics or forming a back space. did not become.

However, the improvement of the sound absorption effect by such means is subject to considerable restrictions depending on the shape and dimensions of the buildings, articles, etc. in which the sound absorbing material is intended to be used, and it is difficult to achieve sufficient technical and economical satisfaction in practice. isn't it.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional sound absorbing materials described above and to provide a sound absorbing material that exhibits effective and high sound absorbing properties for sounds in a wide range of frequency bands using only a single material. be.

The present inventors have been conducting research on the development of sound-absorbing materials for many years, and found that the sound-absorbing mechanism of rigid materials is due to energy loss due to viscous resistance of air on the inner wall surface of the pores of the material, and compression of air within the pores. The present invention was completed as a result of intensive research based on the knowledge that sound absorption properties are caused by thermal energy loss during expansion and that sound absorption properties are closely related to the pore structure.

In other words, cement concrete generally has high mechanical strength, excellent fire resistance and heat resistance, and is a relatively inexpensive material, but the pore distribution of its porous body must be defined under certain conditions. It was discovered that this material exhibits excellent sound absorption properties for sounds in a wide range of frequency bands.

The sound absorbing material according to the present invention is characterized in that it consists of a cement concrete porous body, and that at least 70 percent of the total pore volume of this porous body consists of pores with a diameter of 200 μm to 650 μm.

Even if the cement concrete porous body is made from the same material and has the same pore volume, the pore size is 200 mm in diameter.
Even if the distribution is biased toward the small pore diameter side of less than μ, on the contrary, the diameter of 65
Even if the distribution is biased toward the large pore diameter side exceeding 0μ, the sound absorption characteristics are not good.

Examples of the present invention will be described below in comparison with comparative examples.

In this example and comparative example, cement concrete porous bodies with various pore conditions were prepared, and the pore distribution and sound absorption coefficient were measured.

Example 1 Preparation of cement concrete slurry Cement concrete material' Early strength cement 40.0 kgΦ Silica sand powder (250) 15.0 kg Foaming agent Dodecylbenzenesulfonate 1-IJium 0.9
kg kneading water 33. O1*
Cement concrete materials were mixed in advance and used.

The above-mentioned kneading water and foaming agent were mixed in a batch mixer (capacity 30
M) and foamed by rotating the stirring blade (1,00 rpm) to prepare a foamed liquid with a foam specific gravity of 0.10.

Next, a mixture of early strength cement and silica sand powder was added thereto at a rate of 15 kg per minute to prepare foamed concrete slurry.

Curing The above foamed concrete slurry was poured into a mold kept at a temperature of 30° C., solidified, and then cured in an autoclave under the following conditions to produce a porous body.

Maximum temperature: 182°C Pressure: 10 atm° Maximum temperature holding time: 5 hours After drying this porous body at a temperature of 70°C for 24 hours, its pore distribution and sound absorption coefficient were measured.

Moreover, the apparent specific gravity of this porous body was 0.38.

The measurement results of pore distribution and sound absorption coefficient are shown in FIG. 1 and FIG. 2, respectively.

As can be understood from the graph in Figure 1, this porous body has the largest number of pores with a diameter of 400 to 430μ, and 7 of the total pore volume.
0% is occupied by pores with a diameter of 250μ to 600μ.

Example 2 Preparation of cement concrete slurry Cement concrete material Early strength cement 40.0 kg Silica sand powder (250) 12.0 kg Foamed silica (5-10'') 8.0 kg Asbestos fiber 0.8 kg Foaming agent Dodecyl Sodium benzenesulfonate 0.8 kg
Polyvinyl alcohol 0.5kg kneading water
27.5 #* Cement concrete materials were mixed in advance and used.

※※Foamed silica is heated to a temperature of 650℃ and rapidly cooled in air, so there are cracks on the particle surface.

A porous concrete body was produced in exactly the same manner as described in Example 1, except that the rotational speed of the stirring blade of the mixer was 700 rpm.

The apparent specific gravity of this porous body was 0.44.

The measurement results of the pore distribution and sound absorption coefficient of this porous body are shown in FIGS. 1 and 2, respectively.

From the pore distribution graph in Figure 1, this porous body has a diameter of 45 mm.
The largest number of pores is 0μ, with 70% of the total pore volume having a diameter of 28
It can be seen that the pores are occupied by 0μ to 550μ pores.

