Rapid detection method for cleaning degree of fine aggregate

Abstract

The invention belongs to the technical field of constructional engineering material detection, and particularly relates to a rapid detection method for the cleanliness degree of fine aggregate. The rapid detection method comprises the following steps: (1) preparing a detection reagent saturated azure I solution and a standard sample required by rapid detection; (2) field spot check and color comparison: carrying out field spot check on a representative fine aggregate sample to be detected, and weighing the sample to be detected and a standard sample with the same mass; the method comprises the following steps: respectively adding a to-be-detected sample solution and a standard sample solution into a detection reagent to obtain the to-be-detected sample solution and the standard sample solution, carrying out color comparison, and judging whether the cleanliness of the spot-detected fine aggregate sample is qualified or not according to the colorimetric standard. The detection method provided by the invention not only has accuracy, but also has timeliness, and meets the urgent demand for improving the detection efficiency in actual engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of building engineering material testing, and particularly relates to a rapid detection method for the cleanliness of fine aggregates. Background Art

[0002] In the fields of building and road engineering materials, fine aggregates play a key role in concrete and asphalt mixtures, and their cleanliness directly affects the performance of the materials. For example, the cleanliness of fine aggregates has important impacts on the strength, durability, workability, volume stability, appearance quality, economy, and construction performance of concrete. The cleanliness of fine aggregates also has important impacts on the high-temperature stability, water stability, skid resistance performance, etc. of asphalt mixtures. Therefore, it is necessary to strictly control the cleanliness of fine aggregates to ensure that they meet relevant standards and requirements. And how to accurately evaluate whether the cleanliness of fine aggregates is qualified has become a key link in engineering construction.

[0003] Currently, the test methods for evaluating the cleanliness of fine aggregates mainly include the water washing and sieving method, sand equivalent method, and methylene blue MB value method. The water washing and sieving method is to remove the soil and mud lumps in the fine aggregates through water washing and sieving, so as to evaluate their cleanliness. This method requires the fine aggregates to be tested to be successively subjected to high-temperature drying, soaking for 2 h or 24 h, sieving, and then drying. The whole process is complex and time-consuming, and cannot be operated at the spot during sampling inspection.

[0004] The sand equivalent method is based on the different gravitational settlement velocities of clay powder and stone powder, and judges the cleanliness of fine aggregates by measuring the final precipitation height. Through flushing and precipitation, the clay and dust in the fine aggregates are separated, and the sand equivalent value (SE) is calculated, that is, the ratio of the height of clean sand to the height of the total suspension, expressed as a percentage. This method requires flushing and relies on professional laboratory equipment (such as an oscillator), and can only be determined in the laboratory, and cannot be determined at the spot during sampling inspection.

[0005] The methylene blue MB value method utilizes the adsorption between methylene blue and clay minerals to evaluate the cleanliness of fine aggregates by the amount of methylene blue solution adsorbed. According to the operating steps of the current methylene blue MB value method, the final determination of the methylene blue MB value method requires a blue color halo to appear when the suspension is dropped on the filter paper. The generation of the blue color halo requires first meeting relatively strict preconditions, that is, the diameter of the precipitate of the taken suspension droplet should be within 8 mm - 12 mm and the surface of the filter paper should not contact any solid or liquid. And it is necessary to continuously repeat the operation until a stable light blue color halo of about 1 mm appears; after the color halo appears, a staining test needs to be carried out every 1 minute until the color halo can last for 5 minutes. The operation process is quite complex, time-consuming, and the operating conditions are harsh. It can only be completed in the laboratory and cannot quickly determine whether the cleanliness of the fine aggregates is qualified at the sampling site, thus unable to meet the urgent need for improving the detection efficiency in actual projects.

[0006] In summary, the existing test methods for evaluating the cleanliness of fine aggregates in the prior art all need to be completed through professional equipment in the laboratory and cannot achieve the purpose of quickly issuing test results at the sampling site; moreover, the operating steps are complex and time-consuming, and cannot meet the high requirements for timeliness in current engineering inspections.

[0007] In view of this, it is extremely urgent to develop a detection method that can be applied to the on-site sampling scenario and can quickly determine the cleanliness of fine aggregates. Summary of the Invention

[0008] The purpose of the present invention is to provide a rapid detection method for the cleanliness of fine aggregates in view of the above-mentioned existing defects. This detection method only requires simple weighing tools, graduated glass bottles, standard samples, samples to be tested, and detection reagents. At the sampling site, through simple visual colorimetry, it can clearly and quickly determine whether the cleanliness of the sampled fine aggregate samples meets the standard requirements. The detection method of the present invention has both accuracy and timeliness, meeting the urgent need for improving the detection efficiency in actual projects.

[0009] The technical solution of the present invention is: a rapid detection method for the cleanliness of fine aggregates, which includes the following steps:

[0010] (1) Prepare the detection reagents and standard samples required for rapid detection:

[0011] Prepare the detection reagent saturated Azure I solution:

[0012] Add an excessive amount of Azure I solid to distilled water at 15 - 25 °C, stir well, and let it stand for at least 24 h to obtain a saturated Azure I solution; when in use, take the supernatant as the detection reagent.

[0013] Let it stand for at least 24 h to ensure that the added solid Azure I is fully dissolved. If a large amount of powdered Azure I solid sinks to the bottom of the solution after standing, it indicates that the obtained Azure I solution is saturated. At this time, the color of the Azure I solution will no longer deepen and remains unchanged.

[0014] If standing is not carried out, the content of Azure I in the detection reagent will decrease. Then, when the cleanliness of the sampled test specimen is poor, the color of the test sample solution will be concentrated in the pink range, resulting in insignificant color change, which is not conducive to detection.

[0015] Prepare standard samples:

[0016] First, determine the standard limit of the technical indicators that the cleanliness of the fine aggregate for the engineering use should meet according to the engineering use of the sampled fine aggregate.

[0017] Then, prepare the standard sample of the fine aggregate according to the standard limit of the corresponding technical indicators for standby. The method for preparing the standard sample of the fine aggregate can refer to the current corresponding standards, such as Standard GB / T 14684-2022 "Sand for construction", JTG / T 3650-2020 "Technical specifications for highway bridge and culvert construction", JTG / T F20-2015 "Technical rules for highway pavement base construction", JTGF40-2004 "Technical specifications for highway asphalt pavement construction", etc.

