Method for evaluating water stability of asphalt mixture

Abstract

The application discloses a kind of asphalt mixture water stability evaluation methods, according to the adhesion binding energy of asphalt and filler, asphalt cohesion binding energy, and the volume fraction of filler in asphalt mortar, the critical volume fraction of filler determines the interaction parameter of asphalt and filler, to express the interaction problem between asphalt and filler;Then the state equation method is used to calculate the cohesion binding energy of asphalt mortar, and then the surface energy of asphalt mortar is approximately calculated, and the asphalt mixture water stability index considering filler is proposed based on this, and the prediction effect of the index on water stability is analyzed.The application more reasonably describes the process of asphalt mortar itself fracture in pavement water damage from the energy angle, so that the evaluation of asphalt mixture water stability is more in line with the actual situation, and it is of great significance for asphalt pavement performance evaluation.

Description

Technical Field

[0001] This invention belongs to the field of road engineering, and specifically relates to a method for evaluating the water stability of asphalt mixtures. Background Technology

[0002] Asphalt pavement is widely used as one of the main structural forms of highways in my country. During its all-weather service life, water damage caused by factors such as temperature and vehicle load is one of the main forms of early pavement distress, directly affecting driving safety, speed, and comfort, reducing pavement service life, and increasing maintenance costs. Water damage to asphalt pavement is a phenomenon caused by the presence of liquid or gaseous water, leading to a decrease in the mechanical properties of the asphalt mixture. Specific forms of damage include spalling, loosening, particle loss, and water erosion. Spalling is the first stage of water damage in asphalt pavement. The subsequent repeated traffic loads cause the asphalt mixture to loosen and lose particles, eventually leading to large-scale water erosion. Spalling occurs when, under vehicle load and water conditions, the adhesion between asphalt and aggregate is disrupted, or the asphalt material itself fractures, causing the asphalt film to peel off from the aggregate surface. Domestic and international research on adhesion mechanisms mainly focuses on five theories: mechanical theory, chemical reaction theory, surface energy theory, molecular orientation theory, and electrostatic theory. Related studies suggest that surface energy theory is the most powerful theoretical method in the study of asphalt-aggregate adhesion.

[0003] Asphalt mixtures are rheological composite materials composed of irregular particles of multiple scales, including asphalt materials, fillers, fine aggregates, and coarse aggregates, stacked together. The fillers are dispersed within the asphalt to form an asphalt mastic system, which plays a crucial role in binding the coarse and fine aggregates, filling voids, and transferring loads, thus significantly influencing the structure and strength of the asphalt mixture. From a microscopic perspective, spalling can be attributed to two failure modes: adhesive failure occurring at the asphalt-aggregate interface and cohesive loss occurring within the asphalt matrix. The former is related to the adhesive bonding energy between the asphalt mastic and the aggregates, while the latter is related to the cohesive bonding energy between the asphalt and the asphalt mastic.

[0004] Current methods for evaluating the surface energy of adhesion between asphalt and aggregates often use asphalt as an approximation to replace asphalt mastic, neglecting the enhancing effect of fillers on the adhesion of asphalt mastic. This results in underestimating the cohesive and adhesive binding energy, affecting the accuracy of the evaluation of the water stability of asphalt mixtures.

[0005] Some scholars have conducted research on the adhesive properties of asphalt mastic, but these studies have largely copied the evaluation approaches and methods used for asphalt adhesive properties. Asphalt and fillers have significantly different bulk properties, making mastic essentially a two-phase material. However, due to the high viscosity of asphalt at room temperature, even with uneven dispersion of its components, phase separation does not occur, and it maintains macroscopic homogeneity. Only the high mobility of flexible asphalt molecules in small regions causes the incompatible two phases to separate, forming a microscopic multiphase morphology. Using methods for evaluating asphalt to evaluate asphalt mastic yields ideal results for macroscopic mechanical properties such as complex shear modulus and creep compliance. However, when studying interfacial issues such as surface energy and bonding properties, the results are not significantly different from those of undisturbed asphalt. Therefore, it is necessary to improve experimental methods and theoretical calculation approaches for the two-phase material properties of asphalt mastic, and to conduct interfacial studies that better reflect the actual conditions of asphalt mastic. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for evaluating the water stability of asphalt mixtures. This invention proposes a novel water stability evaluation index based on the surface energy of asphalt mastic, taking into account the influence of fillers on the internal adhesion of asphalt mixtures, thus making the evaluation of the water stability of asphalt mixtures more consistent with actual conditions.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for evaluating the water stability of asphalt mixtures includes the following steps:

[0009] S1. The surface energy of asphalt was determined by the plate insertion method, and the surface energy of filler was determined by the improved capillary rise method.

