Modified asphalt concrete and its preparation method and application

Abstract

The present invention discloses a modified asphalt concrete, its preparation method, and application, belonging to the field of asphalt concrete technology. Sodium silicate, sodium hydroxide, and water are stirred and mixed, then transferred to a blender as an alkali activator. Fly ash, electrolytic manganese slag, cement, modified sugarcane fiber, and fine sand are then added to the blender and stirred and mixed. The mixture is vibrated to expel internal gas, allowed to stand, demolded, and crushed to obtain a geopolymer aggregate. The modified asphalt, geopolymer coarse aggregate, and basalt fine aggregate are then mixed in proportion to obtain the modified asphalt concrete. The geopolymer aggregate uses electrolytic manganese slag and fly ash as its primary raw materials, improving the utilization rate of waste resources. The addition of modified sugarcane fiber improves the mechanical properties of the geopolymer, meeting the application requirements of asphalt road aggregate. Compared to adding steel fiber and polymer fiber, sugarcane fiber is biodegradable, more environmentally friendly, and facilitates the demoulding and recycling of temporary asphalt roads.

Description

Technical Field

[0001] The present invention belongs to the technical field of asphalt concrete, and in particular relates to a modified asphalt concrete and a preparation method and application thereof. Background Art

[0002] Electrolytic manganese slag is a waste product generated during the manufacture of electrolytic manganese metal. The use of low-grade manganese ore, in particular, leads to increased waste generation. This waste contains significant amounts of heavy metal ions. Directly dumping or landfilling these wastes, along with rainfall, can cause heavy metal ions to seep into the soil, leading to severe environmental pollution. While green energy is being vigorously developed, traditional coal-fired power generation remains an irreplaceable alternative. The amount of fly ash emitted by thermal power plants continues to increase, and the accumulation and disposal of this large amount of fly ash is a pressing issue.

[0003] With the development of the construction and transportation industries, geopolymers are being widely used in the concrete industry due to their excellent properties. Geopolymers are formed by the interaction of aluminum-silicic acid and silicate components in an alkaline environment. They are a cement-like binder, with the Al-O-Si polymer structure forming the primary component of the geopolymer structure. Electrolytic manganese slag and fly ash contain complex components, including Al and Si. Geopolymers prepared from these components can be used as a cement-replacing grouting material.

[0004] When faced with poor road conditions during construction, temporary roads are often constructed to ensure smooth access for heavy machinery and vehicles. These roads are typically demolished or restored to their original state after construction is complete. Asphalt concrete is a high-performance pavement material primarily composed of aggregate, asphalt, and fillers. Using geopolymers as aggregates in asphalt concrete not only recycles waste but also reduces construction costs, aligning with the philosophy of green and environmentally friendly development.

[0005] Geopolymers have low flexural strength and are brittle, requiring the incorporation of reinforcing fibers to improve their mechanical properties. Chinese Patent Publication No. CN114149209B discloses a steel fiber geopolymer concrete material and its performance calculation method, which improves the mechanical performance shortcomings of conventional geopolymer concrete, such as low tensile and flexural strength, high shrinkage, and brittleness. However, the incorporation of steel fibers is costly and hinders the demolition of temporary roads and the recycling of asphalt concrete. Summary of the Invention

[0006] The purpose of the present invention is to provide a modified asphalt concrete and a preparation method and application thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for preparing modified asphalt concrete comprises the following steps:

[0009] Step 1: Sodium silicate, sodium hydroxide and water are stirred and mixed and then transferred to a blender as an alkali activator. Fly ash, electrolytic manganese slag, cement, modified sugarcane fiber and fine sand are then added to the blender and stirred at 200-300 r / min for 10-15 minutes. The slurry is poured into a mold and vibrated on a cement vibration table for 60-100 seconds to expel internal gas. The slurry is allowed to stand at 20-25°C for 24 hours, demolded, and crushed to obtain a geopolymer aggregate with a particle size of 8-12 mm.

