A composite cement-based material and its application in the reinforcement of concrete structures

Abstract

This invention relates to a composite cement-based material and its application in the reinforcement of concrete structures, comprising the following raw materials: cement, carbon dioxide, silica fume, slag, fine aggregate, quartz powder, water-reducing agent, and water. By adding appropriate amounts of crack-resistant fibers, silica fume, carbon dioxide, and a high-efficiency water-reducing agent to cement, this invention produces a composite cement-based material with high packing density, extremely low porosity, higher reinforcement layer strength, and durability, ductility, and strength properties far exceeding those of ordinary concrete materials. It does not contain large-diameter coarse aggregate blocks, making construction easier and exhibiting stronger flowability and plasticity. Especially in the repair of concrete structures in highly corrosive environments, the composite cement-based material combined with glass fiber materials can completely replace steel reinforcement. This not only prevents steel reinforcement from corroding and causing damage to the reinforcement layer in highly acidic environments but also improves the alkali resistance of the reinforcement layer and reduces project costs.

Description

Technical Field

[0001] This invention relates to the field of building structure reinforcement technology, specifically to a composite cement-based material and its application in the reinforcement of concrete structures. Background Technology

[0002] In concrete structures, the strength of concrete increases with age. Under normal conditions, the reinforcing steel is protected by concrete, resulting in minimal corrosion. Therefore, as long as the protective layer thickness is appropriate, the durability of the concrete structure is relatively good. With industrial development and continuous technological reforms, it is often necessary to modify and reinforce existing concrete components. Alternatively, due to aging, damage, or corrosion, the structural components themselves need to be reinforced to directly improve their resistance and stiffness. Concrete beams are the most basic load-bearing components in building structures; their failure can cause significant casualties and severe economic losses. Therefore, the reinforcement of concrete beams is particularly important, especially in corrosive environments (such as highly acidic environments), where the surface concrete is eroded much faster than in ordinary environments. For example, in paper mills, acidic gases (mainly oxalic acid) are produced during production. These gases react with water to form a strong acid. When the pH of the concrete slab becomes acidic, the reinforcing steel in the concrete begins to corrode. The lower the pH value, the faster the steel corrodes. Therefore, highly acidic environments can rapidly corrode the surface concrete, significantly reducing the service life of the structure. Therefore, most concrete structures in acidic environments are covered with a protective layer of acid-resistant concrete or acid-resistant mortar to protect the main structure from acid corrosion.

[0003] Existing acid-resistant concrete mainly involves adding acid-resistant materials to ordinary concrete to improve its acid resistance. Depending on the added acid-resistant materials, acid-resistant concrete can be classified into water glass acid-resistant concrete, resin-based acid-resistant concrete, asphalt acid-resistant concrete, sulfur acid-resistant concrete, and high-alumina cement acid-resistant concrete, among others. Water glass acid-resistant concrete is widely used in engineering projects, but it also has certain limitations. For example, while sodium water glass acid-resistant concrete has a wide availability and low cost, it is highly viscous and has low fluidity, making its construction process complex. It also has poor impermeability and water resistance and is highly toxic. Potassium water glass acid-resistant concrete has fewer construction steps and a simpler construction process, allowing for more precise control of construction quality. However, the added acid-resistant materials (potassium silicate, condensed aluminum phosphate, etc.) are difficult to obtain, resulting in a higher price and significantly increasing the overall cost of the reinforcement project. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention aims to provide a composite cement-based material. By adding appropriate amounts of crack-resistant fibers, silica fume, carbon ash and high-efficiency water-reducing agents to cement, the resulting composite cement-based material has high packing density, extremely low porosity, higher reinforcement layer strength, and durability, ductility and strength properties far exceeding those of ordinary concrete materials. It does not contain large-diameter coarse aggregate blocks, is easy to construct, and has stronger flowability and plasticity.

[0005] The purpose of this invention is to provide a method for preparing composite cement-based materials. The preparation method is simple to operate, easy to control, has high production efficiency, low production cost, and the resulting composite cement-based materials have excellent comprehensive performance.

[0006] The purpose of this invention is to provide an application of composite cement-based materials in the reinforcement of concrete structures. This material can be used to repair concrete structures in ordinary environments, as well as in highly corrosive environments. It can completely replace steel reinforcement with composite cement-based materials combined with glass fiber or carbon fiber materials. This avoids damage to the reinforcement layer caused by steel corrosion in highly acidic environments, improves the alkali resistance of the reinforcement layer, and reduces project costs. When it is necessary to increase the strength of the concrete structure, steel fibers can be used to increase the strength of the composite cement-based material layer. When it is necessary to increase the high-temperature resistance of the concrete structure, carbon fiber can be used to increase the high-temperature resistance of the composite cement-based material layer.

[0007] The objective of this invention is achieved through the following technical solution: a composite cement-based material comprising the following raw materials in parts by weight: 70-90 parts cement, 2-6 parts carbon ash, 6-10 parts silica fume, 2-6 parts slag, 10-20 parts fine aggregate, 80-120 parts quartz powder, 2-6 parts water-reducing agent, and 50-80 parts water; wherein the silica fume contains ≥95% active SiO2.

