Basic magnesium sulfate cement early strength agent as well as preparation method and application thereof
The early strength agent, which is formed by mixing crystal nuclei prepared by diaphragm electrolysis with calcium oxide and silica fume, solves the problem of insufficient early strength of basic magnesium sulfate cement and achieves a significant improvement in early strength and a synergistic improvement in later strength.
Patent Information
- Application Number
- CN202511725374.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-01-23
AI Technical Summary
When no suitable admixtures are added, the hydration reaction of existing basic magnesium sulfate cement is incomplete, resulting in low mechanical strength, especially insufficient early strength, which affects production efficiency.
Crystal nuclei were prepared using a diaphragm electrolysis method to act as an early strength agent. By mixing crystal nuclei, calcium oxide, and silica fume, a basic magnesium sulfate cement early strength agent was formed. The high specific surface area and active sites of the crystal nuclei were used to promote early crystallization and solidification of cement.
It significantly improves the early strength of basic magnesium sulfate cement and achieves a synergistic improvement in early strength and high strength, with early strength increasing by 104.8%-235.3% and later strength increasing by 6.5%-8.3%.
Smart Images
Figure CN121377587A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of concrete, and particularly relates to an alkali magnesium sulfate cement early strength agent. BACKGROUND
[0002] Alkali magnesium sulfate cement is a magnesium cement developed after magnesium oxychloride cement, and is mainly composed of light-burned magnesia, magnesium sulfate and water. The alkali magnesium sulfate cement has low alkalinity, high bonding strength, excellent salt corrosion resistance, good reinforcement protection, high toughness and excellent processability, and is widely used in the production of various partition boards, fireproof boards, purification boards, vegetable greenhouse skeletons and artware. However, a large number of studies in recent years have shown that the mechanical strength of the alkali magnesium sulfate cement is low due to incomplete hydration reaction of the system when no suitable additive is added.
[0003] At present, the use of additives is a mainstream and effective means to improve the mechanical properties of the cement. For example, citrate and tartaric acid additives can greatly improve the late strength of the alkali magnesium sulfate cement. However, these additives generally have a retarding effect, which leads to low early strength of the cement, especially the strength after 1 day of maintenance, and seriously affects the production efficiency of the product (such as prolonging the demolding time of the prefabricated component and delaying the construction progress). SUMMARY
[0004] To solve the above problem, the purpose of the present application is to provide an alkali magnesium sulfate cement early strength agent, which can improve the late strength and the early strength.
[0005] To achieve the above purpose, the technical solution adopted by the present application is as follows: An alkali magnesium sulfate cement early strength agent, the raw materials of the early strength agent include 100 parts of crystal nucleus, 100-300 parts of calcium oxide and 100-200 parts of silica ash in terms of mass fraction. The crystal nucleus is prepared by a diaphragm electrolysis method, the anode electrolyte includes a magnesium chloride solution, and the cathode electrolyte includes a mixed solution of sodium citrate and magnesium sulfate.
[0006] Further, the anode area and the cathode area of the diaphragm electrolysis system used in the diaphragm electrolysis method are separated by a cation exchange membrane, and the crystal nucleus is obtained by filtering the emulsion in the cathode area after the electrolysis reaction.
[0007] Further, the anode of the diaphragm electrolysis system is graphite, and the cathode is stainless steel.
[0008] Further, the mass fraction of magnesium chloride is 10%-30%, the mass fraction of sodium citrate or citric acid is 1%-5%, and the mass fraction of magnesium sulfate is 10%-20%.
[0009] Further, the preparation method of the crystal nucleus includes the following steps: S1, constructing a diaphragm electrolysis system: the diaphragm electrolysis system comprises an anode region and a cathode region separated by a cation exchange membrane, the anode region is injected with a magnesium chloride solution, and the cathode region is injected with a mixed solution of sodium citrate and magnesium sulfate; the electrodes are respectively selected as graphite and stainless steel as the anode and the cathode; S2, electrolysis reaction: a direct current power supply is supplied to the above-mentioned diaphragm electrolysis system to carry out electrolysis reaction, and after the reaction is completed, the emulsion generated in the cathode region is collected; S3, crystal nucleus separation and drying: filtering the emulsion, collecting the solid phase material obtained by filtering; drying the solid phase material to obtain the crystal nucleus required for preparing the early strength agent.
[0010] Further, the reaction parameters in step S2 are controlled to be a volume current density of 4mA / mL-20mA / mL, and the power is continuously supplied for 0.1h-0.5h.
