CN114002273A - Concrete degradation process monitoring device and monitoring method thereof - Google Patents
Concrete degradation process monitoring device and monitoring method thereof Download PDFInfo
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- 239000004567 concrete Substances 0.000 title claims abstract description 189
- 238000006731 degradation reaction Methods 0.000 title claims abstract description 22
- 238000012544 monitoring process Methods 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000012806 monitoring device Methods 0.000 title claims abstract description 13
- 238000012360 testing method Methods 0.000 claims abstract description 78
- 230000003628 erosive effect Effects 0.000 claims abstract description 34
- 239000003822 epoxy resin Substances 0.000 claims description 21
- 229920000647 polyepoxide Polymers 0.000 claims description 21
- 230000006866 deterioration Effects 0.000 claims description 13
- 230000015556 catabolic process Effects 0.000 claims 1
- 230000007797 corrosion Effects 0.000 abstract description 3
- 238000005260 corrosion Methods 0.000 abstract description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 13
- 239000010949 copper Substances 0.000 description 13
- 229910052802 copper Inorganic materials 0.000 description 13
- 239000000203 mixture Substances 0.000 description 6
- 101100356682 Caenorhabditis elegans rho-1 gene Proteins 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000004593 Epoxy Substances 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical class [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000000378 calcium silicate Substances 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 125000001309 chloro group Chemical class Cl* 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 229910001653 ettringite Inorganic materials 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/045—Circuits
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Abstract
The invention discloses a concrete degradation process monitoring device and a monitoring method thereof, the device comprises a cathode tank and an anode tank, the cathode tank is provided with a first electrode and a second electrode, the anode tank is provided with a third electrode and a fourth electrode, one end of a concrete test piece extends into the cathode tank to be contacted with the second electrode, the other end of the concrete test piece extends into the anode tank to be contacted with the third electrode, the first electrode and the fourth electrode are respectively connected with a positive electrode and a negative electrode of a power supply, and the second electrode and the third electrode are connected with a voltage testing device. The invention has the advantages that two mutually independent cathode tanks and anode tanks are arranged, so that two ends of a concrete test piece are respectively contacted with the cathode solution and the anode solution, the concrete test piece not only can be used as a corrosion device, but also can reflect the degradation process of the concrete test piece in real time by measuring the resistance of the test piece; and the erosion resistance of the concrete test piece can be evaluated by comparing the change rules of the resistance of different concrete test pieces along with the erosion time.
Description
Technical Field
The invention relates to a resistance testing device and a method, in particular to a concrete degradation process monitoring device and a monitoring method thereof.
Background
Concrete, as a building material having the widest application range in civil engineering, is affected by different factors of deterioration in durability in different engineering environments. For example, in subway construction, a reinforced concrete structure is in a geological structure rich in underground water for a long time, and after sulfate ions in underground water invade into concrete, the sulfate ions are mixed with Ca (OH)2Calcium silicate hydrate and calcium aluminate hydrate react to generate expansive products such as gypsum, ettringite (AFt) and the like, expansion stress is generated, and when the expansion stress exceeds the tensile strength of the concrete, the concrete cracks. The erosion of sulfate ions to concrete is a process from the outside to the inside, and the change of microstructures such as porosity, pore structure and microcracks in the concrete is accompanied, so that the conductivity of the concrete is influenced. Therefore, the resistivity of the concrete can reflect the change of the microstructure in the concrete, and the durability degradation process of the concrete is monitored and characterized.
At present, the research on the concrete resistivity mainly focuses on the influence of the doping mode and the type of the material on the concrete resistivity, and the resistivity change rule and prediction research of the concrete in the actual engineering environment are rarely reported. In addition, most concrete samples adopted for the research on the concrete resistivity need to embed electrodes in advance, the operation is complicated, errors caused by inconsistent electrode positions are large, and on the other hand, the difference between a laboratory environment and an actual engineering environment is large, so that a research conclusion cannot be well applied to actual engineering. Therefore, a resistance testing device and a method capable of accurately, simply and conveniently reflecting the evolution rule of the concrete microstructure in the actual engineering environment and monitoring the concrete degradation process are urgently needed.
