Interface and fiber modified synergistic composite modified cement-based material and preparation method thereof

Abstract

The invention relates to an interface and fiber modified synergistic composite modified cement-based material and a preparation method thereof. On the basis of collaborative design of interface modification and grading processes, tin-titanium alloy sand, grass ash powder, nano molybdenum trioxide and sisal hemp / ramie fibers are used for constructing a composite system, and component dispersion and interface combination are optimized through a titanate coupling agent: the mechanical strength is innovatively improved through a three-dimensional network enhanced structure, and plant fibers cooperatively inhibit microcrack propagation through rigidity and softness; and hydrophobic modification of the nano material is combined with a pore filling mechanism to enhance impermeability and freezing resistance. Tests show that the comprehensive performance of the material is remarkably superior to that of a common cement-based material, the mechanical strength, crack resistance and durability are comprehensively improved, and drying shrinkage and freeze-thaw damage are greatly reduced. The graded mixing process ensures that the material is homogeneous and stable, and is suitable for ocean engineering, alpine regions and anti-seismic buildings. The raw materials are environment-friendly, the cost advantage is outstanding, and the requirements of green building material development are met.

Description

Technical Field

[0001] The present invention relates to the technical field of building engineering materials, and in particular to a composite modified cement-based material with synergistic interface and fiber modification and a preparation method thereof. Background Art

[0002] With the rapid development of modern infrastructure, the demand for high-performance engineering materials in areas such as roads, buildings, and water conservancy is increasing. As the most commonly used building material, cement-based composite materials have long dominated the building materials market, thanks to their readily available raw materials, mature production processes, and low costs. These materials, with cement as the main binder, are combined with sand, gravel, water, and other components to form a porous network structure. These materials combine ease of construction, fire resistance, seismic resistance, and environmental adaptability, making them widely used in various civil engineering fields and a vital material foundation supporting the development of modern society.

[0003] However, the brittle nature of traditional cement-based materials limits their performance boundaries. Limited by the porous characteristics and microcrack defects of hydration products, the materials generally have technical bottlenecks such as low tensile strength, poor deformation capacity, and low fracture energy. Under load or in an environment of alternating temperature and humidity, microcracks easily expand to form macrocracks, resulting in a decrease in structural bearing capacity and durability, significantly shortening the service life of the engineering structure. Especially in high-rise buildings, long-span bridges and extreme environment projects, the problem of brittle cracking has become a key technical problem restricting the application of cement-based materials.

[0004] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] The inventors have found that in cement-based composite materials, carbonamide is used as a hydration temperature rise inhibitor, and its dissolution and hydrolysis processes are accompanied by endothermic reactions, which can effectively absorb the heat released by cement hydration, reduce the temperature rise gradient and temperature shrinkage stress inside the concrete, and thus reduce the risk of cracking. Nano-molybdenum trioxide is used as a modifier, which has high hardness, excellent chemical stability and nanoscale effect. It can not only refine the cement hydration products through the action of crystal nucleation and improve the density of the material, but also exert the fiber reinforcement effect to improve toughness, and simultaneously solve the brittle defects of cement-based materials; its nano-particle size can also optimize the pore structure, enhance the impermeability and resistance to chemical corrosion, while improving the fluidity of the slurry and reducing water seepage.

[0006] The present application provides a composite modified cement-based material with synergistic interface and fiber modification, aiming to solve the problem of poor comprehensive performance of cement-based materials (such as low flexural strength, low compressive strength, low splitting tensile strength, poor resistance to drying shrinkage and insufficient frost resistance, etc.), so as to achieve the improvement of toughness and durability while ensuring the strength of cement-based materials.