[0008] Preferably, the composite cement-based material comprises the following raw materials in parts by weight: 70-90 parts cement, 2-6 parts carbon ash, 6-10 parts silica fume, 2-6 parts slag, 10-20 parts fine aggregate, 80-120 parts quartz powder, 70-90 parts crack-resistant fiber, 2-6 parts water-reducing agent, and 50-80 parts water; wherein the silica fume contains ≥95% active SiO2. Preferably, the crack-resistant fiber is composed of stainless steel fiber or carbon fiber and PP, PE or PVA fiber in a weight ratio of 6-8:3-6.

[0009] The composite cement-based material of this invention, obtained by adding appropriate amounts of crack-resistant fibers, silica fume, carbon ash and high-efficiency water-reducing agent to cement, has high packing density, extremely low porosity, higher reinforcement layer strength (up to 150~230MPa), and durability, ductility and strength properties far exceeding those of ordinary concrete materials. It does not contain large-diameter coarse aggregate blocks, making construction more convenient and with stronger flowability and plasticity. In terms of acid and alkali resistance, thanks to its low porosity and density, its impermeability is more than three times that of ordinary concrete, making it more difficult for water and gas to penetrate its interior. Acid and alkali ions also have great difficulty penetrating, thus exhibiting excellent durability. In terms of strength and toughness, composite cement-based materials not only have compressive strength more than five times and flexural strength more than ten times that of ordinary concrete, but also fracture toughness more than 200 times that of ordinary concrete. They are not prone to cracking and can effectively absorb seismic energy, improving the seismic performance of the structure. In terms of construction, it mainly uses carbon ash, silica fume, slag, and fine aggregates as raw materials, without large-particle aggregates such as stones. It has excellent plasticity, is easy to mix, and the production process is more environmentally friendly, effectively reducing the pollution of the environment by construction waste. By replacing the cementitious materials in traditional UHPC with a large amount of inert materials (such as carbon ash and silica fume), and by adding quartz powder and fine aggregate with a certain gradation to replace the original coarse aggregate, the internal porosity is reduced, resulting in excellent mechanical and durability properties of the material. At the same time, an appropriate amount of water-reducing agent is added to reduce the shrinkage of the composite cementitious material without affecting the later strength development. Crack-resistant fibers can be quickly and uniformly dispersed to form a multi-directional support system and help disperse the directional stress inside the concrete. Stainless steel fibers or carbon fibers have a synergistic effect with PP, PE or PVA fibers, which can effectively prevent or inhibit cracks caused by concrete volume shrinkage during hydration, which is conducive to quickly eliminating or reducing the generation of cracks, thereby improving the toughness of concrete.

[0010] Preferably, the cement is silicate cement, and the silicate cement has a strength grade of 525.

[0011] Preferably, the quartz powder contains four particle sizes: fine particles with a diameter of 310-330 mesh, medium particles with a diameter of 70-110 mesh, medium particles with a diameter of 40-70 mesh, and coarse particles with a diameter of 26-40 mesh, and the weights are blended in a ratio of 0.5-0.7:2-4:5-7:2-3.

[0012] Preferably, the crack-resistant fiber is composed of stainless steel fiber and PP, PE or PVA fiber in a weight ratio of 6-8:3-6.

[0013] Preferably, the water-reducing agent comprises the following raw materials in parts by weight: 20-30 parts sodium aminobenzenesulfonate, 10-15 parts alkali lignin, 1-3 parts functionalized graphene, 1-3 parts polyvinylpyrrolidone, 2-6 parts p-nitrostyrene, 5-10 parts sodium β-naphthalenesulfonate, 4-8 parts iron powder, 1-3 parts ethanol, and 1-5 parts modifier; wherein the modifier is sodium carbonate.

[0014] Preferably, the water-reducing agent is prepared by the following method: S1. According to the weight parts, mix sodium aminobenzenesulfonate, alkali lignin and functionalized graphene, heat to 40-60℃ and stir for 30-60 minutes to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50-70℃ for 1-3 hours. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70-80℃ for 30-60 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, and stir continuously at a rate of 150-250 r / min for 40-60 min at 50-70℃. Cool to room temperature to obtain the water-reducing agent.

[0015] The water-reducing agent in this invention is prepared using the above-mentioned raw materials and preparation method. The water-reducing agent prepared by the above method has good compatibility and enhances the strength and hardness of concrete during use. It also has good effects on the corrosion resistance of concrete, improving the water reduction rate and extending the service life of engineering structures. The production materials are simple and readily available, and the process is simple and feasible. p-Nitrostyrene is reduced with iron powder, converting the nitro group at the para-position of the benzene ring to an amino group, thus producing p-aminostyrene. This p-aminostyrene is then mixed with polyvinylpyrrolidone to prepare an additive. This additive enhances the toughness of concrete and improves its structure, reducing total porosity and capillary size, thereby increasing the concrete's impermeability and preventing cracking. The active functional groups on the surface of functionalized graphene catalyze the reaction between functionalized graphene and alkali lignin, allowing for efficient binding of functionalized graphene to alkali lignin. This effectively prevents the aggregation of functionalized graphene, improving its dispersibility in water-reducing agent systems. Furthermore, the introduction of this additive into the water-reducing agent, along with the functionalized graphene-modified alkali lignin... It can play a synergistic role, with a high water reduction rate, which can significantly improve the compatibility between the water-reducing agent and the concrete substrate, thereby improving the temperature adaptability of the final concrete material system, significantly reducing concrete shrinkage and minimizing slump loss. At the same time, alkali lignin molecules have a three-dimensional network structure and contain a large number of phenolic hydroxyl groups. Through the Mannich reaction, the alkali lignin is used to modify sodium p-aminobenzenesulfonate, which improves the main chain length and structural stability of the water-reducing agent. It is not easy to shrink in the cement pore solution. Meanwhile, the surface of cement particles carries the same charge due to the directional adsorption of modified water-reducing agent molecules. The repulsive force generated between them will disperse and disintegrate the flocculated structure of cement particles, enhance the dispersibility of cement, release water, and increase the fluidity of cement paste.

