JP6910678B1 - Cement sound absorbing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement sound absorbing material having the same strength as that of a conventional concrete panel and having improved sound absorbing characteristics. A cement sound absorbing material 1 according to the present invention includes surface layers 10 and 11 containing cement as a main component and containing cellulose nanofibers, and an intermediate layer 12 containing cement as a main component and containing cellulose nanofibers and polyvinyl alcohol. A film-like bubble sheet 20 is provided so as to be laminated on the intermediate layer 12 and air is sealed in a large number of protruding voids 21, and a large number of small holes reaching the bubble sheet 20 from the surface layer 10 on one side. 13 is formed. [Selection diagram] Fig. 1

Description

The present invention relates to a cement sound absorbing material such as mortar and concrete having sound absorbing properties suitable for buildings.

Cement compositions such as mortar and concrete are mainly used as structural materials in the fields of civil engineering and construction, but they are also incorporated into buildings as functional materials other than structural materials. In recent years, concrete buildings have been constructed in urban office districts, and buildings and other buildings have come to stand on both sides of the road. Therefore, the noise from the vehicle traveling on the road echoes and spreads on the wall surface of the building, which has become a noise problem. Various soundproof walls have been proposed to address these issues.

For example, Patent Document 1 describes a building material in which a member having a honeycomb structure is sandwiched or attached to a member obtained by laminating a layer made of a hydraulic substance as a main raw material and a hard foamed synthetic resin layer. Further, Patent Document 2 describes a lightweight cellular concrete panel in which non-through holes are formed on the plate surface of the panel, mainly includes independent pores, and the absolute dryness specific gravity is 0.45 or less. Further, in Patent Document 3, a mortar or concrete linear body containing short plant fibers that has not yet hardened is bent and entangled to form a three-dimensional shape, and this is cured to partially bond the linear bodies to each other. A sound wave absorbing panel with a shrunken block attached to the surface is described.

Japanese Unexamined Patent Publication No. 10-30301 Japanese Unexamined Patent Publication No. 11-303304 Japanese Unexamined Patent Publication No. 2004-238844

In Patent Document 1, the honeycomb structure is used as the core material, and the laminated structure is sandwiched between the plate materials of water-hard materials such as cement and gypsum. However, in terms of strength, the honeycomb structure secures the strength. Therefore, there is a drawback that the strength of the surface plate material itself tends to be weakened and cracks or the like are likely to occur on the surface. Patent Document 2 describes a lightweight concrete panel containing air bubbles, but since the strength of such a concrete panel is lowered, the place where it is used as a structural material is restricted. In Patent Document 3, the concrete linear body is formed into a three-dimensional shape to improve the sound absorbing characteristics, but it is considered that the concrete linear body is fragile and difficult to use as a structural material.

Therefore, an object of the present invention is to provide a cement sound absorbing material having the same strength as a conventional concrete panel and having improved sound absorbing characteristics.

The cement sound absorbing material according to the present invention is arranged between the front and back surface layers containing cellulose nanofibers containing cement as a main component and the surface layers on the front and back sides, and the cellulose nanofibers containing cellulose as a main component. And an intermediate layer containing polyvinyl alcohol, and a film-like bubble sheet arranged so as to be laminated on the intermediate layer and air-sealed in a large number of protruding voids, and the bubble sheet from the surface layer on the front side. A large number of small holes reaching the space are formed so as to communicate with the voids. Further, the surface layer contains cellulose nanofibers in a blending ratio of 0.1% by mass to 5.0% by mass with respect to cement. Further, the intermediate layer contains cellulose nanofibers in a blending ratio of 0.01% by mass to 0.1% by mass with respect to cement and polyvinyl alcohol in an amount of 1.0% by mass to 15.0% by mass with respect to cement. It is contained in a blending ratio of%.

The present invention is arranged so as to be laminated on a surface layer containing cement and cellulose nanofibers, an intermediate layer containing cement, cellulose nanofibers and polyvinyl alcohol, and air is sealed in a large number of protruding voids. Since a large number of small holes reaching the bubble sheet from the surface layer are formed, the sound absorbing material has the same strength as the conventional concrete panel and has improved sound absorbing characteristics. Obtainable.

It is a partially enlarged sectional view which concerns on embodiment of this invention. It is explanatory drawing about the manufacturing process of the cement sound absorbing material. It is a graph which shows the measurement result of the sound absorption test on the front side. It is a graph which shows the measurement result of the sound absorption test on the back side.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Since the embodiments described below are preferable specific examples for carrying out the present invention, various technical restrictions are made, but the present invention particularly limits the present invention in the following description. Is not limited to these forms unless otherwise specified.