[0010] Step 2: Mix the modified asphalt, geopolymer coarse aggregate and basalt fine aggregate with a particle size of 2-3 mm in a mass ratio of 2.5-3:10:3-5 to obtain modified asphalt concrete.

[0011] Furthermore, in step 1, the mass ratio of sodium silicate, sodium hydroxide, water, fly ash, electrolytic manganese slag, cement, modified sugarcane fiber and fine sand is 2:2:100-110:200:80-85:2-3:5-8:3-5.

[0012] Furthermore, the modified asphalt in step 2 is prepared by the following steps:

[0013] The matrix asphalt is transferred to an oven and heated to a molten state at 160-170°C. The molten matrix asphalt, SBS rubber powder and nano boron nitride powder are then transferred to a high-speed shearing machine and shear-mixed at 170-180°C and 4500-5000r / min for 30-40min. After shear mixing, the mixture is transferred to a high-speed mixer. Silica aerogel powder and asphalt stabilizer are added to the high-speed mixer, and stirred at 170-180°C and 1000-1200r / min for 3-3.5h to obtain modified asphalt.

[0014] Furthermore, the mass ratio of the matrix asphalt, SBS rubber powder, nano boron nitride powder, silica aerogel powder and asphalt stabilizer is 90:5-6:0.8-1.2:0.3-0.5:2-3.

[0015] Furthermore, the modified sugarcane fiber in step 1 is prepared by the following steps:

[0016] Step 1: Calcium chloride and zinc chloride are mixed and dissolved in a 2.5% by mass acetic acid solution, to obtain an acetic acid mixture; sugarcane fiber is soaked in a 5% by mass sodium hydroxide solution for 1.5-2 hours, then washed with deionized water 2-3 times and transferred to a reactor, the acetic acid mixture is added to the reactor, stirred at 200-300 r / min for 1-1.5 hours, filtered, and the retained fiber is washed with deionized water 2-3 times, dried at 60-80° C. to constant weight, and crushed to obtain pretreated sugarcane fiber with a length of 5-6 mm;

[0017] Step 2: Add pretreated sugarcane fiber and N,N-dimethylformamide to the reactor, stir and disperse at 20-25°C and 200-300 r / min for 10-15 minutes, then add phosphorus pentoxide to the reactor under the protection of nitrogen, stir continuously and heat to 120-125°C at a rate of 2-3°C / min, keep stirring for 3-3.5 hours, cool naturally, filter, wash the filter cake with deionized water and anhydrous ethanol for 3-5 times respectively, and vacuum dry to obtain modified sugarcane fiber.

[0018] Furthermore, in step 1, the usage ratio of calcium chloride, zinc chloride and acetic acid solution is 0.4-0.8 g:19-20 g:100-120 mL.

[0019] Furthermore, in step 2, the usage ratio of pretreated sugarcane fiber, N,N-dimethylformamide and phosphorus pentoxide is 4-5 g:180-200 mL:1.2-1.5 g.

[0020] Beneficial effects of the present invention:

[0021] The modified asphalt concrete of this invention uses geopolymer as the coarse aggregate. The geopolymer aggregate is primarily made from electrolytic manganese slag and fly ash, improving the utilization of waste resources. The addition of modified sugarcane fiber improves the mechanical properties of the geopolymer, meeting the application requirements of asphalt road aggregates. Compared to adding steel fiber and polymer fiber, sugarcane fiber is biodegradable, more environmentally friendly, and facilitates the dismantling and recycling of temporary asphalt roads.

[0022] Soaking sugarcane fiber in sodium hydroxide solution removes impurities such as colloids. In the acetic acid mixture, zinc chloride swells the sugarcane fiber, exposing more hydroxyl groups. This encourages the entry of water, zinc ions, and calcium ions into the fiber's interstices. This coordination and crosslinking between the hydroxyl groups and the ions on the fiber enhances the pretreated fiber's toughness. After the modified sugarcane fiber absorbs water, the zinc ions and other substances lower its freezing point, improving its frost resistance and ultimately increasing the freeze-thaw splitting strength ratio of the modified asphalt concrete.