[0016] This invention also provides a method for preparing a composite cement-based material, comprising the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8-16 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0017] This invention also proposes the application of a composite cement-based material in the reinforcement of concrete structures for the repair of concrete structures.

[0018] Preferably, the reinforcement structure for repairing concrete beams and slabs includes: a main structural wall, the original floor slab, the original beams, formwork, an upper repair layer, a lower repair layer, a beam reinforcement material layer, and several reinforcing components. The main structural wall is located on both sides of the original floor slab, the original beams are located on the lower end face of the original floor slab, the formwork is fixed to the lower end face of the original floor slab and the outer surface of the original beams, and a gap is left between the formwork and the lower end face of the original floor slab and the outer surface of the original beams. The upper repair layer is poured on the upper surface of the original floor slab, the lower repair layer is poured between the lower surface of the original floor slab and the formwork, the beam reinforcement material layer is poured between the formwork and the outer surface of the original beam, and the reinforcing members are evenly embedded in the upper repair layer, the lower repair layer and the beam reinforcement material layer; the original floor slab has a circular through hole penetrating the upper and lower surfaces of the original floor slab, and the lower end of the circular through hole is connected to the gap between the formwork, the lower surface of the original floor slab and the outer surface of the original beam.

[0019] The reinforcing member is made of glass fiber or steel bar; the thickness of the upper repair layer, the lower repair layer, and the beam reinforcement material layer is 3~5cm; the reinforcing member in the upper repair layer is parallel to the original floor slab, and the reinforcing member in the lower repair layer is perpendicular to the reinforcing member in the beam reinforcement material layer.

[0020] The reinforcement method for concrete beams and slabs in corrosive environments includes the following steps: 1) Scrape off the corroded surface concrete in the original floor slabs and beams, remove the rusted steel bars, and roughen the surface. 2) Drill a small number of circular through holes at regular intervals in the floor slab, away from the reinforcing mesh; 3) Mark the lines for positioning and overlap the reinforcing material with the beam reinforcement material; 4) Support the formwork according to the thickness of the repair layer; 5) The composite cement-based material is poured from the top of the floor slab. Due to its excellent fluidity, the composite cement-based material will flow into the formwork below the floor slab through the through holes, gradually filling the lower repair layer of the floor slab. After filling the lower repair layer of the floor slab and compacting it, the composite cement-based material will continue to fill the upper repair layer of the floor slab until the pouring is completed.

[0021] In this invention, the aforementioned reinforcement structure, based on the ultra-high packing density and ultra-low porosity of the composite cement-based material, exhibits excellent corrosion resistance. The strength of the repair layer generally reaches C80 or higher, far exceeding that of existing acid-resistant concrete. Furthermore, the composite cement-based material possesses excellent flowability, plasticity, and toughness, making the reinforcement layer construction more convenient and less prone to cracking after curing. During the repair of concrete beams and slabs, circular through-holes are drilled vertically through the floor slab, avoiding the reinforcing steel bars. Utilizing the excellent flowability of the composite cement-based material, the repair layers on both the upper and lower surfaces of the beams and floor slabs can be poured in one go. During repair, formwork is supported on the bottom surface of the original floor slab and beams, but not on the top surface. With this structure, the composite cement-based material is poured from the top of the floor slab downwards through the circular through-holes, flowing into the formwork at the bottom of the original floor slab and beams. When the repair layer of the lower part of the floor slab and beams is completed... When the concrete is fully poured, the composite cement-based material will continue to cover the upper repair layer of the original floor slab, achieving a one-time integral pour. This saves construction time and improves the integrity of the repair layers on both sides of the beam and floor slab. During the repair process, depending on the actual situation, in a weakly corrosive environment, steel bars can still be used as floor slab and beam reinforcements in the repair layer, effectively ensuring that the internal steel bars are not corroded during their service life. In a strongly corrosive environment, the steel bars can be replaced with glass fiber to further reduce the impact of corrosion. Based on the excellent tensile strength, corrosion resistance, light weight, and low price of glass fiber, it can be used as a reinforcement material for the repair layer to replace additional stirrups, web bars, bottom bars, etc., which can reduce the self-weight of the structure and reduce the repair cost. At the same time, the glass fiber can be prefabricated into a mesh and then overlapped on site, saving a lot of time on steel bar binding and improving construction efficiency.

