Preparation method of modified fly ash and application of modified fly ash in concrete

Abstract

The invention discloses a preparation method of modified fly ash and application of the modified fly ash in concrete, and belongs to the technical field of fly ash resource development.The preparation method comprises the steps that firstly, 3-aminopropyltriethoxysilane is used for conducting surface modification on fly ash, the dispersity and compatibility of the fly ash are improved, and aminated fly ash is prepared; according to the present invention, the aminated fly ash is modified by using the self-made branching auxiliary agent to obtain the modified fly ash, the prepared modified fly ash is applied to the concrete, and the prepared concrete has excellent porosity (the effective porosity is 18.21-18.64%) and excellent water permeability (the water permeation coefficient is 4.14-4.37 mm / s).

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash resource development, and in particular relates to a preparation method of modified fly ash and application of the modified fly ash in concrete. Background Art

[0002] At present, the concept of "sponge city" is attracting more and more attention. Among them, permeable concrete has become one of the important raw materials for building "sponge city" due to its good water permeability and air permeability, sound absorption and noise reduction, and water filtration properties.

[0003] Permeable concrete is a concrete material with high water permeability that allows water to pass through its surface and interior, thereby reducing ground runoff and reducing water resource pollution. Permeable concrete is usually composed of cement, aggregate (crushed stone, coal gangue, etc.), fly ash, water reducer and water.

[0004] The existing technology for improving permeable concrete mainly focuses on the overall raw material usage ratio and aggregate gradation, and the improvement of raw material fly ash mainly focuses on acid modification and alkali modification, aiming to improve the compatibility of fly ash with cement matrix. There are relatively few studies on modifying fly ash to improve the porosity and water permeability of concrete. Based on this, the present invention aims to improve the porosity and water permeability of the final prepared concrete by modifying fly ash. Summary of the invention

[0005] The invention provides a preparation method of modified fly ash and application of the modified fly ash in concrete, and the porosity and water permeability of the finally prepared concrete are improved by modifying the fly ash.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing modified fly ash comprises the following steps:

[0008] The fly ash is ground through a 200-300 mesh sieve to obtain fly ash fine powder, water is added to the fly ash fine powder, mixed and stirred to obtain fly ash liquid, 3-aminopropyltriethoxysilane is added to the fly ash liquid, mixed and stirred, and a branching aid is added thereto, the temperature is raised to 50-60° C., and stirred at a constant temperature for 5-6 hours, and then filtered, and the solid component is dried at 60-80° C. for 12 hours to obtain modified fly ash.

[0009] Furthermore, the fly ash comprises the following components in percentage by mass:

[0010] SiO2 52.82%~57.13%;

[0011] Al2O3 21.30%~23.40%;

[0012] Fe2O3 7.11%~7.53%;

[0013] CaO 4.44%~4.85%;

[0014] K2O 2.09%~2.26%;

[0015] MgO 1.55%~1.80%.

[0016] Furthermore, the mass ratio of the fly ash fine ash to water is 1:4.

[0017] Furthermore, the amount of 3-aminopropyltriethoxysilane used is 6% to 10% of the mass of the fly ash fine powder.

[0018] Furthermore, the amount of the branching auxiliary agent is 12% to 15% of the mass of the fly ash fine powder.

[0019] Furthermore, the branching aid is prepared by the following steps:

[0020] S1. Add 2-carboxyphenyl phosphate, diethanolamine and p-toluenesulfonic acid to toluene, heat the system to 80-90°C, stir and react at constant temperature for 4-5h. After the reaction is completed, cool to room temperature, remove toluene by rotary evaporation, and wash with water to obtain intermediate 1.

[0021] S2. In a nitrogen atmosphere, add intermediate 1 to methanol, stir at room temperature for 20 to 30 minutes, then add methyl acrylate, heat the system to 30 to 40°C, stir at constant temperature for 4 to 5 hours, and after the reaction is completed, remove methanol by rotary evaporation to obtain intermediate 2;

[0022] S3. Add intermediate dimethylolpropane and trimethylolpropane and p-toluenesulfonic acid to toluene, heat the system to 120-130° C., stir and react at constant temperature for 4-5 hours. After the reaction is completed, cool to room temperature, and then remove toluene by rotary evaporation to obtain a branching auxiliary agent.

