High-strength self-compacting micro-expansive concrete and preparation method thereof

Abstract

The invention relates to the field of concrete, and particularly discloses high-strength self-compacting micro-expansive concrete and a preparation method thereof. The high-strength self-compacting micro-expansive concrete is prepared from the following raw materials in parts by weight: 240 to 270 parts of cement, 580 to 700 parts of sand, 800 to 900 parts of gravel, 50 to 70 parts of fly ash, 40 to 60 parts of mineral powder, 16 to 24 parts of a composite expanding agent, 7.2 to 8.8 parts of an additive, 24 to 30 parts of composite fiber, 30 to 40 parts of composite filler and 130 to 140 parts of water, the composite expanding agent is prepared from calcium sulphoaluminate loading material cetostearyl alcohol, polycaprolactone glycol coated calcium oxide and loading material magnesium oxide according to the mass ratio of 1: (0.8 to 1.2): (0.2 to 0.3); the preparation method comprises the following steps: mixing raw materials, pouring and curing to obtain a finished product. The concrete has the advantages of being good in self-compaction performance, few in cracks and high in strength.

Description

Technical Field

[0001] This application relates to the field of concrete, and more specifically, to a high-strength self-compacting micro-expansion concrete and its preparation method. Background Technology

[0002] Micro-expansion concrete refers to ordinary concrete with the addition of a certain amount of expansive agent, which allows the concrete to expand to a certain extent during long-term hydration due to the action of the expansive agent, thereby compensating for the shrinkage of the concrete, preventing concrete cracks, and improving the performance of the concrete.

[0003] When preparing concrete for high-rise buildings, basement construction, and long-span bridges, it is generally necessary to have high strength and good density to achieve good impermeability and a long service life.

[0004] In bridge construction, self-compacting concrete has a high bond strength with steel reinforcement and can fully fill the formwork space without vibration, accelerating the rapid processing of bridge concrete. However, due to its good fluidity, self-compacting concrete has a high shrinkage rate. Under the condition of rapid increase in the heat of hydration of large-volume concrete, the expansion agent is prone to abnormal expansion. Furthermore, the expansion agent is also easily affected by temperature and humidity, which can lead to a decrease in the expansion effect. This can easily result in problems such as excessive expansion causing cracks or insufficient expansion failing to compensate for the shrinkage cracks in large-volume concrete. The presence of cracks can easily affect the strength and service life of concrete.

[0005] Therefore, how to prepare a type of concrete that simultaneously possesses good self-compacting properties, few cracks, and high strength for use in large-volume concrete components is an urgent problem to be solved. Summary of the Invention

[0006] In order to prepare a type of concrete that simultaneously possesses good self-compacting properties, few cracks, and high strength for use in large-volume concrete components, this application provides a high-strength self-compacting micro-expansion concrete and its preparation method.

[0007] Firstly, this application provides a high-strength self-compacting micro-expansion concrete, employing the following technical solution: A high-strength self-compacting micro-expansion concrete comprises the following raw materials in parts by weight: 240-270 parts cement, 580-700 parts sand, 800-900 parts crushed stone, 50-70 parts fly ash, 40-60 parts mineral powder, 16-24 parts composite expansion agent, 7.2-8.8 parts admixture, 24-30 parts composite fiber, 30-40 parts composite filler, and 130-140 parts water; the composite expansion agent is composed of calcium sulfoaluminate carrier cetearyl alcohol, polycaprolactone-coated calcium oxide, and carrier magnesium oxide in a mass ratio of 1:0.8-1.2:0.2-0.3.

[0008] By adopting the above technical solutions and limiting the amount of cement, sand, crushed stone, fly ash, mineral powder, and water added, the concrete has the advantages of self-compacting and high strength. Combined with the micro-expansion filling effect of the composite expansion agent, it fills the internal structural cracks of the concrete, thereby reducing the number of cracks in the concrete. Combined with the connection and filling effect of composite fibers and composite fillers, the connection bridge of composite fibers and the filling of composite fillers further improve the internal structural density of the concrete, thus making the self-compacting concrete have the advantages of high strength and fewer cracks.

[0009] The calcium sulfoaluminate carrier cetearyl alcohol, polycaprolactone-coated calcium oxide, and magnesium oxide carrier work together. The lubricating and barrier effects of the film formed by cetearyl alcohol and polycaprolactone-coated calcium oxide can prevent calcium sulfoaluminate and calcium oxide from being affected by the ambient temperature and humidity, ensuring the expansion effect of the expansion agent and the fluidity of the concrete during the mixing process, thereby ensuring its pumpability and self-compacting characteristics.

