CN101226167A - Method for rapidly measuring reinforcing steel tarnishing criticality chlorine ion concentration - Google Patents

Abstract

The invention discloses a method for quickly measuring steel bar corrosion critical chloride ion density, belonging to steel corrosion detection technique. The method comprises arranging prepared a concrete sample with a non-immersion reference electrode and an immersion working electrode into an electro-osmosis tank, adding 3-20V direct-current voltages at two sides of the concrete sample, detecting the current of the macro battery composed of the immersion working electrode and the non-immersion reference electrode, if the macro battery current reaches the value of corrosion germination, stopping the electro-osmosis test, or else, continuing and repeating the processes as adding voltage, stopping powering and macro battery current detection until the macro battery current reaches the value of corrosion germination, stopping the electro-osmosis test. And after the electro-osmosis test, the invention uses potential titration to test chloride ion density in concrete. The inventive method can significantly reduce critical chloride ion density test time and realize automatic test control via detecting macro battery current.

Description

A kind of method of fast measuring reinforcing steel tarnishing criticality chlorine ion concentration

Technical field

The invention belongs to steel corrosion degree detecting method field, more particularly, the invention relates to a kind of method of fast measuring reinforcing steel tarnishing criticality chlorine ion concentration.

Background technology

Reinforced concrete is as structural timber, is widely used in the construction work such as highway, bridge, harbour in the chlorine salt corrosion environment.The destroying concrete structure that the reinforcement corrosion that chlorion causes extensively causes, the security that has a strong impact on even jeopardize buildingss such as building construction, bridge.Adopt various high performance concretes, the structure that improve protection level to reinforcing bar in the concrete, corrosion is taken place is keeped in repair repairing have been become when last urgent work.At present, the generaI investigation to the concrete-bridge potential safety hazard is in full swing the standard criterion progressively foundation of employing durability index design xoncrete structure in China.The reinforcement corrosion criticality chlorine ion concentration be in the decision concrete corrosiveness of the environment size and select concrete material and structure important parameter.

Usually adopt the drying and watering cycle method to measure reinforcing steel tarnishing criticality chlorine ion concentration at present, the shortcoming of the method is that the test duration is long, though and in the ASTM G109-92 standard macro cell electric current is detected, but can not monitor in real time corrosion cell, can not implement continuous monitoring to corrosion cell simultaneously.The electric osmose test method has been widely used in the coefficient of diffusion of test chlorion in concrete, the general electric osmose voltage that adopts is the 30-60 volt, its shortcoming is added overtension, can influence test findings at the certain heat of inner generation of concrete time in experimentation.

Summary of the invention

The objective of the invention is to overcome the shortcoming of prior art, a kind of method of fast measuring reinforcing steel tarnishing criticality chlorine ion concentration is provided.Utilize this method can make the rebar surface chlorine ion concentration reach critical value fast, shorten the criticality chlorine ion concentration minute greatly.

The present invention is achieved by the following technical programs: the concrete sample that comprises non-steeped contrast electrode and immersion working electrode that will prepare, place the electric osmose pond, apply the DC voltage of lower voltage 3-20 volt after a period of time on the concrete sample both sides, stop to power up a period of time, then the macro cell electric current that soaks working electrode and non-steeped contrast electrode formation is detected, (generally adopt 1 μ A/cm if the macro cell electric current reaches the current value of corrosion sprouting ²) time stop electric osmose test, otherwise continue to repeat " apply voltage-stop to power up-the macro cell current detecting " process, reach the current value that corrosion is sprouted up to the macro cell electric current, stop the electric osmose test.After the electric osmose off-test, concrete sample is split out from the electric osmose groove, in the drill hole sampling of concrete immersion part, in addition, also the concrete that soaks working electrode surface is taken a sample, adopt the method for potentiometric titration to measure chlorine ion concentration in the concrete.

The present invention has following beneficial effect compared with prior art:

1. to a great extent, reduced chlorion critical concentration minute;

2. can not produce a large amount of heat at inside concrete, can be not influential to experimental result;

3. the criterion that takes place as critical corrosion with the macro cell current value is implemented monitoring to the macro cell electric current, can realize the automatic stepless control of testing.

