Design methods for asphalt mixtures that maintain skid resistance over a long period and asphalt mixtures

Abstract

This invention relates to the field of highway engineering technology, and provides a design method and a method for asphalt mixtures that maintain long-term skid resistance. The method includes the following steps: testing the basic characteristics of multi-lithological aggregates and constructing an aggregate characteristic database; controlling the volumetric blending ratio of the mixed aggregates based on the volumetric method; initially selecting mixed aggregate combinations based on the differences in polishing effects and complementary performance principles of mixed aggregates from different lithologies, and setting a blending ratio gradient; conducting abrasion and polishing tests on the initially selected mixed aggregates, and determining the optimal combination based on the experimental results; designing and verifying the mix proportion of the asphalt mixed aggregates based on the optimal combination; and determining the final mix proportion based on the experimental results through balanced optimization. This approach helps guide the rational selection and optimized mix proportion of mixed aggregates, ensuring the long-term, stable maintenance and even improvement of skid resistance, while simultaneously achieving the goals of saving high-quality aggregates and controlling and reducing costs in the anti-skid surface layer of asphalt pavements.

Description

Technical Field

[0001] This invention relates to the field of highway engineering technology, and in particular to a design method for asphalt mixtures that maintain skid resistance for a long time, and an asphalt mixture thereof. Background Technology

[0002] With the rapid development of modern transportation towards high speeds, heavy loads, and large traffic volumes, the excessively rapid decline in the skid resistance of asphalt pavements has become a key issue restricting road operational safety. The skid resistance of the asphalt pavement surface layer is directly related to driving safety and is one of the most important functional properties of the pavement. Its long-term maintenance capability not only affects the quality of road service but is also closely related to traffic safety assurance and operation and maintenance cost control. Currently, the design of asphalt pavement surface layers in my country focuses more on structural load-bearing performance, with insufficient systematic consideration of long-term skid resistance and durability, and a lack of targeted mixture design.

[0003] To improve and maintain the skid resistance of asphalt pavements, traditional methods include using a single high-quality abrasion-resistant polished aggregate (such as basalt, diabase, etc.) or even steel slag aggregate in the surface layer of the asphalt pavement, or using discontinuous graded asphalt mixtures to increase the texture depth of the surface layer, in order to resist the degradation of the skid resistance of the surface layer under the wear and polishing of vehicle tires and the compaction of loads, so as to maintain the skid resistance performance index of the pavement to meet the requirements.

[0004] However, in practical applications, it has been found that even when the mixture uses aggregates with high hardness, good angularity, and excellent abrasion resistance, it can only slow down the rate of decline in skid resistance. After a period of time, the wear and abrasion caused by vehicle loads will eventually wear it down, resulting in a continuous decrease in the texture depth of the asphalt pavement surface layer. This leads to the inability of relevant skid resistance indicators to meet design requirements, causing traffic safety hazards and significantly increasing operation and maintenance costs. At the same time, with the continuous expansion of highway construction in my country, the increasing demand for maintenance, and environmental protection policies, the resources of high-quality abrasion-resistant polished aggregates are becoming increasingly scarce and their prices are rising. Moreover, resources are scarce in some areas, requiring long-distance transportation, which greatly increases construction and maintenance costs.

[0005] To alleviate the aforementioned contradictions, the industry has begun to explore the use of mixed aggregates (such as mixing high-quality basalt with limestone and other aggregates in a certain proportion) to pave anti-skid surface layers. Although some existing studies have preliminarily verified the technical feasibility of mixed aggregates, the following prominent problems still exist: First, the design process is disconnected from the skid resistance and durability objectives; the current design method fails to integrate "long-term maintenance of skid resistance performance" as a clear design objective and control indicator into the entire mix design process, resulting in weak prediction and guarantee capabilities of the design results for the service life of the pavement skid resistance.

[0006] Secondly, there is insufficient understanding of the long-term decay law and mechanism of anti-skid performance. Existing studies mostly focus on the initial anti-skid performance of the mixture, but lack systematic and quantitative research models and prediction methods for its anti-skid performance decay behavior under the coupled effects of long-term traffic loads and environmental factors, its impact on macro / micro texture evolution, and technical countermeasures.

[0007] Third, there is a lack of dedicated mix design methods for mixed aggregates; existing designs usually simply apply the mix design methods for single aggregates without fully considering the significant differences in performance between different lithological aggregates. This results in inaccurate calculation of mixed aggregate parameters and uneven road performance, making it difficult to fully leverage the synergistic advantages of mixed aggregates.

[0008] In view of the above problems, how to provide a scientific and systematic design method for asphalt mixtures to guide the rational selection and optimized proportion of aggregates, and ensure that the anti-skid surface layer of asphalt pavement can achieve long-term, stable maintenance or even improvement of anti-skid performance while saving high-quality stone materials and controlling costs, has become an important technical problem that urgently needs to be solved.

[0009] It should be clarified here that the above description is intended to facilitate understanding of the overall background of the present invention, and should not be construed as an admission or implication in any way that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0010] This invention provides a design method and a mixture of asphalt mixtures that maintain skid resistance for a long time. This method addresses the shortcomings of existing technologies where using a single aggregate of the same rock type is insufficient to solve the problem of skid resistance degradation in the surface layer. It helps guide the rational selection and optimized mix proportion of aggregates, ensuring that the skid resistance of the asphalt pavement surface layer is maintained stably and even increased while saving high-quality stone and controlling costs.

