Fly ash-based foam geopolymer, preparation method therefor, and use thereof

Abstract

Disclosed herein are a fly ash-based foam geopolymer, a preparation method therefor, and the use thereof. The fly ash-based foam geopolymer is prepared from raw materials comprising the following components in parts by weight: 900-1000 parts of a fly ash-based material; 600-700 parts of a composite alkali solution; 0-10 parts of a thickening agent; 2-6 parts of a foam stabilizer A; 5-10 parts of a water reducer; and 20-40 parts of a foaming agent. The preparation method of the present application is simple, and processes such as ball milling, water washing and calcining do not need to be carried out on the raw materials, such that the investment in a grinding equipment, a water washing equipment, a sewage treatment equipment, and a calcining equipment is reduced, and the energy consumption and carbon emissions are reduced. The fly ash-based foam geopolymer prepared by using the fly ash-based material as the main raw material in the present application has a low apparent density and a high early strength, and can be used in the field of fabricated buildings.

Claims

1. A fly ash-based foamed geopolymer, wherein raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 900-1000 parts of a fly ash-based material; 600-700 parts of a composite alkali solution; 0-10 parts of a thickener; 2-6 parts of a foam stabilizer A; 5-10 parts of a water reducer; and 20-40 parts of a foaming agent; wherein when a calcareous material is present, the fly ash-based material is prepared by the following preparation method: mixing fly ash with the calcareous material to obtain the fly ash-based material; wherein based on a mass of the fly ash-based material being 100%, the fly ash has a content of 90%-100%, and the calcareous material has a content of 0%-10%; wherein the calcareous material comprises any one or a combination of at least two of cement, ore slags, gypsum or metakaolin; wherein the composite alkali solution is prepared by the following preparation method: mixing a composite alkali activator, a metal complexing agent and a foam stabilizer B to obtain the composite alkali solution; based on a mass of the composite alkali solution being 100%, the composite alkali activator has a content of 95%-98%, the metal complexing agent has a content of 0.05%-0.5%, and the foam stabilizer B has a content of 1.95%-4.5%; wherein the foam stabilizer A comprises trisodium phosphate and/or calcium stearate powders; the foam stabilizer B comprises any one or a combination of at least two of sodium dodecylbenzenesulfonate powders, sodium dodecyl sulfate powders, trisodium phosphate powders or calcium dodecyl sulfate powders.

2. The fly ash-based foamed geopolymer according to claim 1, wherein the composite alkali activator has a modulus of 1.0-1.5.

3. The fly ash-based foamed geopolymer according to claim 1, wherein the metal complexing agent comprises any one or a combination of at least two of triethanolamine, methyldiethanolamine, diisopropanolamine, diethanolisopropanolamine, triethanolamine or triisopropanolamine.

4. The fly ash-based foamed geopolymer according to claim 3, wherein the metal complexing agent has a solid content of not less than 78%.

5. The fly ash-based foamed geopolymer according to claim 1, wherein the foam stabilizer B has a purity of not less than 88%.

6. The fly ash-based foamed geopolymer according to claim 1, wherein the composite alkali activator is prepared by the following preparation method: adding sodium hydroxide powders and water into water glass, and stirring to obtain the composite alkali activator.

7. The fly ash-based foamed geopolymer according to claim 6, wherein based on a mass of the composite alkali activator being 100%, the sodium hydroxide powders have a content of 8.5%-9%, the water has a content of 4.5%-7%, and the water glass has a content of 84%-87%.

8. The fly ash-based foamed geopolymer according to claim 6, wherein the sodium hydroxide powders have a purity of not less than 96%.

9. The fly ash-based foamed geopolymer according to claim 6, wherein the water is tap water.

10. The fly ash-based foamed geopolymer according to claim 6, wherein the water glass has a modulus of 1.0-3.8 and a Baume degree of 34.0-42.0.

11. The fly ash-based foamed geopolymer according to claim 1, wherein the thickener comprises methyl cellulose ether and/or carboxymethyl cellulose ether.

12. The fly ash-based foamed geopolymer according to claim 11, wherein the thickener comprises methyl cellulose ether and carboxymethyl cellulose ether.

13. The fly ash-based foamed geopolymer according to claim 11, wherein the thickener has a purity of not less than 96%.

14. The fly ash-based foamed geopolymer according to claim 11, wherein the thickener has a viscosity of not less than 30000 cp.

