TECHNICAL FIELD OF THE INVENTION :

The present invention relates to a precast concrete panel to use for building, such as structural walls and floors and more particularly to a reinforced concrete panel with an inner layer made of with rubber aggregate concrete.

BACKGROUND OF THE INVENTION

The precast panel, also called a concrete sandwich or multilayer panel, is composed of two outer layers (or wythes) made of reinforced concrete, separated by an insulating and lightening layer. The two outer layers are connected by shear connectors passing through the insulation wythe. These connectors, tension/compression ties, are spaced at regular intervals to avoid the wythes from separating.

One type of prior art precast concrete sandwich panel of this class is US3996713 (A). In this Patent the shape of panel can be only a plane plate, that is the unique geometry which permits to place their special type of anchor. This panel requires an adequate structural thickness of all concrete layers but cannot permit the design of slim panels. The metal anchor readily transfer heat from one concrete layer to the other through the metal. Consequently there is a low resistance transfer path heat throughout the entire sandwich panel. Normally for the insulation layer are used materials of mineral, vegetable, animal and synthetic origins. These materials have the form of panels and require many working operations also during the panel casting. The higher is the number of operations performed (cutting, position of isolation panel, etc.,) the greater is the possibility of an error during the execution and consequently the insulating thermal/acoustical properties can be reduced and worsen. Also many insulating materials, specially the bio-materials, have high thickness, prone to deterioration with time and humidity and beside have a fairly high cost.

The rubber aggregates obtained from recycled tires, are commonly used as flooring substrates with subflooring functions and with bituminous binders for roads. In the prior art the rubber particles are used also as structural concrete, the rubber size less than 1mm and amount of rubber is between 1% and 30% of the cement weight. In other patents the rubber particle size is less than 3/8 inch (9.51 mm) and the amount of rubber is between 0.05% and 20% of the weight of the concrete composition.

The rubber aggregates are also used for the acoustic barriers along the roads. The panel for the acoustic barrier is composed of a concrete substrate and a thin layer (thicker than 1 inch= 2,54 cm) made of a material containing binder and particles of rubber (with a volume of 25% of the binder) . The panels of a Patent are 5 x 16 sq.in., the two layers are joined together by a chemical bond.

DISCLOSURE OF INVENTION

concrete multilayer panel with rubber aggregate wythe is composed of insulating inner layers and two concrete outer layers. The two concrete layers are reinforced (e.g. welded wire fabric, bars, etc), are continuous and are connected together by shear connectors (e.g. truss, bending reinforcement bars, etc). The inner layer is made of concrete which contains rubber aggregates that improve heat and sound insulation and reduce the thermal and acoustic bridges. The panel can have either a shape of a plane plate, or a double T section, or a shell, or any other section. This panel have a static and insulating function, it can be used either as a load-bearing wall, or as partitions, or as a floor.

The preferred panel according to this invention is illustrated in Figure.1 and in Figure 3.

Figurel is a cross section of a three layers panel composed of two reinforced concrete outer layers (1 and 3) and an inner layer made of concrete containing rubber aggregates (2), shear connectors (5) that link the layers 1 and 3, (4) reinforcement system of the layers 1 and 3.

Another embodiment with the best thermal insulation characteristics is illustrated in Figure 2 where the inner layer is composed of two sub-layers.

Figure 2 is a cross section of four layers panel: two reinforced concrete outer layers (1 and 3), a first inner layer in concrete with rubber aggregates (2); a second inner made of plastic cellular material (6); connectors (5) that link the layers 1 and 3; (4) reinforcement system of the layers 1 and 3.

Another embodiment of this invention relates the bio-materials use with a further benefit for the environment and for man. The hydraulic binder of concrete layers is Portland cement without blast furnace slag to remove radioactivity, the aggregates are natural quarry and/or recycled from demolition of concrete. The reinforcements are made of austenitic steel or FRP to eliminate the Faraday's cage effect.