[0011] This invention provides a method for designing asphalt mixtures that maintain skid resistance over a long period, comprising the following steps: Test the basic properties of multi-lithological aggregates and construct an aggregate property database; The volumetric blending ratio of mixed aggregates is controlled based on the volumetric method. Based on the differential polishing effect and complementary performance principle of mixed aggregates of different lithologies, the initial selection of mixed aggregate combinations was made, and the blending ratio gradient was set. Abrasion and polishing tests were conducted on the initially selected mixed aggregates, and the optimal combination was determined based on the experimental results; Based on the optimal combination, the mix design and verification of asphalt mixture aggregates were carried out. Based on the experimental results, the final mix proportion was determined by balancing and selecting the optimal ratio.

[0012] According to the present invention, a design method for asphalt mixtures that maintains long-term skid resistance includes testing the basic properties of multi-lithological aggregates and constructing an aggregate property database, comprising: Based on the principle of using local materials, representative aggregates of different rock types that are available along the project route are selected; Conduct comprehensive or key performance tests on each type of aggregate and establish a database.

[0013] According to the design method of asphalt mixture for long-term maintenance of anti-skid performance provided by the present invention, the key performance indicator test contents include: physical properties and the influence of processing technology; The key physical properties include: polishing value and Los Angeles abrasion value; The impact of the processing technology includes: assessing the changes in the key physical properties of the aggregates after mixing, heating, and screening processes.

[0014] According to the design method for asphalt mixtures that maintain skid resistance for a long time provided by the present invention, the comprehensive index characteristic test contents also include: geometric morphological characteristics, mineral chemical composition or interfacial bonding performance. The geometric morphological features include: the shape index of the aggregate, angularity, and surface texture; The mineral chemical composition includes: the main mineral components and content of the aggregate; The determination of the interfacial bonding performance includes: testing the adhesion grade of the aggregate to the selected asphalt, surface energy, or evaluating the interfacial bonding strength using a pull-out test method.

[0015] According to the present invention, a method for designing asphalt mixtures that maintains skid resistance over a long period of time includes controlling the volumetric blending ratio of aggregates based on a volumetric method, comprising: Based on the density differences of different aggregates, a volume-density-mass ratio conversion relationship is established, and the volume blending ratio of mixed aggregates is indirectly controlled through mass measurement.

[0016] According to the present invention, a design method for asphalt mixtures that maintains long-term skid resistance is provided. The initial selection of aggregate combinations based on the differential polishing effect and complementary performance principle of aggregates of different lithologies includes: The quantity of mixed aggregates is controlled, limiting the number of different aggregate types to 2-3; and / or, The aggregate size should be matched with the lithology; fine aggregates smaller than 5mm should use alkaline aggregates, while aggregates of different hardness can be used for 5–10mm and 10–15mm aggregates, respectively; and / or, The difference in polishing value was used for quantitative screening. Coarse aggregates with different hardness were labeled as PSV from low to high polishing value. M1 PSV M2 PSV M3The combination is selected according to the preset polishing value difference standard: the two aggregates meet the PSV when mixed. M3 -PSV M2 ≥10 and PSVL M3 -PSVL M2 ≥12; PSV is satisfied when the three aggregates are mixed. M3 -PSV M2 ≥10, and PSVL M3 -PSVL M2 ≥12, PSV M2 -PSV M1 ≥5, PSVL M2 -PSVL M1 ≥6; where PSV is the test value of the aggregate after polishing at 57600 rpm for 3 hours, and PSVL is the test value of the aggregate after polishing at 460800 rpm for 24 hours.

[0017] According to the design method of asphalt mixture for long-term maintenance of skid resistance provided by the present invention, abrasion and polishing tests are carried out on the initially selected aggregate mixture, and the optimal combination is determined based on the experimental results, including: Abrasion tests were conducted on the preliminary selected mixed aggregate combination based on the test methods and instruments specified in the current technical specifications. Polishing tests were conducted on the initially selected mixed aggregate combination based on the test methods and instruments specified in the current technical specifications or an accelerated loading polishing test machine. Add polishing tests under asphalt film coating conditions as needed; Based on the test results, the optimal aggregate combination and blending ratio with the best polishing value were selected.

[0018] According to the design method for asphalt mixtures that maintain skid resistance for a long time provided by the present invention, the specimen preparation steps in the polishing test under the condition of asphalt film coating include: The mixed aggregate and hot asphalt are thoroughly and evenly mixed. The amount of asphalt is determined by the calculation method of coarse aggregate specific surface area and effective asphalt film thickness or by the asphalt-aggregate ratio estimated by experience. After the asphalt aggregate is mixed, it is distributed and cooled to prepare test specimens according to the current specifications. For conventional asphalt, the curing time at room temperature shall not be less than 24 hours, and for high-viscosity asphalt, it shall be cured at 40℃ for not less than 3 hours, followed by curing at room temperature for not less than 9 hours.

