Method for judging whether recycled asphalt mixture is doped with old material or not

Abstract

The invention discloses a method for judging whether a recycled asphalt mixture is doped with an old material or not. The method comprises the following steps: acquiring an asphalt sample of a service pavement; a layered extraction and recovery method is adopted to obtain a three-layer cementing material sample from the designed recycled asphalt mixture; carrying out quantitative characterization on characteristic functional groups of the asphalt sample by adopting Fourier infrared spectrum test to obtain a carbonyl index; a dynamic shear rheometer is adopted to test the complex shear moduli of the cementing material samples in different layers, and the complex shear moduli of the cementing material samples in different layers are obtained; and according to the change rate of the carbonyl index and the change rate of the complex shear modulus, judging whether the recycled asphalt mixture of the service pavement contains the old material or not. On the basis, through the microscopic uniformity angle of the asphalt mixture, asphalt is recycled through layered extraction, the aging condition difference of different layers of the mixed asphalt is determined, and the change gradient of a new and old asphalt fusion area is quantified by adopting a carbonyl index and a complex shear modulus, so that whether the recycled asphalt mixture is doped with the old material or not can be judged.

Description

Technical Field

[0001] The embodiment of the present invention relates to the technical field of road engineering, and in particular to a method for determining whether recycled asphalt mixture is mixed with old material. Background Art

[0002] In-situ hot recycling technology is widely used in preventive maintenance projects due to its good economic, social and environmental benefits. However, due to the limitations of traditional machinery and processes, the mixing quality of new and old materials is difficult to guarantee, which directly affects the long-term service performance of the recycled pavement. Therefore, it is necessary to accurately identify the serving asphalt pavement materials. And there is no clear and effective engineering detection method to determine whether the layer contains old materials. Therefore, conducting relevant research on the rapid identification of recycled asphalt mixtures in pavement maintenance projects is an important technical guarantee for promoting the standardization of the pavement recycling industry.

[0003] Regarding hot-recycled asphalt mixtures, the identification of the degree of aging of asphalt in old materials at home and abroad mainly involves first using solution extraction to recover the aged asphalt, and then testing the conventional performance indicators of a single asphalt to determine the degree of aging of the asphalt. Taking into account the uneven aging of the pavement, a single conventional performance indicator of asphalt cannot well evaluate its aging. And compared with the aging of a single asphalt, the aging of asphalt in the mixture is affected by more factors and exhibits heterogeneity. The existing technology generally uses a rotary evaporator to recover asphalt from old materials. However, the sources of recycled materials from old pavements are diverse and the degree of aging varies, which makes it difficult to use them in the field of pavement regeneration. Based on this, in the field of pavement regeneration, how to determine whether old materials are mixed in the recycled asphalt mixture has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] An embodiment of the present invention provides a method for determining whether old materials are mixed in a recycled asphalt mixture. Starting from the heterogeneous characteristics of the old materials, the asphalt is recovered by layered extraction from the perspective of the microscopic uniformity of the asphalt mixture to determine the differences in aging conditions of different layers of the mixed asphalt. The carbonyl index and complex shear modulus are also used to quantify the gradient of the fusion zone between the new and old asphalt, thereby determining whether the recycled asphalt mixture is mixed with old materials.

[0005] In a first aspect, an embodiment of the present invention provides a method for determining whether recycled asphalt mixture is mixed with old material, comprising the following steps:

[0006] Step S1, obtaining an asphalt sample of a service road surface;

[0007] Step S2, using a layered extraction recovery method to obtain a three-layer binder sample from the designed recycled asphalt mixture;

[0008] Step S3, using Fourier transform infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample to obtain a carbonyl index;

[0009] Step S4, using a dynamic shear rheometer to test the complex shear modulus of the binder samples of different layers to obtain the complex shear modulus of the binder samples of different layers;

[0010] Step S5, judging whether the regenerated asphalt mixture of the service road surface contains old material according to the change rate of the carbonyl index and the change rate of the complex shear modulus.