[0023] Furthermore, the usage ratio of toluene, 2-carboxyphenyl phosphate and diethanolamine in S1 is 100-200 mL: 0.2 mol: 0.1 mol.

[0024] Furthermore, the usage ratio of methanol, intermediate 1 and methyl acrylate in S2 is 100-200 mL: 50.5-51 g: 0.1 mol.

[0025] Furthermore, the usage ratio of toluene, intermediate dimethylolpropane and trimethylolpropane in S3 is 100-200 mL:59.2 g:0.03-0.04 mol.

[0026] Furthermore, an application of modified fly ash in concrete comprises the following steps:

[0027] The silicate cement, granite crushed stone, modified fly ash, polypropylene fiber, water reducing agent and water are stirred and mixed at a stirring rate of 100 to 200 r / min for 1 to 2 hours to obtain permeable concrete.

[0028] Furthermore, the permeable concrete comprises the following raw materials in parts by mass: 100 parts of Portland cement, 320-400 parts of granite crushed stone, 20-25 parts of modified fly ash, 1-5 parts of polypropylene fiber, 1-2 parts of water reducing agent and 75-100 parts of water.

[0029] Furthermore, the silicate cement is P·Ⅱ52.5R silicate cement.

[0030] Furthermore, the water reducing agent is water reducing agent YNH-1.

[0031] Furthermore, the granite crushed stone is mixed with granite crushed stone with a median particle size of 9 to 11 mm, granite crushed stone with a median particle size of 5 to 8 mm and granite crushed stone with a median particle size of 1 to 3 mm in a mass ratio of 1 to 2:3 to 4:5.

[0032] Beneficial effects of the present invention:

[0033] The present invention provides a method for preparing modified fly ash. The present invention firstly uses 3-aminopropyltriethoxysilane to perform surface modification on fly ash to improve the dispersibility and compatibility of fly ash, and prepares amino fly ash. Then, the amino fly ash is modified by using a self-made branching auxiliary agent of the present invention to obtain modified fly ash. The present invention applies the prepared modified fly ash to concrete, and the prepared concrete has excellent porosity (effective porosity is 18.21% to 18.64%) and water permeability (water permeability coefficient is 4.14 to 4.37 mm / s). It has been verified by experiments that the modification of amino fly ash by using a self-made branching auxiliary agent is the key point to improve porosity and water permeability, and its principle is as follows:

[0034] Firstly, the branched auxiliary agent prepared by the present invention has a macromolecular segment structure, which can increase the steric hindrance between fly ash particles and improve the dispersion performance between fly ash particles. At the same time, in the subsequent process of preparing concrete, it helps to improve the dispersion between concrete particles, thereby improving the porosity of concrete. Porosity is a key factor in determining the water permeability of concrete.

[0035] Then, when the concrete comes into contact with rainwater during its service life, the terminal phosphate group of the branched additive has negative charge and can coordinate with metal ions (calcium ions, etc.) in the concrete. Its complexation and adsorption ability is stronger than that of the carboxyl group, which can make the surface of the concrete particles carry a charge, thereby preventing the coagulation between the concrete particles through electrostatic action, ensuring the smoothness of the water permeable passage in the concrete; at the same time, the terminal phosphate group is a hydrophilic group, which helps to improve the penetration of rainwater into the concrete, and at the same time helps to improve the hydrophilicity of the inner wall of the pores in the concrete. The hydrophilic inner wall of the pore can reduce the contact angle of water, which is beneficial to the flow and penetration of water in the pores, thereby comprehensively improving the water permeability of the concrete.

[0036] Finally, the present invention also optimizes the gradation of aggregate granite crushed stones in permeable concrete, and increases the porosity in the concrete by regulating the particle size of the granite crushed stones and increasing the proportion of small-size granite crushed stones, thereby further improving the water permeability. DETAILED DESCRIPTION

[0037] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0038] First, the fly ash raw material studied in the present invention is purchased from Guodian Yangzonghai Power Generation Co., Ltd. The manufacturer gives the main component percentages of the fly ash as follows: SiO2 52.82% to 57.13%; Al2O3 21.30% to 23.40%; Fe2O3 7.11% to 7.53%; CaO 4.44% to 4.85%; K2O 2.09% to 2.26%; MgO1.55% to 1.80%. The present invention samples and tests the purchased fly ash raw material, and uses it as a research object. The research content is specifically shown in the following embodiment. In the sampling results, the main component percentages of the fly ash are as follows: SiO2 55.53%; Al2O3 22.64%; Fe2O3 7.25%; CaO4.64%; K2O 2.22%; MgO 1.70%.