FIG. 1 is a partially enlarged cross-sectional view of the embodiment according to the present invention. The cement sound absorbing material 1 is laminated on the surface layers 10 and 11 containing cement as a main component and cellulose nanofibers, an intermediate layer 12 containing cement as a main component and cellulose nanofibers and polyvinyl alcohol, and an intermediate layer 12. A film-like bubble sheet 20 that is arranged and has air sealed in a large number of protruding voids 21 is provided, and a large number of small holes 13 that reach the bubble sheet 20 from the surface layer 10 on one side are formed.

<About the surface layer>
Specific examples of the raw materials used for the surface layers 10 and 11 include the following.

Cement, preferably Portland cement, the compressive strength, in terms of tensile strength and fluidity, mineral composition C ₃ S (alite) 45 wt% to 55 wt%, C ₂ S (belite) 15% to 25 wt%, C ₃ a (aluminate phase) 5 wt% to 10 wt%, C ₄ AF (ferrite phase) is preferably 8 wt% to 10 wt%. When a reinforcing material such as a mesh-like three-dimensional structure is built in, a composition in which the amount of _{C 3 A component that promotes condensation is suppressed in order to secure fluidity for easily filling the inside of the reinforcing material.} Is more preferable.

Cellulose nanofibers (hereinafter abbreviated as "CNF") are ultrafine fiber materials in which cellulose molecules are linearly arranged, and are nano-sized (nano-sized) by chemically and mechanically treating wood fibers or plant fibers obtained from wood. It is a biomass material that has been finely crushed to ^{10-9 m).}

CNF is known to disperse in water to form a three-dimensional network structure, and has many excellent properties such as high strength, high elastic modulus, low coefficient of linear expansion, high transparency, and gas barrier property. It also has merits in terms of weight reduction and reduction of environmental load in production and disposal, and research and development are being promoted for applications in various fields.

The blending ratio of CNF to cement is preferably 0.1% by mass to 5.0% by mass, and if it is smaller than 0.1% by mass, there is a demerit that the characteristics of CNF are not sufficiently exhibited, and 5.0% by mass. If it is larger than that, it will be a disadvantage in terms of high strength.

When producing CNF, raw materials used such as wood chips are pulped and then further finely divided into a slurry or powder by performing known treatments such as a mechanical treatment method, a TEMPO oxidation method, and a water jet method. Is used. Those that have been miniaturized by the underwater counter-collision method (ACC method) have different characteristics derived from the raw materials. For example, those using pulp made from coniferous trees are preferable because they can increase the strength. .. Further, when the TEMPO oxidation treatment is performed, nanofibers having a uniform fiber width can be obtained, which is preferable in terms of high strength.

When CNF is used, it is preferable to add mineral grains. The mineral grains preferably have a particle size of 1 mm to 4 mm, and preferably contain borosilicate minerals (mainly composed of _{SiO 2} , Na ₂ O and B ₂ O _3). By using a particle size in such a particle size range in combination with CNF, high strength can be exhibited. _{Further, by containing SiO 2} as a component, it is possible to obtain an action effect similar to that of fly ash.

The mixing ratio of the mineral grains to the cement is preferably 2% by mass to 20% by mass, and if it is less than 2% by mass, there is a demerit such as a decrease in strength. There is a problem such as occurrence.

As the aggregate used for cement, known aggregates such as sand and gravel can be used. For the size of the aggregate, in the case of fine aggregate such as sand, use a size that passes through all 10 mm sieves and 85% or more of those that pass through the 5 mm sieve, and coarse aggregate such as gravel. In the case of, it is preferable to use a size in which 85% or more of the material does not pass through a 5 mm sieve.

Tap water can be used as the water to be mixed with the cement and the curing water, and it is preferable to add 5% by mass to 15% by mass.

Examples of the admixture to be added include a water reducing agent. Examples of the water reducing agent include lignin-based, naphthalene sulfonic acid-based, amino sulfonic acid-based, and polycarboxylic acid-based water reducing agents, high-performance water reducing agents, and high-performance AE water reducing agents. High-performance water reducing agents improve water reduction by increasing the amount used, but even if the amount used is increased, the unit water amount is significantly reduced because excessive air entrainment and abnormal condensation delay are small. It can be used and is preferable for the production of high-strength concrete. The water reducing agent is preferably added in an amount of 0.3% by mass to 1.0% by mass from the viewpoint of reducing the viscosity of concrete.

