WO2008052753A2 - Process for producing lightweight rock particles, lightweight rock particles which can be obtained by this process and use of these for producing building materials - Google Patents

Abstract

The present invention relates to a process for producing lightweight, homogenous rock particles, in which exclusively cement and one or more industrial by-products selected from among incineration slags and ashes and milled rock are firstly premixed dry, reaction water and one or more additives are then added to and mixed with the resulting dry premix and the mixture is subsequently mixed and granulated to form the lightweight rock particles. In another process, fibres are firstly coated with inorganic crystals and lightweight rock particles are produced from the resulting fibres together with cement, the one or more industrial by-products, reaction water and one or more additives. In a further process for producing lightweight rock particles, cement, hydrated lime, silicon oxide and/or aluminium oxide particles and optionally one or more industrial by-products selected from among incineration slags and ashes and milled rock are firstly premixed dry and reaction water and one or more additives are subsequently added and the resulting reaction mixture is mixed with incorporation of air, exclusively by means of stirring, until a foamy mineral slurry is formed. The resulting mineral slurry is then cured in a mould to give a mineral foam block and, after removal from the mould, is comminuted to give lightweight rock particles. The present invention also relates to lightweight rock particles which can be obtained by these processes and are very suitable for the production of building materials, in particular lightweight concrete, lightweight mortar, lightweight plaster or render, etc.

Description

 Process for the preparation of light aggregates, light aggregates obtainable by these processes, and use thereof for the production of

building materials

The present invention relates to processes for the preparation of lightweight aggregates for building materials, light aggregates obtainable by these processes and the use of such light aggregates for the production of building materials.

Aggregates are granular substances containing mineral and / or organic constituents, formerly known as aggregates. In addition to binders such as cement, aggregates are a major constituent of industrially extremely important building materials such as concrete, mortar, plaster and screed. The rock streams currently used are predominantly natural, such as e.g. However, sand, gravel or grit can also be artificially produced, for example by thermal treatment of clay or by incorporation of recycled materials such as coal combustion products.

In the construction industry, huge quantities of aggregates are needed to produce the building materials mentioned above. In Germany alone, about 800 million tonnes of aggregates are used each year. However, the resources of natural aggregates are limited. In view of the sustainable use of available resources, it has become clear in many developed countries that all residual, by-products or waste materials arising in an economy must be recycled, in order to save primary material and reduce land use. and aftercare needs of landfills. Despite this sustainable resource management, which is also enshrined in law in some European countries, there are still large amounts of unused mineral and non-mineral residual, Nebenbzw. Waste materials. For example, the recycling of residual, secondary or waste materials in the construction industry is essentially restricted to the recycling of rubble that is crushed, crushed and sieved. There is therefore the use in large quantities and cheaply available residual, products or waste materials for the production of Gesteinskörnun ^¬ gen considerable interest. In particular, the light aggregates are in the foreground, ie aggregates with a grain density of <2000 kg / m ³ , since in recent years, the need has shifted from heavier to lighter Gesteinskörnun ^¬ gen. Among other things, this is due to the endeavor of weight reduction and a lower thermal conductivity.

For further explanation of aggregates in general and the demarcation to light aggregates, which are the subject of the present invention, reference is made to the following Tables 1 and 2 (according to the manual "Concrete Technical Data", 2005 edition, ed. HeidelbergCement AG).

Table 1. Classification of aggregates

Table 2. Classification of light aggregates

As can be seen from Table 1, as light aggregates in addition to natural minerals, such as pumice, lava varnishes and the like, so far mainly thermally expanded minerals, such as expanded clay, intumescent, etc., used. The latter are prepared by the starting material, a porosity agent is mixed, which abruptly burns when suddenly exposed to high temperatures of about 1200 ⁰ C. The resulting combustion gases drive up the mineral melt. After cooling, the resulting gases are enclosed in vacuoles in the material. Suitable porosifying agents are organic compounds, such as polystyrene derivatives, plastic flakes, polyphenylglycol,

Polyphenylacetate, or organic materials such as paper scraps and organic natural fibers are used.

This principle is realized, for example, in the spherical gas and / or aerated concrete particles known from DE 1 811 033 B, whose surface is additionally treated by steam hardening or by sealing by means of a film-forming synthetic resin in order to prevent unwanted absorption of water.

A process for the production of pore granules is also described in DE 10 2005 049 389 A1, in which a known for the production of gas concrete mixture of quartz sand, lime, cement, water and the blowing agent aluminate introduced into a mold, the mixture in the mold hardened and the resulting pore granules is then broken into desired sizes.

Furthermore, DE 196 32 711 A1 discloses a process for the production of an aggregate for light-weight concrete provided with a coating, in which the lightweight aggregate grains, for example expanded clay aggregates, are subjected to a continuous rolling movement using a granulating plate or a granulating drum and during this Rolling motion with the finely dispersed solid, ie the cement and optionally concrete additives / additives (especially stabilizers) and other aids, while spraying with a binder liquid, preferably water, evenly coated or coated thinly to prevent unwanted water absorption. A further modification of this basic principle is described in DE 1 813 881 B, according to which granules of gas or foam concrete are coated with a crust consisting of a calcareous binder, such as cement, and subsequently steam-hardened.

In addition, a number of processes for producing artificial, lightweight aggregates using combustion products such as ashes and slags, as well as cement and lime are known. For example, DE 699 02 288 T2 describes the production of light aggregates from combustion by-products. This involves blending a sulfur-containing by-product of combustion, preferably wet flue-desulphurisation sludge, and calcium hydroxide-containing fines obtained and recycled in the process, and an aluminum-containing material such as pulverized coal (PC) - fly ash, and water. to produce a starting mixture. The starting mixture is then agglomerated using a granulating plate and the resulting pellets are combined with hardening calcium oxide-containing fines, such as a mixture of finely divided Brantkalk (CaO) and P.C. fly ash. The hardening fines coat the pellets and react exothermically with moisture, generating heat in situ and hardening the pellets. Finally, the generated aggregates are separated from the calcium hydroxide-containing dry recycle fines, the latter being recycled to the first mixing step.

