A geopolymer based on calcium-based material activation, a preparation method thereof and a setting time regulation method thereof

Abstract

The application provides a kind of geopolymer based on calcium-based material activation and its preparation method and its setting time regulation method.The geopolymer includes metakaolin, alkali activator, calcium-based material A and calcium-based material B, the reaction product is optimized by calcium-based material A, the rapid setting risk of metakaolin geopolymer thermal shrinkage and high temperature environment is improved;Early reaction is promoted by calcium-based material B, and the setting and hardening time of metakaolin geopolymer is adjusted, and the reaction rate in low temperature environment is improved.A kind of geopolymer setting time regulation method, the setting time regulation method can predict the setting time of the geopolymer involved under different temperature conditions according to the raw material ratio and environmental temperature, and by adjusting the weight percentage of calcium-based material A and B, the geopolymer can meet the setting time requirement under different environmental temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of geopolymer technology, specifically to a geopolymer that can be adapted to different ambient temperatures and is activated based on calcium-based materials, its preparation method, and its method for controlling the setting time. Background Technology

[0002] Geopolymers are a novel low-carbon material with excellent strength and acid and alkali resistance. Their production process emits only 10% to 30% of the carbon emissions of ordinary silicate cement, thus being considered a "green" cement. Current research on geopolymers focuses on their application in high-strength, fire-resistant, corrosion-resistant, and high-durability building materials. However, the setting and hardening process of geopolymers is significantly affected by temperature, thus impacting their mechanical properties. At low temperatures, the setting time of geopolymers is significantly prolonged, and strength development is slow, resulting in lower final strength. Conversely, at high temperatures, the setting time is drastically shortened, the material's fluidity is rapidly lost, and shrinkage due to temperature strain affects strength. Therefore, controlling the setting time of geopolymers under different temperature conditions to ensure their workability is crucial for promoting their application in more engineering projects; currently, there is no specific method to address this problem.

[0003] Regarding the preparation of geopolymer materials suitable for different temperature scenarios, patent "A rapidly curing geopolymer at room temperature and its preparation method" (CN105621911A) uses metakaolin to be added to an alkali activator in steps and mixed to prepare the geopolymer. However, this method involves multiple additions, long mixing times, and is only applicable to room temperature conditions. Patent "A rapidly curing geopolymer based on low-temperature crystallization and its preparation method" (CN118307245A) proposes a method based on the low-temperature crystallization principle of metakaolin and an alkali activator, but it requires curing at 20°C before use in low-temperature environments. Patent "Metakaolin-slag-based geopolymer for oilfield cementing and its high-temperature retarder" (CN200810020859.3) proposes a geopolymer that can also be prepared and used at high temperatures, but this material is also only applicable to high temperatures. In summary, these patents all have limitations in their application to geopolymers under different temperature conditions, failing to cover a wide temperature range, and their long setting times make them inconvenient for engineering applications. Furthermore, the implementation of the aforementioned patent is based solely on material design with a specific mixing ratio and does not involve the calculation and optimization methods for polymer coagulation time under different temperature conditions. Summary of the Invention

[0004] The purpose of this invention is to address existing problems by providing a geopolymer based on calcium-based materials that can be used in different environmental temperatures, along with its preparation method and a method for controlling its setting time. The proposed method for controlling the setting time utilizes the properties of calcium-based materials A and B to regulate the setting time of the geopolymer, improving its applicability to different temperatures and possessing certain research reference value.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A geopolymer activated by calcium-based materials, wherein the geopolymer comprises, by weight percentage, 40-50% metakaolin, 42-50% alkali activator, 2-10% calcium-based material A, and 2-8% calcium-based material B, and the sum of the weight percentages of each raw material is 100%.

[0007] The preparation method of the geopolymer includes the following steps:

[0008] 1) Mixing: Pour metakaolin, calcium-based material A and calcium-based material B into a cement paste mixer and mix at low speed. Add alkali activator while mixing at low speed, then mix at low speed until the mixture is uniform. Finally, mix at high speed to obtain geopolymer paste.

[0009] 2) Molding and curing: Pour the geopolymer slurry prepared in step 1) into a mold, vibrate it on a vibration platform for 60 seconds, and place it in a specified temperature environment for curing for 24 hours to obtain the geopolymer based on calcium-based material activation.

[0010] Furthermore, the mesh size of the metakaolin is not less than 1250 mesh.