[0018] For example, for the fine aggregate used in asphalt pavement, according to the requirements of JTGF40-2004 "Technical specifications for highway asphalt pavement construction", its cleanliness should meet the sand equivalent ≥ 60%. Then, prepare a standard sample of the fine aggregate with a sand equivalent of 60% according to the standard lower limit value of this technical indicator.

[0019] Another example is that for the fine aggregate used in concrete, according to the requirements of GB / T 14684-2022 "Sand for construction", its cleanliness should meet the silt content ≤ 5%. Then, the silt content of the prepared standard sample of the fine aggregate is 5%. And for the fine aggregate used in cement stabilized macadam, according to the requirements of JTG / T F20-2015 "Technical rules for highway pavement base construction", its cleanliness should meet the silt content ≤ 15%. Then, the silt content of the prepared standard sample of the fine aggregate is 15%.

[0020] (2) On-site sampling inspection and color comparison:

[0021] First, on-site sample and inspect the representative fine aggregate sample to be tested.

[0022] Then, weigh the same mass of the test sample and the standard sample prepared in step (2) respectively; add them to the respective detection reagents with the same volume, oscillate and let stand to obtain the test sample solution and the standard sample solution respectively.

[0023] Finally, compare the color of the obtained sample solution to be tested with that of the standard sample solution, and determine whether the cleanliness of the sampled fine aggregate sample is qualified according to the following colorimetric criteria:

[0024] a. If the color of the standard sample solution is within the blue range, and when comparing the color of the sample solution to be tested with that of the standard sample solution, the color of the sample solution to be tested is darker blue than that of the standard sample solution, then it is determined that the cleanliness of the sampled fine aggregate sample is qualified.

[0025] When comparing the color of the sample solution to be tested with that of the standard sample solution, if any of the following situations ① - ③ occurs, then it is determined that the cleanliness of the sampled fine aggregate sample is unqualified;

[0026] ① The color of the sample solution to be tested is lighter blue than that of the standard sample solution;

[0027] ② The color of the sample solution to be tested is within the purple range; among which the cleanliness of the fine aggregate sample within this color range is lower than that of the fine aggregate sample under the color of situation ①.

[0028] ③ The color of the sample solution to be tested is within the pink range; among which the cleanliness of the fine aggregate sample within this color range is lower than that of the fine aggregate sample under the color of situation ②.

[0029] b. If the color of the standard sample solution is within the purple range, and when comparing the color of the sample solution to be tested with that of the standard sample solution, if any of the following situations ① - ② occurs, then it is determined that the cleanliness of the sampled fine aggregate sample is qualified;

[0030] ① The color of the sample solution to be tested is bluer than the purple of the standard sample solution;

[0031] ② The color of the sample solution to be tested is within the blue range; among which the cleanliness of the fine aggregate sample within this color range is higher than that of the fine aggregate sample under the color of situation ①.

[0032] When comparing the color of the sample solution to be tested with that of the standard sample solution, if any of the following situations ③ - ④ occurs, then it is determined that the cleanliness of the sampled fine aggregate sample is unqualified;

[0033] ③ The color of the sample solution to be tested is redder than the purple of the standard sample solution;

[0034] ④ The color of the sample solution to be tested is within the pink range; among which the cleanliness of the fine aggregate sample within this color range is lower than that of the fine aggregate sample under the color of situation ③.

[0035] c. If the color of the standard sample solution is within the pink range, and the color of the test sample solution shows any of the following situations ① - ③ when compared with the color of the standard sample solution, then it is determined that the cleanliness of the sampled fine aggregate sample is qualified;

[0036] ① The color of the test sample solution is darker pink than the standard sample solution;

[0037] ② The color of the test sample solution is within the purple range; among which the cleanliness of the fine aggregate sample within this color range is higher than that of the fine aggregate sample under the color of situation ①;

[0038] ③ The color of the test sample solution is within the blue range; among which the cleanliness of the fine aggregate sample within this color range is higher than that of the fine aggregate sample under the color of situation ②.

[0039] When the color of the test sample solution is lighter pink than the standard sample solution when compared with the color of the standard sample solution, it is determined that the cleanliness of the sampled fine aggregate sample is unqualified.

[0040] The present invention innovatively proposes a detection method that can quickly determine whether the cleanliness of a fine aggregate sample is qualified by visual colorimetry at the sampling site, achieving the purpose of being able to operate on-site and obtain the test results immediately. The detection reagent selected for the rapid detection method is Azure Ⅰ, with the CAS number 531 - 55 - 5 and the molecular formula C 15 H 16 ClN 3 S, with a molecular weight of 305.83, which is a phenothiazine dye. Its molecular structural formula is as follows:

[0041]

[0042] In order to achieve the technical purpose of obtaining the test results on-site through visual colorimetry, the present invention has found through a large number of systematic studies that when the detection reagent Azure Ⅰ is selected, the color of the detection reagent solution can change significantly, and the color change has three different color ranges: blue - purple - pink.

[0043] More importantly, during the colorimetry process of the rapid detection method described in the present invention, the different color ranges reflected can characterize the different cleanliness levels of the fine aggregate. According to the cleanliness level of the fine aggregate from high to low, the color change of the solution will successively change in three color spans: the blue range (from deep to light), the purple range, and the pink range. The color change is obvious and more conducive to visual discrimination by the naked eye; and a more explicit assessment of the cleanliness level of the fine aggregate can be made based on the color range to which the color change belongs.

[0044] It can be seen that the detection method described in the present invention can not only directly and quickly and truly judge whether the cleanliness of the fine aggregate to be tested is qualified by simply observing with the naked eye and comparing the color between the solution to be tested and the standard solution, and referring to the colorimetric standard, but also evaluate the level of the cleanliness of the fine aggregate.