[0022] Preferably, the reinforcement structure for repairing a concrete column includes the original concrete column, external longitudinal reinforcement, external dowel bars, external stirrups, a composite cement-based material layer, and a formwork. One end of the external dowel bars is inserted into the original concrete column. The external stirrups are fixed to the outside of the original concrete column by the external dowel bars. The external longitudinal reinforcement is evenly distributed around the periphery of the original concrete column along its extension direction. The formwork is fixed to the outside of the external stirrups, and a gap is left between the formwork and the original concrete column. The composite cement-based material layer is poured into the gap between the formwork and the original concrete column.

[0023] The reinforcement methods for concrete columns include the following steps: 1) Scrape off the corroded surface concrete in the original concrete column, remove the rusted steel bars, and roughen its surface. 2) Install reinforcing bars around the original concrete column, insert reinforcing bars outside the column, and tie the longitudinal bars and stirrups outside the column; 3) Support the formwork, wet the surface, and treat the concrete interface according to the thickness of the repair layer; 4) The composite cement-based material is poured from the top of the original concrete column. Due to its excellent fluidity, the composite cement-based material will flow into the gap between the formwork and the original concrete column. After being vibrated and compacted, a layer of composite cement-based material is formed until the pouring is completed.

[0024] The beneficial effects of this invention are as follows: By adding appropriate amounts of crack-resistant fibers, silica fume, carbon ash, and high-efficiency water-reducing agents to cement, the composite cement-based material obtained by this invention has high packing density, extremely low porosity, higher reinforcement layer strength, and durability, ductility, and strength properties far exceeding those of ordinary concrete materials. It does not contain large-diameter coarse aggregate blocks, making construction more convenient and exhibiting stronger flowability and plasticity. Furthermore, the method for preparing the composite cement-based material is simple to operate, easy to control, has high production efficiency, and low production cost, resulting in a composite cement-based material with excellent comprehensive performance.

[0025] This invention relates to the application of a composite cement-based material in the reinforcement of concrete structures. In the repair of concrete structures in highly corrosive environments, the composite cement-based material combined with glass fiber material can completely replace steel bars. This not only avoids damage to the reinforcement layer caused by steel bar corrosion in highly acidic environments, but also improves the alkali resistance of the reinforcement layer and reduces project costs. Attached Figure Description

[0026] Figure 1 This is a front sectional view of the repair structure of concrete beams and slabs in a corrosive environment according to the present invention; Figure 2 This is a top view of the repair structure of concrete beams and slabs in a corrosive environment according to the present invention; Figure 3 This is a cross-sectional view of the concrete column structure repaired by this invention; Figure 4 This is a top view of the concrete column structure repaired by the present invention; Figure 5 Test diagram of pull-out resistance test of new and old concrete in concrete structure repaired using the composite cement-based material of this invention.

[0027] The attached diagram is labeled as follows: 1-Main structural wall, 2-Circular through hole, 3-Existing floor slab, 4-Upper repair layer, 5-Existing beam, 6-Lower repair layer, 7-Reinforcing member, 8-Beam reinforcement material layer, 9-Formwork, 10-Existing concrete column, 11-Column external longitudinal reinforcement, 12-Column external dowel bar, 13-Column external stirrup, and 14-Composite cement-based material layer. Detailed Implementation

[0028] To facilitate understanding by those skilled in the art, the following description is provided in conjunction with embodiments and appendices. Figure 1-5 The present invention will be further described below, and the content mentioned in the embodiments is not intended to limit the present invention.

[0029] Example 1 See Figure 1-2 A reinforcement structure for repairing concrete beams and slabs under corrosive conditions includes a main structural wall 1, an existing floor slab 3, an existing beam 5, a formwork 9, an upper repair layer 4, a lower repair layer 6, a beam reinforcement material layer 8, and several reinforcing members 7. The main structural wall 1 is located on both sides of the existing floor slab 3, and the existing beam 5 is located on the lower end face of the existing floor slab 3. The formwork 9 is fixed to the lower end face of the existing floor slab 3 and the outer surface of the existing beam 5, with a gap between the formwork 9 and the lower end face of the existing floor slab 3 and the outer surface of the existing beam 5. The upper repair layer 4 is poured onto the upper end face of the existing floor slab 3. The lower repair layer 6 is poured between the lower end face of the original floor slab 3 and the formwork 9. The beam reinforcement material layer 8 is poured between the formwork 9 and the outer surface of the original beam 5. The reinforcing member 7 is evenly embedded in the upper repair layer 4, the lower repair layer 6 and the beam reinforcement material layer 8. The original floor slab 3 has a circular through hole 2 that penetrates the upper and lower end faces of the original floor slab 3. The lower end of the circular through hole 2 is connected to the gap between the formwork 9, the lower end face of the original floor slab 3 and the outer surface of the original beam 5. The upper repair layer 4, the lower repair layer 6 and the beam reinforcement material layer 8 are all made of composite cement-based material.

[0030] The reinforcing member 7 is made of glass fiber or steel bar; the thickness of the upper repair layer 4, the lower repair layer 6, and the beam reinforcement material layer 8 is 3~5cm. The reinforcing member 7 in the upper repair layer 4 is parallel to the original floor slab 3, and the reinforcing member 7 in the lower repair layer 6 is perpendicular to the reinforcing member 7 in the beam reinforcement material layer 8.

