Spraying ECC material for inhibiting fiber damage and preparation method thereof

Abstract

The invention discloses a jet ECC material for inhibiting fiber damage and a preparation method thereof, and the jet ECC material comprises the following components in parts by mass: 700-850 parts of a cementing material, 800-1000 parts of machine-made sand, 10-20 parts of UHMWPE fiber, 20-40 parts of an antifriction shell-making component, 8-12 parts of a water reducer and 180-220 parts of water, the gel material is prepared by mixing cement and a mineral admixture; the antifriction shell-making component is prepared by mixing silica fume and hydroxypropyl methyl cellulose; the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is greater than or equal to 30%. According to the preparation method, a step-by-step stirring process is adopted, particularly, the strict sequence of shell making, fiber adding and slurry forming and matched water consumption control are adopted, a lubricating buffer wrapping layer is constructed on the surface of machine-made sand, the problem of fiber damage is solved, the cohesiveness and thixotropy of slurry are improved through anti-friction shell making components (silica fume and HPMC), and the wear resistance of the machine-made sand is improved. The grouting material is free of coarse aggregate, self-compacting and self-leveling, has excellent pumping and spraying construction performance, and is suitable for engineering scenes such as tunnel support and building reinforcement.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a sprayed ECC material that inhibits fiber damage and its preparation method. Background Technology

[0002] Engineering cement-based composites (ECCs), as an advanced building material with high toughness and durability, are increasingly widely used in modern engineering fields through sprayed ECC technology, which involves applying ECC materials to the surface of a substrate in a sprayed form. Ultra-high molecular weight polyethylene (UHMWPE) fibers, due to their superior properties such as ultra-high strength, high modulus, and strong corrosion resistance, have become the core reinforcing component for improving the mechanical properties of ECC materials. However, in practical engineering applications, to reduce material costs and improve resource utilization, manufactured sand is gradually replacing natural sand as the main aggregate in ECC materials.

[0003] However, manufactured sand has inherent defects such as sharp edges and rough surfaces. During mixing and construction, sharp manufactured sand particles can easily cause mechanical scratches and cuts to UHMWPE fibers, resulting in a decrease in fiber strength and an inability to fully exert their reinforcing effect. At the same time, the high coefficient of friction between fibers and rough aggregates can easily cause fiber entanglement and agglomeration, resulting in uneven internal properties of the material. In addition, the thixotropic properties of ECC slurry prepared by traditional mixing processes are difficult to control, and problems such as high pumping resistance and easy pipe blockage are likely to occur during spraying construction, which seriously affects the construction quality and efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a jet-embedded ECC material that inhibits fiber damage and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To address the aforementioned technical problems, this invention provides a sprayed ECC material for inhibiting fiber damage, comprising the following components by mass parts:

[0006] 700-850 parts of cementitious material, 800-1000 parts of manufactured sand, 10-20 parts of UHMWPE fiber, 20-40 parts of friction-reducing shell-forming component, 8-12 parts of water-reducing agent, and 180-220 parts of water;

[0007] The gel material is made from a mixture of cement and mineral admixtures;

[0008] The friction-reducing shell-forming component is made from a mixture of silica fume and hydroxypropyl methylcellulose;

[0009] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate of ≥30%.

[0010] Further, the cement is ordinary Portland cement of P·O 42.5 grade or above, the mineral admixture is fly ash and / or slag powder, the fly ash conforms to GB / T1596-2017 "Fly Ash for Cement and Concrete" Grade II or above standard, the slag powder conforms to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement and Concrete" Grade S95 or above standard, and the mass ratio of the cement to the mineral admixture is 1:(0.3~0.6).

[0011] Furthermore, the fineness modulus of the manufactured sand is 2.3~3.0, the particle size is ≤4.75mm, and the content of stone powder with a particle size less than 0.075mm is 10%~15%.

[0012] Furthermore, the proportion of particles with a size of 2.36~4.75mm in the manufactured sand is ≥60%.

