Water absorbing-releasing floating bead for internal curing of ternary cementing material and normal-temperature preparation method of water absorbing-releasing floating bead

Abstract

The invention provides a water-absorbing-water-releasing floating bead for internal curing of a ternary cementing material and a normal-temperature preparation method of the water-absorbing-water-releasing floating bead, and the method comprises the following steps: step 1, weighing F-grade fly ash floating beads, and removing impurities; the method comprises the following steps: mixing a 1.0 mol / L ammonium fluoride NH4F solution and a 1.2 mol / L hydrochloric acid HCl solution according to a volume ratio of 1: 1 to obtain a mixed acid etching solution; step 2, completely immersing the pretreated F-grade fly ash floating beads in the mixed acid etching solution, continuously stirring and etching for 2 hours, and standing after the etching is finished until the perforation reaches the standard; 3, carrying out solid-liquid separation on the etched mixture, and collecting perforated floating beads; 4, the collected perforated floating beads are cleaned with deionized water, and residual acid liquor on the surfaces is removed; and 5, the cleaned perforated floating beads are dried for 12 hours at the temperature of 60 DEG C, finished perforated floating beads are obtained, and shells of the perforated floating beads form perforated communicating structures. Directional perforation modification of common floating beads is achieved, and the problems that an existing preparation method is high in energy consumption and uncontrollable in function are solved.

Description

Technical Field

[0001] This invention relates to the field of functional cenosphere preparation technology for building materials, specifically to a water-absorbing and water-releasing cenosphere for internal curing of ternary cementitious materials and its room-temperature preparation method. Background Technology

[0002] Fly ash cenospheres, a byproduct of thermal power plants, are characterized by their hollow structure, low density, and good chemical stability, and are often used as lightweight fillers in the building materials industry. However, the sealed shells of ordinary fly ash cenospheres prevent the storage and release of moisture, making it difficult to meet the internal curing requirements of cement-based materials (especially low water-cement ratio cement-slag-limestone ternary cementitious materials). These ternary cementitious materials are prone to cracking due to self-shrinkage during the hardening process, requiring internal curing agents to replenish moisture to inhibit shrinkage and improve strength.

[0003] Existing methods for preparing porous cenospheres largely rely on high-temperature processes: such as high-temperature sintering (above 1000˚C) combined with a pore-forming agent to generate gas and form a closed-cell structure, or synthesizing artificial hollow microspheres from melted raw materials. These methods are not only energy-intensive and require demanding equipment, but also produce mostly closed-cell structures, making them unsuitable for the "water absorption-release" function of internal curing. Other published technologies use a single acid solution to etch the cenospheres, but do not specify key parameters such as acid concentration and etching time, resulting in uneven pore size, easy breakage of the cenosphere structure, and poor functional controllability. Furthermore, existing technologies do not design directional modification schemes for the compositional characteristics of the cenospheres (e.g., F-grade fly ash cenospheres, with a CaO mass fraction of <10%, and the main components being mullite and quartz), making it difficult to balance perforation effect and cenosphere integrity. Therefore, there is an urgent need to develop a room-temperature, controllable, and low-energy-consumption method for preparing perforated cenospheres to meet the practical needs of internal curing of ternary cementitious materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a room-temperature preparation method for water-absorbing and water-releasing cenospheres used in the internal curing of ternary cementitious materials. By optimizing the mixed acid system and process parameters, the method achieves directional perforation modification of ordinary cenospheres, solving the problems of high energy consumption and uncontrollable function in existing preparation methods, and providing a highly efficient internal curing agent for cement-slag-limestone ternary cementitious materials.

[0005] The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials in the present invention includes steps such as raw material treatment, mixed acid etching, solid-liquid separation, cleaning and drying. A mixed acid solution composed of 1.0 mol / L ammonium fluoride (NH4F) and 1.2 mol / L hydrochloric acid (HCl) is used to etch class F fly ash cenospheres at room temperature. By controlling the etching time (2 hours) and drying conditions (drying at 60 °C for 12 hours), an open-hole connected structure is formed定向 on the cenosphere shell; at the same time, by using the density change of the etched cenospheres (more than 90% of the cenospheres sinking indicates qualification), finally, perforated cenospheres with the function of water storage and release are prepared.

[0006] The present invention can reduce the energy consumption for preparing porous cenospheres (without high-temperature equipment), solve the problem of uncontrollable functions of existing modified cenospheres, help improve the internal curing effect of ternary cementitious materials of cement-slag-limestone, and can be used to synchronously realize the regulation of the perforated structure of cenospheres and the adaptation function of internal curing performance.

