Test paper for rapidly detecting content of phosphoric acid in asphalt as well as preparation method and use method of test paper

Abstract

The invention discloses test paper for rapidly detecting the content of phosphoric acid in asphalt as well as a preparation method and a use method of the test paper. The test paper for rapidly detecting the content of phosphoric acid in asphalt comprises a base layer, an extraction layer, a reaction layer and a color development layer which are sequentially stacked from bottom to top, dilute nitric acid is adsorbed on the extraction layer, the reaction layer is obtained by dipping in a mixed solution of ammonium molybdate and ascorbic acid and drying, and the color development layer is obtained by dipping in a sodium citrate solution and drying. By implementing the method, the content of the phosphoric acid in the asphalt can be rapidly and stably detected, and data support is provided for subsequent asphalt performance research.

Description

Technical Field

[0001] This invention relates to the field of highway engineering material testing technology, and in particular to a rapid test paper for detecting the phosphoric acid content in asphalt, its preparation method, and its application method. Background Technology

[0002] The sources of phosphoric acid (mainly phosphate) in asphalt mainly include raw material impurities and additive residues. To explore the potential impact of phosphoric acid content in asphalt on its core properties such as adhesion, aging resistance, and interfacial interaction with aggregates, it is first necessary to establish a method for detecting phosphoric acid content in asphalt. Existing methods for detecting phosphoric acid content mainly include molybdenum blue spectrophotometry, ion chromatography, and reagent kit methods. Among these methods, the molybdenum blue spectrophotometric method requires high-temperature ashing at 550℃~600℃ to destroy the organic matrix. However, asphalt is a high-viscosity, high-carbon organic system, and during the ashing process, phosphate ions are encapsulated by carbonized residues, resulting in an extraction rate of only 30%~50% and poor detection stability. Ion chromatography requires wet digestion of asphalt with nitric acid and perchloric acid, but the gums and asphaltenes in asphalt are prone to violent reactions with perchloric acid, posing a risk of boiling over. Furthermore, residual organic impurities in the digested solution can contaminate the chromatographic column, leading to increased instrument maintenance costs. Additionally, the aromatic compounds that may be present in asphalt can interfere with the detection results, with quantitative deviations reaching ±30%. Rapid industrial phosphate detection kits (such as the Hach Company's general-purpose kit) are mainly used for water samples or low-viscosity industrial samples. High-viscosity asphalt samples are difficult to mix thoroughly with the reagents in the kit, and the reagents cannot penetrate the organic matrix of asphalt to extract phosphate ions, resulting in low practical reference value of the detection results. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a rapid test paper for detecting the phosphoric acid content in asphalt, and its preparation and use methods, which can quickly and stably detect the phosphoric acid content in asphalt, providing data support for subsequent asphalt performance research.

[0004] To address the aforementioned problems, this invention discloses a rapid test paper for phosphoric acid content in asphalt, comprising a base layer, an extraction layer, a reaction layer, and a colorimetric layer stacked sequentially from bottom to top; the extraction layer is adsorbed with dilute nitric acid, the reaction layer is obtained by impregnation and drying with a mixed solution of ammonium molybdate and ascorbic acid, and the colorimetric layer is obtained by impregnation and drying with a sodium citrate solution.

[0005] As an improvement to the above technical solution, the extraction layer is a degreased cotton fiber adsorbed with dilute nitric acid, the porosity of the degreased cotton fiber is 75%~85%; the concentration of the dilute nitric acid is 0.3mol / L~0.6mol / L, and the adsorption capacity is 0.15mL / piece~0.25mL / piece.

[0006] As an improvement to the above technical solution, the reaction layer is a quantitative filter paper impregnated with a mixed solution of ammonium molybdate and ascorbic acid and then dried, wherein the pore size of the quantitative filter paper is 3μm~5μm; the pH of the mixed solution of ammonium molybdate and ascorbic acid is 1.2~1.5, and the mass fraction of ammonium molybdate in the mixed solution is 1.5%~2.5%, and the mass fraction of ascorbic acid is 0.5%~1.5%.