[0013] Furthermore, the UHMWPE fiber has a volume content of 1.0%~2.5%, a length of 8mm~12mm, a diameter of 20~50μm, a tensile strength ≥2800MPa, and an elastic modulus ≥100GPa.

[0014] Further, the mass ratio of the silica fume to the hydroxypropyl methylcellulose is 1:(0.1~0.3), wherein the silica fume has a specific surface area ≥15000m² / kg and an active silica content ≥90%, and the hydroxypropyl methylcellulose has a viscosity of 10000~20000mPa·s.

[0015] A method for preparing a jet-embedded ECC material for inhibiting fiber damage as described in any one of the above claims includes the following steps:

[0016] S1. Weigh the manufactured sand and friction-reducing shell-forming components into a forced mixer and add 30% to 40% water. Stir before adding the cementitious material so that the silica fume and hydroxypropyl methylcellulose in the friction-reducing shell-forming components are preferentially adsorbed on the surface of the manufactured sand particles and form a continuous lubricating buffer coating layer.

[0017] S2. After the lubricating buffer coating layer is formed, keep the forced mixer running and add UHMWPE fibers evenly and continue stirring so that the UHMWPE fibers are evenly dispersed under the condition of contact with the lubricating buffer coating layer.

[0018] S3. Add the weighed cementitious material, the remaining 60% to 70% of the total water volume, and the water-reducing agent to the system obtained in step S2, and stir evenly to form a sprayed ECC slurry.

[0019] Further, in step S1, the forced mixer is a forced concrete mixer conforming to JG244 or a forced mortar mixer conforming to JG / T3033. The mixing volume per batch is 1 / 4 to 3 / 4 of the nominal capacity of the forced mixer, the mixing speed of the forced mixer is 150 to 200 r / min, and the mixing time is 180 to 240 seconds.

[0020] Furthermore, in step S2, the mixing speed of the forced mixer is 150~200 r / min, and the mixing time is 300~360 seconds.

[0021] Furthermore, in step S3, the mixing speed of the forced mixer is 300~400 r / min, and the mixing time is 120~180 seconds.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention utilizes a micro-aggregate shelling process to construct a lubricating and buffering coating layer on the surface of manufactured sand. This not only solves the fiber damage problem (fiber strength retention rate ≥90%), but also enhances the cohesiveness and thixotropy of the slurry through the friction-reducing shelling components (silica fume + HPMC), achieving an elongation at break ≥3%, no coarse aggregate, and self-compacting and self-leveling properties. Simultaneously, it further reduces material costs, aligning with the development trend of green building.

[0024] This invention employs a step-by-step mixing process, particularly the strict sequence of first forming a shell, then adding fibers, and finally slurrying, along with corresponding water volume control. This pre-constructs a complete and stable friction-reducing, lubricating, and buffering layer on the surface of the manufactured sand particles, fundamentally isolating the subsequently added UHMWPE fibers from direct contact with the sharp edges of the sand particles. Because a slurry shell has already formed on the surface of the manufactured sand, during the mixing process, the manufactured sand particles encased in this shell form rolling slurry balls, causing the fibers to slide and disperse rapidly. This effectively prevents fiber entanglement and clumping, achieving non-destructive and uniform fiber dispersion. ECC slurry prepared by the stepwise mixing process has excellent thixotropic properties, combining self-compacting and self-leveling characteristics (filling the voids in the template or sprayed surface without vibration) with good cohesiveness (no fiber segregation or slurry bleeding during pumping). The slurry flow resistance during pumping is reduced by 30% to 40% compared to traditional processes, facilitating long-distance transportation and spraying operations. After being sprayed onto the sprayed surface, the thixotropic structure of the slurry recovers rapidly, and the "interlocking effect" between the manufactured sand particles manifests promptly. The slurry has strong adhesion, significantly improving construction efficiency and material utilization, and is suitable for engineering scenarios such as tunnel support and building reinforcement. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are merely one embodiment of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments.

