Fly ash adhesive and preparation method thereof

Abstract

The invention discloses a fly ash adhesive and a preparation method thereof, and relates to the technical field of fly ash, the fly ash adhesive comprises the following components by weight: 50-60 parts of fly ash, 18-30 parts of Portland cement, 5-15 parts of an activator and 0.5-3 parts of a functional auxiliary agent; the functional additive comprises modified polypropylene fibers, and the modified polypropylene fibers are active polypropylene fibers grafted by a first active group and a second active group; the first active group is a sulfonic group, and the second active group is a polar group. The method has the effects of enhancing interface bonding force, improving structural stability, prolonging corrosion resistance and durability, promoting reduction of water consumption and being suitable for large-area construction scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of fly ash, and more particularly to a fly ash adhesive and a preparation method thereof. Background Art

[0002] Fly ash binder is primarily made of fly ash, supplemented by an activator to activate the fly ash. This allows the fly ash's active ingredients to serve as the primary source of cementitious binders, transforming it into a highly adhesive cementitious material. This reduces reliance on traditional binders like cement, aligning with the development of green building materials and the circular economy.

[0003] In the prior art, activators such as alkaline activators are used and applied to building walls and temporary road bases, and when gypsum and lime are used, they are applied to fly ash bricks and blocks, and when composite activators are used, they are applied to non-load-bearing walls and landscape materials.

[0004] However, since the strength of existing fly ash adhesives after use and application in production is generally around 10 MPa, and it is difficult to reach 20 MPa even after further adding reinforcing materials, this affects the application scenario range of the fly ash adhesive and is difficult to provide effective compressive strength, which needs to be improved. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the first object of the present invention is to provide a fly ash binder, which has the effect of improving compressive strength.

[0006] To achieve the above object, the present invention provides the following technical solutions: A fly ash adhesive comprises, by weight, 50-60 parts of fly ash, 18-30 parts of Portland cement, 5-15 parts of an activator, and 0.5-3 parts of a functional additive; the functional additive comprises modified polypropylene fiber, which is an active polypropylene fiber grafted with a first active group and a second active group; the first active group is a sulfonic acid group, and the second active group is a polar group.

[0007] Preferably, the second reactive group is an amide group, a carboxyl group or a hydroxyl group.

[0008] Preferably, the grafting rate of the first active group is 2-3 wt %, and the grafting rate of the second active group is 1-2.2 wt %.

[0009] Preferably, the method for preparing the activated polypropylene fiber comprises the following steps: ① pretreatment, treating the polypropylene fiber with radiation or plasma to obtain activated polypropylene fiber with free active groups formed on the surface; ② base material preparation, placing the activated polypropylene fiber in a solvent and heating it to swell it; ③ solution preparation, adding fuming sulfuric acid dropwise to the solvent, controlling the temperature to 0-4°C, and adding the solvent dropwise to the fuming sulfuric acid in a ratio of 10ml:1-1.5ml, then adding acrylic acid, sodium styrene sulfonate and initiator after stirring, and adding the acrylic acid to sodium styrene sulfonate, initiator, and solvent in a ratio of 0.5-1g:0.2-0.5g:0.01-0.03g:10ml, stirring and dissolving to obtain a prepared solution; ④ sulfonation grafting, placing the swollen activated polypropylene fiber into the prepared solution under inert gas protection, controlling the temperature to 70-85°C and stirring for reaction for 2-3h to obtain a reactant; and ⑤ separation, cooling the reactant, neutralizing it with sodium bicarbonate, and washing it with deionized water to obtain a finished activated polypropylene fiber.

[0010] Preferably, the initiator is potassium persulfate, and the amount used is 2% of the total mass of the fuming sulfuric acid, acrylic acid and sodium styrene sulfonate.

[0011] Preferably, the solvent is a dichloromethane / DMSO mixed solution with a volume ratio of 9:1.

