Concrete block and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and particularly relates to a concrete block and a preparation method thereof. The concrete block is prepared from the following raw materials in parts by mass: 18-25 parts of cement, 10-15 parts of fly ash, 20-25 parts of lime, 25-35 parts of sand, 7-10 parts of aluminum powder, 3-5 parts of composite filler, 4-6 parts of modified basalt fiber, 2-4 parts of nano silicon dioxide, 1-3 parts of a water reducing agent, 1-3 parts of a repairing agent and 30-40 parts of water. All the raw materials in the concrete block have a synergistic effect, so that the mechanical properties such as pressure resistance of the concrete block are improved; the modified basalt fiber and the repairing agent improve the durability of the concrete block and prolong the service life of the concrete block.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to a concrete block and a preparation method thereof. Background Art

[0002] Autoclaved aerated concrete blocks are mainly made of siliceous materials (such as fly ash, quartz sand, steel slag, iron tailings, and slag, etc.) and calcareous materials (lime and cement, etc.) as cementitious materials, with aluminum powder, hydrogen peroxide, calcium carbonate, etc. as foaming agents, supplemented with water reducing agents, early strength agents, foam stabilizers and other admixtures to prepare porous silicate product materials.

[0003] With the development of building technology, autoclaved aerated concrete masonry has become the main wall material of modern buildings due to its advantages of light weight, heat insulation, and environmental protection. However, there are microscopic structural defects inside the concrete blocks. During the process of using concrete blocks as building materials, they are easily affected by external factors such as moisture and oxygen, resulting in a decrease in the anti-corrosion and waterproof performance of the concrete blocks.

[0004] The Chinese patent application document with the application publication number CN110342870A discloses an autoclaved aerated concrete block, which includes the following components in parts by mass: 60 - 70 parts of water; 15 - 20 parts of portland cement; 25 - 30 parts of sand; 30 - 35 parts of stone; 0.5 - 1 part of aluminum powder; 3 - 5 parts of water reducing agent; 3 - 5 parts of methyl o - hydroxybenzoate; 1 - 3 parts of lecithin; 5 - 8 parts of acrylic emulsion. This technical solution enhances the corrosion resistance of the autoclaved aerated concrete block by the synergistic cooperation of methyl o - hydroxybenzoate, lecithin and acrylic emulsion, making the compressive strength of the autoclaved aerated concrete block not easily affected by factors such as moisture and ultraviolet rays. However, when cracks or local deterioration occur in the concrete block during service and need to be repaired, it can only rely on externally added cement - based materials or sealants to improve, and the operation is inconvenient. Summary of the Invention

[0005] When cracks appear in the existing concrete blocks and need to be repaired, it can only rely on externally added substances to improve. To solve this problem, the present invention provides a concrete block and a preparation method thereof.

[0006] To achieve the purpose of the present invention, the following technical solutions are adopted in the present invention: In the first aspect, the present invention provides a concrete block, which is made of the following raw materials in parts by mass: 18 - 25 parts of cement, 10 - 15 parts of fly ash, 20 - 25 parts of lime, 25 - 35 parts of sand, 7 - 10 parts of aluminum powder, 3 - 5 parts of composite filler, 4 - 6 parts of modified basalt fiber, 2 - 4 parts of nano - silica, 1 - 3 parts of water reducing agent, 1 - 3 parts of repair agent, 40 - 50 parts of water.

[0007] By adopting the above technical solution, cement is used as the main cementitious material. The active components in lime and fly ash are stimulated by the hydration products of cement to generate more cementitious substances, filling the pores, which can improve the strength of the concrete block; sand is used as the aggregate, playing a skeleton role, filling with the cementitious material mutually, enhancing the structural stability of the concrete block; aluminum powder can react with water in the presence of calcium hydroxide to generate bubbles, forming a porous structure inside the concrete block, improving the heat insulation and sound insulation performance; the composite filler can improve the strength of the concrete block; the addition of modified basalt fiber can prevent the expansion of cracks, improving the crack resistance of the concrete block; the repair agent can repair the cracks that appear inside the concrete block, maintaining the integrity of the concrete structure.

[0008] Preferably, the preparation method of the composite filler comprises the following steps: (1) Mix carbon nanotubes and nitric acid evenly, heat up for reflux reaction, cool down, filter, wash, and dry to obtain carbon nanotubes with carboxyl groups; (2) Ultrasonically disperse the carbon nanotubes with carboxyl groups, graphene oxide, absolute ethanol, and water for 1.5 - 2 h; adjust the pH to 9 - 10, add a silane coupling agent and ultrasonically disperse for 0.5 - 1 h; dropwise add a mixed solution of tetraethyl orthosilicate and ethanol and ultrasonically disperse for 2 - 3 h to obtain a dispersion; react the dispersion, centrifuge, wash, and dry to obtain a mixture; (3) Ultrasonically disperse the mixture, cement, absolute ethanol, and water for 0.5 - 1 h, and freeze-dry to obtain the composite filler.