[0011] In one embodiment, in step S1, an asphalt sample of the in-service road surface is obtained by on-site core drilling, the size of the asphalt sample is 150 mm in diameter, and the height of the asphalt sample is the thickness of the in-service road surface.

[0012] In one embodiment, in step S2, a sample of asphalt mixture of a serving pavement is crushed, 1200 g of hot-regenerated asphalt mixture is weighed, and the mixture is immersed in 300 ml, 300 ml and 700 ml of a solvent trichloroethylene solution for 5 minutes, 5 minutes and 60 minutes respectively to obtain an asphalt solution, and the asphalt solution is divided into three layers of recovered asphalt, namely T1, T2 and T3.

[0013] In one embodiment, in step S2, the asphalt solution is placed in a beaker and allowed to settle for 24 hours to obtain an upper layer of asphalt solution to reduce the impact of mineral powder on subsequent experiments.

[0014] In one embodiment, in step S2, the Absen method is used to recover the residual liquid from three immersions to obtain asphalt samples at different levels.

[0015] In one embodiment, in step S2, the recovered solution is placed in a container and heated in an oven at 120° C. for 4 hours to evaporate trichloroethylene to reduce its influence on subsequent experimental results.

[0016] In one embodiment, in step S3, the asphalt sample is subjected to Fourier infrared spectroscopy test, and the carbonyl index is used to quantify the aging degree of the asphalt, and the calculation method is as follows:

[0017]

[0018] Among them, I C＝O is the carbonyl index; is the absorption peak area near wave number 1700.

[0019] In one embodiment, step S4 includes:

[0020] (1) The mixed asphalt sample after extraction and recovery was injected into a 25 mm silicone mold for dynamic shear rheology test in a flowing state with a thickness greater than 3 mm;

[0021] (2) After the asphalt sample in the silicone mold has cooled, place it on a 25 mm fixture and preheat it to 50 °C;

[0022] (3) Start the dynamic shear rheology test program to press the sample, and press the distance between the two clamps to 1.0 mm;

[0023] (4) The termination temperature of the dynamic shear rheology test was set at 60°C ± 0.1°C;

[0024] (5) The complex shear modulus of the mixed asphalt samples was determined by performing a time sweep test at 10 rad / s using the strain control mode.

[0025] In one embodiment, in step S5, the rate of change of the carbonyl index and the rate of change of the complex shear modulus of the first layer and the third layer of the binder sample are calculated. When the rate of change of the carbonyl index and the rate of change of the complex shear modulus are within a preset threshold range, it is determined that no old material is mixed in the asphalt mixture; when the rate of change of the carbonyl index and the rate of change of the complex shear modulus are beyond the preset threshold range, it is determined that old material is mixed in the asphalt mixture.

[0026] In one embodiment, in step S5, the change rate of the carbonyl index and the change rate of the complex shear modulus of the first layer and the third layer of the binder sample are calculated, and the calculation method is as follows:

[0027]

[0028] Where S1 is the rate of change of the carbonyl index; S2 is the rate of change of the complex shear modulus; I C＝On is the carbonyl index at layer n; is the complex shear modulus of the binder sample at layer n.

[0029] The embodiment of the present invention includes: a method for determining whether the regenerated asphalt mixture contains old materials, comprising the following steps: step S1, obtaining an asphalt sample of a service road surface; step S2, using a layered extraction and recovery method to obtain a three-layer binder sample from the designed regenerated asphalt mixture; step S3, using Fourier infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample to obtain a carbonyl index; step S4, using a dynamic shear rheometer to test the complex shear modulus of different layers of binder samples to obtain the complex shear modulus of different layers of binder samples; step S5, judging whether the regenerated asphalt mixture of the service road surface contains old materials according to the change rate of the carbonyl index and the change rate of the complex shear modulus. Based on this, the embodiment of the present invention starts from the heterogeneous characteristics of the old materials, and through the perspective of the microscopic uniformity of the asphalt mixture, uses layered extraction to recover asphalt to determine the difference in aging conditions of different layers of the mixed asphalt, and also uses the carbonyl index and the complex shear modulus to quantify the change gradient of the fusion zone of the new and old asphalt, so as to determine whether the regenerated asphalt mixture contains old materials.