[0039] Example 1

[0040] Preparation of branching aid:

[0041] S1. Add 2-carboxyphenyl phosphate (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.), diethanolamine (AR, 98.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.) to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 80°C, stir at constant temperature for 4 hours, and after the reaction is completed, cool to room temperature, remove toluene by rotary evaporation, and then wash with water to obtain intermediate 1, in which 2-carboxyphenyl phosphate is added to the mixture. The molar ratio of 2-carboxyphenyl phosphate and diethanolamine is 2:1, and the amount of solvent toluene is appropriate. In this embodiment, the amount ratio of toluene, 2-carboxyphenyl phosphate and diethanolamine is 100mL:0.2mol:0.1mol, and the amount of catalyst p-toluenesulfonic acid is 1.5% of the total mass of toluene, 2-carboxyphenyl phosphate and diethanolamine. During the above reaction, under the catalytic action of p-toluenesulfonic acid, the carboxyl group in 2-carboxyphenyl phosphate and the hydroxyl group in diethanolamine undergo esterification reaction to obtain intermediate 1;

[0042] S2. Under nitrogen atmosphere, add intermediate 1 to methanol (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), stir at room temperature for 20 min, then add methyl acrylate (AR, 99.0%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 30°C, stir and react at constant temperature for 4 h, after the reaction is completed, remove methanol by rotary evaporation to obtain intermediate 2, wherein the amount of solvent methanol is appropriate, in this embodiment, the amount ratio of methanol, intermediate 1 and methyl acrylate is 100 mL: 50.5 g: 0.1 mol, during the above reaction, the secondary amine group in intermediate 1 and the unsaturated double bond in methyl acrylate undergo Michael addition reaction to obtain intermediate 2 containing terminal phosphate groups;

[0043] S3, to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), add intermediate dimethylolpropane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.), the system is heated to 120 ° C, and the reaction is stirred at a constant temperature for 4 hours. After the reaction is completed, it is cooled to room temperature, and the toluene is removed by rotary evaporation to obtain a branching auxiliary agent, wherein the amount of solvent toluene is appropriate. In the present embodiment, the amount ratio of toluene, intermediate dimethylolpropane and trimethylolpropane is 100mL:59.2g:0.03mol, and the amount of catalyst p-toluenesulfonic acid is 1.5% of the total mass of toluene, intermediate dimethylolpropane and trimethylolpropane. In the above reaction process, under the catalytic action of p-toluenesulfonic acid, intermediate dimethylolpropane undergoes an ester exchange reaction with trimethylolpropane to obtain a branching auxiliary agent.

[0044] Example 2

[0045] Preparation of branching aid:

[0046] S1. Add 2-carboxyphenyl phosphate (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.), diethanolamine (AR, 98.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.) to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 85°C, stir at constant temperature for 5h, and after the reaction is completed, cool to room temperature, remove toluene by rotary evaporation, and then wash with water to obtain intermediate 1, wherein 2- The molar ratio of carboxyphenyl phosphate and diethanolamine is 2:1, and the amount of solvent toluene is appropriate. In this embodiment, the amount ratio of toluene, 2-carboxyphenyl phosphate and diethanolamine is 150mL:0.2mol:0.1mol, and the amount of catalyst p-toluenesulfonic acid is 2% of the total mass of toluene, 2-carboxyphenyl phosphate and diethanolamine. In the above reaction process, under the catalytic action of p-toluenesulfonic acid, the carboxyl group in 2-carboxyphenyl phosphate and the hydroxyl group in diethanolamine undergo esterification reaction to obtain intermediate 1;

[0047] S2. Under nitrogen atmosphere, add intermediate 1 to methanol (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), stir at room temperature for 30 min, then add methyl acrylate (AR, 99.0%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 40°C, stir and react at constant temperature for 5 h, after the reaction is completed, remove methanol by rotary evaporation to obtain intermediate 2, wherein the amount of solvent methanol is appropriate, in this embodiment, the amount ratio of methanol, intermediate 1 and methyl acrylate is 200 mL: 51 g: 0.1 mol, during the above reaction, the secondary amine group in intermediate 1 and the unsaturated double bond in methyl acrylate undergo Michael addition reaction to obtain intermediate 2 containing terminal phosphate groups;