[0010] As the concrete hydration reaction proceeds, the calcium sulfoaluminate carrier, cetearyl alcohol, gradually undergoes micro-expansion. At locations coated with cetearyl alcohol, the expansion efficiency of calcium sulfoaluminate is slowed, preventing the rapid expansion of calcium sulfoaluminate due to the high heat of hydration in large-volume bridge concrete, which would increase internal cracks. Where cetearyl alcohol is not adhered, calcium sulfoaluminate gradually expands upon contact with water, forming ettringite. The barrier effect of cetearyl alcohol buffers internal expansion stress, preventing excessive growth of ettringite in large-volume concrete and the formation of micro-cracks. As the temperature gradually increases during hydration heat generation and ettringite formation, cetearyl alcohol gradually melts and becomes fluid. This fluidity both prevents excessive expansion of ettringite and fills internal micro-cracks in the concrete, thereby increasing the structural density of the concrete and giving it the advantages of high strength and fewer cracks.

[0011] Since cetearyl alcohol has a melting point of 48-50℃, while polycaprolactone (PVC) has a melting point of 59-64℃, the cetearyl alcohol, as a carrier of calcium sulfoaluminate, ensures that it plays an expansion and filling role in the early stage. As the hydration reaction proceeds, the temperature gradually increases. When the hydration temperature of the large-volume concrete reaches the melting point of PVC, PVC gradually melts. Calcium oxide reacts with some of the water in the concrete to generate calcium hydroxide, which expands and fills the cracks generated in the middle stage of concrete hydration. Combined with the exothermic effect of calcium hydroxide, this further promotes the hot melt flow and distribution of surrounding PVC around the calcium hydroxide expansion particles, filling the micro-gaps. This further improves the internal density of the concrete structure, giving the concrete the advantages of high strength and fewer cracks.

[0012] In the later stages of hydration, the magnesium oxide material gradually undergoes micro-expansion, further filling the micro-cracks inside the concrete, thereby improving the structural density of the concrete and giving it the advantages of high strength and fewer cracks.

[0013] Preferably, the calcium sulfoaluminate carrier cetearyl alcohol is prepared from a calcium sulfoaluminate-loaded cetearyl alcohol solution and tartaric acid microparticles in a mass ratio of 1:0.2-0.5:0.1-0.2.

[0014] By adopting the above technical solution, tartaric acid microparticles are loaded onto the surface of calcium sulfoaluminate after being bonded with cetearyl alcohol solution. The carboxyl groups in the tartaric acid microparticles can form complexes with the cementitious materials, delaying the rapid expansion of calcium sulfoaluminate in large-volume concrete due to high hydration temperatures. This allows the cetearyl alcohol carrier of calcium sulfoaluminate to expand and fill gaps without easily causing micro-cracks due to excessive stress. Furthermore, the carboxyl groups in tartaric acid, combined with the hydroxyl groups in cetearyl alcohol, can form a network with the cementitious materials, inhibiting the excessive growth of ettringite and promoting its filling effect at multiple directional sites. This reduces the risk of local stress concentration and ensures that cracks are not easily generated inside the concrete. At the same time, the bonding effect of tartaric acid and cetearyl alcohol with the concrete cementitious materials further improves the density and strength of the concrete.

[0015] Preferably, the polycaprolactone-coated calcium oxide is prepared by loading a polycaprolactone solution with calcium oxide in a mass ratio of 1:0.9-1.2:0.1-0.2 and then bonding it with molecular sieve microparticles.

[0016] By adopting the above technical solution, molecular sieve particles are adhered to the surface of calcium oxide after being bonded with polycaprolactone glycol solution. First, the barrier effect of molecular sieve particles and polycaprolactone glycol is used to delay the hydration reaction, thereby preventing the calcium oxide from expanding too quickly in large-volume concrete. Furthermore, since large-volume concrete has a high hydration problem, the porous barrier effect of molecular sieve particles and the heat adsorbed by the thermal melt of polycaprolactone glycol are used to further regulate the heat generated by the reaction between calcium oxide and water and the heat of hydration, preventing excessive temperature from causing cracks inside the concrete. At the same time, the barrier effect of molecular sieve particles is used to refine the expansion size of calcium hydroxide, and the flow of polycaprolactone glycol solution fills the contact gaps between calcium hydroxide and cementitious materials, crushed stone, and sand, further improving the density of the concrete structure. As a result, the concrete has the advantages of high strength and fewer cracks.

[0017] Preferably, the magnesium oxide loading is prepared by loading a polyvinyl alcohol-1788 solution with magnesium oxide at a mass ratio of 1:0.2-0.3.

[0018] By adopting the above technical solution, magnesium oxide reacts with water slowly and gradually undergoes micro-expansion in the later stage of hydration. The film layer formed by polyvinyl alcohol-1788 can absorb part of the heat of hydration, reduce the local temperature rise, and minimize the decomposition of ettringite while delaying the premature expansion of magnesium oxide in large-volume concrete, resulting in better expansion effect in 14-28 days. Furthermore, the barrier effect of polyvinyl alcohol-1788 can disperse the expansion stress of magnesium hydroxide crystallization and refine the crystal size to the micro-nano scale, thereby further filling the micro-gaps in the later stage. At the same time, the bonding effect of the hydroxyl groups in polyvinyl alcohol-1788 with cementitious materials and other materials can further improve the crack resistance, impermeability and freeze-thaw resistance of concrete.