[0019] According to the present invention, a method for designing asphalt mixtures that maintains long-term skid resistance is provided, wherein the asphalt mixture aggregate mix design and verification are carried out based on the optimal combination, including: Based on the mix design test of asphalt mixture aggregate, the gradation and the optimal asphalt-aggregate ratio were determined; Test the various volumetric and performance indicators of the mixture; based on this, add tests such as texture depth test, dynamic friction coefficient test, and polishing test for the mixture specimens; The improvement effect was compared and analyzed with conventional aggregate mixtures or previous experience data, and the law of skid resistance decay and long-term performance prediction were analyzed.

[0020] The present invention also provides an asphalt mixture prepared by the asphalt mixture design method for maintaining anti-skid performance for a long time as described in any one of the above-mentioned methods.

[0021] The present invention provides a design method and an asphalt mixture for maintaining long-term skid resistance. The design method takes the "differential abrasion and polishing effect of aggregates of different rock types" as the core technology and approach, and takes "maintaining or even increasing skid resistance" as the core objective throughout. Through systematic evaluation of aggregate characteristics, mixture composition design, research on skid resistance attenuation law and life prediction, a closed-loop mixture design system that can quantitatively guide engineering practice is formed.

[0022] This method has at least the following advantages: 1) High scientific rigor; a complete technical chain has been established, from aggregate characteristics to mixture design, and then to attenuation law and long-term performance prediction, overcoming the drawbacks of simply applying traditional methods. The design process has sufficient experimental and theoretical basis.

[0023] 2) Clear objectives: "Long-term maintenance of anti-skid performance" is taken as the core design objective and is implemented throughout the process. By utilizing the differential wear and polishing effect of mixed aggregates and the technical approach of differential wear and polishing rate, the design results can be directly related to and ensure the long-term safety performance of the road surface.

[0024] 3) Superior performance; By constructing an aggregate characteristic database, optimizing the blending ratio of mixed aggregates based on the volumetric method and the principle of complementary performance of differential abrasion and polishing effects of mixed aggregates, and combining abrasion and polishing tests with texture depth verification, the optimal mix ratio is achieved. Due to the differential abrasion and polishing effects and differential abrasion and polishing rates of mixed aggregates, under the action of vehicle tire abrasion and polishing and vehicle load compaction, the inconsistent abrasion and polishing rates of different aggregates ensure that the micro-texture of asphalt pavement always maintains a high texture depth and anti-skid performance, achieving long-term, stable maintenance and even improvement of the anti-skid performance of asphalt mixtures; and while slowing down the rate of decline of anti-skid performance and improving service life, the water stability and fatigue performance of the mixture can also be improved.

[0025] 4) Resource conservation and cost reduction: It can guide engineers to make scientific and maximum use of local high-quality stone resources while ensuring anti-skid durability, reduce dependence on single high-quality stone, maximize the use of local resources, reduce the amount of high-quality stone used, save resources and control the cost of construction and maintenance.

[0026] 5) High operability; it provides a clear design process that includes specific steps, test methods and evaluation criteria, which is easy for engineering technicians to understand and apply, and easy to promote. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating the design method for asphalt mixtures that maintain long-term skid resistance, as provided in an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] To better understand the asphalt mixture design method and asphalt mixture for long-term maintenance of skid resistance provided by this invention, its application background is first introduced. With the rapid development of modern transportation towards high speed, heavy load, and large traffic volume, the rapid decline in the skid resistance of asphalt pavements has become a key issue restricting road operation safety. To improve and maintain the skid resistance of asphalt pavements, traditional methods involve using a single high-quality abrasion-resistant polished aggregate (such as basalt, diabase, etc.) or even steel slag aggregate in the surface layer of the asphalt pavement, or using discontinuously graded asphalt mixtures to increase the texture depth of the surface layer, in order to resist the decline in the skid resistance of the surface layer under the wear and polishing of vehicle tires and the compaction of loads, so as to maintain the skid resistance performance index of the pavement to meet the requirements.

[0031] However, in practical applications, it has been found that even when the mixture uses aggregates with high hardness, good angularity, and excellent abrasion resistance, it can only slow down the rate of decline in skid resistance. After a period of time, the wear and abrasion caused by vehicle loads will eventually wear it down, resulting in a continuous decrease in the texture depth of the asphalt pavement surface layer. This leads to the inability of relevant skid resistance indicators to meet design requirements, causing traffic safety hazards and significantly increasing operation and maintenance costs. At the same time, with the continuous expansion of highway construction in my country, the increasing demand for maintenance, and environmental protection policies, the resources of high-quality abrasion-resistant polished aggregates are becoming increasingly scarce and their prices are rising. Moreover, resources are scarce in some areas, requiring long-distance transportation, which greatly increases construction and maintenance costs.

[0032] To alleviate the aforementioned contradictions, the industry has begun to explore the use of mixed aggregates (such as mixing high-quality basalt with limestone and other aggregates in a certain proportion) to pave anti-skid surface layers. Although some existing studies have preliminarily verified the technical feasibility of mixed aggregates, the following prominent problems still exist: First, the design process is disconnected from the skid resistance and durability objectives; the current design method fails to integrate "long-term maintenance of skid resistance performance" as a clear design objective and control indicator into the entire mix design process, resulting in weak prediction and guarantee capabilities of the design results for the service life of the pavement skid resistance.

