A design method for the mix ratio of remixed hot-in-place recycled asphalt mixture

Abstract

The present invention discloses a method for designing the proportion of a remixed hot-regenerated asphalt mixture, comprising: sampling a construction road surface to obtain old asphalt recycling material; determining the proportion of a new aggregate by determining the proportion of a regenerating agent. nb Mixing ratio R with old asphalt recycled material ob , determine the optimal asphalt dosage P of recycled asphalt mixture b ; Determine the asphalt dosage P of the new asphalt mixture nb , determine the optimal new asphalt dosage K, and finally determine the mix ratio of the recycled asphalt mixture. The mixed type in-situ hot recycled asphalt mixture mix ratio design method of the present invention is more detailed, complete and operable, and the mix ratio design of the recycled asphalt mixture is clearer, thereby determining the specific amount of each material in the recycled asphalt mixture, improving the construction efficiency and construction quality, and is easy to promote and implement.

Description

Technical Field

[0001] The invention belongs to the technical field of maintenance and repair of old asphalt pavement, and specifically relates to a method for designing the mix proportion of a remixed hot-in-situ regenerated asphalt mixture. Background Art

[0002] In-situ hot regeneration technology uses special in-situ hot regeneration equipment to heat and mill the asphalt pavement, add a certain amount of new asphalt, new asphalt mixture, regeneration agent, etc. on-site, and through hot mixing, paving, rolling and other processes, it can regenerate the old asphalt concrete pavement within a certain depth range on the surface at one time. Among them, the multi-mix in-situ hot regeneration technology is to heat and mill the old asphalt pavement, add a certain amount of regeneration agent, new asphalt and new asphalt mixture on-site, and then mix, pave and compact to form it in a hot state. The mix ratio design of the asphalt mixture for in-situ hot regeneration of asphalt pavement is one of the core of in-situ hot regeneration construction. During construction, the mix ratio of old asphalt recycled materials, regeneration agents, new asphalt and new asphalt mixture needs to be determined before construction operations can be carried out. The old asphalt recycled materials, regeneration agents, new asphalt and new asphalt mixture constitute the recycled asphalt mixture.

[0003] In the existing technology, the asphalt mixture mix design methods in the remix type in-situ hot recycling technology are mostly general and not detailed. There are many misunderstandings and ambiguities in actual operation. The amount of various materials in the recycled asphalt mixture is often determined based on experience, which is not easy to implement and promote. This affects the performance of the recycled asphalt mixture and the quality of the asphalt pavement to a certain extent. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for designing the mix ratio of a remixed hot-in-situ recycled asphalt mixture. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] A method for designing the proportion of a remixed hot-in-place recycled asphalt mixture, comprising:

[0006] Step 10, sampling the construction road surface to obtain old asphalt recycling material;

[0007] Step 20: Determine the old aggregate gradation range and the old asphalt content P based on the old asphalt recycled material. ob and aging performance index; the old aggregate gradation range is the gradation of the old aggregate of the old asphalt recycling material, and the aging performance index is the performance index of the old asphalt of the old asphalt recycling material;

[0008] Step 30, determining the blending ratio of the regeneration agent based on the initial asphalt grade of the road to be constructed, the regeneration agent, the aging performance index and the old asphalt;

[0009] Step 40: Determine the new aggregate blending ratio R based on the old aggregate gradation range and the target gradation type. nb Mixing ratio R with old asphalt recycled material ob ; Wherein, the target gradation type is the same as the initial gradation type of the construction road surface or a gradation type coarser than the initial gradation type;

[0010] Step 50: Determine the optimal asphalt dosage P of the recycled asphalt mixture based on the pavement information of the construction pavement. b ; Among them, the recycled asphalt mixture includes old asphalt recycling material, regeneration agent, new asphalt and new asphalt mixture;

[0011] Step 60, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb , pavement information and target gradation type, determine the asphalt content P of the new asphalt mixture nb ;

[0012] Step 70, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb and asphalt dosage P nb , determine the optimal new asphalt dosage K;

[0013] Step 80, based on the new aggregate blending ratio R nb , the proportion of old asphalt recycling material R ob , regeneration agent blending ratio, optimal asphalt dosage P b , Asphalt dosage P nb And the optimal new asphalt dosage K, determine the mix ratio of recycled asphalt mixture.

[0014] In one embodiment of the present invention, step 10 includes:

[0015] Step 101, dividing the construction road surface into a plurality of sub-sections based on the road surface structure and historical maintenance records of the construction road surface;

[0016] Step 102: determine the location of a sampling point for each sub-section based on a random sampling method, and sample the location to obtain old asphalt recycling material.

[0017] In one embodiment of the present invention, step 20 includes:

[0018] Step 201, dividing the old asphalt recycling material into a combustion sample, an extraction sample and a test sample;

[0019] Step 202, using a combustion test method or an extraction test method to process the combustion sample to obtain old aggregate and determine the old asphalt content;

[0020] Step 203, based on the old aggregate, determine the gradation range of the old aggregate;

[0021] Step 204, using an extraction test method to process the extracted sample to obtain old asphalt;

[0022] Step 205, determining an aging performance index based on the old asphalt.

[0023] In one embodiment of the present invention, step 30 includes:

[0024] Step 301, determining the grade of old asphalt based on the aging performance index;

[0025] Step 302, determining a target grade of the recycled asphalt sample based on the initial asphalt grade of the construction road surface;

[0026] Step 303, based on the old asphalt grade and the target grade, a plurality of regeneration agents in different preset proportions are added to the old asphalt by a trial mixing method to obtain a plurality of regenerated asphalt samples;

[0027] Step 304, detecting the performance indicators of a plurality of regenerated asphalt samples, and determining the preset proportion of the regenerating agent corresponding to the regenerated asphalt samples meeting the performance indicators of the target grade as the regenerating agent blending proportion.

