CN117865558A - Mix proportion design method of framework compact type plant-mixed hot recycled asphalt mixture - Google Patents
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- CN117865558A CN117865558A CN202311799530.2A CN202311799530A CN117865558A CN 117865558 A CN117865558 A CN 117865558A CN 202311799530 A CN202311799530 A CN 202311799530A CN 117865558 A CN117865558 A CN 117865558A
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- 239000010426 asphalt Substances 0.000 title claims abstract description 97
- 239000000203 mixture Substances 0.000 title claims abstract description 95
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000013461 design Methods 0.000 title claims abstract description 19
- 238000002156 mixing Methods 0.000 claims abstract description 38
- 238000012216 screening Methods 0.000 claims abstract description 29
- 238000012360 testing method Methods 0.000 claims abstract description 28
- 239000002994 raw material Substances 0.000 claims abstract description 21
- 238000004364 calculation method Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 14
- 238000000605 extraction Methods 0.000 claims abstract description 12
- 239000000945 filler Substances 0.000 claims abstract description 12
- 238000011049 filling Methods 0.000 claims abstract description 9
- 239000011148 porous material Substances 0.000 claims abstract description 8
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 28
- 239000011707 mineral Substances 0.000 claims description 28
- 239000000843 powder Substances 0.000 claims description 25
- 238000010276 construction Methods 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000010521 absorption reaction Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 239000004568 cement Substances 0.000 abstract description 5
- 238000009827 uniform distribution Methods 0.000 abstract description 3
- 238000001514 detection method Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- 235000019738 Limestone Nutrition 0.000 description 2
- 239000006028 limestone Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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Abstract
The invention discloses a mix proportion design method of a framework compact type plant-mixed hot recycled asphalt mixture, which relates to the technical field of road engineering and comprises the following steps: selecting raw materials; the raw materials comprise newly added aggregate and RAP, the performance of the newly added aggregate is detected, and the RAP is subjected to extraction screening test; the method comprises the steps that the mixture adopts SAC framework compact grading, raw materials are divided into framework aggregates and filling materials in the mixing proportion design, the volume ratio of the framework aggregates to the filling materials is 70:30, then coarse aggregate blending proportion calculation with the diameter of more than 4.75mm is carried out according to a SAC framework aggregate grading key sieve pore passing rate calculation method, a new aggregate screening result and a RAP screening result, and the blending proportion of RAP in the raw materials is consistent with the grading proportion of coarse aggregates in the RAP in the calculation; and (3) carrying out a Marshall test on the hot recycled asphalt mixture in the plant, and adjusting the filler according to the actually measured porosity. The invention can realize the uniform distribution of asphalt cement in RAP and improve the high-temperature rutting resistance of the mixture.
Description
Technical Field
The invention relates to the technical field of road engineering, in particular to a mix proportion design method of a framework compact type plant-mixed hot recycled asphalt mixture.
Background
The hot mix plant recycled asphalt mixture technology is a mature pavement recycling technology at present, the high-temperature performance of the hot recycled asphalt mixture is obviously improved compared with that of a common asphalt mixture, and the low-temperature performance and the water damage resistance can meet the technical requirements of specifications.
However, variability and performance instability of RAP (waste asphalt mixture) materials often affect the blending amount of the RAP (waste asphalt mixture) materials in the production and application processes of the Chinese plant-mix hot recycled asphalt mixture technology. The Chinese RAP blending amount is generally 20% -30%, and the high blending amount of the hot recycled asphalt mixture in the factory with the blending amount of more than 30% -40% can be rarely applied to the road surface in a large area, and mainly takes the test road section as the main part, so that the effective recycling rate of the RAP is greatly limited. In the design process of the mixing proportion of the high-mixing-amount plant-mixed hot recycled asphalt mixture, the RAP is supposed to be fully melted and dispersed after being mixed with the new aggregate, however, the research shows that the stirring time of 60s cannot achieve the effect of fully melted and dispersed, so that part of RAP asphalt cement is dispersed in the mixture in a bulk shape. The hot recycled asphalt mixture is generally applied to the lower layer of the pavement, and the grading adopts AC continuous grading, and belongs to a suspension compaction type. The suspension compact type asphalt mixture has poor extrusion subdivision effect on RAP asphalt cement clusters in the rolling forming process, so that the high-mixing-amount plant-mixed hot recycled asphalt mixture has poor grading stability, the detection process shows small stability, large flow value, large rutting deformation within 45min of a rutting test and the like, and the suspension compact type grading is not suitable for the high-mixing-amount recycled asphalt mixture.
