An evaluation method for the fusion of new and old asphalt in recycled asphalt mortar

Abstract

An evaluation method for the fusion of new and old asphalt in recycled asphalt mortar is as follows: First, prepare a slurry of the refined and separated oil-rich RAP fine material and new asphalt to obtain partially fused recycled asphalt mortar with different degrees of fusion on-site, and prepare a completely fused recycled asphalt mortar for comparison; Second, use the bending beam rheology test to obtain the low-temperature rheological indexes at different temperatures; Then, based on the time-temperature equivalence principle, draw a low-temperature master curve according to the obtained low-temperature rheological indexes; Finally, use the Fréchet distance to evaluate the similarity between the low-temperature master curves of mortars with different degrees of fusion and the standard curve of complete fusion, which is used as an evaluation method for the fusion of new and old asphalt in recycled asphalt mortar. The present invention evaluates the fusion degree of new and old asphalt in recycled asphalt mortar through in-situ technology, avoiding problems such as the mismatch between the existing simulated new and old asphalt fusion test and the actual situation, the negative impact of the extraction test on the evaluation of new and old asphalt fusion, and the high cost and difficult operation of microscopic tests.

Description

Technical Field

[0001] The present invention relates to the technical field of detection and evaluation of physical properties of new and old asphalt in regenerated asphalt mortar, and in particular to an evaluation method for the fusion of new and old asphalt in regenerated asphalt mortar. Background Art

[0002] At present, the utilization rate of solid waste is still relatively low, and the comprehensive utilization level of bulk solid waste needs to be further improved, and the direction of transformation from "inefficient, low-value, and scattered utilization" to "efficient, high-value, and large-scale utilization" needs to be changed.

[0003] Asphalt pavement regeneration technology has been widely used in road engineering, especially in the repair of pavement performance and the comprehensive utilization of large amounts of solid waste. In order to transform asphalt pavement regeneration technology from "low efficiency, low value, and scattered utilization" to "high efficiency, high value, and large-scale utilization", it is necessary to improve the efficiency of asphalt pavement regeneration. At present, the main reason restricting the amount of RAP material in factory-mixed hot regeneration is the variability of RAP and the degree of fusion of new and old asphalt. Studies have shown that the variability of RAP materials can be effectively controlled through fine separation technology. The variability of RAP coarse material after fine separation is small, and the surface asphalt content is low. The performance of the recycled asphalt mixture produced by it is no different from that of hot-mix asphalt mixture; however, after separation, the proportion of RAP fine material (oil-rich RAP fine material) is high and the surface asphalt content is high (up to 13%). The existing addition method cannot be effectively applied, and large-scale accumulation will cause land waste and environmental pollution. At present, the accumulated RAP fines can be treated by pre-mixing the oil-rich RAP fines with new asphalt in a certain proportion and then adding them into the mixture mixing tank for production. However, due to the inconsistent sources of RAP fines, the fusion time of the aged asphalt on its surface and the new asphalt is different. However, in the actual production process, due to the efficient linkage between the pulping equipment and the mixing plant, the production time of a batch of mixture in the mixing plant is generally 70-80s. The production efficiency of the recycled asphalt mortar needs to match the production of the mixing plant. Therefore, it is urgent to evaluate whether the asphalt material used for pulping can quickly and effectively penetrate into the deep layer of the aged asphalt on the surface of RAP, that is, how to evaluate the fusion of new and old asphalt in the recycled asphalt mortar.

[0004] In the prior art, the degree of fusion between new and old asphalt is usually evaluated by layered extraction, simulation of fusion between new and old asphalt, and microscopic tests such as AFM and SEM. However, the solvent used in the layered extraction test and the heating process during recovery will affect the performance of asphalt, the simulation experiment of fusion between new and old asphalt cannot fully simulate the actual construction situation, and the microscopic test has problems such as high price and difficulty in operation. Summary of the invention

[0005] Technical problem to be solved: In view of the problems in the prior art such as the mismatch between the simulated new and old asphalt fusion test and the actual situation, the negative impact of the extraction test on the evaluation of the fusion of new and old asphalt, and the high price and difficulty of operation of the microscopic test, the present invention aims at the demand for the fusion effect of new and old asphalt during the production of regenerated asphalt mortar, and proposes an evaluation method for the fusion of new and old asphalt in regenerated asphalt mortar. The method can evaluate the fusion degree of new and old asphalt in the regenerated asphalt mortar through in-situ technology, avoiding the problems existing in the existing evaluation methods.