[0028] In one embodiment of the present invention, step 50 includes:

[0029] Step 501, determining the estimated optimal asphalt dosage of at least five recycled asphalt mixtures based on the pavement information of the construction pavement;

[0030] Step 502, performing a Marshall test based on the asphalt-stone ratios and test samples corresponding to at least five estimated optimal asphalt dosages, to obtain a first test result;

[0031] Step 503: Determine the optimal asphalt dosage P based on the Marshall test standard value of the target gradation type and the first test result. b .

[0032] In one embodiment of the present invention, step 60 includes:

[0033] Step 601, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb Determine the calculated value of asphalt dosage P' nb ;in,

[0034]

[0035] Step 602: Determine the estimated asphalt usage P″ of the new asphalt mixture based on the pavement information and the target gradation type. nb ;

[0036] Step 603: Calculate the asphalt usage value P' nb and estimated asphalt consumption P″ nb The minimum value of asphalt dosage P nb .

[0037] In one embodiment of the present invention, step 70 includes:

[0038] Step 701, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb and asphalt dosage P nb Determine the optimal new asphalt dosage calculation value K'; where,

[0039]

[0040] Step 702, determining at least five optimal new asphalt usage estimates based on the optimal new asphalt usage calculation value K';

[0041] Step 703, performing a Marshall test based on the asphalt-stone ratios and test samples corresponding to at least five optimal new asphalt dosage estimates, to obtain a second test result;

[0042] Step 704, determining the optimal new asphalt dosage K based on the Marshall test standard value of the target gradation type and the second test result.

[0043] Beneficial effects of the present invention:

[0044] The present invention collects representative reclaimed asphalt pavement (RAP) for extraction and screening to obtain the old asphalt content and old aggregate particle composition in the reclaimed asphalt asphalt, which are used as the basis for the target mix design. According to the aging degree of the old asphalt and the asphalt performance requirements, a suitable regeneration agent is selected, and the regeneration agent blending ratio is determined by experiment. The gradation and blending ratio of the added new aggregate are determined by comprehensively considering the regeneration thickness and the gradation range of the old aggregate, the oil-stone ratio of the old asphalt, the target gradation range, and the utilization ratio of RAP. The gradation of the new aggregate should meet the engineering design requirements of the target gradation type to ensure the uniformity of the new asphalt mixture. According to the target gradation type, the proportion of each level of new aggregate is formulated. The synthetic gradation of the new aggregate and the old aggregate in the RAP is used as a mineral material in the remixed regenerated asphalt mixture for mineral material gradation design to determine the blending ratio of the new aggregate.

[0045] The method for designing the proportion of the remixed hot-in-situ recycled asphalt mixture of the present invention is more refined and perfect, and the determination of the proportion of the recycled asphalt mixture is more clear, so that the specific amount of each material in the recycled asphalt mixture can be determined, the construction efficiency and construction quality are improved, and it is easy to promote and implement. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for designing a mix ratio of a multiple-mix hot-in-situ recycled asphalt mixture provided by an embodiment of the present invention;

[0047] Figure 2 It is a gradation curve diagram of recycled asphalt old asphalt pavement material (RAP) provided by an embodiment of the present invention;

[0048] Figure 3 is a gradation curve diagram of a new asphalt mixture (AC-16) provided in an embodiment of the present invention;

[0049] Figure 4 is a gradation curve diagram of a hot-regenerated asphalt mixture synthesized from 20% new asphalt mixture provided by an embodiment of the present invention;

[0050] Figure 5-1 is a stability curve diagram of the Marshall test results of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0051] Figure 5-2 is a void ratio curve diagram of the Marshall test result of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0052] Figure 5-3 is a maximum theoretical relative density curve of the Marshall test results of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0053] Figure 5-4 is a saturation curve diagram of the Marshall test results of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0054] Figure 5-5 is a flow value curve diagram of the Marshall test result of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0055] Figure 5-6 is a mineral void ratio curve diagram of the Marshall test result of the hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0056] Figure 6-1 is another stability curve diagram of the Marshall test results of hot-regenerated asphalt mixture provided by an embodiment of the present invention;

[0057] Figure 6-2 is another void ratio curve diagram of Marshall test results of hot regenerated asphalt mixture provided by an embodiment of the present invention;

[0058] Figure 6-3 is another maximum theoretical relative density curve of the Marshall test results of hot-regenerated asphalt mixture provided by an embodiment of the present invention;

[0059] Figure 6-4 is another saturation curve diagram of Marshall test results of hot-regenerated asphalt mixture provided by an embodiment of the present invention;

[0060] Figure 6-5 Another flow value curve diagram of the Marshall test result of hot-regenerated asphalt mixture provided by an embodiment of the present invention;

[0061] Figure 6-6 This is another mineral void ratio curve diagram of the Marshall test results of hot-regenerated asphalt mixture provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0063] Embodiment 1

[0064] See also Figure 1 , a method for designing the proportion of a remixed hot-in-place recycled asphalt mixture, comprising:

[0065] Step 10, sampling the construction road surface to obtain old asphalt recycling material.

[0066] Specifically, step 10 specifically includes: step 101 and step 102.

