CS208263B1 - Autoclave structural insulating lime-silicon element - Google Patents

Abstract

The autoclaved structural insulating lime-silicate element according to the invention consists of a silica component, lime and reinforcing fibers and exhibits high tensile strength in bending and compression, high heat resistance and a low degree of shrinkage. High strengths are maintained even after prolonged heating to temperatures approaching the limit temperature of use (approx. 65C °C). With regard to the above properties, the autoclaved structural insulating lime-silicate element is suitable for the construction of various thermal aggregates, dryers, flues, permanently exposed to the above temperatures.

Description

The invention relates to an autoclaved calcium silicate structural insulating element consisting of a silica component, lime and reinforcing fibers having high flexural and compressive strength, high heat resistance and a low degree of shrinkage. In particular, it relates to a calcium silicate element having high strengths even after prolonged heating to temperatures close to the limit of use.

It is known that a common asbestos-cement element has some disadvantages besides a number of positive properties. These include, in particular, low resistance to higher temperatures, caused, in particular, by the destruction of low-porous mass escaping by water vapor when heated above 400 to 500 ° C, as well as brittleness and poor mechanical machinability. Due to these drawbacks, the asbestos-cement element does not meet the requirements for some building applications, particularly in terms of fire resistance. Furthermore, it is known that due to the urgent requirements of fire protection as well as the need for workability in applications in mantle constructions such as cladding material, etc., a fire-resistant, stable asbestos-cement element with increased porosity has been developed. without breaking the material, and further reduced volume weight, good workability, including the possibility of nailing and bolting, etc. A variant exhibiting high elasticity has also been developed. A disadvantage of said materials is that they do not possess certain properties which are required for specific purposes in the building industry and in thermal heating. In addition to good workability, low alkalinity as well as elimination of efflorescence compared to cementitious elements, low thermal conductivity and high strength characteristics even at temperatures close to the limit of application temperature (about 650 ° C) allow application for construction various heat units and the like.

The above-mentioned deficiencies are eliminated and the desired properties have the autoclaved structural insulating calcium silicate element according to the invention, characterized in that it contains 25 to 55% by weight of silica component, 15 to 40% by weight lime, 3 to 15% by weight Portland cement, 10 to 25% by weight. Short fibers or Class 6 or 7 asbestos asbestos with a maximum sieve residue of 1,6 mm mesh size 40 5 to 20% by weight Class 3 to 5 class of asbestos asbestos fibers with a minimum sieve residue of 4,8 mm mesh size 50%. The silica component may comprise up to 60% by weight of diatomaceous earth or spongillite and 40 to 100% by weight of silica sand. The autoclaved structural insulating calcium silicate element of the invention may further comprise up to 5% by weight of the fibers, improving filter suspensions such as synthetic anorgric fibers or amosite asbestos, and up to 20% by weight of a lightening component such as expanded perlite and up to 5% by weight of wet production waste.

An advantage of the autoclaved structural insulating calcium silicate element according to the invention is that, unlike asbestos-cement elements, it is resistant to temperatures up to 650 ° C in continuous operation and substantially higher at one time, while exhibiting low thermal conductivity and very good thermal insulation properties. Due to its simultaneously high strength properties, it is therefore suitable for the construction of various thermal aggregates, heat exchangers, flue-gas ducts and the like, permanently exposed to the above-mentioned temperatures, in building industry for fire protection purposes and the like. Another advantage of the elements according to the invention, in contrast to the asbestos-cement elements, is that they make it possible to substitute a number of commonly used asbestos by less valuable species, i.e. asbestos of class 6 and 7 according to ON 72 1760, respectively. during autoclaving and thus contribute to the formation of binder phases together with the silica component. In particular, a certain proportion of asbestos fiber splits within this range promotes dispersion of the components in the initial suspension and improves the formation and cohesiveness of the wet carpet. Compared to cementitious products as the main binder component, the element according to the invention has the advantage that it does not contain free lime and does not produce efflorescence and its alkalinity is substantially lower, which enables inter alia post-treatment treatment by coating, lamination and the like. paints and sealants in an alkaline environment.

It is also possible to use a lime hydrate as the calcium component. It is also possible to use finely ground high percentage leached lime which is pre-heated in the required amount of water and dosed as lime milk. As the silicic component uses DC high percentage of silica sand containing SiO preferably above 90%, on the ground surface above speoifloký 2700 M ² / g Blaine, either alone or in combination with diatomaceous earth, or spongilit in said percentage ranges. Diatomites are known as rocks formed by the accumulation of shells of unicellular algae, while spongility consists mainly of needles of siliceous fungi. Both are a type of opal Si.Og that reacts more rapidly with lime than quartz and provides products with somewhat lower strengths, but with better thermal insulation parameters. It is expedient to select the amount of silica and calcium components so that the molar CaO / SiO2 molar ratio is 0.7 to 0.8. For products which are subject to high insulation performance requirements or for elements of particularly low bulk density, the addition of expanded perlite is expedient. Unsorted perlite of density 100 is suitable

0 to 150 kg / m. In addition, synthetic or inorganic fibers such as mineral wool, basalt fibers, glass fibers and the like, or amosite asbestos can be used to improve the filtering properties of the suspension and increase the yield. It is expedient to use inorganic fibers of increased resistance in an alkaline environment which are retained even in the finished element after autoclaving and further contribute to improving its physico-meobane properties.

