Concrete for super-high column and method for pouring super-high column

Abstract

The present application relates to the field of building materials and specifically discloses a concrete for super-high columns and a method for casting super-high columns. A super-high column concrete comprises the following raw materials in parts by weight: 460-550 parts of cement, 40-50 parts of fly ash, 600-650 parts of natural sand, 300-500 parts of crushed stone, 12-15 parts of water reducer, 6-12 parts of mixed fiber, 0.9-2.5 parts of expansion agent, 240-300 parts of water, 40-60 parts of reinforcing agent, and 20-30 parts of water retaining agent; the water retaining agent comprises the following raw materials in parts by weight: 1-3 parts of bacterial cellulose, 0.5-1 parts of polysaccharide hydrolysate from polygonatum sibiricum, and 3-7 parts of MOFs-polyacrylamide composite microspheres. The super-high column concrete of the present application can be used to cast super-high columns and has the advantages of low early hydration heat and minimal shrinkage cracking.

Description

Technical Field

[0001] The present application relates to the technical field of building materials, and more specifically, to a concrete for super-high columns and a method for casting super-high columns. Background Art

[0002] With the development of cities and the growth of population, the height of buildings has gradually increased. In super-high-rise buildings, super-high concrete columns are important components that support floors and the entire building. The formula and construction process of super-high column concrete are crucial to ensuring the stability and safety of the building.

[0003] As a new type of concrete material, ultra-high performance concrete usually achieves performance improvement by doping with reinforcing fibers and optimizing the mix ratio. It has excellent properties such as ultra-high strength, ultra-high toughness and ultra-high durability. The strength of ultra-high performance concrete is greater than 100MPa. Its application in super-high-rise structures has the following advantages: ① It can greatly reduce the size of columns in the building structure; ② It can increase the span of the beams in the building structure and increase the available space; ③ The durability of the construction project is improved, the chloride ion diffusion coefficient is very low, and it has strong resistance to sulfate corrosion and good wear resistance. Therefore, super-high concrete columns are generally cast with ultra-high performance concrete.

[0004] While ultra-high performance concrete (UHPC) has achieved significant improvements in mechanical properties and durability compared to conventional concrete, it still suffers from inherent concrete defects. Shrinkage cracking during placement and curing persists in UHPC. This is particularly true given UHPC's high cement content and low water-cement ratio, resulting in high hydration heat release and significant autogenous shrinkage. This early shrinkage cracking is more severe than in conventional concrete, significantly hindering its development and application. Summary of the Invention

[0005] In order to reduce the early hydration heat of ultra-high concrete and reduce early shrinkage cracking, the present application provides concrete for ultra-high columns and a method for casting ultra-high columns.

[0006] In a first aspect, the present application provides a concrete for super-high columns, which adopts the following technical solution:

[0007] A concrete for super-high columns, comprising the following raw materials in parts by weight: 460-550 parts of cement, 40-50 parts of fly ash, 600-650 parts of natural sand, 300-500 parts of crushed stone, 12-15 parts of water reducer, 6-12 parts of mixed fiber, 0.9-2.5 parts of expansion agent, 240-300 parts of water, 40-60 parts of reinforcing agent, and 20-30 parts of water retaining agent;

[0008] The water-retaining agent comprises the following raw materials in parts by weight: 1-3 parts of bacterial cellulose, 0.5-1 parts of polygonatum polysaccharide enzymatic hydrolysate and 3-7 parts of MOFs-polyacrylamide composite microspheres.

[0009] By adopting the above technical solution, a reinforcing agent is added to the concrete to improve the compressive strength of the concrete, and an expansive agent is used to alleviate the early hydration thermal cracking of the concrete, and mixed fibers are used to increase the crack resistance of the concrete and slow down the development of early cracks, and a water-retaining agent containing components such as bacterial cellulose is added. Bacterial cellulose is an ultra-fine pure cellulose synthesized by microorganisms. It not only has the advantages of high strength and large modulus of carbon fibers, but also has high hydrophilicity and viscosity that carbon fibers do not have, and has a strong entanglement and binding ability to objects. In addition, bacterial cellulose has a strong water holding capacity and can reduce the drying shrinkage of concrete. Moreover, it is an ultra-fine network structure formed by the interweaving of microfiber bundles, so it has many opportunities to contact with concrete and a strong mutual force, thereby reducing the porosity of concrete, increasing density, and improving the compressive strength of concrete. Metal-organic framework composite material (MOF) is a new type of organic-inorganic hybrid The material has the characteristics of large specific surface area, high porosity, structural diversity and modifiable pore surface. The spherical material has good mechanical properties, wear resistance and small fluid resistance, and can be used as the matrix material of MOFs. MOFs-polyacrylamide composite microspheres have higher mechanical strength than MOFs, and MOFs-polyacrylamide composite microspheres contain thermal conductive metal compared with pure polyacrylamide microspheres, which can increase the heat dissipation effect, reduce the hydration heat, and alleviate the drying shrinkage of concrete; after moderate enzymatic hydrolysis of Polygonatum sibiricum polysaccharide, the chain end hydrophilic groups per unit mass increase, and these hydrophilic groups easily form hydrogen bonds with water molecules, so that more physically adsorbed water in the concrete is converted into chemically bound water, reducing the water activity of the concrete and increasing the water stability, thereby achieving a long-term water retention effect. Therefore, the water-retaining agent used in this application has a strong water retention and water release effect, can alleviate the hydration heat of concrete, and reduce the early shrinkage and cracking of concrete.

