CN109358098B - Method for testing concentration of chloride ions on surface of cement-based material - Google Patents
Method for testing concentration of chloride ions on surface of cement-based material Download PDFInfo
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- CN109358098B CN109358098B CN201811589558.2A CN201811589558A CN109358098B CN 109358098 B CN109358098 B CN 109358098B CN 201811589558 A CN201811589558 A CN 201811589558A CN 109358098 B CN109358098 B CN 109358098B
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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
- G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
- G01N27/07—Construction of measuring vessels; Electrodes therefor
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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
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/226—Construction of measuring vessels; Electrodes therefor
Abstract
The invention discloses a method for testing the concentration of chloride ions on the surface of a cement-based material, which comprises the steps of manufacturing two test pieces arranged at intervals through an insulated die and a baffle, arranging an internal electrode and an external electrode on each test piece, removing the baffle arranged between the two test pieces after the test pieces are solidified, enabling the die and the test pieces to form a containing cavity between the test pieces, curing the test pieces under set conditions to a specified age period to obtain a test sample, adding a chloride ion solution into the containing cavity of the test sample, testing the alternating current impedance spectrum of the test pieces by adopting an alternating current impedance four-point measurement method, calculating the thickness of an adsorption layer on the surface of the test pieces, and obtaining the concentration of the chloride ions in the adsorption layer based on the thickness of the adsorption layer, wherein the concentration is the concentration of the chloride ions on. The method has the advantages of low cost, convenience, rapidness, accurate and reliable test result, contribution to the evaluation of the characteristic of physically adsorbing the chloride ions on the surface of the concrete, contribution to the determination of the migration coefficient of the chloride ions in the concrete and contribution to more accurately measuring the durability of the concrete.
Description
Technical Field
The invention relates to the field of concrete chloride ion permeability resistance tests, in particular to a method for testing the concentration of chloride ions on the surface of a cement-based material.
Background
In the field of buildings, the content of chloride ions in concrete has an important influence on the durability of a reinforced concrete structure, the chloride ions have the characteristics of small ionic radius, strong penetrating capability and strong adsorption by a metal surface, the possibility of forming a passivation film on the surface of a reinforced steel bar can be reduced or the damage of the passivation film can be accelerated, the local corrosion is promoted, especially when the concentration ratio of the chloride ions to hydroxide ions exceeds the limit, the passivation film of the reinforced steel bar can be caused to fall off, the corrosion of the reinforced steel bar is further caused, the bearing capacity of the reinforced steel bar is reduced, and the concrete is cracked and peeled off, so that the measurement of the content of the chloride ions in the concrete is important for evaluating the durability design and construction of the concrete structure and predicting the service life.
Free chloride ions and chemically bound chloride ions in the concrete have been tested by corresponding methods, but the property of the concrete surface to physically adsorb chloride ions due to contact with a solution containing chloride ions has not been easily measured, which facilitates a more accurate evaluation of the durability of the concrete structure. For example, conventional and commonly used concrete chloride ion permeability resistance test methods include the RCM method and the soaking method. The RCM method is a test method based on unsteady electromigration of chloride ions inside a test piece, and the diffusivity of chloride ions is calculated from the penetration depth of chloride ions measured during the test. The soaking method is that the test piece is soaked or diffused for a certain time, the content of chloride ions at different depths of the test piece is measured, and then the transmission speed of the chloride ions in the concrete is calculated by utilizing a mathematical model. None of the above methods accurately characterize the physically adsorbed surface chloride ions, and thus it is difficult to more accurately measure concrete durability.
The principle of the rapid determination method for the concrete chloride ion diffusion coefficient in northern Europe concrete specifications NT Build 443 and 492 which is widely adopted at present is as follows: the method comprises the steps of utilizing the action of an external electric field to enable chloride ions outside a test piece to migrate to the interior of the test piece, splitting the test piece along the axial direction after a period of time, spraying a silver nitrate solution on a newly split section, measuring the penetration depth of the chloride ions according to generated white silver chloride precipitates, and calculating the diffusion coefficient of the concrete chloride ions.
In addition, in cement-based materials, chloride ions and free chloride ions in the electric double layer are collectively referred to as "transportable chloride ions", and characterization of chloride ion migration based on transportable chloride ion concentration profiles is considered to be a more accurate measure of concrete durability. The determination of the surface chloride ion concentration is also required when calculating the transportable chloride ion diffusion coefficient.
An effective and simple method for testing the chloride ion concentration on the surface of the cement-based material has not been found, and therefore, the defect needs to be improved.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for effectively and simply testing the concentration of chloride ions on the surface of a cement-based material. The invention is realized by the following technical scheme: a method for testing the concentration of chloride ions on the surface of a cement-based material comprises the steps of manufacturing two test pieces arranged at intervals through an insulated die and a baffle, arranging two internal electrodes and two external electrodes on each test piece, removing the baffle arranged between the two test pieces after the test pieces are solidified, enabling the die and the test pieces to form a containing cavity between the test pieces, curing under set conditions to a specified age period to obtain a test sample, adding a chloride ion solution into the containing cavity of the test sample, testing the alternating current impedance spectrum of the test piece by adopting an alternating current impedance four-point measurement method, calculating the thickness of an adsorption layer on the surface of the test piece, and obtaining the concentration of the chloride ions in the adsorption layer based on the thickness of the adsorption layer, wherein the concentration is the concentration of the chloride ions on the surface of the cement-based material.
