Ultrasonic triggering type rapid hardening capsule and application method thereof in 3D printing concrete

Abstract

The invention relates to an ultrasonic trigger type quick-setting capsule and an application method thereof in 3D printing concrete, the ultrasonic trigger type quick-setting capsule comprises a gel carrier, an additive and an encapsulation, the additive is mixed in the gel carrier, the encapsulation wraps the gel carrier, the gel carrier is semi-solid gel, and the gel carrier is a semi-solid polymer. The additive is an alkali-free liquid accelerator or a water-soluble concrete accelerator solution, the material of the encapsulation is the same as or similar to that of the gel carrier, the density of the encapsulation is greater than or equal to that of the gel carrier, and the encapsulation can be broken through ultrasonic waves. Compared with the prior art, the method has the advantages that the property change of the concrete can be avoided, and the setting rate is controllable.

Description

Technical Field

[0001] The present invention relates to the field of civil engineering technology, and in particular to an ultrasonically triggered rapid gel capsule and an application method thereof in 3D printing concrete. Background Art

[0002] Concrete material is one of the most widely used building materials in the civil engineering industry. As a new type of concrete forming technology, 3D printed concrete can efficiently print various curved surface entities and has great application potential in construction projects, bridge projects, and tunnel projects.

[0003] 3D printing construction technology places higher demands on concrete materials, and one of the important problems is the contradiction between fluidity and rapid setting. On the one hand, concrete pumping requires high fluidity, and on the other hand, concrete needs to set quickly after being squeezed out of the print head to meet construction needs. Therefore, how to control the fluidity of concrete before and after printing is crucial. Ordinary concrete has a certain time interval from adding water to mixing to solidification and hardening. Its pumping and printing can only be limited to the time period before hardening, otherwise the solidified concrete will block the pumping pipe and print head, making it difficult to clean. At present, there are two main methods for the engineering community to solve the contradiction between the pumpability and constructability of 3D concrete: one is to strictly control the proportion of multiple admixtures and the printing time. Under this restriction, the operation window time of printing is limited by the setting time, and the application is mostly limited to factories, which is difficult to apply to construction sites; the other is to use a double-tube pumping system, and the components containing the accelerator and the components containing cement are pumped to the print head through a pipe respectively, and mixed by stirring at the print head position. This technical path has broken through the limitation of the material setting time on the printing operation window time to a certain extent, but the stirring and mixing effect at the print head position is poor, and the molding material often has an obvious weak layer. Recently, there is a technology that discloses the addition of alkali-free accelerators to 3D printed concrete for gelation, and the installation of heating equipment at the print head position to melt the capsule. This method controls the contact between the accelerator and cement to a certain extent, but the heating affects the hydration process of cement, increases the risk of shrinkage cracking, and generates a temperature gradient between the surface and the interior of the concrete, and the capsule inside the concrete may not be able to melt.

[0004] Therefore, a method should be used to achieve rapid setting control of concrete in a way that does not affect the properties of concrete when releasing the accelerator and mixing. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrasonically triggered quick-gelling capsule and its application method in 3D printing concrete in order to overcome the defect of the above-mentioned prior art that temperature changes will affect the properties of concrete.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] An ultrasonically triggered quick-setting gel capsule comprises a gel carrier, an admixture and an encapsulation, wherein the admixture is mixed in the gel carrier, the encapsulation wraps the gel carrier, the gel carrier is a semi-solid gel, the admixture is an alkali-free liquid quick-setting agent or a water-soluble concrete quick-setting agent solution, the encapsulation is made of the same or similar material as the gel carrier, the density of the encapsulation is greater than or equal to the density of the gel carrier, and the encapsulation can be broken by ultrasonic waves.