[0012] Preferably, the functional additives include a water reducer and a retarder.

[0013] A second object of the present invention is to provide a method for preparing a fly ash binder, which is used to prepare the fly ash binder as described above, comprising the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer to obtain a mixed material; Step 2: Add an activator to the mixture, continue stirring until uniform, then add water, control the water-binder ratio to 0.38-0.42, and obtain a uniform slurry by high-speed stirring; Step 3: introduce the uniform slurry into a sealed container and age it for 20-30 minutes to obtain a finished adhesive.

[0014] Preferably, the fly ash is dried at a controlled temperature of 105° C. for 2 hours.

[0015] Preferably, the activator is water glass, and the modulus is controlled to be 2.0 and the concentration is 32%; the silicate cement is P·O 42.5 grade, and the specific surface area is ≥300m² / kg.

[0016] Through the above scheme, it can be seen that the present application provides a fly ash adhesive and its preparation method, which has the following beneficial effects: through the ionic bond of active polypropylene fiber and cations such as calcium ions and aluminum ions in fly ash and silicate cement, chemical adsorption is formed, and the first active group and the second active group cooperate to activate silicon oxide and aluminum oxide to participate in the secondary hydration reaction and form CSH gel, thereby utilizing hydrogen bonds to enhance the interfacial bonding force, thereby further forming a denser transition layer to reduce the interfacial pores from 60-80nm to 25-40nm. At the same time, the formation of a three-dimensional skeleton structure will enhance stability, thereby effectively transmitting compressive stress and tensile stress, and obtaining an increase of more than 50% in 28d tensile strength. In terms of corrosion resistance, due to the synergistic hydrophobicity of polypropylene fiber and the hydrophilicity of the first active group and the second active group, water absorption and expansion are avoided and the penetration of corrosive ions into the interior is reduced, thereby achieving the purpose of long-term corrosion resistance and durability. DETAILED DESCRIPTION

[0017] To make the technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0018] It should be mentioned that the addition ratios in the examples of the present application are all mass ratios.

[0019] The fly ash binder and its preparation method of the present application will be described in detail below.

[0020] A fly ash adhesive comprises, by weight, 50-60 parts of fly ash, 18-30 parts of Portland cement, 5-15 parts of an activator, and 0.5-3 parts of a functional additive; the functional additive comprises modified polypropylene fiber, which is an active polypropylene fiber grafted with a first active group and a second active group; the first active group is a sulfonic acid group, the second active group is a polar group, and the polar group is an amide group, a carboxyl group, or a hydroxyl group.

[0021] In the examples of this application, the polar groups are carboxyl groups, the grafting rate of the first active group is 2-3 wt %, and the grafting rate of the second active group is 1-2.2 wt %. The grafting rate is calculated by dissolving the ungrafted monomer and homopolymer and weighing the change in fiber mass before and after grafting. This is not detailed here.

[0022] It should be noted that the preparation method of the activated polypropylene fiber includes the steps of ① pretreatment, treating the polypropylene fiber by irradiation or plasma to obtain activated polypropylene fiber with free active groups formed on the surface; ② base material preparation, placing the activated polypropylene fiber in a solvent and heating it to swell it; ③ solution preparation, adding fuming sulfuric acid dropwise to the solvent, controlling the temperature to 0-4°C, and adding the solvent dropwise to the fuming sulfuric acid in a ratio of 10ml:1-1.5ml, then adding acrylic acid, sodium styrene sulfonate and initiator after stirring, and adding the acrylic acid to sodium styrene sulfonate, initiator and solvent in a ratio of 0.5-1g:0.2-0.5g:0.01-0.03g:10ml, stirring and dissolving to obtain a prepared solution; ④ sulfonation grafting, placing the swollen activated polypropylene fiber into the prepared solution under the protection of inert gas, controlling the temperature to 70-85°C and stirring for reaction for 2-3h to obtain a reactant; and ⑤ separation, cooling the reactant, neutralizing it with sodium bicarbonate and washing it with deionized water to obtain a finished active polypropylene fiber.

