CN113024190A

CN113024190A - High-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete and preparation method thereof

Info

Publication number: CN113024190A
Application number: CN202011010532.5A
Authority: CN
Inventors: 郑山锁; 明铭; 阮升; 姬金铭; 龙立; 周炎; 刘晓航; 郑捷; 郑淏; 李磊; 段培亮; 张晓宇; 郑跃; 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: CN113024190B

Abstract

The invention discloses a high-toughness high-cohesiveness C200 strength ultrahigh-strength 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: hydroxyl modified single-walled carbon nanotube dispersion: carboxyl modified polyvinyl alcohol polymer 507 ═ 518: 720-730: 945: 60-68: 80-90: 70-78: 4.6-4.8: 85-90: 16.8-18: 14.5-15: 2.5-2.9: 14.5-15: 6.2-6.4: 11.3-11.5: 31-32: 20.5-21.5. And (3) uniformly mixing all the materials at intervals by a layered stirring method, and preparing and maintaining. The mechanical property, the bonding property with the section steel, the cooperative working capability and the durability of the concrete are all obviously improved.

Description

High-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete and preparation method thereof

Technical Field

The invention belongs to the field of building materials, and relates to concrete doped with ramie fibers, basalt fibers, a carboxyl modified polyvinyl alcohol polymer, a hydroxyl modified single-walled carbon nanotube dispersion liquid, straw ash, fly ash, silica fume and nano-silicon and having high toughness, high cohesiveness, high durability and high volume stability, in particular to high-toughness high-cohesiveness C200 strength ultrahigh-strength 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. Ordinary concrete and high-performance concrete materials have poor anti-cracking performance and high brittleness, and the brittleness characteristic is more obvious along with the improvement of the concrete strength grade, under the high stress or complex stress state, concrete with specific high strength grade is often needed to be used, for example, in different reinforcing layers of a super high-rise structure, an anti-seismic reinforcing area, frame columns (especially corner columns) of a bottom frame shear layer, a shear wall and different floors of a huge super high-rise structure, the strength index is small, the section of a component is overlarge, the rigidity is overlarge, a fat beam column is caused, the structure use function is limited, the rigidity of the component is insufficient or the material is wasted due to the overlarge strength index, therefore, the concrete with the C200 strength grade is sometimes needed to be used in consideration of the bearing capacity, the rigidity requirement, the economic benefit, the design requirement and the like, at the brittleness characteristic of the concrete can reduce the anti-seismic bearing capacity of the component and the structure, or even affect its safety and reliability. 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 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.

The carbon nano tube is a one-dimensional fiber material with nano-scale diameter and micron-scale length, has excellent physical and mechanical properties, has the elastic modulus of about 1TPa which is about 5 times of that of steel, and has the density of only 1/6 of the steel; the tensile strength of the carbon nano tube can reach 60-150GPa, the compressive strength reaches 100-170GPa, and the breaking strain is 30-50 percent. However, the carbon nanotube has complete and smooth surface, less defects and active groups, lower relative solubility in water and various solutions or composite materials, larger van der waals force and surface free energy, and spontaneous agglomeration or winding is easy to occur, which seriously affects the uniform dispersion of the carbon nanotube in the polymer. The carbon nano tubes are divided into single-walled carbon nano tubes and multi-walled carbon nano tubes according to the number of layers, and the multi-walled carbon nano tubes are easy to capture various defects among the layers during formation, so that the defects that the tube walls are full of small hole-shaped defects are caused, and the mechanical properties of the multi-walled carbon nano tubes are influenced.

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 C200, has 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 C200-strength ultrahigh-strength fiber concrete used in different reinforcement layers, anti-seismic reinforcement areas, frame columns (particularly corner columns) of a bottom frame shear layer, shear walls and different floors of a giant ultrahigh-rise structure and a preparation method thereof, wherein the concrete has high toughness, high cohesiveness, high durability, high volume stability and better cooperative deformability, and can better cooperate with steel.

