A design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions

Abstract

This invention provides a design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions, comprising the following steps: (1) taking mineral aggregates; (2) taking modified emulsified asphalt binder; (3) determining the estimated asphalt-aggregate ratio of the modified emulsified asphalt binder based on the gradation of the mineral aggregates, determining the water content and the amount of cement used as an admixture; and adjusting the amount of binder using the estimated asphalt-aggregate ratio as the median, and preparing standard specimens for wet tire abrasion tests and load-bearing wheel sand adhesion tests with different asphalt-aggregate ratios; (4) forming an asphalt-aggregate ratio-performance coordinate diagram to obtain the optimal asphalt-aggregate ratio; and (5) testing whether the road performance of the micro-surfacing mixture under the optimal asphalt-aggregate ratio is qualified. Based on the characteristics of emulsified asphalt materials, this invention proposes a design method based on the wet tire abrasion test and the load-bearing wheel sand adhesion test. This design method is simple to operate, comprehensively considers the performance characteristics of micro-surfacing mixtures, and has good applicability.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to a design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions. Background Technology

[0002] Microsurfacing is a thin, skid-resistant layer formed by mixing emulsified asphalt as the binder with a certain graded aggregate and admixtures. Its construction process is simple and energy-efficient, while also possessing excellent anti-skid, anti-wear, and impermeability properties, making it widely used in preventative road maintenance. Traditional microsurfacing mix design primarily determines the lower and upper limits of binder dosage through 1-hour wet tire abrasion tests and loaded wheel sand adhesion tests, specifically using the wet tire abrasion test result of 540 g / m³. 2 The lower limit of the binder dosage corresponding to the wear value is based on the result of the wheel sand adhesion test at 450 g / m. 2 The amount of binder used corresponds to the upper limit of the amount of adhering sand. Because the upper and lower limit standard values ​​are relatively low, the range of binder usage determined by traditional methods is quite wide. Traditional design methods rely on experienced experimental personnel, especially in determining the estimated and optimal asphalt-aggregate ratio, and also lack long-term performance verification indicators. Furthermore, emulsified asphalt materials are more susceptible to water erosion. In the hot and rainy regions of southern my country, micro-surfaced mixtures designed using traditional methods often exhibit spalling defects due to the humid and hot environment. Therefore, traditional design methods have certain limitations in designing micro-surfaced mixtures for humid and hot environments. Summary of the Invention

[0003] To address the problems of existing technologies, the present invention aims to provide a design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions. The design method is based on hot water immersion wet wheel abrasion test and load wheel sand adhesion test, and is simple to operate.

[0004] This invention achieves its objective through the following technical solution: a design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions, characterized by comprising the following steps:

[0005] (1) Take mineral aggregates according to the "Technical Specifications for Construction of Asphalt Pavement on Highways" and determine the gradation of mineral aggregates;

[0006] (2) Modified emulsified asphalt binder shall be selected in accordance with the Technical Guidelines for Microsurfacing and Slurry Seal;

[0007] (3) Determine the estimated asphalt-aggregate ratio of the modified emulsified asphalt binder based on the gradation of the mineral aggregates, conduct mixing tests and cohesion tests, and determine the water content and the amount of cement used as admixtures; adjust the binder content using the estimated asphalt-aggregate ratio as the median, and prepare standard specimens for wet wheel abrasion tests and load wheel sand adhesion tests with different asphalt-aggregate ratios, and cool them after curing for later use; the method for determining the estimated asphalt-aggregate ratio is as follows:

[0008] ω 预 = (0.06A + 0.12B + 0.2C) × P,

[0009] In the formula, ω is the estimated asphalt-aggregate ratio (%), A is the mass percentage of aggregate with a particle size greater than 2.36 mm in the total aggregate, B is the mass percentage of aggregate with a particle size between 0.075 and 2.36 mm in the total aggregate, C is the mass percentage of aggregate with a particle size less than 0.075 mm in the total aggregate, and P is the residual content of emulsified asphalt.

