CN103698259B - A kind of cement-based material sulfate radical erosion depth method of testing - Google Patents
A kind of cement-based material sulfate radical erosion depth method of testing Download PDFInfo
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- CN103698259B CN103698259B CN201310693920.1A CN201310693920A CN103698259B CN 103698259 B CN103698259 B CN 103698259B CN 201310693920 A CN201310693920 A CN 201310693920A CN 103698259 B CN103698259 B CN 103698259B
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- 239000004568 cement Substances 0.000 title claims abstract description 179
- 239000000463 material Substances 0.000 title claims abstract description 65
- 230000003628 erosive effect Effects 0.000 title claims abstract description 28
- 238000010998 test method Methods 0.000 title abstract description 4
- 238000012360 testing method Methods 0.000 claims abstract description 148
- 230000035515 penetration Effects 0.000 claims abstract description 93
- 238000000034 method Methods 0.000 claims abstract description 47
- 230000008569 process Effects 0.000 claims abstract description 24
- 229910001220 stainless steel Inorganic materials 0.000 claims description 36
- 239000010935 stainless steel Substances 0.000 claims description 36
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 24
- 238000001453 impedance spectrum Methods 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 238000009413 insulation Methods 0.000 claims description 16
- 229920000620 organic polymer Polymers 0.000 claims description 16
- 238000009792 diffusion process Methods 0.000 claims description 11
- 150000002500 ions Chemical class 0.000 claims description 10
- 230000008595 infiltration Effects 0.000 claims description 9
- 238000001764 infiltration Methods 0.000 claims description 9
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- 239000011398 Portland cement Substances 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 6
- 239000011148 porous material Substances 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 5
- 238000010351 charge transfer process Methods 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 230000037427 ion transport Effects 0.000 claims description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 4
- 238000007790 scraping Methods 0.000 claims description 2
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 abstract description 5
- 238000012423 maintenance Methods 0.000 abstract description 5
- 230000008859 change Effects 0.000 abstract description 3
- 230000036571 hydration Effects 0.000 abstract description 3
- 238000006703 hydration reaction Methods 0.000 abstract description 3
- 239000012466 permeate Substances 0.000 abstract 1
- 238000000465 moulding Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 3
- 241000258957 Asteroidea Species 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- 208000003464 asthenopia Diseases 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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Abstract
The invention provides a kind of cement-based material sulfate radical erosion depth method of testing, this method carries out maintenance and the sulfate radical penetration testing of whole process by using the mould for cement hydration process electrochemical impedance spectroscopy on-line testing disclosed in Patent No. " ZL201120473976.2 " to cement material, when sulfate radical permeates by laying down both mold ends 40mm × 40mm battery lead plates, cement material is allowed to receive sulfate radical erosion, need both mold ends are loaded onto into battery lead plate again to carry out electrochemical impedance spectroscopy test during test, change the sulfate radical penetration depth to reflect and calculate cement material finally by the rule of electrochemical parameter.The present invention has the advantages that mould and cement specimen are hardly damaged, energy repeatability is detected, error is small and easy to operate.
Description
Technical Field
The invention belongs to the field of cement material penetration testing methods, and particularly relates to a method for testing sulfate radical erosion depth of a cement-based material.
Background
The existing traditional barium nitrate reagent method for testing the penetration depth of sulfate radicals has the following defects:
(1) the cement test piece in the mold needs to be disassembled, which easily causes the damage of the mold, and the actual operation process is very inconvenient, and the cement test piece can not be repeatedly corroded and tested.
(2) The test piece needs to be damaged, the component is often repaired after the test is finished, and sometimes the damage to the component caused by the method is even unrepairable.
(3) The failure to detect repeatedly, the method can damage the cement test piece, and even if the component is repaired, the later penetration process is affected, so that the penetration depth measured again is inaccurate.
(4) The error is large, and the method adopts a manual measuring tape for measurement during testing, so that the great reading error is often caused by improper operation or visual fatigue.
(5) The operation is inconvenient, the workload of the method is large, and a large amount of manpower and time are often needed in batch detection.
Disclosure of Invention
The invention aims to provide a method for testing the sulfate radical erosion depth of a cement-based material, and aims to solve the problems that a mould and a cement test piece are easy to damage, cannot be repeatedly detected, have large errors, are inconvenient to operate and the like in the conventional testing method.
