CN113024184A

CN113024184A - High-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete and preparation method thereof

Info

Publication number: CN113024184A
Application number: CN202011010506.2A
Authority: CN
Inventors: 郑山锁; 阮升; 郑捷; 郑跃; 杨松; 姬金铭; 曹琛; 温桂峰; 王斌; 龙立; 李磊; 杨建军; 段培亮; 董立国
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2020-09-23
Filing date: 2020-09-23
Publication date: 2021-06-25
Anticipated expiration: 2040-09-23
Also published as: CN113024184B

Abstract

The invention discloses a high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete and a preparation method thereof, wherein the mixing ratio comprises the following steps: cement: sand: crushing stone: fly ash: straw ash: silica fume: nano silicon: water: water reducing agent: exciting agent: defoaming agent: shrinkage reducing agent: ramie fiber: basalt fiber: CaCO₃Whisker: carboxyl-modified polyvinyl alcohol polymer: the nano titanium/graphene oxide dispersion liquid is 545-550: 750-760: 850-860: 68-73: 100-105: 120-130: 5.2-5.4: 72-76: 19-20: 16-17: 2.8-3.2: 14-15: 7.2-7.5: 13-13.3: 20-21: 21.5-23: 40-44. Mixing the materials uniformly by a layered stirring method, discharging, forming and maintaining. The concrete mechanics including the adhesive property and durability between the section steels are obviously improved.

Description

High-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete and preparation method thereof

Technical Field

The invention belongs to the field of building materials, and relates to a ramie fiber, basalt fiber and CaCO doped fiber₃The concrete comprises whiskers, a carboxyl modified polyvinyl alcohol polymer, nano titanium/graphene oxide dispersion liquid, straw ash, fly ash, silica fume and nano silicon, and has high toughness, high cohesiveness, high durability and high volume stability, and particularly relates to high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete and a preparation method thereof.

Background

In the structural design, the requirements of use function, member rigidity and construction convenience are considered, and concrete with different grades is generally adopted according to different stress conditions so as to meet the requirements of compression strength, bending strength and split tensile strength required by the member when the member is loaded and ensure the bonding strength of cooperative work of the concrete and steel. The concrete materials with different labels have different elastic moduli and different deformation properties, so that the too large or too small strength index can cause the deformation of steel and concrete to be inconsistent when the member is stressed, thereby causing that the two materials can not work in cooperation completely or one material can not fully exert the mechanical property, and causing the material waste. The common concrete and the high-performance concrete have poor crack resistance and large brittleness, and the brittleness characteristic is more obvious along with the improvement of the strength grade of the concrete, under high stress or complex stress conditions, concrete with specific high strength grade is often used, for example, in the different floors of the huge super high-rise structure including the bottom stress layer, the reinforcing layer and the industrial building, in super-large span and heavy-load structures with different span and bearing requirements, super-large span bridge girders and piers thereof, and super-durable hydraulic structures, the requirements for the bearing capacity, rigidity and structural use function of the member are strict, so that concrete with the strength grade of C240 is sometimes required to be specially used in consideration of the bearing capacity, the rigidity requirement, the economic benefit, the design requirement and the like, and at this time, under complex stress and severe environment, the brittle characteristics of concrete will reduce the anti-seismic bearing capacity of members and structures, and even affect the safety and reliability of the members and structures. Meanwhile, with the gradual improvement of the mechanical property of steel, the toughness, the deformation property and the bonding property of common concrete are difficult to meet the synergistic action between the concrete and the section steel.

The silica fume has excellent particle size and pozzolanic activity, is an important mineral admixture for preparing high-performance concrete, but has low annual output in China, only 3000t-4000t, can only meet the requirements of partial high-performance concrete, and limits the use of the silica fume in large quantity. As a big agricultural country, China has more than 7 hundred million t of straw output every year and is the first place in the world. At present, only a small part of straws are used for power generation of a biomass energy power plant, and most of straws are still naturally stacked or burned in the open air, so that resource waste and environmental pollution are caused. If the straw ash generated by power generation of the power plant is not developed and utilized properly, secondary pollution to the environment can be caused. With the scientific and technological progress, the straw ash prepared by burning the corn straws under proper conditions contains about 85 percent of amorphous SiO₂And a certain amount of active Al₂O₃The content of the metal oxide K, Na is less, the volcanic ash effect and the micro aggregate filling effect can be fully exerted, and the metal oxide can be applied to concrete to improve the mechanical property.

The cement and mineral admixture acts in concrete through hydration products generated by hydration reaction, the nature of the hydration products is poor, the brittleness of the formed needle-shaped and sheet-shaped hydration products is high, and the brittleness of a concrete matrix is high, so that a template is provided for the hydration reaction of a cementing material, the hydrate reacts in the template to generate stout and compact hydrated crystals, and the method is an effective method for improving the internal structure of concrete. Graphene oxide and nano TiO₂The template effect and the nucleation effect of the two materials can provide good attachment points for hydration products, so that the hydration products are thicker and tighter, and the brittleness problem of concrete is fundamentally improved.

The toughness of concrete and cement-based composite materials is improved by adding fibers, the existing steel fibers and synthetic fibers are difficult to popularize in concrete engineering application due to complex process, high cost and low yield, and the engineering industry gradually searches for high-performance plant fibers with rich sources to replace the steel fibers and the synthetic fibers. The ramie fiber has high cellulose content, high strength, high toughness, high acid and alkali resistance, is green and pollution-free, and can effectively replace steel fiber and synthetic fiber in engineering application. China is the main production area of ramie, and the yield accounts for more than 90% of the world, so that the ramie fibers are convenient to obtain in China, are low in price and have great popularization and application values. Meanwhile, because cracks with different sizes exist in concrete, the best toughening effect cannot be achieved by doping a single fiber.

In summary, from the viewpoints of environmental protection, cost saving and effective resource utilization, the improvement and the enhancement of the internal structure of the concrete are realized by adopting multistage crack control and macroscopic-microscopic grain composition optimization design and considering the organic combination of the multistage crack control and the macroscopic-microscopic grain composition optimization design, and the preparation of the high-toughness high-cohesiveness ultrahigh-strength concrete which has the strength grade of C240, higher toughness, high cohesiveness, high durability, better cooperative deformability and can cooperate with high-performance steel becomes a technical problem to be solved urgently in the field at present.