[0009] By adopting the above technical solution, carbon nanotubes and graphene oxide have extremely high strength and modulus. Introducing them into the concrete block can improve the compressive strength of the concrete block; however, the bonding force between carbon nanotubes and graphene oxide and cement is poor. Therefore, a silane coupling agent is attached to the surfaces of carbon nanotubes and graphene oxide, enabling them to participate in the hydration reaction of cement and strengthening the bonding force between the two and cement; then mixing with a small amount of cement and replacing part of the cement and adding it to the concrete block can better fill the pores and defects in the concrete block, making the microstructure of the concrete more dense and improving the overall performance of the concrete block.

[0010] Preferably, in the step (1), the concentration of nitric acid is 8%, and the dosage ratio of carbon nanotubes to nitric acid is 1 g∶(50 - 80) mL; the reaction temperature is 130 - 140 °C, and the reaction time is 12 - 15 h.

[0011] By adopting the above technical solution, carboxyl groups are introduced into the carbon nanotubes through nitric acid, improving the dispersibility of the carbon nanotubes; at the same time, the carbon nanotubes with carboxyl groups can form a better combination with substances such as cement in the concrete block compared with the carbon nanotubes. The amount of nitric acid should not be excessive, as excessive nitric acid may over-oxidize the carbon nanotubes, resulting in defects in their structure and affecting the performance of the concrete block.

[0012] Preferably, in the step (2), the dosage ratio of the carbon nanotubes with carboxyl groups, graphene oxide, absolute ethanol and water is 1 g∶(1 - 2) g∶(200 - 300) mL∶(30 - 50) mL; the dosage ratio of the carbon nanotubes with carboxyl groups, silane coupling agent and the mixed solution of tetraethyl orthosilicate and ethanol is 1 g∶(0.3 - 0.5) mL∶(15 - 25) mL; the mixed solution of tetraethyl orthosilicate and ethanol is prepared from tetraethyl orthosilicate, absolute ethanol and water according to the volume ratio of (2 - 3)∶(2 - 4)∶1; the reaction time is 18 - 24 h.

[0013] By adopting the above technical solution, the composite filler prepared with the carbon nanotubes with carboxyl groups and graphene oxide in this ratio has the optimal performance. Excessive graphene oxide may cover the carboxyl groups on the surface of the carbon nanotubes, making it difficult for them to react with the silane coupling agent or causing agglomeration, and it is difficult to form a good composite filler, affecting the performance of the concrete block.

[0014] Preferably, in the step (3), the dosage ratio of the mixture, cement, absolute ethanol and water is 1 g∶(0.5 - 1) g∶(5 - 8) mL∶(65 - 80) mL.

[0015] By the above technical solution, mixing a small amount of cement with the carbon nanotubes with carboxyl groups and graphene oxide can be more evenly mixed with the cement in the concrete block when added to the concrete block later, and better play the strengthening role of the carbon nanotubes and graphene oxide on the concrete block.

[0016] Preferably, the preparation method of the repair agent is as follows: Granulate the core material of the repair agent to obtain core material particles of the repair agent; sieve, spray the coating liquid on the core material particles of the repair agent with a particle size between 80 - 90 mesh, and dry to obtain repair agent particles.

[0017] Preferably, select the repair agent with a particle size between 65 - 75 mesh as the repair agent in the concrete block.

[0018] By adopting the above technical solution, the repair agent with a particle size of 65 - 75 mesh can better fill the tiny pores and cracks inside the concrete block, improve the compactness of the concrete block, and thus enhance its compressive strength.

[0019] Preferably, the core material of the repair agent is composed of the following components in parts by mass: 20 - 30 parts of sodium hexametaphosphate, 4 - 8 parts of potassium nitrate, 10 - 15 parts of lithium phosphate, 15 - 20 parts of microcrystalline cellulose, 1 - 4 parts of polyvinylpyrrolidone, and 30 - 40 parts of water.

[0020] By adopting the above technical solution, sodium hexametaphosphate in the repair agent core material can combine with calcium ions to form an unstable complex. When encountering unhydrated cement particles, it decomposes itself, catalyzes the continuous hydration of unhydrated cement particles, and repairs the cracks in the concrete block through continuous penetration and complexation cycles; lithium phosphate improves the impermeability of the concrete block, and at the same time, potassium ions can be filled into the crystal lattice of the cement hydration products to improve the stability of the hydration products; potassium nitrate can provide an ionic environment to promote the hydration reaction; the three act together to achieve the repair of cracks in the concrete block and improve the overall performance of the concrete block.

[0021] Preferably, the coating liquid is prepared from ethyl cellulose, polyethylene wax, acetone, and absolute ethanol according to a mass ratio of 1∶(0.2 - 0.5)∶(7 - 8)∶(1.5 - 2).

[0022] By adopting the above technical solution, under this ratio, the components in the coating liquid cooperate with each other to form a coating layer with good performance, which can effectively protect and slowly release the repair agent core material, thereby better exerting the self - repair performance of the repair agent in the concrete block.

