Textile Reinforced Concrete:
Slim concrete components with enormous load-bearing capacity, low weight and high durability even under extreme environmental conditions. Textile reinforced concrete offers these opportunities. This can make an important contribution to sustainable construction: Slim components mean less building material required and thus conserves natural resources and low emissions in the production of building materials.
Concrete is a building material with very high compressive strength. But, the high bending tensile strength required for many tasks only gives it reinforcement. In classic reinforced concrete, this is steel reinforcement. With its alkaline environment, concrete provides protection against corrosion, without which steel reinforcement would rust. But, this requires a large and dense concrete covering for the steel reinforcement.
The reinforcement of a textile concrete made of high-performance fiber materials such as B. Carbon, but, does not rust. Here you can work with much lower concrete covers. Carbon also has a higher tensile strength than steel. The interaction of slim components with low dead weight and high load-bearing capacity allows filigree components and shell structures.
These are the reasons why textile concrete is one of ten projects funded by the Federal Ministry of Education and Research as part of “Twenty20 – Partnership for Innovation”: The C³ – Carbon Concrete Composite e. V. networked universities and companies want to create the conditions within the project that by 2030 at least 20% of the steel reinforcement can replace by carbon reinforcement in new buildings.
Textile concrete or textile-reinforced concrete is an innovative composite material made of a fine concrete matrix and high-performance fiber materials made of carbon, alkali-resistant glass (AR glass) or basalt. Carbon fibers have the best mechanical properties. They are also not attacked by the alkaline environment in the concrete and keep their strength despite aging.
Overview of the relevant parameters of high-performance textile fibers:
The main difference between textile concrete and the fiber-reinforced concrete that has used for decades is that the fibers connect to textile structures using methods and equipment used in textile technology and can thus align in the direction of a force in the concrete component.
Applications of Textile Reinforced Concrete
Textile concrete can use to make very thin, yet stable shells. This is also an advantage when applying thin reinforcement layers when repairing components. The composite material is currently used in bridge construction, in the construction of shells for roofs, in the manufacture of facade elements and in repair. At present, the use of components made of textile concrete for load-bearing components is possible with approval in individual cases or general building inspectorate approvals.
Light and delicate bridges made of textile concrete:
The use of textile reinforcement in bridge construction began in 2005 on a 9 m long pedestrian and cycle path bridge in Oschatz (Saxony). The world’s first bridge that is only reinforced with carbon is the pedestrian and cycle path bridge in Albstadt-Ebingen, which completed in 2015. The textile concrete trough bridge requires only a 90 mm thick base plate and 70 mm thick through walls. Another special feature of the 2.94 m wide and 15.55 m long bridge is that there is no more covering. The concrete surface is so slip-resistant that it can walk on or driven on – even with walkers. The bridge manufacturer in a precast concrete plant regardless of the weather under optimal conditions, transported to the construction site and lifted. The low weight also had a very positive effect here.
The structural engineers calculated the bridge to a reinforced concrete structure and chose an epoxy resin-impregnated carbon textile with a mesh size of 38 mm and a cross-sectional area of 95 mm² / m in both directions. A self-compacting concrete of strength class C 70/85 used as concrete. The component concrete “upside-down”. The formwork cover with a perforated mat, so that the surface received the roughness required for later use. The bridge in Albstadt-Ebingen developed as a prototype for future bridges with similar spans in connection with a general building inspectorate approval.
Already in 2010, the longest textile concrete bridge built with the bridge over federal road 463 in Albstadt-Reutlingen. The circular arch plan of the bridge resulted from the demand for a harmonious connection to the existing route networks. The even division into equal spans with a length of 17.20 m allowed a segmented construction from six prefabricated parts. The prefabricated parts are seven-bar slab beams that prestress in the longitudinal direction. The combination of textile reinforcement and mono strands for pre-tensioning allowed a superstructure height of only 43.5 cm. The textile web reinforcement used to transfer the transverse forces.
Facades made of textile concrete:
The world’s largest sandwich facade made of textile concrete realized in 2015 at “Eastside VIII” in Mannheim. At the same time, they give the facade a high architectural quality. The sandwich panels consist of an inner shell made of reinforced concrete, which uses for load transfer and the facing shell with a textile reinforcement made of AR glass. The facing shells, which are only 30 mm thick, provide the building owner with more interior space than comparable conventional reinforced concrete components with a thickness of 100 mm to 120 mm with the same built-up area. Since the inner and outer shells connect with so-called sliding grids made of an epoxy resin-soaked AR glass textile, thermal bridges can cut without great design effort.
A curtain wall made of textile concrete also protects and designs up to 320 m high pylons of the third Bosporus Bridge in Istanbul, which completed in 2016. The extreme wind loads were a particular challenge when installing the panels, which were only 30 mm thick and had the greatest size of 3.0 MX 4.5 m.
