RU2415824C2 - Sound absorbing light concrete - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to construction, sound absorbing wall structures or face work in form of blocks. The sound absorbing light concrete contains coarse light aggregate, cement and water and is in form of a coarse-pored structure. Cells between separate fractions of the coarse aggregate are formed on an integral principle from fine fractions on the periphery to coarse fractions at the middle of the block with the following layers: outer layers based on fine fractions from the coarse light aggregate with diametre 5-10 mm; middle layers from coarse aggregate with diametre 10-20 mm and inner layers from coarse aggregate with diametre 20-40 mm.

EFFECT: wider range of damped frequencies.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of construction, and in particular to the design of sound-absorbing walls or claddings in the form of blocks, panels or monolithic manufacturing, which can be used in industrial and civil engineering.

Sound absorbing wall panels are known, including external plates, one of which is made with perforations of variable diameter, and intermediate layers with cells formed by hexagonal cells, or wall structures made of various lightweight concrete with large porous aggregates [1-4]. A disadvantage of the known structures is that with an increase in the diameter of the perforations, the dissipative losses in the array of the wall structure decrease, which leads to a decrease in the sound absorption efficiency. In addition, these technical solutions are aimed strictly at fixed frequencies of the sound stream, therefore they provide noise suppression in a very narrow frequency range and are ineffective in their sound-absorbing properties.

The closest technical solution to the proposed invention is a sound-absorbing panel, including outer plates, one of which is made with perforations, and the intermediate layer with cells is formed by hexagonal cells, arranged in rows with different cell volumes have different sizes [5]. However, these designs have a small interval of strictly fixed damped frequencies from 250 to 500 Hz.

The objective of the invention is to expand the range of muffled frequencies.

The problem is achieved in that the cells of all adjacent layers are arranged in the form of a communicating porous structure with a change in the pore parameters according to the integral principle, which ensures damping in a wide frequency range. In addition, porous cells of the same size and volume are arranged in separate rows, passing from the periphery from small pores to large ones and then vice versa.

The drawing shows the design of the proposed wall block with increased sound absorption capacity, which is formed from large-pore lightweight concrete with the following layers: an outer layer based on small fractions of large lightweight aggregate with a diameter of 5-10 mm; then the middle layer of coarse aggregate with a diameter of 10-20 mm, then the inner layer of coarse concrete from coarse aggregate with a diameter of 20-40 mm (figure 1).

When forming large-pore concrete from a coarse aggregate of the same diameter, two options are possible for laying individual aggregate grains. If a cubic stack is formed, then the voids will be octahedral; however, such styling is very rare. In the case of the formation of the rhombohedral configuration, the voids will have a tetrahedral form. In the first case, the volume of voids can reach 48-50%, and in the second - 26-30%. In this case, the size of voids in large-pore lightweight concrete will not exceed the diameter of the coarse aggregate, i.e. will correspond to the size of the coarse aggregate fraction, however, it will vary along the cross section (Fig. 2). Given this fact, the noise (sound) stream passing through the section of the wall block is absorbed in the entire frequency range.

The wall block of this design provides sound attenuation at all studied frequencies from 50 to 8000 Hz. At the indicated frequencies, the absorption coefficient reached up to 0.6.

The absorption capacity of a porous unit cell of large-porous concrete was calculated by the resonance frequency using the following Helmholtz formula

where c = 344 m / s is the speed of sound in air;

S is the cross-sectional area of the inlet into the pore (void);

V is the volume of the inner cavity of the void;

l _to - the equivalent value of the length of the neck (entrance) into the porous space.

Cells are a collection of n elementary porous cells, each of which is (from a geometric point of view) a cavity in the form of a tetrahedral geometric figure with a base edge α _{h of} height h.

Then

Finally, the correspondence between the damped (resonant) frequency and the cell size can be calculated by the formula

Given the design characteristics: the thickness of the elementary layer with one size l of the outer protective layer, the conditional radius r of the hole in the pore structure, the distance h between the individual layers, the resonant frequency is a function of the edge α of a single cell and the number of unit cells n. The maximum resonant frequency that occurs at n = 1 is a single-valued function of the edge length α.

For an elementary pore cell, n = 1-∞, h = 0.001-0.04 m, r = 0.0005-0.02 m, l = 0.05-0.15 m. Then, for any value of a, the frequency can be calculated muffled by a cell of a given size or consisting of n elementary equal cells:

And the total effect of noise protection will be represented by the integral component and will take the following generalized form

Sound waves incident on the surface of a lightweight concrete block with an integrated arrangement of coarse aggregate pass through the porous structure and are subjected to intense resistance of both the air particles themselves in pores of various sizes and in the pore openings in separate layers with different coarse aggregate diameters at natural frequencies for a given volume . Due to internal friction between air particles and the surface of a large aggregate in pores and voids, part of the energy of the incident wave is lost due to friction, due to which sound is absorbed. Since the wall block contains voids (cells) of different volumes, and the resonant frequency is determined by the cell volume, this absorption occurs at all resonant frequencies for a given block, which leads to sound absorption in a wide frequency range. The results of experimental studies are shown in the table, from which it follows that the proposed method for the formation of coarse-grained concrete by the principle of the integral arrangement of coarse aggregate allows two to three times to increase the sound-absorbing (sound-absorbing) ability of the material and bring these indicators closer to one of the best materials - felt.

Table. Sound absorbing ability of light concrete walls with integrated coarse aggregate location (IRKZ) Name of material 63 Hz 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz Felt (reference) 0.16 0.18 0.36 0.71 0.78 0.83 0.85 0.87 Expanded clay (traditional) 0.06 0.06 0.08 0.08 0.12 0.28 0.27 0.23 Expanded clay wall with IRKZ 0.12 0.15 0.20 0.28 0.37 0.48 0.47 0.51 Granular peat concrete wall with IRKZ 0.23 0.24 0.32 0.44 0.49 0.57 0.64 0.61 Reed concrete wall with IRKZ 0.14 0.19 0.28 0.41 0.54 0.56 0.58 0.58 Korobeton wall with IRKZ 0.18 0.21 0.26 0.30 0.39 0.53 0.55 0.52

A factory technology for producing lightweight concrete with an integrated arrangement of large porous aggregate with the development of operational processes was developed, which allowed us to design wall structures, design and manufacture special formwork and a set of equipment. Thus, the proposed method for the formation of large-pore lightweight concrete allows to obtain a material with sufficient low thermal conductivity, improved soundproofing characteristics and other performance indicators.

Information sources

1. US patent No. 3380552, CL. 181-33, 1969.

2. GDR patent No. 30948, cl. 37 in 6, 1966.

3. RF patent No. 2211196, 2002.

4. RF patent №2255920, 2003.

5. Copyright certificate No. 610956. M.C. 3 EB04 1/74.

Claims (1)

Sound-absorbing lightweight concrete, including large lightweight aggregate, cement and water, molded in the form of a large-pore structure, characterized in that the cells between the individual fractions of the large aggregate are formed according to the integral principle from small ones on the periphery to large ones in the middle of the block with the following layers: outer layers based on fine fractions from a large light aggregate with a diameter of 5-10 mm; middle layers of coarse aggregate with a diameter of 10-20 mm and inner layers of coarse aggregate with a diameter of 20-40 mm.

Images