NO743868L - - Google Patents

Description

"Procedure for the production of fire-resistant building elements"..

The present invention relates to a method for production

of a building element with high fire resistance, formed from a hydraulic binder and aggregate material.

The peculiarity of the method according to the invention is that

the hydraulic binder is added to an inorganic aggregate material which liquefies under the influence of heat on the building element and forms a coherent structure with the solid components of the hydraulic binder.

These and other features of the method according to the invention appear in the patent claims.

The fire resistance of building elements, whether these are manufactured

of concrete, wood or other common materials, is a criterion which determines the approval of the building elements for building constructions. The fire resistance or fire resistance is defined on the basis of so-called fire classification,

which for each class, among other things, prescribes a specific time duration during which the room-closing building element must prevent through-,

time of a flame, e.g.; a flame outside the element, j Building elements that resist a flame or fire passage for 60 minutes are designated as fire-resistant, building elements with a fire-impermeability of up to 120 minutes as fire-resistant, and building elements that prevent a fire passage for more than 180 minutes are termed according to this classification as highly fire-resistant.

Building elements, produced from a hydraulic binder on the side

of inorganic aggregates such as sand, crushed stone or porous clay balls belong in principle - especially when they are dimensioned to take over a building static function - in the class of highly fire-resistant or semi-resistant elements. If elements with this material composition are only to serve as protection against a fire passage from one room to another, they must already be dimensioned differently for the arrangement in the different fire resistance classes with regard to thickness, then as stated below, hydraulic binders on impact of a fire source acting outside the element shows a special behaviour.

In connection with newer building methods, people have switched to cladding

of prefab concrete facade elements and internal partitions Such facade elements have very poor thermal insulation, such

that extra measures must be taken for thermal insulation.

Furthermore, these facade elements and internal partitions are relatively heavy, and this must be taken into account in the static calculations. Thus, they have moved on to producing building elements by mixing special aggregate material into the concrete, which does not suffer from these defects. An aggregate material that is widely used today for facades, partition walls and roof elements is pre-foamed plastic balls, which contribute to such building elements having lower volume weights of e.g. 400 kg/m 3 with good thermal insulation at the same time. Admittedly, this development, due to the organic aggregate materials, has led to a considerable reduction in fire resistance. By at least one-sided coating of the building element using a fire-resistant coating, e.g. of cement mortar or a cement-asbestos mixture, an attempt was made to remedy this weakness, in order to achieve the fire resistance classes required for building constructions. 1 The coating not only entails considerable production technical difficulties and also does not provide any decisive improvement in fire resistance, as the bond in these "sandwich" constructions very quickly fprs disappears due to the properties of the hydraulic binder when exposed to a fire source.

The unsatisfactory duration of fire resistance for these

so-called light building elements formed from organic aggregates and hydraulic binders are not only in the flammability of the aggregate material, but also in the relative instability of the skeleton of hardened hydraulic binder that surrounds the aggregate components, and this also applies to such constructions that contain aggregate material in the form of asbestos fibres, porous clay balls and the like. During practical fire tests, one notices that this skeleton collapses relatively quickly under the continued influence of a fire source, so that after a correspondingly short time the fire has already led to the "burning through" of the building element. (The collapse is due to the fact that the hydraulic binder already at relatively low temperatures of around 150°C begin

give off the water portion while canceling the binding forces in the solids

constituents, whereby a breakdown of the entire skeleton occurs. This breakdown also means that a ceramic bond of the solid components in the binder at 900 - 1200°C while maintaining the ehstructure cannot be restored.

It is thus an aim of the present invention to provide a manufacturing method suitable for fire-resistant building elements where special components are used to substantially eliminate the missing bond..

The essential aspect of the present invention is thus the addition of a component which is carried out during the conventional mixing process, as this component works to replace the crystal water that is expelled.)

At the time of water expulsion or later, this component must change its aggregate state from solid to liquid, preferably during the passage through all intermediate viscosity phases, possibly also. a sintering process, in order in this way to take over the function of the water that is driven out.) The breakdown of the hydraulic binder is suppressed to such a great extent and the cohesion of a support structure that envelops, for example, an aggregate material for light building constructions is ensured in the event of a fire load .. With the cohesion of the structure, the fire resistance is increased,

as the fire source only causes the building element to burn through after a considerably longer time., This precaution is not limited to building elements with easy-to-impact materials, but can also be applied with favorable results to building elements that consist of a hydraulic binder with or without additional aggregate materials. In the case of these building elements, in order to achieve a certain necessary fire resistance, one can go back to smaller thicknesses, when they are used as pure fire protection cladding.

