In-place thermal regeneration mixture based on intermittent blending strategy and targeted design method thereof

Abstract

The invention discloses an intermittent blending strategy-based hot in-place recycling mixture and a targeted design method thereof, and belongs to the technical field of hot in-place recycling technologies. Targeted matching of the regenerated mixture is achieved through the first step and the second step, that is, the adding amount of mineral aggregate of each particle size is calculated in a targeted mode according to mineral aggregate gradation of the regenerated mixture and mineral aggregate gradation of RAP; according to the present invention, the mineral aggregate with the corresponding particle size is precisely added in the targeted manner, such that the situation that the mineral aggregate is too fine does not occur in the asphalt mixture compared with the existing addition of the mineral aggregate with the whole particle size so as to ensure the compactness and the durability of the road surface, such that the road surface is not easily cracked and broken, the bearing capacity and the durability of the road surface are improved, and the flatness of the road surface is improved; a regenerant needing to be added into the regenerated mixture is adjusted through the fifth step and the sixth step, it is guaranteed that the recycled materials and the added materials can be evenly mixed, and therefore it is guaranteed that the regenerated mixture has good high-temperature stability, low-temperature stability and water stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ heat regeneration technology, and in particular relates to an in-situ heat regeneration mixture based on an intermittent blending strategy and a targeted design method thereof. Background Art

[0002] A large amount of waste materials are generated during the maintenance and renovation and expansion of asphalt pavement. Recycling these waste materials not only reduces environmental pollution but also reduces material consumption. It is an important means and urgent need to achieve sustainable development of highway transportation. Asphalt pavement recycling equipment should be used to mix a certain proportion of new aggregates, recycled binders, asphalt regeneration agents and other new materials with asphalt mixture recycled materials, inorganic recycled materials and other asphalt pavement recycled materials to obtain recycled mixtures. The materials are spread and compacted to form the pavement structure layer.

[0003] Existing recycled mixtures generally select a certain proportion of new aggregate and use this material as an additive; because the new aggregate is an asphalt mixture with a determined proportion; the additive contains minerals of all particle sizes, but RAP does not necessarily lose minerals of all particle sizes, and minerals of some particle sizes may not need to be added at all; in this case, using a determined proportion of new aggregate as an additive may cause the synthetic gradation of the recycled round material to be too fine after addition. In order to eliminate this deviation, it is necessary to adjust the amount of asphalt or the mixing ratio of the regeneration agent; this results in a very complicated process for forming the recycled mixture, and also causes the process of forming the recycled mixture to take too long and have low mixing efficiency.

[0004] In summary, the existing design scheme of recycled mixture has the problems of complicated process and low efficiency. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an in-situ hot recycled mixture based on an intermittent blending strategy and a targeted design method thereof in view of the deficiencies in the above-mentioned prior art. The design is novel and reasonable, the design time is short, the obtained recycled mixture has good laying effect, and is easy to promote and use.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A targeted design method for in-situ hot-recycling mixture based on discontinuous blending strategy includes the following steps:

[0008] Step 1: Obtain recycled asphalt mixture (RAP), conduct indoor tests on the RAP, and determine the asphalt dosage and mineral aggregate gradation of the RAP;

[0009] Step 2: Determine the mineral gradation of the recycled mixture according to the pavement performance requirements and the recycled thickness, and then calculate the addition ratio of minerals of different particle sizes in combination with the mineral gradation of RAP;

[0010] Step 3: Calculate the amount of asphalt to be added based on the asphalt content of RAP, the mineral aggregate gradation and the total asphalt amount of the recycled mixture;

[0011] Step 4: Determine the additive according to the calculated asphalt dosage and the addition ratio of each particle size mineral aggregate, and mix the additive with RAP to form a recycled mixture;

[0012] Step 5: Add regeneration agent according to the set regeneration agent blending ratio, and compare whether the calculated value and the test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent are consistent. If not, increase the regeneration agent blending ratio according to the set interval and add it again; if so, use the current regeneration agent blending ratio as the final regeneration agent blending ratio; the set regeneration agent blending ratio is expressed by the following formula:

[0013]

[0014] Among them, β is the mixing ratio of the regeneration agent, P b is the total asphalt content of the recycled mixture, P nb is the amount of asphalt to be added, K is the percentage, K∈[0%,20%];

[0015] Step six: conduct a leakage test on the recycled mixture to obtain the corresponding asphalt loss rate. When the leakage loss rate exceeds the set threshold, reduce the amount of asphalt to be added, repeat step four: conduct a leakage test on the recycled mixture until the corresponding asphalt loss rate is ≤ the set threshold, and use the corresponding recycled mixture as the final recycled mixture.