[0010] Preferably, the bacterial cellulose is pretreated as follows:

[0011] Disperse bacterial cellulose in distilled water, add sodium periodate, mix and stir for 3-4 hours, add ethylene glycol, continue stirring for 1-2 hours, and wash with deionized water until neutral to obtain oxidized bacterial cellulose;

[0012] The oxidized bacterial cellulose is dispersed in deionized water to prepare a dispersion with a concentration of 1-1.5 wt%, tannic acid is added, ultrasonic dispersion is performed, the mixture is frozen at -(20-25)°C for 10-12 hours, and freeze-dried at -(70-80)°C for 2-3 days to prepare a bacterial cellulose gel;

[0013] Add polyvinyl alcohol to deionized water, heat to 90-95°C, stir evenly to prepare a solution with a concentration of 3-5wt%, add silicon dioxide and graphene oxide, and stir at 80-85°C for 20-30 minutes to prepare an infiltration solution;

[0014] The bacterial cellulose gel is immersed in the impregnation solution at room temperature for 20-24 hours, filtered, dried and crushed.

[0015] By adopting the above technical scheme, the bacterial cellulose is first oxidized with sodium periodate to oxidize the hydroxyl groups on the bacterial cellulose into dialdehyde groups, and then the oxidized bacterial cellulose is cross-linked and chemically treated with tannic acid to promote entanglement and chemical bonding of the cellulose network, strengthen the interaction between the fiber network, and enhance the mechanical strength. Then, freeze-drying is used to sublimate the water to form a bacterial cellulose gel with pores; polyvinyl alcohol is a highly crystalline, linear, soluble macromolecular polymer with good film-forming properties. The impregnation solution containing polyvinyl alcohol, silicon dioxide and graphene oxide is mixed with the bacterial cellulose gel for impregnation and then frozen, and the network pores of the bacterial cellulose gel are filled with polyvinyl alcohol polymer macromolecules, while silicon dioxide can combine with polyvinyl alcohol macromolecules to form a three-dimensional network structure. Graphene oxide contains a variety of hydrophilic groups and has hydrogen bonds with polyvinyl alcohol and silicon dioxide. Therefore, the impregnation solution can form a hydrophilic and water-retaining three-dimensional network structure on the bacterial cellulose gel, thereby further improving the moisturizing effect of the bacterial cellulose, alleviating the early hydration heat of concrete, and reducing early shrinkage cracks.

[0016] Preferably, the weight parts of the raw materials during the bacterial cellulose pretreatment are as follows: 5-10 parts of bacterial cellulose, 50-100 parts of sodium periodate, 10-20 parts of ethylene glycol, 1.25-3 parts of tannic acid, 3-5 parts of polyvinyl alcohol, 0.2-0.4 parts of silicon dioxide, and 0.1-0.5 parts of graphene oxide.

[0017] By adopting the above technical solution, when the bacterial cellulose is pretreated with the above amounts of the components, the water holding capacity of the bacterial cellulose can be further improved and the early cracking of the concrete can be reduced.

[0018] Preferably, the hybrid fibers include steel fibers and polypropylene fibers in a mass ratio of 1:0.1-0.2.

[0019] By adopting the above technical solution, polypropylene fiber has a large specific surface area and needs to absorb a large amount of cement slurry to wrap around it, while steel fiber is relatively coarse and will support the concrete components to form a network structure, thereby increasing the viscosity of the concrete and meeting the construction performance. Moreover, the addition of polypropylene can enable the concrete to withstand greater tensile stress. Due to the bond strength between polypropylene fiber and concrete, pre-tension stress is generated in the concrete, which compensates for shrinkage and limits the development of cracks, thereby improving the early crack resistance of concrete. The addition of steel fiber reduces the porosity in the concrete, improves the performance of the interface transition zone between the fiber and the matrix concrete, improves the compressive strength of the concrete, and effectively delays the development and expansion of cracks. Therefore, adding polypropylene fiber and steel fiber as mixed fibers can effectively reduce the internal porosity of the concrete, increase the tensile strength of the concrete, and reduce the generation of microcracks.

[0020] Preferably, the steel fiber is pretreated as follows:

[0021] The polyvinyl alcohol fiber is crushed and added to the epoxy resin emulsion. After ultrasonic homogenization, the steel fiber is added and immersed for 20-30 minutes. The steel fiber is taken out and dried. The mass ratio of steel fiber, polyvinyl alcohol fiber and epoxy resin emulsion is 1:0.1-0.2:0.08-0.1.

[0022] Concrete structures have been exposed to the natural environment and will continue to be carbonized by carbon dioxide in the atmosphere. Long-term and continuous carbonization will cause the materials in the concrete structure to undergo a neutralization reaction, resulting in rust of steel fibers and cracks in the concrete. By adopting the above technical solution, the polyvinyl alcohol fiber is crushed and then coated on the surface of the steel fiber with epoxy resin emulsion. As a low elastic modulus fiber, polyvinyl alcohol fiber has a certain inhibitory effect on macro cracks and micro cracks. Compared with steel fiber, polyvinyl alcohol fiber is more corrosion-resistant and has better adhesion, dispersibility and alkali resistance to cement. In addition, after being coated on the surface of the steel fiber with epoxy resin emulsion and dried, a coating layer with polyvinyl alcohol fiber is formed on the surface of the steel fiber. The epoxy resin emulsion has strong corrosion resistance and carbonization resistance, which can further improve the carbonization resistance of the steel fiber, thereby further improving the carbonization cracking resistance of the concrete.

[0023] Preferably, the reinforcing agent comprises steel slag powder and silica fume in a mass ratio of 3-4:1.

[0024] By adopting the above technical solution, steel slag powder is a mineral admixture obtained by grinding waste slag from the steelmaking industry. It contains a certain flow of clinker minerals such as C2S and C3S, as well as a large amount of components such as calcium oxide and magnesium oxide. It not only has high potential activity and makes an outstanding contribution to inhibiting shrinkage, but also can reduce hydration heat shrinkage when combined with an expansion agent. After the steel slag powder is ground, its potential activity is stimulated, and it can fully exert its active and filling effects, thereby reducing cement consumption and hydration heat. Components such as CaO and MgO contained in it also have a certain inhibitory effect on the drying shrinkage of UHPC. The addition of a composite expansion agent can significantly inhibit the drying shrinkage of UHPC. Silica fume can reduce the plastic viscosity and pumping pressure of the concrete slurry, and can improve the long-distance pumping effect of ultra-high column concrete.