[0010] S2. Calculate the cohesive bonding energy of the asphalt and the cohesive bonding energy of the filler based on the surface energy of the asphalt and the surface energy of the filler, and calculate the energy difference coefficient between the asphalt and the filler.

[0011] S3. Determine the adhesive bonding energy between asphalt and filler based on the cohesive bonding energy of the asphalt, the cohesive bonding energy of the filler, and the energy difference coefficient between asphalt and filler.

[0012] S4. Determine the interaction parameters between asphalt and filler based on the adhesive bonding energy between asphalt and filler, the cohesive bonding energy of asphalt, the volume fraction of filler in asphalt mastic, and the critical volume fraction of filler.

[0013] S5. Calculate the cohesive energy of the asphalt mastic based on the interaction parameters between the asphalt and the filler, the adhesive bonding energy between the asphalt and the filler, and the cohesive bonding energy of the filler, and calculate the surface energy of the asphalt mastic based on the cohesive bonding energy of the asphalt mastic.

[0014] S6. Calculate the adhesion work between the asphalt mastic and the aggregate, and the stripping work of the asphalt mastic, aggregate, and water three-phase materials based on the surface energy of the asphalt mastic.

[0015] S7. Based on the adhesion work between the asphalt mastic and the aggregate, the stripping work of the three-phase materials of asphalt mastic, aggregate, and water, as well as the specific surface area of ​​the aggregate and the thickness of the asphalt mixture oil film, calculate the water stability evaluation index of the asphalt mixture and evaluate the water stability of the asphalt mixture.

[0016] Furthermore, the formulas for calculating the cohesive binding energy of asphalt, the cohesive binding energy of filler, and the energy difference coefficient between asphalt and filler in step S2 are as follows:

[0017] W AA =2γ A

[0018] W FF =2γ F

[0019]

[0020] In the formula: W AA W is the cohesive bonding energy of asphalt. FF The cohesive binding energy of the filler; γ A γ represents the total surface energy of asphalt; F This represents the total surface energy of the filler. α is the energy difference coefficient between asphalt and filler; α is the experimental fitting parameter.

[0021] Furthermore, the formula for calculating the adhesive bonding energy between asphalt and filler in step S3 is as follows:

[0022]

[0023] In the formula: W AM The adhesive bonding energy between asphalt and filler; This is the energy difference coefficient between asphalt and filler.

[0024] Furthermore, the calculation formula for the interaction parameters between asphalt and filler in step S4 is as follows:

[0025]

[0026] In the formula: β is the interaction parameter between asphalt and filler; W AM W represents the adhesive bonding energy between asphalt and filler. AA η is the cohesive binding energy of asphalt; η is the volume fraction of filler; η MAX This represents the critical volume fraction of the packing material.

[0027] Furthermore, the formula for calculating the cohesive bonding energy of the asphalt mastic in step S5 is as follows:

[0028]

[0029] In the formula: ΔG M The cohesive bonding energy of asphalt mastic; W AM W represents the adhesive bonding energy between asphalt and filler. AA It represents the cohesive bonding energy of asphalt.

[0030] Furthermore, the formula for calculating the surface energy of the asphalt mastic in step S5 is as follows:

[0031] ΔG M =-2γ M

[0032] In the formula: ΔG M The cohesive energy of asphalt mastic; γ M It is the surface energy of asphalt mortar.

[0033] Furthermore, the formula for calculating the adhesion work between the asphalt binder and the aggregate in step S6 is as follows:

[0034]

[0035] In the formula: ΔG SM The adhesion work between asphalt mortar and aggregate; γ is the energy difference coefficient between asphalt binder and aggregate; S For aggregate surface energy; γ M It is the surface energy of asphalt mortar.

[0036] Furthermore, the formula for calculating the stripping energy of the asphalt binder, aggregate, and water three-phase material in step S6 is as follows:

[0037]

[0038] In the formula: ΔG SWM The stripping work of the asphalt mortar, aggregate, and water three-phase materials; The energy difference coefficient between aggregates and water; γ is the energy difference coefficient between asphalt mortar and water; W It is the surface energy of water.

[0039] Furthermore, the calculation formula for the water stability evaluation index of asphalt mixture in step S7 is as follows:

[0040]

[0041] In the formula, ΔG SMΔG is the adhesion work between asphalt mastic and aggregate; SSA is the specific surface area of ​​aggregate; DA is the asphalt film thickness; ΔG SWM The stripping work of the three-phase materials of asphalt mortar, aggregate, and water.

