A super-fast-setting early-strength sulphoaluminate cement-based repair material, a preparation method and applications thereof

Abstract

This invention discloses a rapid-setting, early-strength sulfoaluminate cement-based repair material, its preparation method, and its application, belonging to the field of concrete technology. The raw materials for the sulfoaluminate cement-based repair material include the following components: a mixed powder composed of iron powder particles and sulfoaluminate cement, and water; in the mixed powder, the volume ratio of iron powder particles to sulfoaluminate cement is 2.5:97.5 to 1:9; the mass ratio of water to the mixed powder is 0.3:1 to 0.6:1. These raw material components are inexpensive and widely available. This invention, by controlling the specific proportions between the components, enables the material to possess the advantages of rapid setting, early strength, and erosion resistance in dynamic water environments. The preparation method of the repair material is convenient and simple to operate, requiring no complex personnel training. When used in sealing projects, it exhibits excellent adaptability under various construction conditions, expanding the application range of this material.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a sulfoaluminate cement-based repair material with ultra-fast setting and early strength, its preparation method, and its application. Background Technology

[0002] Currently, ultra-fast-setting, early-strength cementitious materials exhibit rapid setting time and strength development, making them significant in special construction environments such as flood and mudslide containment. To meet the demands of these challenging environments, various admixtures are often added to adjust the setting time and mechanical strength of the cement. However, current admixtures have limited ability to control the setting time and mechanical strength of cementitious materials. Traditional fast-setting, early-strength cement typically has a final setting time of around 10 minutes and requires approximately 1 hour to reach higher strength, which fails to meet the engineering application requirements in these special environments.

[0003] Sulfoaluminate cement, primarily composed of calcium sulfoaluminate and belite in the clinker phase, is a low-carbon and inexpensive cement material. It possesses excellent properties, including rapid setting, high early strength, and good durability. Furthermore, the hydration kinetics of sulfoaluminate cement are temperature-dependent, conforming to the Arrhenius equation, indicating that higher temperatures accelerate the hydration reaction and the precipitation of hydration products, thereby enhancing early strength. This temperature-sensitive behavior has led to the use of heating to accelerate the development of early strength in cementitious materials, such as steam curing to expedite the turnaround time for precast concrete production. However, this concept has not yet been applied to sealing projects because on-site heating is considered impractical, especially in emergency situations such as sudden influxes of water and slurry. Moreover, traditional contact heating methods have low energy transfer efficiency, generate thermal gradients, and cannot control the overall setup within minutes. Therefore, introducing effective heating methods would be beneficial for setting control and early strength development.

[0004] Electromagnetic induction heating technology is an advanced non-contact heating method. Induction heating in ferromagnetic and conductive materials is based on eddy current induction and magnetic polarization effects. These materials undergo induction heating when exposed to alternating electromagnetic fields with frequencies ranging from kilohertz to megahertz. Furthermore, electromagnetic induction heating is characterized by high efficiency, simple process, and potential for integration with traditional grouting equipment.

[0005] For example, Chinese invention patent CN114455902A discloses an alkali-activated low-calcium cementitious material retarder binder based on an electromagnetic induction heating setting mechanism, its preparation method, and its application. The components and their weight percentages include: 400-500 parts low-calcium cementitious material, 1300-1400 parts aggregate, 80-160 parts activator, 15-20 parts magnetocaloric component, 0-30 parts retarder, and 150-200 parts water. This invention introduces a magnetocaloric component into the alkali-activated low-calcium cementitious material mortar system and combines it with electromagnetic heating to achieve controllable adjustment of the setting rate and curing time. When applied to the preparation of retarder-bonded prestressed steel bars, it exhibits good fluidity before and after tensioning, better encapsulating the retarder-bonded prestressed steel bars, and excellent bond strength after hardening, effectively solving the problem of voids easily appearing after tensioning in traditional retarder-bonded mortars. However, the material requires an excessively long setting time, making it unsuitable for leak sealing or emergency repairs under flowing water conditions.

[0006] Chinese invention patent CN115159870A discloses an induction-induced thermo-accelerated gelling material and its activation method. By weight, it comprises the following components: rheology modifier: 0.01–5 parts, thermo-accelerated accelerator: 0.01–5 parts, electromagnetic induction heating agent: 0.01–10 parts, supersulfate cement: 60–75 parts, and water: 10–35 parts. Under the action of an alternating magnetic field, the induction heating element in the gelling material generates heat, inducing the nearby thermo-accelerated accelerator to react and generate accelerating components, accelerating the setting and solidification of the gelling material, reducing the setting time from several hours to several seconds. This invention's thermo-accelerated gelling material and its activation method can achieve precise control over the setting behavior of the gelling material, reducing the risk of pipe blockage. Although the material achieves solidification in a short time, it is designed to avoid the risk of pipe blockage and has good fluidity; however, when used for leak sealing or emergency repairs in flowing water environments, the gelling material is easily washed away, failing to achieve the repair purpose.

