Asphalt ultraviolet-visible absorption spectrum testing method based on integrating sphere

Abstract

The invention discloses an asphalt ultraviolet-visible absorption spectrum testing method based on an integrating sphere, belongs to the field of road petroleum asphalt, and solves the problem that asphalt cannot be uniformly mixed with powder to prepare a sample suitable for an integrating sphere method. The method comprises the following steps: adding an asphalt sample into an n-heptane-toluene mixed solution to form an asphalt dispersion solution; adding BaSO4 into the asphalt dispersion liquid, carrying out sealed standing, and then carrying out reduced pressure distillation to remove n-heptane and toluene so as to obtain BaSO4 powder with asphalt uniformly adsorbed on the surface as a to-be-detected sample; the method comprises the following steps: adding BaSO4 into an n-heptane-toluene mixed solution, sealing, standing, and carrying out reduced pressure distillation to remove n-heptane and toluene to obtain BaSO4 powder of which the surface does not adsorb asphalt as a blank sample; a to-be-tested sample and a blank sample are prepared into test pieces respectively, and the test pieces are tested by using an ultraviolet-visible spectrograph equipped with an integrating sphere. According to the method disclosed by the invention, the asphalt ultraviolet-visible spectrum which is more complete and accurate and has more obvious characteristics can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of road petroleum asphalt, and particularly relates to an asphalt ultraviolet-visible absorption spectrum testing method based on an integrating sphere. Background Art

[0002] During the service life of asphalt pavements, the asphalt on their surface is exposed to solar radiation, inevitably undergoing UV aging. Adding UV absorbers to asphalt is currently one of the primary methods for improving asphalt's resistance to UV aging. However, different types of UV absorbers have varying UV absorption characteristics and compatibility with asphalt. Analyzing and characterizing asphalt's UV-visible absorption characteristics can identify UV absorbers suitable for specific asphalts, helping to improve asphalt's resistance to UV aging, extend the service life of asphalt pavements, reduce maintenance frequency, and reduce energy and material consumption in road operations, thereby lowering resulting carbon emissions.

[0003] Currently, UV-visible spectroscopy analysis of asphalt primarily utilizes the cuvette method, where the asphalt is dispersed in an organic solvent, primarily n-heptane and toluene, and tested as a liquid sample. This method dissolves the larger molecular weight asphaltenes in the asphalt and primarily disperses them in the solvent as particles with diameters ranging from 1 to 5 μm. These particles cause Rayleigh scattering during UV-visible spectroscopy, interfering with the characterization of absorption features. While organic solvents such as trichloroethylene can completely dissolve asphalt, they strongly interfere with the test at wavelengths below 265 nm, making them unsuitable for UV-visible absorption spectroscopy analysis of asphalt. Currently, the primary challenge in using the integrating sphere method for UV-visible spectroscopy analysis of asphalt lies in its high viscosity at room temperature and pressure, making it difficult to uniformly mix with a powder to prepare a sample suitable for the integrating sphere method. Summary of the Invention

[0004] The purpose of the present invention is to provide an asphalt UV-visible absorption spectrum testing method based on an integrating sphere to solve the problem that asphalt cannot be uniformly mixed with powder to prepare a sample suitable for the integrating sphere method.

[0005] The technical solution of the present invention is: a method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere, comprising the following steps: A. Prepare an n-heptane-toluene mixture, add the asphalt sample into the mixture, and perform ultrasonic treatment to uniformly disperse the asphalt sample in the mixture to form an asphalt dispersion; B. Add a certain amount of BaSO4 to the asphalt dispersion and perform ultrasonic treatment to uniformly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 24-36 hours, and then the n-heptane and toluene are removed by vacuum distillation to obtain a BaSO4 powder with asphalt uniformly adsorbed on its surface as a test sample; C. Prepare an n-heptane-toluene mixture, add BaSO4 thereto, and perform ultrasonic treatment to uniformly disperse the BaSO4 to obtain a BaSO4 dispersion. Seal the BaSO4 dispersion and let it stand for 24-36 hours. Then, remove the n-heptane and toluene by vacuum distillation to obtain a BaSO4 powder with no asphalt adsorbed on the surface as a blank sample. D. Prepare the test sample and blank sample into test pieces that can be tested by UV-visible spectrometer by using a tablet pressing method, and use a UV-visible spectrometer equipped with an integrating sphere to test the UV-visible absorption spectrum of the test piece to obtain the UV-visible absorption spectrum curve of the test sample.