[0011] Further, the drying temperature in step S3 is 40℃~80℃.
[0012] Another object of the present application is to provide a preparation method of an alkali magnesium sulfate cement early strength agent, wherein the crystal nucleus, calcium oxide and silica fume are weighed according to the mass fraction, and the above-mentioned raw materials are mixed and ground to obtain the early strength agent.
[0013] The alkali magnesium sulfate cement early strength agent is added to the alkali magnesium sulfate cement, and is used for repairing the damage of roads, bridges and tunnels, and preparing prefabricated components, special building materials and handicrafts.
[0014] Due to the adoption of the above technical scheme, the present application has the following technical effects: After the early strength agent of the present application is added to the alkali magnesium sulfate cement slurry, the early strength of the cement stone is significantly improved, and the synergy of early strength and high strength is realized. The crystal nucleus has a low crystallization degree, a high specific surface area, active sites for inducing crystal growth on the crystal nucleus, and a higher surface activity for inducing crystallization. When the crystal nucleus is added to the alkali magnesium sulfate cement, the early strength effect of the alkali magnesium sulfate cement can be realized, and the functions of rapid setting and rapid development of strength can be played. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 is the SEM graph of the crystal nucleus prepared in Example 1, A and B are different magnifications, respectively; Figure 2 is the XRD graph of the crystal nucleus prepared in Example 1; Figure 3 is the XRD graph of 5Mg(OH)2·MgSO4·7H2O prepared in Comparative Example 5. DETAILED DESCRIPTION
[0016] The technical scheme of the present application will be described in detail below in combination with the specific embodiments.
[0017] Example 1 I. Preparation of Crystal Nuclei: (1) Construct a membrane electrolysis system. The membrane electrolysis system includes an anode region and a cathode region, which are separated by a cation exchange membrane. The anode solution is a 10% magnesium chloride solution, and the cathode solution is a mixed solution containing 5% sodium citrate and 10% magnesium sulfate. Graphite is used as the anode and stainless steel is used as the cathode. (2) A DC power supply is applied to the diaphragm electrolysis system in step (1), and the current parameters are controlled at a volume current density of 4 mA / mL and continuous power supply for 0.5 h. After the reaction is completed, a cathode emulsion is obtained. (3) Filter the cathode emulsion obtained in step (2), and dry the solid material obtained after filtration at 60°C to obtain crystal nuclei.
[0018] The prepared crystal nuclei were analyzed by SEM, such as... Figure 1 The images shown are SEM images at different magnifications. It can be seen from the images that the crystal nuclei in this application exhibit agglomeration, forming agglomerates of varying sizes. Furthermore, the surface of the crystal nuclei is not smooth but rather has a relatively rough structure.
[0019] like Figure 2 The image shows the XRD pattern of the prepared crystal nucleus. As can be seen from the image, the crystal nucleus is in a near-amorphous state with low crystallinity and a large specific surface area. Therefore, this crystal nucleus has a large number of crystallization sites. Adding it to basic magnesium sulfate cement can enable the cement to crystallize and solidify rapidly in the early stages.
[0020] II. Preparation of early strength agent: By mass fraction, 100 parts of crystal nuclei, 100 parts of calcium oxide and 200 parts of silica fume are mixed and ground to obtain an early strength agent; III. Preparation of Basic Magnesium Sulfate Cement Sample raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 5g of the above-mentioned early strength agent, and 100g water; Preparation and curing: After the raw materials of the sample are mixed evenly, the mixture is stirred and shaped, and placed in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 28.5 MPa after 1 day of curing, 65.3 MPa after 3 days of curing, and 78.5 MPa after 28 days of curing.
[0021] Example 2 I. Preparation of Crystal Nuclei: (1) Construct a membrane electrolysis system, which includes an anode region and a cathode region, separated by a cation exchange membrane; wherein the anode solution is a 30% magnesium chloride solution, and the cathode solution is a mixed solution containing 1% sodium citrate and 20% magnesium sulfate; graphite is used as the anode and stainless steel is used as the cathode; (2) A DC power supply is applied to the diaphragm electrolysis system in step (1), and the current parameters are controlled as a volume current density of 20 mA / mL and continuous power supply for 0.1 h. After the reaction is completed, a cathode emulsion is obtained. (3) Filter the cathode emulsion obtained in step (2), and dry the solid material obtained after filtration at 80°C to obtain crystal nuclei.