[0011] Furthermore, the alkali activator, by weight percentage, comprises 70-72% liquid water glass, 12-14% solid sodium hydroxide, and 16-18% water, and the modulus of the alkali activator is adjusted to 1.4-1.6 using solid sodium hydroxide;

[0012] The preparation method of the alkaline activator is as follows:

[0013] a) Preparation of sodium hydroxide solution: Mix solid sodium hydroxide and water, stir until a uniform and transparent solution is obtained, and use it after the solution temperature drops to room temperature;

[0014] b) Preparation of alkali activator: Mix liquid water glass with the sodium hydroxide solution prepared in step a) and stir until homogeneous to obtain alkali activator.

[0015] Furthermore, the liquid water glass has a modulus of 3.1-3.3 and a solid content of 42.5%.

[0016] Furthermore, the calcium-based material A is high-calcium fly ash, and its composition includes: SiO2: 45-55wt%, Al2O3: 25-35wt%, CaO: 10-15wt%, with the remainder being impurities; the calcium-based material B is either calcium oxide or cement clinker, preferably calcium oxide.

[0017] Furthermore, in step 2), the ambient temperature of the site is 5-50℃.

[0018] Furthermore, in step 1), the stirring speeds of the low-speed stirring and the high-speed stirring are 90-100 r / min and 250-260 r / min, respectively.

[0019] A method for controlling the setting time of metakaolin soil polymer based on calcium-based material activation, as described in any one of the claims, wherein the method for controlling the setting time includes the following steps:

[0020] Step 1: Based on the selected initial raw material ratio, calculate the molar ratio of Na2O / Al2O3. The average site temperature over 72 hours was obtained as the ambient temperature T based on the site temperature conditions.

[0021] Step 2: By substituting the ambient temperature T and the initial raw material ratio into the formula for calculating the geopolymer setting time, the setting time of the geopolymer activated by calcium-based materials is calculated. The setting time includes the initial setting time and the final setting time.

[0022] Step 3: Compare the initial setting time and final setting time calculated in Step 2 with the initial setting time and final setting time required for construction. If they do not meet the construction requirements, adjust the weight percentages of calcium-based material A and calcium-based material B based on the formula for calculating the setting time of the geopolymer to correct the setting time so that it meets the construction requirements. Based on the optimized raw material ratio, prepare a metakaolin geopolymer based on calcium-based material activation suitable for the current ambient temperature T.

[0023] Furthermore, in step two, the formula for calculating the geopolymer setting time is:

[0024] Initial setting time:

[0025] Final setting time:

[0026] In the formula: CaA is the weight percentage of calcium-based material A; CaB is the weight percentage of calcium-based material B.

[0027] Furthermore, in step three, the initial setting time required for construction is 45-120 minutes, and the final setting time is 120-360 minutes.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) This invention provides a technical method that can stably control the setting time of geopolymers over a wide temperature range. Compared with the prior art, which is only applicable to room temperature or specific temperature conditions, this invention solves the problem of difficulty in controlling the setting time of geopolymers under low and high temperature conditions, enabling geopolymer materials to be efficiently constructed in various temperature environments and expanding their application scenarios.

[0030] (2) This invention utilizes the thermal mitigation effect and pozzolanic effect of calcium-based material A to optimize the temperature range (25-50℃).

[0031] The construction performance of metakaolin polymer materials activated by calcium-based materials is improved, avoiding rapid solidification and reducing thermal shrinkage.

[0032] (3) This invention utilizes the high heat of hydration of calcium-based material B to achieve self-heating internal curing of metakaolin geopolymer material activated by calcium-based material at low temperature (5-25℃), thereby promoting the hydration rate of geopolymer material at low temperature, shortening the setting time and achieving early strength effect.

[0033] (4) This invention regulates the setting time of the geopolymer through a designed calculation formula, which can prevent slow setting or low early strength in low-temperature environments, and prevent excessively rapid setting or loss of fluidity in high-temperature environments. This technology ensures that the geopolymer has good construction performance under different construction temperature conditions, which helps to improve construction efficiency and project quality.

[0034] (5) The method of the present invention simplifies the preparation process by rationally proportioning and controlling the temperature. Compared with the complex curing or cumbersome feeding steps required in the prior art, the present invention provides a more efficient and industrially feasible production process.

[0035] (6) Since the present invention uses geopolymer, a new type of low-carbon material, the energy consumption during the production process is reduced compared with traditional building materials such as cement. The present invention helps to achieve the goals of low-carbon emissions and sustainable development in the construction industry.

[0036] (7) This invention provides a formula for calculating the coagulation time of geopolymers. By adjusting the ratio of geopolymers, the coagulation time at different temperatures can be controlled, thereby quantitatively correcting the design of geopolymer ratios. This has certain reference value for the design of geopolymer ratios at different temperatures. Detailed Implementation

[0037] To make the usage and features of this invention more apparent and understandable, specific embodiments are provided below for detailed explanation. Unless otherwise specified, the methods of this invention are conventional methods in the art.

