CN113024189B - High-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete and preparation method thereof - Google Patents

High-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete and preparation method thereof Download PDF

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CN113024189B
CN113024189B CN202011010525.5A CN202011010525A CN113024189B CN 113024189 B CN113024189 B CN 113024189B CN 202011010525 A CN202011010525 A CN 202011010525A CN 113024189 B CN113024189 B CN 113024189B
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water
concrete
strength
polyvinyl alcohol
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CN113024189A (en
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郑山锁
董晋琦
阮升
刘晓航
杨松
郑淏
温桂峰
刘华
龙立
尚志刚
郑捷
张晓辉
曹琛
董立国
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Xian University of Architecture and Technology
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C04B28/04—Portland cements
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C04B20/023—Chemical treatment
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    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C04B40/0039—Premixtures of ingredients
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C04B40/0039—Premixtures of ingredients
    • C04B40/0046—Premixtures of ingredients characterised by their processing, e.g. sequence of mixing the ingredients when preparing the premixtures
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/2015—Sulfate resistance
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/22—Carbonation resistance
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/27—Water resistance, i.e. waterproof or water-repellent materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/29—Frost-thaw resistance
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    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/34—Non-shrinking or non-cracking materials
    • C04B2111/343—Crack resistant materials
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    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
    • C04B2201/52—High compression strength concretes, i.e. with a compression strength higher than about 55 N/mm2, e.g. reactive powder concrete [RPC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

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  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention discloses a high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete and a preparation method thereof, wherein the mixing proportion comprises the following components: and (3) cement: sand: broken stone: fly ash: straw ash: silica fume: nano silicon: water: water reducing agent: exciting agent: defoaming agent: shrinkage reducing agent: ramie fiber: basalt fiber: caCO (CaCO) 3 Whisker: carboxyl modified polyvinyl alcohol polymer: nano titanium/graphene oxide dispersion = 550-560:760-770:830-840:65-70:103-108:125-135:5.4-5.6:70-75:20-21:16-17:3-3.3:14.5-15:7.5-8:13.3-13.6:21-21.5:22-23.5:42-46. Uniformly mixing the materials by a layered stirring method, discharging, forming and maintaining. The concrete mechanics, durability and the bonding performance between the profile steel are all obviously improved.

Description

High-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete and preparation method thereof
Technical Field
The invention belongs to the field of building materials, and relates to a composite material which is doped with ramie fibers, basalt fibers and CaCO 3 Whisker, carboxyl modified polyvinyl alcohol polymer, nano titanium/graphene oxide dispersion liquid, straw ash, fly ash, silica fume and nano silicon concrete with higher toughness, high cohesiveness, high durability and high volume stability, and in particular relates to high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete and a preparation method thereof.
Background
In structural design, considering the demands of using functions, member rigidity and construction convenience, different grade concrete is generally adopted according to different stress conditions so as to meet the compressive strength, bending resistance and splitting tensile strength required by the members when the members are stressed and ensure the bonding strength of the concrete and steel for cooperative work. The concrete materials with different labels have different elastic moduli and different deformation properties, so that excessive or insufficient strength indexes can cause uncoordinated deformation of steel and concrete when the member is stressed, thereby causing that the two materials cannot fully cooperate or a certain material cannot fully exert mechanical properties, and causing material waste. The common concrete and the high-performance concrete materials have poor cracking resistance and large brittleness, and the brittleness characteristics are more obvious along with the improvement of the strength grade of the concrete, and in a high-stress or complex stress state, concrete with a specific high strength grade is often needed to be used, for example, in the ultra-large span, heavy-load structure, ultra-large span bridge and bridge pier and ultra-durable hydraulic structure with different span and bearing requirements in different floors including a bottom stress layer, a reinforcing layer and industrial buildings, the requirements on the bearing capacity, rigidity and structure using functions of the components are strict, so that the concrete with the C250 strength grade is sometimes needed to be used specifically in consideration of the bearing capacity, rigidity requirements, economic benefits, design requirements and the like, and at the moment, the brittleness characteristics of the concrete can reduce the anti-seismic bearing capacity of the components and the structure under complex stress and severe environments, and even influence the safety and reliability of the components. Meanwhile, with the gradual improvement of the mechanical properties of steel, the toughness, the deformation performance and the bonding performance of common concrete are difficult to meet the synergistic effect between the concrete and the profile steel.
The silica fume has excellent particle size and volcanic ash activity, is an important mineral admixture for preparing high-performance concrete, but has lower annual output in China, only has 3000t-4000t, can only meet the requirement of partial high-performance concrete, and limits the mass use of the silica fume. And the yield of straw per year is more than 7 hundred million t, which is the first place in the world. At present, only a small part of straws are used for power generation of biomass energy power plants, and most of straws are still naturally piled up or burned in the open air, so that resource waste and environmental pollution are caused. Straw ash generated by power generation of a power plant can cause secondary pollution to the environment if the straw ash is not properly developed and utilized. Along with the technological progress, cornStraw ash prepared by burning straw under proper conditions contains about 85% of amorphous SiO 2 And a certain amount of active Al 2 O 3 The content of the metal oxide K, na is less, the pozzolan 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 are used in concrete through hydration products generated by hydration reaction, and the nature of the hydration products is often poor, so that the formed needle-shaped and flake-shaped hydration products have larger brittleness, and further the brittleness of a concrete matrix is larger, so that a template is provided for the hydration reaction of the cementing material, the hydration products react in the template, and thick and dense hydration crystals are generated, and the method is an effective method for improving the internal structure of the concrete. Graphene oxide and nano TiO 2 The template effect and the nucleation effect of the two materials can provide good attachment points for hydration products, so that the hydration products are stronger and tighter, and the brittleness problem of the concrete is radically improved.
The toughness of concrete and cement-based composite materials is generally improved by adding fibers, and the existing steel fibers and synthetic fibers are difficult to popularize in concrete engineering application due to complex process, high cost and low yield, so that the engineering community gradually starts to search 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 pH resistance, green and pollution-free performance, and can effectively replace the application of steel fibers and synthetic fibers in engineering. The method is mainly used for producing the ramie in China, and the yield of the ramie accounts for more than 90% of the world, so that the ramie fibers are convenient to obtain in China, low in price and high in popularization and application value. Meanwhile, because cracks with different sizes exist in the concrete, the optimal toughening effect cannot be achieved by adding single fibers.