[0006] As a further improvement of the present invention, in step A and step C, the volume ratio of n-heptane to toluene in the n-heptane-toluene mixture is 60-150:1.

[0007] As a further improvement of the present invention, in step A, the concentration of asphalt in the n-heptane-toluene mixture is 0.2~2.0 mg / mL; in step B, the concentration of the added BaSO4 in the n-heptane-toluene mixture is 2~18 mg / mL; and the mass ratio of asphalt to BaSO4 is 1:9-19.

[0008] As a further improvement of the present invention, the asphalt is road petroleum asphalt, including one of various grades of base asphalt, SBS modified asphalt, rubber modified asphalt, and SBS-rubber composite modified asphalt.

[0009] The beneficial effects of the present invention are: The present invention adopts a method of first dissolving and dispersing and then evaporating the solvent to prepare an asphalt-BaSO4 solid sample suitable for ultraviolet-visible spectrum testing, solving the problem of uniformly dispersing high-viscosity asphalt in powder for sample preparation.

[0010] The present invention adopts the integrating sphere method to directly test the asphalt solid sample, solving the problem that the scattering generated by the undissolved components interferes with the test results when the asphalt solution / suspension is tested by the cuvette method.

[0011] The present invention tests the ultraviolet-visible spectrum of asphalt using the integrating sphere method, and can directly obtain the ultraviolet-visible spectrum of different asphalts in the entire band, thereby achieving direct characterization of the absorption characteristics of asphalt in the ultraviolet-visible region.

[0012] The present invention can perform full-band ultraviolet-visible spectrum testing on base asphalt, SBS modified asphalt, rubber modified asphalt, and SBS-rubber composite modified asphalt.

[0013] In actual application, the method of the present invention can be used to test the UV-visible spectrum of aged asphalt to obtain a more complete, accurate, and more characteristic UV-visible spectrum of asphalt, and thereby select the most suitable anti-UV aging agent for road petroleum asphalt, providing data support for accurately improving the UV aging resistance of asphalt and increasing the aging resistance of asphalt pavement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a comparison diagram of the ultraviolet-visible spectrum of Example 1 of the present invention; Figure 2 This is a comparison chart of the UV-visible spectra of Comparative Example 1 of the present invention; Figure 3 is a comparison diagram of the UV-visible spectrum of Example 2 of the present invention; Figure 4 This is a comparison chart of the UV-visible spectra of Comparative Example 2 of the present invention; Figure 5 is a comparison diagram of the UV-visible spectrum of Example 3 of the present invention; Figure 6 This is a comparison chart of the UV-visible spectra of Comparative Example 3 of the present invention; Figure 7 is a comparison diagram of the UV-visible spectrum of Example 4 of the present invention; Figure 8 It is a comparison diagram of the ultraviolet-visible spectrum of Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below with reference to specific embodiments.

[0016] The n-heptane, toluene and BaSO4 used in the following examples and comparative examples were all of analytical grade.

[0017] The UV-visible spectrometer used in the following examples and comparative examples is a Shimadzu UV-3600 UV-visible-near-infrared spectrophotometer equipped with an integrating sphere. The UV-visible spectrum test range selected is 200-800 nm, and the scanning interval is 0.05 nm.

[0018] Example 1 Matrix asphalt was selected for testing.

