A design method of high-performance ultra-thin overlay asphalt mixture for road surface performance requirements

Abstract

The application discloses a design method of high-performance ultra-thin surface course asphalt mixture aiming at road surface performance requirements. The design method introduces the index of the mutual contact degree (CCD) of coarse aggregates on the basis of the single index control of coarse aggregates forming a skeleton structure in the existing specification. Through double index control, a stable skeleton interlocking structure is ensured, and the probability and stability of the skeleton interlocking structure are improved through the control of the passing rate under a specific sieve. Moreover, the low-temperature crack resistance and fatigue toughness are improved through additives and control of the gap rate of mineral aggregates, a variety of grading indexes are synergistically controlled to reduce the grading fluctuation range and reduce the grading sensitivity, and the surface large structure and internal compactness are realized. The ultra-thin surface course asphalt mixture obtained according to the design method has the anti-skid durability and anti-seepage water performance, and has excellent high-temperature anti-deformation property, low-temperature crack resistance, water damage resistance and fatigue resistance, and can greatly improve the use durability and driving safety of the asphalt pavement.

Description

Technical Field

[0001] This invention belongs to the field of road surface material design technology, specifically, it relates to a design method for high-performance ultra-thin overlay asphalt mixtures that meet the performance requirements of road surfaces. Background Technology

[0002] In my country's asphalt pavement design specifications, the surface layer refers to a structural layer with a thickness of 4cm to 5cm. Because it is directly subjected to the coupled effects of vehicle loads, solar radiation, rain, snow, and temperature cycles, it often suffers from skid resistance degradation, cracking, water damage, and deformation during its service life, typically failing to reach its design life. A poor surface layer condition can also reduce driving comfort and threaten vehicle safety. The conventional treatment is milling and repaving. However, considering that the wear in this case only occurs within 1cm of the surface layer, under the dual-carbon context, a more economical and environmentally friendly treatment method needs to be found.

[0003] Ultra-thin overlay technology is an asphalt pavement maintenance technology that implements a thickness of 10mm to 25mm. The maximum thickness is only half that of traditional thick surface layers. It can not only reduce resource consumption and carbon emissions, but also save on engineering costs and maintenance costs.

[0004] However, reduced thickness inevitably leads to a decrease in the aggregate size of the asphalt mixture, while also placing higher demands on the mixture's performance. Under increasing traffic loads, conventional polymer-modified asphalt is also difficult to match. Furthermore, the design of ultra-thin overlay asphalt mixtures typically follows the existing design methods for thick-layer asphalt mixtures, focusing more on structural performance and not paying enough attention to surface performance requirements. Consequently, the control indicators in the mixture design will inevitably differ from those of conventional thick-layer asphalt mixtures. Summary of the Invention

[0005] To address the current lack of dedicated design methods for ultra-thin overlay asphalt mixtures for asphalt pavements, and the insufficient consideration given to the surface performance requirements of asphalt pavements by existing design methods, this invention provides a design method for high-performance ultra-thin overlay asphalt mixtures tailored to road surface performance needs. The ultra-thin overlay asphalt mixture designed based on this method, when used as an ultra-thin overlay layer on asphalt pavements, combines skid resistance and durability with water permeability resistance. It also exhibits excellent high-temperature deformation resistance, low-temperature crack resistance, water damage resistance, and fatigue resistance, significantly improving the service durability and driving safety of asphalt pavements.

[0006] The present invention specifically provides the following technical solutions:

[0007] A design method for high-performance ultra-thin overlay asphalt mixtures to meet road surface performance requirements, wherein the ultra-thin overlay asphalt mixture includes coarse aggregate, fine aggregate, asphalt, additives, fibers, and mineral powder; the design method specifically includes the following steps:

[0008] S1. Using a 2.36mm sieve as the dividing line between coarse and fine aggregates, obtain the passing rates of each grade of coarse and fine aggregates under different sieve sizes, and determine the corresponding densities of each grade of coarse and fine aggregates, as well as asphalt, fiber and mineral powder.

[0009] S2. Based on the passing rate and density of each grade of coarse aggregate and fine aggregate under different sieve openings obtained in step S1, the blending ratio of each grade of coarse aggregate, fine aggregate and mineral powder is initially determined to obtain the synthetic mineral gradation.

[0010] S3. Based on the synthetic aggregate gradation obtained in step S2, determine the passing rate of the synthetic aggregate gradation under 2.36mm and 0.075mm sieves respectively; if both passing rates are within the control range, proceed to step S4; if at least one passing rate is not within the control range, return to step S2 to redesign and determine the blending ratio of each grade of coarse aggregate, fine aggregate and mineral powder.

