1 APPLICATIONS OF TEXTILE REINFORCED CONCRETE APPLICATIONS OF TEXTILE REINFORCED CONCRETE J. Hegger, N. Will, Institute of Structural Concrete at RWTH Aachen University, Germany C. Aldea, Saint-Gobain Technical Fabrics, Northborough, USA W. Brameshuber, T. Brockmann, Institute of Building Materials Research (ibac) at RWTH Aachen University, Germany M. Curbach, J. Jesse, Institut für Tragwerke und Baustoffe at Dresden University, Germany ABSTRACT: The new composite material TRC offers a number of advantages. The textile reinforcement and the possible thin concrete cover enable the construction of thin-walled structural elements. This opens up new ways for the construction material concrete and gives architects and engineers more freedom in the design. Based on the results of investigations in the characteristics of the new composite material already today TRC can be used in structural elements. Furthermore the advantages of TRC lead to an entirely new application potential for concrete as a building material and open up new fields for the application of concrete in the future. 8.1 Introduction In the architecture of the last two decades can be observed among other things, that materials and her natural surface conditions are in the field of vision of the architects. Under these aspects the development of the textile-reinforced concrete shows a significant technological and creative contribution in the civil engineering. This new composite material allows by the production of filigree concrete elements a completely new architectural appearance of the building material concrete. Highquality exposed concrete surfaces with sharp edged appearance can be realised with the new material. An overview is given in [Heg2004c]. The reinforcement of concrete with technical textiles extends its application to completely new fields. Because of the corrosion resistance of the textile materials, thick concrete covers as known in ordinary reinforced concrete are no longer needed. Thus, slender structural members with a wall thickness as low as ten millimetres are possible. In addition, fine grain concrete matrices guarantee an even and sharp-edged high quality surface, so that TRC is predestinated for architectural applications. Although the knowledge about the load bearing behaviour of TRC is still limited, applications such as cladding panels [Heg2001b] and an integrated framework system [Bra2003] have already been implemented. Textile-reinforced concrete offers already today a wide spectrum of applications, either as an alternative to customary building materials or on account of his favourable characteristics for entirely new ranges of application. In the following some of these projects are introduced. 8.2 Textile concrete facades Introduction By replacing the ordinary steel reinforcement by textile reinforcement, filigree-cladding panels with a broad range of design options can be created. Profile thickness, previously known only from steel construction and composite fibre plastics structures, can be achieved with textile reinforcement as well as high quality homogenous surfaces. These advantages lead to an entirely new application potential for concrete as a building material, especially for façade construction. The small panel thickness achieved by textile reinforced concrete, compared to the 70 to 100 mm required by ordinary reinforced concrete panels, results in a lower dead load and also eliminates the need for complex façade anchors.
2 238 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Exterior cladding panels Cladding panels made of TRC have been used for the extension building shown in Fig. 8.1 of the Institute of Structural Concrete, RWTH Aachen University. The existing single-aisle hall with a span of 12.0 m has been extended by four axes of 5.4 m spacing each. The upper part of the facade is cladded with curtain wall elements, sandwich plates of 35 mm thick facing shells were placed at the lower part (socket) of the building (Fig. 8.2). Facade Panels made of Textile Reinforced Concrete Existing Hall Extension Fig New extension of the testing hall of the Structural Concrete Institute [bauko2 RWTH Aachen University]. sandwich elements with facing shell of textile concrete structural reinforcedconcrete shell facing shell of textilereinforced concrete loadbearing structure air gap thermal insulation a) Fig b) thermal insulation Sandwich elements and cladding panels out of textile reinforced concrete: a) Sandwich elements with facing shell of textile concrete, b) Textile-reinforced cladding panels [IMB RWTH Aachen University]. The design of the curtain wall panels is shown in Fig At this time the sun-protection made of textile reinforced concrete lamellae in Fig. 8.3 b is only added by a computer. Innovative, textile reinforced concrete components have been developed for this purpose [Heg2001b]. On the longitudinal side of the hall, 2685 x 325 x 25 mm curtain wall panels have been applied instead of hitherto natural stone, which would have been the typical choice. The high cost of the natural stone and its manufacture restricts its use to high quality administrative buildings. Textile reinforced cladding panels are notably less expensive and are therefore a cost efficient alternative for residential and commercial structures.
3 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 239 Fig a) b) c) Curtain wall construction of the Structural Concrete Institute, RWTH Aachen University; a) View, b) Detail, c) Section [IMB RWTH Aachen University]. The design and calculation of the required textile reinforcement is based on the information from the knowledge of the Collaborative Research Center 532 in Aachen [Heg2001]. The dimensions and reinforcement is shown in Fig ,5 50 y x 268,5 a) Dimensions and support conditions of panels (in cm). 7 18,5 7 32,5 [cm] 2, , Fig ,5 20 laminated alkali resistant 20 vertical extra layer glass fiber fabrics MAG vertical extra layer 0 -direction horizontal 90 -direction vertical b) Arrangement of textile reinforcement. 7 18,5 32,5 Dimensions and reinforcement of textile reinforced concrete panels used [IMB RWTH Aachen University]. [cm] The dimensions of panels are 2685 x 325 x 25 mm³. The reinforcement layer in longitudinal direction ranges about 4 mm from the surface of the panel. This leaves a concrete cover of at least 3 mm. In the horizontal direction the panels are clamped at four points. In the vertical direction they are supported by two thrust bearings, the other bearings only admit horizontal forces. Thus, no stresses due to temperature changes are generated by the support conditions. The facade is subjected to wind load. The design of the panels was made under the condition of no cracking under service loads.
4 240 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Considering the results of the described experimental investigations a coated alkali resistant glass fibre fabric (2200 tex and 8.33 mm mesh size in longitudinal direction, and 320 tex and 8.4 mesh size in the transverse direction) has been chosen for the reinforcement of the panels. The fabrics are arranged in two layers close to the surface, thus, providing an upper and lower reinforcement layer. In the area of the bearings an additional layer has been provided in the vertical direction as shown in Fig. 8.4 b. The load bearing capacity has been checked in four-point-bending tests as shown in Fig LVDT LVDT Fig Bending tests performed on textile reinforced concrete panels [IMB RWTH Aachen University]. An agraffe fixing device shown in Fig. 8.6 is used for the fixing of the curtain wall panels. Pull out and shearing tests have been carried out in order to check the load bearing capacity of the dowels. The results showed that the dowels can resist more than seven times the load they are actually subjected to in practice even if they are positioned in cracked concrete. Vertical Substructure (plugged at steelreinforced wall) Agraffe Agraffe Horizontal Profiles Dowel in cone-shaped borehole Panel Fig Fixing technique of the curtain wall panels [bauko2 RWTH Aachen University]. For the production of the panels a self-compacting fine-grained concrete (maximum particle size of approximately 1 to 2 mm) having an optimum consistency capable of fully soaking the textiles was used. Smooth surface finishes as well as sharp-edged profiles and joints could be achieved. The results are concrete surfaces with a completely new look. Fig. 8.7 gives an impression of the finished façade.