[0027] In the following description, references to "an embodiment," "an embodiment," "an example," "example," etc., indicate that the described embodiment or example may include a particular feature, structure, characteristic, property, element, or limitation, but not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element, or limitation. Furthermore, the repeated use of the phrase "an embodiment according to this application," while possibly referring to the same embodiment, does not necessarily refer to the same embodiment.

[0028] This invention discloses a sprayed ECC material for inhibiting fiber damage, comprising the following components by mass parts:

[0029] 700-850 parts of cementitious material, 800-1000 parts of manufactured sand, 10-20 parts of UHMWPE fiber, 20-40 parts of friction-reducing shell-forming component, 8-12 parts of water-reducing agent, and 180-220 parts of water;

[0030] The gel material is made from a mixture of cement and mineral admixtures;

[0031] The friction-reducing shell-forming component is made by mixing silica fume and hydroxypropyl methylcellulose (HPMC). Silica fume has extremely strong adsorption and filling properties, and can tightly bind to the surface of manufactured sand to form a physical barrier. Hydroxypropyl methylcellulose (HPMC) acts as a thickening and water-retaining agent, and works synergistically with silica fume to form a thixotropic slurry layer that coats the surface of manufactured sand particles to form a slurry shell.

[0032] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate of ≥30%. It is chloride-free, has good compatibility with cementitious materials, and is used to reduce the water-cement ratio of slurry and improve its fluidity and density.

[0033] This invention utilizes a micro-aggregate shelling process to construct a lubricating and buffering coating layer on the surface of manufactured sand. This not only solves the fiber damage problem (fiber strength retention rate ≥90%), but also enhances the cohesiveness and thixotropy of the slurry through the friction-reducing shelling components (silica fume + HPMC), achieving an elongation at break ≥3%, no coarse aggregate, and self-compacting and self-leveling properties. Simultaneously, it further reduces material costs, aligning with the development trend of green building.

[0034] In one embodiment, the cement is ordinary Portland cement of P·O 42.5 grade or higher, ensuring a wide availability of cement materials, stable performance, and sufficient early and late strength benchmarks. The mineral admixture is fly ash and / or slag powder, i.e., one or both of fly ash and slag powder. The fly ash conforms to GB / T1596-2017 "Fly Ash for Cement and Concrete" Grade II or higher standard, used to improve slurry fluidity and lubricity, and reduce heat of hydration. The slag powder conforms to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement and Concrete" Grade S95 or higher standard, used to enhance late-stage strength and durability, and improve microstructure. The mass ratio of cement to mineral admixture is 1:(0.3~0.6), maximizing the advantages of mineral admixtures in improving workability, reducing temperature rise, enhancing durability, and reducing costs while ensuring sufficient hydration strength of the cement.

[0035] In one embodiment, the fineness modulus of the manufactured sand is 2.3~3.0, and the particle size is ≤4.75mm. No complex edge grinding is required; the requirements can be met simply through particle shaping or gradation adjustment. Furthermore, the content of stone powder with a particle size less than 0.075mm is 10%~15%. This stone powder is a naturally occurring calcium carbonate powder produced during the manufactured sand processing and contains no harmful impurities such as clay or silt, ensuring the cleanliness and rational particle size distribution of the manufactured sand. Using manufactured sand as the main aggregate ensures good workability of the slurry (pumping and spraying) and provides a stable micro-skeleton for the material, effectively utilizing construction waste resources and reducing material costs.

[0036] In one embodiment, the proportion of particles with a diameter of 2.36~4.75mm in the manufactured sand is ≥60%. Medium to coarse particles dominate the entire manufactured sand composition, accounting for over 60%. This ensures a sufficient number of surface-stable coarse particles as a core, providing a substantial and stable substrate for the friction-reducing shell-forming components. Each coarse particle is fully coated, forming numerous uniformly sized slurry shells.