Moreover, DE 197 35 063 A1 describes a process for the production of coated aggregates for structural concrete in which on the grain surface of a round or crushed aggregate, such as quartzite, various clay and sandstones, expanded clay, expanded slate, lava slag, brick chippings, masonry mortar , Putz, Blähtonbeton and boiler slag and blast furnace slag, a compact and dense coating of a mixture of cements, concrete admixtures and / or concrete additives is applied by means of buildup agglomeration.

From DE 32 42 992 Al finally a method for the production of fly ash in storable form and / or for use as an aggregate, especially for the construction industry, known fly ash dust with the hydraulic binders cement, gypsum and carbide with the addition of water and additives homogeneously mixed and converted into a granular form. A disadvantage of the aggregates used hitherto is that they often do not have the desired chemical and / or physical properties. Thus, natural aggregates often show a relatively uncontrolled water absorption. Furthermore, thermally produced, expanded industrial rock granules are constructed inhomogeneous, which can lead to a varying compressive strength. In addition, these often show an uncontrolled water absorption. Even industrial aggregates produced by roll agglomeration and sintering or pelleting often have an inhomogeneous structure due to the layered structure of sheaths around a core. Another undesirable feature is the uncontrolled hydration of not yet hydrated cement or lime, which can lead to undesirable properties of Baustoffendprodukts.

Furthermore, the properties of conventional light aggregates such as grain size, bulk density, grain density and corepole strength can not or hardly be influenced. In the case of thermally produced, expanded industrial aggregates comes as a further disadvantage that the annealing or sintering usually takes place at 1200 ⁰ C and the production thereof is therefore associated with a high energy consumption and high costs. Furthermore, the provision of natural starting materials is not very economical due to the considerable procurement costs. The use of natural aggregates is also unsatisfactory from an ecological point of view due to the degradation of natural resources and associated emissions. Furthermore, the industrial aggregates of ashes and slags as well as cement and lime produced by roll agglomeration and sintering or pelletization have the disadvantage that the molding of the corresponding granules due to the use of special Granuliereinrichtungen, such as a pelletizing or granulating, is expensive in terms of apparatus.

In view of the above disadvantages of the previously known light rock aggregates, the present invention is therefore based on the object of providing lightweight aggregates for the production of building materials that are simple, cost-effective and resource-friendly and environmentally friendly to produce and excellent chemical and physical properties for use in Have building materials.

This object is achieved by the technical teaching specified in claims 1, 4, 5, 6, 12, 13, 14, 18 and 19. Advantageous embodiments will be apparent from the dependent claims. The lightweight aggregates according to the invention have the advantage that they are completely homogeneous even with different particle sizes, show a controlled water absorption capacity and have preferred chemical and / or physical properties for their use in building materials. Furthermore, the aggregates according to the invention are inexpensive to produce, because they can be produced at low temperatures and with a low expenditure on equipment and the industrial by-products used are relatively cheap and may be additionally subsidized by disposal premiums. In addition, the use of these industrial by-products sustainably protects the environment.

Another advantage of the lightweight aggregates according to the invention is that the chemical and physical properties can be adjusted in a targeted manner depending on their future use in a wide range. The following Table 3 illustrates the influence of the starting materials, the mixing technique, the reaction water and the additive on the bulk density, grain density, grain size distribution, Korneigenfestigkeit, water absorption, thermal conductivity (λ value) and the content of cations and anions. A person skilled in the art of producing aggregates can therefore adjust the properties of a desired "designer ^w aggregate grain" according to the invention in a targeted manner.

Table 3. Main influencing factors on chemical and physical properties of the rock granules according to the invention

A first aspect of the present invention relates to a first method for producing a light aggregate, a lightweight aggregate obtainable by this method and their use for building materials.

A first subject of the present invention is therefore a process for the production of a lightweight, homogeneously constructed aggregate having a grain density of <2.0 kg / dm ³ or a bulk density of <1.2 kg / dm ³ , in which initially only cement and a or multiple industrial by-products selected from the group consisting of incineration slags and ash and rock meal, dry premixed. Then, water of reaction and one or more additives are added to the resulting dry premix with mixing, and the resulting reaction mixture is further mixed and granulated until formation of the light aggregate.

According to the invention, any known cement can be used, with Portland cement or Aluminatzement are particularly suitable. Particularly good results in terms of strength are achieved with CEM 1 42.5 grade cement. The cement is used in the process according to the invention in an amount of 8 to 14 wt .-%, particularly preferably in an amount of 10 to 12 wt .-%, based on the total weight of all added components. The amount of cement required in an individual case essentially results from the resistance of the grain the materials used and the desired compressive strength of the final aggregate and can be readily determined by one skilled in the art.

The industrial by-products used in the process according to the invention are selected from the group consisting of incineration slags and ash, in particular incineration slags and ash resulting from the combustion of coal, for example in power plants in hard coal combustion, such as boiler sand, coal coke and fly ash, and paper ash and Filter dusts or residues from the exhaust gas cleaning (furnace filter dusts), and rock flour, in particular rock flour from the ceramic or stone production or the ceramic or stone processing, and fine particles from the sand and gravel processing, by-products from the lime production, papermaking, Smelting of ferrous and non-ferrous products and by-products of the foundry industry. Preferably, the one or more combustion slags and pockets are used in combination with a rock meal.