The invention is realized in this way, a cement-based material sulfate radical erosion depth test method, comprising the following steps:
injecting the composite Portland cement into a mold disclosed in patent No. ZL201120473976.2 for cement test piece maintenance, then removing electrode plates at two ends of the mold, and placing the mold in sulfate radical solutions with different sulfate radical concentrations for infiltration; the die comprises a bottom plate and two side plates, and comprises two end plates, wherein the end plates are electrode plates, rectangular square frames are enclosed by the end plates and the side plates, the side edges of the end plates are connected with the side edges of the side plates through screws, and the lower ends of the end plates and the side plates are connected with the bottom plate through screws; the electrode comprises an electrode post, wherein the electrode post comprises a mounting thread, the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, and the mounting thread of the electrode post is screwed into the threaded hole of the stainless steel electrode plate; the bottom plate, the side plate and the cover plate are made of high-insulation organic polymers; the bottom plate, the side plates and the stainless steel electrode plate of the high-insulation organic polymer form a cavity of 40mm multiplied by 160mm together for sample forming and online testing;
taking part of cement test pieces at different penetration time points, removing the cement test pieces from the mold, and measuring the actual penetration depth value;
assembling the electrode plates at two ends of the mold of the cement test piece which is not removed for measurement, then carrying out impedance spectrum test and obtaining each impedance spectrogram, fitting each impedance spectrogram by using an electrochemical model to obtain an actual electrochemical parameter value, and fitting a functional relation between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value and the actual electrochemical parameter value;
and calculating a predicted electrochemical parameter value according to the water-cement ratio and the penetration time point of the cement test piece, and obtaining a predicted penetration depth value according to the functional relation.
Preferably, the cement test pieces have water cement ratios of 0.25, 0.3, 0.4 and 0.5, respectively.
Preferably, the two-end electrode plate is an electrode plate with 40mm × 40mm at both ends, which is described in paragraph 0030 of the embodiment of the patent document disclosed in patent No. ZL201120473976.2, the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate includes a threaded hole, and the mounting thread of the electrode post is screwed into the threaded hole of the stainless steel electrode plate; the bottom plate, side plates and stainless steel electrode plates of the high-insulation organic polymer together form a cavity of 40mm x 160mm for molding samples and on-line testing.
Preferably, the sulfate concentration in different sulfate solutions is 300mg/L, 3000mg/L and 6000mg/L respectively.
Preferably, the infiltration time points are 0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days, and 270 days, respectively.
Preferably, the step of taking a part of the cement test pieces at different penetration time points, detaching the cement test pieces from the mold, and then measuring the actual penetration depth value comprises the following specific steps:
preparing 3 cement test pieces cured under the same conditions, taking the cement test pieces out of a mould, splitting the cement test pieces into two halves, scraping off powder remaining on a fracture surface, immediately coating a dilute nitric acid solution with the concentration of 1mol/L, after reaction, coating a silver nitrate solution with the concentration of 0.05mol/L, and respectively measuring the penetration depth value of each point on two side surfaces of each cement test piece according to one measuring point per 5 mm after 30 seconds;
and respectively taking 7 measuring points on each side surface, calculating the average penetration depth value of each side surface of each cement test piece, finally calculating the total average value of the penetration depth values of 3 cement test pieces according to the average penetration depth value of each side surface, and selecting the total average value as the actual penetration depth value.
Preferably, the impedance spectrogram comprises a Nyquist diagram and a Bode diagram.
Preferably, the electrochemical model is: rs(Q1(Rct1W1))(Q2(Rct2W2) ); wherein,
Rsis the pore solution resistance, Q, of a cement sample1Double electric layer capacitance of solid/liquid two phase in cement materialct1Is ion transport process resistance, W, inside the cement material1Is the ionic diffusion process resistance, Q, inside the cement material2Is an electric double layer capacitor between the cement material and the electrode plate, Rct2Is the charge transfer process resistance, W, of the electrode plate surface2Is the ion diffusion process resistance of the electrode plate surface.
Preferably, the functional relationship between the depth of penetration value and the electrochemical parameter value is defined as:
Rct1＝aDb(ii) a Wherein D is the penetration depth value, Rct1A and b are constants for electrochemical parameter values.