[0016] Furthermore, if the added asphalt is modified asphalt, the threshold is set to 0.2, and if the added asphalt is unmodified asphalt, the threshold is set to 0.1.

[0017] Furthermore, in step six, if the amount of asphalt to be added after reduction is less than the set asphalt amount threshold, the amount of asphalt to be added will no longer be reduced, but the amount of coarse material added in the mineral material will be increased and the amount of fine material added in the mineral material will be reduced. The asphalt amount threshold is set in the range of 30% to 40%.

[0018] Furthermore, in step three, the calculation formula for the amount of asphalt to be added is:

[0019]

[0020] Among them, P nb is the amount of asphalt to be added, P b is the total asphalt content of the recycled mixture, P ob is the asphalt content in RAP, and R is the blending ratio of RAP.

[0021] Furthermore, the test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent is obtained by measuring the viscosity test; the calculated value of the dynamic viscosity of the recycled mixture after adding the regeneration agent is calculated by the following formula:

[0022] lgη mix =(1-α-β)lgη old +(α+β)lgη new

[0023] Among them, η mix is the dynamic viscosity of the regenerated mixture at the first temperature after adding the regeneration agent, η old is the dynamic viscosity of RAP at the first temperature, η new is the dynamic viscosity of the additive at the first temperature after adding the regeneration agent, α is the proportion of added asphalt, and β is the blending proportion of the regeneration agent;

[0024] The calculation formula for the proportion of added asphalt is as follows:

[0025]

[0026] Among them, P nb is the amount of asphalt to be added, P b It is the total asphalt content of recycled mixture.

[0027] Furthermore, indoor tests employ extraction tests or combustion tests.

[0028] Furthermore, the method also includes: adding a first set amount and a second set amount of asphalt to the final recycled mixture determined in step six, respectively, to form a first recycled mixture and a second recycled mixture respectively; performing a Marshall test on the final recycled mixture, the first recycled mixture and the second recycled mixture, respectively, and selecting the recycled mixture with the highest stability in the Marshall test as the best recycled mixture; the second set amount is equal to twice the first set amount, and the range of the first set amount is 0.1% to 0.3%.

[0029] The present invention also discloses an in-situ hot-regenerated mixture based on an intermittent blending strategy, and the in-situ hot-regenerated mixture is prepared by using the above-mentioned targeted design method for in-situ hot-regenerated mixture based on an intermittent blending strategy.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The targeted design method of in-situ hot recycled mixture based on the discontinuous blending strategy realizes the targeted proportioning of the recycled mixture through steps one and two, that is, according to the mineral grading of the recycled mixture and the mineral grading of RAP, the addition amount of minerals of various particle sizes is targetedly calculated; by adding minerals of corresponding particle sizes in a targeted and precise manner, compared with the existing addition of minerals of all particle sizes, the asphalt mixture of the present application will not have the problem of too fine minerals, thereby ensuring the density and durability of the road surface, making the road surface less prone to cracking and fragmentation, improving the bearing capacity and durability of the road surface, and improving the flatness of the road surface; by step Step three calculates the additives for asphalt, and step four realizes the mixing of recycled materials and additives, which is convenient for calculation and adjustment in subsequent steps; then steps five and six are used to adjust the regeneration agent that needs to be added to the recycled mixture to ensure that the recycled material and the added material can be evenly mixed; specifically, the calculated value and the test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent are compared to determine the regeneration agent blending ratio, and the amount of regeneration agent and asphalt is adjusted through leakage test to improve the accuracy of the components of the recycled mixture; thereby ensuring that the recycled mixture has good high and low temperature stability and water stability.

