A geopolymer silver nitrate color development method variable color boundary chloride ion measuring device and method

Abstract

The application discloses a device and method for determining the chloride ion concentration at the color change boundary of geopolymer-silver nitrate color development, and belongs to the technical field of chloride ion detection of geopolymer materials. The device comprises a fixing support, a cutting device, a powder grinding device, an illumination device, an imaging analysis device, a silver nitrate spraying device, a dustproof protection device, a display and setting device, and a precision propulsion device. The method comprises the following steps: automatically cutting a fresh cross section, quantitatively spraying a silver nitrate solution, collecting a color development image, identifying a white silver chloride region, a brown silver oxide region and a dark brown to black silver sulfide interference region, cutting off a 25 mm pollution section and grinding the powder after the white color development criterion corrected by sulfide interference is first met, determining the free chloride ion content by using a free chloride ion content detection device, and obtaining the chloride ion concentration at the color change boundary. The application realizes automatic and standardized detection, eliminates sulfide interference and improves detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of chloride ion detection technology for geopolymers and alkali-activated cementitious materials, specifically relating to a device and method for determining chloride ion at the color change boundary using the silver nitrate colorimetric method for geopolymers. Background Technology

[0002] Geopolymer materials, using silica-alumina raw materials such as slag, fly ash, and metakaolin as precursors, are alkali-activated to form cementitious materials, possessing potential applications in terms of low carbon content and durability. The free chloride ion content in geopolymer materials and its binding state with the solid phase directly affect the stability of the steel reinforcement passivation film and the evaluation of chloride salt corrosion; therefore, it is necessary to establish critical parameters for free chloride ions applicable to geopolymer materials.

[0003] The silver nitrate colorimetric method involves spraying a silver nitrate solution onto a fresh cut surface of the material and identifying the chloride ion color boundary by the color difference between chloride-containing and low-chloride areas. In chloride-containing areas, silver ions react with chloride ions to form white silver chloride; in low-chloride and alkaline areas, brown silver oxide is formed. Traditional methods rely mainly on manual cutting, manual spraying, and visual observation. The spraying amount, spraying distance, color development waiting time, ambient light, and differences in the person making the judgment can all affect the determination of the "brown to white transition."

[0004] Slag-containing geopolymers also exhibit significant interferences that distinguish them from ordinary silicate cement. Reduced sulfides in slag can release or transform into sulfhydryl and / or sulfide ions in the pore solution during strong alkali activation and hydration. After spraying silver nitrate, silver ions, in addition to reacting with chloride or hydroxide ions, can also rapidly react with sulfhydryl or sulfide ions to form dark brown to black silver sulfide. Silver sulfide may cover white silver chloride, causing areas that should be white to appear gray, dark brown, or black. If the traditional "brown-white" binary classification is still used, sulfide interference can easily be mistaken for chloride ions not yet reaching the color development threshold, leading to a delay in the critical moment and a shift in chloride ion concentration at the color change boundary.

[0005] Existing color boundary models for ordinary silicate cement systems typically only consider the competitive reactions between silver ions and chloride and hydroxide ions, failing to incorporate the stoichiometric relationship of sulfide and hydrothionions preferentially consuming silver ions into the effective silver ion content. Furthermore, they cannot determine the condition where all silver ions are consumed by sulfide and hydrothionions, resulting in a completely black cross-section and the inability to form a discernible color change boundary. Therefore, directly applying ordinary silicate cement models will introduce systematic biases in the selection of color development conditions and the prediction of color change boundary concentrations for slag-containing geopolymers.

[0006] Furthermore, the cross-section after silver nitrate spraying cannot be directly used for free chloride ion detection. Residual silver ions can continue to react with chloride ions in the powder sample, resulting in a lower measured free chloride ion content. Manually transferring the specimen for further cutting and grinding can easily introduce positional errors and cross-contamination. Therefore, a front-end device and method are needed to be added before the existing free chloride ion detection method. This device and method can fix a 50 mm diameter cylindrical specimen, automatically cut it according to time, standardize spraying and imaging conditions, identify silver sulfide interference, and automatically remove the contaminated section and perform grinding and sampling after the first whitening. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for determining chloride ions at the color change boundary using a geopolymer silver nitrate colorimetric method, in order to solve the problems of inconsistent cutting and spraying conditions, subjective colorimetric judgment, interference from silver sulfide formation in slag sulfides, lack of a colorimetric prediction model for sulfur-containing hydrogen ion systems, and subsequent determination of free chloride ions after silver nitrate spraying pollution in existing methods.

[0008] To address the aforementioned technical problems, this invention provides a device for determining chloride ions at the color change boundary of geopolymers using a silver nitrate colorimetric method. This device is used to measure the color of cylindrical geopolymer specimens and includes a fixed support, a cutting device, a grinding device, a lighting device, an imaging analysis device, a silver nitrate spraying device, a dust protection device, a display and setting device, and a precision propulsion device.

[0009] A fixed bracket is used to clamp and support the geopolymer cylindrical specimen, and the fixed bracket is provided with a vertical guide groove. The cutting device includes a movable cutting disc bracket embedded in the vertical guide groove and capable of reciprocating vertically between a standby position and a working position, and a circular cutting disc mounted on the movable cutting disc bracket. The cutting device is used to cut the geopolymer cylindrical specimen at a preset detection time to form a fresh cross-section. The grinding device includes a movable grinding disc bracket embedded in the vertical guide groove and capable of reciprocating vertically between a standby position and a working position, a circular grinding disc mounted on the movable grinding disc bracket, and a powder collecting device located below the grinding station. The grinding device is used to grind the fresh cross-section. A lighting device is used to provide fixed lighting for the fresh cross-section. The imaging analysis device includes a camera and a computer communicatively connected to the camera. The camera is used to acquire reference images and color images, and the computer is used to analyze the images. The silver nitrate spraying device includes a nozzle lifting mechanism, a nozzle, a silver nitrate conduit, and a silver nitrate storage tank. The nozzle is connected to the silver nitrate storage tank via the silver nitrate conduit. The spray axis of the nozzle is parallel to the normal of the fresh cross-section. The nozzle lifting mechanism can move between a spraying position and an avoidance position, the avoidance position being outside the camera's line of sight. The dust protection device includes a thin dustproof cover disposed between the cutting device and the grinding device and the silver nitrate spraying device, the lighting device, and the imaging analysis device; an automatic start / stop mechanism for automatically deploying and retracting the thin dustproof cover; and a negative pressure dust suction port. The display and setting device is used to set detection parameters and display the operating status and judgment results. The precision propulsion device includes a propulsion driver, a telescopic push rod, and a sample push plate, used to quantitatively propel the geopolymer cylindrical specimen along the axial direction of the specimen.

[0010] This invention also provides a method for determining chloride ion at the color change boundary using the above-mentioned device with silver nitrate colorimetric method for geopolymers, comprising the following steps: clamping the geopolymer cylindrical specimen to the fixed bracket, and using the precision propulsion device to complete the axial reference positioning of the geopolymer cylindrical specimen; after reaching the preset detection time, the automatic start-stop mechanism automatically unfolds the thin dustproof protective cover, and the precision propulsion device pushes the geopolymer cylindrical specimen toward the cutting side to a preset cutting thickness; the movable cutting disc bracket descends from the standby position to the working position and drives the circular cutting disc to cut the geopolymer cylindrical specimen and form a new specimen. After cutting the fresh cross-section, the movable cutting disc support rises and resets to the standby position. After dust removal via the negative pressure suction port, the thin dustproof protective cover is retracted by the automatic start / stop mechanism. The lighting device is activated, and the camera captures a reference image of the fresh cross-section before spraying. The nozzle lifting mechanism raises the nozzle to the spraying position and sprays a measured amount of silver nitrate solution along the normal direction of the fresh cross-section. After spraying, the nozzle lifting mechanism lowers the nozzle to the avoidance position. The camera captures a colorimetric image after spraying, and the computer, based on the reference image before spraying and the colorimetric image after spraying,... The color image identifies white silver chloride areas, brown silver oxide areas, and dark brown to black silver sulfide interference areas, and determines whether the white color development criterion corrected for sulfide interference is met for the first time. If not, the steps are repeated at the next preset detection time. When the criterion is met for the first time, the critical color development time is recorded. The precision propulsion device advances the sample 25 mm, the automatic start-stop mechanism unfolds the thin dustproof protective cover, and the cutting device cuts off a 25 mm contaminated section from the sprayed section to the inside of the specimen. The precision propulsion device then advances the fresh, uncontaminated cross-section exposed after the cut to the grinding station, and the thin dustproof protective cover... While in the extended state, the movable grinding disc support descends from the standby position to the working position, driving the circular grinding disc to grind the powder sample. After grinding, the movable grinding disc support rises back to the standby position. After dust removal through the negative pressure dust suction port, the thin dustproof protective cover is retracted by the automatic start-stop mechanism, and the powder sample is collected by the powder collection device. The free chloride ion content of the powder sample is determined using a free chloride ion content detection device and method capable of crushing, sieving, alkaline extraction, solid-liquid separation, and chloride ion detection, and the measured value of chloride ion concentration at the color change boundary of the powder sample by silver nitrate colorimetric method is calculated.