[0010] (4) Conduct hot water immersion wet wheel wear test and load wheel sand adhesion test. Using the asphalt-aggregate ratio as the abscissa and the hot water immersion wear value and the amount of sand adhered to the load wheel as the ordinate, form an asphalt-aggregate ratio-performance coordinate graph. Then, obtain the optimal asphalt-aggregate ratio using the balance design formula. The optimal asphalt-aggregate ratio is determined as follows:

[0011]

[0012] In the formula, ω is the optimal oil-stone ratio, %.

[0013] ω1 is the value obtained from the oil-aggregate ratio-wear value relationship graph, which uses the oil-aggregate ratio as the abscissa and the wet wheel wear value after immersion in hot water as the ordinate. 500g / m 2 The wear value corresponds to the lower limit of the oil-stone ratio;

[0014] ω2 is the value obtained from the relationship diagram of oil-aggregate ratio and adhered sand content, which is plotted with oil-aggregate ratio as the x-axis and adhered sand content as the y-axis. 450g / m 2 The oil-stone ratio corresponding to the amount of adhering sand is the upper limit;

[0015] (5) Check whether the road performance of the micro-surfaced mixture under the optimal asphalt-aggregate ratio is qualified. If it is qualified, the mix design is completed. If it is not qualified, return to step (1) to redesign.

[0016] In the above scheme, in step (1), the mineral aggregate includes one or more of limestone, granite, diabase and basalt.

[0017] In the above scheme, in step (2), the modified emulsified asphalt binder is cationic emulsified asphalt, which is SBS modified emulsified asphalt, SBR modified emulsified asphalt or chloroprene latex modified emulsified asphalt, with a solid content greater than 60%.

[0018] In the above scheme, in step (3), the pre-oil-stone ratio is used as the median value, and five oil-stone ratios are taken at 0.5% intervals to prepare standard specimens for wet wheel wear and load wheel sand adhesion.

[0019] In the above scheme, in step (4), the wet wheel wear test is to place the wet wheel wear specimen after the curing is placed in a 40℃ water bath for 1 hour, then take it out and place it at room temperature for 1 hour, and then carry out the wet wheel wear test.

[0020] In the above scheme, in step (5), the performance of the micro-surfaced mixture under the optimal asphalt-aggregate ratio is verified, including wet wheel abrasion performance, anti-skid performance, anti-rutting performance, and anti-permeability performance after soaking in hot water for 12 hours.

[0021] In the above scheme, the water consumption is 5-7%, and the cement dosage of the admixture is 1%.

[0022] Beneficial Effects: This invention addresses the shortcomings of existing micro-surfacing mixture design methods, which often result in a wide range of binder dosages that rely on experience. Furthermore, it lacks a design method specifically for micro-surfacing mixtures under humid and hot environments. Based on the characteristics of emulsified asphalt materials, this invention proposes a design method grounded in hot water immersion wet tire abrasion tests and loaded wheel sand adhesion tests. This design method is simple to operate, comprehensively considers the performance characteristics of micro-surfacing mixtures, and has good applicability. Attached Figure Description

[0023] Figure 1 The diagram shows the optimal asphalt-aggregate ratio and performance of SBS-modified emulsified asphalt under MS-2 gradation in Example 1.

[0024] Figure 2 The graph shows the optimal asphalt-aggregate ratio and performance of SBR-modified emulsified asphalt under MS-3 gradation in Example 2.

[0025] Figure 3 The graph shows the optimal asphalt-aggregate ratio and performance of the chloroprene latex-modified emulsified asphalt MS-3 gradation in Example 3. Detailed Implementation

[0026] The present invention will now be further described in conjunction with the embodiments and accompanying drawings.

[0027] A design method for modified emulsified asphalt micro-surfacing mixtures under high humidity and heat conditions, characterized by comprising the following steps:

[0028] (1) Take mineral aggregates according to the Technical Specification for Construction of Asphalt Pavement of Highway and determine the gradation of mineral aggregates; mineral aggregates include one or more of limestone, granite, diabase and basalt.