[0023] The hydroxyl groups in the pretreated sugarcane fiber react with phosphorus pentoxide, grafting a large number of phosphate groups onto the fiber. This, through chemical adsorption and complexation, helps increase the modified sugarcane fiber's adsorption of heavy metals. Nano-boron nitride helps improve the durability and stability of modified asphalt, thereby enhancing the frost resistance of modified asphalt concrete. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Example 1: This example provides a modified asphalt concrete, which is prepared by the following method:

[0026] S1: 4 kg of calcium chloride and 190 kg of zinc chloride were mixed and dissolved in 1000 L of 2.5% acetic acid solution, to obtain an acetic acid mixture; 200 kg of sugarcane fiber was soaked in 5% sodium hydroxide solution for 1.5 hours, then washed twice with deionized water and transferred to a reactor, the acetic acid mixture was added to the reactor, stirred at 200 r / min for 1 hour, filtered, and the retained fiber was washed twice with deionized water, dried at 60°C to constant weight, and crushed to obtain pretreated sugarcane fiber with a length of 5-6 mm.

[0027] Soaking sugarcane fiber in sodium hydroxide solution can remove impurities such as colloids. In the acetic acid mixture, zinc chloride can swell the sugarcane fiber, causing the sugarcane fiber to expose more hydroxyl groups, promoting water, zinc ions and calcium ions to enter the gaps of the sugarcane fiber, and providing toughness to the pretreated sugarcane fiber through coordination and cross-linking between the hydroxyl groups on the fiber and the ions.

[0028] S2: Add 40 kg of pretreated sugarcane fiber and 1800 L of N,N-dimethylformamide to the reactor, stir and disperse at 20°C and 200 r / min for 10 minutes, then add 12 kg of phosphorus pentoxide to the reactor under the protection of nitrogen, stir continuously and raise the temperature to 120°C at a rate of 2°C / min, keep stirring for 3 hours, cool naturally, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and vacuum dry to obtain modified sugarcane fiber.

[0029] Through the reaction, the hydroxyl groups in the pretreated sugarcane fiber react with phosphorus pentoxide, and a large number of phosphate groups are grafted onto it, thereby increasing the adsorption effect of the modified sugarcane fiber on heavy metals through chemical adsorption and complexation.

[0030] S3: 2kg of sodium silicate, 2kg of sodium hydroxide and 100kg of water were stirred and mixed and then transferred to a blender as an alkali activator. 200kg of fly ash, 80kg of electrolytic manganese slag, 2kg of cement, 5kg of modified sugarcane fiber and 3kg of fine sand were added to the blender and stirred at 200r / min for 10min. The slurry was poured into a mold and vibrated on a cement vibration table for 60s to expel the internal gas. The slurry was allowed to stand at 20°C for 24h, demolded and crushed to obtain a geopolymer aggregate with a particle size of 8-12mm.

[0031] S4: Transfer the matrix asphalt to an oven and heat it to a molten state at 160°C. Then transfer the molten 90kg matrix asphalt, 5kg SBS rubber powder and 0.8kg nano-boron nitride powder to a high-speed shearing machine and shear mix them at 170°C and 4500r / min for 30min. After shear mixing, transfer the mixture to a high-speed mixer. Then add 0.3kg silica aerogel powder and 2kg asphalt stabilizer to the high-speed mixer and stir at 170°C and 1000r / min for 3h to obtain modified asphalt.

[0032] Nano-boron nitride helps to improve the durability and stability of modified asphalt, thereby improving the antifreeze effect of modified asphalt concrete.

[0033] S5: 2.5 kg of modified asphalt, 10 kg of geopolymer coarse aggregate and 3 kg of basalt fine aggregate with a particle size of 2-3 mm were stirred and mixed to obtain modified asphalt concrete.