Description of drawings

Fig. 1 is the concrete sample structural representation

Fig. 2 is an electric osmose pool device synoptic diagram

Fig. 3 is concrete sample sampling synoptic diagram

Fig. 4 is the potentiometric titrimeter synoptic diagram

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in detail.

1. concrete sample preparation: make concrete sample 1 shown in Figure 1.Chloride solution will be immersed in the lower part of concrete sample 1, and top will be exposed in the air.Non-steeped contrast electrode 2 is connected with copper conductor 4 with immersion working electrode 3, and non-steeped contrast electrode 2 adopts epoxy resin 5 to seal with the side that immersion working electrode 3 is connected with copper conductor 4 and is coated with, and opposite side is exposed in the chloride solution.Concrete sample is after 1 moulding a period of time, and maintenance is carried out in form removal then.

2. installation concrete sample: concrete sample is installed in the electric osmose pond 8 shown in Figure 2, and electric osmose pond 8 is divided into left and right sides two parts, and concrete sample 1 is installed front surface should be clean, no greasy dirt, sand-lime and water.Electric osmose pond 8 left-hand components are used for displaying left electric osmose liquid 10, and its composition is 0.2mol/LNaOH; Electric osmose pond 8 right-hand components are used for displaying right electric osmose liquid 9, and its composition is 0.2mol/LNaOH+5wt%NaCl, and right electric osmose liquid 9 provides the chlorion of test usefulness; Electric osmose pond lid 7 is used to reduce the evaporation of electric osmose liquid, DC power supply 11 can apply the DC voltage of 3-20 volt by connected positive plate 12 and 13 pairs of concrete samples 1 of negative plate, chlorion under effect of electric field to soaking working electrode 3 surface seepages, soak working electrode 3 and non-steeped working electrode 2 formation macro cells, thermometer 5 is used for measuring the temperature variation of right electric osmose liquid 9 in the electric osmose pond 8.

3. electric osmose test: DC power supply 11 applies the DC voltage of 3-20 volt by connected positive plate 12 and 13 pairs of concrete samples 1 of negative plate, in the electric osmose process of the test, the temperature variation of right electric osmose liquid 9 can be controlled in 20 ± 0.2 ℃ the scope, stop then powering up, measure in the concrete sample 1 macro cell current value between two electrodes with the zero resistance amp gauge.If the electric current of being surveyed also surpasses the current value that corrosion is sprouted, then system continues to repeat " apply voltage-stop to power up-the macro cell current detecting " process, reaches the current value that corrosion is sprouted up to the macro cell electric current, stops the electric osmose test.

4. chlorine ion concentration is measured: concrete sample 1 is split out from electric osmose pond 8, after the concrete surface drying, near the immersion immersion working electrode 3 partly of concrete sample 1, holed for 14 (as shown in Figure 3), with boring powder as sampling, the drilling depth of each sampling is 10mm ± 1mm, in addition, also the concrete on electrode 3 surfaces is taken a sample, powdered sample separates preservation.Powdered sample is taken by weighing the weight quality to the constant weight and is M through drying, to be measured.Device shown in Figure 4 is adopted in potentiometric titration, dripping phenolphthalein indicator 3-5 in titration cell 17 drips, dropwise add salpeter solution then, use magnetic stirring apparatus 19 to cooperate magnetic stirring bars 16 constantly to stir simultaneously and heat, when solution becomes redness never again, stop to add salpeter solution, this moment the chlorion in the concrete powder is dissolved into to generate in the solution and waits to drip solution 15.Drip with concentration C in titration cell 17 by titration apparatus 22 then _AgNO3Liquor argenti nitratis ophthalmicus, and make contrast electrode 21 with saturated calomel electrode, make indicator electrode 18 with silver electrode, the potential difference (PD) that adopts pot 20 to measure between indicator electrodes 18 and the contrast electrode 21, and the volume V of the record potential difference (PD) and the liquor argenti nitratis ophthalmicus that consumes _AgNO3, the V of correspondence when serving as zero with the secondary difference quotient _AgNO3Value both had been the volume that adds silver nitrate when obtaining terminal point.The content of cement is C% in the concrete, then the chlorine ion concentration D in the concrete _Cl-(by mass of cement percentage composition) is:

