Small-particle-size high-anti-sliding cold-mixed and cold-laid asphalt ultra-thin wearing layer mixture and design method thereof

Abstract

The application discloses a kind of small particle size high anti-skid cold mixing and cold paving asphalt ultra-thin wearing layer mixture and its design method, belong to road engineering test field.The mixture, the aggregate 9.5mm aggregate screening passing rate 100%, 4.75mm screening passing rate range is 80%-100%, 2.36mm aggregate screening passing rate ≤35%, 0.075mm screening passing rate is 4%-15%;Mixture binder uses emulsified asphalt, emulsified asphalt residual evaporation softening point ≥65 DEG C, 60 DEG C dynamic shear complex modulus G*≥3.5kPa;Mixture asphalt film thickness DA ≥8.5 μm, gum content is 10%-20%, gum film thickness DA* is 30 μm-40 μm.Compared with prior art, the cold mixing and cold paving asphalt mixture design method of the application is scientific, practical, and the mixture road performance is balanced, and the pavement noise is low, the anti-skid effect is good, and safe and durable.

Description

Technical Field

[0001] This invention relates to the field of road engineering, specifically providing a small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture and its design method. Background Technology

[0002] With the extension of road pavement design concepts and service life in my country, road pavement maintenance methods have shifted from structural repair to preventative maintenance focused on surface function restoration. Against this backdrop, ultra-thin asphalt wearing courses have gained widespread demand. The current application status of ultra-thin asphalt wearing courses is as follows:

[0003] I. Hot-mix asphalt ultra-thin wearing course

[0004] Hot-mix asphalt ultra-thin wearing course is currently the most widely used ultra-thin asphalt wearing course. The binder is high-viscosity modified asphalt, and the construction temperature of the mixture is as high as 180-200℃, resulting in high on-site emissions. The construction process is demanding, difficult, and slow.

[0005] II. Micro-surfacing and other surface treatment types: cold-mixed, cold-laid, ultra-thin abrasion-resistant layer

[0006] Cold-mixed, cold-laid ultra-thin wearing course, represented by surface treatment maintenance, is characterized by its cold-mixed, cold-laid construction method. The mixture provides functions such as water sealing and rut filling, and the construction process is green, environmentally friendly, and fast. However, micro-surfacing technology is sensitive to the construction environment, exhibits significant early material separation, and faces challenges in process quality control. Furthermore, it cannot simultaneously achieve optimal noise reduction and skid resistance, resulting in unsatisfactory performance.

[0007] III. Single-particle-size spreadable ultrathin asphalt wearing course

[0008] The spread-type single-size asphalt ultra-thin wearing course uses single-size aggregate (excluding fillers) and fast-setting high-viscosity modified emulsified asphalt as the binder. Its construction process employs a spreading technique, resulting in rapid construction and environmental friendliness. While it offers relatively low road noise and fast construction speed, this technology has high requirements for the working environment, poor process stability, and because it involves spreading, the mixture does not have the function of filling ruts. Therefore, its effectiveness in treating road surface defects such as ruts and unevenness is limited, and it cannot effectively address the technical restoration of road surface conditions. Summary of the Invention

[0009] This invention addresses the shortcomings of the prior art by providing a design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wear course mixtures.

[0010] A further technical aspect of this invention is to provide a small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture.

[0011] The technical solution adopted by this invention to solve its technical problem is: a design method for a small-particle-size, high-skid-resistance cold-mixed and cold-laid asphalt ultra-thin wearing course mixture, wherein the aggregate used in the mixture has a 100% sieve passing rate for 9.5mm aggregate, a sieve passing rate of 80%-100% for 4.75mm aggregate, a sieve passing rate of ≤35% for 2.36mm aggregate, and a sieve passing rate of 4%-15% for 0.075mm aggregate;

[0012] The binder of the mixture is emulsified asphalt, the softening point of the residual evaporation of the emulsified asphalt is ≥65℃, and the dynamic shear complex modulus G* at 60℃ is ≥3.5kPa;

[0013] The asphalt film thickness DA of the mixture is ≥8.5μm, the mortar content is 10%-20%, and the mortar film thickness DA* is 30μm-40μm.

[0014] As a preferred approach, the mixture design method includes:

[0015] S1. Preset the composition ratio of each raw material;

[0016] S2. Conduct residual evaporation softening point tests and 60℃ dynamic shear tests on emulsified asphalt; simultaneously, calculate the asphalt film thickness and mastic film thickness of the mixture;

[0017] S3. If the key sieve aperture passing rate, residual evaporation softening point, dynamic shear complex modulus at 60℃, asphalt film thickness, mastic film thickness, or mastic content do not meet the requirements, return to step S1 and redesign; if the requirements are met, verify the performance of the mixture according to the determined material composition.

