A new 3D printable, sprayable self-leveling early-strength high-strength repair mortar material

Abstract

The application discloses a new 3D-printable, self-leveling, early-strength and high-strength repairing mortar material, which comprises the following components: 400-450 parts of ordinary Portland cement, 100-85 parts of silica ash, 475-525 parts of English sand, 7.5-10 parts of PCE water reducing agent, 5-7.5 parts of nano early-strength agent, 12.5-15 parts of composite quick-setting agent, 3-6 parts of carboxymethyl chitosan-g-polyether, and 98-105 parts of tap water. The new repairing mortar material has the advantages of high early strength, rapid setting, fast molding, self-leveling, spraying, precise positioning construction, and effective completion of a tunnel concrete lining structure.

Description

Technical Field

[0001] This invention belongs to the field of tunnel concrete repair mortar technology, specifically involving a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level. Background Technology

[0002] Currently, common tunnel hazards are mainly divided into two categories: lining damage and tunnel frost damage. Lining damage mainly includes: 1. Lining deformation, cracking, and water leakage. 2. Displacement and cracking of end walls, side walls, and wing walls. 3. Road surface arching, subsidence, misalignment, and cracking. 4. Damage and cracking of precast tunnel segments. Tunnel frost damage mainly includes: 1. Frost heave damage of surrounding rock, causing lining deformation and damage. 2. Icing on the arch and sidewalls.

[0003] Current tunnel reinforcement methods typically require a high level of specialized technical expertise, involve intensive construction, and are expensive. They also face numerous problems, including long construction periods, poor durability, and potential safety accidents during construction. Therefore, there is an urgent need to develop an efficient and rapid tunnel reinforcement technology to improve the safety, economy, and sustainability of tunnel construction and operation. Summary of the Invention

[0004] The purpose of this invention is to provide a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level, featuring high early strength, rapid setting, fast molding, self-leveling capability, and spraying capability for precise positioning during construction, effectively completing tunnel concrete lining structures.

[0005] This invention adopts the following technical solution: a new early-strength, high-strength repair mortar material that can be 3D printed, sprayed, self-leveling, intelligent, rapid, and precise in repair, comprising the following components:

[0006] 400-450 parts of ordinary Portland cement

[0007] 100-85 parts silica fume

[0008]

[0009] Furthermore, this nano-early strength agent is a nano-CSH crystal nucleation early strength agent.

[0010] Furthermore, the quartz sand is divided into sand-1, sand-2 and sand-3 according to the particle size, and the mass ratio of sand-1, sand-2 and sand-3 is S1:S2:S3=1:1:1.

[0011] Furthermore, the particle sizes of sand-1, sand-2 and sand-3 are 16-24 mesh, 24-40 mesh and 40-70 mesh, respectively.

[0012] Furthermore, the composite quick-setting agent is composed of aluminum sulfate, sodium alginate and poly(N-isopropylacrylamide) in a mass ratio of 6.5:1.2:2.3.

[0013] This invention also discloses a method for preparing the above-mentioned 3D printable and sprayable self-leveling early-strength high-strength repair mortar material, which includes the following steps:

[0014] Step 1: Mix ordinary silicate cement, silica fume, and quartz sand using a forced mixer for 2 minutes to obtain a mixed dry powder.

[0015] Step 2: Pour PCE water-reducing agent, nano early strength agent, composite quick-setting agent, and carboxymethyl chitosan-g-polyether into tap water and stir slowly for 2 minutes to obtain a mixture.

[0016] Step 3: After adding the mixed liquid to the mixed dry powder, stir slowly for 2 minutes, then stir quickly for 3 minutes to obtain a high-strength repair mortar material that can be 3D printed and sprayed for intelligent, fast and precise repair.

