Low microcellular polyurethane compound, its preparation method and application

Abstract

The application discloses a kind of low microbubble polyurethane mixtures, its preparation method and application, belong to road engineering technical field.The low microbubble polyurethane mixtures, by following raw materials and its mass fraction composition: polyurethane 3-10 parts, aggregate 85-120 parts, mineral powder 1-7 parts;Wherein, mineral powder is composed of acid stone mineral powder 0.5-6.5 parts and defoaming type mineral powder 0.5-6.5 parts.The polyurethane mixture prepared by the application has excellent road performance, and the preparation process does not need to add defoaming agent, has no pollution, low cost, high efficiency.The defoaming type mineral powder used in the application has simple preparation method and is convenient to use, which can not only play the role of filler, but also effectively eliminate CO2 microbubble, not only reduce the void ratio of polyurethane mixture, significantly improve the pavement durability, but also effectively reduce carbon emission.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, specifically relating to a low-microfoam polyurethane mixture, its preparation method and application. Background Technology

[0002] Currently, approximately 90% of highways use hot-mix asphalt mixtures for their surface layers. The construction of hot-mix asphalt mixtures consumes a significant amount of energy and generates carbon emissions, which contradicts the concept of green and low-carbon development. Furthermore, due to the high temperature sensitivity of asphalt materials, they are prone to aging under external environmental conditions and vehicle loads, leading to early pavement damage, shortened service life, and increased maintenance costs. Therefore, there is an urgent need to develop and apply low-carbon, durable road paving materials.

[0003] The new polyurethane mixture pavement structure adopts a cold-mix, cold-lay process. Compared with traditional hot-mix asphalt mixtures, this process not only eliminates the need for heating and heat loss, but also significantly reduces carbon emissions to only 1% of the latter. Furthermore, this material exhibits marked improvements in high-temperature rutting resistance and fatigue resistance, increasing by approximately 10 times and 2 times respectively. These performance enhancements not only align with the green and low-carbon construction philosophy but also contribute to the green upgrading of the highway construction industry chain.

[0004] Because a large number of CO2 microbubbles are generated during the curing process of single-component polyurethane, moisture can easily penetrate the interior of the polyurethane pavement, causing water damage. The presence of CO2 microbubbles leads to poor water stability, which is a significant factor restricting the widespread application of polyurethane mixtures. Currently, there are two main methods to improve its water stability: The first method is to improve the water stability of polyurethane by adjusting the polyurethane production formula. However, changes in the production formula often lead to a decrease in other properties. For example, reducing the proportion of isocyanate in polyurethane will improve the freeze-thaw splitting strength ratio and water damage resistance of the polyurethane mixture, but will lead to a decrease in its low-temperature and high-temperature performance. The second method is to improve its water stability by eliminating or absorbing CO2 microbubbles generated during the polyurethane curing process. Some studies have attempted to eliminate microbubbles by adjusting the polyurethane curing time. This involves adjusting the curing time based on the CO2 generation time, allowing CO2 microbubbles to rise and burst before the polyurethane fully cures. However, CO2 microbubbles do not completely burst before curing, and the curing time is difficult to control manually. Other studies have tried adding adsorbent materials to the polyurethane to eliminate microbubbles. However, some adsorbent materials can affect other properties of polyurethane concrete, and others can release absorbed CO2 when heated, causing the polyurethane mixture to contain microbubbles again. Neither of these methods can effectively and permanently eliminate CO2. Summary of the Invention

[0005] This invention provides a low-microbubble polyurethane mixture, which is composed of the following raw materials and their mass fractions: 3-10 parts polyurethane, 85-120 parts aggregate, and 1-7 parts mineral powder.

[0006] Preferably, the above-mentioned low-microbubble polyurethane mixture is composed of the following raw materials and their mass fractions: 5-8 parts polyurethane, 95-110 parts aggregate, and 3-5 parts mineral powder.

[0007] In one specific implementation, the low-microbubble polyurethane mixture is composed of the following raw materials and their mass fractions: 7.7 parts polyurethane, 100 parts aggregate, and 4 parts mineral powder.

