A rapid curing agent for 3D printing of shotcrete and a method for preparing the same

Abstract

The present application relates to the technical field of building materials, in particular to a rapid curing agent for 3D printing of shotcrete and a preparation method thereof. The raw materials of the curing agent include capsule core material, capsule wall material, modified carrier, emulsifier, organic solvent and dispersant. The rapid curing agent is microencapsulated, the capsule core curing component is wrapped by the capsule wall material, the slow release or triggered reaction of the curing agent can be realized, the premature contact of the curing agent with the cement-based material is avoided, and thus the demand for workability and rapid curing is balanced.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a rapid curing agent for 3D printed sprayed concrete and its preparation method. Background Technology

[0002] 3D printed concrete and shotcrete technologies have been widely used in building structure construction, tunnel support, and emergency engineering due to their advantages such as high efficiency, flexible shaping, and low labor requirements. The core performance requirement for cement-based materials in these technologies is rapid curing. During 3D printing, the material needs to reach sufficient strength in a short time to support subsequent printed layers and prevent collapse and deformation. Similarly, during shotcrete application, the material needs to quickly solidify and adhere to the substrate surface to reduce rebound loss and construction waiting time.

[0003] However, existing cement-based rapid curing agents suitable for such scenarios still face numerous technical bottlenecks in practical applications. Most traditional rapid-setting agents are instantaneous reactants, which easily trigger a rapid hydration reaction when mixed with cement-based materials, leading to a sharp loss of material workability. This not only affects the smoothness of the printing paste delivery or the uniformity of spraying, but may also cause internal micro-cracks due to concentrated heat release during hydration. Excessive addition may significantly reduce the later-stage strength, impermeability, and other durability properties of concrete, making it difficult to balance construction compatibility and long-term service stability. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a rapid curing agent for 3D printed sprayed concrete and a method for preparing the same.

[0005] The technical solution adopted in this invention is as follows: A rapid curing agent for 3D printed sprayed concrete, comprising, by weight, 10-20 parts of core material, 5-10 parts of wall material, 2-10 parts of modified carrier, 1-6 parts of emulsifier, 80-160 parts of organic solvent and 100-200 parts of dispersant.

[0006] The core material is one or more of dopamine hydrochloride, catechol, and ethyl catechol.

[0007] The modified carrier consists of 1-5 parts of nano-SiO2 and 1-5 parts of graphene oxide.

[0008] The particle size of the nano-SiO2 is 50-200nm; the lateral dimension of the graphene oxide sheets is 1-5μm, and the sheet thickness is 1-3 layers.

[0009] The capsule wall material is ethyl cellulose; the emulsifier is one or more of Tween 20, Tween 40, Tween 80, Span 40, and Span 80; the organic solvent is one or more of anhydrous ethanol, ethyl acetate, butyl acetate, and methyl ethyl ketone; and the dispersant is one or more of soybean oil and liquid paraffin.

[0010] A method for preparing a rapid curing agent includes the following steps: 1) Add the modified carrier to 40-80 parts of organic solvent for dispersion (ultrasonic dispersion, ultrasonic power of 200-300w, ultrasonic time of 30-60 min), then add the core material and stir (stirring rate of 200-400r / min, stirring time of 15-30 min) to obtain solution A; 2) Dissolve the capsule wall material in 40-80 parts of organic solvent to obtain solution B; 3) Add solution A to solution B and stir (stirring speed 200-400 r / min, stirring time 5-30 min) to obtain solution C; 4) Add the emulsifier to the dispersant and stir (stirring speed 400-600 r / min, stirring time 5-10 min) to obtain liquid D; 5) Add liquid C to liquid D, then heat and stir (temperature 60-80℃, stirring time 2-4 h, stirring speed 400-600 r / min) until the organic solvent is completely evaporated, vacuum filter, wash with deionized water, and dry (air dry for 24-48 h or put in a forced-air drying oven at 40℃ for 24-36 h) to obtain the fast curing agent.

[0011] The rapid curing agent of the present invention is added to cement-based materials at a dosage of 0.5-2% of the cementitious material.