Preferably, the predicted electrochemical parameter value is exponential as a function of the permeation time point.
The invention overcomes the defects of the prior art, and provides a method for testing the sulfate radical erosion depth of a cement-based material, which carries out the whole-process maintenance and sulfate radical penetration test on the cement material by adopting a mould for the electrochemical impedance spectrum on-line test in the cement hydration process, which is disclosed by the patent number of ZL201120473976.2 and the name of 'an on-line test mould for the electrochemical impedance spectrum in the cement hydration process', wherein the mould comprises a bottom plate and two side plates, and comprises two end plates, the end plates are electrode plates, the end plates and the side plates surround a rectangular square frame, the side edges of the end plates are connected with the side edges of the side plates through screws, and the lower ends of the end plates and the side plates are connected with the bottom plate; the electrode comprises an electrode post, wherein the electrode post comprises a mounting thread, the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, and the mounting thread of the electrode post is screwed into the threaded hole of the stainless steel electrode plate; the bottom plate, the side plate and the cover plate are made of high-insulation organic polymers; the bottom plate, side plates and stainless steel electrode plates of the high-insulation organic polymer together form a cavity of 40mm x 160mm for molding samples and on-line testing. Firstly, preparing and curing a cement material by using the mould, and removing electrode plates with the two ends of 40mm multiplied by 40mm after curing for 28 days, wherein the electrode plates are stainless steel electrode plates, the middle parts of the stainless steel electrode plates comprise threaded holes, and mounting threads of electrode posts are screwed into the threaded holes of the stainless steel electrode plates; the bottom plate, the side plates and the stainless steel electrode plates of the high-insulation organic polymer jointly form a cavity of 40mm x 160mm for sample forming and online testing, so that the cement material is subjected to sulfate radical corrosion, and when the test is needed, the electrode plates are arranged at two ends of the mould to perform electrochemical impedance spectroscopy test, thereby tracking the corrosion process of the cement material. The cement is always in the mould in the whole process and is not damaged, so that nondestructive testing is realized. Because the electrode plates at the two ends of the mould can be disassembled and assembled, the cement material can be repeatedly corroded and tested, and the repeated test is realized. The mould is easy to disassemble and assemble, and the test is convenient and feasible.
In addition, the invention relates to the test of cement-based material sulfate radical penetration depth, because the parameters of the elements forming the electrochemical model are regularly changed along with the erosion process and are in mathematical connection with the sulfate radical penetration depth, the proper electrochemical model is used for representing the cement material under the erosion action, and the sulfate radical penetration depth of the cement material is reflected and calculated through the regular change of the electrochemical parameters, so that the generation of large reading errors caused by manually reading the penetration depth according to the vision is avoided, and a large amount of test labor and time can be saved. The electrochemical impedance spectrum method can effectively characterize the microstructure of the cement material, and has the advantages of high sensitivity, good repeatability, short test time and nondestructive testThe method is a quick and effective method for researching the structure and the performance of the cement-based material. The electrochemical impedance spectrum is effective for researching the structural change of the cement-based material and the sensitivity of the interface between slurry and aggregate, and the structure of materials such as cement, mortar, concrete and the like can become compact along with the ion erosion, so that the impedance spectrum of the materials is obviously changed. Using an electrochemical equivalent circuit model Rs(Q1(Rct1W1))(Q2(Rct2W2) ) the ionic attack process of the cement-based material can be characterized. This circuit was not used in the testing, but only in fitting the data, and was used to characterize the sulfate attack process of cement-based materials. The model consists of the following parameters: rsIs the pore solution resistance, Q, of a cement sample1Double electric layer capacitance of solid/liquid two phase in cement materialct1Is ion transport process resistance, W, inside the cement material1Is the ion diffusion process resistance (Warburg resistance), Q, inside the cement material2Is an electric double layer capacitor between the cement material and the electrode plate, Rct2Is the charge transfer process resistance, W, of the electrode plate surface2Is the ion diffusion process resistance (Warburg resistance) of the electrode plate surface. Model Rs(Q1(Rct1W1))(Q2(Rct2W2) The) process not only considers the reaction effect of an external electrode plate in the test process, but also considers the solid/liquid interaction inside the cement material, namely the double electric layer capacitance effect between solid and liquid, the ion diffusion process in the pore solution and the ion transfer process inside the sample, so the model can effectively track the ion erosion process of the cement-based material.
