Lightweight high-toughness durable cover plate for replacing existing cover plate and preparation method of lightweight high-toughness durable cover plate

Abstract

The invention provides a lightweight high-toughness durable cover plate for replacing an existing cover plate and a preparation method of the lightweight high-toughness durable cover plate, and relates to the technical field of cover plates. The cover plate comprises a cover plate main body and a heightening pad, the cover plate main body is prepared from the following raw materials: Portland cement, mineral powder, fly ash, silica fume, composite fibers, artificial sand, a water reducing agent, a modified additive, a defoaming agent and water; the heightening pad comprises the following raw materials: Portland cement, a cement expanding agent, metakaolin, fly ash, silica fume, composite fibers, artificial sand, hydroxypropyl methyl cellulose ether, a water reducing agent and water. The cover plate has the advantages of light weight, high toughness, durability, convenience in installation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of cover plates, and in particular to a lightweight, high-toughness and durable cover plate for replacing an existing cover plate and a preparation method thereof. Background Art

[0002] In the fields of highways, railways, electricity, petroleum, energy, etc., covers are important basic components and are widely used in tunnels, pipelines, cable troughs and equipment protection. At present, ordinary reinforced concrete covers are widely used due to their mature production process, but they have exposed many problems in actual use, especially when it is necessary to replace existing covers, which are not ideal, mainly reflected in the following aspects:

[0003] Heavy weight, difficult to construct and replace: The thickness of traditional reinforced concrete cover plates is generally 70mm, the common size is 600mm×500mm, and the weight of a single piece exceeds 50kg. Its heavy weight requires a lot of manpower and mechanical assistance during the construction and replacement process, which not only has low construction efficiency, but is also particularly inconvenient in scenarios where space is limited or emergency replacement is required.

[0004] Easy to damage and short service life: Traditional reinforced concrete cover plates usually use C30 or lower grade concrete materials, which have limited impact resistance and strength. During transportation, installation and service, the cover plates are prone to corner loss, cracks, and damage, which not only affects the overall aesthetics of the project, but also increases the potential safety hazards in use.

[0005] Poor durability and high maintenance cost: Due to the poor impermeability, frost resistance and corrosion resistance of traditional reinforced concrete cover plates, performance degradation is prone to occur in humid, frequent freeze-thaw cycles or highly corrosive environments. This defect not only shortens the service life, but also significantly increases the subsequent maintenance and replacement costs.

[0006] Difficult replacement and insufficient adaptability: In existing projects, replacement of traditional cover plates often faces construction difficulties due to problems such as excessive weight, easy damage, and insufficient size adaptability. Especially in old facilities, traditional cover plates are difficult to meet the needs of rapid replacement and long-term use.

[0007] The above problems are particularly prominent in highway and railway projects, and are also extremely prominent in scenarios involving cable troughs, pipeline protection and equipment maintenance in industries such as electricity, petroleum, and energy. These industries have put forward higher requirements for the lightness, high strength, durability and convenient construction of the cover. Summary of the invention

[0008] The object of the present invention is to provide a lightweight, high-toughness, durable cover plate for replacing an existing cover plate, which has multiple advantages such as light weight, high toughness, durability and convenient installation.

[0009] Another object of the present invention is to provide a method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate, which is used to prepare the above-mentioned lightweight, high-toughness and durable cover plate.

[0010] The present invention is achieved through the following technical solutions:

[0011] A lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising a cover plate body and a height-increasing pad;

[0012] The cover plate body comprises, by weight, 30-40 parts of silicate cement, 10-20 parts of mineral powder, 15-20 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.2-0.5 parts of water reducing agent, 1-5 parts of modified additive, 0.01-0.05 parts of defoaming agent and 15-20 parts of water;

[0013] The height-increasing pad comprises, by weight, 20-30 parts of silicate cement, 5-10 parts of cement expansion agent, 2-5 parts of metakaolin, 20-30 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.01-0.05 parts of hydroxypropyl methylcellulose ether, 0.1-0.2 parts of water reducing agent and 5-10 parts of water.

