Ultrasonic-triggered rapid-gel capsule and its application method in 3D printing concrete

Abstract

The present invention relates to an ultrasonically triggered rapid-setting gel capsule and its application method in 3D concrete printing. The ultrasonically triggered rapid-setting gel capsule comprises a gel carrier, an admixture, and an encapsulation. The admixture is mixed in the gel carrier, and the encapsulation surrounds the gel carrier. The gel carrier is a semi-solid gel, and the admixture is an alkali-free liquid accelerator or a water-soluble concrete accelerator solution. The encapsulation is made of the same or similar material as the gel carrier, has a density greater than or equal to that of the gel carrier, and can be broken by ultrasonic waves. Compared with the existing technology, the present invention has the advantages of preventing changes in concrete properties and controlling the setting rate.

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 is one of the most widely used building materials in the civil engineering industry. 3D printing concrete, as a new type of concrete forming technology, can efficiently print various curved entities and has huge application potential in construction projects, bridge projects, and tunnel projects.

[0003] 3D printing construction processes place higher demands on concrete materials. One key challenge is the conflict between fluidity and rapid setting. On the one hand, concrete requires high fluidity for pumping, while on the other, it needs to set quickly after being extruded from the print head to meet construction requirements. Therefore, controlling the fluidity of concrete before and after printing is crucial. Conventional concrete requires a certain time interval between adding water and mixing and setting and hardening. Pumping and printing must be limited to the period before hardening. Otherwise, the solidified concrete will clog the pumping pipes and print head, making it difficult to clean. Currently, there are two main approaches to addressing the conflict between pumpability and buildability in 3D concrete: one is to strictly control the ratio of multiple admixtures and the printing time. Under these constraints, the printing window is limited by the setting time, limiting its application to factories and making it difficult to apply to construction sites. The other is to use a dual-tube pumping system, where the components containing the accelerator and the cement are pumped to the print head through separate pipes and then mixed at the print head. This technical approach partially overcomes the limitation of the material setting time on the printing window, but the mixing effect at the print head is poor, and the molded material often has a significant weak layer. Recently, a technology has been disclosed that incorporates an alkali-free accelerator into 3D printed concrete for gelation and installs a heating device at the print head to melt the capsules. This method controls the contact between the accelerator and cement to a certain extent, but the heating affects the cement hydration process, increases the risk of shrinkage cracking, and creates a temperature gradient between the concrete surface and the interior, which may not melt the capsules inside the concrete.

[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 rapid gel capsule and its application method in 3D printing concrete in order to overcome the defect of the above-mentioned prior art that temperature changes can 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. The admixture is mixed in the gel carrier and the encapsulation wraps the gel carrier. The gel carrier is a semi-solid gel and 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 ultrasound.

[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℃, and stir for 0.5h to obtain a carrier solution; dissolve 10g sodium aluminate in 100mL distilled water and 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 gel 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 admixture is aluminate.

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

[0015] A second aspect of the present invention is a method for applying an ultrasonically triggered rapid gel capsule to 3D printing concrete, characterized by comprising 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 up the ultrasound-triggered rapid 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 ultrasonically triggered quick gel capsule, so that the concrete and the contents of the ultrasonically triggered quick gel capsule are fully mixed for 3D printing;

[0019] The ultrasonically triggered fast-gelling capsule is an ultrasonically triggered fast-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 concrete preparation;

[0022] Adding capsules: Add ultrasonically triggered quick-release gel capsules to the concrete and stir for 30 seconds to disperse the controlled-release capsules in 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 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 rapid-setting gel capsule, which stores the concrete accelerating agent components through the cross-linked network of the gel carrier and then encapsulates them to prevent the accelerating agent components from coming into contact with the concrete and causing premature solidification. The resulting rapid-setting gel capsule can be broken by ultrasound to release the contents, avoiding the temperature changes that occur when the capsule is broken by heating in the prior art. This makes the concrete material more stable and has better practicality.

