Ternary hybrid fiber reinforced geopolymer suitable for fire-resistant bending-resistant member and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to a ternary hybrid fiber reinforced geopolymer suitable for fire-resistant and bending-resistant members and a preparation method thereof, and the geopolymer comprises the following raw material components: metakaolin, fly ash, potash water glass solution, water, corundum aggregate, wollastonite fiber, steel fiber and basalt fiber. Through the high strength of the steel fibers and the high temperature resistance of the basalt fibers and the wollastonite fibers, a fiber reinforced network is formed. Wherein the wollastonite fibers are microscale high-temperature-resistant fibers and can be used for bridging microscopic cracks, so that the high-temperature resistance of a matrix is effectively enhanced. In addition, the ternary hybrid fiber geopolymer disclosed by the invention has relatively good bending resistance. A three-point bending test shows that the bending strength of the ternary hybrid fiber geopolymer can reach 20MPa in a normal-temperature environment; after high-temperature exposure at 400 DEG C, the bending strength of the ternary hybrid fiber geopolymer can reach more than 30 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a ternary hybrid fiber-reinforced geopolymer suitable for fire-resistant flexural members and a preparation method thereof. Background Art

[0002] With the increasing engineering applications in high-temperature environments, refractory materials play an increasingly important role in the industrial, construction, and energy fields. For example, in high-temperature working conditions such as metallurgy, aerospace, nuclear energy, and tunnel fire protection, materials need to have excellent heat resistance stability and crack resistance to ensure structural safety and long-term service performance. Fire-resistant flexural members (such as beams, slabs, arches, tunnel linings, furnace lining structures, and high-temperature pipeline support members in high-temperature environments) not only need to have fire resistance but also need to bear large bending moments. Traditional refractory materials such as refractory bricks and cement-based refractory concretes have certain high-temperature resistance capabilities, but they often have problems such as high brittleness, poor thermal shock resistance, and high environmental loads, which limit their applications in high-temperature engineering. In recent years, new low-carbon and environmentally friendly refractory materials have become a research hotspot. Among them, geopolymer materials are considered to be powerful alternatives to traditional refractory materials due to their excellent fire resistance, high-temperature stability, relatively high mechanical strength, and good chemical corrosion resistance. However, a single geopolymer material is prone to crack propagation and significant strength reduction in high-temperature environments. When used as a flexural member, there are still potential hazards in its mechanical stability under high-temperature working conditions. Therefore, improving the flexural performance and high-temperature resistance of geopolymers has become a key requirement for their engineering applications.

[0003] Fiber reinforcement technology is an effective way to improve the brittleness of geopolymers. Steel fibers can significantly improve the insufficient ductility of concrete due to their high strength and high fracture toughness. However, in an environment above 400°C, steel fibers are prone to oxidation, and the generated oxides may expand in volume and squeeze the matrix, thereby triggering microcracks and leading to material property degradation. Basalt fibers exhibit good heat resistance stability and low thermal expansion coefficient in a high-temperature environment up to 650°C, and can effectively improve the structural integrity and performance stability of concrete under extreme temperature conditions. Wollastonite fiber is a natural calcium silicate mineral with excellent high-temperature resistance. Its melting point is about 1540°C, and it still shows good stability in a high-temperature environment up to 1000°C. In addition, wollastonite fiber has a low thermal expansion coefficient, enabling it to maintain the structural integrity under high-temperature conditions. Although basalt fibers and wollastonite fibers can effectively enhance the high-temperature resistance of the matrix, there are still certain limitations in improving the flexural performance and ductility of geopolymer materials. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a ternary hybrid fiber-reinforced geopolymer suitable for refractory flexural members and a preparation method thereof. The steel fibers in the present invention provide high strength and high toughness, and the basalt fibers and wollastonite fibers make up for their deficiencies in high-temperature performance. This geopolymer material has high-temperature resistance and better flexural performance at the same time.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] On the one hand, the present invention provides a ternary hybrid fiber-reinforced geopolymer suitable for refractory flexural members, and the geopolymer includes the following raw material components: metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, steel fiber, and basalt fiber.