$D_{{\mathrm{Cl}}^{-}}=\frac{V_{\mathrm{AgN}{\mathrm{<figure-callout\; id="3"\; label="O"\; filenames="S2008100578444E00011.png"\; state="\{\{state\}\}">O</figure-callout>}}_3}\&times;C_{\mathrm{AgNO}3}\&times;35.5}{1000\&times;M\&times;C\%}\&times;100\%---\left(1\right)$

Chloride ion content is as causing the Rust of Rebar in Concrete criticality chlorine ion concentration in the concrete on employing electrode 3 surfaces.Better the present invention is illustrated below by embodiment.

Embodiment 1

In certain test, be 6.9g in the concrete of the electrode surface concrete powder quality that obtains of taking a sample, employed silver nitrate concentration C _AgNO3=0.01mol/l, the cement content C%=17.58% in the concrete, and the volume relationship of the liquor argenti nitratis ophthalmicus of current potential of measuring during titration and consumption and one-level thereof, secondary difference quotient are as shown in the table:

V AgNO3	Potential difference (PD) E/mV	ΔE/ΔV(mV/ml)	ΔE 2/ΔV 2(mV/ml 2)
				0.0	211.0
2.0	221.0	5
				4.0	248.4	13.7	4.35
5.5	281.8	22.3	5.73
				6.0	289.3	15.0	-14.6
8.0	312.5	11.6	-1.7
				10.0	321.6	4.5	-14.2

Calculate corresponding to secondary difference quotient Δ E with interpolation method ²/ Δ V ²V when being zero _AgNO3Value

$V_{\mathrm{<figure-callout\; id="3"\; label="AgNO"\; filenames="S2008100578444E00011.png"\; state="\{\{state\}\}">AgNO</figure-callout>}3}=5.5\mathrm{mL}+0.5\mathrm{mL}\&times;\left(\frac{5.73\mathrm{mV}/{\mathrm{<figure-callout\; id="2"\; label="ml"\; filenames="S2008100578444E00011.png,S2008100578444E00021.png"\; state="\{\{state\}\}">ml</figure-callout>}}^2}{5.73\mathrm{mV}/{\mathrm{<figure-callout\; id="2"\; label="ml"\; filenames="S2008100578444E00011.png,S2008100578444E00021.png"\; state="\{\{state\}\}">ml</figure-callout>}}^2+14.6\mathrm{mV}/{\mathrm{ml}}^2}\right)=5.64\mathrm{mL}$

According to formula (1), can calculate D again _Cl-Be 0.165%, the critical concentration that promptly causes corrosion in the concrete is 0.165%)

Claims (3)

1. the method for a fast measuring reinforcing steel tarnishing criticality chlorine ion concentration, it is characterized in that, the concrete sample that comprises non-steeped contrast electrode and immersion working electrode with preparation, place the electric osmose pond, apply DC voltage 10-60 minute of lower voltage 3-20 volt on the concrete sample both sides after, stop to power up, after 10-60 minute, the macro cell electric current that soaks working electrode and non-steeped contrast electrode formation is detected, if the macro cell electric current reaches the current value 1 μ A/cm that corrosion is sprouted ²The time stop electric osmose test, otherwise continue to repeat " apply voltage one and stop to power up a macro cell current detecting " process, reach the current value 1 μ A/cm that corrosion is sprouted up to the macro cell electric current ², stop the electric osmose test; After the electric osmose off-test, concrete sample is split out from the electric osmose groove, in the drill hole sampling of concrete immersion part, in addition, also the concrete that soaks working electrode surface is taken a sample, adopt the method for potentiometric titration to measure chlorine ion concentration in the concrete.

