A high-strength fly ash-based polymer mortar and its preparation method

Abstract

The present invention relates to the field of geopolymer technology, and discloses a high-strength fly ash-based polymer slurry and a preparation method thereof. The polymer slurry comprises 62-70 parts by weight of an activated geopolymer precursor, 7-11 parts by weight of an alkali activator, 80-95 parts by weight of aggregate, 0.4-2 parts by weight of a silica-grafted polyester fiber, and 18-22 parts by weight of water. Fly ash and slag are ball-milled and activated using triethanolamine to obtain an activated geopolymer precursor. Nano-silica is grafted onto the surface of the polyester fiber, forming a good interfacial compatibilizer with the silica phase and silicate phase in the fly ash and slag, thereby improving the compatibility between the polyester fiber and the geopolymer precursor. At the same time, hydrophilic groups such as carboxyl and imino groups are introduced into the fiber surface, resulting in better dispersibility in aqueous slurry. Under a synergistic effect, the compressive strength and flexural strength of the geopolymer slurry specimen are improved.

Description

Technical Field

[0001] The invention relates to the technical field of geopolymers, in particular to a high-strength fly ash-based polymer mortar and a preparation method thereof. Background Art

[0002] Geopolymers are inorganic polymers with a tetrahedral three-dimensional network structure formed by a chemical reaction between precursors and activators. Precursors primarily include industrial solid wastes such as slag, steel slag, silica fume, fly ash, and red mud, while activators include alkali metal hydroxides, carbonates, and phosphates. Geopolymers exhibit excellent mechanical and durability properties, effectively replacing traditional cement while absorbing significant amounts of industrial solid waste. They are crucial for reducing carbon emissions and achieving lifecycle cost savings in the transportation industry. Geopolymers are gaining increasing attention as a low-carbon, green cementitious material. With appropriate materials and proportions, they can exhibit superior mechanical properties compared to Portland cement. Compared to traditional cement-based cementitious materials, geopolymer cementitious materials have a more complex composition, and the performance of systems composed of different precursors and alkali activators varies significantly. Therefore, selecting the appropriate geopolymer cementitious material system and focusing on the proportions and properties of the geopolymer mortar are prerequisites for producing high-performance, low-carbon, and environmentally friendly permeable geopolymer concrete.

[0003] Polyester fiber is a chemically synthesized fiber with high mechanical strength, good chemical stability, and strong resistance to high and low temperatures. It is widely used in building materials such as cement, asphalt, and concrete. Patent CN113026360B discloses the process of hydrolyzing polyester fibers with alkali to produce hydrolyzed polyester fibers. An acidic crosslinking agent and polyvinyl alcohol are then cured on the hydrolyzed polyester fibers to form a submicron or micron-thick coating. The resulting modified polyester fibers can be used in engineering cement-based composites. However, this modified polyester fiber does not improve the compressive and flexural strength of cement materials. Summary of the Invention

[0004] The invention solves the problem of low flexural and compressive strength of fly ash-based polymer mortar.

[0005] The technical solution provided by the present invention is: a high-strength fly ash-based polymer mortar, characterized in that it includes 62-70 parts by weight of an activated polymer precursor, 7-11 parts by weight of an alkali activator, 80-95 parts by weight of aggregate, 0.4-2 parts by weight of silica-grafted polyester fiber, and 18-22 parts by weight of water.

[0006] The preparation method of the activated geopolymer precursor comprises the following steps: adding fly ash, slag and grinding aid triethanolamine into a ball mill, performing ball milling, and discharging the materials to obtain the activated geopolymer precursor.

[0007] The preparation method of silica-grafted polyester fiber is as follows: adding serine-grafted polyester fiber to N,N-dimethylformamide, heating to 50-60°C, stirring for 2-3 hours, then adding toluene diisocyanate-modified nano-silica and dibutyltin dilaurate, heating to 80-90°C, reacting for 12-24 hours, filtering, washing with ethanol, and drying to obtain silica-grafted polyester fiber.

