Optimized graded high temperature reinforced corundum aggregate geopolymer mortar and preparation method thereof

Abstract

The application discloses a kind of high-temperature reinforced corundum aggregate geopolymer mortar of optimized gradation and preparation method thereof, and geopolymer mortar includes the following raw materials according to weight fraction: metakaolin 172-193 parts, fly ash 400-450 parts, potassium water glass solution 221-249 parts, corundum aggregate 1925-2142 parts and water 76-86 parts.Method includes: metakaolin, fly ash, potassium water glass solution, corundum aggregate of different particle size range and water are weighed according to mixing ratio and placed for standby; metakaolin and fly ash are added into stirring pot together, and powder is uniformly mixed under low-speed stirring, slowly add potassium water glass solution and mixing water, first medium-speed stirring is adjusted to high-speed stirring, and mixture is obtained; corundum aggregate of different particle size range is slowly added into mixture in turn, and high-speed stirring is continued, and geopolymer mortar is obtained.The application uses optimized gradation corundum as the replacement aggregate of natural sand, greatly improves the high-temperature resistance of geopolymer mortar, so that it has higher normal-temperature mechanical property and excellent high-temperature post-mechanical property.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation and its preparation method. Background Technology

[0002] Fire is a highly frequent, destructive, and unpredictable disaster, and its frequency has been increasing in recent years. With rapid urbanization and increasing building density, the fire resistance of buildings has become a critical issue. Fires can occur due to various reasons (such as natural events or human activity), often causing severe damage to building structures or even collapse, resulting in significant casualties and economic losses. Therefore, fire safety is a crucial consideration in building engineering. Building materials are essential for structural fire safety, and research on the fire resistance of building materials has always been an important research direction in the field of fire resistance and disaster prevention and mitigation in building structures.

[0003] Geopolymers are amorphous, three-dimensional network inorganic polymers formed from aluminosilicate materials as precursors through a process of "dissolution-monomer reconstruction-condensation" under the action of an alkaline activator. Compared to ordinary silicate cement-based concrete, geopolymers exhibit better high-temperature resistance, attributed to the superior thermal stability of their three-dimensional aluminosilicate structure. However, thermal incompatibility at high temperatures is a major cause of strength reduction in geopolymer mortar. This thermal incompatibility is primarily caused by two factors: first, the existence of an uneven temperature field within the geopolymer mortar, with temperature gradients causing displacement incompatibility between the exterior and interior; second, the different coefficients of thermal expansion of the components, leading to aggregate expansion and mortar shrinkage at high temperatures, which disrupt the internal structure of the mortar. This displacement incompatibility promotes crack development, resulting in a decrease in the strength of the geopolymer mortar. The extent of the damage depends on the coefficient of thermal expansion of the aggregates used, the degree of mortar shrinkage, and the ductility of the mortar. Natural sand is the most commonly used aggregate, but quartz aggregates have a high coefficient of thermal expansion. In particular, when the temperature approaches 573℃ and an α-β phase transformation occurs, quartz expands rapidly, which can damage the mortar. Therefore, finding an aggregate with excellent mechanical properties at high temperatures and a smaller difference in thermal deformation compared to geopolymers is key to improving the high-temperature resistance of geopolymer mortars.

[0004] Furthermore, the volume fraction and particle size distribution of aggregates in geopolymer mortars significantly influence their behavior at high temperatures. Current research on the high-temperature performance of geopolymer mortars largely focuses on the impact of different aggregate types on thermal incompatibility. These studies primarily aim to mitigate thermal incompatibility by selecting different aggregates to improve the overall high-temperature resistance of geopolymer mortars. However, there are limitations in the comprehensive study of the influence of aggregate parameters on the high-temperature resistance of geopolymer mortars, which may restrict a deeper understanding of the evolution of the microstructure of geopolymer mortars under high-temperature conditions.

