Geopolymer recycled fire‑resistant mortar based on porous lightweight filler and preparation method therefor

Abstract

Geopolymer recycled fire‑resistant mortar based on a porous lightweight filler and a preparation method therefor. The recycled fire‑resistant mortar comprises the following raw materials: 460-520 parts of a cementitious material, 210-360 parts of a porous lightweight filler, 330-380 parts of an alkali activator, 120-500 parts of a recycled fine aggregate, and 180-280 parts of water, wherein the porous lightweight filler is fly ash hollow microspheres. The preparation method for the recycled fire‑resistant mortar comprises: uniformly mixing the cementitious material, the porous lightweight filler, and the recycled fine aggregate to obtain a dry mixture; adding the alkali activator to the dry mixture to obtain the geopolymer recycled fire‑resistant mortar, loading the geopolymer recycled fire‑resistant mortar into a mold, compacting the loaded geopolymer recycled fire‑resistant mortar layer by layer, and after a particular age is reached, performing demolding and curing. The recycled fire‑resistant mortar realizes the utilization of solid waste as resources, and the thermal insulation and heat shielding capabilities of the geopolymer recycled mortar are improved by means of the properties, such as high porosity and low thermal conductivity, of the porous lightweight filler, thereby greatly improving the fire‑resistant performance of the geopolymer mortar.

Description

A geopolymer-based recycled fireproof mortar based on porous lightweight fillers and its preparation method Technical Field

[0001] This invention relates to the field of building materials, and more specifically to a geopolymer-based recycled fireproof mortar based on porous lightweight fillers and its preparation method. Background Technology

[0002] With the continuous advancement of urbanization, the environmental harm caused by construction waste is intensifying. Recycled fine aggregate, consisting of solid particles smaller than 4.75 mm in diameter obtained during the crushing process of construction solid waste, has high water absorption, low crushing index, and cannot be directly recycled. Open-air stockpiles of recycled fine aggregate easily pollute air and water resources. Developing recycled fine aggregate into a recycled fireproof mortar can effectively solve the problem of recycling construction waste.

[0003] Building fires are a major threat to human life and property. While coatings are a primary method of fire protection in buildings, large-scale application is costly and they can easily release irritating gases under high temperatures. Porous lightweight fillers, on the other hand, possess characteristics such as large specific surface area, abundant pores, low thermal conductivity, and low density. Furthermore, under high temperatures, they can promote the pozzolanic effect, generating a zeolite-like structure that provides strength support for hydration products. Replacing geopolymer recycled mortar, made from recycled fine aggregates from crushed construction waste and alkali activators, with these fillers offers significant improvement in the fire resistance of recycled fireproof mortar.

[0004] Ordinary silicate mortar is susceptible to high-temperature cracking, leading to structural loss of load-bearing capacity. Geopolymers, on the other hand, are amorphous three-dimensional structures generated through alkaline activators (NaOH and Na₂SiO₃ or KOH and Na₂SiO₃) and precursor materials (metakaolin, fly ash, red mud, etc.). These inorganic three-dimensional structures are non-combustible and possess high-temperature stability, making them promising for applications in building fire protection. Their preparation process is low-carbon and clean, reducing CO₂ emissions by approximately 80%–90%, decreasing the frequency of use of natural resources such as sand and stone, and increasing the utilization rate of industrial waste or by-products. Furthermore, their resistance to acid and alkali corrosion and high strength significantly enhance their potential value as green cementitious materials. However, metakaolin-based geopolymer mortar exhibits rapid performance degradation at temperatures above 600℃. In the early stages of hydration, the high water absorption of metakaolin leads to incomplete geopolymerization, resulting in significant early strength loss. During curing, geopolymer mortar undergoes a certain degree of self-shrinkage, experiencing a shrinkage-expansion process at high temperatures, inducing the development of microcracks. Technical issues

[0005] To address the shortcomings of existing technologies, this invention provides a geopolymer-based recycled fireproof mortar and its preparation method. This achieves resource utilization of solid waste, extends the high-temperature degradation time, improves residual compressive strength after high-temperature exposure, maintains high-temperature integrity, and can significantly reduce the damage caused by fire. Technical solutions

[0006] The first aspect of the present invention provides a geopolymer recycled fireproof mortar based on porous lightweight filler, comprising the following components by weight: 460-520 parts of cementitious material, 210-360 parts of porous lightweight filler, 330-380 parts of alkali activator, 120-500 parts of recycled fine aggregate, and 180-280 parts of water.

