Fabric suitable to the application as reinforcement of building works

Abstract: Fabric suitable to the application as reinforcement of building works, wherein the warp consists of threads of fibers having high modulus and the weft consists of glass threads coated with thermoadhesive

Description: PRIOR ART Processes for the reinforcement of building structures such as brick walls, stone walls, reinforced concrete structures, vaults, pilasters, beams, galleries, retaining walls etc., by application of fibers or reinforcement fabrics made to adhere with thermosetting type resins with a lamination and impregnation technique, are a well known art. A first process has been disclosed in the Swiss Patent CH-365517 of 1960, August 11, claiming the reinforcement of plain concrete or stone material elements by the application on the surface of fibers and fabrics with a synthetic resin. Subsequently several kinds of reinforcement have been developed which, using the normal procedures of manual lamination, well known in the composite materials (hand lay up) field, allow to reinforce several kinds of building structures. For example in the Patent EP 0441519 B1 of 01.30.1991 and in the Patent EP 598591 A of 05.25.1994 (Tonen Corp. Patents) a reinforcement element for structures in reinforced concrete is claimed, substantially consisting of an unidirectional reinforcement fiber sheet bound by a thin net of plastic adhesive and supported on a siliconed paper sheet. Even though this method has been used for some time it has considerable drawbacks: the fibers being perfectly aligned do not show any porosity and they do not allow the leaving of the air during the lamination; so displaced fibers, bound by the net only by one side, turn out to be very delicate at handling during the installation therefore they must always be supported by a paper (siliconed paper) or by an inert film. This fact strongly impedes the manual skill during the installation de facto reducing the size of the sheet which may be laminated at a 2 meters length. The Patent EP 9628117 B of 20.01.1993 (Hexcell Patent) claims the reinforcement of columns by coating with resin impregnated fabrics, such fabrics being characterized in that the warp is perpendicular to the column axis and the weft is parallel to the column axis. Otherwise the reinforcement fibers may be with angles ranging from 20° and 70° with respect to the column axis and -20° and -70° with respect to the direction perpendicular to the column axis. The fibers may be further bound among themselves with an auxiliary sewing. This Patent results in a limited reinforcement effect owing to the imperfect linearity of the fibers, which being disposed at different angles, do not all contribute to the reinforcement effect in the desired direction. The U.K. Patent 2,295,637A (Sho Bond Corp.) of 12.02.1994, discloses a method for the reinforcement of reinforced concrete structures by lamination of a reinforcement fiber in the form of a fabric having the fiber unidirectionally disposed and with auxiliary threads in the weft and in the warp which binding among themselves keep the unidirectional reinforcement fibers in the desired position. As auxiliary threads thermoplastic polymer threads may be used which by hot-treating bind among themselves. This method turns out to be rather complex as the introduction in the warp of auxiliary threads creates a notable complication in the production of the fabric. Moreover only the auxiliary threads bind among themselves and the reinforcement fibers are kept only by the auxiliary threads and in the case of use of thermoplastic polymer threads, after the fusion thermal treatment of these ones, there are points of heat seal only by segments. All-that may notably compromise the sheet stability-and-its installation. The Patent EP 3782232 A of 18.07.1990 (Mitsubishi Patent) discloses the Application on building structures of reinforcement fibers pre-impregnated (pre-preg) with the aid of an adhesive. The adhesive and the pre-impregnation resin are subsequently hardened together. This method involves all the drawbacks typical of the pre-pregs (low temperature stocking, limited duration and high cost) and needs however the use of an adhesive, with a further complication during the application. EP 859085 discloses a method for reinforcing structures wherein a material, comprising reinforcement fibers disposed along one direction and heat-fusible fibers perpendicularly to the reinforcement fibers, is applied to a structure by means of impregnation resins. In all the examples the heat fusible fibers are obtained by a mixture of high melting point fibers with low melting point fibers twisted together. An adhesive resin is also present