[0033] Secondly, there is insufficient understanding of the long-term decay law and mechanism of anti-skid performance. Existing studies mostly focus on the initial anti-skid performance of the mixture, but lack systematic and quantitative research models and prediction methods for its anti-skid performance decay behavior under the coupled effects of long-term traffic loads and environmental factors, its impact on macro / micro texture evolution, and technical countermeasures.

[0034] Third, there is a lack of dedicated mix design methods for mixed aggregates; existing designs usually simply apply the mix design methods for single aggregates without fully considering the significant differences in performance between different lithological aggregates. This results in inaccurate calculation of mixed aggregate parameters and uneven road performance, making it difficult to fully leverage the synergistic advantages of mixed aggregates.

[0035] In view of the above problems, the present invention provides a design method and an asphalt mixture for maintaining anti-skid performance over a long period of time. This method is beneficial for guiding the rational selection and optimized mix proportion of aggregates, and ensuring that the anti-skid surface layer of asphalt pavement can maintain or even increase anti-skid performance over a long period of time while saving high-quality stone materials and controlling and reducing costs.

[0036] The following is combined Figure 1 This invention describes a design method for asphalt mixtures that maintain skid resistance over a long period, as well as the asphalt mixture itself.

[0037] Reference Figure 1 A design method for asphalt mixtures that maintain skid resistance over a long period, comprising the following: Step S10: Conduct basic characteristic tests on multi-lithological aggregates and construct an aggregate characteristic database.

[0038] Step S20: Control the volumetric blending ratio of the mixed aggregates based on the volumetric method.

[0039] Step S30: Based on the different wear and polishing effects of mixed aggregates of different lithologies and the principle of complementary performance, a preliminary selection of mixed aggregate combinations is made, and a blending ratio gradient is set.

[0040] Step S40: Conduct abrasion and polishing tests on the initially selected mixed aggregates, and determine the optimal combination based on the experimental results.

[0041] Step S50: Based on the optimal combination, conduct mix design and verification of asphalt mixture aggregates.

[0042] Step S60: Based on the test results, determine the final mix proportion by balancing and selecting the best option.

[0043] The aforementioned asphalt mixture design method takes the "differential abrasion and polishing effect of aggregates" as its core technology and approach, and aims to "maintain or even increase skid resistance over a long period" throughout. Through systematic evaluation of aggregate characteristics, mixture composition design, research on skid resistance attenuation laws, and service life prediction, it forms a closed-loop mixture design system that can quantitatively guide engineering practice. This method has at least the following advantages: 1) High scientific rigor; a complete technical chain has been established, from aggregate characteristics to mixture design, and then to attenuation law and long-term performance prediction, overcoming the drawbacks of simply applying traditional methods. The design process has sufficient experimental and theoretical basis.

[0044] 2) Clear objectives: "Long-term maintenance of anti-skid performance" is taken as the core design objective and is implemented throughout the process. By utilizing the differential wear and polishing effect of mixed aggregates and the technical approach of differential wear and polishing rate, the design results can be directly related to and ensure the long-term safety performance of the road surface.

[0045] 3) Superior performance; By constructing an aggregate characteristic database, optimizing the blending ratio of mixed aggregates based on the volumetric method and the principle of complementary performance of differential abrasion and polishing effects of mixed aggregates, and combining abrasion and polishing tests with texture depth verification, the optimal mix ratio is achieved. Due to the differential abrasion and polishing effects and differential abrasion and polishing rates of mixed aggregates, under the action of vehicle tire abrasion and polishing and vehicle load compaction, the inconsistent abrasion and polishing rates of different aggregates ensure that the micro-texture of asphalt pavement always maintains a high texture depth and anti-skid performance, achieving long-term, stable maintenance and even improvement of the anti-skid performance of asphalt mixtures; and while slowing down the rate of decline of anti-skid performance and improving service life, the water stability and fatigue performance of the mixture can also be improved.

[0046] 4) Resource conservation and cost reduction: It can guide engineers to make scientific and maximum use of local high-quality stone resources while ensuring anti-skid durability, reduce dependence on single high-quality stone, maximize the use of local resources, reduce the amount of high-quality stone used, save resources and control the cost of construction and maintenance.

[0047] 5) High operability; it provides a clear design process that includes specific steps, test methods and evaluation criteria, which is easy for engineering technicians to understand and apply, and easy to promote.

[0048] In one example of the present invention, step S10 includes: Step S101: Based on the principle of using local materials, select representative aggregates of different rock types that are available along the project route.

[0049] In detail, based on the principle of using local materials, engineering experience, and previous test data, representative lithological aggregates that are available along the project route should be selected. Considering the economic efficiency of testing, the number of types should not exceed five. Hard aggregates include steel slag and non-natural lithological artificial aggregates, while softer aggregates include calcined bauxite, waste ceramics, and non-natural non-lithological artificial aggregates.

[0050] This setup maximizes the use of local aggregate resources along the project route, broadens the aggregate selection channels, reduces reliance on high-quality natural hard aggregates, and at the same time, by selecting renewable aggregates, it meets environmental protection requirements, reduces the additional costs of long-distance aggregate transportation, and balances technical feasibility, economic rationality, and environmental friendliness.