[0007] Preferably, the geopolymer recycled fireproof mortar based on porous lightweight filler comprises, by weight: 460-520 parts of cementitious material, 210-290 parts of porous lightweight filler, 330-380 parts of alkali activator, 240-500 parts of recycled fine aggregate, and 180-280 parts of water.

[0008] More preferably, the geopolymer recycled fireproof mortar based on porous lightweight filler comprises, by weight: 490 parts of cementitious material, 210-290 parts of porous lightweight filler, 353 parts of alkali activator, 240-500 parts of recycled fine aggregate, and 210 parts of water.

[0009] Preferably, the cementing material is metakaolin with a moisture content of less than 30%, a SiO2 content of more than 40%, and an Al2O3 content of more than 30%.

[0010] Preferably, the porous lightweight filler is fly ash hollow microspheres with a particle size of 0.074~0.15 mm, a water absorption rate of less than 20%, a SiO2 content of more than 50%, and an Al2O3 content of more than 30%. Fly ash hollow microspheres are an ultrafine powder material obtained by screening fly ash from power plants, and have the characteristics of being lightweight, having high compressive strength, and good thermal stability.

[0011] Preferably, the volume of the porous lightweight filler accounts for 60% to 100% of the total volume of the porous lightweight filler and the recycled fine aggregate.

[0012] Preferably, the alkaline activator is a mixed solution of NaOH and Na2SiO3, wherein the NaOH solid purity is greater than 92%, the Na2SiO3 solution modulus is 1.2, the Na2O·nSiO2 content is 42%, and the Baume degree is 50.

[0013] Preferably, the recycled fine aggregate is solid particles made from crushed and ground construction waste with a particle size of less than 4.75 mm and an apparent density of 2000~2600 kg / m³. 3It has a water absorption rate of less than 10% and a mud content of less than 3%.

[0014] A second aspect of the present invention provides a method for preparing the above-mentioned geopolymer recycled fireproof mortar based on porous lightweight fillers, comprising the following steps:

[0015] Cementitious materials, porous lightweight fillers, and recycled fine aggregates are dry-mixed evenly to obtain a dry mixture; alkali activator and water are added to the dry mixture, and the mixture is stirred to obtain a viscous fluid, which is the geopolymer recycled fireproof mortar; it is then molded and compacted in layers, and demolded for curing after reaching the required age.

[0016] Preferably, the dry mixing time of the cementitious material, porous lightweight filler and recycled fine aggregate is 60 s to 120 s; the alkali activator is added to the dry mixture and stirred for 120 s to 180 s.

[0017] Preferably, the curing conditions are natural curing for 1 to 2 days, high-temperature curing at 60℃ to 100℃ for 1 to 2 days, and standard curing (temperature 20±2℃, relative humidity ≥95%) for 5 to 10 days.

[0018] Preferably, the dimensions of the geopolymer high-temperature fireproof mortar test blocks before and after high temperature are 50 mm*50 mm*50 mm.

[0019] Preferably, a GS-60-1200F type fire-resistant high-temperature testing machine is used to simulate the high-temperature test. The simulated high-temperature test temperature is 800℃, the heating rate is 700℃ / h, and the temperature is kept constant for 2 hours after reaching the target temperature. After the high-temperature test, the temperature is naturally cooled to room temperature. Beneficial effects

[0020] Porous lightweight fillers, primarily composed of fly ash hollow microspheres, have low thermal conductivity, significantly reducing the density of geopolymer mortar. Their hollow interior, filled with inert gas, hinders heat conduction, achieving thermal insulation. Simultaneously, the fly ash hollow microspheres possess pozzolanic activity, enhancing the initial strength of the geopolymer mortar during high-temperature curing and maintaining volume stability under high temperatures, making them a potentially advantageous high-temperature resistant material. This invention utilizes the lightweight and high-strength properties of fly ash hollow microspheres to reduce the thermal conductivity of geopolymer mortar, hindering heat conduction. Furthermore, the high pozzolanic activity of the fly ash hollow microspheres improves the early strength of the geopolymer slurry, reducing strength degradation caused by thermal expansion and deformation.