[0008] In the above-mentioned low-microfoam polyurethane mixture, the mineral powder is composed of the following raw materials and their mass fractions: 0.5 to 6.5 parts of acidic stone mineral powder and 0.5 to 6.5 parts of defoaming mineral powder.

[0009] Preferably, the mineral powder is composed of the following raw materials and their mass fractions: 0.5 to 3 parts of acidic stone mineral powder and 2 to 4.5 parts of defoaming mineral powder.

[0010] In one specific implementation, the mineral powder is composed of the following raw materials and their mass fractions: 0.8 parts of acidic stone mineral powder and 3.2 parts of defoaming mineral powder.

[0011] In the above-mentioned low-microbubble polyurethane mixture, the polyurethane is a one-component polyether polyurethane.

[0012] In the above-mentioned low-microbubble polyurethane mixture, the aggregate is selected from limestone, granite, basalt or diabase with a particle size of 0.075 to 30 mm.

[0013] In the above-mentioned low-microbubble polyurethane mixture, the acidic stone mineral powder is selected from granite powder with a particle size of less than 0.075 mm.

[0014] In the above-mentioned low-microfoam polyurethane mixture, the defoaming mineral powder is bio-type zeolite powder.

[0015] This invention provides a method for preparing the above-mentioned defoaming mineral powder, the steps of which are as follows:

[0016] Zeolite powder is added to a Bacillus subtilis culture solution for cultivation. After cultivation, the pores of the zeolite powder are filled with bacteria by vacuuming. The zeolite powder is then filtered out of the culture solution, dried, and defoaming mineral powder is obtained.

[0017] In the above-mentioned method for preparing defoaming mineral powder, the ratio of zeolite powder to Bacillus subtilis bacterial solution is selected from 10-70:10-200, g:mL; preferably 63:100, g:mL.

[0018] In the above-mentioned method for preparing defoaming mineral powder, the cultivation conditions are selected from: a temperature of 25-40℃ and a cultivation time of 15-48h; preferably: a temperature of 35℃ and a cultivation time of 36h.

[0019] In the above-mentioned method for preparing defoaming mineral powder, the drying is selected from the following conditions: drying at 40°C, in a dry environment (relative humidity of air below 35%) and without CO2 for 3 hours.

[0020] In the above-mentioned method for preparing defoaming mineral powder, the Bacillus subtilis bacterial solution is prepared by the following method:

[0021] The activated Bacillus mucilaginosus was inoculated into the culture medium and cultured in a shaker at 35℃ and 200r / min for 12h to obtain the Bacillus mucilaginosus bacterial solution.

[0022] The inoculation amount of the activated Bacillus subtilis was selected from 5% to 15%.

[0023] The formulation of the above culture medium is as follows:

[0024] Sucrose 14–30 g / L, Na2HPO4·12H2O 2.45–2.85 g / L, MgSO4 0.5–1.1 g / L, CaCl2 3.22–7.66 g / L, (NH4)2SO4 0.9–1.65 g / L, yeast extract 0.5–3.8 g / L, soybean meal 0.3–0.55 g / L; pH 7.0–8.0.

[0025] The formulation of the culture medium can preferably be:

[0026] Sucrose 21 g / L, Na2HPO4·12H2O 2.66 g / L, MgSO4 0.7 g / L, CaCl2 5.11 g / L, (NH4)2SO4 1.35 g / L, yeast extract 2.74 g / L, soybean meal 0.4 g / L; pH 7.0~8.0.

[0027] This invention provides a method for preparing the above-mentioned low-microbubble polyurethane mixture, the steps of which are as follows:

[0028] First, add the aggregate to the mixing pot and dry mix for 30-60 seconds. Then add the polyurethane and continue mixing during the process. After all the polyurethane is added, mix for another 30-60 seconds. Finally, add the acidic stone powder and defoaming mineral powder at the same time, continue mixing for 80-150 seconds, and then discharge the material to obtain a low-micro-foam polyurethane mixture.