[0067] Step 101: Divide the construction road surface into a plurality of sub-sections based on the road surface structure and historical maintenance records of the construction road surface.

[0068] When dividing the sub-sections, the road condition can be analyzed based on the road structure and historical maintenance records, such as the degree of damage to the road surface, and then sections with the same or similar road conditions can be considered as a sub-section. The construction road surface is the road surface that needs to be hot-regenerated in situ.

[0069] Step 102: determine the location of a sampling point for each sub-section based on a random sampling method, and sample the location to obtain old asphalt recycling material.

[0070] Among them, when determining the location of the sampling point, according to the random sampling method in the "Highway Roadbed and Pavement Field Test Regulations" (JTG3450), one sampling point should be taken for each lane of each sub-section, and the mixture within the regeneration depth range should be cut by mechanical cutting. The cut mixture is also the old asphalt recycled material (Reclaimed Asphalt Pavement, RAP). The regeneration depth refers to the scarification depth set by the regeneration equipment, that is, the difference between the old pavement elevation and the bottom elevation of the regeneration layer.

[0071] Step 20: Determine the old aggregate gradation range and the old asphalt content P based on the old asphalt recycled material. ob And aging performance index; the aging performance index is the performance index of the old asphalt of the old asphalt recycling material.

[0072] Specifically, step 20 includes: step 201-step 205.

[0073] Step 201, dividing the old asphalt recycling material into combustion samples, extraction samples and test samples.

[0074] Step 202, using a combustion test method or an extraction test method to process the combustion sample to obtain old aggregate and determine the old asphalt content, that is, the old asphalt-to-rock ratio can be obtained.

[0075] Step 203, based on the old aggregate, determine the gradation range of the old aggregate. The gradation range of the old aggregate of the old asphalt recycled material can be determined by screening the old aggregate.

[0076] Step 204, using an extraction test method to process the extracted sample to obtain old asphalt.

[0077] Step 205, based on the old asphalt, determine the aging performance index. The aging performance index includes three major indicators: penetration, softening point and ductility. The old asphalt can be divided into multiple samples, a part of which can be taken for performance testing experiments to determine the aging performance index. A part of the old asphalt can also be taken as samples for subsequent regeneration agent experiments.

[0078] Step 30, determining the regeneration agent blending ratio of the regeneration agent based on the initial asphalt grade of the construction road surface, the regeneration agent, the aging performance index and the old asphalt.

[0079] Specifically, step 30 includes: step 301-step 304.

[0080] Step 301, determine the grade of the old asphalt based on the aging performance index. For example, according to the needle penetration, it can be determined that the needle penetration of the old asphalt meets the needle penetration standard of No. 50 asphalt, so the grade of the old asphalt is determined to be No. 50.

[0081] Step 302, determine the target grade of the recycled asphalt sample based on the initial asphalt grade of the construction road surface. The grade of asphalt used in the initial design of the construction road surface is the initial asphalt grade, such as No. 90 asphalt, and the target grade is the initial asphalt grade reduced by one grade, such as No. A-70 asphalt.

[0082] Step 303, based on the old asphalt grade and the target grade, a plurality of regeneration agents of different preset proportions are added to the old asphalt by a trial mixing method to obtain a plurality of regenerated asphalt samples. The sample of the regeneration agent experiment of the old asphalt is divided into a plurality of sub-samples. After the regeneration agent is added to the old asphalt, the performance can be restored to a certain extent. In a feasible implementation, the regeneration agent is added to each sub-sample of the sample of the regeneration agent experiment of the old asphalt according to the proportion of an arithmetic progression. For example, the proportion of the regeneration agent is 5%, 7% and 9%. The three regeneration agents of the three preset proportions (in terms of percentage to the old asphalt) are added to the three sub-samples of the sample of the regeneration agent experiment of the old asphalt to obtain three kinds of regenerated asphalt samples.

[0083] Step 304, detect the performance indicators of multiple regenerated asphalt samples, and determine the preset proportion of the regenerating agent corresponding to the regenerated asphalt samples that meet the performance indicators of the target grade as the regenerating agent blending ratio. In this step, multiple regenerated asphalt samples are tested for performance indicators of needle penetration, softening point and ductility, and curves of the three indicators are drawn. By using the interpolation method, the preset proportion of the regenerating agent of the regenerated asphalt samples that meet the target grade is determined as the regenerating agent blending ratio. For example, if the performance indicators of the regenerated asphalt obtained by mixing 9% of the regenerating agent into the old asphalt meet the performance indicators of A-70 asphalt, then 9% is determined as the regenerating agent blending ratio.

[0084] Step 40, based on the old aggregate gradation range and the target gradation type, determine the new aggregate blending ratio and the old asphalt recycled material blending ratio; wherein the target gradation type is the same as the initial gradation type of the construction road surface or a gradation type coarser than the initial gradation type.

[0085] Specifically, step 40 includes: step 401-step 405.

[0086] Step 401, determine the target gradation type according to the initial gradation type of the construction road surface, the target gradation type is the gradation type of the recycled asphalt mixture to be used when performing in-situ hot construction, and the target gradation type is the same as the initial gradation type of the construction road surface or a gradation type coarser than the initial gradation type. The initial gradation type is AC-13, and the target gradation type can be AC-13 or AC-16.

[0087] Among them, when determining the target gradation type and the gradation range corresponding to the target gradation type, the target gradation type and the gradation range of the target gradation type can also be determined by comprehensively considering information such as traffic load level, project nature, traffic type information, material type, historical usage information records of the same or similar projects, etc.