[0008] Preferably, the alkali activator is water glass with a modulus of 1.4-1.6; the aggregate is basalt with an average particle size of 4.75-9.5 mm.

[0009] Preferably, the slag is alkaline slag, and the slag includes the following components in mass fractions: a CaO mass fraction of 38.55%, a Al2O3 mass fraction of 11.69%, a Fe2O3 mass fraction of 1.04%, a SiO2 mass fraction of 32.95%, and a MgO mass fraction of 9.11%; the fly ash includes the following components in mass fractions: a CaO mass fraction of 10.4%, a Al2O3 mass fraction of 20.3%, a Fe2O3 mass fraction of 5.30%, a SiO2 mass fraction of 55.0%, and a MgO mass fraction of 0.98%.

[0010] Preferably, in the method for preparing the activated geopolymer precursor, the mass ratio of fly ash, slag and triethanolamine is (35-45):(55-65):(0.01-0.02).

[0011] Preferably, in the method for preparing the activated geopolymer precursor, the ball milling speed is 300-600 r / min, and the ball milling time is 45-90 min.

[0012] Preferably, in the preparation method of silica-grafted polyester fiber, the mass ratio of serine-grafted polyester fiber, toluene diisocyanate-modified nano-silica, and dibutyltin dilaurate is 100:(15-60):(0.12-0.5).

[0013] Preferably, the preparation method of serine grafted polyester fiber is:

[0014] (1) Add glycidyl methacrylate and benzoin ethyl ether to acetone, stir and dissolve to obtain a monomer solution, control the concentration of glycidyl methacrylate to (0.6-1.8) mol / L, and the concentration of benzoin ethyl ether to (0.05-0.15) mol / L; then add polyester fiber and soak for 2-3 hours, then irradiate the fiber under a 400-600W high-pressure mercury lamp to carry out ultraviolet grafting reaction for 10-20 minutes, wash with xylene, ethanol and water in sequence, and dry to obtain GMA grafted polyester fiber.

[0015] (2) Add GMA grafted polyester fiber to N,N-dimethylformamide, heat to 50-60°C, stir for 2-3 hours, then add serine (8-36% by weight of the GMA grafted polyester fiber), stir and react for 12-18 hours, filter, wash with water and ethanol in turn, and dry to obtain serine grafted polyester fiber.

[0016] Preferably, the preparation method of high-strength fly ash-based polymer slurry is: add silica-grafted polyester fiber to water, disperse it by ultrasound, then add alkali activator, stir for 30-60s, and then continuously add activated polymer precursor, controlling the addition time to 120-180s, stirring while adding, and finally add aggregate, stir for 60-120s, then pour the material into a mold, vibrate to degas, and cure to form, so as to obtain high-strength fly ash-based polymer slurry.

[0017] The technical effect of the present invention is as follows: the present invention uses glycidyl methacrylate to perform ultraviolet grafting modification on polyester fibers, introduces epoxy groups on the surface of the polyester fibers, and then uses the amino groups of serine to react with the epoxy groups to obtain serine-grafted polyester fibers, thereby introducing active hydroxyl groups, as well as carboxyl and imino hydrophilic groups on the surface of the polyester fibers, and further the active hydroxyl groups react with the isocyanate groups of toluene diisocyanate-modified nano-silica, thereby modifying the nano-silica on the surface of the polyester fibers to obtain silica-grafted polyester fibers.