[0011] S4. Based on the density obtained in step S1 and the synthetic aggregate gradation obtained in step S2, determine the coarse aggregate skeleton compaction gap ratio (VCA) of the synthetic aggregate gradation. DRC ;

[0012] S5. Based on the passing rate of the synthetic mineral gradation obtained in step S2 under a 0.075mm sieve, and in combination with the powder-to-binder ratio, determine the oilstone-to-aggregate ratio.

[0013] S6. Based on the synthetic aggregate gradation obtained in step S2 and the asphalt-aggregate ratio obtained in step S5, prepare an ultra-thin overlay asphalt mixture, determine the density and volume parameters of the ultra-thin overlay asphalt mixture, and make a judgment.

[0014] If all three of the following conditions are met simultaneously, the sample is deemed qualified and proceeds to step S7. If at least one condition is not met, the sample is deemed unqualified and the process returns to step S2 to redesign and determine the blending ratios of each grade of coarse aggregate, fine aggregate, and mineral powder.

[0015] ① Coarse aggregate skeleton compaction gap ratio (VCA) DRC Coarse skeleton void ratio (VCA) of asphalt mixture mix The difference is ≥0.2%.

[0016] ② The contact density (CCD) of coarse aggregates in ultra-thin overlay asphalt mixtures is ≥85%.

[0017] ③ The aggregate void ratio (VMA) of ultra-thin overlay asphalt mixture is between 17.5% and 24%;

[0018] S7. The qualified ultra-thin overlay asphalt mixture obtained in step S6 is subjected to the following road performance verification.

[0019] If all three of the following road performance characteristics are qualified, the mixture is deemed qualified; if at least one road performance characteristic is unqualified, the mixture is deemed unqualified. The process then returns to step S2 to redesign and determine the blending ratios of each grade of coarse aggregate, fine aggregate, and mineral powder until an ultra-thin overlay asphalt mixture meeting the following road performance characteristics is obtained:

[0020] a. The structural depth is not less than 0.8mm.

[0021] b. The permeability coefficient is not higher than 30 mL / min.

[0022] c. The four-point bending fatigue life (at 15℃ and 400με) reaches 1 million cycles and the modulus decay is no more than 40%.

[0023] Specifically, in step S3 above, the control range refers to:

[0024] ① When the nominal maximum particle size of the ore gradation is 9.5mm, the passing rate under a 2.36mm sieve is 20% to 28%, and the passing rate under a 0.075mm sieve is 2% to 10%;

[0025] ② When the nominal maximum particle size of the ore gradation is 4.75 mm, the passing rate under a 2.36 mm sieve is 20% to 40%, and the passing rate under a 0.075 mm sieve is 2.5% to 12.5%.

[0026] Specifically, in step S5 above, the powder-to-adhesive ratio is 1.0 to 2.0.

[0027] Specifically, in step S6 above, the degree of contact (CCD) between coarse aggregates in the ultra-thin overlay asphalt mixture is calculated using the following formula (1):

[0028] CCD=(ρ G ×ρ GCA ) / VCA DRC (1)

[0029] Where, ρ G This is the bulk density of the ultra-thin overlay asphalt mixture (derived from the density determination in step S6 above), in g / cm³. 3 ;ρ GCA This is the bulk density of the coarse aggregate (derived from the density measurement in step S2 above), in g / cm³. 3 .

[0030] Generally, the coarse aggregate skeleton compaction gap ratio (VCA) in step S4 above is... DRC The coarse skeleton void ratio (VCA) of the asphalt mixture in step S6 above. mixThe aggregate void ratio (VMA) of ultra-thin overlay asphalt mixtures can be determined by referring to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011).