Disclosure of Invention

The invention aims to provide high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete used in ultrahigh-span and heavy-load structures, ultrahigh-span bridge girders, piers thereof and ultrahigh-durability hydraulic structures with different spans and bearing requirements in different floors of a huge ultrahigh-rise structure, including a bottom stress layer, a reinforcing layer and an industrial building, and a preparation method thereof.

In order to achieve the purpose, the technical scheme disclosed by the invention is as follows: the high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete comprises the following raw materials in parts by weight:

545-550 parts of cement, 750-760 parts of sand, 850-860 parts of gravel, 68-73 parts of fly ash, 100-105 parts of straw ash, 120-130 parts of silica fume, 5.2-5.4 parts of nano silicon, 72-76 parts of water, 19-20 parts of water reducing agent, 16-17 parts of exciting agent, 2.8-3.2 parts of defoaming agent, 14-15 parts of shrinkage reducing agent, 7.2-7.5 parts of ramie fiber, 13-13.3 parts of basalt fiber, CaCO₃20-21 parts of whisker, 40-44 parts of nano titanium/graphene oxide dispersion liquid and carboxyl modified polyvinyl alcohol polymerization21.5-23 parts of the compound.

Further, the cement is P. I62.5R-grade portland cement, and a cement variety with good compatibility with the polycarboxylic acid water reducing agent is selected.

The fine aggregate is composed of hard sand and high-quality quartz sand with good gradation according to the mass ratio of 1:1, the fineness modulus of the sand is 2.8-3.0, the content of silicon dioxide in the quartz sand is not less than 98%, the particle size is 0.3-0.6mm, and the density is 2.62g/cm³；

The crushed stone is prepared from basalt crushed stone with good grading, compactness, hardness and rough surface, the particle size range is 5-10mm, and grading is carried out according to continuous particle size.

The fly ash is high-quality class I fly ash of a power plant, the sieve residue of a 45-micron square-hole sieve is not more than 10 percent, the water demand ratio is not more than 95 percent, and the specific surface area is more than 400m²/kg。

The straw ash is prepared by burning stems of mature corn straws at the temperature of 650-820 ℃, removing potassium, and then grinding for 25min by using a ball mill, wherein the content of silicon dioxide is 84.1%, the average particle size is 6-12 mu m, and the specific surface area is more than 12m²/g。

Further, the potassium removal treatment method comprises the following steps:

1) placing the straw ash in distilled water, stirring and soaking, standing, pouring out supernatant, continuing adding distilled water, stirring and soaking, repeating the process for more than 5 times, and keeping the soaking time for one week;

2) pouring out the supernatant for the last time, heating to 90 ℃ with distilled water, preserving heat for 15-20min, pouring out the supernatant after heat preservation, adding distilled water for soaking, and repeating the step 1);

3) repeating the steps 1) and 2) for two more times in sequence;

4) and finally, preserving the heat at 60 ℃ for 2h, pouring out the supernatant and drying for later use.

The silica fume has a silica content of more than 95%, a pozzolan activity index of more than 95%, an average particle size of 0.1-0.15 μm, and a specific surface area of more than 28m²/g；

The nano silicon is high-purity nano silicon dioxide prepared by a vapor phase method, and the purity of the nano silicon dioxideThe degree is more than 99%, the average grain diameter is 10nm-40nm, the specific surface area is more than 130m²/g。

The water reducing agent is a polycarboxylic acid high-performance water reducing agent suitable for a cementing material system with low water-cement ratio and high silica fume mixing amount, the solid content is 20%, the water reducing rate is more than 38%, the compressive strength ratio of 7d to 28d is not less than 180%, and the water reducing agent has no adverse effect on the compressive strength of concrete.

The shrinkage reducing agent is SU-SRA type shrinkage reducing agent.

The defoaming agent is a high-efficiency concrete defoaming agent of the Liqi X-2756.

The excitant is an organic-inorganic composite excitant which is compounded by the following raw materials in percentage by mass:

50-58% of dihydrate gypsum, 40-48% of calcium chloride and 1.5-2% of triethanolamine.

The ramie fiber is refined dry ramie fiber after alkali treatment and drying, has the length of 40-50mm, the diameter of 30-40 mu m, the tensile strength of more than or equal to 1000MPa, the elastic modulus of more than or equal to 11.4GPa, the breaking elongation of 8.9 percent and the specific gravity of 1.54-1.55g/cm3, and has good hydrophilicity, higher bond strength and acid and alkali resistance.

The length of the basalt fiber is 12mm, the diameter is 7-15 μm, the tensile strength is more than or equal to 3000MPa, the elastic modulus is more than or equal to 91GPa, and the specific gravity is 2.63-2.65g/cm³；

The CaCO₃The length of the whisker is 20-30 μm, the diameter is 0.5-2 μm, the tensile strength is more than or equal to 3000MPa, the elastic modulus is more than or equal to 410GPa, and the specific gravity is 2.86g/cm³。

The carboxyl modified polyvinyl alcohol polymer is an organic polymer obtained by uniformly mixing carboxyl modified polyvinyl alcohol, water and an auxiliary agent, and comprises the following raw materials in percentage by mass:

36-39% of carboxyl modified polyvinyl alcohol, 60-63% of water and 1-1.5% of auxiliary agent;

further, the polymerization degree of the carboxyl-modified polyvinyl alcohol is 2400, the alcoholysis degree is 99%, the carboxyl/hydroxyl molar ratio is 3/97, and the pH value is 7;

further, the auxiliary agent is a polyacrylate defoamer;

further, the uniform mixing method comprises the following steps: placing the carboxyl modified polyvinyl alcohol into water, standing for 30min at normal temperature to fully swell the polyvinyl alcohol, then placing the polyvinyl alcohol into a constant-temperature water tank at 95 ℃ to be heated and dissolved, adding the auxiliary agent, continuously stirring until a uniform transparent solution is formed, and keeping the temperature for later use.