[0018] The present invention utilizes triethanolamine as a grinding aid to perform ball milling activation on fly ash and slag to obtain an activated geopolymer precursor. After ball milling activation with the triethanolamine grinding aid, the obstructive effect of the double-layer glass protective layer rich in SiO2 and SiO2-Al2O3 in the fly ash and slag is reduced, and the internal soluble SiO2 and Al2O3 phases can be dissolved, thereby improving the chemical properties of the geopolymer precursor. Silica-grafted polyester fiber is used as a fiber reinforcement and compounded with water, aggregate, and water glass activator to obtain a geopolymer mortar specimen. Nano-silica is grafted on the surface of the polyester fiber. Nano-silica not only has the advantages of high strength and high structural stability, but also has good interface compatibilizer with the silica phase and silicate phase in the fly ash and slag, thereby improving the compatibility between the polyester fiber and the geopolymer precursor and playing a better reinforcing role. In addition, the grafting modification of polyester fiber grafting surface by serine and the introduction of hydrophilic groups such as carboxyl and imino groups on the fiber surface can improve the dispersion of the fiber in the aqueous slurry and further enhance the reinforcing effect of the polyester fiber. Under the synergistic effect, the compressive strength and flexural strength of the geopolymer slurry specimens are improved. DETAILED DESCRIPTION

[0019] The technical solutions of the present invention are further illustrated by specific examples below. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0020] The slag in the embodiment of the present invention is alkaline slag, and the mass fraction of CaO in the slag is 38.55%, the mass fraction of Al2O3 is 11.69%, the mass fraction of Fe2O3 is 1.04%, the mass fraction of SiO2 is 32.95%, and the mass fraction of MgO is 9.11%.

[0021] The mass fraction of CaO in fly ash is 10.4%, the mass fraction of Al2O3 is 20.3%, the mass fraction of Fe2O3 is 5.30%, the mass fraction of SiO2 is 55.0%, and the mass fraction of MgO is 0.98%.

[0022] The preparation method of toluene diisocyanate modified nano-silica is as follows: 2 g of nano-silica (average particle size 30 nm) and 2 g of toluene-2,4-diisocyanate are added to 150 mL of toluene, heated to 90° C., reacted for 12 h, centrifuged, washed with toluene, and dried to obtain toluene diisocyanate modified nano-silica.

[0023] Example 1

[0024] (1) Add 180 mmol of glycidyl methacrylate and 15 mmol of benzoin ethyl ether to 100 mL of acetone, stir and dissolve to obtain a monomer solution, then add 8 g of polyester fiber and soak for 2 h. Then irradiate the fiber under a 400 W high-pressure mercury lamp to carry out ultraviolet light grafting reaction for 20 min, wash with xylene, ethanol, and water in sequence, and dry to obtain GMA-grafted polyester fiber.

[0025] (2) Add 5 g of GMA grafted polyester fiber to 300 mL of N,N-dimethylformamide, heat to 50 ° C, stir for 3 h, then add 1.8 g of serine, stir and react for 18 h, filter, wash with water and ethanol in turn, and dry to obtain serine grafted polyester fiber.

[0026] (3) Add 5 g of serine-grafted polyester fiber to 400 mL of N,N-dimethylformamide, heat to 55 °C, stir for 3 h, then add 3 g of toluene diisocyanate-modified nanosilica and 25 mg of dibutyltin dilaurate, heat to 80 °C, react for 24 h, filter, wash with ethanol, and dry to obtain silica-grafted polyester fiber.

[0027] (4) 35 g of fly ash, 65 g of slag, and 0.01 g of triethanolamine as a grinding aid were added to a ball mill and ball milled for 60 min at a ball mill speed of 500 r / min to obtain an activated geopolymer precursor.

[0028] (5) Add 4 g of silica-grafted polyester fiber to 180 g of water and disperse it by ultrasonication. Then add 110 g of water glass, an alkali activator with a modulus of 1.5, and stir for 60 seconds. Then continuously add 650 g of activated geopolymer precursor, controlling the addition time to 120 seconds while stirring. Finally, add 860 g of basalt aggregate with an average particle size of 9.5 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0029] Example 2

[0030] (1) Add 120 mmol of glycidyl methacrylate and 10 mmol of benzoin ethyl ether to 100 mL of acetone, stir and dissolve to obtain a monomer solution, then add 8 g of polyester fiber and soak for 3 hours. Then irradiate the fiber under a 400 W high-pressure mercury lamp to carry out ultraviolet light grafting reaction for 20 minutes, wash with xylene, ethanol, and water in sequence, and dry to obtain GMA-grafted polyester fiber.