[0030] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0032] Figure 1 A flow chart of a method for determining whether recycled asphalt mixture is mixed with old material provided by one embodiment of the present invention;

[0033] Figure 2 A schematic diagram of estimating the amount of old material in an on-site pavement asphalt mixture based on the test results of step S3 and step S4 is provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] It should be understood that in the description of the embodiments of the present invention, the meaning of multiple (or multiple) is more than two, greater than, less than, and exceeding are understood to exclude the number itself, and above, below, and within are understood to include the number itself. If there is a description of "first", "second", etc., it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0036] In-situ hot recycling technology is widely used in preventive maintenance projects due to its good economic, social and environmental benefits. However, due to the limitations of traditional machinery and processes, the mixing quality of new and old materials is difficult to guarantee, which directly affects the long-term service performance of the recycled pavement. Therefore, it is necessary to accurately identify the serving asphalt pavement materials. And there is no clear and effective engineering detection method to determine whether the layer contains old materials. Therefore, conducting relevant research on the rapid identification of recycled asphalt mixtures in pavement maintenance projects is an important technical guarantee for promoting the standardization of the pavement recycling industry.

[0037] Regarding hot-recycled asphalt mixtures, the identification of the degree of aging of asphalt in old materials at home and abroad mainly involves first using solution extraction to recover the aged asphalt, and then testing the conventional performance indicators of a single asphalt to determine the degree of aging of the asphalt. Considering the uneven aging of the pavement, a single conventional performance indicator of asphalt cannot well evaluate its aging. And compared with the aging of a single asphalt, the aging of asphalt in the mixture is affected by more factors and exhibits heterogeneity. The existing technology generally uses the Absen method and the rotary evaporator method to recover asphalt from old materials. However, the sources of recycled materials from old pavements are diverse and the degree of aging varies, which makes it difficult to use them in the field of pavement regeneration. Based on this, in the field of pavement regeneration, how to determine whether old materials are mixed in the recycled asphalt mixture has become a technical problem that needs to be solved urgently.

[0038] In view of the above problems in the prior art, the embodiment of the present invention provides a method for determining whether the regenerated asphalt mixture contains old materials, including the following steps: step S1, obtaining an asphalt sample of a service road surface; step S2, using a layered extraction and recovery method to obtain a three-layer binder sample from the designed regenerated asphalt mixture; step S3, using Fourier infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample to obtain a carbonyl index; step S4, using a dynamic shear rheometer to test the complex shear modulus of different layers of binder samples to obtain the complex shear modulus of different layers of binder samples; step S5, judging whether the regenerated asphalt mixture of the service road surface contains old materials according to the change rate of the carbonyl index and the change rate of the complex shear modulus. Based on this, the embodiment of the present invention starts from the heterogeneous characteristics of the old materials, and through the perspective of the microscopic uniformity of the asphalt mixture, uses layered extraction to recover asphalt to determine the difference in aging conditions of different layers of the mixed asphalt, and also uses the carbonyl index and complex shear modulus to quantify the change gradient of the fusion zone of the new and old asphalt, so as to determine whether the regenerated asphalt mixture contains old materials.

[0039] like Figure 1 As shown, Figure 1 The flowchart of a method for determining whether recycled asphalt mixture contains old materials is provided in one embodiment of the present invention. The method for determining whether recycled asphalt mixture contains old materials may include but is not limited to the following steps:

[0040] Step S1, obtaining an asphalt sample of a service road surface;

[0041] Step S2, using a layered extraction recovery method to obtain a three-layer binder sample from the designed recycled asphalt mixture;

[0042] Step S3, using Fourier transform infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample to obtain a carbonyl index;

[0043] Step S4, using a dynamic shear rheometer to test the complex shear modulus of the binder samples of different layers to obtain the complex shear modulus of the binder samples of different layers;

[0044] Step S5, judging whether the regenerated asphalt mixture of the service road surface contains old material according to the change rate of the carbonyl index and the change rate of the complex shear modulus.

