CN103278429A - Method for indirectly measuring concrete chloride ion diffusion coefficient - Google Patents

Abstract

The invention discloses a method for indirectly measuring concrete chloride ion diffusion coefficient. The method comprises the following steps of: preparing a test piece; performing electromigration test: in the electromigration test, injecting KOH solution into a test piece barrel, injecting Nal-containing KOH solution into a test flume; performing iodide ion diffusion depth determination; correcting the iodide ion diffusion depth, and converting the iodide ion diffusion depth into chloride and iodide ion diffusion depth; and calculating the chloride ion diffusion coefficient according to the obtained chloride and iodide ion diffusion depth. According to the method, a test method for measuring the concrete chloride ion diffusion coefficient is established, in the test process, the method is not affected by the chloride ion in the concrete, high data precision is realized by correction on the iodide ion diffusion depth, and the method can be used for durability design and life prediction for the internally doped concrete structures and the chloride ion corroded structures.

Description

A kind of method of indirect determination concrete chloride ion coefficient of diffusion

[technical field]

The present invention relates to measure the method for concrete chloride ion coefficient of diffusion, relate in particular to a kind of method of indirect determination concrete chloride ion coefficient of diffusion.

[background technology]

The permanance of xoncrete structure depends on the process that lewis' acid entered or passed material with the form of liquid or gas in essence, and structural life-time depends on that these materials enter concrete speed.The harmfulness medium is invaded the influence that concrete process mainly is subjected to concrete permeability." perviousness " this word is widely used, and being often referred under general situation influences the characteristic that medium is invaded.Chloride diffusion coefficient has crucial influence for the prediction rate of propagation.The most frequently used method still is unstable state electromigration test (RCM) at present, by measuring anolyte initially and the mean value (T) of finishing temperature, test specimen height (h), chlorion diffusion depth (x _d) and the energizing test time (t), the chlorion rapid diffusion coefficient of calculating concrete sample, expression formula is as follows:

$D_{\mathrm{RCM},0}=2.872\×{10}^{-6}\frac{\mathrm{Th}(x_d-\mathrm{\α}\sqrt{x_d})}{t}---\left(1\right)$

$a=3.338\×{10}^{-3}\sqrt{\mathrm{Th}}---\left(2\right)$

This method test cycle is short, test apparatus is simple, easy to operate, and directly derive coefficient of diffusion according to the measured value of the chlorion intrusion concrete degree of depth, rather than by electric weight, resistance or the electric mensuration of leading, advantage is more, be widely adopted in the world, " the concrete structure durability design and construction guide " of China also recommended to use.But RCM requirement of experiment inside concrete is chloride ion-containing not.If inside concrete has contained chlorion at the beginning of experiment, in the experimentation of RCM, inner chlorion will produce two kinds of effects: 1. they can move under electric field environment; 2. they are also and indicator reaction.These two kinds of effects can have influence on the accuracy of RCM experimental result, adopt the experimental technique of RCM can not measure chloride diffusion coefficient when serious.

As mentioned above, in carrying out the process of RCM experiment, chloride ion-containing also can move under electric field action in the structure, and can and indicator react.These two kinds of effects all can have influence on the accuracy of RCM experimental result, the chlorion that includes in xoncrete structure exceeds a threshold value, the experimental technique of employing RCM can not be measured the chloride diffusion coefficient of structure, therefore, present test method can not be used for following two kinds of situations: one, the mensuration of internal doping type chlorion xoncrete structure infiltration coefficient; Two, be subjected to the mensuration of chlorion corrosion concrete structure infiltration coefficient.But in actual engineering, the mensuration of this part structure chloride diffusion coefficient is particularly important.

The applicant had once submitted to name to be called the application for a patent for invention of " assay method of iodide ion length of penetration in a kind of concrete " on January 13rd, 2012, and (application number is: 201210010833.7) to State Intellectual Property Office, this process of the test is not subjected to the influence of inside concrete chlorion, and process is simply quick; But the mensuration of iodide ion length of penetration can't directly replace chloride diffusion coefficient to use.

Utilize solution that the iodide ion coefficient of diffusion replaces chloride diffusion coefficient in " New method measure the rapid migration coefficient of chloride-contaminated concrete (cement and research; 2004,34:421-427) " literary composition, to set forth to some extent.But, this article thinks that the effect of iodide ion coefficient of diffusion and chloride diffusion coefficient is identical, and the ability of chloride ion-containing concrete opposing ions diffusion will inevitably produce very big error to concrete durability Design and life prediction in alternative chloride diffusion coefficient was estimated simply with the iodide ion coefficient of diffusion.