The strength of the surface layer, it is preferable compressive strength by compression strength testing (JIS A 1108) is ^{10N / mm 2 ~30N / mm 2} .

<About the middle class>
Specific examples of the raw materials used for the intermediate layer 12 include the following.

Examples of cement, CNF, water, mineral grains, aggregates and admixtures are the same as those used as the raw materials used for the surface layer described above. By using the same raw material, it becomes possible to integrally mold.

Polyvinyl alcohol (hereinafter abbreviated as "PVA") is a saponified product of polyvinyl acetate, which has strong hydrophilicity and is soluble in warm water. Although many types of PVA have been developed according to the intended use, in the present invention, a partially saponified type is preferable.

The blending ratio of PVA to cement is preferably 1.0% by mass to 15.0% by mass, and if it is less than 1.0% by mass, elastic properties that are easily deformed are less likely to be exhibited, and 15.0% by mass. If it is larger than that, the swelling action becomes remarkable, and the dimensional stability is lowered.

The blending ratio of CNF to cement is preferably 0.01% by mass to 0.1% by mass in view of the balance between the development of elastic properties and the strength of PVA.

The strength of the intermediate layer, the compressive strength by compression strength testing (JIS A 1108) is preferably used as the ^{2N / mm 2 ~6N / mm 2} . Further, in the compressive strength test, the cement composition containing PVA does not break even if it is deformed to the upper limit of the compressive deformation amount, and immediately after the load is released, the deformation is restored like an elastic body. Will be. It can be said that it has elastic properties because it shows such early deformation recovery.

<About bubble wrap>
As the bubble sheet, a film-like sheet in which air is sealed in a large number of protruding voids 21 and made of synthetic resin and used as a cushioning sheet can be used. As a typical one, a cap film having a large number of irregularities formed is known to be bonded to a base film. The air-sealed protruding voids 21 preferably have a diameter of 5 mm to 20 mm and a height of 2 mm to 10 mm. The distance between the protruding gaps 21 is preferably set narrower than the distance between the small holes 13, and specifically, it is preferably set to 1 mm to 5 mm.

The bubble sheet 20 may be arranged and laminated inside the intermediate layer as in the above-mentioned example, or may be arranged at the boundary between the intermediate layer and the surface layer. Further, a plurality of bubble sheets 20 may be stacked and arranged, and in that case, the voids 21 may be overlapped with each other or the base films may be overlapped with each other, and the sound absorption effect and the strength may be balanced. The number of sheets and the arrangement may be set as appropriate.

<About small holes>
The large number of small holes 13 reaching from the surface layer 10 on one side to the bubble sheet 20 preferably have a hole diameter of 2 mm to 4 mm, and if it is smaller than 2 mm, the sound absorbing effect is insufficient, and if it is larger than 4 mm, the strength of the sound absorbing material is lowered. Will be. The small holes are preferably formed at equal intervals in the entire surface layer, and the larger the number, the better, but it is preferable to set the pores to such an extent that the strength of the sound absorbing material is not affected. Further, by communicating the small holes with the voids 21 of the bubble sheet 20, the air layer formed by the bubble sheet 20 can communicate with the small holes to improve the sound absorption effect.

FIG. 2 is an explanatory diagram relating to a manufacturing process of a cement sound absorbing material. First, a layer to be the front surface layer 11 on the back surface side is formed. In this example, CNF mortar is used for the surface layer. CNF mortar can be prepared by adding CNF and an admixture to cement and kneading them, and then adding mineral grains and kneading them. The obtained kneaded product is poured into a mold 30 to form a uniform layer having a predetermined thickness (FIG. 2A).

Next, a layer to be the intermediate layer 12 is formed. In this example, PVA mortar is used for the intermediate layer. PVA mortar can be prepared by adding water and an admixture to PVA and kneading, then adding cement and kneading again, and then adding CNF and kneading.

In this example, since the bubble sheet 20 is built in the intermediate layer 12, the bubble sheet 20 is separately poured into the lower layer 12a and the upper layer 12b. First, in order to form the lower layer 12a, a kneaded product is poured to form a uniform layer having a predetermined thickness (FIG. 2B). Next, the bubble sheet 20 cut to a predetermined size according to the size of the mold 30 is placed on the upper surface of the lower layer 12a (FIG. 2C). The kneaded product is poured again from above the arranged bubble sheet 20 to uniformly form the upper layer 12b with a predetermined thickness (FIG. 2D). Since the air is sealed inside the protruding gap 21 of the bubble sheet 20, the gap is maintained without being crushed.