[0018] S4. Determine whether the test parameters of each performance of the mixture meet the requirements. If a certain performance does not meet the requirements, return to step S1, change the amount of emulsified asphalt and retest, or return to step S1 to redesign the gradation and retest. If all the performance of the mixture meets the test requirements, the mixture design process is completed.

[0019] Preferably, the mixture of the present invention further includes mineral powder and / or additives.

[0020] When the mineral powder content in the aggregate is insufficient, an appropriate amount of mineral powder can be added to adjust the mixing and molding state of the mixture and the filling effect of the mortar.

[0021] When the strength, construction characteristics, and road performance of the mixture need to be improved, appropriate admixtures, such as cement and hydrated lime powder, can be added.

[0022] Preferably, the raw materials of the mixture of the present invention also include water, which is used to adjust the mixing time.

[0023] Preferably, the thickness of the adhesive film is calculated according to the following formula:

[0024] SA=∑(P i ×FA i ) Formula 1

[0025]

[0026]

[0027]

[0028] In Equation 1:

[0029] SA is the specific surface area of ​​the aggregate, in kg / m². 2 ;

[0030] P i The sieve passing rate (%) of aggregates of various particle sizes;

[0031] FA i This refers to the surface area coefficient corresponding to aggregates of various particle sizes;

[0032] When calculating the specific surface area SA of aggregates, aggregates smaller than 0.075 mm are not included;

[0033] In Equation 2:

[0034] P fb The percentage of binder in asphalt mixture;

[0035] P b The content of residual evaporates in emulsified asphalt, in %;

[0036] P 0.075mm This indicates the pass rate (%) of aggregates with a screen aperture of less than 0.075 mm.

[0037] In Equation 3:

[0038] γ fb This represents the relative density of the adhesive.

[0039] γ f The bulk relative density of the filler is given, wherein the filler comprises all substances in the mixture smaller than 0.075 mm.

[0040] γ b The relative density of residual evaporated matter from emulsified asphalt (25℃).

[0041] In Equation 4:

[0042] DA* represents the thickness of the adhesive film, in μm.

[0043] When calculating the data for Formulas 2, 3, and 4, substances smaller than 0.075mm in the mixture, such as aggregates, mineral powder, and additives smaller than 0.075mm, are all included in the mortar.

[0044] As a preferred method, the dynamic shear complex modulus at 60℃ was tested using a dynamic shear rheometer, under the following test conditions:

[0045] Test spacing 1000μm; parallel plate diameter Strain control range: 5%-12%; sinusoidal loading.

[0046] Preferably, the emulsified asphalt is a slow-cracking, fast-setting type emulsified asphalt.

[0047] Preferably, the performance tests in step S4 mainly include tests on mixing time, molding strength, and water stability.

[0048] As a preferred method, when conducting water stability tests, after the wet wheel wear specimen has been cured, a rubber sheet with a Rockwell hardness of 60-70 HRC is placed on the surface of the specimen. Then, the wet wheel wear specimen covered with the rubber sheet is rolled using a wheel rutting machine, with 10-20 round trips.

[0049] Through extensive indoor research and engineering practice, the applicant discovered a strong correlation between the softening point of asphalt, the complex modulus at 60℃, and the molding strength of asphalt mixtures. The workability, water stability, and low-temperature performance of the mixture are determined by the thickness of the asphalt film and the thickness of the binder film: the asphalt film thickness provides the necessary mixing characteristics, while the thickness of the binder film determines the low-temperature and water stability of the mixture. The passing rates of key aggregate sieves (9.5mm, 4.75mm, 2.36mm, etc.) are highly correlated with pavement skid resistance and durability, as well as vehicle noise levels. Based on this, the applicant proposes a small-particle-size, high-skid-resistance cold-mixed, cold-laid asphalt ultra-thin wearing course mixture obtained using the design method of this invention.

[0050] The small-particle-size, high-skid-resistance cold-mixed and cold-laid asphalt ultra-thin wearing course mixture of the present invention can meet the pavement design requirements specified in various existing road engineering specifications. However, if it is necessary to further improve certain aspects of the pavement performance of the mixture, other existing road engineering additives can be added.

[0051] Compared with existing technologies, the small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture of the present invention has the following outstanding advantages:

[0052] (i) For the first time, the thickness of the adhesive film is proposed as the design standard for preparing cold-mixed and cold-laid asphalt ultra-thin wear course mixtures, and the key sieve holes are controlled, which is more scientific and practical than the existing design methods;

[0053] (ii) The designed mixture exhibits balanced road performance, low road noise, and good anti-skid effect.

