Preparation method of a porous alkali-activated fly ash-based asphalt filler

Abstract

The present invention belongs to the technical field of road construction materials, and particularly relates to a preparation method of a porous alkali-activated fly ash-based asphalt filler. The method comprises the following steps: weighing 50 parts of fly ash, 25 parts of sodium hydroxide solution with a concentration of 10 mol / L and an appropriate amount of water according to the mass ratio, stirring for 8 min to obtain a uniform geopolymer slurry with a liquid-solid mass ratio of 0.35; pouring the geopolymer slurry into a mold, vibrating for 1 min to remove the air bubbles in the slurry, and curing for 24 h by wrapping with a plastic film at room temperature; demolding the test block, and after demolding, placing the test block in a curing box at a temperature of 40 °C and a humidity of 60% for curing for 2 days; after curing, grinding the test block with a grinder, and passing the ground powder through a 200-mesh sieve to remove the screen residue. The preparation method of the present invention can reduce the viscosity of asphalt, reduce the usage amount of limestone filler, and improve the performance of asphalt mortar, which is of great significance for energy conservation, emission reduction and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of road construction materials, and particularly relates to a preparation method of a porous alkali-activated fly ash-based asphalt filler. Background Art

[0002] The heating temperature of hot mix asphalt is usually 150 - 180 °C, which consumes a large amount of energy and generates a large amount of polluting gases, being unfavorable for energy conservation, emission reduction and environmental protection. The warm mix technology can reduce the heating temperature of asphalt. The heating temperature of warm mix asphalt is generally 20 - 40 °C lower than that of hot mix asphalt. The lower heating temperature can not only reduce energy consumption and cost, but also make it possible to carry out construction operations in special environments such as winter and night. The core of the warm mix technology is to reduce the mixing and paving temperature.

[0003] Porous alkali-activated fly ash-based asphalt filler can be synthesized by alkali activation using fly ash and other reactive aluminosilicate minerals. This filler has a rich pore structure and a large specific surface area, and can adsorb free water and hydrated metal ions. These waters will be slowly released and evaporated into water vapor within 90 - 140 °C, generating a large amount of foam and reducing the viscosity of asphalt. When the porous alkali-activated fly ash-based asphalt filler is added to asphalt, as the temperature gradually rises, the crystal water is released and vaporized, causing the asphalt to expand in volume and foam, which can improve the workability of asphalt and reduce the mixing and paving temperature of the asphalt mixture.

[0004] Adding the porous alkali-activated fly ash-based asphalt filler to asphalt can also reduce the use of traditional limestone filler and lower the construction cost. At the same time, when asphalt comes into contact with the porous alkali-activated fly ash-based asphalt filler, small molecules in the asphalt can enter the interior of the porous alkali-activated fly ash-based asphalt filler along the pores, forming a more stable structure and improving the performance of the asphalt mortar.

[0005] In the prior art CN109336456A, the raw materials are calcined at high temperature and a surfactant is added, which not only consumes more energy but also is unfavorable for cost control. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the invention object of the present invention is to propose a preparation method of a porous alkali-activated fly ash-based asphalt filler, which can not only reduce the viscosity of asphalt, but also reduce the use of limestone filler and improve the performance of the asphalt mortar. In addition, it provides a new idea for the efficient utilization of fly ash and has important significance for energy conservation, emission reduction and environmental protection.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A preparation method of a porous alkali-activated fly ash-based asphalt filler, comprising the following steps:

[0009] Step 1: Weigh 50 parts of fly ash, 25 parts of alkali activator and an appropriate amount of water according to the mass ratio. Stir with an electronic stirrer for 8 minutes to obtain a uniform geopolymer slurry with a liquid-solid mass ratio of 0.35.

[0010] Step 2: Pour the geopolymer slurry obtained in Step 1 into a mold of 80mm×20mm×20mm, vibrate for 1 minute to remove the air bubbles in the slurry, and wrap and cure it with a plastic film at room temperature for 24 hours.

[0011] Step 3: Demold the specimen obtained by curing the geopolymer slurry in Step 2. After demolding, place the specimen in a curing box at a temperature of 40°C and a relative humidity of 60% for 2 days.

[0012] Step 4: After curing, grind the specimen with a grinder, pass the ground powder through a 200-mesh sieve, remove the residues on the sieve, and the obtained powder is the porous alkali-activated fly ash-based asphalt filler.