[0007] The present invention achieves the above technical objectives through the following technical means.

[0008] A room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials includes the following steps: Step 1, raw material pretreatment: Weigh class F fly ash cenospheres and remove impurities; mix a 1.0 mol / L ammonium fluoride NH4F solution and a 1.2 mol / L hydrochloric acid HCl solution in a volume ratio of 1:1 to obtain a mixed acid etching solution; Step 2, mixed acid etching: Completely immerse the pretreated class F fly ash cenospheres in the mixed acid etching solution, continuously stir and etch for 2 hours, and after the etching is completed, let it stand until the perforation meets the standard; Step 3, solid-liquid separation: Perform solid-liquid separation on the etched mixture and collect the perforated cenospheres; Step 4, cleaning treatment: Wash the collected perforated cenospheres with deionized water to remove the residual acid solution on the surface; Step 5, drying treatment: Dry the washed perforated cenospheres at 60 °C for 12 hours to obtain the finished product of perforated cenospheres, and an open-hole connected structure is formed on the shell of the perforated cenospheres.

[0009] In the above solution, in step 2, the mass ratio of the class F fly ash cenospheres to the mixed acid etching solution is 1:6.

[0010] In the above solution, in step 2, the rotation speed of the stirring is 300 rpm; the standing time is 5 minutes In the above solution, in step 2, after the etching is completed, let it stand. When it is observed that the volume fraction of the sinking cenospheres in the etched mixture exceeds 90%, it is determined that the perforation meets the standard.

[0011] In the above scheme, in step three, filter paper or filter screen with a pore size of 7-8 μm is used for solid-liquid separation.

[0012] In the above scheme, in step four, the cleaning is a double rinse, with each rinse lasting 10 minutes.

[0013] The above scheme also includes step six, finished product inspection: determining the absorbance of the perforated cenospheres using the vacuum saturation method. The water absorption rate is ≥80% to be considered qualified; the vacuum saturation method is as follows: the perforated bead is placed in a 30 kPa vacuum environment and kept under pressure for 30 minutes to remove the gas in the pores, and then restored to normal pressure to absorb water. The entire pressure return process takes more than 2 minutes. The water absorption rate is obtained by calculating the mass difference before and after water absorption.

[0014] Furthermore, it also includes step seven, water release behavior detection: placing the water-saturated perforated cenospheres that passed the inspection in step six into a warm environment. In an environment with a temperature of 20℃ and a relative humidity of 75%, the water release rate was calculated by weighing the samples at regular intervals of 0 hours, 3 hours, 3 days, 7 days, and 28 days.

[0015] A water-absorbing and water-releasing bead for internal curing of ternary cementitious materials is disclosed. The bead is a perforated bead prepared at room temperature according to the method for preparing the water-absorbing and water-releasing bead for internal curing of ternary cementitious materials. The shell of the perforated bead has an open and interconnected structure and a water absorption rate of not less than 80%. It is used as an internal curing agent in cement-slag-limestone ternary cementitious materials.

[0016] A cement-slag-limestone ternary cementitious material, comprising the aforementioned perforated cenospheres.

[0017] The shell of F-grade fly ash cenospheres mainly consists of mullite and quartz. Mullite readily reacts with fluoride ions (F⁻) to form soluble fluoroaluminate, while quartz dissolves slowly with the aid of hydrochloric acid. This invention uses a mixed acid system of 1.0 mol / L NH₄F and 1.2 mol / L HCl. By selectively etching mullite with F⁻ and dissolving impurities with HCl while adjusting the pH value, interconnected pores are formed in the cenosphere shell.

[0018] Preliminary systematic experiments revealed that when the NH4F concentration was below 1.0 mol / L, the etching rate was too slow, making it difficult to achieve ≥90% bead sinking within 2 hours; when the HCl concentration was below 1.2 mol / L, the pH was too high, resulting in insufficient F⁻ activity and uneven etching; excessively high concentrations led to excessive corrosion of the shell and loss of strength. A 1:1 volume ratio of 1.0 mol / L ammonium fluoride (NH4F) solution to 1.2 mol / L hydrochloric acid (HCl) solution achieves the optimal balance between etching rate and structural integrity, ensuring interconnected channels and appropriate pore size, and preventing "penetration" (etch-through). Figure 9 (as shown) or "closed hole".

