Method for discriminating whether old material is mixed in recycled asphalt mixture

Abstract

The application discloses a method for judging whether old materials are mixed in regenerated asphalt mixture, and the method is: obtaining an asphalt sample of a service road; using a layered extraction recovery method to obtain three-layer binder samples of designed regenerated asphalt mixture; using Fourier infrared spectrum testing to quantitatively characterize characteristic functional groups of the asphalt sample, and obtaining a carbonyl index; using a dynamic shear rheometer to test complex shear modulus of different layer binder samples, and obtaining the complex shear modulus of the different layer binder samples; and judging whether the regenerated asphalt mixture of the service road contains old materials according to the change rate of the carbonyl index and the change rate of the complex shear modulus. Based on this, by the micro-uniformity angle of the asphalt mixture, the layered extraction recovery asphalt is used to determine the aging difference of the mixed asphalt at different layers, and the carbonyl index and the complex shear modulus are also used to quantitatively change the gradient of the fusion area of new and old asphalt, so that whether the regenerated asphalt mixture is mixed with old materials can be judged.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of road engineering, in particular to a method for judging whether old material is mixed in regenerated asphalt mixture. BACKGROUND

[0002] The in-situ hot recycling technology is widely used in preventive maintenance engineering due to its good economic, social and environmental benefits. However, due to the limitation of traditional machinery and process, 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 service asphalt pavement material. And there is no clear and effective engineering detection method for whether the old material is mixed in the layer. Therefore, it is an important technical guarantee for promoting the standardization of the pavement recycling industry to carry out related research on the rapid identification of regenerated asphalt mixture in pavement maintenance engineering.

[0003] In view of the identification of the aging degree of asphalt in old material at home and abroad, the aging degree of asphalt is judged by testing the conventional performance index of single asphalt after recovering the aged asphalt by solution extraction. Considering the non-uniformity of the internal aging of the pavement, the single asphalt conventional performance index cannot well evaluate the aging condition. And compared with single asphalt aging, the influencing factors of asphalt aging in the mixture are more, and show non-homogeneity. The existing technology generally recovers the asphalt in the old material by using a rotary evaporator. However, the old pavement recycling material has various sources and different aging degrees, and there are difficulties in the field of pavement recycling. Therefore, in the field of pavement recycling, how to judge whether the old material is mixed in the regenerated asphalt mixture becomes a technical problem to be solved. SUMMARY

[0004] The embodiment of the present application provides a method for judging whether old material is mixed in regenerated asphalt mixture. Starting from the non-homogeneous characteristics of the old material, the aging condition difference of mixed asphalt in different layers is determined by using the hierarchical extraction and recovery of asphalt from the micro-uniformity angle of asphalt mixture, and the change gradient of the fusion area of new and old asphalt is quantified by using the carbonyl index and the complex shear modulus, so that whether the old material is mixed in the regenerated asphalt mixture can be judged.

[0005] In the first aspect, the embodiment of the present application provides a method for judging whether old material is mixed in regenerated asphalt mixture, comprising the following steps:

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

[0007] Step S2, obtaining a three-layer binder sample of the designed regenerated asphalt mixture by using a hierarchical extraction and recovery method;

[0008] Step S3, quantitatively characterizing the characteristic functional groups of the asphalt sample by using a Fourier infrared spectrum test to obtain a carbonyl index.

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

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

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

[0012] In an embodiment, in the step S2, the service road asphalt mixture sample is crushed, 1200g of hot reclaimed asphalt mixture is weighed, and then sequentially immersed in 300ml, 300ml and 700ml of solvent trichloroethylene solution for 5 minutes, 5 minutes and 60 minutes to obtain an asphalt solution, and the asphalt solution is divided into T1, T2 and T3 three layers of reclaimed asphalt.

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

[0014] In an embodiment, in the step S2, the Abson method is used to recover the three times of immersion residual liquid to obtain asphalt samples of different layers.

[0015] In an embodiment, in the step S2, the recovered solution is placed in a container and heated in a 120℃ oven for 4h to evaporate trichloroethylene to reduce its influence on the results of subsequent experiments.

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

[0017]

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

[0019] In an embodiment, the step S4 comprises:

[0020] (1) The mixed asphalt sample after extraction and recovery is injected into a 25mm silica gel mold of dynamic shear rheological test in a flow state, and the thickness is greater than 3mm;

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

[0022] (3) Start the dynamic shear rheometry procedure to compress the sample, compressing the two platens to 1.0 mm apart;

[0023] (4) Set the dynamic shear rheometry end temperature to 60°C ± 0.1°C;

[0024] (5) Perform a time sweep test at 10 rad / s using the strain control mode to determine the complex shear modulus of the blended bitumen sample.