[0013] Preferably, the fly ash is Class F fly ash.

[0014] Preferably, the alkali activator is a sodium hydroxide solution with a concentration of 10 mol / L; the amount of water is 3 parts.

[0015] A preparation method of a highly extensible and elastic modified asphalt mortar uses highly extensible and elastic modified asphalt, limestone powder, and the above-mentioned porous alkali-activated fly ash-based asphalt filler as raw materials. The mass ratio of highly extensible and elastic modified asphalt:(limestone powder + porous alkali-activated fly ash-based asphalt filler) is 1:0.8, and the mass percentage of the porous alkali-activated fly ash-based asphalt filler in the mixture of limestone powder and the porous alkali-activated fly ash-based asphalt filler is 10-20%; the preparation method includes the following steps: 1. Weigh the highly extensible and elastic modified asphalt and place it in an oven at 160°C and continuously heat until it melts; 2. Weigh the limestone powder and place it in an oven at 150°C for preheating; 3. Weigh the porous alkali-activated fly ash-based asphalt filler, mix it evenly with the limestone powder preheated to 150°C in Step 2, divide it into 5 equal parts, and add 1 part each time in 5 times while stirring to the melted asphalt in Step 1. After all are added, continue to stir with a stirrer at a speed of 1000 r / min at a temperature of 160°C for 0.5 h to obtain the asphalt mortar.

[0016] Preferably, in the above steps, the highly extensible and elastic modified asphalt is 100 g; the limestone powder is 72 g and the porous alkali-activated fly ash-based asphalt filler is 8 g, or the limestone powder is 68 g and the porous alkali-activated fly ash-based asphalt filler is 12 g, or the limestone powder is 64 g and the porous alkali-activated fly ash-based asphalt filler is 16 g;

[0017] The high elongation elastic modified asphalt is prepared from SBS modified asphalt and a high elongation elastic asphalt modifier, and its preparation method includes the following steps:

[0018] Step 1: Weigh 94 g of SBS modified asphalt and heat it to 180 °C, and weigh 6 g of the high elongation elastic asphalt modifier; while stirring at a speed of 60 r / min, add the high elongation elastic asphalt modifier to the SBS modified asphalt that has been heated to 180 °C. After completely adding the high elongation elastic asphalt modifier, continue to stir at 180 °C for 10 min;

[0019] Step 2: Put the mixture into an oven at 180 °C for 30 min to obtain the high elongation elastic modified asphalt;

[0020] Among them, the preparation process of the high elongation elastic asphalt modifier is as follows. In the following steps, when calculated by mass fraction, 1 unit mass fraction in each step represents the same mass:

[0021] 1.1. Pretreatment of glass fiber: According to the mass fraction, use a 1% silane coupling agent to perform surface treatment on 10 parts of glass fiber, and dry it for later use after treatment.

[0022] The process of using a 1% silane coupling agent to perform surface treatment on glass fiber is as follows:

[0023] 1.1.1. Prepare a 1% silane coupling agent solution: Add 10 g of γ-aminopropyltriethoxysilane to 990 ml of deionized water, and use a stirring device to stir until γ-aminopropyltriethoxysilane is completely dissolved;

[0024] 1.1.2. Completely immerse the glass fiber to be treated in the silane coupling agent solution prepared in step 1.1.1 to ensure that the fiber surface is fully in contact with the solution; the immersion time is 10 - 30 minutes. To ensure uniform immersion, the container can be appropriately stirred or slightly vibrated;

[0025] 1.1.3. After immersion, take out the glass fiber from the silane coupling agent solution and gently shake off the excess solution;

[0026] 1.1.4. Spread the glass fiber evenly, hang it in a well-ventilated place to dry naturally or put it into an oven for drying. The drying temperature in the oven is 110 - 120 °C and the time is 1 - 2 hours to ensure that the glass fiber is completely dry;

[0027] 1.1.5. After drying, gently loosen the glass fiber to ensure that the fibers do not stick together and maintain their good dispersibility.

[0028] Through the above treatment, the surface of the glass fiber is covered with a silane coupling agent, thereby improving its bonding performance with the polymer matrix. The above pretreatment steps can improve the bonding strength between the glass fiber and the matrix resin, thereby enhancing the mechanical properties of the modifier.