[0008] Furthermore, the preparation process of the ultrasound-triggered rapid gel capsule includes the following steps:

[0009] Solution preparation: dissolve 5g gelatin in 100mL distilled water, control the temperature at 50-55℃, stir for 0.5h to obtain a carrier solution; dissolve 10g sodium aluminate in 100mL distilled water, stir to obtain an accelerator solution;

[0010] Stirring and cooling: Add the accelerator solution to the carrier solution, evaporate the water to the predetermined gelatin concentration, cool for 1 hour until a gelatin block with the accelerator adsorbed is formed, and cut into blocks;

[0011] Soaking and encapsulating: Soak the quick-setting agent block in the carrier solution again, take it out after a period of time, and cool it for 1 hour to form an ultrasonically triggered quick-setting gel capsule.

[0012] Furthermore, the shape of the ultrasound-triggered rapid gel capsule is block-shaped, with an average diameter of less than 5 mm.

[0013] Furthermore, the material of the additive is aluminate.

[0014] Furthermore, the material of the semi-solid gel is gelatin or sodium alginate.

[0015] The second aspect of the present invention is a method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete, characterized in that it comprises the following steps:

[0016] S1: mixing the ultrasonically triggered quick-gelling capsule with concrete to obtain mixed concrete;

[0017] S2: Install an ultrasonic device capable of breaking the ultrasonically triggered quick gel capsule at the nozzle of the 3D printer;

[0018] S3: injecting the mixed concrete into the nozzle of the 3D printer, starting the ultrasonic device to break the ultrasonic-triggered quick gel capsule, so that the concrete and the contents of the ultrasonic-triggered quick gel capsule are fully mixed for 3D printing;

[0019] The ultrasonically triggered quick-gelling capsule is an ultrasonically triggered quick-gelling capsule according to any one of claims 1-5.

[0020] Furthermore, step S1 includes the following steps:

[0021] Prepare concrete: dry mix cement, fine aggregate and admixtures, pre-mix for 60 seconds; then add coarse aggregate and mix for 30 seconds; finally gradually add water and mix for 120 seconds to complete the preparation of concrete;

[0022] Adding capsules: Add ultrasonically triggered quick-release capsules into the concrete and stir for 30 seconds to disperse the controlled-release capsules into the concrete.

[0023] Furthermore, the frequency of the ultrasonic device is at least 20 kHz and the power is at least 400 W.

[0024] Furthermore, the ultrasonic device is installed at the inner center of the 3D printer nozzle.

[0025] Furthermore, the ultrasonic device surrounds the outside of the 3D printer nozzle.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention proposes an ultrasonically triggered quick-setting gel capsule, which stores concrete accelerating agent components through the cross-linked network of the gel carrier, and then wraps it through encapsulation to prevent the accelerating agent components from contacting with concrete in advance and causing solidification. The encapsulation of the obtained quick-setting gel capsule can be broken by ultrasound to release the contents, avoiding the change in concrete properties caused by temperature changes when the capsule is encapsulated and broken by heating in the prior art, so that the stability of the concrete material is stronger and has better practicality.

[0028] 2) The present invention also proposes a specific application method of ultrasonically triggered quick gel capsules in 3D printed concrete. Through ultrasonic crushing, the real-time power of the ultrasonic equipment can be controlled to quickly change the crushing effect of the sound wave environment on the quick gel capsules, and the degree of concrete coagulation can be quickly adjusted, which is suitable for complex construction needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the ultrasound-triggered rapid gel capsule.

[0030] Figure 2 This is a flow chart for the preparation of ultrasound-triggered rapid gel capsules.

[0031] Figure 3 This is a flow chart for the application of ultrasonically triggered quick-gel capsules in 3D printed concrete.

[0032] Explanation of the markings in the figure: 1. gel carrier, 2. additive, 3. encapsulation. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] The present invention discloses an ultrasonically triggered quick-setting gel capsule, comprising a gel carrier 1, an admixture 2 and an encapsulation 3, wherein the admixture 2 is mixed in the gel carrier 1, the encapsulation 3 wraps the gel carrier 1, the gel carrier 1 is a semi-solid gel, the admixture 2 is an alkali-free liquid quick-setting agent or a concrete quick-setting agent solution soluble in water, the material of the encapsulation 3 is the same as or similar to that of the gel carrier 1, the density of the encapsulation 3 is greater than or equal to the density of the gel carrier 1, and the encapsulation 3 can be broken by ultrasonic waves.