[0007] According to one aspect of the present disclosure, a composite modified cement-based material with synergistic interface and fiber modification is provided, which is made from the following raw materials in parts by weight: 180-220 parts of tin-titanium alloy sand, 70-90 parts of cement, 15-25 parts of rice ash powder, 0.15-0.19 parts of nano-molybdenum trioxide modifier, 0.07-0.11 parts of carbonamide, 0.6-0.8 parts of modified sisal fiber, and 0.4-0.6 parts of modified ramie fiber, wherein the nano-molybdenum trioxide modifier is modified by an isopropoxy tristearate acyloxy titanate coupling agent; the modified sisal fiber and modified ramie fiber are both modified by an isopropoxy tristearate acyloxy titanate coupling agent.

[0008] In some embodiments of the present disclosure, the composite modified cement-based material is made of the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 20 parts of rice ash powder, 0.17 parts of nano-molybdenum trioxide modifier, 0.08 parts of carbonamide, 0.75 parts of modified sisal fiber, and 0.47 parts of modified ramie fiber.

[0009] In some embodiments of the present disclosure, the cement is ordinary Portland cement, and the cement model and strength grade are P.O42.5.

[0010] In some embodiments of the present disclosure, the nano molybdenum trioxide modifier is prepared by the following method: nano molybdenum trioxide, isopropoxy tristearyl titanate coupling agent and water are mixed evenly in a mass ratio of 1:0.16~0.20:0.40~0.60, soaked for 3.0~4.0h, filtered and dried at 50~60°C to obtain the modified product.

[0011] In some embodiments of the present disclosure, the modified sisal fiber is prepared by the following method: sisal fiber, isopropoxy tristearate acyloxy titanate coupling agent and water are uniformly mixed in a mass ratio of 1:0.09~0.16:0.30~0.38, soaked for 4.0~6.0 hours and then dried at 50~60°C.

[0012] In some embodiments of the present disclosure, the modified ramie fiber is prepared by the following method: ramie fiber, isopropoxy tristearate acyloxy titanate coupling agent and water are uniformly mixed in a mass ratio of 1:0.10~0.20:0.35~0.45, soaked for 5.0~7.0 hours and then dried at 50~60°C.

[0013] According to another aspect of the present disclosure, a method for preparing a composite modified cement-based material is provided, wherein after the raw materials are configured according to the above weight ratio, the following steps are performed: (1) Mix the nano-molybdenum trioxide modifier, tin-titanium alloy sand, and carbonamide evenly and stir for 2 to 3 minutes. Add cement and ash powder and continue stirring for 1 to 2 minutes. Then put the modified sisal fiber and modified ramie fiber mixture into the mixer in five batches. The stirring time for each batch is 1 to 2 minutes. Finally, add water (the amount of water added can refer to the general cement amount) and continue stirring for 3 to 5 minutes until the slurry is uniform. (2) The obtained slurry is cast and then cured in a constant temperature and humidity environment with a temperature of 20℃~24℃ and a humidity of ≥90%; demoulding is carried out after 20~25 hours, and the product is cured under the same environmental conditions until the specified age.

[0014] The technical solution of the present invention achieves a breakthrough improvement in the mechanical properties, durability and functionality of cement-based materials through innovative material system design and interface modification technology. Its core beneficial effects are as follows: 1. Synergistic Optimization of Environmental Protection and High Performance: This invention utilizes a composite system of natural plant fibers (sisal and ramie fibers) and industrial-grade raw materials (tin-titanium alloy sand, ordinary Portland cement, and ash powder (fly ash replacement)), ensuring a broad range of raw materials, non-toxic and environmentally friendly. Through scientific proportioning and a step-by-step dry-mixing process, the resulting cement-based material achieves both low cost and high performance. ①Excellent mechanical properties: flexural strength, compressive strength and splitting tensile strength are significantly better than traditional cement-based materials; ②Outstanding durability: Anti-drying shrinkage is reduced, and the ability to resist freeze-thaw cycles is increased by more than 20%, effectively extending the service life of the building structure; ③Green and low-carbon: The whole process is pollution-free and suitable for industrial production, reducing the overall cost by 10%-20%.