The thicknesses of the lower layer 12a and the upper layer 12b may be changed depending on the position of the intermediate layer in which the bubble sheet 20 is arranged. When the bubble sheet 20 is arranged on the lower surface or the upper surface of the intermediate layer, the intermediate layer is used. The bubble sheets 20 may be arranged so as to be laminated before and after the formation.

Next, a layer to be the surface layer 10 is formed. In this example, the same CNF mortar as the surface layer 11 is used. A kneaded product similar to the kneaded product used for the surface layer 11 is prepared, poured into the mold 30 to the upper surface, and uniformly formed to a predetermined thickness (FIG. 2 (e)). Then, the lid plate 31 is arranged and fixed on the upper surface of the mold 30. A large number of screws 32 are driven into the lid plate 31 so as to project toward the lower surface side, and by pushing the screws 32 from above the surface layer 10 so as to pierce the surface layer 10, the intermediate layer 12 penetrates the surface layer 10. The bubble sheet 20 inside reaches (FIG. 2 (f)).

The screw 32 is provided to form the small hole 13, and the diameter of the screw portion is preferably set to 2 mm to 4 mm, and the length is about the same as the total thickness of the surface layer 10 and the upper layer 12b. The length can be set to reach the bubble sheet 20. In addition, the length that penetrates to the intermediate layer 12 affects the strength, so it should be avoided. The intervals of the screws 32 are preferably set to be evenly spaced, and the number of screws to be attached per unit area may be appropriately set in consideration of the sound absorbing effect of the small holes and the influence on the strength.

The screw 32 is screwed into the lid plate 31 so as not to reach the bubble sheet 20, and is set so as to reach the bubble sheet 20 by screwing the screw 32 when the surface layer 10 and the intermediate layer 12 are cured to some extent. You can also. By tightening the screw 32 so as to break through the bubble sheet 20 in the cured state, it is possible to prevent the shape of the protruding gap 21 from collapsing and to form a structure in which the small hole 13 and the gap 21 communicate with each other.

A member other than the screw 32 can be used for forming the small hole 13, and is not particularly limited. For example, it may be driven with a nail, or a rod-shaped protrusion may be integrally formed on the lower surface side of the lid plate 31.

After the lid plate 31 is attached, it is cured by performing air curing in accordance with JIS A 1132, and the sound absorbing material can be obtained by removing the mold from the mold 30. The obtained sound absorbing material has a structure in which a large number of small holes 13 are formed in the surface layer 10 on the front side and no small holes are formed in the surface layer 11 on the back side.

The sound absorption effect can be quantitatively shown by performing a sound absorption test (based on JIS A 1409) on the front side and the back side and measuring the sound absorption coefficient. The sound absorption coefficient α is calculated by the following formula as the sound intensity (e) emitted toward the surface of the sound absorbing material and the reflected sound intensity (e _1).
α (%) = [(1-e ₁ ) / e] × 100
In this case, the smaller the reflected sound, the larger the sound absorption coefficient, and the sound absorption effect can be determined.

As will be described later, when a sound absorption test was performed in which a conventional cement material (eg, sand mortar) was formed to have the same thickness as the sound absorbing material and small holes were formed on only one side in the same manner as the sound absorbing material. It has been confirmed that the sound absorption coefficient of the sound absorbing material is greatly increased on the formed front side, and the sound absorbing effect is significantly improved as compared with the conventional cement material. It is considered that this is because the air layer formed by the bubble sheet and the small holes communicate with each other inside, so that the sound waves generated from the outside are introduced into the air layer from the small holes and absorbed.

Since the surface layer containing CNF has high strength, a sound absorbing material can be applied in the same manner as a conventional cement panel. Further, since the surface layer and the intermediate layer are mainly composed of cement, the entire sound absorbing material is integrally formed, and it can be used as a lightweight panel material that is less likely to be damaged such as peeling.

<About property testing>
The following tests were conducted as characteristic tests.

〇 Sound absorption test (compliant with JIS A 1409)
The sound absorption test was conducted at the Fukui Prefectural Industrial Technology Center (Fukui City, Fukui Prefecture). In the reverberation room constructed in the center, a steady sound pressure generator (manufactured by Spectris Co., Ltd.) and an acoustic intensity measuring device (manufactured by Spectris Co., Ltd.) were used.

Specimens having a length of 35 cm, a width of 35 cm, and a thickness of 2 cm were prepared, placed flat on the floor in the reverberation room in three vertical and horizontal directions, and a commercially available vinyl tape was attached to the gaps between the specimens to seal them. Four rafters were placed along the periphery of the arranged specimens, and vinyl tape was attached to the gap between the specimens and sealed.