5 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 241 Fig Curtain wall construction of the Structural Concrete Institute, RWTH Aachen University [bauko2 RWTH Aachen University]. The first facade panels with an approval of the German building inspection are available on the market. They have the dimensions 1200 mm length, 600 mm width and 20 mm thickness. Producer of the panels is Hering-Hochbauen GmbH, Burbach, Germany. Fig betoshell façade panels (Hering GmbH, Germany). The facade of this school building in Düsseldorf, Germany shown in Fig. 8.9 is a further example of the sharp-edged appearance and the high grade surfaces of TRC-elements. The producer of these facade elements is the company Fydro from the Netherlands. The dimensions of the elements are 1250 x 3100 x 25 mm³, the overall amount of TRC cladding panels was about m². In 2003/2004 also an office building in Dortmund, Germany was cladded by 3.500m² of TRC façade panels (Fig. 8.10). Another current project of Fydro are the dark elements of an office building in Arnhem (2005). They have the dimensions 1150 x 3450 mm² and are 22 mm thick (Fig. 8.11).
6 242 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Fig School centre, Düsseldorf, Germany (Fydro BV, NL). Fig Office building, Dortmund, Germany (Durapact, Germany - Fydro BV, NL). Fig Office building, Arnhem, NL (Fydro BV, NL) Sandwich elements The other type of facade-elements are sandwich elements consisting of two bearing shells and an inner insulation layer. The concreting of the sandwich elements is performed in analogy to the production of ordinary reinforced concrete elements. The textile reinforcement (in this case a contoured profiled spacer fabric, consisting of two cover layers and yarns in between as shown in
7 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 243 Fig a) is placed in the formwork, which is then filled with highly liquid fine concrete. Before that, the anchors connecting the facing shell elements with the reinforced concrete bearing elements are put in place. After the hardening of the facing shells, the reinforced concrete bearing element is poured. a) b) Fig Sandwich elements made of TRC: a) profiled spacer fabric, b) completed sandwich element [ITA, IMB RWTH Aachen University]. In Fig b) a completed sandwich element is shown, which was used in the lower part of the extension building in Fig It consists of a reinforced concrete wall, an rigid foam insulation layer and a TRC shell Parapet sheet The design of multi-storey car-park constructions follows mainly functional and economic aspects. In precast structures the thickness of the facade elements arise about 100 mm due to the corrosive protection of the reinforcement. This leads to heavy elements with restricted possibilities in design. Therefore, the Dresden University developed a prototype of a parapet element with dimensions of m² [Cur2003b] (Fig. 8.13). Fig Prototype of the parapet sheet [Technical University Dresden]. The ordinary steel reinforcement was substituted in the 20 mm panel by an biaxial textile reinforcement made from AR-Glass. The edge stiffening is reinforced by fibre bars. The dimensions
8 244 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE and the dead weight of the element were reduced to a minimum. Besides the lower transport and mounting weights advantages exist also for the anchorage constructions. 8.3 Enviromental protection elements Decentralised wastewater treatment plants made of textile reinforced concrete Decentralised wastewater treatment is very important in sparsely populated areas. Technical, environmental and economic reasons oppose connecting a few households with waste water treatment plants. In the next years the wastewater of 7 to 8 million citizens in Germany will be treated decentralised. For this purpose, durable and cost-efficient wastewater treatment plants are needed. Due to their high load-bearing capacity and lower-cost fabrication, tanks made of reinforced concrete have the biggest market share. Steel-reinforcement is normally arranged to provide its load bearing capacity and tightness. Depending on the type of the plant (aerobic or anaerobic) and the composition of the wastewater the reinforcement or the concrete may be damaged by corrosion. The risk of a corrosive attack by biogeneous sulfuric acid in anaerobic parts of a wastewater treatment plant is usually higher than in aerobic parts, but even there it may occur, e.g. due to insufficient service. Decentralised wastewater treatment plants made of textile reinforced concrete offer many advantages such as a lower wall thickness and a higher durability against corrosion attacks. Because no experiences were present for the construction and the application of decentralised wastewater treatment plants made of textile reinforced concrete, suitable fine concrtes and textiles were developed at the RWTH Aachen University within the scope of an AiF research project as well as calculation and production procedure for this application [Heg2003, Heg2004b]. The practical applicability of the research results was proved by the realisation of a prototype shown in Fig in cooperation with the industrial partner Mall GmbH, Donaueschingen, Germany, a manufacturer of prefabricated decentralised wastewater treatment plants. Fig a) b) Prototype of a decentralised wastewater treatment plants made of textile reinforced concrete: a) Geometry, b) Prototype (filled with water) [ibac, IMB RWTH Aachen Universtiy + Fa. Mall]. The geometry of the planned tank is defined according to custom and usage requirements and to the demands of the available German Standards. The wall of the basin has a thickness of 40 mm, which is less than half of the thickness of a steel-reinforced tank. The textile reinforcement will consist of two layers which are arranged one at each side of the wall. The chosen biaxial carbon fibre fabric has a
9 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 245 weight of 160 g/m² in each direction. Fig shows the prepared reinforcement with arranged concrete spacers.the concrete cover is about 5 mm. concrete spacer carbon layer spacer fabric Fig Reinforcement of the tank with arranged concrete spacers [ITA, ibac, IMB RWTH Aachen University]. The 1650 tex-rovings have a spacing of 10 mm. The carbon fibre fabrics will be glued on a spacer fabric that ensures the distance between the inner and the outer layer of the reinforcement. The concrete cover will be achieved by gluing concrete pieces of about 5 mm thickness on the reinforcement. The concrete pieces ensure the distance between reinforcement and formwork during the pouring of the concrete Noise protection wall systems Fig Railway Amsterdam Paris, aprox m², realisation 2003 Netherlands (left) Reflecting panel system, Netherlands (Durapact, Germany - Fydro BV, NL) (right).