[0031] The method for strengthening concrete beams and slabs under corrosive environments includes the following steps: 1) Scrape off the corroded surface concrete in the original floor slab 3 and original beam 5, remove the rusted steel bars, and roughen the surface. 2) Drill a small number of circular through holes at regular intervals in the floor slab, away from the steel mesh; 3) Mark the lines to position and overlap the reinforcing material 7 with the beam reinforcement material; 4) Support the formwork according to the thickness of the repair layer; 5) The composite cement-based material is poured from the top of the floor slab. Due to its excellent fluidity, the composite cement-based material will flow into the formwork 9 below the floor slab through the through hole, gradually filling the lower repair layer 6 of the floor slab. After filling the lower repair layer 6 of the floor slab and compacting it, the composite cement-based material will continue to fill the upper repair layer 4 of the floor slab until the pouring is completed.

[0032] Example 2 See Figure 3-4A reinforcement structure for repairing a concrete column includes an original concrete column 10, external longitudinal reinforcement 11, external insert reinforcement 12, external stirrups 13, a composite cement-based material layer 14, and a formwork 9. One end of the external insert reinforcement 12 is inserted into the original concrete column 10. The external stirrups 13 are fixed to the outside of the original concrete column 10 through the external insert reinforcement 12. The external longitudinal reinforcement 11 is evenly distributed around the original concrete column 10 along its extension direction. The formwork 9 is fixed to the outside of the external stirrups 13, and a gap is left between the formwork 9 and the original concrete column 10. The composite cement-based material layer 14 is poured into the gap between the formwork 9 and the original concrete column 10. The composite cement-based material layer 14 is made of composite cement-based material.

[0033] The method for strengthening the concrete column includes the following steps: 1) Scrape off the corroded surface concrete of the original concrete column 10, remove the rusted steel bars, and roughen its surface. 2) Install external reinforcing bars 12 on the outer perimeter of the original concrete column 10, and tie the external longitudinal bars 11 and external stirrups 13. 3) Support the formwork according to the thickness of the repair layer, wet the concrete interface, and treat it. 4) The composite cement-based material is poured from the top of the original concrete column 10. Due to its excellent fluidity, the composite cement-based material will flow into the gap between the formwork 9 and the original concrete column 10. After being vibrated and compacted, a composite cement-based material layer 14 is formed until the pouring is completed.

[0034] Example 3 The difference between this embodiment and the above embodiment 1 is that: a composite cement-based material includes the following raw materials in parts by weight: 70 parts cement, 2 parts carbon ash, 6 parts silica fume, 2 parts slag, 10 parts fine aggregate, 80 parts quartz powder, 2 parts water-reducing agent and 50 parts water.

[0035] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0036] The active SiO2 in the silicon powder is ≥95%.

[0037] The quartz powder contains four particle sizes: fine particles with a diameter of 310 mesh, medium particles with a diameter of 70 mesh, medium particles with a diameter of 40 mesh, and coarse particles with a diameter of 26 mesh, and the weights are blended in a ratio of 0.5:2:5:2.

[0038] The water-reducing agent comprises the following raw materials in parts by weight: 20 parts sodium aminobenzenesulfonate, 10 parts alkali lignin, 1 part functionalized graphene, 1 part polyvinylpyrrolidone, 2 parts p-nitrostyrene, 5 parts sodium β-naphthalenesulfonate, 4 parts iron powder, 1 part ethanol, and 1 part modifier; the modifier is sodium carbonate.

[0039] The water-reducing agent is prepared by the following method: S1. According to the weight parts, sodium aminobenzenesulfonate, alkali lignin and functionalized graphene are mixed and heated to 40°C and stirred for 60 min to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 50°C, stir continuously at a rate of 250 r / min for 60 min, and cool to room temperature to obtain the water-reducing agent.

[0040] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0041] The rest of the content of this embodiment is the same as that of Embodiment 1, and will not be repeated here.

[0042] Example 4 The difference between this embodiment and the above embodiment 3 is that: a composite cement-based material includes the following raw materials in parts by weight: 70 parts cement, 2 parts carbon ash, 6 parts silica fume, 2 parts slag, 10 parts fine aggregate, 80 parts quartz powder, 70 parts crack-resistant fiber, 2 parts water-reducing agent and 50 parts water.

[0043] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0044] The active SiO2 in the silicon powder is ≥95%.

[0045] The quartz powder contains four particle sizes: fine particles with a diameter of 310 mesh, medium particles with a diameter of 70 mesh, medium particles with a diameter of 40 mesh, and coarse particles with a diameter of 26 mesh, and the weights are blended in a ratio of 0.5:2:5:2.

[0046] The crack-resistant fiber is composed of stainless steel fiber and PP fiber in a weight ratio of 6:3.

[0047] The water-reducing agent comprises the following raw materials in parts by weight: 20 parts sodium aminobenzenesulfonate, 10 parts alkali lignin, 1 part functionalized graphene, 1 part polyvinylpyrrolidone, 2 parts p-nitrostyrene, 5 parts sodium β-naphthalenesulfonate, 4 parts iron powder, 1 part ethanol, and 1 part modifier; the modifier is sodium carbonate.

[0048] The water-reducing agent is prepared by the following method: S1. According to the weight parts, sodium aminobenzenesulfonate, alkali lignin and functionalized graphene are mixed and heated to 40°C and stirred for 60 min to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 50°C, stir continuously at a rate of 250 r / min for 60 min, and cool to room temperature to obtain the water-reducing agent.