Drawings
FIG. 1 is a Nyquist plot of a cement test piece with a water cement ratio of 0.3 at a sulfate concentration of 6000mg/L after being soaked for 150 days in example 1 of the present invention;
FIG. 2 is a Bode diagram of cement test pieces with a water cement ratio of 0.3 soaked for 150 days at a sulfate concentration of 6000mg/L in example 1 of the invention;
FIG. 3 is a Nyquist plot of cement test pieces of 0.4 water cement ratio soaked for 15 days at a sulfate concentration of 6000mg/L in example 2 of the present invention;
FIG. 4 is a bode plot of cement test pieces having a water cement ratio of 0.4 in example 2 of the present invention soaked for 15 days at a sulfate concentration of 6000 mg/L.
Detailed Description
The technical scheme provided by the invention is as follows: carrying out impedance spectrum test on the corroded hardened cement material test block to obtain an impedance spectrum; fitting an impedance spectrogram by using an electrochemical circuit model of the cement material to obtain electrochemical parameters, and then testing the actual sulfate radical penetration depth of the cement material; and establishing a functional relation between the electrochemical parameters and the actual penetration depth, and calculating the later-stage penetration depth of the cement material by calculating the electrochemical parameters so as to finish the test of the later-stage penetration depth of the cement material.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A method for testing the sulfate radical erosion depth of a cement-based material comprises the following specific steps:
(1) injecting the composite Portland cement into a mold disclosed in patent No. ZL201120473976.2 for cement test piece maintenance, then removing electrode plates at two ends of the mold and placing the mold in sulfate radical solutions with different sulfate radical concentrations for infiltration, wherein the mold comprises a bottom plate and two side plates, the mold comprises two end plates, the end plates are the electrode plates, the end plates and the side plates form a rectangular square frame in a surrounding mode, the side edges of the end plates are connected with the side edges of the side plates through screws, and the end plates and the lower ends of the side plates are connected with the bottom plate through screws; the electrode comprises an electrode post, wherein the electrode post comprises a mounting thread, the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, and the mounting thread of the electrode post is screwed into the threaded hole of the stainless steel electrode plate; the bottom plate, the side plate and the cover plate are made of high-insulation organic polymers; the bottom plate, side plates and stainless steel electrode plates of the high-insulation organic polymer together form a cavity of 40mm x 160mm for molding samples and on-line testing.
In the step (1), injecting 525 composite Portland cement produced by Shenzhen Starfish Xiao Yetian cement Limited into a mold disclosed by patent No. ZL201120473976.2 (the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, the mounting thread of an electrode pole is screwed into the threaded hole of the stainless steel electrode plate, the materials of the bottom plate, the side plate and the cover plate are high-insulation organic polymers, the bottom plate, the side plate and the stainless steel electrode plate of the high-insulation organic polymers jointly form a cavity of 40mm multiplied by 160mm for molding a sample and online testing), removing the 40mm multiplied by 40mm electrode plates at two ends of the mold after a cement test piece in the mold is maintained for 28 days, wherein the water cement ratio of the cement test pieces formed in the die is 0.25, 0.3, 0.4 and 0.5 respectively, 24 test pieces are prepared from each cement test piece with the water cement ratio, and the test piece size is 160mm multiplied by 40 mm.
The mould with the electrode plates of 40mm multiplied by 40mm at two ends and the cement test piece in the mould are immersed into an erosion box, and sulfate radical solutions with the sulfate radical concentration of 300mg/L, 3000mg/L and 6000mg/L are respectively arranged in the erosion box.
(2) And taking part of the cement test piece at different penetration time points, and measuring the actual penetration depth value after detaching the cement test piece from the mold.
