WO2012062769A1

WO2012062769A1 - Mineralized wood chip

Info

Publication number: WO2012062769A1
Application number: PCT/EP2011/069671
Authority: WO
Inventors: Robert Kuhnhenn
Original assignee: Robert Kuhnhenn
Priority date: 2010-11-11
Filing date: 2011-11-08
Publication date: 2012-05-18
Also published as: DE102010051059A1; DE102010051059B4

Abstract

The invention relates to an aggregate consisting of wood chips with a coating consisting of a mineral binder. The coating contains other extremely fine mineral particles together with the mineral binder, at least 50% of said other mineral particles having a diameter of 0.05 to 0.7 µm.

Description

Mineralized woodchip

The present invention relates to an aggregate consisting of wood chips with a coating of a mineral binder, and the use of this additive and a process for its preparation.

In the construction industry aggregates are generally understood to mean natural or artificially produced aggregates (such as expanded clay), which are used for the production of hydraulically bound building materials (eg concretes). At bulk densities of not more than 2000 kg / m ³ or bulk densities of not more than 1200 kg / m ³ one speaks of lightweight aggregates and the European standard DIN EN 13055-1 applies. To protect the natural resources, it is particularly advantageous to use renewable raw materials as building material in the form of aggregates. However, the quality of the building material must not suffer from the use of renewable raw materials, but the building material must be generally and extensively processed and processed on the market and can be offered inexpensively.

An example of such renewable raw materials are wood chips, which are either obtained as a waste product in woodworking or specifically obtained from logs. However, unprocessed wood chips, like wood, have the disadvantage that they are susceptible to pest and mold infestation. An improvement of the biocidal properties of wood chips can u. a. be achieved by a protective sheath.

The strength (compressive strength) of a mineral-bonded component with mineral-coated wood chips as aggregate is significantly higher than in conventional wood concretes produced with untreated wood shavings as aggregate. The increase in strength will be up to 50 percent, but varies slightly upwards or downwards with respect to the chosen mixture constituents.

Untreated organic aggregates such as wood chips are not designed for structural applications. The reason given for the exclusion of organic aggregates on the one hand with a low grain density, which has a negative impact on the achievable compressive strength of the concrete produced by a general reduction in the aggregate performance. On the other hand, the exclusion takes into account the fact that organic aggregates in the alkaline environment of the hardening concrete are not inert. Already in low concentration lead, occurring in almost all organic supplements sugar, to considerable hydration problems to complete inhibition of the hydration processes.

The mineralization of wood chips described in this application effectively addresses the above limitations. The mineralization significantly increases the aggregate grain density of the aggregate and thus leads to an increased aggregate efficiency. In addition, the sugars found in the wood chips were already dissolved during the mineralization process, so that the inhibiting effect of the mineralized chips is much lower than with untreated shavings. Thus, organic aggregates through the mineralization become an attractive aggregate in the construction industry.

From DE 27 15 533 A1 a process for the production of wood concrete is known, by which both a mineralization and a biocidal impregnation of the wood chips to be achieved. For this purpose, an additive consisting of alkaline earth oxides or alkaline earth metal hydroxides is mixed to form a hydraulic binder and this mixture is used to encase the individual chipboard. In DE 19 13 939 A1, formic acid or formates of the alkali metal or alkaline earth metal elements and of ammonium are proposed as the mineralizing agent for such a coating.

In DE 24 35 105 A1, preservation and mineralization of the wood chips is achieved by adding activated sulfur to a mixture of wood-concrete, wherein the activation of the sulfur is achieved by the use of metal oxides and metal hydroxides as well as acidic salts.

A similar aggregate is also known from US 1 762 267 A, in which individual pieces of wood are surrounded by a coat of gypsum, lime or cement. For a hydrophobic aggregate, the admixture requires further substances with hydrophobic properties.

From FR 863 626 A an aggregate of wood chips is known, in which the wood chips are sheathed with calcium carbonate. The hydration of the powdered quicklime is carried out by means of the absorbed CaC salt solution in the impregnated pieces of wood.