[0019] Preferably, the composite fiber is prepared from fiber material, rosin pentaerythritol ester solution and N-isopropylacrylamide in a mass ratio of 1:0.1-0.25:0.05-0.15.

[0020] By adopting the above technical solution, the fiber material, rosin pentaerythritol ester solution and N-isopropylacrylamide are combined. The viscosity of the rosin pentaerythritol ester solution makes it easy to adhere N-isopropylacrylamide crystals to the surface of the fiber material.

[0021] During concrete mixing, when the water temperature is below 32℃, the hydrophilic N-isopropylacrylamide combined with the friction-reducing effect of rosin pentaerythritol ester allows the composite fibers to have good fluidity and dispersion in the concrete, making them less prone to agglomeration. During the self-compacting process of concrete, the composite fibers are evenly dispersed and tightly filled.

[0022] During the hydration process of concrete, as the hydration level increases, N-isopropylacrylamide gradually becomes insoluble in water above 32°C, thus playing a filling and swelling role. The carboxyl groups in pentaerythritol rosin and the amide groups in N-isopropylacrylamide are further used to connect with the composite expansive material and cementitious materials, improving the bonding effect of fiber materials with other raw materials in concrete, thereby improving the structural density of concrete. Combined with the strength of fiber materials, this gives the concrete better strength.

[0023] Preferably, the fiber material is composed of hooked steel fibers and polypropylene fibers in a mass ratio of 1:0.2-0.5.

[0024] By adopting the above technical solution, the hook-shaped steel fiber can form a good anchoring effect in concrete with the hook shape at its end, enhance the bonding force between the fiber and the concrete matrix, and thus effectively prevent the generation and propagation of concrete cracks. Combined with the high toughness and good ductility of polypropylene fiber, it can effectively absorb and disperse the energy generated by concrete during the stress process, reduce the generation of cracks, and make the concrete have the advantages of high strength and fewer cracks.

[0025] Preferably, the composite filler is prepared by mixing silica microspheres, silica microparticles and organosilicon microspheres in a mass ratio of 1:0.4-0.6:0.1-0.3 after being treated with silane coupling agent KH-570.

[0026] By adopting the above technical solution, the silane coupling agent KH-570 can hydrophobically treat silica microspheres, silica particles and organosilicon microspheres, ensuring that the composite filler is not easily absorbed by mixing water and is not easily affected by moisture and humidity in the external environment, thereby ensuring the strength and durability of concrete.

[0027] Preferably, the silica microspheres have an average particle size of 80-200 nm, the silica microparticles have an average particle size of 2-6 μm, and the organosilicon microspheres have an average particle size of 10-15 μm.

[0028] By adopting the above technical solution, the particle sizes of silica microspheres, silica microparticles, and organosilicon microspheres are limited. The nano-sized silica microspheres fill the pores between cement particles; the silica microparticles fill the pores between mortar and crushed stone, and can also fix free calcium ions; the organosilicon microspheres play an elastic buffering role, not only buffering expansion and contraction stress, but also reducing the frictional resistance between aggregates and ensuring the fluidity of concrete. By utilizing the filling of the three, the concrete has the advantages of fewer cracks and higher strength.

[0029] Preferably, the admixture is composed of a polycarboxylate superplasticizer and an air-entraining agent in a mass ratio of 10:0.5-1.

[0030] By adopting the above technical solution, polycarboxylate superplasticizer and air-entraining agent are combined. Polycarboxylate superplasticizer can effectively improve the fluidity of concrete while reducing the water-cement ratio and ensuring the density of concrete. Combined with the filling effect of air-entraining agent, it further reduces the generation of cracks, giving the concrete the advantages of high strength and fewer cracks.

[0031] Secondly, this application provides a method for preparing high-strength self-compacting micro-expansion concrete, employing the following technical solution: A method for preparing high-strength self-compacting micro-expansion concrete includes the following steps: S1. Mix cement, fly ash, and mineral powder evenly, then add sand and crushed stone and mix evenly to obtain the initial mixture; S2. Add composite expanding agent, composite fiber and composite filler to the initial mixture and mix evenly. Then add water and admixtures and mix evenly to obtain the mixture. S3. The mixture is poured and cured to obtain finished concrete.

[0032] By adopting the above technical solutions, concrete can be used in the preparation of large-volume bridges and large-volume buildings, and has the advantages of self-compacting, high strength and few cracks.

