Patent Application
20120238163
The invention relates to a reinforcing mesh for a reinforcing mortar or sprayed mortar layer as well as to a method for the installation of a reinforcing mesh of this type in order to obtain a reinforced mortar coating. Particularly, concrete surfaces, reinforced mortar coatings are largely used amongst others for the maintenance of buildings of different types, especially of cracked concrete surfaces in civil engineering and also by the construction of tunnels.
Mortars for coatings with a grid shaped textile reinforcement are known from the EP-A-0 106 986; the reinforcement of these coatings being voluntarily realised flexible and therefore have a low E-module. It is thereby intended to avoid cracks formation in the external layer due to different thermal extension with regard to the reinforcement mesh. These mortars and their reinforcements are determined particularly for cover coatings of hard foam plates in external insulation systems, but are not really appropriate for bearing coatings or for coatings subjected to stronger mechanical stress, for example, not suitable for over coatings used for cracked bridging in bearing concrete constructions.
A development of a reinforcement of this type and the method for its manufacturing and utilisation can be deduced from EP 0 732 464. The reinforcement web shown in this patent is composed of a woven fabric or a meshwork of fibers strands. The fiber bundels are realised at least partially opened so that a flowable or pasty material is able to penetrate which afterwards hardens. The individual fibers of the strands are thus embedded and integrated into the material. It is indicated that the mesh size is about 12 mm and the tear strength is of at least 20 kN/m with a tensile strength of at most 5%. Carbon fibers are particularly suitable as they are fibers which are able to absorb high tensile forces. But the cost for such carbon fibers are very high and are situated at about CHF 30.-per kg. The cost for fibers of glass or Polyester is only approx. CHF 1.50 per kg and therefore 20 times cheaper.
Hybrid grids are known which present carbon fibers extending in a first direction and Aramid fibers extending in the transversal direction. Moreover, Aramid fibers are even more expensive than the carbon fibers, about twice the price and hybrid grids of this type are contrary to the effort of obtaining a reinforcement as resistant as possible with the lowest possible costs, and thereby to use the carbon fibers only in the direction where tensile forces occur.
The object of the present invention is therefore to indicate a reinforcing mesh for a reinforced mortar layer or sprayed mortar layer on an underlayment an a method for the installation thereof, whereby this reinforcing mesh should be suitable to receive high tensile forces in a determined direction for a strong reinforcement and should offer simultaneously a decisive cost advantage with regard to the known reinforcing webs. Moreover, this reinforcing mesh in a special execution should be particularly resistant to alcaline components of the leveling layer or cover layer, especially against Ca3Al2 which is comprised in concrete and therefore made to last indefinitely. Nevertheless, this reinforcing mesh should be easy to apply on the construction site and easy to install. A further object of the present invention is to indicate a produced reinforced mortar layer with a terminal anchoring in a solid underlayment.
This task is solved by a reinforcing mesh for a reinforced mortar or sprayed mortar layer on an underlayment, characterized in that the reinforcing mesh includes carbon fibers extending only in a marked direction, which fibers form together with fibers made of glass or polyester extending in one or more other directions, a woven fabric, a scrim or a knitted fabric having a mesh size of at least 10 mm, whereby the employed carbon fibers have a tensile E-modul of elasticity greater than 200 gigapascals.
The task is further solved by a method for the installation of a reinforcing mesh according to the claims 1 to 8 for producing a reinforced mortar layer or a sprayed mortar layer on an underpayment mostly composed of concrete and according the following method steps:
Finally, the object of the invention is solved in that a reinforced mortar coating is realised according to the method of claim 14 characterised in that the reinforcing mesh of the mortar coating is secured at least on one side of the tensile load of the said mortar coating by means of a corrosion resistant profile which is anchored in the underlayment by means of plugs; the said profile being wrapped at least once by the reinforcing mesh.