[0007] As a further optimized solution of the present invention, the geopolymer includes the following raw material components by weight: 196 parts of metakaolin, 457 parts of fly ash, 252 parts of potassium silicate solution, 100 parts of water, 1762 parts of corundum aggregate, 33 parts of wollastonite fiber, 79 parts of steel fiber, and 13 - 27 parts of basalt fiber. If the dosage range of basalt fiber is too large, the fluidity of the geopolymer will decrease significantly, affecting the development of its strength; if the range is too small, the fibers distributed in the geopolymer matrix are less, and the improvement effect on mechanical properties is not obvious.

[0008] As a further optimized solution of the present invention, the volume fraction of the basalt fiber is 0.5 - 1%.

[0009] As a further optimized solution of the present invention, the potassium silicate solution is prepared from an original modulus of 2.4 by adding potassium hydroxide solid powder to a modulus of 1.0.

[0010] As a further optimized solution of the present invention, the corundum aggregate includes four particle size ranges of 2.36 - 1.18mm, 1.18 - 0.6mm, 0.6 - 0.18mm, and 0.18 - 0.125mm, and the mass ratio is 4:3:2:1.

[0011] As a further optimized solution of the present invention, the wollastonite fiber D 50 is 4.21μm, and the aspect ratio is 15 - 20:1.

[0012] As a further optimized solution of the present invention, the basalt fiber is chopped basalt fiber, the fiber length is 12mm, and the tensile strength is 2100MPa.

[0013] As a further optimized solution of the present invention, the steel fiber is copper-plated steel fiber, the fiber length is 13mm, the diameter is 0.2mm, and the tensile strength is 2850MPa.

[0014] On the other hand, the present invention also provides a preparation method of a ternary hybrid fiber-reinforced geopolymer applicable to a refractory bending member, and the preparation method includes:

[0015] (1) Prepare a potassium silicate solution with a modulus of 1.0, and start the test after standing for 24 hours;

[0016] (2) Weigh metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, basalt fiber, and steel fiber according to the mixing ratio;

[0017] (3) Pour metakaolin and fly ash into the mixing pot, start the low-speed mode, after the two powders are stirred evenly, slowly pour in potassium silicate and water, start medium-speed stirring for 1-2 minutes after the powder is moistened, and start high-speed stirring for 1-2 minutes;

[0018] (4) Adjust the mixer to low speed, slowly add corundum aggregate, stir at medium speed for 1-2 minutes, and start high-speed stirring for 1-2 minutes;

[0019] (5) Adjust the mixer to low speed, slowly add the fiber material, and stir at high speed for 1-3 minutes;

[0020] (6) Cure the obtained geopolymer composite material to obtain a ternary hybrid fiber-reinforced geopolymer.

[0021] As a further optimized scheme of the present invention, in steps (3)-(5), the low speed is 105-110 r / min, the medium speed is 185-190 r / min, and the high speed is 400-405 r / min.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following advantages and beneficial effects:

[0023] (1) The present invention proposes a ternary hybrid fiber-reinforced geopolymer composite material applicable to a refractory bending member. Through the high strength of steel fiber and the high temperature resistance of basalt fiber and wollastonite fiber, a fiber-reinforced network is formed. Among them, wollastonite fiber is a high temperature-resistant fiber at the micro scale, which can bridge microcracks and effectively enhance the high temperature resistance of the matrix. In addition, the invention shows that the ternary hybrid fiber geopolymer has good bending performance. The three-point bending test shows that at room temperature, the bending strength of the ternary hybrid fiber geopolymer can reach 20 MPa; after being exposed to a high temperature of 400 °C, the bending strength of the ternary hybrid fiber geopolymer can reach more than 30 MPa.