[0025] Preferably, the D50 of the steel slag powder is 10.34-14.1 μm, and the D50 of the silica fume is 0.16-0.5 μm.

[0026] By adopting the above technical solution and using steel slag powder and silica fume of different particle sizes, the silica fume can be fully filled between larger cement particles to play its dense filling role, thereby increasing the bulk density of the cementitious system, while the steel slag powder can effectively control the early hydration heat release and reduce the peak hydration heat release rate. The silica fume can also further inhibit the hydration heat release and reduce early temperature cracks. Therefore, the combination of steel slag powder and silica fume as reinforcing agents can effectively enhance the strength of concrete for super-high columns, reduce hydration heat, and reduce temperature cracks.

[0027] In a second aspect, the present application provides a method for casting a super-high column, which adopts the following technical solution:

[0028] A method for casting a super-high column, which is cast using super-high concrete, comprises the following steps:

[0029] Clean the inner surfaces of the four wooden templates of impurities, spray the release agent on them in sequence, and then splice them two by two to form a hollow rectangular wooden mold;

[0030] Place the wooden mold vertically and put the bundled longitudinal steel bars and high-strength stirrups into the wooden mold;

[0031] Cement, fly ash, natural sand, crushed stone, water reducing agent, mixed fiber, expansion agent, water, reinforcing agent and water retaining agent are mixed according to the dosage ratio and stirred evenly to prepare concrete for super high column;

[0032] Spray anti-carbonization coating on the inner surface of the wooden mold, and when the anti-carbonization coating is not yet cured, cast the super-high column into the wooden mold using concrete in sections and vibrating method;

[0033] Evenly cover the wooden mold with a layer of foamed polyethylene as an insulation layer, and bond the foamed polyethylene insulation layer to the wooden mold;

[0034] After curing for 7-10 days, the foamed polyethylene insulation layer is cut along the bonding surface, the wooden mold is removed, and the super-high column is made.

[0035] By adopting the above technical solution, the release agent and anti-carbonization coating are sprayed on the wooden formwork in sequence. The release agent is evenly and fully applied, which can prevent part of the concrete from adhering to the formwork and causing peeling and roughness when the formwork is placed and removed. It also reduces the capillary channels inside the concrete and reduces the carbonization depth of the concrete surface caused by carbon dioxide. A water-based release agent is used, which has a fine emulsion particle size, good film-forming effect, easy spreading, erosion resistance, and a smooth construction surface, thereby improving the smoothness of the anti-carbonization coating on the surface of the super-high column.

[0036] Preferably, the anti-carbonization coating contains an anti-carbonization agent, and the added amount of the anti-carbonization agent is 1-3% of the total weight of the anti-carbonization coating and the anti-carbonization agent. The anti-carbonization agent includes halloysite, rosin and nanocellulose in a mass ratio of 5:1-2:0.5-1.

[0037] By adopting the above technical solution, the halloysite contained in the anti-carbonization coating has a tubular structure. Due to the mismatch between the aluminum oxide octahedron layer and the silicon oxide tetrahedron layer, the flaky crystals curl up to form a multi-walled tubular structure, so it has a certain cavity structure. When the rosin has thermally reversible hydration heat, it absorbs heat and melts, which can reduce the hydration heat and alleviate thermal shrinkage. Nanocellulose can adhere to the outside of the ultra-high column with the anti-carbonization coating, which can improve the density of the anti-carbonization coating formed by the anti-carbonization coating and improve the anti-carbonization effect.

[0038] Preferably, the preparation method of the anti-carbonization agent is as follows:

[0039] Adding halloysite to a sulfuric acid solution, stirring at 80-90° C. for 2-3 hours, washing with distilled water, and vacuum drying to obtain acidified halloysite;

[0040] Mix rosin and deionized water, heat to 60-70℃, stir to dissolve, then add nanocellulose, mix evenly, add acidified halloysite, maintain pressure at -(0.05~0.08)MPa for 20-30min, take out, and dry at room temperature.

[0041] The carbon dioxide in the air penetrates deep into the concrete through the capillary channels inside, and calcium carbonate is generated prematurely, which will lack the protective effect of the alkaline medium on the steel bars, and shorten the strength growth cycle of the concrete, which has an impact on the concrete entity strength and structural durability. By adopting the above technical solution, acidification treatment is first used to make the silicate inside the halloysite react with hydrogen ions, and the generated potassium ions, sodium ions and magnesium ions are dissolved in water, the cavity lattice is cracked, the cavity is expanded, and the adsorption capacity is improved, thereby the dissolved rosin and nano Cellulose is loaded into the cavity of the acidified halloysite through negative pressure adsorption. After drying, the rosin solidifies in the cavity of the acidified halloysite. When the anti-carbonization agent adheres to the periphery of the concrete along with the anti-carbonization coating, the concrete gradually undergoes a hydration reaction, generating hydration heat. The rosin melts under the action of the hydration heat and flows out of the cavity of the acidified halloysite. The rosin contains nanocellulose, which flows with the rosin, thereby further improving the density of the anti-carbonization coating, reducing the penetration of carbon dioxide into the concrete, and improving the concrete's anti-carbonization ability.

[0042] In summary, this application has the following beneficial effects:

[0043] 1. Since this application incorporates reinforcing agents, expansion agents, mixed fibers and water-retaining agents into concrete, and utilizes bacterial cellulose, polysaccharide hydrolysate and MOFs-polyacrylamide composite microspheres as water-retaining agents, it can not only effectively improve the compressive strength and early crack resistance of concrete, but also alleviate the early hydration heat of large-volume concrete and alleviate the generation and development of autogenous shrinkage cracks.

[0044] 2. In this application, sodium periodate is preferably used to oxidize bacterial cellulose, and then tannic acid is used to cause the oxidized bacterial cellulose to produce network entanglement and chemical bonding, increase the interaction between the fiber networks, improve its mechanical strength, and then freeze-dry to form a bacterial cellulose gel with a porous structure. Polyvinyl alcohol is used to attach silicon dioxide and graphene oxide to the bacterial cellulose gel to form a three-dimensional network structure, further improving the water holding and water retention capacity of the bacterial cellulose, prolonging its time to reduce the hydration heat, and alleviating the hydration heat cracking and shrinkage phenomenon.