[0014] A method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate comprises the following steps:

[0015] S1. Add water and a water reducing agent to a mixture of all dry materials except the composite fiber, stir to obtain a soft dough-like material, then disperse the composite fiber in the material, evacuate, extrude and shape, and obtain a height-enhancing pad;

[0016] S2, adding water and a water reducing agent to a mixture of all dry materials except the composite fiber, stirring to obtain a uniformly fluid cement slurry, and then dispersing the composite fiber in the cement slurry to obtain a concrete slurry;

[0017] S3. Pour concrete slurry into the mold, place multiple reinforcing basalt fiber composite bars along the length direction of the mold, place a heightening pad at both ends of the mold, press the reinforcing basalt fiber composite bars down until they are completely covered by the concrete slurry, press the heightening pad down until its upper surface is flush with the edge of the mold, and solidify it to obtain the lightweight, high-toughness and durable cover plate.

[0018] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0019] Using height-raising pads and cover plate bodies to make cover plates can greatly reduce the difficulty of construction and replacement. At the same time, it can adapt to a variety of complex environments and is widely used in highways, railways, electricity, petroleum, energy and other fields, providing an efficient and reliable solution for the renewal and maintenance of related facilities.

[0020] Since concrete structures are subject to internal damage, this damage usually starts from defects at the atomic level, then grows and forms cracks, which propagate in the material. By utilizing the core-shell structure of the A combination and B components in the modified additive, the brittle / weakly inert shell of the core-shell structure is broken under stress, releasing active ingredients that can bridge new early cracks in a short time and can also achieve long-term healing by forming polycrystalline calcite crystals in the presence of moisture and carbon dioxide, thereby improving the durability of concrete by filling gaps.

[0021] When methyl methacrylate monomer is directly added to concrete mixture, methyl methacrylate is hydrolyzed in a highly alkaline environment to produce methacrylic acid and methanol. During cement hydration, the formed methacrylic acid reacts with calcium hydroxide to produce calcium methacrylate, which has high water solubility and may seep out of cement slurry. And because the density of methyl methacrylate monomer is lower than 1, methyl methacrylate monomer may be absorbed by the gelation stage before mixing with the initiator. In order to protect methyl methacrylate monomer from the alkaline environment of cement and achieve long-term healing. The inventor uses polymethyl methacrylate, encapsulates methyl methacrylate resin and N, N-dimethylaniline loaded with graphene oxide in component A, and encapsulates benzoyl peroxide in component B. After mixing methyl methacrylate resin loaded with graphene oxide, benzoyl peroxide and N, N-dimethylaniline, they are bonded and hardened into a solid state through free radical polymerization to achieve repair of cracks. By modifying methyl methacrylate resin with graphene oxide, on the one hand, graphene oxide is stacked layer by layer in the resin to form an orderly arranged reinforced network structure, which greatly lengthens the channel for corrosive media to enter the interior of the concrete and prevents the continued propagation of cracks; on the other hand, graphene oxide can increase the active sites of the resin and promote the polymerization reaction between the resin and other raw materials, which can not only speed up the repair of cracks in the concrete, but also enhance the crack repair strength and improve the durability of the concrete.

[0022] Natural fibers can produce a tight overlapping structure in concrete, fill the gaps between the raw materials, and improve the anti-seepage effect of the cover plate; at the same time, in the unhardened and hardened stages of concrete, they can withstand the tensile stress caused by plastic shrinkage and shrinkage, thereby reducing or preventing the formation of cracks; when concrete cracks, natural fibers can cross the cracks to withstand tensile stress, giving concrete good toughness and resistance to deformation. By modifying polyvinyl alcohol fibers, the interfacial bonding strength between polyvinyl alcohol fibers and cement matrix is ​​improved, so that it can better play a bridging role. Using nanocellulose to modify basalt fibers, the modified basalt fibers can play a bridging and filling role at the same time, promote the overlapping growth of hydration products such as CSH gel, calcium sulfonate and calcium hydroxide in cement, improve the density of the matrix, and provide a favorable effect on the mechanical properties and durability of cement-based materials. In addition, the three-dimensional network structure formed by natural fibers, modified polyvinyl alcohol fibers and modified basalt fibers can inhibit the merging of tiny bubbles into harmful large bubbles during the concrete mixing process, optimize the internal pore structure, and further improve the mesoscopic integrity of the concrete, thereby greatly improving the concrete's durability such as impermeability and frost resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a lightweight, high-toughness and durable cover plate for replacing an existing cover plate provided by the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0025] In one aspect, the present invention provides a lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising a cover plate body and a height-enhancing pad;