[0033] In summary, this application has the following beneficial effects: 1. The addition of cement, sand, crushed stone, fly ash, mineral powder, and water gives the concrete the advantages of self-compacting and high strength. Combined with the micro-expansion filling effect of the composite expansion agent, it fills the internal structural cracks of the concrete, thereby reducing the number of cracks in the concrete. Combined with the connection and filling effect of composite fibers and composite fillers, the composite fiber connecting bridge, combined with the filling of composite fillers, further improves the internal structural density of the concrete, thus giving self-compacting concrete the advantages of high strength and fewer cracks.

[0034] 2. The combination of calcium oxide, polycaprolactone glycol solution, and molecular sieve particles ensures the fluidity of the polycaprolactone-coated calcium oxide in concrete, as polycaprolactone glycol is not easily soluble in water. This satisfies the advantages of self-compacting concrete while controlling its expansion effect in large-volume concrete. Combined with the stress buffering effect of molecular sieves and the flow and filling properties of polycaprolactone glycol after hot melting, self-compacting concrete has the advantages of high strength and fewer cracks.

[0035] 3. The combination of calcium sulfoaluminate carrier cetearyl alcohol, polycaprolactone-coated calcium oxide, and carrier magnesium oxide, during the filling process of concrete, utilizes the hydroxyl and carboxyl groups on the surface of calcium sulfoaluminate, the hydroxyl groups on the surface of calcium oxide, and the hydroxyl groups on the surface of magnesium oxide to create a bonding effect with the cementitious materials. Furthermore, the calcium sulfoaluminate carrier cetearyl alcohol, polycaprolactone-coated calcium oxide, and carrier magnesium oxide, which are in contact with each other, can also connect with each other, further improving the internal density of the concrete structure, giving the concrete the advantages of high strength and fewer cracks.

[0036] 4. Under the rapid hydration and heat generation conditions of large-volume concrete, substances such as cetearyl alcohol and polycaprolactone diol are used to micro-barrier calcium sulfoaluminate, calcium oxide, and other substances, thereby slowing down the expansion rate and balancing the expansion speed at high temperatures, making the concrete less prone to excessive cracking and thus ensuring the strength of the concrete. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments.

[0038] Preparation example of composite expanding agent All of the following ingredients are commercially available.

[0039] Preparation Example 1: The composite expanding agent was prepared using the following method: 0.35 kg of cetearyl alcohol solution was uniformly sprayed onto the surface of 1 kg of calcium sulfoaluminate. The average particle size of the calcium sulfoaluminate was 50 μm. The cetearyl alcohol solution was a 5% (w / w) cetearyl alcohol ethanol solution. Then, 0.15 kg of tartaric acid microparticles with an average particle size of 5 μm were added at a rate of 100 g / min. During the addition process, the calcium sulfoaluminate was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain calcium sulfoaluminate carrier cetearyl alcohol. The calcium sulfoaluminate carrier cetearyl alcohol was then passed through a 200-mesh sieve. 1.05 kg of polycaprolactone glycol solution was uniformly sprayed onto the surface of 1 kg of calcium oxide. The average particle size of the calcium oxide was 40 μm. The polycaprolactone glycol solution was a 3% (w / w) polycaprolactone glycol ethanol solution. Then, 0.15 kg of molecular sieve microparticles with an average particle size of 3 μm were added at a rate of 100 g / min. During the addition process, the calcium oxide was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain polycaprolactone glycol-coated calcium oxide. The polycaprolactone glycol-coated calcium oxide passed through a 250-mesh sieve. 0.25 kg of polyvinyl alcohol-1788 solution was uniformly sprayed onto the surface of 1 kg of magnesium oxide. The polyvinyl alcohol-1788 solution was a 1% (w / w) aqueous solution of polyvinyl alcohol-1788. After drying and dispersion, the loaded magnesium oxide was obtained. The loaded magnesium oxide was then passed through a 400-mesh sieve. Weigh 1 kg of calcium sulfoaluminate carrier cetearyl alcohol, 1 kg of polycaprolactone-coated calcium oxide and 0.25 kg of carrier magnesium oxide and mix them for later use to obtain a composite expansion agent.

[0040] Preparation Example 2: The difference between this preparation example and Preparation Example 1 is that: 0.2 kg of cetearyl alcohol solution was uniformly sprayed onto the surface of 1 kg of calcium sulfoaluminate. The average particle size of the calcium sulfoaluminate was 50 μm. The cetearyl alcohol solution was a 5% (w / w) cetearyl alcohol ethanol solution. Then, 0.1 kg of tartaric acid microparticles with an average particle size of 5 μm were added at a rate of 100 g / min. During the addition process, the calcium sulfoaluminate was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain calcium sulfoaluminate carrier cetearyl alcohol. The calcium sulfoaluminate carrier cetearyl alcohol was then passed through a 200-mesh sieve. 0.9 kg of polycaprolactone glycol solution was uniformly sprayed onto the surface of 1 kg of calcium oxide. The average particle size of the calcium oxide was 40 μm. The polycaprolactone glycol solution was a 3% (w / w) polycaprolactone glycol ethanol solution. Then, 0.1 kg of molecular sieve microparticles with an average particle size of 3 μm were added at a rate of 100 g / min. During the addition process, the calcium oxide was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain polycaprolactone glycol-coated calcium oxide. The polycaprolactone glycol-coated calcium oxide passed through a 250-mesh sieve. 0.2 kg of polyvinyl alcohol-1788 solution was uniformly sprayed onto the surface of 1 kg of magnesium oxide. The polyvinyl alcohol-1788 solution was a 1% (w / w) aqueous solution of polyvinyl alcohol-1788. After drying and dispersion, the loaded magnesium oxide was obtained. The loaded magnesium oxide was then passed through a 400-mesh sieve. Weigh out 1 kg of calcium sulfoaluminate carrier cetearyl alcohol, 0.8 kg of polycaprolactone-coated calcium oxide and 0.2 kg of carrier magnesium oxide and mix them for later use to obtain a composite expansion agent.