in the heat-fusible fibers. The method of production of the material is rather complex, and the alignment of the reinforcement fibers is not completely satisfactory. SUMMARY Now we have found, and it is the main object of the present invention, a thermotreated fabric suitable to the application as reinforcement of building works allowing to overcome the drawbacks of the prior art and to give high characteristics of mechanical resistance to the building work. Said fabric is characterized in that the warp consists of threads of fibers having high modulus, having an elastic modulus in tensile stress greater than 10 GPa (Giga Pascal) and a traction breaking load greater than 600 MPa (Mega Pascal), and the weft consists of threads coated with a thermoadhesive polymeric material, said fabric being optionally reinforced with threads of fibers having the same characteristics and the same direction of the warp threads. The invention also comprises a method for the application of said fabric to the building works. BRIEF DESCRIPTION OF THE FIGURES Figure 1 represents a form of embodiment of the fabric wherein with (11) the warp threads and with (12) the weft threads are shown. Figures 1A, 1B, 1C and 1D represent alternative embodiments of the fabric with different disposition of the warp and of the weft. Figure 2 represents the detail of a weft thread. Figure 3 represents a further form of embodiment of the fabric wherein with (31) the reinforcement threads are represented. Figure 4 represents in section the fabric of Figure 3. Figure 5 represents two layers of fabric applied to a concrete structure. Figure 6 represents the device used for the production of the fabric represented in Figures 3 and 4. DETAILED DESCRIPTION OF THE INVENTION The present invention refers to a fabric for the reinforcement of masonry, concrete, cement and reinforced concrete works, and in particular to a thermotreated fabric wherein the warp consists of threads of fibers having high modulus and the weft consists of glass threads coated with a thermoadhesive polymeric material. The invention moreover relates to a method for the application of said fabric to building works. The fabric has preferably the configuration reported in Figure 1 wherein (46) represents out the fabric in general, (11) represents the threads of high modulus fibers arranged in warp and (12) represents the threads coated with thermoadhesive polymeric material arrangend in weft. In Figure 2 the thread (12) is represented in detail wherein (21) represents the glass thread and (22) represents the coating consisting of thermoadhesive polymeric material. The fabric, after hot-reating with fusion of the thermoadhesive polymeric material along the whole development of the weft, turns out to be completely thermofixed and shows a high dimensional stability with complete blocking of the warp threads which maintain, also during the subsequent application steps, their position in the desired direction. In the representation of Figure 1 the disposition of the weft with respect to the warp is of the plane kind but it may be of any kind according to the techniques well known to the weaving experts (twill kind, batavia, panama, basket weaving) with a different disposition of the weft with respect to the warp. Examples of different kinds of dispositions are represented in the Figures 1A, 1B, 1C and 1D. The warp threads (11) of Figure 1, may vary as a function of the typology of the yarn from 1 thread/cm to 12 threads/cm and preferably from 2 threads/cm to 8 threads/cm. The warp threads (11) may have different titles (deniers) which, expressed in Tex (weight in grams per 1,000 m of thread) may range from 20 Tex to 10,000 Tex and preferably from 40 to 1,000 Tex. The weft thread (12) represented in detail in Figure 2 consists of a low title glass thread, preferably ranging from 20 to 100 Tex, represented by (21), externally coated with a thermoadhesive polymer (22), being the amount of the thermoadhesive polymer ranging from 10 to 300% with respect to the weight of the glass. For example a weft thread used in the present invention consists of a 60 Tex glass thread coated with 40 Tex of thermoadhesive polymer, being the total weight of the thread equal to 100 Tex. The use of a coated glass thread is the most suitable for the objects of the invention. However one may use coated threads, formed also by other materials (carbon, polyester, polyarylamides, aramides etc.). The coating with the thermoadhesive polymer may be obtained in several ways, for example by co-extrusion or by coupling with a thermoadhesive polymer of any kind. The distribution of the thermoadhesive polymer (22) on the thread (21) may be of any kind, but preferably said distribution