[0037] Compared to systems dominated by fine sand, the skeleton composed of coarse particles has a relatively smaller number of particles. During fiber dispersion, the frequency of collisions between fibers and potential damage sources (sand particles) is significantly reduced. The coarse particle skeleton forms a more uniform and moderately sized void, providing smooth channels for fiber movement and orientation during mixing, further avoiding fiber entanglement and mechanical compression damage caused by dense packing. Due to their larger mass, coarse particles have greater inertia in the slurry, making them less prone to separation during pumping or jetting. The high proportion of coarse particles greatly enhances the cohesiveness and anti-segregation ability of the mixture, thereby significantly reducing construction rebound rate and material waste. In other words, the high proportion of coarse particles forms a stable microskeleton in the slurry, which not only reduces the probability of fiber damage but also endows the jetting slurry with excellent thixotropy and anti-segregation properties, making it highly fluid during pumping and able to quickly and stably adhere to the working surface after being sprayed.

[0038] In one embodiment, the UHMWPE fiber volume content is 1.0%~2.5%, and the length is 8mm~12mm. This ensures that the fiber can effectively bridge microcracks while preventing excessively long fibers from tangling and clumping during stirring and pumping, or affecting dispersion uniformity and final properties due to poor orientation during high-flow-rate pumping. The diameter is 20~50μm, ensuring that the fiber can be effectively pulled out of the matrix, consuming energy and providing toughness, without premature breakage. A tensile strength ≥2800MPa ensures that the fiber itself is extremely difficult to break during microcrack opening, thus continuously transferring stress to the uncracked matrix, initiating new microcracks, and achieving continuous strain hardening. An elastic modulus ≥100GPa, combined with strength, ensures that the fiber maintains small elastic deformation under extremely high stress, ensuring sufficient reinforcement potential. At the moment the matrix cracks, the fiber can immediately bear the load, effectively inhibiting rapid crack propagation.

[0039] In one embodiment, the mass ratio of silica fume to hydroxypropyl methylcellulose (HPMC) is 1:(0.1~0.3), used to enhance the structural stability, lubricity, and thixotropy of the slurry shell. The silica fume has a specific surface area ≥15000 m² / kg, allowing it to densely adsorb onto the surface of manufactured sand particles. Its active silica content ≥90% provides high activity, enabling it to undergo a pozzolanic reaction in the alkaline environment generated during cement hydration, producing more CSH gel. This results in chemical bonding between the initially formed slurry shell and the later-stage matrix, creating a stronger and denser interfacial transition zone. The hydroxypropyl methylcellulose has a viscosity of 10000~20000 mPa·s. This viscosity range of HPMC provides sufficient structural viscosity to maintain the coating layer's stability under static or low shear conditions, preventing fiber sedimentation and slurry segregation. It also moderately thins under agitated shear, facilitating fiber dispersion and pumping, and rapidly recovers after shear removal.

[0040] A method for preparing a jet-embedded ECC material for inhibiting fiber damage as described in any of the above claims, comprising the following steps:

[0041] S1. Weigh the manufactured sand and friction-reducing shell-forming components into a forced mixer and add 30% to 40% water. Stir before adding the cementitious material so that the silica fume and hydroxypropyl methylcellulose in the friction-reducing shell-forming components are preferentially adsorbed on the surface of the manufactured sand particles and form a continuous lubricating buffer coating layer.

[0042] This step involves pre-wetting and shell formation (buffer layer formation) of the manufactured sand. By strictly controlling the low water-cement ratio, the limited water is forced to preferentially combine with highly active silica fume and HPMC. The nano-silica fume particles are uniformly adsorbed onto the surface of the manufactured sand by means of intermolecular forces, forming a high-viscosity, thixotropic lubricating buffer coating layer (i.e., slurry shell) with water. This coating layer can effectively fill the pits on the surface of the manufactured sand, wrap the sharp edges, and form a smooth buffer interface.

[0043] S2. After the lubricating buffer coating layer is formed, keep the forced mixer running and add UHMWPE fibers evenly and continue stirring so that the UHMWPE fibers are evenly dispersed under the condition of contact with the lubricating buffer coating layer.