[0011] The present invention has at least the following beneficial effects: (1) The fixed support, cutting device, grinding device, lighting device, imaging analysis device, silver nitrate spraying device and precision propulsion device work together to ensure that the cross-section preparation, spraying and shooting conditions are consistent at different detection times, thereby reducing human error; (2) By registering images before and after spraying and classifying them into three categories—white silver chloride area, brown silver oxide area, and dark brown to black silver sulfide interference area—sulfide interference in slag geopolymers can be identified, thus avoiding directly classifying the black silver sulfide area as a low-chlorine brown area. (3) After the colorimetric criteria are met for the first time, the 25 mm contaminated section is removed, and then the fresh section that has never been in contact with silver nitrate is ground into powder to reduce the measurement deviation caused by the continued consumption of chloride ions by silver ions. (4) The cutting device, grinding device and silver nitrate spraying device are equipped with motion interlocks to improve the safety of equipment operation; (5) The display and setting device uniformly saves specimen information, operating parameters, color images and measurement results to improve traceability; (6) Integrate the preparation of critical chromogenic powder samples with the detection method of free chloride ion content to avoid repeated setting of detection parameters and reduce the difference in results caused by different extraction methods; (7) The two-stage reaction model incorporates the preferential consumption of silver ions by sulfhydryl ions into the calculation, which can identify the invalid working condition in which all silver ions are consumed before the experiment, guide the adjustment of silver nitrate concentration or spraying amount during the experiment, and save the model prediction value with the measured value of free chloride ions, thereby improving the interpretability and traceability of the results. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the device for determining chloride ions at the color change boundary using the geopolymer silver nitrate colorimetric method of the present invention.

[0013] Figure 2 This is a schematic flowchart of the method for determining the chloride ion concentration at the color change boundary according to the present invention.

[0014] Reference numerals: 1. Geopolymer cylindrical specimen; 2. Fixed support; 3. Cutting device; 3-1. Movable cutting disc support; 3-2. Circular cutting disc; 4. Grinding device; 4-1. Movable grinding disc support; 4-2. Circular grinding disc; 4-3. Powder collection device; 5. Dust protection device; 5-1. Thin dustproof protective cover; 5-2. Automatic start / stop mechanism; 6. Silver nitrate spraying device; 6-1. Nozzle lifting mechanism; 6-2. Nozzle; 6-3. Silver nitrate conduit; 6-4. Silver nitrate storage tank; 7. Lighting device; 8-1. Camera; 8-2. Computer; 9. Display and setting device; 10. Precision propulsion device; 10-1. Propulsion driver; 10-2. Telescopic push rod; 10-3. Sample push plate. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0016] Example 1 Combination Figure 1 As shown, this embodiment provides a device for determining chloride ions at the color change boundary using a geopolymer silver nitrate colorimetric method.

[0017] The nominal diameter of the geopolymer cylindrical specimen 1 is 50 mm, extending horizontally into the protective housing of the device. Two fixed supports 2 are spaced apart along the specimen's axis, located on either side of the cutting and grinding stress points. The fixed supports 2 can employ a V-shaped seat with semi-circular jaws, an annular sleeve, or a three-jaw clamping structure, with the clamping surfaces covered with a water-resistant and silver nitrate-resistant elastic anti-slip layer. At least one fixed support 2 is axially adjustable to accommodate specimen length reduction after multiple cuts. The fixed supports 2 are equipped with vertical guide grooves, which can be dovetail grooves, T-grooves, or limiting grooves formed by oppositely arranged linear guides, providing stable vertical guidance for the cutting device 3 and the grinding device 4.

[0018] The cutting device 3 includes a movable cutting disc support 3-1 and a circular cutting disc 3-2. The movable cutting disc support 3-1 includes a cutting lifting slide embedded in a vertical guide groove of a fixed support 2 and a cutting cantilever extending from the cutting lifting slide towards the fresh cross-section. The circular cutting disc 3-2 is mounted at the end of the cutting cantilever. The cutting device 3 also includes a cutting lifting driver, a lead screw or synchronous belt drive mechanism, a position encoder, an upper limit sensor, and a lower limit sensor. The cutting plane of the circular cutting disc 3-2 is perpendicular to the axis of the geopolymer cylindrical specimen 1. During cutting, the movable cutting disc support 3-1 descends from the standby position to the working position, driving the circular cutting disc 3-2 to cut into the geopolymer cylindrical specimen 1. After cutting, the movable cutting disc support 3-1 rises back to the standby position. Through this structure, the cutting device 3 can automatically form a fresh cross-section at a preset detection time, ensuring consistent cross-sectional quality for each detection.

[0019] The grinding device 4 includes a movable grinding disc support 4-1, a circular grinding disc 4-2, and a powder collection device 4-3. The movable grinding disc support 4-1 includes a grinding lifting slide embedded in a vertical guide groove of a fixed support 2 and a grinding cantilever extending from the grinding lifting slide towards the fresh cross-section. The circular grinding disc 4-2 is installed at the end of the grinding cantilever, with its working surface parallel to the fresh cross-section. The fresh cross-section referred to in this specification includes the detection cross-section formed by the cutting device 3 at a preset detection time, and the sampling cross-section exposed after the cutting device 3 removes a 25 mm contaminated section. The grinding object of the grinding device 4 is the sampling cross-section. During grinding, the movable grinding disc support 4-1 descends from the standby position to the working position, causing the circular grinding disc 4-2 to contact the fresh cross-section. After grinding, the movable grinding disc support 4-1 rises back to the standby position. The precision propulsion device 10 advances the fresh cross-section to the grinding station at a preset grinding feed thickness of 0.5–5 mm. The powder collection device 4-3 is located below the grinding station and can be a detachable powder collection cup, powder collection funnel, or negative pressure powder collection box. Through fixed-thickness grinding and sealed collection, representative powder samples uncontaminated by silver nitrate can be obtained.

[0020] The illumination device 7 is positioned above or around the camera 8-1 on the specimen cross-section, providing illumination with a fixed color temperature, illuminance, and incident angle for the fresh cross-section. The imaging analysis device includes the camera 8-1 and a computer 8-2 communicatively connected to the camera 8-1. The camera 8-1 is fixed on a bracket capable of completely capturing the circular cross-section, with its optical axis parallel to the normal of the fresh cross-section, used to acquire reference and colorimetric images. The computer 8-2 is used to analyze the reference and colorimetric images. By fixing the illumination and shooting parameters, the influence of ambient light and shooting conditions on colorimetric determination can be eliminated.

[0021] The silver nitrate spraying device 6 includes a nozzle lifting mechanism 6-1, a nozzle 6-2, a silver nitrate conduit 6-3, and a silver nitrate storage tank 6-4. The nozzle 6-2 is connected to the lifting slider of the nozzle lifting mechanism 6-1 via a short mounting arm and is connected to the silver nitrate storage tank 6-4 via the silver nitrate conduit 6-3. The spray axis of the nozzle 6-2 is parallel to the normal of the fresh cross-section. The nozzle lifting mechanism 6-1 can move between a spraying position and an avoidance position. The spraying position allows the nozzle 6-2 to be close to the fresh cross-section for quantitative spraying, while the avoidance position is outside the field of view of the camera 8-1. The silver nitrate storage tank 6-4 and the silver nitrate conduit 6-3 are made of brown or opaque corrosion-resistant material to reduce the decomposition of silver nitrate upon exposure to light. The silver nitrate spraying device 6 also includes a metering pump, a spray volume calibration unit, and an anti-splash waste liquid collection unit to control the concentration of the silver nitrate solution, spray volume, spray distance, spray pressure, and spray duration. The lifting mechanism 6-1 ensures even spraying at close range during spraying and avoids obstructing the view when taking photos.