[0042] Furthermore, the formulas for calculating the specific surface area of ​​aggregates and the thickness of asphalt film in asphalt mixtures are as follows:

[0043] SSA=∑(P i ·FA i )

[0044]

[0045] In the formula: P i FA represents the percentage of aggregate particles of each size that pass through. i P represents the surface area coefficient of aggregates corresponding to various particle sizes. be Effective asphalt content; γ b ρ is the relative density of asphalt; SSA is the specific surface area of ​​the aggregate.

[0046] The beneficial effects of this invention are:

[0047] This invention calculates the surface energy of asphalt mastic based on the equation of state method. By analyzing the surface energy of asphalt mastic prepared with different asphalt and fillers and corresponding powder-to-binder ratios, the adhesive properties of asphalt mastic are quantified. Furthermore, water stability evaluation indicators are calculated, taking into account the influence of fillers on the internal adhesion of asphalt mixtures. Thus, the water stability of asphalt mixtures can be predicted, providing a more accurate basis for preventing water damage to asphalt pavements.

[0048] This invention uses the surface energy parameters of asphalt and mineral powder to calculate the surface energy of asphalt mastic instead of the surface energy of asphalt to calculate the water stability evaluation index, and predicts the water stability performance of asphalt mixtures. This is more consistent with the internal structure of asphalt mixtures in actual engineering conditions and is of great significance for preventing water damage to asphalt mixtures. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0050] Figure 1 This is a schematic diagram of the process for evaluating the water stability of asphalt mixtures provided by the present invention.

[0051] Figure 2 This is a schematic diagram of the critical volume fraction test method for asphalt mastic filler of the present invention;

[0052] Figure 3 This is a diagram showing the AI ​​water stability test results of asphalt mixture in an embodiment of the present invention;

[0053] Figure 4 The figure shows the JR water stability test results of the asphalt mixture in the embodiment of the present invention. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] Example:

[0056] Please see Figure 1 This embodiment provides a method for evaluating the water stability of asphalt mixtures, including the following steps:

[0057] S1. The surface energy of asphalt was determined using the indenter plate method;

[0058] A K100 fully automatic surface tension meter with an accuracy of 0.1 mN was used. A constant temperature water bath was selected to control the ambient temperature during the test, with a temperature control accuracy of ±0.02℃, which can ensure the stability of the ambient temperature to the greatest extent. The test temperature was 20℃, and the three test reagents used were distilled water, ethylene glycol, and formamide. The specific test steps of the asphalt surface energy insertion plate method are as follows:

[0059] (a) Place the SBS modified bitumen in a 170°C oven and heat for half an hour until it is in a fluid state. Place the metal container containing the bitumen on a constant temperature heating furnace and keep the heating temperature constant.

[0060] (b) Clean the slides with acetone and distilled water respectively, wipe the moisture off the surface of the slides with lint-free test paper, and then dry the slides with a spray gun for later use.

[0061] (c) Insert the cleaned glass slide vertically and slowly into the asphalt at a uniform speed. When the depth reaches about 35 mm, slowly remove the glass slide at a uniform speed. When the bottom of the glass slide leaves the surface of the asphalt, quickly turn it upside down and let the asphalt on the top of the glass slide flow down naturally. When the asphalt at the top of the glass slide flows to the asphalt wetting line, quickly wipe away the excess asphalt with lint-free test paper to obtain the completed asphalt glass slide.

[0062] (d) Place a certain amount of solid desiccant in the drying oven, and then place the finished asphalt glass slide in the drying oven for curing treatment, ensuring that the curing time is not less than 24 hours, in order to remove the residual moisture on the surface of the asphalt glass slide.

[0063] (e) Place the container containing the test reagent on the test bench of the K100 fully automatic surface tension meter, insert the external temperature probe of the device into the test reagent, turn on the constant temperature water bath and set the test temperature.

[0064] (f) Remove the asphalt glass slide from the drying oven, measure the width and thickness of the asphalt glass slide with vernier calipers and record the measurements. The dimension test surface is selected at about 5 mm from the asphalt wetting line to ensure that the integrity of the asphalt glass slide surface above the dimension test surface is not damaged.