[0007] This demonstrates that rapid setting and hardening are crucial for cementitious materials used in emergency repairs and other applications. In underground construction, managing groundwater and flooding caused by mudslides requires grouting materials to solidify within minutes. However, the setting time of traditional cement is measured in hours, making it unsuitable for the challenges of high flood pressures, where sprayed or pumped materials often dilute and are washed away before setting. While organic materials such as polyurethane, acrylic, superabsorbent polymers, and lignin can react quickly, their widespread application is limited by relatively low strength, high cost, and increased toxicity risks. Therefore, there is an urgent need to develop cost-effective cement-based grouts with controllable and ultra-rapid setting properties.

[0008] Therefore, achieving ultra-rapid setting and ultra-early strength of sulfoaluminate cement based on electromagnetic induction heating technology, and enabling its sealing application under dynamic water conditions, is of great significance for expanding the application of cement-based materials. Summary of the Invention

[0009] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a sulfoaluminate cement-based repair material with ultra-fast setting and early strength, erosion resistance and low cost in a dynamic water environment is provided. The raw materials include the following components: a mixed powder composed of iron powder particles and sulfoaluminate cement, and water; in the mixed powder, the volume ratio of iron powder particles to sulfoaluminate cement is 2.5:97.5 to 1:9; and the mass ratio of water to mixed powder is 0.3:1 to 0.6:1.

[0010] Preferably, the iron powder particles have a particle size ≤0.075mm, a purity ≥85%, and a density of 7000~7800kg / m³. 3 .

[0011] Preferably, the sulfoaluminate cement is grade 42.5 or 52.5 sulfoaluminate cement with a density of 2500–3200 kg / m³. 3 .

[0012] The raw material parameters of iron powder particles and sulfoaluminate cement should be appropriately controlled within a suitable range. This will facilitate subsequent raw material mixing and other operations, optimize the rapid setting and early strength of the finished product, and enhance its scouring resistance, thereby further improving the sealing performance of the material.

[0013] In a second aspect of the present invention, a simple and efficient method for preparing sulfoaluminate cement-based repair materials under working conditions is provided, comprising the following steps:

[0014] S1, iron powder particles and sulfoaluminate cement are mixed to form a mixed powder;

[0015] S2. Mix water with the obtained mixed powder to form a sulfoaluminate composite cement slurry with magnetothermal effect, thus obtaining a sulfoaluminate cement-based repair material.

[0016] The preparation steps of sulfoaluminate cement-based repair materials are simple and convenient, requiring no special personnel training, and are more universally applicable to the requirements of construction personnel, which helps to promote the application of this material.

[0017] In a third aspect of the invention, an application of a sulfoaluminate cement-based repair material that is easy to operate and has good construction adaptability is provided, specifically as a cementing material in sealing projects.

[0018] Preferably, the method of application is as follows: the sulfoaluminate cement-based repair material with magnetocaloric effect solidifies at the leakage point under electromagnetic induction heating to complete the curing and achieve sealing.

[0019] More preferably, the electromagnetic induction heating condition uses an alternating magnetic field with a power of 400–2000W and a frequency of 50–200kHz.

[0020] Furthermore, the alternating magnetic field generating device consists of components including a power supply, a magnetic field generator, and coils.

[0021] In applications, the design of the alternating magnetic field generating device can be determined according to the actual working conditions. For example, in general pipe plugging applications, the coil of the generating device can be made of copper tubing with an inner diameter of 5mm, with a diameter of 30mm and a height of 30mm.

[0022] Based on the above technical solutions, the inventive concept of this invention is to use inexpensive and widely available iron powder particles as a magnetothermal material, and to influence the pore structure and heating efficiency of cement by controlling the amount of magnetothermal material, thereby controlling the material hardening process and forming the target microstructure, so as to achieve rapid solidification and sealing under dynamic water conditions.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] This invention provides a sulfoaluminate cement-based repair material with low-cost and widely available raw material components. By controlling the specific proportions between the components, the material exhibits advantages such as rapid setting and early strength, and erosion resistance in dynamic water environments.

