CN-117865558-B - Mix proportion design method of framework compact type plant-mixed hot recycled asphalt mixture

CN117865558BCN 117865558 BCN117865558 BCN 117865558BCN-117865558-B

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 steps of selecting raw materials, wherein the raw materials comprise newly added aggregates and RAP, performing performance detection on the newly added aggregates, performing extraction screening test on the RAP, dividing the raw materials into framework aggregates and filling materials by adopting SAC framework compact type grading, dividing the raw materials into the framework aggregates and the filling materials in the mix proportion design, wherein the volume ratio of the framework aggregates to the filling materials is 70:30, then performing coarse aggregate mix proportion calculation of more than 4.75mm according to the SAC framework aggregate grading key sieve pore passing rate calculation method, the newly added aggregate screening result and the RAP screening result, performing Marshall test on the plant-mixed hot recycled asphalt mixture when the calculation is performed, and performing filler adjustment according to the actual measured porosity. The invention can realize the uniform distribution of asphalt cement in RAP and improve the high-temperature rutting resistance of the mixture.

Inventors

YOU JIAHUA
XI CONG
ZHANG ZHAOJIE
WANG YIMING
FU GUOHUA
ZHANG HUAN
XUAN HAO
YUAN ZHAODI
ZHANG JIAQI

Assignees

中国建筑第八工程局有限公司
山东省交通科学研究院

Dates

Publication Date: 20260512
Application Date: 20231226

Claims (4)

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 recycled asphalt mixture, wherein the raw materials comprise newly added aggregates and RAP, performing performance detection on the newly added aggregates to determine that the newly added aggregates meet the current standard requirements, performing extraction screening test on the RAP to determine asphalt content, grain size distribution, coarse aggregate proportion of more than 4.75mm and apparent density of the aggregates in the RAP, and performing the following steps: The new aggregate comprises coarse aggregate, fine aggregate, mineral powder and asphalt, wherein the new 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, performance detection is carried out on the coarse aggregate and the fine aggregate in the new aggregate, each index of detection meets the technical requirements in JTG F40-2004 technical Specification for construction of highway asphalt pavement, then the coarse aggregate and the fine aggregate in the new aggregate are screened, SBS modified asphalt is selected for the asphalt in the new aggregate, each index of detection meets the technical requirements in JTG 40-2004 technical Specification for construction of highway asphalt pavement, and each index of detection meets the technical requirements in JTG 40-2004 technical Specification for construction of highway asphalt pavement; The RAP comprises coarse aggregates, fine aggregates, mineral powder and asphalt, wherein the RAP is milled and crushed by counterattack and is divided into two specifications of 0-10mm and 10-20mm, an extraction screening test is carried out on the RAP to determine the asphalt content in the RAP, coarse aggregates and fine aggregates are classified on the old aggregates after the extraction screening test, wherein more than 4.75mm is the coarse aggregates, less than 4.75mm is the fine aggregates, and the apparent relative density and the water absorption rate of the old aggregates are 0-4.75mm, 4.75-9.5mm and 9.5-19mm after the classification are detected and determined, and the duty ratio of the old aggregates is 0-10mm and 10-20 mm; 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, then calculating coarse aggregate mixing proportion 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, and the mixing proportion of RAP in the raw materials is consistent with the grading proportion of coarse aggregates in RAP during calculation, wherein in the steps: the skeleton aggregate comprises coarse aggregate in newly added aggregate and coarse aggregate in RAP, and the filler comprises fine aggregate and mineral powder in newly added aggregate and fine aggregate and mineral powder in RAP, and the critical sieve pore passing rate P di of the gradation of SAC skeleton aggregate is calculated according to the following formula: , Wherein P di is the throughput of the sieve pore size di,%; D max is the maximum particle size of the mineral aggregate, mm, di is a certain sieve pore size, mm, and A, B are coefficients respectively; Calculating the blending proportion of coarse aggregates with the diameter of more than 4.75mm according to the calculation result of the grading key sieve aperture passing rate of SAC skeleton aggregates, the new aggregate screening result and the RAP screening result, and synthesizing the blending proportion of RAP in raw materials according to the grading proportion of RAP coarse aggregates under two specifications of RAP0-10mm and RAP10-20mm 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 mix proportion design method of the framework compact type hot mix plant recycled asphalt mixture according to claim 1, which is characterized in that the RAP mixing proportion is converted into volume proportion 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 RAP is the total RAP ratio,% >, m RAPsi is the mass ratio of the old aggregate of the specification s i in the mixture ratio,% >, ρ asi is the apparent density g/cm 3 ;ρ aRAPsi of the new aggregate of the specification s i and g/cm 3 ;ω RAPsi of the old aggregate of the specification s i in the RAP is the mass ratio of the old aggregate of the specification s i in the RAP; The mass ratio of the grading of the mixture after the equal volume replacement is calculated as follows: , , Wherein m tsi is the new aggregate mass ratio of the specification s i , m RAPsi is the mass ratio of the specification s i in the RAP,% m si is the new aggregate mass ratio of the specification s i after 100 percent conversion, m' RAPsi is the old aggregate mass ratio of the specification si in the RAP after 100 percent conversion, and m k is the mineral powder mass ratio.
3. The method for designing the blending ratio of the hot recycled asphalt mixture for the plant mix with dense framework according to claim 1, 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.
4. 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%.

Description

Mix proportion design method of framework compact type plant-mixed hot recycled asphalt mixture 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 mixing amount is generally 20% -30%, and the high mixing amount of the hot recycled asphalt mixture with the mixing amount of more than 30% -40% can be rarely applied to the road surface in a large area, mainly takes a test road section as a 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 recycled asphalt mixture, wherein the raw materials comprise newly added aggregates and RAP, performing performance detection on the newly added aggregates to determine that the newly added aggregates meet the current standard requirements, performing extraction screening test on the RAP, and determining asphalt content, grain size distribution, coarse aggregate duty ratio of more than 4.75mm and apparent density of the aggregates 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 new aggregate comprises four specifications of 10-20mm, 10-15mm, 5-10mm and 0-3mm, wherein more than 4.75mm is coarse aggregate, less than 4.75mm is fine aggregate, performance detection is carried out on the coarse aggregate and the fine aggregate in the new aggregate, and each index detected meets the technical requirements in JTG F40-2004 technical Specification for construction of highway asphalt pavement; The asphalt in the newly added aggregate is SBS modified asphalt, the SBS modified asphalt is detected, and all indexes detected meet