[0045] 3. The method of the present application preferably adopts spraying anti-carbonization coating inside the wooden formwork before pouring, and pouring concrete before the coating is cured. The anti-carbonization coating can adhere to the concrete to form an anti-carbonization coating. Rosin with a phase change function is added to the anti-carbonization coating. When the hydration heat reaches the melting point of the rosin, the rosin drives the nanocellulose to flow, fill the anti-carbonization coating, improve the density of the anti-carbonization coating, and further enhance the anti-carbonization effect. DETAILED DESCRIPTION

[0046] The following examples further illustrate the present application in detail.

[0047] The performance parameters of each raw material in the embodiment are as follows:

[0048] Table 1 Main performance indicators of cement, steel slag powder and silica fume

[0049]

[0050] Table 2 Particle size distribution of cement, steel slag powder and silica fume

[0051]

[0052] Table 3 Chemical composition of cement, steel slag powder and silica fume

[0053] Material / μm <![CDATA[SiO2]]> CaO <![CDATA[Al2O3]]> MgO <![CDATA[SO3]]> <![CDATA[Ti02]]> <![CDATA[K20]]> <![CDATA[Fe2O3]]> cement 25.37 54.68 6.77 2.55 2.63 0.3 1.04 3.12 Steel slag powder 17.31 45.87 4.61 5.12 0.77 / 0.18 21.77 silica fume 95.55 0.95 0.17 0.68 0.32 / 0.13 0.12

[0054] Table 4 Steel fiber performance parameters

[0055]

[0056] Table 5 Performance parameters of polypropylene fiber

[0057] Example

[0058] Example 1: A concrete for super-high columns, comprising the following raw materials: 50 kg of cement, 4.5 kg of fly ash, 63 kg of natural sand, 40 kg of crushed stone, 1.3 kg of water reducer, 0.8 kg of mixed fiber, 0.17 kg of expansive agent, 27 kg of water, 5 kg of reinforcing agent, and 2.5 kg of water-retaining agent; wherein the cement is P.O42.5 Portland cement with a 28-day compressive strength of 49.3 MPa, the fineness modulus of the natural sand is 2.7, the crushed stone is graded crushed stone with a particle size range of 2-25 mm, the fly ash is Class F II fly ash with a 45 μm square mesh sieve retention of 8%, a water requirement ratio of 95%, and a loss on ignition of 2%, the water reducer is HSP-2005 new polycarboxylic acid high-efficiency water reducer, and the expansive agent is SY-K type expansive fiber anti-cracking waterproofing agent. The mixed fibers include steel fibers and polypropylene fibers in a mass ratio of 1:0.2, the reinforcing agent includes steel slag powder and silica fume in a mass ratio of 4:1, the D50 of the steel slag powder is 14.10 μm, and the D50 of the silica fume is 0.5 μm. The water-retaining agent is made by mixing the following raw materials: 0.3 kg bacterial cellulose, 0.1 kg polysaccharide hydrolysate and 0.7 kg MOFs-polyacrylamide composite microspheres. The bacterial cellulose is obtained by crushing the bacterial cellulose gel and has a length of 3 μm. The polysaccharide hydrolysate is obtained by adding 0.1% composite cellulase based on the mass of polysaccharide to a 4% polysaccharide solution at 50°C and pH 5, and then enzymatically hydrolyzing for 2 hours. The MOFs-polyacrylamide composite microspheres are selected from Ruixi Biotechnology, model R-MOF-0618.

[0059] Example 2: A concrete for super high columns, comprising the following raw materials: 46 kg cement, 4 kg fly ash, 60 kg natural sand, 30 kg crushed stone, 1.2 kg water reducer, 0.6 kg mixed fiber, 0.09 kg expansion agent, 24 kg water, 4 kg reinforcing agent, 2.0 kg water retaining agent; wherein the cement is P.O42.5 Portland cement, with a 28d compressive strength of 49.3 MPa, the fineness modulus of natural sand is 2.7, the crushed stone is a graded crushed stone with a particle size range of 2-25 mm, the fly ash is F Class II fly ash, the 45 μm square hole sieve residue is 8%, the water requirement ratio is 95%, the loss on ignition is 2%, the water reducer is HSP-2005 new polycarboxylic acid high efficiency water reducer, the expansion agent is SY-K type expansion fiber anti-cracking waterproofing agent, and the concrete is as follows: The miscellaneous fibers include steel fibers and polypropylene fibers in a mass ratio of 1:0.1, the reinforcing agents include steel slag powder and silica fume in a mass ratio of 3:1, the D50 of the steel slag powder is 14.1 μm, and the D50 of the silica fume is 0.5 μm. The water-retaining agent is made by mixing the following raw materials: 0.1 kg bacterial cellulose, 0.05 kg polygonatum polysaccharide hydrolysate and 0.3 kg MOFs-polyacrylamide composite microspheres. The bacterial cellulose is obtained by crushing the bacterial cellulose gel and has a length of 3 μm. The polygonatum polysaccharide hydrolysate is obtained by adding 0.1% composite cellulase based on the mass of polygonatum polysaccharide to a 4% polygonatum polysaccharide solution at 50°C and pH 5, and then enzymolyzing for 2 hours. The MOFs-polyacrylamide composite microspheres are selected from Ruixi Biotechnology, model R-MOF-0618.