[0038] Furthermore, the numerical range in this invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range, and the values ​​should not be limited to the upper and lower limits or specific instances.

[0039] This invention discloses a geopolymer adaptable to different ambient temperatures and based on calcium-based material activation, its preparation method, and its setting time control method. The geopolymer material comprises metakaolin, an alkali activator, calcium-based material A, and calcium-based material B.

[0040] By weight percentage, metakaolin 40-50%, alkali activator 42-50%, calcium-based material A 2-8%, and calcium-based material B 2-15%, with the sum of the weight percentages of each raw material being 100%.

[0041] When using, prepare according to the following steps: (1) Prepare sodium hydroxide solution: Mix solid sodium hydroxide and water, stir until a uniform and transparent solution is obtained, and use after the solution temperature drops to room temperature; (2) Prepare alkali activator: Mix liquid water glass with the sodium hydroxide solution prepared in (1) in proportion and stir evenly to obtain alkali activator; (3) Prepare geopolymer slurry: Pour metakaolin, calcium-based material A and calcium-based material B into a cement paste mixer, stir at low speed for 30s, and at the same time slowly and evenly pour in the alkali activator, stir for 15-30s until uniformly mixed, and continue to stir at high speed for 60s to obtain geopolymer slurry; (4) Molding and curing: Pour the geopolymer slurry prepared in (3) into a mold, vibrate on a vibration platform for 60s, and place it in a specified temperature environment for curing for 24h to obtain geopolymer based on calcium-based material activation. The specified temperature is the ambient temperature during actual application, i.e., 5-50℃.

[0042] Furthermore, the mesh size of the metakaolin is not less than 1250 mesh.

[0043] Furthermore, the alkali activator, by weight percentage, comprises 70-72% liquid water glass, 12-14% solid sodium hydroxide, and 16-18% water, and the modulus of the alkali activator is adjusted to 1.4-1.6 using solid sodium hydroxide.

[0044] Furthermore, the calcium-based material A is high-calcium fly ash.

[0045] Furthermore, the calcium-based material B is calcium oxide.

[0046] Furthermore, the water glass is liquid water glass with a modulus of 3.1-3.3 and a solid content of 42.5%.

[0047] To facilitate understanding of the content described in this invention, the technical solutions of this invention will be further explained below with reference to specific implementation examples; however, this invention is not limited thereto. All examples were prepared according to the above-described laboratory methods.

[0048] The composition and content of the raw materials used in each embodiment—metakaolin, high-calcium fly ash, and liquid water glass—are shown in Table 1.

[0049]

[0050] Example 1

[0051] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0052] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 46% metakaolin, 50% alkali activator, 2% calcium-based material A and 2% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0053] Since the setting time was not within the appropriate range (initial setting time greater than 180 min), adjustments were made. After adjustment, an alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight. A geopolymer was prepared by mixing 40% metakaolin, 43% alkali activator, 2% calcium-based material A and 15% calcium-based material B by weight. The setting time met the requirements.

[0054]

[0055] Example 2

[0056] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0057] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 46% metakaolin, 50% alkali activator, 2% calcium-based material A and 2% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0058] Since the setting time was not within the appropriate range (final setting time less than 120 min), adjustments were made. After adjustment, an alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight. A geopolymer was prepared by mixing 46% metakaolin, 46% alkali activator, 6% calcium-based material A and 2% calcium-based material B by weight. The setting time met the requirements.

[0059]

[0060] Example 3

[0061] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0062] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 44% metakaolin, 49% alkali activator, 2% calcium-based material A and 5% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0063] The setting time meets the requirements and no adjustment is needed.

[0064]

[0065] Example 4

[0066] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0067] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 48% metakaolin, 42% alkali activator, 2% calcium-based material A and 8% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0068] The setting time meets the requirements and no adjustment is needed.

[0069]

[0070] Example 5

[0071] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0072] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 44% metakaolin, 40% alkali activator, 2% calcium-based material A and 2% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0073] The setting time meets the requirements and no adjustment is needed.

[0074]

[0075] Example 6

[0076] A method for controlling the setting time of geopolymers activated by calcium-based materials and adaptable to different ambient temperatures

[0077] An alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 49% metakaolin, 47% alkali activator, 2% calcium-based material A and 2% calcium-based material B by weight percentage. The basic parameters and calculated and laboratory values ​​of setting time are shown in the table below.

[0078] Since the setting time was not within the appropriate range (initial setting time greater than 180 min, final setting time greater than 360 min), adjustments were made. After adjustment, an alkali activator was prepared by mixing 70% liquid water glass, 13% solid sodium hydroxide and 17% water by weight percentage. A geopolymer was prepared by mixing 42% metakaolin, 45% alkali activator, 2% calcium-based material A and 11% calcium-based material B by weight percentage. The setting time met the requirements.