Disclosure of Invention
Aiming at the defects of the grading design of the conventional high-mixing-amount plant-mixed hot-recycled asphalt mixture and the development requirement of low carbon and environment protection of asphalt pavement, the invention provides a mixing proportion design method of a framework compact plant-mixed hot-recycled asphalt mixture.
The invention relates to a mix proportion design method of a framework compact type plant-mixed hot recycled asphalt mixture, which solves the technical problems and adopts the following technical scheme:
a mix proportion design method of a framework compact type plant-mixed hot recycled asphalt mixture comprises the following steps:
s1, selecting raw materials of a hot mix plant reclaimed asphalt mixture, wherein the raw materials comprise newly added aggregate and RAP; detecting the performance of the newly added aggregate to determine that the newly added aggregate meets the current specification requirements; carrying out an extraction screening test on the RAP to determine the asphalt content, the grain composition and the coarse aggregate ratio of more than 4.75mm and the apparent density of the aggregate in the RAP;
s2, adopting SAC skeleton compact grading to divide raw materials into skeleton aggregates and filling materials in SAC mixing proportion design, wherein the volume ratio of the skeleton aggregates to the filling materials is 70:30, and then carrying out coarse aggregate mixing proportion calculation of more than 4.75mm according to SAC skeleton aggregate grading key sieve pore passing rate calculation method, new aggregate screening result and RAP screening result, wherein the mixing proportion of RAP in the raw materials is consistent with the grading proportion of coarse aggregates in RAP during calculation;
s3, carrying out a Marshall test on the hot mix plant recycled asphalt mixture, and adjusting the filler according to the actually measured porosity.
Optionally, the related newly added aggregates comprise coarse aggregates, fine aggregates, mineral powder and asphalt;
the newly added aggregate comprises four specifications of 10-20mm, 10-15mm, 5-10mm and 0-3mm, wherein more than 4.75mm is coarse aggregate and less than 4.75mm is fine aggregate, the performance of the coarse aggregate and the fine aggregate in the newly added aggregate is detected, and all indexes detected meet the technical requirements in JTG F40-2004 technical Specification for highway asphalt pavement construction; then screening coarse aggregates and fine aggregates in the newly added aggregates;
the asphalt in the newly added aggregate is SBS modified asphalt, the SBS modified asphalt is detected, and all indexes detected meet the technical requirements in JTG F40-2004 technical Specification for construction of Highway asphalt pavement;
and detecting mineral powder in the newly added aggregate, wherein each index meets the technical requirements of JTG F40-2004 technical Specification for highway asphalt pavement construction.
Further optionally, the RAP involved comprises coarse aggregate, fine aggregate, mineral powder, asphalt;
the RAP is milled and broken by impact and then divided into two specifications of 0-10mm and 10-20mm, the extraction screening test is carried out on the RAP, the asphalt content in the RAP is determined, coarse and fine aggregate classification is carried out on the old aggregate after the extraction screening test, wherein more than 4.75mm is coarse aggregate, less than 4.75mm is fine aggregate, and the apparent relative density, the water absorption rate and the duty ratio of the old aggregate under the specification of 0-10mm and the specification of 10-20mm of the RAP are detected and determined after classification, wherein the old aggregate is 0-4.75mm, the old aggregate is 4.75-9.5mm and the old aggregate is 9.5-19 mm.
Further optionally, the skeleton aggregate includes coarse aggregate in newly added aggregate and coarse aggregate in RAP, and the filler includes fine aggregate and mineral powder in newly added aggregate and fine aggregate and mineral powder in RAP;
calculating the passing rate P of critical sieve holes of SAC skeleton aggregate grading di The formula is as follows:
P di ＝A(d i /D max ) B ，
wherein: p (P) di For the throughput of the mesh size di,%; d (D) max Is the maximum particle size of the mineral aggregate,mm; di is a certain sieve pore size, mm; A. b is a coefficient respectively;
according to the calculation result of the SAC skeleton aggregate grading key sieve aperture passing rate, the newly added aggregate screening result and the RAP screening result, the coarse aggregate blending proportion of more than 4.75mm is calculated, and the blending proportion of RAP in raw materials is synthesized according to the grading proportion of RAP coarse and fine aggregates under two specifications of RAP0-10mm and RAP10-20mm during calculation.