In summary, from the perspective of green environmental protection, cost saving and effective utilization of resources, the adoption of multistage crack control and macroscopic to microscopic particle grading optimization design, and the organic combination of the multistage crack control and the macroscopic to microscopic particle grading optimization design are considered to form a unified whole, so that the improvement and the enhancement of the internal structure of the concrete are realized, and the high-toughness high-cohesiveness ultra-high-strength concrete with the C250 strength grade, higher toughness, high cohesiveness, high durability and better cooperative deformability and capable of cooperating with high-performance steel is prepared to be the technical problem to be solved in the current field.
Disclosure of Invention
The invention aims to provide high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete used in ultrahigh-rise structures with different spans and bearing requirements, ultrahigh-span and heavy-load structures, ultrahigh-span bridges and piers thereof and ultrahigh-durability hydraulic structures in different floors of a giant ultrahigh-rise structure, comprising a bottom stress layer, a reinforcing layer and industrial buildings, and a preparation method thereof.
In order to achieve the above purpose, the technical scheme disclosed by the invention is as follows: the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete comprises the following raw materials in parts by weight:
550-560 parts of cement, 760-770 parts of sand, 830-840 parts of crushed stone, 65-70 parts of fly ash, 103-108 parts of straw ash, 125-135 parts of silica fume, 5.4-5.6 parts of nano silicon, 70-75 parts of water, 20-21 parts of water reducer, 16-17 parts of excitant, 3-3.3 parts of defoamer, 14.5-15 parts of shrinkage reducer, 7.5-8 parts of ramie fiber, 13.3-13.6 parts of basalt fiber, 21-21.5 parts of CaCO3 whisker, 42-46 parts of nano titanium/graphene oxide dispersion liquid and 22-23.5 parts of carboxyl modified polyvinyl alcohol polymer.
The cement is P I62.5R-grade silicate cement, and a cement variety with good compatibility with the polycarboxylic acid water reducer is selected.
The fine aggregate adopts hard sand with mass ratio of 1:1 and high-quality quartz sand with good grading, the fineness modulus of the sand is 2.8-3.0, the silicon dioxide content in the quartz sand is not less than 98%, the grain diameter is 0.3-0.6mm, and the density is 2.62g/cm 3 ；
The basalt crushed stone with good grading, compactness, hardness and rough surface is selected, the grain size range is 5-10mm, and the basalt crushed stone is graded according to continuous grain grades.
The fly ash adoptsThe high-quality I-grade fly ash of the power plant has a screen residue of 45 μm square hole screen not more than 10%, a water demand ratio not more than 95% and a specific surface area of 400m 2 /kg。
The straw ash is prepared by burning stems of mature corn straw at 650-820 deg.C, removing potassium, grinding for 25min with ball mill, and has silicon dioxide content of 84.1%, average particle diameter of 6-12 μm, and specific surface area of more than 12m 2 /g。
Further, the potassium removal treatment method comprises the following steps:
1) Placing the straw ash into distilled water for stirring and soaking, then standing, pouring out supernatant, continuously adding distilled water for stirring and soaking, and repeating the process for more than 5 times, wherein the soaking time lasts for one week;
2) Pouring out the supernatant liquid for the last time, heating to 90 ℃ with distilled water, preserving heat for 15-20min, pouring out the supernatant liquid after preserving heat, adding distilled water for soaking, and repeating the step 1);
3) Repeating steps 1) and 2) twice in sequence;
4) Finally, the temperature is kept at 60 ℃ for 2 hours, and the supernatant is poured out and dried for standby.
The silica fume has silica content greater than 95%, volcanic ash activity index greater than 95%, average particle size of 0.1-0.15 μm, and specific surface area greater than 28m 2 /g；
The nano silicon is high-purity nano silicon dioxide prepared by a gas phase method, the purity is more than 99%, the average particle size is 10nm-40nm, and the specific surface area is more than 130m 2 /g。
The water reducer is a polycarboxylic acid high-performance water reducer suitable for a cementing material system with low water-cement ratio and high silica fume content, the solid content is 20%, the water reducing rate is more than 38%, and the compression strength ratio of 7d to 28d is not less than 180%, so that the compression strength of concrete is not adversely affected.
The shrinkage reducing agent is SU-SRA type shrinkage reducing agent.
The defoaming agent is a Liqi X-2756 efficient concrete defoaming agent.
The exciting agent is an organic-inorganic composite exciting agent, and the composite exciting agent is prepared by compounding 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, the length is 40-50mm, the diameter is 30-40 mu m, the tensile strength is more than or equal to 1000MPa, the elastic modulus is more than or equal to 11.4GPa, the breaking elongation is 8.9%, and the specific gravity is 1.54-1.55g/cm 3 Has good hydrophilicity, high bond strength and acid and alkali resistance.
The basalt fiber has a length of 12mm, a diameter of 7-15 μm, a tensile strength of not less than 3000MPa, an elastic modulus of not less than 91GPa and a specific gravity of 2.63-2.65g/cm 3 ；
Said CaCO 3 The whisker length 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/cm 3 。
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 carboxyl modified polyvinyl alcohol has a degree of polymerization of 2400, an alcoholysis degree of 99%, a carboxyl/hydroxyl molar ratio of 3/97, and a ph=7;
further, the auxiliary agent is polyacrylate defoamer;
further, the mixing and homogenizing method comprises the following steps: placing carboxyl modified polyvinyl alcohol into water, standing for 30min at normal temperature to fully swell, then placing into a constant temperature water tank at 95 ℃ for heating and dissolving, adding an auxiliary agent, continuously stirring until a uniform transparent solution is formed, and preserving heat for later use.