[0079]

[0080]

[0081] As can be seen from the above embodiments, the geopolymer prepared by the present invention is applicable to different ambient temperatures and is activated based on calcium-based materials. Its applicable ambient temperature range can reach 5-50℃, and it can maintain good performance within this temperature range. The present invention can rapidly solidify under normal temperature conditions. It can utilize the thermal mitigation effect and volcanic ash effect of calcium-based material A in high-temperature (25-50℃) environments to avoid rapid solidification and reduce thermal shrinkage. It can utilize the high heat of hydration of calcium-based material B in low-temperature (5-25℃) environments to achieve self-heating internal curing, thereby promoting the hydration rate of geopolymer materials at low temperatures, shortening the solidification time, and achieving early strength.

[0082] This invention provides a formula for calculating the setting time of geopolymers with optimized formulation. By adjusting the formulation ratio of geopolymers, the setting time at different temperatures can be controlled, thereby quantitatively correcting the formulation design of geopolymers. This formula has certain reference value for the formulation design of geopolymers under different ambient temperatures.

Claims

1. A geopolymer activated based on calcium-based materials, characterized in that, The geopolymer comprises, by weight percentage, 40-50% metakaolin, 42-50% alkali activator, 2-10% calcium-based material A, and 2-8% calcium-based material B, with the sum of the weight percentages of each raw material being 100%. The preparation method of the geopolymer includes the following steps: 1) Mixing: Pour metakaolin, calcium-based material A and calcium-based material B into a cement paste mixer and mix at low speed. Add alkali activator while mixing at low speed, then mix at low speed until the mixture is uniform. Finally, mix at high speed to obtain geopolymer paste. 2) Molding and curing: Pour the geopolymer slurry prepared in step 1) into a mold, vibrate it on a vibration platform for 60 seconds, and place it in a specified temperature environment for curing for 24 hours to obtain the geopolymer based on calcium-based material activation. The alkaline activator, by weight percentage, comprises 70-72% liquid water glass, 12-14% solid sodium hydroxide, and 16-18% water, and uses solid sodium hydroxide to adjust the modulus of the alkaline activator to 1.4-1.

6. The calcium-based material A is high-calcium fly ash, with the following composition: SiO2: 45-55wt%, Al2O3: 25-35wt%, CaO: 10-15wt%, and the remainder being impurities; the calcium-based material B is either calcium oxide or cement clinker. The method for controlling the setting time of the calcium-based activated geopolymer includes the following steps: Step 1: Based on the selected initial raw material ratio, calculate the molar ratio of Na2O / Al2O3. The average site temperature over 72 hours was obtained as the ambient temperature T based on the site temperature conditions. Step 2: By substituting the ambient temperature T and the initial raw material ratio into the formula for calculating the geopolymer setting time, the setting time of the geopolymer activated by calcium-based materials is calculated. The setting time includes the initial setting time and the final setting time. Step 3: Compare the initial setting time and final setting time calculated in Step 2 with the initial setting time and final setting time required for construction. If they do not meet the construction requirements, adjust the weight percentages of calcium-based material A and calcium-based material B based on the formula for calculating the setting time of the geopolymer to correct the setting time so that it meets the construction requirements. Based on the optimized raw material ratio, prepare a metakaolin geopolymer based on calcium-based material activation suitable for the current ambient temperature T.

2. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, The mesh size of the metakaolin is not less than 1250 mesh.

3. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, The preparation method of the alkaline activator is as follows: a) Preparation of sodium hydroxide solution: Mix solid sodium hydroxide and water, stir until a uniform and transparent solution is obtained, and use it after the solution temperature drops to room temperature; b) Preparation of alkali activator: Mix liquid water glass with the sodium hydroxide solution prepared in step a) and stir until homogeneous to obtain alkali activator.

4. The geopolymer based on calcium-based material activation according to claim 3, characterized in that, The liquid water glass has a modulus of 3.1-3.3 and a solid content of 42.5%.

5. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, In step 2), the ambient temperature of the site is 5-50℃.

6. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, In step 1), the stirring speeds of the low-speed stirring and the high-speed stirring are 90-100 r / min and 250-260 r / min, respectively.

7. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, In step two, the formula for calculating the coagulation time of the geopolymer is: In the formula: CaA is the weight percentage of calcium-based material A; CaB is the weight percentage of calcium-based material B.

8. The geopolymer based on calcium-based material activation according to claim 1, characterized in that, In step three, the initial setting time required for construction is 45-120 minutes, and the final setting time is 120-360 minutes.

Images