[0023] Preferably, the preparation method of the modified basalt fiber includes the following steps: Mix basalt fiber, silane coupling agent, acetic acid, and water evenly according to a dosage ratio of 1 g∶(20 - 30) mL∶(5 - 10) mL∶(20 - 30) mL, adjust the pH to 6 - 7, ultrasonically disperse for 4 - 6 h, wash, and dry to obtain the modified basalt fiber.

[0024] By adopting the above technical solution, one end of the silane coupling agent KH - 550 molecule can be grafted onto the surface of the basalt fiber; the other end can interact with the hydration products in the concrete block, etc., thereby forming a good interfacial bond between the basalt fiber and the concrete block, improving the interfacial bond strength between the basalt fiber and the concrete block. Therefore, when the concrete block is subjected to external forces, the basalt fiber can more effectively prevent the generation and expansion of micro - cracks; too much modified basalt fiber added to the concrete block is likely to cause agglomeration phenomena, reducing the improvement effect of the modified basalt fiber on the concrete block.

[0025] In the second aspect, the present invention provides a preparation method of the above - mentioned concrete block, including the following steps: S1: Mix cement, fly ash, lime, sand, aluminum powder, composite filler, modified basalt fiber, and nano - silica evenly to obtain a mixture; S2: Add water-reducing agent, repair agent and water to the mixture and mix evenly to obtain a mixed slurry. S3: Pour and cure the mixed slurry to obtain concrete blocks.

[0026] By adopting the above technical solution, the whole preparation method mainly includes three steps: mixing, pouring and curing. The preparation method is simple and the mixing uniformity is good.

[0027] In summary, the beneficial effects of the present invention are as follows: (1) In the present invention, silane coupling agent is attached to the surface of carbon nanotubes and graphene oxide, so that the prepared composite filler can participate in the hydration reaction of cement, strengthening the bonding ability between the composite filler and the cement matrix; the composite filler has high strength and can play a role of reinforcing skeleton in concrete, improving the mechanical properties of concrete blocks. (2) The present invention selects sodium hexametaphosphate, potassium nitrate and lithium phosphate as the main components of the repair agent. When cracks appear in the concrete blocks, the repair agent breaks and releases the core material of the repair agent. Components such as sodium hexametaphosphate and lithium phosphate can react with calcium ions in the concrete blocks, etc., promoting the formation of hydration products or secondary hydration products, filling the cracks and preventing the cracks from further expanding; the presence of potassium nitrate can promote the hydration reaction, realizing the repair of cracks in the concrete blocks and effectively improving the durability of the concrete blocks. (3) The present invention introduces basalt fibers into the concrete blocks. The modified fibers can play a "bridging" role in the concrete, reducing the shrinkage deformation of the concrete, inhibiting the generation and expansion of microcracks, making the internal structure of the concrete blocks more dense, improving its stability and enhancing the mechanical properties of the concrete blocks. (4) The various raw materials in the concrete blocks of the present invention act synergistically to improve the mechanical properties such as the compressive strength of the concrete blocks; the presence of modified basalt fibers and the repair agent improves the durability of the concrete blocks and extends the service life of the concrete blocks. Specific Embodiments

[0028] The technical solution of the present invention will be elaborated in detail below with reference to several representative embodiments of the present invention.

[0029] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are all conventional methods. The materials, reagents, etc. used in the following examples and comparative examples can all be obtained from commercial channels unless otherwise specified.

[0030] Cement: P·O42.5 ordinary Portland cement, strength grade C35; Fly ash: Grade II; Sand: Medium sand in Zone II, fineness modulus 2.8; Aluminum powder: Active aluminum content ≥85%; Nano-silica: average particle size 30nm; Basalt fiber: length 12mm.

[0031] Example 1 A concrete block of this example is made of raw materials with the following masses: 1.8 kg of cement, 1.2 kg of fly ash, 2.3 kg of lime, 3 kg of sand, 0.8 kg of aluminum powder, 0.5 kg of composite filler, 0.5 kg of modified basalt fiber, 0.2 kg of nano-silica, 0.2 kg of water reducing agent, 0.3 kg of repair agent, 4.5 kg of water.

[0032] A preparation method of a concrete block of this example is as follows: S1: Add 1.8 kg of cement, 1.2 kg of fly ash, 2.3 kg of lime, 3 kg of sand, 0.8 kg of aluminum powder, 0.5 kg of composite filler, 0.5 kg of modified basalt fiber and 0.2 kg of nano-silica into a cement mixer, and stir at a speed of 100 r / min for 2 min to obtain a mixture; S2: Add 0.2 kg of water reducing agent, 0.3 kg of repair agent and 4.5 kg of water into the mixture, and stir at a speed of 100 r / min for 3 min to obtain a mixed slurry; S3: Pour the mixed slurry into a mold, then place the mold on a vibrating table and vibrate for 2 min. Use a scraper to remove the excess slurry and air bubbles on the surface, and cure at room temperature for 1 d; After the curing is completed, remove the mold and cure for 28 d under the conditions of a temperature of 20°C and a humidity of 95% to obtain a concrete block.

