CN115417631A - Low-shrinkage low-creep concrete serving in plateau complex environment and preparation method thereof - Google Patents
Low-shrinkage low-creep concrete serving in plateau complex environment and preparation method thereof Download PDFInfo
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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
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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
- 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
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- 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
Abstract
The invention discloses a low-shrinkage low-creep concrete used in a complex plateau environment and a preparation method thereof, wherein the concrete comprises 300-400 kg/m 3 150 to 200kg/m of cement 3 10-20 kg/m of mineral admixture 3 600-700 kg/m of dense modified material 3 1000 to 1200kg/m of fine aggregate 3 The coarse aggregate, the admixture accounting for 0.5 to 5 weight percent of the total amount of the cement and the mineral admixture and water; the dense modified material comprises CaSO 4 Whisker and nano SiO 2 In which CaSO 4 Whisker and nano SiO 2 The mass ratio of (A) to (B) is 1.5-2.5: 1. the low-shrinkage low-creep concrete has good mechanical property and durability while ensuring good volume stability, meets the requirement of shrinkage and creep of the concrete in a complex plateau environment, and can be used in long-life engineering in the complex plateau environment.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to low-shrinkage low-creep concrete serving in a complex plateau environment and a preparation method thereof.
Background
The Sichuan railway has the advantages that the Sichuan railway has the east-start success, the West-arrival Russa railway has the total length of 1838 kilometers, 7 rivers and 8 snow mountains are penetrated along the way, the altitude difference is more than 3000 meters, the eight-start and eight-volt railway has the expected bridge-tunnel ratio of 81 percent, and more large-span and ultra-large-span bridges are arranged. The field environment is severe, the temperature difference between day and night is more than 10 ℃, and the total annual solar radiation amount is 5000-8000 MJ/m 2 Most of the areas have eight-grade gale (more than 17 m/s) days as many as 150 days, and have the environmental characteristics of large temperature difference, strong radiation and gale drying. The problems of shrinkage and creep of the beam concrete and the like are easily caused under severe natural conditions, the quality of the concrete is reduced, the service life of the bridge concrete is shortened, and the running risk of trains is increased.
The requirement of the bridge body high-performance concrete on the shrinkage creep in the complex environment of the Sichuan-Tibet railway is high, the dry shrinkage rate is less than or equal to 0.035% in 56 days, and the creep degree is less than or equal to 20 multiplied by 10 in 90 days -6 In MPa. The cementing material composition of the traditional low-shrinkage low-creep concrete comprises cement with coarse grain size, fly ash and mineral powder, and is suitable for general environmental conditions, but under severe environmental conditions of large temperature difference in plateau and extreme dryness, the temperature effect is increased, the water loss is accelerated, and the traditional low-shrinkage low-creep concrete cannot effectively improve different pore structures in a concrete system and cannot meet the requirements of engineering construction. Patent No. 201811323941.3 discloses a low shrinkage, low creep, crack resistance and high performance mass concrete which is prepared by using cement and fly ash as cementing materials, but has higher requirements on mineral composition of cement, and is only suitable for simple construction of reactor plants and raft-based concrete. Patent No. 202210370864.7 discloses a low shrinkage high strength concrete and its preparation method, but vacuum nitrogenThe large-scale application of the chemical and microwave radiation treatment process in the plateau environment is difficult, and the transportation of nitrogen gas increases the preparation of concrete and increases the cost. Therefore, a low-shrinkage low-creep concrete material which can be used in a complex environment of a plateau for a long time is urgently needed to be developed.
Disclosure of Invention
In view of the above, the invention discloses a low-shrinkage low-creep concrete serving in a complex plateau environment and a preparation method thereof, and the low-shrinkage low-creep concrete has good mechanical properties and durability while ensuring good volume stability, meets the requirement of the concrete on shrinkage and creep in the complex plateau environment, and can serve in long-life engineering in the complex plateau environment.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a low-shrinkage low-creep concrete used in a complex environment of a plateau comprises the following components:
the dense modified material comprises CaSO 4 Whisker and nano SiO 2 Wherein CaSO 4 Whisker and nano SiO 2 The mass ratio of (A) to (B) is 1.5-2.5: 1.