[0019] A method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere comprises the following steps: A. Prepare an n-heptane-toluene mixture of 500 mL of n-heptane and 5 mL of toluene, add 0.200 g of matrix asphalt into the mixture, and ultrasonicate for 30 minutes to uniformly disperse the matrix asphalt in the mixture to form an asphalt dispersion; B. Add 1.800 g of BaSO4 to the asphalt dispersion and continue ultrasonic treatment for 30 minutes to uniformly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 24 hours, and then the n-heptane and toluene are removed by vacuum distillation to obtain a BaSO4 powder with the matrix asphalt uniformly adsorbed on the surface as the test sample; C. A n-heptane-toluene mixture was prepared by adding 500 mL of n-heptane and 5 mL of toluene, to which 1.800 g of BaSO4 was added. The mixture was ultrasonically treated for 30 minutes to uniformly disperse the BaSO4 to form a BaSO4 dispersion. The BaSO4 dispersion was sealed and allowed to stand for 24 hours, and then the n-heptane and toluene were removed by distillation under reduced pressure to obtain a BaSO4 powder as a blank control sample; D. Prepare the test sample and the blank control sample into test pieces by using the tablet pressing method, and conduct solid UV-visible spectrum test on the test piece by UV-visible spectrometer to obtain the UV-visible absorption spectrum curve of the test matrix asphalt, see Figure 1 .

[0020] Comparative Example 1 The base asphalt in Example 1 was subjected to UV-visible spectroscopy analysis using a cuvette method as follows: S1. Prepare an n-heptane-toluene mixture by mixing 500 mL of n-heptane and 5 mL of toluene, add 0.200 g of matrix asphalt thereto, and ultrasonicate for 30 minutes to uniformly disperse the matrix asphalt in the mixture to form an asphalt dispersion; S2. The asphalt dispersion is tested by UV-visible spectrometer to obtain the UV-visible spectrum of the matrix asphalt based on the cuvette method. Figure 2 .

[0021] Depend on Figure 1 、 Figure 2 By comparison, it can be seen that the UV-visible spectrum measured by the method of the present invention can completely and clearly measure the absorption curve of the matrix asphalt in the UV-visible light region. Compared with the traditional cuvette method, this method has a larger test range and more obvious signal characteristics.

[0022] Example 2 SBS modified asphalt was selected for testing.

[0023] A method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere comprises the following steps: A. Prepare an n-heptane-toluene mixture by adding 600 mL of n-heptane and 10 mL of toluene, add 0.122 g of SBS modified asphalt into the mixture, and ultrasonicate for 30 minutes to uniformly disperse the SBS modified asphalt in the mixture to form an asphalt dispersion; B. Add 2.318 g of BaSO4 to the asphalt dispersion and continue ultrasonic treatment for 30 minutes to uniformly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 36 hours, and then the n-heptane and toluene are removed by vacuum distillation to obtain a BaSO4 powder with SBS-modified asphalt uniformly adsorbed on its surface as a test sample; C. A n-heptane-toluene mixture was prepared by adding 600 mL of n-heptane and 10 mL of toluene, to which 2.318 g of BaSO4 was added, and the mixture was ultrasonically treated for 30 minutes to uniformly disperse the BaSO4 to form a BaSO4 dispersion. The BaSO4 dispersion was sealed and allowed to stand for 36 hours, and then the n-heptane and toluene were removed by distillation under reduced pressure to obtain a BaSO4 powder as a blank control sample; D. Prepare the test sample and the blank control sample into test pieces by using the tablet pressing method, and conduct solid UV-visible spectrum test on the test piece by UV-visible spectrometer to obtain the UV-visible absorption spectrum curve of the test matrix asphalt, see Figure 3 .

[0024] Comparative Example 2 The SBS modified asphalt in Example 2 was analyzed by UV-visible spectroscopy using a cuvette method as follows: S1. Prepare an n-heptane-toluene mixture by mixing 600 mL of n-heptane and 10 mL of toluene, add 0.122 g of SBS modified asphalt into the mixture, and ultrasonicate for 30 minutes to uniformly disperse the SBS modified asphalt in the mixture to form an asphalt dispersion; S2. The asphalt dispersion is tested by UV-visible spectrometer to obtain the UV-visible spectrum of SBS modified asphalt based on the cuvette method. Figure 4 .

[0025] Depend on Figure 3 、 Figure 4 By comparison, it can be seen that the UV-visible spectrum measured by the method of the present invention can completely and clearly measure the absorption curve of SBS modified asphalt in the UV-visible light region. Compared with the traditional cuvette method, this method has a larger test range and more obvious signal characteristics.

[0026] Example 3 Rubber modified asphalt was selected for testing.