[0033] A preparation method of the composite filler of this example is as follows: (1) Add 0.1 kg of carbon nanotubes and 6 L of nitric acid with a concentration of 68% into a reaction kettle, stir for 5 min, heat up to 130°C and reflux for 15 h. After the reaction is completed, cool to room temperature, filter, wash with deionized water until neutral, and place in a vacuum drying oven at 45°C for 12 h to obtain carbon nanotubes with carboxyl groups; (2) Add 0.1 kg of carboxyl-functionalized carbon nanotubes, 0.15 kg of graphene oxide, 25 L of absolute ethanol, and 5 L of water into a reaction kettle and ultrasonically disperse for 1.5 h; adjust the pH to 10, add 0.05 L of silane coupling agent into the reaction kettle and ultrasonically disperse for 0.5 h; continue to dropwise add a mixed solution of 1.5 L of tetraethyl orthosilicate and ethanol into the reaction kettle and ultrasonically disperse for 2 h to obtain a dispersion; react the dispersion at room temperature for 20 h, centrifuge, wash with deionized water 3 times, wash with absolute ethanol 3 times, wash with deionized water until neutral, and place in a vacuum drying oven to dry at 60 °C for 12 h to obtain a mixture; the mixed solution of tetraethyl orthosilicate and ethanol is prepared by stirring 0.2 - 0.3 L of tetraethyl orthosilicate, 0.2 L of absolute ethanol, and 0.1 L of water in a reaction kettle for 10 min; (3) Add 0.1 kg of the mixture, 0.06 kg of cement, 0.8 L of absolute ethanol, and 7 L of water into a reaction kettle and ultrasonically disperse for 0.5 h, then transfer to a freeze dryer and freeze-dry for 36 h to obtain a composite filler.

[0034] The preparation method of the repair agent in this example is as follows: Stir 2 kg of sodium hexametaphosphate, 0.6 kg of potassium nitrate, 1.2 kg of lithium phosphate, 1.5 kg of microcrystalline cellulose, 0.1 g of polyvinylpyrrolidone, and 4 kg of water in a blender for 30 min, extrude into strips through an extruder, granulate in a spherical granulator, and dry to obtain repair agent core material particles; sieve, spray coating liquid on the repair agent core material particles with a particle size between 80 - 90 mesh, and dry to obtain a repair agent; sieve, take the repair agent with a particle size between 65 - 75 mesh and add it into concrete blocks; the coating liquid is prepared by stirring 1 kg of ethyl cellulose, 0.2 kg of polyethylene wax, 8 kg of acetone, and 2 kg of absolute ethanol in a reaction kettle for 30 min.

[0035] The preparation method of the modified basalt fiber in this example is as follows: Add 0.1 kg of basalt fiber, 2 L of silane coupling agent KH550, 0.5 L of acetic acid, and 3 L of water into a reaction kettle, adjust the pH to 7, ultrasonically disperse for 4 h, wash with deionized water 3 times, and place in a vacuum drying oven to dry at 40 °C for 12 h to obtain modified basalt fiber.

[0036] Example 2 A concrete block in this example is made from raw materials with the following masses: 2 kg of cement, 1.5 kg of fly ash, 2 kg of lime, 3.5 kg of sand, 1 kg of aluminum powder, 0.3 kg of composite filler, 0.4 kg of modified basalt fiber, 0.3 kg of nano-silica, 0.2 kg of water reducing agent, 0.2 kg of repair agent, and 4.8 kg of water.

[0037] The preparation method of a concrete block in this example is as follows: S1: Add 2 kg of cement, 1.5 kg of fly ash, 2 kg of lime, 3.5 kg of sand, 1 kg of aluminum powder, 0.3 kg of composite filler, 0.4 kg of modified basalt fiber, and 0.3 kg of nano-silica into a cement mixer, and stir at a speed of 100 r / min for 2 min to obtain a mixture. S2: Add 0.2 kg of water reducer, 0.2 kg of repair agent, and 4.8 kg of water to the mixture, and stir at a speed of 100 r / min for 3 min to obtain a mixed slurry. S3: Pour the mixed slurry into a mold, then place the mold on a vibrating table and vibrate for 2 min. Use a scraper to remove the excess slurry and air bubbles on the surface, and cure at room temperature for 1 d. After the curing is completed, remove the mold and cure for 28 d under the conditions of a temperature of 20°C and a humidity of 95% to obtain a concrete block.