Preferably, the test sample comprises a plurality of samples, and the chloride ion solution with different concentrations is respectively added into the cavities of each test sample.
Preferably, the capacitance value of the adsorption layer is obtained through fitting analysis, and the thickness of the adsorption layer is obtained through a capacitance calculation formula based on the capacitance value.
Preferably, the mold is in a rectangular container shape, and the top of the mold is open.
Preferably, the internal electrode is embedded in the test piece, and the external electrode is attached to the outer end face of the test piece.
Preferably, the inner electrode comprises a titanium rod and the outer electrode comprises an electrode sheet of stainless steel.
Preferably, the periphery and the bottom of the mold are subjected to sealing and waterproof treatment.
The method does not need microcosmic and chemical experiments or cutting samples, has very low cost, is convenient and quick to test, can keep the clean laboratory environment, has accurate and reliable test results, is favorable for evaluating the characteristic of physically adsorbing chloride ions on the surface of concrete, is favorable for measuring the migration coefficient of the chloride ions in the concrete, and is favorable for measuring the durability of the concrete more accurately and quantitatively.
Drawings
The invention is described in further detail below with reference to the figures and specific examples.
FIG. 1 is a schematic top view of a sample preparation stage according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view along AA in FIG. 1;
FIG. 3 is a sectional view taken along line BB in FIG. 1;
fig. 4 is a schematic structural diagram of the electrode sheet in fig. 1.
The reference numerals in the figure correspond to the die 1, the stopper 2, the electrode plate 3, the titanium rod 4, and the fixing member 5.
Detailed Description
The invention is further described below with reference to specific embodiments:
as an example, the method for testing the chloride ion concentration on the surface of the cement-based material, as shown in fig. 1 to 4, comprises the following steps:
1) the mould 1 with a certain size is made of insulating organic glass. The thickness of the organic glass used by the die 1 is 3.7mm, the length of the die 1 is 95.4mm, the width of the die 1 is 47.4mm, and the height of the die 1 is 43.7mm, and the connector of the die 1 is bonded by using a strong adhesive to ensure that the die 1 is watertight.
2) A square stopper 2 is placed in the middle of the mold 1 to block the set concrete. A fixing hole with the diameter of 2mm is arranged at the position of the center line of the side surface of the stopper 2.
3) A fixing hole with the diameter of 2mm is formed in the center of a side plate of the die 1, and the fixing hole corresponds to the fixing hole of the stopper 2. An electrode hole with the diameter of 2mm is arranged at a position 22mm away from the inner side of the end part of the side plate of the die 1 for inserting the cylindrical titanium rod 4.
4) The stopper 2 is placed in the middle of the mold 1, and the fixing member 5 is inserted into the fixing hole, the fixing member 5 penetrates through the stopper 2 and the side surface of the mold 1 to prevent the stopper 2 from moving, and the fixing member 5 of the embodiment is implemented in a steel nail manner.
5) Two stainless electrode plates 3 are preset at two ends inside the die 1 and used as two external electrodes for an alternating current impedance four-point test, and the thickness of each electrode plate 3 is 1.0 mm. Two titanium rods 4 are respectively inserted into the electrode holes and used as two internal electrodes for alternating current impedance four-point test, the two titanium rods 4 are exposed and reserved for 10mm on the same side, and the periphery of the electrode holes is sealed by strong glue to prevent water leakage.
6) Pouring a cement-based material between a stainless steel electrode plate 3 and a stopper 2 to form a sample, preferably, completely attaching the electrode plate 3 to the outer end face of the sample, solidifying the sample, removing the stopper 2 in a mold 1, then maintaining the sample under a set condition to a specified age to obtain a test sample, preferably, the embodiment comprises a plurality of test samples, adding chloride ion solutions with different concentrations to the position where the stopper 2 is originally placed in each test sample, namely, a cavity formed between the mold 1 and the sample, testing the alternating current impedance spectrum of the sample by using a four-point measurement method of alternating current impedance, connecting two RC parallel circuits in series and performing fitting analysis to obtain the capacitance value of an adsorption layer, and further obtaining the thickness of the adsorption layer of the test sample between a few nanometers and a dozen nanometers based on a capacitance calculation formula.
7) And calculating the concentration of chloride ions in the thickness of the adsorption layer, namely the concentration of the chloride ions on the surface of the cement-based material based on the thickness of the adsorption layer.
