CN115791598A - Test method for testing bonding performance of reinforced concrete beam under simultaneous action of corrosion and fatigue load and corrosion acceleration device - Google Patents
Test method for testing bonding performance of reinforced concrete beam under simultaneous action of corrosion and fatigue load and corrosion acceleration device Download PDFInfo
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- CN115791598A CN115791598A CN202211407939.0A CN202211407939A CN115791598A CN 115791598 A CN115791598 A CN 115791598A CN 202211407939 A CN202211407939 A CN 202211407939A CN 115791598 A CN115791598 A CN 115791598A
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Abstract
The invention provides a test method for testing the bonding property of a reinforced concrete beam under the simultaneous action of corrosion and fatigue load and a corrosion acceleration device, wherein the device comprises a water pump, the water pump is arranged in a water tank, a switch is controlled by a timer, and a sodium chloride solution is arranged in the water tank; the solution pumped by the water pump is connected above the bonding area of the reinforced concrete beam to be detected through a water pipe; the bonding area is wrapped with a circle of sponge, and a circle of plastic film is wrapped outside the sponge; a stainless steel wire is pre-buried in advance in the reinforced concrete beam to be detected, the stainless steel wire is connected to the negative pole of an external direct-current power supply, the positive pole of the power supply is connected with the reinforced concrete beam to be detected, and a first displacement meter, a second displacement meter, a first strain gauge and a second strain gauge are fixed on the reinforced concrete beam to be detected. The device and the test method for accelerating corrosion provided by the invention can objectively, accurately and simply measure parameters such as the bonding performance of the reinforced concrete beam under the simultaneous action of corrosion and fatigue load.
Description
The technical field is as follows:
the invention relates to the technical field of civil engineering concrete structure tests, in particular to a test method for testing the bonding property of a reinforced concrete beam under the simultaneous action of corrosion and fatigue load and an accelerated corrosion device.
Background art:
coastal region Reinforced Concrete (RC) bridge structure faces complex service environment including the action of chlorine salt corrosion such as seawater immersion or dry-wet cycle and high-concentration CO in atmospheric environment caused by heavy use of fossil fuel 2 And acid rain. CO 2 2 、O 2 Corrosive media such as water and chloride ions can enter the concrete through the load cracks, so that the concrete is neutralized, the alkalinity is reduced, a passivation film on the surface of the steel bar is damaged, and the steel bar is easily corroded. Meanwhile, the reinforced concrete bridge structure may be subjected to a fatigue action effect by a vehicle load or the like in a normal use state. Fatigue loading results in structural damage and damage accumulation, such as crack propagation in concrete, structural stiffness and ductility degradation, and the like. Although the bearing capacity of the structure cannot be obviously influenced by the generation and the development of cracks, corrosion media in the surrounding corrosion environment can be accelerated to enter the interior of concrete for the engineering structure in the coastal region, and then the corrosion of the reinforcing steel bars is accelerated.
The bonding property between the steel bars and the concrete influences the crack development and stress distribution in a Reinforced Concrete (RC) flexural member and is very important to the mechanical property of the structure. The bonding stress between the deformed steel bars and the concrete is mainly provided by mechanical engagement force, and when corrosion occurs, the volume expansion of corrosion products can cause the change of the bonding force; the bonding performance between the steel bars and the concrete can be obviously influenced by the action of fatigue loads such as train load and the like. When the reinforced concrete structural member is corroded in service, the structure is always under the fatigue stress condition, namely, the corrosion of the reinforced steel bar and the fatigue load function simultaneously. At present, in a test about the influence of steel bar corrosion and fatigue load on the bonding performance of a steel bar and concrete, the adopted method is that the steel bar corrosion process and the fatigue load application process are carried out separately, and the method is not consistent with the situation that the corrosion and the fatigue load are carried out simultaneously in the actual engineering. Therefore, there is a need in the art for a test apparatus that can simultaneously perform corrosion and fatigue loading and is simple to operate.
Also, in the method for testing adhesive properties, the drawing test is widely used because of its simple operation. In the drawing test piece, the steel bar and the concrete around the steel bar are in a compression state and a tensile stress state respectively, and a compression bar is formed between a loading point and the surface of the steel bar to cause the surface of the steel bar to be compressed. However, this stress state is different from that of most reinforced concrete members in which the reinforcing bars and their surrounding concrete are in tension and the reinforcing bar surface compression is due to slippage between the concrete and the reinforcing bars, rather than a load. In addition, during the pull test, the load end constraint limits concrete cracking, which can lead to an overestimation of the bond strength. Therefore, the drawing test has poor applicability to the research of the bonding strength of the actual engineering, and a beam test reflecting the bonding stress state in the reinforced concrete structure of the actual engineering needs to be developed. However, a test method based on the influence of both steel bar corrosion and fatigue load on the bonding performance of the reinforced concrete beam is not available at present.