[0017] Further, the preparation process of the nano-early strength agent is as follows: PCE water-reducing agent powder is weighed and dissolved in water to prepare a stabilizer base solution with a solid content of 1.5%; sodium silicate solution and calcium nitrate solution are slowly added to the stabilizer base solution at the same rate, with the volume ratio of sodium silicate solution 0.8 mol / L, calcium nitrate solution 0.5 mol / L and stabilizer base solution being 2:1.5:1; the mixture needs to be continuously stirred during the dropwise addition process, and stirring needs to be continued after the mixing is completed to obtain a stable nano-CSH crystal nucleus suspension. The obtained suspension is centrifuged (8000 r / min, 10 min), washed 3 times with deionized water, and vacuum dried at 80℃ to obtain the nano-early strength agent.

[0018] The beneficial effects of this invention are as follows: 1. The addition of a nano-early strength agent accelerates the formation of hydration products through a nucleation mechanism, speeding up the hydration reaction process without adversely affecting the later strength development. Because it accelerates the nucleation of external hydration products, it optimizes the slurry pore structure to a certain extent, improving impermeability and freeze resistance, and also enhancing the later strength of the mortar. 2. A "temperature-humidity dual-response" rapid setting mechanism is formed, breaking through the limitations of fixed performance of traditional chlorine-free and alkali-free rapid setting agents. Through the synergistic effect of the temperature-sensitive phase change of PNIPAM and the humidity-sensitive slow release of sodium alginate, an adaptive regulatory network of "delayed release at low temperature and high humidity, accelerated activation at high temperature and low humidity" is constructed. In low temperature and high humidity environments, the synergistic effect of the dissolved state of PNIPAM and the slow release of sodium alginate can appropriately extend the initial setting time, ensuring the operational window for 3D printing path planning or spraying construction. In high temperature and low humidity environments, the phase change precipitation of PNIPAM triggers the rapid release of aluminum sulfate from sodium alginate, controlling the initial setting time to 15-25 minutes, avoiding surface cracking and insufficient strength caused by excessively rapid evaporation of moisture during the initial setting stage. It precisely matches the needs of 3D printing (reducing extrusion resistance and improving interlayer bond strength) and jetting (high fluidity), solving the problem of mutual incompatibility between the two, broadening the range of stable construction, improving the early and late strength of mortar materials without strength shrinkage, and also has the advantages of being chlorine-free and alkali-free (avoiding steel corrosion) and bio-based (sodium alginate is renewable). It also has excellent compatibility with PCE water-reducing agents, nano-CSH early strength agents, etc. 3. Introducing carboxymethyl chitosan-g-polyether, whose molecular chain contains hydroxyl and carboxyl groups, can form a "dynamic hydrogen bond network" with cement particles and nano-CSH. Under shear conditions (3D printing extrusion, jetting), hydrogen bonds break, improving fluidity (adapting to printing / jetting speed); during static (stage), hydrogen bonds recombine to form a weak gel structure, inhibiting aggregate sedimentation and water bleeding, while not affecting the hydration activity of the early strength agent. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments.

[0020] This invention discloses a novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level, comprising the following components:

[0021]

[0022] The ordinary silicate cement is P.O42.5 cement.

[0023] The silica fume has an SiO2 content of ≥95% and a specific surface area of ​​18,000–24,000 m². 2 / kg.

[0024] The quartz sand is divided into sand-1, sand-2 and sand-3 according to the particle size, and the mass ratio of sand-1, sand-2 and sand-3 is S1:S2:S3=1:1:1.

[0025] The particle sizes of sand-1, sand-2 and sand-3 are 16-24 mesh, 24-40 mesh and 40-70 mesh, respectively.

[0026] PCE water-reducing agent is a high-efficiency polycarboxylate water-reducing agent with a water reduction rate of ≥30%.

[0027] The nano-early strength agent is a nano-CSH crystal nucleus early strength agent.

[0028] The composite quick-setting agent is composed of aluminum sulfate, sodium alginate and poly(N-isopropylacrylamide) (PNIPAM) in a mass ratio of aluminum sulfate:sodium alginate:PNIPAM = 6.5:1.2:2.3.