[0045] In the present invention, in the rapid detection method for the cleanliness of fine aggregates, according to the ratio standard of 40 mL of detection reagent per gram of the sample to be tested, a sample solution to be tested is prepared, and by observing the color of the sample solution to be tested, the mud content range of the sample to be tested can be estimated according to the following colorimetric standard:

[0046] If the color of the sample solution to be tested changes within the blue range, then 0% ≤ the mud content of the sample to be tested ≤ 4%; as Figure 4 shown.

[0047] If the color of the sample solution to be tested changes within the purple range, then 4% < the mud content of the sample to be tested ≤ 11%; as Figure 5 shown.

[0048] If the color of the sample solution to be tested changes within the pink range, then 11% < the mud content of the sample to be tested ≤ 15%; as Figure 6 shown.

[0049] The ratio of 40 mL of detection reagent per gram of the sample to be tested basically meets the detection requirements for the cleanliness of fine aggregates. If there are special requirements, the volume of the detection reagent can be increased or decreased according to a certain ratio. The specific description is as follows:

[0050] When taking 40 mL of detection reagent / gram of the sample to be tested as the base, and multiplying the volume of the detection reagent used to dissolve each gram of the sample to be tested by a certain proportional coefficient in multiples, then the mud content range of the sample to be tested corresponding to the solution color range in the above colorimetric standard is multiplied by the same proportional coefficient, which is the mud content range of the prepared sample solution to be tested.

[0051] For example: Increase the volume of the detection reagent according to the proportional coefficient of 1.2, that is, prepare the sample solution to be tested according to the ratio standard of 48 mL of detection reagent / gram of the sample to be tested.

[0052] If the solution changes within the blue range, then 0% ≤ the mud content of the sample to be tested ≤ 4.8%; if the solution changes within the purple range, then 4.8% < the mud content of the sample to be tested ≤ 13.2%; if the solution changes within the pink range, then 13.2% < the mud content of the sample to be tested ≤ 18%. And so on for others.

[0053] When taking 40 mL of the test reagent per gram of the sample to be tested as the base, and reducing the volume of the test reagent used to dissolve each gram of the sample to be tested in multiples according to a certain proportional coefficient, then the silt content range of the sample to be tested corresponding to the solution color range in the above colorimetric standard is multiplied by the same proportional coefficient, which is the silt content range of the prepared sample solution to be tested.

[0054] For example: reduce the volume of the test reagent according to the proportional coefficient of 0.5, that is, prepare the sample solution to be tested according to the ratio standard of 20 mL of the test reagent per gram of the sample to be tested.

[0055] If the solution changes within the blue range, then 0% ≤ the silt content of the sample to be tested ≤ 2%; if the solution changes within the purple range, then 2% < the silt content of the sample to be tested ≤ 5.5%; if the solution changes within the pink range, then 5.5% < the silt content of the sample to be tested ≤ 7.5%. And so on for others.

[0056] It can be seen from this that using the rapid detection method described in the present invention can not only quickly evaluate whether the cleanliness of the fine aggregate is qualified, but also estimate the silt content range of the sample to be tested according to the color range to which the color change belongs.

[0057] In the present invention, in the rapid detection method for the cleanliness of fine aggregates, according to the ratio standard of 40 mL of the test reagent per gram of the sample to be tested, prepare the sample solution to be tested, observe the color of the sample solution to be tested, and estimate the sand equivalent range of the sample to be tested according to the following colorimetric standard:

[0058] When the color of the sample solution to be tested changes within the blue range, then 88% ≤ the sand equivalent of the sample to be tested ≤ 100%;

[0059] When the color of the sample solution to be tested changes within the purple range, then 70% ≤ the sand equivalent of the sample to be tested < 88%;

[0060] When the color of the sample solution to be tested changes within the pink range, then the sand equivalent of the sample to be tested < 70%.

[0061] In the present invention, in the rapid detection method for the cleanliness of fine aggregates, according to the ratio standard of 40 mL of the test reagent per gram of the sample to be tested, prepare the sample solution to be tested, observe the color of the sample solution to be tested, and estimate the methylene blue MB value range of the sample to be tested according to the following colorimetric standard:

[0062] When the color of the sample solution to be tested changes within the blue range, then 0.0 ≤ the methylene blue MB value of the sample to be tested ≤ 0.5;

[0063] When the color of the sample solution to be tested changes within the purple range, then 0.5 < the methylene blue MB value of the sample to be tested ≤ 1.8;

[0064] When the color of the sample solution to be tested changes within the pink range, the methylene blue MB value of the sample to be tested > 1.8.

[0065] In the present invention, for the rapid detection method of the cleanliness of fine aggregates, in step (2), 40 mL of the detection reagent is used per gram of the standard sample; 40 mL of the detection reagent is used per gram of the sample to be tested. Through repeated research, it is found that using 40 mL of the detection reagent per gram of the sample can not only basically meet the detection requirements for the cleanliness of fine aggregates; moreover, the color change effect of the sample solution prepared according to this ratio relationship can be better applied to the on-site visual colorimetric determination method described in the present invention.

[0066] In the present invention, for the rapid detection method of the cleanliness of fine aggregates, in step (2), the oscillation amplitude is 45 - 55 mm; the oscillation frequency is 2 - 3 times per second, for example, 90 oscillations in 30 s.

[0067] When using the rapid detection method described in the present invention for on-site spot checks, only manual oscillation relying on wrist strength is required. At the same time, according to the described amplitude and oscillation frequency, it can be ensured that the coarser particles in the fine aggregates sink to the bottom without being stirred up, and the clay powder in the fine aggregates can be completely suspended in the solution. In this way, it can be ensured that the fine powder fully adsorbs Azure I and the influence that the coarse particles may have on the color change of the solution is avoided.

[0068] In the present invention, for the rapid detection method of the cleanliness of fine aggregates, in step (2), it is left standing for 5 - 10 min.

[0069] In the present invention, for the rapid detection method of the cleanliness of fine aggregates, in step (1), an antioxidant is added to the obtained detection reagent. Based on the fact that the spot check process may last for more than 3 days, adding an antioxidant to prevent the Azure I solution from oxidizing and changing color due to the long spot check time.

[0070] In the present invention, for the rapid detection method of the cleanliness of fine aggregates, the addition amount of the antioxidant is 0.01 - 0.02 g of antioxidant per 1 L of the detection reagent (saturated Azure I solution).