The nano titanium/graphene oxide dispersion liquid is obtained by the following method:
(1) 0.1 to 0.2 part of nano TiO is added according to the mass part 2 Adding 0.1 part of surfactant polyethylene glycol octyl phenyl ether into 100 parts of deionized water, stirring at high speed, then performing ultrasonic dispersion for 20-30min by using an ultrasonic machine, and adding 1-1.5 parts of graphite oxideCarrying out ultrasonic dispersion on the alkene powder for 30min to obtain a nano titanium/graphene oxide aqueous solution;
(2) Adding 0.1 part of water reducer 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 performing ultrasonic dispersion for 10min to obtain nano titanium/graphene oxide dispersion;
further, the graphene oxide is in a powder shape, the purity is more than or equal to 98%, the diameter is 10-20 mu m, the surface of the graphene oxide is provided with a large number of oxygen-containing groups, and the graphene oxide has high dispersity in water;
further, the nano TiO 2 The purity is about 99 percent, the grain diameter is 10nm-50nm, and the product has hydrophilicity;
further, the water reducer is a polycarboxylic acid high-performance water reducer, the solid content is 20%, and the pH value is 7.
The invention also discloses a preparation method of the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete, which comprises the following steps:
1) Adding 20-21 parts by mass of water reducer and 42-46 parts by mass of nano titanium/graphene oxide dispersion liquid into water with two thirds of the total water amount, and marking as a mixed solution 1; adding 14.5-15 parts of the weighed shrinkage reducing agent and 3-3.3 parts of the defoamer into one third of the total water, and marking as a mixed solution 2; preparing 22-23.5 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water quantity is 70-75 parts;
2) 7.5 to 8 parts of ramie fiber, 830 to 840 parts of broken stone, 760 to 770 parts of sand, 550 to 560 parts of cement, 65 to 70 parts of fly ash, 103 to 108 parts of straw ash, 125 to 135 parts of silica fume, 5.4 to 5.6 parts of nano silicon, 13.3 to 13.6 parts of basalt fiber and 21 to 21.5 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding the prepared 22-23.5 parts of carboxyl modified polyvinyl alcohol polymer, and stirring for 2min;
6) Adding 16-17 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method obtained by the preparation method comprises the following steps:
standard curing: pouring the concrete mixture into a cast iron mold for molding and compaction, standing for 1d-2d in a standard curing chamber 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 chamber to the required age.
In order to overcome the problems of high brittleness, low toughness, poor durability, poor bonding performance with section steel and the like of common concrete, the invention utilizes the easily obtained materials in the market and adopts an improved concrete layering stirring process, considers the dosage proportion of each cementing material required by specific concrete strength grade and the number and size distribution of cracks in a cement matrix under the corresponding proportion, and is based on multi-scale crack grading control and continuous grain grading design of the cementing material by adding ramie fibers, basalt fibers and CaCO 3 The active mineral admixture of three kinds of fiber with different sizes, fly ash, straw ash, silica fume, nano silicon and other particle size ranges, carboxyl modified polyvinyl alcohol polymer capable of filling pores and connecting the three kinds of fiber, nano silicon/graphene oxide dispersion liquid playing the role of a template, water reducing agent, excitant and other chemical additives are prepared into the high-toughness high-cohesiveness C250 super-high-strength mixed fiber concrete. Wherein, the ramie fiber with water storage function and toughening function can play an internal curing role in the hydration process of concrete, promote the hydration process of the cementing material, and simultaneously, the basalt fiber and CaCO are matched 3 Whisker and modified polyethylene with carboxylThe enol polymer fills the pores, and three fibers are mutually bonded to form an organic whole, so that cracks with different dimensions 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 also wrap hydration products, so that the hydration products react more fully, and carboxyl contained in the carboxyl modified polyvinyl alcohol polymer reacts with Ca 2+ And an ionic bond is generated, and hydroxyl contained in the ionic bond forms a hydrogen bond with oxygen in a silicon-oxygen hydration product, and the ionic bond is crosslinked with the hydration product, so that the pores are effectively filled, and the structure is more compact. In addition, mineral admixtures with different particle sizes, including fly ash, straw ash, silica fume and nano-scale nano silicon dioxide, are added into the concrete, so that on one hand, continuous particle grading is formed among all cementing materials, the micro aggregate filling effect of the cementing materials can be effectively exerted, on the other hand, each mineral admixtures can exert pozzolan effect and super-superposition effect, further, by adding nano titanium/graphene oxide dispersion liquid, the template effect and nucleation effect of the mineral admixtures are exerted, the structure of a hydration product of the concrete is improved, the pore size is reduced, the number of harmful pores is reduced, the compactness of the concrete is improved, the bonding interface between the concrete and profile steel is more compact under the combined action of the two aspects, the bonding force is further improved along with the improvement of the form of the hydration product, the bonding force between a concrete matrix and the fiber material is enhanced, the fibers can be synergistically exerted, the toughness of the concrete is further improved, and the Cl can be effectively reduced - 、SO 4 2- 、CO 2 And harmful ions such as ions invade, so that the durability of the concrete is improved. According to the invention, through the synergistic effect of the components, the pore structure of the concrete is improved, so that the internal structure of the concrete is more compact, the hydration shrinkage of the concrete and the development of cracks with different dimensions under the stress state are targeted inhibited, 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 fiber used in the invention is long fiber with 40-50mm, has 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 natural hydrophilicity of the ramie fibers enables the surface of the ramie fibers to have strong bond strength, good bonding capability with a cement matrix, and enough anchoring length of the long fibers, so that the ramie fibers can be effectively prevented from being pulled out when the concrete cracks, further development of the cracks is prevented, and the deformation capability and the energy consumption capability of the concrete can be increased due to the bridging effect 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 moisture, so that an internal curing effect is achieved, and the hydration process of concrete is promoted. Therefore, the ramie fiber can improve the mechanical property of the concrete and the durability such as crack resistance, permeability resistance, freeze thawing resistance and the like.
