A high-performance polyurethane mixture mix proportion design method

Abstract

This invention relates to the field of polyurethane pavement technology, and more particularly to a method for designing the mix proportions of high-performance polyurethane mixtures. The method includes: determining the type of polyurethane pavement mixture; designing the composition of the polyurethane mixture using a skeleton-type gradation structure to determine the gradation range; conducting a leakage test on the polyurethane mixture to determine the amount of polyurethane used; and adjusting the mix proportion design based on the performance of the polyurethane mixture. This invention addresses the use of polyurethane, a novel material, as a binder in polyurethane pavement, proposing a mix proportion design method based on comprehensive road performance to determine the optimal binder-aggregate ratio, optimal aggregate gradation, and other parameters for polyurethane pavement, providing a basis for the design of polyurethane pavements.

Description

Technical Field

[0001] This invention relates to the field of polyurethane pavement technology, and in particular to a method for designing the mix proportions of high-performance polyurethane mixtures. Background Technology

[0002] Most existing asphalt pavements adopt the Marshall design method. The general steps of mix design are: 1. Determine the gradation range of the asphalt mixture; 2. Select and determine the raw materials; 3. Select the aggregate gradation; 4. Conduct the Marshall test; 5. Conduct road performance testing; 6. Determine the optimal asphalt content.

[0003] Polyurethane pavement is currently a completely new type of road, and there is no corresponding design method. Since asphalt and polyurethane are entirely different materials with significantly different material properties, it is unreasonable to apply the existing Marshall design method and key technical parameters for asphalt pavement to the design methods for polyurethane pavement.

[0004] Existing technologies lack content related to polyurethane pavement mix design, only covering asphalt pavement mix design methods, such as: 1. A mix design method for recycled asphalt mixture pavements suitable for high-temperature and rainy areas (CN115536310A); 2. A design method for modified asphalt mixtures suitable for areas with different temperature differences (CN106938899B). There is an urgent need to provide a mix design method suitable for polyurethane pavements. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for designing the mix proportions of high-performance polyurethane mixtures.

[0006] According to this invention, polyurethane mixtures, as a novel composite engineering material, exhibit microstructural and mechanical properties distinct from commonly used asphalt mixtures and cement concrete due to interfacial chemical bonding. Furthermore, their raw material technical standards, material composition design methods, and mixture construction processes differ from conventional asphalt and cement concrete pavements. Using polyurethane as a binder in mixing, paving, and curing with aggregates represents a completely new road material. Asphalt and polyurethane are entirely different materials with significantly different material properties. Applying existing Marshall design methods and key technical parameters for asphalt pavements to polyurethane pavement design methods is unreasonable. This invention proposes a mix design method for polyurethane pavements, providing a foundation for their widespread application.

[0007] The high-performance polyurethane compound mix design method provided by this invention includes:

[0008] 1) Determine the type of polyurethane pavement mixture;

[0009] 2) The composition design of polyurethane mixtures is carried out using a skeleton-type gradation structure to determine the gradation range of polyurethane mixtures;

[0010] 3) Conduct a leakage test on the polyurethane mixture to determine the amount of polyurethane used;

[0011] 4) Adjust the mix design according to the properties of the polyurethane mixture.

[0012] The mix design method for polyurethane mixtures provided by this invention differs from conventional asphalt and cement concrete pavements in terms of raw material technical standards, material composition design methods, and mixture construction processes. Starting from raw materials, gradation range, and optimal polyurethane dosage, a mix design method is proposed based on performance. Leakage tests are used to verify the polyurethane dosage, and a unique molding control method for polyurethane mixtures is proposed. A proprietary mix design method for polyurethane mixtures is presented based on performance.

[0013] Preferably, in step 1), the type of polyurethane pavement mixture is determined based on its application scenario and structural layer. The application scenarios include municipal roads, highways, heavy-duty roads, etc. In this invention, the type of polyurethane pavement mixture is selected based on its application scenario and structural layer.