[0015] 2. Coupling agent interface modification to enhance multi-dimensional performance: Surface pretreatment of nano-molybdenum trioxide, sisal fiber, and ramie fiber using isopropoxy tristearate acyloxy titanate coupling agent achieves multi-scale interface enhancement and performance optimization: ① Improved interfacial bonding strength: The coupling agent significantly enhances the bonding strength between nano-molybdenum trioxide, fiber and cement matrix through chemical bonding and physical anchoring, and the interfacial bonding strength is increased by 20%~40%; ② Optimization of dispersibility and stability: Reduce the water absorption rate of nano-molybdenum trioxide and fiber (≤5%), improve its dimensional stability and corrosion resistance, increase surface roughness, and enhance the mechanical bite force with the matrix; ③ Improved processing performance: The modified fibers and nanomaterials are easier to disperse evenly in the matrix, improving the fluidity and molding plasticity of the slurry and reducing process defects.

[0016] 3. Synergistic effect of plant fiber composite system: The composite compatibility of sisal fiber and ramie fiber produces a unique synergistic effect: ① High-strength skeleton construction: Sisal fibers (modulus ≥ 25 GPa) form a rigid support network, maintaining tensile strength stability under extreme temperature and humidity conditions, and increasing ultimate flexural strength by 10%-25%; ② Toughness and functional enhancement: Ramie fiber (elongation ≥3.5%) alleviates interfacial stress concentration through its moisture absorption and humidity regulation properties, improving impact toughness by more than 30% and giving the material excellent fatigue resistance and seismic energy dissipation properties; ③ Enhanced durability: The fiber composite system inhibits the expansion of microcracks, reduces shrinkage and freeze-thaw damage risks, and improves long-term service performance.

[0017] 4. A graded mixing process ensures material homogeneity and performance stability: Using a "dry mix-step addition" process (pre-mixing modified nano-molybdenum trioxide / fiber / sand → dry mixing of cementitious materials / grain ash powder / carbonamide → adding water and stirring), this ensures performance advantages through the following mechanisms: ① Uniform dispersion: Avoid nano-molybdenum trioxide agglomeration and fiber clumping during the premixing stage to ensure uniform distribution of the modifier and fiber; ② Reaction controllability: Step-by-step feeding delays the hydration reaction rate, reduces early shrinkage cracks, and improves the slurry density; ③ Process adaptability: The process is simple and efficient, compatible with existing production equipment, and significantly reduces the cost of process modification.

[0018] 5. Synergistic reinforcement of tin-titanium alloy sand and nano-molybdenum trioxide: Tin-titanium alloy sand as the core aggregate forms a complementary strengthening mechanism with nano-molybdenum trioxide: ① Microstructure densification: Nano-molybdenum trioxide fills the pores between aggregates, and the high hardness of tin-titanium alloy sand (Mohs hardness ≥7) improves the compressive strength of the matrix; ② Enhanced corrosion resistance: Nano-molybdenum trioxide and tin-titanium alloy sand jointly inhibit chloride ion penetration and chemical erosion, and the material's salt spray corrosion resistance is improved by more than 20%.

[0019] In summary, the present invention achieves a comprehensive improvement in the mechanical properties, durability and processing adaptability of cement-based materials through innovative interface modification technology, synergistic compatibility of plant fibers and graded process design, while taking into account both environmental protection and economic requirements. It has important application value in marine engineering, infrastructure in high-altitude cold regions and earthquake-resistant buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a test process diagram of the composite modified cement-based material in one embodiment of the present application, wherein a is a flexural test, b is a compressive test, c is a splitting test, d is a shrinkage test, and e is a freeze-thaw test. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described below in conjunction with examples. However, the following examples are only used to illustrate the present invention in detail and are not intended to limit the scope of the present invention in any way.

[0022] Unless otherwise specified, the instruments and equipment involved in the following examples are all conventional instruments and equipment; the preparation methods involved are all conventional methods unless otherwise specified.