The conventional resistance testing device mainly focuses on the resistance test of the test piece itself, and there are few resistance testing devices reflecting the durability of concrete.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a concrete degradation process monitoring device which can be used as a corrosion device and can reflect the degradation process of a concrete test piece in real time;
a second object of the present invention is to provide a method for monitoring the progress of concrete deterioration.
The technical scheme is as follows: the concrete degradation process monitoring device comprises a cathode tank and an anode tank, wherein the cathode tank is provided with a first electrode and a second electrode, the anode tank is provided with a third electrode and a fourth electrode, one end of a concrete test piece extends into the cathode tank to be contacted with the second electrode, the other end of the concrete test piece extends into the anode tank to be contacted with the third electrode, the first electrode and the fourth electrode are respectively connected with a positive electrode and a negative electrode of a power supply, and the second electrode and the third electrode are connected with a voltage testing device.
In order to ensure that stable current is formed in the solution and the concrete test piece after the power supply is switched on, the transverse distances between the first electrode, the fourth electrode and the concrete test piece are respectively 100-150 mm.
The length that the concrete sample inserted in negative pole groove and positive pole inslot is 1/5 ~ 1/4 of concrete sample length respectively, when guaranteeing that concrete sample and negative pole groove and positive pole groove are good connectivity, has effectively avoided the phenomenon that leads to the epoxy on concrete sample surface to puncture the damage with position solution and the inside electric potential of test piece difference greatly. Here, the shorter the test piece is inserted into the groove, the less easily the epoxy resin of the surface is broken down.
Wherein, the power supply is a direct current power supply or a pulse direct current power supply.
In order to ensure that the electric field formed in the solution after electrification is uniformly distributed and improve the transmission rate of ions, the first electrode, the second electrode, the third electrode and the fourth electrode are respectively made of copper strips which are fixed with copper nets and are vertical to each other; wherein the steel mesh is a high-purity steel mesh; the size of the copper mesh is 100-150 mm multiplied by 100-150 mm, the size of a single aperture is 3-5 mm multiplied by 3-5 mm, the length L1 of a horizontal copper bar at the top of the copper mesh is 100-150 mm, the width W1 is 10-20 mm, the length L2 of a vertical copper bar at the top of the steel mesh is 50-100 mm, and the width W2 is 10-20 mm; the steel mesh and the copper bar are fixed in a welding mode.
Wherein, for accurately simulating the corrosion process of the concrete structure in the actual engineering environment by corrosive media, the cathode solution in the cathode tank is the original solution soaked in the actual engineering concrete structure or the corrosive solution simulating the environment in which the actual engineering concrete structure is located; the anode solution in the anode tank is a saturated calcium hydroxide solution simulating a concrete pore liquid, so that the influence of calcium ion leaching on the resistivity of the concrete test piece is effectively reduced.
Wherein, the cathode groove and the anode groove are arranged side by side in a non-contact way or are nested in a non-contact way.
And the second electrode and the third electrode are respectively connected with a COM jack and a V/omega jack of the multimeter.
Wherein, the positions of the concrete test piece, which are respectively contacted with the cathode tank and the anode tank, are sealed by epoxy resin.
The method for monitoring the concrete degradation process by using the concrete degradation process monitoring device comprises the following steps:
(1) placing two ends of a concrete sample into a cathode tank and an anode tank respectively, and contacting with a second electrode of the cathode tank and a third electrode of the anode tank respectively; putting the catholyte and the anolyte according to the monitoring requirement;
(2) switching on a power supply and a voltage testing device, recording a voltage value corresponding to the current of the power supply, and calculating the initial resistivity of the concrete test piece through data fitting;
(3) turning off the power supply and the voltage testing device, and repeating the step (2) after the concrete test piece is corroded to the expected age; and obtaining the degradation process of the concrete sample by curve fitting of the erosion time and the concrete resistivity.
