FR2754288A1 - Modular absorbent panel for anti-noise screen - Google Patents

Abstract

A modular absorbent panel for making an anti-noise screen is made from moulded concrete containing particles or chips of treated wood and a porous mineral material. The mineral is selected from the group comprising natural pozzuolana of trachy-andesite type, pelleted slag, clay or expanded lava. An anti-noise screen measuring, for example, 12 m<2> has a supporting layer of moulded concrete 13 cm thick, and an absorbent panel of the same thickness made from moulded concrete incorporating the treated wood particles and the porous mineral material.

Description

ABSORBENT MODULAR PANELS AND NOISE SCREENS
INTEGRATING SUCH PANELS
The invention relates to a modular panel intended for the absorption in particular of sound vibrations, with a view to improving and optimizing the performance of anti-noise screens. It also relates to such anti-noise screens incorporating these panels.

Protection against noise nuisance has recently been the subject of significant research, with a view to arriving at a solution that is both technically and economically viable, without altering the basic technical function, namely noise absorption, particularly related to road or rail traffic.

In general, structures are used, interposed between the sound source and the site that it is desired to protect, these structures being capable of absorbing the vibrations generating noise, in particular by trapping within intrinsic cavities.

The most widespread example is that of the protection of dwellings located near communication routes. In fact, the invention will be more particularly described for this application. However, it is obvious that it could be used in other fields, such as for example to isolate - machines, installations, etc., which also generate noise.

These structures are in the form of screens, formed by panels comprising on the face exposed to the noise source an absorbent coating, having the function of absorbing the sound energies emitted, and attenuating the transmission by reflection. or reverberation.

Among the various absorbent materials known and used to date, wood concrete, that is to say the material obtained by mixing shavings or particles of wood treated, in particular by silicification, with cement and water, gives good results.

However, such a material is relatively fragile, even even friable, and given the risk of impacts (chippings, shocks, etc.), it may exhibit spalling.

We have therefore sought to increase the mechanical strength of such panels, and the object of the invention is therefore to provide anti-noise panels, having an increased noise absorption capacity, and also having improved mechanical strength.

According to the invention, these panels are made of a material incorporating wood, belon and a porous mineral material.

Advantageously, the porous inorganic material is chosen from the group comprising natural pozzolans, pelletized slag, clay, expanded lava and macliefer.

Pozzolans are porous volcanic rocks of tnichytic composition. Slag is a by-product of the foundry. In the context of the invention, it is used in the form of balls. Clinker is in a known manner a by-product of the combustion of coal.

We have thus been able to show that by associating wood concrete with such
Inorganic materials, not only was the result of an increase in the mechanical resistance of the panels thus obtained, but the sound absorption quality of the panels thus obtained was also optimized.

Advantageously, the pozzolans used according to the invention are so-called tracky-andesites pozzolans.

The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the exemplary embodiment which follows, given by way of indication and not by way of limitation.

As already stated, the invention will be described more particularly in connection with anti-noise screens, placed along road or rail communication routes.

These anti-noise screens basically comprise a load-bearing structure, generally made of concrete, on which the anti-noise panels according to the invention are fixed, these being positioned on the face of the screen facing the sound source. .

According to the invention, the material used for the production of these panels basically comprises wood chips or sawdust having undergone an imputrecibility treatment consisting in a known manner in heat treating the pieces of wood by heating, up to temperatures between 400 and 800 OC, then subjecting these pieces of wood to a double chemical action, namely by a soluble calcium salt then by a soluble silicate, in order to stabilize the wood fibers and create micro-cavities , allowing the production of inherent aggregates, as described in particular in document FR-A-2 499 551. These wood chips are mixed with natural pozzolans, in particular ground tracky-andesites, as well as cement, the proportions respective pozzolans, wood and cement, being substantially equal in weight. The water dosage of this mixture is adapted to the manufacturing technique.

As already said, it is possible to replace pozzolans with pelletized slag, clay, expanded lava or clinker.

The panels are made by molding or pressing.

By using wood, the panels obtained can be dyed in the mass.

By using pozzolans within the material of the invention, the panels are removed from the mold more easily, given their better mechanical strength, reducing the fragility of the panels made by means of concrete only. wood.

The panels thus obtained are fixed in self-supporting H-structures, or even by means of conventional systems of screws, nails, etc., against the concrete part.

The mechanical strength of the panels, as already said, is greatly increased, and the brittleness and friability of the edges are greatly reduced. Indeed, the addition of pozzolans allows the addition of fines, capable of giving the binder a better hardness.

Furthermore and above all, the sound absorption characteristics are significantly improved compared to a traditional wood concrete panel.

The attached figure represents a curve of variation of the attenuation coefficient as a function of frequency, the solid line curve representing the material according to the invention, while the broken line curve represents a wooden concrete panel of the same dimension.

The measurements were taken on a 12 m2 screen having a thickness of 26 centimeters, namely a concrete support 13 centimeters thick, covered by a panel in accordance with the invention, also 13 centimeters thick.

It is thus observed that the attenuation coefficient is greatly improved in all sound frequency fields, and that moreover, the pure number of the sound absorption performance ratio as defined by the European standard prEN 1793-1 revised is greater than or equal to 17.

This same number, measured under the same conditions, for screens produced using traditional wooden concrete panels, is at most equal to 11, or even sometimes 12 times.

In this way, the panels according to the invention make it possible both to increase the mechanical resistance of the panels and to increase their sound absorption capacity, and therefore to optimize their anti-noise function.

Claims (8)

1 / l> absorbent nodular ring for the production of noise barriers, produced by molding concrete in which particles of treated wood are incorporated, characterized in that, in addition, the material constituting the panel contains a mineral material porous. 2 / the modular ring according to claim 1, c a r a c t é r i s in that the porous mineral material is selected from the group comprising natural pozzolans, slag ball tee, clay, expanded lava and clinker. 3 / modular panel according to claim 2, c a r a c t é r i s é in that the pozzolans are of the tracky-andesite type. 4 / modular panel according to one of claims 1 to 3, characterized in that the number representative of the relative absorption performance ratio, as defined by the revised standard prEN 1793-1 is at least equal to 17. 5 / -crall anti-noise, comprising: - a load-bearing layer, made up of conventional concrete; - and an absorbent layer, positioned opposite the sound source, c a r a c t é r i s é in that the absorbent layer consists of absorbent panels made by molding concrete in which are incorporated particles of treated wood and a porous mineral material. 6 / Anti-noise screen according to claim 5, c a r a c t é r i s in that the porous mineral material is selected from the group comprising natural pozzolans, slag ball tee, clay, expanded lava and nlacllefer. 7 / Anti-noise screen according to claim 6, c a r a c t é r i s é in that the pozzolans are of the tracky-andesite type. 8 / Anti-noise screen according to one of claims 5 to 7, characterized in that the number representative of the relative absorption performance ratio, as defined by the revised standard prEN 17931 is at least equal to 17.