Geopolymer-based heat-resistant cementitious material and method of making same

Abstract

The application discloses a geopolymer-based heat-resistant cementitious material and a preparation method thereof, and belongs to the technical field of heat-resistant materials. The heat-resistant cementitious material comprises the following raw materials in parts by weight: fly ash 10-20 parts, metakaolin 10-20 parts, modified rice husk ash 60-70 parts, an activator 1-5 parts and aluminate cement 5-10 parts; the metakaolin, the fly ash and the modified rice husk ash are mixed, and a ternary geopolymer is prepared through an alkaline activator; and then, the ternary geopolymer is uniformly ground with the aluminate cement to prepare a high-performance heat-resistant cementitious material. The obtained heat-resistant cementitious material has excellent fireproof and high-temperature resistant performances, can be applied to 500-700 DEG C heat-resistant concrete engineering, provides a new train of thought for developing heat-resistant cementitious materials, widens the use field of solid waste materials, and promotes the rational use of resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat-resistant materials, and particularly relates to a geopolymer-based heat-resistant cementitious material and a preparation method thereof. BACKGROUND

[0002] Heat-resistant concrete refers to special concrete capable of enduring high temperature of 200 DEG C or above for a long time and maintaining required physical and mechanical properties under high temperature. Heat-resistant concrete can be generally divided into hydraulic concrete and air-hardening heat-resistant concrete according to different cementitious materials. The ordinary portland cement heat-resistant concrete, slag portland cement heat-resistant concrete and high-alumina cement heat-resistant concrete are collectively referred to as hydraulic concrete, and the water glass heat-resistant concrete is composed of water glass, sodium fluorosilicate, ground admixture and coarse and fine aggregates in a certain mixing ratio. However, the traditional cementitious material still has many defects in the design of heat-resistant concrete, and therefore it is urgent to develop a new type of heat-resistant cementitious material.

[0003] Geopolymer is an inorganic polymer cementitious material composed of [AlO4] and [SiO4] tetrahedral structural units in a three-dimensional network structure. Geopolymer has excellent mechanical properties, high-temperature resistance and corrosion resistance. Therefore, how to prepare a geopolymer heat-resistant cementitious material on the basis of traditional heat-resistant cementitious material, which has good high-temperature resistance and compressive strength, excellent heat preservation performance, low thermal conductivity and low cost, becomes a technical problem to be solved. SUMMARY

[0004] The application aims to provide a geopolymer-based heat-resistant cementitious material and a preparation method thereof, which have good high-temperature resistance and compressive strength, excellent heat preservation performance, low thermal conductivity and low cost, and can realize effective comprehensive utilization of solid waste residues and agricultural waste.

[0005] To achieve the above-mentioned purpose, the technical scheme is as follows:

[0006] The application provides a geopolymer-based heat-resistant cementitious material, which comprises the following raw materials in parts by weight:

[0007] fly ash 10-20 parts, metakaolin 10-20 parts, modified rice husk ash 60-70 parts, alkali activator 1-5 parts and aluminate cement 5-10 parts;

[0008] The modified rice husk ash is obtained by mixing and calcining carbonization of rice husk ash and carbon fibers, and then soaking the white rice husk ash powder in hydrochloric acid to obtain a white rice husk ash powder. The emulsifying suspension is prepared by mixing epoxy resin and emulsifier. The white rice husk ash powder and silane coupling agent are added to the emulsifying suspension to react.

[0009] According to the above scheme, the SiO2 content in the rice husk ash is 85-97 wt%, the bulk density is 200-400 kg / m 3 , and the specific surface area is 50-100 m 2 / g.

[0010] According to the above scheme, the carbon fiber is a high-performance fiber material with a carbon content of 90% or more, a length of 5.0-6.0 mm, a density of 1600-2000 kg / m 3 , and an elastic modulus of 240-280 GPa.

[0011] According to the above scheme, the epoxy resin is a combination of modified alicyclic epoxy resin and bisphenol A type epoxy resin, with a mass ratio of 1.0-1.25:1. The modified alicyclic epoxy resin is formed by the oxidation of 1,2-epoxy cyclohexane and n-hexane with oxalic acid. According to the above scheme, the emulsifier is one or more of polyethylene glycol, phthalic anhydride, and hexamethylene diisocyanate. According to the above scheme, the amount of emulsifier added is 1.0%-1.5% of the mass of the epoxy resin.