[0051] Step S102: Conduct comprehensive or key indicator characteristic tests on each type of aggregate and establish a database.

[0052] In one optional example of the present invention, comprehensive characteristic tests can be performed on each type of aggregate to systematically understand the complete performance characteristics of each aggregate. The purpose is to balance the scientific nature and adaptability of the technology itself, and to achieve the maximum optimal matching of different rock aggregates through multi-dimensional index detection. This provides complete and accurate basic data support for the comprehensive evaluation of the long-term road performance of the mixture, while accumulating detailed experimental data for the subsequent progress and iteration of the patented technology and process optimization. It can also provide data support for the continuous improvement of other properties of asphalt mixtures such as skid resistance, water stability, and fatigue.

[0053] In another optional example of the present invention, local engineering practice experience and the economic and efficiency requirements of testing and inspection can be combined to selectively screen the key technical indicators of each aggregate for testing. Under the premise of meeting the requirements of mixed aggregate blending design and long-term maintenance of anti-skid performance, the testing process can be simplified and the testing cost can be controlled.

[0054] Understandably, both of the above testing methods can establish a complete aggregate characteristic database based on the obtained data, providing data support and basis for subsequent steps.

[0055] Furthermore, the performance testing of aggregates includes: physical properties, geometric morphology, mineral chemical composition, interfacial bonding performance, and the influence of processing technology; among these, Physical properties include: Power Stain Value (PSV), Los Angeles Abrasion Value, Crushing Value, Impact Value, Density, and angularity.

[0056] Geometric morphological characteristics include: using digital image processing technology and other means to quantitatively characterize the shape index, angularity, surface texture, etc. of aggregates.

[0057] Mineral chemical composition analysis includes the analysis of major mineral components and contents (especially SiO2, Al2O3, CaO, etc.) using X-ray diffraction (XRD) and other methods.

[0058] Interfacial bonding performance includes: testing the adhesion grade between aggregate and selected asphalt, surface energy, or evaluating interfacial bond strength using pull-out tests.

[0059] The impact of processing technology includes: assessing the changes in key physical properties of aggregates (PSV, Los Angeles abrasion value, crushing value, impact value, density, angularity) after processing such as heating in a mixing plant (or equivalent treatment) and screening.

[0060] In detail, among the above-mentioned aggregate characteristic tests, physical properties and the impact of processing technology should be tested as key indicators. Other tests can be selectively conducted based on actual conditions (such as actual engineering needs, regional testing conditions, and testing costs).

[0061] To achieve the best possible matching of aggregates, the principle of "complementary performance and synergistic effect" is adopted for mixing and combination: high PSV aggregates provide long-term anti-skid foundation and differential foundation, high adhesion aggregates improve the durability of the mixture, and specific morphological aggregates optimize gradation and interlocking.

[0062] In addition, in areas where there is limited choice of aggregate types or where engineering experience is extensive, the design phase, which aims to maintain anti-skid performance over a long period, can use and analyze the polishing value (PSV) and Los Angeles abrasion value of different aggregates to determine the anti-abrasion polishing performance and long-term maintenance of the mixed aggregates.

[0063] In one example of the present invention, step S20, which controls the volumetric blending ratio of the mixed aggregates based on the volumetric method, includes: Based on the density differences of different aggregates, a volume-density-mass ratio conversion relationship is established, and the volume blending ratio of mixed aggregates is indirectly controlled through mass measurement.

[0064] In detail, since single aggregates have uniform lithology, specifications, and roughly the same density, when they are mixed according to mass as the measurement index, their mass ratio and volume ratio are basically consistent, which can accurately match the design requirements. Therefore, in traditional design, mass is generally used as the aggregate measurement index, and this measurement method has long been used in actual engineering mixing and production.

[0065] However, for mixed aggregates of different lithologies and specifications, their densities vary significantly. If traditional mass measurement methods are directly applied for blending, the mass ratio will not match the actual volume ratio, failing to achieve the designed volumetric blending ratio. This, in turn, affects the gradation and interlocking structure and volumetric parameters of the mixture, making it difficult to guarantee the differential abrasion and polishing effect of the mixed aggregates. Therefore, this embodiment uses volume as the indicator for calculation. By establishing a volume-density-mass ratio conversion relationship, the volumetric blending ratio of the mixed aggregates is indirectly controlled by leveraging the equivalence of mass measurement.

[0066] In one example of the present invention, step S30, which involves initially selecting a mixed aggregate combination based on the principle of complementary performance, includes: 1) Control the quantity of mixed aggregate combinations, and control the number of mixed aggregate combinations to 2 to 3 types.

[0067] In detail, from the perspective of practical engineering applications, taking into account the types of aggregates available on site, the economics of aggregate production, the feasibility of mixing production processes, and the economics of the overall technical solution, it is generally advisable to use 2 to 3 types of mixed aggregates, with 2 being the best.

[0068] 2) The aggregate size should be matched with the lithology. For fine aggregates smaller than 5mm, alkaline aggregates should be used. For aggregates of 5-10mm and 10-15mm, aggregates of different hardness can be used respectively.