[0088] Step 402, the gradation of the new aggregate to be added and the blending ratio of the old asphalt recycled material should be determined according to the recycled thickness and the gradation range of the old aggregate, the target gradation type, the old asphalt content, etc. The gradation of the new aggregate should meet the gradation range of the target gradation type to ensure the uniformity of the new asphalt mixture.

[0089] Step 403, determining the proportion of each level of new aggregate according to the new aggregate gradation and the target gradation type.

[0090] Step 404: The composite gradation of the old aggregate and the new aggregate in the RAP is used as an aggregate in the recycled asphalt mixture to perform aggregate gradation design, and the new aggregate blending ratio R is determined. nb Mixing ratio R with old asphalt recycled material ob .

[0091] Step 405: when the composite gradation of the old aggregate and the new aggregate in the RAP cannot satisfy the gradation range corresponding to the target gradation type, the proportion of each grade of the new aggregate is readjusted, and steps 403 and 404 are repeated.

[0092] Step 50: Determine the optimal asphalt dosage P of the recycled asphalt mixture based on the pavement information of the construction pavement. b ; Among them, the recycled asphalt mixture includes old asphalt recycling material, regeneration agent, new asphalt and new asphalt mixture. The old asphalt recycling material includes old asphalt and old aggregate, and the new asphalt mixture includes new aggregate and new asphalt. The optimal asphalt dosage P b It is the mass percentage of the sum of new asphalt and old asphalt in the recycled asphalt mixture.

[0093] Specifically, step 50 includes: step 501-step 503.

[0094] Step 501, based on the pavement information of the construction road surface, determine the estimated optimal asphalt dosage of at least five recycled asphalt mixtures.

[0095] In this step, the estimated asphalt consumption value P′ can be estimated based on the highway grade, climate information, road traffic type information and historical engineering construction information records. b , then P′ b , P′ b ±0.3, P′ b The five asphalt dosages of ±0.6 are used as five estimated optimal asphalt dosages. Of course, more than five estimated optimal asphalt dosages can also be estimated.

[0096] Step 502, based on the five asphalt-stone ratios corresponding to the five estimated optimal asphalt dosages and the test samples, a Marshall test is performed to obtain a first test result. The test sample can be divided into two parts, namely a first test sample and a second test sample, and the first test sample is divided into five sub-samples, and the second test sample is divided into five sub-samples. The Marshall test is performed according to the method in the "Testing Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20).

[0097] Among them, the Marshall specimen preparation process is:

[0098] 5.1. Place the first test sample in an oven and heat it to 140°C. The heating time should not exceed 2 hours to prevent further aging of the first test sample.

[0099] 5.2. Place new aggregate and new asphalt in an oven and heat them separately: the new aggregate is heated to 190°C, the heating temperature should be 150°C to 160°C when the new asphalt is base asphalt, and the heating temperature should be 160°C to 170°C when the new asphalt is modified asphalt;

[0100] 5.3. Add a subsample of the heated first test sample, a regenerator, new aggregate, and new asphalt into a preheated mixing pot in sequence and mix them evenly to obtain a test piece; wherein the amount of the regenerator added is the regenerator blending ratio determined in step 30, the amount of the new aggregate is the new aggregate blending ratio determined in step 40, and the amount of the new asphalt is the proportion of the new asphalt in the estimated optimal asphalt dosage.

[0101] 5.4. Pour the mixture required for one specimen into the preheated test mold. The molding method is the same as that of hot mix asphalt mixture.

[0102] 5.5. After testing the formed specimens, draw a relationship diagram with the oil-stone ratio as the horizontal axis and the mineral gap ratio, maximum theoretical relative density, void ratio, gross volume density, stability, flow value and saturation as the vertical axis.

[0103] 5.6. Carry out five Marshall tests according to steps 5.1-5.5, and obtain the test results of the five Marshall tests as the first test results.

[0104] Step 503: Determine the optimal asphalt dosage P based on the Marshall test standard value of the target gradation type and the first test result. b .

[0105] Among them, since there is no peak value in density, the asphalt-stone ratio corresponding to the standard value of porosity is a, so the initial value of the optimal asphalt-stone ratio is OAC1=a;

[0106] The range of asphalt-to-stone ratio (OAC) of each index that meets the Marshall test standard value of the target gradation type min ~OAC max ;

[0107] OAC2=(OAC min +OAC max ) / 2;

[0108] Therefore, the optimal asphalt-to-stone ratio is (OAC1+OAC2) / 2, so the optimal asphalt dosage P can be converted. b .

[0109] Step 60, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb , pavement information and target gradation type, determine the asphalt content P of the new asphalt mixture nb .

[0110] Specifically, step 60 includes: step 601-step 603.

[0111] Step 601, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb Determine the calculated value of asphalt dosage P' nb ;in,

[0112]

[0113] Among them, P' nb Should be greater than the minimum asphalt dosage P mb (The best asphalt-stone ratio for the local design gradation type of the project is -0.6). Minimum asphalt dosage P mb Please refer to Table 1.

[0114] Gradation type <![CDATA[P mb (%)]]> AC-25 3.5 AC-20 3.7 AC-16 4.0 AC-13 4.2 AC-10 4.5

[0115] Table 1

[0116] Step 602: Determine the estimated asphalt usage P″ of the new asphalt mixture based on the pavement information and the target gradation type. nb ;

[0117] In this step, the estimated asphalt usage P″ of the new asphalt mixture can be determined based on the target gradation type, highway grade, climate information, road traffic type information, and historical engineering construction information records. nb .