[0031] The present invention proposes a design method for high-performance ultra-thin overlay asphalt mixtures to meet the surface performance requirements of road surfaces. The ultra-thin overlay, as the surface layer of the asphalt pavement, requires priority consideration of its skid resistance, water permeability, water damage resistance, aging resistance, high-temperature deformation resistance, low-temperature crack resistance, and fatigue life. Whether the coarse aggregate of the ultra-thin overlay asphalt mixture forms a skeleton structure is related to its high-temperature deformation resistance and skid resistance. Existing technologies only rely on "VCA" (vegetable core aggregate) for this purpose. DRC ≥VCA mix "Based on the single-index control of the coarse aggregate skeleton structure of the ultra-thin overlay asphalt mixture, the CCD of the mutual contact degree of coarse aggregates is introduced. Through dual-index control, a stable skeleton interlocking structure is ensured for the ultra-thin overlay asphalt mixture. By controlling the passing rate of the 2.36mm sieve, the probability and stability of the coarse aggregate forming a skeleton interlocking structure are improved. Under this premise, on the one hand, the toughness of the asphalt mastic is enhanced by direct-injection high-viscosity and high-elasticity additives, and the aging of toughening components during the mixing process is reduced, thereby improving the low-temperature crack resistance of the ultra-thin overlay asphalt mixture. On the other hand, by controlling the aggregate void ratio VMA≥17.5% and limiting the passing rate of aggregates through the 0.075mm sieve, more space is provided to accommodate the high-toughness asphalt mastic. This not only increases the percentage of high-toughness asphalt mastic but also avoids the asphalt mastic floating under compaction, thus achieving a large surface structure and dense interior of the ultra-thin overlay asphalt mixture. Through the synergistic control of multiple gradation indicators, the gradation fluctuation range of the ultra-thin overlay asphalt mixture is reduced, and the gradation sensitivity of the ultra-thin overlay asphalt mixture is decreased."

[0032] Furthermore, in the aforementioned ultra-thin overlay asphalt mixture, the asphalt is SBS modified asphalt, and the mass percentage of SBS in the total asphalt is 2% to 6%.

[0033] Furthermore, in the above-mentioned ultra-thin overlay asphalt mixture, the additive is a high-viscosity additive, which enables the added asphalt to have the following properties: ductility at 5℃ ≥ 40cm, elastic recovery rate ≥ 97%, and dynamic viscosity at 60℃ ≥ 500000Pa·s.

[0034] Preferably, the additive is added by direct dosing.

[0035] The aforementioned high-viscosity additives can be selected from products such as the high-viscosity modifier MA200 from Jiangsu Subote New Material Co., Ltd., or other commercially available products that can achieve the aforementioned modified properties.

[0036] Furthermore, in the aforementioned ultra-thin overlay asphalt mixture, the fibers are selected from lignin fibers and / or polyester fibers.

[0037] Compared with existing technologies, the ultra-thin overlay asphalt mixture designed using the design method provided by this invention has the following advantages:

[0038] (1) The surface texture depth is large (the existing specifications require the texture depth to be ≤120mL / min and ≥0.5mm), which has good anti-skid performance, especially good anti-skid durability. The large surface texture depth can also reduce the generation of road surface water film in rainy weather to a certain extent, thereby greatly improving vehicle driving safety.

[0039] (2) The interior is dense. When used as a surface layer, it can effectively prevent rainwater from entering the interior of the ultra-thin overlay asphalt mixture, reduce the incidence of water damage, and further prevent rainwater from entering the asphalt surface layer and damaging the interlayer bonding layer, thus avoiding damage between pavement layers.

[0040] (3) It has strong high-temperature resistance to deformation. The coarse aggregate forms a skeleton interlocking structure. The softening point of the asphalt mortar modified by the direct injection high viscosity and high elasticity additive is higher and the viscosity is greater under high temperature conditions. The ultra-thin overlay asphalt mixture has excellent resistance to shear deformation.

[0041] (4) It has good low-temperature crack resistance. The asphalt mortar modified with direct-injection high-viscosity and high-elasticity additives has high ductility, good toughness, and low aging degree during the production process. The larger aggregate gap ratio can accommodate more high-toughness asphalt mortar, which enhances the crack resistance of ultra-thin overlay asphalt mixture.

[0042] (5) Improve the gradation stability of ultra-thin overlay asphalt mixtures by controlling multiple gradation indicators in a coordinated manner, thereby reducing the gradation fluctuation range of ultra-thin overlay asphalt mixtures and reducing the gradation sensitivity of ultra-thin overlay asphalt mixtures.

[0043] (6) The gradation design method is simple and efficient, and it is designed for standard sieve aperture sizes, avoiding the use of non-standard sieve aperture sizes, making it more feasible, widely applicable and suitable for engineering projects. Attached Figure Description

[0044] Figure 1 This is a flowchart of a design method for high-performance ultra-thin overlay asphalt mixtures according to the present invention, which addresses the performance requirements of road surfaces. Detailed Implementation

[0045] The design method for high-performance ultra-thin overlay asphalt mixtures targeting road surface performance requirements provided by this invention is as follows: Figure 1 As shown.

[0046] Specifically, it includes the following steps:

[0047] S1. Screen the coarse and fine aggregates and determine the density of each component.