[0024] (2) The raw materials of basalt fiber and wollastonite fiber are derived from natural minerals (basalt, wollastonite), and there are no toxic by-products in the preparation process, and its carbon emission is more in line with the development trend of green building materials compared with synthetic fibers. Description of the Drawings

[0025] Figure 1 Results of the flexural strength of the geopolymers of the present invention at room temperature and after different high temperatures.

[0026] Figure 2 Load-displacement curves of three-point bending tests of Example 1 of the present invention at room temperature and after different high temperatures.

[0027] Figure 3 Load-displacement curves of three-point bending tests of Example 2 of the present invention at room temperature and after different high temperatures.

[0028] Figure 4 Load-displacement curves of three-point bending tests of Comparative Example 1 of the present invention at room temperature and after different high temperatures. Detailed implementation manners

[0029] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the preferred implementation manners of the present invention will be described below in conjunction with specific embodiments. However, it should not be construed as a limitation of the present invention, and only by way of example.

[0030] In the following embodiments, the test methods or testing methods described, unless otherwise specified, are all conventional methods; the reagents and materials described, unless otherwise specified, are all obtained from conventional commercial channels or prepared by conventional methods.

[0031] Example 1

[0032] In this example, the volume fraction of basalt fibers is 0.5% (referring to the percentage of the total volume of the geopolymer).

[0033] The geopolymer includes the following raw materials: by mass fraction, 196 parts of metakaolin, 457 parts of fly ash, 252 parts of potassium silicate solution, 100 parts of water, 1762 parts of corundum aggregate, 33 parts of wollastonite fiber, 78.5 parts of steel fiber, and 13.5 parts of basalt fiber. The preparation method of the geopolymer is as follows:

[0034] (1) Prepare a potassium silicate solution with a modulus of 1.0, and start the test after standing for 24 h.

[0035] (2) Weigh metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, basalt fiber, and steel fiber according to the mixing ratio.

[0036] (3) Pour the powder into the mixing pot, turn on the low-speed mode, stir the two powders evenly, and then slowly pour in the potassium silicate and water. After the powder is moistened, turn on the medium-speed stirring for 1 - 2 min, and then turn on the high-speed stirring for 1 - 2 min.

[0037] (4) Adjust the mixer to low speed, slowly add the corundum aggregate, stir at medium speed for 1 - 2 min, and then turn on the high-speed stirring for 1 - 2 min

[0038] (5) Set the mixer to low speed, slowly add the fiber material, and stir at high speed for about 2 minutes.

[0039] (6) Pour the obtained geopolymer composite into a mold of 40 mm × 40 mm × 160 mm, vibrate it densely, remove the mold after 24 hours under the state of covering with a plastic mold, and cure it under standard conditions for 28 days.

[0040] Preferably, in steps (3)-(5), the so-called low speed is 108 r / min, the so-called medium speed is 188 r / min, and the so-called high speed is 403 r / min.

[0041] Preferably, place the geopolymer test block cured for 28 days in a high-temperature test furnace, and set the heating rate to 10 °C / min. The target temperatures for the high-temperature test are 400 °C, 800 °C, and 1000 °C. After reaching the target temperature, keep it warm for one hour, and wait for the test block to cool naturally before performing the three-point bending test.

[0042] Example 2

[0043] In this example, the volume fraction of basalt fiber is 1% (referring to the percentage of the entire geopolymer volume).

[0044] The geopolymer includes the following raw materials: by mass fraction, 196 parts of metakaolin, 457 parts of fly ash, 252 parts of potassium silicate solution, 100 parts of water, 1762 parts of corundum aggregate, 33 parts of wollastonite fiber, 78.5 parts of steel fiber, and 27 parts of basalt fiber. The preparation method of the geopolymer is as follows:

[0045] (1) Prepare a potassium silicate solution with a modulus of 1.0, and start the test after standing for 24 hours.

[0046] (2) Weigh metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, basalt fiber, and steel fiber according to the mixing ratio.

[0047] (3) After pouring the powder materials into the mixing pot, turn on the low-speed mode. After the two powder materials are stirred evenly, slowly pour in the potassium silicate and water. After the powder is moistened, turn on the medium-speed stirring for 1-2 minutes, and then turn on the high-speed stirring for 1-2 minutes.