[0045] By obtaining the asphalt concrete core sample of the in-service pavement and obtaining the same asphalt in its design data; using the layered extraction and recovery method to obtain three-layer binder samples from the designed recycled asphalt mixture; using Fourier infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample and obtain the carbonyl index; using a dynamic shear rheometer to test the complex shear modulus of different layers of binder samples; judging whether the in-service pavement asphalt mixture contains old materials according to the change rate of the carbonyl index and the change rate of the complex shear modulus. Starting from the heterogeneous characteristics of the old materials, the embodiment of the present invention proposes a method for judging whether the in-service pavement asphalt mixture contains old materials based on the characterization of the fusion zone of new and old asphalt.

[0046] Based on the feature recognition of the interface fusion zone, the embodiment of the present invention constructs the rheological property gradient model and the carbonyl index gradient model of the fusion zone, and uses the carbonyl index and complex shear modulus to quantify the gradient of the fusion zone between the new and old asphalt. A method suitable for on-site determination of whether there is old material in the asphalt mixture is proposed, which provides technical support for obtaining the aging status of old materials in pavement maintenance projects.

[0047] Compared with the existing old material identification method, the embodiment of the present invention analyzes the aging gradient of the binder in the old material at the microscopic scale, adopts a step-by-step extraction and recovery method, and constructs a three-layer structural gradient model of the new and old asphalt fusion zone to determine the difference in aging conditions of different layers of the mixed asphalt, thereby judging whether the asphalt mixture contains old materials.

[0048] The embodiment of the present invention starts from the heterogeneous characteristics of old materials, uses the perspective of microscopic uniformity of asphalt mixture, and utilizes layered extraction to recover asphalt to determine the differences in aging conditions of different layers of the mixed asphalt. It also uses the carbonyl index and complex shear modulus to quantify the gradient of the fusion zone between new and old asphalt, so as to determine whether old materials are mixed in the recycled asphalt mixture.

[0049] In one embodiment, in step S1, an asphalt sample of the in-service road surface is obtained by on-site core drilling, the size of the asphalt sample is 150 mm in diameter, and the height of the asphalt sample is the thickness of the in-service road surface.

[0050] In one embodiment, in step S2, a sample of asphalt mixture of a serving pavement is crushed, 1200 g of hot-regenerated asphalt mixture is weighed, and the mixture is immersed in 300 ml, 300 ml and 700 ml of a solvent trichloroethylene solution for 5 minutes, 5 minutes and 60 minutes respectively to obtain an asphalt solution, and the asphalt solution is divided into three layers of recovered asphalt, namely T1, T2 and T3.

[0051] In one embodiment, in step S2, the obtained asphalt solution is placed in a beaker and allowed to settle for 24 hours to obtain an upper layer of asphalt solution to reduce the impact of mineral powder on subsequent experiments.

[0052] In one embodiment, in step S2, the Absen method is used to recover the residual liquid from three immersions to obtain asphalt samples at different layers.

[0053] In one embodiment, in step S2, it is recommended to use the Absen method to recover the residual liquid from three immersions to obtain binder samples of different layers, place the recovered solution in a container, and heat it in an oven at 120°C for 4 hours to evaporate trichloroethylene to reduce its impact on subsequent experimental results.

[0054] In one embodiment, in step S3, a Fourier transform infrared spectroscopy test is performed on the asphalt sample, and the carbonyl index is used to quantify the aging degree of the asphalt. The calculation method is as follows:

[0055]

[0056] Among them, I C＝O is the carbonyl index; is the absorption peak area near wave number 1700.