[0031] (2) Add 5 g of GMA grafted polyester fiber to 300 mL of N,N-dimethylformamide, heat to 50 ° C, stir for 2 h, then add 1.2 g of serine, stir and react for 12 h, filter, wash with water and ethanol in turn, and dry to obtain serine grafted polyester fiber.

[0032] (3) Add 5 g of serine-grafted polyester fiber to 350 ml of N,N-dimethylformamide, heat to 50 ° C, stir for 3 h, then add 1.8 g of toluene diisocyanate-modified nanosilica and 15 mg of dibutyltin dilaurate, heat to 80 ° C, react for 24 h, filter, wash with ethanol, and dry to obtain silica-grafted polyester fiber.

[0033] (4) 35 g of fly ash, 65 g of slag, and 0.015 g of triethanolamine as a grinding aid were added to a ball mill and ball milled for 60 min at a ball mill speed of 300 r / min to obtain an activated geopolymer precursor.

[0034] (5) Add 12 g of silica-grafted polyester fiber to 220 g of water and disperse it by ultrasonication. Then add 70 g of water glass, an alkali activator with a modulus of 1.6, and stir for 30 seconds. Then continuously add 700 g of activated geopolymer precursor, controlling the addition time to 180 seconds while stirring. Finally, add 800 g of basalt aggregate with an average particle size of 9.5 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0035] Example 3

[0036] (1) Add 60 mmol of glycidyl methacrylate and 5 mmol of benzoin ethyl ether to 100 mL of acetone, stir and dissolve to obtain a monomer solution, then add 8 g of polyester fiber and soak for 2 hours. Then irradiate the fiber under a 600 W high-pressure mercury lamp to carry out ultraviolet light grafting reaction for 10 minutes, wash with xylene, ethanol, and water in sequence, and dry to obtain GMA-grafted polyester fiber.

[0037] (2) Add 5 g of GMA grafted polyester fiber to 200 mL of N,N-dimethylformamide, heat to 60 ° C, stir for 2 h, then add 0.4 g of serine, stir and react for 12 h, filter, wash with water and ethanol in turn, and dry to obtain serine grafted polyester fiber.

[0038] (3) Add 5 g of serine-grafted polyester fiber to 300 mL of N,N-dimethylformamide, heat to 60 ° C, stir for 2 h, then add 0.75 g of toluene diisocyanate-modified nanosilica and 6 mg of dibutyltin dilaurate, heat to 90 ° C, react for 12 h, filter, wash with ethanol, and dry to obtain silica-grafted polyester fiber.

[0039] (4) 40 g of fly ash, 60 g of slag, and 0.02 g of triethanolamine as a grinding aid were added to a ball mill and ball milled for 60 min at a ball mill speed of 600 r / min to obtain an activated geopolymer precursor.

[0040] (5) Add 20 g of silica-grafted polyester fiber to 220 g of water and disperse it by ultrasonication. Then add 95 g of water glass, an alkali activator with a modulus of 1.4, and stir for 60 seconds. Then continuously add 620 g of activated geopolymer precursor, controlling the addition time to 120 seconds while stirring. Finally, add 950 g of basalt aggregate with an average particle size of 4.75 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0041] Comparative Example 1

[0042] (1) Silica-grafted polyester fibers were prepared according to the method of Example 1.

[0043] (2) 35 g of fly ash and 65 g of slag were added to a ball mill and ball milled for 60 min at a ball mill speed of 500 r / min to obtain a geopolymer precursor.

[0044] (3) Add 4 g of silica-grafted polyester fiber to 180 g of water and disperse it by ultrasonication. Then add 110 g of water glass, an alkali activator with a modulus of 1.5, and stir for 60 seconds. Then continuously add 650 g of geopolymer precursor, controlling the addition time to 120 seconds while stirring. Finally, add 860 g of basalt aggregate with an average particle size of 9.5 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0045] Comparative Example 2

[0046] (1) Prepare an activated geopolymer precursor according to the method of Example 1.