[0060] Example 3: A concrete for super high columns, comprising the following raw materials: 55 kg cement, 5.0 kg fly ash, 65 kg natural sand, 50 kg crushed stone, 1.5 kg water reducer, 1.2 kg mixed fiber, 0.25 kg expansion agent, 30 kg water, 6 kg reinforcing agent, 3.0 kg water retaining agent; wherein the cement is P.O42.5 Portland cement with a 28d compressive strength of 49.3 MPa, the fineness modulus of natural sand is 2.7, the crushed stone is a graded crushed stone with a particle size range of 2-25 mm, the fly ash is F Class II fly ash with a 45 μm square hole sieve residue of 8%, a water demand ratio of 95%, a loss on ignition of 2%, the water reducer is HSP-2005 new polycarboxylic acid high efficiency water reducer, the expansion agent is SY-K type expansion fiber anti-cracking waterproofing agent, the mixed The fibers include steel fibers and polypropylene fibers in a mass ratio of 1:0.15, the reinforcing agent includes steel slag powder and silica fume in a mass ratio of 3.5:1, the D50 of the steel slag powder is 14.10 μm, and the D50 of the silica fume is 0.5 μm. The water-retaining agent is made by mixing the following raw materials: 0.2 kg bacterial cellulose, 0.08 kg polygonatum polysaccharide hydrolysate and 0.5 kg MOFs-polyacrylamide composite microspheres. The bacterial cellulose is obtained by crushing the bacterial cellulose gel and has a length of 3 μm. The polygonatum polysaccharide hydrolysate is obtained by adding 0.1% composite cellulase based on the mass of polygonatum polysaccharide to a 4% polygonatum polysaccharide solution at 50°C and pH 5, and then enzymolyzing for 2 hours. The MOFs-polyacrylamide composite microspheres are selected from Ruixi Biotechnology, model R-MOF-0618.

[0061] Example 4: A concrete for super-high columns, which differs from Example 1 in that the mixed fibers are all steel fibers.

[0062] Example 5: A concrete for super-high columns, which differs from Example 1 in that the mixed fibers are all polypropylene fibers.

[0063] Example 6: A concrete for super-high columns, which differs from Example 1 in that the reinforcing agent is steel slag powder.

[0064] Example 7: A concrete for super-high columns, which differs from Example 1 in that the reinforcing agent is silica fume.

[0065] Example 8: A concrete for ultra-high columns, which differs from Example 1 in that the bacterial cellulose is pretreated as follows:

[0066] (1) Disperse 10 g of bacterial cellulose in 1 L of distilled water, add 100 g of sodium periodate, mix and stir for 4 h, add 20 g of ethylene glycol, continue stirring for 2 h, and wash with deionized water until neutral to obtain oxidized bacterial cellulose;

[0067] (2) dispersing the oxidized bacterial cellulose prepared in step (1) into deionized water to obtain a dispersion with a concentration of 1.5 wt%, adding 3 g of tannic acid, ultrasonically dispersing the dispersion, freezing at -25°C for 10 h, and freeze-drying at -80°C for 2 days to obtain a bacterial cellulose gel;

[0068] 5 g of polyvinyl alcohol 1788 was added to deionized water, heated to 95°C, and stirred to obtain a 5 wt% solution. 0.4 g of silicon dioxide and 0.5 g of graphene oxide were added and stirred at 85°C for 20 min to obtain an infiltration solution.

[0069] The bacterial cellulose gel was immersed in the soaking solution at room temperature for 24 h, frozen at -20°C for 8 h, thawed at room temperature for 4 h, repeated three times, and then crushed.

[0070] Example 9: A concrete for ultra-high columns, which differs from Example 1 in that the bacterial cellulose is pretreated as follows:

[0071] (1) Disperse 5 g of bacterial cellulose in 1 L of distilled water, add 50 g of sodium periodate, mix and stir for 3 h, add 10 g of ethylene glycol, continue stirring for 1 h, and wash with deionized water until neutral to obtain oxidized bacterial cellulose;

[0072] (2) dispersing the oxidized bacterial cellulose prepared in step (1) into deionized water to obtain a dispersion with a concentration of 1 wt%, adding 1.25 g of tannic acid, ultrasonically dispersing the dispersion, freezing at -20°C for 12 h, and freeze-drying at -70°C for 3 days to obtain a bacterial cellulose gel;

[0073] 3 g of polyvinyl alcohol 1788 was added to deionized water, heated to 90°C, and stirred to obtain a 3 wt% solution. 0.2 g of silicon dioxide and 0.1 g of graphene oxide were added and stirred at 80°C for 30 min to obtain an infiltration solution.

[0074] The bacterial cellulose gel was immersed in the soaking solution at room temperature for 20 h, frozen at -20°C for 10 h, thawed at room temperature for 4 h, repeated twice, and crushed.

[0075] Example 10: A concrete for super-high columns, which differs from Example 8 in that no silicon dioxide is added to the impregnating liquid.

[0076] Example 11: A concrete for ultra-high columns, which differs from Example 8 in that graphene oxide is not added to the impregnation liquid.

[0077] Example 12: A concrete for ultra-high columns, which differs from Example 8 in that the bacterial cellulose is pretreated by adding 5 g of polyvinyl alcohol 1788 to deionized water, heating the mixture to 95° C., and stirring uniformly to obtain a 5 wt % solution, adding 0.4 g of silicon dioxide and 0.5 g of graphene oxide, and stirring the mixture at 85° C. for 20 min to obtain an impregnation solution.

[0078] The bacterial cellulose is immersed in the impregnation solution at room temperature for 24 hours, filtered, dried and crushed.

[0079] Example 13: A concrete for super-high columns, which differs from Example 8 in that the steel fibers are pretreated as follows: the polyvinyl alcohol fibers are crushed and added to the epoxy resin emulsion. After ultrasonic homogenization, the steel fibers are added and immersed for 30 minutes. The steel fibers are taken out and dried. The mass ratio of the steel fibers, polyvinyl alcohol fibers and epoxy resin emulsion is 1:0.2:0.1. The model of the epoxy resin emulsion is E44. The diameter of the polyvinyl alcohol fibers is 10 μm and the length is 3 mm.

[0080] Example 14: A concrete for super-high columns, which differs from Example 8 in that the steel fibers are pretreated as follows: the steel fibers are added to an epoxy resin emulsion, ultrasonically homogenized, and then immersed for 30 minutes. The steel fibers are taken out and dried. The mass ratio of the steel fibers to the epoxy resin emulsion is 1:0.1, and the epoxy resin emulsion model is E44.

