Composition for geopolymer, geopolymer and preparation method thereof

Abstract

The present invention relates to the field of building materials, and discloses a composition for geopolymers, a geopolymer and a preparation method thereof. The composition contains a composite foaming agent, a cementitious material and water in a mass ratio of 1:110-250:40-50; the composite foaming agent contains a foaming agent, sodium dodecyl sulfate and sodium dodecyl sulfonate in a mass ratio of 10:0.5-2:0.5-2; the pH value of the foaming agent is ≥8; the modulus of the alkali activator is 1-1.2; the admixture contains metakaolin and slag. The geopolymer material of the present invention has excellent heat insulation performance and lightweight characteristics.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and particularly to a composition for geopolymers, a geopolymer and a preparation method thereof. Background Art

[0002] Geopolymers are a class of inorganic polymers synthesized by alkali activation reactions. Due to their good physical and chemical properties, such as high strength, high temperature resistance, corrosion resistance and low shrinkage, geopolymers have been applied in the construction industry, especially in fields such as concrete, refractory materials and thermal insulation materials. In addition, geopolymers also show certain application potential in environmental engineering, such as in fields like wastewater treatment and harmless treatment of solid waste. Although certain progress has been made in these traditional applications of geopolymers, their applications in some emerging fields are still limited.

[0003] Porous geopolymers can significantly reduce their thermal conductivity by introducing a large number of uniformly distributed pores inside the material, while maintaining certain mechanical properties. This porous structure provides the possibility for the light weight, improved thermal insulation performance and enhanced sound insulation performance of geopolymers.

[0004] At present, the preparation methods of porous geopolymers mainly include introducing foaming agents, pore-forming agents or using the template burning-out method, etc. However, these methods often have the following problems: First, the pore distribution is uneven, resulting in unstable material properties; Second, pore wall collapse is likely to occur during the preparation process, affecting the overall thermal insulation effect; Third, some pore-forming agents may cause environmental pollution, not meeting the requirements of green development.

[0005] Therefore, how to obtain a porous-structured geopolymer with high thermal insulation performance by optimizing the preparation process while maintaining the good mechanical properties of geopolymers has become a key issue in current research and applications.

[0006] CN102617106A discloses a mineral polymer foaming material, which contains the following components in parts by weight: 50 - 100 parts of metakaolin, 0 - 50 parts of admixture, 50 - 100 parts of water glass, 0.1 - 15 parts of foaming agent, 0 - 10 parts of foam stabilizer and 10 - 90 parts of water. However, this solution has the problems that the multi-component system ratio is complex, resulting in insufficient controllability of the preparation process, and the matching of the light weight and strength of the prepared samples is insufficient (for example, when the density is 320 kg / m³, the compressive strength is only 0.8 MPa), leading to insufficient practicality of the material.

[0007] Therefore, it is of great significance to invent a porous-structured geopolymer with high thermal insulation performance. Summary of the Invention

[0008] The object of the present invention is to overcome the problems of poor heat insulation performance and insufficient light weight of geopolymer materials.

[0009] To achieve the above object, a first aspect of the present invention provides a composition for geopolymer, which composition contains a composite foaming agent, a gelling material and water in a mass ratio of 1:110 - 250:40 - 50;

[0010] The composite foaming agent contains a foaming agent, sodium dodecyl sulfate and sodium dodecyl sulfonate in a mass ratio of 10:0.5 - 2:0.5 - 2; the pH value of the foaming agent is ≥8; the gelling material contains an alkali activator and a filler in a mass ratio of 1:10 - 13;

[0011] The modulus of the alkali activator is 1 - 1.2; the filler contains metakaolin and slag.

[0012] A second aspect of the present invention provides a method for preparing geopolymer, which method is carried out by using the composition for geopolymer described in the first aspect, and the method includes:

[0013] (1) Foaming the composite foaming agent and water to obtain foam; and,

[0014] First mixing the gelling material and water to obtain solution 1;

[0015] (2) Second mixing the foam and solution 1 to obtain the geopolymer.