[0044] This step involves fiber introduction and non-destructive dispersion. Since a slurry shell has been formed on the surface of the manufactured sand, the fibers only interact with the lubricating and buffering coating layer when they come into contact with the aggregate, avoiding direct rigid contact with sharp edges. At the same time, the manufactured sand particles wrapped in the slurry shell form rolling slurry balls during the stirring process, which drives the fibers to slide and disperse rapidly, effectively preventing fiber entanglement and clumping, and achieving non-destructive and uniform dispersion of the fibers.

[0045] S3. Add the weighed cementitious material, the remaining 60% to 70% of the total water volume, and the water-reducing agent to the system obtained in step S2, and stir evenly to form a sprayed ECC slurry.

[0046] This step involves matrix shaping and rheological conditioning (matrix homogenization). The remaining large amount of water and water-reducing agent are added at this stage, forming a fluid slurry with the cementitious material. Under stirring and shearing action, this slurry penetrates and fuses with the pre-formed lubricating buffer coating layer, creating a seamless transition from the aggregate interface to the matrix's intrinsic properties. Simultaneously, the thixotropic structure is optimized, giving it both pumpable fluidity and spray adhesion.

[0047] This invention employs a step-by-step mixing process, particularly the strict sequence of first forming a shell, then adding fibers, and finally slurrying, along with corresponding water volume control. This pre-constructs a complete and stable friction-reducing, lubricating, and buffering layer on the surface of the manufactured sand particles, fundamentally isolating the subsequently added UHMWPE fibers from direct contact with the sharp edges of the sand particles. Because a slurry shell has already formed on the surface of the manufactured sand, during the mixing process, the manufactured sand particles encased in this shell form rolling slurry balls, causing the fibers to slide and disperse rapidly. This effectively prevents fiber entanglement and clumping, achieving non-destructive and uniform fiber dispersion. ECC slurry prepared by the stepwise mixing process has excellent thixotropic properties, combining self-compacting and self-leveling characteristics (filling the voids in the template or sprayed surface without vibration) with good cohesiveness (no fiber segregation or slurry bleeding during pumping). The slurry flow resistance during pumping is reduced by 30% to 40% compared to traditional processes, facilitating long-distance transportation and spraying operations. After being sprayed onto the sprayed surface, the thixotropic structure of the slurry recovers rapidly, and the "interlocking effect" between the manufactured sand particles manifests promptly. The slurry has strong adhesion, significantly improving construction efficiency and material utilization, and is suitable for engineering scenarios such as tunnel support and building reinforcement.

[0048] In one embodiment, in step S1, the forced mixer is a forced concrete mixer conforming to JG244 or a forced mortar mixer conforming to JG / T3033, ensuring the repeatability of the process and the feasibility of industrial-scale promotion. The mixing volume per batch is 1 / 4 to 3 / 4 of the nominal capacity of the forced mixer, ensuring sufficient space for the material to be thrown, fallen, and sheared, preventing material from adhering to the mixing blades and drum wall when there is insufficient material, leading to uneven mixing. This provides the necessary space margin for the material to flow, collide, and exchange within the mixing drum. Overfilling will severely reduce mixing efficiency, preventing sand particles at the edges and bottom from participating in effective shell formation; this range is a prerequisite for ensuring that all aggregate particles are uniformly coated. The forced mixer's mixing speed is 150~200 r / min, and the mixing time is 180~240 seconds. Gently and continuously knead the slurry onto the surface of the abrasive particles. Too low a speed results in insufficient shear force, preventing the slurry from effectively coating the particles and leading to clumping. Too high a speed generates excessive centrifugal and impact forces, potentially peeling away or destroying the already formed, fragile slurry shell, and even causing an unnecessary increase in material temperature. The wetting, dispersion, and adsorption of silica fume particles, as well as the hydration of HPMC to form a gel network and bind with silica fume, all require a certain amount of time. Too short a time results in an incomplete and uneven slurry shell; too long a time leads to low efficiency and may cause some slurry to begin losing water or undergoing changes in properties.