2) Basalt fiber and CaCO used in the present invention 3 Whisker has the characteristics of high strength and high elastic modulus, the lengths are respectively 12mm and 20-30 mu m, the formation and development of cracks caused by factors such as plastic shrinkage, temperature change and the like of concrete can be effectively inhibited, the whisker and ramie fiber work cooperatively to play a bridging role, the crack development of different scales in the concrete is controlled in a grading manner, and the strength, toughness, deformation performance 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 action of the aggregate surface, improve the bonding capability between the aggregate and a matrix, and simultaneously, the polymer forms a film to wrap hydration products and unhydrated particles in the concrete to form a space three-dimensional continuous network structure, so that microcracks among the matrixes are reduced, the network structure of the polymer is mutually connected with three fibers to jointly form a more dense space three-dimensional network structure, the toughness of the concrete and the bonding performance of the concrete and profile steel are improved, further, the polymer and a cementing material have a certain degree of chemical reaction, the crosslinking of the polymer and the hydration products is enhanced, the bond strength of the matrix to the fibers is also enhanced, the fibers are prevented from being pulled out when the concrete is cracked, and the crack is further prevented from developing. In addition, when the invention is used for the steel reinforced concrete composite structure, three fibers and polymers are uniformly dispersed in the concrete and are mutually connected to form a space three-dimensional net structure, so that the invention is effective When the section steel is constrained to bear force, the cracks of surrounding concrete develop, a circular constraint effect is formed on the section steel, so that the friction force and mechanical biting 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 work better in a cooperative mode.
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. Nanometer TiO 2 On the one hand, the nano titanium dioxide has a filling effect with graphene oxide, and on the other hand, the nano titanium dioxide has a larger surface energy, so that hydration products, particularly Ca (OH), are formed 2 The graphene oxide is a known thinnest two-dimensional material, has a large specific surface area, contains a large number of functional groups on the surface, has an adsorption effect on hydration products, and plays a role of a template, so that the hydration products become thick cluster crystals, the mechanical and durability of the concrete are further improved, on the other hand, the oxygen-containing functional groups on the surface of the graphene oxide can further react with cement hydration products such as calcium hydroxide, ettringite, calcium silicate hydrate and the like, the shape of the cement hydration crystal products is changed, the toughness of the cement matrix is enhanced, the concrete structure has higher fracture resistance, compressive strength and the like, and the bonding performance between the concrete and the section steel is enhanced.
4) The invention takes into consideration that the potassium ions in the straw crops are mainly enriched in new leaves and spores, the content of the mature stems is lower, the potassium ion content of the straw crops of different types is different, the mature stems of the corn straw with low potassium ion content are selected to burn at a certain temperature, then the corn straw is treated by removing potassium and sodium in a simple and easy-to-operate and low-cost potassium removing mode, the alkali aggregate reaction in the concrete can be effectively prevented, the straw ash obtained by grinding after the potassium removing treatment contains more than 84.1 percent of silicon dioxide and a certain amount of active Al and Fe oxides, the volcanic ash activity is higher, the particles of the straw ash are tiny (the average particle diameter is 6-12 mu m), the porous and net channel structure in the straw ash particles enables the straw ash to have larger specific surface area, and the energyUp to 12m 2 And/g. The straw ash is doped, so that the cementing material particles are more uniform, the gradation is good, the filling compaction effect can be achieved, and the cohesiveness of the concrete is further improved; in addition, because the straw ash has volcanic ash activity similar to that of the silica fume, the straw ash can replace part of the silica fume and can be used for Ca (OH) in a concrete system 2 The reaction generates compact and hard hydrated calcium sulfoaluminate and more stable C-S-H gel, and improves the flexural strength, compressive strength, splitting tensile strength and durability of the concrete; finally, the straw ash is used as agricultural waste, and the treated straw ash is used as a building material to replace part of cement, so that CO in the straw burning and cement production process can be reduced 2 The discharge amount is reduced, so that the cost of concrete is reduced, the reutilization of agricultural wastes is realized, and the purposes of energy conservation and environmental protection are achieved.
5) The fly ash, the straw ash, the silica fume and the nano silicon dioxide which are mixed in the invention have different particle size ranges to form more continuous grain composition of the cementing material, can better exert the filling effect of the micro aggregate, and simultaneously, the fly ash, the straw ash, the silica fume and the nano silicon generate a super-superposition effect to further promote the hydration of the cementing material, so that more hydration products are converted into C-S-H gel, the pore structure and the cohesiveness of the concrete are improved, and in addition, the nano silicon dioxide has larger surface energy due to the particle diameter of the nano silicon dioxide, has nucleation effect, and ensures that the hydration products, especially Ca (OH), are formed 2 The C-S-H gel is quickly gathered on the surface of the gel to react, so that the C-S-H gel is promoted to grow by taking the gel as a core, the generation of harmful crystals is limited, the interface structure of a cement matrix is strengthened, meanwhile, the gel can enter into tiny pores, the surface of the gel contains a large amount of unsaturated bonds, the gel can be fully dispersed in gaps among other particles to hydrate, and the flexural 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 the capillary holes of the concrete, compact the concrete structure, further control the shrinkage of the concrete mass, the plastic shrinkage at early hardening and the like, further improve the crack resistance and the permeability resistance of the concrete, and strengthen the durability of the concrete.
7) The exciting agent adopts an organic-inorganic composite exciting agent, and the exciting agent plays a role in jointly exciting by the dihydrate gypsum, the calcium chloride and the triethanolamine, so that ettringite is promoted to be generated, the concrete doped with the fly ash, the silica fume, the nano silicon dioxide and the straw ash has certain micro-expansibility, and the shrinkage performance of the concrete is improved. The glass body reticular structure on the surface of the fly ash is depolymerized by the composite excitant, so that the potential activity of the fly ash is excited, the corrosion effect of the glass body with the three-dimensional space structure taking aluminosilicate as a main hydration component in the fly ash hydration process can be enhanced, the power of forward hydration reaction is improved, more C-S-H gel, hydrated calcium aluminate and other crystals are generated, and the fly ash is promoted to participate in early hydration process. The excitation effect of the dihydrate gypsum on the mineral admixture is shown as follows: SO (SO) 4- Gel with the surface of fly ash particles and AlO dissolved in liquid phase 2- Reacting to generate hydrated calcium sulfoaluminate AFt; in addition, SO 4 2- Can also replace part of SiO in the hydrated calcium silicate 2 2- Displaced SiO 2 2- At the outer layer with Ca 2+ 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 hydrate 2+ SiO in fly ash, silica fume, nano silicon dioxide and straw ash 2 、Fe 2 O 3 、Al 2 O 3 And reacting to generate hydrated calcium silicate, hydrated calcium ferrite, hydrated calcium aluminate and the like. The excitation of calcium chloride to mineral admixture is mainly achieved by increasing Ca in hydration system 2+ The concentration, the formation of the hydrated chloroaluminate gel phase and the hydrated calcium aluminate are realized, besides, the calcium chloride as a strong electrolyte can also supplement Ca required by the reaction of silica fume, straw ash and nano silicon dioxide in the process of exciting the activity of the fly ash by sulfate 2+ . As an organic fly ash activity excitant, triethanolamine can complex Fe and Al phases in fly ash and the like in the hydration process, promote corrosion of the surfaces of fly ash particles and further hydrate active substances in the fly ash. The synergistic effect among the dihydrate gypsum, the calcium chloride and the triethanolamine can fully excite 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, durability and the like of the concrete.