[0081] Example 15: A concrete for super-high columns, which differs from Example 8 in that the steel fibers are pretreated as follows: the polyvinyl alcohol fibers are crushed and added to distilled water. After ultrasonic homogenization, the steel fibers are added and immersed for 30 minutes. The steel fibers are taken out and dried. The mass ratio of the steel fibers, polyvinyl alcohol fibers and distilled water is 1:0.2. The diameter of the polyvinyl alcohol fibers is 10 μm and the length is 3 mm.

[0082] Example 16: A method for casting a super-high column, comprising the following steps:

[0083] S1. Clean the inner surfaces of four wooden templates from impurities, spray a release agent onto them in sequence, and then splice them two by two to form a hollow rectangular wooden mold. The release agent is a water-based release agent, model K100;

[0084] S2. Place the wooden mold vertically and place the bundled longitudinal steel bars and high-strength stirrups into the wooden mold;

[0085] S3, cement, fly ash, natural sand, crushed stone, water reducing agent, mixed fiber, expansion agent, water, reinforcing agent and water retaining agent are mixed according to the dosage ratio in Example 1, and stirred evenly to prepare concrete for super high columns;

[0086] S4. Spray anti-carbonization coating on the inner surface of the wooden mold. When the anti-carbonization coating is not solidified, the super-high column concrete is vibrated and poured into the wooden mold in sections. The anti-carbonization coating is CPC anti-carbonization coating. The free fall height of concrete pouring shall not exceed 2m. The pouring layer height of each section shall be 1.25 times the length of the active part of the vibrator. When using the vibrator, it should be inserted quickly and removed slowly. The insertion points should be evenly arranged and moved point by point in sequence to achieve even vibration and compaction. The moving spacing should not be greater than 1.5 times the vibration effective radius. When vibrating the previous layer, it should be inserted into the next layer to a depth of 10cm to ensure that the two layers of concrete are combined and firm. The pouring of adjacent two layers should be carried out continuously. The vibration time of each vibrator is 30s. The spraying height of the anti-carbonization coating is the pouring layer height of each section. That is, spray a section of anti-carbonization coating before pouring a section of super-high column concrete.

[0087] S6. Evenly cover the wooden mold with a layer of foamed polyethylene as a thermal insulation layer, and bond the foamed polyethylene thermal insulation layer to the wooden mold;

[0088] S7. After curing for 7 days, cut the foamed polyethylene insulation layer along the bonding surface, remove the wooden mold, and make the super-high column.

[0089] Example 17: A method for casting an ultra-high column, which differs from Example 16 in that the anti-carbonization coating contains an anti-carbonization agent, the amount of the anti-carbonization agent added is 3% of the total weight of the anti-carbonization coating and the anti-carbonization agent, the anti-carbonization agent comprises halloysite, rosin, and nanocellulose in a mass ratio of 6:2:1, and the preparation method of the anti-carbonization agent is: adding halloysite to a 1 mol / l sulfuric acid solution, stirring at 90°C for 3 hours, washing with distilled water, and vacuum drying at 50°C to obtain acidified halloysite, and the nanocellulose is nano-sized;

[0090] Mix rosin and deionized water twice its mass, heat to 70°C, stir to dissolve, then add nanocellulose, mix evenly, add acidified halloysite, maintain pressure at -0.08 MPa for 30 minutes, take out, and dry at room temperature.

[0091] Example 18: A method for casting an ultra-high column, which differs from Example 17 in that nanocellulose is not added to the anti-carbonization agent.

[0092] Example 19: A method for casting an ultra-high column, which differs from Example 17 in that anti-carbonization coating is not sprayed.

[0093] Example 20: A method for casting an ultra-high column, which differs from Example 17 in that the concrete used for casting adopts the raw material ratio in Example 8.

[0094] Example 21: A method for casting an ultra-high column, which differs from Example 17 in that the concrete used for casting adopts the raw material ratio in Example 12.

[0095] Example 22: A method for casting an ultra-high column, which differs from Example 17 in that the concrete used for casting adopts the raw material ratio in Example 13.

[0096] Example 23: A method for casting an ultra-high column, which differs from Example 17 in that the concrete used for casting adopts the raw material ratio in Example 14.

[0097] Example 24: A method for casting an ultra-high column, which differs from Example 17 in that the concrete used for casting adopts the raw material ratio in Example 15. Comparative Example

[0098] Comparative Example 1: A concrete for super-high columns, which differs from Example 1 in that no mixed fibers are added.

[0099] Comparative Example 2: A concrete for super-high columns, which differs from Example 1 in that no reinforcing agent is added.

[0100] Comparative Example 3: A concrete for super-high columns, which differs from Example 1 in that bacterial cellulose is not added to the water-retaining agent.

[0101] Comparative Example 4: A concrete for ultra-high columns, which differs from Example 1 in that MOFs-polyacrylamide composite microspheres are not added to the water-retaining agent.

[0102] Comparative Example 5: A concrete for ultra-high columns, which differs from Example 1 in that no enzymatic hydrolysate of polygonatum polysaccharide is added to the water-retaining agent.

[0103] Comparative Example 6: A method for preparing high-strength concrete, comprising the following steps:

[0104] S1. Synthesis of reinforcing agent: vacuum residue oil is taken. The vacuum residue oil of the present application comes from Jinan Refining and Chemical, and then the vacuum residue oil is first crushed to less than 20 mesh. Then, the vacuum residue oil and hydrogen peroxide are placed in a ball mill in a mass ratio of 1:2 under the condition that the operating temperature is not higher than 20°C, and ball milled for not less than 20 minutes. The obtained mixture is used as the reinforcing agent, and the hydrogen peroxide is an aqueous solution of hydrogen peroxide with a concentration of 30wt%; S2. Mixing of coagulant water: 30kg of cement with a label number of 42.5, 3kg of fly ash, 65kg of sand, 100kg of crushed stone, 8kg of reinforcing agent, and 1kg of redispersible rubber powder are mixed evenly, and then water and 1kg of water-to-material ratio are added at a ratio of 0.08. The mixture is stirred and mixed evenly before use.