[0023] The initiator in this embodiment is potassium persulfate, used in an amount of 2% of the total mass of oleum, acrylic acid, and sodium styrene sulfonate. The solvent is a dichloromethane / DMSO mixed solution with a volume ratio of 9:1. Functional additives include a water reducer and a retarder.

[0024] A method for preparing a fly ash binder, for preparing the fly ash binder as described above, comprises the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer, and dry the fly ash at a controlled temperature of 105° C. for 2 hours to obtain a mixed material; Step 2: adding water glass as an activator to the mixture, controlling the modulus of the water glass to 2.0 and the concentration to 32%, adding water after continuous stirring, controlling the water-binder ratio to 0.38-0.42, and obtaining a uniform slurry by high-speed stirring; Step 3: introduce the uniform slurry into a sealed container and age it for 20-30 minutes to obtain a finished adhesive.

[0025] Among them, the silicate cement is of P·O 42.5 grade and has a specific surface area of ​​≥300m² / kg.

[0026] Example 1

[0027] A fly ash binder comprises 50 parts by weight of fly ash, 18 parts of Portland cement, 5 parts of an activator, and 0.5 parts of a functional additive. The functional additive comprises modified polypropylene fiber, which is an activated polypropylene fiber grafted with sulfonic acid and carboxyl groups. The grafting rate of sulfonic acid groups is 2-3% by weight, and the grafting rate of carboxyl groups is 1-2.2% by weight. Testing showed that the grafting rate of sulfonic acid groups in Example 1 of the present application was 2.05% by weight, and the grafting rate of carboxyl groups was 1.17% by weight.

[0028] It should be noted that the preparation method of the activated polypropylene fiber includes the steps of ① pretreatment, irradiation treatment of polypropylene fiber to obtain activated polypropylene fiber with free active groups formed on the surface; step ② base material preparation, the activated polypropylene fiber is put into a solvent and heated to swell; step ③ solution preparation, taking a solvent and adding fuming sulfuric acid dropwise, controlling the temperature to 0-4°C, the addition ratio of the solvent dropwise addition to the fuming sulfuric acid is 10ml:1ml, and then adding acrylic acid, sodium styrene sulfonate and potassium persulfate after stirring, and the addition ratio of acrylic acid to sodium styrene sulfonate, potassium persulfate and solvent is 0.5g:0.2g:0.01g:10ml, stirring and dissolving to obtain a configuration solution; step ④ sulfonation grafting, under the protection of inert gas, the swollen activated polypropylene fiber is put into the configuration solution, the temperature is controlled to 70°C and stirred for reaction for 3h to obtain a reactant; step ⑤ separation, the reactant is cooled, neutralized with sodium bicarbonate and washed with deionized water to obtain a finished active polypropylene fiber.

[0029] The amount of potassium persulfate used was 2% of the total mass of fuming sulfuric acid, acrylic acid, and sodium styrene sulfonate. The solvent was a dichloromethane / DMSO mixed solution with a volume ratio of 9:1.

[0030] A method for preparing a fly ash binder, for preparing the fly ash binder as described above, comprises the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer, and dry the fly ash at a controlled temperature of 105° C. for 2 hours to obtain a mixed material; Step 2: adding water glass as an activator to the mixture, controlling the modulus of the water glass to 2.0 and the concentration to 32%, adding water after continuous stirring, controlling the water-binder ratio to 0.42, and obtaining a uniform slurry by high-speed stirring; Step 3: The uniform slurry is introduced into a sealed container and aged for 20 minutes to obtain a finished adhesive.

[0031] Among them, the silicate cement is of P·O 42.5 grade and has a specific surface area of ​​≥300m² / kg.