Further alternatively, the RAP blending proportion is converted into the volume proportion by considering that the density of the RAP aggregate is different from that of the new aggregate, and the asphalt content is determined through past engineering experience;
the calculation formula of the aggregate equivalent volume replacement in RAP is as follows:
wherein: m is m RAP Total RAP ratio,%; m is m RAPsi Is of the specification s in the mixing proportion i The mass ratio of the old aggregate of (3) is percent; ρ asi Is of specification s i Apparent density g/cm of newly added aggregate 3 ；ρ aRAPsi For specification s in RAP i Apparent density g/cm of old aggregate 3 ；ω RAPsi For specification s in RAP i Old aggregate ratio,%;
the mass ratio of the grading of the mixture after the equal volume replacement is calculated as follows:
wherein: m is m tsi Is of specification s i The new added aggregate mass of (1) is replaced by the new added aggregate mass; m is m RAPsi For specification s in RAP i Is the mass ratio,%; m is m si Is converted into 100% of post-specification s i The new aggregate mass ratio,%; m's' RAPsi In the converted RAP of 100%The mass ratio of the old aggregate of the specification si,%; m is m k The weight percentage of the mineral powder is percent.
Further alternatively, after the grading is determined, a Marshall test is performed according to engineering experience,
when the test results of the grading porosity, the stability and the flow value meet the related requirements of JTG F40-2004 (highway asphalt pavement construction technical Specification), evaluating the high-temperature performance, the low-temperature performance and the water damage resistance of the hot mix plant recycled asphalt mixture;
when the test result of grading porosity exceeds the related requirement of JTG F40-2004 technical Specification for highway asphalt pavement construction, on the premise of ensuring that the volume ratio of skeleton aggregate to filler is unchanged 70:30, the ratio of mineral powder, fine aggregate or asphalt in the filler is increased or reduced to carry out grading adjustment of the mixture, or the fluctuation of initial asphalt content is +/-0.3%, so as to carry out the determination of the optimal asphalt content of the mixture.
Optionally, the RAP is incorporated in the raw material in an amount of not less than 30%.
The mix proportion design method of the framework compact type plant-mixed hot recycled asphalt mixture has the beneficial effects that compared with the prior art:
(1) The invention can realize the uniform distribution of asphalt cement in RAP, so that the stability of the mixture is higher, and the high-temperature rut resistance of the mixture is improved;
(2) The invention is suitable for the grading design of the mixture composed of aggregates with different regions and different specifications, improves the rationality and pertinence of the design of the mixing proportion of the high-mixing-amount hot-recycled asphalt mixture, can improve the mixing amount and grading control of RAP compared with the traditional design method of the mixing proportion of the asphalt mixture, and has remarkable social benefit and market popularization value.
Drawings
FIG. 1 is a graph showing the gradation of the mixing ratio after the equal volume replacement of SAC-20 in the first embodiment of the present invention;
FIG. 2 is a longitudinal section view of a SAC-20 specimen according to a first embodiment of the present invention.
Detailed Description
In order to make the technical scheme, the technical problems to be solved and the technical effects of the invention more clear, the technical scheme of the invention is clearly and completely described below by combining specific embodiments.
Embodiment one:
the embodiment provides a mix proportion design method of a framework compact type plant-mixed hot recycled asphalt mixture, which comprises the following steps:
s1, selecting raw materials of a hot mix plant recycled asphalt mixture, wherein the raw materials comprise newly added aggregates and RAP, the newly added aggregates comprise coarse aggregates, fine aggregates, mineral powder and asphalt, and the RAP comprises the coarse aggregates, the fine aggregates, the mineral powder and the asphalt.
Taking 40% of RAP as an example.
In this embodiment, the new coarse aggregate and fine aggregate are typical limestone in the region of water and Yishui in Shandong province, and include four specifications of 10-20mm, 10-15mm, 5-10mm and 0-3mm, wherein more than 4.75mm is coarse aggregate, and less than 4.75mm is fine aggregate, and the performance of the coarse aggregate and fine aggregate in the new aggregate is detected, and the detection results are shown in table 1 below.
TABLE 1 Performance test results of coarse and Fine aggregates in freshly added aggregates
As can be seen from Table 1, the detection indexes meet the technical requirements in JTG F40-2004 technical Specification for Highway asphalt pavement construction.
Coarse aggregate and fine aggregate in the newly added aggregate were then screened, and the screening results are shown in table 2 below.
