A morphological method for evaluating the regeneration performance of modified common RAP

Abstract

The present invention discloses a method for evaluating the regeneration performance of common RAP modification based on morphology, which specifically involves two aspects: viscosity-toughness test and theoretical calculation. The viscosity-toughness curve is obtained by the viscosity-toughness test of asphalt. Based on the morphological analysis of the viscosity-toughness curve, an evaluation index for quantifying the regeneration effect of common RAP modification is proposed, and finally the range of values ​​of the toughness deformation rate of regenerated asphalt is defined. In particular, the toughness deformation rate is discriminative for evaluating the regeneration effect of common RAP modification, and can effectively identify the degree of performance recovery of old common modified regeneration, and has a good correlation with rheological indicators. The toughness deformation rate has good discrimination as an evaluation index, and still has good discrimination for asphalts with similar general performance, and is cheap, the instrument and equipment are relatively simple to operate, and the requirements for testers are relatively low.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt aging regeneration performance evaluation, and in particular to a method for evaluating the modified regeneration performance of common RAP based on morphology. Background Art

[0002] A large amount of common asphalt RAP material will be produced during the renovation process of asphalt pavement surface layers of domestic provincial trunk roads and some expressways. The increasingly heavy traffic conditions require the road surface to have better high-temperature rutting resistance and fatigue performance. The unique viscoelastic properties of SBS modified asphalt can significantly improve the high-temperature performance and fatigue performance of the road surface. Therefore, SBS modified thermal regeneration of common asphalt RAP material has become one of the best solutions.

[0003] Fatigue life decay is the weakness of recycled pavement. Therefore, fatigue life is an important indicator for evaluating the effect of modified thermal regeneration. However, the fatigue test method is very cumbersome, has high requirements on personnel and equipment, and has a long test cycle. The "Technical Specifications for Regeneration of Highway Asphalt Pavement" promulgated in 2008 and revised in 2019 in my country did not address the issue of modified regeneration of ordinary RAP materials, and there are few related studies. In order to reflect the effect of modified thermal regeneration of ordinary asphalt RAP materials, it is urgent to propose a test method related to the key performance of recycled asphalt and reflecting the degree of SBS characteristics, as well as a simple, easy-to-obtain, and highly distinguishable identification indicator.

[0004] The toughness part of the viscosity-toughness curve of modified hot recycled asphalt reflects the reinforcing and toughening effect of SBS block copolymer, which is an important manifestation of SBS modification characteristics. However, relevant test results show that the size of the toughness value is not sufficient to distinguish its modification effect, and the curve shape can better reflect the SBS characteristics. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned defects in the prior art and to provide a method for evaluating the modified regeneration performance of ordinary RAP based on morphology. Through simple viscosity and toughness tests, the quality of modified regeneration of old ordinary asphalt can be effectively identified, modified asphalt can be screened, the maximum RAP dosage can be determined, and the range of morphological indicators can be defined.

[0006] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0007] A method for evaluating the regeneration performance of common RAP based on morphology, the method comprising the following steps:

[0008] S1. Obtaining a viscosity-toughness curve through a viscosity-toughness test: Under specified test conditions, a fully automatic viscosity-toughness tester is used to conduct a viscosity-toughness test on the regenerated asphalt obtained after the modification and regeneration of old ordinary asphalt to obtain a viscosity-toughness curve of the regenerated asphalt;

[0009] S2. Classify the viscosity-toughness curves: classify the curves according to the trend and shape of the viscosity-toughness curves of the recycled asphalt;

[0010] S3. Quantitative evaluation of the quality of modified regeneration of old common asphalt: Based on the shape of the viscosity-toughness curve of the regenerated asphalt, the toughness deformation rate is obtained, and the toughness deformation rate is used as an indicator to quantitatively evaluate the quality of modified regeneration of old common asphalt; this indicator is an indicator based on differential calculus, and the physical meaning of the toughness deformation rate represents the toughness deformation under the action of unit force and unit time. The larger the value, the better the regeneration performance.