A steady sound pressure generator was placed at a height of 1 m from the center position of the arranged specimens, and an acoustic intensity measuring device was placed at a predetermined position. Then, a sound wave having a predetermined intensity was emitted from the steady sound pressure generator toward the specimen, and the intensity of the sound reflected by the specimen was measured by the acoustic intensity measuring apparatus. The intensity of the reflected sound was measured by changing the frequency of the sound wave, and the sound absorption coefficient of each was calculated. The sound absorption coefficient α was calculated based on the following formula.
α (%) = A / S × 100
Here, S is the area of the specimen (m ² ), and A is the equivalent sound absorption area (m ² ) calculated by the following formula.
A = 55.3 × (V / c ) × (1 / T 2 -1 / T 1)
c is the speed of sound in the air (m / s), V is the volume of the reverberation room when the ^{specimen is not installed (m 3} ), and T ₁ is the reverberation time in the reverberation room when the specimen is not installed (m 3). s) and T ₂ are the reverberation time (s) in the reverberation room with the specimen installed.

○ Compressive strength test (based on JIS A 1108)
A compressive strength test was carried out on a specimen (a cylinder having a diameter of 50 mm and a height of 100 mm) 7 days after curing using an Amsler type compression tester (manufactured by Technoenami Co., Ltd .; model compression tester Amsler type 1000 kN).

<About raw materials used>
The following materials were prepared as raw materials for the concrete composition.
○ Ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.)
(Density 3.16 g / cm ³ , specific surface area 3330 ^{cm 2} / g)
(Mineral composition; C ₃ S 56%, C ₂ S 18%, C ₃ A 9%, C _{4 AF 9%)}
〇Cellulose nanofiber (CNF)
CNF1 (nanoforcest-S manufactured by Chuetsu Pulp & Paper Co., Ltd.)
Manufactured by the ACC method. Fiber width 20 nm or less, CNF concentration 2%
〇Polyvinyl alcohol (PVA)
PVA1 (Polyvinyl alcohol PVA1500 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd .; degree of polymerization of about 1500)
〇Bubble wrap sheet Petit sheet manufactured by Kawakami Sangyo Co., Ltd. (registered trademark) (projection diameter 10 mm and height 3.5 mm, protrusion spacing 1 mm)
〇Mineral grains (Brazilian shawl tourmaline manufactured by Chie, particle size 1 to 4 mm, density 3.18 g / cm ³ )
According to the explanatory material for sale, it is explained that it is a borosilicate mineral grain containing silicic acids such as sodium, calcium, magnesium, iron, manganese, and aluminum.
○ Fine aggregate (manufactured by Nakanihon Gravel Co., Ltd.)
(Maximum aggregate size 2 mm, surface dry density 2.63 g / cm ³ )
○ Coarse aggregate (manufactured by Mitani SEKISAN Co., Ltd.)
(Maximum aggregate size 10 mm, surface dry density 2.70 g / cm ³ )

<About admixture>
The following were used as admixtures.
○ High-performance water reducing agent (manufactured by BASF Japan Ltd .; Master Grenium SP8HU)

<About kneading water>
Tap water (Echizen City Waterworks Bureau; hardness 23 mg / liter) was used.

[Example 1]
A cement panel material having a structure similar to that of the three-layer structure shown in FIG. 1 was produced.

<CNF mortar composition for surface layer>
The following unit amounts were prepared as raw materials to be used.
Cement; 1198 kg / m ³
CNF1; 616 kg / m ³
(CNF amount; 12.32 kg / m ³ , cement ratio; 1.0 mass%)
Mineral grains; 34 kg / m ³ (cement ratio: 2.8% by mass)
Admixture; 35.94 kg / m ³

<PVA mortar composition for intermediate layer>
The following unit amounts were prepared as raw materials to be used.
Cement; 1093 kg / m ³
Water; 565 kg / m ³
CNF1; 18kg / m ³
(CNF amount; 0.36 kg / m ³ , cement ratio; 0.03 mass%)
PVA1; 91 kg / m ³ (cement ratio; 8.3% by mass)
Admixture; 32.79 kg / m ³

<Preparation of specimen for sound absorption test>
For CNF mortar, CNF and an admixture were added to cement and kneaded for 5 minutes, and then mineral grains were added and kneaded for 5 minutes to prepare a kneaded product. The obtained kneaded product was poured into a mold (length 35 cm × width 35 cm × height 2 cm) to form a uniform layer having a thickness of about 5 mm. It was allowed to stand at room temperature for several hours to form a film on the surface so that the kneaded material would not be mixed even if it was poured upward. The kneading work was carried out by stirring with a commercially available hammer drill.