[0012] Compared with the prior art, the beneficial technical effects of the present invention are: The rapid curing agent of this invention is made into microcapsules. The core curing components are encapsulated by the capsule wall material, which enables the slow release or triggered reaction of the curing agent, avoiding premature contact with cement-based materials, thereby balancing the requirements of workability and rapid curing. Specifically, by precisely controlling the preparation process parameters, a suitable microsphere-type rapid curing agent can be stably prepared. The size of the microspheres and the strength of the capsule wall are well matched, which can avoid the tube blockage problem caused by the premature rupture of too small microspheres at low pressure, and also avoid the problem of delayed curing after exiting the tube caused by the ultra-high pressure required for the rupture of too large microspheres. Ultimately, the rapid curing agent microspheres can be synchronously ruptured within the mainstream pumping pressure range, so that the core and modified carrier are evenly distributed in the slurry, avoiding strength fluctuations caused by local curing rate differences, and effectively ensuring the molding accuracy of 3D printed components and the adhesion stability of the sprayed layer.

[0013] In this invention, nano-SiO2 and graphene oxide are introduced as modified carriers, which are released synchronously with the core material under pumping pressure, forming a "curing-strengthening" synergistic effect: nano-SiO2 can act as crystal nuclei to promote the cement hydration reaction, help generate more hydration products, and significantly improve the early density of the material; graphene oxide, with its two-dimensional sheet structure, can effectively fill the pores of the cement matrix and form a strong interfacial bond with the hydration products; when the two work together, they can promote the interwoven growth of hydration products at the interlayer interface of 3D printed concrete, greatly improve the interlayer bonding performance, effectively solve the weakness problem of easy cracking and peeling of interlayers in existing 3D printed concrete, and strengthen the overall structure and long-term service stability.

[0014] The core material, containing dopamine hydrochloride, undergoes oxidative self-polymerization under alkaline conditions to form polydopamine (PDA). This PDA-SiO2 composite system is then constructed by coating the surface of nano-silica with hydrogen bonds and covalent bonds. The PDA, relying on Ca... 2+ The complexation effect accelerates the cement hydration process, while nano-silica optimizes the structure of hydration products with its high pozzolanic activity and micro-filling effect, generating more dense CSH gel and reducing porosity. Under the synergistic effect of the two, the polymer network formed by PDA intertwines with the cement hydration products, while strengthening the interfacial transition zone, achieving a synergistic amplification of hydration promotion, structural density and interfacial enhancement, thereby significantly improving the early and late mechanical properties of cement-based materials.

[0015] Dopamine hydrochloride undergoes oxidative self-polymerization in the alkaline environment of cement to form polydopamine (PDA). Through hydrogen bonding, covalent bonding, and π-π stacking interactions, PDA achieves efficient coating and dispersion modification of graphene oxide. PDA, relying on Ca... 2+ The complexation effect accelerates the dissolution and hydration process of cement clinker, while its polymer network enhances the interfacial bonding strength. Graphene oxide, with its high specific surface area and two-dimensional sheet structure, exerts a template effect, inducing the directional growth of CSH gel to form dense hydration products. Through sheet filling and network construction, a dense microstructure is formed, reducing pores and defects. The two work together to solve the problem of graphene oxide agglomeration in cement paste, achieving synergistic effects of hydration promotion, structural density, and interfacial strengthening.

[0016] 4. When the rapid curing agent of the present invention is added to cement-based materials, the curing agent can remain intact during non-specific pressure stages such as slurry storage and mixing. Under specific pumping pressure, the bladder wall ruptures, the bladder core and modified carrier are released, generating more hydration products and increasing the structural integrity and stability of the concrete material. Attached Figure Description

[0017] Figure 1 Photograph of the rapid curing agent prepared in Example 1. Detailed Implementation

[0018] The following examples illustrate specific implementations of the present invention. However, these examples are merely for illustrative purposes and do not limit the scope of the invention in any way. Example 1:

[0019] A method for preparing a rapid curing agent for 3D printed sprayed concrete includes the following steps: 1) Take 20 g of dopamine hydrochloride, 10 g of ethyl cellulose, 3 g of nano SiO2 (particle size 200 nm), 2 g of graphene oxide (sheet transverse size 5 μm, thickness 3 layers), 6 g of Tween 80, 160 g of methyl ethyl ketone, and 200 g of liquid paraffin. 2) Add nano-SiO2 and graphene oxide to 80g of methyl ethyl ketone and disperse with ultrasonic power of 300w for 60 min. Then add ethyl catechol and stir magnetically at 400r / min for 60 min to obtain solution A. 3) Dissolve ethyl cellulose in 80 g of methyl ethyl ketone and stir at 400 r / min for 30 min until completely dissolved to obtain solution B; 4) Add solution A to solution B and stir at 400 r / min for 30 min to obtain a homogeneous solution C; 5) Add Tween 80 to liquid paraffin and stir at 600 r / min for 10 min to form a stable dispersion system, thus obtaining liquid D; 6) Slowly add liquid C to liquid D, heat to 80℃, heat and stir at 600r / min for 4 h until methyl ethyl ketone is completely evaporated, vacuum filter, wash 3 times with deionized water, put in a forced-air drying oven and dry at 40℃ for 36 h, and collect the rapid curing agent with a size of 200μm.

[0020] Photographs of the obtained curing agent are as follows Figure 1 As shown, the curing agent appears to be spherical. Example 2:

[0021] A method for preparing a rapid curing agent for 3D printed sprayed concrete includes the following steps: 1) Take 15g of catechol, 6g of ethyl cellulose, 1.5g of nano SiO2 (particle size 80nm), 0.5g of graphene oxide (sheet transverse size 2μm, thickness 1 layer), 2g of Span 80, 100g of butyl acetate, 120g of soybean oil and an appropriate amount of deionized water. The above deionized water is only used for the washing step and does not participate in the formulation. 2) Add nano-SiO2 and graphene oxide to 50 g of butyl acetate and disperse with ultrasonic power of 220 W for 35 min. Then add a mixture of dopamine hydrochloride and catechol and stir magnetically at 250 r / min for 35 min to obtain solution A (modified carrier: core material: organic solvent = 2:15:50). 3) Dissolve ethyl cellulose in 50 g butyl acetate and stir at 250 r / min for 18 min until completely dissolved to obtain solution B (capsule wall material: organic solvent = 6:50). 4) Add solution A to solution B and stir at 250 r / min for 20 min to obtain a homogeneous solution C; 5) Add Span 80 to soybean oil and stir at 450 r / min for 6 min to form a stable dispersion system, thus obtaining liquid D (emulsifier:dispersant = 2:120). 6) Slowly add liquid C to liquid D, heat to 65℃, heat and stir at 450r / min for 2.5 h until butyl acetate is completely evaporated, vacuum filter, wash 3 times with deionized water, air dry for 36 h, and collect the rapid curing agent with a size of 120μm. Example 3:

[0022] 1) Take 12 g of dopamine hydrochloride, 8 g of ethyl catechol, 8 g of ethyl cellulose, 2.5 g of nano SiO2 (particle size 150 nm), 1.5 g of graphene oxide (sheet lateral size 4 μm, thickness 2 layers), 4 g of Tween 40, 160 g of anhydrous ethanol, 180 g of liquid paraffin and an appropriate amount of deionized water. The above deionized water is only used for the washing step and does not participate in the formulation. 2) Add nano-SiO2 and graphene oxide to 70g of anhydrous ethanol and disperse with ultrasonic power of 280w for 50 min. Then add a mixture of catechol and ethyl catechol and stir magnetically at 350r / min for 50 min to obtain solution A (modified carrier: core material: organic solvent = 4:15:70). 3) Dissolve ethyl cellulose in 90 g of anhydrous ethanol and stir at 350 r / min for 25 min until completely dissolved to obtain solution B (capsule wall material: organic solvent = 8:90). 4) Add solution A to solution B and stir at 350 r / min for 28 min to obtain homogeneous solution C; 5) Add Tween 40 to liquid paraffin and stir at 550 r / min for 9 min to form a stable dispersion system, thus obtaining liquid D (emulsifier:dispersant = 4:180). 6) Slowly add liquid C to liquid D, heat to 75℃, heat and stir at 550r / min for 3.5 h until the anhydrous ethanol is completely evaporated, vacuum filter, wash 3 times with deionized water, put in a forced-air drying oven and dry at 40℃ for 30 h, and collect the rapid curing agent with a size of 180μm. Example 4