15. The fly ash-based foamed geopolymer according to claim 1, wherein the trisodium phosphate has a purity of not less than 98%.

16. The fly ash-based foamed geopolymer according to claim 1, the calcium stearate powders have a purity of not less than 99%.

17. The fly ash-based foamed geopolymer according to claim 1, wherein the water reducer comprises any one or a combination of at least two of a polycarboxylic acid water reducer, a naphthalene sulfonate water reducer, an aliphatic water reducer, a lignosulfonate water reducer or an amino-sulfonate water reducer.

18. The fly ash-based foamed geopolymer according to claim 1, wherein the foaming agent comprises a hydrogen peroxide solution.

19. The fly ash-based foamed geopolymer according to claim 18, wherein the hydrogen peroxide solution has a concentration of not less than 30%.

20. A preparation method for the fly ash-based foamed geopolymer according to claim 1, comprising the following steps: (1) stirring the fly ash-based material, the composite alkali solution, the thickener, the foam stabilizer A and the water reducer according to formula amounts to obtain a slurry; (2) adding the foaming agent into the slurry obtained in step (1), stirring to obtain a mixture, and then injecting the mixture into a mold; and (3) placing the mixture and the mold in step (2) in a curing chamber for curing, demoulding, and then placing the demoulded sample in a curing environment for curing, so as to obtain the fly ash-based foamed geopolymer.

21. The preparation method according to claim 20, wherein the stirring in step (1) is carried out in a mixing kettle.

22. The preparation method according to claim 20, wherein a stirring blade for the stirring in step (1) has a revolution speed of 115-135 r/min and a rotation speed of 275-295 r/min.

23. The preparation method according to claim 20, wherein the stirring in step (1) is performed for a period of 4-6 min.

24. The preparation method according to claim 20, wherein a stirring blade for the stirring in step (2) has a revolution speed of 57-67 r/min and a rotation speed of 135-145 r/min.

25. The preparation method according to claim 20, wherein the stirring in step (2) is performed for a period of 20-40 s.

26. The preparation method according to claim 20, wherein the process of injecting the mixture into the mold in step (2) is to inject the mixture into a depth of of the mold.

27. The preparation method according to claim 20, wherein the curing chamber in step (3) has a temperature of 65-75 C.

28. The preparation method according to claim 20, wherein the process of curing in the curing chamber in step (3) is performed for a period of 12-24 h.

29. The preparation method according to claim 20, wherein the curing environment in step (3) has a temperature of 18-22 C. and a humidity of at least 95%.

30. The preparation method according to claim 20, wherein a process of curing in the curing environment in step (3) is performed for a period of 7 days.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The accompanying drawings are used to provide a further understanding of the technical solutions herein and constitute a part of the specification, which are used to explain the technical solutions herein in conjunction with the examples of the present application and have no limitation on the technical solutions herein.

(2) FIG. 1 is a schematic diagram of raw materials used for a fly ash-based foamed geopolymer in the examples of the present application.

(3) FIG. 2 is an appearance view of a finished fly ash-based foamed geopolymer prepared in Example 1.

(4) FIG. 3 is an X-ray tomographic reconstruction projection of a fly ash-based foamed geopolymer prepared in Example 1.

(5) FIG. 4 is a pore distribution diagram of a fly ash-based foamed geopolymer prepared in Example 1 after X-ray tomographic reconstruction.

(6) FIG. 5 is an appearance view of a finished fly ash-based foamed geopolymer prepared in Example 2.

(7) FIG. 6 is an X-ray tomographic reconstruction projection of a fly ash-based foamed geopolymer prepared in Example 2.

(8) FIG. 7 is a pore distribution diagram of a fly ash-based foamed geopolymer prepared in Example 2 after X-ray tomographic reconstruction.

DETAILED DESCRIPTION

(9) The technical solutions of the present application will be further illustrated below in terms of specific embodiments. It should be clear to those skilled in the art that the examples are only used for a better understanding of the present application and should not be regarded as a specific limitation to the present application.

(10) Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the art to which the present application pertains. The terms used in the specification of the present application are only used for describing specific examples and are not intended to limit the present application.