preferably, the mineral admixture consists of a coarse-scale mineral admixture, a medium-scale mineral admixture and a fine-scale mineral admixture;
the coarse mineral admixture is at least one of fly ash and mineral powder, and the using amount of the coarse mineral admixture is 50-70 wt% of the total amount of the mineral admixture;
the medium-scale mineral admixture is at least one of metakaolin, finely ground zeolite powder and highland barley straw ash, and the using amount of the medium-scale mineral admixture is 20-40 wt% of the total amount of the mineral admixture;
the fine-scale mineral admixture is silica fume, and the using amount of the fine-scale mineral admixture is 5-15 wt% of the total amount of the mineral admixture.
Further preferably, in the coarse mineral admixture, the fly ash is fly ash obtained by cooling fire coal in a thermal power plant and is used as the fly ashThe sphericity is more than or equal to 80 percent, the average particle diameter is 17 mu m, and the specific surface area is 1.1-1.2 m 2 (ii)/g; the mineral powder is obtained by dry grinding blast furnace slag, the average particle size is 15 mu m, and the specific surface area is 1.7-2.0 m 2 /g；
In the medium-scale mineral admixture, metakaolin is prepared by heating and dehydrating kaolin, the average particle size is 5 mu m, and the specific surface area is 14-20 m 2 (iv) g; the finely ground zeolite powder is formed by finely grinding natural zeolite rock, the average grain diameter is 9 mu m, and the specific surface area is 500-1100 m 2 (ii)/g; the highland barley straw ash is prepared by burning highland barley straws, removing impurities and grinding, the average particle size is 10 mu m, and the specific surface area is 15-20 m 2 /g；
In the fine mineral admixture, the siliceous dust is SiO volatilized from an ore-smelting electric furnace when ferroalloy is used for smelting ferrosilicon or industrial silicon (metallic silicon) 2 And Si gas is quickly oxidized, condensed and precipitated in the air, the sphericity degree of the Si gas is more than or equal to 90 percent, the particle size is 0.5 to 1 mu m, and the specific surface area is 22 to 30m 2 /g。
Preferably, the dense modified material further comprises graphene oxide, and the addition amount of the graphene oxide is CaSO 4 Whisker and nano SiO 2 0.5-0.8 wt% of the total amount and 0.01-0.03 wt% of the total amount of the cement and the mineral admixture.
Preferably, caSO 4 The microscopic appearance of the crystal whisker is columnar fiber, the length is 10-100 mu m, the diameter is 1-10 mu m, the length-diameter ratio is 5-40 4 The whisker has the characteristics of high strength, high modulus and high toughness, can reduce the stress concentration phenomenon at the crack tip of a cement test block, improve the elastic modulus of C-S-H gel, and reduce deformation by consuming energy through the actions of bridging, deflecting and pulling out. Meanwhile, the wetting function of the whiskers can absorb part of water, reduce bleeding pores and block internal water migration, thereby reducing the drying shrinkage of a concrete system.
The microscopic morphology of the graphene oxide is lamellar, the diameter of the lamellar is 300-500 nm, the thickness of the lamellar is 0.3-1 nm, and the specific surface area of the graphene oxide is 2600m 2 The graphene oxide has the characteristics of high activity and excellent mechanical property, can form hydrogen bonds with the C-S-H gel, improves the cohesive force, and promotes the ordered growth of the C-S-H gel.
Nano SiO 2 The micro-morphology of the nano-particles is spherical particles, the average particle diameter is 40nm, and the specific surface area is 150m 2 G, nano SiO 2 Has the characteristics of high strength, high toughness, high surface energy and strong stability, and can be mixed with Ca (OH) 2 The secondary hydration reaction is carried out to generate more high-density C-S-H gel, and simultaneously, the filling effect of the micro-aggregate is exerted, and the porosity is reduced.