[0025] This invention provides a method for preparing sulfoaluminate cement-based repair materials, which is convenient and simple to operate.

[0026] This invention provides an application of a sulfoaluminate cement-based repair material, which has excellent adaptability under various sealing engineering construction conditions. Attached Figure Description

[0027] Figure 1 A schematic diagram of the structure of the dynamic water grouting and sealing experimental platform;

[0028] Figure 2 Photos of actual equipment used in the sealing process;

[0029] Figure 3 A schematic diagram illustrating the application principle of sulfoaluminate cement-based repair materials;

[0030] Figure 4 The graphs show the temperature change over time under a set magnetic field during the curing of the sulfoaluminate cement-based repair materials in Examples 1-4.

[0031] Figure 5(a) to (d) are X-ray diffraction (XRD) patterns of the hydration products of the sulfoaluminate cement-based repair materials of Examples 1 to 4 at 5 min, 10 min, 20 min, and 30 min, respectively.

[0032] The diffraction peak numbers are as follows: 1. Electrite; 2. Aluminum hydroxide; 3. Calcium sulfoaluminate; 4. Anhydrite; 5. Iron oxide; 6. Dicalcium silicate; 7. Calcium sulfoaluminate monosulfate hydrate; 8. Hemicarbonate; 9. Monocarbonate.

[0033] Figure 6 The graphs show the relationship between pore volume increment and pore diameter for the sulfoaluminate cement-based repair materials in Examples 1 and 4 at a set time.

[0034] Figure 7 The graph shows the relationship between cumulative pore volume and pore diameter of the sulfoaluminate cement-based repair materials in Examples 1 and 4 at a set time. Detailed Implementation

[0035] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0036] In the following embodiments:

[0037] The alternating magnetic field generating device is self-made and consists of a power supply, a magnetic field generator, and a coil. The coil is made of copper tubing with an inner diameter of 5mm, a diameter of 30mm, and a height of 30mm. In use, the leaking pipe is inserted into the coil so that it is within the range of the alternating magnetic field.

[0038] The dynamic water grouting and sealing experimental platform was self-built to verify the practical application effect of sulfoaluminate cement-based repair materials in the dynamic water grouting and sealing process. Its structure is shown in Figure 1. The simulated dynamic water environment parameters are as follows: the inner diameter of the pipe is 28 mm, and the flow rate in the pipe is 2 m³ / s. 3 / h, pipeline water pressure is 0.05MPa, grouting volume is 500mL;

[0039] The sulfoaluminate cement used is a crack-resistant, fast-cracking, high-grade 42.5 sulfoaluminate cement produced by Tangshan Arctic Bear Company, with a density of 2.85 g / cm³. 3 Its components are shown in Table 1.

[0040] Table 1:

[0041]

[0042] Example 1

[0043] The application steps for sulfoaluminate cement-based repair materials are as follows:

[0044] (1) Mix the iron powder particles and sulfoaluminate cement in a volume ratio of 2.5:97.5 to prepare a mixed powder; mix the distilled water and the mixed powder in a mass ratio of 0.4:1 to form a sulfoaluminate composite cement slurry with a magnetothermal effect, and obtain a sulfoaluminate cement-based repair material.

[0045] (2) Start the water injection grouting and sealing test platform to simulate the dynamic water flow environment in the pipeline; under normal working conditions, the water flows through the pipeline to the recovery water tank without obstruction; when sealing, inject sulfoaluminate cement-based repair material into the grouting port section, and simultaneously turn on the alternating magnetic field generating equipment. The alternating magnetic field power is 400W and the frequency is 50kHz, so that the material solidifies and completes the curing under the magnetothermal effect.

[0046] Example 2

[0047] This embodiment is basically the same as Embodiment 1, except that the preparation method of the sulfoaluminate cement-based repair material in this embodiment is different. The steps are as follows: the volume ratio of iron powder particles to sulfoaluminate cement is 5:95, and the two are mixed evenly to form a mixed powder; the mass ratio of distilled water to mixed powder is 0.4:1, and the two are mixed evenly to form a sulfoaluminate composite cement slurry with magnetothermal effect, thus obtaining the sulfoaluminate cement-based repair material.

[0048] Example 3

[0049] This embodiment is basically the same as Embodiment 1, except that the preparation method of the sulfoaluminate cement-based repair material in this embodiment is different. The steps are as follows: the iron powder particles and sulfoaluminate cement are mixed evenly to form a mixed powder according to a volume ratio of 7.5:92.5; the distilled water and the mixed powder are mixed evenly according to a mass ratio of 0.4:1 to form a sulfoaluminate composite cement slurry with a magnetothermal effect, thus obtaining the sulfoaluminate cement-based repair material.