[0032] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic flow chart of an embodiment of a method for targeted design of in-situ hot regeneration mixture based on a discontinuous blending strategy of the present invention;

[0034] Figure 2 It is a schematic representation of the mineral gradation data of RAP of an embodiment of the method for targeted design of in-situ hot regeneration mixture based on the discontinuous blending strategy of the present invention;

[0035] Figure 3 It is a schematic diagram of a line graph of mineral gradation data of RAP of an embodiment of a targeted design method for in-situ hot regeneration mixture based on a discontinuous blending strategy of the present invention;

[0036] Figure 4 It is a schematic diagram of the mineral material gradation data of the recycled mixture of the embodiment of the method for targeted design of in-situ hot recycled mixture based on the discontinuous blending strategy of the present invention;

[0037] Figure 5 It is a schematic diagram of a line graph of mineral material gradation data of a recycled mixture according to an embodiment of a targeted design method for an in-situ hot recycled mixture based on an intermittent blending strategy of the present invention;

[0038] Figure 6 A bar chart schematic diagram of three major indicators and dynamic viscosity of recycled mixtures according to an embodiment of the method for targeted design of in-situ hot recycled mixtures based on a discontinuous blending strategy of the present invention;

[0039] Figure 7 It is a schematic diagram of the gradation data of the additive mineral material in the embodiment of the targeted design method of the in-situ hot regeneration mixture based on the discontinuous blending strategy of the present invention;

[0040] Figure 8 It is a schematic diagram of synthetic gradation data of recycled mixture of an embodiment of the method for targeted design of in-situ hot recycled mixture based on discontinuous blending strategy of the present invention;

[0041] Fig. 9 This is a schematic diagram of the fatigue life of two recycled mixtures at different strain levels in an embodiment of the targeted design method for in-situ hot recycled mixture based on the discontinuous blending strategy of the present invention. DETAILED DESCRIPTION

[0042] Example of targeted design method for in-situ hot-regeneration mixture based on discontinuous blending strategy:

[0043] like Figure 1-9 As shown in FIG. 1 , the targeted design method of in-situ hot recycling mixture based on the discontinuous blending strategy includes the following steps:

[0044] Step 1: Obtain recycled asphalt mixture (RAP), conduct indoor tests on the RAP, and determine the asphalt dosage and mineral gradation of the RAP. The indoor test adopts an extraction test or a combustion test.

[0045] Specifically, RAP is an AC-16 asphalt concrete block cut from the original road surface of a highway. The corresponding original road surface AC-16 asphalt top layer. According to the JTGE20-2011 test procedure, the RAP is subjected to an extraction test to determine the asphalt dosage and mineral gradation of the RAP. The asphalt dosage of the RAP is 4.58%, and the mineral gradation of the RAP is as follows: Figure 2 and Figure 3 shown.

[0046] Depend on Figure 2 and Figure 3 It can be seen that the RAP gradation has exceeded the upper limit of the AC-16 gradation required by the project, and a certain proportion of new mineral materials should be added to fine-tune the RAP gradation. Further aggregate tests were conducted on the RAP, and the results of the aggregate tests are shown in Table 1; the three major index tests were conducted on the RAP, and the three major index data of the RAP are shown in Table 2. These tests were used to observe the current performance of the RAP.

[0047] Table 1

[0048]

[0049] Table 2

[0050]

[0051] Step 2: Determine the mineral gradation of the recycled mixture according to the pavement performance requirements and the recycled thickness, and then combine it with the mineral gradation of RAP to calculate the addition ratio of each particle size, that is, the mineral gradation of the additive. Optimize and adjust the synthetic gradation of the recycled mixture. The gradation design aims to improve the surface function of the pavement and enhance the anti-skid performance, and to supplement the coarse aggregate lost in the original pavement. Specifically, the corresponding data of the mineral gradation of RAP, the mineral gradation of the recycled mixture and the mineral gradation of the additive are as follows: Figure 4 and Figure 5 As shown. Figure 4 and Figure 5 It can be seen that: without adding 0-4mm and 4-7mm stone grades to the additives, only targeted addition of coarse aggregate and mineral powder, the synthetic gradation of the recycled mixture is effectively adjusted, and the design goal of restoring the anti-skid performance of the road surface can be achieved. This shows that the RAP gradation itself has replaced part of the fine aggregate. If a continuously graded new material containing a certain proportion of fine aggregate is added, the synthetic gradation of the recycled mixture may be too fine. In the synthetic gradation of the recycled mixture, RAP accounts for 80%, and new mineral materials account for 20%. The new mineral materials are composed of 16-22mm, 11-16mm, 7-11mm, and mineral powder, accounting for 2.0%, 13.0%, 3.0%, and 2.0% respectively. According to the conversion of pure new materials, the gradation of the added mineral materials is 16-22mm: 11-16mm: 7-11mm: mineral powder = 10%: 65%: 15%: 10%, and it is an intermittently graded mineral material. The specific mineral gradation is as follows Figure 7 shown.