TABLE 2 screening results of coarse and Fine aggregates in freshly added aggregates
| Screen mesh | 26.5 | 19 | 16 | 13.2 | 9.5 | 4.75 | 2.36 | 1.18 | 0.6 | 0.3 | 0.15 | 0.075 |
| Coarse aggregate 10-20mm | 100 | 89.8 | 2.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 |
| Coarse aggregate 10-15mm | 100 | 100 | 96.3 | 60.2 | 1.2 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 |
| Coarse aggregate 5-10mm | 100 | 100 | 100 | 100 | 93.4 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 |
| Fine aggregate 0-3mm | 100 | 100 | 100 | 100 | 100 | 100 | 67.8 | 46.1 | 25.2 | 11.5 | 5.6 | 3.2 |
The new asphalt is SBS modified asphalt produced by Shandong high-speed materials, the SBS modified asphalt is detected, and the detection result of the SBS modified asphalt is shown in table 3.
TABLE 3 SBS modified asphalt detection results
As can be seen from Table 3, the detection indexes meet the technical requirements in JTG F40-2004 technical Specification for Highway asphalt pavement construction.
The newly added mineral powder adopts qualified mineral powder processed by the typical limestone of Yishui, and the detection result is shown in the following table 4.
TABLE 4 mineral powder detection results
In this example, the RAP (old pavement asphalt milling material) is subjected to an extraction screening test, the RAP is from the upper surface layer of basalt SMA-13 of a major maintenance project of a highway in Qingdao region, the RAP is divided into two specifications of 0-10mm and 10-20mm in consideration of secondary crushing grading stability of the RAP, and the RAP is subjected to an extraction screening test, and the specific test detection results are shown in the following table 5.
TABLE 5 RAP extraction screening test results
Coarse and fine aggregate classification is carried out on the old aggregate after the extraction screening test, wherein the coarse aggregate is more than 4.75mm, and the fine aggregate is less than 4.75 mm.
Further measurements were made to determine the apparent relative densities, water absorption, and the ratios of the old aggregate 0-4.75mm, the old aggregate 4.75-9.5mm, and the old aggregate 9.5-19mm after classification, and at the RAP0-10mm and RAP10-20mm specifications, the measurements are shown in table 6 below.
TABLE 6 aggregate classification Density results after RAP extraction screening
S2, adopting SAC framework compact grading to divide raw materials into framework aggregates and filling materials in SAC mixing proportion design, wherein the framework aggregates comprise coarse aggregates in newly added aggregates and coarse aggregates in RAP, and the filling materials comprise fine aggregates in newly added aggregates, mineral powder and fine aggregates and mineral powder in RAP, wherein the volume ratio of the framework aggregates to the filling materials is 70:30.
Calculating the passing rate P of critical sieve holes of SAC skeleton aggregate grading di The formula is as follows:
P di ＝A(d i /D max ) B ，
wherein: p (P) di For the throughput of the mesh size di,%; d (D) max The maximum grain diameter of the mineral aggregate is mm; di is a certain sieve pore size, mm; A. b is the coefficient respectively.
Referring to tables 5 and 6, coarse aggregate blending proportion calculation of more than 4.75mm is carried out according to the calculation result of the SAC skeleton aggregate grading key sieve aperture passing rate and the newly added aggregate screening result and the RAP screening result; when calculated, 40% of the RAP in the raw materials is synthesized according to the grading proportion of the RAP coarse-fine aggregate under the two specifications of RAP0-10mm and RAP10-20 mm.
According to the selected coarse aggregate, fine aggregate, RAP, mineral powder screening result and RAP coarse and fine blending proportion, the proportion of the newly added coarse aggregate, fine aggregate and mineral powder is adjusted by referring to the critical sieve pore passing rate, so that the synthetic grading passing rate is as close to the critical sieve pore as possible to calculate the passing rate.
In the embodiment, the RAP mixing proportion is converted into the volume proportion by considering that the densities of RAP aggregates and new aggregates are different, and the asphalt content is determined through past engineering experience;
the calculation formula of the aggregate equivalent volume replacement in RAP is as follows:
wherein: m is m RAP Total RAP ratio,%; m is m RAPsi Is of the specification s in the mixing proportion i The mass ratio of the old aggregate of (3) is percent; ρ asi Is of specification s i Apparent density g/cm of newly added aggregate 3 ；ρ aRAPsi For specification s in RAP i Apparent density g/cm of old aggregate 3 ；ω RAPsi For specification s in RAP i Old aggregate ratio,%;
the mass ratio of the grading of the mixture after the equal volume replacement is calculated as follows:
wherein: m is m tsi Is of specification s i The new added aggregate mass of (1) is replaced by the new added aggregate mass; m is m RAPsi For specification s in RAP i Is the mass ratio,%; m is m si Is converted into 100% of post-specification s i The new aggregate mass ratio,%; m's' RAPsi The mass ratio of the old aggregate of specification si in the RAP after conversion of 100 percent is shown as percent; m is m k The weight percentage of the mineral powder is percent.