[0034] Example 2: This example provides a modified asphalt concrete, which is prepared by the following method:

[0035] S1: 6 kg of calcium chloride and 195 kg of zinc chloride were mixed and dissolved in 1100 L of 2.5% acetic acid solution, to obtain an acetic acid mixture; 200 kg of sugarcane fiber was soaked in 5% sodium hydroxide solution for 1.8 hours, then washed twice with deionized water and transferred to a reactor, the acetic acid mixture was added to the reactor, stirred at 250 r / min for 1.2 hours, filtered, and the retained fiber was washed twice with deionized water, dried at 70°C to constant weight, and crushed to obtain pretreated sugarcane fiber with a length of 5-6 mm.

[0036] S2: Add 45 kg of pretreated sugarcane fiber and 1900 L of N,N-dimethylformamide to the reactor, stir and disperse at 22°C and 250 r / min for 12 minutes, then add 13.5 kg of phosphorus pentoxide to the reactor under the protection of nitrogen, stir continuously and raise the temperature to 122°C at a rate of 2.5°C / min, keep stirring for 3.2 hours, cool naturally, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and vacuum dry to obtain modified sugarcane fiber.

[0037] S3: 2kg of sodium silicate, 2kg of sodium hydroxide and 105kg of water were stirred and mixed and transferred to a blender as an alkali activator. 200kg of fly ash, 82.5kg of electrolytic manganese slag, 2.5kg of cement, 6.5kg of modified sugarcane fiber and 4kg of fine sand were added to the blender and stirred at 250r / min for 13min. The slurry was poured into a mold and vibrated on a cement vibration table for 80s to expel the internal gas. The slurry was allowed to stand at 22°C for 24h, demolded and crushed to obtain a geopolymer aggregate with a particle size of 8-12mm.

[0038] S4: Transfer the matrix asphalt to an oven and heat it to a molten state at 160-170°C. Then transfer the molten 90kg matrix asphalt, 5-6kg SBS rubber powder and 0.8-1.2kg nano boron nitride powder to a high-speed shearing machine, shear and mix them at 170-180°C and 4500-5000r / min for 30-40min. After shearing and mixing, transfer the mixture to a high-speed mixer, add 0.3-0.5kg silica aerogel powder and 2-3kg asphalt stabilizer to the high-speed mixer, and stir at 170-180°C and 1000-1200r / min for 3-3.5h to obtain modified asphalt.

[0039] S5: 2.8 kg of modified asphalt, 10 kg of geopolymer coarse aggregate and 4 kg of basalt fine aggregate with a particle size of 2-3 mm were stirred and mixed to obtain modified asphalt concrete.

[0040] Example 3: This example provides a modified asphalt concrete, which is prepared by the following method:

[0041] S1: 8 kg of calcium chloride and 200 kg of zinc chloride were mixed and dissolved in 1200 L of 2.5% acetic acid solution, to obtain an acetic acid mixture; 200 kg of sugarcane fiber was soaked in 5% sodium hydroxide solution for 2 hours, then washed three times with deionized water and transferred to a reactor, the acetic acid mixture was added to the reactor, stirred at 300 r / min for 1.5 hours, filtered, and the retained fiber was washed three times with deionized water, dried at 80°C to constant weight, and crushed to obtain pretreated sugarcane fiber with a length of 5-6 mm.

[0042] S2: Add 50 kg of pretreated sugarcane fiber and 2000 L of N,N-dimethylformamide to the reactor, stir and disperse at 25°C and 300 r / min for 15 minutes, then add 15 kg of phosphorus pentoxide to the reactor under the protection of nitrogen, stir continuously and raise the temperature to 125°C at a rate of 3°C / min, keep stirring for 3.5 hours, cool naturally, filter, wash the filter cake with deionized water and anhydrous ethanol respectively for 5 times, and vacuum dry to obtain modified sugarcane fiber.

[0043] S3: 2kg of sodium silicate, 2kg of sodium hydroxide and 110kg of water were stirred and mixed, and then transferred to a blender as an alkali activator. 200kg of fly ash, 85kg of electrolytic manganese slag, 3kg of cement, 8kg of modified sugarcane fiber and 5kg of fine sand were added to the blender. The mixture was stirred at 300r / min for 15min. The slurry was poured into a mold and vibrated on a cement vibration table for 100s to discharge the internal gas. The mixture was allowed to stand at 25°C for 24h, demolded and crushed to obtain a geopolymer aggregate with a particle size of 8-12mm.