[0052] Step 3: Calculate the amount of asphalt to be added based on the asphalt content of RAP, the aggregate gradation and the total asphalt content of the recycled mixture.

[0053] In step 3, the calculation formula for the amount of asphalt to be added is:

[0054]

[0055] Among them, P nb is the amount of asphalt to be added, P b is the total asphalt content of the recycled mixture, P ob is the asphalt content in RAP, and R is the blending ratio of RAP.

[0056] According to the characteristics of engineering materials, climate and traffic volume, the total asphalt consumption of AC-16 hot-in-place recycled mixture is estimated to be P b (%) is 4.4%. RAP asphalt content P ob is 4.58%, and the RAP content R is 80%, then the corresponding asphalt dosage P nb It is 0.74%.

[0057] Step 4: Determine the additive according to the calculated amount of asphalt to be added and the addition ratio of mineral aggregates of various particle sizes, and mix the additive with RAP to form a recycled mixture.

[0058] Step 5: Add regeneration agent according to the set regeneration agent blending ratio, and compare whether the calculated value and the test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent are consistent. If not, increase the regeneration agent blending ratio according to the set interval and add it again; if so, use the current regeneration agent blending ratio as the final regeneration agent blending ratio; the set regeneration agent blending ratio is expressed by the following formula:

[0059]

[0060] Among them, β is the mixing ratio of the regeneration agent, P b is the total asphalt content of the recycled mixture, P nb is the amount of asphalt to be added, K is the percentage, K∈[0%,20%].

[0061] Specifically, the asphalt used as the additive is SBSI-C modified asphalt, and the regeneration agent is HH-X type asphalt regeneration agent.

[0062] Specifically, the test value of the dynamic viscosity of the regenerated mixture after adding the regeneration agent is obtained by measuring the viscosity test. The calculated value of the dynamic viscosity of the regenerated mixture after adding the regeneration agent is calculated by the following formula:

[0063] lgη mix =(1-α-β)lgη old +(α+β)lgη new

[0064] Among them, η mix is the dynamic viscosity of the regenerated mixture at the first temperature after adding the regeneration agent, η o ld is the dynamic viscosity of RAP at the first temperature, η new is the dynamic viscosity of the additive at the first temperature after adding the regeneration agent, α is the proportion of added asphalt, and β is the blending proportion of the regeneration agent;

[0065] The calculation formula for the proportion of added asphalt is as follows:

[0066]

[0067] Among them, P nb is the amount of asphalt to be added, P b It is the total asphalt content of recycled mixture.

[0068] In this embodiment, the first temperature is 60°C. The values ​​of K are 0, 0.03, 0.05, and 0.07, and the corresponding values ​​of β are 0.00, 0.02, 0.04, and 0.06. The corresponding η of each β value is old , η new and η mix The calculated values ​​are shown in Table 3.

[0069] Table 3

[0070] Parameter Value <![CDATA[η o ld test value]]> <![CDATA[η new Test value]]> <![CDATA[η mix Calculated value]]> α＝0.17，β＝0 362.5 122.4 301.4 α＝0.17，β＝0.03 362.5 122.4 291.7 α＝0.17，β＝0.05 362.5 106.2 276.7 α＝0.17，β＝0.07 362.5 93.8 262.1

[0071] According to the test and calculation results in Table 5, as the proportion of regeneration agent increases, the 60℃ dynamic viscosity of the mixed asphalt gradually decreases, indicating that the addition of the regeneration agent effectively improves the fluidity of the old asphalt. Specifically, when the proportion of the regeneration agent is 0%, the 60℃ dynamic viscosity of the regenerated asphalt after adding asphalt is 301.4 (Pa·s), and when the proportion increases to 3%, 5%, and 7%, the corresponding dynamic viscosity decreases to 291.7 (Pa·s), 276.7 (Pa·s), and 262.1 (Pa·s), respectively. This trend shows that the addition of the regeneration agent restores the performance of the old asphalt to a certain extent, making it closer to the fluidity of the additive, thereby helping to improve the overall performance of the recycled mixture. The regeneration viscosity values ​​of the mixed asphalt are all in the range of 260 to 300 Pa·s, and with the increase in the amount of the regeneration agent, the change range of the viscosity value is relatively stable, without sudden changes or abnormal phenomena. It shows that the type and blending ratio of the selected regeneration agent are basically appropriate and can meet the actual needs of the project.