[0007] As an improvement to the above technical solution, the color development layer is a quantitative filter paper impregnated with sodium citrate solution and dried, the pore size of the quantitative filter paper is 1μm~3μm; the mass fraction of the sodium citrate solution is 0.25%~0.75%.

[0008] As an improvement to the above technical solution, the base layer is provided with holes, and the extraction layer completely covers the holes.

[0009] As an improvement to the above technical solution, the rapid test paper for phosphoric acid content in asphalt further includes a protective layer, which covers the base layer, extraction layer, reaction layer and color development layer; The protective layer is a transparent polyethylene film with a thickness of 0.01mm to 0.03mm; The thickness of the base layer is 0.2mm to 0.4mm.

[0010] Accordingly, the present invention also discloses a method for preparing the above-mentioned rapid test paper for detecting phosphoric acid content in asphalt, comprising the following steps: The extraction layer material is immersed in dilute nitric acid for 4 to 6 minutes, and excess dilute nitric acid is squeezed out to obtain the extraction layer. Nitric acid is added to water to adjust the pH to 1.2-1.5. Ammonium molybdate and ascorbic acid are added separately to obtain a mixed solution of ammonium molybdate and ascorbic acid. The reaction layer material is immersed in the mixed solution of ammonium molybdate and ascorbic acid for 12-20 minutes and then dried at 50-70°C for 2-4 hours to obtain the reaction layer. The color development layer material is immersed in sodium citrate solution for 8 min to 12 min, and then dried in a forced-air dryer at 50℃ to 70℃ for 1 h to 3 h to obtain the color development layer. By stacking the base layer, extraction layer, reaction layer, and color development layer, a rapid test paper for the phosphoric acid content in asphalt is obtained.

[0011] As an improvement to the above technical solution, holes are made in the base layer, and the extraction layer completely covers the holes; A protective layer is applied over the base layer, extraction layer, reaction layer, and color development layer using a hot-press bonding process.

[0012] Accordingly, the present invention also discloses a method for using the rapid test strip for phosphoric acid content in asphalt as described above, comprising the following steps: Asphalt samples were obtained through sampling; Apply the extraction layer of the rapid test paper for phosphoric acid content in asphalt tightly to the asphalt sample and press for 25s~35s. Lay the rapid test paper for phosphoric acid content in asphalt flat and let it stand for 4 to 7 minutes. Observe the color of the developing layer to obtain the range of phosphoric acid content.

[0013] As an improvement to the above technical solution, if the color of the developing layer is almost colorless or light blue, the phosphoric acid content is <0.05%; If the color of the developing layer is light blue, the phosphoric acid content is 0.05% ≤ < 0.1%; If the color of the developing layer is medium blue, the phosphoric acid content is 0.1% ≤ < 0.5%; If the color of the developing layer is dark blue, the phosphoric acid content is 0.5% ≤ < 1%; If the color of the developing layer is dark blue, the phosphoric acid content is >1%.