[0006] Technical solution: A method for evaluating the fusion of new and old asphalt in recycled asphalt mortar, the steps are as follows:

[0007] Step 1: heating the oil-rich RAP fine material to 165° C., heating the new asphalt to 160° C., adding the heated new asphalt to the heated oil-rich RAP fine material, and keeping the temperature at 165° C. to obtain a mixture;

[0008] Step 2, obtaining partially fused recycled asphalt mortars with different fusion degrees: stirring the mixture to make pulp at 165°C, setting at least three groups of pulping conditions according to the preparation process of the on-site recycled asphalt mortar, each group having different stirring speeds and stirring times, producing at least three partially fused recycled asphalt mortars with different fusion degrees, and obtaining different samples;

[0009] Step 3, prepare a completely fused recycled asphalt mortar: perform an extraction test on an amount of oil-rich RAP fine material equal to that in step 1 to obtain recycled asphalt and recycled aggregate, heat the recycled asphalt to 160°C, then add an amount of new asphalt equal to that in step 1, stir evenly, and completely blend it; then heat the recycled aggregate to 165°C, add the completely fused recycled asphalt and new asphalt, stir evenly at 165°C to obtain a completely fused recycled asphalt mortar;

[0010] Step 4: Using a bending beam rheological test (BBR) to obtain the rheological performance index of the partially fused samples with different fusion degrees prepared in step 2 and the fully fused recycled asphalt mortar prepared in step 3, the rheological performance index is the low temperature stiffness modulus, and the low temperature range is -12°C to -27°C;

[0011] Step 5, drawing a low temperature master curve according to the rheological performance index of step 4;

[0012] Step six: Use the Flechet distance to evaluate the similarity between the master curves of different fusion degrees and the master curve of complete fusion. The smaller the Flechet distance, the closer the fusion degree of the recycled asphalt mortar is to complete fusion, and the better the fusion degree.

[0013] Preferably, the oil-rich RAP fine material in step 1 is RAP with a particle size of less than 3 mm after fine separation, and the new asphalt is 70# base asphalt.

[0014] Preferably, in step 1, the mass ratio of the oil-rich RAP fines to the new asphalt is 8:2.

[0015] Preferably, three groups of pulping conditions are set in step 2, the first group has a stirring speed of 200 RPM and a time of 15 min; the second group has a stirring speed of 500 RPM and a time of 10 min; the third group has a stirring speed of 800 RPM and a time of 8 min; and the stirring conditions in step 3 are a stirring speed of 200 RPM and a time of 15 min.

[0016] Preferably, the test method for the bending beam rheological test in step 4 adopts the asphalt bending creep stiffness modulus test method of section T0627-2011 in the test procedures for asphalt and asphalt mixtures in highway engineering JTG E20-2011.

[0017] Preferably, the test temperatures of the bending beam rheological test are -12°C, -15°C, -18°C, -21°C, -24°C and -27°C, the loading times are 8, 15, 30, 60, 120 and 240 s respectively, and the initial test load is 980 mN±50 mN.

[0018] Preferably, in step 5, the Sigmoid empirical model is used to fit the low-temperature master curve of the rheological performance index, and the calculation expression of the Sigmoid empirical model is as follows (1):

[0019] (1)

[0020] In the formula, a, b, d, and g are regression coefficients;

[0021] E * is the low temperature stiffness modulus, MPa, obtained from step 4;

[0022] f red The calculation expression is as follows (2):

[0023] (2)

[0024] In this experiment, f red is defined as the reduction time, f is the test time in step 4, s;

[0025] is the temperature shift factor, and the calculation expression is as follows (3):

[0026] (3)

[0027] Where T is the actual test temperature in step 4, °C;

[0028] T 0is the reference temperature, °C;

[0029] C 1 , C 2 is the fitting parameter.

[0030] Based on the time-temperature equivalence principle, the stress relaxation modulus curves obtained at different temperatures are parallel moved along the logarithmic time axis and superimposed together to couple into a smooth curve, namely, the low-temperature master curve.

[0031] Preferably, the reference temperature is -15°C.