[0072] As the proportion of regeneration agent increases, the dynamic viscosity tends to be stable; therefore, there is no need to keep increasing the proportion of regeneration agent. Therefore, the specific value of the proportion of regeneration agent is determined by the dynamic viscosity calculation value of the recycled mixture. The three major indicators of the recycled asphalt and the dynamic viscosity at 60°C after adding asphalt and regeneration agent were measured. The specific measurement data are shown in Table 4 and Figure 6 shown.

[0073] Table 4

[0074]

[0075] In Table 4 and Figure 6In the results, with the increase of the amount of regeneration agent, the performance of the recycled mixture has changed significantly. Specifically, first, as the proportion of regeneration agent increases from 0% to 7%, the penetration value increases significantly from 28.4 (0.1mm) to 68.4 (0.1mm); the ductility value increases to more than 100cm, and the softening point decreases, but the decrease is not large and remains within a reasonable range. This shows that the addition of the regeneration agent does not significantly weaken the thermal stability of the asphalt, but achieves the regeneration effect by improving its fluidity and low-temperature performance. This shows that the addition of the regeneration agent effectively reduces the viscosity of the asphalt, improves its softness and fluidity, and is beneficial to the construction of the recycled mixture. Secondly, with the increase of the amount of regeneration agent, the 60°C dynamic viscosity gradually decreases, and the test value of the 60° viscosity test of the recycled asphalt when the amount of regeneration agent added is 5% is different from the calculated value η mix Basically close. That is to say, when the amount of regeneration agent added is 5% (as a percentage of the mass of the old asphalt), the performance of the regenerated asphalt meets the three major indicators and requirements of A-70 asphalt, so it is preliminarily determined that the amount of regeneration agent added is 5% (as a percentage of the mass of the old asphalt).

[0076] Step six: conduct a leakage test on the recycled mixture to obtain the corresponding asphalt loss rate. When the leakage loss rate exceeds the set threshold, reduce the amount of asphalt to be added, repeat step four: conduct a leakage test on the recycled mixture until the corresponding asphalt loss rate is ≤ the set threshold, and use the corresponding recycled mixture as the final recycled mixture.

[0077] Specifically, if the added asphalt is modified asphalt, the threshold is set to 0.2, and if the added asphalt is non-modified asphalt, the threshold is set to 0.1. In this embodiment, the added asphalt is modified asphalt, and the corresponding threshold is set to 0.2; according to step three, it can be known that the amount of asphalt to be added is 0.74%, and the amount of asphalt in the recycled mixture is calculated to be 20% of the added amount. The amount of asphalt in the recycled mixture is about 3.7%, so the leakage test is carried out according to the asphalt amount of the recycled mixture of 3.5%, 3.7%, and 3.9%. The specific leakage test results are shown in Table 5.

[0078] Table 5

[0079]

[0080] According to the results of the leakage test, the asphalt dosage of the recycled mixture is 3.5% and 3.7%, and the leakage loss meets the specification requirements. Therefore, 3.7% is used as the asphalt dosage of the recycled asphalt. Furthermore, when the asphalt dosage of the additive is 3.7%, the degree of asphalt precipitation is still relatively large; therefore, 3.5% can be preferably used as the asphalt dosage of the recycled mixture.

[0081] In order to further ensure the performance of the recycled mixture, in step 6, if the amount of asphalt to be added after the reduction is less than the set asphalt amount threshold, the amount of asphalt to be added will no longer be reduced, but the amount of coarse material added in the mineral material will be increased and the amount of fine material added in the mineral material will be reduced. The range of the asphalt amount threshold is set to 30% to 40%. In this embodiment, in step 6, when adjusting the recycled asphalt material, since the amount of asphalt to be added basically does not need to be adjusted, the step of adjusting the mineral material gradation is not performed. It can also be found that the means of discontinuous mineral material gradation makes the preparation of the recycled mixture not only high in precision, but also high in batching efficiency.