[0019] The shell of F-grade fly ash cenospheres is mainly composed of mullite and quartz. In the NH4F–HCl mixed acid system, the etching of mullite by fluoride ions is the controlling step. Experiments show that when the etching time is less than 1.5 hours, the shell is not fully dissolved, resulting in low porosity and poor connectivity, leading to a sinking cenosphere ratio of less than 90% and insufficient water absorption. When the etching time is greater than 2.5 hours, the shell becomes excessively thin and may even crack locally, significantly reducing the strength of the cenospheres and affecting their load-bearing capacity and durability in cementitious materials. An etching time of 2 hours is the optimal time window for forming uniform and interconnected channels while maintaining the integrity of the shell structure.

[0020] During the etching process, the density of the cenospheres increases due to changes in their shell structure (the density of ordinary cenospheres is about 0.64 g / cm³), causing them to float on the surface of the mixed acid solution. After the etching is completed (the shell forms an opening), the density increases to close to the solution density (1.02 g / cm³), and more than 90% of the cenospheres sink to the bottom of the beaker. This phenomenon can be used to visually verify the perforation effect.

[0021] In addition, the present invention uses a low temperature drying of 60℃ to avoid damage to the hollow structure of the cenospheres by high temperature, while ensuring that the internal moisture is completely removed; the perforated cenospheres prepared in the end have a highly efficient water absorption and release capacity due to their open and interconnected structure. After being mixed with cement-slag-limestone ternary cementitious materials, they can inhibit the self-shrinkage of the materials through internal curing, and at the same time improve the compressive strength of the materials by means of the volcanic ash reaction of the cenospheres.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. Low energy consumption: The entire process uses room temperature etching (no need for high-temperature sintering or melting), and the drying temperature is only 60℃. Energy consumption is reduced by more than 80% compared with the existing high-temperature preparation process, which significantly reduces production costs. 2. Controllable function: By specifying parameters such as mixed acid concentration, etching time, and stirring speed, the size and distribution of the pores of the float beads can be controlled in a targeted manner to ensure that the water absorption rate is ≥80%, meet the internal curing function requirements, and solve the problem of "disordered pores" in existing technologies; 3. High raw material utilization rate: Using F-grade fly ash cenospheres, an industrial by-product, as raw material, the high-value utilization of industrial solid waste (fly ash cenospheres) is realized. At the same time, the process steps are simple and easy to industrialize and mass-produce. 4. Strong compatibility: The prepared perforated cenospheres have good compatibility with cement-slag-limestone ternary cementitious materials. They can not only reduce the material's self-shrinkage through internal curing, but also improve the material's 28-day compressive strength through pozzolanic reaction (more than 4 MPa higher than the control group), providing support for the crack resistance and strength improvement of engineering structural materials. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the raw material pretreatment of the present invention; In the diagram, 1. F grade fly ash cenospheres, 2. Weighing balance, 3. 1.0 mol / L NH4F solution, 4. 1.2 mol / L HCl solution, 5. Mixed acid etching solution, and 6. Glass rod.

[0024] Figure 2 This is a schematic diagram of the mixed acid etching method of the present invention; In the figure, 1. Weighed F-grade fly ash cenospheres, 5. Mixed acid solution, 21. Etched cenospheres that did not sink, 22. Etched cenospheres that sink, and 23. Magnetic stirrer.

[0025] Figure 3 This is a schematic diagram of solid-liquid separation according to the present invention; In the figure, 5. Mixed acid etching solution, 22. Etching unfiltered beads, 31. Filtration liquid holding device, 32. Filter paper placement device, 33. Filtration waste liquid collection device, 34. Vacuum pump, 35. Etching filtered beads.

[0026] Figure 4 This is a schematic diagram of the cleaning process of the present invention; In the diagram, 31. Filtration liquid holding device, 32. Filter paper placing device, 33. Filtration waste liquid collection device, 34. Vacuum pump, 35. Filter beads to be cleaned, 40. Cleaning process time 10 minutes and cleaning twice, 41. Processing tray, 42. Deionized water, 43. Cleaning gun, 44. Filter beads to be cleaned, 45. Filter beads after cleaning.

[0027] Figure 5 This is a schematic diagram of the drying process of the present invention; In the diagram, 45. Flour beads after washing and drying, 51. Drying oven, 52. Flour beads after drying.