(11) The fly ash used in the examples of the present application is the fly ash of Grade II or above specified in the national standard GB/T 1596-2017 Fly Ash Used for Cement and Concrete, with SO.sub.33.0; the slag used in the examples of the present application is the ground granulated blast furnace slag of S95 grade or above specified in GB/T 18046-2017 Ground Granulated Blast Furnace Slag Used for Cement, Mortar and Concrete.

Example 1

(12) This example provides a fly ash-based foamed geopolymer, and raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 900 parts of a fly ash-based material; 600 parts of a composite alkali solution; 2 parts of a foam stabilizer A; 5 parts of a water reducer; and 20 parts of a foaming agent.

(13) In the raw materials, the foam stabilizer A is calcium stearate powders with a purity of not less than 99%; the water reducer is a polycarboxylic acid water reducer; the foaming agent is a hydrogen peroxide solution with a concentration of 30%; the fly ash-based material is 100% fly ash.

(14) The composite alkali solution is prepared by the following preparation method: a composite alkali activator, a metal complexing agent and a foam stabilizer B were stirred and mixed thoroughly, so as to obtain the composite alkali solution.

(15) Based on a mass of the composite alkali solution being 100%, the composite alkali activator had a content of 96%, the metal complexing agent had a content of 0.3%, and the foam stabilizer B had a content of 3.7%; the composite alkali activator had a modulus of 1.0; the metal complexing agent was triethanolamine with a solid content of not less than 78%; the foam stabilizer B was sodium dodecylbenzenesulfonate powders with a purity of not less than 88%.

(16) The composite alkali activator is prepared by the following preparation method: sodium hydroxide powders and water were added to water glass, stirred thoroughly, then sealed and put aside for later use, so as to obtain the composite alkali activator; based on a mass of the composite alkali activator being 100%, the sodium hydroxide powders had a content of 9%, the water had a content of 5.8%, the water glass had a content of 85.2%; the sodium hydroxide powders had a purity of not less than 96%; the water was tap water; the water glass had a modulus of 1.0 and a Baume degree of 34.0.

(17) A preparation method of the fly ash-based foamed geopolymer comprises the following steps: (1) the fly ash-based material, the composite alkali solution, the foam stabilizer A and the water reducer were put in a mixing kettle according to the formula amounts, and rapidly stirred for 6 min where the stirring blade had a revolution speed of 115 r/min and a rotation speed of 275 r/min, such that the neat slurry was uniform and no solid powders were settled down, so as to obtain a slurry; (2) the foaming agent was quickly added into the slurry obtained in step (1), and slowly stirred for 40 s where the stirring blade had a revolution speed of 57 r/min and a rotation speed of 135 r/min, so as to obtain a mixture, and subsequently the mixture was quickly injected into a mold to the depth, and then the mold was covered with a polyethylene film to avoid water loss; and (3) the mixture obtained in step (2) and the mold were placed in a curing cabin at 65 C. and cured for 24 h and then demoulded, and subsequently, the demoulded sample was placed in a standard curing environment where a temperature was 20 C. and a humidity was 95% and cured for 7 days, so as to obtain the fly ash-based foamed geopolymer.

(18) The schematic diagram of raw materials used for the fly ash-based foamed geopolymer in this example is shown in FIG. 1.

(19) The appearance view of the finished fly ash-based foamed geopolymer prepared in this example is shown in FIG. 2, the X-ray tomographic reconstruction projection is shown in FIG. 3, and the pore distribution diagram after X-ray tomographic reconstruction is shown in FIG. 4. As can be seen from the drawings, the sample of fly ash-based foamed geopolymer prepared in this example has dense and uniform pores, good pore independence, high restriction on pore connectivity, no visible defects in the sample skeleton, and strong structural support for the pores. The size of the sample of fly ash-based foamed geopolymer in FIG. 2 does not represent the size of the sample prepared in this example, which is only the size taken for testing.

Example 2

(20) This example provides a fly ash-based foamed geopolymer, and raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 1000 parts of a fly ash-based material; 700 parts of a composite alkali solution; 10 parts of a thickener; 6 parts of a foam stabilizer A; 10 parts of a water reducer; and 40 parts of a foaming agent.