Figure 3 shows a plant and a schematic arrangement of the connectors (5).

The connectors (5) that link the reinforced concrete layers 1 and 3 are preferably trusses (fig.l, fig.2) arranged according to the two axes of the panel (fig. 3). These reinforcements may be chosen from materials such as steel, stainless steel, austenitic steel or FRP (Fiber Reinforced

Polymer).

The rubber concrete inner layer ( 2) is composed of hydraulic binder, filler, rubber aggregates and additives. The hydraulic binder is preferably Portland cement but can also be any kind of hydraulic cementicious binder chosen from a group including: alumina cement, , blast furnace slag cement, calcined pozzolan cement, gypsum hemihydrates, polymeric binder or any mixtures thereof. The filler is preferably fine silica sand but can also be any material chosen from the group including: limestone filler, amorphous silica, rice powder, silica fume, microsilica, furnace slag, granulated slag, blast steel slag, fly ash, metal oxides and hydroxides, clay, polymeric fiber or spheres, or any mixtures thereof.

The rubber aggregate is preferably obtained from the recycled tyres but can also be rubber waste.

It is important to note that the rubber aggregate can directly be used without any preliminary treatment. The rubber sizes are between 0,1 mm e 30,0 mm in order to the necessity and insulating capacity requested.

The admixture ( additives ) can be chosen from a group including water-reducing, accelerating, retarding, admixture foaming, flocculating, puffing, homogenization agents, clayite, metakaolin, aluminium powder.silica fume, pigments, colorants, plasticizersmineral oxides, mineral hydroxides, clays, magnesite or dolomite, metal oxides and hydroxides, pumice, slag,granulated volcanic scoria tuff, shale, slate, perlite, vermiculite, polymeric beads.calcium silicatehydrate and polymeric resin, or any mixtures thereof.

The mix- design of rubber concrete is:

100 parts by weight of hydraulic binder, from 0 to 90 parts by weight of filler, from 10 to 250 parts by weight of rubber ,from 0 to 3 parts by weight of additive, from 25 to 55 parts by weight of water.

The rubber concrete composition with polymeric binder is:

100 parts by weight of polymeric binder, from 0 to 160 parts by weight of filler, from 10 to 500 parts by weight of rubber aggregates, from 0 to 3 parts by weight of additive, from 25 to 55 parts by weight of water.

The panel of our invention have an inner layer made of rubber aggregates concrete that have special properties and advantages as compared to the prior art of reinforced concrete multilayer panels:

- Low acoustic transmission at least 30% less than a prior art panel.

- Low thermal conductivity with λ between 0.25 and 0.6 W/mK

- Reduction of the thickness and the weight of panel if compared to the prior art with the same static functions.

- Corrosion inhibition of reinforcement for basic pH. - The concrete with rubber have a high "not connected porosity" and low weight about 1/3 if compared to a normal concrete.

- Reduction of times for the preparation and positioning of insulating materials, because the rubber layer is casted directly in the mould.

- Easy adaptation to all shapes, also with a convex or concave mould.

- Durability.

- High fire resistance more than traditional insulating materials.

- Environmental and ecological advantages because the rubber aggregates can be made of recycling tyres.

- Easy laying of the panels and easy connecting between them. BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a cross-section view of three layer panel according to the present invention comprising two outer reinforced concrete layers, one inner rubber concrete layer, connections between outer layers.

Figure 2 shows a cross-section view of a four layer panel according to the present invention comprising two outer reinforced concrete layers, two inner layers: one made of rubber concrete, the other made of plastic cellular material, connections between outer layers.

Figure 3 shows a schematic plan view of connections between concrete outer layers in both directions of panel.

BEST MODE FOR CARRYING OUT THE INVENTION

The panel can be used in green building, either as a a load-bearing wall, or as a partitions, or as a floor, with low acoustic transmission, low thermal conductivity, low thickness and low weight.