[0014] Implementing this invention has the following beneficial effects: The rapid test paper for detecting phosphate content in asphalt provided by this invention comprises, from bottom to top, a base layer, an extraction layer, a reaction layer, and a colorimetric layer. The extraction layer can penetrate the organic matrix of asphalt to rapidly extract phosphate ions. The reaction layer can react with phosphate ions to form a stable colored product. The colorimetric layer eliminates resins and Fe in the asphalt. 3+ Al 3+ Despite the influence of interfering substances, the color of the color development layer is positively correlated with the phosphate content. The phosphate content in asphalt can be quickly obtained by observing the color of the color development layer. The detection time for a single sample is ≤10 minutes, and stable detection data can be obtained in batches, providing data support for subsequent asphalt performance research. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the rapid test paper for detecting phosphoric acid content in asphalt provided in an embodiment of the present invention; Figure 2 This is a flowchart of the preparation method of the rapid test paper for detecting phosphoric acid content in asphalt provided in this embodiment of the invention; Figure 3 This is a flowchart illustrating the usage method of the rapid test strip for detecting phosphoric acid content in asphalt provided in this embodiment of the invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0017] like Figure 1As shown, the present invention provides a rapid test paper for the phosphoric acid content in asphalt, comprising a base layer 1, an extraction layer 2, a reaction layer 3, and a color development layer 4 stacked sequentially from bottom to top; the extraction layer 2 is adsorbed with dilute nitric acid, the reaction layer 3 is obtained by impregnation and drying with a mixed solution of ammonium molybdate and ascorbic acid, and the color development layer 4 is obtained by impregnation and drying with a sodium citrate solution.

[0018] Specifically, the base layer 1 supports the various layers of the test paper, facilitating hand operation and preventing asphalt from sticking to the hands; the extraction layer 2 adsorbs dilute nitric acid, which penetrates into the asphalt sample to dissolve soluble phosphate ions. The phosphate ions inside the asphalt sample diffuse with the dilute nitric acid to the reaction layer 3, where they react with ammonium molybdate to form yellow phosphomolybdic acid, which is then reduced to blue molybdenum blue by ascorbic acid; the sodium citrate in the color development layer 4 acts as a specific masking agent, reacting with Fe in the asphalt... 3+ Al 3+ It also binds to some of the resin, preventing it from forming precipitates or colored substances that would interfere with the results when combined with ammonium molybdate. Ultimately, the depth of the blue color directly corresponds to the phosphoric acid content; the deeper the blue, the higher the phosphate content in the asphalt sample, providing a quantifiable content basis for subsequent performance studies.

[0019] In one embodiment, the extraction layer 2 is degreased cotton fiber adsorbed with dilute nitric acid. The porosity of the degreased cotton fiber is 75%~85%. The extraction layer 2 adopts a loose degreased cotton structure, which is suitable for the viscosity of asphalt and facilitates penetration. The concentration of the dilute nitric acid is 0.3mol / L~0.6mol / L. This concentration can extract phosphate ions from asphalt without causing side reactions with asphaltene. Specifically, the amount of dilute nitric acid adsorbed by each piece of the extraction layer 2 is 0.15mL~0.25mL, ensuring that the extraction amount is sufficient to dissolve the phosphate ions in the asphalt sample.

[0020] In one embodiment, the reaction layer 3 is a quantitative filter paper impregnated with a mixed solution of ammonium molybdate and ascorbic acid and then dried. The pore size of the quantitative filter paper is 3μm~5μm. The pH of the mixed solution of ammonium molybdate and ascorbic acid is 1.2~1.5. The strong acid environment is suitable for the asphalt matrix and avoids interference from gum. In the mixed solution, the mass fraction of ammonium molybdate is 1.5%~2.5%, and the mass fraction of ascorbic acid is 0.5%~1.5%. This concentration ratio can ensure that even trace amounts of phosphate in the asphalt sample can be colorimetrically detected.

[0021] In one embodiment, the colorimetric layer 4 is a quantitative filter paper impregnated with sodium citrate solution and dried, the pore size of the quantitative filter paper being 1μm~3μm; the mass fraction of the sodium citrate solution is 0.25%~0.75%. Sodium citrate solution is a specific masking agent for asphalt, eliminating Fe in asphalt. 3+ Al 3+ It avoids interference from colloids, carries the colorimetric products, and facilitates observation.

[0022] It is understood that the rapid test paper for phosphoric acid content in asphalt provided by the present invention consists of a base layer 1, an extraction layer 2, a reaction layer 3, and a color development layer 4 stacked together from bottom to top. In order to clearly show the layer structure of each layer, each layer is displayed separately.