[0012] According to the above scheme, the silane coupling agent is vinyl triethoxysilane.

[0013] According to the above scheme, the amounts of suspension, silane coupling agent, and carbon fiber added are 4-6%, 1.5-2.5%, and 1-2% of the mass of the rice husk ash, respectively.

[0014] According to the above scheme, the calcination and carbonization conditions are as follows: calcination at a temperature of 800-900℃ for 1.5-2h, preferably with a heating rate of 15-30℃ / min.

[0015] According to the above scheme, the reaction conditions for adding white rice husk ash powder and silane coupling agent to the emulsified suspension are as follows: control the temperature at 50-60℃, continuously stir for 180-240s, and let it stand for 2-3h.

[0016] According to the above scheme, the preparation method of the modified rice husk ash is as follows:

[0017] Step 1: Mix the rice husk ash and carbon fiber uniformly, calcine at 800-900℃ for 1.5-2h, and obtain a black carbonized R-RHA rice husk ash mixture after burning;

[0018] Step 2: Mix the R-RHA rice husk ash mixture with hydrochloric acid and soak for 2-3h, then filter, dry, and grind, and pass through an 800 mesh sieve to obtain white rice husk ash powder;

[0019] Step 3: Mix the epoxy resin with the emulsifier and stir to obtain an emulsified suspension;

[0020] Step 4: Add the rice husk ash powder obtained in Step 2 and a silane coupling agent to the emulsified suspension obtained in Step 3, control the temperature at 50-60℃, continuously stir for 180-240s, stand for 2-3h, and then obtain the modified rice husk ash powder by cooling, filtering, drying and grinding through an 800 mesh sieve.

[0021] Preferably, in Step 2, the concentration of hydrochloric acid is 0.4-0.8mol / L.

[0022] Preferably, in Step 3, the stirring process is as follows: stirring at a speed of 1500-2500r / min for 60-90min at 40-60℃.

[0023] According to the above scheme, the alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus 1.5), and the mass percentage of each component is as follows: sodium silicate 70-90%, NaOH 5-15%, and KOH 5-15%.

[0024] According to the above scheme, the aluminate cement has a specific surface area >420m 2 / kg and an aluminum oxide content ≥68%.

[0025] According to the above scheme, the fly ash is F-class I-grade fly ash with a 45μm sieve residue of 5%-6%, and the main chemical components are as follows: SiO2 50-65%, Al2O3 15-30%, Fe2O3 5-10%, CaO 3-5%, MgO 1-1.5%, and SO3 1-2% by weight.

[0026] According to the above scheme, the metakaolin has a specific surface area ≥420m 2 / kg, and the main chemical components are as follows: SiO2 50-55%, Al2O3 40-45%, Fe2O3 1-5%, CaO 0-0.5%, MgO 0-0.5%, and SO3 1-4% by weight.

[0027] According to the above scheme, the geopolymer-based heat-resistant cementitious material is prepared by mixing metakaolin, fly ash and modified rice husk ash in an alkaline activator to form a ternary geopolymer, and then uniformly grinding with aluminate cement.

[0028] A preparation method of the above-mentioned geopolymer heat-resistant cementitious material is provided, which comprises the following steps:

[0029] (1) uniformly mix the fly ash, metakaolin and modified rice husk ash powder, stir for 60-90s, add an alkali activator and water, stir for 200-300s, mix uniformly, stand for 24-30h, and react to prepare a geopolymer;

[0030] (2) mixing the aluminate cement with the geopolymer, adding triethanolamine powder and grinding for 60-90 minutes to obtain the geopolymer heat-resistant cementitious material.

[0031] According to the above scheme, in the step (1), the liquid-solid ratio (i.e. the ratio of water to solid powder) for preparing the geopolymer is 0.3-0.5.

[0032] According to the above scheme, in the step (2), the amount of triethanolamine is 3‰-5‰ of the total mass of the aluminate cement and the geopolymer.