[0041] Preparation Example 3: The difference between this preparation example and Preparation Example 1 is that: 0.5 kg of cetearyl alcohol solution was uniformly sprayed onto the surface of 1 kg of calcium sulfoaluminate. The average particle size of the calcium sulfoaluminate was 50 μm. The cetearyl alcohol solution was a 5% (w / w) cetearyl alcohol ethanol solution. Then, 0.2 kg of tartaric acid microparticles with an average particle size of 5 μm were added at a rate of 100 g / min. During the addition process, the calcium sulfoaluminate was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain calcium sulfoaluminate carrier cetearyl alcohol. The calcium sulfoaluminate carrier cetearyl alcohol was then passed through a 200-mesh sieve. 1.2 kg of polycaprolactone glycol solution was uniformly sprayed onto the surface of 1 kg of calcium oxide. The average particle size of the calcium oxide was 40 μm. The polycaprolactone glycol solution was a 3% (w / w) polycaprolactone glycol ethanol solution. Then, 0.2 kg of molecular sieve microparticles with an average particle size of 3 μm were added at a rate of 100 g / min. During the addition process, the calcium oxide was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed to obtain polycaprolactone glycol-coated calcium oxide. The polycaprolactone glycol-coated calcium oxide passed through a 250-mesh sieve. 0.3 kg of polyvinyl alcohol-1788 solution was uniformly sprayed onto the surface of 1 kg of magnesium oxide. The polyvinyl alcohol-1788 solution was a 1% (w / w) aqueous solution of polyvinyl alcohol-1788. After drying and dispersion, the loaded magnesium oxide was obtained. The loaded magnesium oxide was then passed through a 400-mesh sieve. Weigh out 1 kg of calcium sulfoaluminate carrier cetearyl alcohol, 1.2 kg of polycaprolactone diol-coated calcium oxide and 0.3 kg of carrier magnesium oxide and mix them for later use to obtain a composite expansion agent.

[0042] Example of composite fiber preparation N-Isopropylacrylamide was purchased from Shandong Xinghai Chemical Co., Ltd.; the other raw materials were all commercially available.

[0043] Preparation Example 4: Composite fibers were prepared using the following method: Weigh 1 kg of hook-shaped steel fiber and 0.4 kg of polypropylene fiber, mix and stir evenly to obtain fiber material; the average length of the hook-shaped steel fiber is 30 mm, and the average length of the polypropylene fiber is 30 mm. A 0.2 kg solution of pentaerythritol rosin was uniformly sprayed onto the surface of 1 kg of fiber material. The pentaerythritol rosin solution was 1% by mass, and the solvent was ethyl acetate. Then, 0.1 kg of N-isopropylacrylamide was added. The average particle size of N-isopropylacrylamide was 20 μm, and the addition rate was 100 g / min. During the addition process, the fiber material was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed until the fibers did not stick together or agglomerate, thus obtaining composite fiber.

[0044] Preparation Example 5: The difference between this preparation example and Preparation Example 4 is that: Weigh 1 kg of hook-shaped steel fiber and 0.2 kg of polypropylene fiber, mix and stir evenly to obtain fiber material; the average length of the hook-shaped steel fiber is 30 mm, and the average length of the polypropylene fiber is 30 mm. A 0.1 kg solution of pentaerythritol rosin was uniformly sprayed onto the surface of 1 kg of fiber material. The pentaerythritol rosin solution was 1% by mass, and the solvent was ethyl acetate. Then, 0.05 kg of N-isopropylacrylamide was added. The average particle size of N-isopropylacrylamide was 20 μm, and the addition rate was 100 g / min. During the addition process, the fiber material was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed until the fibers did not stick together or agglomerate, thus obtaining composite fiber.