[0023] The preparation method of the composite modified cement-based material in the following examples comprises the following steps: (1) Raw material configuration: 200 parts of tin-titanium alloy sand (Tongling City Fusulphur Mineral Products Industry and Trade Co., Ltd., 0.5mm-3mm), 80 parts of cement (Henan Tianrui Group Cement Co., Ltd., ordinary Portland cement, P.O42.5), 20 parts of ash powder (Hebei Lingshou County Yuxin New Materials Co., Ltd.), 0.1 parts of nano-molybdenum trioxide (Shanghai MacLean Biological Reagent Co., Ltd., model number Cas No.: 1313275, purity 99.9%, density 4.692 g / mL). 5~0.19 parts, carbonamide (Sweier Experimental Reagent Enterprise Store, grade is analytical pure AR grade, model is 500g) 0.07~0.10 parts, sisal fiber (Nanning Naizhelu Fiber Products Co., Ltd., fiber length 5mm) 0.6~0.8 parts, ramie fiber (Nantong Yemeng New Materials Co., Ltd., fiber length 6mm) 0.4~0.6 parts, isopropoxy tristearate acyloxy titanate coupling agent (Nanjing Herun Coupling Agent Co., Ltd.) 0.05~0.11 parts.

[0024] (2) Preparation of nano-molybdenum trioxide modifier: Prepare the raw materials according to the above weight ratio: mix nano-molybdenum trioxide, isopropoxy tristearate acyloxy titanate coupling agent and water in a mass ratio of 1:0.18:0.50, soak for 3.5 hours, filter and dry at 60°C.

[0025] (3) Preparation of modified sisal fiber: Mix sisal fiber, isopropyl tristearate acyloxy titanate coupling agent and water in a mass ratio of 1:0.12:0.35, soak for 5 hours and then dry at 60°C to obtain the fiber.

[0026] (4) Modified ramie fiber: Mix ramie fiber, isopropyl tristearate titanate coupling agent and water in a mass ratio of 1:0.15:0.40, soak for 6.0 hours and then dry at 60°C.

[0027] (5) Use a cement slurry mixer to stir the nano-molybdenum trioxide modifier, tin-titanium alloy sand, and carbonamide for about 3 minutes. While maintaining the stirring of the equipment, add cement and ash powder and stir for 2 minutes. Secondly, put the modified sisal fiber and modified ramie fiber into the mixer in five batches. The stirring time of each batch is 2 minutes. Finally, add water into the mixer and continue stirring for 4 minutes to obtain a uniform cement slurry. Pour the slurry into the oil-coated mold and cure it under standard conditions of 24°C and relative humidity ≥90%. After 24 hours, demold it and continue to cure it in a constant temperature and humidity curing box at 24°C and relative humidity ≥90% to the specified age.

[0028] Example 1: A composite modified cement-based material is made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 16 parts of rice ash powder, 0.15 parts of nano-molybdenum trioxide modifier, 0.07 parts of carbonamide, 0.63 parts of modified sisal fiber, and 0.44 parts of modified ramie fiber.

[0029] Example 2: A composite modified cement-based material is made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 18 parts of rice ash powder, 0.16 parts of nano-molybdenum trioxide modifier, 0.08 parts of carbonamide, 0.66 parts of modified sisal fiber, and 0.47 parts of modified ramie fiber.

[0030] Example 3: A composite modified cement-based material, made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 20 parts of rice ash powder, 0.17 parts of nano-molybdenum trioxide modifier, 0.09 parts of carbonamide, 0.69 parts of modified sisal fiber, and 0.50 parts of modified ramie fiber.

[0031] Example 4: A composite modified cement-based material, made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 22 parts of rice ash powder, 0.18 parts of nano-molybdenum trioxide modifier, 0.10 parts of carbonamide, 0.72 parts of modified sisal fiber, and 0.53 parts of modified ramie fiber.

[0032] Example 5: A composite modified cement-based material, made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 24 parts of rice ash powder, 0.19 parts of nano-molybdenum trioxide modifier, 0.11 parts of carbonamide, 0.75 parts of modified sisal fiber, and 0.56 parts of modified ramie fiber.