[0025] In an embodiment, in the 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 in a case where the change rate of the carbonyl index and the change rate of the complex shear modulus are within a preset threshold range, it is determined that no reclaimed material is mixed in the bitumen mixture; and in a case where the change rate of the carbonyl index and the change rate of the complex shear modulus exceed the preset threshold range, it is determined that the reclaimed material is mixed in the bitumen mixture.

[0026] In an embodiment, in the 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 in a case where the change rate of the carbonyl index and the change rate of the complex shear modulus are within a preset threshold range, it is determined that no reclaimed material is mixed in the bitumen mixture; and in a case where the change rate of the carbonyl index and the change rate of the complex shear modulus exceed the preset threshold range, it is determined that the reclaimed material is mixed in the bitumen mixture.

[0027]

[0028] wherein S1 is the change rate of the carbonyl index; S2 is the change rate 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 application comprises a method for determining whether old material is mixed in reclaimed asphalt mixture, comprising the following steps: step S1, obtaining an asphalt sample of a service road; step S2, obtaining a three-layer binder sample of a designed reclaimed asphalt mixture by using a layered extraction recovery method; step S3, quantitatively characterizing the characteristic functional groups of the asphalt sample by using Fourier infrared spectrum testing to obtain a carbonyl index; step S4, testing the complex shear modulus of different layer binder samples by using a dynamic shear rheometer to obtain the complex shear modulus of different layer binder samples; and step S5, determining whether the reclaimed asphalt mixture of the service road contains old material 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 application starts from the characteristics of the old material heterogeneity, uses the layered extraction recovery asphalt from the micro-uniformity angle of the asphalt mixture to determine the aging difference of the mixed asphalt at different layers, and further uses the carbonyl index and the complex shear modulus to quantify the change gradient of the new and old asphalt fusion zone, so as to determine whether the reclaimed asphalt mixture contains old material.

[0030] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0032] Figure 1 A flowchart of a method for determining whether old material is mixed in reclaimed asphalt mixture provided by an embodiment of the present application;

[0033] Figure 2 A schematic diagram of estimating the old material mixing amount of the field road asphalt mixture according to the test results of step S3 and step S4 provided by an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0035] It should be understood that in the description of the embodiments of the present application, the meaning of multiple (or multiple) is more than two, greater than, less than, more than, etc. is not included in the number, above, below, within, etc. is understood to include the number. If there is a description of "first", "second", etc. 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 indicated technical features or implicitly indicating the order of the indicated technical features.

[0036] The in-situ heat regeneration technology is widely used in preventive maintenance engineering due to its good economic, social and environmental benefits. However, due to the limitations of traditional machinery and process, the mixing quality of new and old materials is difficult to guarantee, which directly affects the long-term service performance of the regenerated pavement. Therefore, it is necessary to accurately identify the service asphalt pavement material. And there is no clear and effective engineering detection method for whether the old material is mixed in the layer. Therefore, it is necessary to carry out related research on the rapid identification of regenerated asphalt mixture in pavement maintenance engineering, which is an important technical guarantee for promoting the standardization of pavement regeneration industry.

[0037] Around the identification of the aging degree of asphalt in old materials of hot recycled asphalt mixture at home and abroad, the aging asphalt is first extracted and recovered by solution, and then the conventional performance index of single asphalt is tested to determine the aging degree of asphalt. Considering the non-uniformity of internal aging of pavement, single asphalt conventional performance index cannot well evaluate the aging condition. And compared with single asphalt aging, the influencing factors of asphalt aging in mixture are more, and show non-homogeneity. The existing technology generally uses Abson method and rotary evaporator method to recover asphalt in old materials. But the old pavement recycled materials are diverse in source and aging degree, which has difficulties in the field of pavement regeneration. Based on this, in the field of pavement regeneration, how to determine whether the old material is mixed in the regenerated asphalt mixture becomes a technical problem to be solved.

[0038] In view of the above problems in the prior art, the embodiment of the present application provides a method for determining whether old material is mixed in recycled asphalt mixture, which comprises the following steps: step S1, obtaining an asphalt sample of a service road; step S2, obtaining a three-layer binder sample of a designed recycled asphalt mixture by using a layered extraction recovery method; step S3, quantitatively characterizing the characteristic functional groups of the asphalt sample by using a Fourier infrared spectrum test to obtain a carbonyl index; step S4, testing the complex shear modulus of different layer binder samples by using a dynamic shear rheometer to obtain the complex shear modulus of different layer binder samples; and step S5, determining whether the recycled asphalt mixture of the service road contains old material 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 application starts from the heterogeneous characteristics of the old material, uses the layered extraction recovery asphalt from the micro-uniformity angle of the asphalt mixture to determine the aging difference of the mixed asphalt at different layers, and further uses the carbonyl index and the complex shear modulus to quantify the change gradient of the fusion area of new and old asphalt, so that whether the recycled asphalt mixture contains old material can be determined.