[0033] According to the above scheme, in the step (2), the process for preparing the heat-resistant cementitious material is carried out in an environment with a temperature of 20-22℃ and a humidity of 60-70%.

[0034] The present application utilizes fly ash-metakaolin-modified rice husk ash to obtain a ternary geopolymer system, the modified rice husk ash is obtained by mixing and calcining the rice husk ash and carbon fibers, and then soaking the carbonized rice husk ash in hydrochloric acid to obtain white rice husk ash powder, and an emulsified suspension is obtained by mixing epoxy resin and emulsifier; the white rice husk ash powder and silane coupling agent are added to the emulsified suspension to prepare the modified rice husk ash. Wherein: by high-temperature calcination of rice husk ash and carbon fibers, the properties of carbon fibers such as high-temperature resistance and fiber toughness are well utilized, and a fiber-reinforced and high-temperature-resistant carbonized rice husk ash mixture is obtained; further soaking in acid solution effectively reduces the impurity content of the carbonized rice husk ash mixture and increases the active SiO2 content, significantly improving the pozzolanic activity of the rice husk ash; by adding the epoxy resin emulsified suspension and the coupling agent and ball milling, the high-temperature resistance and stability of the rice husk ash can be further enhanced. The modified rice husk ash is combined with fly ash and metakaolin to obtain a geopolymer, and the modified rice husk ash cooperates with the fly ash and metakaolin to form a certain amount of micropores and capillaries during the process of obtaining the geopolymer, which promotes the chemical reaction between the active substances of the geopolymer and the cement, increases the capacity of the geopolymer heat-resistant cementitious material to accommodate hydrates, and thus improves the density of the geopolymer heat-resistant cementitious material and enhances the cohesion, durability and heat resistance of the cementitious material.

[0035] The beneficial effects of the present application are as follows:

[0036] 1. The geopolymer heat-resistant cementitious material of the present application uses fly ash, metakaolin and modified rice husk ash as the basic raw materials for geopolymer, obtains a geopolymer with good temperature resistance through an alkali activator, and finally combines with aluminate cement to obtain a geopolymer heat-resistant cementitious material with good high-temperature resistance and compressive strength, excellent thermal insulation performance, low thermal conductivity and low cost. The material can effectively utilize solid waste and agricultural waste, can be applied to 500-700℃ heat-resistant concrete engineering, provides a new idea for developing heat-resistant cementitious materials, broadens the use field of solid waste materials, and promotes the rational utilization of resources.

[0037] 2. The preparation method of the geopolymer heat-resistant cementitious material according to the present application, which is prepared by using fly ash and rice husk ash, the industrial and agricultural by-products, to effectively solve the problem of waste disposal; the modified rice husk ash is used as the raw material, and an alkali activator and triethanolamine are added to strengthen the gelatinization and dispersion effect, improve the hydration rate of the high-activity substance in the geopolymer, and enhance the compactness, high-temperature resistance, corrosion resistance and other durability of the cementitious material; the preparation method is simple, the conditions are mild, the cost is low, and the method has important industrial application value. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application is further described in detail below with examples, and the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0039] The preparation method of the modified rice husk ash in the examples and comparative examples comprises the following steps:

[0040] Step 1: uniformly mix the rice husk ash and carbon fibers, place them in a muffle furnace, and raise the temperature from room temperature to 850℃ at a rate of 20℃ / min, collect the incineration residues after 2h of combustion, and obtain a black carbonized R-RHA rice husk ash mixture.

[0041] Step 2: mix the incineration residues with 0.5mol / L hydrochloric acid and soak for 2h, then filter, dry and grind, and pass through an 800-mesh sieve to obtain white rice husk ash powder.

[0042] Step 3: mix the epoxy resin and the emulsifier in a beaker, place it on a magnetic stirrer with a stirring speed of 2000r / min and a temperature of 50℃, and stir for 60min to prepare an emulsified suspension.

[0043] Step 4: add the rice husk ash powder prepared in step 2 and the silane coupling agent to the above emulsified suspension, control the temperature at 50℃, continuously stir for 240s, and stand for reaction for 3h, then cool, filter, dry and grind, and pass through an 800-mesh sieve to obtain modified rice husk ash powder; wherein:

[0044] The rice husk ash is carbonized RHA, which is incompletely carbonized at 850℃, has a pH of 7.6, and mainly contains 89.4% of SiO2.