[0032] Preferably, in step 6, the Fréchet distance is used to evaluate the similarity between the master curves of different fusion degrees and the fully fused master curve, as follows:

[0033] Step 1: Obtain the low-temperature stiffness modulus master curve E of the fully integrated recycled asphalt mortar * C , as shown in the following formula (4):

[0034] E * C ={(t 1 ,E * C (1)), (t 2 ,E * C (2)), …, (t n ,E * C (n)), …, (t N ,E * C (N))} (4)

[0035] Where 1-N is the serial number of the sampling points on the fully fused master curve, and N is a natural number greater than 2;

[0036] n is a natural number between 1 and N;

[0037] t n is the time of the nth sampling point, s;

[0038] E * C (n) is t n Corresponding low temperature stiffness modulus, MPa;

[0039] t N is the time of the Nth sampling point, s;

[0040] E * C (N) is t N Corresponding low temperature stiffness modulus, MPa;

[0041] Step 2: Obtain the low-temperature stiffness modulus master curve E of partially fused recycled asphalt mortar * P , as shown in the following formula (5):

[0042] E * P ={(t 1 , E * P (1)), (t 2 , E * P (2)), …, (t m , E * P (m)), …, (t M , E * P (M))} (5)

[0043] Where 1-M is the serial number of the sampling points on the partially fused main curve, and M is a natural number greater than 2;

[0044] m is a natural number between 1 and M;

[0045] t m is the time of the mth sampling point, s;

[0046] E * P (m) is t m Corresponding low temperature stiffness modulus, MPa;

[0047] t M is the time of the Mth sampling point, s;

[0048] E * P (M) is t M Corresponding low temperature stiffness modulus, MPa;

[0049] Step 3: Calculate the distances between the sampling points on the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar to obtain the distance matrix D, as shown in the following formula (6):

[0050] (6)

[0051] In the formula, , 1≤n≤N, 1≤m≤M;

[0052] Step 4: Find d in the distance matrix D mn The maximum value d max With the minimum value d min, set the initial target distance f=d min , and set the loop interval ;

[0053] Step 5: Binarize the distance matrix D to obtain the binary matrix D', as shown in the following formula (7):

[0054] (7)

[0055] In the formula, , 1≤n≤N, 1≤m≤M;

[0056] Step 6. Find a path R in the binary matrix D' that satisfies the following conditions: The starting point of R is d' 11 , the end point is d' MN ; The path passes through point d' mn After that, the next passing point can only be d' (m+1)n , d' m(n+1) and d' (m+1)(n+1) The value of all points in path R must be 1;

[0057] Step 7. If no path that meets the conditions is found in step 6, reset the target distance to f+r, and then loop through steps 5 and 6. The relationship between the number of loops x and the target distance is as follows: loop 1, target distance f; loop 2, target distance f+r; loop 3, target distance f+2r; ...; loop x, target distance f+(x-1)r, see Table 1 for details; if the target distance f+(x-1)r of the path that meets the conditions is found in step 6 in the xth loop, proceed to the next step;

[0058] Table 1 Relationship between cycle number and target distance

[0059]

[0060] Step 8. The Frechet distance F=f+(x-1)r of the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar.

[0061] Beneficial effect: The present invention starts from the oil-rich RAP fine material pulping technology that increases the factory-mixed hot-regenerated RAP dosage, and evaluates the fusion degree of new and old asphalt in the regenerated asphalt mortar through in-situ technology. On the one hand, it avoids the problem that the quality of the regenerator is uneven due to the inability to accurately evaluate the fusion degree of the new and old asphalt, and there are multiple weak interfaces in the regenerated asphalt mixture after the fusion of the new and old asphalt, which leads to the insufficient low-temperature crack resistance and water stability of the regenerated asphalt mixture. On the other hand, it avoids the problems that the existing simulation of the fusion test of new and old asphalt is not matched with the actual situation, the negative impact of the extraction test on the evaluation of the fusion of new and old asphalt, and the high price and difficulty of operation of the microscopic test, and provides an effective way to judge the fusion degree of new and old asphalt in on-site rapid pulping. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a flow chart of an evaluation method for fusion of new and old asphalt in a regenerated asphalt mortar according to the present invention;

[0063] Figure 2 Schematic diagram of the low temperature master curve of an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the present invention. It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0065] like Figure 1 As shown, a method for evaluating the fusion of new and old asphalt in recycled asphalt mortar is provided, and the steps are as follows:

[0066] Step 1: heating the oil-rich RAP fine material to 165° C., heating the new asphalt to 160° C., adding the heated new asphalt to the heated oil-rich RAP fine material, and keeping the temperature at 165° C. to obtain a mixture;

[0067] Step 2, obtaining partially fused recycled asphalt mortars with different fusion degrees: stirring the mixture to make pulp at 165°C, setting at least three groups of pulping conditions according to the preparation process of the on-site recycled asphalt mortar, each group having different stirring speeds and stirring times, producing at least three partially fused recycled asphalt mortars with different fusion degrees, and obtaining different samples;

