Gradation-optimized high-temperature reinforced corundum aggregate geopolymer mortar and preparation method thereof

Abstract

The invention discloses graded high-temperature reinforced corundum aggregate geopolymer mortar and a preparation method thereof. The geopolymer mortar is prepared from the following raw materials in parts by weight: 172 to 193 parts of metakaolin, 400 to 450 parts of fly ash, 221 to 249 parts of potash water glass solution, 1925 to 2142 parts of corundum aggregate and 76 to 86 parts of water. The method comprises the following steps: weighing metakaolin, fly ash, a potash water glass solution, corundum aggregates with different particle size ranges and water according to a mixing ratio, and standing for later use; adding metakaolin and fly ash into a stirring pot together, uniformly mixing the powder under low-speed stirring, slowly adding a potash water glass solution and mixing water, stirring at a medium speed and then stirring at a high speed to obtain a mixture; and sequentially and slowly adding corundum aggregates with different particle size ranges into the mixture, and continuously stirring at a high speed to obtain the geopolymer mortar. According to the invention, the optimally-graded corundum is used as a substitute aggregate of natural sand, so that the high-temperature resistance of the geopolymer mortar is greatly improved, and the geopolymer mortar has relatively high normal-temperature mechanical properties and excellent mechanical properties after high temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to an optimized-gradation high-temperature reinforced corundum aggregate geopolymer mortar and a preparation method thereof. Background Art

[0002] Fire is a frequent, destructive and accidental disaster today. The frequency of fire has been increasing in recent years. With the rapid advancement of modern urbanization and the increasing building density, the fire resistance of buildings has become a critical issue. Fires may occur due to various reasons (such as natural events or human factors), often causing serious damage to or even collapse of building structures, often resulting in significant casualties and economic losses. Therefore, fire safety is also an important consideration in construction projects. Building materials are crucial to the fire safety of structures. 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 of building structures.

[0003] Geopolymer is an inorganic polymer with an amorphous three-dimensional network structure formed by "dissolution-monomer reconstruction-condensation" under the action of alkaline activators using silicon-aluminum materials as precursors. Compared with ordinary Portland cement-based concrete, geopolymer exhibits better high temperature resistance, which is attributed to the good thermal stability of its three-dimensional aluminosilicate structure. However, thermal incompatibility at high temperature is a major reason for the decrease in strength of geopolymer mortar. Thermal incompatibility is mainly caused by two aspects. First, there is an uneven temperature field inside the geopolymer mortar, and the temperature gradient causes the displacement incompatibility between the outside and inside of the geopolymer mortar; second, the thermal expansion coefficients of different components are different. At high temperatures, the expansion of aggregates and the contraction of slurry destroy the internal structure of the mortar. The displacement incompatibility between the two promotes the development of cracks, resulting in a decrease in the strength of geopolymer mortar. The magnitude of the damage depends on the thermal expansion coefficient of the aggregate used, the degree of contraction of the slurry, and the ductility of the slurry. Natural sand is the most commonly used aggregate, but quartz aggregate has a high thermal expansion coefficient, especially when its temperature approaches 573℃, α-β phase transition occurs, quartz will expand rapidly, thus damaging the mortar. Therefore, finding an aggregate with excellent mechanical properties at high temperature and small difference in thermal deformation with geopolymer is the key to improving the high temperature resistance of geopolymer mortar.

[0004] In addition, the volume fraction and particle size gradation of aggregates in geopolymer mortar also have a significant impact on its behavior at high temperatures. At present, most of the studies on the performance of geopolymer mortar under high temperature conditions focus on the effect of different aggregate types on thermal incompatibility. These studies mainly alleviate the thermal incompatibility problem by selecting different aggregates to improve the overall high temperature resistance of geopolymer mortar. There are certain limitations in the comprehensive study of the effect of aggregate parameters on the high temperature resistance of geopolymer mortar, which may limit the in-depth understanding of the evolution of the microstructure of geopolymer mortar under high temperature conditions.