The selection of industrial by-products used in individual cases depends on various criteria, such as homogeneity, bulk density, free chalk content, heavy metal content and content of other substances, such as chlorine and sulfur. The most important parameter for a constant quality of the light rock streams according to the invention is the free-lime content, since the lime acts as a binder and is related to the liquid components in a specific ratio. This should therefore be determined regularly and the other starting materials used to be adjusted accordingly. Also very important in the context of quality assurance and control is the determination of the concentration of oxide compounds in the industrial by-products, such as Al ₂ O ₃ , CaO, Fe ₂ O ₃ , SiO ₂ and Na ₂ O, K ₂ O and MgO, and the Determination of the heavy metal content and the content of other substances, such as chlorine and sulfur. With regard to the use of aggregates in building materials, the pollutant content of the by-products is particularly important, since the building materials must be harmless to health and comply with statutory regulations, such as the DIN and EU standards prescribed for building materials. Therefore, the industrial by-products used in the process according to the invention should be permanently monitored for pollutant content.

The industrial by-product is preferably used in an amount of 40 to 90% by weight, more preferably in an amount of 60 to 90% by weight, and especially in one Amount of 70 to 90 wt .-%, based on the total weight of all added components used.

The industrial by-products influence the physical properties of the lightweight aggregates of the invention, in particular the bulk density, the grain density, the grain endurance and the thermal conductivity. The chemical properties are also influenced by the industrial by-products. These have, for example, an importance with regard to possible reactions in the integration into the cement matrix, in particular with recurring contact with moisture. In addition, acid-forming components in the industrial by-products may eventually lead to the corrosion of reinforcements in concrete products.

Reaction water and one or more additives are also added in the process according to the invention. Tap water can be used as reaction water. The amount of water of reaction is usually in the range of 1 to 30 wt .-%, in particular in the range of 5 to 20 wt .-%, preferably in the range of 7 to 15 wt .-%, based on the total weight of all added components.

The additive is selected from the group consisting of flow agents, pore formers, foaming agents, solidification accelerators, sedimentation reducers, or a mixture thereof. A suitable flow agent is, for example, Sika Addiment product ViscoCrete-20 Gold. For example, Sika Addiment Product LPS A-94 can be used as a pore former. A suitable foaming agent is, among others, Sika Addiment product SB2 or SB41 ™. As a solidification accelerator, for example, Sika add-on product Sigunit 49 AF can be used. A preferred sedimentation reducer is Sika Addiment product Sika Control-5 SVB. An additive which is preferably used in the context of the present invention is sodium hypochlorite, which serves as a flow agent and for shifting the pH to the alkaline range.

The amount of the additive makes up at most 3% by weight of the added amount of water of reaction. Usually, the additive is used in an amount of 0.01 to 1.0 wt .-%, in particular in an amount of 0.1 to 0.3 wt .-%, based on the total weight of all added components. The amount of reaction water and additive added in the individual case depends primarily on the moisture content of the starting material, the concentration of certain components in the starting material and the desired chemical and physical properties. characteristics of the lightweight aggregate to be produced and can be readily determined by a person skilled in the art by appropriate tests.

The water of reaction and the additive are preferably added as a mixture to the dry premix. Before use, the mixture of the water of reaction and the additive can also be stored in a separate tank.

The amount of water of reaction used and the amount and type of additive used directly affect the physical properties of the resulting lightweight aggregate. Thus, the reaction water in particular the particle size distribution, the Korneigenfestigkeit and the water absorption can be influenced, while the additive in particular on the bulk density, the grain density, the grain size distribution and the λ-value.

Preferably, in the process of the invention described above, cement in an amount of 10 to 12% by weight, a mixture of various industrial by-products, namely 20 to 50% by weight flyash, 20 to 40% by weight boiler edge and 20 to 40% Wt .-% rock flour, and 15 to 25 wt .-% water of reaction as a function of the residual moisture content of the materials, preferably 20% by weight of water of reaction, and 0.1 to 0.3 wt .-% additive, based on the total weight of all added components.

In addition to the amount and type of starting materials, the mixing technique used also plays an important role in the production according to the invention of all light aggregates described in the context of the present invention. Thus, for example, the surface texture, the shape and size and the compressive strength of the lightweight aggregates are particularly influenced by the speed or rotational speed of the mixing tools and the mixing time.

In the processes described in the context of the present invention, it is possible to use for all mixing or granulation steps specially equipped mixing devices, such as batch or continuous mixers. In the case of batch mixers, these should be additionally equipped with agitators for the high input of energy at the beginning of the mixing process. If a continuous mixer is used, the dry starting materials should first be premixed dry in any mixer. The water of reaction is then added to the dry mix in the continuous mixer. The mixing devices used are equipped with probes that allow computer-aided monitoring of humidity and temperature throughout the manufacturing process. Together with other recorded parameters such as time duration, speed, etc., an optimal process control can be achieved and the process can be largely automated.

The dry premixing in the method according to the invention described above is preferably carried out at a speed of 150 to 250 U / min, in particular at a speed of 150 to 200 U / min. The mixture is mixed until a completely homogeneous dry premix is present. The mixing time is preferably 2 to 5 minutes, more preferably 2.5 to 4 minutes. A preferred combination of speed and mixing time is 200 rpm for 3 min. For mixing, a vertical single-shaft mixer is preferably used.

The step of adding the water of reaction and the additive is preferably carried out with stirring or mixing at a speed of 350 to 750 U / min., In particular 350 to 550 U / min. The mixing time is typically 20 seconds to 3 minutes. When using a batch mixer, the water of reaction and the additive is continuously added over a certain period of time, usually 20 to 60 seconds, especially 20 to 30 seconds. When using a continuous mixer, the water of reaction and the additive are added continuously throughout the production. The reaction water and the additive are preferably injected via a nozzle into the mixing device, wherein the amount of the injected reaction water and / or additive can be detected for example by means of a flow meter.