[0028] Figure 6 This is a schematic diagram of the finished product inspection of the present invention; In the figure, 2. Weighing balance, 52. Beads to be tested, 31. Filtration liquid container, 32. Filter paper placement device, 33. Filtration waste liquid collection device, 34. Vacuum pump, 60. Bead mass before vacuum sealing, 61. Clean water, 62. Vacuum sealing bottle, 63. Vacuum sealed beads, 64. Bead mass after vacuum sealing.

[0029] Figure 7 This is a schematic diagram of the water release behavior detection method of the present invention; In the figure, 2. Weighing balance, 63. Encapsulated float beads, 64. Mass of encapsulated float beads, 71. Water-released float beads, and 72. Mass of water-released float beads.

[0030] Figure 8 This is a schematic diagram of the bead morphology before and after two hours of etching in Embodiment 1 of the present invention, wherein, Figure 8 (a) shows the morphology of the floating beads before etching; Figure 8 (b) shows the morphology of the perforated beads after 2 hours of etching and a magnified view of a local area; Figure 9 This is a schematic diagram of the morphology of the over-etched perforated float bead in Embodiment 2 of the present invention, wherein, Figure 9 (a) Over-etched beads due to excessive etching time; 9 (b) Over-etched broken beads due to excessive acid solution concentration; Figure 10 This is a schematic diagram illustrating the actual application effect of the perforated floating beads prepared in Example 3 of the present invention. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0033] A method for preparing water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials at room temperature. The equipment required for preparation includes: an electronic balance 2, a glass rod 6, a magnetic stirrer 23, a container for holding the filtrate 31, a filter paper placement device 32, a waste filtrate collection device 33, a vacuum pump 34, a processing tray 41, a cleaning gun 43, an oven 51, a vacuum sealing bottle 62, and a constant temperature and humidity curing chamber 71. The raw materials include F-grade fly ash cenospheres (CaO mass fraction <10%, average particle size about 88.6 μm, particle size range: 10 μm-100 μm, density about 0.64 g / cm³), 1.0 mol / L ammonium fluoride (NH4F) solution, 1.2 mol / L hydrochloric acid (HCl) solution, and deionized water. Among them, the 1.0 mol / L NH4F solution and the 1.2 mol / L HCl solution are mixed at a volume ratio of 1:1 to prepare a mixed acid etching solution.

[0034] Combination Figure 1-7 As shown, a method for preparing perforated beads according to the present invention includes the following steps: Step 1: Weigh F-grade fly ash cenospheres 1 (e.g., manufacturer: Henan Hengyuan New Material Co., Ltd.; product model: high-quality first-grade ash) using an electronic balance 2, and remove surface impurities and agglomerated particles; mix 1.0 mol / L NH4F solution 3 and 1.2 mol / L HCl solution 4 at a volume ratio of 1:1, and stir evenly with a glass rod 6 to obtain a mixed acid etching solution 5, as shown below. Figure 1 As shown; Step 2: Immerse the pretreated Grade F fly ash cenospheres 1 completely in the mixed acid etching solution 5 at a mass ratio of 1:6. Continuously stir the "cenosphere-etching solution" using a magnetic stirrer 23 at 300 rpm for 2 hours. After etching, let it stand for 5 minutes to observe the cenosphere state. If, by volume estimation, ≥90% of the etched unfiltered cenospheres 22 sink from the solution surface to the bottom of the container (visually, the volume fraction of cenospheres sinking to the bottom exceeds 90%), the perforation is considered successful. Figure 2 As shown; Step 3: A filtration device equipped with medium-speed qualitative filter paper (containing a liquid to be filtered 31, a filter paper placement device 32, a waste liquid collection device 33, and a vacuum pump 34) is used to perform solid-liquid separation on the mixture of "etched cenospheres-solution" (mixed acid solution 5 and etched and settled cenospheres 22). The filter paper traps perforated cenospheres with a particle size of 8μm or larger to remove fine particles, and the filtered cenospheres to be cleaned 35 are collected. Figure 3 As shown; Step four: Rinse the collected etched and filtered microspheres 35 with deionized water 42 (rinsing time 10 minutes). Then, use a filtration device (filtrate holding device 31, filter paper placing device 32, filtrate waste collection device 33, vacuum pump 34) to remove the residual mixed acid solution on the surface of the perforated microspheres, obtaining the cleaned perforated microspheres 45. Rinse and filter the cleaned microspheres 45 again to ensure thorough cleaning. Figure 4 As shown; Step 5: Place the cleaned flocculants 45 into the drying oven 51, set the drying temperature to 60℃, and maintain this temperature for 12 hours to remove excess moisture from the perforated flocculants, resulting in dried flocculants 52. Figure 5 As shown; Step 6: Observe the opening state of the shell of the dried cenosphere 52: Weigh the dried cenosphere 52 to obtain mass X, which is the mass of the cenosphere before vacuum sealing (60). Vacuum seal the perforated cenosphere through vacuum sealing bottle 62. After filtration through a filtration device (filtrate holding device 31, filter paper placing device 32, filtration waste liquid collection device 33, vacuum pump 34), weigh the vacuum-sealed perforated cenosphere 63 to obtain mass Y, which is the mass of the vacuum-sealed cenosphere (64). Measure its water absorption performance (water absorption rate = (YX) / X ≥ 80%). This indicates a qualified saturated perforated cenosphere product. Figure 6 As shown; Step 7: Place the water-saturated perforated cenospheres (vacuum-sealed cenospheres 63) on a sample tray and then place them in a constant temperature and humidity curing chamber 71 at 20°C and 75% RH. Weigh the released cenospheres at regular intervals (0h, 3h, 3d, 7d, 28d) 72. Calculate the water release rate after normalization. Figure 7 As shown.