[0021] This invention utilizes porous lightweight fillers to prepare geopolymer recycled fireproof mortar, which exhibits excellent high-temperature resistance. The preparation process is simple, reduces production costs, and yields significant socio-economic benefits. Compared to silicate mortar, geopolymer mortar reduces carbon emissions during preparation and transportation, mitigating CO2 pollution. By using recycled fine aggregates and porous lightweight fillers, waste materials can be recycled to obtain lightweight, high-strength, and fire-resistant geopolymer recycled mortar. The geopolymer recycled fireproof mortar prepared by this invention extends fire degradation time and improves residual compressive strength after a fire, providing protection for human life and property in fire scenarios. Embodiments of the present invention

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] This invention provides a geopolymer recycled fireproof mortar based on porous lightweight fillers, wherein the mass ratio of each component is determined as follows:

[0025] The aggregate (recycled fine aggregate + porous lightweight filler) accounts for 51.6% of the total mortar volume, the porous lightweight filler accounts for 60%~80% of the total aggregate volume, the cementitious material accounts for 19.2% of the total volume, the alkali activator (NaOH+Na2SiO3+H2O) accounts for 23.96% of the total volume, and the water accounts for 5.3% of the total volume.

[0026] The porous lightweight filler used in the following specific embodiments of the present invention is fly ash hollow microspheres, produced by Henan Borun Foundry Materials Co., Ltd., with a water absorption rate of 15% and a bulk density of 300 kg / m³. 3 The particle size is 0.074~0.15 mm, the SiO2 content is 60.12%, and the Al2O3 content is 33.27%.

[0027] The chemical composition of metakaolin is 44.17% SiO2, 38.22% Al2O3, 8.16% Fe2O3, 4.91% CaO, and 1.72% TiO2, with a moisture content of 29%. Its activity index is 103% after 7 days and 112% after 28 days.

[0028] The porous lightweight filler has the following chemical composition: 60.12% SiO2, 33.27% Al2O3, 2.34% Fe2O3, and 1.12% MgO. It has a water absorption rate of 20% and a bulk density of 400 kg / m³. 3 ;

[0029] The NaOH solution concentration is 12 mol / L; the Na2SiO3 modulus is 1.2, the Na2O·nSiO2 content is 42%, and the Baumé degree is 50.

[0030] The apparent density of the recycled fine aggregate is 2396 kg / m³. 3 The water absorption rate is 8.8%.

[0031] Example 1

[0032] This embodiment provides a method for preparing geopolymer recycled fireproof mortar, including the following steps:

[0033] (1) Weigh the raw materials according to the following formula:

[0034] 490 parts of cementitious material (metakaolin), 210.5 parts of porous lightweight filler (fly ash hollow microspheres), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, and 75 parts of distilled water), 495.4 parts of recycled fine aggregate, and 210 parts of water.

[0035] (2) Preparation of geopolymer recycled fireproof mortar

[0036] Prepare the alkali activator 24 hours in advance. Pour measured distilled water into a beaker, then add NaOH solid particles and stir with a glass rod to dissolve. Finally, pour in Na2SiO3 solution and stir clockwise for 15 seconds. Dry mix the recycled fine aggregate, cementitious material, and porous lightweight material for 60 seconds to obtain a dry mixture. Slowly add the alkali activator to the dry mixture while stirring for 60 seconds. After all the alkali activator has been added, stir for another 60 seconds.

[0037] (3) Molding and curing

[0038] A release agent was sprayed into the mold, and the recycled geopolymer fireproof mortar was poured into the mold and compacted in layers. The mold was then placed on a vibrating table and vibrated for 10 seconds. After the surface solidified, it was wrapped with a polyethylene film. The recycled geopolymer fireproof mortar, along with the mold, was placed in a natural environment at 25°C for 1 day. After demolding, the test blocks were placed in sealed bags and placed in an oven at 85°C for 1 day of high-temperature curing. After high-temperature curing, the test blocks were removed, cooled, and then placed in a standard curing environment at 20±2°C and relative humidity ≥95% for 7 days. The corresponding physical and mechanical properties were then tested.

[0039] (4) High temperature test

[0040] The geopolymer recycled fireproof mortar was placed in a high-temperature test chamber, simulating a high-temperature test temperature of 800℃ and a heating rate of 700℃ / h. After reaching the target temperature, the temperature was kept constant for 2 hours. After the high-temperature test, the mortar was allowed to cool naturally to room temperature, and the corresponding physical and mechanical properties were tested.

[0041] Example 2

[0042] This embodiment provides a method for preparing geopolymer recycled fireproof mortar, with the following raw material formula:

[0043] 490 parts of cementitious material (metakaolin), 245.6 parts of porous lightweight filler (fly ash hollow microspheres), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, and 75 parts of distilled water), 371.5 parts of recycled fine aggregate, and 210 parts of water.