[0071] In the present invention, in the rapid detection method for the cleanliness of fine aggregates, the antioxidant is selected from at least one of tert-butylhydroquinone (TBHQ), ascorbic acid (vitamin C), butylated hydroxyanisole (BHA), or dibutylhydroxytoluene (BHT). The selected antioxidant is water-soluble and colorless, and can play a good antioxidant role. For example, tert-butylhydroquinone contains two phenolic hydroxyl groups (-OH). In an oxidative environment, when free radicals are generated, tert-butylhydroquinone can provide hydrogen atoms through the phenolic hydroxyl groups, thereby fully exerting its antioxidant effect. Butylated hydroxyanisole and dibutylhydroxytoluene also react with free radicals through their own hydroxyl groups and other functional groups to prevent oxidation reactions. In addition, fine aggregates are usually processed from rocks, minerals, etc. through crushing, screening, etc., and their main components are inorganic substances such as silicon dioxide, calcium carbonate, and aluminum oxide. The above-mentioned antioxidants selected in the present invention will not react with fine aggregates and Azure I, avoiding affecting color changes.

[0072] The beneficial effects of the present invention are as follows: The present invention innovatively proposes a detection method that can quickly determine whether the cleanliness of a fine aggregate sample is qualified only by simple visual colorimetry at the spot check site. Using Azure I as the detection reagent, directly observing with the naked eye at the spot check site, comparing the color of the solution to be measured with that of the standard solution, and quickly judging whether the cleanliness of the fine aggregate to be measured is qualified according to the colorimetric standard described in the present invention. At the same time, the level of the cleanliness of the fine aggregate can also be evaluated.

[0073] It can be seen that the rapid detection method using Azure I as the detection reagent described in the present invention is easy to operate, does not require complex instrument equipment, is easy to quickly sample and judge at the construction site or the spot check site of raw materials. Compared with the current traditional method of first sampling and then testing in the laboratory, which often takes 2 - 3 days to obtain results, the on-site rapid colorimetry method of Azure I solution greatly improves the detection efficiency, and will provide strong support for the quality control of building materials and the smooth progress of engineering construction, and has extremely important practical significance and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a color comparison diagram of each solution of the sample to be measured and the standard sample solution obtained in Example 1 of the present invention.

[0075] Figure 2 It is a color comparison diagram of each solution of the sample to be measured and the standard sample solution obtained in Example 2 of the present invention.

[0076] Figure 3 It is a color comparison diagram of each solution of the sample to be measured and the standard sample solution obtained in Example 3 of the present invention.

[0077] Figure 4 It is a corresponding diagram of the color change - mud content of the fine aggregate sample solution described in the present invention within the blue range.

[0078] Figure 5 It is the corresponding diagram of the color change - mud content in the purple range of the fine aggregate sample solution described in the present invention.

[0079] Figure 6 It is the corresponding diagram of the color change - mud content in the pink range of the fine aggregate sample solution described in the present invention.

[0080] Figure 7 It is the absorbance - mud content curve graph drawn in Example 4.

[0081] Figure 8 It is the absorbance - methylene blue MB value curve graph drawn in Example 4.

[0082] Figure 9 It is the absorbance - sand equivalent curve graph drawn in Example 4.

[0083] Figure 10 It is the color comparison diagram of each solution obtained in Application Example 1 of the present invention.

[0084] Figure 11 It is the color comparison diagram of each sample solution obtained by using methylene blue as a reagent in Comparative Example 1 of the present invention.

[0085] Figure 12 It is the color comparison diagram of each sample solution obtained by using saturated azurin I solution as a reagent in Comparative Example 1 of the present invention.

[0086] Figure 13 It is the color comparison diagram of each sample solution obtained by using methyl orange as a reagent in Comparative Example 2 of the present invention.

[0087] Figure 14 It is the color comparison diagram of each sample solution obtained by using potassium permanganate as a reagent in Comparative Example 3 of the present invention. Detailed implementation manners

[0088] The present invention will be described in detail below with reference to the accompanying drawings.

[0089] The detection reagent azurin I used in the examples was purchased from PHYGENE, REF: PH9288 - 10g.

[0090] Example 1

[0091] The rapid detection method for the cleanliness of fine aggregates is as follows:

[0092] (1) Prepare the detection reagents and standard samples required for rapid detection:

[0093] Prepare the detection reagent saturated azurin I solution:

[0094] Add an excessive amount of Azure I solid to distilled water at 25 °C, stir well, and let it stand for 24 h to obtain a saturated Azure I solution. When in use, take the supernatant as the detection reagent.

[0095] Prepare standard samples:

[0096] The client stipulates that fine aggregates should meet the requirements of Class II natural sand in GB / T 14684-2022 "Sand for construction", and the requirement for the cleanliness of fine aggregates is that the mud content should be ≤ 3.0%. Therefore, according to the standard of this technical index, prepare a standard sample of fine aggregates with a mud content of 3.0% for standby.

[0097] (2) On-site sampling inspection and color comparison:

[0098] First, on-site sample and inspect 4 representative fine aggregate samples to be tested, denoted as sample to be tested I, sample to be tested II, sample to be tested III, and sample to be tested IV.

[0099] Then, weigh 10 g of sample to be tested I, 10 g of sample to be tested II, 10 g of sample to be tested III, 10 g of sample to be tested IV, and 10 g of the standard sample respectively.

[0100] Add the weighed sample to be tested I, sample to be tested II, sample to be tested III, sample to be tested IV, and the standard sample into the detection reagent saturated Azure I solution of 400 mL each, and manually oscillate with an oscillation amplitude of 45 - 55 mm; oscillate 90 times within 30 s; let it stand for 10 min to obtain sample solution to be tested I, sample solution to be tested II, sample solution to be tested III, sample solution to be tested IV, and standard sample solution respectively.

[0101] Finally, compare the colors of the obtained sample solutions to be tested with the standard sample solution. For details, see Figure 1 :

[0102] The color of the obtained standard sample solution (with a mud content of 3.0%) is blue.