[0005] Corundum has excellent mechanical properties and fire resistance, such as high hardness and specific gravity, excellent thermal stability, low thermal expansion coefficient, good chemical stability, etc. It is one of the most widely used materials for high-temperature furnace working linings. However, so far, there has been no detailed study on the effect of corundum on the high-temperature resistance of geopolymer mortar. In addition, the influence of corundum aggregate volume fraction and particle size gradation on thermal incompatibility and high-temperature resistance has not been fully studied in the prior art.

[0006] Using corundum as a substitute for natural sand in geopolymer mortar can not only effectively alleviate the thermal incompatibility inside the mortar and reduce the occurrence of cracks, but also improve the high temperature resistance and increase the compressive strength of the geopolymer mortar after high temperature. However, in the existing research on the high temperature resistance of geopolymer mortar, fixed particle size or partially continuous grading is often used when replacing natural sand, and there is a lack of research on the grading of different aggregate particle sizes. Summary of the invention

[0007] In view of the technical problems existing in the prior art, the purpose of the present invention is to propose a high-temperature reinforced corundum aggregate geopolymer mortar with optimized grading and a preparation method thereof. The use of optimized graded corundum as an alternative aggregate to natural sand greatly improves the high temperature resistance of the geopolymer mortar, so that it has higher mechanical properties at room temperature and excellent mechanical properties after high temperature.

[0008] To achieve the above object, the present invention is implemented by the following technical solutions:

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

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

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

[0012] As a further optimization scheme of the present invention, the corundum aggregate includes the following raw materials in different particle size ranges by weight: 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.

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

[0014] As a further optimization solution of the present invention, the modulus of the potassium water glass is 1.0 and the concentration is 49%.

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

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

[0017] (2) adding metakaolin and fly ash into a stirring pot, mixing the powders uniformly under low-speed stirring, slowly adding potassium water glass solution and mixing water, stirring at medium speed first and then adjusting to high-speed stirring to obtain a mixture;

[0018] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and stirred at a high speed to obtain geopolymer mortar.

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

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

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

[0024] (2) The present invention utilizes corundum aggregate to replace natural sand as the aggregate of geopolymer mortar, which can not only effectively alleviate the thermal incompatibility inside the mortar and reduce the generation of cracks, but also improve the high temperature resistance and increase the compressive strength of the geopolymer mortar after high temperature. In addition, by optimizing the grading design of corundum aggregate, the thermal incompatibility inside the mortar can be further improved, and the high temperature resistance of the geopolymer mortar can be greatly improved, so that it has ultra-high compressive strength after high temperature. At the same time, the excellent mechanical properties and high temperature resistance make it have more application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the fluidity of the comparative example and the example of the present invention.

[0026] Figure 2 Comparison of the compressive strength of geopolymer mortar with different aggregate volume fractions after high temperature exposure.

[0027] Figure 3 This is a comparison chart of the compressive strength of geopolymer mortar with different aggregate size gradations after high temperature exposure.

[0028] Figure 4 It is a comparison chart of the compressive strength of the comparative example and the embodiment of the present invention after high temperature exposure. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments, but it should not be understood as limiting the present invention and is only used as an example.

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

[0031] Example 1

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

[0033] Calculated by mass, the main materials include: 193 parts of metakaolin, 450 parts of fly ash, 249 parts of potassium water glass solution, 1925 parts of corundum aggregate (0 parts of 4.75-2.36mm corundum aggregate, 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) and 86 parts of water.

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

[0035] (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside.

[0036] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

[0037] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and the mixture is stirred at a high speed of 403 r / min for 2-3 min to obtain geopolymer mortar.

[0038] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0040] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0041] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0042] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

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

[0045] The geopolymer mortar has a compressive strength of 71.3 MPa after being subjected to a high temperature of 200°C.

[0046] The geopolymer mortar has a compressive strength of 85.6 MPa after being subjected to a high temperature of 400°C.