In the production of the autoclaved structural insulating calcium silicate element according to the invention, for example, asbestos, pre-pulled by conventional methods, is mixed in water to a slurry in which lime hydrate, silica and Portland oement are added, and the loose wet waste from production and optionally expanded perlite and eynthetic inorganic fibers. If desired, it is possible to use small amounts of substances such as flocculants, namely polyacrylamide, solidification regulators, wetting agents, antifoams and the like. The resulting suspension of ingredients is dewatered in a conventional manner on a Hatsohek-type molding machine after the concentra- ture is adjusted to the desired value, and the wet kobsreo obtained is sprayed onto pressed or unalloyed elements, which are subjected to auto-peeling. The initial suspension of the components can also be dewatered in a filter press, in particular in the manufacture of elements of greater thickness, optionally using another forming system. The process of autoclaving is governed by known laws and regulations relating to the progress of the increase and in particular to the reduction of pressure and isothermal residence time, which, together with the temperature used, determines the course of hydrothermal reactions and product properties. It is expedient to autoclave the elements according to the invention for at least 5 to 8 hours at a saturated steam pressure of min. 0.8 to 1.2 MPa. Finally, the elements are dried and optionally further treated by calibration, coating, and the like

Examples: Example 1

73.0 kg of ground silica sand

79.0 kg of lime

13.0 kg of cement

9.0 kg of Chrysotile Asbestos No.3 10.0 kg of Chrysotile Asbestos No.4 10.0 kg of Chrysotile Asbestos No.5 26.0 kg of Chrysotile Asbestos No.6

The products were slurried in water to a final concentration of about 5 and 5. The products prepared on a Hatsch molding machine were autoclaved for 8 hours at 0.8 MPa. The finished products exhibited a bulk density of 1000 kg / m < 3 > and a flexural tensile strength in a direction parallel to the fibers of 21 MPa, perpendicular to the fibers of 19 MPa.

Example 2

70.0 kg of ground silica sand

75.0 kg of lime

13.0 kg of cement

13.0 kg of Chrysotile Asbestos No.4

15.0 kg of Chrysotile Asbestos No.5

35.0 kg of Chrysotile Asbestos No.6

10.0 kg of amozlt asbestos

30.0 kg of expanded perlite 9.0 kg of wet production waste

The bulk density of the products obtained as in Example 1 was 800 kg / m ³ , the flexural tensile strength in the direction parallel to the fibers was 15.5 MPa, perpendicular to the fibers 13.5 MPa.

Example 3

43.0 kg of ground silica sand

25.0 kg of diatomaceous earth

70.0 kg of lime

15.0 kg of cement

15.0 kg of Chrysotile Asbestos No.3

10.0 kg of Chrysotile Asbestos No.4

15.0 kg of Chrysotile Asbestos No.5

208 283

40.0 kg of bituminous asbestos 8.6 7.0 kg of wet production waste

O

The bulk density of the products obtained as in Example 8.1 was 910 kg / m 2, the flexural tensile strength in a parallel direction and the fibers 81nl were 19.0 MPa, perpendicular to the fibers 16.5 MPa.

Example 4

1.9 kg of ground silica sand

1.1 kg of diatomaceous earth

2.7 kg of lime

0,6 kg oement

0,8 kg of bituminous asbestos 8.4

0,8 kg of bituminous asbestos 8.5

1.3 kg of bituminous asbestos 8.6

0.3 kg of amosite asbestos

0.5 kg of expanded perlite

These products were distributed in water to a suspension of konoentraoi ooa 10 The products drained on a laboratory filter apparatus were applied at a pressure of 1.0 MPa and subjected to autoclaving for 8 hours at a pressure of 0.8 MPa. The finished products exhibited a bulk density of 590 kg / nr and a flexural strength of 6.5 MPa.

Claims (5)

P 6 E D MEASURES OF THE INVENTION CLAIMS 1. An autoclaved insulating calcium silicon element comprising 25 to 55% by weight of silica, 15 to 40% by weight of lime, 3 to 15% by weight of Portland oement, 10 to 15% by weight of short-fiber bituminous asbestos or class 6 asbestos. 7, e a maximum residue on meshes with a mesh size of 1.6 mm 40 #, 5 to 20 wt% of asbestos asbestos fibers of Class 3 to 5 with a minimum residue on meshes with a mesh size of 4.8 mm 50%. 2. An autoclaved structural insulating calcium silicate element according to claim 1, wherein the silica component comprises up to 60% by weight of diatomaceous earth or spongility and 40 to 100% by weight of silica sand. 3. The autoclaved contraceptive insulating calcium silicate element according to items 1 and 2, characterized in that it contains up to 5% by weight of the fibers, improves the filtration of the starting suspension such as synthetic inorganic fibers or amosite asbestos. 4. An autoclaved structural insulating calcium silicate element according to claims 1 to 3, characterized in that it comprises up to 20% by weight of lightening components such as expanded perlite. 5. An autoclaved contraceptive-insulating calcium silicate element according to claims 1 to 4, characterized in that it comprises up to 5% by weight of the wet production waste.