10 246 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Fig Panel system with high noise absorption (perforated concrete shield, insulation, structural plate out of trc) near airport Düsseldorf (Durapact, Germany - Fydro BV, NL) Water protection wall systems The flood protection plate AQUA STOP is supposed to be used as facing plate for a stationary flood control system of the AQUA STOP GmbH. Sheet pile walls rammed into the bottom prevent the penetration of water. A mobile flood protection wall can be mounted upon the U-shaped head profile of the sheet pile wall formation in extreme flood situations. The lining to the landside occurred with clinker, natural stone or wood up to now. In addition a cost-efficient, durable, lightweight facing plate made of TRC is supposed to be used as covering of the sheet pile wall. The facing plate is regular loaded only by permanent weight. Impact and shock loads caused by pedestrians are to be considered as additional loads. To enable a mounting without lifting tools the weight of the plate should be small. Different designs and structuring of the visible surface is supposed to be possible. The geometry of the facing plate is based on the dimensions of the sheet pile wall formation. The dimensions of the plate were established by length x height x thickness = 2400 x 1000 x 25 mm³. The mass is 135 kg by using normal weight concrete and 100 kg in case of use of light weight concrete. A biaxial AR-glass warp knitted fabric is used as reinforcement. Warp thread and weft thread are orthogonal orientated and has a yarn count of 1100 tex both. The thread separation distance is 7.5 mm in both directions. Therefore the cross-section of AR-glass is approx. 55 mm²/m in each direction. The textile fabric was impregnated with a special polymer mix subsequent reaching a better fibre utilization in the core zone of the threads. The facing plate is reinforced with 2 layers of the textile fabric. Two different concrete mixtures were used to limit the shrinkage and deformation potential of the thin plate. On the one hand a finegrade concrete with 1mm maximum grain diameter and rich in binding material, on the other hand a concrete with reduced binding material and maximum grain diameter of 4 mm was designed. To increase the fracture resistance of the coarse concrete 0.4 volume parts of short glass fibres were added to the mixture. The short fibre length is 9 mm. The facing plate is a 5 layer sandwich element. The two face layers are 4 mm thick and are made of fine grained concrete. The core of the sandwich is filled with the coarse concrete. Between the concrete layers the textile reinforcement layers are placed. The bond between textile reinforcement and concrete is ensured by the fine grained concrete. The remaining concrete cover is 3 mm. The surface layer can be designed in different manner by use of white cement and addition of colour pigments to the mixture. In the same way structuring of the surface (washed-out concrete, profiling) up to a depth of 2 mm is possible (Fig. 8.18).
11 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 247 Fig Design example of the facing plate. Red surface layer concrete and washed-out concrete picturing the Dresden-skyline. A serial production of the facing plate by a medium-sized company is planned in case of an award at a tender still running. The development has been ordered by Hochwasserschutz GmbH, Neuwied, and carried out at the Building Materials Institute, Technische Universität Dresden, in cooperation with Institute of Textile and Clothing Technology, Technische Universität Dresden. Further water protection wall systems have been developed by Fydro BV, Netherlands, as shown in Fig Fig Bank protection elements, Netherlands (Fydro BV, NL) Subsequent sealing of basements with a waterproof TRC construction In many regions of Germany the rising level of ground water leads to the situation of pressing groundwater forces on residential buildings. As these buildings originally were not designed for this load case they have to be retrofitted (approx units estimated). Many of the possible techniques offered on the market only consider the technical aspects of sealing whereas the static problems resulting from the rising water pressure are often ignored. For this reason, a new construction method, which makes use of textile reinforced concrete (TRC), is being developed for the subsequent sealing of the basements of common residential buildings, which in general consist of a concrete floor base and masonry walls. The use of thin-structured textile reinforced concrete sealings with a thickness of about 20 mm only allows for a minimal reduction of usable living space. See Fig as an example. At the same time this innovative building material offers the possibility to meet the requirements regarding the sealing function and static demands as well as economical aspects.
12 248 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE 1. layer of textile 2. layer of textile layer of fine grained concrete 2. layer of fine grained concrete 1. layer of fine grained concrete Fig Waterproof TRC construction for subsequent sealing of basements [Bro2006]. At Aachen University within a joint project with industy partners, i.e. Saint-Gobain Vetrotex (France) and Rombold & Gföhrer GmbH & Co. KG, HeidelbergCement AG, fischerwerke (Germany), for a realisation of the proposed TRC sealing construction different material combinations of textile reinforcement (e.g. AR-glass, carbon) and fine grained concrete mixtures (maximum grain size of about 1 to 2 mm) are being investigated regarding strength and load carrying capacity. Furthermore detail solutions like anchoring of the masonry building wall to the TRC sealing are considered. Different application and production techniques (spray method, injection) are carried out in order to find the most economic solution for this innovative construction approach. 8.4 Load-bearing structures Integrated formwork element for steel reinforced concrete floors Within the scope of a DBV/AiF research project [Bra2003] a integrated formwork element was developed in Aachen RWTH together with the university of Stuttgart which should be used for a steel reinforced concrete floors. It is capable to carry the load in the erection state and is integrated in the construction member after concreting (Fig. 8.21). In the final state an additional steel reinforcement carries the tensile forces. In addition, the necessary concrete cover can be reduced by the application of the fine concrete matrix, so that a better exploitation of the cross section becomes possible. The industrially precast elements can be moved due to their low weight by hand on the building site. The durability of the textile fibreglass reinforcement is not so important, because the textile reinforcement has to take over a load bearing function according only during the erection state. Near the optimisation of the formwork cross section and the first tips for the rational production of the elements are the cooperation of formwork and concrete as well as the fire behaviour the main investigation targets.