[0039] As shown in Figure 1 , Figure 1 is a flow chart of a method for determining whether old material is mixed in recycled asphalt mixture provided by an embodiment of the present application. The method for determining whether old material is mixed in recycled asphalt mixture can include but is not limited to the following steps:

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

[0041] Step S2, obtaining a three-layer binder sample of a designed recycled asphalt mixture by using a layered extraction recovery method;

[0042] Step S3, quantitatively characterizing the characteristic functional groups of the asphalt sample by using a Fourier infrared spectrum test to obtain a carbonyl index;

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

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

[0045] The old material in the service pavement asphalt mixture is determined by obtaining the service pavement asphalt concrete core sample and the same kind of asphalt in the design data, obtaining the three-layer binder samples of the designed recycled asphalt mixture by the layered extraction recovery method, quantitatively characterizing the characteristic functional groups of the asphalt sample by the Fourier infrared spectrum test, obtaining the carbonyl index, and testing the complex shear modulus of the different layer binder samples by the dynamic shear rheometer.

[0046] The embodiment of the present application is based on the interface fusion zone feature recognition, constructs the rheological property gradient model and the carbonyl index gradient model of the fusion zone, quantifies the change gradient of the new and old asphalt fusion zone by the carbonyl index and the complex shear modulus, and proposes a method suitable for determining whether the old material is in the asphalt mixture on site, thereby providing technical support for obtaining the aging condition of the old material in the pavement maintenance engineering.

[0047] Compared with the existing old material identification method, the embodiment of the present application analyzes the aging gradient of the binder in the old material at the microscale, constructs the three-layer structure gradient model of the new and old asphalt fusion zone by the step-by-step extraction recovery method, determines the aging condition difference of the mixed asphalt at different layers, and judges whether the old material is mixed in the asphalt mixture.

[0048] The embodiment of the present application starts from the heterogeneous characteristics of the old material, determines the aging condition difference of the mixed asphalt at different layers by the layered extraction recovery asphalt from the micro-uniformity angle of the asphalt mixture, quantifies the change gradient of the new and old asphalt fusion zone by the carbonyl index and the complex shear modulus, and can judge whether the old material is mixed in the recycled asphalt mixture.

[0049] In an embodiment, in step S1, the asphalt sample of the service pavement is obtained by field core drilling, the size of the asphalt sample is 150mm in diameter, and the height of the asphalt sample is the thickness of the service pavement.

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

[0051] In an embodiment, in step S2, the obtained asphalt solution is placed in a beaker and is left to settle for 24 hours to obtain the upper asphalt solution, so as to reduce the influence of the mineral powder on the subsequent experiment.

[0052] In an embodiment, in step S2, the Abson method is used to recover the third soaking residual liquid to obtain asphalt samples of different layers.

[0053] In an embodiment, in step S2, the Abson method is used to recover the third soaking residual liquid to obtain binder samples of different layers, and the recovered solution is placed in a container and heated in an oven at 120°C for 4h to evaporate trichloroethylene to reduce its impact on subsequent experimental results.

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

[0055]

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

[0057] In an embodiment, step S4 includes:

[0058] (1) The mixed asphalt sample recovered by extraction is injected into a 25mm silica gel mold of a dynamic shear rheological test DSR in a flowing state, with a thickness greater than 3mm;

[0059] (2) After the asphalt sample in the silica gel mold is cooled, it is placed on a 25mm clamp and preheated to 50°C;

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

[0061] (4) Set the dynamic shear rheological test termination temperature to 60°C±0.1°C;

[0062] (5) Perform a time sweep test at 10rad / s using a strain control mode to measure the complex shear modulus of the mixed asphalt sample.

[0063] In an embodiment, in step S5, the change rates of the carbonyl index and the complex shear modulus of the first layer and the third layer of the binder sample are calculated, and in the case that the change rates of the carbonyl index and the complex shear modulus are within a preset threshold range, it is determined that the asphalt mixture does not contain old materials; in the case that the change rates of the carbonyl index and the complex shear modulus exceed the preset threshold range, it is determined that the asphalt mixture contains old materials.