[0048] Coarse and fine aggregates were sieved using a 2.36 mm sieve as the boundary. The passing rates of each grade of coarse and fine aggregates under different sieve sizes were statistically analyzed, and the corresponding densities of each grade of coarse and fine aggregates, as well as asphalt, fiber, and mineral powder, were measured.

[0049] S2. Based on the throughput and density, the initial blending ratios of coarse aggregate, fine aggregate and mineral powder for each grade are determined to obtain the synthetic mineral gradation.

[0050] S3. Based on the gradation of the synthetic ore, determine the passing rate of the synthetic ore gradation under sieves of 2.36 mm and 0.075 mm.

[0051] Specifically, if both pass rates are within the control range, proceed to step S4 below;

[0052] If at least one is outside the control range, return to step S2 above to redesign the proposed blending ratio to obtain a new synthetic mineral gradation.

[0053] The above control range is divided into two different cases based on the different nominal maximum particle size of the mineral gradation, specifically referring to:

[0054] ① When the nominal maximum particle size of the ore gradation is 9.5mm, the passing rate under a 2.36mm sieve is 20% to 28%, and the passing rate under a 0.075mm sieve is 2% to 10%;

[0055] ② When the nominal maximum particle size of the ore gradation is 4.75 mm, the passing rate under a 2.36 mm sieve is 20% to 40%, and the passing rate under a 0.075 mm sieve is 2.5% to 12.5%.

[0056] S4. Determine VCA based on density and the gradation of the synthetic mineral aggregate. DRC .

[0057] S5. Based on the passing rate of the synthetic ore gradation under a 0.075mm sieve, and in conjunction with the powder-to-binder ratio, determine the oilstone ratio.

[0058] S6. Based on the gradation of the synthetic aggregate and the asphalt-aggregate ratio, prepare an ultra-thin overlay asphalt mixture, determine the density and volume parameters of the ultra-thin overlay asphalt mixture, and make a judgment.

[0059] The judgment criteria include the following three aspects:

[0060] ① Coarse aggregate skeleton compaction gap ratio (VCA) DRC Coarse skeleton void ratio (VCA) of asphalt mixture mix The difference is ≥0.2%;

[0061] ② The contact degree (CCD) of coarse aggregates in ultra-thin overlay asphalt mixtures is ≥85%;

[0062] ③ The aggregate void ratio (VMA) of ultra-thin overlay asphalt mixture is between 17.5% and 24%.

[0063] Specifically, if all three conditions above are met, the result is deemed qualified, and the following step S7 is continued.

[0064] If at least one condition is not met, the product is deemed unqualified, and the process returns to step S2 above to redesign and determine the blending ratio in order to obtain a new synthetic mineral gradation.

[0065] More specifically, in the above-mentioned judgment criteria, CCD is calculated according to the following formula:

[0066] CCD=(ρ G ×ρ GCA ) / VCA DRC (1)

[0067] Where, ρ G This is the bulk density of ultra-thin overlay asphalt mixture, expressed in g / cm³. 3 ;ρ GCA This is the bulk density of coarse aggregate, expressed in g / cm³. 3 .

[0068] S7. Verify the road performance of the above-mentioned ultra-thin overlay asphalt mixture.

[0069] Road performance includes the following three aspects:

[0070] a. The construction depth is not less than 0.8 mm;

[0071] b. The permeability coefficient is not higher than 30 mL / min;

[0072] c. The four-point bending fatigue life (at 15℃ and 400με) reaches 1 million cycles and the modulus decay is no more than 40%.

[0073] Specifically, if all three road performance requirements are met, the product is deemed qualified, indicating that the ultra-thin overlay asphalt mixture prepared in step S6 meets the requirements and is a high-performance ultra-thin overlay asphalt mixture designed for road surface performance.

[0074] If at least one road performance does not meet the requirements, it is deemed unqualified, and the process returns to step S2 above to redesign and determine the blending ratio to obtain a new synthetic aggregate gradation, until an ultra-thin overlay asphalt mixture that meets the above road performance requirements is obtained.

[0075] The embodiments of the present invention will now be described in detail. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the various embodiments of the invention and various modifications suitable for particular intended applications.

[0076] Example 1

[0077] The design method provided in this embodiment includes an ultra-thin overlay asphalt mixture comprising two grades of coarse aggregate (5mm-10mm and 3mm-5mm), fine aggregate (0-3mm), SBS modified asphalt, direct-injection high-viscosity additive, lignin fiber, and mineral powder.

[0078] First, the coarse and fine aggregates are screened, and the density of each component is measured.

[0079] Coarse and fine aggregates were sieved using a 2.36 mm sieve as the boundary. The passing rates of each grade of coarse and fine aggregates under different sieve sizes were statistically analyzed, and the corresponding densities of each grade of coarse and fine aggregates, as well as asphalt, fiber, and mineral powder, were measured.