[0048] (4) Set the mixer to low speed, slowly add the corundum aggregate, stir at medium speed for 1-2 minutes, and then turn on the high-speed stirring for 1-2 minutes.

[0049] (5) Set the mixer to low speed, slowly add the fiber material, and stir at high speed for about 2 minutes.

[0050] (6) Pour the obtained geopolymer composite material into a mold of 40mm×40mm×160mm, vibrate it until it is dense, remove the mold after 24 hours under the condition of covering with a plastic mold, and cure it under standard conditions for 28 days.

[0051] Preferably, in steps (3)-(5), the low speed referred to is 108 r / min, the medium speed referred to is 188 r / min, and the high speed referred to is 403 r / min.

[0052] Preferably, place the geopolymer test blocks cured for 28 days in a high-temperature test furnace, and set the heating rate to 10°C / min. The target temperatures for the high-temperature test are 400°C, 800°C, and 1000°C. After reaching the target temperature, keep it warm for one hour, and wait for the test blocks to cool naturally before performing the three-point bending test.

[0053] Comparative Example 1

[0054] In this comparative example, the fiber volume fraction of the geopolymer selected is 0%.

[0055] The geopolymer includes the following raw materials: by mass fraction, 196 parts of metakaolin, 457 parts of fly ash, 252 parts of potassium silicate solution, 100 parts of water, and 1762 parts of corundum aggregate. The preparation method of the geopolymer is as follows:

[0056] (1) Prepare a potassium silicate solution with a modulus of 1.0, and start the test after standing for 24 hours.

[0057] (2) Weigh metakaolin, fly ash, potassium silicate solution, water, and corundum aggregate according to the mix ratio.

[0058] (3) After pouring the powder materials into the mixing pot, turn on the low-speed mode. After the two powder materials are stirred evenly, slowly pour in the potassium silicate and water. After the powder is moistened, turn on the medium-speed stirring for 1-2 minutes, and then turn on the high-speed stirring for 1-2 minutes.

[0059] (4) Adjust the mixer to low speed, slowly add the corundum aggregate, stir at medium speed for 1-2 minutes, and then turn on the high-speed stirring for 2-3 minutes.

[0060] (5) Pour the obtained geopolymer composite material into a mold of 40mm×40mm×160mm, vibrate it until it is dense, remove the mold after 24 hours under the condition of covering with a plastic mold, and cure it under standard conditions for 28 days.

[0061] Preferably, in steps (3) and (4), the low speed referred to is 108 r / min, the medium speed referred to is 188 r / min, and the high speed referred to is 403 r / min.

[0062] Preferably, place the geopolymer specimens cured for 28 days in a high-temperature test furnace and set the heating rate at 10 °C / min. The target temperatures for the high-temperature tests are 400 °C, 800 °C, and 1000 °C. After reaching the target temperature, hold for one hour, and wait for the specimens to cool naturally before performing a three-point bending test.

[0063] From Figure 1 the flexural strength, it can be seen that for the ternary hybrid fiber geopolymer of the present invention, the flexural strength is significantly enhanced at room temperature and after high-temperature exposure below 1000 °C. Especially after exposure to 400 °C, the flexural strength is as high as 30 MPa. After exposure to 1000 °C, the flexural strengths of the geopolymer with ternary fibers, without ternary fibers, and with binary fibers are comparable, indicating that the ternary hybrid fiber geopolymer of the present invention has a more significant flexural strength advantage after high-temperature exposure at 800 °C and below.

[0064] From Figures 2 - 4 the load-displacement curve, it can be seen that for the ternary hybrid fiber geopolymer of the present invention, the peak load is significantly enhanced at room temperature and after high-temperature exposure below 1000 °C. For the geopolymer of Example 1 after exposure to 400 °C, the peak load reaches 14 kN, and for the geopolymer of Example 2 after exposure to 400 °C, the maximum load it can withstand reaches 13 kN. At room temperature (20 °C) and after exposure to 200 °C, the displacements corresponding to the peak loads of the ternary hybrid fiber geopolymer of the present invention also increase significantly, indicating that the material has good toughness and excellent ductility.