The reinforcing mesh is shown in the figures in different embodiments and in the following the construction and installation thereof will be described and explained in order to produce a reinforced mortar oder a sprayed mortar layer. The figures show:
The carbon fibers are high tensile resistant and offer tensile-E-module from 230 to 240 Giga-Pascal. These type of fibers are the so called Rovings. These are fiber bundels or fibers strands of endless, untwisted, and elongated fibers (filaments). If the individual filaments made of glass, Aramid or carbon are combined without being rotated, they are first considered as smooth filament yarns, and when they have a certain thickness (yarn count>68 tex), they are considered as a Roving. Rovings of this type are designated by the number of their filaments or by their weight per length. When indicating the filaments' number, the number is given in full 1000 filaments (1 k). Usual forms of delivery are 1 k (1000 filaments), and also 3 k, 6 k, 12 k and 24 k filaments. The unit for the Tex-number is g/km. It depends on the density of the material which has been used. A Roving-carbon fiber of 12 k has a weight in length of approximately 800 tex. Usual Roving of 800 tex weight therefore 800 g/km or 0.8 g/Meter. Two Rovings of 800 Tex generate a roving of 1600 Tex with then weight of 1.6 g/Meter etc. For usual sprayed mortar meshes, approximately 200 g of carbon fibers per m2 are introduced. This generates, when introducing a double thread made of 2×1600-Roving 2×1.6 g per Meter=3.2 g per meter. Therefore, the result is: (200 g./m2)/(3.2 g./m)=62.5 parts/m,→distance/meter between two rovings=1.6 cm mesh size because 1.6 cm×62.5=100 cm.
The weft laid woven fibers of glass or polyester can pass alternatively over and under the warp carbon fibers 1 spaced from one another at about 1.6 cm, or pass respectively over two or more warp threads 1 and then under two or more warp threads again in order to minimize its bending. The following weft thread 2, i.e. the following fibers extending parallely can similarly also pass beneath two or several warp threads 1 made of carbon fibers and therefore pass again over the same number of warp threads 1. The changement from passing over to passing under of the warp threads 1 can be offset from weft to weft in order to increase the stability of the woven fabric. The woven fabric is then coated as described in the following. The main advantage of a reinforcing mesh 11 of this type is that the traction reinforced carbon fibers extending exclusively in the direction here necessary, i.e. in the direction of the warp threads 1 of the woven fabric and extend in other directions which are not subjected to tensile forces on the building, are completely saved. Therefore, with the same carbon fiber cost you can use twice carbon fibers compared to a reinforcing mesh 11 in the traction reinforcing direction; the said reinforcing mesh 11 being traditionally made of carbons fibers and therefore half of the carbon fibers can be saved and be replaced by cheap glass or polyester fibers which are fully sufficient to support the stress in the transversal direction relatively to the traction reinforcement direction. Their function is only to maintain the carbon fibers in their position until the mortar has been installed and set.
As shown in
The employed carbon fibers 3 can be realised in a form of open carbon fibers bundels to avoid that the gaps between the fibers and the capillaries are also not filled or closed with a binding agent or an adhesive. The consequence of this is that the flowable or pasty coating material, i.e. normally concrete or mortar reinforced by plastic fibers enter into the gaps between the fibers and form a micro-interlocking together with the fiber structure after the setting, i.e. produce a high positive fit. Moreover, if the choice of the material which is used between the coating material and the fibers' surface is approximately appropriate, the result is an important adhesion between the materials by coating or impregnation of the fibers, particularly by means of a water solvable adhesion promoting agent based on a polymer base. The composition of the adhesion promoting agent is advantageously selected in order to create simultaneously an amplification of the capillary effect and thus support the penetration of the coating material into the gaps between the fibers.
It is essential to have sufficiently large gaps or passage surfaces in the reinforcement in order to form a direct material connection between the leveling layer and the coating layer. The concrete-concrete connection in the mesh area and the concrete-fiberbundel-connection ensure with security the transfer of high shearing stresses resulting from torsion and thermal expansion and therefore avoid the formation of cracks on the surface also under difficult conditions. The overall coating can also have important static functions because of the reinforced, respectively, the reinforcing mesh with a breaking strength of at least 20 kN/m and an elongation at rupture of at most 5%.