[0029] 1.2. Preliminary mixing: Weigh 50 parts of styrene-butadiene-styrene copolymer (SBS), 30 parts of polyurethane (TPU), 20 parts of ethylene-vinyl acetate copolymer (EVA), and 20 parts of cis-butadiene rubber by mass, and add all of them to a high-speed mixer. Mix them preliminarily at a speed of 1200 rpm for 5 minutes until the polymers in the mixture are evenly dispersed.

[0030] 1.3. Adding additives and crosslinking agents: Add 2 parts of tricresyl phosphate, 5 parts of C9 petroleum resin, 10 parts of the pretreated glass fiber in step 1.1, 3 parts of polyethylene wax (PE wax), 1 part of maleic anhydride, 0.5 part of dicumyl peroxide, and 1 part of 2,2'-methylenebis(4-methyl-6-tert-butylphenol) to the mixture obtained by preliminary mixing in step 1.2 in sequence by mass; after the addition is completed, continue to mix at a speed of 800 rpm for 10 minutes to ensure that all components are evenly dispersed.

[0031] 1.4. Extrusion process: Add the mixture obtained in step 1.3 to a twin-screw extruder and carry out melt blending extrusion at a barrel temperature of 170°C and a screw speed of 35 rpm; during the extrusion process, use a vacuum exhaust device to remove the gas generated during the mixing process to ensure the purity and performance of the product.

[0032] 1.5. Cooling and pelletizing: Quickly cool the melt extruded in step 1.4 through a cooling device, and cut it into pellets after cooling to obtain a granular product.

[0033] 1.6. Standing of pellets: Let the granular product obtained in step 1.5 stand at room temperature for 24 hours to release internal stress, improve the stability and performance of the product, and finally obtain the high-ductility elastic asphalt modifier.

[0034] Compared with the prior art, the advantages and beneficial effects of the present invention:

[0035] 1. The porous alkali-activated fly ash-based asphalt filler of the present invention has a rich pore structure and a large specific surface area, and can adsorb free water and hydrated metal ions. These water are slowly released and evaporated into water vapor during the heating process of the asphalt mixture, generating a large amount of foam and reducing the viscosity of the asphalt. At the same time, when the asphalt contacts the porous alkali-activated fly ash-based asphalt filler, small molecules in the asphalt can enter the interior of the porous alkali-activated fly ash-based asphalt filler along the pores, forming a more stable structure and improving the performance of the asphalt mortar.

[0036] 2. The porous alkali-activated fly ash-based asphalt filler prepared by the present invention can not only reduce the viscosity of asphalt, but also reduce the dosage of limestone filler, reduce energy consumption during construction, and lower construction costs.

[0037] 3. In the prior art CN109336456A, the raw materials are calcined at high temperature and surfactants are added, which not only consumes more energy, but also is not conducive to cost control. However, the present invention does not adopt a calcination process and does not add surfactants, reducing production costs and energy consumption. Description of the Drawings

[0038] Figure 1 It is the thermogravimetric curve of the porous alkali-activated fly ash-based asphalt filler of the present invention;

[0039] Figure 2 It is the microscopic morphology diagram of the porous alkali-activated fly ash-based asphalt filler of the present invention;

[0040] Figure 3 It is the relationship diagram of the rotational viscosity and temperature of the asphalt mortar added with the porous alkali-activated fly ash-based asphalt filler of the present invention: Figure 3 (a) is the test result of the rotational viscosity of the matrix asphalt mortar, Figure 3 (b) is the test result of the rotational viscosity of the SBS modified asphalt mortar, Figure 3 (c) is the test result of the rotational viscosity of the highly elastic modified asphalt mortar;

[0041] Figure 4 It is the relationship diagram of the temperature and the scanned complex shear modulus of the asphalt mortar added with the porous alkali-activated fly ash-based asphalt filler of the present invention at a constant frequency of 10 rad / s: Figure 4 (a) is the test result of the temperature scan of the matrix asphalt mortar, Figure 4 (b) is the test result of the temperature scan of the SBS modified asphalt mortar, Figure 4 (c) is the test result of the temperature scan of the highly elastic modified asphalt mortar;

[0042] Figure 5 It is the relationship diagram of the temperature and the scanned phase angle of the asphalt mortar added with the porous alkali-activated fly ash-based asphalt filler of the present invention at a constant frequency of 10 rad / s: Figure 5 (a) is the test result of the temperature scan of the matrix asphalt mortar, Figure 5 (b) is the test result of the temperature scan of the SBS modified asphalt mortar, 5(c) is the test result of the temperature scan of the highly elastic modified asphalt mortar;