In the invention, caSO is prepared according to a certain proportion 4 Whisker and nano SiO 2 Added into concrete as a dense modified material, firstly, nano SiO 2 Is a nanoscale granular zero-dimensional material, caSO 4 The crystal whisker is a micron-sized columnar one-dimensional material, and the crystal whisker can fill pores with different sizes and shapes in a cement system in a synergistic manner, so that the number of gel pores and capillary pores is greatly reduced, and shrinkage creep caused by water evaporation in the concrete under a plateau extreme drying environment is prevented; second, caSO 4 The crystal whisker is added into nano SiO 2 The C-S-H gel generated by hydration reaction provides more nucleation sites, promotes the aggregation of the C-S-H gel along the crystal whisker instead of the dispersion growth to form a columnar hydration group, and the increase of the hydration degree and the hydration product leads the concrete system to be more compact. At the same time, caSO 4 The crystal whiskers are subjected to hydration reaction to generate ettringite which can be quickly crystallized and has expansibility, the solid phase volume is increased, and a hard framework structure is formed to inhibit the deformation of the concrete under shrinkage creep; again, the inventors found that nano SiO 2 When the mixing amount is excessive, agglomeration phenomenon can occur to influence the exertion of the effect, and CaSO 4 When the amount of the whisker is too much, the volume is excessively expanded, the surface is cracked and the like, so that the amount of the two materials needs to be strictly controlled to achieve the synergistic effect of reducing shrinkage and creep.
The inventors have also found that in CaSO 4 Whisker and nano SiO 2 On the basis of the doping amount of 1.5-2.5, graphene oxide is further doped into the dense modified material, so that the shrinkage creep of concrete can be further reduced. Firstly, the graphene oxide is a nano-scale lamellar honeycomb two-dimensional material, and the graphene oxide with high surface energy can be mixed with nano SiO 2 Form good covalent link, throughEffectively inhibiting nano SiO under the action of electrostatic repulsion 2 Agglomeration of particles and graphene oxide, and is nano SiO 2 The pozzolan reaction of (a) provides nucleation sites with nano-SiO 2 The volcanic ash reaction is carried out on the graphene oxide lamella, a more compact graphene oxide nanosheet network structure is formed, and columnar or flower-shaped hydrated groups, nano SiO 2 -CaSO 4 Columnar hydrated group of crystal whisker and nano SiO 2 The synergistic effect of the graphene oxide columnar hydration groups forms the enhancement effects of filling pores in a multi-scale mode, bridging cracks and inhibiting deformation. Secondly, active functional groups on the surface of graphene oxide and CaSO 4 The crystal whiskers are combined to form negative charges, so that CaSO can be increased 4 Compatibility and interface adhesive force of the whisker and a cement matrix, and simultaneously, the CaSO can be improved by the graphene oxide 4 The length-diameter ratio of the crystal whisker is reduced, and CaSO is reduced 4 The diameter of the whisker can be increased to increase the CaSO 4 The whiskers reinforce and toughen the glass, absorb and dissipate the energy in the deformation process; thirdly, the graphene oxide is expensive and is easy to agglomerate under high doping amount, so that the main part of the dense modified material is nano SiO 2 And CaSO 4 The crystal whisker and the graphene oxide can be used as auxiliary materials for further improving the performance of concrete.
Preferably, the fine aggregate is river sand or machine-made sand, and the fineness modulus is 2.8-4.0.
Preferably, the coarse aggregate is limestone or basalt macadam, the particle size is less than or equal to 15mm, and the part with the particle size of 10-15 mm is not less than 20%.
Preferably, the additive is at least one of a water reducing agent, a defoaming agent and a shrinkage reducing agent;
the water reducing agent is at least one of a polycarboxylic acid high-efficiency water reducing agent, a naphthalene high-efficiency water reducing agent, a melamine high-efficiency water reducing agent and an amino acid salt high-efficiency water reducing agent, and is adsorbed on the surface of cement particles, so that the unit water consumption is reduced, the cement particles are dispersed, and the fluidity of concrete mixtures is improved;
the defoaming agent is at least one of an organic silicon defoaming agent, a polyether modified silicon defoaming agent, a high-alcohol defoaming agent, a silicon-free defoaming agent and a mineral oil defoaming agent, and the surface tension of bubbles is reduced to destroy the elastic film of the bubbles, inhibit the generation and development of the bubbles and reduce the porosity;
the shrinkage reducing agent is at least one of polyhydroxy compound NA-SP series concrete shrinkage reducing agents, alkyl polyoxyethylene ether JM-SRA series concrete shrinkage reducing agents, polyether and aliphatic organic JSJ type shrinkage reducing agents, methyl ether-based polymers and ethylene glycol polymers ZZD-A type concrete shrinkage reducing agents, and the effect of reducing shrinkage is achieved by reducing the surface tension of a liquid phase in a concrete capillary.