And evaluating the erosion resistance of the concrete test piece by comparing parameters after different concrete curves are fitted.
Wherein the applied current is 1-10 mA.
In the step (2), the initial resistivity ρ 0 of the concrete sample is calculated by the formula (1).
In the formula (1), rho is the resistivity of the test piece and the unit k omega cm; u is the voltage at two ends of the test piece and has a unit V; i is the current passing through the test piece in mA; s is the cross-sectional area of the test piece in cm2(ii) a L is the length of the specimen in cm.
Has the advantages that: compared with the prior art, the invention has the following remarkable effects: 1. the device of the invention is provided with two mutually independent cathode tanks and anode tanks, so that two ends of a concrete test piece are respectively contacted with a cathode solution and an anode solution. 2. The invention can also evaluate the erosion resistance of the concrete test piece by comparing the change rule of the resistance of different concrete test pieces along with the erosion time; 3. the testing method of the invention obtains the regular curve of the erosion time and the concrete resistivity by recording the voltage value of the concrete specimen under the specific current and fitting the data, thereby obtaining the degradation process of the concrete specimen and evaluating the erosion resistance of the concrete specimen.
Drawings
FIG. 1 is a schematic view of the apparatus of the present invention;
FIG. 2 is a schematic view of an electrode structure according to the present invention;
FIG. 3 is a graph of the fitting result of voltage and current at two sides of a concrete sample in example 1;
FIG. 4 is a graph of the fitted function of resistivity and erosion time of a concrete sample of example 1;
FIG. 5 is a graph of the fitting result of the voltage and the current at the two sides of the concrete specimen in example 2;
FIG. 6 is a graph of the fitting function of the resistivity of a concrete sample and the erosion time in example 2;
FIG. 7 is a graph of the fitting result of voltage and current at two sides of a concrete sample in example 3;
FIG. 8 is a graph of the fit function of resistivity to erosion time for a concrete specimen of example 3;
FIG. 9 is a graph of the fitting result of the voltage and the current at the two sides of the concrete sample in example 4;
FIG. 10 is a plot of the resistivity as a function of erosion time for the concrete samples of example 4.
Detailed Description
The present invention is described in further detail below.
As shown in fig. 1, the present embodiment provides a device for monitoring a concrete degradation process in a metro engineering environment, which includes a cathode tank and an anode tank, which are independently placed side by side, wherein the cathode tank and the anode tank may also be nested; a gap is reserved between the cathode slot and the anode slot, and through holes are respectively formed in two sides, close to each other, of the cathode slot and the anode slot and used for enabling one end of the concrete test piece to stretch into the cathode slot and the other end of the concrete test piece to stretch into the anode slot. The cathode solution 7 and the anode solution 8 are respectively put in the cathode tank and the anode tank. The cathode tank is provided with a first electrode 1 and a second electrode 2, and the anode tank is provided with a third electrode 3 and a fourth electrode 4. One end of the concrete test piece extends into the cathode tank to be contacted with the second electrode, the other end of the concrete test piece extends into the anode tank to be contacted with the third electrode, the first electrode and the fourth electrode are respectively connected with the anode and the cathode of the power supply, and the second electrode and the third electrode are connected with the voltage testing device. The voltage testing device of the present embodiment is a multimeter. The first electrode 1 and the cathode solution 7 are connected with the negative electrode of a power supply 10, the fourth electrode 4 and the anode solution 8 are connected with the positive electrode of the power supply 10, the second electrode 2 and the cathode solution 7 are connected with a COM jack of a desk multimeter, and the third electrode 3 and the anode solution 8 are connected with a V/omega jack of the desk multimeter.