[0068] Step 3, prepare a completely fused recycled asphalt mortar: perform an extraction test on an amount of oil-rich RAP fine material equal to that in step 1 to obtain recycled asphalt and recycled aggregate, heat the recycled asphalt to 160°C, then add an amount of new asphalt equal to that in step 1, stir evenly, and completely blend it; then heat the recycled aggregate to 165°C, add the completely fused recycled asphalt and new asphalt, stir evenly at 165°C to obtain a completely fused recycled asphalt mortar;

[0069] Step 4: Using a bending beam rheological test to obtain the rheological performance index of the partially fused samples with different fusion degrees prepared in step 2 and the fully fused recycled asphalt mortar prepared in step 3, the rheological performance index is the low-temperature stiffness modulus, and the low-temperature range is -12°C to -27°C;

[0070] Step 5, drawing a low temperature master curve according to the rheological performance index of step 4;

[0071] Step six: Use the Flechet distance to evaluate the similarity between the master curves of different fusion degrees and the master curve of complete fusion. The smaller the Flechet distance, the closer the fusion degree of the recycled asphalt mortar is to complete fusion, and the better the fusion degree.

[0072] As one of the preferred embodiments of the present invention, the oil-rich RAP fine material in step 1 is RAP with a particle size of less than 3 mm after fine separation, and the new asphalt is 70# base asphalt.

[0073] As one of the preferred embodiments of the present invention, the mass ratio of the oil-rich RAP fines to the new asphalt in step 1 is 8:2.

[0074] As one of the preferred embodiments of the present invention, three groups of pulping conditions are set in the step 2, the first group of stirring speed is 200 RPM, time 15 min; the second group of stirring speed is 500 RPM, time 10 min; the third group of stirring speed is 800RPM, time 8 min; the stirring conditions in step 3 are stirring speed of 200 RPM, time 15 min.

[0075] As one of the preferred embodiments of the present invention, the test method of the bending beam rheological test in step 4 adopts the asphalt bending creep stiffness modulus test method of part T0627-2011 in the test procedures for asphalt and asphalt mixtures in highway engineering JTG E20-2011.

[0076] As one of the preferred embodiments of the present invention, the test temperatures of the bending beam rheology test are -12°C, -15°C, -18°C, -21°C, -24°C and -27°C, the loading times are 8, 15, 30, 60, 120 and 240 s respectively, and the initial test load is 980 mN±50 mN.

[0077] As one of the preferred embodiments of the present invention, in step 5, the Sigmoid empirical model is used to fit the low-temperature master curve of the rheological performance index. The calculation expression of the Sigmoid empirical model is as follows (1):

[0078] (1)

[0079] In the formula, a, b, d, and g are regression coefficients;

[0080] E * is the low temperature stiffness modulus, MPa, obtained from step 4;

[0081] f red The calculation expression is as follows (2):

[0082] (2)

[0083] In this experiment, f red It is defined as the reduction time, f is the test time in step 4, s;

[0084] is the temperature shift factor, and the calculation expression is as follows (3):

[0085] (3)

[0086] Where T is the actual test temperature in step 4, °C;

[0087] T 0 is the reference temperature, °C;

[0088] C 1 , C 2 is the fitting parameter.

[0089] As one of the preferred embodiments of the present invention, the reference temperature is -15°C.

[0090] As one of the preferred embodiments of the present invention, the Fréchet distance is used in step 6 to evaluate the similarity between the master curves of different fusion degrees and the fully fused master curve, as follows:

[0091] Step 1: Obtain the low-temperature stiffness modulus master curve E of the fully integrated recycled asphalt mortar * C , as shown in the following formula (4):

[0092] E * C ={(t 1 ,E * C (1)), (t 2 ,E* C (2)), …, (t n ,E * C (n)), …, (t N ,E * C (N))} (4)

[0093] Where 1-N is the serial number of the sampling points on the fully fused master curve, and N is a natural number greater than 2;

[0094] n is a natural number between 1 and N;

[0095] t n is the time of the nth sampling point, s;

[0096] E * C (n) is t n Corresponding low temperature stiffness modulus, MPa;

[0097] t N is the time of the Nth sampling point, s;

[0098] E * C (N) is t N Corresponding low temperature stiffness modulus, MPa;

[0099] Step 2: Obtain the low-temperature stiffness modulus master curve E of partially fused recycled asphalt mortar * P , as shown in the following formula (5):