[0014] Preferably, in step 2), based on the characteristics of the polyurethane mixture, a skeleton-type gradation structure is used to design the composition of the polyurethane mixture and determine the gradation range of the polyurethane mixture.

[0015] In this invention, polyurethane is used as the binder for the road surface. Polyurethane possesses extremely high modulus and bonding properties. The gradation range of the polyurethane is determined based on its service performance. Due to the special properties of polyurethane, a skeleton-type gradation structure is adopted for the design of the polyurethane mixture composition, thus proposing the polyurethane gradation range. The polyurethane color is adjustable, and its properties are designable.

[0016] Further optimization, in step 2), when the polyurethane mixture structural layer is the upper pavement layer, MDI-13 is used.

[0017] Preferably, the design gradation range of the MDI-13 is as follows: 100% mass percentage passing through a 16mm sieve, 90-100% mass percentage passing through a 13.2mm sieve, 60-80% mass percentage passing through a 9.5mm sieve, 15-40% mass percentage passing through a 4.75mm sieve, 10-25% mass percentage passing through a 2.36mm sieve, 5-18% mass percentage passing through a 1.18mm sieve, 2-15% mass percentage passing through a 0.6mm sieve, 0-8% mass percentage passing through a 0.3mm sieve, 0-6% mass percentage passing through a 0.15mm sieve, and 0-5% mass percentage passing through a 0.075mm sieve.

[0018] Through experimental research, this invention has found that when MDI-13 gradation is used for the upper layer design of polyurethane mixtures, combined with a two-way gradation design aimed at target porosity and service performance, the overall structural modulus of the polyurethane mixture can be improved, the fatigue life of the polyurethane pavement can be enhanced, and the polyurethane pavement can exhibit excellent road performance. Its high-temperature performance and modulus are 8 times that of conventional asphalt mixtures, its low-temperature crack resistance is 2-3 times that of conventional asphalt mixtures, its fatigue resistance is about 3 times that of conventional asphalt mixtures, and its water damage resistance is about 2 times that of conventional asphalt mixtures.

[0019] Further optimization, in step 2), when the polyurethane mixture structural layer is the lower pavement layer, MDI-16 is used.

[0020] Preferably, the design gradation range of the MDI-16 is as follows: 100% mass percentage passing through a 19mm sieve, 90-100% mass percentage passing through a 16mm sieve, 60-85% mass percentage passing through a 13.2mm sieve, 40-70% mass percentage passing through a 9.5mm sieve, 20-45% mass percentage passing through a 4.75mm sieve, 8-25% mass percentage passing through a 2.36mm sieve, 5-20% mass percentage passing through a 1.18mm sieve, 5-16% mass percentage passing through a 0.6mm sieve, 0-10% mass percentage passing through a 0.3mm sieve, 0-8% mass percentage passing through a 0.15mm sieve, and 0-5% mass percentage passing through a 0.075mm sieve.

[0021] Preferably, in step 3), the basket method is used to test the leakage loss of the polyurethane mixture to determine the initial optimal dosage of polyurethane. In this invention, the single-component moisture-curing polyurethane binder is a modified isocyanate containing a certain amount of terminal NCO groups (i.e., isocyanate groups). NCO groups are chemically extremely reactive and can react with moisture in the air when exposed to air. As the curing reaction proceeds, the NCO groups transform into urea groups, and the material gradually forms a cross-linked network structure, increasing its strength. The leakage test used in this invention can verify the optimal polyurethane dosage, ensuring complete coating of the aggregate without excessive free polyurethane flow.

[0022] According to the present invention, a single-component polyurethane material is used, and the performance indicators of the polyurethane are tested, including melting temperature, tensile strength and elongation at break.

[0023] Further optimization, in step 3), the amount of polyurethane is set at intervals of 0.2% to 0.5% according to the estimated amount of polyurethane, and the leakage loss of the polyurethane mixture is tested using the basket method. The amount of polyurethane with leakage <0.1% is the initial optimal amount of polyurethane.