[0065] (g) After the dimensions of the asphalt slide are recorded, suspend and fix it on the fixture of the fully automatic surface tension meter, and ensure that its bottom is horizontal. Then adjust the lifting platform so that the reagent liquid surface is about 2 mm away from the bottom of the asphalt slide. Finely adjust the tilt angle of the slide so that it is flush with the reagent liquid surface, but do not let it touch the reagent liquid surface.

[0066] (h) Replace the asphalt glass slide and test reagent in sequence. Input the glass slide size measured in step (f) into the fully automatic surface tension meter software, set the initial wetting depth to 2 mm, the final wetting depth to 10 mm, and the wetting speed to 3 mm / min.

[0067] (i) Read and record the contact angle data between the asphalt slide and each test reagent. Each asphalt sample should be tested in at least three parallel tests. The maximum difference in contact angle between each test should not exceed 1°, and the coefficient of variation should not exceed 10%. Otherwise, the test should be repeated. The asphalt contact angle test data are shown in Table 1.

[0068] Table 1. Contact angles between asphalt and various test reagents

[0069]

[0070] The total surface energy of asphalt is calculated based on the equation of state, and the calculation equation is shown in formula (1):

[0071]

[0072] In the formula: γ L To test the total surface energy of the reagent, mJ / m 2 ;γ A The total surface energy of asphalt, in mJ / m 2 ;α A θ represents the experimental fitting parameters, which are dimensionless; θ is the contact angle between asphalt and the test reagent.

[0073] The surface energy parameters of the modified asphalt calculated according to the above formula are shown in Table 2:

[0074] Table 2 Test results of surface energy parameters of SBS modified asphalt

[0075] Asphalt type Fit factor <![CDATA[Surface energy / (mJ / m 2 )]]> <![CDATA[R 2 ]]> SBS-1 0.1076 18.94 0.9982 SBS-2 0.1046 18.25 0.9998 SBS-3 0.1619 21.30 0.9996

[0076] S2. The surface energy of the filler was determined using an improved capillary rise method.

[0077] Based on the traditional capillary rise method, an improved capillary rise method considering diffusion pressure is proposed to avoid inaccurate test results caused by the traditional method where the test reagent and filler are completely wetted and do not form a stable contact angle. Therefore, the capillary rise method considering diffusion pressure, based on the original capillary rise method test conditions, first measures the effective radius of the capillary, then calculates the diffusion pressure value of the filler sample on the test reagent, and substitutes it into the Young-Dupre equation considering the reagent diffusion pressure to solve for the surface energy parameters of powdered solid materials such as mineral powder.

[0078] This embodiment uses a K100 fully automatic surface tension meter to test two types of limestone mineral powder using an improved capillary rise method. A constant temperature water bath is used to control the ambient temperature during the test, with a temperature control accuracy of ±0.02℃, which can ensure the stability of the ambient temperature to the greatest extent. Three test reagents, toluene, n-hexane, and formamide, are used to test the mineral powder with no liquid film on its surface and completely dry. Linear fitting is used to obtain the m-response ratio of the mineral powder to each reagent. 2 The effective capillary radius of the mineral powder is calculated by combining the / t ratio with formula (2).

[0079]

[0080] In the formula: R e η is the effective synthetic radius of the filler, in meters; η is the viscosity of the test reagent, in mPa·s; ρ L To test the density of the reagent, g / cm³ 3 m is the mass of the mineral powder absorbed by the test reagent, in g; t is the test time, in s.

[0081] The diffusion pressure π of the packing material on each reagent is calculated using equation (3). e .

[0082]

[0083] The surface energy of the mineral powder is calculated using equation (4).

[0084]

[0085] In the formula: γ F The total surface energy of the mineral powder is expressed in mJ / m³. 2 ;α M The experimental fitting parameters are dimensionless; γ L To test the surface energy of the reagent, mJ / m 2 .

[0086] The surface energy parameters of the mineral powder were tested and the results are shown in Table 3.

[0087] Table 3 Surface Energy Test Results of Mineral Powder

[0088] Mineral powder type <![CDATA[Effective radius / 10 -4 m]]> Fit factor <![CDATA[Surface energy / (mJ / m 2 )]]> <![CDATA[R 2 ]]> Limestone-1 4.72 0.1277 132.79 0.9995 Limestone-2 4.95 0.2289 136.81 0.9996

[0089] S3. Preparation of asphalt mortar using a high-speed shear tester

[0090] SBS modified asphalt was heated in a 170℃ oven for half an hour until it was in a fluid state. The metal container containing the asphalt was placed in a constant temperature electric heating mantle to keep the heating temperature constant. A certain mass of mineral powder was calculated and weighed according to the mass of asphalt and the powder-to-binder ratio in the metal container. After the asphalt was stirred by starting the agitator, the mineral powder was added to the asphalt in three batches at a speed of 1500 r / min for 5 minutes each time. After the three batches were completed, the mixture was stirred for another 3 minutes to complete the preparation of the asphalt mortar.

