USE OF PREPREGS IN STRUCTURES AS A REINFORCING MATERIAL

Abstract

A prepreg suitable for use in order to reinforce a concrete or a load bearing material is provided, and the prepreg includes a polymer matrix comprising at least two components, and at least one fiber. The polymer matrix is in a ratio of 50-70% by weight relative to a total weight of the prepreg and the at least one fiber is in a ratio of 30-50% by weight relative to the total weight of the prepreg. Furthermore, the prepreg is used for damaged structures, structures with a modified structural function, or reinforcement in concretes.

Claims

1. A prepreg suitable for use in order to reinforce a concrete or a load bearing element comprising a polymer matrix, wherein the polymer matrix comprises at least two resins and at least one fiber, and the polymer matrix is in a ratio of 50-70% by weight relative to a total weight of the prepreg and the at least one fiber is in a ratio of 30-50% by weight relative to the total weight of the prepreg.

2. The prepreg according to claim 1, wherein the prepreg is cured with a temperature and/or a pressure.

3. The prepreg according to claim 1, wherein the at least two resins are selected from the group consisting of epoxy, phenolic, polyurethane, vinylester and polyester or combinations of the epoxy, the phenolic, the polyurethane, the vinylester and the polyester.

4. The prepreg according to claim 1, wherein the at least one fiber is manufactured from a fiber selected from the group consisting of carbon, aramid, glass, polyester, polyethylene, nylon and polyolefin, or combinations of the carbon, the aramid, the glass, the polyester, the polyethylene, the nylon and the polyolefin.

5. The prepreg according to claim 1, wherein the at least one fiber is carbon.

6. A prepreg suitable for use in order to reinforce a concrete or a load bearing element, wherein the prepreg is used for reinforcing damaged structures, construction with a modified structural function or concretes.

7. The prepreg according to claim 1, wherein the prepreg is applied on a concrete surface or on a carrier material without a gap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is the view of granulometry graphic formed as a result of test graphic of designing aggregates used in concrete manufacture compatible with EN 1766-2000 standard such that the largest aggregate size will be 16-20 mm.

[0015] FIG. 2 is the view of comparison graphic between breaking behavior of concrete samples with prepreg under bending effect and breaking behavior of reference concrete.

[0016] FIG. 3 is the view of normal concrete designed as C30 and reinforced concrete sample wound 2 times.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Concrete which is made of aggregate, cement and water mixture is commonly used as construction material. In time, damage is experienced in concrete due to environmental conditions, the content of the concrete and the disadvantages caused by the application errors. Solutions have been found in the state of the art for the reduction of these damages before or reinforcing the damaged concretes. One of these solutions is to form reinforced concrete by using steel reinforcements in the concrete structures, and thus the concrete is reinforced. However, corrosion of steels in the reinforced concrete, being heavy and low tensile strength are not enough for achieving ductile behavior of the concrete. Another solution for this problem is to develop a composite material manufactured from fiber and polymer resins, the said composite material is applied on the concrete surface with hand lay-up method. However, the composite materials applied with this method not being homogeneous and not being able to provide a standard quality causes them being costly and harmful to the environment. A prepreg suitable for use in reinforcing the concrete or a load bearing material is developed with the present invention.

[0018] The prepreg which is developed with the present invention comprises a polymer matrix comprising at least two resins (preferably in ratio of 50-70% relative to the total weight of the prepreg) and at least one giber (preferably carbon) (preferably in ratio of 30-500% relative to the total weight of the prepreg).

[0019] Since fiber/resin ratio of the prepreg developed with the present invention, maximum load bearing is achieved in unit material use. The prepreg layers are made ready to be cured upon the application of the prepreg developed with the present invention on the surface of the concrete or a material to be reinforced. The prepreg which is developed is cured with temperature and pressure.

[0020] In a preferred embodiment of the invention, the said at least two resins are selected from the group consisting of epoxy, phenolic, polyurethane, vinylester, polyester or combinations thereof.

[0021] In another preferred embodiment of the present invention, the said fiber is manufactured from a fiber selected from the group consisting of carbon, aramid, glass, polyester, polyethylene, nylon, polyolefin or combinations thereof. The shelf life of the prepreg that is developed is 1-1 year at −10° C./−20° C. and the operation life under room conditions is 3-6 weeks.

TABLE-US-00001 TABLE 1 Fiber Fiber Shelf life (−10° Operation life type content C./−20° C.)) under room Carbon, glass, 50-70% 1-2 y.sub.1l 3-6 hafta aramid, nylon, indicates data missing or illegible when filed

[0022] An application of the present invention is shown in Table 2, wherein the said fiber is carbon having 12 k filament number. Furthermore, the strength of the said carbon is 5000 Mpa, and its elasticity modulus is 250 GPa.

TABLE-US-00002 TABLE 2 Number of Elasticity Yarn Filaments Strength modulus Carbon 12k 5000 MPa 250 GPa

[0023] The prepreg which is developed with the present invention is applied on the concrete surface or on the load bearing material without gap.