[0024] As a preferred option, in step 4), the high-temperature performance, low-temperature performance, and water damage resistance of the polyurethane mixture are tested, and the mix design of the polyurethane mixture is optimized and adjusted based on the test performance.

[0025] Further optimization involves, in step 4), preparing at least three sets of indoor specimens at the optimal initial polyurethane dosage ±0.2%, testing the high-temperature performance, low-temperature performance, and water stability of the polyurethane mixture, and determining the target polyurethane dosage based on the performance test results; preferably, the polyurethane dosage with the best performance is adopted as the target polyurethane dosage. If the performance parameters do not meet the requirements, the gradation and polyurethane dosage are readjusted and redesigned.

[0026] Further preferably, the molding of the polyurethane mixture includes: after mixing the polyurethane, placing it under curing conditions of 20±2℃ and 50%±2% humidity for 4±0.5h, and then rotary compacting it into shape.

[0027] Preferably, the method also includes conducting a rotary compaction test to test the volume parameters of the polyurethane mixture, plotting the change curve of porosity with the number of compaction times, and determining the number of compaction times to achieve the target porosity; preferably, the target porosity is 4% ± 0.5%.

[0028] Further optimization was achieved by using an SGC rotary compactor with a rotational compaction angle of 1.16°±0.02° and a vertical pressure of 600 kPa. The test was terminated after 125 rotational compaction cycles. The volume parameters of the polyurethane mixture were tested, and the change curve of porosity with the number of compaction cycles was plotted to determine the number of compaction cycles required for a porosity of 4.5%±0.5%.

[0029] The beneficial effects of this invention are at least as follows: The polyurethane mix design method of this invention can guide the design of polyurethane pavement mixtures, obtaining the optimal gradation range, optimal polyurethane dosage, and key control parameters for molding of the polyurethane mixture through design. The indoor testing and molding methods can guide the actual construction of polyurethane pavements. Polyurethane pavement is a completely new pavement material structure. Currently, there is no corresponding mix design method. This invention proposes the gradation range, optimal polyurethane dosage, and key control parameters for molding of polyurethane mixtures. These include key factors such as the method for determining the optimal polyurethane dosage, the method for controlling the target porosity, and the conditions for curing before molding. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available products. Where specific techniques or conditions are not specified in the examples, they are performed using conventional methods or in accordance with techniques or conditions described in the literature in this field, or according to the product instructions. Reagents and instruments whose manufacturers are not specified are all conventional products that can be purchased from legitimate channels.

[0032] In this embodiment of the invention, the polyurethane performance testing was conducted in accordance with GB / T19250. The service performance testing of the polyurethane mixture used the following test methods: uniaxial penetration strength (high temperature performance) JTG D50-2017, low temperature crack resistance: low temperature beam bending test (JTG E20 T0715), dynamic modulus JTG E20 T0738, fatigue life: four-point bending fatigue test (JTGE20T0739).

[0033] The single-component moisture-curing polyurethane raw material used was 6750 purchased from Wanhua Chemical Group Co., Ltd.

[0034] The present invention will be further described below with reference to embodiments.

[0035] Example 1

[0036] 1) Types of polyurethane pavement mixtures:

[0037] The polyurethane mixture is selected based on its application scenario (such as municipal roads, highways, heavy-duty roads, etc.) and its location in the structural layer.

[0038] 2) Determine the gradation range of the aggregates:

[0039] Based on the unique adhesive properties of polyurethane materials, the following table is used as the design gradation range for polyurethane mixtures.

[0040] Table 1 Design Grading Range

[0041]

[0042] 3) Determine the optimal dosage of polyurethane.

[0043] The single-component polyurethane material produced by Wanhua Chemical Group Co., Ltd. was tested according to GB / T19250, and the relevant indicators are shown in Table 2.

[0044] Table 2 Performance Indicators of Polyurethane

[0045] Test Project Test Results Melting temperature 309.7℃ Tensile strength / MPa 18.6 Elongation at break / % 210

[0046] Based on empirically derived polyurethane dosage ranges, the appropriate polyurethane dosage is estimated, and the dosage is set at 0.2% intervals. The basket method (AASHTO T305) is used to test the leakage loss of the polyurethane mixture; a polyurethane dosage with leakage <0.1% is considered the initial optimal dosage. The leakage test verifies the optimal polyurethane dosage, ensuring complete coating of the aggregate without excessive free polyurethane flow.