[0029] The carboxymethyl chitosan-g-polyether is a white powder with a particle size range of 100-500 micrometers.

[0030] The preparation process of the nano-early strength agent is as follows: PCE water-reducing agent powder is weighed and dissolved in water to prepare a stabilizer base solution with a solid content of 1.5%; sodium silicate solution and calcium nitrate solution are slowly added to the stabilizer base solution at the same rate, with the volume ratio of sodium silicate solution 0.8 mol / L, calcium nitrate solution 0.5 mol / L and stabilizer base solution being 2:1.5:1; the mixture needs to be stirred continuously during the dropwise addition process, and stirring should continue after the mixture is completed to obtain a stable nano-CSH crystal nucleus suspension. The obtained suspension is centrifuged (8000 r / min, 10 min), washed 3 times with deionized water, and vacuum dried at 80℃ to obtain the nano-early strength agent.

[0031] Example 1

[0032] Taking the preparation of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as an example, the raw materials include the following parts: 450 parts of ordinary silicate cement, 85 parts of silica fume, 475 parts of quartz sand, 10 parts of PCE water-reducing agent, 5 parts of nano early-strength agent, 15 parts of composite quick-setting agent, 9 parts of carboxymethyl chitosan-g-polyether, and 105 parts of tap water.

[0033] The preparation method of the above-mentioned new early-strength and high-strength repair mortar material that can be 3D printed and sprayed self-leveling includes the following steps:

[0034] Step 1: Mix ordinary silicate cement, silica fume, and quartz sand using a forced mixer for 2 minutes to obtain a mixed dry powder.

[0035] Step 2: Pour PCE water-reducing agent, nano early strength agent, composite quick-setting agent, and carboxymethyl chitosan-g-polyether into tap water and stir slowly for 2 minutes to obtain a mixture.

[0036] Step 3: After adding the mixed liquid to the mixed dry powder, stir slowly for 2 minutes, then stir quickly for 3 minutes to obtain a high-strength repair mortar material that can be 3D printed and sprayed for intelligent, fast, and precise repair. It can then be used for 3D printing or spraying construction.

[0037] Example 2

[0038] Taking the preparation of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as an example, the raw materials include the following parts: 450 parts of ordinary silicate cement, 85 parts of silica fume, 475 parts of quartz sand, 10 parts of PCE water-reducing agent, 5 parts of nano early-strength agent, 12.5 parts of composite quick-setting agent, 11 parts of carboxymethyl chitosan-g-polyether, and 105 parts of tap water.

[0039] In this embodiment, the preparation method of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling is the same as in Example 1.

[0040] Example 3

[0041] Taking the preparation of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as an example, the raw materials include the following parts: 450 parts of ordinary silicate cement, 85 parts of silica fume, 525 parts of quartz sand, 10 parts of PCE water-reducing agent, 7.5 parts of nano early-strength agent, 12.5 parts of composite quick-setting agent, 9 parts of carboxymethyl chitosan-g-polyether, and 105 parts of tap water.

[0042] In this embodiment, the preparation method of a new high-strength repair mortar material that can be 3D printed and sprayed for intelligent, rapid, and precise repair is the same as in Example 1.

[0043] Example 4

[0044] Taking the preparation of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as an example, the raw materials include the following parts: 400 parts of ordinary silicate cement, 100 parts of silica fume, 500 parts of quartz sand, 7.5 parts of PCE water-reducing agent, 7.5 parts of nano early-strength agent, 12.5 parts of composite quick-setting agent, 11 parts of carboxymethyl chitosan-g-polyether, and 100 parts of tap water.

[0045] In this embodiment, the preparation method of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling is the same as in Example 1.

[0046] Example 5

[0047] Taking the preparation of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as an example, the raw materials include the following parts: 400 parts of ordinary silicate cement, 100 parts of silica fume, 500 parts of quartz sand, 7.5 parts of PCE water-reducing agent, 5 parts of nano early-strength agent, 15 parts of composite quick-setting agent, 11 parts of carboxymethyl chitosan-g-polyether, and 98 parts of tap water.