In order to achieve the purpose, the technical scheme disclosed by the invention is as follows: the high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete comprises the following raw materials in parts by weight:

cement 507-containing material 518 parts, sand 720-containing material 730 parts, broken stone 945 parts, fly ash 60-68 parts, straw ash 80-90 parts, silica fume 70-78 parts, nano-silicon 4.6-4.8 parts, water 85-90 parts, water reducing agent 16.8-18 parts, exciting agent 14.5-15 parts, defoaming agent 2.5-2.9 parts, shrinkage reducing agent 14.5-15 parts, ramie fiber 6.2-6.4 parts, basalt fiber 11.3-11.5 parts, carboxyl modified polyvinyl alcohol polymer 20.5-21.5 parts, and hydroxyl modified single-walled carbon nanotube dispersion 31-32 parts.

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 sand adopts hard river sand and high-quality quartz sand with good gradation according to the mass ratio of 7:3, the fineness modulus of the river 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；

Selecting basalt macadam with good grading, compactness, hardness and rough surface from the macadam, mixing the macadams with continuous grain size of 5-10mm and 10-15mm according to the mass ratio of 7:3 for use, wherein the strength of a parent rock is not lower than 250MPa, and the maximum grain size is not more than 15 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 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 more than 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 at the last time, heating to 90 ℃ with distilled water, preserving heat for 15-20min, adding distilled water for soaking after heat preservation, 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 silica content higher than 93%, volcanic ash activity index higher than 95%, average grain size of 0.1-0.15 micron and specific surface area greater than 25m²/g；

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 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 35%, 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 μm, 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/cm³Has good hydrophilicity, higher bond stress 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 hydroxyl modified single-walled carbon nanotube dispersion liquid is prepared by the following method:

1) adding 2 parts of single-walled carbon nanotube into 120 parts of NaOH aqueous solution with the concentration of 3.0-5.0M according to the mass parts, carrying out ultrasonic treatment for 15-20min, and stirring; sealing the carbon nano tube dispersion liquid at high pressure, and reacting for 180min at the temperature of 200-; cooling to room temperature, performing centrifugal separation, adding deionized water for dilution, and removing supernatant; performing ultrasonic treatment for 20min, stirring, filtering with hydrophilic polytetrafluoroethylene filter membrane, and washing the obtained solid product to neutrality; drying at 40 ℃ for 12h to obtain the modified single-walled carbon nanotube with the surface containing hydroxyl and oxygen-containing functional groups;

2) sequentially dispersing 1 part of surfactant polyethylene glycol octyl phenyl ether and 2 parts of modified single-walled carbon nanotube into 98 parts of deionized water, stirring to enable the modified single-walled carbon nanotube to be completely soaked by surfactant aqueous solution, carrying out ultrasonic treatment for 30min, and carrying out centrifugal sedimentation on dispersion liquid;

3) filtering the upper layer liquid through 500-mesh filter cloth to obtain carbon nano tube dispersion liquid 1; carrying out ultrasonic treatment on the liquid with the precipitated and aggregated carbon nanotubes at the bottom for 60min again to obtain carbon nanotube dispersion liquid 2, wherein the carbon nanotube dispersion liquid obtained twice is hydroxyl modified single-walled carbon nanotube dispersion liquid;

the single-walled carbon nanotube has an average tube diameter of 1-2nm, a length of 10-20 μm and a purity of more than or equal to 98.

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 invention also discloses a preparation method of the high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete, which comprises the following steps:

1) adding 16.8-18 parts by mass of water reducing agent and 31-32 parts by mass of hydroxyl modified single-walled carbon nanotube dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 14.5-15 parts of shrinkage reducing agent and 2.5-2.9 parts of defoaming agent into one third of water in the total water amount, marking as mixed solution 2, and preparing 20.5-21.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 85-90 parts;