[0005] Corundum possesses excellent mechanical properties and refractoriness, such as high hardness and specific gravity, excellent thermal stability, low coefficient of thermal expansion, and good chemical stability, making it one of the most widely used materials for high-temperature furnace working linings. However, to date, there has been no detailed study on the influence of corundum on the high-temperature resistance of geopolymer mortars. Furthermore, the effects of corundum aggregate volume fraction and particle size distribution on thermal incompatibility and high-temperature resistance in existing technologies have not been adequately investigated.

[0006] Using corundum as a substitute for natural sand in geopolymer mortar can not only effectively alleviate the thermal incompatibility within the mortar and reduce crack formation, but also improve its high-temperature resistance and increase its compressive strength after high temperatures. However, existing studies on the high-temperature resistance of geopolymer mortar often use fixed particle size or partially continuous gradation when replacing natural sand, lacking research on different aggregate particle size gradations. Summary of the Invention

[0007] In view of the technical problems existing in the prior art, the purpose of this invention is to propose a high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation and its preparation method. By using optimized gradation corundum as a substitute for natural sand aggregate, the high-temperature resistance of the geopolymer mortar is greatly improved, giving it high room temperature mechanical properties and excellent high-temperature mechanical properties.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] This invention provides a high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation. The geopolymer mortar comprises the following raw materials by weight: 172-193 parts metakaolin, 400-450 parts fly ash, 221-249 parts potassium silicate solution, 1925-2142 parts corundum aggregate, and 76-86 parts water.

[0010] As a further optimization of the present invention, the geopolymer mortar comprises the following raw materials by weight: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1925 parts corundum aggregate, and 86 parts water, wherein the volume fraction of the corundum aggregate is 49.2%.

[0011] As a further optimization of the present invention, the corundum aggregate comprises the following raw materials with different particle size ranges in parts by weight: 192-536 parts of corundum aggregate with a particle size of 2.36-1.18 mm, 385-750 parts of corundum aggregate with a particle size of 1.18-0.6 mm, 577-643 parts of corundum aggregate with a particle size of 0.6-0.18 mm, and 192-770 parts of corundum aggregate with a particle size of 0.18-0.08 mm.

[0012] As a further optimization of the present invention, the corundum aggregate comprises the following raw materials with different particle size ranges in parts by weight: 192 parts of 2.36-1.18mm corundum aggregate, 385 parts of 1.18-0.6mm corundum aggregate, 577 parts of 0.6-0.18mm corundum aggregate, and 770 parts of 0.18-0.08mm corundum aggregate.

[0013] As a further optimization of the present invention, the fineness modulus of the corundum aggregate is 1.55.

[0014] As a further optimization of the present invention, the potassium silicate has a modulus of 1.0 and a concentration of 49%.

[0015] This invention also provides a method for preparing high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation, comprising the following steps:

[0016] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0017] (2) Add metakaolin and fly ash together to a mixing pot, mix the powder evenly under low speed, slowly add potassium glass solution and mixing water, first mix at medium speed and then adjust to high speed to obtain a mixture.

[0018] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) slowly and continue to stir at high speed to obtain geopolymer mortar.

[0019] As a further optimization of the present invention, in step (2), the speed of low-speed stirring is 100-110 r / min and the stirring time is 1-2 min.

[0020] As a further optimization of the present invention, in step (2), the speed of medium-speed stirring is 180-190 r / min, and the stirring time is 0.5-1 min.

[0021] As a further optimization of the present invention, in step (2), the speed of high-speed stirring is 400-405 r / min and the stirring time is 3-5 min; in step (3), the speed of high-speed stirring is 400-405 r / min and the stirring time is 2-3 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 optimized gradation high-temperature reinforced corundum aggregate geopolymer mortar prepared by this invention has excellent mechanical properties and high-temperature resistance. Its compressive strength can reach more than 55 MPa after 28 days at room temperature, and more than 80 MPa after exposure to high temperature of 1000℃. Furthermore, the compressive strength of the geopolymer mortar with further optimized gradation (1.55 gradation) continues to increase with temperature. After exposure to high temperature of 1000℃, the highest compressive strength can reach 148.5 MPa, which is 177% and 442% higher than that of the other two gradation designs (2.55 gradation and 3.98 gradation), respectively, and 741% higher than that of the geopolymer mortar prepared using ISO standard sand.