[0118] Step 603, calculate the asphalt usage value P' nb and estimated asphalt consumption P″ nb The minimum value of asphalt dosage P nb That is, P nb =min{P′ nb , P″ nb}.

[0119] Step 70, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb and asphalt dosage P nb , determine the optimal new asphalt dosage K.

[0120] Specifically, step 70 includes: step 701-step 704.

[0121] Step 701, based on the optimal asphalt dosage P b , old asphalt content P ob , the proportion of old asphalt recycling material R ob , new aggregate mixing ratio R nb and asphalt dosage P nb Determine the optimal new asphalt dosage calculation value K' (mass percentage of RAP); where,

[0122]

[0123] Step 702: Determine at least five optimal new asphalt dosage estimates based on the optimal new asphalt dosage calculated value K'. The five optimal new asphalt dosage estimates are K', K'±0.2 and K'±0.4, and Marshall specimens are formed using the five oil-stone ratios corresponding to the five optimal new asphalt dosage estimates.

[0124] Step 703: Perform a Marshall test based on the five asphalt-to-stone ratios and test samples corresponding to the five best new asphalt usage estimates to obtain a second test result. The Marshall test is performed according to the Marshall test method in the Technical Specifications for Asphalt Pavement Construction of Highway Engineering (JTGF40).

[0125] Among them, the Marshall specimen preparation process is:

[0126] 7.1. Place the second test sample in an oven and heat it to 140°C.

[0127] 7.2. Heat the new aggregate and new asphalt in an oven: the new aggregate should be heated to 190°C, the heating temperature should be 150-160°C when the new asphalt is base asphalt, and the heating temperature should be 160-170°C when the new asphalt is modified asphalt;

[0128] 7.3. According to the requirements of the preparation of Marshall specimens of asphalt mixtures in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20), according to the asphalt dosage P nb Add new asphalt to mix new asphalt mixture, and place the mixed new asphalt mixture in an oven at 150-160℃ for insulation;

[0129] 7.4. Add the heated second test sample and regeneration agent, and the new asphalt with the best estimated amount of new asphalt into the preheated mixing pot and mix evenly, then add the new asphalt mixture in 7.3 and mix evenly to obtain a test piece. The amount of regeneration agent added is the regeneration agent blending ratio determined in step 30.

[0130] 7.5. Pour the mixture required for one specimen into the preheated test mold. The molding method is the same as that of hot mix asphalt mixture.

[0131] 7.6. After testing the formed specimens, draw a relationship diagram with the oil-stone ratio as the horizontal axis and the mineral gap ratio, maximum theoretical relative density, void ratio, gross volume density, stability, flow value and saturation as the vertical axis.

[0132] 7.7. Carry out five Marshall tests according to steps 7.1-5.6, and obtain the test results of the five Marshall tests as the second test results.

[0133] Step 704, determining the optimal new asphalt dosage K based on the Marshall test standard value of the target gradation type and the second test result.

[0134] Among them, since there is no peak value in density, the oil-stone ratio corresponding to the standard value of void ratio is a, so the initial value of the optimal asphalt dosage OAC1=a;

[0135] The range of asphalt-to-stone ratio (OAC) of each index that meets the Marshall test standard value of the target gradation type min ~OAC max ;

[0136] OAC2=(OAC min +OAC max ) / 2;

[0137] Therefore, the optimal new asphalt to stone ratio is (OAC1+OAC2) / 2. Therefore, the optimal new asphalt dosage K can be obtained by converting the asphalt to stone ratio.

[0138] Step 80, based on the new aggregate blending ratio R nb , the proportion of old asphalt recycling material R ob , regeneration agent blending ratio, optimal asphalt dosage P b , Asphalt dosage P nb And the optimal new asphalt dosage K, determine the mix ratio of recycled asphalt mixture.

[0139] In the present invention, the mix design inspection should be carried out according to the method of the current "Technical Specification for Highway Asphalt Pavement Construction" (JTG F40).

[0140] The test section tests the performance of the recycled asphalt mixture, and the performance of the hot-recycled asphalt mixture in situ should be tested in the test section. The main test items include: technical indicators of on-site recycled asphalt, Marshall stability, gradation of recycled mixture, rutting dynamic stability, Marshall residual stability after immersion, freeze-thaw splitting strength ratio, low-temperature failure strain, etc., to test whether the above indicators meet the design requirements.

[0141] Embodiment 2

[0142] The mix design method of hot-regenerated asphalt mixture for asphalt pavement is one of the cores of hot-regeneration construction. Due to the different climate, topography, pavement conditions, construction and maintenance conditions of the original pavement, the design of the recycled asphalt mixture has certain regional characteristics. In principle, the type of hot-regenerated asphalt mixture for in-situ regeneration should be consistent with the type of asphalt mixture for the upper layer of the original pavement, or according to the gradation of the asphalt mixture for the upper layer of the original pavement, traffic load level, engineering properties, traffic type information, material variety and other information, after analysis, the type of hot-regenerated asphalt mixture for in-situ regeneration is allowed to be one type coarser than the type of asphalt mixture for the upper layer of the original pavement. The type of newly added asphalt should be consistent with the type of asphalt in RAP, or according to the information of traffic load level, engineering properties, traffic type information, material variety and other information, after analysis, modified asphalt can be used as the newly added asphalt.