In the invention, the water reducing agent, the defoaming agent, the shrinkage reducing agent and other additives are used, the agglomeration phenomenon of particles is reduced through the electrostatic repulsion, the uniform dispersion of the particles in a concrete system is ensured, the effective discharge of air bubbles and the reduction of capillary pore pressure are ensured, the mineral admixture and the dense modification material are assisted, the uniformity and compactness of the concrete system are further increased, and the volume stability of the system is maintained.
The invention also provides a preparation method of the low-shrinkage low-creep concrete serving in the complex environment of the plateau, which comprises the following steps:
the method comprises the following steps: mixing the dense modified material, the additive and water, magnetically stirring at the rotating speed of 500-1500 r/min for 5-20 min, placing in an ultrasonic cell disruption instrument, keeping the power at 60-70%, alarming at 80 ℃, and ultrasonically dispersing for 10-15 min to obtain a dense modified dispersion liquid;
step two: mixing cement and mineral admixture, placing the mixture in a mixer, and fully mixing the mixture to obtain a dry powder mixture;
step three: and pouring the dry powder mixture, the coarse aggregate and the fine aggregate into a concrete mixer in sequence, fully and uniformly stirring, then adding the dense modifier dispersion liquid, stirring for 2-5 min, and curing after casting the model.
In the invention, standard curing or steam curing can be selected by combining site construction conditions. When standard curing is carried out, the molded test piece is placed in an environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95% for curing to a specified age; when steam curing is carried out, the molded test piece is placed in an environment of 20 +/-2 ℃ and is kept still for 1-3 h, the steam curing box is controlled to reach the peak temperature of 60-80 ℃ at the heating rate of 20 ℃/h for a period of time, the peak temperature is maintained for 8h and then is naturally cooled, and the molded test piece is transferred to a standard drying and shrinking environment of 20 +/-2 ℃ and relative humidity of 60% and is continuously cured to the specified age.
Based on the closest packing theory, the invention adds mineral admixtures with different microscopic morphologies to carry out reasonable grain composition design, realizes the all-round filling from the coarse scale to the fine scale, and promotes Ca (OH) 2 The aggregate particles and the cementing material cooperatively reach the maximum dense accumulation through the particle grading of coarse and fine aggregates, and the volume stability of the concrete is improved. In the high-performance concrete with low water-cement ratio, the mineral admixture has the effects that on one hand, a large amount of unhydrated mineral admixture exists in the system, so that the macroscopic elastic modulus of the concrete is improved, the creep value is reduced, and the completion of the creep of the concrete is accelerated. In another aspect, mineral admixtures with Ca (OH) 2 The crystal part generates secondary hydration reaction, the early stage is mainly the secondary hydration of the medium and fine mineral admixtures such as silica fume, metakaolin and the like, the middle and later stages are mainly the secondary hydration of the mineral powder and/or fly ash coarse mineral admixtures, the front and back collocation leads the hydration reaction to be more thorough, the structural compactness is better, and simultaneously, a large amount of Ca (OH) is avoided 2 The directional arrangement of the crystal formation optimizes the interface structure of the set cement, reduces the porosity, fills up macropores in the concrete (Jawed classification method), increases the channel resistance of capillary tubes, reduces the water evaporation and inhibits the drying shrinkage and creep of the concrete. More importantly, the invention adds the compact modified material, on one hand, the compact modified material has huge specific surface area, provides more nucleation sites for C-S-H gel, and the nano SiO 2 、CaSO 4 The crystal whisker and the graphene oxide provide zero-dimensional, one-dimensional and two-dimensional nucleation sites for the growth of the C-S-H gel, and a firmer C-S-H gel framework is constructed by the disordered distribution of two point-line layers or three point-line-plane layers, so that the viscous flow under the external interference is effectively reduced. On the other hand, the particle size of the compact modified material is below 10 μm or even up toThe nano-scale cement paste can block a pore channel of a set cement, increase the compactness of a concrete system and optimize an interface transition region, thereby restricting the migration of internal moisture.