[0105] Performance testing

[0106] 1. Concrete was prepared according to the amounts in Examples 1-15 and Comparative Examples 1-6, and the raw materials were mixed to prepare concrete slurry. The properties of the concrete were tested according to the following methods, and the test results are recorded in Table 6.

[0107] 1. Compressive strength: The concrete slurry was made into a standard cubic specimen with a side length of 100 mm. The specimen was cured under standard conditions for 28 days. The mechanical properties were tested using a universal testing machine at a loading rate of 1 MPa / s. The compressive strength of the concrete was measured after 7 days and 28 days of curing.

[0108] 2. Shrinkage strain: The concrete slurry was made into a cylindrical test block with a diameter of 100 mm and a height of 400 mm. The test was carried out in a constant temperature and humidity environment with a temperature of 20°C and a relative humidity of 60%. After the concrete hardened, the surface was sealed with paraffin and placed on a test stand. The initial length L0 after standing for 4 hours was measured using a micrometer scale, and then the length L after 7 days was measured. t Calculate the shrinkage strain according to the formula: N = (L0-L t ) / L0×10 6 ;

[0109] Table 6 Performance test of concrete for super high columns

[0110]

[0111] It can be seen from the data in Table 6 that the concrete prepared in Examples 1-3 has high initial strength and small 7d strain shrinkage, indicating that the early hydration heat is small and cracks are not easily generated.

[0112] In Examples 4 and 5, steel fibers and polypropylene fibers were used as hybrid fibers, respectively. The concrete prepared in Example 4 had larger pores and decreased compressive strength. The concrete prepared in Example 5 had significantly decreased compressive strength both in the initial and later stages.

[0113] Examples 6 and 7 respectively use steel slag powder and silica fume as reinforcing agents. The concrete prepared in Example 6 has a decreased density, a decreased compressive strength, a weakened hydration heat reduction effect, and an increased strain shrinkage. The concrete prepared in Example 7 has high late strength, but poor early strength.

[0114] In Examples 8 and 9, bacterial cellulose was also pretreated. Table 6 shows that the compressive strength of the concrete prepared in Examples 8 and 9 was increased, and the strain shrinkage was further reduced.

[0115] Compared with Example 8, in Examples 10 and 11, silicon dioxide and graphene oxide were not added during the pretreatment of bacterial cellulose, and the compressive strength and anti-shrinkage effect of the concrete prepared in Examples 10 and 11 decreased.

[0116] In Example 12, the bacterial cellulose was not cross-linked, and the compressive strength of the concrete produced did not change much, but the strain shrinkage was significantly reduced.

[0117] Compared with Example 8, Example 13 also uses epoxy resin emulsion and polyvinyl alcohol fiber to treat the steel fiber, and the compressive strength of the prepared concrete is increased. In Examples 14 and 15, polyvinyl alcohol fiber and epoxy resin emulsion are not added during the pretreatment of the steel fiber. As shown in Table 6, the various properties of the concrete are slightly weakened.

[0118] No mixed fiber was added in Comparative Example 1, and no reinforcing agent was added in Comparative Example 2. Compared with Example 1, the compressive strength of the concrete prepared in Comparative Example 1 and Comparative Example 2 decreased, and the strain shrinkage increased.

[0119] In Comparative Examples 3-5, the raw materials in the water-retaining agent were adjusted respectively. Table 6 shows that the strain shrinkage of the concrete prepared in Comparative Examples 3-5 increased. It can be seen that the components in the water-retaining agent have a good effect on reducing the hydration heat of concrete and can prevent early drying shrinkage.

[0120] Comparative Example 6 is a high-strength concrete prepared using the prior art, the strength of which needs to be improved, mainly due to the large strain shrinkage.

[0121] 2. Cast according to the method in Examples 16-24 to produce columns with a length, width and height of 100 mm × 100 mm × 400 mm. The anti-carbonization effect after curing was tested according to the following method, and the test results are recorded in Table 7.

[0122] Splitting tensile strength after carbonization: (1) The four-point bending test was carried out on a microcomputer-controlled electronic pressure testing machine (model: CBT1105-D) with a maximum force of 100 kN. During the test, the 100 mm × 100 mm × 400 mm prism specimens cured for 28 days were first taken out of the standard curing room and then placed in a constant temperature oven controlled at (60 ± 5) °C for 48 h; (2) The dried specimens were subjected to carbonization test in accordance with GB / T50082-2009 "Test methods for long-term properties and durability of ordinary concrete"; (3) The carbonized specimens were taken out and loaded with a three-point simply supported beam in accordance with CECS13:2009 "Fiber Concrete Test Method Standard". Before the test, the specimens were wiped clean to ensure that there was no obvious damage on the surface. Marking lines were drawn at 50 mm, 3 × 100 mm, and 50 mm. Adjust the spacing between the supports and place the specimen on the supports according to the marked lines, ensuring that the specimen remains horizontal and that the specimen marking lines are in the same plane as the supports. At the same time, place the load sensor above the specimen to measure the load; then install a laser displacement meter to measure the mid-span deflection. After all measuring instruments are installed, first slowly increase the load to 1KN, stop the machine, and check the contact between the specimen and the pressure head and supports to ensure that the specimen position does not shift, then continue pressurizing for the test. The loading system shall be implemented in accordance with the "Standard for Test Methods of Fiber Concrete" (CECS13:2009). If the specimen cracks outside the three-point span of the tensile surface, the test results of the specimen shall be invalidated.