[0143] Collect representative old recycled asphalt material (RAP) for extraction and screening to obtain the asphalt content and the composition of the old material mineral particles as the basis for the target mix design. According to the aging degree of the old asphalt and the asphalt performance requirements, select the appropriate regeneration agent, and test to determine the mixing ratio of the regeneration agent. According to the selected target gradation range and the utilization ratio of old recycled asphalt material (RAP), determine the proportion of new aggregates in each grade. The gradation composition, asphalt content and asphalt properties of old recycled asphalt material (RAP) have a great influence on the regenerated asphalt pavement, and must be determined by multiple tests in strict accordance with the requirements.

[0144] The mineral gradation, technical requirements and performance inspection of the hot-mix asphalt mixture in situ shall comply with the technical requirements of the corresponding hot-mix asphalt mixture type in JTG F40. In addition, in this embodiment, the mix ratio design method of the hot-mix asphalt mixture in situ is specifically described in combination with the current status of the asphalt pavement structure in Shaanxi. The design principle of the new asphalt mixture mix ratio in the remixed hot-mixed asphalt mixture in situ shall be in accordance with JTG F40. A certain proportion of new asphalt mixture should be added to the remixed recycled asphalt mixture to improve the mineral gradation of the original pavement. The mixing ratio of the new asphalt mixture should be controlled within 30% of the RAP mass. 1. In this embodiment, the remixed hot-mixed in-situ regeneration project of a national highway section is taken as an example to verify the mix ratio design method of the hot-mixed asphalt mixture in situ.

[0145] A section of a national highway is an asphalt concrete road. After years of operation, the road surface has been damaged to varying degrees due to the natural climate conditions and vehicle load along the route. According to the Highway Asphalt Pavement Maintenance Design Specification (JTG5142), sections with a pavement damage index PCI of "medium" should adopt a functional repair plan. This time, a 4cm pavement plan of a remixed in-situ hot-recycled asphalt concrete top layer with some new AC-16 SBS modified asphalt mixture is proposed.

[0146] 2.1 Material Description

[0147] 2.1.1 Recycled Asphalt (RAP)

[0148] Recycled asphalt material (RAP) is AC-16 asphalt concrete slabs cut from the original road surface.

[0149] 2.1.2 Regeneration agent

[0150] The regeneration agent used is asphalt regeneration agent purchased from the material market.

[0151] 2.1.3 Aggregates

[0152] The mix design of hot recycled materials uses aggregates of 9.5-16mm, 4.75-9.5mm, 2.36-4.75mm, and 0-2.36mm.

[0153] 2.1.4 Mineral powder

[0154] The mix design of hot recycled materials uses mineral powder provided by the construction unit.

[0155] 2.2 Sampling and evaluation of recycled asphalt

[0156] 2.2.1 Grading of recycled asphalt and amount of recycled asphalt

[0157] According to the T0727-1993 (JTG E20) test procedure, the asphalt content and gradation of the old asphalt recycled material were determined by combustion. The old asphalt content of the old asphalt recycled material was 4.60% (oil-to-stone ratio 4.82%). The gradation analysis results are shown in Table 2 and Figure 2 .

[0158] Table 2 Recycled Asphalt (RAP) Grading and AC-16 Grading Range Requirements

[0159]

[0160] Note: This gradation range refers to the AC-16 gradation range requirements in the "Technical Guidelines for Rutting Prevention and Control of Asphalt Pavement on Expressways in Shaanxi Province".

[0161] 2.2.2 Recycling of old asphalt and dosage of regeneration agent

[0162] The old asphalt was extracted and recycled according to the T0727-1993 (JTG E20) test procedure. The three major indexes of the recycled old asphalt were tested, and the test results are shown in Table 3.

[0163] 2.3 Hot recycled mixture design

[0164] 2.3.1 Determination of the amount of regeneration agent added

[0165] Different doses of regeneration agent (measured as a percentage of the old asphalt) were added to the recycled old asphalt, and the degree of asphalt performance recovery at various doses was determined through the three major index tests of asphalt binder. The test results are shown in Table 3.

[0166] Table 3 Asphalt properties after adding different doses of rejuvenating agent

[0167]

[0168] The initial asphalt grade is No. 90. When the regeneration agent mixing ratio is 9% (as a percentage of the old asphalt), its asphalt performance meets the three major indicators and requirements of A-70 asphalt. Therefore, it is preliminarily determined that the regeneration agent mixing ratio of the pavement is 9% (as a percentage of the old asphalt).

[0169] 2.3.2 Determination of the mix ratio of new asphalt mixture

[0170] The original road surface had serious coarse aggregate loss and the overall structure was too fine, so the design used AC-16 asphalt mixture to fine-tune the original grading. The screening results of the mineral materials used in the new asphalt mixture are shown in Table 4.

[0171] Table 4 Ore screening results

[0172] Screen diameter(mm) 9.5-16mm 4.75-9.5mm 2.36-4.75mm 0-2.36mm Mineral powder 19 100.0 100.0 100.0 100.0 100.0 16 93.9 100.0 100.0 100.0 100.0 13.2 62.5 99.8 100.0 100.0 100.0 9.5 12.9 93.9 100.0 100.0 100.0 4.75 1.4 5.1 82.1 98.8 100.0 2.36 1.0 1.0 0.9 87.6 100.0 1.18 0.8 0.9 0.6 68.3 100.0 0.6 0.6 0.9 0.5 57.7 100.0 0.3 0.4 0.9 0.5 41.9 100.0 0.15 0.3 0.9 0.5 24.9 95.4 0.075 0.2 0.9 0.5 11.3 85.9

[0173] The above materials are used to design the asphalt aggregate gradation curve. After trial mixing, the AC-16 asphalt mixture ratio is: 9.5-16mm: 4.75-9.5mm: 2.36-4.75mm: 0-2.36mm: mineral powder = 45:19:6:27:3. The gradation curve is detailed in Figure 3 The synthetic gradation of the new asphalt mixture is shown in Table 5.