[0045] Preparation Example 6: The difference between this preparation example and Preparation Example 4 is that: Weigh 1 kg of hook-shaped steel fiber and 0.5 kg of polypropylene fiber, mix and stir evenly to obtain fiber material; the average length of the hook-shaped steel fiber is 30 mm, and the average length of the polypropylene fiber is 30 mm. 0.25 kg of pentaerythritol rosin solution was uniformly sprayed onto the surface of 1 kg of fiber material. The pentaerythritol rosin solution was 1% by mass and the solvent was ethyl acetate. Then, 0.15 kg of N-isopropylacrylamide was added. The average particle size of N-isopropylacrylamide was 20 μm. The addition rate was 100 g / min. During the addition process, the fiber material was continuously stirred at a speed of 120 r / min. After uniform mixing, the mixture was dried and dispersed until the fibers did not stick together or agglomerate, thus obtaining composite fiber.

[0046] Preparation example of composite fillers The organosilicon microparticles in the following raw materials were purchased from Shanghai Huiyan New Materials Co., Ltd.; the other raw materials are all commercially available.

[0047] Preparation Example 7: The composite filler was prepared using the following method: 1 kg of silica microspheres were immersed and dispersed in 10 kg of silane coupling agent KH-570. The average particle size of the silica microspheres was 100 nm. Then the silica microspheres were separated, dried, and dispersed until they did not stick together or agglomerate, to obtain treated material A. 0.5 kg of silica particles were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the silica particles was 4 μm. Then the silica particles were separated, dried, and dispersed until the silica particles did not stick together or agglomerate, to obtain processed material B. 0.2 kg of organosilicon microspheres were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the organosilicon microspheres was 12 μm. The organosilicon microspheres were then separated, dried, and dispersed until they did not stick together or agglomerate, thus obtaining the treated material C. The composite filler is obtained by mixing treatment material A, treatment material B, and treatment material C.

[0048] Preparation Example 8: The difference between this preparation example and Preparation Example 7 is that: 1 kg of silica microspheres were immersed and dispersed in 10 kg of silane coupling agent KH-570. The average particle size of the silica microspheres was 80 nm. Then the silica microspheres were separated, dried and dispersed until they did not stick together or agglomerate, to obtain treated material A. 0.4 kg of silica particles were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the silica particles was 2 μm. Then the silica particles were separated, dried and dispersed until the silica particles did not stick together and agglomerate, to obtain treated material B. 0.1 kg of organosilicon microspheres were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the organosilicon microspheres was 10 μm. The organosilicon microspheres were then separated, dried, and dispersed until they did not stick together or agglomerate, thus obtaining the treated material C. The composite filler is obtained by mixing treatment material A, treatment material B, and treatment material C.

[0049] Preparation Example 9: The difference between this preparation example and Preparation Example 7 is that: 1 kg of silica microspheres were immersed and dispersed in 10 kg of silane coupling agent KH-570. The average particle size of the silica microspheres was 200 nm. Then the silica microspheres were separated, dried and dispersed until they did not stick together and agglomerate, to obtain treated material A. 0.6 kg of silica particles were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the silica particles was 6 μm. The silica particles were then separated, dried, and dispersed until they did not stick together or agglomerate, thus obtaining processed material B. 0.3 kg of organosilicon microspheres were immersed and dispersed in 5 kg of silane coupling agent KH-570. The average particle size of the organosilicon microspheres was 15 μm. The organosilicon microspheres were then separated, dried, and dispersed until they did not stick together or agglomerate, thus obtaining the treated material C. The composite filler is obtained by mixing treatment material A, treatment material B, and treatment material C. Example

[0050] The polycarboxylate superplasticizer in the following raw materials was purchased from Liaoning Hengda New Materials Co., Ltd.; the other raw materials are all commercially available.

[0051] Example 1: A high-strength self-compacting micro-expansion concrete: The mixture consisted of 255 kg of cement, 640 kg of sand, 860 kg of crushed stone, 60 kg of fly ash, 50 kg of mineral powder, 20 kg of composite expansive agent, 8.0 kg of admixture, 26 kg of composite fiber, 35 kg of composite filler, and 136 kg of water. The composite expansive agent used was the one prepared in Preparation Example 1, the composite fiber used was the one prepared in Preparation Example 4, and the composite filler used was the one prepared in Preparation Example 7. The cement was ordinary Portland cement of PO42.5. The crushed stone had a continuous gradation of 5-25 mm. The sand was medium sand with a mud content <1.0%. The fly ash had a moisture content <0.2%. The mineral powder was S95 grade slag powder with a moisture content of 0.2%. The admixture consisted of a polycarboxylate superplasticizer and an air-entraining agent in a mass ratio of 10:0.8, with the air-entraining agent being a triterpenoid saponin. The preparation method is as follows: S1. Mix cement, fly ash, and mineral powder evenly, then add sand and crushed stone and mix evenly to obtain the initial mixture; S2. Add composite expanding agent, composite fiber and composite filler to the initial mixture and mix evenly. Then add water and admixtures and mix evenly to obtain the mixture. S3. The mixture is poured and cured to obtain finished concrete.