[0023] In a preferred embodiment, the base layer 1 has holes 11, and the extraction layer 2 completely covers the holes 11. The holes 11 are used to expose the extraction layer 2, ensuring that the extraction layer 2 is in full contact with the asphalt sample. Specifically, the base layer 1 has dimensions of 3cm × 6cm, and circular holes 11 with a diameter of 1cm are formed in the corresponding area of ​​the extraction layer 2. Correspondingly, the dimensions of the extraction layer 2, the reaction layer 3, and the color developing layer 4 can all be 2cm × 5cm.

[0024] To prevent the dilute nitric acid in the extraction layer 2 from evaporating and the reagent from becoming damp during storage, and to adapt to on-site storage environments such as construction sites and recycling plants, the rapid test paper for phosphoric acid content in asphalt also includes a protective layer. This protective layer covers the base layer 1, extraction layer 2, reaction layer 3, and colorimetric layer 4. Specifically, the protective layer is a transparent polyethylene film with a thickness of 0.01 mm to 0.03 mm.

[0025] Furthermore, the thickness of the base layer 1 is 0.2mm~0.4mm, providing support for the other layers and preventing the test paper from deforming during use. The area of ​​the base layer 1 other than the extraction layer 2 can also be coated with an anti-stick coating to prevent asphalt residue from remaining on the surface of the base layer 1.

[0026] Correspondingly, such as Figure 2 As shown, the present invention also provides a method for preparing the above-mentioned rapid test paper for detecting phosphoric acid content in asphalt, comprising the following steps: S11. Immerse the extraction layer material in dilute nitric acid for 4 to 6 minutes, squeeze out excess dilute nitric acid, and obtain the extraction layer.

[0027] S12. Add nitric acid to water to adjust the pH to 1.2-1.5, then add ammonium molybdate and ascorbic acid separately to obtain a mixed solution of ammonium molybdate and ascorbic acid. Immerse the reaction layer material in the mixed solution of ammonium molybdate and ascorbic acid for 12-20 minutes, then dry it at 50-70°C for 2-4 hours to obtain the reaction layer. In preparing the mixed solution of ammonium molybdate and ascorbic acid, nitric acid is added first to adjust the pH to 1.2-1.5 before adding ammonium molybdate and ascorbic acid to prevent the mixed solution from becoming ineffective. Preferably, the pH is adjusted to 1.2.

[0028] S13. Immerse the color development layer material in sodium citrate solution for 8 min to 12 min, and dry it in a forced-air dryer at 50℃ to 70℃ for 1 h to 3 h to obtain the color development layer.

[0029] S14. The base layer, extraction layer, reaction layer and color development layer are stacked together to obtain the rapid test paper for the phosphoric acid content in the asphalt.

[0030] In a preferred embodiment, the preparation method further includes: creating holes in the base layer and completely covering the holes with the extraction layer. The extraction layer is exposed through the holes to allow for sufficient contact with the asphalt sample.

[0031] In a preferred embodiment, the preparation method further includes: applying a protective layer to the base layer, extraction layer, reaction layer, and color development layer using a hot-pressing bonding process. Specifically, tear-off notches are provided at the edges of the protective layer to ensure a tight bond between the protective layer and the base layer, extraction layer, reaction layer, and color development layer, preventing delamination during asphalt adhesion. The bonding strength of the protective layer is verified by 50 adhesion tests.

[0032] Correspondingly, such as Figure 3 As shown, the present invention also provides a method for using the above-mentioned rapid test strip for phosphoric acid content in asphalt, comprising the following steps: S21. Obtain asphalt samples. To accommodate the size of the test paper, the sample size of the asphalt can be 0.05g to 0.15g. Specifically, a sampling scraper can be used for sampling. The sampling scraper can be made of stainless steel, and the scraper head area is 1cm². 2 ~2cm 2 The handle should be 10cm-15cm long to avoid hand contact with asphalt. Use the sampling scraper to scrape samples from the surface of asphalt, such as road surfaces, raw material piles, and recycled materials, to ensure uniform sampling volume and reduce batch testing errors. Avoid mixing in sand, dust, or other impurities during sampling, as these will interfere with color development. If impurities are present, gently sift them out with filter paper.