[0174] Table 5 New AC-16 asphalt mixture gradation composition and requirements

[0175]

[0176] Note: This gradation range refers to the AC-16 gradation range requirements in the "Technical Guidelines for Rutting Prevention and Control of Asphalt Pavement on Expressways in Shaanxi Province".

[0177] Taking into account the road deformation, rutting and similar project engineering record information, it is preliminarily determined that the addition ratio of the new asphalt mixture is about 20% of the old asphalt mixture, that is, the content of the new asphalt mixture and the old asphalt recycled material in the synthesized hot recycled asphalt mixture is 17% and 83% respectively. The new aggregate blending ratio is calculated based on the addition ratio of the new asphalt mixture, the content of the new asphalt mixture and the old asphalt mixture in the synthesized hot recycled asphalt mixture, etc. The synthetic gradation of the hot recycled asphalt mixture obtained according to this addition ratio is shown in Table 6, and the gradation curve is shown in Figure 4 .

[0178] Table 6 Hot recycled asphalt mixture gradation composition and requirements

[0179]

[0180] Note: The gradation range refers to the gradation range requirements of "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40).

[0181] 2.3.3 Optimal asphalt dosage P for remixed recycled asphalt mixture b Determination

[0182] According to the highway grade, climate information, road traffic type information and historical engineering construction information records of a certain national road section, the estimated asphalt content of the recycled asphalt mixture is 4.4% (oil-to-stone ratio 4.6%), and the asphalt is added according to the oil-to-stone ratio plus or minus 0.3 and plus or minus 0.6, which is 4.0%, 4.3%, 4.6%, 4.9%, and 5.2%. According to the T0727-1993 (JTG E20) test procedure, the Marshall new asphalt content test of the hot recycled mixture was carried out. The test results are shown in Tables 7 and Figure 5-1 to Figure 5-6 The optimal asphalt-to-stone ratio of the remixed recycled asphalt mixture is 4.6%, that is, the optimal asphalt dosage P b =4.4%. The Marshall test results for the optimum asphalt dosage are shown in Table 8.

[0183] Table 7 Marshall test results of hot recycled mixture

[0184]

[0185] Table 8 Marshall test results for optimal asphalt dosage

[0186]

[0187] 2.3.4 Asphalt dosage of new asphalt mixture P nb Determination

[0188] According to the formula 1 in Example 1, the calculated value P' of asphalt dosage in the new asphalt mixture is obtained nb =4.3, referring to the best asphalt dosage experience record value of AC-16 asphalt mixture in the past, the asphalt dosage of the new asphalt mixture P is finally determined. nb =4.3.

[0189] 2.3.5 Determination of the optimal new asphalt dosage K

[0190] According to the formula 2 in Example 1, the optimal new asphalt dosage K'=0.3% is obtained. The newly added SBS modified asphalt dosage is based on the mass of RAP and is added at 0.1%, 0.3%, 0.5%, and 0.7% of the oil-stone ratio. The Marshall new asphalt dosage test of the hot recycled mixture was carried out according to the T0727-1993 (JTG E20) test procedure. The test results are shown in Table 9 and Figure 6-1 to Figure 6-6 Considering that the Marshall volume index of adding 0.1% new asphalt is close to the design target, according to the AC-16 Marshall mix design requirements and the hot mix asphalt mix design method in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40), the optimal new asphalt dosage (asphalt-stone ratio) K is 0.1%. Considering the various variability factors in actual construction, the new asphalt dosage can be increased by 0-0.2%. The Marshall test results at the optimal asphalt-stone ratio are shown in Table 10.

[0191] Table 9 Marshall test results of hot recycled mixture

[0192]

[0193] Table 10 Marshall test results for optimal asphalt dosage

[0194]

[0195] 3. Road performance test of remixed hot recycled mixture

[0196] The hot recycled asphalt mixture was prepared according to the following composition: old asphalt recycled material + 9% regeneration agent (calculated as a percentage of the old asphalt mass) + 20% new asphalt mixture (calculated as a percentage of the old asphalt recycled material, the asphalt dosage of the new asphalt mixture is 4.3%) + 0.1% SBS modified asphalt (calculated as a percentage of the RAP mass), and the asphalt mixture was subjected to rutting test, low temperature bending test, immersion Marshall test, and freeze-thaw splitting test, respectively, to test the high and low temperature stability and water stability of the recycled asphalt mixture at the optimal asphalt content. The test results are shown in Table 11.

[0197] Table 11 Test results of road performance of hot recycled asphalt mixture

[0198] project Recycled asphalt mixture Specification requirements in conclusion Residual stability (%) 87.3 ＞80 qualified Freeze-thaw splitting strength ratio (%) 82.5 ＞75 qualified Dynamic stability (times / mm) 6517 ≥1000 qualified <![CDATA[Maximum flexural tensile strain ε B (με)]]> 2310.4 ≥2000 qualified

[0199] 4. Conclusion

[0200] It can be seen from the above test results that the road performance of the designed hot-recycled asphalt mixture mix meets the Marshall mix design technical requirements and mix design inspection requirements of ordinary AC-16 asphalt concrete. The mix design result is: old asphalt recycled material + 9% regeneration agent (calculated as a percentage of the mass of the old asphalt) + 20% new asphalt mixture (calculated as a percentage of the mass of the old asphalt recycled material, the asphalt content of the new asphalt mixture is 4.3%) + 0.1% SBS modified asphalt (calculated as a percentage of the mass of RAP).