The nano titanium/graphene oxide dispersion liquid is obtained by the following method:

(1) 0.1 to 0.2 portion of nano TiO according to the mass portion₂Adding 0.1 part of surfactant polyethylene glycol octyl phenyl ether into 100 parts of deionized water, stirring at a high speed, then performing ultrasonic dispersion for 20-30min by using an ultrasonic machine, adding 1-1.5 parts of graphene oxide powder, and performing ultrasonic dispersion for 30min to obtain a nano titanium/graphene oxide aqueous solution;

(2) adding 0.1 part of water reducing agent into 50 parts of deionized water, uniformly stirring, then adding the nano titanium/graphene oxide aqueous solution prepared in the step (1), stirring, and then carrying out ultrasonic dispersion for 10min to obtain a nano titanium/graphene oxide dispersion solution;

furthermore, the graphene oxide is powdery, has the purity of more than or equal to 98 percent and the diameter of 10-20 μm, has a large amount of oxygen-containing groups on the surface and has high dispersity in water;

further, the nano TiO₂The purity is about 99%, the particle size is 10nm-50nm, and the hydrophilic property is achieved;

further, the water reducing agent is a polycarboxylic acid high-performance water reducing agent, the solid content is 20%, and the pH value is 7.

The invention also discloses a preparation method of the high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete, which comprises the following steps:

1) adding 19-20 parts by mass of water reducing agent and 40-44 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 14-15 parts of weighed shrinkage reducing agent and 2.8-3.2 parts of defoaming agent into one third of water in total water amount, and marking as a mixed solution 2; preparing 21.5-23 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 72-76 parts;

2) 7.2 to 7.5 portions ofRamie fiber, 850-containing broken stone 860 parts, 750-containing sand 760 parts, 545-containing cement 550 parts, 68-73 parts of fly ash, 100-containing straw ash 105 parts, 120-containing silica fume 130 parts, 5.2-5.4 parts of nano silicon, 13-13.3 parts of basalt fiber, 20-21 parts of CaCO₃Dividing the crystal whisker into three parts, and then, adding one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

3) adding the other two materials into a disc type stirrer in the same way and stirring uniformly;

4) adding the mixed solution 1 in the step 1) into a disc type stirrer, and uniformly stirring for 2-3 min;

5) adding 21.5-23 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 16-17 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min;

7) finally, observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc type stirrer, uniformly stirring for 2-3min, stirring for 2-3min after 3min intervals until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and molding and maintaining.

The concrete molding and curing method obtained by the preparation method comprises the following steps:

standard maintenance: pouring the concrete mixture into a cast iron mold for molding, compacting, standing for 1d-2d in a standard curing room with the temperature of 20 +/-2 ℃ and the relative humidity of more than or equal to 95 percent, removing the mold, and curing in the standard curing room to the required age.

In order to overcome the problems of large brittleness, low toughness, poor durability, poor bonding performance with section steel and the like of common concrete, the invention utilizes materials which are easy to obtain in the market, adopts an improved concrete layered stirring process, considers the dosage proportion of each cementing material required by a specific concrete strength grade and the number and size distribution of cracks in a cement matrix under corresponding proportion, controls the continuous grain composition design with the cementing material based on multi-scale crack classification, and adds ramie fibers, basalt fibers and CaCO₃The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete is prepared from three active mineral admixtures with different particle size ranges, such as fibers with different sizes, fly ash, straw ash, silica fume, nano-silicon, carboxyl modified polyvinyl alcohol polymer capable of filling pores and connecting the three fibers, nano-silicon/graphene oxide dispersion liquid playing a role of a template, a water reducing agent, an exciting agent and other chemical admixtures. Wherein, the ramie fiber with water storage function and toughening function is adopted, which can play an 'internal curing' role in the hydration process of concrete, can promote the hydration process of a cementing material, and simultaneously, the basalt fiber and CaCO are used in a matching way₃The crystal whisker uses carboxyl modified polyvinyl alcohol polymer to fill the pores, and the three fibers are mutually bonded to form an organic whole body, so that cracks with different sizes in concrete are bridged, the development of the cracks is effectively inhibited, and the toughness of the concrete is enhanced; meanwhile, the carboxyl modified polyvinyl alcohol polymer can wrap hydration products, so that the hydration products react more fully, and the carboxyl and Ca contained in the polymer²⁺Generate ionic bonds, and hydroxyl contained in the ionic bonds and oxygen in the silicon-oxygen hydration product form hydrogen bonds to be crosslinked with the hydration product, thereby effectively filling pores and leading the structure to be more compact. In addition, mineral admixtures with different particle sizes are added into the concrete, including fly ash, straw ash, silica fume and nano-scale nano-silica, so that on one hand, continuous particle gradation is formed among all cementing materials, the filling effect of the micro-aggregate can be more effectively exerted, on the other hand, all the mineral admixtures can exert the volcanic ash effect and the super superposition effect, further, the template effect and the nucleation effect are exerted by adding nano-titanium/graphene oxide dispersion liquid, the structure of a concrete hydration product is improved, the pore size is reduced, the number of harmful pores is reduced, the compactness of the concrete is improved, thus under the combined action of the two aspects, the bonding interface between the concrete and the section steel is more compact, the bonding force is further improved along with the improvement of the form of the hydration product, and the bonding property between the concrete matrix and the fiber material is enhanced, so that each fiber can act synergistically, the toughness of the concrete is further improved, and Cl can be effectively reduced^-、SO₄ ^2-、CO₂Plasma ionThe penetration of the particles improves the durability of the concrete. According to the invention, through the synergistic effect among the components, the pore structure of the concrete is improved, the internal structure of the concrete is more compact, the hydration shrinkage of the concrete and the development of cracks with different scales under a stress state are inhibited in a targeted manner, and finally, the novel fiber concrete material with high toughness, high bonding performance, high strength and high durability is prepared.