[0069] In detail, for fine aggregates smaller than 5mm, alkaline aggregates such as limestone aggregates must be used to improve the adhesion, water stability, and fatigue resistance of asphalt mixtures. For aggregates of 5–10mm and 10–15mm (or only 10–15mm), aggregates with different hardness (abrasion, polishing, crushing, etc.) can be used (marked by hardness as: M1 < M2 < M3, and their corresponding polishing values ​​are marked as PSV). M1 <PSV M2 <PSV M3 For example, softer aggregates can be made of limestone, tuff, etc., while harder aggregates can be made of basalt, diabase, gneiss, etc. Depending on the type of asphalt mixture, 10-15mm aggregates can be replaced with 10-20mm aggregates to suit the gradation design requirements of different mixtures.

[0070] 3) Quantitative screening based on the difference in polishing value; coarse aggregates of different hardness are labeled as PSV according to their polishing value from low to high. M1 PSV M2 PSV M3 The combination is selected according to the preset polishing value difference standard: the two aggregates meet the PSV when mixed. M3 -PSV M2 ≥10 and PSVL M3 -PSVL M2 ≥12; PSV is satisfied when the three aggregates are mixed. M3 -PSV M2 ≥10, and PSVL M3 -PSVL M2 ≥12, PSV M2 -PSV M1 ≥5, PSVL M2 -PSVL M1 ≥6; where PSV is the test value of the aggregate after polishing at 57,600 rpm for 3 hours, and PSVL is the test value of the aggregate after polishing at 460,800 rpm for 24 hours. This setting takes into account the variation law of polishing value and the influence of anti-slip performance decay in different use stages in the short term (standard) and long term (when it tends to be stable), so as to ensure that the selected mixed aggregate can form a reasonable difference in wear and polishing rate.

[0071] Furthermore, after the initial selection of the mixed aggregates, it is necessary to set differentiated blending ratio gradients for aggregates with different hardness levels. These gradients will serve as the basis for subsequent abrasion and polishing tests and mix design. Specifically, when mixing two aggregates, the gradient should be set according to the ratio range of high and low anti-skid aggregates, such as 30:70 to 70:30, to achieve comprehensive testing of the anti-skid performance of aggregate combinations under different ratios. When mixing three aggregates, the ratio gradient should be set according to the principle of minimizing the content of medium-hardness aggregates, such as 35:30:35. This balances the complementary performance of different hardness aggregates while highlighting the different abrasion and polishing effects of high and low anti-skid aggregates. Through comparative testing of multiple gradient ratios, detailed experimental data will be provided to support the subsequent selection of the optimal blending ratio.

[0072] In one example of the present invention, step S40 includes: conducting abrasion and polishing tests on the initially selected mixed aggregate combination, adding polishing tests under the condition of asphalt film coating as needed, and screening the mixed aggregate combination and blending ratio with the optimal polishing value based on the test results.

[0073] In detail, for large-sized mixed aggregates, abrasion and polishing tests are conducted: Abrasion tests use the test methods and instruments specified in the current technical specifications, such as the coarse aggregate abrasion test (Los Angeles method), or other new instruments such as domestically produced flat plate polishing machines (to increase the specimen area and reduce error); Polishing tests also use the test methods and instruments specified in the current technical specifications. For coarse aggregate polishing value tests, new polishing test methods and instruments can also be used as needed, such as accelerated loading polishing test machines with larger loads and faster wheel speeds; Compared with the specifications, if necessary, polishing tests under standard polishing conditions (polishing at 57,600 rpm for 3 hours) with an asphalt film coating on the surface of the mixed aggregates are added to simulate the polishing conditions under asphalt pavement conditions.

[0074] It should be noted that before the test, the aggregates should be thoroughly mixed to ensure that the different aggregates are evenly distributed.

[0075] Furthermore, in the polishing test under the condition of being coated with an asphalt film, the specimen preparation steps include: Step S401: Mix the aggregate and hot asphalt thoroughly and evenly. The amount of asphalt is determined by the calculation method of the specific surface area of ​​coarse aggregate and the effective asphalt film thickness or by the asphalt-aggregate ratio estimated by experience.

[0076] Step S402: Distribute the mixed asphalt aggregate, and after cooling, prepare test specimens according to the current specifications. For conventional asphalt, the curing time at room temperature shall not be less than 24 hours, and for high-viscosity asphalt, the curing time shall be not less than 3 hours at 40℃, followed by curing at room temperature for not less than 9 hours.

[0077] Furthermore, based on the experimental results, the combination with the highest polishing value was selected as the optimal combination. The polishing values ​​of various single and mixed aggregates were compared and analyzed to determine the improvement of the polishing value by the proposed mixed combination.

[0078] In detail, through extensive experimental statistical analysis, the optimal mixing ratio is generally between 40:60 and 60:40; in the absence of extensive experimental conditions, 50:50 can be directly selected, and 55:45 can be selected when high-quality stone is abundant.

[0079] In one example of the present invention, step S50 includes: based on the optimal combination, conducting mix design and verification of asphalt mixture aggregates, including: Step S501: Based on the mix design test of asphalt mixture aggregate, determine the gradation and the optimal asphalt-aggregate ratio.