13 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 249 Fig Integrated formwork elements made of TRC for steel reinforced concrete floors [Bra2003] Integrated formwork element for steel reinforced walls A traditional wall formwork system is designed to transfer the horizontal loads resulting from the concrete pressure of the newly placed concrete into the holdings (girders, tie rods and brace frames). One of the fundamental ideas within the technical concept to design the integrated formwork system made of TRC (Fig. 8.22, left) is to use the advantages of these already commercially available holdings (e.g. Doka-systems), but only to replace the plywood by integrated formwork elements and possibly increase the spacing of the supporting girders [Ban2005, Bra2003, Bra2003b]. Hence the overall dimensions of an integrated formwork element are chosen as 2.7 x 1.0 m² (standard size Doka). Fig Integrated formwork elements made of TRC for steel reinforced concrete walls [Bra2003]. Under the assumption of a single-span system over the short length of 1.0 m, the ratio of load carrying capacity and weight of these elements is optimised insofar, that a thin reinforced plate in the tensile
14 250 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE zone carries the flexural loads and a system of concrete grids in the compression zone carries the compression forces. A design concept has been developed and verified in four point bending tests. To check for the allowed deflection and applicability the integrated formwork elements have been applied in a real concreting situation (Fig. 8.22, right). It has shown that the developed integrated formwork element can be introduced in practice Balcony floor sheet The supplement of balconies in existing old dwellings or their renewal can be realised economically by metal-lightweight constructions. As an alternative of the metal foot grounds which are rejected by the majority of the users the Textile research institute in Chemnitz, Saxony developed together with the Dresden University a slender rib slab with dimensions of m² (Fig. 8.23) with similar geometrical qualities like the parapet sheet in Section a) b) Fig Prototype of a balcony floor sheet: a) Cross section of compact prototypes with reinforcing bar elements in the ribs and in the edge stiffening frame, b) Orthogonal textile reinforcement with worked in reinforcing bar elements [Heg2004c]. The ordinary steel reinforcement was substituted in the 20 mm panel by an biaxial textile reinforcement made from AR-Glass. The ribs of a total height of 70 mm were reinforced by fibre bars Diamond-shaped framework In the chair of construction 2 RWTH Aachen University architectures examined the possibilities for the application of textile concrete in structures. The following project shows in Fig one solution, the diamond-shaped framework. This construction principle has got numerous historical examples [Mok1968, Ner1957], in particular in the industrial construction in the 1950s till the 1960s, applied as an ordinary reinforced precast concrete structure.
15 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 251 a) b) Fig Diamond-shaped framework: a) Isometric projection of a diamond-shaped framework, b) Spatial appearance of the diamond-shaped framework [bauko2, RWTH Aachen Germany]. The structure is mainly stressed by pressure. Only with eccentric load cases, e.g., wind effect on the long sides bending moment occur. The whole construction is stabilised by the diagonal position of the curves without additional elements in longitudinal direction. Furthermore the complex geometry of the structure can be composed with very easy elements shown in Fig Fig Diamond-shaped framework - elements and jointing [bauko2, RWTH Aachen Germany]. The diamond-shaped element, with dimensions of 1000 x 600 mm², a height of 160 mm and a thickness of 25 mm has a weight of approx. 23 kgs. The approximated curve form is generated by coupling the elements in each joint with an offset of 5º. The framework was realised in February 2005, Fig presents the architectural appearance of the new building material TRC.
16 252 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Fig Diamond shaped framework Realisation and spatial appearance from the inside [bauko2, RWTH Aachen Germany]. The example shows that already today textile reinforced concrete can be used for structures. Easy connecting technologies, flexible textiles and the first static calculation models form the bases for the development of structures which point up the constructive and creative characteristics of the new material like slimness of the elements, sharp edged appearance and excellent concrete surfaces. 8.5 Exterior insulation systems General remarks Exterior insulation systems are currently being used worldwide, and known as Exterior Insulation and Finish Systems (EIFS) in North America and External Thermal Insulating Composite Systems (ETICS) in Europe. Between the North American and European systems there are differences including substrate (in North America mainly sheathing and framing, but also concrete and masonry, typically found as a substrate primarily in retrofit applications and in Europe concrete and masonry) and system elements (lamina thickness, polymer content, cement content, insulation types, mechanical fasteners, and type of reinforcement and accessories), therefore they will be treated separately [Day] Exterior insulation and finish systems EIFS EIFS are non-load bearing exterior wall cladding systems. EIFS are designed as a barrier wall system rather than a cavity wall, which implies that they must prevent the intrusion of water into the structure. EIFS are a very effective means of insulating buildings from the extremes of hot and cold ambient temperatures. New systems have been developed with drainage control. They allow water from intrusion to escape and thus prevent damage to the wall structure. EIFS are used as exterior retrofits for existing buildings to improve the insulation value. There is also a large emphasis on the use of EIFS for new designs and construction. EIFS has proven cost effective for a wide range of buildings including office structures, retail establishments, industrial plants, schools and residences. Buildings manufactured using an EIFS are 30% more energy efficient than traditional methods where the insulation is on the inside of the building. The more even surface temperature distribution inside the building increases the comfort of the occupants. Other benefits include: Light weight for reduced dead load on superstructure Design flexibility Low cost
17 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 253 Wide range of finish colors and textures offered for retrofit as well as new construction Many installation options from field applied to prefabricated panels Many installation options from field applied to prefabricated panels Architectural freedom of design (can design more ornate facades) EIFS is a laminated composite consisting of layers of the following components: insulation boards which are bonded or mechanically attached to a substrate such as plywood; a polymer modified cement base coat reinforced with a fibreglass mesh; and a finish coat with integral color and texture (Fig. 8.27). Fig EIFS composition [ETA2000]. EIFS are proprietary systems and the components are all provided by an EIFS manufacturer. The insulation board is generally composed of polystyrene or polyisocyanurate foam. The cement base coat and finish coat (typically acrylic modified cement) serve as water barriers and also as a matrix to transfer loads to the fibreglass mesh. The fibreglass mesh is needed to prevent cracking of the base coat and finish coat due to thermal loads on the panel as well as to protect the panel from impact damage. In some instances, two layers of mesh are used for high impact resistance, or meshes of higher areal weight. Reinforcing meshes are available in the following typical configurations: Table 8.1. Textile reinforcement used for EIFS. Feature Range Coated fabric weight (g/ m 2 ) Ends/10 cm Warp Yarn (tex) Weft Yarn (tex) Fabric thickness (mm) Aperture area (mm 2 ) 7-20 Fabric tests (typically carried out by fabric manufacturers): 1) Weave Identification: according to SGTF ) Fabric Construction: according to ASTM D ) Fabric Weight: according to ASTM D ) Thickness: according to ASTM D ) Tensile Strength: according to ASTM D ) Fire Resistance: according to D-568 7) Alkali Resistance: according to EIMA