EP 0 735 162 A discloses the strengthening of plant fibers by a metal compound in combination with an inorganic or organic binder.

WO 93/09943 A discloses an aggregate of lignocellulose with a core of a wood chip and a double coating of kaolin.

Finally, WO 2007/124727 A2 describes a lignocellulosic aggregate of wood, shives and / or straw plant particles, which are provided with a hardened mineral binder are coated. The binder consists of dolomitic lime and / or cement. The aim of the above-mentioned method is to avoid a renewed water absorption of the lignocellulosic additive. To achieve this, water repellents are applied to the surface of the sheath. In addition, the lignocellulosic core of each individual element is provided with a salt load. By using salts, however, there is a considerable risk of corrosion. Also, the salts used are chlorides, so that released in a concrete with the appropriate aggregate chlorides and thereby embedded reinforcing steels, pipes and all metallic materials can be attacked. If soaked, the chlorides would be dissolved and could additionally attack neighboring components. In the construction industry it is known that a variety of building damage can be attributed to chloride pollution.

A disadvantage of all these known sheaths is the use of additional substances that do not correspond to those commonly used in the construction industry. Long-term effects, such as structural changes in the building fabric due to interactions with other substances, can therefore be ruled out just as little as the pollution of (residential) buildings with pollutants.

The object of the present invention is therefore to provide a mineralized wood chip as an additive, without the use of materials that can later cause damage as a construction material when used as a building material and thus can be safely used in all concrete applications.

This object is achieved with the features of claim 1, characterized in that the sheathing of the wood chips next to the hardened mineral mineral binder contains more mineral fines, wherein at least 50%, preferably 85%, of these further mineral fines have a predominant particle size of 0.05 to 0.7 pm, preferably 0.06 to 0, 15 pm. On average, these particles are about 100 times smaller than the particles of a conventional mineral binder (eg cement CEM I 42/5 with an average particle size of 16 pm). The fineness of the particles allows a completely closed sheath which causes an increased adhesion between the wood cell wall and the mineral sheath in the individual shavings, which can not be achieved with pure binder due to the coarser grain size in this quality.

It has turned out to be particularly advantageous to use mineral color pigments as mineral fines, since these are available relatively inexpensively in the required particle diameters. In addition, such pigments are known in the construction industry from their use in whitening and concrete products. This can be dispensed with a very expensive production or a very expensive purchase of special nano-materials. It is also advantageous that at the same time a coloring of the product can be achieved without further steps are necessary.

The proportion of mineral fines is between 0.5 and 2 wt .-%, preferably between 0.5 and 1, 5 wt .-% and particularly preferably at about 1, 3 wt .-% based on the total weight of the fixed surcharge (consisting of Wood chips, mineral binder and mineral fines) or between 1 and 6 wt .-% based on the mineral binder amount. As a result, sufficient particles are present to guarantee complete encasing at the nano level. The proportion of wood chips is between 55 and 75 wt .-%, preferably between 65 and 70 wt .-%, and the proportion of the mineral binder is between 23 and 44 wt .-%, preferably between 28 and 34 wt .-%, in each case based on the total weight of the fixed surcharge (consisting of wood shavings, mineral binder and mineral fines). The proportions referred in each case relate to oven-dry mixture constituents.

Longitudinal wood chips with a length of 20 to 65 mm are mainly available industrially. However, it has been found that, in particular, short, cubic woodchips are suitable for wood chips. For the use of thermal insulation elements are particularly suitable in the planing industry accumulating residues in the form of very thin shavings, the usual manner incurred in rolled form. In acoustic and constructional use, longitudinal chips in a mixed structure are preferably used.