[0052] Example 2: The difference between this example and Example 1 is that: The mixture consists of 240 kg of cement, 580 kg of sand, 800 kg of crushed stone, 50 kg of fly ash, 40 kg of mineral powder, 16 kg of composite expansive agent, 7.2 kg of admixture, 24 kg of composite fiber, 30 kg of composite filler, and 130 kg of water. The composite expansive agent is the one prepared in Preparation Example 2, the composite fiber is the one prepared in Preparation Example 5, and the composite filler is the one prepared in Preparation Example 8. The admixture is composed of polycarboxylate superplasticizer and air-entraining agent in a mass ratio of 10:0.5.

[0053] Example 3: The difference between this example and Example 1 is that: The mixture consists of 270 kg of cement, 700 kg of sand, 900 kg of crushed stone, 70 kg of fly ash, 60 kg of mineral powder, 24 kg of composite expansive agent, 8.8 kg of admixture, 30 kg of composite fiber, 40 kg of composite filler, and 140 kg of water. The composite expansive agent is the one prepared in Preparation Example 3, the composite fiber is the one prepared in Preparation Example 6, and the composite filler is the one prepared in Preparation Example 9. The admixture is composed of polycarboxylate superplasticizer and air-entraining agent in a mass ratio of 10:1.

[0054] Example 4: The difference between this example and Example 1 is that: Tartaric acid microparticles were not added during the preparation of calcium sulfoaluminate carrier cetearyl alcohol.

[0055] Example 5: The difference between this example and Example 1 is that: No molecular sieve particles were added during the preparation of polycaprolactone-coated calcium oxide.

[0056] Example 6: The difference between this example and Example 1 is that: No rosin pentaerythritol ester solution or N-isopropylacrylamide was added during the preparation of the composite fiber.

[0057] Example 7: The difference between this example and Example 1 is that: The composite filler has an average particle size of 12 μm for silica microspheres, 12 μm for silica microparticles, and 12 μm for organosilicon microspheres.

[0058] Comparative Example Comparative Example 1: The difference between this comparative example and Example 1 is that: In the composite expanding agent, the calcium sulfoaluminate carrier cetearyl alcohol is replaced with an equal mass of calcium sulfoaluminate.

[0059] Comparative Example 2: This comparative example differs from Example 1 in that: In the composite expanding agent, the same mass of calcium oxide replaces the polycaprolactone-coated calcium oxide.

[0060] Comparative Example 3: This comparative example differs from Example 1 in that: In the composite expanding agent, the carrier magnesium oxide is replaced with an equal mass of magnesium oxide.

[0061] Performance testing 1. Strength testing Concrete was prepared using the methods of Examples 1-7 and Comparative Examples 1-3, respectively. The compressive strength after 7 days and 28 days of curing was tested according to GB / T50081, and the data were recorded.

[0062] 2. Crack resistance test Concrete was prepared using the methods of Examples 1-4 and Comparative Example 1, and the concrete specimen size was 1m. 3 The square shape was used to calculate the total number of cracks per unit area on the surface of the test block after 24 hours of curing, and the data was recorded.

[0063] 3. Self-compacting test Concrete was prepared using the methods in Examples 1 and 6, respectively. The slump spread of the mass concrete was tested according to GB / T50080. The mass concrete had a length and width of 1 meter and a height of 3 meters.

[0064] Table 1 Performance Test Table (In the table, " / " indicates that the corresponding embodiment or comparative example did not test this item, so there is no data)

[0065] As can be seen from Examples 1-3 and Table 1, the concrete prepared in this application has high strength, low number of cracks, and good slump expansion, indicating good fluidity. The concrete has the advantages of self-compacting, high strength, and few cracks.

[0066] Combining Examples 1 and 4-7 with Table 1, it can be seen that no tartaric acid microparticles were added during the preparation of calcium sulfoaluminate carrier cetearyl alcohol in Example 4. Compared with Example 1, the 7-day and 28-day strengths of the concrete prepared in Example 4 were lower than those in Example 1, and the number of cracks was greater than that in Example 1. This indicates that tartaric acid microparticles can control the expansion rate of large-volume concrete in the early stage, ensuring that the concrete has a high density while having a low number of cracks, thereby improving the strength of the concrete.

[0067] In Example 5, no molecular sieve particles were added during the preparation of polycaprolactone-coated calcium oxide. Compared with Example 1, the 7-day and 28-day strengths of the concrete prepared in Example 5 were lower than those in Example 1, indicating that the polycaprolactone-coated calcium oxide exerted an expansion and filling effect in the middle stage, and the connection of molecular sieves further improved the strength of the concrete.

[0068] In Example 6, no rosin pentaerythritol ester solution and N-isopropylacrylamide were added during the preparation of the composite fiber. Compared with Example 1, the 28-day strength and slump expansion of the concrete prepared in Example 6 were lower than those in Example 1. This indicates that the combination of rosin pentaerythritol ester and N-isopropylacrylamide can ensure the fluidity of the concrete and improve the bonding effect between the fiber material and the cementitious materials and other raw materials, thereby increasing the structural density of the concrete and giving it higher strength.