[0038] The preparation method of the composite filler in this embodiment is as follows: (1) Add 0.1 kg of carbon nanotubes and 5 L of nitric acid with a concentration of 68% into a reaction kettle, stir for 5 min, heat up to 135°C and reflux for 15 h. After the reaction is completed, cool to room temperature, filter, wash with deionized water until neutral, and dry in a vacuum drying oven at 45°C for 12 h to obtain carboxyl-functionalized carbon nanotubes. (2) Add 0.1 kg of carboxyl-functionalized carbon nanotubes, 0.15 kg of graphene oxide, 20 L of absolute ethanol, and 5 L of water into a reaction kettle and ultrasonically disperse for 2 h. Adjust the pH to 10, add 0.03 L of silane coupling agent KH550 to the reaction kettle and ultrasonically disperse for 1 h. Continue to add 2 L of a mixed solution of tetraethyl orthosilicate and ethanol to the reaction kettle and ultrasonically disperse for 3 h to obtain a dispersion. React the dispersion at room temperature for 18 h, centrifuge, wash 3 times with deionized water, wash 3 times with absolute ethanol, wash with deionized water until neutral, and dry in a vacuum drying oven at 60°C for 12 h to obtain a mixture. The mixed solution of tetraethyl orthosilicate and ethanol is prepared by stirring 0.25 L of tetraethyl orthosilicate, 0.3 L of absolute ethanol, and 0.1 L of water in a reaction kettle for 10 min. (3) Add 0.1 kg of the mixture, 0.05 kg of cement, 0.5 L of absolute ethanol, and 6.5 L of water into a reaction kettle and ultrasonically disperse for 1 h, then transfer to a freeze dryer and freeze-dry for 36 h to obtain the composite filler.

[0039] The preparation method of the repair agent in this embodiment is as follows: Mix 3 kg of sodium hexametaphosphate, 0.8 kg of potassium nitrate, 1.5 kg of lithium phosphate, 2 kg of microcrystalline cellulose, 0.2 g of polyvinylpyrrolidone, and 3 kg of water in a blender for 30 min. Extrude it into strips through an extruder, granulate it in a spherical granulator, and dry it to obtain the core particles of the repair agent. Screen it, spray the coating liquid on the core particles of the repair agent with a particle size between 80 and 90 mesh, and dry it to obtain the repair agent. Screen it again, and add the repair agent with a particle size between 65 and 75 mesh to the concrete block. The coating liquid is prepared by stirring 1 kg of ethyl cellulose, 0.3 kg of polyethylene wax, 7 kg of acetone, and 1.5 kg of absolute ethanol in a reaction kettle for 30 min.

[0040] The preparation method of the modified basalt fiber in this example is as follows: Add 0.1 kg of basalt fiber, 3 L of silane coupling agent KH550, 0.6 L of acetic acid, and 2 L of water to a reaction kettle, adjust the pH to 7, ultrasonically disperse for 5 h, wash with deionized water 3 times, and dry in a vacuum drying oven at 40 °C for 12 h to obtain the modified basalt fiber.

[0041] Example 3 A concrete block in this example is made of the following raw materials by mass: 2.5 kg of cement, 1 kg of fly ash, 2.1 kg of lime, 2.5 kg of sand, 0.7 kg of aluminum powder, 0.3 kg of composite filler, 0.4 kg of modified basalt fiber, 0.4 kg of nano-silica, 0.1 kg of water reducing agent, 0.1 kg of repair agent, and 4 kg of water.

[0042] The preparation method of a concrete block in this example is as follows: S1: Add 2.5 kg of cement, 1 kg of fly ash, 2.1 kg of lime, 2.5 kg of sand, 0.7 kg of aluminum powder, 0.3 kg of composite filler, 0.4 kg of modified basalt fiber, and 0.4 kg of nano-silica to a cement mixer, and stir at a speed of 100 r / min for 2 min to obtain a mixture. S2: Add 0.1 kg of water reducing agent, 0.1 kg of repair agent, and 4 kg of water to the mixture, and stir at a speed of 100 r / min for 3 min to obtain a mixed slurry. S3: Pour the mixed slurry into a mold, then place the mold on a vibrating table and vibrate for 2 min. Use a spatula to remove the excess slurry and air bubbles on the surface, and cure at room temperature for 1 d. After curing, remove the mold and cure at a temperature of 20 °C and a humidity of 95% for 28 d to obtain the concrete block.

[0043] The preparation method of the composite filler in this example is as follows: (1) Add 0.1 kg of carbon nanotubes and 7 L of 68% nitric acid to a reaction kettle, stir for 5 min, heat up to 140 °C and reflux for 13 h. After the reaction, cool to room temperature, filter, wash with deionized water until neutral, and dry in a vacuum drying oven at 45 °C for 12 h to obtain carbon nanotubes with carboxyl groups. (2) Add 0.1 kg of carbon nanotubes with carboxyl groups, 0.2 kg of graphene oxide, 30 L of absolute ethanol and 3 L of water to a reaction kettle and ultrasonically disperse for 2 h; adjust the pH to 9, add 0.04 L of silane coupling agent KH550 to the reaction kettle and ultrasonically disperse for 1 h; continue to add 1.8 L of a mixed solution of tetraethyl orthosilicate and ethanol dropwise to the reaction kettle and ultrasonically disperse for 2.5 h to obtain a dispersion; react the dispersion at room temperature for 24 h, centrifuge, wash 3 times with deionized water, wash 3 times with absolute ethanol, wash with deionized water until neutral, and dry in a vacuum drying oven at 60 °C for 12 h to obtain a mixture; the mixed solution of tetraethyl orthosilicate and ethanol is prepared by stirring 0.3 L of tetraethyl orthosilicate, 0.4 L of absolute ethanol and 0.1 L of water in a reaction kettle for 10 min. (3) Add 0.1 kg of the mixture, 0.1 kg of cement, 0.7 L of absolute ethanol and 8 L of water to a reaction kettle, ultrasonically disperse for 1 h, transfer to a freeze dryer and freeze dry for 36 h to obtain a composite filler.