[0080] The screening curves of coarse and fine aggregates and mineral powder are shown in Table 1 below.

[0081] Table 1. Screening curves of coarse aggregate, fine aggregate, and mineral powder.

[0082]

[0083] The densities of coarse and fine aggregates are shown in Table 2 below.

[0084] Table 2 Density of coarse and fine aggregates

[0085]

[0086] In this embodiment, the relative density of the SBS asphalt used to prepare the ultra-thin overlay asphalt mixture is 1.013 g / cm³. 3 The relative density of the mineral powder is 2.802 g / cm³. 3 The relative density of lignin fibers is taken as 0.351 g / cm³. 3 .

[0087] Secondly, the preliminary blending ratios of coarse aggregate, fine aggregate, and mineral powder for each grade are shown in Table 3 below.

[0088] Table 3. Proportions of coarse and fine aggregates and mineral powder

[0089]

[0090] Based on the sieving curves of coarse aggregate, fine aggregate and mineral powder in Table 1 and the blending ratios of coarse aggregate, fine aggregate and mineral powder in Table 3, the synthetic mineral gradation shown in Table 4 is obtained.

[0091] Table 4. Gradation of Synthetic Minerals

[0092]

[0093] Furthermore, based on the synthetic mineral gradation obtained in Table 4, the nominal maximum particle size is 9.5 mm, and the passing rates under 2.36 mm and 0.075 mm sieves are 19.1% and 5.4%, respectively. It is determined that the passing rates of the synthetic mineral gradation under 2.36 mm and 0.075 mm sieves are in the range of 20%–28% and 2%–10%, respectively.

[0094] The pass rate through the 2.36mm sieve was outside the control range, indicating that the synthetic gradation was unqualified. Therefore, we returned to the second step above and re-determined the blending ratio of coarse and fine aggregates and mineral powder, as shown in Table 5 below.

[0095] Table 5. Proportions of coarse and fine aggregates and mineral powder

[0096]

[0097] Based on the sieving curves of coarse aggregate, fine aggregate and mineral powder in Table 1 and the blending ratios of coarse aggregate, fine aggregate and mineral powder in Table 5, the synthetic mineral gradation shown in Table 6 is obtained.

[0098] Table 6. Gradation of Synthetic Minerals

[0099]

[0100] Next, based on the synthetic mineral gradation obtained in Table 6, the nominal maximum particle size is 9.5 mm. The passing rates under 2.36 mm and 0.075 mm sieves are 24.8% and 8.2%, respectively. It is determined that the passing rates of the synthetic mineral gradation under 2.36 mm and 0.075 mm sieves are in the range of 20% to 28% and 2% to 10%, respectively. Both passing rates are within the control range, so the following steps can be continued.

[0101] The fourth step is to calculate the VCA based on the density and gradation of the synthetic aggregate, referring to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). DRC The result was 41.3%.

[0102] The fifth step is to determine the asphalt-aggregate ratio based on the passing rate of the synthetic aggregate gradation through a 0.075mm sieve, which is 11.8%. Combined with the powder-to-binder ratio, it is initially proposed to be 1.3. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011), the asphalt-aggregate ratio is calculated to be 7.5%.

[0103] The SBS content in the SBS modified bitumen is 4%, and the amount of SBS bitumen used is 6.9% of the aggregate.

[0104] The dosage of the high-viscosity and high-elasticity additive is 0.6% of the mineral aggregate. The specific properties of the modified high-viscosity and high-elasticity asphalt are: ductility at 5℃ is 44cm, elastic recovery rate is 99.1%, and dynamic viscosity at 60℃ is 630000Pa·s.

[0105] The fiber is specifically lignin fiber, and its usage is 0.3% of the mineral.

[0106] Step 6: Based on the synthetic aggregate gradation and asphalt-aggregate ratio, prepare ultra-thin overlay asphalt mixture, determine the density and volumetric parameters of the ultra-thin overlay asphalt mixture, and calculate the VCA (Variable Accumulation Capacity) with reference to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). mix And VMA, and calculate CCD according to the above formula (1); and make a judgment, the results are shown in Table 7 below.

[0107] Table 7. Volumetric parameters of ultra-thin overlay asphalt mixtures

[0108]

[0109] If all three conditions are met, the test is considered successful, and the following steps can be continued.

[0110] Finally, referring to the corresponding test methods in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011), the road performance of the above-mentioned ultra-thin overlay asphalt mixture was verified, and the results are shown in Table 8.