In the aspect of physical filling, the particle grading is reasonably arranged based on the closest packing theory, the number of system pores is reduced, and a concrete interface transition area is improved; in the aspect of chemical modification, a compact modified material with small particle size, high hardness and high elastic modulus is designed, the elastic modulus and the compact degree of C-S-H gel are improved, and water constraint is performed among reinforcing layers, so that the effects of comprehensively reducing the shrinkage and creep of concrete and improving the strength are achieved.
Drawings
FIG. 1 is a diagram of a prism concrete test piece and a performance test object obtained in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
In the present invention, the cement has an average particle diameter of 20 μm and a specific surface area of 1.6 to 1.8m 2 /g；
The fly ash is fly ash obtained by cooling fire coal of a thermal power plant, the sphericity of the fly ash is more than or equal to 80 percent, the average grain diameter of the fly ash is 17 mu m, and the specific surface area of the fly ash is 1.1-1.2 m 2 (ii)/g; the mineral powder is obtained by dry grinding blast furnace slag, the average particle size is 15 mu m, and the specific surface area is 1.7-2.0 m 2 /g；
The metakaolin is prepared by heating and dehydrating kaolin, the average particle size is 5 mu m, and the specific surface area is 14-20 m 2 (ii)/g; the finely ground zeolite powder is formed by finely grinding natural zeolite rock, the average grain diameter is 9 mu m, and the specific surface area is 500-1100 m 2 (ii)/g; the highland barley straw ash is prepared by burning highland barley straws, removing impurities and grinding, and has an average particle size of 10 μm, the specific surface area is 15 to 20m 2 /g；
The silicon ash is SiO volatilized by an ore-smelting electric furnace when ferrosilicon or industrial silicon (metallic silicon) is smelted by ferroalloy 2 And Si gas is quickly oxidized, condensed and precipitated in the air, the sphericity degree of the Si gas is more than or equal to 90 percent, the particle size is 0.5 to 1 mu m, and the specific surface area is 22 to 30m 2 /g。
CaSO 4 The microscopic appearance of the whisker is columnar fiber, the length is 10-100 μm, the diameter is 1-10 μm, and the length-diameter ratio is 5-40.
The microscopic morphology of the graphene oxide is lamellar, the diameter of the lamellar is 300-500 nm, the thickness of the lamellar is 0.3-1 nm, and the specific surface area is 2600m 2 /g。
Nano SiO 2 The micro-morphology of the nano-particles is spherical particles, the average particle diameter is 40nm, and the specific surface area is 150m 2 /g。
The fine aggregate is river sand or machine-made sand, and the fineness modulus is 2.8-4.0.
The coarse aggregate is limestone or basalt broken stone, the grain size is less than or equal to 15mm, and the part with the grain size of 10-15 mm is not less than 20%.
In the present invention, kg/m 3 Represented is the mass of material added per cubic meter of concrete.
Example 1
A preparation method of low-shrinkage low-creep concrete serving in a complex environment of a plateau comprises the following steps:
the method comprises the following steps: preparation of a dense modified Material Dispersion
Step 1.1, weighing the materials. CaSO 4 The crystal whisker dosage is 9.6kg/m 3 Nano SiO 2 The dosage is 4.8kg/m 3 The dosage of the polycarboxylic acid high-efficiency water reducing agent is 8.2kg/m 3 The dosage of the concrete shrinkage reducing agent of the alkyl polyoxyethylene ether JM-SRA series is 4kg/m 3 The dosage of the polyether modified silicon defoamer is 0.5kg/m 3 The amount of water used was 126kg/m 3 。
Step 1.2, stirring by magnetic force. And (3) mixing the materials in the step 1.1, placing the materials in a magnetic stirrer, and magnetically stirring the materials for 5min at the rotating speed of 1000 r/min.