[0029] This invention provides the application of the above-mentioned low-microfoam polyurethane mixture in special paving structures for roads, bridges, tunnels or airports.

[0030] The beneficial effects of this invention are as follows:

[0031] The defoaming mineral powder prepared by this invention is simple to prepare and easy to use. It acts as a filler and effectively eliminates CO2 microbubbles, reducing the porosity of polyurethane mixtures, significantly improving pavement durability, and effectively reducing carbon emissions. The polyurethane mixture of this invention exhibits excellent road performance, and the preparation process requires no defoamer, resulting in no pollution, low cost, and high efficiency. The acidic aggregate mineral powder used in this invention is low-cost and cost-effective, expanding the application of acidic aggregates in road surfaces. Attached Figure Description

[0032] Figure 1 Photographs showing the application and paving of polyurethane mixtures. Detailed Implementation

[0033] The materials used in this invention are as follows:

[0034] Bacillus subtilis was purchased from the China Industrial Microbial Culture Collection Center, number CICC 21699; the polyurethane was a single-component polyether polyurethane, purchased from Wanhua Chemical Group Co., Ltd. in Yantai City, Shandong Province; the aggregate was limestone, granite, basalt or diabase with a particle size of 0.075-30 mm; the acidic stone powder was a mineral powder with a particle size of less than 0.075 mm, mainly composed of silicates, obtained by fine grinding of granite; the defoaming mineral powder was a bio-type zeolite powder with the function of eliminating CO2 microbubbles.

[0035] The above-mentioned bio-type zeolite powder is made from zeolite powder and Bacillus subtilis, and its preparation method is as follows:

[0036] (1) Preprocessing

[0037] The zeolite rock was ground into zeolite powder with a particle size of less than 0.075 mm using a grinding mill. The zeolite powder was washed with water and then placed in a dry heat sterilization chamber at 250°C for 45 minutes and dried for 4 hours. After that, the zeolite powder was placed in a dry and sterile environment and cooled to room temperature for later use.

[0038] (2) Prepare the culture medium

[0039] Prepare the liquid culture medium for Bacillus mucilage according to the component ratios in Table 1. Dissolve the weighed components in 1L of distilled water and stir with a glass rod. To facilitate subsequent bacterial growth, adjust the pH of the culture medium to 7.0–8.0 using 1–3 mol / L NaOH.

[0040] Table 1. Composition of Bacillus mucilaginosus liquid culture medium

[0041] Element Content (g / L) Sucrose (monosaccharide) 14～30 <![CDATA[Na2HPO4·12H2O]]> 2.45～2.85 <![CDATA[MgSO4]]> 0.5～1.1 <![CDATA[CaCl2]]> 3.22～7.66 <![CDATA[(NH4)2SO4]]> 0.9～1.65 Yeast extract 0.5～3.8 Soybean cake powder 0.3～0.55

[0042] The optimal content of sucrose is 21 g / L, the optimal content of Na2HPO4·12H2O is 2.66 g / L, the optimal content of MgSO4 is 0.7 g / L, the optimal content of CaCl2 is 5.11 g / L, the optimal content of (NH4)2SO4 is 1.35 g / L, the optimal content of yeast extract is 2.74 g / L, and the optimal content of soybean meal is 0.4 g / L.

[0043] (3) High-temperature sterilization

[0044] Place 100 mL of culture medium into an Erlenmeyer flask, quickly seal the flask with a rubber stopper (do not tighten), fill the Erlenmeyer flask with oxygen by upward displacement of air, and immediately place it in an autoclave at 130°C for 20 minutes. Then quickly place the Erlenmeyer flask in a sterile environment to cool to room temperature.

[0045] (4) Activation of microbial strains

[0046] Bacillus mucilaginosus was activated on a slant culture medium at 30°C for 24–36 h. The slant culture medium consisted of 0.4% sucrose, 0.3% (NH4)2SO4, 0.2% dipotassium hydrogen phosphate, 0.12% MgSO4, 0.27% yeast extract, 0.04% CaCl2, and 2.4% agar, with a pH of 7.0.