Also for roof coverings, which consist of a hydraulic binder

with an aggregate material of asbestos or similar fibres, either smaller thicknesses can be used or the achievement of a considerable increase in resistance to the spread of fire and radiant heat. ,

Advantageously, an inorganic aggregate material can be added which remains liquid until a ceramic bond of the solid components in the liquid binder occurs, and then reacts with the solid components (e.g. the cement) in the hydraulic binder. This reaction can be an absorption, sticking or also a sintering. This ensures a cohesion of the binder structure until the ceramic bond occurs., In the case of fire protection linings, roof linings, smoke pipes which are exposed to strong heat, etc. and which do not contain any impact materials for light constructions, the surface facing the fire thereby remains in strong intake.

A ceramic frit can be advantageously mixed as an aggregate material. Ceramic frits soften or become liquid first •

at considerably higher temperatures than those which lead to water separation from the hydraulic binder., The separation of the water already begins at approx. 150 - 200°C, while the softening of the frit e.g. can start at.500°C.” This apparently with a view to the replacement of the expelled water uncovered temperature range of approximately 300°C should actually counteract an increase in the duration of the fire resistance.|This range is, however, of no importance, when during a fire a building element is shock-loaded with the heat from a fire source.

Depending on the size of the thermal load that can be expected from the fire source, it may be advantageous to use a frit that softens at lower or higher temperatures and then liquefies.

A frit used with good results that already softens at approx. 510°C consists of 0.15 to 0.6, preferably 0.18 - 0.(42 mol Al^,

1.4 - 12.f), preferably 2.0 - 9.5 mol SiO2 and 0.4 - 3.5,

preferably 0.6 - 3.0 mol B^O^ per ..mol Na2O. Should an effective replacement of the water in the hydraulic binder be achieved by, for example, approx. 610°C, it is advantageous to use a frit consisting of

• a mixture of 0.1 - 0.25 preferably 0.\ 5 - 0.2 mol A12O3,

1.(0 - 2.5, preferably 1.5 - 2.0 mol SiO2, 0.3 - 1.0, preferably 0.3 - 1.0 mol Q2°31 mo1 alkali metal oxide, the metal oxide consisting of 0.3 - 0.6, preferably 0.35 - 0.45 mol Na2O, 0..04 -

0.08, preferably 0.045 - 0.Q6 mol K20 and 0.4 - 0.7, preferably 0.5 - 0.6 mol CaO.

You can also advantageously use the frit in a weight ratio

to the hydraulic binder (without water) of 1:0.5 - 10, preferably 1:5., This mixing ratio depends to a large extent on the static requirements of the building element during fire and normal use, on the nature and composition of the easy-to-impact materials and the desired duration of fire resistance. The ratio 1:5 is for most requirements for a building element a satisfactory ratio when the hydraulic binding agent is a cement., When instead of hydraulic binding agent e.g. ■, gypsum, magnesium oxide binder, etc. inorganic binders, in order to achieve comparable results, the ratio can be varied within the specified limits.r

Optionally, glass powder and/or a suitable slag powder can also be used as aggregate material instead of a frit, which is usually preferred. With good results, the aforementioned frits can also be added to slag powder that melts below the temperature at which the ceramic bonding of the solid particles begins and then to influence the otherwise decreasing viscosity of the molten frit at high temperatures.The frit components ('frit and/or glass powder, respectively t slag powder) for good results with regard to the duration of the fire resistance should be based on a mixture of one part frit to 0.5 - 2 parts slag powder and/or glass powder. For the design, the strength (compressive strength, buckling resistance, bending resistance) and for the duration - of the fire resistance in the "fire resistant" range, which is absolutely necessary for the use of the elements in building constructions, and for most common aggregate materials, it is particularly advantageous when the production of the binder is made with 1-7 parts, preferably 5 parts cement, 'Z- 3 - 6 parts, preferably 2 parts water and . 1 - 7 parts preferably 1 part frit and/or other impact materials with a low softening point.