The invention content is as follows:
the invention aims to provide a test method for testing the bonding property of a reinforced concrete beam under the simultaneous action of corrosion and fatigue load and a corrosion acceleration device, so as to efficiently and simply simulate the bonding property degradation process of the reinforced concrete beam under the simultaneous action of corrosion and fatigue load in actual engineering and make up for the vacancy in the prior art.
The technical scheme adopted for achieving the purpose of the invention is as follows:
a test device for testing the bonding performance of a reinforced concrete beam under the simultaneous action of corrosion and fatigue load comprises a water pump, wherein the water pump is placed in a water tank, a switch is controlled by a timer, a sodium chloride solution is placed in the water tank, and the solution pumped out by the water pump is connected above a bonding area of the reinforced concrete beam to be tested through a water pipe; the bonding area is wrapped with a circle of sponge, and a circle of plastic film is wrapped outside the sponge; a stainless steel wire is pre-buried in advance in the reinforced concrete beam that awaits measuring, and stainless steel wire is connected to outside DC power supply negative pole, and the reinforcing bar that awaits measuring is connected to the power positive pole, and the reinforcing bar both sides that await measuring of bonding area are fixed with first displacement meter, second displacement meter, are fixed with first foil gage, second foil gage on the reinforcing bar that awaits measuring in the recess.
Preferably, a circle of sponge is pasted outside the surface of the bonding area of the reinforced concrete beam and covers a plastic film, and a stainless steel wire needs to be pre-embedded in the reinforced concrete in advance.
Preferably, the accelerated tarnishing process is performed simultaneously with the fatigue load application process.
A test method for testing the bonding performance of a reinforced concrete beam based on the simultaneous action of corrosion and fatigue load comprises the following steps:
(1) Pouring the reinforced concrete beam: manufacturing a wood mould, sequentially placing and binding PVC pipes, longitudinal bars and stirrups in the wood mould, pouring concrete on the top of the wood mould, reserving stainless steel wires, vibrating, maintaining and removing the mould to obtain a reinforced concrete beam test piece;
(2) Installing a loading device: fixing the test piece on an MTS fatigue testing machine;
(3) Preloading: preloading a test piece, firstly applying a vertical load not exceeding 5kN to enable the test piece to be in close contact with a support of the MTS fatigue testing machine, then unloading to zero, and fixing a first displacement meter at a free end and fixing a second displacement meter at a loading end;
(4) The corrosion and loading of the test piece are accelerated: wetting sponge with a sodium chloride solution, carrying out accelerated corrosion on a test piece, operating an MTS fatigue testing machine to enter a loading mode, selecting fatigue loading in the loading mode, and sampling test data required by displacement, load and the like;
(5) Data processing and analysis: processing the test, calculating the actual quality loss rate and the relative slip of the steel bars and the average bonding stress of the bonding area, and accordingly judging the bonding slip performance of the test piece under different fatigue load amplitudes;
preferably, in the step (1), a groove with a length of 100mm is left on one side of the bonding region at one end.
Preferably, in step (3), the displacement meter used is an eddy current displacement sensor.
Preferably, in the step (4), the mass fraction of the sodium chloride solution is 3.5% when the corrosion is accelerated, and the corrosion current density is not more than 200 mu A/cm 2 。
Compared with the prior art, the invention has the following beneficial effects:
the test method for testing the bonding and sliding performance of the reinforced concrete under the simultaneous action of the corrosion and the fatigue load, provided by the invention, has the advantages of simplicity and convenience in operation, high measurement precision and high coincidence degree with the actual engineering, and supplements the defects of the test method under the simultaneous action of the corrosion and the fatigue load.
The invention also provides a corrosion acceleration device which can be widely used for the related test of the bonding and sliding performance of the reinforced concrete under the simultaneous action of corrosion and fatigue load.
At present, in the test for detecting the adhesiveness of the corroded reinforced concrete beam under the action of fatigue load, the method is to electrify in a set environment in advance to accelerate corrosion, and apply fatigue load to a component after the corrosion is finished. However, this error is much larger than the actual error, and therefore, a device in which the fatigue load and the corrosion are simultaneously performed is desired.
Considering that the displacement of the beam is changed frequently in the loading process, the eddy current displacement sensor adopting non-contact measurement ensures accurate data.
In the current experiment, because the fatigue load and the corrosion are separately carried out, and the fatigue load and the corrosion process are simultaneously carried out, other students fix iron sheets and the like outside the beam as a negative electrode to easily damage a corrosion device in the experiment process, so a stainless steel wire is pre-buried in advance as the negative electrode.
In order to ensure that the bonding area has enough salt solution, the automatic spraying is controlled by a water pump and a timer.