[0044] The preparation method of the repair agent in this example is as follows: Stir 2 kg of sodium hexametaphosphate, 0.4 kg of potassium nitrate, 1 kg of lithium phosphate, 1.5 kg of microcrystalline cellulose, 0.3 g of polyvinylpyrrolidone and 3 kg of water in a blender for 30 min, extrude into strips through an extruder, granulate in a spherical granulator, and dry to obtain repair agent core particles; sieve, spray coating liquid on the repair agent core particles with a particle size between 80 - 90 mesh, and dry to obtain a repair agent; sieve, take the repair agent with a particle size between 65 - 75 mesh and add it to concrete blocks; the coating liquid is prepared by stirring 1 kg of ethyl cellulose, 0.5 kg of polyethylene wax, 8 kg of acetone and 1.5 kg of absolute ethanol in a reaction kettle for 30 min.

[0045] The preparation method of the modified basalt fiber in this example is as follows: Add 0.1 kg of basalt fiber, 2 L of silane coupling agent KH550, 0.8 L of acetic acid and 2 L of water to a reaction kettle, adjust the pH to 6, ultrasonically disperse for 6 h, wash 3 times with deionized water, and dry in a vacuum drying oven at 40 °C for 12 h to obtain modified basalt fiber.

[0046] Example 4 A concrete block in this example is made of raw materials with the following masses: 2.3 kg of cement, 1.3 kg of fly ash, 2.5 kg of lime, 3 kg of sand, 0.9 kg of aluminum powder, 0.4 kg of composite filler, 0.6 kg of modified basalt fiber, 0.2 kg of nano-silica, 0.3 kg of water reducer, 0.2 kg of repair agent, 5 kg of water.

[0047] The preparation method of a kind of concrete block in this embodiment is as follows: S1: Add 2.3 kg of cement, 1.3 kg of fly ash, 2.5 kg of lime, 3 kg of sand, 0.9 kg of aluminum powder, 0.4 kg of composite filler, 0.6 kg of modified basalt fiber and 0.2 kg of nano-silica into a cement mixer, and stir at a speed of 100 r / min for 2 min to obtain a mixture; S2: Add 0.3 kg of water reducer, 0.2 kg of repair agent and 5 kg of water into the mixture, and stir at a speed of 100 r / min for 3 min to obtain a mixed slurry; S3: Pour the mixed slurry into a mold, then place the mold on a vibrating table and vibrate for 2 min. Use a scraper to remove the excess slurry and bubbles on the surface, and cure at room temperature for 1 d; After the curing is completed, remove the mold and cure at a temperature of 20 °C and a humidity of 95% for 28 d to obtain a concrete block.

[0048] The preparation method of the composite filler in this embodiment is as follows: (1) Add 0.1 kg of carbon nanotubes and 8 L of nitric acid with a concentration of 68% into a reaction kettle, stir for 5 min, heat up to 140 °C and reflux for 12 h. After the reaction is completed, cool to room temperature, filter, wash with deionized water until neutral, and place in a vacuum drying oven at 45 °C for 12 h to obtain carboxyl-functionalized carbon nanotubes; (2) Add 0.1 kg of carboxyl-functionalized carbon nanotubes, 0.18 kg of graphene oxide, 28 L of absolute ethanol and 4 L of water into a reaction kettle and ultrasonically disperse for 1.5 h; Adjust the pH to 9, add 0.04 L of silane coupling agent KH550 into the reaction kettle and ultrasonically disperse for 0.5 h; Continue to add 2.5 L of the mixed solution of tetraethyl orthosilicate and ethanol into the reaction kettle and ultrasonically disperse for 3 h to obtain a dispersion; React the dispersion at room temperature for 20 h, centrifuge, wash 3 times with deionized water, wash 3 times with absolute ethanol, wash with deionized water until neutral, and place in a vacuum drying oven at 60 °C for 12 h to obtain a mixture; The mixed solution of tetraethyl orthosilicate and ethanol is prepared by stirring 0.28 L of tetraethyl orthosilicate, 0.4 L of absolute ethanol and 0.1 L of water in a reaction kettle for 10 min; (3) Add 0.1 kg of the mixture, 0.08 kg of cement, 0.5 L of absolute ethanol and 8 L of water into a reaction kettle and ultrasonically disperse for 0.5 h, then transfer to a freeze dryer and freeze dry for 36 h to obtain a composite filler.