[0027] A method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere comprises the following steps: A. Prepare an n-heptane-toluene mixture of 600 mL of n-heptane and 4 mL of toluene, add 1.208 g of rubber-modified asphalt into the mixture, and ultrasonicate for 30 minutes to uniformly disperse the rubber-modified asphalt in the mixture to form an asphalt dispersion; B. Add 10.872 g of BaSO4 to the asphalt dispersion and continue ultrasonic treatment for 30 minutes to uniformly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 30 hours, and then the n-heptane and toluene are removed by vacuum distillation to obtain a BaSO4 powder with rubber-modified asphalt uniformly adsorbed on its surface as a test sample; C. A n-heptane-toluene mixture was prepared by adding 600 mL of n-heptane and 4 mL of toluene, and 10.872 g of BaSO4 was added thereto. The mixture was ultrasonically treated for 30 minutes to uniformly disperse the BaSO4 to form a BaSO4 dispersion. The BaSO4 dispersion was sealed and allowed to stand for 30 hours, and then the n-heptane and toluene were removed by distillation under reduced pressure to obtain a BaSO4 powder as a blank control sample; D. Prepare the test sample and the blank control sample into test pieces by using the tablet pressing method, and conduct solid UV-visible spectrum test on the test piece by UV-visible spectrometer to obtain the UV-visible absorption spectrum curve of the test matrix asphalt, see Figure 5 .

[0028] Comparative Example 3 The rubber-modified asphalt in Example 3 was subjected to UV-visible spectroscopy analysis using a cuvette method as follows: S1. Prepare an n-heptane-toluene mixture by adding 500 mL of n-heptane and 5 mL of toluene, add 1.208 g of rubber-modified asphalt to the mixture, and ultrasonicate for 30 minutes to uniformly disperse the rubber-modified asphalt in the mixture to form an asphalt dispersion; S2. The asphalt dispersion is tested by UV-visible spectrometer to obtain the UV-visible spectrum of the rubber modified asphalt based on the cuvette method. Figure 6 .

[0029] Depend on Figure 5 、 Figure 6 By comparison, it can be seen that the UV-visible spectrum measured by the method of the present invention can completely and clearly measure the absorption curve of rubber-modified asphalt in the UV-visible light region. Compared with the traditional cuvette method, this method has a larger test range and more obvious signal characteristics.

[0030] Example 4 SBS-rubber composite modified asphalt was selected for testing.

[0031] A method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere comprises the following steps: A. Prepare an n-heptane-toluene mixture of 660 mL of n-heptane and 10 mL of toluene, add 0.140 g of SBS-rubber composite modified asphalt to the mixture, and ultrasonicate for 30 minutes to uniformly disperse the SBS-rubber composite modified asphalt in the mixture to form an asphalt dispersion; B. Add 1.340 g of BaSO4 to the asphalt dispersion and continue ultrasonic treatment for 30 minutes to uniformly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 24 hours, and then the n-heptane and toluene are removed by vacuum distillation to obtain a BaSO4 powder with the SBS-rubber composite modified asphalt uniformly adsorbed on its surface as a test sample; C. Prepare an n-heptane-toluene mixture by adding 660 mL of n-heptane and 10 mL of toluene, add 1.340 g of BaSO4 thereto, and ultrasonicate for 30 minutes to uniformly disperse the BaSO4 to form a BaSO4 dispersion. The BaSO4 dispersion is sealed and allowed to stand for 24 hours, and then the n-heptane and toluene are removed by distillation under reduced pressure to obtain a BaSO4 powder as a blank control sample; D. Prepare the test sample and the blank control sample into test pieces by using the tablet pressing method, and conduct solid UV-visible spectrum test on the test piece by UV-visible spectrometer to obtain the UV-visible absorption spectrum curve of the test matrix asphalt, see Figure 7 .

[0032] Comparative Example 4 The SBS-rubber composite modified asphalt in Example 3 was analyzed by UV-visible spectroscopy using a cuvette method as follows: S1. Prepare an n-heptane-toluene mixture by mixing 660 mL of n-heptane and 10 mL of toluene, add 0.140 g of SBS-rubber composite modified asphalt into the mixture, and ultrasonicate for 30 minutes to uniformly disperse the SBS-rubber composite modified asphalt in the mixture to form an asphalt dispersion; S2. The asphalt dispersion is tested by UV-visible spectrometer to obtain the UV-visible spectrum of SBS-rubber composite modified asphalt based on the cuvette method, see Figure 8 .