[0022] The dust protection device 5 includes a thin dustproof cover 5-1, an automatic start-stop mechanism 5-2, and a negative pressure dust extraction port. The thin dustproof cover 5-1 is positioned between the cutting device 3 and the grinding device 4, and the silver nitrate spraying device 6, lighting device 7, and imaging analysis device. It is a transparent or semi-transparent flexible film, folding curtain, or roller blind with a thickness of 0.1–1.0 mm, and has a flexible seam or a closable opening at the position corresponding to the geopolymer cylindrical specimen 1. The automatic start-stop mechanism 5-2 is an electric roller mechanism or a linear drive mechanism. Before cutting or grinding, it automatically unfolds the thin dustproof cover 5-1, isolating the dust-generating cutting and grinding area from the nozzle 6-2, lighting device 7, and camera 8-1. After the operation is completed and negative pressure dust removal is finished, it automatically retracts the thin dustproof cover 5-1. The dust protection device 5 also includes a differential pressure sensor on the cutting and grinding side and a dust concentration sensor; the cutting device 3 or grinding device 4 is only allowed to start when the thin dust protection cover 5-1 is in the unfolded position and the negative pressure or dust concentration meets the preset conditions. Through the above dust protection, dust can be prevented from contaminating the optical components and silver nitrate solution, and the automatic retraction does not affect spraying and photography.

[0023] The display and setting device 9 is used to set detection parameters and display the operating status and judgment results. The display and setting device 9 is electrically connected to the cutting device 3, grinding device 4, automatic start / stop mechanism 5-2, nozzle lifting mechanism 6-1, lighting device 7, camera 8-1, computer 8-2, and precision propulsion device 10, and is equipped with the following interlocks: The cutting device 3 and grinding device 4 are prohibited from starting when the thin dustproof protective cover 5-1 is not unfolded; the silver nitrate spraying device 6 is prohibited from spraying and the camera 8-1 is prohibited from taking pictures when the movable cutting disc support 3-1 or the movable grinding disc support 4-1 is not in the standby position; the nozzle 6-2 is prohibited from entering the spraying position when the thin dustproof protective cover 5-1 is not retracted; and the camera 8-1 is prohibited from taking pictures when the nozzle 6-2 is not in the avoidance position. Through these motion interlocks, the safety of equipment operation can be improved, and interference between mechanisms can be avoided.

[0024] The precision propulsion device 10 includes a propulsion driver 10-1, a telescopic push rod 10-2 driven by the propulsion driver 10-1, and a sample push plate 10-3. The sample push plate 10-3 is perpendicular to the axis of the geopolymer cylindrical specimen 1 and abuts against the end of the specimen. The precision propulsion device 10 also includes an encoder or displacement sensor connected to the propulsion driver 10-1. The computer 8-2 controls the propulsion distance of the telescopic push rod 10-2 in a closed loop according to the preset cutting thickness, the 25 mm contaminated section removal length, and the grinding feed thickness. Through the precision propulsion device 10, a unified coordinate system can be provided for timed cutting, 25 mm contaminated section removal, and grinding feed, ensuring the positional accuracy of each step.

[0025] Computer 8-2 is configured to register, color correct, and effectively segment the pre-spray reference image and post-spray color development image, and to identify at least white silver chloride areas, brown silver oxide areas, and dark brown to black silver sulfide interference areas formed by the reaction of sulfide ions and / or sulfide ions in slag-containing geopolymers with silver ions. Computer 8-2 is also configured to calculate the proportion of white areas and the proportion of silver sulfide interference areas; when the proportion of silver sulfide interference areas is below a preset sulfide interference threshold and the proportion of white areas reaches a preset white threshold and remains stable in continuous images, a white color development result is output; when the proportion of silver sulfide interference areas reaches or exceeds the preset sulfide interference threshold, a sulfide interference alarm, a correction judgment result, or an invalid judgment result is output. Through the above image analysis, white silver chloride, brown silver oxide, and silver sulfide interference areas can be accurately distinguished, avoiding misjudging sulfide interference as low-chlorine areas.

[0026] Computer 8-2 also includes a two-stage reaction model calculation module and a parameter calibration module. The two-stage reaction model calculation module is configured to calculate the concentrations of hydroxide ions in the receiving pore solution, the concentrations of sulfide ions in the pore solution, the concentration of silver ions in the silver nitrate solution, the volume of the silver nitrate solution participating in the colorimetric reaction, and the volume of the pore solution participating in the colorimetric reaction, and to calculate the volume ratio R² and the minimum volume ratio R. 2,minand critical volume ratio R 2,crit When the volume ratio R2 is less than or equal to the minimum volume ratio R 2,min When the output cannot form a recognizable color change boundary; when the volume ratio R2 is greater than the minimum volume ratio R... 2,min And less than the critical volume ratio R 2,crit At that time, according to the chloride ion concentration C at the color change boundary d =Calculated as coefficient a × hydroxide ion concentration in pore solution + coefficient b × (silver ion concentration in silver nitrate solution × volume ratio R2 - 2 × sulfide ion concentration in pore solution); when volume ratio R2 is greater than or equal to critical volume ratio R 2,crit At that time, according to the chloride ion concentration C at the color change boundary d =The coefficient c × the hydroxide ion concentration of the pore solution is calculated. The volume of the pore solution participating in the colorimetric reaction is determined by multiplying the effective spraying reaction area, the effective penetration reaction depth of silver nitrate, the connectivity porosity of the effective reaction layer, and the pore liquid saturation before spraying. The parameter calibration module is configured to use a series of specimens with known free chloride ion concentrations to calibrate the critical silver chloride mass ratio and critical volume ratio R. 2,crit The coefficients a, b, and c are calibrated, and 0.00695, 0.608, and 1.6 are used as initial reference values ​​for coefficients a, b, and c, respectively. The critical silver chloride mass ratio is the mass ratio of silver chloride in the mixed precipitate of silver chloride and silver oxide. Through a two-stage reaction model, the preferential consumption of silver ions by sulfide ions can be incorporated into the calculation, allowing for the identification of ineffective operating conditions before the experiment and guiding the adjustment of silver nitrate concentration or spraying rate.

[0027] Example 2 Combination Figure 2 As shown, this embodiment provides a method for determining chloride ions at the color change boundary using the geopolymer silver nitrate colorimetric method with the above-mentioned apparatus, including the following steps: (1) Clamp the geopolymer cylindrical specimen 1 to the fixed bracket 2, and complete the axial reference positioning of the geopolymer cylindrical specimen 1 by the precision propulsion device 10. Prepare a geopolymer cylindrical specimen 1 with a diameter of 50 mm and a length that meets the requirements for multiple cutting. Chloride ions can be added by mixing water. At least three parallel specimens are set up with the same mix ratio. Install the specimen on the fixed bracket 2 and clamp it. Enter the mix ratio, slag content, chloride ion content, molding time, curing conditions and preset detection time sequence into the display and setting device 9. Obtain pore solution or extract from parallel specimens with the same mix ratio and age or reserved samples adjacent to the colorimetric section, and determine the hydroxide ion concentration and sulfide ion concentration of the pore solution. The hydroxide ion concentration of the pore solution is determined by acid-base titration or converted according to pH value; the sulfide ion concentration of the pore solution is determined by methylene blue spectrophotometry or iodometric titration. Zinc acetate is added immediately after the solution is extracted to fix the sulfide and the solution is sealed to reduce the error caused by air oxidation. Enter the concentrations of hydroxide ions in the pore solution, the concentration of sulfide ions in the pore solution, the concentration of silver ions in the silver nitrate solution, the volume of the silver nitrate solution participating in the colorimetric reaction, and the volume of the pore solution participating in the colorimetric reaction into the computer (8-2).