[0048] In this embodiment, the preparation method of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling is the same as in Example 1.

[0049] Comparative Example 1

[0050] The comparative example was prepared from the following raw materials by weight: 450 parts ordinary silicate cement, 85 parts silica fume, 475 parts quartz sand, 10 parts PCE water-reducing agent, 0 parts nano-early strength agent, 12.5 parts composite quick-setting agent, 11 parts carboxymethyl chitosan-g-polyether, and 105 parts tap water. The above materials were prepared according to the preparation method of this invention to obtain the product.

[0051] Comparative Example 2

[0052] The comparative example was prepared from the following raw materials by weight: 450 parts ordinary silicate cement, 85 parts silica fume, 525 parts quartz sand, 10 parts PCE water-reducing agent, 7.5 parts nano-early strength agent, 0 parts composite quick-setting agent, 9 parts carboxymethyl chitosan-g-polyether, and 105 parts tap water. The above materials were prepared according to the preparation method of this invention to obtain the product.

[0053] Comparative Example 3

[0054] The comparative example was prepared from the following raw materials by weight: 400 parts ordinary silicate cement, 100 parts silica fume, 500 parts quartz sand, 7.5 parts PCE water-reducing agent, 7.5 parts nano-early strength agent, 12.5 parts composite quick-setting agent, 0 parts carboxymethyl chitosan-g-polyether, and 100 parts tap water. The above materials were prepared according to the preparation method of this invention to obtain the product.

[0055] In Comparative Examples 1 to 3, the preparation methods of each product are based on a new material preparation method for a high-strength repair mortar that can be 3D printed and sprayed for intelligent, rapid, and precise repair. In each step, if a certain raw material is missing, the preparation process involving the missing raw material is reduced accordingly.

[0056] Performance comparison:

[0057] The properties of Examples 1-5 and Comparative Examples 1-3 were tested in accordance with GB / T 1346-2024 "Standard Consistency Water Requirement, Setting Time and Soundness Test Methods for Cement", GB / T2419-2005 "Determination of Flowability of Cement Mortar", GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and JGJ / T 70-2009 "Standard for Test Methods of Basic Performance of Building Mortar". Table 1 below shows the test results of each property.

[0058] Table 1. Performance test results of the examples and comparative examples.

[0059]

[0060] As demonstrated by the performance of Examples 1-3 and Comparative Example 1, the nano-accelerator can synergistically promote the hydration reaction rate of cement in the material with the accelerator, shorten the setting time of the material, and improve the strength development at all ages. The nano-accelerator is a nano-CSH crystal nucleus, which acts as a "seed" for cement hydration, providing growth sites for cement hydration products (CSH gel) and thus shortening the setting time of the material. The micro-filling effect of nano-CSH can also optimize the material's structural density and improve the interfacial transition zone, avoiding later strength reduction and inhibiting solidification shrinkage.

[0061] The performance results of Examples 1 and 2, and Examples 3 and Comparative Example 2, show that the composite accelerator can significantly shorten the setting time of materials at room temperature. Tests conducted under low-temperature, high-humidity and high-temperature, low-humidity conditions demonstrate that the incorporation of the composite accelerator effectively controls the setting time, preventing slow setting at low temperatures and high humidity, and excessive moisture evaporation at high temperatures and low humidity, which can lead to surface cracking and insufficient strength. This ensures the material can be used for normal 3D printing and spraying. In the composite accelerator, aluminum sulfate is the core component that accelerates cement hydration. Sodium alginate and PNIPAM act as a humidity-sensing slow-release shell and a temperature-sensing control unit, respectively, encapsulating the aluminum sulfate component. At low temperatures and high humidity, the dissolved state of PNIPAM synergistically works with the strong slow-release effect of sodium alginate to control the release rate of aluminum sulfate, ensuring the operational window for 3D printing path planning and spraying. At high temperatures and low humidity, the phase change precipitation of PNIPAM triggers the rapid release of aluminum sulfate from sodium alginate, accelerating the hydration reaction of cement, consuming tap water, and preventing tap water evaporation loss.