The mixing or granulation of the reaction mixture obtained after the addition of the water of reaction and the additive to the dry premix takes place in a batch mixer or a continuous mixer, wherein a batch mixer preferably additionally comprises agitators for the input of mechanical energy at the beginning of the mixing process. According to the method of the invention, in the formation of the light aggregates for the formation of the light aggregates, no additional granulating means such as a granulating dish or a granulating drum are used as "forming" means, rather the light rock granules are directly in the mixer or granulator The agglomeration, ie the caking, of the fine particles in the reaction mixture during the mixing process is thereby added used free hydration energy, so that no heat must be supplied from the outside ^¬ leads.

The granulation is carried out at a lower speed compared to the mixing when adding the reaction water and the additive, for example at a speed of 150 to 250 U / min, in particular at 150 to 200 U / min, directly in the mixer. The mixing and granulation is done until the light aggregate forms, usually for about 1.5 to 5 minutes. When using batch mixers, the mixing time is generally 3 to 5 minutes, in particular 4 to 5 minutes. When using continuous mixers, the mixing and granulation time depends directly on the

Speed of the mixer and the dosing of the dry premixed material. With optimally adjusted parameters, the residence time in the continuous mixer is usually between 1.5 and 3 minutes.

The light aggregate obtained at the end of the mixing and granulating step may further be subjected to fractionation. For this purpose, sieve devices with different mesh and hole dimensions can be used. Preferred screening devices are wire screens, perforated screens, drum screens and screen decks. Preferably, the light aggregate is temporarily stored prior to fractionation, more preferably for at least 12 hours, especially for 12 to 48 hours, to cure the light aggregate. If it falls below 12 h, the light aggregate is not hard enough so that the sieves stick together. If they are exceeded for 48 h, the pellets of the light aggregate easily adhere to one another and can no longer be separated well when sieving.

Another object of the present invention is a lightweight aggregate obtainable by the above-described method. The mean grain size of the aggregate according to the invention is typically 0.1 to 10 mm, in particular 1 to 5 mm. The bulk density is usually in the range of 0.6 to 1.7 kg / dm ³ , in particular in the range of 0.7 to 1.2 kg / dm ³ . The mean grain density is usually 0.9 to 1.9 kg / dm ³ , in particular 1.0 to 1.5 kg / dm ³ . The grain endurance of the lightweight aggregate according to the invention is typically in the range of 3.5 to 25 N / mm ² , in particular 10 to 20 N / mm ² .

Another object of the present invention relates to the use of the light aggregate according to the invention described above for the production of building materials, which preferably meet the standard according to DIN EN 13 0 55-1. The fractionated light aggregates are preferably not immediately, but At the earliest after 3 days, they are used for the production of the building materials, since the light aggregates only reach about 85% of their final hardness after this period of time and the hydration is largely completed. If the light aggregates are used earlier, they withdraw water of reaction from the hardening building material, such as a stone, which leads to a considerably lower pressure resistance.

Preferably, the lightweight aggregates of the invention in building materials selected from light screed, light mortar, light plaster, lightweight concrete, in particular lightweight concrete LC 16/18 or LC 20/28, fillings for stones, bricks, drain boards and layers, insulation boards and layers, and Base layers under floors, in particular base layers under industrial floors used. The lightweight aggregates according to the invention are particularly preferably used in light screed, light mortar, light plaster or lightweight concrete.

A second aspect of the present invention relates to a second alternative method for producing a light aggregate, a lightweight aggregate obtainable by this method and their use for building materials.

Accordingly, another object of the present invention is an alternative process for producing a lightweight aggregate containing fibers coated in addition to cement and industrial by-products and having a bulk density of <2.0 kg / dm ³ or a bulk density of <1.2 kg / dm ³ has.

In this method, in a first step, fibers are first coated with inorganic crystals by dry premixing the fibers with quicklime or fine aluminum powder and cement and then adding water of reaction and one or more first additives, followed by storage to cool and reactivate the resulting coated layer fibers.

In this exothermic coating step, in which the temperature of the reaction mixture can increase to up to 9O ⁰ C, grow on the surface of the acting as a substrate fibers finest inorganic crystals. For example, lime and cement absorb carbon dioxide from the air in a moist medium and become carbonic acid salts (carbonates). Accordingly, in the alternative use of fine aluminum powder, aluminosilicate, aluminum carbonate and alumina crystals are formed. The coatings coated in this way with calcium carbonate and calcium oxide or aluminosilicate and aluminum carbonate and aluminum oxide crystals. In the subsequently produced lightweight aggregate, fibers take over the function of reinforcing products and give the lightweight aggregate produced by the process according to the invention an additional flexural tensile strength with reduced specific weight.

The fine aluminum powder, which can be used instead of lime, due to the higher reactivity leads to a very fine and homogeneous inorganic coating, which is even better than those with quicklime. However, due to the high risk of fire and explosion, aluminum powder can only be processed wet with great care.

The amount of cement used in the first step, as defined above, is preferably 10 to 20% by weight, more preferably 12 to 18% by weight, and most preferably 16% by weight, based on the total weight of all in the first Step added components. The amount of the quicklime or the fine aluminum powder is preferably 10 to 20% by weight, more preferably 12 to 18% by weight, and most preferably 16% by weight, based on the total weight of all the components added in the first step.

The fibers used in the process according to the invention are preferably vegetable fibers. Particularly suitable fibers are cellulose fibers. Paper scavengers are most preferably used, especially high-definition paper scavengers. The fibers preferably constitute from 40 to 75% by weight, more preferably from 50 to 65% by weight, in particular from 55 to 60% by weight and particularly preferably 63% by weight, based on the total weight of all components added in the first step ,

As reaction water, for example tap water in an amount of 1 to 10 wt .-%, in particular 2 to 6 wt .-%, based on the total weight of all components added in the first step, are added. The amount of water of reaction added varies depending on the residual moisture in the non-liquid components added in the first step, the total amount of water, i.e., the total amount of water added. the amount of water of reaction and the residual moisture, 6 to 9 wt .-%, in particular 6 to 8 wt .-%, based on the total weight of all components added in the first step, makes up.