[0049] The preparation method of the repair agent in this embodiment is as follows: Mix 3 kg of sodium hexametaphosphate, 0.4 kg of potassium nitrate, 1.5 kg of lithium phosphate, 2 kg of microcrystalline cellulose, 0.4 g of polyvinylpyrrolidone, and 4 kg of water in a blender for 30 min, extrude it into strips through an extruder, granulate it in a spherical granulator, and dry it to obtain the core particles of the repair agent; sieve it, spray the coating liquid on the core particles of the repair agent with a particle size between 80 and 90 mesh, and dry it to obtain the repair agent; sieve it, and add the repair agent with a particle size between 65 and 75 mesh to the concrete block; the coating liquid is prepared by stirring 1 kg of ethyl cellulose, 0.4 kg of polyethylene wax, 7 kg of acetone, and 2 kg of absolute ethanol in a reaction kettle for 30 min.

[0050] The preparation method of the modified basalt fiber in this embodiment is as follows: Add 0.1 kg of basalt fiber, 3 L of silane coupling agent KH550, 1 L of acetic acid, and 3 L of water to a reaction kettle, adjust the pH to 6, ultrasonically disperse for 6 h, wash with deionized water 3 times, and dry in a vacuum drying oven at 40 °C for 12 h to obtain the modified basalt fiber.

[0051] Comparative Example 1 The difference from Example 1 is that no composite filler is added to the concrete block in this comparative example, and the rest are the same as in Example 1.

[0052] Comparative Example 2 The difference from Example 1 is that no repair agent is added to the concrete block in this comparative example, and the rest are the same as in Example 1.

[0053] Comparative Example 3 The difference from Example 1 is that in the raw materials of the concrete block in this comparative example, 0.2 kg of carbon nanotubes and 0.3 kg of graphene oxide are used to replace 0.5 kg of the composite filler, and the rest are the same as in Example 1.

[0054] Comparative Example 4 The difference from Example 1 is that in the raw materials of the concrete block in this comparative example, an equal amount of basalt fiber is used to replace an equal amount of the modified basalt fiber, and the rest are the same as in Example 1.

[0055] Comparative Example 5 The difference from Example 1 is that in the components of the repair agent in this comparative example, 0.3 kg of sodium hexametaphosphate, 1.2 kg of potassium nitrate, and 0.4 kg of lithium phosphate are used to replace 2 kg of sodium hexametaphosphate, 0.6 kg of potassium nitrate, and 1.2 kg of lithium phosphate, and the rest are the same as in Example 1.

[0056] Comparative Example 6 The difference from Example 1 is that the concrete block in this comparative example is made of raw materials with the following masses, and the rest are the same as in Example 1: 1.8 kg of cement, 0.9 kg of fly ash, 2.3 kg of lime, 3 kg of sand, 1.3 kg of aluminum powder, 0.1 kg of composite filler, 1.6 kg of modified basalt fiber, 0.7 kg of nano-silica, 0.2 kg of water reducer, 0.3 kg of repair agent, 4.5 kg of water.

[0057] Comparative Example 7 The difference from Example 1 is that the concrete block in this comparative example is made of raw materials with the following masses, and the rest are the same as in Example 1: 1.2 kg of cement, 1.2 kg of fly ash, 2.7 kg of lime, 3 kg of sand, 0.8 kg of aluminum powder, 2 kg of composite filler, 0.1 kg of modified basalt fiber, 3 kg of nano-silica, 0.2 kg of water reducer, 0.01 kg of repair agent, 4.5 kg of water.

[0058] Relevant performance tests Perform relevant performance tests on the concrete blocks prepared in the above Examples 1 - 4 and Comparative Examples 1 - 7. According to GB / T 4111 - 2013 "Test Methods for Concrete Blocks and Bricks", detect the compressive strength of the above concrete blocks, and the test results are shown in Table 1.

[0059] Table 1 Test Results

[0060] It can be seen from the comparison between Comparative Example 1 and Example 1 that the addition of the composite filler can improve the compressive performance of the concrete block.

[0061] It can be seen from the comparison between Comparative Example 2 and Example 1 that the repair agent has a great influence on the concrete block. The repair agent can slowly repair the microcracks inside the concrete block during the curing process and improve the mechanical properties of the concrete block.

[0062] It can be seen from the comparison between Comparative Example 3 and Example 1 that directly adding carbon nanotubes and graphene oxide into the concrete block is likely to result in uneven mixing, poor bonding force with substances such as cement, and easy occurrence of local overreaction or underreaction, leading to a decrease in the performance of the concrete block. The bonding performance between the composite filler of the present invention and materials such as cement in the concrete block is high, and the performance of the concrete block is good.

[0063] It can be seen from the comparison between Comparative Example 4 and Example 1 that when basalt fiber is added to the concrete block without modification, the bonding force between the basalt fiber and the concrete block is poor, and cracks are likely to occur in the interfacial transition zone, reducing the performance of the concrete block.