[0201] Due to the variations in the actual uniformity of pavement construction and the variations in maintenance and repair materials, the on-site hot regeneration construction process, regeneration agent, and amount of new asphalt mixture should be finally determined through a test section. During the construction process, appropriate adjustments can be made to the amount of regeneration agent and modified asphalt added based on actual site conditions.

[0202] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0203] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0204] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0205] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0206] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0207] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for designing the proportion of a multiple-mix hot-in-situ recycled asphalt mixture, characterized in that: include: Step 10, sampling the construction road surface to obtain old asphalt recycling material; Step 20, based on the old asphalt recycling material, determine the old aggregate gradation range, the old asphalt content P ob and aging performance index; the aging performance index is a performance index of the old asphalt of the old asphalt recycling material; the old asphalt recycling material is divided into a combustion sample, an extraction sample and a test sample; Step 30, determining a regeneration agent blending ratio of the regeneration agent based on the initial asphalt grade of the construction road surface, the regeneration agent, the aging performance index and the old asphalt; Step 40: Determine the new aggregate blending ratio R based on the old aggregate gradation range and the target gradation type. nb Mixing ratio R with old asphalt recycled material ob ; Wherein, the target gradation type is the same as the initial gradation type of the construction road surface or a gradation type coarser than the initial gradation type; Step 50: Determine the optimal asphalt dosage P of the recycled asphalt mixture based on the pavement information of the construction pavement. b ; comprising: step 501, based on the pavement information of the construction pavement, determining at least five estimated optimal asphalt amounts of the recycled asphalt mixture; step 502, based on the oil-stone ratios corresponding to the at least five estimated optimal asphalt amounts and the test samples, performing a Marshall test to obtain a first test result; step 503, based on the Marshall test standard value of the target gradation type and the first test result, determining the optimal asphalt amount P b ; Wherein, the regenerated asphalt mixture includes the old asphalt recycling material, the regeneration agent, new asphalt and new asphalt mixture; Step 60, based on the optimal asphalt dosage P b , the old asphalt content P ob , the blending ratio of the old asphalt recycling material R ob , the new aggregate blending ratio R nb , the pavement information and the target gradation type, determine the asphalt dosage P of the new asphalt mixture nb ; comprising: step 601, based on the optimal asphalt dosage P b , the old asphalt content P ob , the blending ratio of the old asphalt recycling material R ob and the new aggregate blending ratio R nb Determine the calculated asphalt dosage value P' nb ,in, Step 602: Determine the estimated asphalt usage P' of the new asphalt mixture based on the pavement information and the target gradation type. n ' b ; Step 603, the asphalt dosage calculation value P' nb and estimated asphalt consumption P' n ' b The minimum value of the asphalt dosage P is determined as nb ; Step 70, based on the optimal asphalt dosage P b , the old asphalt content P ob , the blending ratio of the old asphalt recycling material R ob , the new aggregate blending ratio R nb and the asphalt dosage P nb , determine the optimal new asphalt dosage K; comprising: step 701, based on the optimal asphalt dosage P b , the old asphalt content P ob , the blending ratio of the old asphalt recycling material R ob , the new aggregate blending ratio R nb and the asphalt dosage P nb Determine the optimal new asphalt dosage calculation value K', where: Step 702, determining at least five optimal new asphalt dosage estimates based on the optimal new asphalt dosage calculated value K'; Step 703, performing a Marshall test based on the oil-stone ratios and the test samples corresponding to the at least five optimal new asphalt dosage estimates, to obtain a second test result; Step 704, determining the optimal new asphalt dosage K based on the Marshall test standard value of the target gradation type and the second test result; Step 80, based on the new aggregate blending ratio R nb , the blending ratio of the old asphalt recycling material R ob , the mixing ratio of the regeneration agent, the optimal asphalt dosage P b , the asphalt dosage P nb and the optimal new asphalt dosage K, determine the mix ratio of the recycled asphalt mixture.

2. The design method according to claim 1, characterized in that: The step 10 comprises: Step 101, dividing the construction road surface into a plurality of sub-sections based on the road surface structure and historical maintenance records of the construction road surface; Step 102: determining the location of a sampling point for each sub-section based on a random sampling method, and sampling at the location to obtain the old asphalt recycling material.

3. The design method according to claim 2, characterized in that: The step 20 comprises: Step 201, using a combustion test method or an extraction test method to process the combustion sample to obtain the old aggregate and determine the old asphalt content; Step 202, based on the old aggregate, determining the gradation range of the old aggregate; Step 203, using an extraction experiment method to process the extracted sample to obtain the old asphalt; Step 204, determining the aging performance index based on the old asphalt.

4. The design method according to claim 3, characterized in that: The step 30 comprises: Step 301, determining the grade of old asphalt based on the aging performance index; Step 302, determining a target grade of the recycled asphalt sample based on the initial asphalt grade of the construction road surface; Step 303, based on the old asphalt grade and the target grade, a plurality of regeneration agents in different preset proportions are added to the old asphalt by a trial mixing method to obtain a plurality of regenerated asphalt samples; Step 304, detecting the performance indicators of the plurality of the regenerated asphalt samples, and determining the preset proportion of the regeneration agent corresponding to the regenerated asphalt samples that meet the performance indicators of the target number as the regeneration agent blending proportion.

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