[0045] The carbon fiber parameters are: length 5.5mm, density 1780kg / m 3 , and elastic modulus 247GPa.

[0046] The epoxy resin is a combination of modified alicyclic epoxy resin + bisphenol A type epoxy resin, with a mass ratio of 1.2:1. The modified alicyclic epoxy resin is formed by oxidation of 1,2-epoxy cyclohexane and n-hexane with acetic acid. The emulsifier is polyethylene glycol. The amount of emulsifier added is 1.5% of the mass of the epoxy resin.

[0047] The silane coupling agent is vinyl triethoxysilane.

[0048] The amounts of emulsified suspension, silane coupling agent and carbon fiber added are 5%, 2% and 1.5% of the mass of rice husk ash, respectively.

[0049] The method for preparing the heat-resistant cementitious material in the examples and comparative examples comprises the following steps:

[0050] (1) The fly ash, metakaolin and modified rice husk ash powders are mixed uniformly and stirred for 60 s, the alkali activator and water are added and stirred for 200-240 s to mix uniformly, and then the mixture is left to stand for 24 h to react, thereby preparing a geopolymer; the liquid-solid ratio (i.e. the mass ratio of water to solid powder) is 0.3-0.5.

[0051] (2) The aluminate cement and the geopolymer are mixed, triethanolamine is added, and the mixture is ground in a ball mill for 60 min, thereby obtaining a geopolymer heat-resistant cementitious material; the amount of triethanolamine is 5‰ of the total mass of the aluminate cement and the geopolymer; the preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20-22°C and a humidity of 60-70%.

[0052] Example 1

[0053] A geopolymer heat-resistant cementitious material, the raw materials of which are as follows in terms of weight fraction: fly ash 10 parts, metakaolin 10 parts, modified rice husk ash 65 parts, alkali activator 5 parts, and aluminate cement 10 parts.

[0054] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus 1.5), and the mass percentages of the components are as follows: sodium silicate 80%, NaOH 10%, and KOH 10%.

[0055] The specific surface area of the aluminate cement is 450 m 2 / kg, and the content of aluminum trioxide is 68%.

[0056] The fly ash is F-class grade I fly ash, with a 45 μm sieve residue of 6%, and the main chemical components are as follows in terms of weight fraction: SiO2 60%, Al2O3 25%, Fe2O3 5%, CaO 5%, MgO 1.5%, and SO3 1.5%; the specific surface area of the metakaolin is 420 m 2 / kg, and the density is 2.38 g / cm 3, the main chemical components are SiO2 55%, Al2O3 40%, Fe2O3 2%, CaO 0.5%, MgO 0.5%, SO3 1% by weight.

[0057] The liquid-solid ratio for preparing the geopolymer is 0.3.

[0058] The preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20±2℃ and a humidity of 65±2%.

[0059] Example 2

[0060] A geopolymer heat-resistant cementitious material, raw materials are as follows by weight fraction: fly ash 10 parts, metakaolin 10 parts, modified rice husk ash 70 parts, alkali activator 5 parts, aluminate cement 5 parts.

[0061] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus is 1.5), and the mass percentage of each component is as follows: sodium silicate 80%, NaOH 10%, KOH 10%.

[0062] The specific surface area of the aluminate cement is 450m 2 / kg, and the aluminum oxide content is 68%.

[0063] The fly ash is F-class I-grade fly ash, the 45μm sieve residue is 6%, and the main chemical components are SiO2 60%, Al2O3 25%, Fe2O3 5%, CaO 5%, MgO 1.5%, SO3 1.5% by weight fraction; the specific surface area of the metakaolin is 420m 2 / kg, the density is 2.38g / cm 3 , and the main chemical components are SiO2 55%, Al2O3 40%, Fe2O3 2%, CaO 0.5%, MgO 0.5%, SO3 1% by weight fraction.

[0064] The liquid-solid ratio for preparing the geopolymer is 0.5.

[0065] The preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20±2℃ and a humidity of 65±2%.