[0028] (2) Upon reaching the preset detection time, the thin dustproof protective cover 5-1 is automatically deployed by the automatic start-stop mechanism 5-2. The precision propulsion device 10 pushes the geopolymer cylindrical specimen 1 toward the cutting side to the preset cutting thickness. The movable cutting disc support 3-1 descends from the standby position to the working position and drives the circular cutting disc 3-2 to cut the geopolymer cylindrical specimen 1 and form a fresh cross-section. After the cutting is completed, the movable cutting disc support 3-1 rises back to the standby position. After dust removal through the negative pressure dust suction port, the thin dustproof protective cover 5-1 is retracted by the automatic start-stop mechanism 5-2. Dry low-speed cutting with simultaneous dust collection is preferred for cutting. When wet cutting is used, the cooling medium must not contain chlorine, and free water on the cross-section must be removed in a uniform manner before shooting.

[0029] (3) Turn on the lighting device 7 and use the camera 8-1 to capture a reference image of the fresh cross section before spraying.

[0030] (4) The nozzle lifting mechanism 6-1 raises the nozzle 6-2 to the spraying position and sprays a quantitative amount of silver nitrate solution along the normal direction of the fresh cross-section. After spraying, the nozzle lifting mechanism 6-1 lowers the nozzle 6-2 to the avoidance position. 0.1 mol / L silver nitrate can be used as the baseline concentration; when the model indicates insufficient silver ions or the cross-section is blackened, 0.5 mol / L silver nitrate can be used and the spraying conditions can be recalibrated. The spraying volume, spraying distance, pressure and duration should be kept consistent in the same group of tests.

[0031] (5) Camera 8-1 acquires the color development image after spraying. Computer 8-2 identifies the white silver chloride area, brown silver oxide area, and dark brown to black silver sulfide interference area based on the reference image before spraying and the color development image after spraying, and determines whether the white color development criterion corrected by sulfide interference is met for the first time. If not, steps (2) to (5) are repeated at the next preset detection time. When the proportion of silver sulfide interference area reaches or exceeds the preset sulfide interference threshold, a sulfide interference alarm is output and the parallel specimen is clamped to the fixed bracket 2 and re-detected from step (1), or the result is marked as invalid. The white threshold and sulfide interference threshold should be established in advance using blank specimens without added chlorine, specimens with known chloride ion concentration, and calibration specimens with different soluble sulfide levels, all from the same slag source, under the same excitation regime, and at the same age.

[0032] (6) When the critical color development moment is first met, the precision propulsion device 10 advances the specimen 25 mm. The thin dustproof protective cover 5-1 is deployed by the automatic start-stop mechanism 5-2. The cutting device 3 cuts off a 25 mm contaminated section from the sprayed section to the inside of the specimen. Taking the sprayed section as the axial zero point, the precision propulsion device 10 advances the specimen 25 mm towards the cutting side, so that the sprayed section crosses the cutting plane of the circular cutting disk 3-2 by 25 mm. After the cutting device 3 cuts in, it completely removes the sprayed section and the 25 mm inward section of the specimen. This cutting length is used to remove the contaminated area where silver nitrate may seep in along the pores. Before the formal test, the depth of silver nitrate penetration can be verified by the distribution of silver elements along the depth to be less than 25 mm.

[0033] (7) The fresh, uncontaminated cross-section exposed after cutting is advanced to the grinding station by the precision propulsion device 10. With the thin dustproof protective cover 5-1 in the extended state, the movable grinding disc support 4-1 descends from the standby position to the working position and drives the circular grinding disc 4-2 to grind the powder sample. After grinding, the movable grinding disc support 4-1 rises back to the standby position. After dust removal through the negative pressure dust suction port, the thin dustproof protective cover 5-1 is retracted by the automatic start-stop mechanism 5-2, and the powder sample is collected by the powder collection device 4-3. The temperature rise is controlled during the grinding process, and the use of chlorine-containing coolant, chlorine-containing cleaning solution, or equipment that comes into contact with silver nitrate is avoided.

[0034] (8) The free chloride ion content of the powder sample is determined by a device and method capable of crushing, sieving, alkaline extraction, solid-liquid separation, and chloride ion detection, and the measured value of chloride ion concentration at the color change boundary of the powder sample by silver nitrate colorimetric method is calculated. Preferably, the fully automatic free chloride ion content detection device and method for geopolymer materials described in Chinese Patent No. ZL202511183767.7 is used. According to this method, the powder sample is first crushed and sieved to obtain particles with a particle size of 0.160 to 0.315 mm; a sodium hydroxide solution with a pH of 13 to 13.5 is added to the extraction container, the liquid-solid mass ratio is 10:1, and the stirring speed is set to 1000 rpm, the extraction temperature to 20°C, and the extraction time to 5 minutes. After extraction, solid-liquid separation was performed using a suspension separator to obtain filtrate. Quantitatively, 10 mL of filtrate, 12–15 mL of 0.1 mol / L nitric acid solution, 1–2 mL of 0.04% mercuric thiocyanate solution, and 3–5 mL of 30% hydrogen peroxide solution were added to the test cell. The nitric acid solution was used to adjust the acidity of the filtrate, the mercuric thiocyanate solution to eliminate bromide interference, and the hydrogen peroxide solution to eliminate sulfide interference. The chloride ion concentration was measured using a chloride ion probe and detection equipment. The free chloride ion detection result of the powder sample was obtained according to the formula and conversion method specified in the patent, and then converted to the measured value of the chloride ion concentration at the color change boundary expressed in mol / L according to a unified metrological standard. The measured values ​​of at least three parallel specimens with the same mix ratio were averaged. The average measured value was correlated with the model prediction value, as well as the corresponding hydroxide ion concentration, sulfide ion concentration, silver ion concentration in the silver nitrate solution, and volume ratio R², and stored for model verification and comparison of results from different material systems.

[0035] Example 3 This example illustrates the calculation of the two-stage reaction model and the prediction of spraying conditions.

[0036] In slag-containing geopolymers, the reduced sulfur from the slag exists primarily as hydrosulfide ions and / or sulfide ions in alkaline pore solutions. After spraying silver nitrate, silver ions compete with chloride ions, hydroxide ions, and hydrosulfide ions for precipitation in the following manner: Ag ＋ +Cl － →AgCl↓ (white), Ksp,AgCl=1.8×10 －10 (1) In the formula, Ag ＋ It is silver ion, Cl － Ksp is the chloride ion, AgCl is silver chloride, and Ksp,AgCl is the solubility product constant of silver chloride, with units of (mol / L). 2 .

[0037] Ag ＋ +OH－ →AgOH→1 / 2Ag₂O↓ (brown), Ksp,AgOH=2.6×10 －8 (2) In the formula, OH － For example, is the hydroxide ion, AgOH is silver hydroxide, Ag₂O is silver oxide, and Ksp,AgOH is the solubility product constant of silver hydroxide, in units of (mol / L). 2 .

[0038] 2Ag ＋ +HS － →Ag2S↓+H ＋ (Dark brown to black), Ksp,Ag2S≈6×10 －50 (3) In the formula, HS － It is a hydrosulfide ion, Ag₂S is silver sulfide, H ＋ For hydrogen ions, Ksp,Ag₂S is the solubility product constant of silver sulfide, in units of (mol / L). 3 .

[0039] Under the baseline condition of 25℃, the apparent solubility product equilibrium of silver chloride and silver hydroxide in the second stage can be written as follows: C a-Ag＋ ·C a-Cl－ =1.8×10 －10 (3a) In the formula, C a-Ag＋ To achieve the equilibrium concentration of silver ions in the liquid phase, C a-Cl－ To achieve equilibrium, the concentration of chloride ions in the liquid phase is given, with the unit of concentration being moles per liter.

[0040] C a-Ag＋ ·C a-OH－ =2.6×10 －8 (3b) In the formula, C a-OH－ To achieve equilibrium, the concentration of hydroxide ions in the liquid phase is expressed in moles per liter.

[0041] The mass ratio of silver chloride to the mixed precipitate of silver chloride and silver oxide is defined as P. AgCl : P AgCl =m AgCl / (m AgCl +m Ag2O (3c) In the formula, P AgCl m represents the mass ratio of silver chloride in the mixed precipitate of silver chloride and silver oxide. AgCl For the mass of silver chloride formed in the second stage, m Ag2OThe mass of silver oxide formed in the second stage is expressed in grams. Silver sulfide formed in the first stage is not included in the denominator.