[0111] Table 8 Test methods and road performance of ultra-thin overlay asphalt mixtures

[0112]

[0113] All three road performance characteristics mentioned above are met, and the mixture is deemed qualified. This indicates that the asphalt mixture prepared in the above steps meets the requirements and is a high-performance ultra-thin overlay asphalt mixture designed to meet the surface performance needs of roads.

[0114] Other application properties of the high-performance ultra-thin overlay asphalt mixture obtained above were tested, and the test results are shown in Table 9 below.

[0115] Table 9 Other Application Performance of High-Performance Ultra-Thin Overlay Asphalt Mixture

[0116]

[0117] a The technical requirements refer to "JTG 5142-2019 Technical Specification for Highway Asphalt Pavement Maintenance".

[0118] From the test results of other properties of the ultra-thin overlay asphalt mixture obtained by the above design method in Table 9, it can be seen that the ultra-thin overlay asphalt mixture also exhibits excellent high-temperature deformation resistance, low-temperature crack resistance, and water damage resistance.

[0119] Example 2

[0120] The design method provided in this embodiment includes an ultra-thin overlay asphalt mixture comprising 3mm-5mm coarse aggregate, 0-3mm fine aggregate, SBS modified asphalt, direct-injection high-viscosity additive, lignin fiber, and mineral powder.

[0121] First, the coarse and fine aggregates are screened, and the density of each component is measured.

[0122] Coarse and fine aggregates were sieved using a 2.36 mm sieve as the boundary. The passing rates of each grade of coarse and fine aggregates under different sieve sizes were statistically analyzed, and the corresponding densities of each grade of coarse and fine aggregates, as well as asphalt, fiber, and mineral powder, were measured.

[0123] The screening curves of coarse and fine aggregates and mineral powder are shown in Table 10 below.

[0124] Table 10 Screening curves of coarse aggregate, fine aggregate, and mineral powder

[0125]

[0126] The densities of coarse and fine aggregates are shown in Table 11 below.

[0127] Table 11 Density of coarse and fine aggregates

[0128]

[0129] In this embodiment, the relative density of the SBS asphalt used to prepare the asphalt mixture is 1.013 g / cm³. 3 The relative density of the mineral powder is 2.802 g / cm³. 3 The relative density of lignin fibers is taken as 0.351 g / cm³. 3 .

[0130] Secondly, the preliminary blending ratios of coarse aggregate, fine aggregate, and mineral powder for each grade are shown in Table 12 below.

[0131] Table 12 Blending ratio of coarse and fine aggregates and mineral powder

[0132]

[0133] Based on the sieving curves of coarse aggregate, fine aggregate and mineral powder in Table 10 and the blending ratios of coarse aggregate, fine aggregate and mineral powder in Table 12, the synthetic mineral gradation shown in Table 13 is obtained.

[0134] Table 13 Synthetic Mineral Gradation

[0135]

[0136] Next, based on the synthetic mineral gradation obtained in Table 13, the nominal maximum particle size is 4.75 mm. The passing rates under 2.36 mm and 0.075 mm sieves are 37.1% and 10.7%, respectively. It is determined that the passing rates of the synthetic mineral gradation under 2.36 mm and 0.075 mm sieves are in the range of 20% to 40% and 2.5% to 12.5%, respectively. Both passing rates are within the control range, so the following steps can be continued.

[0137] The fourth step is to calculate the VCA based on the density and gradation of the synthetic aggregate, referring to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). DRC The result was 36.3%.

[0138] The fifth step is to determine the asphalt-aggregate ratio based on the passing rate of the synthetic aggregate gradation through a 0.075mm sieve, which is 6.4%. Combined with the powder-to-binder ratio, it is initially proposed to be 1.7. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011), the asphalt-aggregate ratio is calculated to be 7.4%.

[0139] The SBS content in the SBS modified bitumen is 4%, and the amount of SBS bitumen used is 6.6% of the aggregate.

[0140] The dosage of the high-viscosity and high-elasticity additive is 0.5% of the mineral aggregate. The specific properties of the modified high-viscosity and high-elasticity asphalt are: ductility at 5℃ is 41cm, elastic recovery rate is 98.7%, and dynamic viscosity at 60℃ is 540000Pa·s.

[0141] The fiber is specifically lignin fiber, and its usage is 0.3% of the mineral.

[0142] Step 6: Based on the synthetic aggregate gradation and asphalt-aggregate ratio, prepare the asphalt mixture, determine the density and volumetric parameters of the ultra-thin overlay asphalt mixture, and calculate the VCA (Variable Accumulation Capacity) with reference to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). mixAnd VMA, and calculate CCD according to the above formula (1); and make a judgment, the results are shown in Table 14 below.