8) The invention adopts a layered stirring method, and determines the particle size of the maximum broken stone particles through experiments, so that long fibers and aggregates can be dispersed uniformly to the greatest extent, the mutual interference of the long fibers and coarse aggregates is avoided, the aggregation of the fibers is avoided, and larger holes are generated in a cement matrix, and even the honeycomb pitting surface phenomenon is caused.
The measures can effectively improve the compressive strength, toughness, deformability, durability and the like of the concrete, and enhance the bonding strength and the collaborative deformability between the concrete and the profile steel. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete prepared by the method provided by the invention has the advantages that the particle sizes of various cementing materials with different particle diameters in the concrete are uniformly distributed from large to small, the micro aggregate filling effect of each cementing material is fully exerted, the hydration products of the cementing materials can be stacked and compacted, and the high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete is prepared by the method provided by the invention, wherein the high-cohesiveness C250 ultrahigh-cohesiveness hybrid fiber concrete is prepared by the method provided by the invention 2 The template effect and the nucleation effect of the modified polyvinyl alcohol polymer improve the physical and mechanical properties of hydration products, further improve the pore structure of the concrete, simultaneously uniformly disperse the multi-scale fibers, organically unify under the bonding effect of the modified polyvinyl alcohol polymer to form a three-dimensional space reticular 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 the section steel, further improves the deformability, and enhances the synergy with the section steel. The fiber concrete has 28d cube compressive strength not less than 255.19MPa, flexural strength not less than 59.35MPa, split tensile strength not less than 28.66MPa, bonding strength with section steel not less than 11.83MPa, and chloride ion migration coefficient not greater than 5×10 -14 m 2 And/s. The high-performance hybrid fiber concrete with high volume stability, high durability and high toughness is prepared by the method, 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 high-performance hybrid fiber concrete material is a novel green and environment-friendly high-performance hybrid fiber concrete material.
Detailed Description
The present invention is further described in the following with reference to specific embodiments, using examples, to make the advantages of the present invention more easily understood by those skilled in the art, but not to limit the scope of the present invention.
The invention relates to high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete, which is prepared by the following method:
1) Adding 20-21 parts by mass of water reducer and 42-46 parts by mass of nano titanium/graphene oxide dispersion liquid into water with two thirds of the total water amount, and marking as a mixed solution 1; adding 14.5-15 parts of the weighed shrinkage reducing agent and 3-3.3 parts of the defoamer into one third of the total water, and marking as a mixed solution 2; preparing 22-23.5 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water quantity is 70-75 parts;
2) 7.5 to 8 parts of ramie fiber, 830 to 840 parts of broken stone, 760 to 770 parts of sand, 550 to 560 parts of cement, 65 to 70 parts of fly ash, 103 to 108 parts of straw ash, 125 to 135 parts of silica fume, 5.4 to 5.6 parts of nano silicon, 13.3 to 13.6 parts of basalt fiber and 21 to 21.5 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding the prepared 22-23.5 parts of carboxyl modified polyvinyl alcohol polymer, and stirring for 2min;
6) Adding 16-17 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete forming and curing method in the invention comprises the following steps:
pouring the concrete mixture into a cast iron mold for molding, compacting by using a vibrating table, and then performing contact vibration along the outer wall of the test mold by using a vibrating rod so as to discharge redundant 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 wetted geotextile, standing for 1d, removing the mold, and curing in a standard curing room with the temperature of 20+/-2 ℃ and the relative humidity of more than or equal to 95% until the required age.
Wherein:
the cement is P I62.5R-grade silicate cement, and a cement variety with good compatibility with the polycarboxylic acid water reducer is selected.
The fine aggregate adopts hard sand with mass ratio of 1:1 and high-quality quartz sand with good grading, the fineness modulus of the sand is 2.8-3.0, the silicon dioxide content in the quartz sand is not less than 98%, the grain diameter is 0.3-0.6mm, and the density is 2.62g/cm 3 。
The basalt crushed stone with good grading, compactness, hardness and rough surface is selected, the grain size range is 5-10mm, and the basalt crushed stone is graded according to continuous grain grades.
The fly ash adopts high-quality class I fly ash of a power plant, the screen residue of a 45 mu m square-hole screen is not more than 10%, the water demand ratio is not more than 95%, and the specific surface area is not more than 400m 2 Per kg, the average particle diameter is in the range of 10-30. Mu.m.
The straw ash is prepared by burning stems of mature corn straw at 650-820 deg.C, removing potassium, grinding for 25min with ball mill, and has silicon dioxide content of 84.1%, average particle diameter of 6-12 μm, and specific surface area of more than 12m 2 /g。
The potassium removing treatment method comprises the following steps:
1) Placing the straw ash into distilled water for stirring and soaking, then standing, pouring out supernatant, continuously adding distilled water for stirring and soaking, and repeating the process for more than 5 times, wherein the soaking time lasts for one week;
2) Pouring out the supernatant liquid for the last time, heating to 90 ℃ with distilled water, preserving heat for 15-20min, pouring out the supernatant liquid after preserving heat, adding distilled water for soaking, and repeating the step 1);
3) Repeating steps 1) and 2) twice in sequence;
4) Finally, the temperature is kept at 60 ℃ for 2 hours, and the supernatant is poured out and dried for standby.
The silica content of the silica fume is more than 95%, the volcanic ash activity index is more than 95%, the average grain diameter is 0.1-0.15 mu m, and the specific surface area is more than 28m 2 /g；
The nano silicon is high-purity nano silicon dioxide prepared by a gas phase method, the purity is more than 99%, the average grain diameter is 10nm-40nm, and the specific surface area is more than 130m 2 /g。
The water reducer is a polycarboxylic acid high-performance water reducer which is suitable for a cementing material system with low water-cement ratio and high silica fume content, the solid content is 20%, the water reducing rate is more than 38%, and the compression strength ratio of 7d and 28d is not less than 180%, so that the compression strength of concrete is not adversely affected.