Repair of buildings with textile concrete
Aachen Cathedral adds to the list of UNESCO World Heritage Sites in 1978 as the first German monument. In 2016, textile concrete made an important contribution to maintaining the structure without deep intervention in the building structure. Aachen locates in the earthquake area of the Cologne Bay and there were cracks in the ceiling of the hexagonal central building of the cathedral. To prevent the cracks from opening further, a flexible and force-transmitting connection of the two crack banks should create, on the one hand, and the crack should protect against the ingress of water. Furthermore, it was important to ensure that the repair measures applied do not interfere with the height and function of the existing roof structure. The classic method with rigid brackets over steel tabs was out of the question due to the negative effects on the construction. The repair carried out using a textile-reinforced mortar bandage. A total of three modular carbon-reinforced mortar bandages with the greatest layer thickness of 3 cm produce.
In Koblenz, the client decided to reinforce the floor above the ground floor of a production building with textile concrete, since the exposed concrete ceiling surfaces should not have any noticeable offset on the surface after the reinforcement. The reinforcement was necessary since too little reinforcement had installed in some ceiling areas during the construction of the hall. In the manufacture of the textile-reinforced reinforcement layer, fine spray mortar, and textile reinforcement apply in three layers to the prepared reinforced concrete surface.
Manufacture of components made of textile concrete
To manufacture the textile reinforcement, depending on the process, fiber strands (roving’s) are first produced from up to 10,000 continuous filaments with a diameter of a few micrometers. The textile fabrics with a grid in the desired mesh size created on knitting machines.
The textile reinforcement is then embedded in formwork in a mortar or fine concrete. The mortar must be as fine and flowable as possible to form a force-fit connection with the textile. The usual production techniques are laminating, casting and spraying. Another method is spinning.
When laminating, fine concrete and textiles placed in layers in the formwork until the required component thickness reached. The process is suitable for the production of two-dimensional plates. The plates can only produce in a horizontal position. In the pouring process, textile reinforcement inserted into the formwork poured with the concrete in one operation. High levels of reinforcement cannot create in the casting process, since then the fine concrete can no longer flow around all roving in such a way that enough bond of roving’s and fine concrete matrix is created.
The process of spraying is very like that of laminate. Here too, fine concrete and textile apply in layers. It is possible to manufacture components in both horizontal and vertical positions with a high degree of reinforcement.
When spinning, the concrete compact by rotating it around the longitudinal axis in the formwork. The process used for the production of pipes, masts, and piles. To insert the textile reinforcement, the spinning process must interrupt so that the process takes a lot of time.
Load behavior and dimensioning
The decisive factor for the load-bearing capacity of textile concrete is the transfer of forces from the fine concrete matrix to the filaments of a roving. But only a small part of the filaments is completely integrated into the fine concrete matrix. The size of the contact area and the quality of the bond between filament and matrix determine the bond properties of the reinforcement and are decisive for the use of the theoretical load-bearing capacity of the textile reinforcement. This gave rise to the idea of first “cementing” the filaments together using an epoxy resin that can penetrate all cavities.
The load-bearing behavior of textile concrete is like that of reinforced concrete, but, the design methods for reinforced concrete cannot apply unchanged to textile concrete due to the different material and composite properties. Within the framework of a Collaborative Research Center SFB 532s, theoretical and experimental investigations carried out, from which empirical factors for the calculation of the load-bearing capacity of textile-reinforced elements derived.
The stress-strain curves determined in stretch body tests on textile concrete test specimens can divide into three areas state I, state IIa and state IIb, analogous to reinforced concrete.
A research project has already dealt with the separation of fibers and concrete after the demolition of a building made of textile concrete. This is the prerequisite for the high-quality recycling of concrete. Processes that known from the aviation, automotive and sporting goods industries use.
- Build easier – shape the future. Magazine No. 9 September 2013 (PDF)
- Textile concrete in practice: Eastsite VIII sandwich wall in Mannheim. Magazine No. 14 February 2016 (PDF)
- Pioneering steel-free pedestrian bridge made of carbon concrete; Magazine No. September 15, 2016 (PDF)
- Curbach, M.; Schladitz, F.; Müller, E.: Carbon concrete – from research to practice. BFT International (2017) 1, pp. 36-41
- Groz-Beckert KG: the textile-reinforced concrete bridge.
- Schorn, Harald: fiber concrete for structures. Verlag Bau + Technik GmbH, Düsseldorf 2010
- Brameshuber, Wolfgang: RILEM-Report rep036: Textile Reinforced Concrete – State-of-the-Art Report of RILEM TC 201-TRC, 2006.
- RWTH Aachen Competence Center Textile Concrete
- SIT grid – V. FRAAS Solutions in Textile GmbH
Author of this Article:
Md. Raisul Islam Rifat
Dept. of Textile Engineering
Daffodil International University, Dhaka
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.