[0024] (2) This invention utilizes corundum aggregate to replace natural sand as the aggregate in geopolymer mortar. This not only effectively alleviates the internal thermal incompatibility of the mortar and reduces crack formation, but also improves its high-temperature resistance and increases the compressive strength of the geopolymer mortar after high temperatures. Furthermore, by optimizing the gradation design of the corundum aggregate, the internal thermal incompatibility of the mortar can be further improved, significantly enhancing the high-temperature resistance of the geopolymer mortar and enabling it to possess ultra-high compressive strength after high temperatures. Simultaneously, its excellent mechanical properties and high-temperature resistance make it suitable for a wider range of applications. Attached Figure Description

[0025] Figure 1 The flowability of the comparative examples and embodiments of the present invention is shown.

[0026] Figure 2 A comparison chart of the compressive strength of geopolymer mortars with different aggregate volume fractions after high-temperature exposure.

[0027] Figure 3 A comparison of the compressive strength of geopolymer mortars with different aggregate particle size distributions after high-temperature exposure.

[0028] Figure 4 This is a comparison chart of the compressive strength of the comparative examples and embodiments of the present invention after high-temperature exposure. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, these should not be construed as limiting the present invention and are merely examples.

[0030] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0031] Example 1

[0032] In this example, corundum aggregate is selected as the aggregate for the geopolymer mortar. The aggregate volume fraction is 49.2%, and a gradation design with a fineness modulus of 1.55 is adopted.

[0033] The main components, by weight, are: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1925 parts corundum aggregate (0 parts of 4.75–2.36 mm corundum aggregate, 192 parts of 2.36–1.18 mm corundum aggregate, 385 parts of 1.18–0.6 mm corundum aggregate, 577 parts of 0.6–0.18 mm corundum aggregate, and 770 parts of 0.18–0.08 mm corundum aggregate), and 86 parts water.

[0034] The preparation method of the geopolymer mortar is as follows:

[0035] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0036] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0037] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) in sequence and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain geopolymer mortar.

[0038] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0039] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0040] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0041] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0042] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0043] The flowability of the geopolymer mortar is 180 mm.

[0044] The geopolymer mortar has a compressive strength of 54.7 MPa at room temperature over 28 days.

[0045] The compressive strength of the geopolymer mortar after being heated to 200℃ is 71.3MPa.

[0046] The compressive strength of the geopolymer mortar after being heated to 400℃ is 85.6MPa.

[0047] The compressive strength of the geopolymer mortar after being heated to 600℃ is 90.8MPa.

[0048] The compressive strength of the geopolymer mortar after being heated to 800℃ is 97.0MPa.

[0049] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 148.5MPa.

[0050] Example 2

[0051] In this example, corundum aggregate is selected as the aggregate for the geopolymer mortar. The aggregate volume fraction is 49.2%, and a gradation design with a fineness modulus of 2.55 is adopted.

[0052] The main components, by weight, are: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1925 parts corundum aggregate (0 parts of 4.75–2.36 mm corundum aggregate, 481 parts of 2.36–1.18 mm corundum aggregate, 674 parts of 1.18–0.6 mm corundum aggregate, 577 parts of 0.6–0.18 mm corundum aggregate, and 192 parts of 0.18–0.08 mm corundum aggregate), and 86 parts water.

[0053] The preparation method of the geopolymer mortar is as follows:

[0054] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0055] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0056] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) in sequence and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain geopolymer mortar.

[0057] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0058] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0059] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0060] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0061] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0062] The flowability of the geopolymer mortar is 205 mm.

[0063] The geopolymer mortar has a compressive strength of 60.0 MPa at room temperature over 28 days.

[0064] The compressive strength of the geopolymer mortar after being heated to 200℃ is 76.1MPa.

[0065] The compressive strength of the geopolymer mortar after being heated to 400℃ is 86.2MPa.

[0066] The compressive strength of the geopolymer mortar after being heated to 600℃ is 92.6MPa.

[0067] The compressive strength of the geopolymer mortar after being heated to 800℃ is 92.3MPa.