[0047] The geopolymer mortar has a compressive strength of 90.8 MPa after being subjected to a high temperature of 600°C.

[0048] The geopolymer mortar has a compressive strength of 97.0 MPa after being subjected to a high temperature of 800°C.

[0049] The geopolymer mortar has a compressive strength of 148.5 MPa after being subjected to a high temperature of 1000°C.

[0050] Example 2

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

[0052] Calculated by mass, the main materials include: 193 parts of metakaolin, 450 parts of fly ash, 249 parts of potassium water glass solution, 1925 parts of corundum aggregate (0 parts of 4.75-2.36mm corundum aggregate, 481 parts of 2.36-1.18mm corundum aggregate, 674 parts of 1.18-0.6mm corundum aggregate, 577 parts of 0.6-0.18mm corundum aggregate and 192 parts of 0.18-0.08mm corundum aggregate) and 86 parts of water.

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

[0054] (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside.

[0055] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

[0056] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and the mixture is stirred at a high speed of 403 r / min for 2-3 min to obtain geopolymer mortar.

[0057] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0059] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0060] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0061] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

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

[0064] The geopolymer mortar has a compressive strength of 76.1 MPa after being heated to 200°C.

[0065] The geopolymer mortar has a compressive strength of 86.2 MPa after being subjected to a high temperature of 400°C.

[0066] The geopolymer mortar has a compressive strength of 92.6 MPa after being subjected to a high temperature of 600°C.

[0067] The geopolymer mortar has a compressive strength of 92.3 MPa after being subjected to a high temperature of 800°C.

[0068] The geopolymer mortar has a compressive strength of 83.7 MPa after being subjected to a high temperature of 1000°C.

[0069] Example 3

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

[0071] Calculated by mass, the main materials include: 172 parts of kaolin, 400 parts of fly ash, 221 parts of potassium water glass solution, 2142 parts of corundum aggregate (0 parts of 4.75-2.36mm corundum aggregate, 536 parts of 2.36-1.18mm corundum aggregate, 750 parts of 1.18-0.6mm corundum aggregate, 643 parts of 0.6-0.18mm corundum aggregate and 214 parts of 0.18-0.08mm corundum aggregate) and 76 parts of water.

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

[0073] (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside.

[0074] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

[0075] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and the mixture is stirred at a high speed of 403 r / min for 2-3 min to obtain geopolymer mortar.

[0076] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0078] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0079] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0080] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

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

[0083] The geopolymer mortar has a compressive strength of 78.7 MPa after being subjected to a high temperature of 200°C.

[0084] The geopolymer mortar has a compressive strength of 87.1 MPa after being subjected to a high temperature of 400°C.

[0085] The geopolymer mortar has a compressive strength of 94.7 MPa after being subjected to a high temperature of 600°C.

[0086] The geopolymer mortar has a compressive strength of 96.1 MPa after being subjected to a high temperature of 800°C.

[0087] The geopolymer mortar has a compressive strength of 93.6 MPa after being subjected to a high temperature of 1000°C.

[0088] Comparative Example 1

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

[0090] Calculated by mass, the main materials include: 193 parts of kaolin, 450 parts of fly ash, 249 parts of potassium water glass solution, 1301 parts of Chinese ISO standard sand and 86 parts of water.

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

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

[0093] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

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

[0095] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0097] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0098] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0099] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

[0101] The geopolymer mortar has a 28d compressive strength of 46.3 MPa at room temperature.

[0102] The geopolymer mortar has a compressive strength of 60.1 MPa after being heated to 200°C.

[0103] The geopolymer mortar has a compressive strength of 63.1 MPa after being heated to 400°C.

[0104] The geopolymer mortar has a compressive strength of 52.8 MPa after being subjected to a high temperature of 600°C.

[0105] The geopolymer mortar has a compressive strength of 44.7 MPa after being subjected to a high temperature of 800°C.