[0062] The performance comparison results of Examples 4-5 and Comparative Example 3 show that carboxymethyl chitosan-g-polyether improves the bonding performance of repair mortar materials, but significantly reduces the fluidity of the materials, with almost no effect on the setting time and mechanical properties. However, during the 3D printing, extrusion, spraying, or molding of material specimens, the material maintains high fluidity and hardens quickly after standing. The molecular chain of carboxymethyl chitosan-g-polyether contains hydroxyl and carboxyl groups, which can form a "dynamic hydrogen bond network" with cement particles and nano-CSH. Under shear force, the hydrogen bonds break, maintaining the fluidity of the slurry. Upon standing, the hydrogen bonds recombine, forming a weak gel structure, without affecting the hydration activity of the accelerator and quick-setting agent. Carboxymethyl chitosan-g-polyether improves compatibility with PCE through its polyether side chains, avoiding the problems of rapid loss of fluidity and shortened operating window caused by traditional thixotropic agents (such as bentonite).

Claims

1. A novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling, characterized in that, The raw material components include the following: 400-450 parts of ordinary Portland cement 100-85 parts silica fume 475-525 parts of quartz sand 7.5-10 parts of PCE water-reducing agent, 5-7.5 parts of nano-early strength agent, 12.5-15 parts of composite quick-setting agent, 3-6 parts of carboxymethyl chitosan-g-polyether 98-105 units of tap water; The composite quick-setting agent is composed of aluminum sulfate, sodium alginate and poly(N-isopropylacrylamide) in a mass ratio of 6.5:1.2:2.

3.

2. The novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling as described in claim 1, characterized in that, The nano-early strength agent is a nano-CSH crystal nucleus early strength agent.

3. The novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as described in claim 2, characterized in that, The quartz sand is divided into sand-1, sand-2 and sand-3 according to the particle size, and the mass ratio of sand-1, sand-2 and sand-3 is S1:S2:S3=1:1:

1.

4. The novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as described in claim 3, characterized in that, The particle sizes of sand-1, sand-2 and sand-3 are 16-24 mesh, 24-40 mesh and 40-70 mesh, respectively.

5. A method for preparing a novel early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Mix ordinary silicate cement, silica fume, and quartz sand using a forced mixer for 2 minutes to obtain a mixed dry powder. Step 2: Pour PCE water-reducing agent, nano early strength agent, composite quick-setting agent, and carboxymethyl chitosan-g-polyether into tap water and stir slowly for 2 minutes to obtain a mixture. Step 3: After adding the mixed liquid to the mixed dry powder, stir slowly for 2 minutes and then stir quickly for 3 minutes to obtain a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed to self-level.

6. The preparation method of a new early-strength, high-strength repair mortar material that can be 3D printed and sprayed self-leveling as described in claim 5, characterized in that, The preparation process of the nano-early strength agent is as follows: PCE water-reducing agent powder is weighed and dissolved in water to prepare a stabilizer base solution with a solid content of 1.5%; sodium silicate solution and calcium nitrate solution are slowly added to the stabilizer base solution at the same rate, with the volume ratio of sodium silicate solution 0.8 mol / L, calcium nitrate solution 0.5 mol / L and stabilizer base solution being 2:1.5:1; the mixture needs to be stirred continuously during the dropwise addition process, and stirring should continue after the mixture is completed to obtain a stable nano-CSH crystal nucleus suspension. The obtained suspension is centrifuged at 8000 r / min for 10 min, washed 3 times with deionized water, and vacuum dried at 80℃ to obtain the nano-early strength agent.

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