WO1996033142A1 - Process for producing a construction element incorporating mineral wool - Google Patents

Abstract

The invention concerns a process for producing construction elements of the terracotta-based brick or tile type incorporating a given amont of mineral wool. According to the invention, between 0.5 and 25 wt.% of mineral wool waste is incorporated in the paste which consists essentially of clay. The addition of these fibres accelerates the drying of the unbaked bricks, improves the mechanical properties and permits baking at a slightly lower temperature.

Description

 METHOD FOR MANUFACTURING A CONSTRUCTION ELEMENT

INCORPORATING MINERAL WOOL

The invention relates to a method of manufacturing building elements of the brick or tile type based on baked clay incorporating a certain amount of mineral wool, as well as to the building elements in question.

The production of bricks or tiles, although subject to proven techniques, remains subject to the need for improvements, particularly in production costs and / or in the characteristics of the products prepared.

An important item in the cost of production is that of the energy required for cooking. Any operation which makes it possible to reduce this cost without causing other charges is therefore particularly desired.

In this sense, the use of “fondants” in the composition of bricks or tiles is a measure that allows cooking to be carried out at a lower temperature than with clay alone. The cost of materials usually capable of serving as fluxing agents does not lead to a economically advantageous together.

The inventors have shown that the use of waste from the mineral wool industry could lead, when these are incorporated in adequate quantities, to energy savings for the firing of bricks or tiles. Indeed, the incorporation in the raw bricks or tiles (in the uncooked state) of an adequate quantity of this waste makes it possible in particular to operate the cooking at a slightly lower temperature and facilitates the cooking of these bricks or tiles .

The use of waste is also economically advantageous. The inventors have also shown that this same use has other advantageous side effects such as limiting shrinkage on drying or leading to products with reduced density for unchanged mechanical performance. The incorporation of the abovementioned waste also leads to faster drying of the raw bricks or tiles and to an improvement in the mechanical properties of the bricks or tiles, in particular in the uncooked state.

In practice, the waste from the mineral wool industry which can be used can be very diverse. They can be scrap or by-products from manufacturing or used products, etc. They must essentially allow a convenient incorporation in the clay and lead to an easily crumbly non-friable dough. Such products are in particular the fibers recovered in the washing water which is used permanently in the production installations, in particular on the conveyors and on the walls of the enclosures in which the newly formed fibers are collected. The fibers entrained by these washing waters are recovered in particular by decantation or filtration in the form of wet cakes. Apart from these products coming directly from the production lines, any mineral wool material, provided that the dimensions have been adjusted as indicated below, is suitable for implementing the invention. Those are very widely the insulating products themselves or fragments thereof which constitute a significant fraction of the wool produced.

In this case, the possibility of incorporation depends mainly on the dimensions of the particles introduced into the clay. There is also the possibility of incorporating the content of fibers introduced.

If scrap or by-products from manufacturing in the mineral wool production industry constitute the most important source of material for the implementation of the invention, another source consists of used materials, which these are used insulation application products or more particularly used horticultural substrates made of mineral wool. These latter products, which are widely used for soilless crops, are renewed periodically, among others every year or every two years. After one or more cultures, they no longer have the necessary qualities, in particular sterility. Users must be rid of these very bulky materials which they no longer use. Until now, these products have been landfilled or used as industrial fill. Their ability to integrate into a clay paste - they are indeed very easily wettable - makes them products well suited for the implementation of the invention, these products being more specially adapted for the manufacture of elements of brick type construction.

In practice, mineral wool waste is mixed with wet clay in the form of either unbound fibers, such as those recovered in washing water, or in the form of small felt particles. The latter case is notably that of products recovered after use and which are originally in the form of felts. The felt is, in this case, shredded or ground to form particles whose dimensions are such that they do not prevent a homogeneous mixture with the clay in the presence of water in quantity adequate. For usually shredded products, suitable particle sizes are usually less than 20 mm and preferably less than 10 mm. Under these conditions, regardless of their initial structure, kneading in the clay paste which aims at good homogenization, results in good dissociation of these particles. In the case of incorporation of waste in the form of unbound fibers, these also preferably have a length of between 0.5 and 2 mm to facilitate in particular their dosage and the mixing with the clay. The fibers used also have a diameter preferably less than 7