[0022] Preparation of early strength agent: By mass, the early strength agent is obtained by mixing and grinding 100 parts of crystal nuclei, 300 parts of calcium oxide and 200 parts of silica fume. Preparation of basic magnesium sulfate cement: Sample raw material ratio: Take 100g of magnesium oxide, 100g of magnesium sulfate heptahydrate, 3g of the above-mentioned early strength agent, and 100g of water; Preparation and curing: After the raw materials of the sample are mixed evenly, the mixture is stirred and shaped, and placed in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength of the samples at different curing ages was tested. The results showed that the compressive strength was 21.5 MPa after 1 day of curing, 55.3 MPa after 3 days of curing, and 77.2 MPa after 28 days of curing.
[0023] Comparative Example 1: No Early Strength Agent Preparation of basic magnesium sulfate cement: Raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 100g water; Preparation and curing: Mix the above raw materials evenly and stir to form a mold. Place the mold in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 10.5 MPa after 1 day of curing, 25.3 MPa after 3 days of curing, and 32.5 MPa after 28 days of curing. Comparative Example 2: Citric acid as an early-strength agent Preparation of basic magnesium sulfate cement: Raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 0.5g citric acid, 100g water; Preparation and curing: Mix the above raw materials evenly and stir to form a mold. Place the mold in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 8.5 MPa after 1 day of curing, 45.3 MPa after 3 days of curing, and 72.5 MPa after 28 days of curing.
[0024] Comparative Example 3: Crystal nuclei were used directly as an early strength agent. The method for preparing crystal nuclei is the same as in Example 1.
[0025] Preparation of basic magnesium sulfate cement: Raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 100g water, 5g crystal nuclei; Preparation and curing: Mix the above raw materials evenly and stir to form a mold. Place the mold in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 20.1 MPa after 1 day of curing, 45.6 MPa after 3 days of curing, and 70.0 MPa after 28 days of curing. Comparative Example 4: The early-strength agent contained no crystal nuclei, only the other two components: calcium oxide and silica fume. Preparation of basic magnesium sulfate cement: Raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 100g water, 5g calcium oxide and silica fume (mass ratio of calcium oxide to silica fume 3:2); Preparation and curing: Mix the above raw materials evenly and stir to form a mold. Place the mold in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 12.8 MPa after 1 day of curing, 27.2 MPa after 3 days of curing, and 40.3 MPa after 28 days of curing.
[0026] Comparative Example 5 uses 517 whiskers as a component of an early strength agent. I. Preparation of 5Mg(OH)₂·MgSO₄·7H₂O whiskers: (1) Construct a membrane electrolysis system. The membrane electrolysis system includes an anode region and a cathode region, which are separated by a cation exchange membrane. The anode solution is a 10% magnesium chloride solution, and the cathode solution is a mixed solution containing 5% sodium citrate and 10% magnesium sulfate. Graphite is used as the anode and stainless steel is used as the cathode. (2) A DC power supply is applied to the diaphragm electrolysis system in step (1), and the current parameters are controlled at a volume current density of 4 mA / mL and continuous power supply for 2.5 h. After the reaction is completed, a cathode emulsion is obtained. (3) Filter the cathode emulsion obtained in step (2), wash the solid material obtained after filtration with water and ethanol, and dry the solid material at 60°C to obtain crystals.
[0027] like Figure 3The image shows the XRD pattern of the prepared crystal, which was confirmed to be 5Mg(OH)2·MgSO4·7H2O whiskers.