[0016] A third aspect of the present invention provides a geopolymer, which geopolymer is prepared by the method described in the second aspect.

[0017] The present invention has at least the following advantages:

[0018] (1) The geopolymer of the present invention not only realizes the light weight of the material, but also has excellent mechanical strength and stability.

[0019] (2) The geopolymer of the present invention has a low thermal conductivity, effectively enhancing the thermal insulation performance of the material.

[0020] (3) The process for preparing geopolymer in the present invention is simple and has low energy consumption, and has excellent application prospects. Description of the Drawings

[0021] Figure 1 is a scanning electron microscope image of the geopolymer prepared in Example 6;

[0022] Figure 2 is a computed tomography (CT) image of the geopolymer prepared in Example 6. Detailed Description

[0023] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] It should be noted that in various aspects of the present invention, for the same components or terms in each aspect, the present invention only describes them once in one aspect without repeating the description. Those skilled in the art should not understand this as a limitation of the present invention.

[0025] As mentioned above, the first aspect of the present invention provides a composition for geopolymers, which contains a composite foaming agent, a gelling material, and water with a mass ratio of 1:110 - 250:40 - 50;

[0026] The composite foaming agent contains a foaming agent, sodium dodecyl sulfate, and sodium dodecyl sulfonate with a mass ratio of 10:0.5 - 2:0.5 - 2; the pH value of the foaming agent ≥ 8; the gelling material contains an alkali activator and an admixture with a mass ratio of 1:10 - 13;

[0027] The modulus of the alkali activator is 1 - 1.2; the admixture contains metakaolin and slag.

[0028] In the technical solution of the present invention, a composite foaming agent with specific components is used, in combination with a specific gelling material including an alkali activator with a modulus of 1 - 1.2, metakaolin, and slag, so that the prepared geopolymer has excellent heat insulation performance and mechanical strength, while maintaining the lightweight characteristics of the material, and is suitable for high-temperature heat insulation material fields such as construction, energy conservation, and aviation, providing an excellent solution for engineering applications in high-temperature environments.

[0029] Preferably, the mass ratio of the composite foaming agent, the gelling material, and the water is 1:120 - 150:40 - 50.

[0030] Preferably, the foaming agent is selected from Enlin 12# and / or HZ - 1.

[0031] It should be noted that Enlin 12# and HZ - 1 are the models of the foaming agent. Enlin 12# is purchased from Hebei Enlin Building Materials Company, and HZ - 1 is purchased from Jiangsu Sobute New Materials Co., Ltd.

[0032] More preferably, the foaming agent is Enlin 12#. The geopolymer prepared by using this foaming agent in combination with the remaining components of the present invention has more excellent heat insulation performance and mechanical properties.

[0033] Preferably, the alkali activator is a combination of potassium silicate and potassium hydroxide.

[0034] It should be noted that the modulus of the alkali activator refers to the ratio of the total molar number of silicon dioxide (SiO2) to the total molar number of alkali metal oxides (K2O) in the alkali activator system, where silicon dioxide and alkali metal oxides are obtained by chemical equivalent conversion of the actual components of the raw materials.

[0035] Preferably, the metakaolin accounts for 70 - 95% of the total mass of the admixture, and the slag accounts for 5 - 30% of the total mass of the admixture. Under this preferred condition, it is helpful to significantly improve the foaming stability of the geopolymer foaming material and the final cell structure, improve the strength and rigidity of the material, while maintaining its light weight and good heat insulation and sound insulation properties. The active components in the slag can synergistically interact with the components of the metakaolin, effectively control the expansion of the foaming agent during the foaming process, reduce the dosage of the foaming agent, and endow the foaming material with stronger impermeability and durability.

[0036] Preferably, the admixture is a combination of metakaolin and slag.

[0037] Preferably, the slag in the present invention is the slag meeting the GB / T 18046 - 2017 standard.