In the step (2), 3 pieces of the test piece cured under the same conditions were taken at each infiltration time point (0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days, and 270 days) in the infiltration process, the test piece was taken out from the mold, split into two halves in the longitudinal direction, the powder remaining on the fracture surface was scraped off, and then a dilute nitric acid solution having a concentration of 1mol/L was applied, and after the reaction, a silver nitrate solution having a concentration of 0.05mol/L was applied. After 30 seconds, the penetration depth of each point on the two side surfaces is measured by a vernier caliper according to the originally marked measuring point of every 5 mm. There were 7 measurement points on each side, averaged to 0.01 mm as follows:
Dx＝(D1+D2+D3+D4+D5+D6+D7)/7
wherein Dx is the average penetration depth of each side of the current cement test piece, D1To D7The penetration depth of the measuring point is shown.
The total average value of the penetration depths of the above 3 cement test pieces was taken as the actual penetration depth value at a certain penetration time point, and for example, the actual penetration depth values at 0.3 water-cement ratio in 6000mg/L sulfate solution at penetration time points of 0, 15 and 30 days are shown in table 1 below:
TABLE 1
(3) And (3) assembling the two-end electrode plates of the residual cement test piece which is not removed for measurement, then carrying out impedance spectrum test to obtain each impedance spectrogram, fitting each impedance spectrogram by using an electrochemical model to obtain an actual electrochemical parameter value, and fitting a functional relation between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value and the actual electrochemical parameter value.
In step (3), at each permeation time point (0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days and 270 days), other cement test pieces which are not removed from the mold are taken to be subjected to impedance spectrum test (two 40mm × 40mm electrode plates which are removed are reinstalled at two ends of the mold before the impedance spectrum test is carried out) to obtain each impedance spectrum, for example, as shown in fig. 1 and 2, fig. 1 is a Nyquist diagram of the cement test piece with 0.3 water cement ratio in the embodiment 1 of the present invention, when the cement test piece is soaked for 150 days at 6000mg/L sulfate radical concentration; FIG. 2 is a Bode plot of cement test pieces of 0.3 water cement ratio soaked for 150 days at a sulfate concentration of 6000mg/L in example 1 of the present invention. In this embodiment, the electrochemical impedance spectroscopy tester is a 283 potentiostat/galvanostat, a 2000-type frequency response detector, a Single powersine input signal, a Model283at address14 electrode plate, and a test frequency of 100.0mHz to 1.000 mHz.
Using electrochemical model R to make each impedance spectrograms(Q1(Rct1W1))(Q2(Rct2W2) Fitting (fitting using software Zsimpwin), where RsIs the pore solution resistance, Q, of a cement sample1Double electric layer capacitance of solid/liquid two phase in cement materialct1Is ion transport process resistance, W, inside the cement material1Is the ionic diffusion process resistance, Q, inside the cement material2Is an electric double layer capacitor between the cement material and the electrode plate, Rct2Is the charge transfer process resistance, W, of the electrode plate surface2Is the ion diffusion process resistance of the electrode plate surface.
Actual electrochemical parameter values R were obtained after fitting for 0, 15, 30, 60, 90, 120, 150, 210 and 270 daysct1Values of (b), e.g. the actual electrochemical parameter values R of 0.3 water-cement test pieces in 6000mg/L sulphate solution at 0, 15 and 30 daysct1The values of (A) are shown in Table 2:
TABLE 2
Fitting a functional relationship between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value obtained in the step (2) and the actual electrochemical parameter value obtained in the step (3) to fit the sulfate radical penetration depth D and the parameter Rct1The relation of values, e.g. the functional relation between the value of the penetration depth and the value of the electrochemical parameter for a cement specimen with a water-cement ratio of 0.3Comprises the following steps: rct1＝aDb(constants a and b are related to the sulfate radical concentration of the soaking solution, the water cement ratio, the curing age and the cement variety).
(4) And calculating a predicted electrochemical parameter value according to the water-cement ratio and the penetration time point of the cement test piece, and obtaining a predicted penetration depth value according to the functional relation.