is continuous throughout the whole length of the thread (21). The thermoadhesive polymers used to coat the glass thread (21) belong to the class of the polyolefinic, polyvinylic, polyamidic, polyester and polyurethanic polymers and copolymers well known in the art of the thermoadhesive polymers (Hot melts) and they are characterized by a melting temperature ranging from 40 to 250 °C and preferably from 80 to 200 °C. In a further form of embodiment of the invention the fabric of Figure 1 may be coupled to a series of threads of high modulus fibers, arranged on a face of the fabric of Figure 1 parallelly to the warp (11) and thermofixed on such surface by the heat-sealable weft thread (12). In this way one obtains the structure represented in Figure 3 (perspective view) and in Figure 4 (section), substantially consisting of the fabric of Figure 1, coupled to reinforcement threads (31) oriented along the warp (11) direction and kept in such position by thermoadhesion of the weft thread (12) of the fabric of Figure 1. The fabrics represented in Figures 1, 1A, 1B, 1C and 1D, may show the two surfaces perfectly symmetrical and equal among themselves, for example the fabric represented in Figures 1, 1B and 1C, whereas other fabrics may show the two fabric faces different among themselves, and more precisely a face richer in weft, that is a face wherein the weft thread appears more frequently, and a face poorer in weft, wherein the weft thread appears less frequently, for example Figures 1A and 1D. The threads represented with (11) and with (31) consist of fibers having high modulus, characterized in that they have an elastic modulus in tensile stress greater than 10 GPa (Giga Pascal) and a tensile strength greater than 600 MPa (Mega Pascal). Such fibers include the following groups of materials: rayon fibers, high modulus polyester fibers, polyvinyl alcohol fibers, polyethylene fibers, aramidic fibers, carbon fibers, glass fibers, fibers from liquid crystal polymers. The threads represented with (11) and (31) may be equal among themselves or of different nature and title (hybrid fabrics). For example one may simultaneously use carbon fibers, glass fibers, aramidic fibers and polyester fibers in the same structure. The fabrics according to the present invention are applied for the reinforcement of building works by impregnation resins including all the resins generally used for the production of components in composite material and in particular polyester resins, vinyl ester resins, phenolic resins, epoxy resins, polyurethanic resins, acrylic resins, bismaleimidic resins. Moreover said fabrics may be used in the preparation of composite materials too. The general procedure for the application of the fabrics for the coating of building works is well known and it is normally carried out by manual lamination (Hand Lay Up) of the fabric and impregnation with the above listed resins. In general before applying the fabrics it is advisable to carry out an accurate cleaning of the surface to treat and then to proceed to the spreading of a first layer of resin (already catalysed) arranged to the hardening, application of the fabric, spreading of a second layer of resin in order to obtain the complete impregnation of the fabric and application of possible subsequent layers of fabric, repeating the above listed operations. The resin hardening is carried out by the techniques well known to the experts of the field, generally at temperatures ranging from 5 to 40°C, according to the used resin system. The number and the disposition of the fabrics to apply vary as a function of the reinforcement effect which one wants to obtain and of the shape and structure of the manufacture to reinforce. A process for the application of the fabric on the surface of building structures, according to the present invention, comprises the sequence of the following operations: application on that surface of a layer of impregnation resin, application of the fabric in the reinforced form, application of a second layer of impregnation resin, application of the fabric in the not reinforced form and the application of a third layer of impregnation resin. In a preferred form of this invention the first fabric applied on the surface to be reinforced is of the kind described in Figure 3 and Figure 4, taking care to put into contact with the surface to be treated the face B of the fabric itself, according to the configuration of Figure 5, in which also a subsequent fabric of Figure 1 kind is represented. Considering Figure 5: (41) is a concrete structure to be reinforced, (42) is the first layer of impregnation resin, (45) is the fabric of Figures 3 and 4 applied on the surface of the concrete with the face B (43) facing the plain concrete and the face A (44) facing the outside, (47) is a second layer of impregnation resin, (46) is a second fabric layer according to Figure 1 and (48) is another layer of impregnation resin. This applicative configuration is optimal in order to obtain the maximum of the reinforcement effect where the face B of the fabric of Figures 3 and 4, in contact with the surface to be reinforced carries out the best effect in limiting the formation of superficial "cracks" and their propagation. The face A exerts a high reinforcement effect. The fabrics with the structure of Figure 1 subsequently applied exert a high reinforcement effect. In a second preferred form the fabrics of the kind represented in Figure 1, may be directly applied to the surface to be reinforced. In the case of fabrics in which the two faces are equal among them, for example Figures 1, 1B and 1C there is no preferential side for the application, in the case of fabrics having the two faces different among themselves, for example the fabric of Figures 1A and 1D, it is preferable to apply the fabric on the surface to be reinforced by the side poorer in weft. A further advantage of the fabrics according to the present invention consists in that on them a plaster layer may be applied, which often is very important for the aesthetical aspect. The following examples are reported for illustrative aim. EXAMPLE 1 (Example of production of the fabric of Figure 1). 1a - Fabric Production: In a loom of Dornier kind Mod. HTV4/SD, having a lance with positive pliers a creel is mounted on which n. 380 reels of carbon threads of 12K kind with a title of 800 Tex are positioned. This creel is used to feed the warp threads of the loom. The weft of the loom is fed with a glass thread having a 60 Tex title coated with 40 Tex of a Hot-Melt adhesive of the copolyamidic kind with a melting temperature of about 160 °C. The loom is operated with 3.8 threads/cm of warp and with no. 2 insertions of weft thread per centimetre. A fabric having a 100 cm height is produced, gathered in the form of reels. The fabric shows a structure consisting of 3.8 threads/cm of warp of 12 K carbon threads and 2 threads/cm of weft of glass thread coated with Hot-Melt. The weight of the fabric turns out to be equal to 324 g/m 2 . 1b - Thermotreatment This fabric undergoes a thermotreatment in an apparatus consisting of one unroller, of an infrared ray heating system and of a rewinding machine. The infrared ray heating system is set to a temperature such that with a fabric passing velocity of 6 meters/minute one obtains the melting of the thermoplastic (Hot-Melt) polymer coating the weft thread. After heat treatment and subsequent cooling, the fabric is rolled up and it shows up perfectly consolidated, with the weft thread heat sealed to the warp threads. The so obtained fabric shows the following characteristics: weight = 324 g/m 2 , tensile strength, in the direction of the warp > 600 N/mm of fabric width, elastic modulus in tensile stress, in the direction of the warp = 40 KN/mm of fabric width. EXAMPLE 2 (Example of Production of the Fabric of Figures 3 and 4) A fabric produced as at the point 1a of the Example 1, with a weight equal to 324 g/m 2 , is treated for the thermal reinforcement as at point 1 b of the Example 1. To the so treated fabric, for reinforcement aim, threads of 800 Tex 12K carbon are coupled in an amount equal to 3.8 threads/cm parallelly disposed with respect to the warp threads, operating with an apparatus as schematized in Figure 6. In said Figure with (51) it is meant the fabric (46) unroller, (52) is the infrared ray heating system, (53) is the reel carrying creel feeding the threads (31) to couple to the fabric (46), (54) are the coupling rollers, (55) are pressure rollers, (45) is the fabric (46) coupled to the threads (31) and (56) is the winding machine. The so obtained reinforced fabric shows the structure represented in Figures 3 and 4, a weight equal to 628 g/m 2 , a tensile strength, in the direction of the warp > 1200 N/mm of fabric width, and an elastic modulus in tensile strength in the direction of the warp equal to 80 KN/mm of fabric width. EXAMPLE 3 (Application to building structures) 3a - Not reinforced beam A prestressed concrete beam having the following dimensions: length 2300 mm, width 190 mm, height 160 mm, reinforced inside with 4 high quality steel rods having a 8 mm diameter placed on the stretched side plus 2 rods having a 8 mm diameter on the compressed side, undergoes a three points bending load test, with a support distance equal to 1,430 mm and arranging the central load on the side 190 mm wide. A first crack formation load equal to 5,000 Kg and a breaking load of the beam equal to 8,200 Kg are determined. 