[0068] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 83.7MPa.

[0069] Example 3

[0070] In this example, corundum aggregate is selected as the aggregate for the geopolymer mortar. The aggregate volume fraction is 54.8%, and a gradation design with a fineness modulus of 2.55 is adopted.

[0071] The main components, by weight, are: 172 parts metakaolin, 400 parts fly ash, 221 parts potassium silicate solution, 2142 parts corundum aggregate (0 parts of 4.75–2.36 mm corundum aggregate, 536 parts of 2.36–1.18 mm corundum aggregate, 750 parts of 1.18–0.6 mm corundum aggregate, 643 parts of 0.6–0.18 mm corundum aggregate, and 214 parts of 0.18–0.08 mm corundum aggregate), and 76 parts water.

[0072] The preparation method of the geopolymer mortar is as follows:

[0073] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0074] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0075] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) in sequence and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain geopolymer mortar.

[0076] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0077] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0078] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0079] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0080] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0081] The flowability of the geopolymer mortar is 165 mm.

[0082] The geopolymer mortar has a 28-day compressive strength of 62.5 MPa at room temperature.

[0083] The compressive strength of the geopolymer mortar after being heated to 200℃ is 78.7MPa.

[0084] The compressive strength of the geopolymer mortar after being heated to 400℃ is 87.1MPa.

[0085] The compressive strength of the geopolymer mortar after being heated to 600℃ is 94.7MPa.

[0086] The compressive strength of the geopolymer mortar after being heated to 800℃ is 96.1MPa.

[0087] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 93.6MPa.

[0088] Comparative Example 1

[0089] In this comparative example, the aggregate in the geopolymer mortar is Chinese ISO standard sand, with an aggregate volume fraction of 49.2% and a particle size distribution that conforms to the national standard "Sand for Construction" (GB / T 14684-2022).

[0090] The main components, by mass, are: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1301 parts Chinese ISO standard sand, and 86 parts water.

[0091] The preparation method of the geopolymer mortar is as follows:

[0092] (1) Weigh out the metakaolin, fly ash, potassium silicate solution, Chinese ISO standard sand and water according to the mixing ratio and set aside for later use.

[0093] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0094] (3) Slowly add the Chinese ISO standard sand to the mixture in step (2), and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain the geopolymer mortar.

[0095] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0096] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0097] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0098] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0099] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0100] The flowability of the geopolymer mortar is 210 mm.

[0101] The compressive strength of the geopolymer mortar at room temperature for 28 days is 46.3 MPa.

[0102] The compressive strength of the geopolymer mortar after being heated to 200℃ is 60.1MPa.

[0103] The compressive strength of the geopolymer mortar after being heated to 400℃ is 63.1MPa.

[0104] The compressive strength of the geopolymer mortar after being heated to 600℃ is 52.8MPa.

[0105] The compressive strength of the geopolymer mortar after being heated to 800℃ is 44.7MPa.

[0106] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 20.0MPa.

[0107] Comparative Example 2

[0108] In this example, corundum aggregate is selected as the aggregate for the geopolymer mortar. The aggregate volume fraction is 42.1%, and a gradation design with a fineness modulus of 2.55 is adopted.

[0109] The main components, by weight, are: 220 parts metakaolin, 513 parts fly ash, 284 parts potassium silicate solution, 1646 parts corundum aggregate (0 parts of 4.75–2.36 mm corundum aggregate, 412 parts of 2.36–1.18 mm corundum aggregate, 576 parts of 1.18–0.6 mm corundum aggregate, 494 parts of 0.6–0.18 mm corundum aggregate, and 165 parts of 0.18–0.08 mm corundum aggregate), and 98 parts water.

[0110] The preparation method of the geopolymer mortar is as follows:

[0111] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0112] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0113] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) in sequence and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain geopolymer mortar.

[0114] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0115] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0116] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0117] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0118] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0119] The flowability of the geopolymer mortar is 230 mm.

[0120] The geopolymer mortar has a compressive strength of 53.8 MPa at room temperature over 28 days.