[0066] Example 3

[0067] A geopolymer heat-resistant cementitious material, raw materials are as follows by weight fraction: fly ash 10 parts, metakaolin 10 parts, modified rice husk ash 70 parts, alkali activator 5 parts, aluminate cement 5 parts.

[0068] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus 1.5), each component is 85% sodium silicate, 7.5% NaOH and 7.5% KOH by mass percentage.

[0069] The aluminate cement has a specific surface area of 450 m 2 / kg and an alumina content of 68%.

[0070] The fly ash is F-class I-grade fly ash with a 45 μm residue of 6%, and the main chemical components are 60% SiO2, 25% Al2O3, 5% Fe2O3, 5% CaO, 1.5% MgO and 1.5% SO3 by weight fraction; the metakaolin has a specific surface area of 420 m 2 / kg and a density of 2.38 g / cm 3 , and the main chemical components are 55% SiO2, 40% Al2O3, 2% Fe2O3, 0.5% CaO, 0.5% MgO and 1% SO3 by weight fraction.

[0071] The liquid-solid ratio for preparing the geopolymer is 0.5.

[0072] The preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20±2℃ and a humidity of 65±2%.

[0073] Example 4

[0074] A geopolymer heat-resistant cementitious material, the raw materials are as follows by weight fraction: fly ash 15 parts, metakaolin 15 parts, modified rice husk ash 60 parts, alkali activator 1 part and aluminate cement 9 parts.

[0075] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus 1.5), each component is 90% sodium silicate, 5% NaOH and 5% KOH by mass percentage.

[0076] The aluminate cement has a specific surface area of 450 m 2 / kg and an alumina content of 68%.

[0077] The fly ash is F-class I-grade fly ash with a 45 μm residue of 6%, and the main chemical components are 60% SiO2, 25% Al2O3, 5% Fe2O3, 5% CaO, 1.5% MgO and 1.5% SO3 by weight fraction; the metakaolin has a specific surface area of 420 m 2 / kg and a density of 2.38 g / cm 3The main chemical components are SiO2 55%, Al2O3 40%, Fe2O3 2%, CaO 0.5%, MgO 0.5%, and SO3 1% by weight.

[0078] The liquid-solid ratio for preparing the geopolymer is 0.5.

[0079] The preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20±2℃ and a humidity of 65±2%.

[0080] Example 5

[0081] A heat-resistant geopolymer cementitious material, raw materials of which are as follows by weight: fly ash 20 parts, metakaolin 10 parts, modified rice husk ash 60 parts, alkali activator 5 parts, and aluminate cement 5 parts.

[0082] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide, and sodium silicate (water glass, modulus 1.5), and the components are as follows by mass percentage: sodium silicate 75%, NaOH 12.5%, and KOH 12.5%.

[0083] The aluminate cement has a specific surface area of 450 m 2 / kg and an aluminum trioxide content of 68%.

[0084] The fly ash is F-class I-grade fly ash with a 45 μm sieve residue of 6%, and the main chemical components are as follows by weight: SiO2 60%, Al2O3 25%, Fe2O3 5%, CaO 5%, MgO 1.5%, and SO3 1.5%; the metakaolin has a specific surface area of 420 m 2 / kg and a density of 2.38 g / cm 3 , and the main chemical components are as follows by weight: SiO2 55%, Al2O3 40%, Fe2O3 2%, CaO 0.5%, MgO 0.5%, and SO3 1%.

[0085] The liquid-solid ratio for preparing the geopolymer is 0.5.

[0086] The preparation of the heat-resistant cementitious material is carried out in an environment with a temperature of 20±2℃ and a humidity of 65±2%.

[0087] Example 6

[0088] A heat-resistant geopolymer cementitious material, raw materials of which are as follows by weight: fly ash 10 parts, metakaolin 20 parts, modified rice husk ash 60 parts, alkali activator 5 parts, and aluminate cement 5 parts.

[0089] The alkali activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate (water glass, modulus 1.5), each component is 70% of sodium silicate, 15% of NaOH and 15% of KOH by mass percentage.

[0090] The specific surface area of the aluminate cement is 450 m 2 / kg, and the content of aluminum oxide is 68%.