3b - Beam reinforced with fabric (46) A concrete beam as at the point 3a is laminated with 3 layers of fabric prepared as in the Example 1. The application of the fabric is carried out with a bicomponent kind epoxy resin. The reinforcement having size equal to 1180 mm x 190 mm, is applied on the face of the beam having width equal to 190 mm taking care that the warp threads are disposed in the direction of the beam length. The reinforced beam is submitted to a three points bending test, as at the point 3a, taking care to arrange the reinforced face on the side opposite to the face submitted to the bending load. A first fessuration load equal to 7,800 Kg and a breaking load of the beam equal to 11,500 Kg are determined. 3c - A concrete beam as at point 3a, is laminated with a fabric prepared as in Example 2, following the lamination scheme represented in Figure 5 and according to the patterns reported at point 3b. The reinforcement having size equal to 1,180 mm x 190 mm, is applied on the beam face having a width equal to 190 mm. The so reinforced beam is submitted to a three points bending load test, with the same patterns of point 3b. A first fessuration load equal to 8,500 Kg and a breaking load equal to 11,800 Kg are determined. EXAMPLE 4 (Production of a fabric according to the Figure 1D with hot-treating carried out directly on the production loom) A fabric having the structure represented in Figure 1D is produced according to the patterns of the Example 1, using as warp a 12 K carbon thread with a title of 800 Tex and as weft a 40 Tex glass thread coated with a copolyamidic kind hot-melt adhesive, and with a melting temperature about equal to 140 °C. The hot-melt amount is such that the final deniers of the weft thread turn out to be equal to 100 Tex. The Dornier loom Mod. HTV4/SV has been modified introducing an infrared ray lamp, in order to heat the fabric produced on the loom, before the rolling up on the winding machine of the loom, with an operation wholly similar to that one described in the example 1 b. In this way one obtains directly on the loom a hot thermofixed fabric. During the weaving the loom is programmed to obtain a weaving kind as represented in Figure 1D. With this weaving style the fabric shows the two faces different one from the other, one side with a greater amount of weft, and the other one with a lower amount of weft. The so produced fabric is characterized by 3.8 threads/cm of 800 Tex 12K carbon warp and 100 Tex 1.5 weft threads, the total weight of the fabric turns out to be 320 g/m 2 . This fabric shows a tensile strength in the warp direction > 600 N/mm of fabric width and an elastic modulus in tensile stress in the warp direction equal to 40 KN/mm of fabric width. EXAMPLE 5 (Application to building structures of the fabric of the Example 4) 5a - Not reinforced beam A concrete beam having the following dimensions: length 2,300 mm, width 200 mm, height 200 mm reinforced with a reinforcement consisting of 2 steel bars located in the stretched side and 2 steel bars located on the compressed side, is submitted to a four points bending load test, with a supports distance equal to 2,000 mm and exerting a load on two points at a distance from the supports equal to 750 mm. A load of the first crack, which shows a dimension equal to 0.1 mm, equal to a 1,100 Kg total load and a breaking load of the beam about equal to 2,200 Kg are determined. 5b - Beam reinforced with a layer of a fabric according to Figure 1D. A concrete beam as at point 5a, is laminated with a layer of fabric prepared as by Example 4, taking care of applying the face of the fabric with a lower amount of weft, directly in contact with the concrete surface. The reinforcement having a dimension of 2,000 mm of length and of 160 mm of width, is applied on the beam in a way such that the warp threads are parallel to the principal direction of the beam. The lamination of the reinforcement is carried out with a bicomponent kind epoxy resin. The reinforced beam is submitted to a 4 points bending test, as by the Example 5a, taking care to arrange the reinforced face on the opposite side with respect to the face submitted to the bending load. A load of the first crack, showing a 0.1 mm dimension, equal to 2,400 Kg total load, and a breaking load equal to 5,500 Kg are determined. 5c - Beam reinforced with three layers of a fabric according to Figure 1D A second beam, reinforced with three layers of fabric 1D according to the patterns described in the Example 5b, submitted to a bending test as by the Example 5b, shows a load of the first crack, having dimensions equal to 0.1 mm, corresponding to 4,500 Kg and a breaking load equal to 8,200 Kg.