[0047] 4) Mix design of polyurethane blends based on performance verification

[0048] This embodiment tests the high-temperature performance, low-temperature performance, and water loss resistance of the polyurethane mixture, optimizing the mix design to achieve optimal performance. An SGC rotary compactor was used with a compaction angle of 1.16° ± 0.02° and a vertical pressure of 600 kPa. The test ended with 125 compaction cycles. The volumetric parameters of the polyurethane mixture were tested. A curve showing the change in porosity with the number of compaction cycles was plotted, and the number of compaction cycles at which the porosity reached 4.5% ± 0.5% was determined as the molding test condition.

[0049] The molding conditions are determined in this embodiment:

[0050] The single-component moisture-curing polyurethane binder is a modified isocyanate containing a certain amount of terminal NCO groups (i.e., isocyanate groups). NCO groups are chemically highly reactive and can react with moisture in the air when exposed. As the curing reaction proceeds, the NCO groups transform into urea groups, and the material gradually forms a cross-linked network structure, increasing its strength. According to the curing mechanism of polyurethane mixtures, the strength formation process releases CO2 and increases volume. By tracking the height of the specimens during curing, it was found that direct rotation molding after mixing would result in volume expansion. The curing reaction occurs within the first 4 hours after preparing the polyurethane mixture, releasing CO2. Therefore, the polyurethane mixture of this invention is placed at 20°C and 50% humidity for 4 hours after mixing. After preparing the PU mixture, the PU binder undergoes a curing reaction within the first 4 hours, releasing O2. After 4 hours, it is rotated and compacted. If the standing time is too long, the polyurethane strength gradually develops, making it impossible to achieve the target porosity of 4.5% ± 0.5% through compaction. Indoor specimens were prepared according to the optimal initial polyurethane dosage ±0.2% (three groups in total) to test the high-temperature performance, low-temperature performance, and water stability of the polyurethane mixture. The optimal polyurethane dosage was taken as the target polyurethane dosage. If the performance parameters did not meet the requirements, the gradation and polyurethane dosage were readjusted and redesigned.

[0051] Example 2

[0052] The specific implementation method is the same as in Example 1; the difference is that in Example 2, the basket method (AASHTO T305) is used to test the leakage loss of the polyurethane mixture; the initial optimal amount of polyurethane is when the leakage is <0.5%. Using a 0.5% leakage control in Example 2 would result in a higher amount of binder and poorer economic efficiency.

[0053] Example 3

[0054] The specific implementation method is the same as in Example 1; the difference is that in Example 3, the curve of the change of porosity with the number of compaction times is plotted, and the number of compaction times with a porosity of 5.0% ± 0.5% is found as the test condition for molding.

[0055] Example 4

[0056] The specific implementation method is the same as in Example 1; the difference is that in Example 4, the beaker method (JTG E20 T0732) is used to test the leakage loss of the polyurethane mixture; the amount of polyurethane with leakage <0.1% is the initial optimal amount of polyurethane.

[0057] Example 5

[0058] The specific implementation method is the same as in Example 1; the difference is that in Example 5, Marshall compaction molding is used, with 75 compactions on both sides.

[0059] Example 6

[0060] The specific implementation method is the same as in Example 1; the difference is that in Example 6, rotary compaction molding is used, and the number of rotary compaction cycles is 50, and the control of porosity is not the most important controllable test parameter.

[0061] Example 7

[0062] The specific implementation method is the same as in Example 1; the difference is that in Example 7: after the polyurethane binder and aggregate are mixed, they are rotated and compacted, and then left to stand for 4 hours.

[0063] Example 8

[0064] The specific implementation method is the same as in Example 1; the difference is that in Example 8, the optimal initial amount of polyurethane is used as the amount of binder, and the high-temperature performance, low-temperature performance and water stability of the polyurethane mixture are tested.