[0080] In detail, according to the methods or design requirements of the current relevant specifications, mix design tests of asphalt mixture aggregates are carried out. During the test, the mixed aggregates that have completed performance matching and preliminary proportion screening in the early stage are considered as a single aggregate class and participate in the gradation design in conjunction with other aggregates of different specifications. The precise blending ratio of each aggregate class (each particle size specification) is determined through the standardized test procedure to form a mixture gradation system that meets the engineering requirements. At the same time, through the comparison and optimization of multiple sets of asphalt-aggregate ratio tests, the optimal asphalt-aggregate ratio that enables all performance indicators of the mixture to meet the specifications and design requirements is finally determined.

[0081] Step S502: Test the volume and performance indicators of the mixture; on this basis, add the texture depth test, dynamic friction coefficient test and polishing test of the mixture specimen.

[0082] In detail, according to the requirements of current relevant specifications, various volumetric and pavement performance indicators of asphalt mixtures are tested. Volumetric indicators include void ratio, aggregate void ratio, and asphalt saturation, while pavement performance indicators include high-temperature stability, low-temperature crack resistance, and water stability, ensuring that the basic performance of the mixture meets engineering design and specification standards. Based on this, texture depth tests, dynamic friction coefficient tests, and polishing tests are added to the mixture specimens to characterize the surface texture features, friction and skid resistance under actual driving conditions, and the characteristics of skid resistance degradation under long-term wear, verifying the skid resistance and long-term retention capacity of the mixture.

[0083] Step S503: Compare and analyze the improvement effect with conventional aggregate mixtures or previous experience data, and analyze the law of skid resistance decay and long-term performance prediction.

[0084] In detail, the various test indicators of the asphalt mixture designed by this method are compared and analyzed with the measured indicators or past experience data of conventional single aggregate mixtures. The improvement effect and optimization range of this design scheme in terms of volume parameters, road performance, especially anti-skid indicators such as texture depth, friction coefficient, and polishing value are evaluated. At the same time, based on the aforementioned wear, polishing and anti-skid related test data, combined with the test results, the anti-skid performance decay law of the mixture under long-term traffic load and environmental factors is analyzed, a corresponding performance decay model is established, and long-term prediction of pavement anti-skid performance is carried out. This provides data support and theoretical basis for the anti-skid durability assessment and maintenance cycle planning of subsequent engineering applications.

[0085] The asphalt mixture provided by the present invention is described below. The asphalt mixture described below and the asphalt mixture design method for maintaining long-term skid resistance described above can be referred to in correspondence.

[0086] An asphalt mixture is prepared using the asphalt mixture design method for maintaining long-term skid resistance provided in any of the above examples.

[0087] It is understood that, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0088] The asphalt mixture design method and asphalt mixture for long-term maintenance of anti-skid performance provided in this invention have at least the following advantages: 1) High scientific rigor; a complete technical chain has been established, from aggregate characteristics to mixture design, and then to attenuation law and long-term performance prediction, overcoming the drawbacks of simply applying traditional methods. The design process has sufficient experimental and theoretical basis.

[0089] 2) Clear objectives: "Long-term maintenance of anti-skid performance" is taken as the core design objective and is implemented throughout the process. By utilizing the differential wear and polishing effect of mixed aggregates and the technical approach of differential wear and polishing rate, the design results can be directly related to and ensure the long-term safety performance of the road surface.

[0090] 3) Superior performance; By constructing an aggregate characteristic database, optimizing the blending ratio of mixed aggregates based on the volumetric method and the principle of complementary performance of differential abrasion and polishing effects of mixed aggregates, and combining abrasion and polishing tests with texture depth verification, the optimal mix ratio is achieved. Due to the differential abrasion and polishing effects and differential abrasion and polishing rates of mixed aggregates, under the action of vehicle tire abrasion and polishing and vehicle load compaction, the inconsistent abrasion and polishing rates of different aggregates ensure that the micro-texture of asphalt pavement always maintains a high texture depth and anti-skid performance, achieving long-term, stable maintenance and even improvement of the anti-skid performance of asphalt mixtures; and while slowing down the rate of decline of anti-skid performance and improving service life, the water stability and fatigue performance of the mixture can also be improved.

[0091] 4) Resource conservation and cost reduction: It can guide engineers to make scientific and maximum use of local high-quality stone resources while ensuring anti-skid durability, reduce dependence on single high-quality stone, maximize the use of local resources, reduce the amount of high-quality stone used, save resources and control the cost of construction and maintenance.

[0092] 5) High operability; it provides a clear design process that includes specific steps, test methods and evaluation criteria, which is easy for engineering technicians to understand and apply, and easy to promote.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for asphalt mixtures that maintains skid resistance over a long period, characterized in that, Includes the following steps: Test the basic properties of multi-lithological aggregates and construct an aggregate property database; The volumetric blending ratio of mixed aggregates is controlled based on the volumetric method. Based on the differential polishing effect and complementary performance principle of mixed aggregates of different lithologies, the initial selection of mixed aggregate combinations was made, and the blending ratio gradient was set. Abrasion and polishing tests were conducted on the initially selected mixed aggregates, and the optimal combination was determined based on the experimental results; Based on the optimal combination, the mix design and verification of asphalt mixture aggregates were carried out. Based on the experimental results, the final mix proportion was determined by balancing and selecting the optimal ratio.