[0049] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0050] The rest of this embodiment is the same as that of embodiment 3, and will not be repeated here.

[0051] Example 5 The difference between this embodiment and the above embodiment 4 is that: a composite cement-based material includes the following raw materials in parts by weight: 70 parts cement, 2 parts carbon ash, 6 parts silica fume, 2 parts slag, 10 parts fine aggregate, 80 parts quartz powder, 70 parts crack-resistant fiber, 2 parts water-reducing agent and 50 parts water.

[0052] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0053] The active SiO2 in the silicon powder is ≥95%.

[0054] The quartz powder contains four particle sizes: fine particles with a diameter of 310 mesh, medium particles with a diameter of 70 mesh, medium particles with a diameter of 40 mesh, and coarse particles with a diameter of 26 mesh, and the weights are blended in a ratio of 0.5:2:5:2.

[0055] The crack-resistant fiber is composed of glass fiber and PP fiber in a weight ratio of 6:3.

[0056] The water-reducing agent comprises the following raw materials in parts by weight: 20 parts sodium aminobenzenesulfonate, 10 parts alkali lignin, 1 part functionalized graphene, 1 part polyvinylpyrrolidone, 2 parts p-nitrostyrene, 5 parts sodium β-naphthalenesulfonate, 4 parts iron powder, 1 part ethanol, and 1 part modifier; the modifier is sodium carbonate.

[0057] The water-reducing agent is prepared by the following method: S1. According to the weight parts, sodium aminobenzenesulfonate, alkali lignin and functionalized graphene are mixed and heated to 40°C and stirred for 60 min to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 50°C, stir continuously at a rate of 250 r / min for 60 min, and cool to room temperature to obtain the water-reducing agent.

[0058] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0059] The rest of this embodiment is the same as that of embodiment 4, and will not be repeated here.

[0060] Example 6 The difference between this embodiment and the above embodiment 5 is that: a composite cement-based material includes the following raw materials in parts by weight: 70 parts cement, 2 parts carbon ash, 6 parts silica fume, 2 parts slag, 10 parts fine aggregate, 80 parts quartz powder, 70 parts crack-resistant fiber, 2 parts water-reducing agent and 50 parts water.

[0061] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0062] The active SiO2 in the silicon powder is ≥95%.

[0063] The quartz powder contains four particle sizes: fine particles with a diameter of 310 mesh, medium particles with a diameter of 70 mesh, medium particles with a diameter of 40 mesh, and coarse particles with a diameter of 26 mesh, and the weights are blended in a ratio of 0.5:2:5:2.

[0064] The crack-resistant fiber is composed of carbon fiber and PP fiber in a weight ratio of 6:3.

[0065] The water-reducing agent comprises the following raw materials in parts by weight: 20 parts sodium aminobenzenesulfonate, 10 parts alkali lignin, 1 part functionalized graphene, 1 part polyvinylpyrrolidone, 2 parts p-nitrostyrene, 5 parts sodium β-naphthalenesulfonate, 4 parts iron powder, 1 part ethanol, and 1 part modifier; the modifier is sodium carbonate.

[0066] The water-reducing agent is prepared by the following method: S1. According to the weight parts, sodium aminobenzenesulfonate, alkali lignin and functionalized graphene are mixed and heated to 40°C and stirred for 60 min to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 50°C, stir continuously at a rate of 250 r / min for 60 min, and cool to room temperature to obtain the water-reducing agent.

[0067] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0068] The rest of this embodiment is the same as that of embodiment 5, and will not be repeated here.

[0069] Example 7 The difference between this embodiment and the above embodiment 5 is that: a composite cement-based material includes the following raw materials in parts by weight: 70 parts cement, 2 parts carbon ash, 6 parts silica fume, 2 parts slag, 10 parts fine aggregate, 80 parts quartz powder, 70 parts crack-resistant fiber, 2 parts water-reducing agent and 50 parts water.

[0070] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0071] The active SiO2 in the silicon powder is ≥95%.

[0072] The quartz powder contains four particle sizes: fine particles with a diameter of 310 mesh, medium particles with a diameter of 70 mesh, medium particles with a diameter of 40 mesh, and coarse particles with a diameter of 26 mesh, and the weights are blended in a ratio of 0.5:2:5:2.

[0073] The crack-resistant fiber is carbon fiber.

[0074] The water-reducing agent comprises the following raw materials in parts by weight: 20 parts sodium aminobenzenesulfonate, 10 parts alkali lignin, 1 part functionalized graphene, 1 part polyvinylpyrrolidone, 2 parts p-nitrostyrene, 5 parts sodium β-naphthalenesulfonate, 4 parts iron powder, 1 part ethanol, and 1 part modifier; the modifier is sodium carbonate.

[0075] The water-reducing agent is prepared by the following method: S1. According to the weight parts, sodium aminobenzenesulfonate, alkali lignin and functionalized graphene are mixed and heated to 40°C and stirred for 60 min to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 50°C, stir continuously at a rate of 250 r / min for 60 min, and cool to room temperature to obtain the water-reducing agent.

[0076] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0077] The rest of this embodiment is the same as that of embodiment 5, and will not be repeated here.