[0123] Table 7 Performance test of prefabricated parts made by casting method of super high column

[0124]

[0125] As can be seen from the data in Table 2, Example 16 uses the raw material dosage in Example 1 to prepare ultra-high column concrete, and uses anti-carbonization coating for protection. After the carbonization test, its splitting tensile strength after carbonization is greater than the splitting tensile strength after carbonization of Example 19 without using anti-carbonization coating, indicating that spraying anti-carbonization coating on wooden formwork can improve the carbonization resistance of concrete; Example 17, an anti-carbonization agent made of components such as halloysite and rosin is added to the anti-carbonization coating. Compared with Example 16, the carbonization resistance of Example 17 is enhanced, and the carbonization resistance of Example 1 is improved. 8. No nanocellulose was added to the anti-carbonization agent. After 28 days of carbonization, the anti-carbonization ability of the concrete was weaker than that of Example 17, indicating that the addition of nanocellulose can improve the anti-carbonization effect of concrete. The concrete for super-high columns prepared in Examples 8, 12 and 13 in Examples 20-22 had increased anti-carbonization ability compared with Example 17. The concrete prepared in Examples 14 and 15 in Examples 21 and 22, respectively, had better anti-carbonization ability compared with Example 17, but decreased anti-carbonization ability compared with Example 22.

[0126] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A concrete for super high columns, characterized in that: The material comprises the following raw materials in parts by weight: 460-550 parts of cement, 40-50 parts of fly ash, 600-650 parts of natural sand, 300-500 parts of crushed stone, 12-15 parts of water reducer, 6-12 parts of mixed fiber, 0.9-2.5 parts of expansion agent, 240-300 parts of water, 40-60 parts of reinforcing agent, and 20-30 parts of water retaining agent; The water-retaining agent comprises the following raw materials in parts by weight: 1-3 parts of bacterial cellulose, 0.5-1 parts of polysaccharide hydrolysate from polygonatum and 3-7 parts of MOFs-polyacrylamide composite microspheres; The bacterial cellulose is pretreated as follows: Disperse bacterial cellulose in distilled water, add sodium periodate, mix and stir for 3-4 hours, add ethylene glycol, continue stirring for 1-2 hours, and wash with deionized water until neutral to obtain oxidized bacterial cellulose; The oxidized bacterial cellulose is dispersed in deionized water to prepare a dispersion with a concentration of 1-1.5 wt%, tannic acid is added, ultrasonic dispersion is performed, the mixture is frozen at -(20-25)°C for 10-12 hours, and freeze-dried at -(70-80)°C for 2-3 days to prepare a bacterial cellulose gel; Add polyvinyl alcohol to deionized water, heat to 90-95°C, stir evenly to prepare a solution with a concentration of 3-5wt%, add silicon dioxide and graphene oxide, and stir at 80-85°C for 20-30 minutes to prepare an infiltration solution; The bacterial cellulose gel was immersed in the soaking solution at room temperature for 20-24 hours, frozen at -20°C for 8-10 hours, thawed at room temperature for 4 hours, repeated 2-3 times, and crushed.

2. The concrete for super high columns according to claim 1, characterized in that: The weight proportions of the raw materials during the bacterial cellulose pretreatment are as follows: 5-10 parts of bacterial cellulose, 50-100 parts of sodium periodate, 10-20 parts of ethylene glycol, 1.25-3 parts of tannic acid, 3-5 parts of polyvinyl alcohol, 0.2-0.4 parts of silicon dioxide, and 0.1-0.5 parts of graphene oxide.

3. The concrete for super high columns according to claim 1, characterized in that: The hybrid fibers include steel fibers and polypropylene fibers in a mass ratio of 1:0.1-0.

2.

4. The concrete for super high columns according to claim 3, characterized in that: The steel fibers are pretreated as follows: The polyvinyl alcohol fiber is crushed and added to the epoxy resin emulsion. After ultrasonic homogenization, the steel fiber is added and immersed for 20-30 minutes. The steel fiber is taken out and dried. The mass ratio of steel fiber, polyvinyl alcohol fiber and epoxy resin emulsion is 1:0.1-0.2:0.08-0.

1.

5. The concrete for super high columns according to claim 1, characterized in that: The reinforcing agent includes steel slag powder and silica fume in a mass ratio of 3-4:

1.

6. The concrete for super high columns according to claim 5, characterized in that: The D50 of the steel slag powder is 10.34-14.1 μm, and the D50 of the silica fume is 0.16-0.5 μm.

7. A method for casting a super high column, characterized in that: The ultra-high column is cast using the ultra-high column concrete according to any one of claims 1 to 6, comprising the following steps: Clean the inner surfaces of the four wooden templates of impurities, spray the release agent on them in sequence, and then splice them two by two to form a hollow rectangular wooden mold; Place the wooden mold vertically and put the bundled longitudinal steel bars and high-strength stirrups into the wooden mold; Cement, fly ash, natural sand, crushed stone, water reducing agent, mixed fiber, expansion agent, water, reinforcing agent and water retaining agent are mixed according to the dosage ratio and stirred evenly to prepare concrete for super high column; Spray anti-carbonization coating on the inner surface of the wooden mold, and when the anti-carbonization coating is not yet cured, cast the super-high column into the wooden mold using concrete in sections and vibrating method; Evenly cover the wooden mold with a layer of foamed polyethylene as an insulation layer, and bond the foamed polyethylene insulation layer to the wooden mold; After curing for 7-10 days, the foamed polyethylene insulation layer is cut along the bonding surface, the wooden mold is removed, and the super-high column is made.

8. The method for casting a super-high column according to claim 7, characterized in that: The anti-carbonization coating contains an anti-carbonization agent, the addition amount of the anti-carbonization agent is 1-3% of the total weight of the anti-carbonization coating and the anti-carbonization agent, and the anti-carbonization agent includes halloysite, rosin and nanocellulose in a mass ratio of 5:1-2:0.5-1.

9. The method for casting a super-high column according to claim 8, characterized in that: The preparation method of the anti-carbonization agent is as follows: Adding halloysite to a sulfuric acid solution, stirring at 80-90° C. for 2-3 hours, washing with distilled water, and vacuum drying to obtain acidified halloysite; Mix rosin and deionized water, heat to 60-70℃, stir to dissolve, then add nanocellulose, mix evenly, add acidified halloysite, maintain pressure at -(0.05~0.08)MPa for 20-30min, take out, and dry at room temperature.

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