[0026] The cover plate body includes 30-40 parts of silicate cement, 10-20 parts of mineral powder, 15-20 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.2-0.5 parts of water reducing agent, 1-5 parts of modified additive, 0.01-0.05 parts of defoaming agent and 15-20 parts of water by weight;

[0027] The height-increasing pad comprises, by weight, 20-30 parts of silicate cement, 5-10 parts of cement expansion agent, 2-5 parts of metakaolin, 20-30 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.01-0.05 parts of hydroxypropyl methylcellulose ether, 0.1-0.2 parts of water reducing agent and 5-10 parts of water.

[0028] Mineral powder contains substances such as silica and aluminate, which can increase the production of cement stone in concrete, thereby improving the strength and hardness of concrete. Under the stimulation of cement hydration products, mineral powder can undergo hydration reaction to form a large amount of gel, filling the voids in concrete and increasing its density. The microparticles in mineral powder can fill cracks in concrete, reduce the number and width of cracks, and improve the bearing capacity and impact performance of concrete. The microparticles in mineral powder are finer and more active than cement ions, and can form a porous structure in concrete, making it easier for water molecules, carbon dioxide and other substances to enter and react chemically, thereby making the concrete structure denser and improving its durability.

[0029] Fly ash can fill voids in concrete, reduce cement usage, and reduce the heat and shrinkage of concrete. At the same time, the silicates and aluminates in fly ash can react with calcium compounds such as calcium hydroxide in cement to form new hydration products. The two aspects work synergistically to improve the strength and durability of concrete.

[0030] The particles in silica fume can play a micro-filling effect, refine the concrete structure, significantly increase the density of concrete, and improve its impermeability and chemical corrosion resistance. The rheological effect and good lubrication of silica fume can improve the fluidity of concrete and enhance its cohesion.

[0031] Artificial sand has high quartz and silicate content, which will not cause concrete shrinkage due to water evaporation, and its low moisture content will not cause corrosion on the concrete surface, which helps to reduce concrete shrinkage and improve concrete durability. Preferably, the particle size of artificial sand is 0.15-0.5mm, which can make concrete have better density and strength.

[0032] Metakaolin has an amorphous aluminum silicate structure, which can significantly improve the compressive strength, flexural strength and durability of concrete; it can reduce the pores inside the concrete, making the concrete structure denser, thereby improving its freeze-thaw resistance. Metakaolin can improve the working performance of concrete, and it has good low-temperature hydration performance in the alkaline environment of cement hydration products, which can significantly improve the early strength of concrete, especially in the low temperature environment of 0-10℃, which greatly shortens the demoulding cycle.

[0033] Furthermore, the modified additive is composed of component A and component B, wherein component A is a resin and N,N-dimethylaniline wrapped in polymethyl methacrylate, component B is benzoyl peroxide wrapped in polymethyl methacrylate, and the resin is a methyl methacrylate resin loaded with graphene oxide. Among them, N,N-dimethylaniline is used as a promoter, and benzoyl peroxide is used as a curing agent, so that the modified additive is a two-component acrylic structural adhesive composed of component A and component B, and the mass ratio of component A to component B is 1-2:1. Under the induced stress of the cement-based material, the methyl methacrylate and N,N-dimethylaniline in component A and the benzoyl peroxide in component B are released and chemically reacted to change from liquid to solid, thereby repairing the concrete cracks and realizing concrete self-healing. The preparation method of methyl methacrylate resin loaded with graphene oxide is as follows: dispersing graphene oxide in methyl isobutyl ketone solvent, adding 1 / 2 initiator (BPO, 2% of the mass of graphene oxide), heating and mixing to obtain a graphene oxide solution; dissolving methyl methacrylate monomer in an organic solvent, adding the remaining initiator, heating and mixing to obtain a monomer solution; then dripping the monomer solution into the graphene oxide solution at a uniform speed within 0.5h, and keeping warm for 2h to obtain the obtained solution.