Next, a layer to be an intermediate layer was formed. For PVA mortar, water and an admixture were added to PVA and kneaded for 5 minutes, then cement was added and kneaded again for 5 minutes, then CNF was added and kneaded for 5 minutes to prepare a kneaded product.

First, in order to form the lower layer, a kneaded product was poured to form a uniform layer having a thickness of about 5 mm, and a bubble sheet cut into a size of 345 mm in length × 345 mm in width was placed on the upper surface of the lower layer. .. The kneaded material was poured again from above the arranged bubble sheet to uniformly form the upper layer with a thickness of about 5 mm, and the entire intermediate layer was formed to a thickness of about 10 mm. Since it takes time for the PVA mortar to cure, it was allowed to stand at room temperature for about one day.

Next, a layer to be a surface layer is formed. A kneaded product made of the same CNF mortar as the already formed surface layer was prepared and poured into the mold to the upper surface to be uniformly formed to a thickness of about 5 mm. Then, the upper surface of the mold was covered with a lid plate and fixed. Screws (manufactured by Wakai Sangyo Co., Ltd .; diameter 3.8 mm, length 25 mm) are driven into the lid plate at a density of 7,860 lines / m ^{2 so as to protrude about 13 mm toward the lower surface at intervals of 1.1 cm.} ing. By pushing the lid plate so as to insert the screw from above the surface layer, the protruding portion of the screw was set to penetrate the surface layer and reach the bubble sheet in the intermediate layer.

After attaching the lid plate, air curing was performed in accordance with JIS A 1132. After curing, the lid plate was removed and the specimen (sound absorbing material) was removed from the mold. The obtained specimen (sound absorbing material) has a size of 35 cm in length × 35 cm in width × 2 cm in height, and a large number of small holes (diameter 4 mm, length 13 mm) are formed in the surface layer on the front side, and the back side has a large number of small holes (diameter 4 mm, length 13 mm). The surface layer had a structure in which no small holes were formed.

A sound absorption test (according to JIS A 1409) was performed on the front side and the back side of the specimen (sound absorbing material), and the sound absorption coefficient was measured. The measurement result on the front side is shown in FIG. 3, and the measurement result on the back side is shown in FIG.

<Preparation of specimen for compression test>
The same CNF mortar as the surface layer is defoamed and driven into the concrete specimen mold (Sonomold manufactured by Marui Co., Ltd.) so that air does not get mixed in, and air curing is performed according to JIS A 1132. (Diameter 50 mm, height 100 mm) was produced. The density of the specimen was 1.88 g / cm ³ .

For the same PVA mortar as the intermediate layer, a cylindrical specimen for compression test was prepared in the same manner as the CNF mortar. The density of the specimen was 1.74 g / cm ³ .

A compression test was performed on the specimen immediately after curing. For CNF mortar, compressive strength is 18N / mm ^2, in the case of PVA mortar was 4N / mm ^2.

[Example 2]
A cement panel material having a structure similar to that of the three-layer structure shown in FIG. 1 was produced.
<CNF mortar composition for surface layer>
The following unit amounts were prepared as raw materials to be used.
Cement; 985 kg / m ³
Water; 185 kg / m ³
CNF1; 308 kg / m ³
(CNF amount; 6.16 kg / m ³ , cement ratio; 0.63 mass%)
Mineral grains; 37 kg / m ³ (cement ratio: 3.8% by mass)
Fine aggregate; 492 kg / m ³
Admixture; 9.85 kg / m ³

<PVA concrete composition for intermediate layer>
The following unit amounts were prepared as raw materials to be used.
Cement; 676 kg / m ³
Water; 349 kg / m ³
CNF1; 11 kg / m ³
(CNF amount; 0.22 kg / m ³ , cement ratio; 0.03% by mass)
PVA1; 56 kg / m ³ (cement ratio; 8.3% by mass)
Fine aggregate; 338 kg / m ³
Coarse aggregate; 676 kg / m ³
Admixture; 6.76 kg / m ³

<Preparation of specimen for sound absorption test>
For CNF mortar, CNF and an admixture were added to cement and kneaded for 5 minutes, and then mineral grains and fine aggregate were added and kneaded for 5 minutes to prepare a kneaded product. The obtained kneaded product was poured into a mold (length 35 cm × width 35 cm × height 2 cm) to form a uniform layer having a thickness of about 5 mm. It was allowed to stand at room temperature for several hours to form a film on the surface so that the kneaded material would not be mixed even if it was poured upward.