Taking the SAC grading type as an example, the equal volume pre-replacement mix ratio of newly added aggregate and RAP in the raw material is shown in table 7 below.
TABLE 7 SAC-20 equal volume Pre-substitution mix ratio
The grading premise is that the density difference of new and old aggregates is small, the mass ratio is approximately equal to the volume ratio, and the apparent relative density of aggregates in RAP is large, so that the mass ratio of various materials after equal volume replacement needs to be calculated. The calculated mass ratios after isovolumetric substitution are shown in table 8 below.
TABLE 8 mixing ratio after isovolumetric substitution of SAC-20
S3, carrying out a Marshall test on the hot mix plant recycled asphalt mixture, and adjusting the filler according to the actually measured porosity.
In the course of the marshall test, the test pieces,
(i) When the test results of the grading porosity, the stability and the flow value meet the related requirements of JTG F40-2004 (Highway asphalt pavement construction technical Specification), as shown in Table 9, the high-temperature performance, the low-temperature performance and the water damage resistance of the hot mix plant recycled asphalt mixture are further evaluated;
table 9 SAC-20 asphalt mixture Performance results
(ii) When the test result of grading porosity exceeds the related requirement of JTG F40-2004 technical Specification for highway asphalt pavement construction, on the premise of ensuring that the volume ratio of skeleton aggregate to filler is unchanged 70:30, the ratio of mineral powder, fine aggregate or asphalt in the filler is increased or reduced to carry out grading adjustment of the mixture, or the fluctuation of initial asphalt content is +/-0.3%, so as to carry out the determination of the optimal asphalt content of the mixture.
In summary, by adopting the mix proportion design method of the framework compact type hot mix plant recycled asphalt mixture, the uniform distribution of asphalt cement in RAP can be realized, the stability of the mixture is higher, and the high-temperature rutting resistance of the mixture is improved.
The foregoing has outlined rather broadly the principles and embodiments of the present invention in order that the detailed description of the invention may be better understood. Based on the above-mentioned embodiments of the present invention, any improvements and modifications made by those skilled in the art without departing from the principles of the present invention should fall within the scope of the present invention.
Claims (7)
1. The method for designing the mixing ratio of the framework compact type hot mix plant recycled asphalt mixture is characterized by comprising the following steps of:
s1, selecting raw materials of a hot mix plant reclaimed asphalt mixture, wherein the raw materials comprise newly added aggregate and RAP; detecting the performance of the newly added aggregate to determine that the newly added aggregate meets the current specification requirements; carrying out an extraction screening test on the RAP to determine the asphalt content, the grain composition and the coarse aggregate ratio of more than 4.75mm and the apparent density of the aggregate in the RAP;
s2, adopting SAC skeleton compact grading to divide raw materials into skeleton aggregates and filling materials in SAC mixing proportion design, wherein the volume ratio of the skeleton aggregates to the filling materials is 70:30, and then carrying out coarse aggregate mixing proportion calculation of more than 4.75mm according to SAC skeleton aggregate grading key sieve pore passing rate calculation method, new aggregate screening result and RAP screening result, wherein the mixing proportion of RAP in the raw materials is consistent with the grading proportion of coarse aggregates in RAP during calculation;
s3, carrying out a Marshall test on the hot mix plant recycled asphalt mixture, and adjusting the filler according to the actually measured porosity.
2. The method for designing the mix proportion of the framework-compacted hot-mix plant recycled asphalt mixture according to claim 1, wherein the newly added aggregates comprise coarse aggregates, fine aggregates, mineral powder and asphalt;
the newly added aggregate comprises four specifications of 10-20mm, 10-15mm, 5-10mm and 0-3mm, wherein more than 4.75mm is coarse aggregate and less than 4.75mm is fine aggregate, the performance of the coarse aggregate and the fine aggregate in the newly added aggregate is detected, and all indexes detected meet the technical requirements in JTG F40-2004 technical Specification for highway asphalt pavement construction; then screening coarse aggregates and fine aggregates in the newly added aggregates;
the asphalt in the newly added aggregate is SBS modified asphalt, the SBS modified asphalt is detected, and all indexes detected meet the technical requirements in JTG F40-2004 technical Specification for construction of Highway asphalt pavement;
and detecting mineral powder in the newly added aggregate, wherein each index meets the technical requirements of JTG F40-2004 technical Specification for highway asphalt pavement construction.