[0048] S3. Add intermediate dimethylolpropane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.) to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 125°C, stir and react at constant temperature for 5 hours. After completion of the reaction, cool to room temperature, and then remove toluene by rotary evaporation to obtain a branching auxiliary agent. The amount of solvent toluene is appropriate. In the present embodiment, the amount ratio of toluene, intermediate dimethylolpropane and trimethylolpropane is 150mL:59.2g:0.04mol, and the amount of catalyst p-toluenesulfonic acid is 2% of the total mass of toluene, intermediate dimethylolpropane and trimethylolpropane. During the above reaction, under the catalytic action of p-toluenesulfonic acid, intermediate dimethylolpropane undergoes an ester exchange reaction with trimethylolpropane to obtain a branching auxiliary agent.

[0049] Example 3

[0050] Preparation of branching aid:

[0051] S1. Add 2-carboxyphenyl phosphate (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.), diethanolamine (AR, 98.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.) to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 90°C, stir at constant temperature for 5h, and after the reaction is completed, cool to room temperature, remove toluene by rotary evaporation, and then wash with water to obtain intermediate 1, wherein 2- The molar ratio of carboxyphenyl phosphate and diethanolamine is 2:1, and the amount of solvent toluene is appropriate. In this embodiment, the amount ratio of toluene, 2-carboxyphenyl phosphate and diethanolamine is 200mL:0.2mol:0.1mol, and the amount of catalyst p-toluenesulfonic acid is 2% of the total mass of toluene, 2-carboxyphenyl phosphate and diethanolamine. During the above reaction process, under the catalytic action of p-toluenesulfonic acid, the carboxyl group in 2-carboxyphenyl phosphate and the hydroxyl group in diethanolamine undergo esterification reaction to obtain intermediate 1;

[0052] S2. Under nitrogen atmosphere, add intermediate 1 to methanol (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), stir at room temperature for 30 min, then add methyl acrylate (AR, 99.0%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 40°C, stir and react at constant temperature for 5 h, after the reaction is completed, remove methanol by rotary evaporation to obtain intermediate 2, wherein the amount of solvent methanol is appropriate, in this embodiment, the amount ratio of methanol, intermediate 1 and methyl acrylate is 200 mL: 51 g: 0.1 mol, during the above reaction, the secondary amine group in intermediate 1 and the unsaturated double bond in methyl acrylate undergo Michael addition reaction to obtain intermediate 2 containing terminal phosphate groups;

[0053] S3. Add intermediate dimethylolpropane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) and p-toluenesulfonic acid (99%, purchased from Sinopharm Chemical Reagent Co., Ltd.) to toluene (AR, 99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.), heat the system to 130°C, stir and react at constant temperature for 5 hours. After the reaction is completed, cool to room temperature, and then remove toluene by rotary evaporation to obtain a branching auxiliary agent. The amount of solvent toluene is appropriate. In the present embodiment, the amount ratio of toluene, intermediate dimethylolpropane and trimethylolpropane is 200mL:59.2g:0.04mol, and the amount of catalyst p-toluenesulfonic acid is 2% of the total mass of toluene, intermediate dimethylolpropane and trimethylolpropane. In the above reaction process, under the catalytic action of p-toluenesulfonic acid, intermediate dimethylolpropane undergoes ester exchange reaction with trimethylolpropane to obtain a branching auxiliary agent.

[0054] Example 4

[0055] Preparation of modified fly ash:

[0056] The fly ash was ground through a 200-mesh sieve to obtain fly ash fine powder, water was added to the fly ash fine powder at a mass ratio of 1:4, and the mixture was mixed and stirred for 20 minutes to obtain fly ash liquid, and 6% of the mass of the fly ash fine powder 3-aminopropyltriethoxysilane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) was added to the fly ash liquid, and the mixture was mixed and stirred for 20 minutes, and then 12% of the mass of the fly ash fine powder The branching auxiliary agent prepared in Example 1 was added thereto, the system was heated to 50°C, and stirred at a constant temperature for 5 hours. After stirring, the solid component was collected by suction filtration, and then dried at 60°C for 12 hours to obtain modified fly ash.