[0038] As described above, the second aspect of the present invention provides a method for preparing geopolymers, which is carried out using the geopolymer composition described in the first aspect. The method includes:

[0039] (1) Foaming the composite foaming agent and water to obtain foam; and,

[0040] Mixing the gelling material and water for the first time to obtain solution 1;

[0041] (2) Mixing the foam and solution 1 for the second time to obtain the geopolymer.

[0042] In the present invention, by controlling the addition sequence of different raw materials, the mixing between different admixtures is made more uniform, ensuring that the geopolymer exhibits more excellent mechanical properties and heat insulation properties on the basis of light weight; in addition, by foaming the composite foaming agent and then mixing it with solution 1 for the second time, the cell structure and uniformity of the foaming material can be further optimized. The foam fully reacts with the active components in solution 1, which can effectively adjust the stability of the foaming agent and ensure the uniform distribution of cells. Through this process, not only the foaming effect is improved, but also the mechanical properties and thermal stability of the foaming material are enhanced.

[0043] It should be noted that the present invention does not particularly limit the operation of the foaming treatment or the equipment used. As long as a uniform creamy-textured foam can be obtained, those skilled in the art can select according to the known technical means in the art, and the present invention will not elaborate herein. Those skilled in the art should not understand this as a limitation to the present invention.

[0044] Preferably, during the foaming treatment in step (1), the mass ratio of the composite foaming agent to the water is 1:10 - 20. When the foam prepared under this specific condition in the present invention is used to prepare geopolymers, it effectively enhances the heat insulation performance of the material and is more conducive to the lightweight of the material.

[0045] Preferably, in step (1), the operation of the foaming treatment includes: the foaming temperature is 30 - 40 °C, and the time is 2 - 5 min.

[0046] Preferably, the first mixing and the second mixing each independently satisfy: the temperature is 20 - 40 °C, the time is 2 - 30 min, and the stirring speed is 500 - 1000 rpm.

[0047] According to another preferred embodiment, the product obtained by the mixing treatment is sequentially subjected to injection molding and curing treatment to obtain the geopolymer.

[0048] Preferably, the conditions of the curing treatment include: the temperature is 60 - 80 °C, the time is 48 - 60 h, and the relative humidity is 85 - 95%.

[0049] The present invention does not particularly limit the operation of the injection molding. Those skilled in the art can select according to the known technical means in the art. The present invention exemplarily provides a preferred specific implementation manner hereinafter and will not elaborate herein. Those skilled in the art should not understand this as a limitation to the present invention.

[0050] As described above, the third aspect of the present invention provides a geopolymer, which is prepared by the method described in the second aspect.

[0051] In the following examples, unless otherwise specified, the raw materials are all ordinary commercially available products.

[0052] Potassium silicate: K2SiO3, CAS number: 1312 - 76 - 1, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0053] Foaming agent Enlin 12#: Model: 12#, pH is 10, purchased from Hebei Enlin Building Materials Company.

[0054] Foaming agent 1: Model: HZ - 1 type, pH is 10.5, purchased from Jiangsu Sobute New Materials Co., Ltd.

[0055] Foaming agent 2: Enlin 85#, model: 85#, pH 7.2, purchased from Hebei Enlin Building Materials Company.

[0056] Example 1

[0057] (1) Foam 3.18 g of composite foaming agent (mass ratio of foaming agent Enlin 12#, sodium dodecyl sulfate and sodium dodecyl sulfonate is 10:1:1) and 31.8 g of water to obtain foam; the conditions for foaming treatment are: temperature 40 °C, time 5 min; the mass ratio of composite foaming agent to water is 1:10;

[0058] (2) First mix 34 g of alkali activator (potassium silicate and potassium hydroxide) with a modulus of 1.1, 350 g of admixture (mass ratio of metakaolin and slag is 95:5) and water to obtain Solution 1; the conditions for the first mixing are: temperature 20 °C, time 3 min, stirring speed 750 rpm;

[0059] Among them, the mass ratio of the total amount of composite foaming agent, gelling material and added water (the water added in Step 1 and Step 2) is 1:120.7:45.54; the mass ratio of alkali activator to admixture is 1:10.29;

[0060] (3) Second mix the foam in Step (2) and Solution 1 to obtain a geopolymer slurry with a creamy texture; the conditions for the second mixing are: first stir at 150 rpm for 2 min, then stir at 750 rpm for 30 s, temperature 20 °C;

[0061] (4) Quickly pour the geopolymer slurry into a triple steel mold with dimensions of 4 cm × 4 cm × 16 cm, and perform sealing and molding treatment. After 24 hours, demold, and then place the demolded product in a steam curing box at 60 °C for 48 h (relative humidity 90%) to obtain a geopolymer.