Claims: Thermotreated fabric suitable to the application as reinforcement of building works, wherein the warp consists of threads (11) of high modulus fibers, having an elastic modulus in tensile stress greater than 10 GPa (Giga Pascal) and a tensile strength greater than 600 MPa (Mega Pascal), and characterized in that the weft consists of glass threads (12) coated with a thermoadhesive polymeric material (22) having a melting temperature-from 40 to 250 °C, the amount of said thermoadhesive polymeric material being from 10 to 300% with respect to the weight of the glass. Fabric as claimed in claim 1, reinforced by thermofixing on one of its faces reinforcement threads (31) of high modulus fibers, having an elastic modulus in tensile stress greater than 10 GPa and a tensile strength greater than 600 MPa said reinforcement threads being arranged parallel with respect to the warp. Fabric as claimed in claim 1, characterized in that said warp consists of an amount of threads ranging from 1 thread/cm to 12 threads/cm. Fabric as claimed in claim 1, characterized in that said warp consists of an amount of threads ranging from 2 threads/cm to 8 threads/cm. Fabric as claimed in claim 1, characterized in that said warp threads have a title expressed in Tex (weight in g per 1,000 m of thread) ranging from 20 Tex to 10,000 Tex. Fabric as claimed in claim 1, characterized in that said warp threads have a title expressed in Tex ranging from 40 Tex to 1,000 Tex. Fabric as claimed in claims from 1 to 6, wherein the warp threads may be of a material different from one another. Fabric as claimed in claim 1, characterized in that said weft threads consist of a glass thread having a title ranging from 20 to 100 Tex. Fabric as claimed in claim 1, characterized in that said weft threads may combine with different dispositions with the warp threads. Fabric as claimed in claim 1, characterized in that said high modulus fibers are selected from the group consisting of rayon fibers, high toughness polyester fibers, polyvinyl alcohol fibers, polyethylene fibers, aramidic fibers, carbon fibers, glass fibers and fibers from liquid crystal polymers. Fabric as claimed in claim 1, characterized in that said thermoadhesive polymer is selected from the group consisting of polyolefinic, polyvinylic, polyamidic, polyester and polyurethanic polymers and copolymers. Process for the application of the fabric as claimed in claims 1 to 11 on the surface (41) of building structures by impregnation resins, characterized in that to said surface are subsequently applied a layer (42) of impregnation resin, the reinforced fabric (45) according to claim 2, a second layer (47) of impregnation resin, the fabric (46) according to any of claims 1 to 11 and a third layer of impregnation resin (48). Process as claimed in claim 12, characterized in that such fabric may show any kind of disposition of the weft with respect to the warp. Process as claimed in claim 12, characterized in that to said surface are subsequently applied a layer of impregnation resin, a layer of fabric and a second layer of resin. Process as claimed in claim 12, characterized in that said reinforced fabric is applied with the face containing the reinforcement threads facing the surface of the building structure. Use of the fabric as claimed in claims from 1 to 11 in the preparation of composite materials.

Inventors: CREDALI LINO, CREDALI, LINO
Applicants: CREDALI LINO, CREDALI, LINO
Application year: 1999
Main classification: E04G23
IPC codes: E04C5, E04G23