[summary of the invention]

The technical problem to be solved in the present invention provides a kind of method of indirect determination concrete chloride ion coefficient of diffusion, can be used under existence conditions internal doping type chlorion xoncrete structure and be subjected to the mensuration of chloride ion-containing xoncrete structure infiltration coefficient in the chlorion corrosion concrete structure etc., with the ability of chloride ion-containing concrete opposing ions diffusion in the accurate evaluation, and enough precision are arranged.

In order to solve the problems of the technologies described above, the technical solution used in the present invention is that a kind of method of indirect determination concrete chloride ion coefficient of diffusion may further comprise the steps:

101) test material preparation;

102) electromigration test: in the electromigration test, inject KOH solution in the test specimen tube, inject the KOH solution that contains NaI in the test flume;

103) the iodide ion diffusion depth is measured;

104) the iodide ion diffusion depth is revised, be converted into chlorine iodide ion diffusion depth;

105) the chlorine iodide ion diffusion depth that obtains with step 104 is calculated chloride diffusion coefficient.

More than the method for indirect determination concrete chloride ion coefficient of diffusion according to claim 1, in step 102, the volumetric molar concentration of KOH solution is 0.2 mol/L; Contain in the KOH solution of NaI, the mass percent concentration of NaI is that the volumetric molar concentration of 11.89%, KOH is 0.2 mol/L.

The method of above-described indirect determination concrete chloride ion coefficient of diffusion in step 104, adopts the iodide ion diffusion depth of diffusion depth correction factor λ x _IdRevise, be converted into chlorine iodide ion diffusion depth x _d:

λ=[1.2+(0.55-W/C)]

In the formula, W/C is concrete water cement ratio.

x _d=λx _id

The present invention sets up the test method of measuring concrete iodide ion coefficient of diffusion, in the process of the test, be not subjected to the influence of inside concrete chlorion, by the correction of iodide ion diffusion depth is obtained the higher data precision, can be used for the internal doping type xoncrete structure and be subjected to the chlorion eating texture to carry out durability Design and life prediction.

[embodiment]

The concrete of test specimen adopts three kinds of water cement ratio, is respectively: 0.39,0.47 and 0.53.Match ratio sees Table 1, is made into diameter 100mm, and height is the cylindrical test specimen blank of 100mm

Table 1 concrete sample match ratio/kg/m ³

Step 1: maintenance 28d under the concrete sample blank standard conditions, each test specimen blank is cut into two diameter 100mm, height is the test specimen of 50mm, carry out the test of RIM(concrete iodide ion coefficient of diffusion respectively) and the RCM test, wherein, the RCM test is undertaken by traditional RCM test method, no longer is described; Below only the process of RIM test of the present invention is described.

Step 2: need carry out 15 min ultrasonic cleaning before the test specimen that carries out RIM test is installed and dry up with the hair dryer (using the cold wind shelves) of 200-300 mm apart.Ultrasonic bath needs water (room temperature) flushing one minute in advance.The surface of test specimen should be totally, no greasy dirt, no sand-lime.

Step 3: the test specimen tube that installs test specimen is installed in the Tang Shi RCM analyzer test flume, installs positive plate, in the test specimen tube, inject the KOH solution of about 300 ml, 0.2 mol/L then, make positive plate and test specimen surface all be immersed in the solution; In test flume, inject solution (solution NaI mass percent concentration is that the volumetric molar concentration of 11.89%, KOH is 0.2 mol/L), to equal with the liquid level of KOH solution in the test specimen tube.

Step 4: when measuring electric current, multimeter is transferred to 200 mA shelves; During measuring voltage, multimeter is transferred to the 200V shelves; The temperature measuring of two kinds of solution should be accurate to 0.2 ℃, determine that according to initial current (table 2) be 8h the conduction time of test specimen 1 and test specimen 2, be 24h the conduction time of test specimen 3, after electric field speeding-up ion process of osmosis finishes, use development process respectively, determine the length of penetration of iodide ion, test findings such as table 3 calculate concrete iodide ion rapid diffusion coefficient.

Step 5: before taking out test specimen, first powered-down disconnects line, takes out the test specimen tube, falls except KOH solution, unclamps the hoop screw, shifts out test specimen then from the top down; After test specimen shifts out from the test specimen tube, cleave in two on pressure testing machine immediately; Spray colored indicator immediately on the test specimen surface of riving; The potassium iodate solution of elder generation's jet quality percent concentration 1% is oxidized to iodine to the iodide ion in the concrete, spray 2% starch suspension again, treat concrete surface colour developing back measurement iodide ion length of penetration, the inclusion compound of iodide ion and starch displaing amaranth in concrete.