[0028] II. Preparation of early strength agent: By mass fraction, 100 parts of 5Mg(OH)2·MgSO4·7H2O whiskers, 100 parts of calcium oxide and 200 parts of silica fume were mixed and ground to obtain an early strength agent. III. Preparation of Basic Magnesium Sulfate Cement: Raw material ratio: 100g magnesium oxide, 100g magnesium sulfate heptahydrate, 100g water, 3g of the above-mentioned early strength agent; Preparation and curing: Mix the above raw materials evenly and stir to form a mold. Place the mold in an environment with a temperature of 20±3℃ and a relative humidity of 60% for curing for 1 day, 3 days and 28 days respectively. Performance testing: The compressive strength is 18.0 MPa after 1 day of curing, 36.7 MPa after 3 days of curing, and 65.4 MPa after 28 days of curing. By comparing the compressive strength data of Comparative Example 1 (without admixture), Comparative Example 2 (with citric acid), and Examples 1-2 (with early-strength agent), the following conclusions can be drawn: Under the same curing conditions, Comparative Example 1, without admixture, has the lowest strength at all ages; Comparative Example 2, although the addition of the traditional admixture citric acid can improve the later strength, will significantly reduce the early strength, resulting in a problem of strong later strength and weak early strength; while Examples 1-2, with the addition of the early-strength agent of this application, have a compressive strength of 21.5-28.5 MPa after 1 day of curing, which is 104.8%-171.4% higher than Comparative Example 1 and 153.5%-235.3% higher than Comparative Example 2; and a compressive strength of 77.2-78.5 MPa after 28 days of curing, which is significantly higher than Comparative Example 1 without early-strength agent and 6.5%-8.3% higher than Comparative Example 2. In Comparative Examples 3-5, the composition of the accelerator was changed, and the effects of different accelerators on the strength of basic magnesium sulfate cement were compared. The experiments showed that using the crystal nuclei prepared in this application alone as an accelerator was less effective than using the accelerator described in this application, with both early strength and later-stage strength being slightly inferior. Furthermore, the use of 5Mg(OH)₂·MgSO₄·7H₂O whiskers as the accelerator also resulted in poor performance; the 517 whiskers had complete crystallinity, which was not as high as the activity of the crystal nuclei described in this application. Therefore, the accelerator described in this application not only significantly improved the early strength of basic magnesium sulfate cement but also outperformed the comparative examples in terms of later-stage strength, achieving a synergistic improvement in both early strength and high strength.
[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A basic magnesium sulfate cement early-strength agent, characterized in that: The early strength agent raw materials include 100 parts by mass of crystal nuclei, 100-300 parts of calcium oxide and 100-200 parts of silica fume; wherein the crystal nuclei are prepared by membrane electrolysis, the anolyte includes magnesium chloride solution and the cathode electrolyte includes sodium citrate or a mixed solution of sodium citrate and magnesium sulfate.
2. The basic magnesium sulfate cement early-strength agent according to claim 1, characterized in that: In the diaphragm electrolysis method, the anode and cathode regions of the diaphragm electrolysis system are separated by a cation exchange membrane, and the crystal nuclei are obtained by filtering the emulsion in the cathode region after the electrolysis reaction.
3. The basic magnesium sulfate cement early-strength agent according to claim 2, characterized in that: The anode of the diaphragm electrolysis system is graphite, and the cathode is stainless steel.
4. The basic magnesium sulfate cement early-strength agent according to claim 3, characterized in that: The mass fraction of magnesium chloride is 10-30%, the mass fraction of sodium citrate or citric acid is 1%-5%, and the mass fraction of magnesium sulfate is 10%-20%.
5. A basic magnesium sulfate cement early-strength agent according to any one of claims 1-4, characterized in that, The method for preparing the crystal nucleus includes the following steps: S1. Constructing a membrane electrolysis system: The membrane electrolysis system includes an anode region and a cathode region separated by a cation exchange membrane. The anode region is injected with magnesium chloride solution, and the cathode region is injected with a mixed solution of sodium citrate and magnesium sulfate. Graphite and stainless steel are selected as the anode and cathode, respectively. S2, Electrolysis reaction: A DC power supply is applied to the above diaphragm electrolysis system to carry out the electrolysis reaction. After the reaction is completed, the emulsion generated in the cathode area is collected. S3. Crystal nucleus separation and drying: Filter the emulsion and collect the solid phase obtained from the filtration; dry the solid phase to obtain the crystal nuclei required for the preparation of the early strength agent.
6. The basic magnesium sulfate cement early-strength agent according to claim 5, characterized in that: In step S2, the reaction parameters are controlled as follows: volumetric current density 4-20 mA / mL, and continuous energization for 0.1-0.5 h.
7. The basic magnesium sulfate cement early-strength agent according to claim 5, characterized in that: The drying temperature in step S3 is 40℃~80℃.
8. A method for preparing an early-strength agent for basic magnesium sulfate cement according to any one of claims 1-4, characterized in that: According to the mass fractions described in claim 1, the crystal nucleus, calcium oxide and silica fume are weighed, and the above raw materials are mixed and ground to obtain the early strength agent.
9. The application of the basic magnesium sulfate cement early-strength agent according to claim 8, characterized in that: The early strength agent is added to basic magnesium sulfate cement, which is used for the repair of damaged roads, bridges, and tunnels, as well as the preparation of precast components, special building materials, and handicrafts.