[0029] (2) Modified emulsified asphalt binder is selected according to the Technical Guidelines for Microsurfacing and Slurry Seal; the modified emulsified asphalt binder is cationic emulsified asphalt, specifically SBS modified emulsified asphalt, SBR modified emulsified asphalt or chloroprene latex modified emulsified asphalt.

[0030] (3) Determine the estimated asphalt-aggregate ratio of the modified emulsified asphalt binder based on the gradation of the mineral aggregates, conduct mixing tests and cohesion tests, and determine the water content and the amount of cement admixtures; the water content is 5-7%, and the amount of cement admixtures is 1%. Adjust the binder content using the estimated asphalt-aggregate ratio as the median, and prepare standard specimens for wet wheel abrasion tests and load wheel sand adhesion tests with different asphalt-aggregate ratios. After curing, cool and set aside for use; the method for determining the estimated asphalt-aggregate ratio is as follows:

[0031] ω 预 = (0.06A + 0.12B + 0.2C) × P,

[0032] In the formula, ω is the estimated asphalt-aggregate ratio (%), A is the percentage of aggregate with a particle size greater than 2.36 mm in the total aggregate mass, B is the percentage of aggregate with a particle size between 0.075 and 2.36 mm in the total aggregate mass, C is the percentage of aggregate with a particle size less than 0.075 mm in the total aggregate mass, and P is the residual content of emulsified asphalt.

[0033] Preparation of standard specimens: Using the pre-asphalt-aggregate ratio as the median, five asphalt-aggregate ratios were prepared at 0.5% intervals to prepare standard specimens for wet wheel wear and load-bearing wheel sand adhesion. Specifically: Mineral aggregates, water, and admixtures were mixed in a mixing pot, then water was added and mixed again. Modified emulsified asphalt was then added and mixed for no more than 30s ± 2s. The mixture was poured into a mold and quickly leveled. The mold was removed, and the specimen was placed in an oven at 60℃ ± 3℃ to constant weight, generally for no less than 16 hours. After curing, the wet wheel wear specimens were placed in a 40℃ water bath for 1 hour, then removed and placed at room temperature for 1 hour before conducting the hot water immersion wet wheel wear test and the load-bearing wheel sand adhesion test.

[0034] (4) Conduct hot water immersion wet wheel wear test and load wheel sand adhesion test. Using the asphalt-aggregate ratio as the abscissa and the hot water immersion wear value and the amount of sand adhered to the load wheel as the ordinate, form an asphalt-aggregate ratio-performance coordinate graph. Then, obtain the optimal asphalt-aggregate ratio using the balance design formula. The optimal asphalt-aggregate ratio is determined as follows:

[0035]

[0036] In the formula, ω is the optimal oil-stone ratio, %.

[0037] ω1 is the value obtained from the oil-aggregate ratio-wear value relationship graph, which uses the oil-aggregate ratio as the abscissa and the wet wheel wear value after immersion in hot water as the ordinate. 500g / m 2 The wear value corresponds to the lower limit of the oil-stone ratio;

[0038] ω2 is the value obtained from the relationship diagram of oil-aggregate ratio and adhered sand content, which is plotted with oil-aggregate ratio as the x-axis and adhered sand content as the y-axis. 450g / m 2 The oil-stone ratio corresponding to the amount of adhering sand is the upper limit;

[0039] (5) Test whether the road performance of the micro-surfaced mixture under the optimal asphalt-aggregate ratio is qualified. Perform performance verification on the micro-surfaced mixture under the optimal asphalt-aggregate ratio, including wet tire abrasion performance after soaking in hot water for 12 hours, anti-skid performance, anti-rutting performance, and anti-permeability performance. If qualified, the mix design is deemed complete. If not qualified, return to step (1) for redesign.