[0106] The geopolymer mortar has a compressive strength of 20.0 MPa after being subjected to a high temperature of 1000°C.

[0107] Comparative Example 2

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

[0109] Calculated by mass, the main materials include: 220 parts of metakaolin, 513 parts of fly ash, 284 parts of potassium water glass solution, 1646 parts of corundum aggregate (0 parts of 4.75-2.36mm corundum aggregate, 412 parts of 2.36-1.18mm corundum aggregate, 576 parts of 1.18-0.6mm corundum aggregate, 494 parts of 0.6-0.18mm corundum aggregate and 165 parts of 0.18-0.08mm corundum aggregate) and 98 parts of water.

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

[0111] (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside.

[0112] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

[0113] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and the mixture is stirred at a high speed of 403 r / min for 2-3 min to obtain geopolymer mortar.

[0114] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0116] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0117] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0118] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

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

[0121] The geopolymer mortar has a compressive strength of 65.3 MPa after being subjected to a high temperature of 200°C.

[0122] The geopolymer mortar has a compressive strength of 72.3 MPa after being subjected to a high temperature of 400°C.

[0123] The geopolymer mortar has a compressive strength of 81.8 MPa after being subjected to a high temperature of 600°C.

[0124] The geopolymer mortar has a compressive strength of 82.1 MPa after being subjected to a high temperature of 800°C.

[0125] The geopolymer mortar has a compressive strength of 65.9 MPa after being subjected to a high temperature of 1000°C.

[0126] Comparative Example 3

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

[0128] Calculated by mass, the main materials include: 193 parts of metakaolin, 450 parts of fly ash, 249 parts of potassium water glass solution, 1925 parts of corundum aggregate (770 parts of 4.75-2.36mm corundum aggregate, 577 parts of 2.36-1.18mm corundum aggregate, 385 parts of 1.18-0.6mm corundum aggregate, 192 parts of 0.6-0.18mm corundum aggregate and 0 parts of 0.18-0.08mm corundum aggregate) and 86 parts of water.

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

[0130] (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside.

[0131] (2) Add kaolin and fly ash into a stirring pot, mix the powders evenly at a low speed of 108 r / min, slowly add potassium water glass solution and mixing water, stir at a medium speed of 188 r / min for 0.5 min, and then adjust to a high speed of 403 r / min for 3-5 min to obtain a mixture.

[0132] (3) Corundum aggregates of different particle size ranges are slowly added to the mixture in step (2) in sequence, and the mixture is stirred at a high speed of 403 r / min for 2-3 min to obtain geopolymer mortar.

[0133] (4) Casting the test piece, and performing standard curing after demoulding to obtain the geopolymer mortar of the present invention.

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

[0135] The size of the geopolymer mortar compressive strength test specimen before and after high temperature is a 40mm*40mm*40mm cube.

[0136] The fluidity is measured according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T2419-2005), using an NLD-3 cement mortar fluidity tester to measure the fluidity of the mortar. The average value of the readings in two vertical directions is taken as the final result of the fluidity.

[0137] The high temperature exposure test uses Anhui Beiyike MF-1200C box furnace, and the test is divided into 5 target temperatures: 200℃, 400℃, 600℃, 800℃, and 1000℃. The test block is taken out after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min. After keeping the temperature constant for 1h, the electric furnace is closed and the exhaust hole is opened. After the test block cools to room temperature, it is taken out for compressive strength test.

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

[0139] The geopolymer mortar has a 28d compressive strength of 63.9 MPa at room temperature.

[0140] The geopolymer mortar has a compressive strength of 76.9 MPa after being subjected to a high temperature of 200°C.

[0141] The geopolymer mortar has a compressive strength of 75.7 MPa after being subjected to a high temperature of 400°C.

[0142] The geopolymer mortar has a compressive strength of 73.6 MPa after being subjected to a high temperature of 600°C.

[0143] The geopolymer mortar has a compressive strength of 60.0 MPa after being subjected to a high temperature of 800°C.