The length of the concrete sample 1/4 is equal to the length of the cathode slot 5 and the anode slot 6 inserted into the two ends of the concrete sample 9. The concrete sample 9 is a concrete sample with the dimension phi 100mm multiplied by 100mm after standard curing for 28d, and the concrete mixing ratio is shown in table 1. The side of the concrete sample 9 was sealed with epoxy. The contact parts of the concrete sample 9 with the cathode tank 5 and the anode tank 6 are sealed by epoxy resin, and the epoxy resin is kept stand for 24h to ensure the hardening.
The cathode tank 5 and the anode tank 6 are both formed by bonding 4 acrylic plates with the size of 200mm multiplied by 200mm and one acrylic plate with the size of 200mm multiplied by 200mm and the central aperture of 101 mm.
The distance between the first electrode 1 and the fourth electrode 4 and the concrete test piece 9 is 100mm, and the second electrode 2 and the third electrode 3 are fixed on the two end surfaces of the concrete test piece 9 through a given clamp.
As shown in fig. 2, each of the first electrode 1, the second electrode 2, the third electrode 3, and the fourth electrode 4 is made of two copper bars welded perpendicularly to each other by a high-purity copper mesh, and the four electrodes are parallel to each other, the size of the copper mesh is 100mm × 100mm, the size of a single aperture is 3mm × 3mm, the length L1 of the horizontal copper bar welded to the upper portion of the copper mesh is 100mm, the width W1 is 10mm, the length L2 of the vertical copper bar is 50mm, and the width W2 is 10 mm.
The anode solution 8 in this example is a saturated calcium hydroxide solution simulating a concrete pore liquid; the cathode solution 7 is 3% NaCl + 5% Na2SO4The composite solution simulates the subway engineering environment containing chlorine salt, sulfate and stray current; the current of the power supply 10 is 5mA, and stray current transmitted from a track to the interior of concrete during the operation of a train in subway engineering is simulated.
TABLE 1 example 1 concrete test piece mix ratio (kg/m)3)
| Species of | Water (W) | Cement | Gravel (5 mm to 20mm) | Sand | Water reducing agent |
| Weight/volume | 144 | 450 | 1112 | 682 | 2.25 |
The resistance testing method for monitoring the concrete degradation process in the subway engineering environment by using the device comprises the following steps:
(1) before testing, the side face of a concrete sample to be tested is uniformly coated with epoxy resin, and the concrete sample is kept stand for 24 hours to ensure that the concrete sample is hardened. And placing the concrete sample to be detected into the device, sealing the contact part of the concrete sample and the device by using epoxy resin, and standing the epoxy resin for 24 hours to ensure that the epoxy resin is hardened. The concrete test piece is immersed by the cathode solution and the anode solution.
(2) Testing the initial resistance rho 0 of the concrete sample: the power supply current is set as direct current, the power supply and the multimeter are sequentially connected, the current is set as 1mA, 2mA, 3mA, 4mA and 5mA in sequence, and the power supply current is recorded as 1mA, 2mA, 3mA, 4mA and 5mA, and the power supply current corresponds to the readings of the desktop multimeter such as U1, U2, U3, U4 and U5. The results of fitting are shown in fig. 3 by straight line fitting of the data, and the initial resistivity ρ 0 of the concrete sample is 13.35k Ω · cm using the above equation (1).
(3) The desk multimeter was turned off and the supply current was set to 5 mA. And (3) after the power is supplied for 10d, 20d, 30d and 40d, repeating the step (2), calculating the resistivities rho 1, rho 2, rho 3 and rho 4 of the concrete samples after the erosion of 10d, 20d, 30d and 40d, and establishing a fitting function of the resistivity rho of the concrete samples and the erosion time t, wherein the fitting function is shown in FIG. 4.