[0034] Specifically, the preparation method of component A is as follows: 2.5g of polymethyl methacrylate is dissolved in 25g of methane, 2.5g of methyl methacrylate resin loaded with graphene oxide and 0.3g of N,N-dimethylaniline are added, and the oil phase is obtained by stirring; 25g of 1% polyvinyl alcohol aqueous solution is mixed with the oil phase and ultrasonically treated; the preparation method of component B is as follows: 2.5g of polymethyl methacrylate is dissolved in 25g of methane, 0.5g of benzoyl peroxide is added, and the oil phase is obtained by stirring; 25g of 1% polyvinyl alcohol aqueous solution is mixed with the oil phase and ultrasonically treated.

[0035] Furthermore, the composite fiber includes natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber in a mass ratio of 1:0.5-0.8:1. Preferably, the natural fiber is cotton fiber or hemp fiber. The fiber structure and porosity of cotton fiber can effectively delay the shrinkage process of concrete, reduce the shrinkage rate of concrete, reduce the internal stress of concrete, and improve the crack resistance of concrete. Hemp fiber can react with cement mortar in concrete to improve its toughness, strength, weathering resistance and durability.

[0036] Specifically, the modified polyvinyl alcohol fiber is obtained by treating the polyvinyl alcohol fiber with a silane coupling agent and an ethylene-vinyl acetate copolymer. The treatment process is: the silane coupling agent and the ethylene-vinyl acetate copolymer are mixed in a mass ratio of 1:1 to form a solution, the polyvinyl alcohol fiber is soaked in the solution for 30-50 minutes, the mass ratio of the polyvinyl alcohol fiber to the solution is 1:20, and the fiber is taken out after soaking and vacuum dried at 80-100°C for 5-10 minutes. By modifying the polyvinyl alcohol fiber, not only can its dispersibility in the concrete system be significantly improved, but also its interface strength with the cement matrix can be improved, and its bonding degree with other raw materials can be improved, so that it can better play a bridging role.

[0037] Modified basalt fiber is obtained by treating basalt fiber with nanocellulose. The treatment process is as follows: first, basalt fiber is soaked in a sodium hydroxide solution with a concentration of 0.5-2 mol / L or a hydrochloric acid solution with a concentration of 0.5-2 mol / L, treated at 40-100°C for 30-80 minutes, washed and dried, and then placed in a nanocellulose solution with a mass percentage concentration of 0.01-0.2%, soaked at 20-80°C for 1-2 hours, taken out, washed with deionized water, and dried at 60-80°C for 2 hours.

[0038] The main hydration product of cement, calcium silicate hydrate (CSH gel), presents a loose arrangement state, scattered and filled between the micro cracks on the surface of aggregates. Nanocellulose is a substance with a smaller size than cement hydration products, calcium silicate hydrate, calcium hydroxide and calcium sulfonate, and is easy to form a dense honeycomb network structure, tightly wrapping fibrous calcium silicate hydrate, flaky calcium hydroxide and needle-shaped calcium sulfonate to form a dense network structure, improving the compactness of the concrete interface. Nanocellulose has a high specific surface area and CSH gel nucleation sites, and has a volcanic ash effect. It can easily react with active substances to produce additional hydration products, namely CSH gel. The formed CSH gel then accumulates and forms a 3D skeleton network along the interface transition zone. At the same time, basalt fibers are used to broaden the spatial structure of the 3D skeleton network, forming a strong chimeric bond, modifying and improving the internal microstructure of cement-based materials.

[0039] Furthermore, the water reducer is a polycarboxylic acid high-performance water reducer, and the defoamer is one or more of fatty alcohol ethers, fatty alcohol esters, fatty alcohol polyoxyethylene ethers and polysiloxanes.

[0040] Furthermore, the cement expansion agent is one or more of sulphoaluminate expansion agent, aluminum powder expansion agent and high alumina expansion agent, preferably a fast-hardening sulphoaluminate expansion agent.