[0143] Table 14. Volumetric Parameter Results of Ultra-thin Overlay Asphalt Mixture

[0144]

[0145] Among the three conditions mentioned above, the coarse skeleton void ratio (VCA) of the asphalt mixture is... mix If the requirements are not met, the material is deemed unqualified. The amount of aggregate with a thickness of 3mm to 5mm is increased, or the amount of aggregate with a thickness of 0mm to 3mm is decreased. The synthetic gradation is then recalculated, as shown in Table 15 below.

[0146] Table 15. Proportions of coarse and fine aggregates and mineral powder

[0147]

[0148]

[0149] Based on the sieving curves of coarse aggregate, fine aggregate and mineral powder in Table 10 and the blending ratios of coarse aggregate, fine aggregate and mineral powder in Table 15, the synthetic mineral gradation shown in Table 16 is obtained.

[0150] Table 16 Synthetic Mineral Gradation

[0151]

[0152] Next, based on the synthetic mineral gradation obtained in Table 16, the nominal maximum particle size is 4.75 mm. The passing rates under 2.36 mm and 0.075 mm sieves are 36.0% and 12.0%, respectively. It is determined that the passing rates of the synthetic mineral gradation under 2.36 mm and 0.075 mm sieves are in the range of 20% to 40% and 2.5% to 12.5%, respectively. Both passing rates are within the control range, so the following steps can be continued.

[0153] The fourth step is to calculate the VCA based on the density and gradation of the synthetic aggregate, referring to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). DRC The result was 39.1%.

[0154] The fifth step is to determine the asphalt-aggregate ratio based on the passing rate of the synthetic aggregate gradation through a 0.075mm sieve, which is 12.0%. Combined with the powder-to-binder ratio, it is initially proposed to be 1.9. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011), the asphalt-aggregate ratio is calculated to be 7.5%.

[0155] The SBS content in the SBS modified bitumen is 4%, and the amount of SBS bitumen used is 6.6% of the aggregate.

[0156] The dosage of the high-viscosity and high-elasticity additive is 0.6% of the mineral aggregate. The specific properties of the modified high-viscosity and high-elasticity asphalt are: ductility at 5℃ is 42cm, elastic recovery rate is 99.2%, and dynamic viscosity at 60℃ is 630000Pa·s.

[0157] The fiber is specifically lignin fiber, and its usage is 0.3% of the mineral.

[0158] Step 6: Based on the synthetic aggregate gradation and asphalt-aggregate ratio, prepare ultra-thin overlay asphalt mixture, determine the density and volumetric parameters of the ultra-thin overlay asphalt mixture, and calculate the VCA (Variable Accumulation Capacity) with reference to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011). mix And VMA, and calculate CCD according to the above formula (1); and make a judgment, the results are shown in Table 17 below.

[0159] Table 17. Volumetric Parameter Results of Ultra-thin Overlay Asphalt Mixture

[0160]

[0161]

[0162] If all three conditions are met, the test is considered successful, and the following steps can be continued.

[0163] Finally, referring to the corresponding test methods in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011, T0705-2011), the road performance of the above-mentioned ultra-thin overlay asphalt mixture was verified, and the results are shown in Table 18.

[0164] Table 18 Test methods and road performance of ultra-thin overlay asphalt mixtures

[0165]

[0166] All three road performance characteristics mentioned above are met, and the mixture is deemed qualified. This indicates that the asphalt mixture prepared in the above steps meets the requirements and is a high-performance ultra-thin overlay asphalt mixture designed to meet the surface performance needs of roads.

[0167] Other application properties of the high-performance ultra-thin overlay asphalt mixture obtained above were tested, and the test results are shown in Table 19 below.

[0168] Table 19 Other Application Performance of High-Performance Ultra-Thin Overlay Asphalt Mixture

[0169]

[0170] aThe technical requirements refer to "JTG 5142-2019 Technical Specification for Highway Asphalt Pavement Maintenance".

[0171] From the test results of other properties of the ultra-thin overlay asphalt mixture obtained by the above design method in Table 19, it can be seen that the ultra-thin overlay asphalt mixture also exhibits excellent high-temperature deformation resistance, low-temperature crack resistance, and water damage resistance.