[0054] Safe and durable;

[0055] (III) The cold-mixed, cold-laid, ultra-thin wearing course asphalt mixture obtained using the design method of this invention: ① can be achieved using existing surface treatment paving equipment, making its widespread application significant. ② The resulting mixture is green and environmentally friendly; ③ the construction process offers stable quality and fast construction speed. Attached Figure Description

[0056] Appendix Figure 1 Here is a flowchart of the mixture design method for an example;

[0057] Appendix Figure 2 This is a flowchart of the mixture preparation method for an example. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0059] Example

[0060] Cold-mixed and cold-laid asphalt ultra-thin wearing course mixture is prepared using emulsified asphalt (slow-cracking and fast-setting type), aggregates, mineral powder (optional), and admixtures (optional, including cement and hydrated lime) as the main raw materials.

[0061] As attached Figure 1 As shown, the design method for cold-mixed, cold-laid asphalt ultra-thin wearing course mixtures includes:

[0062] 1. Determine the composition of raw materials.

[0063] 1.1 Based on the project requirements and the characteristics of the raw materials, the composition ratio of materials such as emulsified asphalt, aggregates, mineral powder, and admixtures is pre-set (see Table 1 and Table 2 for details);

[0064] Table 1 Material Composition

[0065]

[0066] Table 2 shows the gradation composition of each example (including admixtures).

[0067]

[0068] 2. Indicator Verification

[0069] 2.1 Calculation and Verification of Membrane Thickness

[0070] The thickness of the asphalt film and the thickness of the adhesive film were determined according to the raw material ratios in Tables 1 and 2.

[0071] a. The asphalt film thickness was calculated according to the method described in the "Technical Specification for Construction of Asphalt Pavement of Highway" (JTGF40), and the calculation results are shown in Table 3.

[0072] b. The thickness of the adhesive film is calculated according to the following formula steps, and the calculation results are shown in Table 3:

[0073] SA=∑(P i ×FA i ) Formula 1

[0074]

[0075]

[0076]

[0077] In Equation 1:

[0078] SA is the specific surface area of ​​the aggregate, in kg / m². 2 ;

[0079] P i The sieve passing rate (%) of aggregates of various particle sizes;

[0080] FA i This refers to the surface area coefficient corresponding to aggregates of various particle sizes;

[0081] When calculating the specific surface area SA of aggregates, aggregates smaller than 0.075 mm are not included;

[0082] In Equation 2:

[0083] P fb The percentage of binder in asphalt mixture;

[0084] P b The content of residual evaporates in emulsified asphalt, in %;

[0085] P 0.075mm This indicates the pass rate (%) of aggregates with a screen aperture of less than 0.075 mm.

[0086] In Equation 3:

[0087] γ fb This represents the relative density of the adhesive.

[0088] γ f The bulk relative density of the filler (the filler includes aggregates smaller than 0.075 mm, mineral powder, and additives);

[0089] γ b The relative density of residual evaporated matter from emulsified asphalt (25℃);

[0090] In Equation 4:

[0091] DA* represents the thickness of the adhesive film, in μm.

[0092] When calculating the data for Formulas 2, 3, and 4, substances smaller than 0.075mm in the mixture, such as aggregates, mineral powder, and additives smaller than 0.075mm, are all included in the mortar.

[0093] Table 3 shows the calculated asphalt film thickness and sealant film thickness.

[0094]

[0095] 2.2 Performance Verification of Cementitious Material

[0096] The performance of the slow-cracking, fast-setting emulsified asphalt used was tested, and the specific indicators included the softening point of residual evaporates and the dynamic shear complex modulus at 60℃.

[0097] The softening point of residual evaporates was determined according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20), and the test results are shown in Table 4.

[0098] The dynamic shear complex modulus at 60℃ was determined using a dynamic shear rheometer. The test fixture consisted of 25mm circular parallel plates with a spacing of 1000μm. The strain was controlled at 12%, and sinusoidal loading was applied at a frequency of 10rad / s. The scanning time was 10s, and the test temperature was 60℃. The test results are shown in Table 4.

[0099] Table 4 Asphalt Performance Indicators

[0100] project Require Example 1 Example 2 Example 3 Example 4 Example 5 Test methods Softening point (R&B) ≥65 67.9 75.6 85.6 75.5 97.5 JTG E20 G*@60℃(kPa) ≥3.5 4.0 6.7 12.8 5.5 15.4 T 0628

[0101] 3. Performance Testing

[0102] The mixtures for Examples 1-5 were prepared according to the raw material ratios in Tables 1 and 2, and performance tests were conducted.