[0041] In another aspect, the present invention provides a method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising the following steps:

[0042] S1. Add water and a water reducing agent to a mixture of all dry materials except the composite fiber, stir to obtain a soft dough-like material, then disperse the composite fiber in the material, evacuate, extrude and shape, and obtain a height-enhancing pad;

[0043] S2, adding water and a water reducing agent to a mixture of all dry materials except the composite fiber, stirring to obtain a uniformly fluid cement slurry, and then dispersing the composite fiber in the cement slurry to obtain a concrete slurry;

[0044] S3. Pour concrete slurry into the mold, place multiple reinforcing basalt fiber composite bars along the length of the mold, place a heightening pad at both ends of the mold, press the reinforcing basalt fiber composite bars down until they are completely covered by the concrete slurry, press the heightening pad down until its upper surface is flush with the edge of the mold, and solidify it to obtain a lightweight, high-toughness and durable cover plate.

[0045] Furthermore, in step S1, after extrusion molding, the height-enhancing pad is cut, and the cutting surface of the height-enhancing pad is a plane, an inclined surface or a curved surface. The cutting surface of the height-enhancing pad is combined with the substrate body, and different cutting surfaces are used to increase the contact area between the height-enhancing pad and the substrate body, thereby improving the bonding strength between the two.

[0046] Furthermore, after the cutting in step S1 and the curing and forming in step S3, steam curing is performed at 55-60° C. for 6-10 hours.

[0047] In the present invention, the thickness of the lightweight, high-toughness and durable cover plate is 70-100mm, the thickness of the cover plate body is 30mm, and the thickness of the heightening pad is 40-70mm. The concrete density of the cover plate is 1800-1900kg / m1, and the weight of a single cover plate (600*500*30(70)mm) is about 19kg.

[0048] Example 1

[0049] A lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising a cover plate body and a height-increasing pad:

[0050] The raw materials for the main body of the cover are: 35kg of silicate cement, 15kg of mineral powder, 10kg of fly ash, 3kg of silica ash, 1kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.5:1), 15.5kg of artificial sand, 0.46kg of water reducer (polycarboxylic acid high performance water reducer), 2kg of modified additives, 0.04kg of defoaming agent (fatty alcohol ether) and 19kg of water.

[0051] The raw materials of the height-increasing pad are: 25kg of silicate cement, 7kg of cement expansion agent (fast-hardening sulphoaluminate expansion agent), 3kg of kaolin, 25kg of fly ash, 3kg of silica ash, 1.5kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.5:1), 16kg of artificial sand, 0.03kg of hydroxypropyl methylcellulose ether, 0.15kg of water reducer (polycarboxylic acid high-performance water reducer) and 8kg of water.

[0052] Preparation of modified polyvinyl alcohol fiber: silane coupling agent and ethylene-vinyl acetate copolymer are mixed in a mass ratio of 1:1 to prepare a solution, polyvinyl alcohol fiber is immersed in the solution for 40 minutes, the mass ratio of polyvinyl alcohol fiber to solution is 1:20, and then taken out and vacuum dried at 90°C for 8 minutes.

[0053] Preparation of modified basalt fiber: first, soak the basalt fiber in a 1 mol / L sodium hydroxide solution or a 1 mol / L hydrochloric acid solution at 80°C for 50 min, wash and dry, then put it in a 0.1% nanocellulose solution at 60°C for 2 h, take it out, wash it with deionized water, and dry it at 70°C for 2 h;

[0054] Preparation of modified additives:

[0055] Preparation of methyl methacrylate resin loaded with graphene oxide: dispersing graphene oxide in methyl isobutyl ketone solvent, adding 1 / 2 initiator (BPO, 2% of the mass of graphene oxide), heating and mixing to obtain a graphene oxide solution; dissolving methyl methacrylate monomer in an organic solvent, adding the remaining initiator, heating and mixing to obtain a monomer solution; then dripping the monomer solution into the graphene oxide solution at a uniform speed within 0.5 h, and keeping warm for 2 h to obtain;

[0056] Component A: Dissolve 2.5 g of polymethyl methacrylate in 25 g of methane, add 2.5 g of methyl methacrylate resin loaded with graphene oxide and 0.3 g of N,N-dimethylaniline, and stir to obtain an oil phase; mix 25 g of 1% polyvinyl alcohol aqueous solution with the oil phase and perform ultrasonic treatment;

[0057] Component B: Dissolve 2.5 g of polymethyl methacrylate in 25 g of methane, add 0.5 g of benzoyl peroxide, and stir to obtain an oil phase; mix 25 g of a 1% polyvinyl alcohol aqueous solution with the oil phase, and perform ultrasonic treatment.