[0043] Figure 6 It is the relationship diagram of the frequency and the scanned complex shear modulus of the asphalt mortar added with the porous alkali-activated fly ash-based asphalt filler of the present invention at 60 °C: Figure 6(a) Frequency scanning test results of matrix asphalt mortar, Figure 6 (b) Frequency scanning test results of SBS modified asphalt mortar, Figure 6 (c) Frequency scanning test results of highly extensible elastic modified asphalt mortar;

[0044] Figure 7 Relationship diagram of frequency and scanning phase angle at 60°C for asphalt mortar with the porous alkali-activated fly ash-based asphalt filler of the present invention added: Figure 7 (a) Frequency scanning test results of matrix asphalt mortar, and Figure 7 (b) Frequency scanning test results of SBS modified asphalt mortar, and 7(c) Frequency scanning test results of highly extensible elastic modified asphalt mortar. Detailed implementation mode

[0045] The preparation method of a porous alkali-activated fly ash-based asphalt filler and the preparation method of a highly extensible elastic modified asphalt mortar will be described in detail below in conjunction with specific embodiments. However, the described embodiments are only a part of the embodiments of the present invention, and the content of the present invention is not limited to the following embodiments.

[0046] In this application, when calculated by mass fraction, 1 unit mass fraction in each step represents the same mass.

[0047] Example 1

[0048] 1. Raw materials:

[0049] Class F fly ash is taken from a power plant in Shanxi. The main chemical components of Class F fly ash are analyzed by X-ray fluorescence spectrometry (XRF), and the analysis results are shown in Table 1.

[0050] The alkali activator is sodium hydroxide solution with a concentration of 10 mol / L.

[0051] Table 1 Chemical composition of fly ash

[0052] Material <![CDATA[Al2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[Fe2O3]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> <![CDATA[TiO2]]> LOI Fly ash 21.64 48.11 2.66 4.43 ─ 0.65 1.66 1.51

[0053] 2. Preparation method of porous alkali-activated fly ash-based asphalt filler, including the following steps:

[0054] Step 1: Weigh 50 g of fly ash, 25 g of the alkali activator sodium hydroxide solution and 3 g of water according to the ratio, and stir with an electronic stirrer for 8 min to obtain a uniform geopolymer paste with a liquid-solid mass ratio of 0.35;

[0055] Step 2: Pour the geopolymer paste obtained in Step 1 into a mold of 80 mm × 20 mm × 20 mm, vibrate for 1 min to remove the air bubbles in the paste, and cure for 24 h by wrapping with a plastic film at room temperature (25°C, the same below);

[0056] Step 3: Demold the test block obtained by curing the geopolymer paste in Step 2. After demolding, place the test block in a curing box at a temperature of 40°C and a relative humidity of 60% for 2 days of curing.

[0057] Step 4: After the curing is completed, grind the test block using a grinder, pass the powder obtained from grinding through a 200-mesh sieve, remove the residues on the sieve, and the obtained powder is the porous alkali-activated fly ash-based asphalt filler.

[0058] Example 2

[0059] Use the porous alkali-activated fly ash-based asphalt filler prepared in Example 1 as the filler to prepare matrix asphalt mortar, SBS modified asphalt mortar, and highly extensible elastic modified asphalt mortar respectively. The 70# matrix asphalt and SBS modified asphalt are taken from Shanxi Yutong Xiuwen Asphalt Depot, and the highly extensible elastic modified asphalt is self-made in the laboratory. The basic properties of the three asphalts are shown in Table 2.

[0060] Prepare highly extensible elastic modified asphalt using SBS modified asphalt and highly extensible elastic asphalt modifier as raw materials. The preparation process is as follows: Weigh 94 g of SBS modified asphalt and heat it to 180°C, and weigh 6 g of highly extensible elastic asphalt modifier; while stirring at a speed of 60 r / min, add the highly extensible elastic asphalt modifier to the SBS modified asphalt that has been heated to 180°C. After completely adding the highly extensible elastic asphalt modifier, continue to stir at 180°C for 10 min; then place the mixture in an oven at 180°C for 30 min of development to obtain the highly extensible elastic modified asphalt.