[0032] Example 2

[0033] A fly ash binder comprises, by weight, 55 parts fly ash, 24 parts Portland cement, 10 parts activator, and 1 part functional additive. The functional additive comprises modified polypropylene fiber, which is an activated polypropylene fiber grafted with sulfonic acid and carboxyl groups. The grafting rate of sulfonic acid groups is 2-3% by weight, and the grafting rate of carboxyl groups is 1-2.2% by weight. Testing showed that the grafting rate of sulfonic acid groups in Example 2 of this application was 2.52% by weight, and the grafting rate of carboxyl groups was 1.43% by weight.

[0034] It should be noted that the preparation method of the activated polypropylene fiber includes the steps of ① pretreatment, irradiating the polypropylene fiber to obtain activated polypropylene fiber with free active groups formed on the surface; ② base material preparation, adding the activated polypropylene fiber into a solvent and heating it to swell it; ③ solution preparation, adding fuming sulfuric acid dropwise to the solvent, controlling the temperature to 0-4°C, and adding the solvent dropwise to the fuming sulfuric acid in a ratio of 10ml:1.2ml, then adding acrylic acid, sodium styrene sulfonate and potassium persulfate after stirring, and adding the acrylic acid to sodium styrene sulfonate, potassium persulfate and solvent in a ratio of 0.5-1g:0.2-0.5g:0.01-0.03g:10ml, stirring and dissolving to obtain a prepared solution; ④ sulfonation grafting, adding the swollen activated polypropylene fiber into the prepared solution under the protection of inert gas, controlling the temperature to 70-85°C and stirring for reaction for 2-3h to obtain a reactant; and ⑤ separation, cooling the reactant, neutralizing it with sodium bicarbonate and washing it with deionized water to obtain a finished active polypropylene fiber.

[0035] The potassium persulfate dosage is 2% of the combined weight of oleum, acrylic acid, and sodium styrene sulfonate. The solvent is a dichloromethane / DMSO mixture with a volume ratio of 9:1. The temperature in step ② fluctuates due to the addition of oleum, so it needs to be controlled between 0-4°C.

[0036] A method for preparing a fly ash binder, for preparing the fly ash binder as described above, comprises the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer, and dry the fly ash at a controlled temperature of 105° C. for 2 hours to obtain a mixed material; Step 2: adding water glass as an activator to the mixture, and controlling the modulus of the water glass to be 2.0 and the concentration to be 32%, adding water after continuous stirring, controlling the water-binder ratio to be 0.4, and obtaining a uniform slurry by high-speed stirring; Step 3: The uniform slurry is introduced into a sealed container and aged for 25 minutes to obtain a finished adhesive.

[0037] Among them, the silicate cement is of P·O 42.5 grade and has a specific surface area of ​​≥300m² / kg.

[0038] Example 3

[0039] A fly ash binder comprises, by weight, 60 parts fly ash, 30 parts Portland cement, 15 parts activator, and 3 parts functional additive. The functional additive comprises modified polypropylene fiber, which is an activated polypropylene fiber grafted with sulfonic acid and carboxyl groups. The grafting rate of sulfonic acid groups is 2-3% by weight, and the grafting rate of carboxyl groups is 1-2.2% by weight. Testing showed that the grafting rate of sulfonic acid groups in Example 3 of the present application was 2.81% by weight, and the grafting rate of carboxyl groups was 1.98% by weight.

[0040] It should be noted that the preparation method of the activated polypropylene fiber includes the steps of ① pretreatment, irradiating the polypropylene fiber to obtain an activated polypropylene fiber with free active groups formed on the surface; ② base material preparation, placing the activated polypropylene fiber in a solvent and heating it to swell; ③ solution preparation, adding fuming sulfuric acid dropwise to the solvent, controlling the temperature to 0-4°C, and adding the solvent dropwise to the fuming sulfuric acid in a ratio of 10ml:1.5ml, and then adding acrylic acid, sodium styrene sulfonate and potassium persulfate after stirring, and the addition ratio of acrylic acid to sodium styrene sulfonate, potassium persulfate and solvent is 1g:0.5g:0.03g:10ml, stirring and dissolving to obtain a prepared solution; ④ sulfonation grafting, placing the swollen activated polypropylene fiber into the prepared solution under the protection of inert gas, controlling the temperature to 85°C and stirring for 2h to obtain a reactant; and ⑤ separation, cooling the reactant, neutralizing it with sodium bicarbonate and washing it with deionized water to obtain a finished active polypropylene fiber.