2) respectively dividing 6.2-6.4 parts of ramie fibers, 945 parts of broken stone, 720-730 parts of sand, 507-518 parts of cement, 60-68 parts of fly ash, 80-90 parts of straw ash, 70-78 parts of silica fume, 4.6-4.8 parts of nano silicon and 11.3-11.5 parts of basalt fibers into three parts, uniformly spreading one part of ramie fibers and basalt fibers in a disc mixer, sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer, and 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 20.5-21.5 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 14.5-15 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 specific concrete strength grade and the quantity and size distribution of cracks in a cement matrix under corresponding proportion, and is based on multi-scale crack grading control and continuous particle grading design of the cementing material, by adding three fibers with different sizes, such as ramie fiber, basalt fiber and hydroxyl modified single-walled carbon nanotube, active mineral admixtures with different particle size ranges, such as fly ash, straw ash, silica fume, nano-silicon and the like, and carboxyl modified polyvinyl alcohol polymer which can fill pores and connect the three fibers, and chemical additives such as a water reducing agent, an exciting agent and the like to prepare the high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete. The ramie fibers with the water storage function and the toughening function are adopted, the ramie fibers can play a role of internal curing in the hydration process of the concrete, the hydration process of a cementing material can be promoted, and meanwhile, basalt fibers and hydroxyl modified single-walled carbon nanotubes are used in a matching manner, a carboxyl modified polyvinyl alcohol polymer is used for filling up pores, the three fibers are bonded with each other to form an organic whole, so that cracks with different sizes in the 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, and comprise 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, and the micro-aggregate filling effect can be more effectively exerted, and on the other hand, all the mineral admixtures can exert the volcanic ash effect and the super-superposition effect, improve the concrete hydration products, reduce the pore size, reduce the number of harmful pores, and improve the compactness of the concrete, thereby acting together in two aspectsUnder the condition, 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, simultaneously, the bond property between the concrete matrix and the fiber material is enhanced, so that the fibers can act synergistically, the toughness of the concrete is further improved, and Cl can be effectively reduced^-、SO₄ ^2-、CO₂And the invasion of harmful ions 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) The basalt fiber and the hydroxyl modified single-walled carbon nanotube used in the invention both have the characteristics of high strength and high elastic modulus, wherein the single-walled carbon nanotube is modified, and is dispersed by using a surfactant and ultrasonic treatment, so that the hydroxyl modified single-walled carbon nanotube capable of being stably and uniformly dispersed in water is obtained on the basis of not cutting off the carbon nanotube and not damaging the mechanical property of the carbon nanotube, and the nanometer size effect and the surface effect of the hydroxyl modified single-walled carbon nanotube play a bridging role as a nanometer fiber, thereby controlling the occurrence and development of nanometer cracks and increasing the strength of a cement matrix material; the lengths of the basalt fiber and the hydroxyl modified single-walled carbon nanotube are respectively 12mm and 10-20 mu m, the formation and development of cracks caused by factors such as plastic shrinkage, drying shrinkage and temperature change of concrete can be effectively inhibited, the basalt fiber and the ramie fiber work cooperatively to play a bridging role, the development of cracks with different scales in the concrete is controlled in a grading way, and the strength, toughness, deformability and durability of the concrete can be effectively improved; 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 the concrete to wrap hydrated products and unhydrated particles to form a spatial three-dimensional continuous network structure, so that microcracks between the matrix are reduced; 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 to form a spatial three-dimensional network structure, crack development of the surrounding concrete is effectively restrained when the section steel is stressed, and an annular restraining effect is formed on the section steel, so that the friction force and the mechanical occlusion force between the section steel and the concrete are effectively improved, the binding force between the concrete and the section steel is further enhanced, and the concrete and the section steel can better cooperate with each other.

3) The invention considers that potassium ions in the straw crops are mainly enriched in new leaves and spores, the content of the mature stems is lower, the potassium ions in the straw crops of different types are different, the mature stems of the corn straws with low potassium ion content are selected to be burnt at a certain temperature, and then the method is simple and easy to implement and has low costThe alkali aggregate reaction in concrete can be effectively prevented by carrying out potassium and sodium removal treatment on the straw ash in a cheap potassium removal mode, the straw ash obtained by grinding after the potassium removal treatment contains more than 84.1 percent of silicon dioxide and a certain amount of active Al and Fe oxides, has high volcanic ash activity, has fine particles (the average particle size is 6-12 mu m), and has large specific surface area due to the porous gaps and the network structure in the straw ash particles, 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 more stable C-S-H gel are generated by reaction, and the breaking 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.

4) 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 can enter more tiny pores, has more unsaturated bonds on the surface and has larger surface energy, and makes the hydration products, particularly Ca (OH)₂The gel is quickly gathered on the surface to react, thereby promoting the growth of the C-S-H gel by taking the gel as a core, limiting the generation of harmful crystals, strengthening the interface structure of a cement matrix, and further improving the breaking strength, the compressive strength, the splitting tensile strength, the toughness, the bonding property and the durability of the concrete.

5) 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.

6) 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 excitation of the mineral admixture by calcium chloride is mainly realized by increasing Ca in a hydration 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 pass through the triethanolamine in the hydration processComplexing Fe and Al phases in the fly ash and the like, promoting the corrosion of the surfaces of fly ash particles and further hydrating active substances in the fly ash. 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.