[0082] In order to improve the accuracy of the performance of the recycled mixture, the method also includes: respectively adding the first set amount and the second set amount of asphalt to the final recycled mixture determined in step 6, correspondingly forming the first recycled mixture and the second recycled mixture; respectively performing Marshall tests on the final recycled mixture, the first recycled mixture and the second recycled mixture, and selecting the recycled mixture with the highest stability in the Marshall test as the best recycled mixture. The second set amount is equal to 2 times the first set amount, and the range of the first set amount is 0.1% to 0.3%. In this embodiment, the first set amount is 0.2%. The Marshall test is performed according to the JTG E20-2011 test procedure. The test results are shown in Table 6.

[0083] Table 6

[0084]

[0085] According to the stability data in Table 6, it is not necessary to increase the amount of asphalt. The final recycled mixture in step 6 is the best recycled mixture.

[0086] In order to verify the performance of the recycled mixture, the recycled mixture obtained above was tested. Specifically, the ratio of RAP to additives in the recycled mixture was 1:4. The synthetic gradation of the hot recycled mixture was checked according to the additive ratio. The results are shown in Figure 8 By comparison Figure 4 and Figure 8 It can be found that the machine damage results are basically the same.

[0087] In addition, a comparative experiment was conducted to analyze the performance of the recycled mixture. The recycled mixture synthesized by the discontinuous grading method of this embodiment was recorded as type G recycled material; the recycled mixture was generated by the existing continuous grading method, recorded as type C recycled material. The two recycled mixtures were tested for high temperature stability, low temperature crack resistance, water stability, fatigue performance and water seepage, and the performance differences were analyzed and compared.

[0088] Type C recycled material is prepared according to the following data: RAP + 5% regeneration agent (calculated as a percentage of the mass of old asphalt) + 25% continuous AC-16 graded additive (calculated as a percentage of the mass of the old asphalt mixture, the oil-stone ratio is 4.2%, and the mineral aggregate grading is: 16-22mm: 11-16mm: 7-11mm: 4-7mm: 0-4mm: mineral powder = 10:29:15:11:30:5).

[0089] Type G recycled material is prepared according to the following data: RAP + 5% regeneration agent (calculated as a percentage of the mass of old asphalt) + 25% additive (calculated as a percentage of the mass of old asphalt mixture, oil-stone ratio 3.5%, 16-22mm: 11-16mm: 7-11mm: mineral powder = 10:65:15:10).

[0090] The two recycled mixtures were subjected to rutting test, low temperature bending test, water immersion Marshall test, freeze-thaw splitting test, water seepage test and fatigue performance test. The test results are shown in Table 7. The fatigue life of the two recycled mixtures at different strain levels is shown in Tables 8 and Fig. 9 .

[0091] Table 7

[0092] project C type recycled material G type recycled material Project Requirement Value Residual stability (%) 92.1 93.6 ＞90 Freeze-thaw splitting strength ratio (%) 88.7 91.2 ＞85 Dynamic stability (times / mm) 7625 8750 ≥5000 <![CDATA[Maximum flexural tensile strain ε B (με)]]> 2855.6 2828.4 ≥2800 Water permeability coefficient (ml / min) 12 36 ≤80

[0093] Table 8

[0094]

[0095] From Table 6, Table 7 and Fig. 9 The analysis shows that: first, both C-type recycled materials and G-type recycled materials meet or exceed the project requirements in various performance indicators. Specifically, except for the water permeability coefficient, G-type recycled materials perform better in high temperature stability, low temperature crack resistance, water stability and fatigue performance. Due to the addition of discontinuous grading new materials in G-type recycled materials, the gradation of the recycled mixture is reasonably optimized, the corresponding amount of regeneration agent is reliable, and the overall performance of the recycled mixture is better. Secondly, in terms of water permeability coefficient, C-type recycled materials perform better. It shows that C-type recycled materials have better performance in resisting water penetration, because its additives contain more fine aggregates, which help to block pores and reduce water penetration. Finally, in terms of fatigue life, at different strain levels, the fatigue life of G-type recycled materials is generally higher than that of C-type recycled materials. It shows that G-type recycled materials have better fatigue performance under repeated loads, and because the dense skeleton structure of G-type recycled materials is effectively restored, the long-term stability and durability of the recycled pavement are better.