18 254 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE The following tests are performed on EIFS systems to provide a basis for evaluation and selection of a specific proprietary system [Day]. Load Type Load Test Method(s) General Exposure Movement Water Penetration Moisture Barrier Hygrothermal Adhesion Water Vapour Alkali Resistance (Mesh) Salt Resistance Fungus Resistance Ultra-Violet Resistance Air Pressure and Structural Deflection Kinetic (Impact) Forces Abrasion ASTM E 331 Water Penetration ASTM E 1105 Field Testing of Mock-Up EOTA ETAG Water Penetration  CCMC Techn. Guide for EIFS, 1999, A1 Determining the Moisture Absorption Coefficient of a Moisture Barrier CCMC Tech. Guide for EIFS, 1999, A2 Durability ETAG Environmental Durability  CCMC Tech. Guide Wet & Dry State Adhesion ASTM E 96 Dry Cup for Lamina ASTM E 96 Wet Cup for Moisture Barriers EIMA Alkali Resistance of Reinforcing Mesh  CCMC Tech. Guide 5.3 Tensile Strength/Alkali Resistance ASTM E 117 Salt Spray (Fog) Resistance MIL-STD-810E Resistance to Fungal Growth ASTM G23 Carbon Arc Light ASTM G53 Fluorescent UV & Water Condensation ASTM E 283 Air Leakage ASTM E 330 Positive & Negative Wind Load EIMA Kinetic Impact Test EOTA ETAG Puncture Testing ASTM D 968 Abradion Resistance of Coatings Interface Elements Sealant Adhesion ASTM C 1382 Sealant Tensile Adhesion 5 Conditions ASTM C 920 Sealant Classification Fig Tests performed on EIFS systems [Day]. The installation methods are unique to each systems supplier and they are not universal. Little information is on file here in that regard. In general, the cement base coat is applied to the foam board to a closely controlled depth; the fabric is then embedded into the wet base coat such that it is encapsulated entirely. The decorative finish coat is applied after the base coat has cured External thermal insulating composite systems (ETICS) ETICS with rendering are laminar composites comprising prefabricated insulation product bonded, mechanically fastened or both bonded and mechanically fastened onto the walls of the buildings, which are generally made of masonry (bricks, masonry units) or concrete (cast in place or prefabricated panels) [ETA2000]. The system is non-structural. Its role is to provide external thermal insulation and to contribute to wall durability by enhancing weathering protection. Typical elements of ETICS system are presented in Fig
19 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 255 Fig ETICS composition [ETA2000]. ETICS comprise prefabricated insulation product, which is attached to the wall by means of adhesive (2, mechanical fixtures (anchors, profiles, special pieces 4) or both. The prefabricated insulation product includes a reinforcing coat (6) and a mesh fabric (7). Reinforcing meshes (7) are available in the typical configurations shown in Table 8.2: Table 8.2. Textile reinforcement used for ETICS. Feature Range Coated fabric weight (g/ m 2 ) Ends/10 cm Aperture area (mm²) Tensile strength (N/5cm) warp/weft / Elongation (%) warp/weft / A rendering system (9) is applied directly to the insulation product in one or more layers, one of which is reinforced. Rendering system (9) includes all the coats applied to the outer face of the insulation product and the reinforcement. The render coating is applied to the insulation product in ore or several layers. Typical reinforcements are glass fibre mesh, metal lath or plastic mesh, which are embedded in the base coat to improve its mechanical strength and to reduce surface cracking. Reinforcing meshes are available in the typical configurations shown in Table 8.3:
20 256 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Table 8.3. Textile reinforcement used for ETICS. Feature Range Coated fabric weight (g/ m 2 ) Ends/10 cm Aperture area (mm²) Tensile strength (N/5cm) warp/weft / Elongation (%) warp/weft / ETICS tests are detailed in the European Norm ETAG 004 Guideline for European Technical Approval of External Thermal Insulation Composite Systems with Rendering [ETA2000], which includes tests for systems and tests on components. Render reinforced system tests includes render strip tensile test, to assess cracking performance by determining the typical crack width. Reinforcement tests are tailored according to the type of reinforcement: Glass fibre mesh: tearing strength and elongation measured in warp and weft directions unaged after conditioning the samples for 24 hours at 23±2ºC and 50±5 RH, and using accelerated aging procedures, after 28 days soak in a tri-alkali-solution at 23±2ºC. Metal lath or mesh: minimum thickness of the zinc coat required is verified using relevant EN method. 8.6 Gypsum board joint finishing system Stresses caused by movement due to wind and seismic forces, settling foundations, shifting buildings, normal traffic, thermal fluctuations, hygrometric expansion and lumber shrinkage result in load transfer to the drywall panels. Due to the brittle nature of the joint treatments, these imposed stresses are sufficiently strong to overcome the strength of non-reinforced joint treatments and results in cracks. This has the effect of ruining the aesthetic finish of the drywall wall or ceiling, and requires a remedial action. A reinforcement material is needed to protect the joint treatments against these loads. Joint finishing products are an integral part of gypsum board systems. The main function of the joint tape and compound system is to render the surface of the wall smooth, uniform and allow for an aesthetic finish. To be an effective joint reinforcement, the following characteristics need to be addressed: low elongation and high tensile strength (high modulus) compatibility with the joint compound easy to use non-staining not sensitive to temperature and humidity changes no degradation or corrosion with time As the joints are stressed due to loads, a high modulus based reinforcement such as glass is the material of choice. The high modulus material will tend not to stretch whereas a low-modulus material will stretch and allow the joints to crack. Other materials used are: paper tape, fibreglass mat tape and in some countries materials such as polyester are used. Fabric tape is a woven or knitted mesh made of coated fibreglass self-adhesive mesh tape, fibreglass mat tape or polyester tape. The mesh construction allows for the joint compound to penetrate through the mesh openings and encapsulates the fibreglass yarns while ensuring a proper contact and bond to the gypsum board underneath. Most glass mesh tapes have 8 to 9 ends per inch in both the warp and
21 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 257 weft. E or C type glass is used as the tape is not used in a high alkaline environment and does not need to be alkaline resistant. There are two basic types of joint compounds on the market that are used with reinforcement tapes: drying type compounds and setting type compounds. The main ingredient of joint compound is calcium carbonate mixed with other ingredients such as clay, talc, mica, thickeners, resin/latex, perlite, preservatives and water to produce creamy, easily spreadable paste. Calcium sulfate is used only in setting type compounds. Setting type compounds give a harder, stronger binding material compared to drying type compounds. Typical tests are: Physical testing of joint compound, paper joint tape, glass-mesh tape and an assembly of joint compound and joint tape: ASTM C474. Joint treatment materials: ASTM C475. Note: The joint treatment materials described in these standards are for use with gypsum board installed in accordance with specification ASTM C840. tests for glass mesh tapes: ASTM C474; tensile strength width thickness skewness method for evaluating tensile properties of gypsum panel joints An adhesive test for evaluating ability of self-adhesive tape to stick to gypsum board panels is in review with ASTM. specifications for glass mesh tape; ASTM C475 tensile strength shall be not less than 30 lbf/in (5.25 N/mm) in the cross direction width shall be not less than 1 7/8 in (48 mm), no more than 2 ¼ in (60 mm). thickness shall be not more than in. (0.30 mm) skewness shall be not more than 8.75 % when tested in accordance with method ASTM3882 A self adhesive tape is directly applicated to the gypsum board surface. A compound is spread over top of the taped joint with sufficient pressure to allow the compound to penetrate through the mesh and into the joint space. Fig Installation of the Gypsum Board Joint Finishing System.