[0121] The compressive strength of the geopolymer mortar after being heated to 200℃ is 65.3MPa.

[0122] The compressive strength of the geopolymer mortar after being heated to 400℃ is 72.3MPa.

[0123] The compressive strength of the geopolymer mortar after being heated to 600℃ is 81.8MPa.

[0124] The compressive strength of the geopolymer mortar after being heated to 800℃ is 82.1MPa.

[0125] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 65.9MPa.

[0126] Comparative Example 3

[0127] In this example, corundum aggregate is selected as the aggregate for the geopolymer mortar. The aggregate volume fraction is 49.2%, and a gradation design with a fineness modulus of 3.98 is adopted.

[0128] The main components, by weight, are: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1925 parts corundum aggregate (770 parts of 4.75–2.36 mm corundum aggregate, 577 parts of 2.36–1.18 mm corundum aggregate, 385 parts of 1.18–0.6 mm corundum aggregate, 192 parts of 0.6–0.18 mm corundum aggregate, and 0 parts of 0.18–0.08 mm corundum aggregate), and 86 parts water.

[0129] The preparation method of the geopolymer mortar is as follows:

[0130] (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mixing ratio and set aside for later use.

[0131] (2) Add metakaolin and fly ash together into a mixing pot. Mix the powder evenly by stirring at a low speed of 108 r / min. Slowly add potassium glass solution and mixing water. Stir at a medium speed of 188 r / min for 0.5 min, then adjust to a high speed of 403 r / min for 3-5 min to obtain the mixture.

[0132] (3) Add corundum aggregates of different particle size ranges to the mixture in step (2) in sequence and continue to stir at a high speed of 403r / min for 2-3 minutes to obtain geopolymer mortar.

[0133] (4) Cast the test specimens, and after demolding and standard curing, the geopolymer mortar of the present invention is obtained.

[0134] After the geopolymer mortar is poured, it is cured at room temperature for 1 day, then demolded and placed in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days until the test age.

[0135] The test specimens for the compressive strength test of the geopolymer mortar before and after high temperature were 40mm*40mm*40mm cubes.

[0136] The fluidity was determined according to the "Method for Determination of Flowability of Cement Mortar" (GB / T2419—2005), using an NLD-3 type cement mortar fluidity tester. The average value of the readings in two perpendicular directions was taken as the final result of the fluidity.

[0137] The high-temperature exposure test used an Anhui Beiyike MF-1200C box furnace. The test consisted of five target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. After curing the test blocks for 28 days, they were removed and placed in the furnace. The temperature was increased to the target temperature at a rate of 10℃ / min, and held at that temperature for 1 hour. Then, the furnace was turned off and the exhaust vent was opened. After the test blocks cooled to room temperature, they were removed and subjected to compressive strength testing.

[0138] The flowability of the geopolymer mortar is 220 mm.

[0139] The compressive strength of the geopolymer mortar at room temperature for 28 days is 63.9 MPa.

[0140] The compressive strength of the geopolymer mortar after being heated to 200℃ is 76.9MPa.

[0141] The compressive strength of the geopolymer mortar after being heated to 400℃ is 75.7MPa.

[0142] The compressive strength of the geopolymer mortar after being heated to 600℃ is 73.6MPa.

[0143] The compressive strength of the geopolymer mortar after being heated to 800℃ is 60.0MPa.

[0144] The compressive strength of the geopolymer mortar after being heated to 1000℃ is 33.6MPa.

[0145] This invention illustrates the gradation design characteristics of corundum aggregates through embodiments and comparative examples:

[0146] from Figure 1 It is known that both increasing the aggregate volume fraction and decreasing the fineness modulus lead to a significant decrease in the flowability of the geopolymer mortar. Examples 2 and 3 have similar performance, but Example 2 exhibits better flowability than Example 3. Therefore, the volume fraction of Example 2 was selected for further optimization of the gradation design.

[0147] from Figure 2 It can be seen that the compressive strength of geopolymer mortar increases with the increase of aggregate volume fraction at various temperatures. When the aggregate volume fraction is small, increasing the volume fraction has a more significant effect on improving compressive strength. However, when the aggregate volume fraction is too large, the poor fluidity is not conducive to compaction and limits the development of compressive strength of geopolymer mortar.