[0058] The preparation method is as follows:

[0059] S1. Forming of height-increasing pads:

[0060] S11, conveying all dry materials except composite fibers to a mixer and dry mixing for 1 minute;

[0061] S12. While the mixer is working, evenly add water and polycarboxylic acid high-performance water reducing agent into the mixer and stir for 4 minutes until it becomes a soft dough;

[0062] S13. When the mixer is in operation, add the composite fiber into the mixer at a uniform speed, continue stirring for 2 minutes until the composite fiber is evenly dispersed, and discharge the freshly mixed concrete into the temporary storage hopper at one time;

[0063] S14, using an automatic feeder to evenly discharge the freshly mixed concrete in the temporary storage hopper onto the conveyor belt, and transport it to the vacuum filtration equipment to remove the gas inside the mixture;

[0064] S15, the mixture after vacuum treatment enters the extrusion equipment for extrusion molding;

[0065] S16, the height-enhancing pad formed by extrusion is cut into set lengths and cutting surfaces by a synchronous cutting machine on a transmission belt;

[0066] S17, transporting the cut height-enhancing pad to a curing room for steam curing at a temperature of 55° C. for 6 hours, and placing it aside for later use after curing;

[0067] S2. Cover plate main body molding:

[0068] S21, conveying all dry materials except composite fiber to a mixer, and dry mixing for 1 minute;

[0069] S22. While the mixer is working, water and polycarboxylic acid high-performance water reducing agent are evenly added into the mixer and stirred for 4 minutes until a soft dough is formed;

[0070] S23. When the mixer is in operation, add the composite fiber into the mixer at a uniform speed, continue stirring for 2 minutes until the composite fiber is evenly dispersed, and discharge the freshly mixed concrete into the temporary storage hopper at one time;

[0071] S24, placing the cover plate mold on a vibration platform, starting the vibration platform, using an automatic metering feeder to evenly discharge the freshly mixed concrete in the temporary storage hopper into the cover plate mold according to the set weight, and vibrating for 10-15 seconds until the mixture flows horizontally and the mold is completely filled;

[0072] S25. Place a pad of appropriate thickness horizontally at each of the four corners of the mold;

[0073] S26. Place three reinforcing basalt fiber composite bars at equal intervals along the length direction of the mold, and place a heightening pad at both ends of the mold along the width direction of the mold. Press the reinforcing basalt fiber composite bars down until they are completely covered by the concrete slurry, and press the heightening pad down until its upper surface is flush with the edge of the mold.

[0074] S27. Transfer the cured cover plate to a steam curing room and cure it at 60° C. for 10 hours to obtain a lightweight, high-toughness and durable cover plate.

[0075] In this embodiment, the thickness of the lightweight, high-toughness and durable cover plate is 70 mm, the thickness of the cover plate body is 30 mm, and the thickness of the height-increasing pad is 40 mm.

[0076] Example 2

[0077] A lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising a cover plate body and a height-increasing pad:

[0078] The raw materials for the main body of the cover are: 30kg of silicate cement, 10kg of mineral powder, 15kg of fly ash, 5kg of silica ash, 2kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.8:1), 10kg of artificial sand, 0.45kg of water reducer (polycarboxylic acid high-performance water reducer), 5kg of modified additives, 0.05kg of defoaming agent (fatty alcohol ester) and 18.5kg of water.

[0079] The raw materials of the height-increasing pad are: 30kg of silicate cement, 5kg of cement expansion agent (aluminum powder expansion agent), 5kg of kaolin, 20kg of fly ash, 2kg of silica ash, 1kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.8:1), 10kg of artificial sand, 0.01kg of hydroxypropyl methylcellulose ether, 0.2kg of water reducer (polycarboxylic acid high-performance water reducer) and 5kg of water.

[0080] The preparation method and specifications of the lightweight, high-toughness and durable cover plate in this embodiment are the same as those in Example 1.