[0049] In one embodiment, in step S2, the forced mixer operates at a speed of 150-200 r / min for 300-360 seconds. Maintaining the same low speed range as in step S1 ensures that the formed lubricating buffer coating is not damaged by high-speed shearing during fiber addition and dispersion. The shear force at this speed is sufficient to cause the slurry balls to roll and disperse the fibers, but gentle enough not to cause mechanical damage to the fibers themselves. This mixing time is the necessary period to achieve sufficient and uniform monofilament dispersion of the fibers, allowing the fiber bundles to be gradually combed open, separated, and transported to all corners of the system under the rolling and lubricating action of the slurry balls, avoiding localized accumulation.

[0050] In one embodiment, in step S3, the forced mixer's mixing speed is 300-400 r / min, and the mixing time is 120-180 seconds. High-speed shear mixing ensures complete fusion of the external cementitious material slurry with the lubricating buffer coating layer on the surface of the manufactured sand, while simultaneously disrupting the excessive thixotropic structure. The resulting ECC sprayed slurry exhibits excellent thixotropy, no segregation, and good cohesion, meeting the requirements for long-distance pumping and adhesion to the sprayed surface in spraying applications. Furthermore, after the slurry is sprayed onto the sprayed surface, the thixotropic structure rapidly recovers, giving the slurry good adhesion and preventing it from flowing and detaching.

[0051] Embodiments of the present invention:

[0052] The specifications and mixing ratios for ECC material spraying per cubic meter are as follows:

[0053] 750 kg of gel material, including 550 kg of cement, using P・O 42.5 ordinary Portland cement, and 200 kg of mineral admixture, using Class II fly ash, conforming to GB / T 1596-2017 standard;

[0054] 900 kg of manufactured sand, made from crushed limestone, with a fineness modulus of 2.6 and a particle size ≤4.75 mm, of which 65% is composed of particles with a particle size of 2.36–4.75 mm and 12% is stone powder.

[0055] 15kg of UHMWPE fiber, with a volume content of approximately 1.55%, a diameter of 24μm, a length of 12mm, a tensile strength of 2800MPa, and an elastic modulus of 105GPa;

[0056] The friction-reducing shell-forming component is 30 kg, including 24 kg of silica fume with a specific surface area of ​​18000 m² / kg and an active silica content of 92%, and 6 kg of hydroxypropyl methylcellulose (HPMC) with a viscosity of 15000 mPa·s. The mass ratio of the two components is 1:0.25.

[0057] 10kg of water-reducing agent, using polycarboxylate-based high-performance water-reducing agent, with a water reduction rate of 35%;

[0058] 205 kg of water, using tap water.

[0059] The preparation method is as follows:

[0060] S1. Add 900kg of manufactured sand, 30kg of friction-reducing shell-forming component, and 70kg of water to a forced concrete mixer that meets the requirements of JG244, and mix at a low speed of 180r / min for 210 seconds to form manufactured sand particles encased in a slurry shell.

[0061] S2 and 15 kg of UHMWPE fiber were added in batches, and the mixture was stirred at a low speed of 180 r / min for 330 seconds. The fibers were observed to disperse rapidly in the mixture without clumping.

[0062] S3. Add 550kg cement, 200kg fly ash, the remaining 135kg water and 10kg water-reducing agent, and stir at 350r / min for 150 seconds to prepare a sprayed ECC slurry that inhibits fiber damage, and then discharge it.

[0063] S4. After the slurry is sprayed into shape, it is cured for 28 days according to standard.

[0064] Comparative Example 1 (using traditional process):

[0065] The raw material ratio is the same as in this embodiment.

[0066] The preparation method is as follows:

[0067] S1. Add 550kg of cement, 200kg of fly ash, 900kg of manufactured sand, and 30kg of friction-reducing shell-forming components to a forced concrete mixer that meets the requirements of JG244 and mix them evenly.