[0057] In one embodiment, step S4 includes:

[0058] (1) The mixed asphalt sample after extraction and recovery was injected into a 25 mm silicone mold of the dynamic shear rheology test DSR in a flowing state with a thickness greater than 3 mm;

[0059] (2) After the asphalt sample in the silicone mold has cooled, place it on a 25 mm fixture and preheat it to 50 °C;

[0060] (3) Start the dynamic shear rheology test program to press the sample, and press the distance between the two clamps to 1.0 mm;

[0061] (4) The termination temperature of the dynamic shear rheology test was set at 60°C ± 0.1°C;

[0062] (5) The complex shear modulus of the mixed asphalt samples was determined by performing a time sweep test at 10 rad / s using the strain control mode.

[0063] In one embodiment, in step S5, the rate of change of the carbonyl index and the rate of change of the complex shear modulus of the first layer and the third layer of the binder sample are calculated. When the rate of change of the carbonyl index and the rate of change of the complex shear modulus are within the preset threshold range, it is determined that no old material is mixed in the asphalt mixture; when the rate of change of the carbonyl index and the rate of change of the complex shear modulus are beyond the preset threshold range, it is determined that old material is mixed in the asphalt mixture.

[0064] In one embodiment, in step S5, the change rate of the carbonyl index and the change rate of the complex shear modulus of the first layer and the third layer of the binder sample are calculated, and the calculation method is as follows:

[0065]

[0066] Where S1 is the rate of change of the carbonyl index; S2 is the rate of change of the complex shear modulus; I C＝On is the carbonyl index at layer n; is the complex shear modulus of the binder sample at layer n.

[0067] In one embodiment, the carbonyl index of three layers of recycled asphalt (T1, T2, T3) of the sample is obtained by using Fourier infrared spectroscopy to test the carbonyl index, and the rate of change of the carbonyl index is calculated. The complex shear modulus of three layers of recycled asphalt (T1, T2, T3) of the sample is obtained by using a dynamic shear rheometer to test the complex shear modulus, and the rate of change of the complex shear modulus is calculated, and the results are shown in Table 1 below.

[0068] Table 1

[0069] Horizon Complex shear modulus (20℃, Pa) Rate of change Not aged 3830000 - <![CDATA[T1]]> 7090000 85.12％ <![CDATA[T2]]> 5924000 54.67％ <![CDATA[T3]]> 4843000 26.45％

[0070] It can be understood that if there is no old material in the asphalt mixture, the rate of change of the carbonyl index and the rate of change of the complex shear modulus between the first and third layers will not differ too much; on the contrary, if there is old material, the rate of change of the carbonyl index and the rate of change of the complex shear modulus will reach a certain value, thereby realizing the judgment of whether there is old material in the asphalt mixture.

[0071] In one embodiment, a schematic diagram of testing an asphalt sample is shown as follows: Figure 2 As shown, the allowable error range is set to 0% to 2%, and the carbonyl index change rate and the complex modulus change rate are used as judgment indicators. The carbonyl index change rate S1 is 16.2%, and the complex modulus change rate S2 is 12.4%. Since both are greater than the allowable error range of 0% to 2%, it is proved that old materials are mixed in the asphalt mixture, thus completing the judgment.

[0072] Based on this, the embodiment of the present invention starts from the heterogeneous characteristics of old materials, through the perspective of the microscopic uniformity of asphalt mixture, and utilizes layered extraction to recover asphalt to determine the differences in aging conditions of different layers of the mixed asphalt. The carbonyl index and complex shear modulus are also used to quantify the gradient of the fusion zone between new and old asphalt, so as to determine whether old materials are mixed in the recycled asphalt mixture.

[0073] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions under the shared conditions without violating the spirit of the present invention. These equivalent deformations or substitutions are all included in the scope defined by the claims of the present invention.