As can be seen from FIG. 6, the concrete resistivity was 15.46 k.OMEGA.cm, 15.99 k.OMEGA.cm, 16.46 k.OMEGA.cm and 16.77 k.OMEGA.cm, respectively, when the erosion time was 10d, 20d, 30d and 40 d. ρ 13.25 × (t +1.12)0.06Can accurately represent the relationship between the resistivity of the concrete sample and the erosion time, and has good fitting degree, R2＝0.99。
Example 2
The difference between this example and example 1 is that the concrete sample 9 is a concrete sample having a size of Φ 100mm × 100mm after standard curing for 28d, and the concrete formulation is shown in table 2. The distance between the first electrode 1 and the fourth electrode 4 and the concrete sample 9 is 150 mm. The lengths of the concrete samples inserted into the cathode tank and the anode tank are 1/5 of the length of the concrete samples respectively.
TABLE 2 example 2 concrete test piece mixing ratio (kg/m)3)
The resistance testing method for monitoring the concrete degradation process in the subway engineering environment by using the device comprises the following steps:
(1) before testing, the side face of a concrete sample to be tested is uniformly coated with epoxy resin, and the concrete sample is kept stand for 24 hours to ensure that the concrete sample is hardened. And placing the concrete sample to be detected into a resistance testing device, sealing the contact part of the concrete sample and the device by using epoxy resin, and standing the epoxy resin for 24 hours to ensure that the epoxy resin is hardened. The concrete test piece is immersed by the cathode solution and the anode solution.
(2) And testing the initial resistance rho 0 of the concrete sample. And sequentially switching on a power supply and the multimeter, sequentially setting the current sizes to be 6mA, 7mA, 8mA, 9mA and 10mA, and recording the power supply current to be 6mA, 7mA, 8mA, 9mA and 10mA, wherein the power supply current corresponds to the readings of the desktop multimeter such as U6, U7, U8, U9 and U10. The results of fitting are shown in fig. 5 by straight line fitting of the data, and the initial resistivity ρ 0 of the concrete sample is 23.08k Ω · cm using formula (1).
(3) Turn-off desk type universal meterThe power supply current was set to 5 mA. And (3) after the power is supplied for 10d, 20d, 30d and 40d, repeating the step (2), calculating the resistivities rho 1, rho 2, rho 3 and rho 4 of the concrete samples after the erosion of 10d, 20d, 30d and 40d, and establishing a fitting function of the resistivity rho of the concrete samples and the erosion time t, wherein the fitting function is shown in FIG. 6. It can be seen that the concrete resistivity was 24.72 k.OMEGA.cm, 25.04 k.OMEGA.cm, 25.38 k.OMEGA.cm and 25.61 k.OMEGA.cm, respectively, when the erosion time was 10d, 20d, 30d and 40 d. ρ 23.14 × (t +0.92)0.03Can accurately represent the relationship between the resistivity of the concrete sample and the erosion time, and has good fitting degree, R20.99. Fitting function ρ ═ 13.25 × (t +1.12) of comparative example 10.06The fitting function ρ of example 2 is 23.14 × (t +0.92)0.03The increase rate with the erosion time t is low, so the concrete sample in example 2 has good erosion resistance.
Example 3
The difference between this example and example 1 is that the concrete sample 9 is a concrete sample having a size of Φ 100mm × 100mm after standard curing for 28d, and the concrete formulation is shown in table 3. The distance between the first electrode 1 and the fourth electrode 4 and the concrete sample 9 is 120 mm. The lengths of the concrete samples inserted into the cathode tank and the anode tank are 1/5 of the length of the concrete samples respectively.
TABLE 3 example 3 concrete test piece mix ratio (kg/m)3)
The resistance testing method for monitoring the concrete degradation process in the subway engineering environment by using the device comprises the following steps:
(1) before testing, the side face of a concrete sample to be tested is uniformly coated with epoxy resin, and the concrete sample is kept stand for 24 hours to ensure that the concrete sample is hardened. And placing the concrete sample to be detected into a resistance testing device, sealing the contact part of the concrete sample and the device by using epoxy resin, and standing the epoxy resin for 24 hours to ensure that the epoxy resin is hardened. The concrete test piece is immersed by the cathode solution and the anode solution.