Next, a layer to be an intermediate layer was formed. For PVA concrete, add PVA to water with CNF and admixture and knead for 5 minutes, then add cement and knead again for 1 minute, then add fine aggregate and coarse aggregate for 3 minutes. The mixture was kneaded and allowed to stand for 5 minutes, and then kneaded again for 1 minute to prepare a kneaded product.

First, in order to form the lower layer, a kneaded product was poured to form a uniform layer having a thickness of about 5 mm, and a bubble sheet cut into a size of 345 mm in length × 345 mm in width was placed on the upper surface of the lower layer. .. The kneaded material was poured again from above the arranged bubble sheet to uniformly form the upper layer with a thickness of about 5 mm, and the entire intermediate layer was formed to a thickness of about 10 mm. Since it takes time for the PVA concrete to harden, it was allowed to stand at room temperature for about one day.

Next, a layer to be a surface layer is formed. A kneaded product made of the same CNF mortar as the already formed surface layer was prepared and poured into the mold to the upper surface to be uniformly formed to a thickness of about 5 mm. Then, the upper surface of the mold was covered with a lid plate and fixed. Screws (manufactured by Wakai Sangyo Co., Ltd .; diameter 3.8 mm, length 25 mm) are driven into the lid plate at a density of 4,320 lines / m ^{2 so as to protrude about 13 mm toward the lower surface at intervals of 1.5 cm.} ing. By pushing the lid plate so as to insert the screw from above the surface layer, the protruding portion of the screw was set to penetrate the surface layer and reach the bubble sheet in the intermediate layer.

After attaching the lid plate, air curing was performed in accordance with JIS A 1132. After curing, the lid plate was removed and the specimen (sound absorbing material) was removed from the mold. The obtained specimen (sound absorbing material) has a size of 35 cm in length × 35 cm in width × 2 cm in height, and a large number of small holes (diameter 4 mm, length 13 mm) are formed in the surface layer on the front side, and the back side has a large number of small holes (diameter 4 mm, length 13 mm). The surface layer had a structure in which no small holes were formed.

A sound absorption test (according to JIS A 1409) was performed on the front side of the specimen (sound absorbing material), and the sound absorption coefficient was measured. The measurement result on the front side is shown in FIG. 3, and the measurement result on the back side is shown in FIG.

<Preparation of specimen for compression test>
The same CNF mortar as the surface layer is defoamed and driven into the concrete specimen mold (Sonomold manufactured by Marui Co., Ltd.) so that air does not get mixed in, and air curing is performed according to JIS A 1132. (Diameter 50 mm, height 100 mm) was produced. The density of the specimen was 1.92 g / cm ³ .
For the same PVA concrete as the intermediate layer, a cylindrical specimen for compression test was prepared in the same manner as the CNF mortar. The density of the specimen was 1.57 g / cm ³ .

A compression test was performed on the specimen immediately after curing. In the case of CNF mortar, the compressive strength was 29 N / mm ² , and in the case of PVA concrete, it was 3 N / mm ² .

[Comparative Example 1]
A cement panel material composed of a sand mortar composition was produced.

<About the composition of raw materials used>
The following unit amounts were prepared as raw materials to be used.
Cement; 514 kg / m ³
Water; 250 kg / m ³
Sand; 1543 kg / m ³
Admixture; 5.14 kg / m ³

<Preparation of specimen>
Water, fine aggregate and admixture were added to the cement and kneaded for 5 minutes to prepare a kneaded product. The obtained kneaded product was poured into the same mold used in Example 1 until the thickness became 2 cm, and covered with the same lid plate as in Example 1. It was allowed to stand for half a day and air-cured in accordance with JIS A 1132. After curing, the lid plate was removed and the specimen (sand mortar material) was removed from the mold. The obtained specimen (sand mortar material) has a size of 35 cm in length × 35 cm in width × 2 cm in height, and has a large number of small holes (diameter 4 mm, length 13 mm) formed on the front side and small holes on the back side. The structure had no holes.

A sound absorption test (according to JIS A 1409) was performed on the front side and the back side of the specimen (sand mortar material), and the sound absorption coefficient was measured. The measurement result on the front side is shown in FIG. 3, and the measurement result on the back side is shown in FIG.

