KR100811802B1 - Rib materials for use in concrete reinforcing rod - Google Patents

Abstract

The present invention is integrated coating on the surface of the carbon fiber and glass fiber (or non-conductive other fiber) composite rod (bar,) or glass fiber (or non-conductive other fiber such as aramid fiber) that can be used as a rod for concrete reinforcement The present invention relates to a rib material composed of a finely pulverized carbon fiber and coke powder mixed material having electrical conductivity.

Fiber rod, finely ground carbon fiber powder, coke powder, rib material, smart sensor, maintenance

Description

RIB MATERIALS FOR USE IN CONCRETE REINFORCING ROD

1 is a photograph of a composite annular rod of carbon fiber and glass fiber to which the rib material of the present invention is applied.

FIG. 2 is an enlarged photograph of a rib material coated composite annular rod in which the rib material of the present invention is applied to the composite annular rod shown in FIG.

3 is a photograph of a rib material coated composite annular rod to which the rib material of the present invention is applied.

Figure 4 is a photograph of one of the manufacturing process of the concrete test specimen to the rib material coated composite annular rod of the present invention.

5 is a schematic view for testing a test body of a concrete structure with rib material coated composite annular rod of the present invention.

Figure 6 is a graph showing the test results for the test body of the concrete structure of the present invention.

The present invention is a rib material for facilitating the safety diagnosis and maintenance of a concrete structure, when using a continuous fiber rod that is one of the reinforcing bars for reinforcing the concrete structure, the continuous fiber rod itself is determined in advance by the failure prediction information The present invention relates to a rib material having a smart sensor function in a concrete structure to ensure safety.

Recently, a method of constructing a structure by using a continuous fiber rod to replace a reinforcing steel bar when constructing a concrete structure has been examined. In some structures, such a continuous fiber rod is used as a reinforcing material. In this case, however, many studies have been conducted on the fracture characteristics of continuous fiber rods, and there are no clear design guidelines in this field. Therefore, in order to use the continuous fiber rod as a reinforcing bar, special attention must be paid to safety.

In addition, as the interest in effective and efficient maintenance of concrete structures increases, new design methods, materials, and construction methods are being developed. If it is possible to diagnose and predict the destruction of materials on their own, it is possible to cope more effectively. have. Strain gauges and displacement meters have been used for the measurement of material failure, but in the case of concrete materials, the measured values are greatly influenced by the shape of the crack propagation. Therefore, the reproducibility is poor and the initial conditions need to be set. It is difficult. In the large test member, the failure position and the measurement position are difficult to match, and the use of a large number of sensors has not solved the fundamental solution in the conventional method such as the cause of the measurement error and the high cost. Therefore, the development of a new failure prediction sensor for the structure is required.

In this regard, a study has been reported to give a self-diagnostic function to the destruction of concrete from the change of electrical and mechanical properties of the internal carbon fiber using a composite rod composed of carbon fiber and glass fiber. However, such research and development technology must use a hybrid rod in which carbon fiber and glass fiber are combined to give a failure detection function in advance, and has a disadvantage in that it is not sensitive to the detection of fracture signs of concrete.

The present invention is to solve such a problem as to give a sensor function to detect the early signs of destruction in the early stage to the material itself to establish a countermeasure at this stage to prevent the structure from reaching the ultimate destruction It is intended to be. In addition, the main purpose of the present invention is to provide a sensor function to the material itself in order to minimize the economic burden of using a separate sensor.

In order to achieve this purpose, finely pulverized in order to improve friction and adhesion with concrete on the surface of the composite rod of carbon fiber and glass fiber or carbon fiber and aramid fiber, which is already commercialized in Korea, and glass fiber or aramid fiber alone rod A rib material was developed to form the ribs on the rods by selecting the optimum blending condition of milled carbon and coke powder, mixing them with the binder, and integrally coating the rods.

The present invention provides an electrically conductive rib material comprising finely pulverized carbon fiber and coke powder as an electrically conductive rib material applied by a binder on the surface of a glass fiber or a concrete reinforcing rod made of glass fiber and carbon fiber.

Preferably, the present invention is an electrically conductive rib material applied by the binder on the surface of the glass fiber or concrete reinforcing rod made of glass fiber and carbon fiber, 3 to 5% by weight of finely ground carbon fiber and coke powder 95 To about 97% by weight of electrically conductive rib material.

The concrete reinforcing rod to which the rib material of the present invention is applied is preferably a composite annular rod of carbon fiber and glass fiber or a circular rod of glass fiber alone, which is commonly used in the art as an annular rod or a circular rod.

The amount of finely ground carbon fibers used in the electrically conductive rib material of the present invention is 3 to 5% by weight, preferably 4% by weight, and the amount of coke powder is 95 to 97% by weight, preferably 96% by weight. If the amount of finely pulverized carbon fiber is less than 3% by weight, the electrical resistance of the rib made from the rib material is too small, so that the change in electrical resistance that can detect the deformation of the concrete formed with the reinforcing bar containing such rib is detected. Difficult to measure On the other hand, if the amount of finely pulverized carbon fiber exceeds 5% by weight, the electrical resistance of the rib is too large, it is to measure the change in electrical resistance that can detect the deformation of the concrete formed with the reinforcing bar including the rib impossible.