2. according to the method for the described fast measuring reinforcing steel tarnishing criticality chlorine ion concentration of claim 1, it is characterized in that concrete steps are as follows;

1) concrete sample preparation: at the fixing non-steeped contrast electrode (2) in the top of concrete sample (1), the fixing working electrode (3) that soaks in the bottom of concrete sample (1), two electrodes are connected with copper conductor (4); Chloride solution will be immersed in the lower part of concrete sample (1), top will be exposed in the air, non-steeped contrast electrode (2) adopts epoxy resin (5) to seal with the side that immersion working electrode (3) is connected with copper conductor (4) and is coated with, and opposite side is exposed in the chloride solution;

2) concrete sample is installed: concrete sample is installed in the electric osmose pond (8), and electric osmose pond (8) are divided into left and right sides two parts, and concrete sample (1) is installed front surface should be clean, no greasy dirt, sand-lime and water; Electric osmose pond (8) left-hand component is used for displaying left electric osmose liquid (10), and electric osmose pond (8) right-hand component is used for displaying right electric osmose liquid (9), and right electric osmose liquid (9) provides the chlorion of test usefulness; Electric osmose Chi Gai (7) is used to reduce the evaporation of electric osmose liquid, DC power supply (11) can apply DC voltage to concrete sample (1) by connected positive plate (12) and negative plate (13), chlorion under effect of electric field to soaking working electrode (3) surface seepage, soak working electrode (3) and non-steeped working electrode (2) and constitute macro cell, thermometer (5) is used for measuring the temperature variation of right electric osmose liquid (9) in the electric osmose pond (8);

3) electric osmose test: DC power supply (11) applies the DC voltage of 3-20 volt to concrete sample (1) by positive plate (12) and negative plate (13), in the electric osmose process of the test, the temperature variation of right electric osmose liquid (9) can be controlled in 20 ± 0.2 ℃ the scope, stop then powering up, measure in the concrete sample (1) macro cell current value between two electrodes with the zero resistance amp gauge, if the electric current of being surveyed does not also surpass the current value that corrosion is sprouted, then system continue to repeat " apply voltage-stop to power up-the macro cell current detecting " process, reach the current value that corrosion is sprouted up to the macro cell electric current, stop the electric osmose test;

4) chlorine ion concentration is measured: concrete sample (1) is split out from electric osmose pond (8), after the concrete surface drying, near boring (14) the immersion immersion working electrode (3) partly of concrete sample (1), with boring powder as sampling, the drilling depth of each sampling is 10mm ± 1mm, in addition, also the concrete on electrode (3) surface is taken a sample, powdered sample separates preservation; Powdered sample is taken by weighing weight to the constant weight and is M through drying, to be measured; Dripping phenolphthalein indicator 3-5 by titration apparatus (22) in titration cell (17) drips, dropwise add salpeter solution then, use magnetic stirring apparatus (19) to cooperate magnetic stirring bar (16) constantly to stir simultaneously and heat, when solution becomes redness never again, stop to add salpeter solution, this moment the chlorion in the concrete powder is dissolved into to generate in the solution and waits to drip solution (15), drip with concentration C in titration cell (17) by titration apparatus (22) then _AgNO3Liquor argenti nitratis ophthalmicus, and make contrast electrode (21) with saturated calomel electrode, make indicator electrode (18) with silver electrode, adopt the potential difference (PD) between pot (20) measurement indicator electrode (18) and the contrast electrode (21), and the volume V of the record potential difference (PD) and the liquor argenti nitratis ophthalmicus that consumes _AgNO3, the V of correspondence when serving as zero with the secondary difference quotient _AgNO3Value both had been the volume that adds silver nitrate when obtaining terminal point, and the content of cement is C% in the concrete, then the chlorine ion concentration D in the concrete _Cl-(by mass of cement percentage composition) is:

$D_{{\mathrm{Cl}}^{-}}=\frac{V_{\mathrm{AgN}{O}_3}\&times;C_{\mathrm{AgNO}3}\&times;35.5}{1000\&times;M\&times;C\%}\&times;100\%$

Adopt chloride ion content conduct causing Rust of Rebar in Concrete criticality chlorine ion concentration in the surperficial concrete of electrode (3).

3. according to the method for the described fast measuring reinforcing steel tarnishing criticality chlorine ion concentration of claim 2, it is characterized in that described left electric osmose liquid (10) composition is the NaOH of 0.2mol/L; Right electric osmose liquid (9) composition is the NaOH+5wt%NaCl of 0.2mol/L.

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