[0057] Example 5

[0058] Preparation of modified fly ash:

[0059] The above fly ash was ground through a 300-mesh sieve to obtain fly ash fine powder, and water was added to the fly ash fine powder at a mass ratio of 1:4, and the mixture was mixed and stirred for 30 minutes to obtain fly ash liquid, and 3-aminopropyltriethoxysilane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) in an amount of 10% by mass of the fly ash fine powder was added to the fly ash liquid, and the mixture was mixed and stirred for 30 minutes, and then the branching auxiliary agent prepared in Example 2 in an amount of 14% by mass of the fly ash fine powder was added thereto, the system was heated to 55° C., and stirred at a constant temperature for 6 hours. After stirring, the solid components were collected by suction filtration, and then dried at 70° C. for 12 hours to obtain modified fly ash.

[0060] Example 6

[0061] Preparation of modified fly ash:

[0062] The above fly ash was ground through a 300-mesh sieve to obtain fly ash fine powder, and water was added to the fly ash fine powder at a mass ratio of 1:4, and the mixture was mixed and stirred for 30 minutes to obtain fly ash liquid, and 3-aminopropyltriethoxysilane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) in an amount of 10% by mass of the fly ash fine powder was added to the fly ash liquid, and the mixture was mixed and stirred for 30 minutes, and then the branching auxiliary agent prepared in Example 3 in an amount of 15% by mass of the fly ash fine powder was added thereto, the system was heated to 60°C, and stirred at a constant temperature for 6 hours. After stirring, the solid components were collected by suction filtration, and then dried at 80°C for 12 hours to obtain modified fly ash.

[0063] Comparative Example 1

[0064] Comparative Example 1 is the control group of Example 5, in which the branching aid prepared in Example 2 in Example 5 is deleted, and the remaining raw materials, raw material amounts and preparation steps are kept consistent with those in Example 5, and finally modified fly ash is obtained. The preparation steps of the modified fly ash are as follows:

[0065] The fly ash was ground through a 300-mesh sieve to obtain fly ash fine powder, water was added to the fly ash fine powder at a mass ratio of 1:4, and the mixture was mixed and stirred for 30 minutes to obtain fly ash liquid, and 3-aminopropyltriethoxysilane (98%, purchased from Sinopharm Chemical Reagent Co., Ltd.) in an amount of 10% by mass of the fly ash fine powder was added to the fly ash liquid, and the mixture was mixed and stirred for 30 minutes. The system was heated to 55°C and stirred at a constant temperature for 6 hours. After stirring, the solid components were collected by suction filtration and then dried at 70°C for 12 hours to obtain modified fly ash.

[0066] Comparative Example 2

[0067] Comparative Example 2 is the control group of Example 5, in which 3-aminopropyltriethoxysilane in Example 5 and the branching aid prepared in Example 2 are deleted, and the remaining raw materials, raw material amounts and preparation steps are kept consistent with those in Example 5, and finally modified fly ash is obtained. The preparation steps of the modified fly ash are as follows:

[0068] The fly ash was ground through a 300-mesh sieve to obtain fine fly ash powder. Water was added to the fine fly ash at a mass ratio of 1:4, and the mixture was stirred for 1 hour. The system was heated to 55°C and stirred at a constant temperature for 6 hours. After stirring, the solid components were collected by suction filtration and then dried at 70°C for 12 hours to obtain modified fly ash.

[0069] Example 7

[0070] An application of modified fly ash in concrete comprises the following steps:

[0071] First, the raw materials were weighed according to the following mass parts: 100 parts of silicate cement, 320 parts of granite crushed stone, 20 parts of modified fly ash prepared in Example 4, 1 part of polypropylene fiber, 1 part of water reducer and 75 parts of water; wherein the silicate cement was P·Ⅱ52.5R silicate cement purchased from Huaxin Cement (Kunming Dongchuan) Co., Ltd.; wherein the granite was purchased from Kunming Xundian Rende Yongsheng Granite Sales Department, and the purchased granite was crushed to obtain granite crushed stone, and graded. Specifically, the granite crushed stone was mixed with granite crushed stone with a median particle size of 11 mm, granite crushed stone with a median particle size of 8 mm and granite crushed stone with a median particle size of 3 mm in a mass ratio of 1:4:5; wherein the density of the polypropylene fiber was 0.9 g / cm 3 , an average length of 18 mm, a tensile strength of 565 MPa, an elastic modulus of 5.4 GPa, and an elongation at break of 13%; wherein the water reducer is a water reducer YNH-1 purchased from Shandong Wanshan Chemical Co., Ltd. Then, the above raw materials are placed in a mixer and stirred and mixed at a stirring rate of 100 / min for 1 hour to obtain permeable concrete.