The first additive is as defined above. A particularly preferred first additive is sodium hypochlorite. The sodium hypochlorite is usually used as a 0.1% solution used in the reaction water. The amount of the first additive added accounts for at most 0.3% by weight of the added amount of water of reaction. Accordingly, the first additive is usually added in an amount of 0.01 to 0.25% by weight, in particular 0.1 to 0.2% by weight, based on the total weight of all components added in the first step.

The water of reaction and the additive are preferably added as a mixture to the dry premix. Before use, the mixture of the reaction water and the first additive can also be stored in a separate tank.

The amount of water of reaction and of the first additive depends on the residual moisture contained in the starting materials and the desired degree of coating. If the reaction mixture is too wet or too little wet, the precipitation of the calcium carbonate and calcium oxide crystals takes place only incompletely or not at all. A person skilled in the art can easily determine the appropriate amount of water of reaction and additive to be used by experiments.

In the first step of the second process according to the invention, according to a preferred embodiment, at least one of the combustion slags or ash defined above is also present in an amount of 0 to 40% by weight, preferably 10 to 30% by weight, in particular 30% by weight. based on the total weight of all components used in the first step. A particularly preferred combustion ash is fly ash. With regard to the selection of the incineration slags and ash used in the individual case, the above applies accordingly.

Preferably, in the second process of the present invention, fibers in an amount of from 50 to 65% by weight, quicklime or fine aluminum powder in an amount of from 12 to 18% by weight, cement in an amount of from 12 to 18% by weight, optionally combustion slags and ash in an amount of 0 to 5% by weight, water of reaction in an amount of 6 to 9 wt .-% and the first additive in an amount of 0.1 to 0.25 wt .-%, based on the total weight of all components added in the first step.

The storage of the resulting coated fibers is preferably for at least 12 hours, more preferably for 12 to 48 hours, and most preferably for 24 hours. During this time, the fibers coated in the manner described above will react, which will result in further processing the fibers have a positive effect. The step of cooling and storage is required because too hot material would accelerate the pozzolanic reaction in the subsequent step to light aggregate. The light aggregates then harden too quickly and by far do not reach the target coral strength.

The dry premixing in the first step of the second process according to the invention is preferably carried out at a speed of 100 to 300 rpm, in particular at a speed of 150 to 250 rpm. The dry premixing in the first step takes place until homogeneous, preferably for a period of 1 to 4 minutes, in particular for a period of 1.5 to 2 minutes. Preferably, a high energy input batch mixer, optionally provided with agitators, is used for dry premixing.

The addition of the water of reaction and the first additive in the first step takes place continuously over a certain period of time, preferably over 15 seconds to 2 minutes, more preferably over 30 to 60 seconds. During the addition of the reaction water and the additive is preferably mixed at a speed of 100 to 300 U / min, in particular 150 to 250 U / min. The water of reaction and the first additive are preferably injected via a nozzle into the mixing device, wherein the amount of the injected reaction water and / or additive can be detected for example by means of a flow meter.

In a second step of the second process according to the invention, cement and one or more industrial by-products selected from the group consisting of incineration slags and ash and rock dust are added to the coated fibers obtained from the first step, the mixture premixed dry and then Water of reaction and one or more second additives are added to the mixture, followed by mixing and granulating the resulting reaction mixture until the formation of the light aggregate.

The cement and industrial by-product are as defined above. As a second additive, the additives already defined above can be used, preferably sodium hypochlorite, usually as a 0.1% solution in the water of reaction, is used. Furthermore, in the second step of the second process according to the invention, boiler edge and rock flour and / or paper ash or boiler sand and / or rock flour and paper ash are preferably used as industrial by-products. With regard to the selection of industrial by-products used in the individual case, what has been said above applies accordingly. Also the above Notes to the influence of the cement, industrial by-products, the reac ^¬ tion water and additive on the physical and / or chemical properties of the resulting lightweight aggregate shall apply to the second inventive method.

The amount of cement is preferably 7 to 12 wt .-%, in particular 9 to 10 wt .-%, particularly preferably 10 wt .-%, based on the total weight of all components added in the second step. The amount of the industrial by-product is preferably from 10 to 65% by weight, especially from 20 to 40% by weight, based on the total weight of all components added in the second step. The proportion of the coated fibers is preferably 10 to 65 wt .-%, particularly preferably 20 to 40 wt .-%, based on the total weight of all components added in the second step.

The water of reaction is added preferably in an amount of 15 to 26% by weight, more preferably in an amount of 18 to 20% by weight. The amount of the second additive added makes at most 0.2% by weight, preferably 0.01 to 0.2% by weight, especially 0.1 to 0.2% by weight, based on the total weight of all in the second step added components, from. The amount of reaction water and additive added in the individual case depends primarily on the moisture content of the starting material, the concentration of certain components in the starting material and the desired chemical and physical properties of the lightweight aggregate to be produced and can be easily determined by a person skilled in the art by appropriate experiments ,

The water of reaction and the additive are preferably added as a mixture to the dry masterbatch in the second step. The mixture of the water of reaction and the second additive can also be stored in a separate tank before use.

The amount of water of reaction used and the amount and type of additive used directly affect the physical properties of the resulting light aggregate. Thus, in particular the particle size distribution, the grain endurance and the water absorption can be influenced by the water of reaction, while the additive has an effect, in particular, on the bulk density, the grain density, the particle size distribution and the λ value. In addition to the amount and type of starting materials and the liquid components, ie the water of reaction and the additive, the mixing technique used also in the case of the second step of the second method according to the invention an important importance in the production of light rock granules according to the invention, since thereby the physical properties of the finally obtained aggregate are influenced. The comments made above in connection with the mixing technique therefore also apply correspondingly to the second method according to the invention.