[0041] The amount of potassium persulfate used was 2% of the total mass of fuming sulfuric acid, acrylic acid, and sodium styrene sulfonate. The solvent was a dichloromethane / DMSO mixed solution with a volume ratio of 9:1.

[0042] A method for preparing a fly ash binder, for preparing the fly ash binder as described above, comprises the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer, and dry the fly ash at a controlled temperature of 105° C. for 2 hours to obtain a mixed material; Step 2: adding water glass as an activator to the mixture, controlling the modulus of the water glass to 2.0 and the concentration to 32%, adding water after continuous stirring, controlling the water-binder ratio to 0.38, and obtaining a uniform slurry by high-speed stirring; Step 3: The uniform slurry is introduced into a sealed container and aged for 30 minutes to obtain a finished adhesive.

[0043] Among them, the silicate cement is of P·O 42.5 grade and has a specific surface area of ​​≥300m² / kg.

[0044] Example 4

[0045] The difference between Example 4 and Example 3 is that the functional additives in Example 4 include a water reducer and a retarder, and the amounts of the water reducer and the retarder are 0.3 parts and 0.2 parts respectively.

[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the functional additive in Comparative Example 1 is polypropylene fiber.

[0047] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the functional additive in Comparative Example 2 is an active polypropylene fiber grafted with a first active group.

[0048] Performance testing: 1. Interface bonding strength: Interface bonding strength, average pore size in transition zone 2. Mechanical properties: Microcrack suppression width, compressive strength 3. Durable and corrosion-resistant performance: The percentage of mass loss in the anti-freezing cycle test and the percentage of strength retention in the 500d strength test Performance tests were performed based on Examples 1 to 4 and Comparative Examples 1 to 4.

[0049] The test results are shown in Table 1 below:

[0050] As shown in Table 1 above, the synergistic interaction of sulfonic acid groups and polar carboxyl groups achieves a densified interface transition zone through chemical adsorption. This allows the reactive polypropylene fibers and the fly ash binder matrix to synergistically exert forces, enhancing stress transfer efficiency and improving mechanical properties. Furthermore, by inhibiting calcium hydroxide growth, promoting uniform distribution of the CSH gel, and resisting water penetration, durability and corrosion resistance are significantly improved.

[0051] In summary, the present application provides a fly ash adhesive and a preparation method thereof, wherein the fly ash adhesive forms chemical adsorption with cations such as calcium ions and aluminum ions in fly ash and silicate cement through ionic bonds of active polypropylene fibers, and cooperates with the first active group and the second active group to activate silicon oxide and aluminum oxide to participate in the secondary hydration reaction and form a CSH gel, thereby utilizing hydrogen bonds to enhance the interfacial bonding force, thereby further forming a denser transition layer to reduce the interfacial pores from 60-80nm to 25-40nm. At the same time, the formation of a three-dimensional skeleton structure will enhance stability, thereby effectively transmitting compressive stress and tensile stress, and obtaining an improvement of more than 50% in 28d tensile strength. In terms of corrosion resistance, due to the synergistic hydrophobicity of the polypropylene fibers and the hydrophilicity of the first active group and the second active group, the purpose of avoiding water absorption and swelling and reducing the internal penetration of corrosive ions is achieved, thereby achieving the purpose of long-term corrosion resistance and durability. At the same time, the sulfonic acid group and water glass synergistically promote the breaking of Al-O-Si bonds and the formation of CASH gel, and synergize the steric hindrance effect of the polar groups to disperse the silicate cement particles, thereby reducing water consumption while synergizing the sulfonic acid group to extend the construction period, making it suitable for large-area construction scenarios.