[0091] Asphalt mastic has a critical volume fraction for fillers. If the filler content exceeds this ratio, some filler particles will not be fully wetted, leading to agglomeration and clumping of mineral powder, and a rapid decrease in the adhesion of the asphalt mastic. Therefore, the powder-to-binder ratio of the asphalt mastic in the embodiments of the invention is determined to be 0.8, 1.0, and 1.2.

[0092] The test materials were asphalt mortars with three powder-to-binder ratios prepared using three types of asphalt and two types of mineral powder, totaling eighteen types of asphalt mortars. The conversion method between different asphalt powder-to-binder ratios and filler volume fractions is shown in Equation (5), and the conversion results are shown in Table 4.

[0093]

[0094] In the formula: V F Let C be the volume of the mineral powder, in cm. 3 V A The volume of asphalt is in cm³. 3 .

[0095] Table 4. Filler volume fraction for different powder-to-binder ratios in asphalt mastic.

[0096]

[0097] The critical volume fraction of asphalt mastic filler is determined using a two-point method. Specifically, the critical volume fraction is calculated by fitting the reciprocal of the relative creep compliance measure after 20 seconds of load application to the X-axis. The specific method is as follows: Figure 2 As shown in Table 5, the test results of the critical volume fraction of the packing are as follows.

[0098] Table 5. Test results of critical volume fraction of packing material

[0099]

[0100]

[0101] S4. Calculate the cohesive energy of asphalt, the cohesive energy of filler, and the energy difference coefficient between asphalt and filler based on the surface energy of asphalt and filler, respectively.

[0102] The interaction between asphalt and filler leads to the formation of structural asphalt on the surface of the filler. The stronger the interaction, the greater the relative content of structural asphalt, and the greater the influence of the filler on the asphalt mastic. To calculate the interaction parameters of the asphalt mastic, the cohesive binding energy of asphalt and mineral powder must first be obtained. The calculation method is shown in equation (6-7).

[0103] W AA =2γ A (6)

[0104] W FF =2γ F (7)

[0105] In the formula: W AA W is the cohesive bonding energy of asphalt. FF The cohesive binding energy of the filler; γ A γ represents the total surface energy of asphalt; F This represents the total surface energy of the filler.

[0106] The energy difference coefficient between asphalt and filler is calculated based on surface energy test parameters, and the equation is shown in equation (8):

[0107]

[0108] In the formula: γ is the energy difference coefficient between asphalt and filler; α is the experimental fitting parameter. A γ represents the total surface energy of asphalt; F This represents the total surface energy of the filler.

[0109] S5. Determine the adhesive bonding energy between asphalt and filler based on the cohesive bonding energy of asphalt, the cohesive bonding energy of filler, and the energy difference coefficient between asphalt and filler.

[0110] Adhesion bonding energy W between asphalt and filler AM The cohesive bonding energy W of asphalt can be used to... AA Cohesive binding energy W of filler FF and the energy difference coefficient between asphalt and filler The calculation is performed, and the calculation formula is shown in equation (9).

[0111]

[0112] In the formula: W AM The adhesive bonding energy between asphalt and filler; This is the energy difference coefficient between asphalt and filler.

[0113] S6. Determine the interaction parameters between asphalt and filler based on the adhesive bonding energy between asphalt and filler, the cohesive bonding energy of asphalt, the volume fraction of filler in asphalt mastic, and the critical volume fraction of filler.

[0114] Fillers primarily influence the adhesion of asphalt mastic through their own physicochemical properties and the powder-to-binder ratio of asphalt. Existing research indicates that the powder-to-binder ratio of the mastic has a very significant impact on the adhesion of asphalt mastic, far exceeding the influence of other properties. The specific surface area, particle size, and chemical composition of the filler all affect its surface energy. Therefore, this invention uses the filler surface energy to characterize the influence of specific surface area, particle size, and chemical composition, and converts the powder-to-binder ratio into a filler volume fraction. The calculated filler volume fraction and critical volume fraction are shown in Tables 4 and 5, respectively.

[0115] This invention uses an asphalt mastic viscosity enhancement model to characterize the effect of different filler volume fractions on the cohesive bonding energy of asphalt mastic, and the interaction parameter β is determined by equation (10).