[0091] The fly ash is F-class I-grade fly ash with 6% of 45 μm residue, and the main chemical components are 60% of SiO2, 25% of Al2O3, 5% of Fe2O3, 5% of CaO, 1.5% of MgO and 1.5% of SO3 by weight fraction; the specific surface area of the metakaolin is 420 m 2 / kg, and the density is 2.38 g / cm 3 ; the main chemical components are 55% of SiO2, 40% of Al2O3, 2% of Fe2O3, 0.5% of CaO, 0.5% of MgO and 1% of SO3 by weight fraction.

[0092] The liquid-solid ratio of the preparation of geopolymer is 0.5.

[0093] The preparation of the heat-resistant cementitious material is carried out in an environment with temperature of 20±2℃ and humidity of 65±2%.

[0094] Comparative Example 1

[0095] The fly ash is removed, and the remaining raw materials are 20 parts of metakaolin, 65 parts of modified rice husk ash, 5 parts of activator and 10 parts of aluminate cement by weight fraction; the properties of the remaining materials are carried out according to Example 1.

[0096] Comparative Example 2

[0097] The modified rice husk ash is removed, and the remaining raw materials are 20 parts of metakaolin, 65 parts of fly ash, 5 parts of activator and 10 parts of aluminate cement by weight fraction; the properties of the remaining materials are carried out according to Example 1.

[0098] Comparative Example 3

[0099] The modified rice husk ash is replaced by unmodified rice husk ash, and the raw materials are carried out according to Example 1 by weight fraction and the properties of the remaining materials are carried out according to Example 1.

[0100] The 28d and 60d mortar of the geopolymer heat-resistant cementitious material prepared in each of the above examples is prepared according to GB / T 17671-2021 "Cement mortar strength test method ISO method", and the mass weight of each component is: geopolymer heat-resistant cementitious material 450g, standard sand 1350g, and water 225g. Then the mortar of each age is kept at a constant temperature of 500, 600 and 700 DEG C for 3h, and the strength loss rate of the comparison standard curing is compared.

[0101] The compressive strength (MPa) performance test results of the geopolymer heat-resistant cementitious material obtained in each of the above examples are shown in Table 1:

[0102] Table 1 Performance test results of the geopolymer heat-resistant cementitious material

[0103]

[0104]

[0105] As shown in the above table, the geopolymer heat-resistant cementitious material of the present application has good strength loss at 500-700 DEG C, and the minimum strength loss of 60d mortar at 500 DEG C is 10.7%, the minimum strength loss of 60d mortar at 600 DEG C is 12.3%, and the minimum strength loss of 60d mortar at 700 DEG C is 16.5%. In combination with Comparative Examples 1 and 2, the performance of the three-dimensional network structure geopolymer composed of fly ash and modified rice husk ash and metakaolin is more stable, and the strength loss is low. In Comparative Example 3, the unmodified rice husk ash is added, and the strength of the mortar at different temperatures is significantly decreased, which shows that the modification of the rice husk ash in the present application effectively improves the heat resistance of the geopolymer heat-resistant cementitious material. Therefore, the ternary geopolymer prepared by the three raw materials adopted in the present application is very effective and feasible, and can be effectively applied to the selection of cementitious materials for 500-700 DEG C heat-resistant concrete application engineering.

[0106] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above is only a specific embodiment of the present application and does not limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A geopolymer-based heat-resistant cementitious material, characterized in that, By weight, it includes the following ingredients: 10-20 parts fly ash, 10-20 parts metakaolin, 60-70 parts modified rice husk ash, 1-5 parts alkali activator, and 5-10 parts aluminate cement. The modified rice husk ash is prepared by calcining and carbonizing rice husk ash and carbon fibers, then soaking it in hydrochloric acid to obtain white rice husk ash powder. Epoxy resin and emulsifier are mixed to obtain an emulsified suspension. The white rice husk ash powder and silane coupling agent are added to the emulsified suspension and reacted to obtain the modified rice husk ash powder. The emulsified suspension, silane coupling agent, and carbon fibers are 4-6%, 1.5-2.5%, and 1-2% of the mass of rice husk ash, respectively.