The reducer is SU-SRA type reducer. The defoaming agent adopts Liqi X-2756 high-efficiency concrete defoaming agent.
The exciting agent is an organic-inorganic composite exciting agent, and the composite exciting agent is prepared by compounding 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 and dried after alkali treatment and drying, the length is 40-50mm, the diameter is 30-40 mu m, the tensile strength is more than or equal to 1000MPa, the elastic modulus is more than or equal to 11.4GPa, the breaking elongation is 8.9%, and the specific gravity is 1.54-1.55g/cm 3 Has good hydrophilicity, high bond strength and acid and alkali resistance.
Basalt fiber length is 12mm, diameter is 7 μm-15 μm, tensile strength is more than or equal to 3000MPa, elastic modulus is more than or equal to 91GPa, specific gravity is 2.63-2.65g/cm 3 。
CaCO 3 The whisker length 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/cm 3 。
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.
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=7; the auxiliary agent is polyacrylate defoamer.
The mixing method comprises the following steps: placing carboxyl modified polyvinyl alcohol into water, standing for 30min at normal temperature to fully swell, then placing into a constant temperature water tank at 95 ℃ for heating and dissolving, adding an auxiliary agent, continuously stirring until a uniform transparent solution is formed, and preserving heat for later use.
The nano titanium/graphene oxide dispersion liquid is obtained by the following method:
(1) 0.1 to 0.2 part of nano TiO is added according to the mass part 2 Adding 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 reducer 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 performing ultrasonic dispersion for 10min to obtain nano titanium/graphene oxide dispersion;
wherein, the graphene oxide is in powder shape, the purity is more than or equal to 98 percent, the diameter is 10 mu m to 20 mu m, the surface of the graphene oxide has a large number of oxygen-containing groups, and the graphene oxide has higher dispersity in water; nanometer TiO 2 The purity is about 99%, the particle size is 10nm-50nm, and the product has hydrophilicity.
The water reducer is a polycarboxylic acid high-performance water reducer, the solid content is 20%, and the pH value is 7. Specific examples are given below to further illustrate the preparation process of the present invention.
Example 1
1) Adding 21 parts by weight of water reducer and 43 parts by weight of nano titanium/graphene oxide dispersion liquid into two thirds of water of the total water amount, and marking as a mixed solution 1; the weighed 14 will be. 5 parts of shrinkage reducing agent and 3.2 parts of defoamer are added into one third of the total water, and the mixture is marked as a mixed solution 2; preparing 22.4 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water quantity is 70 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.8 graphene oxide powder and 0.5 part of nano TiO 2 Manufacturing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 38.5% of carboxyl modified polyvinyl alcohol, 60.4% of water and 1.1% of polyacrylate defoamer;
2) 7.5 parts of ramie fibers, 830 parts of broken stone, 765 parts of sand, 555 parts of cement, 65 parts of fly ash, 105 parts of straw ash, 130 parts of silica fume, 5.6 parts of nano-silica, 13.4 parts of basalt fibers and 21 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 22.4 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 16.8 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant 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;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this embodiment is as follows:
pouring the concrete mixture into a cast iron mold for molding, compacting by using a vibrating table, and then performing contact vibration along the outer wall of the test mold by using a vibrating rod so as to discharge redundant 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 wetted geotextile, standing for 1d, removing the mold, and curing in a standard curing room with the temperature of 20+/-2 ℃ and the relative humidity of more than or equal to 95% until the required age.
Example 2
1) Adding 20.5 parts by mass of water reducer and 44 parts by mass of nano titanium/graphene oxide dispersion liquid into water of which the total water content is two thirds, and marking the water reducer and the nano titanium/graphene oxide dispersion liquid as a mixed solution 1; adding 14.7 parts of the weighed shrinkage reducing agent and 3.3 parts of the defoamer into one third of the total water, and marking the mixture as a mixed solution 2; preparing 22.8 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water quantity is 70 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.3 parts of graphene oxide powder and 0.5 part of nano TiO 2 Manufacturing; 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 defoamer;
2) 8 parts of ramie fibers, 830 parts of broken stone, 770 parts of sand, 550 parts of cement, 67 parts of fly ash, 105 parts of straw ash, 125 parts of silica fume, 5.5 parts of nano silicon, 13.4 parts of basalt fibers and 21.3 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 22.8 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 16 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant 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;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this example was the same as in example 1.
Example 3
1) Adding 21 parts by weight of water reducer and 46 parts by weight 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 parts of defoamer into one third of the total water, and marking as a mixed solution 2; preparing 22 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 73 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.8 parts of graphene oxide powder and 0.4 part of nano TiO 2 Manufacturing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 36.7% of carboxyl modified polyvinyl alcohol, 62% of water and 1.3% of polyacrylate defoamer;
2) 7.8 parts of ramie fibers, 835 parts of broken stone, 770 parts of sand, 555 parts of cement, 70 parts of fly ash, 103 parts of straw ash, 135 parts of silica fume, 5.5 parts of nano-silica, 13.3 parts of basalt fibers and 21 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 22 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 17 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant is prepared by compounding the following raw materials in percentage by mass: 54% of dihydrate gypsum, 44% of calcium chloride and 2% of triethanolamine;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this example was the same as in example 1.
Example 4
1) Adding 20 parts by weight of water reducer and 42 parts by weight 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 the weighed shrinkage reducing agent and 3.1 parts of the defoamer into one third of the total water, and marking the mixture as a mixed solution 2; preparing 23.5 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 75 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.5 parts of graphene oxide powder and 0.4 part of nano TiO 2 Manufacturing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: carboxyl modified polyvinyl alcohol 37.5%, water 61%, polyacrylate defoamer 1.5%;
2) 7.5 parts of ramie fibers, 835 parts of broken stone, 760 parts of sand, 560 parts of cement, 68 parts of fly ash, 103 parts of straw ash, 130 parts of silica fume, 5.6 parts of nano-silica, 13.5 parts of basalt fibers and 21.5 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 23.5 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 16.3 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant is prepared by compounding the following raw materials in percentage by mass: 52.2% of dihydrate gypsum, 46% of calcium chloride and 1.8% of triethanolamine;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this example was the same as in example 1.