The fiber material of the reinforcing mesh can be protected against the attack of aggressive, particularly alkaline components of the leveling layer or coating layer, particularly against the Ca3Al2 comprised in the concrete. A reinforcing mesh of this type regardless whether it is a woven fabric, a scrim or a knitted fabric can be therefore equipped with a special coating. Styrene-Butadien-rubber SBR is therefore particularly appropriate, whereby this abbreviation comes from the English term “Styrene Butadiene Rubber”. It is a Copolymer consisting of 1,3-Butadien and Styren. SBR comprises traditionally 23.5% Styren and 76.5% Butadien. Higher Styrene contents create thermoplastic rubber but the rubber remains nonetheless curable. If the reinforcing mesh is impregnated in a SBR-bath, then all the fibers are intimately surrounded by this synthetic rubber of latex type and are no more subjected to any chemicals which exist in the concrete. The embedded reinforcing meshes are therefore made to last indefinitely. A very important advantage by the coating of the said reinforcing mesh is that an amorphous silicate (flue ash) can be sprinkled on the said reinforcing mesh when taken out of the bath or flue ash of this type can be immediately mixed in the bath so that the excessive chalk Ca of the lime mortar bonds with the SiO2 of the flue ash to form a calciumsilicate hydrate and thus create a higher adhesion in the mortar because of the effective interlocking.
In a practical application, a reinforcing mesh 11 of this type in form of a netting or a woven fabric or a scrim is unrolled in the practical application on the leveling layer 10 which must be prepared, i.e. and this is very important, the carbon fibers 3 must extend in the direction in which the sprayed mortar layer is subjected to tensile forces. The employed sprayed mortar can be appropriate for the hard concrete support or the stuff mortar can be employed, on the other hand, for supple substrate like brickwork composed of bricks, lime sand bricks, respectively, historical fabric of a building. Reinforcing meshes according to the invention have a high tensile resistance and are easy to cut, to install and to fix in a work saving manner. They can be adapted to the form of the support and can be folded even at the edges and corners. After the application of the reinforcing mesh 11, a coating layer 12 is applied which is also composed of sprayed mortar or stuff and can be applied like the leveling layer. The coating layer 12 forms in the example, the exterior ending of the coating. If necessary, another layer can be equipped without problem with the reinforcing meshes, or even a multiple of the said reinforcing meshes can be provided, whereby each reinforcing mesh has a determined protective function. The coating layer in practise often presents a thickness comprised between 5 and 30 mm.
Traditional sprayed mortar present a tensile resistance of more than 1 N/mm2. If a reinforcing mesh with a width of 1000 mm can be sprayed on a band width of 100 mm with sprayed mortar, the result is an embedding surface of 1000 mm×100 mm and correspondingly this embedding surface receives tensile forces of more than 1000×100=105 N. The reinforcing meshes presented here can be anchored at the terminal in different ways. In some applications, the reinforcing meshes are rolled around an object, for example around a column or they are installed around the corners. On flat surfaces a sufficient overlapping is realised with a solid support for the anchoring, so that the reinforcing mesh is embedded over a sufficient surface in the sprayed mortar. A traditional reinforcing mesh, which present carbon fibers in the transversal direction must be overlapped over at least 65 cm with the solid support (without security values), i.e. with security values of about 100 cm in order to be able to transfer the forces into the mortar. Because of the manufacturing of grid webs with a width situated between 1.5-4 m, this overlapping is very important and represents high material losses. These important overlappings are often necessary and show that the carbon fibers which are embedded transversely to the tensile direction do not realise their function and are nevertheless expensive. The represented reinforcing mesh with carbon fibers extending in one direction, that is exclusively in the following tensile force direction offers important savings. Several layers of reinforcing meshes are often installed which overlap each time the solid support on the terminal side and thus even multiplying the savings.