Compared with the prior art, the invention has the beneficial effects that:

1) the ramie fibers used in the invention are long fibers of 40-50mm, have the characteristics of high tensile strength, high elastic modulus and high toughness, and can effectively inhibit the formation and development of macroscopic cracks of concrete in a complex stress state; the ramie fibers have natural hydrophilicity, so that the surfaces of the ramie fibers have strong bond strength, the ramie fibers have good bonding capacity with a cement matrix, and the long fibers have enough anchoring length, so that the ramie fibers can effectively prevent the fibers from being pulled out when concrete cracks, the further development of the cracks is prevented, and the deformation capacity and the energy consumption capacity of the concrete can be increased by the bridging action of the fibers; in addition, the ramie fiber has a unique fiber cavity structure and a huge specific surface area, and the cavity structure can store partial water, so that the internal curing effect is achieved, and the hydration process of concrete is promoted. Therefore, the ramie fiber can improve the mechanical property and the durability of the concrete, such as crack resistance, permeability resistance, freeze-thaw resistance and the like.

2) Basalt fiber and CaCO used in the present invention₃The whisker has the characteristics of high strength and high elastic modulus, has the lengths of 12mm and 20-30 mu m respectively, can effectively inhibit the formation and development of cracks caused by factors such as plastic shrinkage, drying shrinkage, temperature change and the like of concrete, can work in cooperation with ramie fibers to play a bridging role, can carry out hierarchical control on the development of the cracks with different scales in the concrete, and can effectively improve the strength, toughness, deformability and durability of the concrete; the carboxyl modified polyvinyl alcohol polymer is added, a large amount of surface active substances in the polymer can increase the wetting effect of the aggregate surface and improve the bonding capacity between the aggregate and a matrix, and meanwhile, the polymer forms a film in concrete to wrap hydrated products and unhydrated particlesThe polymer is connected with three fibers to form a more dense space three-dimensional network structure, so that the toughness of concrete and the bonding property of the concrete and section steel are improved, further, the polymer and a cementing material are subjected to a certain degree of chemical reaction, the crosslinking of the polymer and a hydration product is enhanced, the holding power of the matrix to the fibers is also enhanced, the fibers are prevented from being pulled out when the concrete cracks, and the cracks are further prevented from developing. In addition, when the fiber reinforced concrete composite structure is used for a section steel concrete composite structure, three fibers and polymers are uniformly dispersed in concrete and are mutually connected to form a spatial three-dimensional network structure, crack development of surrounding concrete is effectively restrained when the section steel is stressed, an annular restraining effect is formed on the section steel, the friction force and the mechanical engagement force between the section steel and the concrete are effectively improved, the adhesion force between the concrete and the section steel is further enhanced, and the concrete and the section steel can better cooperate.

3) According to the invention, the nano titanium/graphene oxide dispersion liquid capable of being stably dispersed in cement is prepared by adding the dispersing agent. Nano TiO 2₂On one hand, the nano titanium dioxide has filling effect with graphene oxide, and on the other hand, the nano titanium dioxide has larger surface energy, so that hydration products, particularly Ca (OH)₂Quickly gather on the surface to react, thereby promoting the C-S-H gel to grow by taking the C-S-H gel as a core, limiting the generation of harmful crystals, strengthening the interface structure of a cement matrix, graphene is the thinnest two-dimensional material known, the specific surface area is large, the surface of graphene oxide contains a large number of functional groups, the graphene oxide-based composite material has the same adsorption effect on hydration products and plays a role of a template, so that the hydration products become thick and strong cluster crystals, the mechanical property and the durability of concrete are further improved, on the other hand, oxygen-containing functional groups on the surface of the graphene oxide can further react with cement hydration products such as calcium hydroxide, ettringite, hydrated calcium silicate and the like, the shape of the cement hydration crystal products is changed, the toughness of a cement matrix is enhanced, a concrete structure has higher bending strength, compressive strength and the like, and the bonding property between the concrete and the section steel is enhanced.

4) The invention takes into account the straw cropsThe method mainly comprises the steps of enriching potassium ions in new leaves and spores, enabling mature stems of corn straws with low potassium ion content to be low in content and different types of straw crops to have different potassium ion content, burning the mature stems of the corn straws with low potassium ion content at a certain temperature, and performing potassium and sodium removal treatment on the mature stems by a simple and easy potassium removal mode with low cost, so that alkali aggregate reaction in concrete can be effectively prevented, the straw ash obtained by grinding after potassium removal treatment contains more than 84.1% of silicon dioxide and a certain amount of active Al and Fe oxides, has high pozzolan activity, is fine in particle size (the average particle size is 6-12 mu m), and has large specific surface area due to multiple pores and network channel structures inside the straw ash particle, and the specific surface area can reach 12m²(ii) in terms of/g. The straw ash is doped, so that the particles of the cementing material are more uniform, the grading is good, the filling and compacting effects can be achieved, and the cohesiveness of the concrete is further improved; in addition, the straw ash has similar pozzolanic activity with the silica fume, can replace part of the silica fume and is Ca (OH) in a concrete system₂Compact and hard hydrated calcium sulphoaluminate and stable C-S-H gel are generated by reaction, and the flexural strength, the compressive strength, the splitting tensile strength and the durability of the concrete are improved; finally, the straw ash is used as agricultural waste, and is treated to be used as a building material to replace part of cement, so that CO generated in straw burning and cement production processes can be reduced₂The discharge amount is reduced, the manufacturing cost of concrete is further reduced, the agricultural waste is recycled, and the purposes of energy conservation and environmental protection are achieved.

5) The fly ash, the straw ash, the silica fume, the nano-silica and the cement which are added in the invention have different particle size ranges, form more continuous gelled material particle gradation, can better play the filling effect of the micro-aggregate, simultaneously, the fly ash, the straw ash, the silica fume and the nano-silica generate 'super superposition effect', further promote the hydration of the gelled material, convert more hydration products into C-S-H gel, improve the pore structure and the caking property of the concrete, in addition, the nano-silica has larger surface energy and has nucleation effect because the particle diameter of the nano-silica is only nano-scale, so that the hydration products, particularly Ca (OH)₂Rapidly gather on the surface to react, thereby promoting the growth of C-S-H gel taking the C-S-H gel as a core and limitingThe generation of harmful crystals is enhanced, the interface structure of a cement matrix is strengthened, meanwhile, the cement matrix can enter more tiny pores, the surface of the cement matrix contains a large number of unsaturated bonds, the cement matrix can be fully dispersed in the gaps among other particles to be quickly hydrated, and the breaking strength, the compressive strength, the splitting tensile strength, the toughness, the bonding performance and the durability of the concrete are further improved.