[0033] The composite modified cement-based materials in the above examples were subjected to mechanical and durability tests, including flexural strength test, compressive strength test, splitting tensile strength test, drying shrinkage test and freeze-thaw cycle test (see Figure 1 ), used to test the performance of the composite modified cement-based material of the present invention, and compared and analyzed it with ordinary cement-based materials. The test results are shown in Table 1.

[0034] Table 1 Test data of composite modified cement-based materials .

[0035] The mechanical properties and durability test data of the composite modified cement-based materials in the examples (Table 1) show that the materials of the present invention are significantly superior to ordinary cement-based materials in key performance indicators and meet the requirements of national standards such as GB / T 17671-1999, TC / T603-2004 and JGJ / T 70-2009. The specific technical effects are described as follows: 1. Comprehensive improvement in mechanical properties Optimization of flexural strength: The flexural strength of Example 4 reached 10.9 MPa, which was 16% higher than that of the ordinary material (9.4 MPa), indicating that the modified fiber and nano-molybdenum trioxide synergistically effectively enhanced the bending resistance of the matrix; Enhanced compressive strength: The compressive strength of Example 3 reaches 55.9 MPa, which is 10.7% higher than that of ordinary materials (50.5 MPa), reflecting the improvement of the matrix density by tin-titanium alloy sand and nanomaterials; Breakthrough in splitting tensile performance: The splitting tensile strength of Example 4 reached 3.46 MPa, which was 21.8% higher than that of ordinary materials (2.84 MPa), reflecting that the interfacial bonding force between the fiber and the matrix was significantly enhanced after modification with the coupling agent.

[0036] Technical attribution: Isopropoxy tristearate titanate coupling agent improves the dispersibility and surface roughness of nano-molybdenum trioxide and plant fibers, enhances their mechanical bite and chemical bonding with the matrix, thereby forming a high-strength three-dimensional network structure.

[0037] 2. Significantly improved anti-drying shrinkage performance Long-term shrinkage inhibition: The shrinkage rate of Example 4 after 90 days is only 755×10 -6 , compared with ordinary materials (836×10 -6 ) decreased by 9.7%, indicating that the moisture absorption and humidity control function of the modified plant fiber and the micropore filling effect of nano-molybdenum trioxide effectively alleviated the shrinkage stress; Synergistic anti-cracking mechanism: The high modulus skeleton of sisal fiber and the flexible hygroscopic expansion of ramie fiber synergistically inhibit the propagation of microcracks. The shrinkage rate of Examples 3 and 4 decreased by 8.4% to 9.7%, verifying the optimization effect of the interface transition zone structure.

[0038] 3. Enhanced resistance to freeze-thaw cycles Improved durability: After 100 freeze-thaw cycles, the mass loss rate of Example 4 was only 4.48%, which was 16.9% lower than that of the conventional material (5.39%). This proves that the hydrophobic modification of nano-molybdenum trioxide and the densification effect of tin-titanium alloy sand jointly inhibited water penetration and ice crystal damage. Antifreeze mechanism: The coupling agent reduces the water absorption rate of the fiber (≤5%), and nano-molybdenum trioxide fills the pores and blocks the capillary channels, significantly improving the volume stability of the material under extreme temperatures.

[0039] 4. Comprehensive performance benchmarking and advantage analysis (see Table 2) Table 2 Comprehensive performance comparison .

[0040] From the above, it can be seen that Example 4 performs best in flexural strength, splitting tensile strength and freeze-thaw resistance, reflecting the golden ratio advantage of high-content sisal fiber (rigid support) and ramie fiber (flexible moisture absorption); Example 3 has outstanding compressive strength, which is attributed to the optimized proportion of tin-titanium alloy sand and the pore-filling effect of nano-molybdenum trioxide; the shrinkage rate and freeze-thaw loss rate of all examples are lower than those of ordinary materials, verifying that the long-term durability improvement of the present invention is universal.