[0103] The color of sample solution to be tested I is also blue, but it is darker than the blue of the standard sample solution. Referring to the color comparison standard a. for the qualified cleanliness in the described detection method, it can be determined that the cleanliness of sample to be tested I is qualified.

[0104] Although the color of sample solution to be tested II is blue, it is lighter than the blue of the standard sample solution. Referring to the provisions of a.① in the color comparison standard of the described detection method, it is determined that the cleanliness of sample to be tested II is unqualified.

[0105] The color of the test sample solution Ⅲ is purple. Referring to the provisions of a.② in the color comparison standard of the described detection method, it is determined that the cleanliness of the test sample Ⅲ is unqualified. And the cleanliness of the test sample Ⅲ is lower than that of the test sample Ⅱ.

[0106] The color of the test sample solution Ⅳ is pink. Referring to the provisions of a.③ in the color comparison standard of the described detection method, it is determined that the cleanliness of the test sample Ⅳ is unqualified. And the cleanliness of the test sample Ⅳ is lower than that of the test sample Ⅲ.

[0107] To verify the accuracy of the detection method described in the present invention, the test samples Ⅰ, Ⅱ, Ⅲ, and Ⅳ were respectively detected according to the mud content test method in GB / T 14684-2022 "Sand for construction". The mud content of the test sample Ⅰ was measured to be 1.2%; the mud content of the test sample Ⅱ was 3.9%; the mud content of the test sample Ⅲ was 10.3%; the mud content of the test sample Ⅳ was 13.6%. This is completely consistent with the determination conclusion obtained by the rapid detection method described in the present invention.

[0108] According to the methylene blue value test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the MB value of the test sample Ⅰ was measured to be 0.2; the MB value of the test sample Ⅱ was 0.5; the MB value of the test sample Ⅲ was 1.6; the MB value of the test sample Ⅳ was 2.2.

[0109] According to the sand equivalent test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the sand equivalent of the test sample Ⅰ was measured to be 95%; the sand equivalent of the test sample Ⅱ was 89%; the sand equivalent of the test sample Ⅲ was 74%; the sand equivalent of the test sample Ⅳ was 63%.

[0110] Example 2

[0111] The client requests to use the "Design Document" as the basis for judgment in this detection, and the requirement for the cleanliness of fine aggregates in the "Design Document" of this project is that the mud content ≤ 7.0%. Taking this as an example, the rapid detection method is described in detail.

[0112] The specific steps of the rapid detection method for the cleanliness of fine aggregates are as follows:

[0113] (1) Prepare the detection reagents and standard samples required for rapid detection:

[0114] Prepare the detection reagent saturated Azure Ⅰ solution:

[0115] Add an excessive amount of Azure Ⅰ solid to distilled water at 25°C, stir well, and let it stand for 24 hours to obtain a saturated Azure Ⅰ solution; when in use, take the supernatant as the detection reagent.

[0116] Prepare standard samples:

[0117] Prepare a standard sample of fine aggregate with a mud content of 7.0% for standby.

[0118] (2) On-site spot check and color comparison:

[0119] First, spot check 4 representative fine aggregate samples to be tested on-site, denoted as sample to be tested Ⅰ, sample to be tested Ⅱ, sample to be tested Ⅲ, and sample to be tested Ⅳ;

[0120] Then, weigh 10 g of sample to be tested Ⅰ, 10 g of sample to be tested Ⅱ, 10 g of sample to be tested Ⅲ, 10 g of sample to be tested Ⅳ, and 10 g of the standard sample respectively;

[0121] Add the weighed sample to be tested Ⅰ, sample to be tested Ⅱ, sample to be tested Ⅲ, sample to be tested Ⅳ, and the standard sample into the detection reagent saturated Azure Ⅰ solution of 400 mL each, and manually oscillate, where the oscillation amplitude is 45 - 55 mm; oscillate 90 times within 30 s; let it stand for 10 min to obtain sample solution to be tested Ⅰ, sample solution to be tested Ⅱ, sample solution to be tested Ⅲ, sample solution to be tested Ⅳ, and standard sample solution respectively;

[0122] Finally, compare the colors of the obtained sample solutions to be tested with the standard sample solution. See details in Figure 2 :

[0123] The color of the obtained standard sample solution (with a mud content of 7.0%) is purple.

[0124] The color of sample solution to be tested Ⅰ is blue. Referring to the provisions of b.② in the color comparison standard of the said detection method, it is determined that the cleanliness of sample to be tested Ⅰ is qualified.

[0125] The color of sample solution to be tested Ⅱ is bluer than the purple of the standard sample solution. Referring to the provisions of b.① in the color comparison standard of the said detection method, it is determined that the cleanliness of sample to be tested Ⅱ is qualified. And the cleanliness of sample to be tested Ⅱ is lower than that of sample to be tested Ⅰ.

[0126] The color of sample solution to be tested Ⅲ is redder than the purple of the standard sample solution. Referring to the provisions of b.③ in the color comparison standard of the said detection method, it is determined that the cleanliness of sample to be tested Ⅲ is unqualified.

[0127] The color of sample solution to be tested Ⅳ is pink. Referring to the provisions of b.④ in the color comparison standard of the said detection method, it is determined that the cleanliness of sample to be tested Ⅳ is unqualified. And the cleanliness of sample to be tested Ⅳ is lower than that of sample to be tested Ⅲ.

[0128] To verify the accuracy of the detection method described in the present invention, the mud content test method in GB / T 14684-2022 "Sand for construction" was used to detect the samples to be tested Ⅰ, Ⅱ, Ⅲ, and Ⅳ respectively. The mud content of sample Ⅰ to be tested was measured as 1.3%; the mud content of sample Ⅱ to be tested was 5.3%; the mud content of sample Ⅲ to be tested was 9.9%; the mud content of sample Ⅳ to be tested was 12.6%. This is completely consistent with the determination conclusion obtained by the rapid detection method described in the present invention.

[0129] According to the methylene blue value test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the MB values of sample Ⅰ to be tested were measured as 0.2; the MB values of sample Ⅱ to be tested were 0.8; the MB values of sample Ⅲ to be tested were 1.5; the MB values of sample Ⅳ to be tested were 2.1.