[0100] E * P ={(t 1 , E * P (1)), (t 2 , E * P (2)), …, (t m , E * P (m)), …, (t M , E * P (M))} (5)

[0101] Where 1-M is the serial number of the sampling points on the partially fused master curve, and M is a natural number greater than 2;

[0102] m is a natural number between 1 and M;

[0103] t mis the time of the mth sampling point, s;

[0104] E * P (m) is t m Corresponding low temperature stiffness modulus, MPa;

[0105] t M is the time of the Mth sampling point, s;

[0106] E * P (M) is t M Corresponding low temperature stiffness modulus, MPa;

[0107] Step 3: Calculate the distances between the sampling points on the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar to obtain the distance matrix D, as shown in the following formula (6):

[0108] (6)

[0109] In the formula, , 1≤n≤N, 1≤m≤M;

[0110] Step 4: Find d in the distance matrix D mn The maximum value d max With the minimum value d min , set the initial target distance f=d min , and set the loop interval ;

[0111] Step 5: Binarize the distance matrix D to obtain the binary matrix D', as shown in the following formula (7):

[0112] (7)

[0113] In the formula, , 1≤n≤N, 1≤m≤M;

[0114] Step 6. Find a path R in the binary matrix D' that satisfies the following conditions: The starting point of R is d' 11 , the end point is d' MN ; The path passes through point d' mn After that, the next passing point can only be d' (m+1)n , d' m(n+1) and d' (m+1)(n+1) The value of all points in path R must be 1;

[0115] Step 7: If no path that meets the conditions is found in step 6, the distance is reset to f+r, and then steps 5 and 6 are looped. The relationship between the number of loops x and the target distance is shown in Table 1. If the target distance f+(x-1)r of the path that meets the conditions is found in step 6 in the xth loop, proceed to the next step.

[0116] Step 8. The Frechet distance F=f+(x-1)r of the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar.

[0117] Specific application examples are as follows:

[0118] Example 1

[0119] This embodiment provides a method for evaluating the fusion of new and old asphalt in recycled asphalt mortar, and the steps are as follows:

[0120] Step 1, preheat the oil-rich RAP fines and new asphalt, heat the finely separated oil-rich RAP fines (sourced from G205 in Linyi City, Shandong Province, with a particle size of 0-3 mm and an oil-rich content of 11.7 wt%) in an oven to 165°C, and heat the new asphalt, i.e. 70# matrix asphalt (provided by Nantong Tongsha Asphalt Technology Co., Ltd., model Ssangyong 70# matrix asphalt) in an oven to 160°C, first add the heated oil-rich RAP fines to a 5L sample barrel, and then add the heated 70# matrix asphalt, with a mass ratio of 8:2, put the sample barrel into a heating jacket, and the insulation temperature of the heating jacket is 165°C, then immerse the variable speed torque tester stirring paddle in the material, with the paddle being 2 cm away from the bottom of the sample barrel.

[0121] Step 2: Obtain partially fused recycled asphalt mortars with different fusion degrees. The mixture was stirred and slurried at 165°C, and three groups of slurrying conditions were set, namely: stirring paddle speed 200 RPM, fusion 15 min (sample 1); stirring paddle speed 500 RPM, fusion 10 min (sample 2); stirring paddle speed 800 RPM, fusion 8 min (sample 3).

[0122] Step 3, prepare a completely fused recycled asphalt mortar as a control. According to the oil-rich amount of the oil-rich RAP fines, calculate the mass of asphalt and aggregate in the oil-rich RAP fines, then perform an extraction test on the oil-rich RAP fines to recover the same mass of recycled asphalt and recycled aggregate, heat the recycled aggregate to 160°C, then add the same amount of new asphalt as in step 1, and stir at 200 RPM for 15 min at 160°C using a stirrer to completely blend it. Then heat the recycled aggregate recovered by extraction to 165°C, mix with the completely fused recycled asphalt and new asphalt, and add to a 5L sample preparation barrel, put the sample preparation barrel into a heating jacket, and the insulation temperature of the heating jacket is 165°C, then immerse the variable speed torque tester stirring paddle in the material, and the distance between the paddle and the bottom of the sample preparation barrel is 2 cm. The stirring paddle speed is 200 RPM, and stirring is carried out for 15 min to obtain a completely fused sample.