The coke powder used in the electrically conductive rib material of the present invention serves to improve the bonding force and friction between the reinforcing bar and the concrete, and the amount used is determined according to the amount of finely pulverized carbon fiber.

The binder used to apply the rib material of the present invention to the reinforcing bar is preferably an epoxy resin, an acrylic resin, or a fluororesin.

The rib material of the present invention is coated on the surface of the concrete reinforcement by a binder, so that the electrical conductivity is changed when the concrete is deformed to act as a sensor for the deformation of the concrete.

The present invention also provides a rod for concrete reinforcement comprising a rib in which the rib material is coated on the surface by a binder.

In addition, the present invention provides a concrete structure reinforced by the rod for reinforcing concrete.

The electrically conductive rib material of the present invention forms a rib integrated with the concrete reinforcing rod. When concrete is manufactured by reinforcing rods for reinforcing concrete with such ribs for the same use as reinforcing bars, when the load is applied from the outside of the structural member, the reinforcing bar is deformed according to the tensile force applied to the reinforcing bar, and the conductive rib material When the resistance value changes and the change of the electrical resistance value is measured together with the load change, the failure detection information of the rod can be predicted from the initial change characteristic of the electrical resistance value before the reinforcing bar is totally destroyed. Therefore, it is possible to use the rib material of the type developed in the present invention as a smart sensor having a self-diagnostic function, it is possible to detect and notify the risk stage of destruction in advance at a low cost to ensure the safety and maintenance of the structure The management efficiency can be obtained by the structural material itself.

In the present invention, the conventional composite rod having the fracture self-diagnosis function can be further provided with a new rib formed from the rib material having the sensor function with the conductivity added thereto. In the case of the composite rod to which the rib material of the present invention is applied, the reason why the failure detection function is improved is that when the tensile force acts by the external load in the concrete, the force is first transmitted to the outermost rib so that the innermost composite rod It is because it reacts sensitively to the load change step by step before the carbon fiber, and as a result, it is possible to detect the load change of the initial step before the carbon fiber located in the innermost part, so that the signs of destruction can be detected in advance. The rib material of the present invention is also applicable to rods used alone, such as glass fibers, aramid fibers, and the like.

When the concrete reinforcing rod is applied to the rib material of the present invention, the concrete structure itself has a failure prediction function, thereby enabling environmental conservation by reducing life and damage due to accidental reduction of accidents and saving materials. In addition, if a failure prediction sensor is developed in a simple and inexpensive manner that has sufficient time for failure prediction and can be used in a hazardous location or a place where it cannot be visually inspected, there is a great practical effect. One effective method is that the material used in the concrete structure itself is smart (or intelligent) to self-destructive destruction. If the material itself is capable of self-determining the breakdown process, the use of complex circuits and multiple sensors is unnecessary and eliminates the need for a strong and heavy design.

Specific preferred embodiments of the present invention are described below by way of example, but the present invention is not intended to be limited thereby.

Example

Example 1 Preparation of a Carbon Fiber and Glass Fiber Composite Circular Rod Applying Finely Crushed Carbon Fiber and Coke Powder Rib Material

Two materials of finely ground carbon fiber and coke powder having conductivity are mixed at an appropriate ratio (finely ground carbon fiber powder: 0.8 g, coke powder: 19.2 g) to prepare rib materials, and carbon fibers and glass fibers Epoxy resin (brother bond, instant adhesive: sibling chemical company, or Daeho Glutech) is applied on the surface of the composite annular rod (8.5mm, Dongwon Construction Co., Ltd.) in uniform thickness and the rib material is coated (used in the experiment). A rib material coated composite annular rod was manufactured to improve the problem of deterioration of adhesion and friction, which is a disadvantage of the reinforcing bar. The photograph of the manufactured product is shown in FIG. 3.

Experimental Example  One

<Condition Conditions of Concrete and Example  Made in 1 live  Properties of Material Coated Composite Annular Rods>

The concrete mix was formulated according to the standard concrete mix table of 28 N / mm2 design strength, and test specimens for flexural strength (400 mm wide, 100 mm long and 100 mm high) were prepared according to KS F2403 and KS F 2407. The mixing conditions of the concrete are shown in Table 1, and the characteristics of the rib-coated composite annular rod manufactured in Example 1 as the composite annular rod used in this experiment are shown in Table 2.