[0040] Example 1

[0041] Following the specific steps of the above implementation method, performance tests were conducted on three grades of aggregates and mineral powder with particle sizes of 5-10 mm, 3-5 mm, and 0-3 mm. The coarse aggregate was basalt, and the fine aggregate was limestone. The performance of the mineral aggregates met the technical specifications. SBS-modified emulsified asphalt was used as the binder (evaporation residue content of 62%, SBS content of 4%), and its performance met the technical requirements of the "Technical Guidelines for Micro-surfacing and Slurry Seal". MS-2 gradation was used as the design gradation, and the final synthetic gradation is shown in the table below:

[0042]

[0043] ω 预 = (0.06A + 0.12B + 0.2C) × P

[0044] In the formula, ω is the estimated asphalt-aggregate ratio (%), A is the percentage of aggregate with a particle size greater than 2.36 mm in the total aggregate mass (100-77.4), B is the percentage of aggregate with a particle size between 0.075 and 2.36 mm in the total aggregate mass (77.4-9.8), C is the percentage of aggregate with a particle size less than 0.075 mm in the total aggregate mass (9.8), and P is the residual content of emulsified asphalt (62%).

[0045] Based on the estimated asphalt-aggregate ratio formula, the asphalt-aggregate ratio was approximately 7.1%. Mixing and cohesion tests were conducted to determine the total water content as 5.5% and the cement content as 1%. Using the estimated binder content as the median, five asphalt-aggregate ratios (6.1%, 6.6%, 7.1%, 7.6%, and 8.1%) were prepared at 0.5% intervals to represent standard specimens for wet wheel wear and load-bearing wheel sand adhesion. The specimens were cured in a 60℃ oven to constant weight and then removed for later use. The cooled wet wheel wear specimens were placed in a 40℃ water bath for 1 hour, then left at room temperature for 1 hour before undergoing wet wheel wear tests to obtain the asphalt-aggregate ratio-wear value relationship curve. Figure 1A load-bearing wheel sand adhesion test was conducted to obtain the relationship curve between the asphalt-aggregate ratio and the amount of sand adhered; a weight of 500 g / m was taken. 2 The wear value corresponds to an oil-stone ratio at the lower limit (ω1≈6.9%), 450g / m 2 The upper limit of the asphalt-aggregate ratio corresponding to the amount of adhering sand is (ω2≈7.8%). Based on the equilibrium design formula, the optimal asphalt-aggregate ratio is calculated as follows:

[0046]

[0047] A micro-surfaced mixture was prepared using an optimal asphalt-aggregate ratio of 7.4%. The road performance, including wet tire abrasion performance (wet tire abrasion test after immersion in hot water for 12 hours, 40℃ water bath), skid resistance, rutting resistance, and impermeability, was tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20—2011). Finally, the road performance of the mixture under the optimal asphalt-aggregate ratio was verified.

[0048] Example 2

[0049] Following the specific steps of the above implementation method, performance tests were conducted on three grades of aggregates with particle sizes of 5–10 mm, 3–5 mm, and 0–3 mm, as well as mineral powder. The coarse aggregate was granite, and the fine aggregate was limestone. The performance of the mineral aggregates met the technical specifications. SBR-modified emulsified asphalt was used as the binder (evaporation residue content of 61%, SBS content of 4.5%), and its performance met the technical requirements of the "Technical Guidelines for Micro-surfacing and Slurry Seal". MS-3 gradation was used as the design gradation, and the final synthetic gradation is shown in the table below:

[0050]

[0051]

[0052] ω 预 = (0.06A + 0.12B + 0.2C) × P

[0053] In the formula, ω is the estimated asphalt-aggregate ratio (%), A is the percentage of aggregate with a particle size greater than 2.36 mm in the total aggregate mass (100-59.2), B is the percentage of aggregate with a particle size between 0.075 and 2.36 mm in the total aggregate mass (59.2-9.8), C is the percentage of aggregate with a particle size less than 0.075 mm in the total aggregate mass (9.8), and P is the residual content of emulsified asphalt (61%).