[0011] S4. Definition of the range of toughness deformation rate values: In order to ensure the accuracy of toughness and toughness deformation rate indicators in evaluating the regeneration effect of recycled asphalt, the fatigue index and the toughness deformation rate index are used for correlation analysis. At the same time, combined with the fatigue grading standard of asphalt linear amplitude test in AASHTO TP-101 specification, the range of values ​​of the toughness deformation rate of recycled asphalt corresponding to pavements with different traffic load grades is obtained.

[0012] Furthermore, in step S1, the old common asphalt is asphalt obtained after short-term aging in the laboratory, and the regenerated asphalt is asphalt obtained by modifying and regenerating the old common asphalt with SBS modified asphalt. SBS modified asphalt has excellent viscoelastic properties and can restore the properties of old common asphalt. At the same time, the viscosity-toughness curve of SBS modified asphalt is very special and can be clearly distinguished from the viscosity-toughness curve of common asphalt.

[0013] Furthermore, the test conditions specified in step S1 are carried out in accordance with the highway engineering asphalt and mixture test procedures, wherein the tack-toughness tensile rate is 500 mm / min and the temperature is 25°C.

[0014] Furthermore, in step S2, the viscosity-toughness curve of the old common asphalt is a single-peak curve, and the viscosity-toughness curve of the modified regenerated asphalt is a double-peak curve. The viscosity-toughness curve of the old common asphalt has only a viscous part, no tough part, and presents a "narrow and high" single-peak shape. The viscosity-toughness curve of the modified regenerated asphalt has an obvious tough part and presents a double-peak shape. Based on the morphological differences of the viscosity-toughness curves of the regenerated asphalt with different performances, quantitative indicators are sought to complete the evaluation of the regeneration performance of the old common asphalt.

[0015] Furthermore, in step S3, the calculation formula of the toughness deformation rate is as follows:

[0016]

[0017] V rtis the ductile deformation rate, which represents the ductile deformation under unit force and unit time, unit: mm / N·min; assuming that the two peak points of the asphalt viscosity-ductility curve are point B and point F, the straight line segment after the first peak point of the asphalt viscosity-ductility curve is BC, the extension line of the straight line segment BC of the asphalt viscosity-ductility curve intersects the x-axis at point D, the intersection points of the asphalt viscosity-ductility curve and the x-axis are the starting point A and the end point E, respectively, and the ductile deformation Δx is the distance between point D and point E, unit: mm; is the average load value corresponding to the toughness deformation section, which is approximately equal to the ratio of the toughness value to Δx, unit: N; the toughness value is equal to the area of ​​the graph CDEF; Δt is the time experienced by the toughness deformation Δx, unit: min. v is the test tensile rate, which is a constant value of 500mm / min. The toughness deformation rate can quantitatively analyze the modified regeneration performance of old ordinary asphalt, which can further guide the selection of new asphalt and determine the dosage of old ordinary asphalt.

[0018] Furthermore, in step S4, for standard traffic load levels, the toughness deformation rate of the regenerated asphalt should be in the range of 0.7 to 1.7; for heavy traffic load levels, the toughness deformation rate of the regenerated asphalt should be in the range of 1.7 to 4.6; for overweight and extreme traffic load levels, the toughness deformation rate of the regenerated asphalt should be above 4.6. By establishing the correlation between the toughness deformation rate of the regenerated asphalt and fatigue performance, it is ensured that the toughness deformation rate can be accurately applied to evaluate the regeneration performance of old ordinary asphalt modification.