[0042] Since the solubility product of silver sulfide is much smaller than that of silver chloride and silver hydroxide, in this model, sulfide ions are considered to be completely precipitated by silver ions before chloride and hydroxide ions within the color development timescale, establishing a two-stage reaction model of "preferential consumption of sulfide ions—competitive precipitation of chloride / hydroxide ions". The reaction of sulfate ions to form silver sulfate is negligible compared to the above three reactions.

[0043] The amounts of silver ions consumed by sulfide ions in the first stage and the amounts of effective silver ions that can participate in the chloride / hydroxide ion competitive reaction in the second stage are respectively: n Ag＋,consumed =2C HS－ ·V p (4) In the formula, n Ag＋,consumed The amount of silver ions consumed by hydrosulfide ions, in moles; C HS－ V represents the concentration of hydrosulfide ions in the pore solution, expressed in moles per liter. p The volume of the solution in the pores participating in the colorimetric reaction is expressed in liters.

[0044] n Ag＋,eff =C Ag＋ ·V Ag＋ -2C HS－ ·V p (5) In the formula, n Ag＋,eff The amount of effective silver ions that can participate in the chloride / hydroxide ion competitive reaction in the second stage, expressed in moles; C Ag＋ V represents the concentration of silver ions in a silver nitrate solution, expressed in moles per liter. Ag＋ The volume of silver nitrate solution participating in the colorimetric reaction is expressed in liters.

[0045] In this invention, V p Instead of being used as an arbitrary fitting parameter, it is defined as the volume of interconnected pore liquid that can actually contact silver ions and participate in the colorimetric reaction within the effective imaging area and effective penetration reaction depth after spraying. It is determined by the following formula: V p =A eff ·δ eff ·φ c ·S r (5a) In the formula, A eff The effective spray reaction area after removing edge chipping, reflections, and macroscopic holes using an image mask, expressed in square millimeters; δ effThe effective penetration depth of silver nitrate under specified spraying volume, spraying distance, and color development time, expressed in millimeters; φ c S represents the interconnected porosity of the effective reaction layer, dimensionless; r The pore fluid saturation level before spraying is dimensionless. When A... eff In square millimeters, δ eff In millimeters, V p The value (in liters) = A eff ·δ eff ·φ c ·S r ×10 －6 A eff Calculated from the pixel scale and effective cross-sectional pixel count determined by camera 8-1; φ c The porosity was determined by vacuum saturation-drying weighing or other interconnected porosity methods on parallel specimens of the same mix proportion and age; S r Determined by the following formula: S r =(m r -m d ) / (m sat -m d (5b) In the formula, m r The mass of the specimen with the same moisture content before spraying is expressed in grams; m d This refers to the constant weight dried mass, expressed in grams; m sat The saturated surface-dry mass after vacuum saturation is expressed in grams.

[0046] δ eff The preferred method for depth stratification is to use parallel specimens with the same mix proportion: after treatment under the spraying and color development conditions of the formal test, samples are taken along the depth stratification. The first depth at which the silver content drops to 5% of the surface increment or recovers to the mean of the unsprayed blank plus three times the standard deviation is taken as δ. eff The depth distribution of silver can be obtained using energy-dispersive X-ray fluorescence, inductively coupled plasma atomic emission spectroscopy, or other applicable methods.

[0047] For unsaturated parallel specimens, the δ can also be determined by the mass increment Δm before and after spraying. eff Perform an independent verification, assuming the sprayed liquid fills the previously unoccupied interconnected pores within the effective reaction layer, then: δ eff =Δm / [ρ AgNO3 ·A eff ·φ c ·(1-S r (5c) In the formula, Δm is the mass increment before and after spraying, in grams; ρ AgNO3The density of the silver nitrate solution at the test temperature is expressed in grams per cubic centimeter. The gravimetric method is only used to verify the results of the depth stratification method; when S... r When the spray liquid loss is significant or there is cross-sectional runoff, formula (5c) should not be used alone. A from the same series of tests... eff δ eff φ c and S r It should be determined under the same water content, spraying conditions and age as the formal color development test.

[0048] For V p A second independent verification method can be performed on parallel specimens with the same mix proportion using the excess silver nitrate-local reaction laminar flow reverse calibration method. According to known C... Ag+ and V Ag+ Spray, and cut off the A at the preset color development time. eff and δ eff The corresponding local reaction layer was filtered to obtain the liquid phase. The concentrations of residual silver ions, chloride ions, and hydroxide ions were simultaneously measured, and the recovery rate of the filtrate was corrected using inert ion tracers or mass balance. The corrected measured values ​​were substituted into the silver ion mass conservation relationship in equation (6) to back-calculate the equivalent V. p The results were compared with those obtained using the geometry-pore method of equation (5a). This pressure filtration method was used as an auxiliary verification method and was not used alone to determine V when the residual silver ion concentration was not measured or the liquid phase recovery rate was not corrected. p .

[0049] When equilibrium is reached in the second stage, the corrected mass conservation equation considering the consumption of sulfide ions is: V Ag＋ ·C Ag＋ -2V p ·C HS－ -V T ·C a-Ag＋ = V p (C Cl－ -C a-Cl－ )+V p (C OH－ -C a-OH－ (6) In the formula, V T The volume of silver nitrate solution is the sum of the volumes of the solutions in the pores that participate in the colorimetric reaction, expressed in liters (C). Cl－ The concentration of chloride ions in the solution before the reaction is expressed in moles per liter; C OH－ The concentration of hydroxide ions in the solution before the reaction is expressed in moles per liter; C a-Ag＋ C a-Cl－ and C a-OH－ These represent the concentrations of silver ions, chloride ions, and hydroxide ions in the liquid phase after equilibrium has been reached, all in moles per liter.

[0050] The ratio of the volume of silver nitrate solution to the volume of the solution in the pores participating in the colorimetric reaction is defined as: R2=V Ag＋ / V p (7) In the formula, R2 is the ratio of the volume of silver nitrate solution to the volume of the pore solution participating in the colorimetric reaction, which is dimensionless.

[0051] The minimum volume ratio for the effective presence of silver ions and the published benchmark model in P crit,AgCl The reference critical volume ratios for determining whether silver nitrate is sufficient at a concentration of 0.65 are as follows: R 2,min =2C HS－ / C Ag＋ (8) In the formula, R 2,min The minimum volume ratio at which effective silver ions exist is dimensionless.

[0052] R 2,crit =(2.57C OH－ + 2C HS－ ) / C Ag＋ (9) In the formula, R 2,crit To publicly disclose the benchmark model in P crit,AgCl =0.65 is the reference critical volume ratio for whether silver nitrate is sufficient or not, dimensionless.

[0053] With critical silver chloride mass ratio P crit,AgCl Using 0.65 as a reference calculation condition, and incorporating the sulfide ion consumption term into the publicly available benchmark model, the chloride ion concentration C at the color change boundary can be obtained. d Reference segmented prediction model: R2≤R2,min: No identifiable color-changing boundary can be formed, and the cross-section is dark or completely black (10a). R 2,min <R2<R 2,crit :C d =0.00695C OH－ +0.608(C Ag＋ R2-2C HS－ (10b) In the formula, C d The chloride ion concentration at the color change boundary is expressed in moles per liter; coefficients 0.00695 and 0.608 are initial reference values.

[0054] R²≥R 2,crit :C d =1.6C OH－ (10c) In the formula, C dThe chloride ion concentration at the color change boundary is expressed in moles per liter; the coefficient 1.6 is the initial reference value.

[0055] The general form of equation (10b) is C d =aC OH－ +b(C Ag＋ R2-2C HS－ The general form of equation (10c) is C. d =cC OH－ In the formula, a is the hydroxide ion / silver oxide competitive precipitation correction term, b is the comprehensive regression coefficient that converts the amount of silver ions added per unit pore solution into the boundary chloride ion concentration, and c is the critical silver chloride mass ratio P in the published benchmark model. crit,AgCl The single-valued function; 0.00695, 0.608 and 1.6 are the reference initial values ​​of coefficients a, b and c, respectively, and are not considered as invariant constants applicable across slag sources, mix proportions, ages and imaging systems.