[0052] The preparation method of the fly ash binder has the effect of convenient operation.

[0053] References to "first," "second," "third," "fourth," and the like (if any) herein are intended to distinguish similar objects and are not necessarily intended to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, or apparatus.

[0054] It should be noted that the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0055] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A fly ash binder, characterized in that: The invention comprises 50-60 parts by weight of fly ash, 18-30 parts by weight of silicate cement, 5-15 parts by weight of an activator and 0.5-3 parts by weight of a functional additive; the functional additive comprises modified polypropylene fiber, which is an active polypropylene fiber grafted with a first active group and a second active group; the first active group is a sulfonic acid group, and the second active group is a polar group.

2. The fly ash binder according to claim 1, characterized in that: The second active group is an amide group, a carboxyl group or a hydroxyl group.

3. The fly ash binder according to claim 1, characterized in that: The grafting rate of the first active group is 2-3 wt %, and the grafting rate of the second active group is 1-2.2 wt %.

4. The fly ash binder according to claim 1, characterized in that: The preparation method of the activated polypropylene fiber comprises the following steps: (1) pretreatment, in which polypropylene fiber is treated by irradiation or plasma to obtain activated polypropylene fiber with free active groups formed on the surface; (2) base material preparation, in which the activated polypropylene fiber is placed in a solvent and heated to swell; (3) solution preparation, in which fuming sulfuric acid is added dropwise to the solvent, the temperature is controlled at 0-4°C, and the ratio of the added solvent to the fuming sulfuric acid is 10ml:1-1.5ml; acrylic acid, sodium styrene sulfonate and an initiator are added after stirring, in which the ratio of the added acrylic acid to the sodium styrene sulfonate to the initiator to the solvent is 0.5-1g:0.2-0.5g:0.01-0.03g:10ml; and the mixture is stirred and dissolved to obtain a prepared solution; (4) sulfonation grafting, in which the swollen activated polypropylene fiber is placed in the prepared solution under the protection of inert gas, the temperature is controlled at 70-85°C, and the mixture is stirred for reaction for 2-3h to obtain a reactant; and (5) separation, in which the reactant is cooled, neutralized with sodium bicarbonate, and washed with deionized water to obtain a finished active polypropylene fiber.

5. The fly ash binder according to claim 4, characterized in that: The initiator is potassium persulfate, and the amount used is 2% of the total mass of the fuming sulfuric acid, acrylic acid and sodium styrene sulfonate.

6. The fly ash binder according to claim 4, characterized in that: The solvent is a dichloromethane / DMSO mixed solution with a volume ratio of 9:

1.

7. The fly ash binder according to claim 1, characterized in that: The functional additives include water reducers and retarder.

8. A method for preparing a fly ash binder, for preparing the fly ash binder according to any one of claims 1 to 6, comprising the following steps: Step 1: Dry the fly ash in corresponding parts by weight and mix it with Portland cement in a mixer to obtain a mixed material; Step 2: Add an activator to the mixture, continue stirring until uniform, then add water, control the water-binder ratio to 0.38-0.42, and obtain a uniform slurry by high-speed stirring; Step 3: introduce the uniform slurry into a sealed container and age it for 20-30 minutes to obtain a finished adhesive.

9. The method for preparing a fly ash binder according to claim 8, characterized in that: The fly ash is dried at a controlled temperature of 105° C. for 2 hours.

10. The method for preparing a fly ash binder according to claim 8, characterized in that: The activator is water glass, and the modulus is controlled to be 2.0 and the concentration is 32%; the silicate cement is P·O 42.5 grade, and the specific surface area is ≥300m² / kg.

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