[0019] Compared with the prior art, the present invention has the following advantages and effects:

[0020] The viscosity-toughness curve of asphalt can be obtained through a simple viscosity-toughness test. Based on the differences in the viscosity-toughness curves of asphalts with different performances, the toughness deformation rate is proposed for the first time as an evaluation index. This evaluation index has the ability to identify and distinguish the modified regeneration effect of ordinary RAP. It can effectively identify the difference between old ordinary asphalt and modified asphalt and the degree of performance recovery of modified recycled asphalt. It also has a good correlation with rheological indicators. Moreover, compared with the existing asphalt fatigue test methods, the acquisition of identification indicators is cheap, the operation of instruments and equipment is relatively simple, and the requirements for testers are relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0022] Figure 1 It is the viscosity-toughness curve of ordinary RAP;

[0023] Figure 2 This is the viscosity-toughness curve of the new SBS modified asphalt;

[0024] Figure 3 It is the viscosity-toughness curve of recycled asphalt;

[0025] Figure 4 It is a schematic diagram of the calculation of ductile deformation rate;

[0026] Figure 5 This is the effect of the new SBS modified asphalt performance on the viscosity-toughness curve of recycled asphalt;

[0027] Figure 6 This is a graph showing the influence of the amount of aged asphalt on the viscosity-toughness curve of recycled asphalt. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] This example screens modified asphalt based on the effect of SBS modified asphalt performance on the modified regeneration performance of aged common asphalt by studying the difference in the viscosity-toughness curves of SBS modified asphalts with different performances on the same aged common asphalt. The steps are as follows:

[0031] S1. Obtaining the viscosity-toughness curve through the viscosity-toughness test

[0032] Under specific test conditions (test temperature 25°C, pull head running speed 500mm / min), the asphalt obtained after the old modified asphalt was regenerated was subjected to a viscosity-toughness test using a fully automatic viscosity-toughness tester to obtain the viscosity-toughness curve of the regenerated asphalt. In the embodiment, five different penetration levels of SBS modified asphalt were used to regenerate 15% of the old ordinary asphalt R (30-40). The effects of the performance of SBS modified asphalt and the amount of old asphalt on the viscosity-toughness curve of the regenerated asphalt are shown in the figure. Figure 5 shown.

[0033] S2. Classification of viscosity-toughness curve morphology

[0034] According to the trend and shape of the viscosity-toughness curve of recycled asphalt, the curves are mainly divided into single-peak curves and double-peak curves. Figure 5As shown in the figure, when SBS modified asphalt with different grades is used to regenerate 15% of old ordinary asphalt, the load deformation diagram of the regenerated asphalt presents a double peak state. As the grade of SBS modified asphalt increases, the peak values ​​of the first and second peaks of the load are reduced, but the total deformation increases. It can be seen that the toughness part of the viscosity-toughness curve of regenerated asphalt is an important feature to identify its retention of SBS modified characteristics.

[0035] S3. Quantitative evaluation of the quality of modified regeneration of old ordinary asphalt

[0036] Based on the curve shape, the toughness deformation rate is proposed as an evaluation index to quantitatively evaluate the quality of modified regeneration of old ordinary asphalt. The toughness deformation rate is used as an evaluation index to quantitatively analyze the regenerated asphalt, and the linear amplitude test is used to test the fatigue performance of the modified regenerated old ordinary asphalt. The fatigue index N f2.5％ 、N f5.0％ The fatigue performance of recycled asphalt was evaluated. The toughness deformation rate and fatigue index results of recycled asphalt are shown in Table 1.

[0037] Table 1. Toughness deformation rate and fatigue index results of recycled asphalt

[0038]

[0039]

[0040] After the old ordinary asphalt is modified and thermally regenerated, for the same dosage of old ordinary asphalt, the toughness deformation rate of the regenerated asphalt increases with the increase of the SBS modified asphalt grade.

[0041] S4. Definition of the range of values ​​of ductile deformation rate.

[0042] Through the correlation analysis between the fatigue performance and toughness deformation rate of recycled asphalt, combined with the fatigue life grade standard of linear amplitude test, the toughness deformation rate value range of recycled asphalt is recommended to evaluate the quality of ordinary RAP recycling.

[0043] SBS modified asphalt was screened according to the fatigue life grade in the AASHTO specification.

[0044] Table 2. Linear amplitude test fatigue life grade table

[0045] Load level S H V.E <![CDATA[N f2.5％ and N f5.01％ Fatigue life]]> ＞15000 ＞19000 ＞31000

[0046] Among them: four levels: standard traffic (S-Standard Traffic), heavy traffic (H-Heavy Traffic), very heavy traffic (V-Very Heavy Traffic), and extreme traffic (E-Extremely Heavy Traffic).