[0062] Example 2

[0063] This example is carried out using the same process as Example 1, the difference is that: in this example, while keeping the total amount of 350 g of admixture unchanged, the mass ratio of metakaolin and slag is 90:10, and the rest are the same as Example 1, to prepare a geopolymer.

[0064] Example 3

[0065] This example is carried out using the same process as Example 1, the difference is that, in this example, while keeping the total amount of 350 g of admixture unchanged, the mass ratio of metakaolin and slag is 85:15, and the rest are the same as Example 1, to prepare a geopolymer.

[0066] Example 4

[0067] This example is carried out using the same process as Example 1. The difference is that, in this example, while keeping the total amount of admixture at 350 g unchanged, the mass ratio of metakaolin to slag is 80:20, and the rest are the same as in Example 1, to prepare a geopolymer.

[0068] Example 5

[0069] This example is carried out using the same process as Example 1. The difference is that, in this example, while keeping the total amount of admixture at 350 g unchanged, the mass ratio of metakaolin to slag is 75:25, and the rest are the same as in Example 1, to prepare a geopolymer.

[0070] Example 6

[0071] This example is carried out using the same process as Example 1. The difference is that, in this example, while keeping the total amount of admixture at 350 g unchanged, the mass ratio of metakaolin to slag is 70:30, and the rest are the same as in Example 1, to prepare a geopolymer.

[0072] Example 7

[0073] This example is carried out using the same process as Example 6. The difference is that, under the condition of keeping the total amount of added water unchanged, the amount of water used in step (1) is adjusted to 73.14 g, and the amount of water used in step (2) is adjusted to 71.68 g, so that the mass ratio of the composite foaming agent to water is 1:23 during the foaming treatment, and the rest are the same as in Example 6, to prepare a geopolymer.

[0074] Example 8

[0075] This example is carried out using the same process as Example 6. The difference is that: the foaming agent Enlin 12# is replaced with an equal mass of foaming agent 1, and the rest are the same as in Example 6, to prepare a geopolymer.

[0076] Comparative Example 1

[0077] This comparative example is carried out using the same process as Example 6. The difference is that: in this comparative example, while keeping the total amount of 3.18 g of the composite foaming agent unchanged, the mass ratio of the foaming agent Enlin 12#, sodium dodecyl sulfate, and sodium dodecyl sulfonate is 10:4:1, and the rest are the same as in Example 6, to prepare a geopolymer.

[0078] Comparative Example 2

[0079] This comparative example was carried out using the same process as Example 6, with the difference that: in this comparative example, while keeping the total amount of 384 g of gelling material unchanged, the total amount of alkali activator was adjusted to 24 g (modulus 1.1), and the total amount of admixture was adjusted to 360 g, so that the mass ratio of alkali activator to admixture was 1:15, and the rest was the same as in Example 6, and a geopolymer was prepared.

[0080] Comparative Example 3

[0081] This comparative example was carried out using the same process as Example 6, with the difference that: in this comparative example, while keeping the amount of 34 g of alkali activator unchanged, the amounts of potassium silicate and potassium hydroxide were adjusted so that the modulus of the alkali activator was 1.3, and the rest was the same as in Example 6, and a geopolymer was obtained.

[0082] Comparative Example 4

[0083] This comparative example was carried out using the same process as Example 6, with the difference that: the foaming agent Enlin 12# was replaced with foaming agent 2, and the rest was the same as in Example 6, and a geopolymer was prepared.