[0065] Performance tests were performed on each embodiment:

[0066] 1. Uniaxial penetration strength (high temperature performance): Refer to JTG D50-2017.

[0067] 2. Low-temperature crack resistance: Low-temperature beam bending test (JTG E20 T0715).

[0068] 3. Fatigue life: Four-point bending fatigue test (JTG E20 T0739).

[0069] 4. Leakage loss of polyurethane mixture (basket method) (AASHTO T305).

[0070] 5. Leakage loss of polyurethane mixtures (beaker method) (JTG E20 T0732).

[0071] 6. Dynamic modulus: JTG E20 T0738. Test data are listed in Table 1.

[0072] Table 1 Performance Test Data

[0073]

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing the mix proportions of a high-performance polyurethane compound, characterized in that, include: 1) Determine the type of polyurethane pavement mixture; 2) The polyurethane mixture composition design adopts a skeleton-type gradation structure to determine the gradation range of the polyurethane mixture; MDI-13 is used when the polyurethane mixture is the upper layer of the pavement; MDI-16 is used when the polyurethane mixture is the lower layer of the pavement. 3) Based on the estimated amount of polyurethane, set the amount of polyurethane in intervals of 0.2~0.5%, and use the basket method to test the leakage loss of polyurethane mixture. The amount of polyurethane with leakage <0.1% is the initial optimal amount of polyurethane. 4) Adjust the mix design according to the properties of the polyurethane mixture; also includes the molding of the polyurethane mixture, after the polyurethane is mixed, it is placed under curing conditions for 4±0.5h, and then rotary compacted; test the volume parameters of the polyurethane mixture, plot the change curve of porosity with the number of compaction times, and determine the number of compaction times for the target porosity. The target porosity is 4% ± 0.5%; The design gradation range of MDI-13 is as follows: 100% mass percentage passing through a 16mm sieve, 90-100% mass percentage passing through a 13.2mm sieve, 60-80% mass percentage passing through a 9.5mm sieve, 15-40% mass percentage passing through a 4.75mm sieve, 10-25% mass percentage passing through a 2.36mm sieve, 5-18% mass percentage passing through a 1.18mm sieve, 2-15% mass percentage passing through a 0.6mm sieve, 0-8% mass percentage passing through a 0.3mm sieve, 0-6% mass percentage passing through a 0.15mm sieve, and 0-5% mass percentage passing through a 0.075mm sieve. The design gradation range of MDI-16 is as follows: 100% mass percentage passing through a 19mm sieve, 90-100% mass percentage passing through a 16mm sieve, 60-85% mass percentage passing through a 13.2mm sieve, 40-70% mass percentage passing through a 9.5mm sieve, 20-45% mass percentage passing through a 4.75mm sieve, 8-25% mass percentage passing through a 2.36mm sieve, 5-20% mass percentage passing through a 1.18mm sieve, 5-16% mass percentage passing through a 0.6mm sieve, 0-10% mass percentage passing through a 0.3mm sieve, 0-8% mass percentage passing through a 0.15mm sieve, and 0-5% mass percentage passing through a 0.075mm sieve.

2. The polyurethane mixture proportioning design method according to claim 1, characterized in that, In step 1), the type of polyurethane pavement mixture is determined based on the application scenario and structural layer of the polyurethane mixture.

3. The polyurethane mixture proportioning design method according to claim 1 or 2, characterized in that, In step 4), the high-temperature performance, low-temperature performance, and water damage resistance of the polyurethane mixture are tested, and the mix design of the polyurethane mixture is optimized and adjusted based on the test performance.

4. The polyurethane mixture proportioning design method according to claim 3, characterized in that, In step 4), at least three sets of indoor specimens are prepared according to the optimal initial polyurethane dosage ±0.2% to test the high-temperature performance, low-temperature performance and water stability of the polyurethane mixture, and the target polyurethane dosage is determined based on the performance test results.

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