3. The mix proportion design method of the framework compact type hot mix plant recycled asphalt mixture according to claim 2, wherein the RAP comprises coarse aggregate, fine aggregate, mineral powder and asphalt;
the RAP is milled and broken by impact and then divided into two specifications of 0-10mm and 10-20mm, the extraction screening test is carried out on the RAP, the asphalt content in the RAP is determined, coarse and fine aggregate classification is carried out on the old aggregate after the extraction screening test, wherein more than 4.75mm is coarse aggregate, less than 4.75mm is fine aggregate, and the apparent relative density, the water absorption rate and the duty ratio of the old aggregate under the specification of 0-10mm and the specification of 10-20mm of the RAP are detected and determined after classification, wherein the old aggregate is 0-4.75mm, the old aggregate is 4.75-9.5mm and the old aggregate is 9.5-19 mm.
4. The method for designing the mix proportion of the framework compact type hot mix plant recycled asphalt mixture according to claim 3, wherein the framework aggregate comprises coarse aggregate in newly added aggregate and coarse aggregate in RAP, and the filler comprises fine aggregate in newly added aggregate, mineral powder and fine aggregate and mineral powder in RAP;
calculating SAC skeleton aggregate levelRate of pass P of matched key sieve holes di The formula is as follows:
P di ＝A(d i /D max ) B ，
wherein: p (P) di For the throughput of the mesh size di,%; d (D) max The maximum grain diameter of the mineral aggregate is mm; di is a certain sieve pore size, mm; A. b is a coefficient respectively;
according to the calculation result of the SAC skeleton aggregate grading key sieve aperture passing rate, the newly added aggregate screening result and the RAP screening result, the coarse aggregate blending proportion of more than 4.75mm is calculated, and the blending proportion of RAP in raw materials is synthesized according to the grading proportion of RAP coarse and fine aggregates under two specifications of RAP0-10mm and RAP10-20mm during calculation.
5. The method for designing the blending ratio of the framework compact type hot mix plant recycled asphalt mixture according to claim 4, wherein the RAP blending ratio is converted into the volume ratio by considering the difference of the density of RAP aggregate and new aggregate, and the asphalt content is determined through past engineering experience;
the calculation formula of the aggregate equivalent volume replacement in RAP is as follows:
wherein: m is m RAP Total RAP ratio,%; m is m RAPsi Is of the specification s in the mixing proportion i The mass ratio of the old aggregate of (3) is percent; ρ asi Is of specification s i Apparent density g/cm of newly added aggregate 3 ；ρ aRAPsi For specification s in RAP i Apparent density g/cm of old aggregate 3 ；ω RAPsi For specification s in RAP i Old aggregate ratio,%;
the mass ratio of the grading of the mixture after the equal volume replacement is calculated as follows:
wherein: m is m tsi Is of specification s i The new added aggregate mass of (1) is replaced by the new added aggregate mass; m is m RAPsi For specification s in RAP i Is the mass ratio,%; m is m si Is converted into 100% of post-specification s i The new aggregate mass ratio,%; m's' RAPsi The mass ratio of the old aggregate of specification si in the RAP after conversion of 100 percent is shown as percent; m is m k The weight percentage of the mineral powder is percent.
6. The method for designing the blending ratio of the hot recycled asphalt mixture for the plant mix with dense framework according to claim 4, wherein after the grading is determined, a Marshall test is performed according to engineering experience,
when the test results of the grading porosity, the stability and the flow value meet the related requirements of JTG F40-2004 (highway asphalt pavement construction technical Specification), evaluating the high-temperature performance, the low-temperature performance and the water damage resistance of the hot mix plant recycled asphalt mixture;
when the test result of grading porosity exceeds the related requirement of JTG F40-2004 technical Specification for highway asphalt pavement construction, on the premise of ensuring that the volume ratio of skeleton aggregate to filler is unchanged 70:30, the ratio of mineral powder, fine aggregate or asphalt in the filler is increased or reduced to carry out grading adjustment of the mixture, or the fluctuation of initial asphalt content is +/-0.3%, so as to carry out the determination of the optimal asphalt content of the mixture.
7. The method for designing the blending ratio of the skeleton-compacting type hot-mix plant recycled asphalt mixture according to claim 1, wherein the blending amount of RAP in raw materials is not less than 30%.
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