Depending on the thickness of the sheathing of the chips, as well as the number of mineralization, and the selected chip shape, the bulk density for the dry mineralized chips between 50 to 500 kg / m ³ . The mineral binder used is preferably dolomite, lime, anhydrite binder, magnesia binder, gypsum and / or cement, since these are substances which are customary in the construction industry. It is thus avoided to introduce larger amounts of potentially harmful foreign substances in the concrete. In general, hydraulic binders are particularly suitable. Hydraulic binders are binders which, in contrast to the unhydraulic binder, set even in the presence of water and are insoluble in water. These are z. Pozzolans, trass, and cement. The binder is present after the reaction in hydrated form. The invention further includes the use of the aggregate as a lightweight aggregate in the construction industry, wherein the aggregate can be used as a classic coarse aggregate for concretes. It is also within the scope of the invention to produce from the aggregate a bed which, for example, is then covered with screed, mastic asphalt or drywall.

The sheathed wood shavings can be stored indefinitely and can thus be used for the production of lightweight concrete as structural concrete as well as for the production of wall and ceiling elements with very good building physics properties. The properties of such concretes or shaped elements are characterized by an above-average thermal insulation compared to conventional lightweight concretes of the same gross density class. Depending on the type of component (grain-porous with a closed structure or porous with porous structure), lambda values of up to 0.07 W / mK can be achieved for insulating layers. In addition, the material is diffusion-open and therefore provides excellent moisture balance.

Components made from shaved wood chips can absorb dowels, nails and screws and transmit forces. The surface of a wall and ceiling element containing the additive of the invention is suitable as a plaster base as well as an inner shell for ventilated facade elements. Furthermore, such elements in haufwerksporiger execution are excellent absorber media for sound insulation, it can absorption properties of> 8 dB can be achieved. Thus, such elements can be successfully used in noise protection on rail or traffic routes.

The material is also suitable as insulating material in the form of a loose fill under screeds and dry screeds. In addition to an above-average impact sound insulation (up to 26 db), excellent thermal achieved (up to λ = 0.07 W / mK). The bed can be described as non-migratory and may therefore be installed dry according to current regulations. Monolithic wall or ceiling portions of the mineralized chips as aggregate have a bulk density between 200 and 1600 kg / m ³ The density varies greatly depending on the embodiment. Aggregated insulating layers and absorber materials with mineralized wood chips as aggregate have a bulk density of between 200 and 1000 kg / m ³ , structural solids with a closed structure are between 500 and 1600 kg / m ³ at gross densities.

The invention also provides a process for the production of the additive according to the invention, wherein a) one of the above-mentioned chip fraction and particle type is preferably obtained from debarked tree trunks, b) the chip fraction with mineral binder, further mineral fines with a particle diameter of 0.05 Up to 0.7 pm and water is intensively mixed and coated and c) the jacketed chip fraction is poured into a heap and this heap with sufficient time for hydration, preferably at least 8 hours stored and, if necessary, then in the ambient air or in a thermal Drier is dried.

The cubic chip fraction is produced using specially designed shredding and separation machines. The debarked logs are crushed and then the cubic chip obtained then fractionated through a sieve, preferably vibrating sieves. Coarse particles exceeding a certain size and fine fractions are separated and only the appropriate middle fraction is passed on to the further process. Basically, cubic wood chips can also be produced from industrial chips. All- However, when shredding the industrial chips, the required cubic shape can be achieved less accurately and it is due to the screening with a significantly higher amount of waste material expected. For use as acoustic insulating material, longitudinal chips made from woodchips with a length of up to 35 mm can also be used, whereby these are processed separately in a separation process in such a way that the chip structure is suitably suited to the formulations of the absorber media. The further processing of the chips takes place in the same production plant as in the production of cubic or planed chip fractions.

In a specially modified concrete mixing plant, the fractionated chips are weighed and then mixed according to the recipe with binder, mineral fines with a particle diameter of 0.05 to 0.7 pm and mixing water. This happens at increased speed of the mixer and associated increased centrifugal forces in the mix. The moisture of the wood chips is measured by moisture sensors before adding to the mixer and adjusted the required amount of mixing water accordingly. The actual mixing process continues until the chips have been coated uniformly with binder consisting of binder, ultrafine particles and water.