6) The shrinkage reducing agent used in the invention can reduce the surface tension of water in concrete capillary pores to compact a concrete structure, further control the volume shrinkage, drying shrinkage, early-stage hardening plastic shrinkage and the like of the concrete, further improve the crack resistance and permeability resistance of the concrete and enhance the durability of the concrete.

7) The activator adopts an organic-inorganic composite activator, and the dihydrate gypsum, the calcium chloride and the triethanolamine play an activating role together to promote the generation of the ettringite, so that the concrete doped with the fly ash, the silica fume, the nano-silica and the straw ash has certain micro-expansibility, and the shrinkage performance of the concrete is improved. The net structure of the fly ash surface vitreous body is depolymerized through the composite activator, so that the potential activity of the fly ash is excited, the corrosion effect of the three-dimensional space structure vitreous body which takes aluminosilicate as a main hydration component in the fly ash hydration process can be enhanced, the power of a forward hydration reaction is improved, more C-S-H gel, hydrated calcium aluminate and other crystals are generated, and the participation of the fly ash in an early hydration process is promoted. The excitation effect of the dihydrate gypsum on the mineral admixture is shown as follows: SO (SO)^4-Gel on the surface of fly ash particles and AlO dissolved in liquid phase^2-Reacting to generate hydrated calcium sulphoaluminate AFt; in addition, SO₄ ^2-Can also replace part of SiO in the hydrated calcium silicate₂ ^2-Replaced SiO₂ ^2-In the outer layer, Ca is further mixed with²⁺The calcium silicate hydrate is generated by the action, the activity of the fly ash is continuously excited, and Ca is provided by the calcium silicate hydrate²⁺Mixing with fly ash, silica fume, nano-silicon dioxide and SiO in straw ash₂、Fe₂O₃、Al₂O₃The reaction generates hydrated calcium silicate, hydrated calcium ferrite, hydrated calcium aluminate and the like. The calcium chloride is used for exciting the mineral admixture mainly by improving hydrationCa in the system²⁺The concentration, the formation of hydrated chloroaluminate gelled phase and the hydrated calcium aluminate are realized, and in addition, the calcium chloride serving as a strong electrolyte can supplement Ca required by the reaction of the siliceous dust, the straw ash and the nano-silica in the process of exciting the activity of the fly ash by the sulfate²⁺. Triethanolamine is used as an organic fly ash activity excitant, and can promote the corrosion of the surface of fly ash particles by complexing Fe and Al phases in the fly ash and the like in the hydration process, so that active substances in the fly ash are further hydrated. The synergistic effect among the dihydrate gypsum, the calcium chloride and the triethanolamine can fully stimulate the activity of the mineral admixture, accelerate the hydration rate of the cementing material in the system, promote the generation of hydration products, and further improve the strength, the durability and the like of the concrete.

8) According to the invention, a layered stirring method is adopted, and the particle size of the largest crushed stone particle is determined through tests, so that long fibers and aggregates can be uniformly dispersed to the greatest extent, and the phenomena of large holes and even honeycomb pitted surface in a cement matrix caused by mutual interference of the long fibers and the coarse aggregates and fiber aggregation are avoided.

The measures can effectively improve the compressive strength, toughness, deformability, durability and the like of the concrete, and enhance the bonding strength and the cooperative deformability between the concrete and the section steel. The high-toughness high-caking property C240 ultrahigh-strength hybrid fiber concrete prepared by the method has the advantages that the particle sizes of various gelled materials with different particle diameters in the concrete are uniformly distributed from large to small, the micro-aggregate filling effect of the gelled materials is fully exerted, the hydration products of the gelled materials can be stacked and compacted, and the graphene oxide and the nano TiO are coated on the hydration products₂The template action and the nucleation action improve the physical and mechanical properties of hydration products, further improve the pore structure of concrete, simultaneously uniformly disperse multi-scale fibers, organically unify under the bonding action of carboxyl modified polyvinyl alcohol polymer to form a three-dimensional space network structure, and effectively inhibit the development of cracks with different sizes, so that the concrete has higher toughness and excellent durability, has better bonding property with section steel, and further obtains deformation capabilityThe cooperativity with the section steel is enhanced. The 28d cubic compressive strength of the fiber concrete is not less than 244.36MPa, the flexural strength is not less than 58.13MPa, the splitting tensile strength is not less than 27.78MPa, the bonding strength between the fiber concrete and the section steel is not less than 11.56MPa, and the chloride ion migration coefficient is not more than 6 multiplied by 10^-14m²And s. The high-performance hybrid fiber concrete with high volume stability, high durability and high toughness is prepared by the method, the raw materials are easy to obtain, the preparation process is simple, the requirements of sustainable development and application and popularization of modern green building materials are met, and the method is a novel green and environment-friendly high-performance hybrid fiber concrete material.

Detailed Description

The present invention will be further described in detail with reference to the following examples, which are provided to enable those skilled in the art to more easily understand the advantages of the present invention, but are not intended to limit the scope of the present invention.

The invention relates to a high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete, which is prepared by the following method:

2) 7.2 to 7.5 portions of ramie fiber, 850 portions of broken stone, 750 portions of sand, 545 portions of cement, 550 portions of fly ash, 100 portions of straw ash, 120 portions of silica fume, 130 portions of nano-silicon, 13 to 13.3 portions of basalt fiber, 20 to 21 portions of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

The concrete forming and curing method comprises the following steps:

pouring the concrete mixture into a cast iron mold for molding, compacting by using a vibration table, and then performing contact vibration along the outer wall of the test mold by using a vibrating rod to discharge redundant air bubbles in the concrete mixture; after molding, placing the test block in an environment with the temperature of 20 +/-2 ℃, covering the surface of the test block with wet geotextile, standing for 1d, removing the mold, and then curing in a standard curing room with the temperature of 20 +/-2 ℃ and the relative humidity of more than or equal to 95% to the required age.