[0096] Example of in-situ hot-regenerated mixture based on discontinuous blending strategy:

[0097] The hot-in-situ recycled mixture based on the discontinuous blending strategy is prepared by using the above-mentioned targeted design method for hot-in-situ recycled mixture based on the discontinuous blending strategy. This embodiment is implemented with reference to the above-mentioned embodiment of the targeted design method for hot-in-situ recycled mixture based on the discontinuous blending strategy, which will not be repeated here.

[0098] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A targeted design method for in-situ hot regeneration mixture based on discontinuous blending strategy, characterized by: The steps include: Step 1: Obtain recycled asphalt mixture (RAP), conduct indoor tests on the RAP, and determine the asphalt dosage and mineral aggregate gradation of the RAP; Step 2: Determine the mineral gradation of the recycled mixture according to the pavement performance requirements and the recycled thickness, and then calculate the addition ratio of minerals of different particle sizes in combination with the mineral gradation of RAP; Step 3: Calculate the amount of asphalt to be added based on the asphalt content of RAP, the mineral aggregate gradation and the total asphalt amount of the recycled mixture; Step 4: Determine the additive according to the calculated asphalt dosage and the addition ratio of each particle size mineral aggregate, and mix the additive with RAP to form a recycled mixture; Step 5: Add regeneration agent according to the set regeneration agent blending ratio, and compare whether the calculated value and the test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent are consistent. If not, increase the regeneration agent blending ratio according to the set interval and add it again; if so, use the current regeneration agent blending ratio as the final regeneration agent blending ratio; the set regeneration agent blending ratio is expressed by the following formula: Among them, β is the mixing ratio of the regeneration agent, P b is the total asphalt content of the recycled mixture, P nb is the amount of asphalt to be added, K is the percentage, K∈[0%,20%]; Step six: conduct a leakage test on the recycled mixture to obtain the corresponding asphalt loss rate. When the leakage loss rate exceeds the set threshold, reduce the amount of asphalt to be added, repeat step four: conduct a leakage test on the recycled mixture until the corresponding asphalt loss rate is ≤ the set threshold, and use the corresponding recycled mixture as the final recycled mixture.

2. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: If the added asphalt is modified asphalt, the threshold is set to 0.2; if the added asphalt is unmodified asphalt, the threshold is set to 0.

1.

3. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: In step six, if the amount of asphalt to be added after reduction is less than the set asphalt amount threshold, the amount of asphalt to be added will no longer be reduced, but the amount of coarse material added in the mineral material will be increased and the amount of fine material added in the mineral material will be reduced. The asphalt amount threshold is set in the range of 30% to 40%.

4. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: In step three, the amount of asphalt to be added is calculated as follows: Among them, P nb is the amount of asphalt to be added, P b is the total asphalt content of the recycled mixture, P ob is the asphalt content in RAP, and R is the blending ratio of RAP.

5. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: The test value of the dynamic viscosity of the recycled mixture after adding the regeneration agent is obtained by measuring the viscosity test; the calculated value of the dynamic viscosity of the recycled mixture after adding the regeneration agent is calculated by the following formula: lg mix =(1-α-β)lgη old +(α+β)lgη new Among them, η mix is the dynamic viscosity of the regenerated mixture at the first temperature after adding the regeneration agent, η o ld is the dynamic viscosity of RAP at the first temperature, η new is the dynamic viscosity of the additive at the first temperature after adding the regeneration agent, α is the proportion of added asphalt, and β is the blending proportion of the regeneration agent; The calculation formula for the proportion of added asphalt is as follows: Among them, P nb is the amount of asphalt to be added, P b It is the total asphalt content of recycled mixture.

6. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: The indoor test adopts an extraction test or a combustion test.

7. The method for targeted design of in-situ hot regeneration mixture based on discontinuous blending strategy according to claim 1, characterized in that: The method also includes: adding a first set amount and a second set amount of asphalt to the final recycled mixture determined in step six, respectively, to form a first recycled mixture and a second recycled mixture respectively; performing Marshall tests on the final recycled mixture, the first recycled mixture and the second recycled mixture, respectively, and selecting the recycled mixture with the highest stability in the Marshall test as the best recycled mixture; the second set amount is equal to twice the first set amount, and the range of the first set amount is 0.1% to 0.3%.

8. In-situ hot-regenerated mixture based on discontinuous blending strategy, characterized by: The in-situ hot recycled mixture is prepared by using the targeted design method for in-situ hot recycled mixture based on the discontinuous blending strategy described in any one of claims 1 to 7.

Images