(2) And testing the initial resistance rho 0 of the concrete sample. And sequentially switching on a power supply and the multimeter, sequentially setting the current sizes to be 3mA, 4mA, 5mA, 6mA and 7mA, and recording the power supply current to be 3mA, 4mA, 5mA, 6mA and 7mA, wherein the power supply current corresponds to the readings of the desktop multimeter such as U3, U4, U5, U6 and U7. The results of fitting are shown in fig. 7 by straight line fitting of the data, and the initial resistivity ρ 0 of the concrete sample is 19.15k Ω · cm using equation (1). Comparing example 1 with example 2, the concrete samples of example 3 had a resistivity between the two.
(3) The desk multimeter was turned off and the supply current was set to 5 mA. And (3) after the power is supplied for 10d, 20d, 30d and 40d, repeating the step (2), calculating the resistivities rho 1, rho 2, rho 3 and rho 4 of the concrete samples after the erosion of 10d, 20d, 30d and 40d, and establishing a fitting function of the resistivity rho of the concrete samples and the erosion time t, wherein the fitting function is shown in FIG. 8. It can be seen that the concrete resistivity was 21.15 k.OMEGA.cm, 21.66 k.OMEGA.cm, 22.09 k.OMEGA.cm and 22.35 k.OMEGA.cm at erosion times of 10d, 20d, 30d and 40d, respectively. ρ 19.05 × (t +1.12)0.04Can accurately represent the relationship between the resistivity of the concrete sample and the erosion time, and has good fitting degree, R20.99. Fitting function ρ ═ 13.25 × (t +1.12) of comparative example 10.06And the fitting function ρ ═ 23.14 × (t +0.92) of example 20.03The fitting function ρ of example 3 is 19.05 × (t +1.12)0.04The rate of increase with erosion time was less than example 1 and greater than example 2. Therefore, compared with examples 1 and 2, the concrete test piece of example 3 has a durability deterioration rate smaller than that of example 1 and larger than that of example 2.
Example 4
The difference between this example and example 1 is that the concrete sample 9 is a concrete sample having a size of Φ 100mm × 100mm after standard curing for 28d, and the concrete formulation is shown in table 4. The distance between the first electrode 1 and the fourth electrode 4 and the concrete test piece 9 is 140 mm. The lengths of the concrete samples inserted into the cathode tank and the anode tank are 6/25 of the length of the concrete samples respectively.
TABLE 4 example 4 concrete test piece mix ratio (kg/m)3)
The resistance testing method for monitoring the concrete degradation process in the subway engineering environment by using the device comprises the following steps:
(1) before testing, the side face of a concrete sample to be tested is uniformly coated with epoxy resin, and the concrete sample is kept stand for 24 hours to ensure that the concrete sample is hardened. And placing the concrete sample to be detected into a resistance testing device, sealing the contact part of the concrete sample and the device by using epoxy resin, and standing the epoxy resin for 24 hours to ensure that the epoxy resin is hardened. The concrete test piece is immersed by the cathode solution and the anode solution.
(2) And testing the initial resistance rho 0 of the concrete sample. And sequentially switching on a power supply and the multimeter, sequentially setting the current sizes to be 2mA, 4mA, 6mA, 8mA and 10mA, and recording the power supply current to be 2mA, 4mA, 6mA, 8mA and 10mA, wherein the power supply current corresponds to the readings of the desktop multimeter such as U2, U4, U6, U8 and U10. The results of fitting are shown in fig. 9 by straight line fitting of the data, and the initial resistivity ρ 0 of the concrete sample is 25.51k Ω · cm using equation (1). Comparing example 1, example 2 and example 3, example 4 had the highest initial resistivity.