The dry pre-mixing in the second step of the second method according to the invention is carried out until homogeneous, preferably for a period of 2 to 6 minutes, in particular for a period of 2 to 4 minutes. The speed is preferably 100 to 300 rpm, more preferably 250 to 300 rpm. Commercially available vertical or horizontal single-shaft mixers which are optionally equipped with additional agitators are particularly suitable as mixing devices. If agitators are used, these are preferably added at the beginning of mixing the dry premix for a period of 3 minutes at a speed of 250 rpm to 300 rpm and then at a speed of 150 to 250 rpm for 3 minutes continued agitators without agitators.

The addition of the water of reaction and the second additive is preferably carried out with stirring or mixing, for example in a batch or continuous mixer with optional agitators, at a speed of 150 to 750 U / min, in particular 200 to 550 U / min. If a batch mixer is used, the speed is preferably 200 to 250 rpm. The liquid components are added continuously over a certain period of time, usually 10 seconds to 2 minutes, in particular 20 seconds to 60 seconds. When using a continuous mixer, the speed is preferably 350 to 550 rpm.

The reaction water and the second additive are preferably injected via a nozzle into the mixing device, wherein the amount of the injected reaction water and / or additive can be detected for example by means of a flow meter.

The step of mixing and granulating to the formation of the light aggregate is preferably carried out for a period of 3 to 5 minutes, in particular for a period of 3 to 4 minutes. The speed in this mixing or granulating step is in the range of 150 to 750 rpm, in particular 200 to 550 rpm. Using of a batch mixer, the speed is preferably 200 to 250 rpm. If a continuous mixer is used, the speed is preferably 350 to 750 rpm, in particular 550 rpm. Also in this case, the released hydration energy is used for the agglomeration of the particles, so that no additional heat from the outside must be supplied. For this step, conventional batch mixers, optionally provided with agitators for additional energy input, or continuous mixers may be used.

The resulting light aggregate may further be fractionated. In this case, sieve devices with different mesh and hole dimensions can be used. Preferred screening devices are wire screens, perforated screens, drum screens and screen decks. Preferably, the light aggregate is temporarily stored prior to fractionation for the reasons stated above, preferably for at least 12 hours, in particular for 12 to 48 hours.

Another object of the present invention is a lightweight aggregate obtainable by the above-described second method of the invention. The mean grain size of this aggregate according to the invention is typically 0.1 to 10 mm, in particular 1 to 5 mm. The bulk density is usually in the range of 0.6 to 1.4 kg / dm ³ , in particular in the range of 0.7 to 1.0 kg / dm ³ . The mean grain density is usually 0.8 to 1.7 kg / dm ³ , in particular 0.9 to 1.4 kg / dm ³ . The grain endurance of the lightweight aggregate according to the invention is typically in the range of 3.5 to 25 N / mm ² , in particular 10 to 20 N / mm ² .

Another object of the present invention relates to the use of the light aggregate according to the invention described above for the production of building materials, which preferably meet the standard according to DIN EN 13 0 55-1. Preferred examples of this are lightweight screed, light mortar, light plaster, lightweight concrete, in particular lightweight concrete LC 16/18 or LC 20/28, fillings for bricks,

Bricks, drain boards and layers, insulation boards and layers, and base courses under floors, in particular base courses under industrial floors.

The light aggregate obtained before or after the fractionation is preferably not used immediately, but for at least 3 days, for the above-mentioned reasons, for the production of the abovementioned building materials. A third aspect of the present invention relates to a third alternative process for producing a light aggregate having a grain density of <2.0 kg / dm ³ or a bulk density of <1.2 kg / dm ³ , a light aggregate obtainable by this process, and the like Use for building materials.

Accordingly, a third object of the present invention is a third alternative process for producing a light aggregate of cement, hydrated lime, particles of silicon and / or alumina and optionally one or more industrial by-products selected from the group consisting of incineration slags and ash and rock flour.

In this alternative method, first cement, hydrated lime, silicon and / or alumina particles and optionally the one or more industrial by-products are dry pre-mixed, then water of reaction and one or more additives are added and the resulting reaction mixture including air in the reaction mixture, exclusively by Stir until mixed to form a foamy mineral paste. Then the mineral pulp is transferred to a mold and cured in the mold to form a mineral foam block. Thereafter, the formed in the form of mineral foam block is turned off and crushed to obtain a light aggregate of the desired shape and size.

Preferred silicon and / or aluminum oxide particles have a particle size of less than 90 μm. Suitable silica particles are fine fractions of quartz sand. Suitable alumina particles are fine fractions of calcined bauxite. The silicon and / or alumina particles preferably constitute from 40 to 60% by weight, in particular from 40 to 55% by weight and more preferably 50% by weight, based on the total weight of the components added to form the mineral slurry.

The cement and is as defined above and is preferably in an amount of 10 to 30 wt .-%, preferably in an amount of 12 to 25 wt .-%, particularly preferably 20 to 24 wt .-%, based on the total weight of used to form the mineral pulp added components.

The hydrated lime is usually used in an amount of 10 to 30% by weight, preferably in an amount of 20 to 30% by weight. Preferred industrial by-products that can be used in the process of the invention are as defined above. Particularly suitable are various quartz sands or flours. In particular, mixtures of at least one of the above-defined incineration slags or ash and a rock meal with a high proportion of quartz sand can also be used. The amount of industrial by-product used is 0 to 40 wt .-%, in particular 20 to 40 wt .-%, preferably 30 to 40 wt .-%, based on the total weight of the added to form a foamy mineral pulp components.