Example 5
1) Adding 20.5 parts by mass of water reducer and 42 parts by mass of nano titanium/graphene oxide dispersion liquid into water of which the total water content is two thirds, and marking the water reducer and the nano titanium/graphene oxide dispersion liquid as a mixed solution 1; adding 15 parts of weighed shrinkage reducing agent and 3.3 parts of defoamer into one third of the total water, and marking as a mixed solution 2; preparing 23.3 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 75 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.6 parts of graphene oxide powder and 0.5 part of nano TiO 2 Manufacturing; 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 1% of polyacrylate defoamer;
2) 8 parts of ramie fibers, 840 parts of broken stone, 760 parts of sand, 560 parts of cement, 65 parts of fly ash, 108 parts of straw ash, 135 parts of silica fume, 5.5 parts of nano silicon, 13.6 parts of basalt fibers and 21.5 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 23.3 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 16.5 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant 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;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this example was the same as in example 1.
Example 6
1) Adding 20 parts by weight of water reducer and 42 parts by weight 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 14.8 parts of weighed shrinkage reducing agent and 3 parts of defoamer into one third of the 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 75 parts; wherein the nano titanium/graphene oxide dispersion liquid consists of 1.4 parts of graphene oxide powder and 0.4 part of nano TiO 2 Manufacturing; the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: carboxyl modified polyvinyl alcohol 37.3%, water 61.5%, polyacrylate defoamer 1.2%;
2) 7.6 parts of ramie fibers, 840 parts of broken stone, 765 parts of sand, 550 parts of cement, 70 parts of fly ash, 108 parts of straw ash, 125 parts of silica fume, 5.4 parts of nano-silica, 13.5 parts of basalt fibers and 21 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading the whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 23 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 17 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min; wherein the excitant is prepared by compounding the following raw materials in percentage by mass: 50% of dihydrate gypsum, 48% of calcium chloride and 2% of triethanolamine;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method in this example was the same as in example 1.
The following comparative examples are given to further illustrate the effects of the present invention in comparison with the examples of the present invention.
Comparative example: the ultra-high strength concrete is prepared by adopting no gelled particle continuous grading design, no fiber, no carboxyl modified polyvinyl alcohol polymer, nano titanium/graphene oxide dispersion liquid and single excitant.
The mixture ratio is as follows: 590 parts of cement, 755 parts of sand, 835 parts of crushed stone, 83 parts of fly ash, 123 parts of silica fume, 114 parts of water, 18 parts of water reducer, 15.3 parts of excitant and 2.7 parts of defoamer.
The preparation method comprises the following steps:
1) Adding 18 parts by weight of water reducer into water of which the total water content is two thirds, and marking the water reducer as a mixed solution 1; adding 2.7 parts of weighed defoamer into one third of the total water, namely a mixed solution 2, wherein the total water is 114 parts;
2) Placing 835 parts of crushed stone, 755 parts of sand, 590 parts of cement, 83 parts of fly ash and 123 parts of silica fume in a stirrer, and stirring for 1min;
3) Adding the mixed solution 1 in the step 1) into a stirrer, and uniformly stirring for 2-3min;
4) Adding 15.3 parts of calcium chloride excitant into the stirrer, and uniformly stirring for 2-3min;
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 intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
The concrete molding and curing method of the comparative example is as follows:
pouring the concrete mixture into a cast iron mold for molding, compacting by using a vibrating table, and then performing contact vibration along the outer wall of the test mold by using a vibrating rod so as to discharge redundant 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 wetted geotextile, standing for 1d, removing the mold, and curing in a standard curing room with the temperature of 20+/-2 ℃ and the relative humidity of more than or equal to 95% until the required age.
The results of the performance test of the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete prepared in examples 1-6 and the comparative concrete are shown in Table 1.
Table 1 comparison of the properties of examples 1-6 and comparative examples
As can be seen from Table 1, the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete prepared by the invention meets the compressive and bending strength required by the member when loaded, and ensures the cohesiveness of the member and steel in cooperation. The 28d cube compressive strength is not less than 255.19MPa, the flexural strength is not less than 59.35MPa, the splitting tensile strength is not less than 28.66MPa, the bonding strength with the section steel is not less than 11.83MPa, and the chloride ion migration coefficient is not more than 5 multiplied by 10 -14 m 2 And/s. Example 1 is an optimal blending ratio, the grain composition of the cementing material is optimal, the mixing amount of the carboxyl modified polyvinyl alcohol polymer is optimal, the mixing amount of the fiber is optimal, and the nano titanium/graphene oxide dispersion liquid is prepared. Has enough toughness and cohesiveness under the C250 strength grade to improve the cooperative working capacity of the profile steel and the concrete, and canAs a modern green building material.
The foregoing is merely illustrative of the present invention and is not intended to limit the scope of the invention in any way, and persons skilled in the art may make simple changes or substitutions without departing from the spirit of the invention. The scope of the invention should be determined by the claims.