[0065] The above is only the preferred embodiment of the present invention. It should be noted that the above preferred embodiment should not be regarded as a limitation of the present invention. The protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A ternary hybrid fiber-reinforced geopolymer applicable to fire-resistant flexural members, characterized in that, The geopolymer includes the following raw material components: metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, steel fiber, and basalt fiber.

2. The ternary hybrid fiber-reinforced geopolymer applicable to refractory flexural members according to claim 1, characterized in that, The geopolymer includes the following raw material components by weight: 196 parts of metakaolin, 457 parts of fly ash, 252 parts of potassium silicate solution, 100 parts of water, 1762 parts of corundum aggregate, 33 parts of wollastonite fiber, 79 parts of steel fiber, and 13 - 27 parts of basalt fiber.

3. The ternary hybrid fiber-reinforced geopolymer applicable to a refractory flexural member according to claim 2, wherein The volume fraction of the basalt fiber is 0.5 - 1%.

4. The ternary hybrid fiber-reinforced geopolymer applicable to refractory flexural members according to claim 3, characterized in that, The potassium silicate solution is prepared by adjusting the original modulus of 2.4 to a modulus of 1.0 with potassium hydroxide solid powder.

5. The ternary hybrid fiber-reinforced geopolymer applicable to a fire-resistant bending member according to claim 1, wherein The corundum aggregate includes four particle size ranges of 2.36 - 1.18 mm, 1.18 - 0.6 mm, 0.6 - 0.18 mm, and 0.18 - 0.125 mm, and the mass ratio is 4:3:2:

1.

6. The ternary hybrid fiber-reinforced geopolymer applicable to refractory flexural members according to claim 1, wherein, The wollastonite fiber D 50 is 4.21 μm, and the aspect ratio is 15-20:

1.

7. The ternary hybrid fiber-reinforced geopolymer applicable to a refractory flexural member according to claim 1, wherein The basalt fiber is chopped basalt fiber with a fiber length of 12 mm and a tensile strength of 2100 MPa.

8. The ternary hybrid fiber-reinforced geopolymer applicable to refractory flexural members according to claim 1, characterized in that, The steel fiber is copper - plated steel fiber with a fiber length of 13 mm, a diameter of 0.2 mm, and a tensile strength of 2850 MPa.

9. A preparation method of a ternary hybrid fiber-reinforced geopolymer applicable to a refractory bending member as described in any one of claims 1-8, characterized in that, The preparation method includes: (1) Prepare a potassium silicate solution with a modulus of 1.0, and start the test after standing for 24 h; (2) Weigh metakaolin, fly ash, potassium silicate solution, water, corundum aggregate, wollastonite fiber, basalt fiber, and steel fiber according to the mix ratio; (3) Pour metakaolin and fly ash into the mixing pot, start in the low - speed mode, after the two powders are evenly mixed, slowly pour in the potassium silicate solution and water, start medium - speed stirring for 1 - 2 min after the powder is moistened, and start high - speed stirring for 1 - 2 min; (4) Adjust the mixer to low - speed, slowly add the corundum aggregate, stir at medium - speed for 1 - 2 min, and start high - speed stirring for 1 - 2 min; (5) Adjust the mixer to low - speed, slowly add the fiber materials, and stir at high - speed for 1 - 3 min; (6) Cure the obtained geopolymer composite material to obtain a ternary hybrid fiber - reinforced geopolymer.

10. The preparation method of the ternary hybrid fiber reinforced geopolymer applicable to refractory flexural members according to claim 9, characterized in that, In steps (3) - (5), the low - speed is 105 - 110 r / min, the medium - speed is 185 - 190 r / min, and the high - speed is 400 - 405 r / min.

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