From 48 to 56% by weight of silica particles, usually in the form of a very fine quartz sand, 22 to 26% by weight of hydrated lime and 22 to 26% by weight of cement, based on the total weight of the dry premix, are preferred in the dry premix , used.

For example, superplasticizers, solidification accelerators and sedimentation reducers can be used as additives. The additive is preferably used in an amount of from 0.1 to 3% by weight, in particular in an amount of from 1 to 3% by weight, more preferably in an amount of 2% by weight, based on the total weight of the product a foamy Mineralbreis added components used.

The water of reaction is, for example, tap water and is used in an amount of 1 to 15 wt .-%, in particular in an amount of 1 to 10 wt .-%, preferably in an amount of 5 to 10 wt .-%, based on the total weight of added to the formation of a foamy Mineralbreis added components.

The water of reaction and the additive are preferably added as a mixture to the dry premix. Before use, the mixture of the reaction water and the first additive can also be stored in a separate tank.

In the step of dry premixing according to a preferred embodiment to shorten the curing time additionally aluminum hydroxide, preferably in an amount of 2 to 5 wt .-%, in particular 3 wt .-%, based on the total weight of the added to form a foamy mineral pulp Components are used.

Cement in an amount of 12 to 24 is particularly preferred for producing a light aggregate according to the third method according to the invention Wt .-%, in particular 22 to 24 wt .-%, hydrated lime in an amount of 22 to 25 wt .-%, silicon and / or alumina particles in an amount of 40 to 50 wt .-%, aluminum hydroxide in an amount of 0 to 5 wt .-%, water of reaction in an amount of 5 to 10 wt .-% and additive in an amount of 1 to 3 wt .-%, based on the total weight of the added to form the foamy mineral pulp components used.

The amount of water of reaction and additive added in the individual case depends primarily on the moisture content of the starting material and the concentration of certain components in the starting material and the desired chemical and physical properties of the lightweight aggregate to be produced and can easily be determined by a person skilled in the art by appropriate experiments be determined.

In addition to the amount and type of starting materials and the water of reaction or additive, the mixing technique used also in the case of the third method according to the invention an important importance in the production of light Gesteinskömungen invention, since thereby the physical properties as already described above are influenced. The comments made above in connection with the mixing technique therefore also apply correspondingly to the third method according to the invention.

The mixing steps of the third process according to the invention are carried out using special double-shaft mixers which, for example, have counter rotating stirring tools and additional agitators.

The dry premixing in the third process according to the invention takes place until homogeneous, usually for a period of 2 to 5 minutes, in particular for a period of 2 to 4 minutes. The speed of mixing the dry premix is preferably in the range of 500 to 700 rpm. Particular preference is dry premixed for 3 min at 600 U / min.

The addition of the water of reaction and the additive is preferably carried out with stirring or mixing at a speed of 500 to 700 U / min, in particular 600 U / min. The liquid components are added continuously over a certain period of time, usually 2 to 6 minutes, in particular 3 to 5 minutes. The water of reaction and the additive are preferably injected via a nozzle in the mixing device, wherein the amount of the injected reaction water and / or additive can be detected for example by means of a flow meter.

The mixing of the reaction mixture resulting after addition of the liquid components until the formation of a foamy mineral slurry is usually carried out for 3 to 8 minutes, in particular for 4 minutes. The speed is preferably 500 to 700 rpm, more preferably 600 rpm. In order to bring as much mechanical energy and thus air into the mixture, the use of special double-shaft mixers, possibly with additional agitators, is required.

In the step of mixing the reaction mixture to form a foamy mineral mash, air is trapped in the mineral slurry, resulting in air pores after curing. The degree of air intake into the mineral pulp can be adjusted over a wide range. The air pores are achieved exclusively by stirring and the associated high mechanical input of energy. Additional hardeners, such as water glass or similar compounds, are not required.

The foamy mineral pulp obtained after mixing is converted into a mold for curing. The mold may be any suitable shape, preferably separable. The curing takes place for at least 12 h, in particular 15 to 72 h.

The formed in the form of cured mineral foam block is subjected to the sheathing of a crushing treatment, such as breaking. The crushed light aggregates may further be subjected to fractionation. For this purpose, sieve devices with different mesh and hole dimensions can be used. Preferred screening devices are wire screens, perforated screens, drum screens and screen decks.

Another object of the present invention is a lightweight aggregate obtainable by the third process of the present invention. The mean grain size of the aggregate according to the invention is typically 0.1 to 10 mm, in particular 1 to 5 mm. The bulk density is usually in the range of 0.3 to 0.9 kg / dm ³ , in particular in the range of 0.4 to 0.7 kg / dm ³ . The mean grain density is usually 0.4 to 1.1 kg / dm ³ , in particular 0.5 to 0.9 kg / dm ³ . The komeigenfestigkeit of the lightweight aggregate according to the invention is typi- usually in the range from 3.5 to 4.5 N / mm ² , in particular in the range from 4.0 to 4.5 N / mm ² .

Another object of the present invention relates to the use of the light aggregate according to the invention described above for the production of building materials, which preferably meet the standard according to DIN EN 13 0 55-1. The light aggregate obtained before or after the fractionation is preferably not used immediately, but for at least 3 days, for the above-mentioned reasons, for the production of the above-mentioned building materials.

The lightweight aggregate according to the invention is preferably used in light screed, light mortar, light plaster, lightweight concrete, in particular lightweight concrete LC 16/18 or LC 20/28, fillings for bricks, bricks, drain boards and layers, insulation boards and layers, and base courses under floors, especially base courses used under industrial floors.