[0054] Based on the estimated asphalt-aggregate ratio formula, the asphalt-aggregate ratio was approximately 6.3%. Mixing and cohesion tests were conducted to determine the total water content as 7% and the cement content as 1%. Using the estimated binder content as the median, five asphalt-aggregate ratios (5.3%, 5.8%, 6.3%, 6.8%, and 7.3%) were prepared at 0.5% intervals to represent standard specimens for wet wheel wear and load-bearing wheel sand adhesion. The specimens were cured in a 60℃ oven to constant weight and then removed for later use. The cooled wet wheel wear specimens were placed in a 40℃ water bath for 1 hour, then left at room temperature for 1 hour before undergoing wet wheel wear tests. The asphalt-aggregate ratio-wear value relationship curve was obtained, as shown in the figure. Figure 2 A load-bearing wheel sand adhesion test was conducted to obtain the relationship curve between the asphalt-aggregate ratio and the amount of sand adhered; a weight of 500 g / m was taken. 2 The wear value corresponds to an oil-stone ratio at the lower limit (ω1≈6.2%), 450g / m 2 The upper limit of the asphalt-aggregate ratio corresponding to the amount of adhering sand is (ω2≈7.0%). Based on the equilibrium design formula, the optimal asphalt-aggregate ratio is calculated as follows:

[0055]

[0056] A micro-surfaced mixture was prepared using an optimal asphalt-aggregate ratio of 6.6%. The road performance, including wet tire abrasion performance (wet tire abrasion test after immersion in hot water for 12 hours, 40℃ water bath), skid resistance, rutting resistance, and impermeability, was tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20—2011). Finally, the road performance of the mixture under the optimal asphalt-aggregate ratio was verified.

[0057] Example 3

[0058] Following the specific steps of the above implementation method, performance tests were conducted on three grades of aggregates with particle sizes of 5-10 mm, 3-5 mm, and 0-3 mm, as well as mineral powder. The coarse aggregate was granite, and the fine aggregate was limestone. The performance of the mineral aggregates met the technical specifications. Chloroprene latex-modified emulsified asphalt was used as the binder (evaporation residue content of 61%, chloroprene latex content of 5.0%), and its performance met the technical requirements of the "Technical Guidelines for Micro-surfacing and Slurry Seal". MS-3 gradation was used as the design gradation, and the final synthetic gradation is shown in the table below:

[0059]

[0060] ω 预 = (0.06A + 0.12B + 0.2C) × P

[0061] In the formula, ω is the estimated asphalt-aggregate ratio (%), A is the percentage of aggregate with a particle size greater than 2.36 mm in the total aggregate mass (100-60.4), B is the percentage of aggregate with a particle size between 0.075 and 2.36 mm in the total aggregate mass (60.4-10.7), C is the percentage of aggregate with a particle size less than 0.075 mm in the total aggregate mass (10.7), and P is the residual content of emulsified asphalt (61%).

[0062] Based on the estimated asphalt-aggregate ratio formula, the asphalt-aggregate ratio was approximately 6.4%. Mixing and cohesion tests were conducted to determine the total water content as 5.0% and the cement content as 1%. Using the estimated binder content as the median, five asphalt-aggregate ratios (5.4%, 5.9%, 6.4%, 6.9%, and 7.4%) were prepared at 0.5% intervals to test wet wheel wear and load-bearing wheel sand adhesion. The specimens were cured in a 60℃ oven to constant weight and then removed for later use. The cooled wet wheel wear specimens were placed in a 40℃ water bath for 1 hour, then left at room temperature for 1 hour before undergoing wet wheel wear tests to obtain the asphalt-aggregate ratio-wear value relationship curve. Load-bearing wheel sand adhesion tests were also conducted to obtain the asphalt-aggregate ratio-adhesive sand content relationship curve. A 500g / m³ asphalt-aggregate ratio was used as the base material. 2 The wear value corresponds to an oil-stone ratio at the lower limit (ω1≈6.0%), 450g / m 2 The upper limit of the asphalt-aggregate ratio corresponding to the amount of adhering sand is (ω2≈7.0%). Based on the equilibrium design formula, the optimal asphalt-aggregate ratio is calculated as follows:

[0063]

[0064] A micro-surfaced mixture was prepared using an optimal asphalt-aggregate ratio of 6.5%. The road performance, including wet tire abrasion performance (wet tire abrasion test after immersion in hot water for 12 hours, 40℃ water bath), skid resistance, rutting resistance, and impermeability, was tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20—2011). Finally, the road performance of the mixture under the optimal asphalt-aggregate ratio was verified.