Comparative Example 1 The amount of mixing water for concrete slurry preparation was 27
．． A cement concrete porous body was manufactured by the same method as in Example 1 except that the material was changed to 513.

The apparent specific gravity of this porous body was 0.43.

The measurement results of the pore distribution and sound absorption coefficient of this porous body are shown in FIGS. 1 and 2, respectively.

From the pore distribution graph in Figure 1, this porous body has a diameter of 2
00μ pores are the most common, with 70% of the total pore volume having a diameter of 1
It is understood that the pores are occupied by 00μ to 400μ pores.

Comparative Example 2 In preparing the foaming liquid, 0.5 kg of polyacrylic acid was added as a foam stabilizer to the kneading water in addition to the foaming agent, and the rotation speed of the stirring blade of the mixer was set to soorpm. A cement concrete porous body was manufactured by the same method as in Example 1.

The apparent specific gravity of this porous body was 0.38.

The measurement results of the pore distribution and sound absorption coefficient of this porous body are shown in FIGS. 1 and 2, respectively.

From the pore distribution graph in Figure 1, this porous body has a diameter of 18
The largest number of pores is 0μ, and 70% of the total pore volume is 70μ in diameter.
It can be seen that the pores are occupied by pores of μ to 410 μm.

Comparative Example 3 A cement concrete porous body was manufactured in the same manner as in Actual Processing Side 1, except that the amount of foaming agent was 1.8 kg and the rotational speed of the stirring blade of the mixer was 1.25 Orpm.

The apparent specific gravity of this porous body was 0.36.

The measurement results of the pore distribution and sound absorption coefficient of this porous body are shown in FIGS. 1 and 2, respectively.

From the graph in FIG. 1, it can be seen that this porous body has the largest number of pores with a diameter of 700 μm, and 70% of the total pore volume is occupied by pores with a diameter of 420 μm to 830 μm.

Comparative Example 4 Except that foamed silica with a particle size of 10 to 2 (l) was used.
A cement concrete porous body was manufactured by the same method as in Example 2.

The apparent specific gravity of this porous body was 0.47.

The measurement results of the pore distribution and sound absorption coefficient of this porous body are shown in FIGS. 1 and 2, respectively.

From the graph of FIG. 1, it can be seen that this porous body has the largest number of pores with a diameter of 250 μm, and 70% of the total pore volume is occupied by pores with a diameter of 120 μm to 330 μm.

Comparative Example 5 Commercially available AL C (Autoclaved Light
weightConcrete) (apparent specific gravity 0.55
), the pore distribution and sound absorption coefficient were measured.

The results of the measurements are shown in FIGS. 1 and 2, respectively.

From the graph in FIG. 1, it can be seen that this porous body has the largest number of pores with a diameter of 1,020 μm, and 70% of the total pore volume is occupied by pores with a diameter of 850 μm to 1.200 μm.

Comparing the sound absorption properties of the porous bodies with the various pore distributions described above (Figure 2), the porous body of Example 1 shows a sound absorption coefficient of 80 to 90% or more in the frequency band of 300 Hz or higher, and has a wide range of sound absorption characteristics. It can be seen that it has extremely high sound absorption properties in the frequency band of .

Furthermore, the porous body of Example 2 exhibits a sound absorption coefficient of 80 to 90% in a frequency band of 650 Hz or higher, and similarly to the porous body of Example 1, it has high sound absorption over a wide range.

On the other hand, the sound absorption coefficients of the porous bodies of Comparative Examples 1, 2, and 5 are all at a low level overall, but the sound absorption coefficients of the porous bodies of Comparative Examples 1 and 5 are particularly low. .

In addition, in the porous bodies of Comparative Examples 3 and 4, 400H
It exhibits maximum sound absorption for sounds at z and 640 Hz, but its sound absorption coefficients are low at 74% and 69%, respectively, and the sound absorption coefficient gradually decreases as the frequency increases.

As described above, the porous bodies of Examples 1 and 2 exhibit high sound absorbing properties over a wide frequency band, and therefore exhibit excellent sound absorbing effects when used as sound absorbing materials.

[Brief explanation of drawings]

Figure 1 is a graph showing the state of pore distribution in various porous bodies.
FIG. 2 is a graph showing the sound absorption coefficient of the porous body shown in FIG.

Claims (1)

[Claims] 1. A sound absorbing material made of a cement concrete porous body, characterized in that at least 70 percent of the total pore volume of the porous body is composed of pores with a diameter of 200 μ to 650 μ. Material.