[0078] Example 8 The difference between this embodiment and the above embodiment 5 is that: a composite cement-based material includes the following raw materials in parts by weight: 80 parts cement, 4 parts carbon ash, 8 parts silica fume, 4 parts slag, 15 parts fine aggregate, 100 parts quartz powder, 80 parts crack-resistant fiber, 4 parts water-reducing agent and 70 parts water.

[0079] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0080] The active SiO2 in the silicon powder is ≥95%.

[0081] The quartz powder contains four particle sizes: fine particles with a diameter of 3120 mesh, medium particles with a diameter of 90 mesh, medium particles with a diameter of 50 mesh, and coarse particles with a diameter of 30 mesh, and the weights are blended in a ratio of 0.6:3:6:2.5.

[0082] The crack-resistant fiber is composed of stainless steel fiber and PE fiber in a weight ratio of 7:5.

[0083] The water-reducing agent comprises the following raw materials in parts by weight: 25 parts sodium aminobenzenesulfonate, 13 parts alkali lignin, 2 parts functionalized graphene, 2 parts polyvinylpyrrolidone, 4 parts p-nitrostyrene, 8 parts sodium β-naphthalenesulfonate, 6 parts iron powder, 2 parts ethanol, and 3 parts modifier; the modifier is sodium carbonate.

[0084] The water-reducing agent is prepared by the following method: S1. According to the weight parts, mix sodium aminobenzenesulfonate, alkali lignin and functionalized graphene, heat to 50°C and stir for 45 minutes to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 60°C for 2 hours. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 75°C for 45 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 60°C, stir continuously at a rate of 200 r / min for 50 min, and cool to room temperature to obtain the water-reducing agent.

[0085] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 14 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0086] The rest of this embodiment is the same as that of embodiment 5, and will not be repeated here.

[0087] Example 9 The difference between this embodiment and the above embodiment 5 is that: a composite cement-based material includes the following raw materials in parts by weight: 90 parts cement, 6 parts carbon ash, 10 parts silica fume, 6 parts slag, 20 parts fine aggregate, 120 parts quartz powder, 90 parts crack-resistant fiber, 6 parts water-reducing agent and 80 parts water.

[0088] The cement is silicate cement, and the strength grade of the silicate cement is 525.

[0089] The active SiO2 in the silicon powder is ≥95%.

[0090] The quartz powder contains four particle sizes: fine particles with a diameter of 330 mesh, medium particles with a diameter of 110 mesh, medium particles with a diameter of 70 mesh, and coarse particles with a diameter of 40 mesh, and the weights are blended in a ratio of 0.7:4:7:3.

[0091] The crack-resistant fiber is composed of stainless steel fiber and PVA fiber in a weight ratio of 8:6.

[0092] The water-reducing agent comprises the following raw materials in parts by weight: 30 parts sodium aminobenzenesulfonate, 15 parts alkali lignin, 3 parts functionalized graphene, 3 parts polyvinylpyrrolidone, 6 parts p-nitrostyrene, 10 parts sodium β-naphthalenesulfonate, 8 parts iron powder, 3 parts ethanol, and 5 parts modifier; the modifier is sodium carbonate.

[0093] The water-reducing agent is prepared by the following method: S1. According to the weight parts, mix sodium aminobenzenesulfonate, alkali lignin and functionalized graphene, heat to 60°C and stir for 30 minutes to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 70°C for 1 hour. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 80°C for 30 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, bring the temperature to 70°C, stir continuously at a rate of 250 r / min for 40 min, and cool to room temperature to obtain the water-reducing agent.

[0094] The composite cementitious material is prepared by the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag and quartz powder evenly, then add water-reducing agent and water and mix for 8-16 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

[0095] The rest of this embodiment is the same as that of embodiment 5, and will not be repeated here.

[0096] Comparative Example 1 The difference between this comparative example and Example 5 above is that no crack-resistant fibers were added to the raw materials of the composite cement-based material in this comparative example. The rest of the contents of this comparative example are the same as those of Example 5, and will not be repeated here.

[0097] Comparative Example 2 The difference between this comparative example and Example 5 above is that the composite cement-based material in this comparative example uses a naphthalene-based high-efficiency water-reducing agent produced by Jinan Qingtian Chemical Technology Co., Ltd. instead of the characteristic water-reducing agent in this application. The rest of the contents of this comparative example are the same as in Example 5, and will not be repeated here.

[0098] The performance of the composite cement-based materials prepared in Example 5 and Comparative Examples 1-2 was tested, and the results are shown in Table 1: The compressive strength and flexural strength tests were conducted in accordance with GB / T50081 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", and the bond strength test was conducted in accordance with the provisions of JGJ 70 "Test Methods for Basic Properties of Building Mortar". Flowability test: The test shall be conducted in accordance with GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures"; Tensile property test results attached Figure 5 As shown: at 10 days, the old ordinary concrete that was pulled up had already fractured internally, with a tensile strength of 3MPa. It is expected that after 28 days, the tensile strength can reach 4-5MPa, while the standard value of tensile strength of C30 ordinary concrete is 2.01MPa.