[0081] Example 3

[0082] A lightweight, high-toughness and durable cover plate for replacing an existing cover plate, comprising a cover plate body and a height-increasing pad:

[0083] The raw materials for the main body of the cover are: 40kg of silicate cement, 20kg of mineral powder, 20kg of fly ash, 2kg of silica ash, 1.5kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.6:1), 20kg of artificial sand, 0.2kg of water reducer (polycarboxylic acid high-performance water reducer), 1kg of modified additive, 0.01kg of defoaming agent (fatty alcohol polyoxyethylene ether) and 15kg of water.

[0084] The raw materials of the height-increasing pad are: 20kg of silicate cement, 10kg of cement expansion agent (high alumina expansion agent), 2kg of kaolin, 30kg of fly ash, 2kg of silica ash, 2kg of composite fiber (the mass ratio of natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber is 1:0.6:1), 20kg of artificial sand, 0.05kg of hydroxypropyl methylcellulose ether, 0.1kg of water reducer (polycarboxylic acid high-performance water reducer) and 10kg of water.

[0085] The preparation method and specifications of the lightweight, high-toughness and durable cover plate in this embodiment are the same as those in Example 1.

[0086] Comparative Example 1

[0087] In this comparative example, no modifying additive is added, and the rest is the same as in Example 1.

[0088] Comparative Example 2

[0089] In this comparative example, the modified additive only includes component A (methyl methacrylate resin loaded with graphene oxide wrapped in polymethyl methacrylate and N,N-dimethylaniline), and the rest is the same as in Example 1.

[0090] Comparative Example 3

[0091] In this comparative example, the modified additive only includes component B (benzoyl peroxide encapsulated by polymethyl methacrylate), and the rest is the same as that in Example 1.

[0092] Comparative Example 4

[0093] In this comparative example, component A in the modified additive is methyl methacrylate resin and N,N-dimethylaniline wrapped by polymethyl methacrylate, and the rest is the same as in Example 1.

[0094] Comparative Example 5

[0095] In this comparative example, the polyvinyl alcohol fiber and the basalt fiber were not modified, and the rest were the same as in Example 1.

[0096] Comparative Example 6

[0097] In this comparative example, only the polyvinyl alcohol fiber was modified, and the rest was the same as in Example 1.

[0098] Comparative Example 7

[0099] In this comparative example, only the basalt fiber was modified, and the rest was the same as in Example 1.

[0100] Test example

[0101] Ordinary reinforced concrete cover plates of the same size and thickness as those in the embodiment were taken, and the performance of the embodiment, the comparative example and the ordinary reinforced concrete cover plates was tested. The cracking load was tested by the vibration method. By applying a periodic load on the cover plate, the self-vibration dynamic response frequency of the cover plate was stimulated and the cracking load was measured; the impact resistance was tested according to the GB / T21120-2018 standard; the frost resistance was tested according to the GB / T50082-2009 standard, and the results were as follows:

[0102] Table 1

[0103]

[0104]

[0105] According to Table 1, compared with the common reinforced concrete cover plate, the cover plate made in the embodiment is lighter in weight, and has better cracking load, impact resistance and frost resistance. Compared with the comparative example, the cover plate made in the embodiment has better cracking load and impact resistance.

[0106] In addition, referring to JGJ 55-2000 "Ordinary Concrete Mix Design Code", the porosity (%) of the concrete specimens obtained after curing under standard conditions in Example 1 and Comparative Examples 1-6 was tested; the concrete specimens obtained under standard conditions for curing for 7 days in Example 1 and Comparative Examples 1-6 were crack suppressed, cracks with a width of 100-400 μm were selected, two points of each crack were measured, and the initial crack width (L0) was recorded. Then, the specimens were placed in water and cured for 7 days again, and the crack width after curing again (L1) was recorded. The crack width healing rate (%) was calculated according to L=(L0-L1) / L0×100%. The test results are as follows:

[0107] Table 2

[0108]

[0109] According to Table 2, the concrete of Example 1 has lower porosity and better crack width healing rate. This shows that adding the modified additive and composite fiber in Example 1 reduces the porosity of concrete and improves the mechanical properties of concrete; at the same time, it also improves the crack width healing rate of concrete, making the concrete have stronger self-healing ability and extending the service life of concrete.