[0130] According to the sand equivalent test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the sand equivalents of sample Ⅰ to be tested were measured as 94%; the sand equivalents of sample Ⅱ to be tested were 82%; the sand equivalents of sample Ⅲ to be tested were 76%; the sand equivalents of sample Ⅳ to be tested were 65%.

[0131] Example 3

[0132] The client requires the "Design Document" to be the basis for the determination of this test, and the "Design Document" of this project requires the cleanliness of fine aggregates to have a mud content ≤ 14.0%. Taking this as an example, the rapid detection method is described in detail.

[0133] The rapid detection method for the cleanliness of fine aggregates is as follows:

[0134] (1) Prepare the detection reagents and standard samples required for rapid detection:

[0135] Prepare the detection reagent saturated Azure Ⅰ solution:

[0136] Add an excessive amount of Azure Ⅰ solid to distilled water at 25°C, stir well, and let it stand for 24h to obtain a saturated Azure Ⅰ solution; when in use, take the supernatant as the detection reagent.

[0137] Prepare the standard sample: Prepare a standard sample of fine aggregates with a mud content of 14.0% for standby.

[0138] (2) Conduct on-site spot checks and color comparison:

[0139] First, conduct on-site spot checks on 4 representative fine aggregate samples to be tested, denoted as sample Ⅰ to be tested, sample Ⅱ to be tested, sample Ⅲ to be tested, and sample Ⅳ to be tested;

[0140] Then, weigh 10 g of test sample Ⅰ, 10 g of test sample Ⅱ, 10 g of test sample Ⅲ, 10 g of test sample Ⅳ, and 10 g of the standard sample respectively;

[0141] Respectively add the weighed test sample Ⅰ, test sample Ⅱ, test sample Ⅲ, test sample Ⅳ, and the standard sample into the saturated Azure Ⅰ solution of the test reagent, each with a volume of 400 mL, and manually oscillate with an oscillation amplitude of 45 - 55 mm; oscillate 90 times within 30 s; let stand for 10 min to obtain test sample solution Ⅰ, test sample solution Ⅱ, test sample solution Ⅲ, test sample solution Ⅳ, and the standard sample solution respectively;

[0142] Finally, compare the colors of the obtained test sample solutions with the standard sample solution, see Figure 3 :

[0143] The color of the obtained standard sample solution (with a mud content of 14.0%) is pink.

[0144] The color of test sample solution Ⅰ is blue. Referring to the provisions of c.③ in the color comparison standard of the described test method, it is determined that the cleanliness of test sample Ⅰ is qualified.

[0145] The color of test sample solution Ⅱ is purple. Referring to the provisions of c.② in the color comparison standard of the described test method, it is determined that the cleanliness of test sample Ⅱ is qualified. And the cleanliness of test sample Ⅰ is higher than that of test sample Ⅱ.

[0146] The color of test sample solution Ⅲ is darker pink than the standard sample solution. Referring to the provisions of c.① in the color comparison standard of the described test method, it is determined that the cleanliness of test sample Ⅲ is qualified. And the cleanliness of test sample Ⅱ is higher than that of test sample Ⅲ.

[0147] The color of test sample solution Ⅳ is lighter pink than the standard sample solution. Referring to the standard for unqualified cleanliness in c. of the described test method, it is determined that the cleanliness of test sample Ⅳ is unqualified.

[0148] To verify the accuracy of the test method described in the present invention, test sample Ⅰ, test sample Ⅱ, test sample Ⅲ, and test sample Ⅳ are respectively tested according to the mud content test method in GB / T 14684 - 2022 "Sand for construction", and the mud contents of test sample Ⅰ, test sample Ⅱ, test sample Ⅲ, and test sample Ⅳ are respectively measured to be 1.4%; 10.1%; 11.3%; 15.4%. It is completely consistent with the determination conclusion obtained by the rapid test method described in the present invention.

[0149] According to the methylene blue value test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the MB values of the samples to be tested, namely Sample I, Sample II, Sample III, and Sample IV, were measured to be 0.4, 1.6, 2.0, and 2.5 respectively.

[0150] According to the sand equivalent test method in the standard of JTG 3432-2024 "Test Regulations for Aggregates in Highway Engineering", the sand equivalents of the samples to be tested, namely Sample I, Sample II, Sample III, and Sample IV, were measured to be 91%, 74%, 68%, and 58% respectively.

[0151] Example 4

[0152] In this example, a series of fine aggregate samples with known mud contents are taken as examples to illustrate the rationality of the detection method described in the present invention.

[0153] The specific steps are as follows:

[0154] (1) Prepare the detection reagent saturated Azure I solution:

[0155] Add an excessive amount of Azure I solid to distilled water at 25°C, stir well, and let it stand for 24 hours to obtain a saturated Azure I solution; when in use, take the supernatant as the detection reagent.

[0156] (2) Prepare a series of standard samples with known mud contents:

[0157] Prepare fine aggregate samples with mud contents of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15% respectively, and prepare 3 fine aggregate samples for each mud content.

[0158] (3) Prepare a series of sample solutions:

[0159] Weigh 10 g of each of the above-prepared fine aggregate samples and add them to the detection reagent saturated Azure I solution with a volume of 400 mL each. Use an impeller stirrer to stir at a speed of 500 r / min for 5 minutes; after stirring evenly, let it stand for 10 minutes to obtain a series of sample solutions.

[0160] Among them, the colors of the series of sample solutions with different mud contents are as Figure 5 and Figure 6 shown.

[0161] (4) Measure the absorbance values of the above series of sample solutions:

[0162] Within 30 minutes after stirring and standing still, use a spectrophotometer to measure the absorbance values of the sample solutions with different mud contents at a wavelength of 450 nm. Among them, the average of the 3 absorbance values obtained under the same mud content is taken as the absorbance value of the sample solution with this mud content, and record the data.

[0163] Then, use the absorbance value as the abscissa and the mud content as the ordinate to draw a curve, as Figure 7 shown.

[0164] It can be clearly seen from Figure 7 that for the sample solutions showing different color changes, there is a linear correlation between their absorbance and the mud content. And according to the drawn curve, the linear regression equation is y = 12.97x + 4.44 (where x is the absorbance value and y is the mud content), and the absolute value of the correlation coefficient is 0.99.