[0033] Depend on Figure 7 、 Figure 8 By comparison, it can be seen that the UV-visible spectrum measured by the method of the present invention can completely and clearly measure the absorption curve of rubber-modified asphalt in the UV-visible light region. Compared with the traditional cuvette method, this method has a larger test range and more obvious signal characteristics.

[0034] It should be noted that in the comparative example, asphalt was dissolved in an n-heptane-toluene mixture. Components such as the saturates, aromatics, and colloids in the asphalt dissolved in the mixture, existing as a solution. However, due to its large molecular weight, the asphaltene component in the asphalt could not completely dissolve in the mixture. Instead, it existed in the mixture as particles with a diameter of 1 to 5 microns, forming a suspension. This suspension caused refraction and reflection of ultraviolet and visible light. The intensity of this refraction and reflection was high, significantly affecting or even overriding the optical signal detected by the instrument during testing. The resulting spectrum was a distorted UV-visible absorption spectrum due to the refraction and reflection caused by the asphaltene particles. However, the barium sulfate powder of the asphalt prepared by the present invention was prepared into a sample using a tableting method and tested using a UV-visible spectrometer equipped with an integrating sphere. Because barium sulfate itself is highly reflective and non-absorbent, the instrument detected the UV-visible absorption signal of the asphalt in the test sample. The resulting spectrum is the UV-visible absorption spectrum of the asphalt. The present invention avoids the influence of reflection and refraction of signal light in the cuvette method and can directly measure the absorption characteristics of the sample. Therefore, there are certain differences in the peak positions of the spectra of the above-mentioned groups of embodiments and comparative examples.

Claims

1. A method for testing asphalt ultraviolet-visible absorption spectra based on an integrating sphere, characterized in that The following steps are involved: A. Prepare a n-heptane-toluene mixed solution, add the asphalt sample into the mixed solution, and perform ultrasonic treatment to evenly disperse the asphalt sample in the mixed solution to form an asphalt dispersion; B. Add BaSO4 to the asphalt dispersion and perform ultrasonic treatment to evenly disperse the BaSO4 to obtain an asphalt-BaSO4 mixed dispersion. The asphalt-BaSO4 mixed dispersion is sealed and allowed to stand for 24-36 hours, and then the n-heptane and toluene are removed by reduced pressure distillation to obtain a BaSO4 powder with asphalt evenly adsorbed on the surface as a sample to be tested; C. Prepare a n-heptane-toluene mixed solution, add BaSO4 thereto, perform ultrasonic treatment to evenly disperse the BaSO4, and obtain a BaSO4 dispersion. The BaSO4 dispersion is sealed and allowed to stand for 24-36 hours, and then the n-heptane and toluene are removed by reduced pressure distillation to obtain a BaSO4 powder with no asphalt adsorbed on the surface as a blank sample; D. Prepare the sample to be tested and the blank sample into test pieces that can be tested by UV-visible spectrometer by using a tablet pressing method, and use a UV-visible spectrometer equipped with an integrating sphere to test the UV-visible absorption spectrum of the test piece to obtain the UV-visible absorption spectrum curve of the sample to be tested.

2. The asphalt UV-visible absorption spectrum testing method based on an integrating sphere according to claim 1, characterized in that: In step A and step C, the volume ratio of n-heptane to toluene in the n-heptane-toluene mixture is 60-150:

1.

3. The asphalt UV-visible absorption spectrum testing method based on integrating sphere according to claim 2, characterized in that: In step A, the concentration of asphalt in the n-heptane-toluene mixture is 0.2-2.0 mg / mL; in step B, the concentration of BaSO4 added in the n-heptane-toluene mixture is 2-18 mg / mL; the mass ratio of asphalt to BaSO4 is 1:9-19.

4. The asphalt UV-visible absorption spectrum testing method based on an integrating sphere according to claim 3, characterized in that: The asphalt is road petroleum asphalt, including base asphalt of various grades, SBS modified asphalt, rubber modified asphalt, and SBS-rubber composite modified asphalt.

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