7) 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-cohesiveness C200 strength ultrahigh-strength fiber concrete prepared by the method has the advantages that the sizes of particles among various cementing materials with different particle diameters in the concrete are uniformly distributed from large to small, the micro-aggregate filling effect of the cementing materials is fully exerted, hydration products of the cementing materials can be stacked and compacted, the pore structure of the concrete is further improved, meanwhile, multi-scale fibers are uniformly dispersed, the multi-scale fibers are organically unified under the bonding action of the carboxyl modified polyvinyl alcohol polymer, a three-dimensional space net structure is formed, the development of cracks with different sizes is effectively inhibited, and therefore, the concrete has high toughness and excellent durability, has good cohesiveness with section steel, the deformability is further improved, and the cooperativity with the section steel is enhanced. The 28d cubic compressive strength of the fiber concrete is not less than 202.89MPa, the flexural strength is not less than 47.65MPa, the splitting tensile strength is not less than 22.55MPa, the bonding strength between the fiber concrete and the section steel is not less than 10.10MPa, and the chloride ion migration coefficient is not more than 10 multiplied by 10^-14m²And s. The high-performance 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, and the method accords with sustainable development and modern green buildingsThe material is a novel green and environment-friendly high-performance fiber concrete material with application and popularization requirements.

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 high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete is prepared by the following method:

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 commercial P & I62.5R-grade portland cement which has good compatibility with polycarboxylic acid water reducing agent.

The sand adopts hard river sand and high-quality quartz sand with good gradation according to the mass ratio of 7:3, the fineness modulus of the river 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 used macadam is selected from basalt macadam with good gradation, compactness, hardness and rough surface, the macadams with continuous grain size of 5-10mm and 10-15mm are mixed according to the mass ratio of 7:3 for use, the strength of a parent rock is not lower than 250MPa, and the maximum grain size is not more than 15 mm.

The fly ash is high-quality class I fly ash in a power plant, the residue of a 0.045mm square-hole sieve is not more than 10 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 by burning stems of mature corn straws at the temperature of 650-820 ℃, removing potassium, and grinding for 25min by using a ball mill, wherein the content of silicon dioxide is more than 84.1%, the average particle size is 6-12 mu m, and the specific surface area is 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;

4) and finally, preserving the heat at 60 ℃ for 2h, replacing supernatant liquor with distilled water, and drying for later use.

The silica fume has silica content of 93% or more, pozzolan activity index of 95% or more, average particle size of 0.1-0.15 μm, and specific surface area of 25m or more²/g。

The high-purity nano silicon dioxide is 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 water reducing agent is a polycarboxylic acid high-performance water reducing agent which is suitable for a cementing material system with low water-cement ratio and high silica fume mixing amount, the solid content is 20 percent, the pH value is 8.0, the water reducing rate is more than 35 percent, 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 used defoamer is a high-efficiency concrete defoamer 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 alkali-treated and dried degummed ramie fiber with the length of 40-50mm, the diameter of 30-40 μm, 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。

The length of the 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, and the specific gravity is 2.63-2.65g/cm³。

1) preparing NaOH aqueous solution with the concentration of 3.0-5.0M, weighing 2 parts of single-walled carbon nanotube, adding into 120 parts of the prepared NaOH aqueous solution, and carrying out ultrasonic treatment for 10-20 min; pouring the carbon nano tube dispersion liquid into a high-pressure reaction kettle, sealing, and reacting for 180min at the temperature of 200-; cooling to room temperature, centrifuging at 2200r/min for 30min, adding deionized water for dilution, removing clear liquid, and repeatedly diluting to remove clear liquid twice; performing ultrasonic treatment for 20min, stirring, filtering with hydrophilic polytetrafluoroethylene filter membrane with filter pore diameter of 0.1 μm, and washing the obtained solid product with water until pH is 7; drying in a vacuum oven at 40 ℃ for 12h to obtain the modified single-walled carbon nanotube with hydroxyl and oxygen-containing functional groups on the surface;