2. The asphalt mixture design method for long-term maintenance of skid resistance as described in claim 1, characterized in that, The testing of basic properties of multilithological aggregates and the construction of an aggregate property database include: Based on the principle of using local materials, representative aggregates of different rock types that are available along the project route are selected; Conduct comprehensive or key performance tests on each type of aggregate and establish a database.

3. The asphalt mixture design method for long-term maintenance of skid resistance as described in claim 2, characterized in that, The key performance indicators tested include: physical properties and the impact of processing technology; The key physical properties include: polishing value and Los Angeles abrasion value; The impact of the processing technology includes: assessing the changes in the key physical properties of the aggregates after mixing, heating, and screening processes.

4. The asphalt mixture design method for long-term maintenance of anti-skid performance according to claim 3, characterized in that, The comprehensive performance test also includes: geometric morphological characteristics, mineral chemical composition or interfacial bonding performance. The geometric morphological features include: the shape index of the aggregate, angularity, and surface texture; The mineral chemical composition includes: the main mineral components and content of the aggregate; The determination of the interfacial bonding performance includes: testing the adhesion grade of the aggregate to the selected asphalt, surface energy, or evaluating the interfacial bonding strength using a pull-out test method.

5. The asphalt mixture design method for long-term maintenance of skid resistance as described in claim 1, characterized in that, The volumetric blending ratio of the mixed aggregates controlled by the volumetric method includes: Based on the density differences of different aggregates, a volume-density-mass ratio conversion relationship is established, and the volume blending ratio of mixed aggregates is indirectly controlled through mass measurement.

6. The design method for asphalt mixtures with long-term maintenance of skid resistance according to any one of claims 1 to 5, characterized in that, The preliminary selection of mixed aggregate combinations based on the differential polishing effect and complementary performance principle of mixed aggregates of different lithologies includes: The quantity of mixed aggregates is controlled, limiting the number of different aggregate types to 2-3; and / or, The aggregate size should be matched with the lithology; fine aggregates smaller than 5mm should use alkaline aggregates, while aggregates of different hardness can be used for 5–10mm and 10–15mm aggregates, respectively; and / or, The difference in polishing value was used for quantitative screening. Coarse aggregates with different hardness were labeled as PSV from low to high polishing value. M1 PSV M2 PSV M3 The combination is selected according to the preset polishing value difference standard: the two aggregates meet the PSV when mixed. M3 -PSV M2 ≥10 and PSVL M3 -PSVL M2 ≥12; PSV is satisfied when the three aggregates are mixed. M3 -PSV M2 ≥10, and PSVL M3 -PSVL M2 ≥12, PSV M2 -PSV M1 ≥5, PSVL M2 -PSVL M1 ≥6; where PSV is the test value of the aggregate after polishing at 57600 rpm for 3 hours, and PSVL is the test value of the aggregate after polishing at 460800 rpm for 24 hours.

7. The design method for asphalt mixtures with long-term maintenance of skid resistance according to any one of claims 1 to 5, characterized in that, Abrasion and polishing tests were conducted on the initially selected mixed aggregates, and the optimal combination was determined based on the experimental results, including: Abrasion tests were conducted on the initially selected mixed aggregate combination based on the test methods and instruments specified in the current technical specifications. Polishing tests were conducted on the initially selected mixed aggregate combination based on the test methods and instruments specified in the current technical specifications or an accelerated loading polishing test machine. Add polishing tests under asphalt film coating conditions as needed; Based on the test results, the optimal aggregate combination and blending ratio with the best polishing value were selected.

8. The design method for asphalt mixtures with long-term anti-skid performance as described in claim 7, characterized in that, In the polishing test under the condition of being coated with asphalt film, the specimen preparation steps include: The mixed aggregate and hot asphalt are thoroughly and evenly mixed. The amount of asphalt is determined by the calculation method of coarse aggregate specific surface area and effective asphalt film thickness or by the asphalt-aggregate ratio estimated by experience. After the asphalt aggregate is mixed, it is distributed and cooled to prepare test specimens according to the current specifications. For conventional asphalt, the curing time at room temperature shall not be less than 24 hours, and for high-viscosity asphalt, it shall be cured at 40℃ for not less than 3 hours, followed by curing at room temperature for not less than 9 hours.

9. The design method for asphalt mixtures with long-term anti-skid performance as described in claim 1, characterized in that, Based on the optimal combination, the asphalt mixture aggregate mix design and verification are carried out, including: Based on the mix design test of asphalt mixture aggregate, the gradation and the optimal asphalt-aggregate ratio were determined; Test the various volumetric and performance indicators of the mixture; based on this, add tests such as texture depth test, dynamic friction coefficient test, and polishing test for the mixture specimens; The improvement effect is compared and analyzed with conventional aggregate mixtures or previous experience data, and the law of deterioration of anti-skid performance and long-term performance prediction are analyzed.

10. An asphalt mixture, characterized in that, It is prepared using the asphalt mixture design method for maintaining long-term skid resistance as described in any one of claims 1 to 9.

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