(21) In the raw materials, the thickener is methyl cellulose ether with a purity of not less than 96% and a viscosity of 30000 cp; the foam stabilizer A is calcium stearate powders with a purity of not less than 99%; the water reducer is a polycarboxylic acid water reducer; the foaming agent is a hydrogen peroxide solution with a concentration of 30%.

(22) The fly ash-based material is prepared by the following preparation method: fly ash and a calcareous material were added in a mixing kettle and stirred and mixed thoroughly, so as to obtain the fly ash-based material.

(23) Based on a mass of the fly ash-based material being 100%, the fly ash had a content of 90%, and the calcareous material had a content of 10%; the calcareous material was ore slags.

(24) The composite alkali solution is prepared by the following preparation method: a composite alkali activator, a metal complexing agent and a foam stabilizer B were stirred and mixed thoroughly, so as to obtain the composite alkali solution.

(25) Based on a mass of the composite alkali solution being 100%, the composite alkali activator had a content of 95%, the metal complexing agent had a content of 0.5%, and the foam stabilizer B had a content of 4.5%; the composite alkali activator had a modulus of 1.5; the metal complexing agent was triethanolamine with a solid content of not less than 78%; the foam stabilizer B was sodium dodecylbenzenesulfonate powders with a purity of not less than 88%.

(26) The composite alkali activator is prepared by the following preparation method: sodium hydroxide powders and water were added to water glass, stirred thoroughly, then sealed and put aside for later use, so as to obtain the composite alkali activator; based on a mass of the composite alkali activator being 100%, the sodium hydroxide powders had a content of 8.5%, the water had a content of 4.5%, the water glass had a content of 87%; the sodium hydroxide powders had a purity of not less than 96%; the water was tap water; the water glass had a modulus of 3.8 and a Baume degree of 42.0.

(27) A preparation method of the fly ash-based foamed geopolymer comprises the following steps: (1) the fly ash-based material, the composite alkali solution, the thickener, the foam stabilizer A and the water reducer were put in a mixing kettle according to the formula amounts, and rapidly stirred for 4 min where the stirring blade had a revolution speed of 135 r/min and a rotation speed of 295 r/min, such that the neat slurry was uniform and no solid powders were settled down, so as to obtain a slurry; (2) the foaming agent was quickly added into the slurry obtained in step (1), and slowly stirred for 20 s where the stirring blade had a revolution speed of 67 r/min and a rotation speed of 145 r/min, so as to obtain a mixture, and subsequently the mixture was quickly injected into a mold to the depth, and then the mold was covered with a polyethylene film to avoid water loss; and (3) the mixture obtained in step (2) and the mold were placed in a curing cabin at 75 C. and cured for 24 h and then demoulded, and subsequently, the demoulded sample was placed in a standard curing environment where a temperature was 20 C. and a humidity was 96% and cured for 7 days, so as to obtain the fly ash-based foamed geopolymer.

(28) The schematic diagram of raw materials used for the fly ash-based foamed geopolymer in this example is shown in FIG. 1.

(29) The appearance view of the finished fly ash-based foamed geopolymer prepared in this example is shown in FIG. 5, the X-ray tomographic reconstruction projection is shown in FIG. 6, and the pore distribution diagram after X-ray tomographic reconstruction is shown in FIG. 7. As can be seen from the drawings, the sample of fly ash-based foamed geopolymer prepared in this example has dense and uniform pores, good pore independence, high restriction on pore connectivity, no visible defects in the sample skeleton, and strong structural support for the pores. The size of the sample of fly ash-based foamed geopolymer in FIG. 5 does not represent the size of the sample prepared in this example, which is only the size taken for testing.

Example 3

(30) This example provides a fly ash-based foamed geopolymer, and raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 920 parts of a fly ash-based material; 620 parts of a composite alkali solution; 2 parts of a thickener; 3 parts of a foam stabilizer A; 6 parts of a water reducer; and 25 parts of a foaming agent.

(31) In the raw materials, the thickener is carboxymethyl cellulose ether with a purity of not less than 96% and a viscosity of 35000 cp; the foam stabilizer A is trisodium phosphate with a purity of not less than 98%; the water reducer is a polycarboxylic acid water reducer; the foaming agent is a hydrogen peroxide solution with a concentration of 30%.

(32) The fly ash-based material is prepared by the following preparation method: fly ash and a calcareous material were added in a mixing kettle and stirred and mixed thoroughly, so as to obtain the fly ash-based material.