[0047] (2) Add 110 g of alkali activator water glass with a modulus of 1.5 to 180 g of water, stir for 60 seconds, then continuously add 650 g of activated geopolymer precursor, control the addition time to 120 seconds, and stir while adding. Finally, add 860 g of basalt aggregate with an average particle size of 9.5 mm, stir for 120 seconds, and then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0048] Comparative Example 3

[0049] (1) Prepare an activated geopolymer precursor according to the method of Example 1.

[0050] (2) Add 4 g of polyester fiber to 180 g of water and disperse it by ultrasonic. Then add 110 g of water glass, an alkali activator with a modulus of 1.5, and stir for 60 seconds. Then continuously add 650 g of activated geopolymer precursor, controlling the addition time to 120 seconds while stirring. Finally, add 860 g of basalt aggregate with an average particle size of 9.5 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0051] Comparative Example 4

[0052] (1) Serine-grafted polyester fibers were prepared according to the method of Example 1.

[0053] (2) Prepare an activated geopolymer precursor according to the method of Example 1.

[0054] (3) Add 4 g of serine grafted polyester fiber to 180 g of water and disperse it by ultrasonication. Then add 110 g of water glass, an alkali activator with a modulus of 1.5, and stir for 60 seconds. Then continuously add 650 g of activated geopolymer precursor, controlling the addition time to 120 seconds while stirring. Finally, add 860 g of basalt aggregate with an average particle size of 9.5 mm and stir for 120 seconds. Then pour the material into a mold, vibrate to deaerate, and cure at 20°C for 7-28 days with a relative humidity of 90% to obtain a high-strength fly ash-based geopolymer mortar.

[0055] The compressive strength and flexural strength of the mortar specimens are tested in accordance with GB / T 17671-2021 standard.

[0056]

[0057] After testing, the fly ash-based polymer mortars of Examples 1-3 all showed good compressive strength and flexural strength. This is mainly because triethanolamine was used as a grinding aid to activate the fly ash and slag by ball milling to obtain an activated geopolymer precursor. At the same time, silica-grafted polyester fibers were added, and nano-silica was grafted on the surface of the polyester fibers. Nano-silica not only has the advantages of high strength and high structural stability, but also has good interfacial compatibilizers with the silica phase and silicate phase in fly ash and slag, thereby improving the compatibility between the polyester fiber and the geopolymer precursor and playing a better reinforcing role. In addition, the grafting modification of the polyester fiber graft surface with serine and the introduction of hydrophilic groups such as carboxyl and imino groups on the fiber surface can improve the dispersibility of the fiber in the aqueous slurry, further enhance the reinforcing effect of the polyester fiber, and under the synergistic effect, improve the compressive strength and flexural strength of the geopolymer mortar specimens.

[0058] Compared with Example 1, Comparative Example 1 did not use triethanolamine to activate the fly ash and slag by ball milling, so the activity of the obtained geopolymer precursor was lower, and the compressive strength and flexural strength of the mortar specimen were lower than those in Example 1.

[0059] In Comparative Example 2, no silica-grafted polyester fiber was added, and the compressive strength and flexural strength of the mortar specimen were significantly lower than those in Example 1.

[0060] In Comparative Example 3, ordinary unmodified polyester fiber is added, which does not contain nano-silica on its surface, has poor compatibility with the geopolymer precursor formed by fly ash and slag, and does not contain hydrophilic groups such as carboxyl and imino groups on its surface. It has poor dispersibility in the aqueous slurry and has poor reinforcing effect on the slurry specimens, resulting in lower compressive strength and flexural strength than Example 1.

[0061] The surface of the serine-grafted polyester fiber added in Comparative Example 4 does not contain nano-silica, and has poor compatibility with the geopolymer precursor, resulting in poor reinforcement effect, resulting in lower compressive strength and flexural strength than Example 1.