[0103] a) The mixing time and molding strength test shall be carried out by compacting and molding the asphalt surface treatment and sealing test method specified in the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20) to obtain the sample;

[0104] b) For water stability, wet tire wear specimens were prepared and cured according to the test methods specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20). After curing, rubber with a Rockwell hardness of 60-70 HRC was applied to the surface of the specimen. Then, the wet tire wear specimen covered with rubber was rolled using a rutting machine, with 16 round trips (e.g., 16 passes). Figure 2 (As shown).

[0105] c) The mixing time, molding strength and water stability tests were conducted on the prepared asphalt mixture according to the relevant test methods in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20). The test results are shown in Table 5.

[0106] Table 5 Performance Verification Results

[0107]

[0108] As can be seen from the test data in Table 5, the mixtures in Examples 1-5 all meet the requirements of the specifications.

Claims

1. A design method for a small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture, characterized in that: The aggregates used in the mixture have a 100% passing rate for 9.5mm aggregates, a passing rate of 80%-100% for 4.75mm aggregates, a passing rate of ≤35% for 2.36mm aggregates, and a passing rate of 4%-15% for 0.075mm aggregates. The binder of the mixture is emulsified asphalt, with a softening point of residual evaporation of emulsified asphalt ≥65℃ and a dynamic shear complex modulus G* ≥3.5kPa at 60℃; The asphalt mixture film thickness DA ≥ 8.5μm, the binder content is 10%-20%, and the binder film thickness DA* is 30μm-40μm. The thickness of the adhesive film is calculated according to the following formula: Official 1 Official 2 Official 3 Official 4 In Equation 1: SA is the specific surface area of ​​the aggregate, kg / m² 2 ; P i The sieve passing rate of aggregates of various particle sizes, % FA i This refers to the surface area coefficient corresponding to aggregates of various particle sizes; When calculating the specific surface area SA of aggregates, aggregates smaller than 0.075mm are not included; In Equation 2: P fb The percentage of binder in asphalt mixture, % P b The content of residual evaporates in emulsified asphalt, % P 0.075mm This indicates the passing rate of aggregates with a screen aperture of less than 0.075mm, expressed as % . In Equation 3: γ fb This represents the relative density of the adhesive. γ f The bulk relative density of the filler is given, wherein the filler comprises all substances in the mixture smaller than 0.075 mm. γ b The relative density of residual evaporated matter from emulsified asphalt at 25℃; In Equation 4: DA* represents the thickness of the adhesive film, in μm; Mixture design methods include: S1. Preset the composition ratio of each raw material; S2. Conduct residual evaporation softening point test and 60℃ dynamic shear test on emulsified asphalt, and calculate the asphalt film thickness and mastic film thickness of the mixture; S3. If the key sieve aperture passing rate, residual evaporation softening point, dynamic shear complex modulus at 60℃, asphalt film thickness, mastic film thickness, or mastic content do not meet the requirements, return to step S1 and redesign; if the requirements are met, verify the performance of the mixture according to the determined material composition. S4. Determine whether the test parameters of each performance of the mixture meet the requirements. If a certain performance does not meet the requirements, return to step S1, change the amount of emulsified asphalt, and retest, or return to step S1 to redesign the gradation and retest. If all the performance of the mixture meets the test requirements, the mixture design process is complete.

2. The design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture according to claim 1, characterized in that: The mixture also includes mineral powder and / or additives. The admixtures are cement and accelerators.

3. The design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture according to claim 1 or 2, characterized in that: The dynamic shear complex modulus at 60℃ was measured using a dynamic shear rheometer under the following conditions: Test spacing 1000μm; parallel plate diameter φ25mm; controlled strain range 5%-12%; sinusoidal loading.

4. The design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture according to claim 1 or 2, characterized in that: The emulsified asphalt is a slow-cracking, fast-setting type of emulsified asphalt.

5. The design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture according to claim 1 or 2, characterized in that: The performance tests described in step S4 mainly include tests on mixing time, molding strength, and water stability.

6. The design method for small-particle-size, high-skid-resistance cold-mix asphalt ultra-thin wearing course mixture according to claim 5, characterized in that: When conducting water stability tests, after the wet wheel wear specimen has been cured, a rubber sheet with a Rockwell hardness of 60-70 HRC is placed on the surface of the specimen. Then, the wet wheel wear specimen covered with the rubber sheet is rolled using a wheel rutting machine, with 10-20 round trips.

7. The small-particle-size, high-skid-resistance cold-mixed and cold-laid asphalt ultra-thin wear-resistant layer mixture obtained by the design method described in any one of claims 1-6.

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