[0116]

[0117] In the formula: β is the interaction parameter between asphalt and filler; W AM W represents the adhesive bonding energy between asphalt and filler. AA η is the cohesive binding energy of asphalt; η is the volume fraction of filler; η MAX It represents the critical volume fraction of asphalt mastic.

[0118] S7. Calculate the cohesive energy of the asphalt mastic based on the adhesive bonding energy between asphalt and filler, the interaction parameters between asphalt and filler, and the cohesive bonding energy of filler. Calculate the surface energy of the asphalt mastic based on the cohesive bonding energy of the asphalt mastic.

[0119] The cohesive energy ΔG of asphalt mastic M As shown in equation (11).

[0120]

[0121] In the formula: ΔG M The cohesive bonding energy of asphalt mastic; W AM W represents the adhesive bonding energy between asphalt and filler. AA It represents the cohesive bonding energy of asphalt.

[0122] The surface energy of the asphalt mastic is calculated according to equation (12):

[0123] ΔG M =-2γ M (12)

[0124] In the formula: ΔG M The cohesive energy of asphalt mastic; γ M It is the surface energy of asphalt mortar.

[0125] The calculation results of the cohesive bonding energy and surface energy of asphalt mastic are taken as absolute values, as shown in Tables 6 and 7, respectively.

[0126] Table 6. Calculation results of cohesive bonding energy of asphalt mastic (mJ / m) 2 )

[0127]

[0128]

[0129] Table 7 Calculation results of surface energy of asphalt mastic (mJ / m) 2 )

[0130]

[0131] S8. The adhesion work between asphalt mastic and filler is calculated based on the surface energy of asphalt mastic and filler; and the exfoliation work of the three-phase materials of asphalt mastic, filler and water is calculated based on the surface energy of asphalt mastic, aggregate and water.

[0132] The calculation formula is shown in equation (13-14):

[0133]

[0134]

[0135] In the formula: ΔG SM The adhesion work between asphalt mortar and aggregate; γ is the energy difference coefficient between asphalt binder and aggregate; S For aggregate surface energy; γ M For the surface energy of asphalt mortar; ΔG SWM The stripping work of the asphalt mortar, aggregate, and water three-phase materials; The energy difference coefficient between aggregates and water; γ is the energy difference coefficient between asphalt mortar and water; W It is the surface energy of water.

[0136] S9. Based on the adhesion work between asphalt mastic and filler, the specific surface area of ​​filler, the thickness of asphalt mixture oil film, and the exfoliation work of asphalt mastic, filler, and water three-phase materials, the water stability evaluation index of asphalt mastic is calculated.

[0137] Studies have shown that fillers also have a significant impact on the water stability of asphalt mixtures. This invention uses the surface energy of asphalt mastic to replace the surface energy of asphalt, and proposes a new evaluation index WS for the water stability of asphalt mixtures. The calculation formula is shown in equation (15).

[0138]

[0139] In the formula, ΔG SM ΔG is the adhesion work between asphalt binder and aggregate; SSA is the specific surface area of ​​aggregate; ΔG M ΔG represents the cohesive bonding energy of the asphalt mastic; DA represents the asphalt mixture film thickness; ΔG SWM The stripping work of the three-phase materials of asphalt mortar, aggregate, and water.

[0140] Among them, the aggregate specific surface area SSA and the asphalt mixture oil film thickness DA are calculated according to formula (16-17).

[0141] SSA=∑(P i ·FA i (16)

[0142]

[0143] In the formula: P i FA represents the percentage of aggregate particles of each size that pass through. i P represents the surface area coefficient of aggregates corresponding to various particle sizes. be Effective asphalt content; γ b ρ is the relative density of asphalt; SSA is the specific surface area of ​​the aggregate.

[0144] Verification experiment:

[0145] (1) Asphalt mortar surface energy insertion plate test

[0146] Three types of SBS modified asphalt (ID class: SBS-1, SBS-2, SBS-3) and two types of fillers (LM-1, LM-2) were selected as described above. The surface energy of the asphalt mastic was tested using a high-speed shear tester and a K100 fully automatic surface tension meter. The test temperature was 20℃. Distilled water, ethylene glycol and formamide were used as test reagents. The test results are shown in Table 8.