[0065] The performance tests of the micro-surfaced mixtures prepared in the above three embodiments are shown in the table below:

[0066]

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for designing micro-surfacing mixture of modified emulsified asphalt in high humidity and heat environment, characterized in that, The method comprises the following steps: (1) Taking mineral aggregate according to the Technical Specification for Construction of Highway Asphalt Pavement, and determining the gradation of the mineral aggregate; the mineral aggregate comprises one or more of the following: limestone, granite, diabase, and basalt; (2) Taking modified emulsified asphalt binder according to the Technical Guide for Micro-surfacing and Slurry Seal; the modified emulsified asphalt binder is cationic emulsified asphalt, and the cationic emulsified asphalt is SBS modified emulsified asphalt, SBR modified emulsified asphalt, or chloroprene latex modified emulsified asphalt, with a solid content greater than 60%; (3) Determining the estimated asphalt-aggregate ratio of the modified emulsified asphalt binder according to the gradation of the mineral aggregate, performing mixing tests and cohesion tests, determining the water content and the cement content of the admixture, and taking five asphalt-aggregate ratios at intervals of 0.5% around the estimated asphalt-aggregate ratio to prepare standard test pieces for wet wheel abrasion tests and load wheel sand adhesion tests, and then cooling the test pieces after curing and waiting for use; the method for determining the estimated asphalt-aggregate ratio is as follows: ， In the formula, A is the mass percentage of the aggregate with a particle size greater than 2.36 mm in the total aggregate, B is the mass percentage of the aggregate with a particle size between 0.075 mm and 2.36 mm in the total aggregate, C is the mass percentage of the aggregate with a particle size less than 0.075 mm in the total aggregate, and P is the residual content of the emulsified asphalt. (4) Performing hot water immersion wet wheel abrasion tests and load wheel sand adhesion tests, taking the asphalt-aggregate ratio as the horizontal coordinate, and taking the hot water immersion abrasion value and the load wheel sand adhesion amount as the vertical coordinate to form an asphalt-aggregate ratio-performance coordinate graph, and then obtaining the optimal asphalt-aggregate ratio through a balance design formula; the determination of the optimal asphalt-aggregate ratio is as follows: ， In the formula, is the optimum oilstone ratio; In the oil / stone ratio-wear value graph based on the oil / stone ratio as the horizontal coordinate and the wet wheel wear value of the water immersion as the vertical coordinate, the oil / stone ratio corresponding to the wear value of 500 g / m 2 is the lower limit. The oilstone ratio-adhesion sand amount relationship diagram is obtained based on the oilstone ratio as the horizontal coordinate and the adhesion sand amount as the vertical coordinate, and the oilstone ratio corresponding to the adhesion sand amount of 450 g / m 2 is the upper limit; The hot water immersion wet wheel abrasion test is performed as follows: placing the wet wheel abrasion test piece after curing in a 40℃ water bath for 1h, then taking out the test piece and placing it at room temperature for 1h, and then performing the hot water immersion wet wheel abrasion test; (5) Detecting whether the road performance of the micro-surfacing mixture at the optimal asphalt-aggregate ratio is qualified, if yes, determining that the mix ratio is designed, and if not, returning to step (1) to redesign; the micro-surfacing mixture at the optimal asphalt-aggregate ratio is subjected to performance verification, including hot water immersion wet wheel abrasion performance for 12h, anti-skid performance, anti-rutting performance, and anti-permeation performance.

2. The method for designing micro-surfacing mixture of modified emulsified asphalt in high humidity and heat environment according to claim 1, characterized in that, The water content is 5-7%, and the cement content of the admixture is 1%.

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