[0056] Critical mass ratio P crit,AgCl It is not fixed at 0.65 for all geopolymers. For the benchmark calibration condition where silver ions are excessive, residual chloride ions are negligible, and silver sulfide interference has been eliminated, the C value can be determined by the measured value during discoloration. Cl－ and C OH－ Approximate inverse calculation: P crit,AgCl ≈C Cl－ / (C Cl－ +0.81C OH－ (10d) In the formula, P crit,AgCl C is the critical silver chloride mass ratio, dimensionless; Cl－ The measured chloride ion concentration during the color change is expressed in moles per liter; C OH－ The measured hydroxide ion concentration during color change is expressed in moles per liter. The coefficient 0.81 is derived from the stoichiometric ratio and molar mass ratio of half a mole of silver oxide generated per mole of hydroxide ions to one mole of silver chloride generated per mole of chloride ions. The publicly disclosed benchmark value for ordinary silicate cement is 0.65, while slag-containing cement systems may exhibit lower values ​​of approximately 0.55. Therefore, for slag-containing geopolymers, 0.55–0.65 can be used as a pre-calibration reference range, but the software should ultimately use the measured calibration value of this material system. When P crit,AgCl When R changes 2,crit The coefficients a, b, and c should be recalibrated simultaneously.

[0057] Determine P crit,AgClThe experimental calibration method is as follows: using the same slag source, activator, mix ratio, age, moisture content, cross-section treatment, lighting, and imaging conditions as the formal test, a series of parallel specimens with known free chloride ion concentrations are prepared; under conditions of sufficient silver ions, at least two silver nitrate concentrations or spray amounts per unit area are sprayed, and the specimen that just reaches the standardized whiteness criterion is determined by continuous image recording; C is measured on parallel sections adjacent to this cross-section or on reserved specimens. Cl－ C OH－ and C HS－ The influence of the silver sulfide region on the silver chloride / silver oxide ratio was eliminated by methods such as co-location of silver, chlorine, and sulfur elements or other phase composition. P was back-calculated from the data satisfying the approximate conditions of equation (10d). crit,AgCl Alternatively, P can be calculated directly through quantitative phase analysis of silver chloride and silver oxide precipitation. AgCl The median or weighted average of all parallel specimens is taken as the P of the current material system. crit,AgCl .

[0058] The experimental calibration method for coefficients a, b, and c is as follows: Prepare at least six series of specimens with known free chloride ion concentration levels according to the same slag source, activation regime, age, and moisture content. Each level should have at least three parallel specimens. Use at least three sets of unit area spraying amounts or silver ion concentrations to ensure data coverage of both silver ion-deficient and silver ion-sufficient regions. Measure the concentration of C in each group. OH－ C HS－ C Ag＋ V Ag＋ and V determined by equation (5a) p The C content was obtained using a free chloride ion content detection device and method. d Measured value. In R 2,min <R2<R 2,crit In the data, C OH－ and (C) Ag＋ R2-2C HS－ ) is the independent variable, C d As the dependent variable, weighted least squares method is used to fit a and b; when R² ≥ R... 2,crit In the data, C OH － For independent variable, C dFor the dependent variable c, a zero intercept can be set initially during regression, and the intercept confidence interval can be used as the basis for deciding whether to retain the intercept. At least 80% of the calibration data should be used for fitting, and at least 20% for independent validation, or leave-one-out concentration level cross-validation can be used. The software saves the fitted values ​​of a, b, and c, the 95% confidence interval, the coefficient of determination, and the root mean square error. Only when a, b, and c are positive, the coefficient of determination of the validation set is not lower than the preset value, and the root mean square error is not higher than the preset value, are these coefficients set as valid parameters for the current material. When the slag source, slag content, activator, age, spraying amount, silver nitrate concentration, light or camera parameters exceed the calibration range, recalibration is required; the initial reference values ​​should not be directly applied.

[0059] When δ under certain working conditions eff or S r When the measurement uncertainty is large, computer 8-2 can also perform sensitivity analysis on R² within the confidence interval determined by the measured value of equation (5a); only in the preliminary experiment can R² = 1 to 10 be used as the literature reference scan interval. Sensitivity analysis does not replace V. p The determination must be made, and the R² used must be greater than the R given in equation (8). 2,min Otherwise, only output a "color display invalid" message, and do not output "C". d Numerical value.

[0060] Example 4 This embodiment illustrates the establishment of sulfide interference identification and white color development criteria.

[0061] Computer 8-2 calculates the proportion P of the white area w The proportion of silver sulfide interference region P s When P s Below the preset sulfide interference threshold, and P w A section is considered white when it reaches the white threshold and remains stable in two or more consecutive images with an interval of 5 to 30 seconds. When P s When the preset sulfide interference threshold is exceeded, the system should not directly output "not white", but should output a sulfide interference alarm. When the silver sulfide area is small and does not overlap with the white area, the proportion of the white area can be recalculated with the remaining effective area after excluding the silver sulfide pixels. When the silver sulfide severely obscures the potential white area, the result should be marked as invalid and a parallel test should be used for retesting.

[0062] The white threshold and sulfide interference threshold should be pre-established using slag samples from the same source, under the same excitation regime, and at the same age, without added chloride, with known chloride ion concentrations, and with different soluble sulfide levels. For representative white, brown, and dark brown to black areas, the colocalization relationship of silver, chloride, and sulfur can be analyzed using scanning electron microscopy (SEM) energy dispersive spectroscopy, or the correspondence between silver chloride, silver oxide, and silver sulfide can be verified using Raman spectroscopy, X-ray diffraction, and other applicable methods. For soluble sulfide levels, independent water extraction can be performed from parallel samples or adjacent pre-reserved powder samples, and auxiliary data for hydrosulfide and sulfide ions can be obtained using applicable sulfide determination methods; this powder sample must not be mixed with the free chloride ion detection powder sample.

[0063] Example 5 This example illustrates the effectiveness verification of 25 mm contaminated segment resection.

[0064] Representative specimens from the initial whitening were selected, and samples were taken from the sprayed section and at distances of 5 mm, 10 mm, 15 mm, 20 mm, and 25 mm from the sprayed section. The silver content or the distribution of silver along the depth was measured, and the free chloride ion content obtained by directly taking powder from the sprayed section was compared with that obtained by taking powder after removing 25 mm. If the silver content at the 25 mm location returned to the level of the unsprayed blank, and the free chloride ion measurement value no longer changed significantly with the removal depth after removal, it proves that the 25 mm removal length can isolate silver nitrate contamination.

[0065] Example 6 This embodiment provides a numerical calculation example of a two-stage reaction model. It assumes that C is measured in parallel specimens with the same mix proportion. HS－ =0.30 mol / L, C OH－ =0.30 mol / L, standard silver nitrate solution C Ag+ =0.10 mol / L, the corresponding volume parameter for spraying and pore solution participation is R2=8. From equation (8), R is obtained. 2,min =6, from equation (9) we get R 2,crit =13.71, therefore this operating condition is in the silver nitrate deficiency range; from equation (10b), C is obtained. d =0.00695×0.30+0.608×(0.10×8-2×0.30), predict C d It is approximately 0.124 mol / L.

[0066] Under other conditions and with R2 remaining constant, when the concentration of silver nitrate is increased to 0.50 mol / L, R 2,min Reduced to 1.2, R 2,crit It decreases to approximately 2.742, R² ≥ R 2,crit The model determines that silver nitrate is sufficient, and C is predicted by equation (10c). d=1.6 × 0.30 = 0.48 mol / L. The above values ​​are used to illustrate the software's interval selection logic and do not replace the actual measured values ​​for specific materials; in practical applications, C... OH－ C HS－ The volume parameters involved in the reaction should be calibrated according to the same batch of materials and verified using the measured results of free chloride ions obtained by the free chloride ion content detection device and method.

[0067] Example 7 This embodiment illustrates P crit,AgCl V p And the calibration of coefficients a, b, and c.