[0147] Table 8 Test values ​​of surface energy of asphalt mastic (mJ / m) 2 )

[0148]

[0149] By comparing the calculated and experimental values ​​in Tables 7 and 8, it was found that the calculated and experimental values ​​of the surface energy of asphalt mastic were not significantly different from those of the original asphalt sample, and the differences between different powder-to-mass ratios were also small. This indicates that directly testing the surface energy of asphalt mastic using the plate insertion method inevitably biases towards the data of the original asphalt sample to some extent, and cannot accurately test the actual adhesion state of the asphalt mastic.

[0150] (2) Asphalt mixture water stability test

[0151] To control experimental variables and facilitate data comparison and analysis, the same limestone aggregate was used for the three different modified asphalts. The aggregate was produced in Ezhou, Hubei Province, and its various indicators are shown in Table 9. Marshall tests were conducted to obtain the optimal gradation of SBS-1 modified asphalt with the limestone aggregate. The mix design is shown in Table 10, and the optimal asphalt-aggregate ratio is 4.1%. The aggregate specific surface area SSA was calculated to be 3.037 according to formula (16).

[0152] Table 9. Test Results of Limestone Aggregate Performance

[0153]

[0154] Table 10 Optimal Grading of Limestone AC-20C

[0155]

[0156]

[0157] Three different asphalt mixtures were prepared according to the optimal gradation and optimal asphalt-aggregate ratio of SBS-1 modified asphalt and limestone aggregate, with asphalt film thicknesses of 6.986, 6.972, and 6.746, respectively. The powder-to-binder ratio in the mixtures was adjusted to achieve effective asphalt to mineral powder ratios of 0.8, 1.0, and 1.2, respectively. Based on the type of asphalt mastic prepared, 18 corresponding Marshall specimens of asphalt mixtures were prepared, numbered sequentially as shown in Table 11. Each mixture underwent a water immersion Marshall test. The average stability of the three groups with coefficients of variation within 5% was calculated, and the water stability of the asphalt mixtures was calculated based on the ratio of the test group to the control group. The water stability test results are shown in Table 12. The water stability index (WS) of the above 18 asphalt mixtures was calculated according to the methods in steps S1-S9, as shown in Table 13.

[0158] Table 11 Mixture Specimen Numbers

[0159]

[0160] Table 12 Marshall Immersion Test

[0161]

[0162]

[0163] Table 13 Water Stability Evaluation Indicators WS

[0164] serial number <![CDATA[ΔG SM ]]> <![CDATA[ΔG M ]]> <![CDATA[ΔG SWM ]]> WS A 27.83 38.78 38.26 2.55 B 34.57 44.82 37.00 3.26 C 42.41 51.36 35.54 4.15 D 25.17 36.27 38.76 2.28 E 30.88 41.57 37.69 2.87 F 37.17 47.03 36.52 3.55 G 35.62 45.72 36.80 3.38 H 44.06 52.68 35.23 4.36 I 53.69 60.11 33.43 5.58 J 29.26 40.10 37.99 2.70 K 37.38 47.21 36.48 3.57 L 48.24 55.97 34.44 4.86 M 27.82 38.77 38.26 2.55 N 36.71 46.65 36.60 3.50 O 51.65 58.57 33.81 5.30 P 35.44 45.56 36.84 3.36 Q 43.83 52.50 35.27 4.33 R 53.42 59.90 33.48 5.54

[0165] Based on the type of mineral powder, the experimental results were divided into two groups for analysis: the first group (AI) used LM-1 mineral powder, and the second group (JR) used LM-2 mineral powder. A relationship curve was established with the water stability index WS proposed in this invention as the abscissa and the residual stability of the Marshall specimen after immersion as the ordinate, as shown below. Figure 3-4 As shown. By Figure 3-4 Analysis shows that, for residual stability after immersion, the goodness of fit between the proposed index WS and the macroscopic water stability index is higher than 0.9, reaching a maximum of 0.9426. In contrast, the goodness of fit of the existing evaluation index EQI is only 0.8771, and the goodness of fit of the evaluation index ER using the GvOC method is only 0.7587, both lower than the goodness of fit of the proposed index WS. Furthermore, these two indices cannot distinguish between asphalt mixtures with different powder-to-binder ratios; constructing an index solely based on asphalt and aggregate data cannot accurately evaluate the water stability of asphalt mixtures that are actually composed of asphalt mastic and aggregates.

[0166] In summary, compared to traditional methods like GvOC and evaluation indices that only target asphalt and aggregates, this invention proposes a novel water stability evaluation index, WS, based on the surface energy of asphalt mastic. This index considers the influence of fillers on the internal adhesion of asphalt mixtures, exhibits a higher goodness of fit with macroscopic experimental indices, and shows a strong positive correlation. Furthermore, the evaluation results have higher discriminative power and wider applicability. Therefore, the index WS provided by this invention can more accurately evaluate the water stability of asphalt mixtures.