The finished jacketed cubic or elongated wood chips or wood shavings fall from the mixer on a conveyor belt and are heaped up airy to a pile. The residence time of the chips in this heap is chosen so that the reaction of the binder used has occurred safely. This takes at least 8 hours, as have proven particularly favorable times of at least 48 hours. In order to prevent a connection of the individual chips with each other, the chips are moved or rearranged at a certain interval. This shift is necessary until the reaction of the binder has occurred. A shift can also be made by Vibrating chutes or other semi - or automated procedures are guaranteed. Once the reaction of the binder has occurred and progressed sufficiently long, the chips are stored for further use. Before further processing, such as bagging or loading, it may be necessary to completely dry the chips in a dryer to the required residual moisture.

It is advantageous to provide the chips for certain applications with a multiple sheathing, for which the process steps b) and c), namely the mixing and the subsequent drying in the heap several times, but at least twice, must be performed. As a result, different binder compositions can be applied and thus the properties of the additive can be varied. Above all doubly sheathed chips are much less flammable than untreated wood shavings. Thus, they are classified as loose fillings in building material class B2 and as bonded bed or as aggregate in the building component in B1.

Simply mineralized chips can be processed in concrete plants, etc. to form bonded, monolithic components. Double mineralized chips are also suitable as a starting material for concrete, but especially for loose fillings, bed covers (especially to prevent weed formation), as a design element and much more.

The aim of the mixing process is to distribute the glue consisting of binder, mineral (ultrafine) particles and water as evenly as possible around the wood particles, thus ensuring a homogeneous sheathing. This is advantageously carried out at rotor speeds between 40 and 120 U / min, preferably about 70 U / min in a three-axis motion. For this purpose, mixer types are used, which ensure increased centrifugal forces in three-dimensional material transport. With this special technique, a goal-oriented and reproducible ensures bare sheathing of the chips, as achieved by increased speeds and specially arranged mixing tools floating mixing conditions in the material. This results in a superimposed axial and radial movement of the mixed material in the form of a helical three-dimensional transport, which continues in a circular manner in the mixing trough.

Claims

claims

1 . Aggregate of wood chips with a coating of a mineral binder, characterized in that the casing contains, in addition to the mineral binder, further mineral fines and at least 50%, preferably at least 80%, of the further mineral particles have a particle diameter of 0.05 to 0, 7 pm, preferably 0.06 to 0, 15 pm.

2. An additive according to claim 1, characterized in that the mineral fines are mineral color pigments.

3. Aggregate according to claim 1 or 2, characterized in that the proportion of mineral fines is between 0.5 and 2 wt .-% based on the total weight of the fixed surcharge.

4. Aggregate according to one of the preceding claims, characterized in that the proportion of preferably oven-dried wood chips between 55 and 75 wt .-% and the proportion of mineral binder between 23 and 44 wt .-% based on the aggregate.

5. Aggregate according to one of the preceding claims, characterized in that the wood chips are cubic, elongated or in the form of wood shavings.

6. Aggregate according to one of the preceding claims, characterized in that the mineral binder dolomite, lime, Anhydritbinder, Magnesiabindemittel, gypsum and / or cement contains.

7. Use of the additive according to any one of the preceding claims as a loose or bound bulk or as lightweight aggregate, for wood concretes in packaged or haufwerksporiger execution for use as heat or noise insulation, or for constructive applications.

8. A process for the production of the aggregate according to one of claims 1 to 6, wherein a) a cubic or elongated chip fraction, or wood shavings, is obtained from entrenched tree trunks,

b) the chip fraction with mineral binder, further mineral particles with a particle diameter of 0.05 to 0.7 pm, preferably 0.06 to 0, 15 pm, and water is thoroughly mixed and sheathed,

c) the jacketed chip fraction is poured into a heap and this is stored for preferably at least 8 hours.

9. The method according to claim 8, characterized in that the process steps b) and c) are repeated at least twice.

10. The method according to claim 8 or 9, characterized in that the mixing takes place at rotor speeds between 40 and 120 U / min in a dreiaxialen movement.