(33) Based on a mass of the fly ash-based material being 100%, the fly ash had a content of 92%, and the calcareous material had a content of 8%; the calcareous material was ore slags.

(34) The composite alkali solution is prepared by the following preparation method: a composite alkali activator, a metal complexing agent and a foam stabilizer B were stirred and mixed thoroughly, so as to obtain the composite alkali solution.

(35) Based on a mass of the composite alkali solution being 100%, the composite alkali activator had a content of 98%, the metal complexing agent had a content of 0.05%, and the foam stabilizer B had a content of 1.95%; the composite alkali activator had a modulus of 1.3; the metal complexing agent was triethanolamine with a solid content of not less than 78%; the foam stabilizer B was sodium dodecylbenzenesulfonate powders with a purity of not less than 88%.

(36) The composite alkali activator is prepared by the following preparation method: sodium hydroxide powders and water were added to water glass, stirred thoroughly, then sealed and put aside for later use, so as to obtain the composite alkali activator; based on a mass of the composite alkali activator being 100%, the sodium hydroxide powders had a content of 9%, the water had a content of 7%, the water glass had a content of 84%; the sodium hydroxide powders had a purity of not less than 96%; the water was tap water; the water glass had a modulus of 2.0 and a Baume degree of 36.0.

(37) A preparation method of the fly ash-based foamed geopolymer comprises the following steps: (1) the fly ash-based material, the composite alkali solution, the thickener, the foam stabilizer A and the water reducer were put in a mixing kettle according to the formula amounts, and rapidly stirred for 5 min where the stirring blade had a revolution speed of 120 r/min and a rotation speed of 280 r/min, such that the neat slurry was uniform and no solid powders were settled down, so as to obtain a slurry; (2) the foaming agent was quickly added into the slurry obtained in step (1), and slowly stirred for 30 s where the stirring blade had a revolution speed of 60 r/min and a rotation speed of 140 r/min, so as to obtain a mixture, and subsequently the mixture was quickly injected into a mold to the depth, and then the mold was covered with a polyethylene film to avoid water loss; and (3) the mixture obtained in step (2) and the mold were placed in a curing cabin at 70 C. and cured for 24 h and then demoulded, and subsequently, the demoulded sample was placed in a standard curing environment where a temperature was 20 C. and a humidity was 97% and cured for 7 days, so as to obtain the fly ash-based foamed geopolymer.

(38) The schematic diagram of raw materials used for the fly ash-based foamed geopolymer in this example is shown in FIG. 1.

Example 4

(39) This example provides a fly ash-based foamed geopolymer, and raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 950 parts of a fly ash-based material; 650 parts of a composite alkali solution; 5 parts of a thickener; 4 parts of a foam stabilizer A; 8 parts of a water reducer; and 30 parts of a foaming agent.

(40) In the raw materials, the thickener is carboxymethyl cellulose ether with a purity of not less than 96% and a viscosity of 40000 cp; the foam stabilizer A is trisodium phosphate with a purity of not less than 98%; the water reducer is a polycarboxylic acid water reducer; the foaming agent is a hydrogen peroxide solution with a concentration of 30%.

(41) The fly ash-based material is prepared by the following preparation method: fly ash and a calcareous material were added in a mixing kettle and stirred and mixed thoroughly, so as to obtain the fly ash-based material.

(42) Based on a mass of the fly ash-based material being 100%, the fly ash had a content of 95%, and the calcareous material had a content of 5%; the calcareous material was ore slags.

(43) The composite alkali solution is prepared by the following preparation method: a composite alkali activator, a metal complexing agent and a foam stabilizer B were stirred and mixed thoroughly, so as to obtain the composite alkali solution.

(44) Based on a mass of the composite alkali solution being 100%, the composite alkali activator had a content of 97%, the metal complexing agent had a content of 0.1%, and the foam stabilizer B had a content of 2.9%; the composite alkali activator had a modulus of 1.2; the metal complexing agent was triethanolamine with a solid content of not less than 78%; the foam stabilizer B was sodium dodecylbenzenesulfonate powders with a purity of not less than 88%.