[0050] Photographs were taken at each stage of the sealing operation, and physical photos of the sealing process are shown below. Figure 2 As shown, the entire operation process is simple and quick. Under flowing water conditions, the sulfoaluminate cement-based repair material resisted the impact of the flowing water and solidified completely 5 minutes after grouting, thus completely sealing the inside of the pipe and preventing water leakage.

[0051] Example 4

[0052] This embodiment is basically the same as Embodiment 1, except that the preparation method of the sulfoaluminate cement-based repair material in this embodiment is different. The steps are as follows: the volume ratio of iron powder particles to sulfoaluminate cement is 10:90, and the two are mixed evenly to form a mixed powder; the mass ratio of distilled water to mixed powder is 0.4:1, and the two are mixed evenly to form a sulfoaluminate composite cement slurry with magnetothermal effect, thus obtaining the sulfoaluminate cement-based repair material.

[0053] Comparative Example 1

[0054] This comparative example is used to study the sealing effect when only conventional sulfoaluminate cement is used. The steps are as follows:

[0055] (1) Mix distilled water and sulfoaluminate cement evenly according to a mass ratio of 0.4:1 to obtain sulfoaluminate cement slurry;

[0056] (2) Start the water injection grouting and sealing test platform to simulate the dynamic water flow environment in the pipeline; under normal working conditions, the water flows through the pipeline to the recovery water tank; when sealing, inject sulfoaluminate cement slurry into the grouting port section, and simultaneously turn on the alternating magnetic field generating equipment. The alternating magnetic field power is 400W and the frequency is 50kHz, so that the material solidifies and completes the curing.

[0057] Comparative Example 2

[0058] This comparative example is used to study the sealing effect when maintenance is not performed using an alternating magnetic field. The steps are as follows:

[0059] (1) Mix the iron powder particles and sulfoaluminate cement in a volume ratio of 10:90 to prepare a mixed powder; mix the distilled water and the mixed powder in a mass ratio of 0.4:1 to form a sulfoaluminate composite cement slurry with a magnetothermal effect, and obtain a sulfoaluminate cement-based repair material.

[0060] (2) Start the water injection grouting and sealing test platform to simulate the dynamic water flow environment in the pipeline; under normal working conditions, the water flows through the pipeline to the recovery water tank; when sealing, sulfoaluminate cement-based repair material is injected into the grouting port section, and then cured under standard curing environment.

[0061] During the above embodiments and comparative experiments, the setting time of the materials was measured simultaneously, and the setting time was determined according to the steps provided in GB / T1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The sealing process was repeated in parallel, and curing was completed at time points of 3, 5, 10, 15, 20, and 30 minutes. Samples were taken and the compressive strength of the solidified cement samples was tested using 15mm × 30mm cylindrical specimens. The loading rate was set to 10 N / s, and the accuracy of the compressive strength tester was 0.01 N. The test results of setting time and compressive strength changes over time are shown in Table 2.

[0062] Table 2:

[0063]

[0064] In the table, " / " indicates that the specimen cannot solidify to form a sample that meets the minimum strength requirement for the test, meaning there is no point where the strength can be measured.

[0065] The schematic diagram of the principle of the sulfoaluminate cement-based repair material and the magnetocaloric effect used in the embodiment is shown below. Figure 3 As shown.

[0066] The temperature change over time of samples from Examples 1-4 during curing was tested using an infrared thermometer under a set magnetic field. The test results are as follows: Figure 4 As shown.

[0067] The hydration products of Examples 1-4 at different time points were characterized by X-ray diffraction analysis, and the results are as follows: Figure 5 As shown. Figure 5 (a) to (d) correspond to the characterization results of hydration products at 5 min, 10 min, 20 min and 30 min respectively.

[0068] Using an Autopore IV 9520 mercury porosimeter (Micromeritics, USA), and taking Examples 1 and 4 as examples, the micropore size variation at different solidification times was studied with iron powder particle contents of 2.5 vol.% and 10 vol.%. The results are as follows: Figure 6 , 7 As shown. Figure 6 In this context, numbers 2.5-10 represent a dosage of 2.5 vol.%, with a curing time of 10 minutes. The numbering rules for the remaining groups are the same.