Gmax ^{1 ).} (mm) Slump (cm) Air volume (%) W / C ^{2 )} (%) s / a ^{3 )} (%) Unit material amount (kg / ㎥) AE agent (g / ㎥) W ^{4 )} C ^{5 )} S ^{6 )} G ^{7 )} 20 mm 10 cm 5% 44% 42% 185 439 671 962 132

                    Characteristics Fiber Type Rod diameter (mm) Tensile Strength ( MPa ) Modulus of elasticity ( MPa ) Electric resistance ( Ω ) Test body No. road CFGFRP ^{8 )} (CF 3.3 Vol.%) GFRP ^{9 )} 11 2500 0.437 × 10 ⁵ 6.0 CG1 to CG2 ¹⁰⁾

1) Maximum value of gravel 2) Water content ratio 3) Fine aggregate content 4) Water 5) Cement 6) Fine aggregate 7) Coarse aggregate 8) Carbon-glass fiber reinforced plastic 9) Glass fiber reinforced plastic 10) CFGFRP

<Bending failure test of test specimen>

The flexural failure test and measurement overview of the test specimen prepared by inserting the rib material coated composite annular rod are shown in FIG. 5. Measurements were performed using LVDTs, strain gauges and electrical resistance measuring instruments and load cells to obtain the relationship between deflection of concrete and flexural strain-carbon fiber rod, flexural tensile strain-electrical resistance of finely ground carbon fiber and coke powder rib material. Was used. The test body produced by FIG. 4 was installed in the bending fracture test apparatus. At this time, as shown in Figure 5, the lower end of the test specimen is provided with a strain gauge for measuring the tensile strain and the electrical resistance-load relationship between the finely pulverized carbon fiber and the coke powder rib material of the rod visible on both ends of the test specimen, carbon To obtain the electrical resistance-load relationship of the fiber rod, fix it at both ends using an electrical resistance measuring device. The data of load-deflection-electrical resistance that appeared while applying a load were obtained.

Experimental Method

As described above, after fabricating a test specimen for testing the concrete bending strength in which the carbon fiber and glass fiber composite annular rods prepared in Example 1 were inserted (reinforced) (see FIG. 4), the electrical resistance-load in the same manner as in FIG. Strain was measured. Photographs of carbon fiber + glass fiber composite annular rods and composite annular rods with rib materials are shown in FIGS. 1 and 2, respectively. The experiment focused on the measurement of the cell resistance change of the carbon fiber rod side of the carbon fiber and glass fiber composite annular rods and the finely pulverized carbon fiber and coke powder rib material at each loading stage. Figure 6 shows the measurement results for these graphically.

<Experiment Result>

The experimental results are as follows. In the relationship between the electrical resistance-load-strain of finely pulverized carbon fiber and coke powder rib material, the change in the electrical resistance starts to be detected immediately after the crack occurs (immediately after sagging) as shown in FIG. 6. It can be seen that the change from the rib material, which is the outer part, appears first, and then as the concrete crack progresses, the electric resistance change in the carbon fiber rod, which is the inner core of the composite rod, is also detected. As the load continues to increase, the carbon fiber rod reaches breakdown, and the electrical resistance progresses to infinity, indicating that this stage is the breakdown stage of the carbon fiber. However, the more ductile glass fibers have not yet been destroyed at this stage, so the entire concrete specimen has not yet been destroyed. Therefore, the electrical resistance change from the ribbed material made of finely pulverized carbon fiber and coke powder imparting conductivity in the present invention starts to be detected first, and thus the failure prediction of the test specimen can be predicted earlier, so that the sensor function is a complex rod. It can be seen that it may be useful to react more sensitively than the carbon fiber rod in the interior. That is, the present invention can be a more advantageous method for ensuring the safety of the structure. In addition, the sensitivity of the failure prediction can be adjusted by appropriately adjusting the finely pulverized carbon fiber and coke powder of the rib material.

In Fig. 6, the dotted line indicates the load-deflection relationship of the test specimen used in the experiment, and the dashed line indicates the electric resistance-deflection relationship between the finely ground carbon fiber and the coke powder rib material, and the solid line indicates the electric resistance-deflection of the carbon fiber rod. The relationship is shown.

The present invention prevents human damage and property loss (disaster) by proactively predicting or predicting the structure completely before it is destroyed, minimizing the economic burden due to the rapid promotion of the remedial measures, maximizing the safety of the structure, It is possible to secure economical and efficient sensor function by applying sensor function of the material used itself, and can greatly contribute to effective and efficient maintenance utilization of concrete structure reinforced with continuous fiber rod.

Claims (7)

An electrically conductive rib material coated by a binder on a surface of a glass fiber or a concrete reinforcing rod made of glass fiber and carbon fiber, comprising 3 to 5% by weight of finely ground carbon fiber and 95 to 97% by weight coke powder Electrically conductive rib material. The electrically conductive rib material according to claim 1, wherein the amount of finely ground carbon fibers is 4% by weight and the amount of coke powder is 96% by weight. The electrically conductive rib material according to claim 1 or 2, wherein the binder is an epoxy resin, an acrylic resin, or a fluororesin. The electrically conductive rib according to claim 1 or 2, wherein the electrically conductive rib material is coated on the surface of the concrete reinforcement by a binder so that the electrical conductivity is changed when the concrete is deformed to act as a sensor for the deformation of the concrete. material. A rod for reinforcement of concrete comprising a rib in which the electrically conductive rib material according to claim 1 is coated on the surface by a binder. The concrete reinforcing rod according to claim 5, wherein the binder is an epoxy resin, an acrylic resin, or a fluororesin. Concrete structure reinforced by a rod for reinforcing concrete according to claim 5.

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