[0084] Test Example 1

[0085] The geopolymer prepared in Example 6 was subjected to scanning electron microscopy testing under the following conditions: carried out at an accelerating voltage of 10 kV and a working distance of 8 mm, and the surface morphology was observed using the secondary electron image (SEI) mode;

[0086] The geopolymer prepared in Example 6 was subjected to CT scanning testing under the following conditions: scanning resolution 22 microns, scanning time 3 hours, and scanning angle from 0° to 180°;

[0087] The test results are shown in Figure 1 and Figure 2 as shown. Among them, Figure 1 in (a) is a scanning electron micrograph at 50 times magnification, Figure 1 in (b) represents a scanning electron micrograph at 300 times magnification; it can be seen from the figure that the prepared geopolymer has a nano-micron-millimeter multi-level pore structure, and the pores do not communicate with each other, synergistically inhibiting molecular heat conduction, convection and radiative heat transfer, and the complex pore network greatly extends the heat transfer path; the low thermal conductivity of the enclosed gas (such as air) in the pores further reduces the overall thermal conductivity of the material. This multi-mechanism synergistic effect endows it with excellent heat insulation performance and is suitable for high-efficiency thermal insulation scenarios such as building energy conservation.

[0088] It can be seen from Figure 2 that the prepared geopolymer has a high porosity, and the high porosity increases the thermal resistance through the solid-gas interface, thereby achieving the purpose of heat preservation.

[0089] Test Example 2

[0090] Measure the thermal conductivity and heat transfer coefficient of the geopolymers prepared in the measurement examples and comparative examples, and the test method refers to GB / T 10295-2008; measure the compressive strength of the geopolymers prepared in the measurement examples and comparative examples, and the test method refers to GB 17671-1999; measure the dry density of the geopolymers prepared in the measurement examples and comparative examples, and the test method refers to GB / T 11969-2020; the specific results are shown in Table 1.

[0091] Table 1

[0092]

[0093] From the above, it can be seen that the geopolymers of the present invention obviously have more excellent heat insulation properties, mechanical strength and light weight characteristics.

[0094] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A composition for geopolymers, characterized in that, The composition contains a composite foaming agent, a gelling material and water with a mass ratio of 1:110 - 250:40 - 50; The composite foaming agent contains a foaming agent, sodium dodecyl sulfate and sodium dodecyl sulfonate with a mass ratio of 10:0.5 - 2:0.5 - 2; the pH value of the foaming agent is ≥8; the gelling material contains an alkali activator and a blending material with a mass ratio of 1:10 - 13; The modulus of the alkali activator is 1 - 1.2; the blending material contains metakaolin and slag; the metakaolin accounts for 70 - 95% of the total mass of the blending material, and the slag accounts for 5 - 30% of the total mass of the blending material.

2. The composition according to claim 1, characterized in that, The alkali activator is a combination of potassium silicate and potassium hydroxide.

3. The composition according to claim 1 or 2, characterized in that, The blending material is a combination of metakaolin and slag.

4. A method for preparing geopolymers, characterized in that, This method is carried out using the geopolymer composition described in any one of claims 1 - 3, and this method includes: (1) Foaming the composite foaming agent and water to obtain foam; and, First mixing the gelling material and water to obtain solution 1; (2) Second mixing the foam and solution 1 to obtain the geopolymer.

5. The method according to claim 4, characterized in that, During the foaming process in step (1), the mass ratio of the composite foaming agent to the water is 1:10 - 20.

6. The method according to claim 4 or 5, characterized in that In step (1), the operations of the foaming process include: the foaming temperature is 30 - 40°C and the time is 2 - 5 min.

7. The method according to claim 4 or 5, characterized in that, Each of the first mixing and the second mixing independently satisfies: the temperature is 20 - 40°C, the time is 2 - 30 min, and the stirring speed is 500 - 1000 rpm.

8. The method according to claim 4 or 5, characterized in that This method includes: sequentially performing mold injection and curing treatment on the product obtained by the mixing treatment to obtain the geopolymer.

9. A geopolymer, characterized in that, This geopolymer is prepared by the method described in any one of claims 4 - 8.

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