[0069] The test results above show that heating efficiency is strongly influenced by the magnetocaloric material content, indicating an almost linear relationship between sample temperature (before reaching 100°C) and alternating magnetic field exposure time. It was also found that a higher magnetocaloric material content accelerates the material hardening process (as reflected in the appearance of the first measurable strength point) and improves early grouting strength. However, this comes at the cost of subsequent strength gains, as reflected in the decreasing slope of the strength curve over time. Specifically, at a magnetocaloric material content of 2.5 vol.%, the compressive strength increased by 3.8 times (from 1.79 MPa at 10 min to 8.62 MPa at 30 min), in stark contrast to the 10 vol.% magnetocaloric material content, where the compressive strength increased by only 0.8 times (from 1.1 MPa at 3 min to 1.99 MPa at 30 min).

[0070] The trade-off in the strength gain of samples with high magnetocaloric content may be related to the effect of temperature on the hydration products of CSA cement and water loss in high-temperature environments. When the system temperature approaches or exceeds 70℃, water bound to ettringite begins to be lost. Under the influence of high temperature, the main hydration products of CSA cement are transformed into monosulfate and aluminum hydroxide gel. The results in the XRD pattern also reflect that the increase in temperature leads to a decrease in the intensity of the peak corresponding to ettringite, proving the changes in hydration products at high temperatures.

[0071] Furthermore, the amount of magnetocaloric material added also affects the pore structure of cement, thus significantly impacting its mechanical properties. Due to the increased magnetocaloric material content and alternating magnetic field exposure time, a coarsened microstructure is generated in samples subjected to high temperatures. For example... Figure 6 , 7 As shown, the average pore size of the 10 vol.% sulfoaluminate cement sample was almost three times that of the 2.5 vol.% sulfoaluminate cement sample at both 10 min and 30 min, due to the increased volume fraction of pores larger than 200 nm. With the alternating magnetic field exposure time increasing from 10 min to 30 min, the total pore volume of the 2.5 vol.% sulfoaluminate cement sample decreased from 0.32 mL / g to 0.27 mL / g, while the total pore capacity of CSA-10.0 remained unchanged. Therefore, the system temperature should not be too high, and a balance must be struck between acceleration settings and later intensity gain.

[0072] In summary, the content of magnetocaloric material and the exposure duration of the alternating magnetic field should be carefully adjusted to avoid overheating. By comparing and analyzing the intensity changes of different groups, the optimal content of magnetocaloric material can be further controlled between 2.5 vol.% and 7.5 vol.%, and the specific dosage can be adjusted according to the actual situation of different sealing projects.

[0073] This invention utilizes electromagnetic induction heating technology to develop a breakthrough ultra-rapid-setting, early-strength sulfoaluminate cement-based repair material for sealing projects. The material has a final setting time as fast as 2 minutes, a compressive strength exceeding 1 MPa in as little as 5 minutes, and a maximum compressive strength of 8.62 MPa after 30 minutes. Its rapid-setting and early-strength performance is far superior to traditional rapid-setting and early-strength cement. Moreover, the preparation method is simple, easy, and convenient, providing a new technical route for solving sealing problems in practical engineering.

[0074] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A sulfoaluminate cement-based repair material, characterized in that, The raw materials include the following components: a mixed powder composed of iron powder particles and sulfoaluminate cement, and water; in the mixed powder, the volume ratio of iron powder particles to sulfoaluminate cement is 2.5:97.5~1:9; the mass ratio of water to mixed powder is 0.3:1~0.6:

1. The iron powder particles have a particle size ≤0.075 mm, a purity ≥85%, and a density of 7000~7800 kg / m³. 3 ; The sulfoaluminate cement used is grade 42.5 or 52.5 sulfoaluminate cement with a density of 2500~3200 kg / m³. 3 ; The preparation method of the sulfoaluminate cement-based repair material includes the following steps: S1, iron powder particles and sulfoaluminate cement are mixed to form a mixed powder; S2. Mix water with the obtained mixed powder to form a sulfoaluminate composite cement slurry with magnetothermal effect, thus obtaining a sulfoaluminate cement-based repair material.

2. An application of the sulfoaluminate cement-based repair material as described in claim 1, characterized in that: Application of cementing materials in sealing projects.

3. The application according to claim 2, characterized in that, The application method is as follows: the sulfoaluminate cement-based repair material with magnetocaloric effect solidifies and cures under electromagnetic induction heating conditions to achieve sealing.

4. The application according to claim 3, characterized in that: The electromagnetic induction heating condition uses an alternating magnetic field with a power of 400~2000 W and a frequency of 50~200 kHz.

5. The application according to claim 4, characterized in that: The alternating magnetic field generating device consists of components including a power supply, a magnetic field generator, and coils.

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