The device can reduce the things needed to be done by experimenters in the experimental process, reduce the disturbance to the experimental result, and can add some instruments to measure the needed data according to the needs. The device is characterized in that a layer of sponge and a steel sheet are wrapped by a plastic film in a bonding area in the process of experiments by current scholars, but fatigue load and corrosion are carried out simultaneously, the steel sheet damages the film in the process of applying the fatigue load, and therefore the problem is avoided by pre-embedding stainless steel wires.
The sensor is adopted because in the application process of corrosion and fatigue load, if the traditional displacement meter (the displacement meter with the thimble) is adopted, the error of the experimental result is large or the displacement meter is damaged
The salt concentration is that many scholars in the corrosion in-process, circular telegram corrosion with the test piece bubble in a large container, has prolonged solution concentration change like this, uses an external pump, only needs the solution concentration who controls the pump place basin in can avoid solution concentration change to experimental influence, and the operation is got up and is simpler than the concentration of controlling every test piece place in the large container.
The specific salt concentration can be configured according to the needs
Drawings
Fig. 1 is a schematic sectional view of a reinforced concrete beam according to the present invention.
Fig. 2 is a schematic front cross-sectional view of a reinforced concrete beam according to the present invention.
Fig. 3 is a schematic diagram of the reinforced concrete beam of the present invention after the form removal.
FIG. 4 is a schematic front view of the apparatus for accelerating rusting in the present invention.
FIG. 5 is a front sectional view of the apparatus for accelerating rusting of a reinforced concrete bonding area according to the present invention.
Detailed Description
The test method for testing the bonding performance of the reinforced concrete beam based on the combined action of corrosion and fatigue load is specifically described below with reference to the accompanying drawings.
The method comprises the following steps: pouring reinforced concrete beam
As shown in FIG. 1, a wooden mold having a length, width, and height of 1500mm × 120mm × 200mm was produced. A100 mm long groove is arranged from the first support to the 150mm position of the other support in the direction, and the depth of the groove is 72mm. The wood pattern is punched at the free end and the groove along the length direction, the aperture is 25mm, the distance between the center of the hole and the bottom is 52.5mm, and the distance between the center of the hole and the two sides is 62.5mm. And (3) penetrating the hot-rolled ribbed steel bar with the diameter of 20mm and a PVC plastic sleeve into the hole, wherein the inner diameter of the PVC plastic sleeve is slightly larger than the diameter of the steel bar, and the steel bar on the other side of the groove is bent. The side surface of the free end wood die is punched, the aperture is 5mm, the distance between the center of the hole and the bottom is 102.5mm, the distance between the center of the hole and the two sides is 60mm, and a stainless steel wire with the length of 400mm penetrates through the hole. The positions of the reinforcing steel bars, the sleeve and the stainless steel wire are adjusted to meet the size requirement shown in figure 1, and the interface of the reinforcing steel bar bonding area and the non-bonding area is sealed by silica gel to prevent slurry leakage. The frame studs and stirrups are tied in the position shown in figure 2. And (5) performing rust prevention treatment on the surfaces of the stirrups and the erection bars by using epoxy resin. Pouring concrete from the top, vibrating, curing, removing the mould, and removing the exposed PVC plastic pipe by using a polishing machine. The final reinforced concrete beam is shown in figure 3 (plus figure).
Step two: installation loading device
And (4) mounting the reinforced concrete beam test piece on an MTS fatigue testing machine. The accelerated corrosion device of the invention is arranged, as shown in figure 4, and comprises a water pump 1, wherein the water pump 1 is arranged in a water tank 2, the switch is controlled by a timer 3, and the water pump is connected above a bonding area of a reinforced concrete beam to be detected through a water pipe; wrapping a circle of water-absorbing sponge with the width of 200mm and the thickness of 30mm around the bonding area, fixing a water pipe at the upper part of the water-absorbing sponge and wrapping a plastic film at the outer side of the water-absorbing sponge as shown in figure 5; the stainless steel wire 4 is connected to the negative electrode of the external direct-current power supply, and the steel bar is connected to the positive electrode of the external direct-current power supply; a first displacement meter 5 is fixed on the steel bar at the free end, and a second displacement meter 6 is fixed on the steel bar in the groove; and a first strain gage 7 and a second strain gage 8 are fixed in the groove along the length direction of the steel bar to be measured.
Step three: preloading
Operating a fatigue testing machine to pre-load a test piece, firstly applying a vertical load not exceeding 5kN to enable the test piece to be in close contact with a fatigue testing machine support, then unloading to zero, and adjusting a first displacement meter 5 and a second displacement meter 6 to enable a probe to be perpendicular to the surface of the test piece to be tested; and zeroing the dynamic data acquisition instrument.