(45) The composite alkali activator is prepared by the following preparation method: sodium hydroxide powders and water were added to water glass, stirred thoroughly, then sealed and put aside for later use, so as to obtain the composite alkali activator; based on a mass of the composite alkali activator being 100%, the sodium hydroxide powders had a content of 8.8%, the water had a content of 5%, the water glass had a content of 86.2%; the sodium hydroxide powders had a purity of not less than 96%; the water was tap water; the water glass had a modulus of 3.0 and a Baume degree of 40.0.

(46) A preparation method of the fly ash-based foamed geopolymer comprises the following steps: (1) the fly ash-based material, the composite alkali solution, the thickener, the foam stabilizer A and the water reducer were put in a mixing kettle according to the formula amounts, and rapidly stirred for 5 min where the stirring blade had a revolution speed of 130 r/min and a rotation speed of 285 r/min, such that the neat slurry was uniform and no solid powders were settled down, so as to obtain a slurry; (2) the foaming agent was quickly added into the slurry obtained in step (1), and slowly stirred for 30 s where the stirring blade had a revolution speed of 65 r/min and a rotation speed of 140 r/min, so as to obtain a mixture, and subsequently the mixture was quickly injected into a mold to the depth, and then the mold was covered with a polyethylene film to avoid water loss; and (3) the mixture obtained in step (2) and the mold were placed in a curing cabin at 70 C. and cured for 24 h and then demoulded, and subsequently, the demoulded sample was placed in a standard curing environment where a temperature was 20 C. and a humidity was 95% and cured for 7 days, so as to obtain the fly ash-based foamed geopolymer.

(47) The schematic diagram of raw materials used for the fly ash-based foamed geopolymer in this example is shown in FIG. 1.

Example 5

(48) This example provides a fly ash-based foamed geopolymer, and raw materials for preparing the fly ash-based foamed geopolymer comprise the following components in parts by weight: 980 parts of a fly ash-based material; 680 parts of a composite alkali solution; 8 parts of a thickener; 5 parts of a foam stabilizer A; 9 parts of a water reducer; and 35 parts of a foaming agent.

(49) In the raw materials, the thickener is carboxymethyl cellulose ether with a purity of not less than 96% and a viscosity of not less than 30000 cp; the foam stabilizer A is trisodium phosphate with a purity of not less than 98%; the water reducer is a polycarboxylic acid water reducer; the foaming agent is a hydrogen peroxide solution with a concentration of 30%.

(50) The fly ash-based material is prepared by the following preparation method: fly ash and a calcareous material were added in a mixing kettle and stirred and mixed thoroughly, so as to obtain the fly ash-based material.

(51) Based on a mass of the fly ash-based material being 100%, the fly ash had a content of 98%, and the calcareous material had a content of 2%; the calcareous material was ore slags.

(52) The composite alkali solution has the same preparation method and raw materials as in Example 1.

(53) The composite alkali activator has the same preparation method and raw materials as in Example 1.

(54) A preparation method of the fly ash-based foamed geopolymer comprises the following steps: (1) the fly ash-based material, the composite alkali solution, the thickener, the foam stabilizer A and the water reducer were put in a mixing kettle according to the formula amounts, and rapidly stirred for 6 min where the stirring blade had a revolution speed of 125 r/min and a rotation speed of 280 r/min, such that the neat slurry was uniform and no solid powders were settled down, so as to obtain a slurry; (2) the foaming agent was quickly added into the slurry obtained in step (1), and slowly stirred for 40 s where the stirring blade had a revolution speed of 60 r/min and a rotation speed of 135 r/min, so as to obtain a mixture, and subsequently the mixture was quickly injected into a mold to the depth, and then the mold was covered with a polyethylene film to avoid water loss; and (3) the mixture obtained in step (2) and the mold were placed in a curing cabin at 75 C. and cured for 24 h and then demoulded, and subsequently, the demoulded sample was placed in a standard curing environment where a temperature was 20 C. and a humidity was 95% and cured for 7 days, so as to obtain the fly ash-based foamed geopolymer.

(55) The schematic diagram of raw materials used for the fly ash-based foamed geopolymer in this example is shown in FIG. 1.

Example 6

(56) This example differs from Example 1 only in that for the preparation of composite alkali solution, no metal complexing agent was added, the composite alkali activator had a content of 96.3% and the foam stabilizer B had a content of 3.7%, and other conditions are the same as in Example 1.