[0023] 1) Take 8 g of catechol, 7 g of ethyl catechol, 9 g of ethyl cellulose, 2 g of nano SiO2 (particle size 120 nm), 1 g of graphene oxide (sheet transverse size 3 μm, thickness 2 layers), 405 g of Span, 150 g of ethyl acetate, 160 g of soybean oil and an appropriate amount of deionized water. The above deionized water is only used for the washing step and does not participate in the formulation. 2) Add nano-SiO2 and graphene oxide to 75g of ethyl acetate and disperse with ultrasonic power of 260w for 40 min. Then add a mixture of dopamine hydrochloride and ethyl catechol and stir magnetically at 320r / min for 40 min to obtain solution A (modified carrier: core material: organic solvent = 3:20:75). 3) Dissolve ethyl cellulose in 75 g of ethyl acetate and stir at 320 r / min for 22 min until completely dissolved to obtain solution B (capsule wall material: organic solvent = 9:75). 4) Add solution A to solution B and stir at 320 r / min for 22 min to obtain homogeneous solution C; 5) Add Span 40 to soybean oil and stir at 520 r / min for 7 min to form a stable dispersion system, thus obtaining liquid D (emulsifier:dispersant = 5:160). 6) Slowly add solution C to solution D, heat to 68℃, heat and stir at 520r / min for 2.8 h until ethyl acetate is completely evaporated, filter under vacuum, wash three times with deionized water, air dry for 48 h, and collect the rapid curing agent with a size of 160μm. Example 5

[0024] A method for preparing a curing agent includes the following steps: Take 20 g of dopamine hydrochloride, 10 g of ethyl cellulose, 6 g of Tween 80, 160 g of methyl ethyl ketone, and 200 g of liquid paraffin; 2) Add ethyl catechol to 80g of methyl ethyl ketone and disperse it with ultrasonic power of 300w for 60 min. Then add ethyl catechol and stir magnetically at 400r / min for 60 min to obtain solution A. Steps 3)-6) Refer to Example 1. Example 6

[0025] A method for preparing a curing agent includes the following steps: Take 20 g of dopamine hydrochloride, 10 g of ethyl cellulose, 5 g of nano-SiO2 (particle size 200 nm), 6 g of Tween 80, 160 g of methyl ethyl ketone, and 200 g of liquid paraffin. 2) Add nano-SiO2 to 80g of methyl ethyl ketone and disperse it with ultrasonic power of 300w for 60 min. Then add ethyl catechol and stir magnetically at 400r / min for 60 min to obtain solution A. Steps 3)-6) Refer to Example 1. Example 7

[0026] A method for preparing a curing agent includes the following steps: Take 20 g of dopamine hydrochloride, 10 g of ethyl cellulose, 5 g of graphene oxide (5 μm transverse dimension and 3 layers thick), 6 g of Tween 80, 160 g of methyl ethyl ketone, and 200 g of liquid paraffin. Graphene oxide was added to 80g of methyl ethyl ketone and dispersed with ultrasonic power of 300W for 60 min. Then, ethyl catechol was added and the mixture was magnetically stirred at 400r / min for 60 min to obtain solution A. Steps 3)-6) Refer to Example 1.

[0027] The curing agents obtained in Examples 1-7 were added to the cement-based materials, with the specific formulations as follows: Experimental Group 1: 300 g cement, 650 g sand, 135 g water, and 1.5 g of the rapid curing agent from Example 1.

[0028] Experimental Group 2: 300 g cement, 650 g sand, 135 g water, and 3 g of the rapid curing agent from Example 2.

[0029] Experimental Group 3: 300 g cement, 650 g sand, 135 g water, and 4.5 g of the rapid curing agent from Example 3.

[0030] Experimental Group 4: 300 g cement, 650 g sand, 135 g water, and 6 g of the rapid curing agent from Example 4.

[0031] Experimental Group 5: 300 g cement, 650 g sand, 135 g water, and 1.5 g curing agent from Example 5.

[0032] Experimental Group 6: 300 g cement, 650 g sand, 135 g water, and 1.5 g curing agent from Example 6.

[0033] Experimental Group 7: 300 g cement, 650 g sand, 135 g water, and 1.5 g curing agent from Example 7.

[0034] Control group: 300 g cement, 650 g sand, 135 g water.

[0035] Traditional quick-setting agent group: 300 g cement, 650 g sand, 135 g water, 9 g commercially available calcium formate quick-setting agent (model: Aladdin, manufacturer: Beijing Inokai Technology Co., Ltd.).