[0041] The material of the present invention achieves performance stability through a graded mixing process, and the test data has low discreteness (for example, the standard deviation of the flexural strength of Examples 1-5 is ≤0.6 MPa), indicating that the process is highly controllable and can meet the stringent requirements for material homogeneity in road paving, marine engineering, and construction in high-altitude and cold regions.

[0042] In summary, the present invention achieves multi-dimensional breakthroughs in mechanical properties, crack resistance and durability through material modification innovation and process collaborative design, providing a reliable technical solution for the engineering application of green and high-performance cement-based materials.

[0043] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, those skilled in the art will appreciate that, without departing from the inventive concept, the specific parameters in the above embodiments may be changed, or the relevant components, structures, and materials may be equivalently replaced, thereby forming multiple specific embodiments, which are all within the common variation scope of the present invention and will not be described in detail here.

Claims

1. A composite modified cement-based material with synergistic interface and fiber modification, characterized in that: Made from the following raw materials in parts by weight: 180-220 parts of tin-titanium alloy sand, 70-90 parts of cement, 15-25 parts of rice ash powder, 0.15-0.19 parts of nano-molybdenum trioxide modifier, 0.07-0.11 parts of carbonamide, 0.6-0.8 parts of modified sisal fiber, and 0.4-0.6 parts of modified ramie fiber; The nano molybdenum trioxide modifier is obtained by modifying an isopropoxy tristearate acyloxy titanate coupling agent; and the modified sisal fiber and the modified ramie fiber are both obtained by modifying an isopropoxy tristearate acyloxy titanate coupling agent.

2. The composite modified cement-based material according to claim 1, characterized in that: Made from the following raw materials in parts by weight: 200 parts of tin-titanium alloy sand, 80 parts of cement, 20 parts of rice ash powder, 0.17 parts of nano-molybdenum trioxide modifier, 0.08 parts of carbonamide, 0.75 parts of modified sisal fiber, and 0.47 parts of modified ramie fiber.

3. The composite modified cement-based material according to claim 1, characterized in that: The cement is ordinary Portland cement, and the cement model and strength grade are P.O42.

5.

4. The composite modified cement-based material according to claim 1, characterized in that: The nano molybdenum trioxide modifier is prepared by the following method: nano molybdenum trioxide, isopropoxy tristearyloxy titanate coupling agent and water are uniformly mixed in a mass ratio of 1:0.16-0.20:0.40-0.60, soaked for 3.0-4.0 hours, filtered and dried at 50-60°C to obtain the modified nano molybdenum trioxide modifier.

5. The composite modified cement-based material according to claim 1, characterized in that: The modified sisal fiber is prepared by the following method: sisal fiber, isopropyl tristearate acyloxy titanate coupling agent and water are uniformly mixed in a mass ratio of 1:0.09-0.16:0.30-0.38, soaked for 4.0-6.0 hours and then dried at 50-60°C to obtain the modified sisal fiber.

6. The composite modified cement-based material according to claim 1, characterized in that: The modified ramie fiber is prepared by the following method: ramie fiber, isopropyl tristearate acyloxy titanate coupling agent and water are uniformly mixed in a mass ratio of 1:0.10-0.20:0.35-0.45, soaked for 5.0-7.0 hours and then dried at 50-60°C.

7. A method for preparing a composite modified cement-based material, characterized in that: The following steps are involved: (1) Prepare the raw materials according to the weight ratio of the raw materials in claim 1; (2) Mix the nano-molybdenum trioxide modifier, tin-titanium alloy sand, and carbonamide evenly and stir for 2 to 3 minutes. Add cement and ash powder and continue stirring for 1 to 2 minutes. Then, add the modified sisal fiber and modified ramie fiber mixture into the mixer in 3 to 6 batches. The stirring time for each batch is 1 to 2 minutes. Finally, add water and continue stirring for 3 to 5 minutes until the slurry is uniform. (3) The obtained slurry is cast and then cured in a constant temperature and humidity environment with a temperature of 20℃~24℃ and a humidity of ≥90%; demoulding is carried out after 20~25 hours, and the product is cured under the same environmental conditions until the specified age.

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