[0036] Preferably, the carrier material is gelatin or sodium alginate, which can absorb additives by virtue of its water absorption and chemical stability.

[0037] Preferably, the material of the admixture is aluminate, which is used to achieve rapid setting of concrete.

[0038] like Figure 2 As shown, the capsule preparation method includes three main steps: solution preparation, stirring and cooling, and soaking and encapsulation. The specific steps are as follows:

[0039] Solution preparation: Dissolve 5g gelatin in 100mL distilled water, control the temperature at 50-55℃, stir for 0.5h to obtain a carrier solution. Dissolve 10g sodium aluminate in 100mL distilled water. Stir to obtain an accelerator solution.

[0040] Stir and cool: Add the accelerator solution to the carrier solution and evaporate the water to the desired gelatin concentration. Cool for 1 hour until a gelatin block with the accelerator adsorbed is formed and cut into blocks.

[0041] Soaking and encapsulating: Soak the quick-setting agent block in the gelatin solution again, take it out after a period of time, cool it for 1 hour, and form the final controlled-release capsule.

[0042] The average diameter of the obtained ultrasonic microcapsules is less than 5 mm. After being fully mixed with concrete, the microcapsules of this size can be evenly distributed inside the concrete, and can evenly release the accelerating agent after ultrasonic crushing. Correspondingly, the ultrasonic frequency of the ultrasonic trigger device is at least 20kHz and the power is at least 400W, so as to fully crush the ultrasonic microcapsules.

[0043] Example 2

[0044] Based on Example 1, the present invention further proposes a specific application method of ultrasonic controlled release capsules in 3D printing concrete.

[0045] like Figure 3 As shown, the method for applying ultrasonic controlled release capsules in 3D printing concrete includes the following steps:

[0046] S1: Dry mix cement, fine aggregate and admixtures, pre-mix for 60 seconds; then add coarse aggregate and mix for 30 seconds; finally, gradually add water and mix for 120 seconds to complete the preparation of concrete.

[0047] S2: Add controlled-release capsules into the concrete and stir for 30 seconds to disperse the controlled-release capsules in the concrete.

[0048] S3: Use an ultrasonic breaker with a frequency of 20 kHz and a power of 400 W to stimulate the controlled-release capsules. Stir thoroughly for 2 minutes.

[0049] A control group was set up for parallel experiments. The penetration resistance method showed that the concrete setting speed was faster and the initial setting time was earlier after ultrasonic triggering.

[0050] Optionally, the print head can be installed by installing an ultrasonic device at the center of the 3D printer nozzle. This design is suitable for 3D printing tasks that require high-precision molding. The ultrasonic emission device can ensure the uniform release of the accelerator and is suitable for use in concrete printing with a smaller flow rate.

[0051] Optionally, the print head can be installed in a manner that an ultrasonic device is surrounded by the outside of the 3D printer nozzle. This design reduces the impact of the ultrasonic device on the concrete flow path and is suitable for a larger flow rate concrete extrusion process. It can ensure the efficient triggering of the accelerator while reducing the obstruction to the concrete pumping flow.

[0052] The ultrasonic controlled release capsule material of the present invention has good compatibility with concrete, has little effect on concrete performance due to ultrasonic triggering, has a high release rate of the accelerating agent after triggering, and can effectively meet the requirements for fluidity before 3D concrete printing and the requirements for rapid setting after printing. Specifically, there are:

[0053] 1. The various components of 3D printed concrete are fully mixed in the mixer, and the uniformity of the mixture is better.

[0054] 2. Gelatin is a surfactant that has a water-reducing effect, which can improve the fluidity of concrete mixtures and facilitate pumping. It can also reduce the bleeding and segregation of concrete mixtures, improve cohesion and compactness, and thus improve the strength and durability of concrete.