[0033] S22. Press the extraction layer of the rapid test paper for phosphate content in asphalt firmly against the asphalt sample for 25-35 seconds. Specifically, press gently to ensure the extraction layer adheres tightly to the asphalt sample, applying enough pressure to prevent the asphalt sample from falling off, and hold for 25-35 seconds to ensure the extraction layer penetrates the asphalt and fully extracts phosphate.

[0034] S23. Lay the rapid test paper for phosphoric acid content in asphalt flat and let it stand for 4 to 7 minutes. Place the test paper flat on a clean surface, avoiding folding or touching the extraction layer. During the standing time, the dilute nitric acid in the extraction layer carries phosphate ions to diffuse to the reaction layer, reacting with the reagent to generate molybdenum blue. The color development layer gradually turns blue. If the standing time is too short, the color development will be incomplete; if the standing time is too long, there will be no color change.

[0035] S24. Observe the color of the developing layer to obtain the range of phosphoric acid content. Specifically, observe the color of the developing layer under natural light, avoiding direct sunlight or direct artificial light to prevent misjudgment of the color.

[0036] Specifically, the color of the color development layer is divided into 5 color gradients, each corresponding to a different range of phosphate content, providing a basic classification for subsequent performance studies: If the color of the developing layer is almost colorless or light blue, the phosphoric acid content is <0.05%; If the color of the developing layer is light blue, the phosphoric acid content is 0.05% ≤ < 0.1%; If the color of the developing layer is medium blue, the phosphoric acid content is 0.1% ≤ < 0.5%; If the color of the developing layer is dark blue, the phosphoric acid content is 0.5% ≤ < 1%; If the color of the developing layer is dark blue, the phosphoric acid content is >1%.

[0037] Understandably, if the color of the developing layer is between two color gradients, the middle value should be taken. For example, if the color of the developing layer is between light blue and medium blue, the phosphoric acid content should be recorded as 0.1% to 0.3%.

[0038] This invention provides a rapid test strip for detecting phosphate content in asphalt, along with its preparation and usage methods. This fills a gap in the dedicated detection of phosphate in asphalt, specifically designed for the asphalt matrix. It supports further research into the potential impact of phosphate content on core properties such as asphalt adhesion, anti-aging properties, and interfacial interaction with aggregates. Firstly, the detection method is reliable. By soaking loose, degreased cotton in dilute nitric acid, adapting to the viscosity of asphalt, and using a dedicated reagent formula, interference from gums is avoided, allowing direct extraction of phosphate ions from the asphalt sample through the matrix. Secondly, it offers high efficiency and batch processing, facilitating data accumulation. Existing phosphate detection methods require 1-2 days for single-sample testing and cannot acquire data in batches. This invention is simple to operate, with a single sample testing time of ≤10 minutes, and can batch test hundreds of samples, rapidly accumulating asphalt phosphate content data under different scenarios. Furthermore, the individually packaged test strips avoid cross-contamination and are suitable for batch operations.

[0039] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A rapid test strip for detecting phosphoric acid content in asphalt, characterized in that, It comprises, from bottom to top, a base layer, an extraction layer, a reaction layer, and a color development layer; the extraction layer is adsorbed with dilute nitric acid, the reaction layer is obtained by impregnation and drying with a mixed solution of ammonium molybdate and ascorbic acid, and the color development layer is obtained by impregnation and drying with a sodium citrate solution.