[0165] In addition, the methylene blue MB values corresponding to the above series of standard samples were also measured respectively, and a curve was drawn with the absorbance value as the abscissa and the methylene blue MB value as the ordinate, as Figure 8 shown.

[0166] It can be clearly seen from Figure 8 that for the sample solutions showing different color changes, there is a linear correlation between their absorbance and the methylene blue MB value. And according to the drawn curve, the linear regression equation is y = 1.53x + 0.30 (where x is the absorbance value and y is the methylene blue MB value), and the absolute value of the correlation coefficient is 0.96.

[0167] The sand equivalent corresponding to the above series of standard samples was measured respectively, and a curve was drawn with the absorbance value as the abscissa and the sand equivalent as the ordinate, as Figure 9 shown.

[0168] It can be clearly seen from Figure 9 that for the sample solutions showing different color changes, there is a linear correlation between their absorbance and the sand equivalent. And according to the drawn curve, the linear regression equation is y = -57.45x + 96.61 (where x is the absorbance value and y is the sand equivalent), and the absolute value of the correlation coefficient is 0.99.

[0169] Application Example 1

[0170] For on-site spot checks of fine aggregates at a certain place, all are basalt manufactured sand from different manufacturers used for the upper layer of asphalt pavement, and their cleanliness should meet the requirement that the methylene blue MB value is less than 2.5.

[0171] First, prepare a standard sample of fine aggregate with MB value = 2.5 and a saturated azure I solution of the test reagent.

[0172] Preparation of saturated Azure I solution: Add an excessive amount of Azure I solid to distilled water at 25°C. After stirring well, let it stand for 24 hours to obtain a saturated Azure I solution. When in use, take the supernatant as the detection reagent.

[0173] Then, take a part of the standard fine aggregate with an MB value of 2.5 and the saturated Azure I solution to the site.

[0174] At the spot check site, take 10 g of each of the 2 representative fine aggregates respectively. Add the same mass of the standard fine aggregate sample and the two samples to be tested into three glass bottles containing 650 ml of saturated Azure I solution respectively. Manually oscillate 90 times within 30 s with an amplitude of 50 mm, and let it stand for 5 min. Observe the color of the solution in the three bottles as Figure 10 .

[0175] It can be seen from Figure 10 that the standard sample solution is purple.

[0176] The solution of the basalt manufactured sand from Manufacturer A is pink, and basically no blue component can be seen. According to item b.④ in the described colorimetric standard, the cleanliness of the basalt manufactured sand from Manufacturer A is unqualified, and its methylene blue MB value > 2.5.

[0177] The solution of the basalt manufactured sand from Manufacturer B is blue. According to item b.② in the described colorimetric standard, the cleanliness of the basalt manufactured sand from Manufacturer B is qualified, and its methylene blue MB value < 2.5.

[0178] Bring the samples of the two manufacturers back to the laboratory for testing according to the methylene blue MB value method in JTG 3432 - 2024 "Test Regulations for Aggregates in Highway Engineering". The measured methylene blue MB value of the basalt manufactured sand from Manufacturer A is 3.2, > 2.5, unqualified; the methylene blue MB value of the basalt manufactured sand from Manufacturer B is 0.5, < 2.5, qualified. The test results are consistent with the results determined by colorimetry at the spot check site using this method.

[0179] Comparative Example 1

[0180] The difference between this comparative example and the present invention is that the detection reagent used is methylene blue. Its molecular structural formula is as follows:

[0181]

[0182] The specific operation steps are as follows:

[0183] (1) Preparation of the detection reagent: Prepare a methylene blue solution with a concentration of 0.02 g / L as the detection reagent.

[0184] (2) Preparation of the fine aggregate samples:

[0185] Prepare fine aggregate sample I with a mud content of 7% and fine aggregate sample II with a mud content of 14% respectively for standby.

[0186] (3) Prepare the sample solution:

[0187] Weigh 10 g of fine aggregate sample I and fine aggregate sample II respectively, add them to 400 mL of each methylene blue solution, and stir with an impeller stirrer at a speed of 500 r / min for 5 min; after stirring evenly, let it stand for 10 min to obtain each sample solution. As Figure 11 shown.

[0188] Through Figure 11 it can be seen that although the methylene blue solution becomes lighter with the increase of the mud content, it is only the difference in the depth of blue. When the mud content intervals are small, it is difficult to observe the change in the depth of blue with the naked eye, which is not conducive to rapid discrimination with the naked eye. Moreover, increasing or decreasing the concentration of the methylene blue solution will only change the depth of color of the two groups of sample solutions at the same time, and cannot make the color difference between the two groups of samples larger. It can be seen that methylene blue is not suitable for the detection method described in the present invention.

[0189] Figure 12 They are the colors of the solutions obtained from fine aggregate sample I and fine aggregate sample II by using saturated Azure I solution as the detection reagent.

[0190] Through Figure 11 and Figure 12 comparison, it can be known that compared with the methylene blue solution, the color of the Azure I solution changes from blue to purple and then to pink with the increase of the mud content, which is obviously conducive to observation and discrimination with the naked eye.

[0191] Comparative Example 2

[0192] The difference between this comparative example and Comparative Example 1 is that methyl orange is used as the detection reagent. Other steps are the same as those in Comparative Example 1. The obtained sample solutions are as Figure 13 shown.

[0193] Although methyl orange, which is also a dye, has certain adsorption ability, after adding fine aggregates with different cleanliness levels, the colors of its solutions cannot be distinguished and it is not applicable to the rapid detection method described in the present invention.

[0194] Comparative Example 3

[0195] The difference between this comparative example and Comparative Example 1 is that potassium permanganate is used as the detection reagent. Other steps are the same as those in Comparative Example 1. The obtained sample solutions are as Figure 14 shown.

[0196] Potassium permanganate is a strong oxidant and can change from purple to colorless under the action of a reducing agent. However, different types of mud powders have different reducibility, and most mud powders do not have reducibility. Therefore, it is also not feasible to reflect the mud content of fine aggregates through the color change of potassium permanganate.