[0047] (5) Cooling inoculation and constant temperature culture

[0048] Under aseptic conditions, activate Bacillus subtilis is inoculated into the liquid culture medium in the conical flask at an inoculation rate of 10%. The rubber stopper is then tightened, and the flask is quickly placed on a shaker at 35°C and 200 rpm for incubation.

[0049] (6) Preparation of defoaming mineral powder

[0050] After 12 hours of constant-temperature incubation of the microbial culture, 63g of zeolite powder was quickly added to the conical flask, the rubber stopper was tightened, and incubation continued for another 36 hours. After incubation, the culture medium and zeolite were quickly poured into a vacuum apparatus (model YDLM-Ⅲ, Jinan Yunda Equipment Testing Co., Ltd.). Vacuuming was performed using a double-cylinder tester for the theoretical density of the mixture, ensuring that the pores of the zeolite powder were filled with the microbial culture. The zeolite powder was then filtered from the culture medium and dried in a 40°C, dry environment (relative humidity below 35%) and CO2-free environment for 3 hours to obtain defoaming mineral powder.

[0051] The above-mentioned defoaming mineral powder needs to be refrigerated at 4℃ and has a shelf life of 7 days. It can only be used after being adapted to the test temperature.

[0052] The test procedure for determining whether the above-mentioned defoaming mineral powder meets the specifications is as follows, in accordance with the Ministry of Transport's standard "Test Procedures for Aggregates in Highway Engineering" (JTG 3432-2024):

[0053] Test instruments:

[0054] The ZJB-20C automatic mixing planter was developed by Beijing Jingu Shenjian Measurement and Control Technology Research Institute; the DZG-3 automatic asphalt mixture compactor was developed by Xi'an Highway Research Institute; the LD-5 fully automatic Marshall tester was produced by Nanjing Tuoxing Instrument Equipment Factory; the research-grade multi-purpose automatic rutting tester, model QCZ-2, was produced by Beijing Jingu Shenjian Measurement and Control Technology Research Institute; and the MTS material testing machine was manufactured in the United States.

[0055] Test results and the Ministry-issued standard "Technical Specification for Polyether-based Polyurethane Concrete Pavement for Highway Bridges" (T / CECS)

[0056] The technical requirements for mineral powder (G:K58-01—2020) are shown in Table 2:

[0057] Table 2. Test Results of Routine Indicators for Defoaming Mineral Powder

[0058]

[0059] As shown in Table 2, all technical indicators of the defoaming mineral powder meet the technical requirements issued by the Ministry.

[0060] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0061] Example 1

[0062] The raw materials and quality ratios of low-microfoam polyurethane mixtures are as follows:

[0063] 7.7 kg of polyurethane, 100 kg of aggregate, 0.8 kg of acidic stone powder, and 3.2 kg of defoaming mineral powder;

[0064] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0065] Example 2

[0066] The raw materials and quality ratios of low-microfoam polyurethane mixtures are as follows:

[0067] 7.7 kg of polyurethane, 100 kg of aggregate, 1.4 kg of acidic stone powder, and 2.6 kg of defoaming mineral powder;

[0068] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0069] Example 3

[0070] The raw materials and quality ratios of low-microfoam polyurethane mixtures are as follows:

[0071] 7.7 kg of polyurethane, 100 kg of aggregate, 2.0 kg of acidic stone powder, and 2.0 kg of defoaming mineral powder;

[0072] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0073] Example 4

[0074] The raw materials and quality ratios of low-microfoam polyurethane mixtures are as follows:

[0075] 7.7 kg of polyurethane, 100 kg of aggregate, 2.6 kg of acidic stone powder, and 1.4 kg of defoaming mineral powder;

[0076] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0077] Example 5

[0078] The raw materials and quality ratios of low-microfoam polyurethane mixtures are as follows:

[0079] 7.7 kg of polyurethane, 100 kg of aggregate, 3.2 kg of acidic stone powder, and 0.8 kg of defoaming mineral powder;

[0080] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0081] The preparation method of the above-mentioned low-microbubble polyurethane mixture includes the following steps:

[0082] The aggregate and acidic stone powder were dried separately in an oven at 105±5℃ for 4 hours to remove moisture, and then cooled to 40℃ for later use. The defoaming mineral powder was placed in a constant temperature oven to adapt to 40℃ for later use. The aggregate was added to the mixing pot and dry-mixed for 45 seconds, followed by the addition of polyurethane. During the addition of polyurethane, the mixture was continuously stirred. After all the polyurethane was added, the mixture was stirred for another 45 seconds. Finally, the acidic stone powder and the defoaming mineral powder were added simultaneously, and the mixture was stirred for another 90 seconds before being discharged to obtain a low-microfoam polyurethane mixture.

[0083] Comparative Example 1

[0084] The raw materials and quality ratios of polyurethane mixtures are as follows:

[0085] 7.7 kg of polyurethane, 100 kg of aggregate, 0.8 kg of acidic stone powder, and 3.2 kg of ordinary zeolite powder;

[0086] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0087] Comparative Example 2

[0088] The raw materials and quality ratios of polyurethane mixtures are as follows:

[0089] 7.7 kg of polyurethane, 100 kg of aggregate, 3.2 kg of acidic stone powder, and 0.8 kg of ordinary zeolite powder;

[0090] The aggregate consists of 15 kg of limestone with a particle size of 0.075–2.36 mm and 85 kg of limestone with a particle size of 2.36–30 mm.

[0091] I. Road performance test

[0092] To test the various road performance characteristics of low-microfoam polyurethane mixtures, relevant tests were conducted in accordance with the Ministry of Transport standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The specific test contents and relevant indicators of polyurethane mixtures in the Ministry of Transport standard "Technical Specification for Polyether-type Polyurethane Concrete Pavement for Highway Bridges" (T / CECS G:K58-01-2020) are as follows.

[0093] 1. Marshall test

[0094] According to the specimen molding method T0702-2011 in the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), six Marshall specimens were molded for each of the above implementation cases. The difference is that the specimens need to be mixed at room temperature, allowed to cure statically, and then molded. After curing at room temperature for 24 hours, the tests were conducted. The stability and flow value were determined according to the test method T0709-2011 in the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The test results should meet the technical requirements of the Ministry of Transport's standard "Technical Specification for Polyether-type Polyurethane Concrete Pavement for Highway Bridges" (T / CECS G:K58-01-2020).

[0095] The experimental results are shown in Table 3:

[0096] Table 3. Marshall Test Results of Low-Microfoam Polyurethane Mixtures

[0097]

[0098]

[0099] As shown in Table 3, the low-microfoam polyurethane mixture prepared in the embodiments of the present invention meets all the technical requirements of the Ministry of Industry and Information Technology in the Marshall test. With the increase of the proportion of defoaming mineral powder, the porosity of the low-microfoam polyurethane mixture is lower. It can be concluded that when the defoaming mineral powder accounts for 80% of the total mineral powder, the polyurethane mixture produces the fewest bubbles during curing. Through comparative examples, it can be concluded that the polyurethane mixture without the addition of defoaming mineral powder has a significantly worse porosity, that is, more bubbles are produced during the curing of the polyurethane mixture.

[0100] 2. Water stability performance test

[0101] The Ministry-issued standard "Technical Specification for Polyether-based Polyurethane Concrete Pavement for Highway Bridges" (T / CECS G:K58-01—2020) states that although the freeze-thaw splitting strength ratio of polyether-based polyurethane concrete after freeze-thaw cycles no longer meets the specifications for asphalt mixtures, the absolute value of its remaining splitting strength is still higher than that of asphalt mixtures and meets the requirements for road performance. Therefore, freeze-thaw splitting strength is used to represent its water stability. Eight Marshall specimens were prepared for each of the above implementation cases, and the freeze-thaw splitting strength was determined according to the test method T0729-2000 in the Ministry of Transport standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0102] The experimental results are shown in Table 4:

[0103] Table 4 Results of Freeze-Thaw Splitting Test

[0104] Group Splitting strength of the test group (MPa) Splitting strength of control group (MPa) TSR (%) Example 1 2.87 3.95 72.66 Example 2 2.58 3.68 70.11 Example 3 2.33 3.41 68.33 Example 4 2.03 3.07 66.12 Example 5 1.81 2.79 64.87 Comparative Example 1 1.53 2.44 62.70 Comparative Example 2 1.27 2.09 60.77

[0105] As shown in Table 4, the low-microfoam polyurethane mixture prepared in the embodiments of the present invention has water stability performance that meets the requirements of the Ministry-issued technical standards. With the increase of the proportion of defoaming mineral powder, the freeze-thaw splitting strength ratio (TSR) will increase accordingly, that is, fewer bubbles will be generated during curing. It can be concluded that when the defoaming mineral powder accounts for 80% of the total mineral powder, the polyurethane mixture generates the fewest bubbles during curing and has the best water stability. Through comparative analysis, it can be concluded that the polyurethane mixture without the addition of defoaming mineral powder has significantly poor water stability, that is, more bubbles are generated during the curing of the polyurethane mixture.

[0106] 3. High-temperature stability test

[0107] Following the specimen molding method in T0703-2011 of the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), three specimens with dimensions of 300mm × 300mm × 50mm were prepared after the polyurethane concrete had been statically cured. After curing for 24 hours, rutting tests were conducted using a multi-purpose automatic rutting apparatus according to the test method in T0719-2011 of the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering," and the test data were recorded. The test results should meet the technical requirements of the Ministry of Transport's standard "Technical Specification for Polyether-type Polyurethane Concrete Pavement for Highway Bridges" (T / CECS G:K58-01-2020).

[0108] The experimental results are shown in Table 5:

[0109] Table 5 Results of the rutting test

[0110]

[0111] As shown in Table 5, the high-temperature stability performance of the low-microfoam polyurethane mixture prepared in the embodiments of the present invention meets the technical requirements of the Ministry. With the increase of the proportion of defoaming mineral powder, the average dynamic stability is greater, that is, the fewer bubbles are generated during curing. It can be concluded that when the defoaming mineral powder accounts for 80% of the total mineral powder, the porosity of the polyurethane mixture is the lowest. Through comparative examples, it can be concluded that the polyurethane mixture without the addition of defoaming mineral powder generates more bubbles during curing.

[0112] 4. Low-temperature performance test

[0113] According to the specimen molding method in T0703-2011 of the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), after the polyurethane concrete has been statically cured, three prism specimens with dimensions of 250mm×30mm×35mm were cut. After curing for 24 hours, bending tests were conducted using an MST material testing machine according to the test method in T0715-2011 of the Ministry of Transport's standard "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering," and the test data were recorded. The test results should meet the technical requirements of the Ministry of Transport's standard "Technical Specification for Polyether-type Polyurethane Concrete Pavement for Highway Bridges" (T / CECS G:K58-01-2020).

[0114] The experimental results are shown in Table 6:

[0115] Table 6 Results of Bending Test

[0116]

[0117]

[0118] As shown in Table 6, the low-temperature performance of the polyurethane mixture prepared in the embodiments of the present invention meets the technical requirements of the Ministry. With the increase of the proportion of defoaming mineral powder, the maximum flexural strain is greater, that is, the fewer bubbles are generated during curing. It can be concluded that when the defoaming mineral powder accounts for 80% of the total mineral powder, the polyurethane mixture generates the fewest bubbles during curing. Through comparative examples, it can be concluded that the polyurethane mixture without the addition of defoaming mineral powder has significantly poor low-temperature performance, that is, more bubbles are generated during curing.

[0119] In summary, the low-microfoam polyurethane mixture prepared in the embodiments of the present invention meets all the technical requirements of the Ministry and has excellent road performance.