Claims

claims A process for producing a light, homogeneously constructed aggregate, comprising the following steps: (a) dry premixing of only cement and one or more industrial by-products selected from the group consisting of incineration slags and ash and rock flour; b) adding water of reaction and one or more additives to the resulting dry masterbatch while mixing, c) further mixing and granulating the resulting reaction mixture without using an additional granulator until the formation of the light aggregate with a grain density of <2.0 kg / dm ³ or a bulk density of <1.2 kg / dm ³ . 2. The method of claim 1, wherein the industrial by-product is selected from the group consisting of boiler sand, coal coke, fly ash, paper ash and filter dust. 3. The method according to claim 1 or 2, wherein the cement in an amount of 8 to 14 wt .-%, the industrial by-product in an amount of 60 to 90% by weight, the water of reaction in an amount of 1 to 30 wt. % and the additive in an amount of 0.01 to 1.0 wt .-%, based on the total weight of the components added in steps a) and b) are used. 4. Lightweight aggregate, obtainable by the process according to any one of claims 1 to 3, wherein the light aggregate has a mean particle size of 0.1 to 10 mm, a bulk density of 0.6 to 1.7 kg / dm ³ , a mean grain density from 0.9 to 1.9 kg / dm ³ and a Korneigenfestigkeit of 3.5 to 25 N / mm ² . 5. Use of the lightweight aggregate according to claim 4 for the production of building materials. 6. A process for producing a light aggregate, comprising the following steps: 5 a) dry premixing of fibers and quicklime or fine aluminum powder, and cement, b) adding water of reaction and one or more first additives to form fibers coated with calcium carbonate, calcium oxide or calcium carbonate, calcium oxide, aluminosilicate, aluminum carbonate and aluminum oxide crystals, c) storing for cooling and reacting the coated fibers, i5 d) adding cement and one or more industrial by-products selected from the group consisting of incineration slags and ash and rock flour to the coated fibers, e) dry premixing of the resulting mixture, 20 Adding reaction water and one or more second additives to the mixture, and g) mixing and granulating the resulting reaction mixture to pH 5 of a light aggregate having a bulk density of <2.0 kg / dm ³ or a bulk density of <1.2 kg / dm ³ . 7. The method according to claim 6, wherein fibers are used as fibers. 0 8. The method of claim 6 or 7, wherein the industrial by-product is selected from the group consisting of boiler sand, rock coal ash, fly ash, paper ash and kiln filter dust. 5 9. The method according to any one of claims 6 to 8, wherein in step a) further combustion slags and ash are used. 10. The method according to any one of claims 6 to 9, wherein in steps a) and b) the fibers in an amount of 40 to 75 wt .-%, the quicklime or the fine aluminum powder in an amount of 10 to 20 wt. %, the cement in an amount of 10 to 20 wt .-%, the optionally used 5 incineration slags and ash in an amount of 0 to 40 wt .-%, the Reaction water in an amount of 1 to 10 wt .-% and the first additive in an amount of 0.01 to 0.25 wt .-%, based on the total weight of the components added in steps a) and b) are used , The process according to any one of claims 6 to 10, wherein in steps d) and O, the cement is used in an amount of from 7 to 12% by weight, the industrial by-product in an amount of from 10 to 65% by weight coated fibers in an amount of 10 to 65 wt .-%, the water of reaction in an amount of 15 to 26 wt .-% and the second additive in an amount of 0.01 to 0.2 wt .-%, relative. 5 to the total weight of the components added in steps d) and f). A light rock aggregate obtainable by the process of any one of claims 9 to 27, wherein the light aggregate has a mean grain size 20 from 0.1 to 10 mm, a bulk density of 0.6 to 1.4 kg / dm ³ , a medium Grain density of 0.8 to 1.7 kg / dm ³ and a Korneigenfestigkeit of 3.5 to 25 N / mm ² . 13. Use of the lightweight aggregate according to claim 12 for the production of 5 building materials. 14. A process for the production of a light aggregate having a grain density of <2,0 kg / dm ³ or a bulk density of <1,2 kg / dm ³ , comprising the following steps: 0 a) dry premixing of cement, hydrated lime, silicium and / or alumina particles or cement, hydrated lime, particles of silicon and / or alumina and one or more industrial by-products selected from the group consisting of incineration slags and ash and rock flour, b) adding reaction water and one or more additives, c) mixing the resulting reaction mixture including air into the reaction mixture, solely by stirring, until a frothy mineral pulp is formed, 5 d) transferring the mineral pulp into a mold, e) curing the mineral slurry in the mold until a mineral foam block is formed, lo f) stripping of the mineral foam block formed in the mold, and g) crushing the mineral foam block to obtain a light aggregate of the desired shape and size. i5 15. The method of claim 14, wherein the industrial by-product is selected from the group consisting of boiler sand, coal coke, fly ash, paper ash and furnace filter dust. 16. The method of claim 14 or 15, wherein in step a) further aluminum 20 hydroxide is used. 17. The method according to any one of claims 14 to 16, wherein in steps a) and b), the cement in an amount of 10 to 30 wt .-%, the hydrated lime in an amount of 10 to 30 wt .-%, the silicon and / or aluminum oxide particles in an amount of 40 to 60 wt .-%, the optionally used industrial By-product in an amount of 0 to 40 wt .-%, the optionally used aluminum hydroxide in an amount of 0 to 5 wt .-%, the water of reaction in an amount of 1 to 10 wt .-% and the additive in an amount of 0 , 1 to 3 wt .-%, based on the total weight of the components added in steps a) and b) are used. A light aggregate obtainable by the process according to any one of claims 14 to 17, wherein the light aggregate has a mean grain size of 0.1 to 10 mm, a bulk density of 0.3 to 0.9 kg / dm ³ , a mean grain density 5 from 0.4 to 1.1 kg / dm ³ and a corepump strength of 3.5 to 4.5 N / mm ² . 19. Use of the lightweight aggregate according to claim 18 for the production of building materials.