[0061] Among them, the preparation process of the highly extensible elastic asphalt modifier is as follows:

[0062] 1. Glass fiber pretreatment: By mass fraction, 10 parts of glass fiber are surface-treated with a 1% silane coupling agent, and after treatment, they are dried and reserved. The process of surface-treating glass fiber with a 1% silane coupling agent is as follows: First, prepare a 1% silane coupling agent solution. Add 10 g of γ-aminopropyltriethoxysilane to 990 ml of deionized water, and use a stirring device to stir until γ-aminopropyltriethoxysilane is completely dissolved. Next, completely immerse the glass fiber to be treated in the prepared silane coupling agent solution to ensure that the fiber surface is fully in contact with the solution. The soaking time is generally 20 minutes, and in order to ensure uniform soaking, appropriate stirring can be carried out. After soaking, take out the glass fiber from the solution and gently shake off the excess solution. Then, spread the glass fiber evenly and place it in an oven for drying. The drying temperature in the oven is 120 °C and the time is 1.5 hours to ensure that the glass fiber is completely dry. After drying is completed, gently loosen the glass fiber to ensure that the fibers do not stick together and maintain their good dispersibility. Through the above treatment, the surface of the glass fiber is covered with a silane coupling agent, thereby improving its bonding performance with the polymer matrix. The above pretreatment steps can improve the bonding force between the glass fiber and the matrix resin, thereby enhancing the mechanical properties of the modifier.

[0063] 2. Preliminary mixing: By mass fraction, weigh 50 parts of styrene-butadiene-styrene copolymer (SBS), 30 parts of polyurethane (TPU), 20 parts of ethylene-vinyl acetate copolymer (EVA), and 20 parts of cis-butadiene rubber, and add them all to a high-speed mixer and mix preliminarily at a speed of 1200 rpm for 5 minutes until the polymers in the mixture are evenly dispersed.

[0064] 3. Adding additives and crosslinking agent: Add 2 parts of tricresyl phosphate, 5 parts of C9 petroleum resin, 10 parts of the pretreated glass fiber in step 1, 3 parts of polyethylene wax (PE wax), 1 part of maleic anhydride, 0.5 part of dicumyl peroxide, and 1 part of 2,2'-methylenebis(4-methyl-6-tert-butylphenol) to the mixture obtained by preliminary mixing in step 2 in sequence, and continue to mix at a speed of 800 rpm for 10 minutes to ensure that all components are evenly dispersed.

[0065] 4. Extrusion process: Add the mixture obtained in step 3 to a twin-screw extruder and carry out melt blending and extrusion at a barrel temperature of 170 °C and a screw speed of 35 rpm. During the extrusion process, use a vacuum exhaust device to remove the gas generated during the mixing process to ensure the purity and performance of the product.

[0066] 5. Cooling and pelletizing: The melt extruded in step 4 is placed in a cooling device for rapid cooling, and then pelletized to obtain granular modifier.

[0067] 6. Granular material static placement: The granular modifier obtained in step 5 is statically placed at room temperature for 24 hours to release internal stress, improve the stability and performance of the product, and finally obtain the high-ductility elastic asphalt modifier.

[0068] Table 2 Basic performance indicators of 70# base asphalt, SBS modified asphalt and high-ductility elastic modified asphalt

[0069] 70# Matrix asphalt SBS modified asphalt High-ductility modified asphalt Penetration (25℃ 100g, 5s) 0.1mm 65.4 59.4 49.3 Softening point (Ring and Ball method) ℃ 46.6 89.1 94.2 Ductility (5℃) cm 7.3 31.5 48.6 Viscosity (135℃) mPa·s 311 2340 5140

[0070] Matrix asphalt mortar, SBS modified asphalt mortar and high-ductility elastic modified asphalt mortar are prepared according to the mass ratio of asphalt:(limestone powder + porous alkali-activated fly ash-based asphalt filler) of 1:0.8 respectively; among them, the porous alkali-activated fly ash-based asphalt filler is used as a substitute for limestone powder, and the mass percentage of the porous alkali-activated fly ash-based asphalt filler in the mixture of limestone powder and porous alkali-activated fly ash-based asphalt filler is 0%, 5%, 10%, 15% and 20% respectively, that is, the substitution rate of the porous alkali-activated fly ash-based asphalt filler gradually increases from 0%, 5%, 10%, 15% to 20%.