[0047] As shown in Table 1 and Table 2, the modified asphalt can be screened by combining the fatigue life grade of the linear amplitude test, the fatigue life of the recycled asphalt, and the toughness deformation rate of the recycled asphalt. For example, when using the aged ordinary R (30-40), the recommended modified asphalt grade is P (40-100) for heavy traffic grades, and the corresponding toughness deformation rate is in the range of 1.7 to 4.6. P (100-120) is suitable for overweight and extreme traffic grades, and the recommended toughness deformation rate of the recycled asphalt is above 4.6.

[0048] Example 2

[0049] This example studies the effect of the amount of old common asphalt on the performance of SBS modified recycled asphalt. The steps are as follows:

[0050] S1. Obtaining the viscosity-toughness curve through the viscosity-toughness test

[0051] By changing the dosage of old asphalt, 15%, 35%, and 50% of old common asphalt R (30-40) and SBS modified asphalt P (40-60) were used for thermal regeneration. The viscosity-toughness curve of the regenerated asphalt was obtained under specific test conditions (test temperature 25°C, pull head running speed 500mm / min). Figure 6 shown.

[0052] S2. Classification of viscosity-toughness curve morphology

[0053] When the old common asphalt R (30-40) is modified and thermally regenerated, the curve has an obvious tough part. As the amount of old asphalt increases, the first peak increases, the position of the yield point is not much different, but the double peak shape gradually disappears. It can be seen that the tough part of the regenerated asphalt viscosity-toughness curve is an important feature to identify its retention of SBS modification characteristics.

[0054] S3. Quantitative evaluation of the quality of modified regeneration of old ordinary asphalt

[0055] The toughness deformation rate index is used to quantitatively analyze the recycled asphalt, and the linear amplitude test is used to test the fatigue performance of the old ordinary asphalt after modification and regeneration. f2.5％ 、N f5.0％ The fatigue performance of recycled asphalt was evaluated. The toughness deformation rate and fatigue index of recycled asphalt are shown in Table 3.

[0056] Table 3. Toughness deformation rate and fatigue index results of recycled asphalt

[0057] New and old asphalt blending scheme Toughness deformation rate (mm / N·min) <![CDATA[N f2.5％ / times]]> <![CDATA[N f5.0％ / times]]> 15% R(30-40)+P(40-60) 1.98 21589 3944 35% R(30-40)+P(40-60) 1.79 19036 3827 50%R(30-40)+P(40-60) 1.72 18270 2660

[0058] S4. Definition of the range of values ​​of ductile deformation rate.

[0059] The RAP dosage is preliminarily determined based on the fatigue life grade in the AASHTO specification.

[0060] Table 4. Linear amplitude test fatigue life grade table

[0061] Load level S H V.E <![CDATA[N f2 . 5％ and N f5.0％ Fatigue life]]> ＞15000 ＞19000 ＞31000

[0062] Among them: four levels: standard traffic (S-Standard Traffic), heavy traffic (H-Heavy Traffic), very heavy traffic (V-Very Heavy Traffic), and extreme traffic (E-Extremely Heavy Traffic).

[0063] It can be seen from Table 3 and Table 4 that, combined with the fatigue life level of the linear amplitude test, when P(40-60)SBS modified asphalt is used to regenerate aged asphalt, it is recommended that the aged asphalt content be within 50% for standard traffic levels and within 35% for heavy traffic. Correspondingly, the toughness deformation rate is in the range of 0.7 to 1.7 for standard traffic levels and 1.7 to 4.6 for heavy traffic.

[0064] Example 3

[0065] This example verifies the correlation between fatigue performance and toughness deformation rate, determines the range of toughness deformation rate values, and provides guidance for selecting modified asphalt or determining the RAP dosage according to traffic load levels.