In step (4), due to the parameter Rct1The value and the time T satisfy an exponential function relation, and for a cement test piece with a water-cement ratio of 0.3, the function relation is as follows:for example, the parameter R for 150 and 270 days of sulfate attack is calculated therefromct1The values are shown in Table 3:
TABLE 3
In calculating the predicted electrochemical parameter Rct1Value can be given by the function Rct1＝aDbAnd (3) calculating the predicted penetration depth value D of sulfate radicals in the cement test piece which is not removed from the mould, so as to realize the nondestructive test of the penetration depth, wherein the calculation result is shown in the following table 4:
TABLE 4
| Number of days of erosion | Predicted penetration depth value (mm) |
| (sky) | 0.3 water cement ratio |
| 150 | 20 |
| 270 | 22 |
Example 2
A method for testing the sulfate radical erosion depth of a cement-based material comprises the following specific steps:
(1) injecting the composite Portland cement into a mold disclosed in patent No. ZL201120473976.2 for cement test piece maintenance, then removing electrode plates at two ends of the mold and placing the mold in sulfate radical solutions with different sulfate radical concentrations for infiltration, wherein the mold comprises a bottom plate and two side plates, the mold comprises two end plates, the end plates are the electrode plates, the end plates and the side plates form a rectangular square frame in a surrounding mode, the side edges of the end plates are connected with the side edges of the side plates through screws, and the end plates and the lower ends of the side plates are connected with the bottom plate through screws; the electrode comprises an electrode post, wherein the electrode post comprises a mounting thread, the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, and the mounting thread of the electrode post is screwed into the threaded hole of the stainless steel electrode plate; the bottom plate, the side plate and the cover plate are made of high-insulation organic polymers; the bottom plate, side plates and stainless steel electrode plates of the high-insulation organic polymer together form a cavity of 40mm x 160mm for molding samples and on-line testing.
In the step (1), injecting 525 composite Portland cement produced by Shenzhen Starfish Xiao Yetian cement Limited into a mold disclosed by patent No. ZL201120473976.2 (the electrode plate is a stainless steel electrode plate, the middle part of the stainless steel electrode plate comprises a threaded hole, a mounting thread of an electrode pole is screwed into the threaded hole of the stainless steel electrode plate, the materials of the bottom plate, the side plate and the cover plate are high-insulation organic polymers, the bottom plate, the side plate and the stainless steel electrode plate of the high-insulation organic polymers jointly form a cavity of 40mm multiplied by 160mm for molding a sample and online testing), removing the electrode plates of 40mm multiplied by 40mm at two ends of the mold after curing the cement test piece in the mold for 28 days, wherein the water cement test piece formed in the mold has the water cement ratio of 0.25, 0.3, 0.4 and 0.5 respectively, preparing 24 test pieces from each cement test piece with the water cement ratio, the test piece size was 160mm × 40mm × 40 mm.
The mould with the electrode plates of 40mm multiplied by 40mm at two ends and the cement test piece in the mould are immersed into an erosion box, and sulfate radical solutions with the sulfate radical concentration of 300mg/L, 3000mg/L and 6000mg/L are respectively arranged in the erosion box.
(2) And taking part of the cement test piece at different penetration time points, and measuring the actual penetration depth value after detaching the cement test piece from the mold.
In the step (2), 3 pieces of the test piece cured under the same conditions were taken at each infiltration time point (0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days, and 270 days) in the infiltration process, the test piece was taken out from the mold, split into two halves in the longitudinal direction, the powder remaining on the fracture surface was scraped off, and then a dilute nitric acid solution having a concentration of 1mol/L was applied, and after the reaction, a silver nitrate solution having a concentration of 0.05mol/L was applied. After 30 seconds, the penetration depth of each point on the two side surfaces is measured by a vernier caliper according to the originally marked measuring point of every 5 mm. There were 7 measurement points on each side, averaged to 0.01 mm as follows:
Dx＝(D1+D2+D3+D4+D5+D6+D7)/7
wherein Dx is the average penetration depth of each side of the current cement test piece, D1To D7The penetration depth of the measuring point is shown.
The actual penetration depth values at a penetration time point were obtained as the total average value of the penetration depths of the above 3 cement test pieces, and for example, the actual penetration depth values at penetration time points of 0, 15 and 30 days for cement test pieces with a water-cement ratio of 0.4 in a 6000mg/L sulfate solution are shown in the following table 5:
TABLE 5
(3) And (3) assembling the two-end electrode plates of the residual cement test piece which is not removed for measurement, then carrying out impedance spectrum test to obtain each impedance spectrogram, fitting each impedance spectrogram by using an electrochemical model to obtain an actual electrochemical parameter value, and fitting a functional relation between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value and the actual electrochemical parameter value.