2) weighing 2 parts of the modified single-walled carbon nanotube with the surface containing hydroxyl and oxygen functional groups prepared in the step 1), 1 part of surfactant and 98 parts of deionized water, sequentially dispersing the surfactant and the modified single-walled carbon nanotube into the deionized water, and stirring to completely soak the carbon nanotube by the surfactant aqueous solution; ultrasonic treatment is carried out for 30 min; then carrying out centrifugal sedimentation on the dispersion liquid, wherein the centrifugal rotating speed is 2200r/min, and the centrifugal time is 30 min;

3) filtering the upper layer liquid through 500-mesh filter cloth to obtain carbon nano tube dispersion liquid 1; and (3) carrying out ultrasonic treatment on the liquid with the precipitated and aggregated carbon nanotubes at the bottom for 60min to obtain a carbon nanotube dispersion liquid 2, wherein the hydroxyl modified single-walled carbon nanotubes in the carbon nanotube dispersion liquids 1 and 2 can be uniformly and stably dispersed in water.

Wherein the single-walled carbon nanotube has an average tube diameter of 1-2nm, a length of 10-20 μm, and a purity of more than or equal to 98%; the surfactant is polyethylene glycol octyl phenyl ether.

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

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.

The following specific examples are given to further illustrate the preparation process of the present invention.

Example 1

1) Adding 17.2 parts by mass of water reducing agent and 31.5 parts by mass of hydroxyl modified single-walled carbon nanotube 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 2.5 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 21.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 90 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 39% of carboxyl modified polyvinyl alcohol, 60% of water and 1% of polyacrylate defoaming agent;

2) respectively dividing 6.3 parts of ramie fibers, 945 parts of broken stone, 720 parts of sand, 510 parts of cement, 64 parts of fly ash, 80 parts of straw ash, 74 parts of silica fume, 4.8 parts of nano silicon and 11.4 parts of basalt fibers into three parts, then uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, and then sequentially placing one 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 21.5 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 14.8 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: 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 16.8 parts by mass of water reducing agent and 31 parts by mass of hydroxyl modified single-walled carbon nanotube 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 2.8 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 20.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 85 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 38.5 percent of carboxyl modified polyvinyl alcohol, 60 percent of water and 1.5 percent of polyacrylate defoamer;

2) respectively dividing 6.2 parts of ramie fibers, 945 parts of broken stone, 720 parts of sand, 507 parts of cement, 60 parts of fly ash, 90 parts of straw ash, 70 parts of silica fume, 4.6 parts of nano silicon and 11.3 parts of basalt fibers into three parts, uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc type stirrer, and stirring for 1 min;

5) adding 20.5 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) adding 14.5 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: 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 17.3 parts by mass of water reducing agent and 31 parts by mass of hydroxyl modified single-walled carbon nanotube dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 14.8 parts of weighed shrinkage reducing agent and 2.7 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 21.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 87 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 37.6 percent of carboxyl modified polyvinyl alcohol, 61 percent of water and 1.4 percent of polyacrylate defoamer;

2) respectively dividing 6.3 parts of ramie fibers, 945 parts of broken stone, 720 parts of sand, 510 parts of cement, 60 parts of fly ash, 90 parts of straw ash, 74 parts of silica fume, 4.7 parts of nano silicon and 11.4 parts of basalt fibers into three parts, then uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, and then sequentially placing one 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 14.7 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;

Example 4

1) Adding 18 parts by mass of water reducing agent and 31.5 parts by mass of hydroxyl modified single-walled carbon nanotube 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 2.9 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 21 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 85 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 38.4 percent of carboxyl modified polyvinyl alcohol, 60.4 percent of water and 1.2 percent of polyacrylate defoamer;

2) respectively dividing 6.3 parts of ramie fibers, 945 parts of broken stone, 730 parts of sand, 507 parts of cement, 64 parts of fly ash, 80 parts of straw ash, 78 parts of silica fume, 4.6 parts of nano silicon and 11.4 parts of basalt fibers into three parts, then uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, and then sequentially placing one 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 21 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2 min;

6) then adding 14.6 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: 55.2% of dihydrate gypsum, 43% of calcium chloride and 1.8% of triethanolamine;

Example 5

1) Adding 16.8 parts by mass of water reducing agent and 32 parts by mass of hydroxyl modified single-walled carbon nanotube dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; adding 14.8 parts of weighed shrinkage reducing agent and 2.9 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 20.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 90 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 37% of carboxyl modified polyvinyl alcohol, 62% of water and 1% of polyacrylate defoaming agent;