[0068] Six levels of known free chloride ion concentrations (0, 0.05, 0.10, 0.20, 0.35, and 0.50 mol / L) were prepared using the same batch of slag and activator, with at least three parallel specimens prepared for each level. First, spraying and continuous imaging were performed under conditions of sufficient silver ions to determine the cross-section that just reached the standardized whiteness criterion. C0 was then measured on adjacent parallel cross-sections. Cl－ C OH－ and C HS－ Excluding silver sulfide pixels in the image, and obtaining P by quantitative phase analysis using formula (10d) or silver chloride and silver oxide. crit,AgCl If the measured value is outside the range of 0.55 to 0.65, it is not directly judged as abnormal. Instead, the slag batch, sulfide interference, matrix color and imaging threshold are checked and the repeatable measured value is retained.

[0069] The pixel scale is determined by a size calibration board, and A is obtained from the effective cross-sectional mask. eff ; φ was measured on parallel specimens c and m r m d m sat From equation (5b), we obtain S r Another group of parallel specimens were treated according to the formal spraying parameters, and the silver element was measured in layers every 0.1–0.5 mm along the depth. The δ value was determined according to the criterion of 5% of the surface layer increment or the mean of the blank plus three times the standard deviation. eff Then calculate V using equation (5a). p Δm is recorded simultaneously on the unsaturated specimen, and δ is obtained from equation (5c). eff Compare with the results of the layering method. Alternatively, parallel specimens were selected and subjected to excess silver nitrate-local reaction laminar flow filtration to determine the concentrations of residual silver ions, chloride ions, and hydroxide ions, and the liquid phase recovery rate was corrected. V was then calculated back according to equation (6). p When the relative difference between the geometric-pore method, the mass method, and the pressure filtration verification method exceeds the preset value, check the cross-sectional loss, evaporation, sampling range, and water content, and recalibrate.

[0070] Three sets of spray volumes or silver ion concentrations were set up for the above-mentioned specimens. R² was calculated for each set, and the corresponding interval was determined. C was obtained using a free chloride ion content detection device and method. d Measured values ​​were used to regress data from the silver ion-deficient region to obtain values ​​a and b, and from the silver ion-sufficient region to obtain value c. The measured values ​​were then used as the basis for the calculation. crit,AgCl Redetermine R 2,crit Using initial values ​​of 0.00695, 0.608, and 1.6 can accelerate regression convergence, but the software ultimately uses independently validated measured fitted values. Each set of parameters is related to the slag batch, mix proportion, age, moisture content, and C2. Ag⁺ The spraying amount per unit area, spraying distance, color development time, lighting and camera parameters are associated and stored to limit its applicable domain.

[0071] The publicly available theoretical sources for the three reference coefficients 0.00695, 0.608, and 1.6 in this specification are: He F, Shi C, Yuan Q, An X, Tong B. Calculation of chloride concentration at color change boundary of AgNO3 colorimetric measurement. Cement and Concrete Research, 2011, 41(11):1095-1103. This invention introduces a preferential consumption term for hydrosulfide ions, silver sulfide image interference correction, and calibration of specific parameters for slag-containing geopolymers based on the silver chloride / silver oxide competitive precipitation model.

[0072] It should be noted that, in this document, the term "comprising" is intended to cover a non-exclusive inclusion, such that an apparatus, method, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the apparatus, method, or system. The method steps in the embodiments of the present invention are not limited to being performed in the listed order. Provided that device interlocking, fresh specimen cross-sections are uncontaminated, and data traceability is satisfied, some steps may be combined, subdivided, or their order adjusted.

[0073] The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative, and equivalent substitutions or modifications made by those skilled in the art without departing from the spirit and scope of the claims should all fall within the scope of protection of the present invention.

Claims

1. A device for determining chloride ion at the color change boundary using a silver nitrate colorimetric method for geopolymers, used for determining chloride ions in cylindrical geopolymer specimens, characterized in that... include: A fixing bracket is used to clamp and support the geopolymer cylindrical specimen, and the fixing bracket is provided with a vertical guide groove; The cutting device includes a movable cutting disc support embedded in the vertical guide groove and capable of reciprocating vertically between a standby position and a working position, and a circular cutting disc mounted on the movable cutting disc support. The cutting device is used to cut the geopolymer cylindrical specimen at a preset detection time and form a fresh cross-section. The grinding device includes a movable grinding disc support embedded in the vertical guide groove and capable of reciprocating vertically between a standby position and a working position, a circular grinding disc mounted on the movable grinding disc support, and a powder collecting device located below the grinding station. The grinding device is used to grind the fresh cross-section. A lighting device for providing fixed lighting for the fresh cross-section; An imaging analysis device includes a camera and a computer communicatively connected to the camera, wherein the camera is used to acquire a reference image and a color image, and the computer is used to analyze the image; The silver nitrate spraying device includes a nozzle lifting mechanism, a nozzle, a silver nitrate conduit, and a silver nitrate storage tank. The spray axis of the nozzle is parallel to the normal of the fresh cross-section. The nozzle lifting mechanism can move between a spraying position and an avoidance position, and the avoidance position is outside the camera's field of view. The dust protection device includes a thin dust cover disposed between the cutting device and the grinding device and the silver nitrate spraying device, the lighting device and the imaging analysis device, an automatic start-stop mechanism for driving the thin dust cover to automatically unfold and retract, and a negative pressure dust suction port. Display and setting device, used to set detection parameters and display operating status and judgment results; A precision propulsion device, including a propulsion driver, a telescopic push rod, and a sample push plate, is used to quantitatively propel the geopolymer cylindrical specimen along its axial direction.

2. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The fixing bracket has a clamping part and an elastic anti-slip layer adapted to the geopolymer cylindrical specimen with a nominal diameter of 50 mm, and the fixing bracket can be adjusted along the axial direction of the geopolymer cylindrical specimen; the vertical guide groove of the fixing bracket is a dovetail groove, a T-shaped groove, or a limiting groove formed by oppositely arranged linear guide rails.

3. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The movable cutting disc support includes a cutting lifting slide embedded in a vertical guide groove of the fixed support and a cutting cantilever extending from the cutting lifting slide toward the fresh cross-section; the circular cutting disc is mounted at the end of the cutting cantilever; the cutting device also includes a cutting lifting driver, a lead screw or synchronous belt transmission mechanism, a position encoder, an upper limit sensor and a lower limit sensor; the cutting plane of the circular cutting disc is perpendicular to the axis of the geopolymer cylindrical specimen.

4. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The movable grinding disc support includes a grinding lifting slide embedded in the vertical guide groove of the fixed support and a grinding cantilever extending from the grinding lifting slide toward the fresh cross-section; the circular grinding disc is installed at the end of the grinding cantilever; the working surface of the circular grinding disc is parallel to the fresh cross-section; the precision feeding device advances the fresh cross-section to the grinding station at a preset grinding feed thickness of 0.5 to 5 mm; the powder collection device is a detachable powder collection cup, powder collection funnel, or negative pressure powder collection box.

5. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The thin dustproof protective cover is a transparent or semi-transparent flexible film, folding curtain, or roller blind with a thickness of 0.1 to 1.0 mm, and has a flexible sealing seam or a closable opening at the position corresponding to the geopolymer cylindrical specimen; the automatic start-stop mechanism is an electric roller mechanism or a linear drive mechanism; the dustproof protection device also includes a differential pressure sensor and a dust concentration sensor disposed on the cutting and grinding side; the cutting device or the grinding device is allowed to start only when the thin dustproof protective cover is in the unfolded position and the negative pressure or dust concentration meets the preset conditions; the display and setting device is equipped with the following interlock: the cutting device and the grinding device are prohibited from starting when the thin dustproof protective cover is not unfolded; When the movable cutting disc support or the movable grinding disc support is not in the standby position, the silver nitrate spraying device is prohibited from spraying and the camera is prohibited from taking pictures; when the thin dustproof protective cover is not retracted, the nozzle is prohibited from entering the spraying position; The camera is prohibited from taking pictures when the nozzle is not in the avoidance position.

6. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The optical axis of the camera is parallel to the normal of the fresh cross-section; the color temperature, illuminance, and incident direction of the lighting device are fixed; the computer is configured to register, color correct, and effectively segment the pre-spray reference image and the post-spray color development image, and to at least identify white silver chloride areas, brown silver oxide areas, and dark brown to black silver sulfide interference areas formed by the reaction of sulfide ions and / or sulfide ions with silver ions in slag-containing geopolymers; the computer is also configured to calculate the proportion of white areas and the proportion of silver sulfide interference areas; when the proportion of silver sulfide interference areas is lower than a preset sulfide interference threshold and the proportion of white areas reaches a preset white threshold and remains stable in continuous images, a white color development result is output; when the proportion of silver sulfide interference areas reaches or exceeds the preset sulfide interference threshold, a sulfide interference alarm, a correction judgment result, or an invalid judgment result is output.

7. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 6, characterized in that, The computer is equipped with a two-stage reaction model calculation module and a parameter calibration module. The two-stage reaction model calculation module is configured to calculate the concentration of hydroxide ions in the receiving pore solution, the concentration of sulfide ions in the pore solution, the concentration of silver ions in the silver nitrate solution, the volume of the silver nitrate solution participating in the colorimetric reaction, and the volume of the pore solution participating in the colorimetric reaction, according to the volume ratio R2 = volume of silver nitrate solution participating in the colorimetric reaction / volume of pore solution participating in the colorimetric reaction, and the minimum volume ratio R. 2,min =2 × (concentration of hydrosulfide ions in the pore solution) / (concentration of silver ions in the silver nitrate solution, critical volume ratio R) 2,crit =(2.57 × hydroxide ion concentration in pore solution + 2 × sulfide ion concentration in pore solution) / silver ion concentration in silver nitrate solution; when the volume ratio R2 is less than or equal to the minimum volume ratio R 2,min When the volume ratio R2 is greater than the minimum volume ratio R, a prompt is output indicating that a recognizable color change boundary cannot be formed; 2,min And less than the critical volume ratio R 2,crit At that time, according to the chloride ion concentration C at the color change boundary d =Calculated as coefficient a × hydroxide ion concentration in pore solution + coefficient b × (silver ion concentration in silver nitrate solution × volume ratio R2 - 2 × sulfide ion concentration in pore solution); when the volume ratio R2 is greater than or equal to the critical volume ratio R 2,crit At that time, according to the chloride ion concentration C at the color change boundary d =Calculated by coefficient c × concentration of hydroxide ions in the pore solution; The volume of the pore solution participating in the colorimetric reaction is determined by the product of the effective spraying reaction area, the effective penetration reaction depth of silver nitrate, the interconnected porosity of the effective reaction layer, and the pore liquid saturation before spraying; the parameter calibration module is configured to use a series of specimens with known free chloride ion concentrations to calibrate the critical silver chloride mass ratio and the critical volume ratio R. 2,crit The coefficients a, b, and c are calibrated, and 0.00695, 0.608, and 1.6 are used as initial reference values ​​for the coefficients a, b, and c, respectively. The critical silver chloride mass ratio is the mass ratio of silver chloride in the mixed precipitate of silver chloride and silver oxide.

8. The apparatus for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 1, characterized in that, The precision propulsion device also includes an encoder or displacement sensor connected to the propulsion driver. The computer controls the propulsion distance of the telescopic push rod in a closed loop according to the preset cutting thickness, the 25 mm contaminated section removal length, and the grinding feed thickness.

9. A method for determining chloride ions at the color change boundary using the geopolymer silver nitrate colorimetric method with the apparatus described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) The geopolymer cylindrical specimen is clamped to the fixed bracket, and the axial reference positioning of the geopolymer cylindrical specimen is completed by the precision propulsion device; (2) After the preset detection time is reached, the thin dustproof protective cover is automatically unfolded by the automatic start-stop mechanism, and the geopolymer cylindrical specimen is pushed to the cutting side by the precision propulsion device to a preset cutting thickness. The movable cutting disc support is lowered from the standby position to the working position and drives the circular cutting disc to cut the geopolymer cylindrical specimen and form a fresh cross-section. After the cutting is completed, the movable cutting disc support is raised and reset to the standby position. After dust removal by the negative pressure dust suction port, the thin dustproof protective cover is retracted by the automatic start-stop mechanism. (3) Turn on the lighting device and have the camera capture a reference image of the fresh cross section before spraying; (4) The nozzle lifting mechanism lifts the nozzle to the spraying position and sprays silver nitrate solution in a quantitative manner along the normal direction of the fresh cross section. After spraying, the nozzle lifting mechanism drives the nozzle to descend to the avoidance position. (5) The camera acquires the color development image after spraying. The computer identifies the white silver chloride area, brown silver oxide area and dark brown to black silver sulfide interference area based on the reference image before spraying and the color development image after spraying. It then determines whether the white color development criterion corrected by sulfide interference is met for the first time. The white color development criterion is that the proportion of silver sulfide interference area is lower than the preset sulfide interference threshold, the proportion of white area reaches the preset white threshold and remains stable in the continuous image. If not met, steps (2) to (5) are repeated at the next preset detection time. When the proportion of silver sulfide interference area reaches or exceeds the preset sulfide interference threshold, a sulfide interference alarm is output and the parallel specimen is clamped to the fixed bracket and re-detected from step (1), or the result is marked as invalid. (6) When the critical color development moment is first met, the precision propulsion device advances the sample 25 mm, the automatic start-stop mechanism unfolds the thin dustproof protective cover, and the cutting device cuts off the 25 mm contaminated section from the sprayed section to the inside of the specimen. (7) The fresh cross-section exposed after cutting and not contaminated by silver nitrate is pushed to the grinding station by the precision propulsion device. While the thin dustproof protective cover is in the extended state, the movable grinding disc support is lowered from the standby position to the working position and drives the circular grinding disc to grind the powder sample. After grinding is completed, the movable grinding disc support is raised and reset to the standby position. After dust removal by the negative pressure dust suction port, the thin dustproof protective cover is retracted by the automatic start-stop mechanism, and the powder sample is collected by the powder collection device. (8) The free chloride ion content of the powder sample is determined by a device and method capable of crushing, sieving, alkaline extraction, solid-liquid separation and chloride ion detection, and the measured value of chloride ion concentration at the color change boundary of the powder sample by silver nitrate colorimetric method is calculated.

10. The method for determining chloride ion at the color change boundary using the geopolymer silver nitrate colorimetric method according to claim 9, characterized in that, Before step (4), the computer calculates the volume ratio R2 and the minimum volume ratio R based on the hydroxide ion concentration in the pore solution, the sulfide ion concentration in the pore solution, the silver ion concentration in the silver nitrate solution, the volume of the silver nitrate solution participating in the colorimetric reaction, and the volume of the pore solution participating in the colorimetric reaction. 2,min and critical volume ratio R 2,crit The effectiveness of the color development is predicted. The volume of the pore solution participating in the color development reaction is determined by the product of the effective spraying reaction area, the effective penetration reaction depth of silver nitrate, the interconnected porosity of the effective reaction layer, and the pore liquid saturation before spraying. The volume ratio R2 is less than or equal to the minimum volume ratio R. 2,min If the silver nitrate concentration or the spraying amount per unit cross-sectional area is increased, the system will prompt an increase in the silver nitrate concentration or the spraying amount per unit cross-sectional area, and recalculate the volume ratio R2. If the recalculated volume ratio R2 is greater than the minimum volume ratio R... 2,min When the adjusted spraying parameters are applied, steps (2) to (5) are executed; when the volume ratio R2 is greater than the minimum volume ratio R 2,min And less than the critical volume ratio R 2,crit At that time, according to the chloride ion concentration C at the color change boundary d =Coefficient a × Hydroxide ion concentration in pore solution + Coefficient b × (Silver ion concentration in silver nitrate solution × Volume ratio R2 - 2 × Sulfide ion concentration in pore solution) Calculate the predicted chloride ion concentration at the discoloration boundary; when the volume ratio R2 is greater than or equal to the critical volume ratio R... 2,crit At that time, according to the chloride ion concentration C at the color change boundary d = The predicted chloride ion concentration at the color change boundary is calculated by multiplying the hydroxide ion concentration in the pore solution by the coefficient c; where the coefficients a, b, and c are the critical silver chloride mass ratio and the critical volume ratio R. 2,crit The slag was calibrated using the same slag source, activation regime, age, water content, spraying parameters, and imaging conditions.

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