And step 1.3, placing the solution prepared in the step 1.2 in an ultrasonic cell disruption instrument, and performing ultrasonic dispersion for 10min under the conditions of 65% of power and 80 ℃ of alarm temperature to obtain a dense modified material dispersion liquid.
Step two: mixed dry powder
According to the cement dosage of 320.4kg/m 3 The dosage of the fly ash is 90kg/m 3 The dosage of metakaolin is 45kg/m 3 The dosage of the silica fume is 15kg/m 3 Mixing, and placing in a mixer for 8h to obtain a dry powder mixture.
Step three: formed concrete
Mixing the dry powder mixture obtained in the step two with river sand 675kg/m 3 1113kg/m limestone macadam 3 Sequentially pouring the mixture into a concrete mixer, carrying out dry stirring for 2min, uniformly adding the dense modifier dispersion liquid prepared in the step one, controlling the stirring time for 4min according to the slurry state, and carrying out model pouring.
Step four: curing concrete
Curing for 1d with a mold after pouring and forming, removing the mold, then curing in a standard environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95 percent, moving a dry shrinkage test piece into a constant temperature and humidity environment with the temperature of 20 +/-2 ℃ and the relative humidity of 60 +/-5 percent for shrinkage test after curing for 3d, and moving a creep test piece into the same constant temperature and humidity environment for creep test after curing for 14 d.
The test method of the drying shrinkage and the creep degree refers to the standard of test methods for the long-term performance and the durability of common concrete GB/T50082-2009 and combines the requirements of related engineering. The drying shrinkage rate is detected by a contact method, a vertical concrete shrinkage instrument and a dial indicator with the precision of +/-0.001 mm are selected for detection, the size of a prism concrete test piece is 100mm multiplied by 400mm, and 3 test pieces are arranged in the same proportion. The creep degree is detected by adopting a pressure creep test method and a spring type creep compression instrument and a dial indicator, the size of a prism concrete test piece is 100mm multiplied by 400mm, and 3 test pieces are arranged in the same proportion.
As a result of the tests, in this example, the concrete has a 28d drying shrinkage of 0.035%, a 56d drying shrinkage of 0.04%, and a 90d creep of 12.84X 10 -6 /MPa。
Example 2
A preparation method of low-shrinkage low-creep concrete serving in a complex plateau environment is characterized by comprising the following steps:
the method comprises the following steps: preparation of a dense modified Material Dispersion
Step 1.1, weighing the materials. CaSO 4 The crystal whisker dosage is 9.6kg/m 3 Nano SiO 2 The dosage is 4.8kg/m 3 The dosage of the graphene oxide is 0.1kg/m 3 The dosage of the polycarboxylic acid high-efficiency water reducing agent is 8.2kg/m 3 The dosage of the concrete shrinkage reducing agent of the alkyl polyoxyethylene ether JM-SRA series is 4kg/m 3 The dosage of the polyether modified silicon defoamer is 0.5kg/m 3 The amount of water used was 126kg/m 3 。
Step 1.2, stirring by magnetic force. And (3) mixing the materials in the step 1.1, placing the materials in a magnetic stirrer, and magnetically stirring the materials for 5min at the rotating speed of 1500 r/min.
And step 1.3, placing the solution prepared in the step 1.2 in an ultrasonic cell disruption instrument, and performing ultrasonic dispersion for 15min under the conditions of power of 65% and alarm temperature of 80 ℃ to obtain a dispersion liquid of the dense modified material.
Step two: mixed dry powder
According to the cement dosage of 320.4kg/m 3 The dosage of the mineral powder is 90kg/m 3 The dosage of the highland barley straw ash is 45kg/m 3 The dosage of the silica fume is 15kg/m 3 Mixing, and placing in a mixer for 8h to obtain a dry powder mixture.
Step three: formed concrete
Mixing the dry powder mixture obtained in the second step with machine-made sand 675kg/m 3 1113kg/m limestone macadam 3 And (3) pouring the mixture into a concrete mixer in sequence, carrying out dry stirring for 2min, uniformly adding the dense modifier dispersion liquid prepared in the step one, controlling the stirring time for 4min according to the slurry state, and carrying out model pouring.