2. The heat-resistant cementitious material according to claim 1, characterized in that, During the preparation of the modified rice husk ash: The calcination and carbonization conditions are: calcination at 800~900℃ for 1.5~2 hours; Add white rice husk ash powder and silane coupling agent to the emulsified suspension. The reaction conditions are: control the temperature at 50-60℃, stir continuously for 180-240s, and let it stand for 2-3h.

3. The heat-resistant cementitious material according to claim 1, characterized in that, During the preparation of the modified rice husk ash: The epoxy resin is a combination of modified alicyclic epoxy resin and bisphenol A type epoxy resin, with a mass ratio of 1.0~1.25:1; The modified alicyclic epoxy resin is formed by oxidizing 1,2-epoxycyclohexane and n-hexane with acetic acid. The emulsifier is one or more of polyethylene glycol, phthalic anhydride and hexamethylene diisocyanate; The silane coupling agent is vinyltriethoxysilane; The carbon fiber is a high-performance fiber material with a carbon content of over 90%, a length of 5.0~6.0 mm, and a density of 1600~2000 kg / m³. 3 Its elastic modulus is 240~280 GPa; The rice husk ash contains 85-97 wt% SiO2 and has a bulk density of 200-400 kg / m³. 3 Specific surface area 50~100m² 2 / g.

4. The heat-resistant cementitious material according to claim 1, characterized in that, The preparation of the modified rice husk ash includes the following steps: Step 1: Mix rice husk ash and carbon fiber evenly, and calcine at 800~900℃ for 1.5~2h. After combustion, a black carbonized R-RHA rice husk ash mixture is obtained. Step 2: Mix the R-RHA rice husk ash mixture with hydrochloric acid and soak for 2-3 hours, then filter, dry and grind, and pass through an 800-mesh sieve to obtain white rice husk ash powder; Step 3: Mix epoxy resin and emulsifier and stir to obtain an emulsified suspension; Step 4: Add the rice husk ash powder obtained in Step 2 and the silane coupling agent to the emulsified suspension obtained in Step 3, control the temperature at 50-60℃ and stir continuously for 180-240s, let it stand for 2-3h, and obtain modified rice husk ash powder by cooling, filtering, drying and grinding, and passing it through an 800-mesh sieve.

5. The heat-resistant cementitious material according to claim 1, characterized in that, The alkaline activator is a mixture of sodium hydroxide, potassium hydroxide and sodium silicate, with each component having the following mass percentages: sodium silicate 70-90%, NaOH 5-15%, KOH 5-15%.

6. The heat-resistant cementitious material according to claim 1, characterized in that, The specific surface area of ​​the aluminate cement is >420m². 2 / kg, and the aluminum oxide content is ≥68%; The fly ash is Class I, Grade F fly ash, with a 45μm sieve residue of 5%-6%, and its main chemical components by weight are SiO2 50-65%, Al2O3 15-30%, Fe2O3 5-10%, CaO 3-5%, MgO 1-1.5%, and SO3 1-2%. The specific surface area of ​​the metakaolin is ≥420m² 2 / kg, the main chemical components by weight are SiO2 50-55%, Al2O3 40-45%, Fe2O3 1-5%, CaO 0-0.5%, MgO 0-0.5%, SO3 1-4%.

7. A method for preparing a geopolymer heat-resistant cementitious material according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix fly ash, metakaolin, and modified rice husk ash powder evenly with dry powder and stir for 60-90s. Add alkali activator and water and stir for 200-300s to mix evenly. Let stand for 24-30h to react and prepare geopolymer. (2) Mix aluminate cement with geopolymer, add triethanolamine and grind for 60~90 minutes to obtain geopolymer heat-resistant cementitious material.

8. The preparation method according to claim 7, characterized in that, In step (1), the liquid-to-solid ratio of the prepared geopolymer is 0.3-0.5; In step (2), the amount of triethanolamine used is 3‰ to 5‰ of the total mass of aluminate cement and geopolymer.

9. The preparation method according to claim 7, characterized in that, In step (2), the process of preparing the heat-resistant cementitious material is carried out in an environment with a temperature of 20-22℃ and a humidity of 60-70%.

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