2. The rapid test paper for phosphoric acid content in asphalt as described in claim 1, characterized in that, The extraction layer is a degreased cotton fiber adsorbed with dilute nitric acid, and the porosity of the degreased cotton fiber is 75%~85%; the concentration of the dilute nitric acid is 0.3mol / L~0.6mol / L, and the adsorption capacity is 0.15mL / piece~0.25mL / piece.

3. The rapid test paper for phosphoric acid content in asphalt as described in claim 1, characterized in that, The reaction layer is a quantitative filter paper impregnated with a mixed solution of ammonium molybdate and ascorbic acid and then dried, the pore size of the quantitative filter paper being 3μm~5μm; the pH of the mixed solution of ammonium molybdate and ascorbic acid is 1.2~1.5, and the mass fraction of ammonium molybdate in the mixed solution is 1.5%~2.5%, and the mass fraction of ascorbic acid is 0.5%~1.5%.

4. The rapid test paper for phosphoric acid content in asphalt as described in claim 1, characterized in that, The colorimetric layer is a quantitative filter paper impregnated with sodium citrate solution and dried, the pore size of the quantitative filter paper being 1μm~3μm; the mass fraction of the sodium citrate solution being 0.25%~0.75%.

5. The rapid test paper for detecting phosphoric acid content in asphalt as described in claim 1, characterized in that, The base layer has holes, and the extraction layer completely covers the holes.

6. The rapid test paper for phosphoric acid content in asphalt as described in claim 1, characterized in that, The rapid test paper for phosphoric acid content in asphalt also includes a protective layer, which covers the base layer, extraction layer, reaction layer and color development layer; The protective layer is a transparent polyethylene film with a thickness of 0.01mm to 0.03mm; The thickness of the base layer is 0.2mm to 0.4mm.

7. A method for preparing a rapid test paper for detecting phosphoric acid content in asphalt as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The extraction layer material is immersed in dilute nitric acid for 4 to 6 minutes, and excess dilute nitric acid is squeezed out to obtain the extraction layer. Nitric acid is added to water to adjust the pH to 1.2-1.

5. Ammonium molybdate and ascorbic acid are added separately to obtain a mixed solution of ammonium molybdate and ascorbic acid. The reaction layer material is immersed in the mixed solution of ammonium molybdate and ascorbic acid for 12-20 minutes and then dried at 50-70°C for 2-4 hours to obtain the reaction layer. The color development layer material is immersed in sodium citrate solution for 8 min to 12 min, and then dried in a forced-air dryer at 50℃ to 70℃ for 1 h to 3 h to obtain the color development layer. By stacking the base layer, extraction layer, reaction layer, and color development layer, a rapid test paper for the phosphoric acid content in asphalt is obtained.

8. The method for preparing the rapid test paper for detecting phosphoric acid content in asphalt as described in claim 7, characterized in that, Holes are made in the base layer, and the extraction layer is completely covered in the holes; A protective layer is applied over the base layer, extraction layer, reaction layer, and color development layer using a hot-press bonding process.

9. A method of using a rapid test strip for detecting phosphoric acid content in asphalt as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Asphalt samples were obtained through sampling; Apply the extraction layer of the rapid test paper for phosphoric acid content in asphalt tightly to the asphalt sample and press for 25s~35s. Lay the rapid test paper for phosphoric acid content in asphalt flat and let it stand for 4 to 7 minutes. Observe the color of the developing layer to obtain the range of phosphoric acid content.

10. The method of using the rapid test strip for phosphoric acid content in asphalt as described in claim 9, characterized in that, If the color of the developing layer is almost colorless or light blue, the phosphoric acid content is <0.05%; If the color of the developing layer is light blue, the phosphoric acid content is 0.05% ≤ < 0.1%; If the color of the developing layer is medium blue, the phosphoric acid content is 0.1% ≤ < 0.5%; If the color of the developing layer is dark blue, the phosphoric acid content is 0.5% ≤ < 1%; If the color of the developing layer is dark blue, the phosphoric acid content is >1%.

Images