[0044] Weigh the raw materials according to the formula, and follow the same steps as in Example 1.

[0045] Example 3

[0046] This embodiment provides a method for preparing geopolymer recycled fireproof mortar, with the following raw material formula:

[0047] 490 parts of cementitious material (metakaolin), 280.7 parts of porous lightweight filler (fly ash hollow microspheres), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, and 75 parts of distilled water), 247.7 parts of recycled fine aggregate, and 210 parts of water.

[0048] Weigh the raw materials according to the formula, and follow the same steps as in Example 1.

[0049] Comparative Example 1

[0050] Comparative Example 1 provides a method for preparing geopolymer recycled fireproof mortar, which differs from Example 1 in that the raw material formula in step (1) is adjusted, and recycled fine aggregate is not added. The specific raw material formula is as follows:

[0051] 490 parts of cementitious material (metakaolin), 350.9 parts of porous lightweight filler (fly ash hollow microspheres), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, 75 parts of distilled water), and 210 parts of water.

[0052] Comparative Example 2

[0053] Comparative Example 2 provides a method for preparing geopolymer recycled fireproof mortar, which differs from Example 1 in that the raw material formulation in step (1) is adjusted, and porous lightweight fillers are not added. The specific raw material formulation is as follows:

[0054] 490 parts of cementitious material (metakaolin), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, 75 parts of distilled water), 1173 parts of recycled fine aggregate, and 210 parts of water.

[0055] Comparative Example 3

[0056] Comparative Example 3 provides a method for preparing geopolymer recycled fireproof mortar, which differs from Example 1 in that the curing conditions in step (3) are adjusted. Specifically, it includes the following steps:

[0057] (1) Weigh the raw materials according to the following formula: Same as in Example 1;

[0058] (2) Preparation of geopolymer recycled fireproof mortar: Same as in Example 1;

[0059] (3) Molding and curing:

[0060] Spray a release agent into the mold, fill the mold with the recycled geopolymer fireproof mortar and compact it in layers, place it on a vibrating table and vibrate for 10 seconds. After the surface has solidified, wrap it with polyethylene film. Place the recycled geopolymer fireproof mortar and the mold in a natural environment at 25℃ for 1 day, and then place it in a standard curing environment at 20±2℃ and relative humidity ≥95% for 7 days. Test the corresponding physical and mechanical properties.

[0061] (4) High temperature test: Same as Example 1.

[0062] Comparative Example 4

[0063] Comparative Example 4 provides a method for preparing geopolymer recycled fireproof mortar, which differs from Example 1 in that the raw materials in step (1) are adjusted, and fly ash hollow microspheres are replaced with vitrified microspheres. The specific raw material formula is as follows:

[0064] 490 parts of cementitious material (metakaolin), 210.5 parts of porous lightweight filler (vitrified microspheres), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, and 75 parts of distilled water), 495.4 parts of recycled fine aggregate, and 210 parts of water.

[0065] Comparative Example 5

[0066] Comparative Example 5 provides a method for preparing geopolymer recycled fireproof mortar, which differs from Example 1 in that the raw materials in step (1) are adjusted, and fly ash hollow microspheres are replaced with fly ash. The specific raw material formula is as follows:

[0067] 490 parts of cementitious material (metakaolin), 210.5 parts of porous lightweight filler (fly ash), 353 parts of alkali activator (40 parts of NaOH solution, 238 parts of Na2SiO3 solution, and 75 parts of distilled water), 495.4 parts of recycled fine aggregate, and 210 parts of water.

[0068] The performance of the geopolymer recycled fireproof mortar specimens prepared in Examples 1-3 and Comparative Examples 1-5 was tested. The physical and mechanical properties of the geopolymer recycled fireproof mortar were measured according to GB / T17671-2021 "Test Method for Strength of Cement Mortar" and JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar". The results are shown in Table 1. The mass loss rate is expressed as the percentage of the difference in mass of the specimen before and after high temperature relative to the initial mass, and the strength loss rate is expressed as the percentage of the difference in strength of the specimen before and after high temperature relative to the initial strength.