[0071] Taking the substitution rate of the porous alkali-activated fly ash-based asphalt filler of 10% as an example, the preparation process of the asphalt mortar is as follows: 1. Weigh 100 g of asphalt and place it in an oven at 160 °C and heat it continuously until it melts; 2. Weigh 72 g of limestone powder and place it in an oven at 150 °C for preheating; 3. Weigh 8 g of the porous alkali-activated fly ash-based asphalt filler, mix it evenly with the limestone powder preheated to 150 °C in step 2, divide it into 5 equal parts, and add 1 part each time while stirring to the melted asphalt in step 1. After all are added, continue to stir at a speed of 1000 r / min with a stirrer at a temperature of 160 °C for 0.5 h to obtain the asphalt mortar; among them, the asphalt is matrix asphalt, SBS modified asphalt or high-ductility elastic modified asphalt respectively.

[0072] Performance test of the porous alkali-activated fly ash-based asphalt filler prepared in Example 1

[0073] Thermogravimetric analysis is used to evaluate the water loss ability of the porous alkali-activated fly ash-based asphalt filler. The attached Figure 1 is the thermogravimetric curve of the porous alkali-activated fly ash-based asphalt filler. In the thermogravimetric test results of the porous alkali-activated fly ash-based asphalt filler, the weight loss rate can reach 12.14% at 200 °C.

[0074] Scanning electron microscopy is used to observe the microscopic morphology of the porous alkali-activated fly ash-based asphalt filler. As shown in the attached Figure 2 of the specification, the porous alkali-activated fly ash-based asphalt filler is an irregular block with a rough surface.

[0075] It can be seen therefrom that the porous alkali-activated fly ash-based asphalt filler of the present invention has good water loss ability; meanwhile, when asphalt comes into contact with the porous alkali-activated fly ash-based asphalt filler, small molecules in the asphalt can enter the interior of the porous alkali-activated fly ash-based asphalt filler along the pores, forming a more stable structure and improving the performance of the asphalt mortar.

[0076] Performance test of the asphalt mortar prepared in Example 2

[0077] Rotational viscosity

[0078] The rotational viscosities of each group of asphalt mortars at different replacement rates were measured using a Brookfield viscometer to evaluate the viscosity reduction effect of the porous alkali-activated fly ash-based asphalt filler on different types of asphalt mortars. The test results of the rotational viscosities of the asphalt mortars at different temperatures are as Figure 3 shown, where Figure 3 (a) are the test results of the rotational viscosity of the base asphalt mortar, Figure 3 (b) are the test results of the rotational viscosity of the SBS modified asphalt mortar, Figure 3 (c) are the test results of the rotational viscosity of the highly extensible and elastic modified asphalt mortar. The porous alkali-activated fly ash-based asphalt filler can reduce the viscosity of the asphalt mortar. Under the condition of 155 °C, compared with the case without the porous alkali-activated fly ash-based asphalt filler of Example 1 (replacement rate of 0), the viscosities of the base asphalt mortar, SBS modified asphalt mortar, and highly extensible and elastic modified asphalt mortar were reduced by 12.3%, 11.5%, and 10.6% respectively when the replacement rate of the porous alkali-activated fly ash-based asphalt filler of Example 1 was 10%.

[0079] Dynamic shear rheometer test

[0080] The dynamic shear rheometer test was used to evaluate the influence of the porous alkali-activated fly ash-based asphalt filler replacing part of the limestone powder on the rheological properties of the asphalt mortar.

[0081] A temperature sweep test was carried out at a constant frequency of 10 rad / s to clarify the deformation behavior and stability of the asphalt mortar at different temperatures. The results of the complex shear modulus and phase angle of each group of asphalt mortars are respectively as Figure 4 and Figure 5 shown, where Figure 4 (a) and Figure 5 (a) are the temperature sweep test results of the base asphalt mortar, Figure 4 (b) and Figure 5 (b) are the temperature sweep test results of the SBS modified asphalt mortar, Figure 4 (c) and 5(c) are the temperature sweep test results of the highly extensible and elastic modified asphalt mortar. From Figure 4It can be found that after replacing part of the limestone powder with the porous alkali-activated fly ash-based asphalt filler, the complex shear modulus of the asphalt mortar increases significantly and further increases with the increase of the replacement rate. At 80 °C, compared with the 0% replacement rate, the complex shear moduli of the matrix asphalt mortar, SBS modified asphalt mortar and highly elastic modified asphalt mortar with a 20% replacement rate increase by 18.1%, 29.4% and 33.7% respectively. From Figure 5 It can be found that replacing part of the limestone powder with the porous alkali-activated fly ash-based asphalt filler can significantly reduce the phase angle of the asphalt mortar, and this effect becomes more obvious with the increase of the replacement rate. At 80 °C, compared with the 0% replacement rate, the phase angles of the matrix asphalt mortar, SBS modified asphalt mortar and highly elastic modified asphalt mortar with a 20% replacement rate decrease by 1.6%, 8.0% and 7.7% respectively. The complex shear moduli of the three asphalt mortars are the smallest at the 0% replacement rate, and with the increase of the replacement rate, the complex shear moduli of the three asphalt mortars also gradually increase. This shows that replacing part of the limestone powder with the porous alkali-activated fly ash-based asphalt filler of the present invention can improve the shear resistance of the asphalt mortar and enhance the high-temperature performance of the asphalt mortar.