[0044] S4: Transfer the matrix asphalt to an oven and heat it to a molten state at 170°C. Then transfer the molten 90kg matrix asphalt, 6kg SBS rubber powder and 1.2kg nano-boron nitride powder to a high-speed shearing machine and shear mix them at 180°C and 5000r / min for 40min. After shear mixing, transfer the mixture to a high-speed mixer. Then add 0.5kg silica aerogel powder and 3kg asphalt stabilizer to the high-speed mixer and stir at 180°C and 1200r / min for 3.5h to obtain modified asphalt.

[0045] S5: 3 kg of modified asphalt, 10 kg of geopolymer coarse aggregate and 5 kg of basalt fine aggregate with a particle size of 2-3 mm were stirred and mixed to obtain modified asphalt concrete.

[0046] Comparative Example 1: Based on Example 3, in step S1, the acetic acid mixture is not used, and the acetic acid mixture is directly replaced by acetic acid solution with a mass fraction of 2.5% to pretreat the sugarcane fiber. The other steps remain unchanged to prepare modified asphalt concrete blue.

[0047] Comparative Example 2: Based on Example 3, the pretreated sugarcane fiber of the same mass in step S1 was directly applied to step S3 without being processed in step S2, and the other steps remained unchanged to prepare modified asphalt concrete.

[0048] Comparative Example 3: Based on Example 3, the same mass of sugarcane fiber was directly used in step S3, and the other steps remained unchanged to prepare modified asphalt concrete blue.

[0049] Comparative Example 4: Based on Example 3, nano boron nitride powder is not added in step S4, and the other steps remain unchanged to prepare modified asphalt concrete.

[0050] The matrix asphalt model in the examples and comparative examples is Zhonghai 90#, and the asphalt stabilizer is purchased from Tianjin Zhongke New Materials Co., Ltd., with a model of WDJ-1.

[0051] Samples were prepared according to the corresponding standards, and the modified asphalt concretes in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to performance tests: the Marshall stability at 60°C (T0709-2011), the elastic recovery rate at 25°C (T0662-2000), and the freeze-thaw splitting strength ratio (T0729-2000; strength after freeze-thaw cycle / strength before freeze-thaw cycle × 100%) of different samples were tested according to JTG E20-2011 "Testing Procedures for Asphalt and Asphalt Mixtures for Highway Engineering". The heavy metal leaching amount of different samples, including Pb, Cd, and Cr, was tested according to HJ557-2010 "Toxicity Leaching Method for Solid Waste Leaching - Horizontal Oscillation Method". The results are shown in Table 1:

[0052] Table 1 Modified asphalt concrete performance test table

[0053]

[0054]

[0055] As can be seen from Table 1, the overall performance of the modified asphalt concrete in Examples 1-3 is better than that of the comparative example. Comparative Example 3 shows that the addition of modified sugarcane fiber can improve the Marshall stability, elastic recovery rate, and freeze-thaw splitting test strength ratio of the modified asphalt concrete specimens compared to geopolymer aggregate prepared with untreated sugarcane fiber. Combined with the analysis of Comparative Example 1, this is because during the sugarcane fiber treatment, zinc chloride can swell the sugarcane fiber, causing the sugarcane fiber to expose more hydroxyl groups, promoting the entry of water, zinc ions, and calcium ions into the interstices of the sugarcane fiber. Through coordination and crosslinking between the hydroxyl groups on the fiber and the ions, the toughness of the pretreated sugarcane fiber is improved. Zinc ions and other substances can also improve the frost resistance of the modified sugarcane fiber, thereby improving the freeze-thaw splitting test strength ratio of the modified asphalt concrete.

[0056] Comparative Examples 1-3 demonstrate that phosphorus pentoxide treatment can enhance the adsorption of heavy metals from geopolymer raw materials by reacting the hydroxyl groups in pretreated sugarcane fibers with phosphate groups. Comparative Example 4 demonstrates that nano-boron nitride can synergistically enhance the frost resistance of modified asphalt concrete.