[0123] Step 4: The fusion test adopts the bending beam rheological test (BBR). The test method adopts T0627-2011 in the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), and BBR test samples are prepared for 4 kinds of recycled asphalt mortars. The bending beam rheological test method is as follows:

[0124] (1) Prepare and assemble the BBR standard test piece mold. The mold is made of aluminum plate. The internal length of the mold is: 127 mm ± 2.0 mm, thickness 6.35 mm ± 0.05 mm, width 12.70 mm ± 0.05 mm (BBR standard test mold);

[0125] (2) Clean the mold, apply a layer of petroleum-based grease on the inner surface of the three long metal parts of the mold, use the grease to stick the plastic sheet to the metal, assemble the mold, and pour four types of recycled asphalt mortars (sample 1, sample 2, sample 3, and fully fused sample) at 165°C into the four molds respectively;

[0126] (3) Cool at room temperature for 45-60 min, and cut the asphalt mortar sample that is higher than the top of the mold after cooling;

[0127] (4) Before demolding, place the cooled mold in a cooling room or cooling water to cool it down to ensure that the specimen does not deform during demolding;

[0128] (5) After demoulding, place the specimen in a constant temperature bath that has reached the test temperature. After maintaining the constant temperature for 60 min ± 5 min, place the specimen on a bracket for testing, and maintain the constant temperature bath temperature within ± 0.1 °C of the test temperature.

[0129] The test conditions were set as follows: the BBR test temperatures were -12°C, -15°C, -18°C, -21°C, -24°C and -27°C, the load times were 8, 15, 30, 60, 120 and 240 s, respectively, and the initial test load was 980 mN ± 50 mN.

[0130] The test results are shown in Table 2 below:

[0131] Table 2 BBR test results (taking sample 3 as an example, others are as follows Figure 2 shown)

[0132]

[0133] Step 5, use the Sigmoid empirical model to fit the low-temperature master curve of the low-temperature stiffness modulus. The calculation expression of the Sigmoid empirical model is shown in the following formula (1):

[0134] (1)

[0135] Where a, b, d, g are regression coefficients, and E* is the low temperature stiffness modulus, MPa. red The original definition is the reduced frequency, the unit is Hz, this test uses the test time instead, the unit is s, f red It is obtained by the following formula (2).

[0136] (2)

[0137] Where f is the test time in step 4, s;

[0138] is the temperature shift factor, and the calculation expression is as follows (3):

[0139] (3)

[0140] Where T is the actual test temperature, °C;

[0141] T 0 is the reference temperature, °C;

[0142] C 1 , C 2 is the fitting parameter.

[0143] Step 6, when establishing the master curve, select -15 ℃ as the reference temperature, and use the Williams-Landel-Ferry (WLF) equation to shift the test data of other temperature points to the reference temperature. In the Excel 2003 data table, the nonlinear least square method can be used to simultaneously obtain the displacement factors of each parameter in the model and each temperature (see Table 3), and then the master curve of the asphalt can be obtained by plotting. The master curves of various asphalts are shown in Figure 3. Figure 2 shown.

[0144] Table 3 Master curve model parameters

[0145]

[0146] Step 7, calculate the Fréchet distance between the master curves of low-temperature stiffness modulus of fully fused and regenerated asphalt mortars with different fusion degrees, and evaluate the fusion degree of each regenerated asphalt mortar. A discrete Fréchet distance algorithm suitable for computers is used to characterize the distance between the master curves of low-temperature stiffness modulus of fully fused and partially fused regenerated asphalt mortars. The smaller the Fréchet distance, the higher the similarity of the two curves, and the closer the fusion degree of the regenerated asphalt mortar is to complete fusion.

[0147] The details are as follows:

[0148] (1) Obtain the main curve E of the low-temperature stiffness modulus of the fully integrated recycled asphalt mortar * C , as shown in the following formula (4):

[0149] E * C ={(t 1 ,E * C (1)), (t 2 ,E * C (2)), …, (t n ,E * C (n)), …, (t N ,E * C (N))} (4)

[0150] Where 1-N is the serial number of the sampling points on the fully fused master curve, and N is a natural number greater than 2;

[0151] n is a natural number between 1 and N;

[0152] t n is the time of the nth sampling point, s;

[0153] E * C (n) is t n Corresponding low temperature stiffness modulus, MPa;

[0154] t N is the time of the Nth sampling point, s;

[0155] E * C (N) is t NCorresponding low temperature stiffness modulus, MPa;

[0156] (2) Obtaining the main curve E of the low-temperature stiffness modulus of partially fused recycled asphalt mortar * P , as shown in the following formula (5):