22 258 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE After the first coat of compound is dried, one or more coats may be applied and sanded after drying. The number of coats of compound applied and amount of sanding done will depend on the desired level of aesthetic finish to be achieved. 8.7 TRC and masonry Strengthening systems for unreinforced masonry Definition and role of the system Traditional unreinforced masonry techniques used for existing buildings include diaphragm stiffening, tying walls to floor diaphragms or adding steel tiles. In such cases load-bearing masonry walls can exhibit direct shear failure mechanisms, mainly depending on the wall geometry, the mechanical properties of the masonry units and mortar, the interactions between them and the type of loads applied. In case of seismic action mode II shear sliding failure occurs in masonry panels along the unit/mortar interface, particularly for low levels of vertical loads and/or low friction coefficient. Therefore the selection of reliable strengthening techniques is very critical, and new composites such as fibre reinforced polymers (FRP) and cement based reinforced composites have been developed. Cement based matrix grid (CMG) systems are composites consisting of a sequence of layers of cement-based matrix and grids developed to enhance masonry load bearing capacity and deformation ability. CMG have the following advantages compared to other existing solutions, including FRP: 1. High compatibility with the masonry substrate in terms of chemical, physical and mechanical properties. 2. Ease of installation. 3. No need for surface preparation or high levels of workmanship. 4. Fire resistance. 5. Excellent bond with the substrate. 6. Breathability of the system, which allows air and moisture transport between the matrix and the substrate. 7. Reversibility, which is of particular interest especially for historic masonry buildings. CMG systems elements are a cement based matrix and the reinforcing grid. Patented systems are available for this application and use greige carbon or coated AR-glass grids and proprietary matrices. Typical tests CMG systems tests for masonry walls are detailed in ICC ES AC218 Acceptance criteria for cementbased matrix-fabric composite systems for reinforced and unreinforced masonry which includes materials and structural tests, as well as quality control guidelines and design guidelines: Materials tests: CMG system tensile test (test method detailed in Annex A of AC218), drying shrinkage (ASTM C157), coefficient of thermal expansion (US Army Corps of Engineers Specification CRD-C 39), void content (ASTM C 138), impact (test method detailed in Annex B of AC218), composite inter-laminar shear strength (ASTM D2344 or ASTM 947 in conjunction with ASTM D2344), freezing and thawing, aging, interior finish (Section 803 of the IBC), lap strength (ASTM D 3165), bond strength (ASTM D4541). Structural tests: wall flexural tests (out-of-plane load), wall shear tests (in-plane shear). [Fae2004] and [Pro2005] present test results for carbon, respectively AR-glass coated grids used for strengthening tuff unreinforced masonry walls. [Mar2002] and [Ald2005] report in-plane shear concrete masonry full scale tests carried out at USACOE-CERL, Champaign, IL to simulate seismic action. The results of the experimental program demonstrated the ability of the CMG system to
23 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 259 strengthen the walls, and showed its superior performance compared to FRP alternatives. Not only it provided a performance within the range of the FRP systems, but one fabric configuration (2 plies 0-90 ) provided the best overall performance. Installation 1. Substrate surface preparation, including repairing any damaged areas to the blocks and placing a terminating strip around perimeter of work area, ensuring blocks are clean free from dirt and any chemicals. 2. Wetting the substrate surface by spraying water. 3. Trowel matrix on substrate. 4. Embed a layer of grid onto the applied matrix. 5. Apply subsequent layers of grid at 90º with respect to the previous layer by repeating steps 3 and Once the desired number of plies of fabric is achieved, apply an additional layer of mortar and trowel to a relatively smooth surface Fig Installation of CMG systems. Design considerations Design considerations are detailed in ICC ES AC218 Acceptance criteria for cement-based matrixfabric composite systems for reinforced and unreinforced masonry and include: flexural strength enhancement, bond strength of the system to the substrate, shear strength enhancement and shear strength reduction factor.
24 260 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE External and internal reinforced render system Rendering in general is a coat of plaster or cement applied to a masonry surface. Coated fibre glass mesh reinforcement is used in: Exposed areas of external and internal plaster, such as wall joints, windows and door corners and the channels for water or gas pipes and electrical wiring. In areas where two materials with different coefficients of expansion are in contact in order to improve cracking performance. The mesh is embedded in the rendering 2-3 mm under the surface. Reinforcing meshes are available in the typical configurations shown in Table 8.4: Table 8.4. Textile reinforcement used for external and internal reinforced render systems. Feature Range Coated fabric weight (g/ m 2 ) Ends/10 cm Aperture area (mm²) Tensile strength (N/5cm) warp/weft / Elongation (%) warp/weft / ETICS tests are detailed in the European Norm ETAG 004 Guideline for European Technical Approval of External Thermal Insulation Composite Systems with Rendering [ETA2000]. Render reinforced system tests includes render strip tensile test, to assess cracking performance by determining the typical crack width. Reinforcement tests are tailored according to the type of reinforcement: Glass fibre mesh: tearing strength and elongation measured in warp and weft directions unaged after conditioning the samples for 24 hours at 23±2 ºC and 50±5 RH, and using accelerated aging procedures, after 28 days soak in a tri-alkali-solution at 23±2 ºC Reinforced stucco: one coat stucco - glass fibre lath wall system Stucco is a common exterior finish material with relatively high moisture and weathering resistance. Traditional stucco is a cement mixture used for siding. The cement is combined with water and inert materials such as sand and lime. Usually, wooden walls are covered with tar paper and chicken wire or galvanized metal screening. This framework is then covered with the stucco mixture. Sometimes, the cement mix is applied directly to specially prepared masonry surfaces. Traditional stucco is three coat stucco and consists of three separate layers of cement plaster materials: a trowel-applied scratch coat, which receives a grooved surface with a special scratching tool, a sand-finished brown coat, which keys into the scratch coat, and a finish, or colour coat, which is usually cementitious. Three coat stucco systems are reinforced with self-furring wire, similar to heavy-gauge chicken wire (17-gauge netting with 1½ inch-diameter holes) and with expanded metal lath around doors, windows, corners, parapets, and any built-up shapes that will be subject to unusual stress. One-Coat Stucco Wall System One-Coat Stucco Wall System is a patented system for use with exterior walls in new or retrofit residential, light commercial and institutional construction as an alternative to 3-coat stucco systems with metal lath [Pru1995].