[0144] The geopolymer mortar has a compressive strength of 33.6 MPa after being subjected to a high temperature of 1000°C.

[0145] The present invention illustrates the gradation design characteristics of corundum aggregate in combination with the embodiments and comparative examples:

[0146] from Figure 1 It can be seen that the increase in aggregate volume fraction and the decrease in fineness modulus will lead to a significant decrease in the fluidity of geopolymer mortar. The performance of Example 2 is similar to that of Example 3, but the fluidity of Example 2 is better than that of Example 3, so the volume fraction of Example 2 is selected to further optimize the gradation design.

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

[0148] from Figure 3 It can be seen that the aggregate particle size gradation greatly affects the strength change of geopolymer mortar at high temperature. Appropriately reducing the fineness modulus can significantly improve the effect 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.

[0149] from Figure 4 It can be seen that Comparative Example 1 is a geopolymer mortar prepared using ISO standard sand, and Example 2 has the same aggregate volume fraction as Comparative Example 1, and the fineness modulus is 2.55, which is close to ISO standard sand. The use of corundum instead of natural sand to prepare geopolymer mortar improves the compressive strength of geopolymer mortar in the entire temperature range. Example 1 adopts a further optimized aggregate grading design, and the compressive strength of the geopolymer mortar continues to increase with the increase in temperature, and after high temperature exposure at 1000°C, it shows an ultra-high compressive strength of 148.5MPa. After high temperature exposure at 1000°C, the compressive strength is 177% and 442% of that of Example 2 and Comparative Example 3, respectively.

[0150] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, 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 regarded as the protection scope 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 in parts by weight: 172-193 parts of metakaolin, 400-450 parts of fly ash, 221-249 parts of potassium water glass solution, 1925-2142 parts of corundum aggregate and 76-86 parts of water.

2. The optimized graded 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 of metakaolin, 450 parts of fly ash, 249 parts of potassium water glass solution, 1925 parts of corundum aggregate and 86 parts of water, wherein the volume fraction of the corundum aggregate is 49.2%.

3. The optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 1 or 2, characterized in that: The corundum aggregate includes the following raw materials of different particle size ranges according to weight percentage: 192-536 parts of corundum aggregate of 2.36-1.18 mm, 385-750 parts of corundum aggregate of 1.18-0.6 mm, 577-643 parts of corundum aggregate of 0.6-0.18 mm and 192-770 parts of corundum aggregate of 0.18-0.08 mm.

4. The optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 3, characterized in that: The corundum aggregate includes the following raw materials of different particle size ranges according to weight percentage: 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.

5. The optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 4, characterized in that: The fineness modulus of the corundum aggregate is 1.

55.

6. The optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 1, characterized in that: The modulus of the potassium water glass is 1.0 and the concentration is 49%.

7. A method for preparing the optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to any one of claims 1 to 6, characterized in that: The steps include: (1) Weigh kaolin, fly ash, potassium water glass solution, corundum aggregates of different particle sizes and water according to the mix ratio and set aside for later use; (2) adding metakaolin and fly ash into a stirring pot, mixing the powders uniformly under low-speed stirring, slowly adding potassium water glass solution and mixing water, stirring at medium speed first and then adjusting to high-speed stirring to obtain a mixture; (3) Slowly adding corundum aggregates of different particle size ranges into the mixture in step (2) in sequence, and continuing to stir at a high speed to obtain geopolymer mortar.

8. The method for preparing the optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 7, characterized in that: In step (2), the rotation speed of low-speed stirring is 100-110 r / min, and the stirring time is 1-2 min.

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

10. The method for preparing the optimized graded high temperature reinforced corundum aggregate geopolymer mortar according to claim 7, characterized in that: In step (2), the rotation speed of high-speed stirring is 400-405 r / min, and the stirring time is 3-5 min; in step (3), the rotation speed of high-speed stirring is 400-405 r / min, and the stirring time is 2-3 min.

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