[0028] 2) The present invention also proposes a specific application method for ultrasonically triggered quick-gelling 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 acoustic environment on the quick-gelling 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 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 rapid gel capsules in 3D printing concrete.

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

[0033] The present invention is described in detail below with reference to 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 is an ultrasonically triggered quick-setting gel capsule, comprising a gel carrier 1, an admixture 2 and an encapsulation 3. The admixture 2 is mixed in the gel carrier 1, and the encapsulation 3 wraps the gel carrier 1. The gel carrier 1 is a semi-solid gel, and 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, and the density of the encapsulation 3 is greater than or equal to the density of the gel carrier 1. The encapsulation 3 can be broken by ultrasound.

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

[0037] Preferably, 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 of gelatin in 100mL of distilled water at 50-55°C and stir for 0.5h to obtain a carrier solution. Dissolve 10g of sodium aluminate in 100mL of distilled water and 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 accelerator adsorption is formed, then cut into blocks.

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

[0042] The resulting ultrasonic microcapsules have an average diameter of less than 5 mm. After thorough mixing with concrete, these microcapsules are evenly distributed throughout the concrete and, after ultrasonic disruption, uniformly release the accelerating setting agent. Accordingly, the ultrasonic triggering device has an ultrasonic frequency of at least 20 kHz and a power of at least 400 W to fully disrupt 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 the controlled-release capsules to the concrete and stir for 30 seconds to disperse the controlled-release capsules in the concrete.

[0048] S3: Stir the controlled-release capsules with an ultrasonic disruptor at a frequency of 20 kHz and a power of 400 W 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 by surrounding the outside of the 3D printer nozzle with an ultrasonic device. This design reduces the impact of the ultrasonic device on the concrete flow path and is suitable for concrete extrusion processes with larger flow rates. 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 properties when triggered by ultrasound, and has a high release rate of the accelerating agent after triggering. It 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 mixture is more uniform.

[0054] 2. Gelatin is a surfactant that reduces water, improving the fluidity of concrete mixes and facilitating pumping. It can also reduce bleeding and segregation of concrete mixes, improve cohesion and compactness, and thus increase 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 uniformly dispersing it in the concrete. There is no chemical reaction involved and it has little effect on other components of the concrete.

[0056] 4. Trigger-type control of 3D printed concrete can effectively resolve 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 above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined 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 density of the encapsulation (3) is greater than or equal to the density of the gel carrier (1), and the material of the encapsulation (3) is gelatin; the shape of the ultrasonic-triggered quick-setting gel capsule is block-shaped, and the average diameter is less than 5 mm; the encapsulation (3) can be broken by an ultrasonic breaking rod installed at the nozzle of a 3D printer; the ultrasonic frequency is at least 20 kHz, and the power is at least 400 W.

2. The ultrasound-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℃, and stir for 0.5h to obtain a carrier solution; dissolve 10g sodium aluminate in 100mL distilled water and 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 gel 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 ultrasound-triggered rapid gel capsule according to claim 1, characterized in that: The material of the admixture (2) is aluminate.

4. 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.

5. 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 up the ultrasonically triggered rapid gel capsule at the nozzle of the 3D printer, wherein the ultrasonic device is installed around the outside of the 3D printer nozzle or at the center of the nozzle of the 3D printer; the frequency of the ultrasonic device is at least 20 kHz and the power is at least 400 W; S3: injecting the mixed concrete into the nozzle of the 3D printer, starting the ultrasonic device to break the ultrasonically triggered quick gel capsule, so that the concrete and the contents of the ultrasonically 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 1-4.

6. The method for applying an ultrasonically triggered rapid gel capsule in 3D printing concrete according to claim 5, 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 concrete preparation; Adding capsules: Add ultrasonically triggered quick-release gel capsules to the concrete and stir for 30 seconds to disperse the controlled-release capsules in the concrete.

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