Step four: accelerated tarnishing and loading of test pieces
As shown in fig. 4, a sodium chloride solution with a mass fraction of 3.5% is placed in a water tank 2, and the solution is delivered to the sponge of the bonding area of the test piece through a water pipe by a water pump 1. The sponge is fully wetted to absorb the solution, and then the water pump timer 3 is arrangedSpraying for 1min every two hours. And electrifying by adopting a direct-current stabilized power supply to accelerate corrosion. The current density is not more than 200 muA/cm 2 . And applying fatigue load to the test piece while accelerating corrosion. When the relative slippage between the steel bar and the concrete measured by the first displacement meter 5 reaches 1mm, the test is finished.
Step five: data processing and analysis
And processing the test data, calculating the actual mass loss rate and the relative slip of the steel bars and the average bonding stress of the bonding area, and accordingly judging the bonding slip performance of the rusted steel bars and the concrete under different fatigue load amplitudes.
Claims (5)
1. The utility model provides a test device based on reinforced concrete roof beam adhesion testing under corrosion and fatigue load simultaneous action, includes: the water pump is arranged in the water tank, the switch of the water pump is controlled by the timer, and the solution is placed in the water tank; the solution pumped by the water pump is connected above the bonding area of the reinforced concrete beam to be detected through a water pipe; the bonding area is wrapped with a circle of sponge, and a circle of plastic film is wrapped outside the sponge; a stainless steel wire is pre-embedded in the reinforced concrete beam to be detected in advance, the stainless steel wire is connected to the negative electrode of an external direct-current power supply, the positive electrode of the power supply is connected with the reinforced steel bar to be detected, a first displacement meter is fixed on the free end of the reinforced steel bar, and a second displacement meter is fixed on the reinforced steel bar in the groove; a first strain gauge and a second strain gauge are fixed on the steel bar to be measured in the groove; the first strain gauge and the second strain gauge are arranged in the direction of the extension degree of the groove steel bar.
2. The test device for testing the bonding property of the reinforced concrete beam based on the simultaneous action of corrosion and fatigue load according to claim 1, wherein a groove with the length of 100mm is reserved on one side of a bonding area at one end of a test piece.
3. The test device for testing the bonding performance of the reinforced concrete beam based on the simultaneous action of corrosion and fatigue load according to claim 1, characterized in that: the displacement meter used was an eddy current displacement transducer.
4. The test device for testing the bonding performance of the reinforced concrete beam under the simultaneous action of corrosion and fatigue load according to claim 1, wherein the mass fraction of the sodium chloride solution is 3.5%, and the corrosion current density is not more than 200 μ A/cm 2 。
5. A method of applying the apparatus of claim 1, comprising the steps of:
(1) Pouring the reinforced concrete beam: manufacturing a wood pattern, sequentially placing and binding PVC pipes, longitudinal bars and stirrups in the wood pattern, pouring concrete at the top of the wood pattern, reserving stainless steel wires, vibrating, curing and removing the pattern to obtain a reinforced concrete beam test piece;
(2) Installing a loading device: fixing the test piece on an MTS fatigue testing machine;
(3) Preloading: preloading a test piece, firstly applying a vertical load not exceeding 5kN to enable the test piece to be in close contact with a support of the MTS fatigue testing machine, then unloading to zero, and fixing a first displacement meter at a free end and fixing a second displacement meter at a loading end;
(4) The corrosion and loading of the test piece are accelerated: wetting sponge with a solution, carrying out accelerated corrosion on a test piece, operating an MTS fatigue testing machine to enter a loading mode, selecting fatigue loading in the loading mode, and sampling displacement and load;
(5) Data processing and analysis: and (4) processing the test, calculating the actual quality loss rate, the relative slip, the average bonding stress of the bonding area and the like of the reinforcing steel bar, and accordingly judging the bonding slip performance of the test piece under different fatigue load amplitudes.
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| CN202211407939.0A CN115791598A (en) | 2022-11-10 | 2022-11-10 | Test method for testing bonding performance of reinforced concrete beam under simultaneous action of corrosion and fatigue load and corrosion acceleration device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117629097A (en) * | 2023-12-26 | 2024-03-01 | 广东省有色工业建筑质量检测站有限公司 | Beam-slab structure steel bar corrosion detection method and detection device |
| CN118565976A (en) * | 2024-07-31 | 2024-08-30 | 江苏承鑫新能源科技有限公司 | High-temperature molten salt dynamic corrosion test device |
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- 2022-11-10 CN CN202211407939.0A patent/CN115791598A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117629097A (en) * | 2023-12-26 | 2024-03-01 | 广东省有色工业建筑质量检测站有限公司 | Beam-slab structure steel bar corrosion detection method and detection device |
| CN118565976A (en) * | 2024-07-31 | 2024-08-30 | 江苏承鑫新能源科技有限公司 | High-temperature molten salt dynamic corrosion test device |
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