2) respectively dividing 6.3 parts of ramie fibers, 945 parts of broken stone, 725 parts of sand, 518 parts of cement, 68 parts of fly ash, 85 parts of straw ash, 70 parts of silica fume, 4.8 parts of nano silicon and 11.4 parts of basalt fibers into three parts, uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc type stirrer, and stirring for 1 min;

6) adding 15 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 6

1) Adding 18 parts by mass of water reducing agent and 32 parts by mass of hydroxyl modified single-walled carbon nanotube 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 2.5 parts of defoaming agent into one third of water of the total water amount, marking as a mixed solution 2, and preparing 20.5 parts of carboxyl modified polyvinyl alcohol polymer for later use, wherein the total water amount is 90 parts; wherein, the carboxyl modified polyvinyl alcohol polymer is prepared by the following raw materials by mass percent: 36% of carboxyl modified polyvinyl alcohol, 62.5% of water and 1.5% of polyacrylate defoamer;

2) respectively dividing 6.4 parts of ramie fibers, 945 parts of broken stone, 730 parts of sand, 518 parts of cement, 68 parts of fly ash, 80 parts of straw ash, 78 parts of silica fume, 4.8 parts of nano silicon and 11.5 parts of basalt fibers into three parts, uniformly spreading one part of ramie fibers and basalt fibers in a disc type stirrer, sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc type stirrer, and stirring for 1 min;

6) adding 15 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;

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 adopting a single excitant without adopting a gelled particle continuous grading design, adding fibers, adding a carboxyl modified polyvinyl alcohol polymer and a hydroxyl modified single-walled carbon nanotube dispersion liquid.

The mixture ratio is as follows: 548 parts of cement, 715 parts of sand, 945 parts of broken stone, 60 parts of fly ash, 80 parts of silica fume, 124 parts of water, 16.5 parts of a water reducing agent, 12.1 parts of an exciting agent and 2.2 parts of a defoaming agent.

The preparation method comprises the following steps:

1) adding 16.5 parts by mass of a water reducing agent into two thirds of the total water amount, and marking as a mixed solution 1; adding 2.2 parts of weighed defoaming agent into one third of water of the total water amount, and marking as a mixed solution 2, wherein the total water amount is 124 parts;

2) placing 945 parts of broken stone, 715 parts of sand, 548 parts of cement, 60 parts of fly ash and 80 parts of silica fume in 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 12.1 parts of excitant calcium chloride 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, C200 strength, ultra high strength 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 C200 strength ultrahigh-strength fiber concrete prepared by the invention meets the compressive strength and bending strength required by the member when loaded, and ensures the cohesive strength of the member working cooperatively with steel. The 28d cubic compressive strength is not less than 202.89MPa, the flexural strength is not less than 47.65MPa, the splitting tensile strength is not less than 22.55MPa, the bonding strength between the structural steel and the structural steel is not less than 10.10MPa, and the chloride ion migration coefficient is not more than 10 multiplied by 10^-14m²And s. Example 4 is the optimum mix proportion, the gelled material particle composition is the optimum, the carboxyl modified polyvinyl alcohol polymer is the optimum, the fiber mix is the optimum. Under the strength grade of C200, 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 C200-strength ultrahigh-strength fiber concrete is characterized by comprising the following raw materials in parts by weight:

2. The high-toughness high-cohesiveness C200 strength ultrahigh-strength 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 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 of the nano silicon dioxide is more than 99 percent, the average grain diameter is 10nm-40nm, and the specific surfaceProduct greater 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 35%;

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 C200 strength ultrahigh-strength fiber concrete according to claim 1, wherein said straw ash is prepared by burning mature stems of corn straws at 650-820 ℃, subjecting to potassium removal treatment, and grinding for 25min 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 C200 strength ultra high strength fiber concrete of 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 C200 strength ultrahigh-strength 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:

6. The high-toughness high-cohesiveness C200 strength ultrahigh-strength 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；

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。

7. The high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete according to claim 1, wherein said hydroxyl-modified single-walled carbon nanotube dispersion is prepared by the following method:

8. The high tenacity high cohesiveness C200 strength ultra high strength fiber concrete of 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.

9. A method for preparing the high-toughness high-cohesiveness C200 strength ultrahigh-strength 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. The forming and curing method of the high-toughness high-cohesiveness C200 strength ultrahigh-strength fiber concrete prepared by the method of claim 9 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.