In step (3), at each permeation time point (0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days and 270 days), other cement test pieces which are not removed from the mold are taken to be subjected to impedance spectrum test (two removed 40mm × 40mm electrode plates are reinstalled at two ends of the mold before the impedance spectrum test is carried out) to obtain each impedance spectrum, as shown in fig. 3 and 4, wherein fig. 3 is a Nyquist diagram of the cement test piece with the water-cement ratio of 0.4 in the embodiment 2 of the invention, when the cement test piece is soaked for 15 days at the sulfate concentration of 6000 mg/L; FIG. 4 is a bode plot of cement test pieces having a water cement ratio of 0.4 in example 2 of the present invention soaked for 15 days at a sulfate concentration of 6000 mg/L. In this embodiment, the electrochemical impedance spectroscopy tester is a 283 potentiostat/galvanostat, a 2000-type frequency response detector, a Single powersine input signal, a Model283at address14 electrode plate, and a test frequency of 100.0mHz to 1.000 mHz.
Using electrochemical model R to make each impedance spectrograms(Q1(Rct1W1))(Q2(Rct2W2) Fitting (fitting using software Zsimpwin), where RsIs the pore solution resistance, Q, of a cement sample1Double electric layer capacitance of solid/liquid two phase in cement materialct1Is ion transport process resistance, W, inside the cement material1Is the ionic diffusion process resistance, Q, inside the cement material2Is an electric double layer capacitor between the cement material and the electrode plate, Rct2Is the charge transfer process resistance, W, of the electrode plate surface2Is the ion diffusion process resistance of the electrode plate surface.
Actual electrochemical parameter values R were obtained after fitting for 0, 15, 30, 60, 90, 120, 150, 210 and 270 daysct1Values of (b), e.g. the actual electrochemical parameter values R of 0.4 water-cement test pieces in 6000mg/L sulphate solution at 0, 15 and 30 daysct1The values of (A) are shown in Table 6:
TABLE 6
Fitting a functional relationship between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value obtained in the step (2) and the actual electrochemical parameter value obtained in the step (3) to fit the sulfate radical penetration depth D and the parameter Rct1The relationship of the values, for example, for a cement specimen with a water-cement ratio of 0.4, the functional relationship between the value of the penetration depth and the value of the electrochemical parameter is defined as: rct1＝aDb(constants a and b are related to the sulfate radical concentration of the soaking solution, the water cement ratio, the curing age and the cement variety).
(4) And calculating a predicted electrochemical parameter value according to the water-cement ratio and the penetration time point of the cement test piece, and obtaining a predicted penetration depth value according to the functional relation.
In step (4), due to the parameter Rct1The value and the time T satisfy an exponential function relation, and for a cement test piece with a water-cement ratio of 0.4, the function relation is as follows:for example, the parameter R for 150 and 270 days of sulfate attack is calculated therefromct1The values are shown in Table 7:
TABLE 7
In calculating the predicted electrochemical parameter Rct1Value can be given by the function Rct1＝aDbAnd (3) calculating the predicted penetration depth value D of sulfate radicals in the cement test piece which is not removed from the mould, so as to realize the nondestructive test of the penetration depth, wherein the calculation result is shown in the following table 8:
TABLE 8
Compared with the defects and shortcomings of the prior art, the invention has the following beneficial effects:
(1) the sulfate radical penetration depth test can keep the integrity of a cement test piece, and is a nondestructive test.
(2) The test method can realize continuous real-time test of sulfate radical penetration depth and can perform repetitive tracking detection on the penetration process.
(3) The invention calculates the penetration depth by testing the electrochemical parameters after the erosion action by utilizing the mathematical relationship between the electrochemical parameters and the time and the penetration depth of sulfate radicals, thereby avoiding the error of manual reading and obtaining more accurate and reliable data.