[0120] Application examples

[0121] Use a light-duty dump truck to transport the mixed polyurethane mixture. To prevent the temperature from dropping too quickly and causing the curing time of the mixture to be too long, cover the hopper with a heat-insulating and moisture-retaining tarpaulin. Place an insertion thermometer inside the mixture to measure the temperature change. During transportation, keep the internal temperature of the mixture between 35 and 40°C.

[0122] Five hours after mixing, the polyurethane mixture was paved on the G6 auxiliary road of S216 in Changping District, Beijing. After paving, the condition of the mixture was constantly monitored. When the mixture reached the state of "solid but not loose", compaction began. The compaction method was as follows: one round trip with a steel wheel roller, two round trips with a rubber-tired roller, and finally, a steel wheel roller to finish the compaction. The final compaction should be completed within 25 minutes after the initial compaction.

[0123] Stall photos as follows Figure 1 As shown:

[0124] To ensure that the pavement reaches the open traffic strength of the low-micro-foam polyurethane mixture as soon as possible, an industrial fuel-fired heater is used for accelerated curing after compaction. The surface temperature of the pavement is around 50°C, and traffic is opened when its strength reaches 2.1 MPa (approximately 38 hours after compaction).

[0125] The tests were conducted according to the "Field Testing Procedures for Highway Subgrade and Pavement" (JTG 3450-2019) issued by the Ministry of Transport. The test results are shown in Table 7.

[0126] Table 7 Quality Inspection Table for Low-Microbubble Polyurethane Mixture

[0127]

[0128]

[0129] As shown in Table 7, the low-microbubble polyurethane mixture prepared in the application examples of the present invention has passed the test and can be transferred for use.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A low-microfoam polyurethane mixture, characterized in that, It is composed of the following raw materials and their mass fractions: 3-10 parts polyurethane, 85-120 parts aggregate, and 1-7 parts mineral powder; The mineral powder is composed of the following raw materials and their mass fractions: 0.5-6.5 parts of acidic stone mineral powder and 0.5-6.5 parts of defoaming mineral powder; The defoaming mineral powder is prepared by the following method: Zeolite powder is added to a Bacillus subtilis culture solution for cultivation. After cultivation, the pores of the zeolite powder are filled with bacteria by vacuuming. Then, the zeolite powder is filtered out of the culture solution, dried, and defoaming mineral powder is obtained. The ratio of zeolite powder to Bacillus subtilis culture is selected from 10~70 : 10~200, g:mL; the culture conditions are selected from: temperature of 25~40℃ and culture time of 15~48h.

2. The low-microfoam polyurethane mixture according to claim 1, characterized in that, The polyurethane is a one-component polyether polyurethane.

3. The low-microfoam polyurethane mixture according to claim 1, characterized in that, The aggregate is selected from limestone, granite, basalt or diabase with a particle size of 0.075~30mm.

4. The low-microfoam polyurethane mixture according to claim 1, characterized in that, The acidic stone powder is selected from granite powder with a particle size of less than 0.075 mm.

5. The low-microfoam polyurethane mixture according to claim 1, characterized in that, The Bacillus mucilaginosus bacterial solution was prepared by the following method: The activated Bacillus mucilaginosus was inoculated into the culture medium and cultured in a shaker at 35℃ and 200r / min for 12h to obtain Bacillus mucilaginosus bacterial solution.

6. A method for preparing the low-microfoam polyurethane mixture according to any one of claims 1 to 5, characterized in that, The steps are as follows: First, add the aggregate to the mixing pot and dry mix for 30-60 seconds. Then add the polyurethane and continue mixing during the process. After all the polyurethane is added, mix for another 30-60 seconds. Finally, add the acidic stone powder and defoaming mineral powder at the same time, continue mixing for 80-150 seconds, and then discharge the material to obtain a low-micro-foam polyurethane mixture.

7. The application of the low-microfoam polyurethane mixture according to any one of claims 1 to 5 in special paving structures for roads, bridges, tunnels or airports.

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