[0072] Example 8

[0073] An application of modified fly ash in concrete comprises the following steps:

[0074] First, the raw materials were weighed according to the following mass parts: 100 parts of silicate cement, 350 parts of granite crushed stone, 20 parts of modified fly ash prepared in Example 5, 3 parts of polypropylene fiber, 2 parts of water reducer and 85 parts of water; wherein the silicate cement was P·Ⅱ52.5R silicate cement purchased from Huaxin Cement (Kunming Dongchuan) Co., Ltd.; wherein the granite was purchased from Kunming Xundian Rende Yongsheng Granite Sales Department, and the purchased granite was crushed to obtain granite crushed stone, and graded. Specifically, the granite crushed stone was mixed with granite crushed stone with a median particle size of 10 mm, granite crushed stone with a median particle size of 6 mm and granite crushed stone with a median particle size of 2 mm in a mass ratio of 2:3:5; wherein the density of the polypropylene fiber was 0.9 g / cm 3 , an average length of 18 mm, a tensile strength of 565 MPa, an elastic modulus of 5.4 GPa, and an elongation at break of 13%; wherein the water reducer is a water reducer YNH-1 purchased from Shandong Wanshan Chemical Co., Ltd. Then, the above raw materials are placed in a mixer and stirred and mixed at a stirring rate of 200 r / min for 2 h to obtain permeable concrete.

[0075] Example 9

[0076] An application of modified fly ash in concrete comprises the following steps:

[0077] First, the raw materials were weighed according to the following mass parts: 100 parts of silicate cement, 400 parts of granite crushed stone, 25 parts of modified fly ash prepared in Example 6, 5 parts of polypropylene fiber, 2 parts of water reducer and 100 parts of water; wherein the silicate cement was P·Ⅱ52.5R silicate cement purchased from Huaxin Cement (Kunming Dongchuan) Co., Ltd.; wherein the granite was purchased from Kunming Xundian Rende Yongsheng Granite Sales Department, and the purchased granite was crushed to obtain granite crushed stone, and graded. Specifically, the granite crushed stone was mixed with granite crushed stone with a median particle size of 9 mm, granite crushed stone with a median particle size of 5 mm and granite crushed stone with a median particle size of 1 mm in a mass ratio of 2:3:5; wherein the density of the polypropylene fiber was 0.9 g / cm 3 , an average length of 18 mm, a tensile strength of 565 MPa, an elastic modulus of 5.4 GPa, and an elongation at break of 13%; wherein the water reducer is a water reducer YNH-1 purchased from Shandong Wanshan Chemical Co., Ltd. Then, the above raw materials are placed in a mixer and stirred and mixed at a stirring rate of 200 r / min for 2 h to obtain permeable concrete.

[0078] Comparative Example 3

[0079] Comparative Example 3 is the control group of Example 8, in which the modified fly ash prepared in Example 5 in Example 8 is replaced by the modified fly ash in Comparative Example 1, and the remaining raw materials, raw material amounts and preparation steps are consistent with those in Example 8, and finally permeable concrete is obtained.

[0080] Comparative Example 4

[0081] Comparative Example 4 is the control group of Example 8, in which the modified fly ash prepared in Example 5 in Example 8 is replaced by the modified fly ash in Comparative Example 2, and the remaining raw materials, raw material amounts and preparation steps are consistent with those in Example 8, and finally permeable concrete is obtained.

[0082] Performance tests were performed on Examples 7 to 9 and Comparative Examples 3 to 4. The performance test standards are as follows. The test results are shown in Table 1:

[0083] Mechanical properties: Tested in accordance with 5 "Compressive strength test" and 10 "Flexural strength test" in the national standard GB / T 50081-2019 "Standard for test methods for physical and mechanical properties of concrete".

[0084] Permeability coefficient: Test according to Appendix A “Test method for permeability coefficient” in the industry standard CJJ / T 135-2009 “Technical specification for permeable cement concrete pavement”.

[0085] Effective porosity: Tested in accordance with Appendix 3 “Test Method for Porosity of Permeable Concrete” in DB11 / T 775-2010 “Technical Specification for Permeable Concrete Pavement”.