[0035] The etching time in step two is controlled at 2 hours. Insufficient etching time will result in insufficient perforation of the float beads (sinking rate <90%), while excessive etching time will result in the float bead shell being too thin and its strength decreasing. The cleaning in step four uses deionized water to prevent impurities in tap water from adhering to the surface of the float beads and affecting their compatibility with the subsequent cementitious materials. The water absorption rate test of the finished product in step six adopts the vacuum saturation method. The perforated beads are placed in a vacuum environment of 30 kPa and pressurized for 30 minutes to remove the gas in the pores. The pressure is slowly returned to absorb water, and the pressure return time is >2 minutes. The water absorption rate is obtained by calculating the mass ratio before and after water absorption. A water absorption rate ≥80% is qualified, ensuring that it meets the internal curing moisture storage requirements of ternary cementitious materials. Example 1

[0036] A method for preparing absorbent-release hydrophobic beads for internal curing of ternary cementitious materials at room temperature includes the following steps: Grade F cenospheres were weighed and impurities removed. A mixed acid etching solution was prepared by mixing 1.0 mol / L NH4F solution and 1.2 mol / L HCl solution. The cenospheres were then immersed in the mixed acid etching solution and stirred at 300 rpm for 2 hours. During the process, some cenospheres were observed to gradually sink. By the end of 2 hours, approximately 90% of the cenospheres had sunk to the bottom of the container, showing a significant perforation effect. After filtration, the cenospheres were rinsed twice with deionized water and dried at 60°C for 12 hours. The final product was tested and found to have transformed from closed microspheres into a hollow porous structure, with a significantly reduced apparent density and increased specific surface area. Figure 8 The diagram shows the morphology of the float beads before and after two hours of etching. Figure 8 (a) shows the morphology of the floating beads before etching; Figure 8 (b) shows the morphology of the perforated float bead after 2 hours of etching, along with a magnified view of a local area. Microstructural analysis reveals through-holes on the surface and walls of the float bead. Its water absorption rate is measured to be approximately 80%. Example 2

[0037] The difference between Example 2 and Example 1 lies in the concentrations of the ammonium fluoride (NH4F) solution and the hydrochloric acid (HCl) solution, as well as the etching time. Figure 9 As shown, in this embodiment, control experiments were conducted with excessively long testing time and excessively high acid solution concentration, and the results are as follows: Figure 9 (a): Excessive etching time leads to excessively large perforation particle size; Figure 9 (b): Excessive acid concentration leads to damage to the structural integrity of the sphere.

[0038] When the concentration of the composite acid solution in the etching process is too high (e.g., 1.5 mol / L NH4F solution and 1.8 mol / L HCl solution) or the etching time is too long (e.g., 3 hours), over-etching is very likely to occur. This abnormality manifests as severe corrosion on the surface of the beads, resulting in damage to their structural integrity, such as... Figure 9 (a) and Figure 9 (b) Significant erosion marks appear in the microstructure, even leading to increased surface roughness and collapse of the edge contour spheres. This process directly weakens the encapsulation effect of the float beads and ultimately affects the water absorption and release function of the perforated float beads, fully demonstrating the necessity of precise control of etching parameters. Example 3