(3) The desk multimeter was turned off and the supply current was set to 5 mA. And (3) after the power is supplied for 10d, 20d, 30d and 40d, repeating the step (2), calculating the resistivities rho 1, rho 2, rho 3 and rho 4 of the concrete samples after the erosion of 10d, 20d, 30d and 40d, and establishing a fitting function of the resistivity rho of the concrete samples and the erosion time t, wherein the fitting function is shown in FIG. 10. It can be seen that the concrete resistivity was 26.83 k.OMEGA.cm, 27 k.OMEGA.cm, 27.19 k.OMEGA.cm and 27.39 k.OMEGA.cm at erosion times of 10d, 20d, 30d and 40d, respectively. Rho 25.88 × (t +0.38)0.02Can accurately represent the relationship between the resistivity of the concrete sample and the erosion time, and has good fitting degree, R20.99. Fitting function ρ ═ 13.25 × (t +1.12) of comparative example 10.06The fitting function ρ of example 2 is 23.14 × (t +0.92)0.03And the fitting function ρ ═ 19.05 × (t +1.12) of example 30.04Example 4 fitting function ρ 25.88 × (t +0.38)0.02The rate of increase with erosion time is slowest. Therefore, the concrete test pieces of example 4 had the highest rate of deterioration in durability as compared with examples 1, 2 and 3Slow.
Claims (10)
1. The utility model provides a concrete degradation process monitoring devices, its characterized in that, includes negative pole groove (5) and positive pole groove (6), negative pole groove (5) are equipped with first electrode (1), second electrode (2), positive pole groove (6) are equipped with third electrode (3), fourth electrode (4), and the one end of concrete test piece (9) stretches into in negative pole groove (5) and contacts with second electrode (2), and the other end stretches into in positive pole groove (6) and contacts with third electrode (3), anodal, the negative pole of power (10) are connected respectively to first electrode (1), fourth electrode (4), voltage testing arrangement is connected in second electrode (2), third electrode (3).
2. The concrete deterioration process monitoring device according to claim 1, wherein the first electrode (1) and the fourth electrode (4) are respectively 100-150 mm apart from the concrete sample (9) in the transverse direction.
3. The concrete deterioration process monitoring device according to claim 1, wherein the concrete specimen (9) is inserted into the cathode tank (5) and the anode tank (6) by 1/5-1/4 of the length of the concrete specimen (9).
4. The apparatus for monitoring the progress of concrete deterioration according to claim 1, wherein said power source (10) is a dc power source or a pulsed dc power source.
5. The apparatus for monitoring the progress of concrete deterioration according to claim 1, wherein the cathode solution (7) in the cathode tank (5) is an original solution soaked in the actual engineering concrete structure or a corrosive solution simulating the environment in which the actual engineering concrete structure is placed.
6. The concrete deterioration process monitoring device according to claim 1, wherein the cathode tank (5) and the anode tank (6) are arranged side by side in a non-contact or nested non-contact manner.
7. The concrete degradation process monitoring device according to claim 1, wherein the second electrode (2) and the third electrode (3) are respectively connected with COM and V/omega of a multimeter (11).
8. The concrete deterioration process monitoring device according to claim 1, wherein the positions where the concrete samples (9) are in contact with the cathode tank (5) and the anode tank (6) are sealed with epoxy resin.
9. A method for monitoring the progress of concrete deterioration by using the apparatus for monitoring the progress of concrete deterioration according to claim 1, comprising the steps of:
(A) putting two ends of a concrete sample (9) into a cathode tank (5) and an anode tank (6) respectively, and contacting with a second electrode (2) of the cathode tank (5) and a third electrode (3) of the anode tank (6) respectively; putting the catholyte and the anolyte according to the monitoring requirement;
(B) switching on a power supply (10) and a voltage testing device, recording a voltage value corresponding to the current of the power supply (10), and calculating the initial resistivity of the concrete test piece (9) through data fitting;
(C) turning off the power supply (10) and the voltage testing device, and repeating the step (B) after the concrete test piece (9) is corroded to the expected age; and obtaining the deterioration process of the concrete sample (9) by curve fitting of the erosion time and the concrete resistivity.
10. The method of monitoring the progress of concrete degradation according to claim 9, wherein the applied current is 1-10 mA.
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