[0110] In addition, compared with traditional ordinary reinforced concrete cover plates, the cover plate of the present invention saves more than 45% of concrete material, thereby significantly reducing carbon emissions, and saving more than 10% in material costs; the weight is reduced by more than 60%, the labor intensity of production and installation workers is greatly reduced, and the installation efficiency is significantly improved, which has excellent economic and social benefits.

[0111] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lightweight, high-toughness and durable cover plate for replacing an existing cover plate, characterized in that: It includes a cover plate body and a height-enhancing pad; The cover plate body comprises, by weight, 30-40 parts of silicate cement, 10-20 parts of mineral powder, 15-20 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.2-0.5 parts of water reducing agent, 1-5 parts of modified additive, 0.01-0.05 parts of defoaming agent and 15-20 parts of water; The height-increasing pad comprises, by weight, 20-30 parts of silicate cement, 5-10 parts of cement expansion agent, 2-5 parts of metakaolin, 20-30 parts of fly ash, 2-5 parts of silica fume, 1-2 parts of composite fiber, 10-20 parts of artificial sand, 0.01-0.05 parts of hydroxypropyl methylcellulose ether, 0.1-0.2 parts of water reducing agent and 5-10 parts of water.

2. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 1, characterized in that: The modified additive consists of component A and component B, wherein the component A is a resin wrapped in polymethyl methacrylate and N,N-dimethylaniline, the component B is benzoyl peroxide wrapped in polymethyl methacrylate, and the resin is a methyl methacrylate resin loaded with graphene oxide.

3. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 2, characterized in that: The preparation method of the component A is as follows: polymethyl methacrylate is dissolved in methane, methyl methacrylate resin loaded with graphene oxide and N,N-dimethylaniline are added, and the oil phase is obtained by stirring; the polyvinyl alcohol aqueous solution is mixed with the oil phase, and ultrasonic treatment is performed; the preparation method of the component B is as follows: polymethyl methacrylate is dissolved in methane, benzoyl peroxide is added, and the oil phase is obtained by stirring; the polyvinyl alcohol aqueous solution is mixed with the oil phase, and ultrasonic treatment is performed.

4. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 1, characterized in that: The composite fiber comprises natural fiber, modified polyvinyl alcohol fiber and modified basalt fiber in a mass ratio of 1:0.5-0.8:

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5. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 4, characterized in that: The modified polyvinyl alcohol fiber is obtained by treating the polyvinyl alcohol fiber with a silane coupling agent and ethylene-vinyl acetate copolymer, and the modified basalt fiber is obtained by treating the basalt fiber with nanocellulose.

6. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to any one of claims 1 to 5, characterized in that: The water reducer is a polycarboxylic acid high-performance water reducer, and the defoamer is one or more of fatty alcohol ethers, fatty alcohol esters, fatty alcohol polyoxyethylene ethers and polysiloxanes.

7. The lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 6, characterized in that: The cement expansion agent is one or more of a sulphoaluminate expansion agent, an aluminium powder expansion agent and a high alumina expansion agent.

8. The method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Add water and a water reducing agent to a mixture of all dry materials except the composite fiber, stir to obtain a soft dough-like material, then disperse the composite fiber in the material, evacuate, extrude and shape, and obtain a height-enhancing pad; S2, adding water and a water reducing agent to a mixture of all dry materials except the composite fiber, stirring to obtain a uniformly fluid cement slurry, and then dispersing the composite fiber in the cement slurry to obtain a concrete slurry; S3. Pour concrete slurry into the mold, place multiple reinforcing basalt fiber composite bars along the length direction of the mold, place a heightening pad at both ends of the mold, press the reinforcing basalt fiber composite bars down until they are completely covered by the concrete slurry, press the heightening pad down until its upper surface is flush with the edge of the mold, and solidify it to obtain the lightweight, high-toughness and durable cover plate.

9. The method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 8, characterized in that: In step S1, after extrusion molding, the height-enhancing pad is further cut, and the cutting surface of the height-enhancing pad is a plane, an inclined surface or a curved surface.

10. The method for preparing a lightweight, high-toughness and durable cover plate for replacing an existing cover plate according to claim 9, characterized in that: After the cutting in step S1 and the curing and forming in step S3, steam curing at 55-60° C. for 6-10 hours is also included.

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