25 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 261 One-Coat Stucco is a Portland cement-based exterior wall system offering fast application time, reduced labor cost, resistance to efflorescence, and a fibre-reinforced, crack resistant base coat. Integrated system components include one-coat stucco Base Coat, tinted primer, 100 % acrylic polymer finish and heavy-gauge chicken wire (20-gauge netting with 1 inch-diameter holes) and expanded metal lath or glass fibre textile. Fig Stucco Wall System [Pru1995]. Glass Fibre Lath Stucco mesh is a three dimensional, patented fibreglass grid designed to replace metal netting (generically known as chicken wire) and metal lath in exterior stucco wall constructions [Ega2005]. Its advantages over metal include lighter weight, faster installation, easier and safer cutting, and most importantly discoloration of the wall surface due to rust migration cannot occur with a fibreglass mesh. The purpose of the stucco mesh is to act as a substrate for wet stucco and thus prevent it sloughing off the wall. The weight of the stucco is borne by the mesh, which in turn transfers the load to fasteners (most commonly 1 staples) affixed to the wooden backer board. Stucco Lath The lath consists of a fibreglass 3D spacer mesh saturated with a polymeric coating. Typically the mesh would be of a fairly open leno weave construction with hole-sizes ranging in area from 0.02 to more than 4.0 square inches. Such an open weave allows the sprayed stucco to easily penetrate the mesh and adhere to the backing material. In addition to this due to its third dimension, e.g. thickness, the mesh is encapsulated by the stucco and provides enhanced bond with the stucco matrix by mechanical anchoring, and thus serves to support the weight of the stucco until it sets. The advantage of this lath lies in its significantly enhanced thickness versus typical fibreglass fabrics of similar construction. Substrates for stucco systems typically must be at least inches thick in order to meet building codes (refer to ASTM C for metal lath, ASTM C933-96a for welded wire lath and ASTM C for woven wire Plaster Base). Such a thickness is impossible to achieve in a cost effective way by normal means of fabric formation. Coating selection is important for this application. In order for the weft yarns to hold their sinusoidal shape the coating must be very rigid and resist softening by the wet stucco. Matrix (One-Coat Stucco Mix) One-coat stucco typically consists of plain silica sand; approximately 0.06% fibres (~50 micron diameter organic fibres, Powder including: Portland cement, fine quartz (typically fine sand particles <75 microns size), Ca(OH)2 and Mg(OH)2, fly ash and gypsum.
26 262 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Typical Tests ICC ES AC275 Evaluation guideline for glass fibre lath used in exterior cementitious wall coatings lists the following: - Basic information: lath specification, including type, input tex used, opening size, thickness, weight, storage instructions and manufacturing process. - Test and performance requirements. Tensile strength, measured according to ASTM E 2098 Standard Test Method for Determining Tensile Breaking Strength of Glass Fibre Reinforcing Mesh for Use in Class PB Exterior Insulation and Finish Systems (EIFS), after Exposure to a Sodium Hydroxide Solution. Tests are conducted both on unexposed and exposed samples in both warp and weft direction. - Structural and fire tests for the exterior wall system including the lath as per ICC AC 11 Listed below are ICC AC 11 required testing for cementitious exterior walls: - Accelerated weathering tests (weatherometer): Representative samples are exposed to simulated UV, humidity, and temperature conditions. Conditions of acceptance ensure that surface changes do not result in cracking, checking, crazing, erosion, or chalking. - Freeze-thaw tests: Samples are prepared, with the exterior coating applied without lath to the normal substrate on the front face and edges. The back of the sample shall be sealed with a material that need not be the coating. Samples are subjected to ten freeze-thaw cycles. Conditions of acceptance will ensure no cracking, checking or crazing of any surface that could promote delamination or moisture intrusion. This shall be based on examination of specimens under magnification. - Transverse load tests (large scale): Specimens with the minimum thickness of coating, insulation board and sheathing shall be prepared in accordance with the manufacturer s recommended installation instructions. Specimens shall be prepared following procedures set forth in ASTM C 109. In addition to the above data, the following shall be reported: - Load-deflection readings. - Compressive strength of cube specimens at 28 days. Typical Installation Directions 1) Attach gypsum sheathing to wood framing with minimum approved fasteners. Install a weatherresistive membrane over the gypsum sheathing. 2) Attach lath with minimum side laps and end laps and in accordance with ASTM C1063, using corrosion resistant fasteners for attachment. 3) Hand-trowel or machine-spray stucco in one or two coats. Trowel stucco into trim to seat trim. Embed the lath in the coating so that it is completely covered. Level surface using rod or darby. 4) After surface has sufficiently hardened, use sponge or hard rubber float as required to fill voids, holes or imperfections, leaving the surface ready to receive Finish. 5) Complete by fog spraying stucco with clean, potable water once or twice daily for 48 hours under normal conditions; fog spray more frequently if hot, dry conditions exist. Allow stucco to cure 6 days prior to Finish Coat application. Design Considerations The maximum allowable deflection is L/240, based on stud properties only. The design wind-load shall not exceed the system s allowable wind-load as stated in applicable code reports. Expansion joints are required in the system where they exist in the substrate, where the system adjoins dissimilar construction, and at floor lines in multilevel wood frame construction. System shall terminate at
27 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 263 expansion joints. Sealant joints shall be detailed and installed per sealant manufacturer s recommendations. A minimum 6:12 slope is required on all horizontal surfaces greater than 1". Backer rod, sealant and flashing are required at door and window openings. Typical Installation 1) Stucco wall is first covered with asphalt roofing paper. The lath is cut with a utility knife. 2) The mesh is stapled to the wall with a pneumatic stapler (Fig. 8.33). Screws and washers may also be used to install the mesh on the wall. Fig Mesh stapled to the wall [Pru1995, Ega2005]. Fig Wall during stucco application [Pru1995, Ega2005]. 8.8 Textile reinforced concrete multi-layer composite pipes Concept of an innovative composite pipe The newly designed multi-layer composite pipe with optimized functional distribution of the used materials combines the positive properties of polymer pipes with the significant increased strength properties of a textile reinforced fine grained concrete layer. The jacket of textile reinforced concrete consists of multi filament yarns made of alkali-resistant glass and bears the stresses from internal pressure as well as external loads (live loads, earth loads, etc). The advantages of the textile reinforced concrete consist in the high strength, ductile behaviour at thin wall-thicknesses and high corrosion resistance. Smaller wall-thicknesses of the interior polymer pipe are necessary for the same or even higher internal pressure loads. The plastic pipe inside s first priority is to lead away the fluids as well as a seal function. It has good hydraulic properties and is highly resistant to many media, corrosion