[0086] Table 1 Test results

[0087]

[0088] It can be seen from Table 1 that the concrete prepared in Examples 7 to 9 of the present invention has both excellent mechanical properties and water permeability.

[0089] It should be noted that, in this article, terms such as "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment.

[0090] Although 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 the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing modified fly ash, characterized in that: The following steps are involved: The fly ash is ground through a 200-300 mesh sieve to obtain fly ash fine powder, water is added to the fly ash fine powder, mixed and stirred to obtain fly ash liquid, 3-aminopropyltriethoxysilane is added to the fly ash liquid, mixed and stirred, and a branching aid is added thereto, the temperature is raised to 50-60° C., and stirred at a constant temperature for 5-6 hours, and then filtered, and the solid component is dried at 60-80° C. for 12 hours to obtain modified fly ash.

2. The method for preparing modified fly ash according to claim 1, characterized in that: The fly ash comprises the following components in percentage by mass: SiO2 52.82%~57.13%; Al2O3 21.30%~23.40%; Fe2O3 7.11%~7.53%; CaO 4.44%~4.85%; K2O 2.09%~2.26%; MgO 1.55%~1.80%.

3. The method for preparing modified fly ash according to claim 1, characterized in that: The mass ratio of fly ash fine ash to water is 1:4; The amount of 3-aminopropyltriethoxysilane used is 6% to 10% of the mass of fly ash fine powder; The amount of the branching auxiliary agent is 12% to 15% by mass of the fly ash fine powder.

4. The method for preparing modified fly ash according to claim 1, characterized in that: The branching auxiliary agent is prepared by the following steps: S1. Add 2-carboxyphenyl phosphate, diethanolamine and p-toluenesulfonic acid to toluene, heat the system to 80-90°C, stir and react at constant temperature for 4-5h. After the reaction is completed, cool to room temperature, remove toluene by rotary evaporation, and wash with water to obtain intermediate 1. S2. In a nitrogen atmosphere, add intermediate 1 to methanol, stir at room temperature for 20 to 30 minutes, then add methyl acrylate, heat the system to 30 to 40°C, stir at constant temperature for 4 to 5 hours, and after the reaction is completed, remove methanol by rotary evaporation to obtain intermediate 2; S3. Add intermediate dimethylolpropane and trimethylolpropane and p-toluenesulfonic acid to toluene, heat the system to 120-130° C., stir and react at constant temperature for 4-5 hours. After the reaction is completed, cool to room temperature, and then remove toluene by rotary evaporation to obtain a branching auxiliary agent.

5. The method for preparing modified fly ash according to claim 4, characterized in that: The usage ratio of toluene, 2-carboxyphenyl phosphate and diethanolamine in S1 is 100-200 mL: 0.2 mol: 0.1 mol.

6. The method for preparing modified fly ash according to claim 4, characterized in that: The usage ratio of methanol, intermediate 1 and methyl acrylate in S2 is 100-200 mL: 50.5-51 g: 0.1 mol.

7. The method for preparing modified fly ash according to claim 4, characterized in that: The usage ratio of toluene, intermediate dimethylolpropane and trimethylolpropane in S3 is 100-200 mL: 59.2 g: 0.03-0.04 mol.

8. Application of modified fly ash in concrete, characterized in that: The use of the modified fly ash prepared by the preparation method described in any one of items 1 to 7 in concrete comprises the following steps: The silicate cement, granite crushed stone, modified fly ash, polypropylene fiber, water reducing agent and water are stirred and mixed at a stirring rate of 100 to 200 r / min for 1 to 2 hours to obtain permeable concrete.

9. The use of modified fly ash in concrete according to claim 8, characterized in that: The permeable concrete comprises the following raw materials by weight: 100 parts of silicate cement, 320-400 parts of granite crushed stone, 20-25 parts of modified fly ash, 1-5 parts of polypropylene fiber, 1-2 parts of water reducing agent and 75-100 parts of water.

10. The use of modified fly ash in concrete according to claim 8, characterized in that: The granite crushed stone is mixed with granite crushed stone with a median particle size of 9 to 11 mm, granite crushed stone with a median particle size of 5 to 8 mm and granite crushed stone with a median particle size of 1 to 3 mm in a mass ratio of 1 to 2:3 to 4:5.

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