[0064] In an embodiment, in step S5, the change rates of the carbonyl index and 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] wherein S1 is the change rate of carbonyl index; S2 is the change rate of complex shear modulus; I C＝On is the carbonyl index of the layer n; is the complex shear modulus of the cement sample of the layer n.

[0067] In an embodiment, the carbonyl index of the three-layer reclaimed asphalt (T1, T2, T3) of the sample is obtained by using Fourier infrared spectrum, and the change rate of the carbonyl index is calculated. The complex shear modulus of the three-layer reclaimed asphalt (T1, T2, T3) of the sample is obtained by using dynamic shear rheometer, and the change rate of the complex shear modulus is calculated, and the results are shown in Table 1.

[0068] Table 1

[0069] Level Complex shear modulus (20°C, Pa) Rate of change Unaged 3830000 - [T1] 7090000 85.12％ [T2] 5924000 54.67％ [T3] 4843000 26.45％

[0070] It can be understood that if the old material is not mixed in the asphalt mixture, the change rates of the carbonyl index and the complex shear modulus of the first layer and the third layer will not be too different; on the contrary, if the old material is mixed, the change rates of the carbonyl index and the complex shear modulus will reach a certain value, so as to realize the identification of whether the old material is mixed in the asphalt mixture.

[0071] In an embodiment, the test schematic diagram of the asphalt sample is shown in Figure 2 The error allowable range is 0% to 2%, the change rate of the carbonyl index and the change rate of the complex modulus are used as the identification indexes, the change rate of the carbonyl index S1 is 16.2%, the change rate of the complex modulus S2 is 12.4%, and since both of them are greater than the error allowable range of 0% to 2%, it is proved that the old material is mixed in the asphalt mixture, so as to complete the identification.

[0072] Based on this, the embodiment of the present application starts from the characteristics of the old material heterogeneity, uses the layered extraction reclaimed asphalt from the micro-uniformity of the asphalt mixture to determine the aging difference 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 new and old asphalt fusion zone, so as to be able to judge whether the old material is mixed in the reclaimed asphalt mixture.

[0073] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the above embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application. These equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A method for determining whether recycled asphalt mixtures contain old materials, characterized in that, Includes the following steps: Step S1: Obtain asphalt samples from the service road surface; Step S2: A three-layer binder sample is obtained from the designed recycled asphalt mixture using a stratified extraction and recovery method. Step S3: The characteristic functional groups of the asphalt sample are quantitatively characterized by Fourier transform infrared spectroscopy to obtain the carbonyl index. Step S4: The complex shear modulus of the cementitious material samples with different layers is tested using a dynamic shear rheometer to obtain the complex shear modulus of the cementitious material samples with different layers. Step S5: Determine whether the recycled asphalt mixture of the service pavement contains recycled material based on the rate of change of the carbonyl index and the rate of change of the complex shear modulus. Specifically, calculate the rate of change of the carbonyl index and the rate of change of the complex shear modulus of the first and third layers of the binder sample. If 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 the asphalt mixture does not contain recycled material; if the rate of change of the carbonyl index and the rate of change of the complex shear modulus exceed the preset threshold range, it is determined that the asphalt mixture contains recycled material.

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

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

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

5. The method for determining whether recycled asphalt mixtures contain old materials according to claim 3, characterized in that, In step S2, the Absen method is used to recover the residual liquid from the three soakings to obtain asphalt samples from different layers.

6. The method for determining whether recycled asphalt mixtures contain old materials according to claim 3, characterized in that, In 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 mixtures contain old materials according to claim 1, characterized in that, In step S3, Fourier transform infrared spectroscopy is performed on the asphalt sample, and the carbonyl index is used to quantify the degree of aging of the asphalt. The calculation formula is as follows: in, Carbonyl index; wave number Area of ​​the nearby absorption peak.

8. The method for determining whether recycled asphalt mixture contains old material according to claim 1, characterized in that, Step S4 includes: (1) The extracted and recovered mixed asphalt sample was injected into a 25mm silicone mold for dynamic shear rheology test in a flowing state, with a thickness greater than 3mm. (2) After the asphalt sample in the silicone mold has cooled, place it on a 25mm clamp and preheat it to 50℃; (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) Set the termination temperature of the dynamic shear rheology test to 60℃±0.1℃; (5) The complex shear modulus of the mixed asphalt sample was determined by performing a time scan test at 10 rad / s using strain control mode.

9. The method for determining whether recycled asphalt mixtures contain 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 and third layers of the binder sample are calculated using the following formulas: in, The rate of change of the carbonyl index; The rate of change of the complex shear modulus; The carbonyl index at layer n; Let be the complex shear modulus of the binder sample at layer n.

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