[0039] In this embodiment, the perforated cenospheres prepared in Example 1 were used as a substitute for the ternary cementitious material in the sample, utilizing their "water absorption-release" characteristics for internal curing. In the experiment, perforated cenospheres were used at a certain dosage (e.g., 6.6%) to replace the ternary cementitious material to prepare samples, which were then compared with a control group without cenospheres. The test results are as follows: Figure 10As shown in the figure. The observation results indicate that the strength of the experimental group initially decreased due to the reduced cement content. However, with the extension of the curing period, the water release from the perforated microspheres promoted and prolonged cement hydration. The strength enhancement from hydration outweighed the strength loss caused by the dilution effect and the hollow structure of the porous microspheres. At 28 days, the compressive strength increased by 4 MPa. Figure 10 As shown in (a), the amount of spontaneous contraction in the experimental group was significantly lower than that in the control group, as... Figure 10 As shown in (b), this phenomenon is because the self-drying caused by the hydration of cement, slag, and limestone is offset by the internal curing provided by the release of water from the perforated cenospheres. During the hardening process, the perforated cenospheres gradually release the absorbed water, providing a continuously moist environment for cement hydration, thereby alleviating capillary negative pressure and reducing autogenous shrinkage. At 7 days, autogenous shrinkage is reduced by approximately 36%. In conclusion, the perforated cenospheres prepared by this experimental method can fully utilize their "water absorption-release" function, playing a significant role in improving the strength of high-performance concrete and reducing autogenous shrinkage as an internal curing agent.

[0040] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials at room temperature, characterized in that, Includes the following steps: Step 1, raw material pretreatment: Weigh F-grade fly ash cenospheres and remove impurities; mix 1.0 mol / L ammonium fluoride NH4F solution and 1.2 mol / L hydrochloric acid HCl solution at a volume ratio of 1:1 to obtain a mixed acid etching solution; Step 2, mixed acid etching: The pretreated F-grade fly ash cenospheres are completely immersed in the mixed acid etching solution and continuously stirred for 2 hours. After etching, the solution is left to stand until the perforation meets the standard. Step 3, solid-liquid separation: perform solid-liquid separation on the etched mixture and collect the perforated beads; Step 4, cleaning treatment: Clean the collected perforated beads with deionized water to remove residual acid from the surface; Step 5, drying treatment: Dry the cleaned perforated beads at 60°C for 12 hours to obtain the finished perforated beads, wherein the shell of the perforated beads forms an open and interconnected structure.

2. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, In step two, the mass ratio of the F-grade fly ash celery beads to the mixed acid etching solution is 1:

6.

3. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, In step two, the stirring speed is 300 rpm; the settling time is 5 minutes.

4. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, In step two, after etching is completed and the mixture is left to stand, when it is observed that the volume fraction of the sinking beads in the etched mixture exceeds 90%, the perforation is deemed to have met the standard.

5. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, In step three, filter paper or filter screen with a pore size of 7-8 μm is used for the solid-liquid separation.

6. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, In step four, the cleaning process involves two rinses, each lasting 10 minutes.

7. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 1, characterized in that, The process also includes step six, finished product inspection: the water absorption rate of the perforated beads is determined by the vacuum saturation method, and a water absorption rate of ≥80% is considered qualified; the vacuum saturation method is as follows: the perforated beads are placed in a 30 kPa vacuum environment and pressurized for 30 minutes to remove the gas in the holes, and then restored to normal pressure to absorb water. The entire pressure return process takes more than 2 minutes, and the water absorption rate is calculated by the difference in mass before and after water absorption.

8. The room-temperature preparation method of water-absorbing and water-releasing cenospheres for internal curing of ternary cementitious materials according to claim 7, characterized in that, It also includes step seven, water release behavior detection: the water-saturated perforated cenospheres that passed the inspection in step six are placed in an environment with a temperature of 20℃ and a relative humidity of 75%, and weighed at regular intervals of 0 hours, 3 hours, 3 days, 7 days and 28 days to calculate their water release rate.

9. A type of water-absorbing and water-releasing float beads for internal curing of ternary cementitious materials, characterized in that, The perforated beads prepared by the room temperature preparation method of the water-absorbing and water-releasing beads for internal curing of ternary cementitious materials according to any one of claims 1-8, wherein the shell of the perforated beads has an open and interconnected structure and a water absorption rate of not less than 80%, are used as internal curing agents in cement-slag-limestone ternary cementitious materials.

10. A cement-slag-limestone ternary cementitious material, characterized in that, Includes the perforated float as described in claim 9.

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