Step 6: concrete iodide ion coefficient of diffusion is calculated as follows (intermediate operations is accurate to four position effective digitals, and end product keeps three position effective digitals):

$D_{\mathrm{RIM},0}=2.872\×{10}^{-6}\frac{\mathrm{Th}(x_{\mathrm{id}}-\mathrm{\α}\sqrt{x_{\mathrm{id}}})}{t}$

$a=3.338\×{10}^{-3}\sqrt{\mathrm{Th}}$

D in the formula _{RIM, 0}The concrete iodide ion coefficient of diffusion (m that-RIM method is measured ²/ s);

T-anolyte is the mean value (K) of gentle finishing temperature just;

H-test specimen height (m);

x _Id-iodide ion diffusion depth (m);

T-energizing test time (s);

α-auxiliary variable.

The detailed results of calculating sees Table 3.

The relation of table 2 initial current and test period

Table 3 RIM test findings

The present invention introduces colour developing degree of depth correction factor λ (diffusion depth correction factor λ), and lambda definition is the develop the color ratio of the degree of depth (chlorion diffusion depth) of chlorion in the iodide ion colour developing degree of depth (iodide ion diffusion depth) and the RCM test in the RIM test.According to water cement ratio and the inversely proportional relation of the colour developing degree of depth, through data fitting, determine that the formula of colour developing degree of depth correction factor (diffusion depth correction factor) is as follows:

λ=[1.2+(0.55-W/C)]

The colour developing degree of depth of iodide ion is x in the RIM test _Id, can calculate the colour developing degree of depth x of corresponding RCM chlorion _dFor:

x _d=λx _id

X _dSubstitution formula 1 gets the present invention calculates chlorion rapid diffusion coefficient by the RIM test formula:

$D_{\mathrm{RCM},0}=2.872\×{10}^{-6}\frac{\mathrm{Th}-\mathrm{\α}\sqrt{\mathrm{\λ}{x}_{\mathrm{id}}}}{t}$

After introducing colour developing degree of depth correction factor, iodide ion colour developing degree of depth correction result is seen Table 4, that revises back RIM the results are shown in Table 5.As can be seen, for test specimen 1, RIM tests the result that revised chlorion rapid diffusion coefficient and RCM record and differs less than 5%; For test specimen 2, it is only suitable with the result that RCM records that RIM tests revised result; For test specimen 3, RIM tests the result that revised result and RCM record and differs less than 1%.If the result of definition RCM test is true value, the error range that the RIM test is calculated is: 0-5.12%.The RIM test findings is higher through revised data precision, can meet general error requirements in the civil engineering work application.

Table 4 colour developing coefficient is to the correction chart of the iodide ion colour developing degree of depth:

It is as follows that the revised chloride diffusion coefficient value of table 5 and traditional RCM method record the contrast of concrete chloride ion coefficient of diffusion value:

At first, for same test specimen, the colour developing degree of depth of iodide ion is lower than chlorion, and when the conversion iontophoretic injection degree of depth, the present invention introduces colour developing degree of depth correction factor (λ), can be close to the result of RCM test by revised iodide ion infiltration result.The reagent concentration of the present invention's employing is more approaching in addition tests with RCM, the mass percent concentration of NaI is 11.89% in the iodide ion permeability test of the present invention, the mass percent concentration of NaCl is 5% in the tradition RCM test, can guarantee the volumetric molar concentration unanimity of the two like this, make both tests have comparability, can be by converting to obtain correct result.

Claims (3)

1. the method for an indirect determination concrete chloride ion coefficient of diffusion is characterized in that, may further comprise the steps:

101) test material preparation;

102) electromigration test: in the electromigration test, inject KOH solution in the test specimen tube, inject the KOH solution that contains NaI in the test flume;

103) the iodide ion diffusion depth is measured;

104) the iodide ion diffusion depth is revised, be converted into chlorine iodide ion diffusion depth;

105) the chlorine iodide ion diffusion depth that obtains with step 104 is calculated chloride diffusion coefficient.

2. the method for indirect determination concrete chloride ion coefficient of diffusion according to claim 1 is characterized in that, in step 102, the volumetric molar concentration of KOH solution is 0.2 mol/L; Contain in the KOH solution of NaI, the mass percent concentration of NaI is that the volumetric molar concentration of 11.89%, KOH is 0.2 mol/L.

3. the method for indirect determination concrete chloride ion coefficient of diffusion according to claim 1 is characterized in that, in step 104, adopts the iodide ion diffusion depth of diffusion depth correction factor λ xid to revise, and is converted into chlorine iodide ion diffusion depth xd:

λ=[1.2+(0.55-W/C)]

In the formula, W/C is concrete water cement ratio;

x _d=λx _id。