The method of the embodiment does not need microcosmic and chemical experiments, does not need to cut the sample, has very low cost, is convenient and quick to test, and can keep the environment of a laboratory clean.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
The invention is described above by way of example, and it is obvious that the implementation of the invention is not limited by the above-mentioned manner, and it is within the scope of the invention to adopt various modifications of the inventive method concept and technical solution, or to apply the inventive concept and technical solution to other occasions without modification.
Claims (7)
1. A method for testing the concentration of chloride ions on the surface of a cement-based material is characterized in that two test pieces which are arranged at intervals are manufactured through an insulated die and a baffle, two internal electrodes and two external electrodes are arranged on each test piece, the baffle arranged between the two test pieces is removed after the test pieces are solidified, so that a containing cavity is formed between the die and the test pieces, a test sample is obtained after the test pieces are maintained to a specified age period under set conditions, a chloride ion solution is added into the containing cavity of the test sample, an alternating current impedance spectrum of the test piece is tested by adopting an alternating current impedance four-point measurement method, the thickness of an adsorption layer on the surface of the test piece is calculated, and the concentration of the chloride ions in the adsorption layer can be obtained based on the thickness of the adsorption layer, wherein the concentration is the concentration of the chloride ions on the surface of the cement-based material.
2. The method as claimed in claim 1, wherein said test sample comprises a plurality of samples, and said chloride ion solutions of different concentrations are respectively added to said cavities of each of said test samples.
3. The method of claim 2, wherein the capacitance value of the adsorption layer is derived by fitting analysis, and the thickness of the adsorption layer is derived by a capacitance calculation formula based on the capacitance value.
4. The method of claim 1, wherein the mold is in the form of a rectangular container with an open top.
5. The method of claim 1, wherein the inner electrode is pre-embedded in the test piece and the outer electrode is attached to an outer end surface of the test piece.
6. The method of claim 5, wherein the inner electrode comprises a titanium rod and the outer electrode comprises an electrode sheet of stainless steel.
7. The method of claim 1, wherein the mold is sealed and waterproofed around and at the bottom of the mold.
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| CN110595975A (en) * | 2019-04-19 | 2019-12-20 | 华北水利水电大学 | Concrete chloride ion diffusion simulation test device and detection method |
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| CN101226167A (en) * | 2008-02-19 | 2008-07-23 | 清华大学 | Method for rapidly measuring reinforcing steel tarnishing criticality chlorine ion concentration |
| CN108204942A (en) * | 2017-12-12 | 2018-06-26 | 佛山科学技术学院 | The accelerated test method that stainless steel reinforced concrete corrodes under a kind of research bar in chlorine salt solution |
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| GB8713589D0 (en) * | 1987-06-10 | 1987-07-15 | Pioneer Aggregates Uk Ltd | Determination of chlorides in aggregate |
| CN103207221A (en) * | 2013-03-22 | 2013-07-17 | 中交四航工程研究院有限公司 | Sensor for monitoring depth distribution of concentration and pH (potential of hydrogen) values of chloride ions in concrete protective layer and method for manufacturing sensor |
| CN103524083B (en) * | 2013-09-22 | 2015-10-07 | 河海大学 | Cement-based mortar sensing electrode mixing nanometer conductive material in a kind of and preparation method thereof and application |
| DK3115781T3 (en) * | 2015-07-09 | 2018-08-13 | Univ Nantes | SYSTEM FOR ASSESSMENT OF CHLORIDE CONCENTRATION AND SIMILAR METHOD AND SENSOR |
| CN105466829B (en) * | 2015-11-17 | 2018-06-22 | 厦门理工学院 | A kind of method for monitoring Chloride Ion in Concrete infiltration forward position |
| KR101695649B1 (en) * | 2015-12-01 | 2017-01-12 | (주)삼일피엔유 | Concrete Rapid chloride permeability test and Chloride migration coefficient test and test methods |
| CN105547988A (en) * | 2016-01-08 | 2016-05-04 | 海南瑞泽新型建材股份有限公司 | Reinforced concrete corrosion test device and test method |
| CN105806838B (en) * | 2016-03-14 | 2017-12-15 | 广西大学 | A kind of method for testing chloride ions concentration of concrete distributed in three dimensions |
| CN107843539A (en) * | 2017-12-13 | 2018-03-27 | 青岛理工大学 | A kind of ion penetration resistance of concrete measuring method |
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|---|---|---|---|---|
| CN101226167A (en) * | 2008-02-19 | 2008-07-23 | 清华大学 | Method for rapidly measuring reinforcing steel tarnishing criticality chlorine ion concentration |
| CN108204942A (en) * | 2017-12-12 | 2018-06-26 | 佛山科学技术学院 | The accelerated test method that stainless steel reinforced concrete corrodes under a kind of research bar in chlorine salt solution |
Non-Patent Citations (1)
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| Corrosion mitigation of steel rebars in chloride contaminated concrete pore solution using inhibitor: An electrochemical investigation;Han-Swung Lee et.al;《Construction and Building Materials》;20180424;第173卷;第443-451页 * |
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