Claims

1. A method for determining whether recycled asphalt mixture contains old material, characterized in that: The following steps are involved: Step S1, obtaining an asphalt sample of a service road surface; Step S2, using a layered extraction recovery method to obtain a three-layer binder sample from the designed recycled asphalt mixture; Step S3, using Fourier transform infrared spectroscopy to quantitatively characterize the characteristic functional groups of the asphalt sample to obtain a carbonyl index; Step S4, using a dynamic shear rheometer to test the complex shear modulus of the binder samples of different layers to obtain the complex shear modulus of the binder samples of different layers; Step S5, judging whether the regenerated asphalt mixture of the service road surface contains old material according to the change rate of the carbonyl index and the change rate of the complex shear modulus.

2. The method for determining whether recycled asphalt mixture contains old materials according to claim 1, characterized in that: In the step S1, an asphalt sample of the in-service road surface is obtained by on-site core drilling, the size of the asphalt sample is 150 mm in diameter, and the height of the asphalt sample is the thickness of the in-service road surface.

3. The method for determining whether recycled asphalt mixture contains old materials according to claim 1, characterized in that: In step S2, a sample of asphalt mixture of a serving road surface is crushed, 1200g of hot-regenerated asphalt mixture is weighed, and the mixture is immersed in 300ml, 300ml and 700ml of trichloroethylene solvent solution for 5 minutes, 5 minutes and 60 minutes respectively to obtain an asphalt solution, and the asphalt solution is divided into three layers of recovered asphalt, namely T1, T2 and T3.

4. The method for determining whether recycled asphalt mixture contains old materials according to claim 3, characterized in that: In step S2, the asphalt solution is placed in a beaker and allowed to settle for 24 hours to obtain an upper layer of asphalt solution.

5. The method for determining whether recycled asphalt mixture contains old materials according to claim 3, characterized in that: In step S2, the Absen method is used to recover the residual liquid from three immersions to obtain asphalt samples at different levels.

6. The method for determining whether recycled asphalt mixture contains old materials according to claim 3, characterized in that: In the step S2, the recovered solution is placed in a container and heated in an oven at 120° C. for 4 hours to evaporate the trichloroethylene.

7. The method for determining whether recycled asphalt mixture contains old materials according to claim 1, characterized in that: In step S3, the asphalt sample is subjected to Fourier transform infrared spectroscopy test, and the carbonyl index is used to quantify the aging degree of the asphalt. The calculation formula is as follows: Among them, I C＝O is the carbonyl index; is the absorption peak area near wave number 1700.

8. The method for determining whether recycled asphalt mixture contains old materials according to claim 1, characterized in that: The step S4 comprises: (1) The mixed asphalt sample after extraction and recovery was injected into a 25 mm silicone mold for dynamic shear rheology test in a flowing state with a thickness greater than 3 mm; (2) After the asphalt sample in the silicone mold has cooled, place it on a 25 mm fixture and preheat it to 50 °C; (3) Start the dynamic shear rheology test program to press the sample, and press the distance between the two clamps to 1.0 mm; (4) The termination temperature of the dynamic shear rheology test was set at 60°C ± 0.1°C; (5) The complex shear modulus of the mixed asphalt samples was determined by performing a time sweep test at 10 rad / s using the strain control mode.

9. The method for determining whether recycled asphalt mixture contains old materials according to claim 1, characterized in that: In step S5, the rate of change of the carbonyl index and the rate of change of the complex shear modulus of the first layer and the third layer of the binder sample are calculated. When the rate of change of the carbonyl index and the rate of change of the complex shear modulus are within the preset threshold range, it is determined that no old material is mixed in the asphalt mixture; when the rate of change of the carbonyl index and the rate of change of the complex shear modulus are beyond the preset threshold range, it is determined that old material is mixed in the asphalt mixture.

10. The method for determining whether recycled asphalt mixture contains old materials according to claim 9, characterized in that: In step S5, the change rate of the carbonyl index and the change rate of the complex shear modulus of the first layer and the third layer of the binder sample are calculated, and the calculation formula is as follows: Where S1 is the rate of change of the carbonyl index; S2 is the rate of change of the complex shear modulus; I C＝On is the carbonyl index at layer n; is the complex shear modulus of the binder sample at layer n.

Images