[0167] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0168] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for evaluating the water stability of asphalt mixtures, characterized in that, Includes the following steps: S1. The surface energy of asphalt was determined by the plate insertion method, and the surface energy of filler was determined by the improved capillary rise method. S2. Calculate the cohesive bonding energy of the asphalt and the cohesive bonding energy of the filler based on the surface energy of the asphalt and the surface energy of the filler, and calculate the energy difference coefficient between the asphalt and the filler. S3. Determine the adhesive bonding energy between asphalt and filler based on the cohesive bonding energy of the asphalt, the cohesive bonding energy of the filler, and the energy difference coefficient between asphalt and filler. S4. Determine the interaction parameters between asphalt and filler based on the adhesive bonding energy between asphalt and filler, the cohesive bonding energy of asphalt, the volume fraction of filler in asphalt mastic, and the critical volume fraction of filler. S5. Calculate the cohesive energy of the asphalt mastic based on the interaction parameters between the asphalt and the filler, the adhesive bonding energy between the asphalt and the filler, and the cohesive bonding energy of the filler, and calculate the surface energy of the asphalt mastic based on the cohesive bonding energy of the asphalt mastic. S6. Calculate the adhesion work between the asphalt mastic and the aggregate, and the stripping work of the asphalt mastic, aggregate, and water three-phase materials based on the surface energy of the asphalt mastic. S7. Based on the adhesion work between the asphalt mastic and the aggregate, the stripping work of the three-phase materials of asphalt mastic, aggregate, and water, as well as the specific surface area of ​​the aggregate and the thickness of the asphalt mixture oil film, calculate the water stability evaluation index of the asphalt mixture and evaluate the water stability of the asphalt mixture. The calculation formulas for the cohesive binding energy of asphalt, the cohesive binding energy of filler, and the energy difference coefficient between asphalt and filler mentioned in step S2 are as follows: In the formula: The cohesive bonding energy of asphalt; The cohesive binding energy of the filler; This represents the total surface energy of asphalt. This represents the total surface energy of the filler. The energy difference coefficient between asphalt and filler; These are the parameters for the experiment fitting. The formula for calculating the adhesive bonding energy between asphalt and filler in step S3 is as follows: In the formula: The adhesive bonding energy between asphalt and filler; The energy difference coefficient between asphalt and filler; The calculation formula for the interaction parameters between asphalt and filler in step S4 is as follows: In the formula: These are the interaction parameters between asphalt and filler; The adhesive bonding energy between asphalt and filler; The cohesive bonding energy of asphalt; This represents the volume fraction of the filler. This represents the critical volume fraction of the filler. The formula for calculating the cohesive energy of the asphalt mastic in step S5 is as follows: In the formula: The cohesive bonding energy of asphalt mastic; The adhesive bonding energy between asphalt and filler; The cohesive bonding energy of asphalt; The formula for calculating the surface energy of the asphalt mortar in step S5 is as follows: In the formula: The cohesive bonding energy of asphalt mastic; The surface energy of asphalt mortar; The formula for calculating the adhesion work between the asphalt mortar and the aggregate in step S6 is as follows: In the formula: The adhesion work between asphalt mortar and aggregate; The energy difference coefficient between asphalt mastic and aggregate; For the surface energy of the aggregate; The surface energy of asphalt mortar; The formula for calculating the stripping energy of the asphalt binder, aggregate, and water three-phase material in step S6 is as follows: In the formula: The stripping work of the asphalt mortar, aggregate, and water three-phase materials; The energy difference coefficient between aggregates and water; This is the energy difference coefficient between asphalt mastic and water; It is the surface energy of water; The calculation formula for the water stability evaluation index of asphalt mixture in step S7 is as follows: In the formula, The adhesion work between asphalt mortar and aggregate; DA represents the specific surface area of ​​the aggregate; DA represents the asphalt mixture oil film thickness. The stripping work of the asphalt mortar, aggregate, and water three-phase materials; The formulas for calculating the specific surface area of ​​aggregates and the thickness of asphalt film in asphalt mixtures are as follows: In the formula: DA represents the specific surface area of ​​the aggregate; DA represents the asphalt mixture oil film thickness. This represents the percentage of aggregate particles of each size that pass through. This refers to the surface area coefficient of aggregates with various particle sizes; Effective asphalt content; This represents the relative density of asphalt.

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