Claims

1. A rapid detection method for the cleanliness of fine aggregate, characterized in that: The following steps are involved: (1) Equipped with the test reagents and standard samples required for rapid testing: Prepare the detection reagent saturated azure I solution: Add an excess of Azure I solid to distilled water at 15-25°C, stir thoroughly, and let stand for at least 24 hours to obtain a saturated Azure I solution; when ready to use, take the supernatant as a detection reagent; Preparation of standard samples: First, according to the engineering purpose of the sampled fine aggregate, determine the standard limit of the technical index that the cleanliness of the fine aggregate for the engineering purpose needs to meet; Then, prepare the standard sample of fine aggregate according to the standard limit of the corresponding technical index and keep it for use; (2) On-site sampling and color comparison: First, representative samples of fine aggregate to be tested are randomly selected on site; Then, weigh the same mass of the sample to be tested and the standard sample prepared in step (1); add them to the same volume of each detection reagent, shake and let stand, to obtain the sample solution to be tested and the standard sample solution; Finally, the obtained sample solution to be tested is compared with the standard sample solution in color, and the cleanliness of the sampled fine aggregate is determined to be qualified according to the following colorimetric standards: a. If the color of the standard sample solution is within the blue range, and the color of the sample solution to be tested is darker than the color of the standard sample solution, then the cleanliness of the fine aggregate sample is determined to be qualified; When the color of the sample solution to be tested is compared with the color of the standard sample solution, if any of the following ①-③ occurs, the cleanliness of the sampled fine aggregate is judged to be unqualified; ①The color of the sample solution to be tested is lighter blue than the standard sample solution; ②The color of the sample solution to be tested is in the purple range; The cleanliness of the fine aggregate samples in this color range is lower than that of the fine aggregate samples in the case of color ①; ③The color of the sample solution to be tested is in the pink range; The cleanliness of the fine aggregate samples in this color range is lower than that of the fine aggregate samples in the case of ②. b. If the color of the standard sample solution is in the purple range, and the color of the sample solution to be tested is compared with the color of the standard sample solution, and any of the following ①-② appears, then the cleanliness of the sampled fine aggregate is judged to be qualified; ① The color of the sample solution to be tested is bluer than the purple of the standard sample solution; ②The color of the sample solution to be tested is in the blue range; The cleanliness of the fine aggregate samples in this color range is higher than that of the fine aggregate samples in the case of color ①; When the color of the sample solution to be tested is compared with the color of the standard sample solution, if any of the following ③-④ occurs, the cleanliness of the sampled fine aggregate is judged to be unqualified; ③ The color of the sample solution to be tested is redder than the purple of the standard sample solution; ④The color of the sample solution to be tested is in the pink range; The cleanliness of the fine aggregate samples in this color range is lower than that of the fine aggregate samples in the case of color ③; c. If the color of the standard sample solution is within the pink range, and the color of the sample solution to be tested is compared with the color of the standard sample solution, and any of the following ①-③ occurs, then the cleanliness of the sampled fine aggregate is determined to be qualified; ① The color of the sample solution to be tested is darker than the pink color of the standard sample solution; ②The color of the sample solution to be tested is in the purple range; The cleanliness of the fine aggregate samples in this color range is higher than that of the fine aggregate samples in the case of color ①; ③The color of the sample solution to be tested is in the blue range; The cleanliness of the fine aggregate samples in this color range is higher than that of the fine aggregate samples in the case of color ②; When the color of the sample solution to be tested is compared with the color of the standard sample solution, and the color of the sample solution to be tested is lighter in pink than the standard sample solution, it is determined that the cleanliness of the fine aggregate sample inspected is unqualified.

2. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: Prepare the sample solution according to the standard ratio of 40 mL of detection reagent per gram of the sample to be tested, observe the color of the sample solution, and estimate the mud content range of the sample to be tested according to the following colorimetric standard: When the color of the sample solution changes within the blue range, 0%≤the mud content of the sample≤4%; When the color of the sample solution changes within the purple range, the mud content of the sample to be tested is 4%<≤11%; When the color of the sample solution changes within the pink range, the mud content of the sample is 11%<≤15%.

3. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: Prepare the sample solution according to the standard ratio of 40 mL of detection reagent per gram of the sample to be tested, observe the color of the sample solution to be tested, and estimate the sand equivalent range of the sample to be tested according to the following colorimetric standard: When the color of the sample solution changes within the blue range, 88%≤the sand equivalent of the sample≤100%; When the color of the sample solution changes within the purple range, 70%≤the sand equivalent of the sample to be tested is <88%; When the color of the sample solution changes within the pink range, the sand equivalent of the sample is less than 70%.

4. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: Prepare the sample solution according to the standard ratio of 40 mL of detection reagent per gram of the sample to be tested, observe the color of the sample solution to be tested, and estimate the methylene blue MB value range of the sample to be tested according to the following colorimetric standard: When the color of the sample solution changes within the blue range, 0.0≤the MB value of the sample≤0.5; When the color of the sample solution changes within the purple range, 0.5<the MB value of the sample ≤1.8; When the color of the sample solution changes within the pink range, the methylene blue MB value of the sample is greater than 1.

8.

5. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: In the step (2), 40 mL of the detection reagent is added to each gram of the standard sample; and 40 mL of the detection reagent is added to each gram of the sample to be tested.

6. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: The amplitude of oscillation in step (2) is 45-55 mm; the oscillation frequency is 2-3 times / second.

7. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: In the step (2), the mixture is allowed to stand for 5-10 minutes.

8. The rapid detection method for the cleanliness of fine aggregate according to claim 1 is characterized in that: In the step (1), an antioxidant is added to the obtained detection reagent.

9. The rapid detection method for the cleanliness of fine aggregate according to claim 8, characterized in that: The antioxidant is added in an amount of 0.01-0.02 g of antioxidant per 1 L of detection reagent.

10. The rapid detection method for the cleanliness of fine aggregate according to claim 8 or 9, characterized in that: The antioxidant is selected from at least one of tert-butylhydroquinone, ascorbic acid, butylated hydroxyanisole or butylated hydroxytoluene.

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