[0057] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0058] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing modified asphalt concrete, characterized in that: The steps include: Step 1: Sodium silicate, sodium hydroxide and water are stirred and mixed and then transferred to a blender as an alkali activator. Fly ash, electrolytic manganese slag, cement, modified sugarcane fiber and fine sand are then added to the blender and stirred at 200-300 r / min for 10-15 minutes. The slurry is poured into a mold and vibrated on a cement vibration table for 60-100 seconds. The mixture is then allowed to stand at 20-25°C for 24 hours, demolded and crushed to obtain a geopolymer aggregate with a particle size of 8-12 mm. Step 2: Mixing the modified asphalt, geopolymer coarse aggregate and basalt fine aggregate with a particle size of 2-3 mm in a mass ratio of 2.5-3:10:3-5 to obtain modified asphalt concrete; The modified sugarcane fiber obtained in step 1 is prepared by the following steps: soaking the sugarcane fiber in a sodium hydroxide solution to expose more hydroxyl groups, thereby obtaining pretreated sugarcane fiber; Add pretreated sugarcane fiber and N,N-dimethylformamide to a reactor, stir and disperse at 20-25°C and 200-300 r / min for 10-15 minutes, add phosphorus pentoxide to the reactor under nitrogen protection, stir continuously and heat to 120-125°C at a rate of 2-3°C / min, keep stirring for 3-3.5 hours, cool naturally, filter, wash the filter cake with deionized water and anhydrous ethanol for 3-5 times respectively, and vacuum dry to obtain modified sugarcane fiber; The modified asphalt in step 2 is prepared by the following steps: The matrix asphalt is heated at 160-170°C to a molten state, and then the molten matrix asphalt, SBS rubber powder and nano boron nitride powder are transferred to a high-speed shearing machine, and shear mixed at 170-180°C and 4500-5000 r / min for 30-40 minutes. The mixture is transferred to a high-speed mixer and silica aerogel powder and asphalt stabilizer are added, and stirred at 170-180°C and 1000-1200 r / min for 3-3.5 hours to obtain modified asphalt.

2. The method for preparing modified asphalt concrete according to claim 1, wherein: The mass ratio of the sodium silicate, sodium hydroxide, water, fly ash, electrolytic manganese slag, cement, modified sugarcane fiber and fine sand in step 1 is 2:2:100-110:200:80-85:2-3:5-8:3-5.

3. The method for preparing modified asphalt concrete according to claim 1, wherein: The usage ratio of the pretreated sugarcane fiber, N,N-dimethylformamide and phosphorus pentoxide is 4-5g:180-200mL:1.2-1.5g.

4. The method for preparing modified asphalt concrete according to claim 1, wherein: The pretreated sugarcane fiber is prepared by the following steps: The sugarcane fiber is soaked in a 5wt% sodium hydroxide solution for 1.5-2 hours, washed and transferred to a reactor, calcium chloride and zinc chloride are mixed and dissolved with a 2.5wt% acetic acid solution, and the obtained acetic acid mixture is added to the reactor, stirred at 200-300 r / min for 1-1.5 hours, filtered, and the retained fiber is washed with deionized water 2-3 times, dried at 60-80°C to constant weight, and crushed to obtain pretreated sugarcane fiber with a length of 5-6 mm.

5. The method for preparing modified asphalt concrete according to claim 4, characterized in that: The usage ratio of the calcium chloride, zinc chloride and acetic acid solution is 0.4-0.8 g:19-20 g:100-120 mL.

6. The method for preparing modified asphalt concrete according to claim 1, characterized in that: The mass ratio of the matrix asphalt, SBS rubber powder, nano boron nitride powder, silicon dioxide aerogel powder and asphalt stabilizer is 90:5-6:0.8-1.2:0.3-0.5:2-3.

7. A modified asphalt concrete, characterized in that: The modified asphalt concrete is prepared by the preparation method of any one of claims 1 to 6.

8. Use of the modified asphalt concrete according to claim 7 in temporary asphalt roads.

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