Step four: curing concrete
After the cast concrete is molded, the cast concrete is static at 20 ℃ for 3h, the temperature is raised to 60 ℃ at the temperature raising rate of 20 ℃/h for 2h, and the steam curing is carried out by maintaining the temperature at 60 ℃ for 8h and then naturally cooling. And (3) removing the mold after steam curing, curing in a standard environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95%, moving the dry shrinkage test piece into a constant-temperature and constant-humidity environment with the temperature of 20 +/-2 ℃ and the relative humidity of 60 +/-5% after curing for 3d for shrinkage test, and moving the creep test piece into the same constant-temperature and constant-humidity environment for creep test after curing for 14 d.
As a result of the tests, in this example, the concrete has a 28d drying shrinkage of 0.025%, a 56d drying shrinkage of 0.03%, and a 90d creep of 11.56X 10 -6 /MPa。
Comparative example 1
The only difference from example 1 is that no solid modifying material is added (i.e. no CaSO is added) 4 Whisker and nano SiO 2 )。
Tests show that in the comparative example, the concrete has a 28d drying shrinkage of 0.06%, a 56d drying shrinkage of 0.068% and a 90d creep of 16.35X 10 -6 /MPa。
Comparative example 2
The only difference from example 1 is that only 14.4kg/m of the additive is added 3 Nano SiO 2 2 。
Tests show that in the comparative example, the concrete has a dry shrinkage of 0.052% in 28 days, 0.057% in 56 days and a creep of 15.98 × 10 in 90 days -6 /MPa。
Comparative example 3
The only difference from example 1 is that only 14.4kg/m of the additive is added 3 CaSO (C) 4 A whisker.
As a result of the test, in the comparative example, the concrete has a 28d drying shrinkage of 0.045%, a 56d drying shrinkage of 0.05%, and a 90d creep of 14.76X 10 -6 /MPa。
Comparative example 4
The only difference from example 1 is that 4.8kg/m are added 3 CaSO (C) 4 Whisker and 9.6kg/m 3 Nano SiO 2 2 。
Tests show that in the comparative example, the concrete has a 28d drying shrinkage of 0.038%, a 56d drying shrinkage of 0.043% and a 90d creep of 13.23X 10 -6 /MPa。
Claims (10)
1. The low-shrinkage low-creep concrete serving in the complex environment of the plateau is characterized by comprising the following components:
the dense modified material comprises CaSO 4 Whisker and nano SiO 2 In which CaSO 4 Whisker and nano SiO 2 The mass ratio of (A) to (B) is 1.5-2.5: 1.
2. the low-shrinkage low-creep concrete serving in a complex environment at plateau as claimed in claim 1, wherein the mineral admixture is composed of a coarse-scale mineral admixture, a medium-scale mineral admixture and a fine-scale mineral admixture;
the coarse mineral admixture is at least one of fly ash and mineral powder, and the using amount of the coarse mineral admixture is 50-70 wt% of the total amount of the mineral admixture;
the medium-scale mineral admixture is at least one of metakaolin, finely ground zeolite powder and highland barley straw ash, and the using amount of the medium-scale mineral admixture is 20-40 wt% of the total amount of the mineral admixture;
the fine-scale mineral admixture is silica fume, and the using amount of the fine-scale mineral admixture is 5-15 wt% of the total amount of the mineral admixture.