(4) The invention can trace the erosion process of the cement material to be tested only by applying electrodes at two ends of the test piece for testing the penetration depth of the sulfate radical, and has convenient operation.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (7)
1. A method for testing the sulfate radical erosion depth of a cement-based material is characterized by comprising the following steps:
injecting the composite portland cement into a mold, curing a cement test piece, removing electrode plates at two ends of the mold, and placing the mold in sulfate radical solutions with different sulfate radical concentrations for infiltration; the die comprises a bottom plate and two side plates, and comprises two end plates, wherein the end plates are electrode plates, rectangular square frames are enclosed by the end plates and the side plates, the side edges of the end plates are connected with the side edges of the side plates through screws, the lower ends of the end plates and the side plates are connected with the bottom plate through screws, the die comprises electrode posts, the electrode posts comprise mounting threads, the electrode plates are stainless steel electrode plates, the middle parts of the stainless steel electrode plates comprise threaded holes, and the mounting threads of the electrode posts are screwed into the threaded holes of the stainless steel electrode plates; the bottom plate (1), the side plate (2) and the cover plate (5) are made of high-insulation organic polymers; the bottom plate (1), the side plate (2) and the stainless steel electrode plate (3) of the high-insulation organic polymer jointly form a cavity of 40mm multiplied by 160mm for sample forming and online testing;
taking part of cement test pieces at different penetration time points, removing the cement test pieces from the mold, and measuring the actual penetration depth value;
assembling the electrode plates at two ends of the mold of the cement test piece which is not removed for measurement, then carrying out impedance spectrum test and obtaining each impedance spectrogram, fitting each impedance spectrogram by using an electrochemical model to obtain an actual electrochemical parameter value, and fitting a functional relation between the penetration depth value and the electrochemical parameter value according to the actual penetration depth value and the actual electrochemical parameter value;
the electrochemical model is as follows: rs (Q)1(Rct1W1))(Q2(Rct2W2) ); wherein,
rs is cement sample pore solution resistance, Q1Double electric layer capacitance of solid/liquid two phase in cement materialct1Is ion transport process resistance, W, inside the cement material1Is the ionic diffusion process resistance, Q, inside the cement material2Is an electric double layer capacitor between the cement material and the electrode plate, Rct2Is the charge transfer process resistance, W, of the electrode plate surface2Is the ion diffusion process resistance of the surface of the electrode plate;
the functional relationship between the depth of penetration value and the electrochemical parameter value is defined as: rct1＝aDb(ii) a Wherein D is the penetration depth value, Rct1A and b are constants for electrochemical parameter values;
and calculating a predicted electrochemical parameter value according to the water-cement ratio and the penetration time point of the cement test piece, and obtaining a predicted penetration depth value according to the functional relation.
2. The method for testing the sulfate erosion depth of a cement-based material according to claim 1, wherein the cement test pieces have water cement ratios of 0.25, 0.3, 0.4 and 0.5, respectively.
3. The method for testing the sulfate erosion depth of a cement-based material according to claim 1, wherein the sulfate concentration in each of the sulfate solutions is 300mg/L, 3000mg/L, and 6000 mg/L.
4. The method for testing the depth of sulfate erosion of a cement-based material of claim 3, wherein the penetration time points are 0 day, 15 days, 30 days, 60 days, 90 days, 120 days, 150 days, 210 days, and 270 days, respectively.
5. The method for testing the sulfate erosion depth of a cement-based material as claimed in claim 4, wherein the step of taking a part of cement test pieces at different penetration time points and then removing the cement test pieces from the mold to measure the actual penetration depth value comprises the following specific steps:
preparing 3 cement test pieces cured under the same conditions, taking the cement test pieces out of a mould, splitting the cement test pieces into two halves, scraping off powder remaining on a fracture surface, immediately coating a dilute nitric acid solution with the concentration of 1mol/L, after reaction, coating a silver nitrate solution with the concentration of 0.05mol/L, and respectively measuring the penetration depth value of each point on two side surfaces of each cement test piece according to one measuring point per 5 mm after 30 seconds;
and respectively taking 7 measuring points on each side surface, calculating the average penetration depth value of each side surface of each cement test piece, finally calculating the total average value of the penetration depth values of 3 cement test pieces according to the average penetration depth value of each side surface, and selecting the total average value as the actual penetration depth value.
6. The method for testing the sulfate erosion depth of a cement-based material of claim 5, wherein the impedance spectrum comprises a Nyquist plot and a Bode plot.
7. The method for testing the sulfate erosion depth of a cement-based material of claim 1, wherein the predicted electrochemical parameter value is exponentially related to the permeation time point.
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