[0024] The prepreg which is developed with the present invention is used reinforcing constructions with modified structural function or concretes.

[0025] In another embodiment of the present invention, the composition of a concrete reinforced with the prepreg is shown in Table 3, wherein the said concrete comprises portland cement (preferably CEM I 42.5 R), water and air. The water/cement ratio of the said portland cement by weight is preferably 0.40-0.65. In addition, the volume of the portland cement is in the range of 49.04-79.62 dm.sup.3, and its weight is between 154-250 kg. The specific weight of the cement is 3.14 g/dm.sup.3. The amounts used for the production of 1 m.sup.3 of concrete wherein the prepreg developed by the present invention is applied, are given in Table 4.

TABLE-US-00003 TABLE 3 DYK, specific Water/ Volume weight Weight Material Grass [dm3] [g/dm3] [kg] CEM I 42.5 R 0.40-0.65 49.04-79.62 3.14 154-250 Water 100 1 100 Air 10-25 Total of partial volume 159.04-204.62

TABLE-US-00004 TABLE 4 DYK specific Volume weight Weight Aggregates % [dm.sup.3] [g/dm.sup.3] [kg/m.sup.3] Sand 45 324.6 2.64 856.9 Crushed stone no 1 25 180.3 2.65 477.8 Crushed stone no 2 30 216.4 2.67 577.7 Total volume of aggregates 721.3 Volume of additives 2.5 Total volume and weight 1000.0 2372.7

[0026] In another embodiment of the present invention, the aggregate properties in the content of a concrete reinforced with the said prepreg were examined, and the obtained results with the experiments are shown in Table 5. Furthermore, the granulometry graphic formed as a result of the test graphic of designing aggregates used in concrete manufacture compatible with EN 1766-2000 standard such that the largest aggregate size will be 16-20 mm is shown in FIG. 1.

TABLE-US-00005 TABLE 5 Aggregates Sieve, mm Natural sand NO1 NO2 Mixture 31.5 100.0 100.0 100.0 100.0 22.4 100.0 100.0 100.0 100.0 20 100.0 100.0 100.0 100.0 16 100.0 100.0 97.9 99.4 10 100.0 95.6 10.2 72.0 8 100.0 64.9 2.6 62.0 5.6 99.3 23.2 0.6 50.7 4 93.3 2.6 0.6 42.8 2 74.1 0.0 0.6 33.5 1 56.8 0.0 0.6 25.7 0.5 38.5 0.0 0.6 17.5 0.25 20.1 0.0 0.6 9.2 0.125 8.4 0.0 0.6 3.9 Mixture 45 25 30 100

[0027] In another embodiment of the present invention, the results obtained as a result of the application of ASTM C1609 (Measuring the flexural tensile strength) test in the beam of a concrete reinforced with prepreg are expressed in Table 6. Samples numbered as 1 and 2 were retrofitted with the same method and materials, and they are casted with same mix design, and the results are aimed to be in a certain value range. In the tests that were performed, sample sizes of the concrete beam were determined as 15*15*50 cm, and the effective span is 45 cm. After this experiment, the behavior of the concrete after the first breaking point (area under the bending-displacement curve) under the tensile effects due to bending and the ductility rate were calculated by using the geometry of the sample. The ductility rate of the concrete reinforced with prepreg is calculated as minimum 74, and the ductility rate of the reference concrete is 20-25. The ductility rate of the concrete applied with prepreg as reinforcing material with the present invention is 3 times of the reference concrete. The comparison graphic of the breaking behavior of the said retrofitted with prepreg concretes under bending effect and the breaking behavior of the reference concrete is shown in FIG. 2. In accordance to this, while the bearing capacity of the reference concrete decreases, the bearing capacity of the concrete reinforced with prepreg is 3 times more than the reference concrete. The average compressive strength tests were performed between the said normal concrete and the concrete reinforced with the prepreg, and the results are given in FIG. 3. The average compressive strength between the twin samples of the concrete designed as C30 has increased from 29.9 MPa to 60.58 MPa.

TABLE-US-00006 TABLE 6 Maximum Maximum Breaking Breaking load stress Area load of stress of carried by carried by below concrete concrete concrete concrete the curve Duc- sample sample sample sample (0-3 mm) tility No [kN] [MPa] [kN] [MPa] [Joule] rate 1 36.95 4.93 52.15 6.95 94.11 84.89 2 37.49 5.00 55.30 7.37 83.55 74.27

[0028] By means of the prepreg which developed with the invention and suitable for use in reinforcing concrete or a load bearing material, occupational safety is ensured, application can be made without exceeding gelling time, and therefore high wrapping quality can be achieved. Furthermore, wrapping times being short enables the viscosity of epoxy which is one of composite components not to change due to weather conditions, and thus prevents the application process to be negatively affected. The amount of material that is used is standardized, and homogenous wrapping is achieved. While labor cost is reduced, the quality is increased with the said application.