[0068] S2. Add 205kg of water and 10kg of water-reducing agent and stir into a slurry;

[0069] S3. After adding 15kg of UHMWPE fiber and stirring for 120 seconds, an ECC slurry is formed and discharged.

[0070] S4. After the slurry is sprayed and molded, it is cured for 28 days according to standard.

[0071] Comparative Example 2 (using a stepwise stirring process, adjusting the addition time of the friction-reducing shell-forming component):

[0072] The raw material ratio is the same as in Example 1.

[0073] The preparation method is as follows:

[0074] S1. Add 900 kg of manufactured sand and 70 kg of water to a forced concrete mixer that meets the requirements of JG244 and mix and pre-wet it at a low speed of 180 r / min for 210 seconds.

[0075] S2. Add 15kg of UHMWPE fiber and stir at a low speed of 180r / min for 330 seconds.

[0076] S3. Add 550kg cement, 200kg fly ash, 30kg friction-reducing shell-forming component, the remaining 135kg water and 10kg water-reducing agent, and stir at 350r / min for 150 seconds to prepare a sprayed ECC slurry that inhibits fiber damage, and discharge it.

[0077] S4. After the slurry is sprayed and molded, it is cured for 28 days according to standard.

[0078] Comparative Example 3 (Conventional ECC material spraying):

[0079] The material specifications and mix design for each cubic meter of manufactured sand concrete are as follows:

[0080] 1250 kg of gel material, including 800 kg of cement (P·O52.5 ordinary Portland cement) and 450 kg of fly ash (Class F, Grade II fly ash).

[0081] 700 kg of manufactured sand, fineness modulus 2.6, continuous particle size 0~1.88 mm, stone powder content 5%;

[0082] UHMWPE fiber 14kg, diameter 20μm, length 15mm, tensile strength 2000MPa, elastic modulus 105GPa;

[0083] 0.4 kg of water-reducing agent, using melamine water-reducing agent;

[0084] 30kg of expanding agent, using shrinkage-reducing expanding agent S-CMA;

[0085] 400 kg of water, using tap water.

[0086] The preparation method is as follows:

[0087] S1. Add 800kg of cement, 450kg of fly ash, 30kg of expansion agent and 700kg of manufactured sand to the mixer and dry mix for 2 minutes.

[0088] S2. Add 400 kg of water and 0.4 kg of water-reducing agent and mix wet for 3 minutes to form a slurry;

[0089] S3. Slowly sprinkle 14 kg of UHMWPE into the mortar being mixed within 90 seconds, continue mixing for 4 minutes to obtain freshly mixed ECC slurry, and then discharge it.

[0090] S4. After the slurry is sprayed and molded, it is cured for 28 days according to standard.

[0091] The specific performance test data is shown in the table below:

[0092]

[0093] As can be seen from the comparison of this embodiment with Comparative Example 1, Comparative Example 2, and Comparative Example 3 in the table above:

[0094] In this embodiment, the fibers are uniformly dispersed, without obvious clumps or scratches. The friction-reducing shell-forming components and shell-forming process significantly reduce frictional wear between the fibers and the manufactured sand, protecting the integrity of the fiber surface. The fiber strength retention rate of this embodiment is 92%, and the ultimate tensile strain is 3.1%, which are significantly better than those of Comparative Examples 1, 2, and 3. The shell-forming process directly ensures the high performance of the fibers, thereby improving the ductility and toughness of the material.