28 264 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE and incrustation. The wall-thicknesses of the high-cost plastic pipes are reduced to a minimum. Thus, it is possible to produce completely sealed high strength tubes. The application of the new composite pipes is supposed to occur in the field of water supply and sewage disposal [Lie2005a]. Fig Samples of composite pipes with plastic pipes inside of different materials (left PVC, right PE) [Lie2005a] Reinforcing structures Several bi-axial reinforcing structures made of alkali-resistant glass filaments have been examined for their processing properties and strength. They differed in aperture size between the reinforcing threads and the amount of reinforcing material. The development of these bi-axial structures was based on the analysis of basic loading cases, the determination of the main load direction and the possible deflection of the reinforcing threads. The main stresses are in the circumference direction to absorb the hoop tension, induced by the internal pressure. In axial direction the longitudinal tension is about 50 % of the hoop tension. Fabrics with 2400 tex in the circumference direction and 1280 tex in longitudinal direction proved to be useful. The dimensioning was kept constant and resulted from empirical knowledge obtained during extensive fundamental research in previous projects. Very positive results could be achieved by adding textile reinforcements with short glass fibre rates of less than 1 Vol.-%. The result is a significant increase of the limit of the linear-elastic range LOP (limit of proportionality) in the characteristic curve obtained from internal pressure and apex pressure test Production technology The designed production facility based on numerous preliminary tests and allows the production of composite pipes by a winding technique. On this machine, pipes can be produced up to 1000 mm in length and the outer diameters range between 150 and 350 mm. The wall-thicknesses of the reinforced concrete layers can be variable adjusted. The winding technology developed especially for this purpose permits the application of the concrete, the insertion of the textile reinforcement, the calibration of the walls and the smoothing of the surface with a consistent and high quality. At the beginning of the process the textile structure is attached to the plastic pipe through adhesive bonding. The textile structure is held under defined tension during the winding process (Fig. 8.36). The freshly applied layer is compacted by a pressuring device with an adjustable compressive force. The optimal guiding of the textile structure determines the homogeneousness of the applied textile reinforced layer.
29 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 265 Fig Winding process [Lie2005b]. Fig Manufactured pipes [Lie2005b] Internal and vertex pressure resistance After 28 days of controlled atmosphere storage, the tube specimen can be used for inner and vertex pressure tests. These tests are carried out on testing machines for vertex pressure (Fig. 8.38) and specially developed machines for the measurement of elongation under inner pressure (Fig. 8.39). The tests show that the extensional stiffness of the tubes increases considerably with a volumetric content of the reinforcing textile between 1 % and 4 % and of short fibres up to 0.85 %. Depending on the amount of the reinforcing material and the thickness of the concrete layer, inner pressures of up to 57 bar and vertex pressures of up to 155 kn/m can be achieved under short-time stress conditions. Fig Vertex pressure test [Lie2005b]. Fig Inner pressure test [Lie2005b]. Fig shows exemplarily the internal pressure over the tangential extension for different reinforcement situations of two textile structure variants. A complement of the textile reinforcement with short glass fibres (SGF) with a content of less than 1 Vol.-% effectuated a clear increase of the linear-elastic distension range. For example, with a 4-layered reinforcement variant the boundary of the linear-elastic distension range (LOP-values) could be increased from 0.3 MPa (3 bar) up to more than 1 MPa (10 bar) by addition of 0.5 Vol.-% short glass fibres. Increasing the amount of reinforcing material by using 2400 tex yarn instead of 1280 tex yarns while maintaining the mesh-distance, results in an increase of the stiffness in the cracked state (concrete) as well as in an increase of the failure pressure of approx. 35 % in the represented case of a 6-layered reinforcement variant [Lie2005b].
30 266 STATE OF THE ART REPORT TEXTILE REINFORCED CONCRETE Fig Characteristic curves of internal pressure for several reinforcement variants [Lie2005b] Conclusion The advantages of textile reinforcements for concrete are clearly visible when applied in composite tubes. The positive properties of the applied materials are combined ideally and compensate for the respective disadvantages. That way it is possible to reduce the amount of material that is necessary for both the inner plastic tube and the concrete layer while the load bearing capacity of the sealed tubes is greatly improved. 8.9 Textile reinforced bridge A small textile-reinforced-concrete footbridge for pedestrians and cyclists for the state horticultural show, to be held in Oschatz in 2006 has been designed by the Institute of Concrete Structures of Dresden University, Germany and built by Betonwerk Oschatz, a local contractor. The attained results of the speculative application in the frame of fundamental research are displayed. Special features of TRC shall be utilised, particulary its low weight in relation to load capacity and the possibility of erecting a slender construction. The horticultural state show will therefore demonstrate and present the new composite material to the public. The cycle-path and footpath descend from a flat meadow, cross over the river Döllnitz and lead upwards into a forest which borderlines the town. The setting is pictured in Fig Regarding the bridge, it is a matter of a single-span girder in a segment construction method with internal post tensioning of textile-reinforced-concrete. The span width of the superstructure averages 8.60 m and the width between the handrails averages 2.50 m. The superstructure will be buoyantly supported.
31 APPLICATIONS OF TEXTILE REINFORCED CONCRETE 267 Fig View from the north: Pedestrian Bridge built of Textile Reinforced Concrete over creek Döllnitz. The cross section of the superstructure will be formed as a trough from organic compound moulds and consists lengthwise of 10 interlinking segments out of textile-reinforced-concrete. The thickness of the segments average 30 mm. Stiffening has been arranged at the end of segments and underneath the tread to limit deformation of the serviceability, despite the low thickness of the structural members on the required level. The pre-cast members will be fixed together according to the principal of the segment construction method with external un-bonded tendons. The bulk of the tension force ensures, that the joints between the segments stay closed due to all load cases and the transmission of shear within the joints is secured. Commercially available un-bonded externally applied tendons (SUSPA DSI mono-lacing prestressing method without bond for post-tensioning) will be chosen. The adjustments of the plastic ducts in the cross-section and the chosen pre-stress loads in the single tendons ensure a central application of the pre-stress force on the concrete cross-section and avert opening joints underneath all construction stages and in the execution stages. Left hand side of Fig shows a prototype of the bridge during proof loading tests in the laboratories of the institute. Right hand side of Fig shows a view on this prototype located at the campus of Dresden University, Germany after exhibition purposes after proof loading. Fig Textile Reinforced Bridge [Technical University Dresden].