[0082] 60 °C is the approximate temperature of the road during summer driving. A frequency sweep test at 60 °C was carried out, and the results of the complex shear modulus and phase angle of each group of asphalt mortar are as Figure 6 and Figure 7 shown. Among them Figure 6 (a) and Figure 7 (a) are the frequency sweep test results of the matrix asphalt mortar, Figure 6 (b) and Figure 7 (b) are the frequency sweep test results of the SBS modified asphalt mortar, Figure 6 (c) and 7(c) are the frequency sweep test results of the highly elastic modified asphalt mortar. High-frequency conditions can simulate the stress change rate experienced by asphalt pavements during actual use, especially under busy traffic and fast vehicle driving. From Figure 6 It can be found that under high-frequency conditions, the complex shear moduli of the three asphalt mortars all gradually increase with the increase of the replacement rate. With the increase of the replacement rate of the porous alkali-activated fly ash-based asphalt filler replacing the mineral powder, the shear deformation resistance of the asphalt mortar is enhanced. Compared with the 0% replacement rate, the complex shear moduli of the matrix asphalt mortar, SBS modified asphalt mortar and highly elastic modified asphalt mortar with a 20% replacement rate increase by 17.4%, 17.0% and 23.3% respectively. From Figure 7It can be found that the variation law of the phase angles of the three asphalt mastics under high-frequency conditions with the substitution rate is opposite to that of the complex shear modulus. As the substitution rate increases, the more elastic recoverable components in the asphalt mastic, the stronger the ability to resist permanent deformation. Compared with the 0% substitution rate, the phase angles of the base asphalt mastic, SBS modified asphalt mastic, and highly extensible elastic modified asphalt mastic decreased by 0.5%, 1.5%, and 2.3% respectively at the 20% substitution rate.

Claims

1. A preparation method of a porous alkali-activated fly ash-based asphalt filler, comprising the following steps: Step 1: Weigh 50 parts of fly ash, 25 parts of sodium hydroxide solution with a concentration of 10 mol / L and an appropriate amount of water according to the mass ratio. Stir with an electronic stirrer for 8 min to obtain a uniform geopolymer slurry. The liquid-solid mass ratio of the geopolymer slurry is 0.

35. The main chemical composition of the fly ash is as follows: Al2O3 21.64%, SiO2 48.11%, CaO 2.66%, Fe2O3 4.43%, Na2O 0%, SO3 0.65%, TiO2 1.66%, LOI 1.51%. Step 2: Pour the geopolymer slurry obtained in Step 1 into a mold of 80 mm×20 mm×20 mm, vibrate for 1 min to remove the air bubbles in the slurry, and wrap it with a plastic film and cure it at room temperature for 24 h. Step 3: Demold the specimen cured from the geopolymer slurry in Step 2. After demolding, place the specimen in a curing box at a temperature of 40 °C and a relative humidity of 60% for 2 days. Step 4: After curing, grind the specimen with a grinder, pass the ground powder through a 200-mesh sieve, remove the residues on the sieve, and the obtained powder is the porous alkali-activated fly ash-based asphalt filler.