[0069] Table 1 Performance test results of geopolymer recycled fireproof mortar test blocks

[0070] Mass loss rate / % Compressive strength loss rate / % Residual bond strength / MPa Example 1 6.74 5 3 2 Example 2 9.34 6 3.7 1.6 Example 3 9.86 8.7 1.4 Comparative Example 1 1 1.95 6 7.5 1.7 Comparative Example 2 6.96 1.1 1.3 Comparative Example 3 7.73 7 0.5 1 Comparative Example 4 7.85 6 9.5 1.1 Comparative Example 5 8.81 5 8.2 1.5

[0071] The results in Table 1 show that the mass loss rate of the geopolymer recycled fireproof mortar prepared according to Examples 1-3 after simulated fire is less than 10%, the strength loss rate is less than 70%, and the residual bond strength is greater than 1.4 MPa. This demonstrates that it can eliminate high-temperature spalling behavior and delay structural failure time, meeting engineering requirements. Fly ash hollow microspheres are an industrial byproduct generated from coal combustion in thermal power plants. Their hollow interiors are filled with negative pressure gas, providing excellent thermal insulation and flame retardant effects. They lower the melting point of the geopolymer slurry, maintaining thermal stability in an environment of 800℃. Simultaneously, the high-temperature melting matrix can repair unfilled pores, thereby reducing damage caused by high temperatures. As the proportion of fly ash hollow microspheres in the total aggregate volume increases, the recycled fine aggregate cannot provide strength support, leading to a decrease in the residual mechanical strength of the geopolymer recycled mortar after high-temperature exposure. Fly ash hollow microspheres have strong adsorption properties for the geopolymer slurry, filling micro-cracks and preventing significant strength loss after high-temperature exposure, making them a lightweight, heat-insulating, and fireproof material.

[0072] Compared to Example 1, Comparative Example 1 showed a 5.21% increase in mass loss rate, a 14.5% increase in strength loss rate, and a 0.3 MPa decrease in residual bond strength. In Comparative Example 1, the porous lightweight filler accounted for 100% of the total aggregate volume. The porous lightweight filler contains numerous micropores, absorbing a large amount of water in the early stages of hydration. Some of this water is used for the geopolymer condensation reaction, while the rest is temporarily stored in the micropores as crystal water. When exposed to high temperatures, the geopolymer recycled mortar with excessive porous lightweight filler loses too much water, which is the main factor causing its mass loss. Excessive porous lightweight filler also causes agglomeration, preventing uniform dispersion in the geopolymer slurry. This results in excessively high local thermal conductivity, hindering heat transfer to the outside environment and inducing internal cracks due to uneven thermal stress. When the porous lightweight filler is used as aggregate instead of recycled fine aggregate, the aggregate gradation is uneven, and the filler particles cannot create air gaps to slow down the heat transfer rate, resulting in more severe high-temperature damage.

[0073] Compared to Example 1, Comparative Example 2 showed a decrease in mass loss rate and residual bond strength, while the strength loss rate increased. Comparative Example 2 did not incorporate porous lightweight filler, whereas in Example 1, the volume of porous lightweight filler accounted for 60% of the total aggregate volume. Compared to recycled fine aggregate, porous lightweight filler has a higher water absorption rate. Therefore, the recycled fireproof mortar prepared in Example 1 contained a large amount of pore water. Under high-temperature conditions, crystal water and pore water changed from liquid to gaseous states, overflowing from the internal pathways of the specimen and escaping into the external environment, resulting in an increased mass loss rate. A 60% volume of porous lightweight filler and a 40% volume of recycled fine aggregate can achieve good particle size distribution, making the solid particles more tightly bonded, hindering the escape path of pore water, and reducing the strength loss caused by pore water escape. Simultaneously, the Si element in the fly ash hollow microspheres participates in the geopolymerization reaction, generating a Si-Al inorganic three-dimensional structure, improving the stability of the geopolymer recycled mortar at high temperatures. Its internal hollow structure can reduce the expansion and contraction rate of the geopolymer recycled mortar, reducing the risk of cracking.

[0074] Compared to Example 1, Comparative Example 3 used different curing conditions, replacing high-temperature curing with standard curing. The results showed a significant increase in strength loss, reaching 70.5%, and the bond strength deteriorated to 1 MPa. High-temperature curing accelerated the alkali activation process, causing the unreacted fly ash hollow microspheres to undergo secondary hydration, fully utilizing their pozzolanic activity. Geopolymers can form zeolite-like structures under high-temperature conditions, possessing a high melting point, thus extending the high-temperature degradation time of the geopolymer-regenerated mortar and compensating for the adverse effects of high-temperature crack propagation. High-temperature curing resulted in a dense cementitious system that encapsulated the fly ash hollow microspheres, delaying crack development under high-temperature conditions.