<Preparation of specimen for compression test>
Sand mortar is defoamed and driven into a concrete specimen mold (Sonomold manufactured by Marui Co., Ltd.) so that air does not get mixed in, and air curing is performed according to JIS A 1132. Cylindrical specimen for compression test (diameter 50 mm, height) 100 mm) was prepared. The density of the specimen was 2.23 g / cm ³ .

As a result of performing a compression test on the specimen immediately after curing, the compressive strength was 26 N / mm ² .

[Comparative Example 2]
A cement panel material having a three-layer structure shown in FIG. 1 and not incorporating a bubble sheet was produced.

<About the composition of raw materials used>
As the raw materials for the surface layer and the intermediate layer, the same raw materials as in Example 2 were used in the same blending ratio.

<Preparation of specimen>
A CNF mortar composition for the surface layer and a PVA concrete composition for the intermediate layer were prepared in the same manner as in Example 2, and the obtained composition was poured into the mold in the same procedure as in Example 2, and bubbles were formed at that time. The sheet was not placed. The lid plate was covered with a mold using a lid plate having screws driven in at the same density as in Example 1.

After attaching the lid plate, air curing was performed in accordance with JIS A 1132. After curing, the lid plate was removed and the specimen (layered structural material) was removed from the mold. The obtained specimen (layer structure material) has a size of 35 cm in length × 35 cm in width × 2 cm in height, and a large number of small holes (diameter 4 mm, length 13 mm) are formed in the surface layer on the front side, and the back side. The surface layer of the above had a structure in which no small holes were formed.

A sound absorption test (according to JIS A 1409) was performed on the front side of the specimen (layered structural material), and the sound absorption coefficient was measured. The measurement result on the front side is shown in FIG. 3, and the measurement result on the back side is shown in FIG.

The CNF mortar material used for the surface layer and the PVA concrete material used for the intermediate layer have the same compressive strength and density as in Example 2.

Looking at the sound absorption coefficient of Example 1 and Comparative Example 1 shown in FIGS. 3 and 4, there is a tendency that the sound absorption coefficient of Example 1 is higher than that of Comparative Example 1 on the front side where the small holes are formed. It was confirmed that the tendency became large in the high frequency range of 1.25 kHz or higher. It can be seen that when the CNF mortar material is used, the sound absorption coefficient is relatively large in the entire frequency range and the tendency is large in the high frequency range as compared with the sand mortar material.

Looking at the sound absorption coefficient of Example 2 and Comparative Example 2 shown in FIG. 3, the sound absorption coefficient of Example 2 having a bubble wrap is higher than that of Comparative Example 2 having no bubble wrap. The sound absorption effect of was confirmed. In particular, it can be seen that the sound absorption effect in the middle to high frequency range is large.

In Comparative Example 1, the sound absorbing effect in the low frequency range is comparable to that of the example, and the sound absorbing effect of the sound absorbing material of the example is high in the high frequency range. Therefore, the panel material made of sand mortar and the example By combining the sound absorbing materials of the above, the sound absorbing effect can be improved in the entire frequency range.

In the embodiment, the thickness of the panel material is formed to 2 cm, but by reducing the thickness, a more stable sound absorption effect can be obtained in the entire frequency range.

Since the cement sound absorbing material according to the present invention has a high affinity with the cement structural material and has improved sound absorption, it can be used in places where noise and vibration are problematic in buildings (eg, stairs, ceilings, walls). Expected to do.

1 ... Cement sound absorbing material, 10, 11 ... Surface layer, 12 ... Intermediate layer, 13 ... Small holes, 20 ... Bubble wrap, 21 ... Protruding voids, 30 ...・ ・ Formwork, 31 ・ ・ ・ lid plate, 32 ・ ・ ・ screw

Claims (3)

A surface layer on the front and back sides containing cement as a main component and cellulose nanofibers, and an intermediate layer containing cement as a main component and cellulose nanofibers and polyvinyl alcohol, which are arranged between the surface layers on the front and back sides, and the above. A film-like bubble sheet is provided so as to be laminated on the intermediate layer and air is sealed in a large number of protruding gaps, and a large number of small holes reaching the bubble sheet from the surface layer on the front side are the gaps. A cement sound absorbing material that is formed so as to communicate with. The cement sound absorbing material according to claim 1, wherein the surface layer contains cellulose nanofibers in a blending ratio of 0.1% by mass to 5.0% by mass with respect to cement. The intermediate layer contains cellulose nanofibers in a blending ratio of 0.01% by mass to 0.1% by mass with respect to cement and polyvinyl alcohol in an amount of 1.0% by mass to 15.0% by mass with respect to cement. The cement sound absorbing material according to claim 1 or 2, which is contained in a blending ratio.

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