[0157] E * P ={(t 1 , E * P (1)), (t 2 , E * P (2)), …, (t m , E * P (m)), …, (t M , E * P (M))} (5)

[0158] Where 1-M is the serial number of the sampling points on the partially fused main curve, and M is a natural number greater than 2;

[0159] m is a natural number between 1 and M;

[0160] t m is the time of the mth sampling point, s;

[0161] E * P (m) is t m Corresponding low temperature stiffness modulus, MPa;

[0162] t M is the time of the Mth sampling point, s;

[0163] E * P (M) is t M Corresponding low temperature stiffness modulus, MPa;

[0164] (3) The distances between the sampling points on the main curves of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortars are calculated to obtain the distance matrix D, as shown in the following formula (6):

[0165] (6)

[0166] In the formula, , 1≤n≤N, 1≤m≤M;

[0167] (4) Find d in the distance matrix D mn The maximum value d max With the minimum value dmin , set the initial target distance f=d min , and set the loop interval ;

[0168] (5) Binarize the distance matrix D to obtain the binary matrix D', as shown in formula (7):

[0169] (7)

[0170] In the formula, , 1≤n≤N, 1≤m≤M;

[0171] (6) Find a path R in the binary matrix D' that satisfies the following conditions: The starting point of R is d' 11 , the end point is d' MN ; The path passes through point d' mn After that, the next passing point can only be d' (m+1)n , d' m(n+1) and d' (m+1)(n+1) The value of all points in path R must be 1;

[0172] (7) If no path that meets the conditions is found in step 6, the distance is reset to f+r, and then steps 5 and 6 are looped. The relationship between the number of loops x and the target distance is shown in Table 1. If the target distance f+(x-1)r of the path that meets the conditions is found in step 6 in the xth loop, proceed to the next step.

[0173] (8) The Fréchet distance F=f+(x-1)r of the main curve of low-temperature stiffness modulus of fully fused and partially fused recycled asphalt mortar.

[0174] In this example, the Fréchet distance of sample 1 is 0.116, the Fréchet distance of sample 2 is 0.0706, and the Fréchet distance of sample 3 is 0.1383. Therefore, the degree of fusion of new and old asphalt in sample 2 is closest to that of fully fused recycled asphalt mortar. Therefore, the optimal pulping conditions are obtained with a stirring paddle speed of 500 RPM and fusion for 10 minutes.

[0175] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned implementation modes, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned implementation modes can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the implementation modes of the present invention.

Claims

1. A method for evaluating the fusion of new and old asphalt in recycled asphalt mortar, characterized in that: Here are the steps: Step 1: heating the oil-rich RAP fine material to 165° C., heating the new asphalt to 160° C., adding the heated new asphalt to the heated oil-rich RAP fine material, and keeping the temperature at 165° C. to obtain a mixture; Step 2, obtaining partially fused recycled asphalt mortars with different fusion degrees: stirring the mixture to make pulp at 165°C, setting at least three groups of pulping conditions according to the preparation process of the on-site recycled asphalt mortar, each group having different stirring speeds and stirring times, producing at least three partially fused recycled asphalt mortars with different fusion degrees, and obtaining different samples; Step 3, prepare a completely fused recycled asphalt mortar: perform an extraction test on an amount of oil-rich RAP fine material equal to that in step 1 to obtain recycled asphalt and recycled aggregate, heat the recycled asphalt to 160°C, then add an amount of new asphalt equal to that in step 1, stir evenly, and completely blend it; then heat the recycled aggregate to 165°C, add the completely fused recycled asphalt and new asphalt, stir evenly at 165°C to obtain a completely fused recycled asphalt mortar; Step 4: Using a bending beam rheological test to obtain the rheological performance index of the partially fused samples with different fusion degrees prepared in step 2 and the fully fused recycled asphalt mortar prepared in step 3, the rheological performance index is the low-temperature stiffness modulus, and the low-temperature range is -12°C to -27°C; Step 5, drawing a low temperature master curve according to the rheological performance index of step 4; Step six: Use the Flechet distance to evaluate the similarity between the master curves of different fusion degrees and the master curve of complete fusion. The smaller the Flechet distance, the closer the fusion degree of the recycled asphalt mortar is to complete fusion, and the better the fusion degree.

2. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: The oil-rich RAP fine material in step 1 is RAP with a particle size of less than 3 mm after fine separation, and the new asphalt is 70# base asphalt.

3. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: In the step 1, the mass ratio of the oil-rich RAP fines to the new asphalt is 8:

2.

4. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: In the step 2, three groups of pulping conditions are set, the first group has a stirring speed of 200 RPM and a time of 15 min; the second group has a stirring speed of 500 RPM and a time of 10 min; the third group has a stirring speed of 800 RPM and a time of 8 min; the stirring condition in step 3 is a stirring speed of 200 RPM and a time of 15 min.

5. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: The test method of the bending beam rheological test in step 4 adopts the asphalt bending creep stiffness modulus test method of part T0627-2011 in the test procedures for asphalt and asphalt mixtures in highway engineering JTGE20-2011.

6. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 5, characterized in that: The test temperatures of the bending beam rheological test are -12°C, -15°C, -18°C, -21°C, -24°C and -27°C, the loading times are 8, 15, 30, 60, 120 and 240 s, respectively, and the initial test load is 980 mN±50 mN.

7. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: In the step 5, the Sigmoid empirical model is used to fit the low-temperature master curve of the rheological performance index. The calculation expression of the Sigmoid empirical model is as follows (1): （1）， In the formula, a, b, d, and g are regression coefficients; E * is the low temperature stiffness modulus, MPa, obtained from step 4; f red The calculation expression is as follows (2): （2）， In this method, f red It is defined as the reduction time, f is the test time in step 4, s; is the temperature shift factor, and the calculation expression is as follows (3): （3）， Where T is the actual test temperature in step 4, °C; T0 is the reference temperature, °C; C1 and C2 are fitting parameters.

8. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 7, characterized in that: The reference temperature is -15°C.

9. The method for evaluating the fusion of new and old asphalt in recycled asphalt mortar according to claim 1, characterized in that: In step 6, the Fleche distance is used to evaluate the similarity between the master curves of different fusion degrees and the fully fused master curve, as follows: Step 1: Obtain the low-temperature stiffness modulus master curve E of the fully integrated recycled asphalt mortar * C , as shown in the following formula (4): AND * C ={(t1,E * C (1)), (t2,E * C (2)), …, (t n ,AND * C (n)), …, (t N ,AND * C (N))} (4), Where 1-N is the serial number of the sampling points on the fully fused master curve, and N is a natural number greater than 2; n is a natural number between 1 and N; t n is the time of the nth sampling point, s; E * C (n) is t n Corresponding low temperature stiffness modulus, MPa; t N is the time of the Nth sampling point, s; E * C (N) is t N Corresponding low temperature stiffness modulus, MPa; Step 2: Obtain the low-temperature stiffness modulus master curve E of partially fused recycled asphalt mortar * P , as shown in the following formula (5): AND * P ={(t1, E * P (1)), (t2, E * P (2)), …, (t m , AND * P (m)), …, (t M , AND * P (M))} (5), Where 1-M is the serial number of the sampling points on the partially fused main curve, and M is a natural number greater than 2; m is a natural number between 1 and M; t m is the time of the mth sampling point, s; E * P (m) is t m Corresponding low temperature stiffness modulus, MPa; t M is the time of the Mth sampling point, s; E * P (M) is t M Corresponding low temperature stiffness modulus, MPa; Step 3: Calculate the distances between the sampling points on the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar to obtain the distance matrix D, as shown in the following formula (6): （6）， In the formula, , 1≤n≤N, 1≤m≤M; Step 4: Find d in the distance matrix D mn The maximum value d max With the minimum value d min , set the initial target distance f=d min , and set the loop interval ; Step 5: Binarize the distance matrix D to obtain the binary matrix D', as shown in the following formula (7): （7）， In the formula, , 1≤n≤N, 1≤m≤M; Step 6. Find a path R in the binary matrix D' that satisfies the following conditions: The starting point of R is d' 11 , the end point is d' MN ; The path passes through point d' mn After that, the next passing point can only be d' (m+1)n , d' m(n+1) and d' (m+1)(n+1) The value of all points in path R must be 1; Step 7. If no path that meets the conditions is found in step 6, reset the target distance to f+r, and then loop through steps 5 and 6. The relationship between the number of loops x and the target distance is as follows: loop 1, target distance f; loop 2, target distance f+r; loop 3, target distance f+2r; ...; loop x, target distance f+(x-1)r; if the target distance f+(x-1)r of the path that meets the conditions is found in step 6 in the xth loop, proceed to the next step; Step 8. The Frechet distance F=f+(x-1)r of the main curve of the low-temperature stiffness modulus of the fully fused and partially fused recycled asphalt mortar.

Images