[0099] Table 1

[0100] The test data above show that the composite cement-based material of the present invention has good fluidity. After repairing concrete beams and slabs in corrosive environments, its 28-day compressive strength, flexural strength, and bond strength are the best, and its shrinkage and water absorption are almost zero. The characteristic particle size of cement is generally between 5-50 μm, with 10-20 μm particles being the most common. The particle size of fly ash is generally between 1-100 μm, the particle size of slag is between 1-100 μm, and the median particle size of silica fume is about 0.1-1 μm. Therefore, the addition of fly ash and silica fume can fully fill the capillary pores in the cement gel, reduce the porosity in concrete, and play a micro-filling role. Fly ash, slag, and silica fume all contain active components such as SiO2, which react with the alkaline component Ca(OH)2 in cement clinker in a secondary hydration reaction, which helps the mixture harden, increases strength, and improves pore structure.

[0101] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. The application of a composite cement-based material in the reinforcement of concrete structures, characterized in that: The composite cement-based material comprises the following raw materials in parts by weight: 70-90 parts cement, 2-6 parts carbon ash, 6-10 parts silica fume, 2-6 parts slag, 10-20 parts fine aggregate, 80-120 parts quartz powder, 70-90 parts crack-resistant fiber, 2-6 parts water-reducing agent, and 50-80 parts water; the silica fume contains ≥95% active SiO2; the crack-resistant fiber is composed of stainless steel fiber or carbon fiber and PP, PE, or PVA fiber in a weight ratio of 6-8:3-6; the water-reducing agent comprises the following raw materials in parts by weight: 20-30 parts sodium aminobenzenesulfonate, 10-15 parts alkali lignin, 1-3 parts functionalized graphene, 1-3 parts polyvinylpyrrolidone, 2-6 parts p-nitrostyrene, 5-10 parts sodium β-naphthalenesulfonate, 4-8 parts iron powder, 1-3 parts ethanol, and 1-5 parts modifier.

2. The application of a composite cement-based material according to claim 1 in the reinforcement of concrete structures, characterized in that: The quartz powder contains four particle sizes: fine particles with a diameter of 310-330 mesh, medium particles with a diameter of 70-110 mesh, medium particles with a diameter of 40-70 mesh, and coarse particles with a diameter of 26-40 mesh, and the weight is blended in a ratio of 0.5-0.7:2-4:5-7:2-3.

3. The application of a composite cement-based material according to claim 1 in the reinforcement of concrete structures, characterized in that: The water-reducing agent is prepared by the following method: S1. According to the weight parts, mix sodium aminobenzenesulfonate, alkali lignin and functionalized graphene, heat to 40-60℃ and stir for 30-60 minutes to obtain mixture A, which is set aside. S2. According to the weight parts, add p-nitrostyrene, ethanol and iron powder into the reaction device and react at 50-70℃ for 1-3 hours. Then add sodium β-naphthalenesulfonate, polyvinylpyrrolidone and modifier and stir evenly at 70-80℃ for 30-60 minutes to obtain mixture B, which is ready for use. S3. Add mixture B to mixture A, and stir continuously at a rate of 150-250 r / min for 40-60 min at 50-70℃. Cool to room temperature to obtain the water-reducing agent.

4. A method for preparing a composite cement-based material as described in any one of claims 1-3, characterized in that: Includes the following steps: E1. According to the weight parts, mix cement, carbon ash, silica fume, slag, fine aggregate and quartz powder evenly, then add water-reducing agent and water and mix for 8-16 minutes to obtain a mixed slurry for later use. E2. Disperse the crack-resistant fibers into the mixed slurry and stir until uniform to obtain the composite cement-based material.

5. The application of the composite cement-based material according to any one of claims 1-3 in the reinforcement of concrete structures, characterized in that: Used for repairing concrete structures.

6. The application of a composite cement-based material according to claim 5 in the reinforcement of concrete structures, characterized in that: The reinforcement structure for repairing concrete beams and slabs includes: main structural walls, existing floor slabs, existing beams, formwork, an upper repair layer, a lower repair layer, beam reinforcement material layers, and several reinforcing components. The main structural walls are located on both sides of the existing floor slabs, and the existing beams are located on the lower end face of the existing floor slabs. The formwork is fixed to the lower end face of the existing floor slabs and the outer surface of the existing beams, with gaps between the formwork and the lower end face of the existing floor slabs and the outer surface of the existing beams. The upper repair layer... The upper repair layer is poured onto the upper surface of the original floor slab, the lower repair layer is poured between the lower surface of the original floor slab and the formwork, the beam reinforcement material layer is poured between the formwork and the outer surface of the original beam, and the reinforcing members are evenly embedded in the upper repair layer, the lower repair layer and the beam reinforcement material layer; the original floor slab has a circular through hole penetrating the upper and lower surfaces of the original floor slab, and the lower end of the circular through hole is connected to the gap between the formwork, the lower surface of the original floor slab and the outer surface of the original beam.

7. The application of a composite cement-based material according to claim 5 in the reinforcement of concrete structures, characterized in that: The reinforcement structure for repairing a concrete column includes the original concrete column, external longitudinal reinforcement, external dowel bars, external stirrups, a composite cement-based material layer, and formwork. One end of the external dowel bars is inserted into the original concrete column. The external stirrups are fixed to the outside of the original concrete column by the external dowel bars. The external longitudinal reinforcement is evenly distributed around the perimeter of the original concrete column along its extension direction. The formwork is fixed to the outside of the external stirrups, and a gap is left between the formwork and the original concrete column. The composite cement-based material layer is poured into the gap between the formwork and the original concrete column.

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