Wherein:

the cement is P. I62.5R-grade portland cement, and a cement variety with good compatibility with the polycarboxylic acid water reducing agent is selected.

The fine aggregate is composed of hard sand and high-quality quartz sand with good gradation at a mass ratio of 1:1, the fineness modulus of the sand is 2.8-3.0, the content of silicon dioxide in the quartz sand is not less than 98%, the particle size is 0.3-0.6mm, and the density is 2.62g/cm³。

The crushed stone is selected from basalt crushed stone with good grading, compactness, hardness and rough surface, the particle size range is 5-10mm, and grading is carried out according to continuous particle size.

The fly ash is high-quality class I fly ash of a power plant, the sieve residue of a 45-micron square-hole sieve is not more than 10 percent, the water requirement ratio is not more than 95 percent, and the specific surface area is more than 400m²Per kg, the average particle diameter is in the range of 10-30 μm.

The straw ash is prepared from ripe corn stalksThe stems of the stalks are burned at the temperature of 650-820 ℃, subjected to potassium removal treatment and then ground for 25min by using a ball mill, and the stalks are prepared by the silicon dioxide content of 84.1 percent, the average particle size of 162-12 mu m and the specific surface area of more than 12m²/g。

The potassium removal treatment method comprises the following steps:

3) repeating the steps 1) and 2) for two more times in sequence;

The silica fume has a silica content of more than 95%, a pozzolanic activity index of more than 95%, an average particle size of 0.1-0.15 μm, and a specific surface area of more than 28m²/g.

The nanometer silicon is high-purity nanometer silicon dioxide prepared by a gas phase method, the purity is more than 99 percent, the average grain diameter is 10nm-40nm, and the specific surface area is more than 130m²/g。

The shrinkage reducing agent is SU-SRA type shrinkage reducing agent. The defoamer is a high-efficiency concrete defoamer of the Liqi X-2756.

The ramie fiber is refined dry ramie fiber after alkali treatment and drying, has the length of 40-50mm, the diameter of 30-40 μm and the tensile strength of more than or equal to 1000MPa,the elastic modulus is more than or equal to 11.4GPa, the elongation at break reaches 8.9 percent, and the specific gravity is 1.54-1.55g/cm³Has good hydrophilicity, higher bond stress and acid and alkali resistance.

The length of basalt fiber is 12mm, the diameter is 7-15 μm, the tensile strength is not less than 3000MPa, the elastic modulus is not less than 91GPa, the specific gravity is 2.63-2.65g/cm³。

CaCO₃The length of the whisker is 20-30 μm, the diameter is 0.5-2 μm, the tensile strength is more than or equal to 3000MPa, the elastic modulus is more than or equal to 410GPa, and the specific gravity is 2.86g/cm³。

36-39% of carboxyl modified polyvinyl alcohol, 60-63% of water and 1-1.5% of auxiliary agent.

Wherein, the polymerization degree of the carboxyl modified polyvinyl alcohol is 2400, the alcoholysis degree is 99%, the carboxyl/hydroxyl molar ratio is 3/97, and the pH value is 7; the auxiliary agent is polyacrylate defoamer.

The uniform mixing method comprises the following steps: placing the carboxyl modified polyvinyl alcohol into water, standing for 30min at normal temperature to fully swell the polyvinyl alcohol, then placing the polyvinyl alcohol into a constant-temperature water tank at 95 ℃ to be heated and dissolved, adding the auxiliary agent, continuously stirring until a uniform transparent solution is formed, and keeping the temperature for later use.

wherein, the graphene oxide is powdery, and the purity is more than or equal to 98 percent, the diameter is 10-20 mu m, the surface of the material has a large amount of oxygen-containing groups, and the material has higher dispersity in water; nano TiO 2₂Has purity of about 99%, particle size of 10nm-50nm, and hydrophilicity.

The water reducing agent is a polycarboxylic acid high-performance water reducing agent, the solid content is 20 percent, and the pH value is 7. The following specific examples are given to further illustrate the preparation process of the present invention.

Example 1

1) Adding 19.5 parts by mass of water reducing agent and 42 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 14.5 parts of weighed shrinkage reducing agent and 3.2 parts of weighed defoaming agent into one third of water of the total water amount, and marking as a mixed solution 2; preparing 22.3 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 72 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.2 parts of graphene oxide powder and 0.5 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 39% of carboxyl modified polyvinyl alcohol, 60% of water and 1% of polyacrylate defoaming agent;

2) 7.5 parts of ramie fiber, 850 parts of broken stone, 760 parts of sand, 545 parts of cement, 70 parts of fly ash, 103 parts of straw ash, 120 parts of silica fume, 5.3 parts of nano-silicon, 13.1 parts of basalt fiber and 20.5 parts of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

5) adding 19.5 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 16 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 54.5% of dihydrate gypsum, 43.7% of calcium chloride and 1.8% of triethanolamine;

The concrete molding and curing method in this example is as follows:

Example 2

1) Adding 20 parts by mass of water reducing agent and 41 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water in total water amount, and marking as a mixed solution 1; adding 14 parts of weighed shrinkage reducing agent and 3 parts of defoaming agent into one third of water in total water amount, and marking as a mixed solution 2; preparing 21.8 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 72 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.7 parts of graphene oxide powder and 0.5 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 38.7 percent of carboxyl modified polyvinyl alcohol, 60 percent of water and 1.3 percent of polyacrylate defoamer;

2) 7.2 parts of ramie fiber, 850 parts of gravel, 755 parts of sand, 547 parts of cement, 68 parts of fly ash, 102 parts of straw ash, 125 parts of silica fume, 5.4 parts of nano-silicon, 13.1 parts of basalt fiber and 20 parts of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃The crystal whiskers are evenly spread in a disc type stirrer, and then a part of broken stone, sand, cement, fly ash, straw ash, silica fume,Placing the nano silicon in a disc type stirrer in sequence, and stirring for 1 min;

6) adding 16.3 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 58% of dihydrate gypsum, 40% of calcium chloride and 1.5% of triethanolamine;

The concrete in this example was formed and cured in the same manner as in example 1.