For the production of particularly light building elements with good thermal insulation properties, it has also proven advantageous to use pre-foamed plastic particles which are introduced into the hydraulic binder next to the aggregates. It is appropriate to coat the plastic particles with an adhesion-improving agent before mixing, as the coating can be very thin. An epoxy resin is preferably used as material for the adhesion-improving agent. It is still possible to produce a building element without such adhesion-enhancing agents. There is then a danger that the cell structure of hydraulic binder that uniformly envelops the plastic particle, preferably in spherical form, is not formed. Empty places can locally form with accumulation in other places of the structure,

which not only adversely affects the mechanical strength of the building element, but also its properties in case of fire load.

Instead of the above-mentioned organic aggregates, inorganic aggregates can also be used, in which case non-combustible fiber material (asbestos fibres) is used, preferably for thin plates, as "thin" usually denotes a thickness of 2 - 10 mm.

These boards can be used as roof cladding or fire protection cladding, e.g. for steel building structures. Porous clay balls, sand or crushed stone can also be used as aggregate.

A particular advantage of the method according to the invention for the production of fire-resistant building elements is that for the design of the elements, methods and means which are commonly known from the concrete industry for carrying out the method can be used. Thus, the building elements can e.g. is given its drorm with the help of a formwork, as one e.g. can vibrate to achieve greater density.; To strengthen the building elements, one can e.g. before filling in the hydraulic binder next to the aggregates, insert a reinforcement in the formwork, e.g. of steel in the form of rods, reinforcing mesh etc. The thus reinforced building elements can then be provided on one or both sides with a plaster or with others, e.g. metallic cover layers.

During the design process with the help of a formwork or a

form, the building element can also be simultaneously supplied on one or both sides with a covering layer of a metallic or non-metallic

material. As metallic materials, iron, aluminium, or, when particularly decorative effects are desired, also copper in the form of plates come into consideration. As non-metallic covering layers, particle boards, plastic boards or also ceramic boards are used with good results.

Similar strength improvements can be achieved with these coatings

which can be achieved with reinforcements. In particular, when metallic cover plates are applied to the building elements produced by the method according to the invention, significant improvements in the strength properties can be achieved with only a small increase in the total thickness. For this purpose, a cover plate is placed directly in the mold or formwork, an adhesive is applied to the cover plate,

and if the adhesive is polyurethane-based, this hardens even under the influence of moisture. The second cover plate is then placed using the same adhesive on the contents of the filled formwork or form, and then a compression is made in the ratio 1:1 - 3, preferably 1:1.5, in order to achieve a dense structure with a good connection between the cover plates and the core material - consisting of hydraulic binder and aggregate material of various kinds.

Example

For the production of a light building element suitable for use in the building industry, 100 1 of polystyrene foam, preferably with a volume weight of 8 - 18 g/l and a particle size of 1 - 5 mm, was coated with 100 g of an adhesion-enhancing agent in the form of a liquid epoxy resin.

Then 17 kg of cement was mixed with 7 kg of water and this mixture

3.5 kg of an inorganic aggregate material, consisting of 0.42 mol Al2O3, 9.6 mol SiC>2 and 2.93 mol B2<D3 per moles of Na2O. The hydraulic binder and aggregate material were then thoroughly mixed with the coated polystyrene foam particles and placed in

■a form whose bottom was covered with an aluminum plate with a thickness of 1.5 mm, which was coated on one side with a polyurethane-based adhesive that hardens under the influence of moisture. After the filling

of the mold, a further aluminum sheet provided with the same adhesive of the same thickness was placed on the content smoothed in the mold and using pressure to achieve a compression ratio of 1:1.5 from uncompressed to compressed core material, whereby the mold for rapid debonding of the hydraulic binder was heated. The building element was shaped into a plate with a thickness of 70 mm. The average surface weight of the plate was 330 kg/m, the insulation value (k-value) approx. 0.8 Kcal/m^hour°C. The bearing capacity at a span of 2 meters was 330 kg/m 2 and the permissible load at a deflection of f= L/300 (L=span height) was 45 kg/m 2 at a span of 4 m.

The building element was subjected to a fire resistance test.