Example 7

(57) This example differs from Example 1 only in that for the preparation of composite alkali solution, the metal complexing agent had a content of 0.7%, the composite alkali activator had a content of 95.6% and the foam stabilizer B had a content of 3.7%, and other conditions are the same as in Example 1.

Comparative Example 1

(58) This comparative example differs from Example 1 only in that for the raw materials for preparing the fly ash-based foamed geopolymer, the composite alkali solution had an addition amount of 500 parts, and other conditions are the same as in Example 1.

Comparative Example 2

(59) This comparative example differs from Example 1 only in that for the raw materials for preparing the fly ash-based foamed geopolymer, the composite alkali solution had an addition amount of 800 parts, and other conditions are the same as in Example 1.

Comparative Example 3

(60) This comparative example differs from Example 1 only in that for the raw materials for preparing the fly ash-based foamed geopolymer, the foaming agent had an addition amount of 45 parts, and other conditions are the same as in Example 1.

(61) The fly ash-based foamed geopolymers prepared in Examples 1-7 and Comparative Examples 1-3 are subjected to performance tests, and the test methods are as follows. (1) The compressive strength and apparent density are tested according to the methods specified in GBT 11969-2008 Test methods of autoclaved aerated concrete; the 7-day compressive strength refers to the compressive strength of a fly ash-based foamed geopolymer which is obtained by conducting the compressive strength test after curing a demoulded sample in a standard curing environment for 7 days. (2) Porosity, porosity roundness and equivalent spherical diameter are tested by micron X-ray tomography.

(62) The results of performance tests are shown in Table 1.

(63) TABLE-US-00001 TABLE 1 Average 7-Day equivalent Apparent compressive spherical Utilization density strength Porosity Porosity diameter efficiency (kg/m.sup.3) (MPa) (%) roundness ESD (mm) of fly ash (%) Example 1 447.1 1.79 71 0.89 0.36 100 Example 2 507.2 3.30 67 0.82 0.38 90 Example 3 521.4 3.60 65 0.88 0.38 92 Example 4 516.2 3.10 65 0.83 0.35 95 Example 5 421.7 1.56 76 0.85 0.37 98 Example 6 494.6 0.91 63 0.87 1.71 100 Example 7 476.9 1.21 66 0.82 0.89 100 Comparative 465.2 1.44 74 0.79 0.54 100 Example 1 Comparative 455.1 1.83 73 0.90 0.39 100 Example 2 Comparative 398.1 1.15 78 0.82 0.39 100 Example 3

(64) As can be seen from Table 1, the fly ash-based foamed geopolymer samples prepared from a large amount of fly ash (utilization efficiency of fly ash: 90%-100%) in Examples 1-5 have the characteristics of low apparent density (421.7-521.4 kg/m.sup.3) and high early strength (1.56-3.60 MPa), and can be used as lightweight porous building materials. In addition, by adding the calcareous material, the apparent density of the sample can be effectively increased in a small range, and at the same time the early compressive strength of the sample can be greatly enhanced; it is realized to adjust and control the strength and apparent density of the sample in the actual use process, which satisfies various use scenarios.

(65) Compared with Example 1, the fly ash-based foamed geopolymer samples prepared in Example 6 and Example 7 both have slightly increased apparent density and significantly reduced compressive strength, which indicates that overly much or little addition amount of metal complexing agent will affect the performance of the samples.

(66) Compared with Example 1, the fly ash-based foamed geopolymer sample prepared in Comparative Example 1 has significantly reduced compressive strength, and although the fly ash-based foamed geopolymer sample prepared in Comparative Example 2 has slightly increased compressive strength, its surface has alkali solids and looks white, which affects the surface quality of the product.

(67) Compared with Example 1, the fly ash-based foamed geopolymer sample prepared in Comparative Example 3 has significantly reduced compressive strength.

(68) The applicant has stated that although the fly ash-based foamed geopolymer, the preparation method therefor and the use thereof are described through the above examples, the present application is not limited to the above examples, which means that the implementation of the present application does not necessarily depend on the above examples. It should be apparent to those skilled in the art that any improvements made to the present application, equivalent substitutions of raw materials selected in the present application, addition of adjuvant ingredients, selection of specific manners, etc. shall all fall within the protection scope and the disclosure scope of the present application.