Claims (7)

1. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete is characterized by comprising the following raw materials in parts by weight:
555 parts of cement, 770 parts of sand, 835 parts of crushed stone, 70 parts of fly ash, 103 parts of straw ash, 135 parts of silica fume, 5.5 parts of nano silicon dioxide, 73 parts of water, 21 parts of water reducer, 17 parts of excitant, 3 parts of defoamer, 15 parts of shrinkage reducer, 7.8 parts of ramie fiber, 13.3 parts of basalt fiber and CaCO 3 21 parts of whisker, 46 parts of nano titanium dioxide/graphene oxide dispersion liquid and 22 parts of carboxyl modified polyvinyl alcohol polymer;
the ramie fiber is refined dry ramie fiber after alkali treatment and drying, the length is 40-50mm, the diameter is 30-40 mu m, the tensile strength is more than or equal to 766MPa, the elastic modulus is more than or equal to 9.1GPa, the breaking elongation is 8.9%, and the specific gravity is 1.54-1.55g/cm 3 ；
The basalt fiber has a length of 12mm, a diameter of 7-15 μm, a tensile strength of not less than 3000MPa, an elastic modulus of not less than 91GPa and a specific gravity of 2.63-2.65 g/cm 3 ；
Said CaCO 3 The whisker length 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 2.86 g/cm 3 ；
The exciting agent is an organic-inorganic composite exciting agent, and the composite 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;
the carboxyl modified polyvinyl alcohol polymer is prepared from the following raw materials in percentage by mass: 36.7% of carboxyl modified polyvinyl alcohol, 62% of water and 1.3% of polyacrylate defoamer, specifically, placing 36.7% of carboxyl modified polyvinyl alcohol into 62% of water, standing at normal temperature to fully swell the carboxyl modified polyvinyl alcohol, then placing the carboxyl modified polyvinyl alcohol into a constant temperature water tank at 95 ℃ for heating and dissolving, adding 1.3% of polyacrylate defoamer, and continuously stirring until a uniform transparent solution is formed, thus obtaining the carboxyl modified polyvinyl alcohol polymer;
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=7;
c250 super high strength mixed fiber concrete 28d cube compressive strength up to 257.55MPa, flexural strength up to 60.39MPa, splitting tensile strength up to 29.51MPa, bonding strength with section steel up to 12.11MPa, chloride ion migration coefficient up to 3×10 - 14 m 2 /s。
2. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the cement is p.i62.5 r-grade portland cement;
the basalt crushed stone with good grading, compactness, hardness and rough surface is selected, the basalt crushed stone is fed according to the continuous grain size of 5-10mm, the parent rock strength is not lower than 300MPa, and the maximum grain size is 10mm;
the fly ash adopts high-quality class I fly ash of a power plant, the screen residue of a 45 mu m square hole screen is not more than 10%, the water demand ratio is not more than 95%, and the specific surface area is more than 400m 2 /kg；
The silica content in the silica fume is more than 95%, the volcanic ash activity index is more than 95%, the average grain diameter is 0.1-0.15 μm, and the specific surface area is more than 28m 2 /g；
The nano silicon dioxide is prepared into high-purity nano silicon dioxide 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 130m 2 /g；
The water reducer is a polycarboxylic acid high-performance water reducer, the solid content is 20%, and the water reducing rate of the water reducer is more than 38%.
3. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the straw ash is prepared by burning mature stems of corn straw at 600-820 ℃, then performing potassium treatment, and grinding 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 12m 2 /g。
4. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete according to claim 3, wherein the potassium removing treatment method comprises the steps of:
1) Placing the straw ash into distilled water for stirring and soaking, then standing, pouring out supernatant, continuously adding distilled water for stirring and soaking, and repeating the process for more than 5 times, wherein the soaking time lasts for one week;
2) Pouring out the supernatant liquid for the last time, heating to 90 ℃ with distilled water, preserving heat for 15-20min, pouring out the supernatant liquid after preserving heat, adding distilled water for soaking, and repeating the step 1);
3) Repeating steps 1) and 2) twice in sequence;
4) Finally, the temperature is kept at 60 ℃ for 2 hours, and the supernatant is poured out and dried for standby.
5. The high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete according to claim 1, wherein the nano-titania/graphene oxide dispersion is obtained by:
(1) Adding 0.4 part of nano titanium dioxide and 0.1 part of surfactant polyethylene glycol octyl phenyl ether into 100 parts of deionized water according to parts by weight, stirring at a high speed, then performing ultrasonic dispersion for 20-30min by using an ultrasonic machine, adding 1.8 parts of graphene oxide powder, and performing ultrasonic dispersion for 30min to obtain a nano titanium dioxide/graphene oxide aqueous solution;
(2) Adding 0.1 part of water reducer into 50 parts of deionized water, uniformly stirring, then adding the nano titanium dioxide/graphene oxide aqueous solution prepared in the step (1), stirring, and then performing ultrasonic dispersion for 10min to obtain nano titanium dioxide/graphene oxide dispersion;
the graphene oxide is in a powder shape, the purity is more than or equal to 98%, and the diameter is 10-20 mu m;
the purity of the nano titanium dioxide is 99%, and the particle size is 10nm-50nm;
the water reducer is a polycarboxylic acid high-performance water reducer, the solid content is 20%, and the pH value is 7.
6. A method for preparing the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete based on any one of claims 1 to 5, which is characterized by selecting a disk mixer, and then comprising the following steps:
1) Adding 21 parts by weight of water reducer and 46 parts by weight of nano titanium dioxide/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 parts of defoamer into one third of the total water, and marking as a mixed solution 2; preparing 22 parts of carboxyl modified polyvinyl alcohol polymer for later use; the total water amount is 73 parts;
2) 7.8 parts of ramie fibers, 835 parts of broken stone, 770 parts of sand, 555 parts of cement, 70 parts of fly ash, 103 parts of straw ash, 135 parts of silica fume, 5.5 parts of nano silicon dioxide, 13.3 parts of basalt fibers and 21 parts of CaCO 3 Whisker, dividing into three parts of ramie fiber, basalt fiber and CaCO 3 Uniformly spreading whiskers in a disc mixer, and sequentially placing one part of broken stone, sand, cement, fly ash, straw ash, silica fume and nano silicon dioxide in the disc mixer for stirring for 1min;
3) Adding the other two parts of materials into a disc stirrer in the same way to stir uniformly;
4) Adding the mixed solution 1 in the step 1) into a disc stirrer, and uniformly stirring for 2-3min;
5) Adding 22 parts of prepared carboxyl modified polyvinyl alcohol polymer and stirring for 2min;
6) Adding 17 parts of exciting agent into the disc mixer, and uniformly stirring for 2-3min;
7) Finally observing the fluidity of the mixture, continuously adding the mixed solution 2 prepared in the step 1) into a disc mixer, uniformly stirring for 2-3min, after 3min intervals, stirring for 2-3min until the mixture is uniform, and discharging to obtain the prepared concrete mixture; and forming and curing.
7. A molding curing method of the high-toughness high-cohesiveness C250 ultrahigh-strength hybrid fiber concrete prepared based on the preparation method of claim 6 is characterized by adopting a standard curing method:
the standard curing method is as follows: pouring the concrete mixture into a cast iron mold for molding and compaction, standing for 1-2d in a standard curing chamber 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 chamber to the required age.
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