3. The low-shrinkage low-creep concrete serving in the complex environment of the plateau as claimed in claim 2, wherein in the coarse mineral admixture, fly ash is fly ash obtained by cooling fire coal of a thermal power plant, the sphericity degree of the fly ash is more than or equal to 80%, the average particle size of the fly ash is 17 μm, and the specific surface area of the fly ash is 1.1-1.2 m 2 (ii)/g; the mineral powder is obtained by dry grinding blast furnace slag, the average particle size is 15 mu m, and the specific surface area is 1.7-2.0 m 2 /g；
In the medium-scale mineral admixture, metakaolin is prepared by heating and dehydrating kaolin, the average particle size is 5 mu m, and the specific surface area is 14-20 m 2 (ii)/g; the finely ground zeolite powder is formed by finely grinding natural zeolite rock, the average grain diameter is 9 mu m, and the specific surface area is 500-1100 m 2 (ii)/g; the ash is prepared by burning highland barley straw, removing impurities, and grinding, has average particle diameter of 10 μm and specific surfaceThe product is 15-20 m 2 /g；
In the fine mineral admixture, the siliceous dust is SiO volatilized by an ore-smelting electric furnace when ferroalloy is used for smelting ferrosilicon or industrial silicon 2 And Si gas is quickly oxidized, condensed and precipitated in the air, the sphericity degree of the Si gas is more than or equal to 90 percent, the particle size is 0.5 to 1 mu m, and the specific surface area is 22 to 30m 2 /g。
4. The concrete with low shrinkage and low creep serving in complex environments in plateaus as claimed in any one of claims 1 to 3, wherein the dense modified material further comprises graphene oxide in an amount of CaSO 4 Whisker and nano SiO 2 0.5-0.8 wt% of the total amount and 0.01-0.03 wt% of the total amount of the cement and the mineral admixture.
5. The low-shrinkage low-creep concrete for the complex environment on plateau as claimed in claim 4, wherein CaSO 4 The microscopic appearance of the whisker is columnar fiber, the length is 10-100 μm, the diameter is 1-10 μm, and the length-diameter ratio is 5-40;
the microscopic morphology of the graphene oxide is lamellar, the diameter of the lamellar is 300-500 nm, the thickness of the lamellar is 0.3-1 nm, and the specific surface area of the graphene oxide is 2600m 2 /g；
Nano SiO 2 The micro-morphology of the nano-particles is spherical particles, the average particle diameter is 40nm, and the specific surface area is 150m 2 /g。
6. The low-shrinkage low-creep concrete serving in the complex plateau environment as claimed in claim 4, wherein the fine aggregate is river sand or machine-made sand, and the fineness modulus is 2.8-4.0.
7. The low-shrinkage low-creep concrete serving in the complex environment of the plateau as claimed in claim 4, wherein the coarse aggregate is limestone or basalt broken stone, the grain size is less than or equal to 15mm, and the part with the grain size of 10-15 mm is not less than 20%.
8. The low-shrinkage low-creep concrete serving in the complex environment of the plateau as claimed in claim 4, wherein the additive is at least one of a water reducing agent, a defoaming agent and a shrinkage reducing agent.
9. The low-shrinkage low-creep concrete serving in the complex environment of the plateau as claimed in claim 8, wherein the water reducing agent is at least one of a polycarboxylic acid-based superplasticizer, a naphthalene-based superplasticizer, a melamine-based superplasticizer and an amino acid salt superplasticizer;
the defoaming agent is at least one of an organic silicon defoaming agent, a polyether modified silicon defoaming agent, a high-carbon alcohol defoaming agent, a silicon-free defoaming agent and a mineral oil defoaming agent;
the shrinkage reducing agent is at least one of polyhydroxy compound NA-SP series concrete shrinkage reducing agents, alkyl polyoxyethylene ether JM-SRA series concrete shrinkage reducing agents, polyether and aliphatic organic matter JSJ type shrinkage reducing agents, methyl ether-based polymers and ethylene glycol series polymers ZZD-A type concrete shrinkage reducing agents.
10. The preparation method of the low-shrinkage low-creep concrete serving in the complex environment of the plateau as claimed in any one of claims 1 to 9, which is characterized by comprising the following steps:
the method comprises the following steps: mixing the dense modified material, the additive and water, magnetically stirring at the rotating speed of 500-1500 r/min for 5-20 min, placing in an ultrasonic cell disruption instrument, keeping the power at 60-70%, alarming at 80 ℃, and ultrasonically dispersing for 10-15 min to obtain a dense modified dispersion liquid;
step two: mixing cement and mineral admixture, placing the mixture in a mixer, and fully mixing the mixture to obtain a dry powder mixture;
step three: and pouring the dry powder mixture, the coarse aggregate and the fine aggregate into a concrete mixer in sequence, fully and uniformly stirring, then adding the dense modifier dispersion liquid, stirring for 2-5 min, and curing after casting the model.
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