In order to reinforce the anchoring on the terminal side, for example, when there is no place for embedding on a large surface on the terminal side, special anchoring elements can be installed. A terminal anchoring of this type is represented in
Load tests are realised with standard-sprayed mortar plates having a size of 60 cm×60 cm and a thickness of 10 cm in order to compare the standard plates with steel reinforcement plates. The sprayed mortar plates are manufactured in wood frames. A reinforcing web made of steel wires with a diameter of 6 mm and a mesh size of 150 mm is installed after having filled the wood frames with a 5 cm sprayed mortar layer and with another 5 cm sprayed mortar layer is then oversprayed on the first layer. A reinforcing mesh with a fiber weight of 200 g/m and a tensile resistance (rupture) of 4300 N/mm2 has been installed in a second sprayed mortar plate of such a type after having filled the wood frames with a 2 cm sprayed mortar layer, and a 6 cm sprayed mortar layer is then oversprayed on the first layer. A reinforcing mesh with a fiber weight of 200 g/m and a tensile resistance (rupture) of 4300 N/mm2 has been installed in a third sprayed mortar plate of such a type after having filled the wood frames with a 2 cm sprayed mortar layer, and a 2 cm thick sprayed mortar layer is again oversprayed on the first layer and then a reinforcing mesh of such a type is installed once more and covered with a further layer of 4 cm to obtain a 8 cm sprayed mortar plate. These three test items were dried during 28 days. Then, the energy was measured, i.e. the integral over the flexion when the charge increases until rupture (force×path). The result is a steel reinforcement of 800 Joule and the alternative with an individual reinforcing mesh is 626 Joule, and the alternative with two reinforcing meshes is 1064 Joule. Moreover, the anchoring of the reinforcing webs in these sprayed mortar plates is not strong enough because the anchoring surface is too small. In a tunnel vault, the anchoring surface is, for example, a multiple of the above mentioned surface. Under these conditions, the working volume for one individual reinforcing mesh is of 1000 to 1200 joule, in any ways much more as for a steel reinforcement with a grid composed of steels having a diameter of 6 mm and a mesh size of 150 mm! It is to consider that a reinforcing mesh of this type is much more lighter and is much easier to install compared to a steel-reinforcement web. Further, the durability of the reinforcing mesh in the sprayed mortar is in practise unlimited, especially when the reinforcing mesh has a SBR-coating compared to a steel-reinforcement where the corrosion is always an issue.
It is a principle in the construction engineering that edifices should be suppler on the exterior side with regard to the interior. Accordingly, a hard sprayed mortar should not be applied on a supple substrate (brickwork). The sprayed mortar has to introduce the forces of the carbon fibers into the substrate. The introduction of the forces into the substrate is only possible when the tensile strength of the substrate is strong enough. The tensile strength of the substrate is a measure to determine the amount of tensile forces which can be introduce because the tensile forces of the sprayed mortar and the connection joints are usually much higher than the tensile forces of the substrate. Accordingly, the sprayed mortar must be adjusted on the quality of the substrate. The tensile strength of concrete which is determined by a device for measuring the adhesive tensile strength, is usually between 1.2-5.0 N/mm2. And the tension modulus of elasticity of concrete is usually between 20-35 GPa. A sprayed mortar of cementitious basis which is at the most modified with plastic fibers or/and other additives is used accordingly on this hard support. In the harden state, the sprayed mortar presents the following quality features: tensile strength 3-10 N/mm2, 20-tension modulus of elasticity 30 GPa.
The tensile strength of the brickwork—determined by a device for measuring the adhesive tensile strength—is usually—on the other hand->0.3-1.0 N/mm2. A sprayed layer of cementitious or lime base with the corresponding additives is used on this supple substrate. In the harden state, the sprayed mortar presents the following quality features: tensile strength 1-5 N/mm2, tension modulus of elasticity 8-20 GPa. In particular, historical brickwork must be treated with much attention. Such historical brickwork has mostly a tensile strength slightly over 0.3 N/mm2. On such soft supports, a sprayed layer of hydraulic chalk basis with the corresponding additives is used. In the harden state, the sprayed mortar presents the following quality features: tensile strength 0.5-3 N/mm2, tension modulus of elasticity 2-15 GPa.
It is of crucial importance that the carbon fibers-reinforcements which are applied on the exterior side or the internal side of an existing brickwork by means of a sprayed mortar are anchored in the adjacent element. Especially when postreinforcement treatments against earthquakes are realised, tensile forces appear also in the vertical direction. An effect of an earthquake is that the edifice is lifted and therefore the edifice can prematurely collapse in case of additional horizontal load. A brickwork which is situated between two concrete plates (base plate as well as ceiling) respectively between the base plate or the base and a wooden ceiling is anchored with the anchoring element in the connected elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1335/09 | Aug 2009 | CH | national |
| 64/10 | Jan 2010 | CH | national |
| 76/10 | Jan 2010 | CH | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CH2010/000193 | 8/5/2010 | WO | 00 | 6/4/2012 |