[0062] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A high-strength fly ash-based polymer mortar, characterized in that: The geopolymer mortar comprises 62-70 parts by weight of an activated geopolymer precursor, 7-11 parts by weight of an alkali activator, 80-95 parts by weight of aggregate, 0.4-2 parts by weight of silica-grafted polyester fiber, and 18-22 parts by weight of water; The preparation method of the activated geopolymer precursor comprises the following steps: adding fly ash, slag and triethanolamine as a grinding aid into a ball mill, performing ball milling, and discharging the materials to obtain the activated geopolymer precursor; The preparation method of the silica-grafted polyester fiber comprises: adding serine-grafted polyester fiber to N,N-dimethylformamide, heating to 50-60° C., stirring for 2-3 hours, then adding toluene diisocyanate-modified nano-silica and dibutyltin dilaurate, heating to 80-90° C., reacting for 12-24 hours, filtering, washing, and drying to obtain the silica-grafted polyester fiber; In the preparation method of the activated geopolymer precursor, the mass ratio of fly ash, slag and triethanolamine is (35-45):(55-65):(0.01-0.02); In the preparation method of the silica-grafted polyester fiber, the mass ratio of the serine-grafted polyester fiber, the toluene diisocyanate-modified nano-silica, and the dibutyltin dilaurate is 100:(15-60):(0.12-0.5); The preparation method of the serine-grafted polyester fiber is as follows: (1) Add glycidyl methacrylate and benzoin ethyl ether to acetone, stir and dissolve to obtain a monomer solution, then add polyester fiber and soak for 2-3 hours, then irradiate the fiber under a 400-600W high-pressure mercury lamp to carry out ultraviolet grafting reaction for 10-20 minutes, wash, and dry to obtain GMA-grafted polyester fiber; (2) Add GMA grafted polyester fiber to N,N-dimethylformamide, heat to 50-60°C, stir for 2-3 hours, then add serine, stir and react for 12-18 hours, filter, wash, and dry to obtain serine grafted polyester fiber.

2. The high-strength fly ash-based polymer mortar according to claim 1, characterized in that: The alkali activator is water glass with a modulus of 1.4-1.6; the aggregate is basalt with an average particle size of 4.75-9.5 mm.

3. The high-strength fly ash-based polymer mortar according to claim 1, characterized in that: The slag is alkaline slag, and the slag includes the following components by mass fraction: a mass fraction of CaO of 38.55%, a mass fraction of Al2O3 of 11.69%, a mass fraction of Fe2O3 of 1.04%, a mass fraction of SiO2 of 32.95%, and a mass fraction of MgO of 9.11%; The fly ash includes the following components in mass fractions: the mass fraction of CaO is 10.4%, the mass fraction of Al2O3 is 20.3%, the mass fraction of Fe2O3 is 5.30%, the mass fraction of SiO2 is 55.0%, and the mass fraction of MgO is 0.98%.

4. The high-strength fly ash-based polymer mortar according to claim 1, characterized in that: In the preparation method of the activated geopolymer precursor, the ball milling speed is 300-600 r / min, and the ball milling time is 45-90 min.

5. The high-strength fly ash-based polymer mortar according to claim 1, characterized in that: In the above (1), the concentration of glycidyl methacrylate in the monomer solution is (0.6-1.8) mol / L, and the concentration of benzoin ethyl ether is (0.05-0.15) mol / L.

6. The high-strength fly ash-based polymer mortar according to claim 1, characterized in that: In the above (2), the mass ratio of GMA grafted polyester fiber to serine is 100:(8-36).

7. A method for preparing the high-strength fly ash-based polymer mortar according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: adding silica-grafted polyester fibers to water, dispersing the fibers by ultrasonication, adding an alkali activator, stirring the mixture for 30-60 seconds, continuously adding an activated geopolymer precursor, controlling the addition time to be 120-180 seconds, stirring the mixture while adding, finally adding aggregate, stirring the mixture for 60-120 seconds, pouring the materials into a mold, vibrating the mold for degassing, and curing the molded materials to obtain a high-strength fly ash-based geopolymer mortar.

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