Example 3

1) Adding 20 parts by mass of water reducing agent and 44 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water in total water amount, and marking as a mixed solution 1; adding 15 parts of weighed shrinkage reducing agent and 2.9 parts of defoaming agent into one third of water in total water, and marking as a mixed solution 2; preparing 21.5 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 74 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.7 parts of graphene oxide powder and 0.4 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 37% of carboxyl modified polyvinyl alcohol, 62% of water and 1% of polyacrylate defoaming agent;

2) 7.3 parts of ramie fiber, 855 parts of crushed stone, 760 parts of sand, 547 parts of cement, 73 parts of fly ash, 100 parts of straw ash, 130 parts of silica fume, 5.3 parts of nano-silicon, 13 parts of basalt fiber and 20 parts of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

5) adding 19 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 17 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 54% of dihydrate gypsum, 44% of calcium chloride and 2% of triethanolamine;

Example 4

1) Adding 19 parts by mass of water reducing agent and 40 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water in total water amount, and marking as a mixed solution 1; adding 14.5 parts of weighed shrinkage reducing agent and 2.8 parts of weighed defoaming agent into one third of water of the total water amount, and marking as a mixed solution 2; preparing 22 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 76 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.4 parts of graphene oxide powder and 0.4 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 37.3 percent of carboxyl modified polyvinyl alcohol, 61.3 percent of water and 1.4 percent of polyacrylate defoamer;

2) 7.3 parts of ramie fiber, 860 parts of broken stone, 755 parts of sand, 545 parts of cement, 73 parts of fly ash, 105 parts of straw ash, 120 parts of silica fume, 5.2 parts of nano silicon, 13.2 parts of basalt fiber and 20 parts ofCaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

6) adding 16.8 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 50% of dihydrate gypsum, 48% of calcium chloride and 2% of triethanolamine;

Example 5

1) Adding 19 parts by mass of water reducing agent and 40 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water in total water amount, and marking as a mixed solution 1; adding 14 parts of weighed shrinkage reducing agent and 2.8 parts of defoaming agent into one third of water in total water, and marking as a mixed solution 2; preparing 23 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 76 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.3 parts of graphene oxide powder and 0.4 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 37.5 percent of carboxyl modified polyvinyl alcohol, 61 percent of water and 1.5 percent of polyacrylate defoamer;

2) 7.2 parts of ramie fibers, 855 parts of broken stones, 750 parts of sand,550 parts of cement, 70 parts of fly ash, 100 parts of straw ash, 125 parts of silica fume, 5.4 parts of nano-silicon, 13.2 parts of basalt fiber and 21 parts of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

5) adding 20 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 16 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 52.2 percent of dihydrate gypsum, 46 percent of calcium chloride and 1.8 percent of triethanolamine;

Example 6

1) Adding 19.5 parts by mass of water reducing agent and 40 parts by mass of nano titanium/graphene oxide dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 15 parts of weighed shrinkage reducing agent and 3.2 parts of defoaming agent into one third of water in total water, and marking as a mixed solution 2; preparing 22.8 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 76 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.5 parts of graphene oxide powder and 0.5 part of nano TiO₂Preparing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 36% of carboxyl modified polyvinyl alcohol, 63% of water and polypropylene1% of enoate defoamer;

2) 7.5 parts of ramie fiber, 860 parts of broken stone, 750 parts of sand, 550 parts of cement, 68 parts of fly ash, 105 parts of straw ash, 130 parts of silica fume, 5.2 parts of nano silicon, 13.3 parts of basalt fiber and 21 parts of CaCO₃Dividing the crystal whisker into three parts, and then dividing one part of ramie fiber, basalt fiber and CaCO₃Uniformly spreading the whiskers in a disc type stirrer, and sequentially placing a part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano-silicon in the disc type stirrer for stirring for 1 min;

6) adding 16.5 parts of exciting agent into the disc type stirrer, and uniformly stirring for 2-3 min; the exciting agent is prepared by compounding the following raw materials in percentage by mass: 54% of dihydrate gypsum, 44.5% of calcium chloride and 1.5% of triethanolamine;

The following is a comparison of comparative examples with examples of the present invention to further illustrate the effects of the present invention.

Comparative example: the ultra-high strength concrete is prepared by using a single activator without adopting a gelled particle continuous grading design, adding fibers, adding a carboxyl modified polyvinyl alcohol polymer and a nano titanium/graphene oxide dispersion liquid.

The mixture ratio is as follows: 565 parts of cement, 750 parts of sand, 860 parts of broken stone, 85 parts of fly ash, 120 parts of silica fume, 115 parts of water, 17.5 parts of water reducing agent, 15 parts of exciting agent and 2.6 parts of defoaming agent.

The preparation method comprises the following steps:

1) adding 17.5 parts by mass of a water reducing agent into two thirds of the total water amount, and marking as a mixed solution 1; adding 2.6 parts of weighed defoaming agent into one third of water in the total water amount, and marking as a mixed solution 2, wherein the total water amount is 115 parts;

2) putting 860 parts of broken stone, 750 parts of sand, 565 parts of cement, 85 parts of fly ash and 120 parts of silica fume into a stirrer, and stirring for 1 min;

3) adding the mixed solution 1 in the step 1) into a stirrer, and uniformly stirring for 2-3 min;

4) adding 15 parts of calcium chloride activator into the stirrer, and uniformly stirring for 2-3 min;

5) finally, observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a stirrer, uniformly stirring for 2-3min, after 3min interval, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and molding and maintaining.

Comparative example the concrete moulding and curing method described above was as follows:

The results of the performance tests of the high tenacity high cohesiveness C240 ultra high strength hybrid fiber concrete prepared in examples 1-6 and the comparative example concrete are shown in Table 1.