The rate of mineral wool introduced into the clay can vary appreciably depending on the importance of the desired effect, the exact nature of the fibrous material, the possible foreign elements it contains, the moisture content of the paste used. , the nature of the clay used and the type of brick or tile to obtain, etc. In practice, to obtain a paste which works properly and in particular which is not too brittle and / or does not require too much high water content, the weight of mineral wool material does not exceed 25% of the total dry weight of the mixture. Preferably, this percentage is less than 15%. Of course, if very small amounts of fibrous material can be introduced, the effects obtained will also be small. For this reason, the fiber content is normally not less than 0.5% and, preferably, not less than 2% by weight, or even 4% by weight. Preferably, the mineral wool waste used is glass wool waste. To obtain a significant drop in the baking temperature, the inventors have also noted the advantage in the composition of the glass fibers used to have a certain amount of boron. The boron content of these fibers is at least equal to 0.4% and preferably 0.5%. In practice, the compositions canopies used in the manufacture of insulation wool contain boron contents of the order of 2 to 20% and, most frequently, from 4 to 1 5% and are well suited to the use corresponding to the invention. In products intended for soilless cultivation, the boron level is around 0.5%. Preferably, the boron content of the fibers is less than 8%

In a particularly preferred manner, the waste is glass wool waste having the following composition expressed in weight percentages:

Si0 ₂ 45 - 70% MgO 1 - 5%

Na ₂ 0 10 - 23% Al ₂ 0 ₃ 0.3 - 7%

K ₂ 0 0 - 3% Fe ₂ 0 ₃ 0 - 1%

CaO 5 - 13% B ₂ 0 ₃ 0.5 - 15% (and

F 0 - 3% preferably less than 8%)

Others 0 - 5%

The preparation of the mineral clay / wool (or fibers) mixture essentially requires a mixing of the constituents. The incorporation can be done gradually to ensure better homogeneity of the dough. Compared to using clay alone, the clay / fibers mixture may require a slightly higher water content to maintain adequate plasticity.

Preferably, the incorporated waste has a density greater than 150 kg / m ³ so that it can easily be extracted from their storage device, be dosed and allow regular feeding at the level of the manufacturing process, and have a density less than 500 kg / m ³ so as to allow a homogeneous mixture with the clay.

According to an advantageous embodiment of the invention, the usual components of bricks or tiles, dosed for example using of a dosing belt, feed a grinding or mixing device, as well as the mineral fibers to be incorporated into the bricks or tiles and having also been dosed beforehand, then the bricks or tiles obtained after kneading the above components and fibers, placing in the form of the mixture obtained (for example by extrusion) and then cut, are optionally stacked before being dried at temperatures preferably of the order of 120 ° C. and then baked at temperatures preferably between 900 and 110 ° C. for the bricks and between 1 OOO and 1 O5O ° C for the tiles, the firing temperature depending on the type of clay used.

Preferably, the mineral fibers are distributed without preferential direction inside the bricks or tiles.

The incorporation of the mineral wool waste according to the invention is particularly advantageous in the case where the bricks or tiles are based on limestone (s) or calcariferous clay (s). The use of mineral wool waste according to the invention makes it possible in particular to lower the frost sensitivity of bricks or tiles based on such clays. It is also observed that the volume porosity (pore volume over total volume) of the bricks or tiles obtained according to the invention increases by at least 5% compared to the porosity of bricks or tiles without mineral wool waste and that the range of pore size (porometric spreading) within bricks or tiles is larger.

The invention is described in detail with reference to the examples of implementation. Three series of tests were carried out with respectively: (A) river clay (bronze in color after firing), (B) the same clay added with 10% by weight of insulation glass wool not containing silicone, (C) the same clay with 10% by weight of horticultural substrate waste. The compositions of these glasses can be, for example, following:

Insulation glass Horticultural glass

Si0 ₂ 64, 1% Si0 ₂ 61, 53%

Al ₂ 0 ₃ 3.4% n / a ₃ 0.28%

CaO 7.2% Fe ₂ 0 ₃ 0.19%

MgO 3% Al ₂ 0 ₃ 6.6%

Na ₂ 0 1 5.75% CaO 7.4%

K ₂ 0 1, 1 5% MgO 2.45%

B ₂ 0 ₃ 4.5% Na ₂ 0 17.6% n / a ₃ + Fe ₂ 0 ₃ 0.9% κ ₂ o 1, 4%

B ₂ 0 ₃ 0.5%

Ti0 ₂ 2.05%

The prepared products were the subject of a study on their drying behavior. A first determination is that of the humidity diffusion coefficient (K) by the "Pfefferkorn" test. This measure compares the ability of the products to dry. The higher the coefficient, the easier the drying of the products. The respective rates of A, B and C are: 4, 1; 4.7 and 4.9. The measurement of the porosity of the products also reveals a higher porosity for the products loaded with glass wool.

The density of dry products is also sensitive to the incorporation of fibers. It is still established, for products A, B and C, at 1,975, 1,645 and 1,800 kg / m ³ . The products prepared with glass wool are therefore appreciably of lower density.

The presence of glass wool in the clay also changes the dimensional stability on drying. The shrinkage of the dry product relative to its dimensions in the wet state in% is respectively 7.8; 3.7 and 5.5. The products obtained by incorporating glass fibers are deformed less, despite the fact indicated above that the dough originally contains more water.

Overall, clay / glass fiber mixtures therefore lead to better drying and a lower risk of deformation or cracking.

Test pieces of the three products were prepared to study their mechanical characteristics. This test was carried out on dry products which have not undergone cooking. The breaking strength at three-point bending is 1,510, 1,860 and 1,760 N, respectively. The presence of the fibers therefore very significantly increases the resistance to bending.

Similar test pieces are baked in a laboratory gas oven at 1050 ° C. The density after cooking is once again significantly lower for the products according to the invention. The results are 1780, 171 5 and 1690 kg / m ³ .

The products are finally observed by thermomechanical analysis in the course of cooking. For this test, the samples are placed in an oven to which a temperature increasing over time is applied at a rate of 1 ° C / min. The dimensional variations follow the evolution of cooking.

The degree of cooking is compared by the withdrawal rate. We set a withdrawal value of 1% and compare the temperatures corresponding to these withdrawals.

For these products and by comparison with two formed from clay alone, the shrinkage of 1% of B is reached 40 ° C lower and for C 25 ° C lower. This significant difference shows the aptitude of the products according to the invention for cooking under more economical conditions.

Claims

1. Process for manufacturing building elements of the brick or tile type in which, apart from traditional materials, essentially clay, waste of mineral fibers is incorporated into the wet paste in an amount between 0.5 and 25% by weight of dry matter. 2. Method according to claim 1 wherein the fibers introduced are either dissociated from each other, or in the form of felt particles whose dimensions are not greater than 20 mm. 3. Method according to one of claims 1 or 2 wherein the fibers have a length between 0.5 and 2 mm. 4. Method according to one of claims 1 to 3, wherein the fibers have a diameter less than 7 / -m. 5. Method according to one of claims 1 to 4 wherein the incorporated fibers come from manufacturing scrap. 6. Method according to one of claims 1 to 4 wherein the incorporated fibers come from used products of insulation application or used soilless growing substrates. 7. Method according to one of claims 1 to 6 wherein the fibers are glass fibers. 8. Method according to one of claims 1 to 7 wherein the incorporated fibers have, in their composition, a boron content greater than 0.4% by weight. 9. Method according to one of claims 7 or 8 in which the fibers are glass fibers having the following composition expressed in percentages by weight: Si0 ₂ 45 - 70% MgO 1 - 5% Na ₂ 0 10 - 23% Al ₂ 0 ₃ 0.3 - 7% K ₂ 0 0 - 3% Fe ₂ 0 ₃ 0 - 1% CaO 5 - 13% B ₂ 0 ₃ 0.5 - 1 5% F 0 - 3% Other O - 5% 10. Method according to one of claims 1 to 9, characterized in that the waste has a density between 150 and 5OO kg / m ³ . 1 1. Brick or tile obtained by the process according to one of the preceding claims. 12. Brick or tile comprising clay and 0.5 and 25% by weight of dry matter of waste mineral fibers. 13. Brick or tile according to one of claims 1 1 or 12, characterized in that it comprises limestone clay.