[0064] It can be seen from the comparison between Comparative Example 5 and Example 1 that the ratio of the three active substances, sodium hexametaphosphate, potassium nitrate, and lithium phosphate, in the repair agent has reached the optimum, and the adjustment of the content of any one component will affect the performance of the concrete block.

[0065] It can be seen from the comparison between Comparative Example 6 and Comparative Example 7 and Example 1 that Comparative Example 6 and Comparative Example 7 adjusted the component content in the concrete block, but the performance of the concrete block decreased, proving that the component ratio of the concrete block in the present invention has reached the optimum.

[0066] The above provides an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent substitution that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A concrete block, characterized in that: Made from the following raw materials in parts by weight: 18-25 parts of cement, 10-15 parts of fly ash, 20-25 parts of lime, 25-35 parts of sand, 7-10 parts of aluminum powder, 3-5 parts of composite filler, 4-6 parts of modified basalt fiber, 2-4 parts of nano-silicon dioxide, 1-3 parts of water reducer, 1-3 parts of repair agent, and 40-50 parts of water.

2. A concrete block according to claim 1, characterized in that: The preparation method of the composite filler comprises the following steps: (1) mixing carbon nanotubes and nitric acid uniformly, heating and refluxing, cooling, filtering, washing, and drying to obtain carbon nanotubes with carboxyl groups; (2) Ultrasonic dispersion of carbon nanotubes with carboxyl groups, graphene oxide, anhydrous ethanol and water for 1.5-2 hours; adjusting the pH to 9-10, adding a silane coupling agent and ultrasonically dispersing for 0.5-1 hour; adding a mixture of ethyl orthosilicate and ethanol and ultrasonically dispersing for 2-3 hours to obtain a dispersion; reacting the dispersion, centrifuging, washing and drying to obtain a mixture; (3) Ultrasonic dispersion of the mixture, cement, anhydrous ethanol and water for 0.5-1h, and freeze-drying to obtain a composite filler.

3. A concrete block according to claim 2, characterized in that: In the step (1), the concentration of nitric acid is 68%, the ratio of carbon nanotubes to nitric acid is 1 g: (50-80) mL; the reaction temperature is 130-140° C., and the reaction time is 12-15 h.

4. A concrete block according to claim 2, characterized in that: In the step (2), the amount ratio of the carbon nanotubes with carboxyl groups, graphene oxide, anhydrous ethanol and water is 1g: (1-2)g: (200-300)mL: (30-50)mL; the amount ratio of the carbon nanotubes with carboxyl groups, the silane coupling agent and the mixed solution of tetraethyl orthosilicate and ethanol is 1g: (0.3-0.5)mL: (15-25)mL; the mixed solution of tetraethyl orthosilicate and ethanol is prepared by tetraethyl orthosilicate, anhydrous ethanol and water in a volume ratio of (2-3): (2-4): 1; and the reaction time is 18-24h.

5. A concrete block according to claim 2, characterized in that: In the step (3), the ratio of the mixture, cement, anhydrous ethanol and water is 1 g: (0.5-1) g: (5-8) mL: (65-80) mL.

6. A concrete block according to claim 1, characterized in that: The preparation method of the repair agent is as follows: The repair agent core material is granulated to obtain repair agent core material particles; the particles are sieved, and the coating liquid is sprayed on the repair agent core material particles with a particle size of 80-90 meshes, and the particles are dried to obtain the repair agent.

7. A concrete block according to claim 6, characterized in that: The repair agent core material is composed of the following components in parts by mass: 20-30 parts of sodium hexametaphosphate, 4-8 parts of potassium nitrate, 10-15 parts of lithium phosphate, 15-20 parts of microcrystalline cellulose, 1-4 parts of polyvinyl pyrrolidone, and 30-40 parts of water.

8. A concrete block according to claim 6, characterized in that: The coating liquid is prepared from ethyl cellulose, polyethylene wax, acetone and anhydrous ethanol according to a mass ratio of 1: (0.2-0.5): (7-8): (1.5-2).

9. The concrete block according to claim 1, characterized in that: The preparation method of the modified basalt fiber comprises the following steps: The basalt fiber, silane coupling agent, acetic acid and water are mixed uniformly according to the dosage ratio of 1g: (20-30) mL: (5-10) mL: (20-30) mL, the pH is adjusted to 6-7, ultrasonically dispersed for 4-6 hours, washed and dried to obtain modified basalt fiber.

10. A method for preparing a concrete block according to any one of claims 1 to 9, characterized in that: The steps include: S1: mixing cement, fly ash, lime, sand, aluminum powder, composite filler, modified basalt fiber and nano-silicon dioxide uniformly to obtain a mixture; S2: adding a water reducing agent, a repairing agent and water to the mixture and mixing them evenly to obtain a mixed slurry; S3: pouring and curing the mixed slurry to obtain concrete blocks.

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