Claims

1. A design method for high-performance ultra-thin overlay asphalt mixtures to meet road surface performance requirements, characterized in that, Including the following steps: S1. Using a 2.36 mm sieve as the dividing line between coarse and fine aggregates, obtain the passing rates of each grade of coarse and fine aggregates under different sieve sizes, and determine the corresponding densities of each grade of coarse and fine aggregates, as well as asphalt, fiber and mineral powder. S2. Based on the passing rate and density of each grade of coarse aggregate and fine aggregate under different sieve openings obtained in step S1, the blending ratio of each grade of coarse aggregate, fine aggregate and mineral powder is initially determined to obtain the synthetic mineral gradation. S3. Based on the synthetic mineral aggregate gradation obtained in step S2, determine the passing rate of the synthetic mineral aggregate gradation under 2.36 mm and 0.075 mm sieves respectively; if both passing rates are within the control range, proceed to step S4; if at least one passing rate is not within the control range, return to step S2 to redesign and determine the blending ratio of each grade of coarse aggregate, fine aggregate and mineral powder. The control range refers to: ① When the nominal maximum particle size of the mineral aggregate is 9.5 mm, the passing rate under a 2.36 mm sieve is 20%~28%, and the passing rate under a 0.075 mm sieve is 2%~10%; ② When the nominal maximum particle size of the ore gradation is 4.75 mm, the passing rate under a 2.36 mm sieve is 20%~40%, and the passing rate under a 0.075 mm sieve is 2.5%~12.5%; S4. Based on the density obtained in step S1 and the synthetic aggregate gradation obtained in step S2, determine the coarse aggregate skeleton compaction gap ratio (VCA) of the synthetic aggregate gradation. DRC ; S5. Based on the passing rate of the synthetic mineral aggregate gradation obtained in step S2 under a 0.075 mm sieve, and in conjunction with the powder-to-binder ratio, determine the oilstone-to-aggregate ratio; wherein the powder-to-binder ratio is 1.0~2.0; S6. Based on the synthetic aggregate gradation obtained in step S2 and the asphalt-aggregate ratio obtained in step S5, prepare an ultra-thin overlay asphalt mixture, determine the density and volume parameters of the ultra-thin overlay asphalt mixture, and make a judgment. If all three of the following conditions are met simultaneously, the sample is deemed qualified and proceeds to step S7. If at least one condition is not met, the sample is deemed unqualified and the process returns to step S2 to redesign and determine the blending ratios of each grade of coarse aggregate, fine aggregate, and mineral powder. ① Coarse aggregate skeleton compaction gap ratio (VCA) DRC Coarse skeleton void ratio (VCA) of asphalt mixture mix The difference is ≥0.2%. ② The contact density (CCD) of coarse aggregates in ultra-thin overlay asphalt mixtures is ≥85%. The CCD is calculated using the following formula (1): CCD=(ρ G ×ρ GCA ) / VCA DRC (1) In equation (1), ρ G This is the bulk density of ultra-thin overlay asphalt mixture, expressed in g / cm³. 3 ;ρ GCA This is the bulk density of coarse aggregate, expressed in g / cm³. 3 ; ③ The aggregate void ratio (VMA) of ultra-thin overlay asphalt mixture is between 17.5% and 24%; S7. The qualified ultra-thin overlay asphalt mixture obtained in step S6 is subjected to the following road performance verification. If all three of the following road performance characteristics are qualified, the mixture is deemed qualified; if at least one road performance characteristic is unqualified, the mixture is deemed unqualified. The process then returns to step S2 to redesign and determine the blending ratios of each grade of coarse aggregate, fine aggregate, and mineral powder until an ultra-thin overlay asphalt mixture meeting the following road performance characteristics is obtained: a. The structural depth is not less than 0.8 mm. b. The permeability coefficient is not higher than 30 mL / min. c. The four-point bending fatigue life reaches 1 million cycles at 15℃ and 400 µε with modulus decay not exceeding 40%.

2. The design method according to claim 1, characterized in that, In the ultra-thin overlay asphalt mixture, the asphalt is SBS modified asphalt, and the mass percentage of SBS in the total asphalt is 2% to 6%.

3. The design method according to claim 1, characterized in that, In the ultra-thin overlay asphalt mixture, the additive is a high-viscosity additive, which enables the asphalt to have the following properties: ductility at 5℃ ≥ 40 cm, elastic recovery rate ≥ 97%, and dynamic viscosity at 60℃ ≥ 500000 Pa·s.

4. The design method according to claim 3, characterized in that, The additive is added via direct dosing.

5. The design method according to claim 3, characterized in that, The additive is a high-viscosity modifier, MA200.

6. The design method according to claim 1, characterized in that, In the ultra-thin overlay asphalt mixture, the fibers are selected from lignin fibers and / or polyester fibers.

Images