[0069] In Example 7, the average particle size of the silica microspheres, silica microparticles, and organosilicon microspheres in the composite filler was 12 μm. Compared with Example 1, the compressive strength of the concrete prepared in Example 7 was lower than that in Example 1. This indicates that fillers of the same particle size cannot specifically fill cracks of different sizes, thereby affecting the structural density of the concrete and leading to a reduction in the strength of the concrete.

[0070] Combining Example 1 and Comparative Examples 1-3 with Table 1, it can be seen that in Comparative Example 1, when the same mass of calcium sulfoaluminate was used to replace the calcium sulfoaluminate carrier cetearyl alcohol in the composite expansion agent, the concrete prepared in Comparative Example 1 had lower strength and more cracks than that in Example 1. This indicates that the coating of cetearyl alcohol can not only regulate the expansion rate of calcium sulfoaluminate in large-volume concrete, but also ensure fluidity and uniform dispersion, thereby giving the concrete the advantages of high strength and fewer cracks.

[0071] In Comparative Example 2, the calcium oxide coated with polycaprolactone was replaced with an equal mass of calcium oxide in the composite expansion agent. Compared with Example 1, the concrete prepared in Comparative Example 2 had a lower strength than that in Example 1. This indicates that the coating of calcium oxide with polycaprolactone can control the expansion and filling effect in the middle stage of hydration of large-volume concrete, ensuring that the concrete is not easily affected by excessive internal expansion.

[0072] In Comparative Example 3, the same mass of magnesium oxide replaced the carrier magnesium oxide in the composite expansion agent. Compared with Example 1, the difference in compressive strength between 28d and 7d of the concrete prepared in Comparative Example 3 was lower than that in Example 1. This indicates that the carrier magnesium oxide exerts an expansion effect in the later stage and can better expand and fill the voids. However, untreated magnesium oxide is prone to affecting the expansion effect under the high temperature of hydration in large-volume concrete.

[0073] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-strength, self-compacting, micro-expansion concrete, characterized in that, It contains the following raw materials in parts by weight: 240-270 parts cement, 580-700 parts sand, 800-900 parts crushed stone, 50-70 parts fly ash, 40-60 parts mineral powder, 16-24 parts composite expansive agent, 7.2-8.8 parts admixture, 24-30 parts composite fiber, 30-40 parts composite filler, and 130-140 parts water; the composite expansive agent is composed of calcium sulfoaluminate carrier cetearyl alcohol, polycaprolactone-coated calcium oxide, and carrier magnesium oxide in a mass ratio of 1:0.8-1.2:0.2-0.

3.

2. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that: The calcium sulfoaluminate carrier cetearyl alcohol is prepared by a calcium sulfoaluminate-loaded cetearyl alcohol solution and tartaric acid microparticles in a mass ratio of 1:0.2-0.5:0.1-0.

2.

3. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that, The polycaprolactone-coated calcium oxide was prepared by loading a polycaprolactone solution with calcium oxide in a mass ratio of 1:0.9-1.2:0.1-0.2 and then bonding it with molecular sieve microparticles.

4. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that, The magnesium oxide loading is prepared by loading a polyvinyl alcohol-1788 solution with magnesium oxide at a mass ratio of 1:0.2-0.

3.

5. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that, The composite fiber is prepared from fiber material, rosin pentaerythritol ester solution and N-isopropylacrylamide in a mass ratio of 1:0.1-0.25:0.05-0.

15.

6. The high-strength self-compacting micro-expansion concrete according to claim 5, characterized in that, The fiber material is composed of hooked steel fibers and polypropylene fibers in a mass ratio of 1:0.2-0.

5.

7. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that, The composite filler is prepared by mixing silica microspheres, silica microparticles and organosilicon microspheres in a mass ratio of 1:0.4-0.6:0.1-0.3 after being treated with silane coupling agent KH-570.

8. The high-strength self-compacting micro-expansion concrete according to claim 7, characterized in that, The silica microspheres have an average particle size of 80-200 nm, the silica microparticles have an average particle size of 2-6 μm, and the organosilicon microspheres have an average particle size of 10-15 μm.

9. The high-strength self-compacting micro-expansion concrete according to claim 1, characterized in that, The admixture consists of a polycarboxylate superplasticizer and an air-entraining agent in a mass ratio of 10:0.5-1.

10. A method for preparing high-strength self-compacting micro-expansion concrete according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix cement, fly ash, and mineral powder evenly, then add sand and crushed stone and mix evenly to obtain the initial mixture; S2. Add composite expanding agent, composite fiber and composite filler to the initial mixture and mix evenly. Then add water and admixtures and mix evenly to obtain the mixture. S3. The mixture is poured and cured to obtain finished concrete.

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