2. A preparation method of a highly extensible and elastic modified asphalt mortar, using highly extensible and elastic modified asphalt, limestone powder, and the porous alkali-activated fly ash-based asphalt filler prepared by the preparation method described in Claim 1 as raw materials. The mass ratio of the highly extensible and elastic modified asphalt to the mixture of limestone powder and the porous alkali-activated fly ash-based asphalt filler is 1﹕0.8, and the mass percentage of the porous alkali-activated fly ash-based asphalt filler in the mixture of limestone powder and the porous alkali-activated fly ash-based asphalt filler is 10-20%; the preparation method includes the following steps: (1) Weigh the highly extensible and elastic modified asphalt and place it in an oven at 160 °C and continuously heat it until it melts; (2) Weigh the limestone powder and place it in an oven at 150 °C for preheating; (3) Weigh the porous alkali-activated fly ash-based asphalt filler, mix it evenly with the limestone powder preheated to 150 °C in Step 2, divide it into 5 equal parts, and add 1 part each time in 5 times while stirring to the melted asphalt in Step 1. After all are added, continue to stir with a stirrer at a speed of 1000 r / min at a temperature of 160 °C for 0.5 h to obtain the highly extensible and elastic modified asphalt mortar; It is characterized in that The highly extensible and elastic modified asphalt is prepared from SBS modified asphalt and a highly extensible and elastic asphalt modifier as raw materials, and its preparation method includes the following steps: Step 1: Weigh 94 g of SBS modified asphalt and heat it to 180 °C, and weigh 6 g of the highly extensible and elastic asphalt modifier; while stirring at a speed of 60 r / min, add the highly extensible and elastic asphalt modifier to the SBS modified asphalt heated to 180 °C. After completely adding the highly extensible and elastic asphalt modifier, continue to stir at 180 °C for 10 min. Step 2: Put the mixture into an oven at 180 °C and develop it for 30 min to obtain the highly extensible and elastic modified asphalt. Among them, the preparation process of the high-elongation elastic asphalt modifier is as follows: 1.

1. Pretreatment of glass fiber: By mass, 10 parts of glass fiber are surface-treated with a 1% silane coupling agent solution, and after treatment, it is dried for standby; The process of surface-treating glass fiber with a 1% silane coupling agent solution is as follows: 1.1.

1. Preparation of a 1% silane coupling agent solution: Add 10 grams of γ-aminopropyltriethoxysilane to 990 milliliters of deionized water, and use a stirring device to stir until γ-aminopropyltriethoxysilane is completely dissolved; 1.1.

2. Completely immerse the glass fiber to be treated in the silane coupling agent solution prepared in step 1.1.1 for 10 - 30 minutes, and stir or slightly vibrate the container during the immersion process; 1.1.

3. After immersion, take out the glass fiber from the silane coupling agent solution and gently shake off the excess solution; 1.1.

4. Spread the glass fiber evenly, hang it in a well-ventilated place to dry naturally or put it in an oven for drying. The drying temperature in the oven is 110 - 120 °C and the time is 1 - 2 hours; 1.1.

5. After drying, gently loosen the glass fiber so that the fibers do not stick together; 1.

2. Preliminary mixing: By mass calculation, weigh 50 parts of styrene-butadiene-styrene copolymer, 30 parts of polyurethane, 20 parts of ethylene-vinyl acetate copolymer, and 20 parts of cis-1,4-polybutadiene rubber, and add them all to a high-speed mixer. Mix preliminarily at a speed of 1200 rpm for 5 minutes until the polymers in the mixture are evenly dispersed; 1.

3. Adding additives and crosslinking agent: By mass, add 2 parts of tricresyl phosphate, 5 parts of C9 petroleum resin, 10 parts of the pretreated glass fiber in step 1.1, 3 parts of polyethylene wax (PE wax), 1 part of maleic anhydride, 0.5 part of dicumyl peroxide, and 1 part of 2,2'-methylenebis(4-methyl-6-tert-butylphenol) to the mixture obtained by preliminary mixing in step 1.2 in sequence; After adding, continue to mix at a speed of 800 rpm for 10 minutes to ensure that all components are evenly dispersed; 1.

4. Extrusion process: Add the mixture obtained in step 1.3 to a twin-screw extruder, and carry out melt blending and extrusion at a barrel temperature of 170 °C and a screw speed of 35 rpm; During the extrusion process, use a vacuum exhaust device to remove the gas generated during the mixing process; 1.

5. Cooling and pelletizing: Quickly cool the melt extruded in step 1.4 through a cooling device, and cut it into pellets after cooling to obtain a granular product; 1.

6. Static placement of pellets: Let the granular product obtained in step 1.5 stand at room temperature for 24 hours to release internal stress, improve the stability and performance of the product, and finally obtain the high-elongation elastic asphalt modifier.

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