On the side exposed to the direct impact of the fire source, the aluminum plate bulged out after 10 minutes of fire duration. After 16 minutes, the slab began to melt and after 18 minutes, the escaping gases from the exposed core material were ignited and burned with modest flame development. With increasing fire duration, the aluminum foil melted over an increasingly large area. After 24 minutes, the core material on the largest part of the side facing the fire source had burned out. The remains of the aluminum plate hung around the edge of the specimen. At this point, the flame formation due to the escaping gases already decreased to a noticeable extent, as

■only weak flames could be observed after 26 minutes. After 36 minutes•of fire duration, only occasional short flames still emerged from the corners of the test piece. After 45 minutes, a thin surface layer (1-2 mm) detached locally from the exposed core material. During the further test, only occasional minor flames occurred in the test piece. Visually, no change could be observed in the core material. On the so-called cold side, i.e. the side opposite to the direct flame impact on the building element, after 9 minutes some wisps of smoke escaped from the edge of the test piece, which then ceased. After 90 minutes of burning time, it was measured on the surface of the cold side

temperatures between 80 and 88°C. The mean value was 84°C and

was thus 62° above the starting temperature and approx. 80° below the mean value which is still considered permissible for heating a cold side. These favorable measurement results allow the building element to be classified as fire-resistant. During an extinguishment attempt .which lasted

for 30 seconds, the extinguishing water jet washed off the core material only to a maximum depth of 3 cm. Locally, no core material was flushed away at all. The surface layer was colored grey-brown at a depth of approx. 1 1/2 cm, and inside black. ;<;>The core material was completely consumed to a thickness of approximately 2 cm.

Claims (18)

1. Method for producing a hydraulic binder as well as aggregate material forming building elements with high fire resistance, characterized by the fact that the hydraulic binder is mixed with an inorganic aggregate material which liquefies under the influence of heat on the building element and with the solid .constituents of the hydraulic binder form.pure coherent structure. 2. Procedure■as stated in claim 1, characterized in that a inorganic aggregate material which remains liquid until ceramic binding of the solid components in the hydraulic binder begins. 3. Procedure as specified in claim 1 or 2, characterized by the fact that a ceramic frit is mixed as an additive. 4. Procedure as stated -in claim 3, characterized in that the frit consists of a mixture of 0.16 - 0.6, preferably 0.18 - 0.42 mol A12 03 , preferred 1.4 - 12.0 preferred 2.0 - 9.5 mol SiC>2 and 0.4 - 3.5 preferred from 0.6 - 3.0 mol B2<D3 per moles of Na2 0. 5. Procedure as stated in claim 3, characterized in that the frit consists of a mixture of 0.1 - 0.25 preferably 0.15 - 0.2 mol Al^, 1.0 - 2.5 preferably 1.5 - 2.0 mol SiC>2 and 0.3 - 1.5 preferably 0.35 - 1.0 mol B2 C>3 per mol of a mixture of alkali and alkaline earth oxides, the mixture of alkali and alkaline earth oxides being formed from 0.3 - 0.6 preferably 0.35 - 0.45 mol Na2 0, 0.04 - 0.08 preferably 0.045 - 0.06 mol K2 0 and 0.4 to 0.7 preferably 0.5 - 0.6 mol CaO. 6. Procedure as stated in claim 3, characterized in that the frit is added in a ratio by weight to hydraulic binder of l:0r 5-10, preferably 1:5. 7. Procedure as stated in claim 1 or 2, characterized in that the hydraulic binder as inorganic aggregate material is mixed with glass powder and/or slag powder. 8. Procedure as stated in claims 2-7, characterized in that 1-7 parts, preferably 5 parts cement, 1-5 parts - preferably 2 parts water and 1-7 parts preferably 1 part aggregate material are mixed together. 9. Procedure as specified in claims 1-8, characterized in that pre-foamed plastic particles are mixed into the hydraulic binder with aggregate material as light aggregate material. 10. Procedure as stated in claim 9, characterized in that the plastic parts before mixing with the hydraulic binder are wrapped with a adhesive agent. 11. Procedure as specified in claim 9, characterized in that an epoxy resin is used as an adhesion-enhancing agent. 12. Procedure as stated in claims 1-8, characterized in that non-combustible fiber material is used as aggregate material, e.g. asbestos fibres. - 13. Procedure as specified in claims 1-8, characterized by the fact that porous clay balls are used as aggregate material. 14. Procedure as specified in claims 1 - 13, characterized in that the shaping takes place using a formwork. 15. Procedure as stated in claim 14, characterized in that compression is carried out using pressure and/or vibration. 16. Method as stated in claim 14 or 15, characterized in that the building element is provided with a steel reinforcement. 17; Procedure as stated in claim 14, characterized in that metallic or non-metallic covering layers are applied to the building element during shaping. 18. Procedure as stated in claims 1-17, characterized in that heat is added for faster curing of the hydraulic binder.