[0055] 3. Ultrasonic triggering uses ultrasonic cavitation to stir the slurry and crush gelatin lumps, thereby releasing the accelerator and dispersing it evenly in the concrete. There is no chemical reaction involved and it has little effect on other components of the concrete.

[0056] 4. The trigger control of 3D printed concrete can effectively solve the contradiction between the pumpability and constructability of 3D printed concrete, so that the concrete printing process is no longer constrained by the setting time, further enhancing the application of 3D printed concrete in intelligent construction.

[0057] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. An ultrasonically triggered rapid gel capsule, characterized in that: The invention comprises a gel carrier (1), an admixture (2) and an encapsulation (3), wherein the admixture (2) is mixed in the gel carrier (1), the encapsulation (3) wraps the gel carrier (1), the gel carrier (1) is a semi-solid gel, the admixture (2) is an alkali-free liquid quick-setting agent or a water-soluble concrete quick-setting agent solution, the encapsulation (3) is made of the same or similar material as the gel carrier (1), the density of the encapsulation (3) is greater than or equal to the density of the gel carrier (1), and the encapsulation can be broken by ultrasonic waves.

2. The ultrasonically triggered rapid gel capsule according to claim 1, characterized in that: The preparation process of the ultrasound-triggered rapid gel capsule comprises the following steps: Solution preparation: dissolve 5g gelatin in 100mL distilled water, control the temperature at 50-55℃, stir for 0.5h to obtain a carrier solution; dissolve 10g sodium aluminate in 100mL distilled water, stir to obtain an accelerator solution; Stirring and cooling: Add the accelerator solution to the carrier solution, evaporate the water to the predetermined gelatin concentration, cool for 1 hour until a gelatin block with the accelerator adsorbed is formed, and cut into blocks; Soaking and encapsulating: Soak the quick-setting agent block in the carrier solution again, take it out after a period of time, and cool it for 1 hour to form an ultrasonically triggered quick-setting gel capsule.

3. The ultrasonically triggered rapid gel capsule according to claim 1, characterized in that: The shape of the ultrasound-triggered rapid gel capsule is block-shaped, and the average diameter is less than 5 mm.

4. The ultrasonically triggered rapid gel capsule according to claim 1, characterized in that: The material of the admixture (2) is aluminate.

5. The ultrasound-triggered rapid gel capsule according to claim 1, characterized in that: The material of the semi-solid gel is gelatin or sodium alginate.

6. A method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete, characterized in that: The following steps are involved: S1: mixing the ultrasonically triggered quick-gelling capsule with concrete to obtain mixed concrete; S2: Install an ultrasonic device capable of breaking the ultrasonically triggered quick gel capsule at the nozzle of the 3D printer; S3: injecting the mixed concrete into the nozzle of the 3D printer, starting the ultrasonic device to break the ultrasonic-triggered quick gel capsule, so that the concrete and the contents of the ultrasonic-triggered quick gel capsule are fully mixed for 3D printing; The ultrasonically triggered fast-gelling capsule is an ultrasonically triggered fast-gelling capsule as described in any one of claims 1-5.

7. The method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete according to claim 1, characterized in that: Step S1 includes the following steps: Prepare concrete: dry mix cement, fine aggregate and admixtures, pre-mix for 60 seconds; then add coarse aggregate and mix for 30 seconds; finally gradually add water and mix for 120 seconds to complete the preparation of concrete; Adding capsules: Add ultrasonically triggered quick-release capsules into the concrete and stir for 30 seconds to disperse the controlled-release capsules into the concrete.

8. The method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete according to claim 1, characterized in that: The frequency of the ultrasonic device is 20kHz and the power is 400W.

9. The method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete according to claim 1, characterized in that: The ultrasonic device is installed at the center of the 3D printer nozzle.

10. The method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete according to claim 1, characterized in that: The ultrasonic device surrounds the outside of the 3D printer nozzle.

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