[0148] from Figure 3 It can be seen that the aggregate particle size distribution greatly affects the strength change of geopolymer mortar at high temperature. Appropriately reducing the fineness modulus can significantly improve the influence of thermal incompatibility on the compressive strength of geopolymer mortar after high temperature exposure, thereby enhancing the compressive strength of geopolymer mortar after high temperature exposure.

[0149] from Figure 4 It can be seen that Comparative Example 1 is a geopolymer mortar prepared using ISO standard sand. Example 2 has the same aggregate volume fraction as Comparative Example 1, and its fineness modulus of 2.55 is close to that of ISO standard sand. Using corundum instead of natural sand to prepare the geopolymer mortar improves the compressive strength of the geopolymer mortar across the entire temperature range. Example 1 employs a further optimized aggregate gradation design, and the compressive strength of the geopolymer mortar continues to increase with rising temperature, exhibiting an ultra-high compressive strength of 148.5 MPa after exposure to 1000℃. After exposure to 1000℃, the compressive strength is 177% and 442% of that of Example 2 and Comparative Example 3, respectively.

[0150] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation, characterized in that, The geopolymer mortar comprises the following raw materials by weight: 172-193 parts metakaolin, 400-450 parts fly ash, 221-249 parts potassium silicate solution, 1925-2142 parts corundum aggregate, and 76-86 parts water; the corundum aggregate comprises the following raw materials with different particle sizes by weight: 192-536 parts corundum aggregate with a particle size of 2.36-1.18 mm, 385-750 parts corundum aggregate with a particle size of 1.18-0.6 mm, 577-643 parts corundum aggregate with a particle size of 0.6-0.18 mm, and 192-770 parts corundum aggregate with a particle size of 0.18-0.08 mm.

2. The optimized gradation high-temperature reinforced corundum aggregate geopolymer mortar according to claim 1, characterized in that, The geopolymer mortar comprises the following raw materials by weight: 193 parts metakaolin, 450 parts fly ash, 249 parts potassium silicate solution, 1925 parts corundum aggregate, and 86 parts water, wherein the volume fraction of the corundum aggregate is 49.2%.

3. The optimized gradation high-temperature reinforced corundum aggregate geopolymer mortar according to claim 1, characterized in that, The corundum aggregate comprises the following raw materials with different particle size ranges by weight: 192 parts of 2.36~1.18mm corundum aggregate, 385 parts of 1.18~0.6mm corundum aggregate, 577 parts of 0.6~0.18mm corundum aggregate, and 770 parts of 0.18~0.08mm corundum aggregate.

4. The optimized gradation high-temperature reinforced corundum aggregate geopolymer mortar according to claim 1, characterized in that, The potassium silicate has a modulus of 1.0 and a concentration of 49%.

5. A method for preparing high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Weigh out the metakaolin, fly ash, potassium water glass solution, corundum aggregate of different particle size range and water according to the mixing ratio and set aside for later use; (2) Add metakaolin and fly ash together to a mixing pot, mix the powder evenly under low speed, slowly add potassium glass solution and mixing water, first mix at medium speed and then adjust to high speed to obtain a mixture; (3) Add corundum aggregates of different particle size ranges slowly to the mixture in step (2) and continue to stir at high speed to obtain geopolymer mortar.

6. The method for preparing high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation according to claim 5, characterized in that, In step (2), the speed of low-speed stirring is 100~110 r / min, and the stirring time is 1-2 min.

7. The method for preparing high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation according to claim 5, characterized in that, In step (2), the speed of the medium-speed stirring is 180~190 r / min, and the stirring time is 0.5-1 min.

8. The method for preparing high-temperature reinforced corundum aggregate geopolymer mortar with optimized gradation according to claim 5, characterized in that, In step (2), the speed of high-speed stirring is 400~405 r / min and the stirring time is 3-5 min; in step (3), the speed of high-speed stirring is 400~405 r / min and the stirring time is 2-3 min.

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