[0095] The slurry in this embodiment exhibits excellent thixotropic properties and good cohesiveness (no segregation), along with self-compacting and self-leveling characteristics. Pumping resistance is reduced by more than 30% compared to traditional processes, fully meeting the fluidity and pumping requirements of shotcrete construction. Simultaneously, the material has low porosity (12%) and a high impermeability grade (P12), ensuring the reliability of engineering applications. Furthermore, it has a 28-day flexural strength of 15.5 MPa and a complete compressive strength system, meeting the requirements of high-load-bearing structures.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sprayed ECC material for inhibiting fiber damage, characterized in that: Based on parts by mass, it includes the following components: 700-850 parts of cementitious material, 800-1000 parts of manufactured sand, 10-20 parts of UHMWPE fiber, 20-40 parts of friction-reducing shell-forming component, 8-12 parts of water-reducing agent, and 180-220 parts of water; The gel material is made from a mixture of cement and mineral admixtures; The friction-reducing shell-forming component is made from a mixture of silica fume and hydroxypropyl methylcellulose; The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate of ≥30%.

2. The jet-embedded ECC material for inhibiting fiber damage according to claim 1, characterized in that: The cement is ordinary Portland cement of P·O 42.5 grade or above, and the mineral admixture is fly ash and / or slag powder. The fly ash conforms to GB / T1596-2017 "Fly Ash for Cement and Concrete" Grade II or above, and the slag powder conforms to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement and Concrete" Grade S95 or above. The mass ratio of the cement to the mineral admixture is 1:(0.3~0.6).

3. The jet-embedded ECC material for inhibiting fiber damage according to claim 1, characterized in that: The manufactured sand has a fineness modulus of 2.3 to 3.0, a particle size of ≤4.75 mm, and a stone powder content of 10% to 15% with a particle size of less than 0.075 mm.

4. The jet-embedded ECC material for inhibiting fiber damage according to claim 3, characterized in that: The manufactured sand contains ≥60% particles with a particle size of 2.36~4.75mm.

5. The jet-embedded ECC material for inhibiting fiber damage according to claim 1, characterized in that: The UHMWPE fiber has a volume content of 1.0%~2.5%, a length of 8mm~12mm, a diameter of 20~50μm, a tensile strength ≥2800MPa, and an elastic modulus ≥100GPa.

6. The jet-embedded ECC material for inhibiting fiber damage according to claim 1, characterized in that: The mass ratio of silica fume to hydroxypropyl methylcellulose is 1:(0.1~0.3), wherein the specific surface area of ​​silica fume is ≥15000m² / kg and the active silica content is ≥90%, and the viscosity of hydroxypropyl methylcellulose is 10000~20000mPa・s.

7. A method for preparing a jet-embedded ECC material for inhibiting fiber damage as described in any one of claims 1-6, characterized in that: Includes the following steps: S1. Weigh the manufactured sand and friction-reducing shell-forming components into a forced mixer and add 30% to 40% water. Stir before adding the cementitious material so that the silica fume and hydroxypropyl methylcellulose in the friction-reducing shell-forming components are preferentially adsorbed on the surface of the manufactured sand particles and form a continuous lubricating buffer coating layer. S2. After the lubricating buffer coating layer is formed, keep the forced mixer running and add UHMWPE fibers evenly and continue stirring so that the UHMWPE fibers are evenly dispersed under the condition of contact with the lubricating buffer coating layer. S3. Add the weighed cementitious material, the remaining 60% to 70% of the total water volume, and the water-reducing agent to the system obtained in step S2, and stir evenly to form a sprayed ECC slurry.

8. The jet-embedded ECC material for inhibiting fiber damage and its preparation method according to claim 7, characterized in that: In step S1, the forced mixer is a forced concrete mixer conforming to JG244 or a forced mortar mixer conforming to JG / T3033. The mixing volume per batch is 1 / 4 to 3 / 4 of the nominal capacity of the forced mixer. The mixing speed of the forced mixer is 150 to 200 r / min, and the mixing time is 180 to 240 seconds.

9. The jet-embedded ECC material for inhibiting fiber damage and its preparation method according to claim 7, characterized in that: In step S2, the mixing speed of the forced mixer is 150~200 r / min, and the mixing time is 300~360 seconds.

10. The jet-embedded ECC material for inhibiting fiber damage and its preparation method according to claim 7, characterized in that: In step S3, the mixing speed of the forced mixer is 300~400 r / min, and the mixing time is 120~180 seconds.

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