[0066] By analyzing the correlation between fatigue index and toughness deformation rate, the accuracy of toughness and toughness deformation rate index in evaluating the regeneration effect is ensured. It can be found that the toughness deformation rate is linearly correlated with the fatigue life of the regenerated asphalt, and the correlation coefficient R 2 The correlation coefficient R between fatigue life and ductile deformation rate under 2.5% strain control is above 0.9. 2 As high as 0.985, the relationship is: N f2.5％ =4096.9V rt +12005.9. Accordingly, to meet the standard traffic load level, it is recommended that the toughness deformation rate of recycled asphalt should be in the range of 0.7 to 1.7. The toughness deformation rate in the range of 1.7 to 4.6 is suitable for heavy traffic levels. For overweight and extreme traffic levels, it is recommended that the toughness deformation rate of recycled asphalt be above 4.6. This indicator can guide the selection of modified asphalt or determine the RAP dosage according to the traffic load level.

[0067] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for evaluating the regeneration performance of common RAP based on morphology, characterized in that: The method comprises the following steps: S1. Obtaining a viscosity-toughness curve through a viscosity-toughness test: Under specified test conditions, a fully automatic viscosity-toughness tester is used to conduct a viscosity-toughness test on the regenerated asphalt obtained after the modification and regeneration of old ordinary asphalt to obtain a viscosity-toughness curve of the regenerated asphalt; S2. Classify the viscosity-toughness curves in terms of their morphology: Classify the curves according to the trend and morphology of the regenerated asphalt viscosity-toughness curves; in step S2, the viscosity-toughness curve of ordinary asphalt is a single-peak curve, and the viscosity-toughness curve of modified regenerated asphalt is a double-peak curve; S3. Quantitative evaluation of the quality of modified regeneration of old common asphalt: Based on the morphology of the viscosity-toughness curve of the regenerated asphalt, the toughness deformation rate is obtained, and the toughness deformation rate is used as an indicator to quantitatively evaluate the quality of modified regeneration of old common asphalt; in step S3, the calculation formula of the toughness deformation rate is as follows: V rt is the ductile deformation rate, which represents the ductile deformation under unit force and unit time, unit: mm / N·min; assuming that the two peak points of the asphalt viscosity-ductility curve are point B and point F, the straight line segment after the first peak point of the asphalt viscosity-ductility curve is BC, the extension line of the straight line segment BC of the asphalt viscosity-ductility curve intersects the x-axis at point D, the intersection points of the asphalt viscosity-ductility curve and the x-axis are the starting point A and the end point E, respectively, and the ductile deformation Δx is the distance between point D and point E, unit: mm; is the average load value corresponding to the toughness deformation section, which is approximately equal to the ratio of the toughness value to Δx, unit: N; the toughness value S is equal to the area of ​​the graph CDEF; Δt is the time experienced by the toughness deformation Δx, unit: min, is the test tensile rate, which is a constant value of 500 mm / min; S4. Definition of the range of toughness deformation rate values: Correlation analysis is performed between fatigue index and toughness deformation rate index, and combined with the fatigue grading standard of asphalt linear amplitude test in AASHTO TP-101 specification, the range of values ​​of the toughness deformation rate of recycled asphalt corresponding to pavements with different traffic load levels is obtained; in step S4, for standard traffic load levels, the toughness deformation rate of recycled asphalt should be in the range of 0.7 to 1.7; for heavy traffic load levels, the toughness deformation rate of recycled asphalt should be in the range of 1.7 to 4.6; for overweight and extreme traffic load levels, the toughness deformation rate of recycled asphalt should be above 4.

6.

2. The method for evaluating the regeneration performance of common RAP based on morphology according to claim 1, characterized in that: In the step S1, the old common asphalt is asphalt obtained after short-term aging in the laboratory, and the regenerated asphalt is asphalt obtained by modifying and regenerating the old common asphalt with SBS modified asphalt.

3. The method for evaluating the regeneration performance of common RAP based on morphology according to claim 1, characterized in that: The test conditions specified in step S1 are carried out in accordance with the highway engineering asphalt and mixture test procedures.

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