[0075] Compared to Comparative Examples 4 and 5 and Example 1, replacing fly ash hollow microspheres with vitrified microspheres and fly ash resulted in varying degrees of weakening of compressive strength and bond strength. During the high-temperature curing process, the vitrified microspheres could not exhibit similar pozzolanic activity as the fly ash hollow microspheres, and failed to generate sufficient CASH gel in the later stages of the geopolymerization reaction. Furthermore, their surface exhibited irregular ridges, preventing them from fully embedding into the geopolymer matrix during stirring. Unlike the fly ash hollow microspheres, the fly ash has a dense internal structure, preventing timely heat release during conduction within the geopolymer mortar, leading to thermal stress accumulation, volume expansion of the geopolymer mortar, and the induction of cracks.

[0076] This invention utilizes porous lightweight fillers to prepare geopolymer recycled fireproof mortar, which exhibits excellent high-temperature resistance. The preparation process is simple, reduces production costs, and yields significant socio-economic benefits. Compared to silicate mortar, geopolymer mortar reduces carbon emissions during preparation and transportation, mitigating CO2 pollution. By using recycled fine aggregates and porous lightweight fillers, waste materials can be recycled to obtain lightweight, high-strength, and fire-resistant geopolymer recycled mortar. The geopolymer recycled fireproof mortar prepared by this invention extends fire degradation time and improves residual compressive strength after a fire, providing protection for human life and property in fire scenarios.

[0077] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A geopolymer recycled fireproof mortar based on a porous lightweight filler, characterized in that, The fireproof mortar comprises, by weight: 460-520 parts of cementitious material, 210-360 parts of porous lightweight filler, 330-380 parts of alkali activator, 120-500 parts of recycled fine aggregate, and 180-280 parts of water; the volume of the porous lightweight filler accounts for 60%-100% of the total volume of the porous lightweight filler and recycled fine aggregate; the porous lightweight filler is fly ash hollow microspheres.

2. Geopolymeric recycled fireproof mortar based on porous lightweight filler according to claim 1, characterized in that, The fireproof mortar comprises, by weight: 460-520 parts of cementitious material, 210-290 parts of porous lightweight filler, 330-380 parts of alkali activator, 240-500 parts of recycled fine aggregate, and 180-280 parts of water.

3. The geopolymer recycled fireproof mortar based on a lightweight filler according to claim 1, characterized in that, The fireproof mortar comprises, by weight: 490 parts of cementitious material, 210-290 parts of porous lightweight filler, 353 parts of alkali activator, 240-500 parts of recycled fine aggregate, and 210 parts of water.

4. The geopolymer recycled fireproof mortar based on a lightweight filler according to claim 1, characterized in that, The cementing material is metakaolin, which has a moisture content of less than 30%, a SiO2 content of more than 40%, and an Al2O3 content of more than 30%.

5. The geopolymer recycled fireproof mortar based on a lightweight filler according to claim 1, characterized in that, The fly ash hollow microspheres have a particle size of 0.074~0.15 mm, a water absorption rate of less than 20%, a SiO2 content of more than 50%, and an Al2O3 content of more than 30%.

6. The geopolymer recycled fireproof mortar based on a lightweight filler according to claim 1, characterized in that, The alkaline activator is a mixed solution of NaOH and Na2SiO3, with the Na2SiO3 solution having a modulus of 1.2, a Na2O·nSiO2 content of 42%, and a Baume degree of 50.

7. The geopolymer recycled fireproof mortar based on a lightweight filler according to claim 1, characterized in that, The recycled fine aggregate is a solid particle obtained by crushing and grinding construction waste to a particle size less than 4.75 mm, and has an apparent density of 2000-2600 kg / m 3 , a water absorption of less than 10%, and a silt content of less than 3%.

8. Process for the preparation of geopolymeric recycled fireproof mortars based on lightweight fillers according to any one of claims 1 to 7, characterized in that, Includes the following steps: The cementitious material, porous lightweight filler and recycled fine aggregate are mixed evenly to obtain a dry mixture; alkali activator and water are added to the dry mixture and stirred until a uniform viscous fluid is formed, which is the geopolymer recycled fireproof mortar; it is then molded and compacted in layers, and demolded and cured after reaching the required age.

9. The method for the preparation of geopolymeric recycled fireproof mortars based on porous lightweight fillers according to claim 8, characterized in that, The curing conditions are: natural curing for 1 to 2 days, high-temperature curing at 60℃ to 100℃ for 1 to 2 days, and standard curing (temperature 20±2℃, relative humidity ≥95%) for 5 to 10 days.