TABLE 1 comparison of the Properties of examples 1-6 with comparative examples

As can be seen from Table 1, the high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete prepared by the inventionThe compression strength and the bending strength required by the member when the member is loaded are met, and the bonding strength of the member and steel cooperative work is ensured. The 28d cubic compressive strength is not less than 244.36MPa, the flexural strength is not less than 58.13MPa, the splitting tensile strength is not less than 27.78MPa, the bonding strength between the structural steel and the structural steel is not less than 11.56MPa, and the chloride ion migration coefficient is not more than 6 multiplied by 10^-14m²And s. Example 2 is the optimal mixing ratio, the gel material particle composition is optimal, the carboxyl modified polyvinyl alcohol polymer doping amount is optimal, the fiber doping amount is optimal, and the nano titanium/graphene oxide dispersion liquid. Under the strength grade of C240, the composite material has enough toughness and cohesiveness to improve the cooperative working capacity of the section steel and the concrete, and can be applied as a modern green building material.

The above description is only an example of the present invention, and is further detailed description of the present invention with reference to specific preferred embodiments, and therefore, the protection scope of the present invention should not be limited thereby, and those skilled in the art can make simple changes or substitutions by using the disclosure and method of the present invention or without departing from the concept of the present invention, and should be considered as being within the protection scope of the present invention. The scope of the present invention shall be subject to the protection scope defined by the claims of the present disclosure.

Claims

1. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete is characterized by comprising the following raw materials in parts by weight:

545-550 parts of cement, 750-760 parts of sand, 850-860 parts of gravel, 68-73 parts of fly ash, 100-105 parts of straw ash, 120-130 parts of silica fume, 5.2-5.4 parts of nano silicon, 72-76 parts of water, 19-20 parts of water reducing agent, 16-17 parts of exciting agent, 2.8-3.2 parts of defoaming agent, 14-15 parts of shrinkage reducing agent, 7.2-7.5 parts of ramie fiber, 13-13.3 parts of basalt fiber, CaCO₃20-21 parts of whiskers, 40-44 parts of nano titanium/graphene oxide dispersion liquid and 21.5-23 parts of carboxyl modified polyvinyl alcohol polymer.

2. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the cement is P-I62.5R-grade portland cement, and a cement variety with good compatibility with a polycarboxylic acid water reducer is selected;

The method comprises the following steps of selecting basalt broken stones with good gradation, compactness, hardness and rough surface, feeding according to continuous grain size of 5-10mm, wherein the strength of a parent rock is not lower than 300MPa, and the maximum grain size is 10 mm;

the fly ash is high-quality class I fly ash of a power plant, the sieve residue of a 45-micron square-hole sieve is not more than 10 percent, the water demand ratio is not more than 95 percent, and the specific surface area is more than 400m²/kg；

The nano silicon is high-purity nano silicon dioxide prepared by a vapor phase method, the purity is more than 99 percent, the average particle size is 10nm-40nm, and the specific surface area is more than 130m²/g；

The water reducing agent is a polycarboxylic acid high-performance water reducing agent, the solid content is 20%, and the water reducing rate of the water reducing agent is more than 38%;

the defoaming agent is a high-efficiency concrete defoaming agent of the Liqi X-2756;

the shrinkage reducing agent is SU-SRA type shrinkage reducing agent.

3. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein said straw ash is prepared by burning mature stems of corn straws at a temperature of 600-820 ℃, subjecting to potassium removal treatment, and grinding for 20min by using a ball mill, and has a silica content of more than 84.1%, an average particle size of 6-12 μm, and a specific surface area of more than 12m²/g。

4. The high tenacity high cohesiveness C240 ultra high strength hybrid fiber concrete according to claim 3, wherein said potassium removing treatment comprises the steps of:

3) repeating the steps 1) and 2) for two more times in sequence;

5. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the activator is an organic-inorganic composite activator, and the composite activator is compounded from the following raw materials in percentage by mass:

50-58% of dihydrate gypsum, 40-48% of calcium chloride and 1.2-1.8% of triethanolamine.

6. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the ramie fibers are degummed ramie fibers after alkali treatment and drying, the length of the degummed ramie fibers is 40-50mm, the diameter of the degummed ramie fibers is 30-40 μm, the tensile strength of the degummed ramie fibers is not less than 766MPa, the elastic modulus of the degummed ramie fibers is not less than 9.1GPa, the elongation at break of the degummed ramie fibers reaches 8.9%, and the specific gravity of the degummed ramie fibers is 1.54-1³；

7. The high tenacity high cohesiveness C240 ultrahigh strength hybrid fiber concrete according to claim 1, wherein said carboxyl modified polyvinyl alcohol polymer is: putting 36-39% of carboxyl modified polyvinyl alcohol in 60-63% of water by mass percent, standing for 30min at normal temperature to fully swell the polyvinyl alcohol, then putting the polyvinyl alcohol in a constant-temperature water tank at 95 ℃ for heating and dissolving, adding 1-1.5% of polyacrylate defoamer, and continuously stirring until a uniform and transparent solution is formed;

the polymerization degree of the carboxyl modified polyvinyl alcohol is 2400, the alcoholysis degree is 99%, the carboxyl/hydroxyl molar ratio is 3/97, and the pH value is 7.

8. The high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the nano titanium/graphene oxide dispersion is obtained by the following method:

the graphene oxide is powdery, the purity is more than or equal to 98%, and the diameter is 10-20 μm;

the nano TiO₂The purity is 99 percent, and the grain diameter is 10nm-50 nm;

the water reducing agent is a polycarboxylic acid high-performance water reducing agent, the solid content is 20%, and the pH value is 7.

9. A method for preparing the high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete based on any one of claims 1 to 8, wherein a disc mixer is selected, and then the method comprises the following steps:

10. A forming and curing method of the high-toughness high-cohesiveness C240 ultrahigh-strength hybrid fiber concrete prepared by the method of claim 9, which is characterized in that a standard curing method is adopted:

the standard maintenance method comprises the following steps: pouring the concrete mixture into a cast iron mold, molding, compacting, standing for 1-2 days in a standard curing room with the temperature of 20 +/-2 ℃ and the relative humidity of more than or equal to 95%, removing the mold, and curing in the standard curing room to the required age.