[0036] The setting time, compressive strength, and interlayer bond strength of each experimental group were tested. Setting time was determined according to GB / T1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". Compressive strength was determined according to GB / T50081-2019 "Standard Test Methods for Physical and Mechanical Properties of Concrete", with 1-day and 28-day compressive strengths measured respectively. Interlayer bond strength was determined according to JGJ / T483-2019 "Technical Specification for 3D Printed Concrete Structures". The test results are shown in the table below: As shown in the table above, the addition of modified carriers (nano-silica and graphene oxide) to the rapid curing agent of this invention shortens the initial setting time of 3D printed sprayed concrete to 25-39 min and the final setting time to 53-78 min, fully meeting the requirements for rapid curing construction. The 1-day compressive strength of the rapid curing agents in Examples 1-4 reached 23.1-27.5 MPa, significantly higher than the control group and comparable to the traditional rapid curing agent group; the 28-day compressive strength of the rapid curing agents in Examples 1-4 was significantly higher than the traditional rapid curing agent group. The interlayer bond strength of the rapid curing agents in Examples 1-4 reached 2.7-3.5 MPa, higher than that in Examples 5-7, and far superior to the control group and the traditional rapid curing agent group, effectively solving the problem of weak interlayer bonding.

[0037] The compressive strength and interlayer bond strength of Examples 1-4 were significantly better than those of Examples 5-7, fully demonstrating that the addition of the modified carrier played a curing-strengthening role. Examples 6 and 7 added the same amount of nano-silica and graphene oxide as modified carriers, respectively. However, the initial setting time and final setting time were longer than those of Examples 1-4 and shorter than those of Example 5. The compressive strength and interlayer bond strength were lower than those of Examples 1-4 but higher than those of Example 5. This indicates that adding nano-silica or graphene oxide alone can shorten the setting time and increase the strength. It also shows that the combined use of nano-silica and graphene oxide as modified carriers has a synergistic effect.

[0038] When dopamine hydrochloride was selected as the core material in Examples 1 and 3, its performance was better than that in Examples 2 and 4. Although catechol and ethyl catechol also have similar effects to dopamine hydrochloride, the stability between catechol and ethyl catechol and nano silica / graphene oxide is worse than that of dopamine hydrochloride. The stability between dopamine hydrochloride and nano silica / graphene oxide is the best.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A rapid curing agent for 3D printed sprayed concrete, characterized in that, By weight, the raw materials used include: 10-20 parts of core material, 5-10 parts of wall material, 2-10 parts of modified carrier, 1-6 parts of emulsifier, 80-160 parts of organic solvent and 100-200 parts of dispersant.

2. The rapid curing agent according to claim 1, characterized in that: The core material is one or more of dopamine hydrochloride, catechol, and ethyl catechol.

3. The rapid curing agent according to claim 1 or 2, characterized in that: The modified carrier consists of 1-5 parts of nano-SiO2 and 1-5 parts of graphene oxide.

4. The rapid curing agent according to claim 1 or 2, characterized in that: The particle size of the nano-SiO2 is 50-200nm; the lateral dimension of the graphene oxide sheets is 1-5μm, and the sheet thickness is 1-3 layers.

5. The rapid curing agent according to claim 1 or 2, characterized in that: The capsule wall material is ethyl cellulose; the emulsifier is one or more of Tween 20, Tween 40, Tween 80, Span 40, and Span 80; the organic solvent is one or more of anhydrous ethanol, ethyl acetate, butyl acetate, and methyl ethyl ketone; and the dispersant is one or more of soybean oil and liquid paraffin.

6. A method for preparing the rapid curing agent according to any one of claims 1-5, characterized in that, Includes the following steps: 1) Take each raw material according to the proportion; 2) Disperse the modified carrier in 40-80 parts of organic solvent, then add the core material and stir to obtain solution A; 3) Dissolve the capsule wall material in 40-80 parts of organic solvent to obtain solution B; 4) Add solution A to solution B and stir to obtain solution C; 5) Add the emulsifier to the dispersant and stir to obtain liquid D; 6) Add liquid C to liquid D, then heat and stir until the organic solvent has completely evaporated, vacuum filter, wash, and dry to obtain a fast curing agent.

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