CN110981400A - Low-shrinkage steam-curing-free self-compacting C140UHPC and preparation method thereof - Google Patents
Low-shrinkage steam-curing-free self-compacting C140UHPC 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
- C04B28/18—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 mixtures of the silica-lime type
- C04B28/186—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 mixtures of the silica-lime type containing formed Ca-silicates before the final hardening step
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/52—Producing shaped prefabricated articles from the material specially adapted for producing articles from mixtures containing fibres, e.g. asbestos cement
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28C—PREPARING CLAY; PRODUCING MIXTURES CONTAINING CLAY OR CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28C5/00—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions
- B28C5/08—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions using driven mechanical means affecting the mixing
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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
-
- 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
- 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
Abstract
The invention discloses a low-shrinkage steam-curing-free self-compacting C140UHPC and a preparation method thereof, belonging to the technical field of building materials. The invention uses the active admixture to replace part of cement, reduces the dosage of cementing material in the concrete, thereby reducing the self-shrinkage and drying shrinkage of the concrete, can also use the active admixture with different grain diameters to replace aggregate, optimizes the aggregate gradation, thereby reducing the shrinkage of the concrete, reducing the dosage of the cement, reducing the environmental pollution, and using renewable resources such as glass powder, ceramic powder, rubber powder and the like to replace non-renewable resources quartz sand, thereby saving resources. The preparation process is simple, and the high-performance concrete with excellent performances in all aspects of environmental protection, good working performance, mechanical property, low shrinkage and the like can be prepared.
Description
Technical Field
The invention relates to the technical field of preparation of civil engineering materials, and provides a low-shrinkage steam-curing-free self-compacting C140UHPC and a preparation method thereof.
Background
The ultra-high performance concrete (UHPC) is different from the traditional high-strength concrete and steel fiber concrete, and refers to a novel cement-based engineering material with various performances such as mechanical property, durability and the like far superior to those of common concrete and high-performance concrete. However, the ultra-high performance concrete developed at present in China has a plurality of problems in the preparation and application processes: (1) the preparation process is complex. The ultra-high performance concrete is prepared according to the maximum compactness theory, and the grain size of the raw materials is optimized during preparation, so that the raw materials can reach the closest packing state. In addition, because the performance of UHPC is greatly influenced by curing regulations, a thermal curing regulation is required to obtain higher mechanical properties, so that the UHPC is more suitable for prefabrication production in a factory at present. (2) Self-contraction is large. When preparing the ultra-high performance concrete, the water-cement ratio is usually about 0.2 or even lower, a plurality of active powder materials mainly comprising silica fume are added, and in addition, the cement consumption is much higher than that of the common concrete, so that the ultra-high performance concrete generates very large self-shrinkage in the early hydration process, and the heat generated in the hydration process is very large. (3) The workability is poor. In order to achieve high strength, UHPC has low water-cement ratio, so that the construction workability of the concrete is poor.
Because the shrinkage cracking of the concrete in the process of pouring and curing still exists in the UHPC, particularly the ultra-high performance concrete has the characteristics of large cement consumption, low water-cement ratio and the like, the subsequent high hydration heat and large self-shrinkage are realized, the early shrinkage cracking of the concrete is more serious than that of the common concrete, and the development and application of the UHPC are greatly restricted, so that the expansion agent is generally added into the concrete to reduce the shrinkage of the concrete so as to prepare the concrete with stable volume. However, the existing concrete added with the expanding agent generally has the following defects: (1) the existing expanding agent generally adopts calcium sulphoaluminate expanding agents, calcium oxide expanding agents, calcium sulphoaluminate-calcium oxide expanding agents and magnesium oxide expanding agents, and the adoption of the expanding agents can cause influences on hydration of mineral admixtures in concrete, carbonization resistance of the concrete, sulfate corrosion resistance and the like. (2) The expanding agent has important influence on the compactness and hydration products of the concrete, the hydration of the expanding agent usually occurs in the early stage, the early stage expansion rate is high, the stability is poor, the hydration moisture of the cement particles in the later stage is possibly insufficient, if the water is not supplemented in time, the hydration is stopped, the drying shrinkage is continued, the strength is not increased, and the cracks are caused to occur in advance.
For example, publication No. CN109503068A discloses a low-frequency vibrating compacting and shrinkage-compensating concrete and a preparation method thereof, wherein an expanding agent is introduced into the concrete, so that the later stage shrinkage-reaching phenomenon and the cracking phenomenon caused by the expanding agent in the later stage of the concrete doped with the expanding agent cannot be solved.
Publication No. CN109369118A discloses a low-shrinkage ultra-high performance concrete and a preparation method thereof, wherein super absorbent resin is loaded on the surface of composite fiber, and the shrinkage of the concrete is reduced by utilizing the water retention property of the super absorbent resin, but the preparation process is complex, the requirement on test equipment is high, the strength of the concrete is low, and the problem of UHPC high-temperature curing cannot be solved. The concrete has the advantages of simple equipment requirement, high concrete strength and low shrinkage, reduces the using amount of cementing materials, reduces the environmental pollution, solves the problem of high-temperature maintenance of UHPC, also improves the fluidity of the UHPC, and enables the UHPC to be cast in situ on site. The publication No. CN109437776A discloses a high-content mixed glass powder C190UHPC and a preparation method thereof, which adopts two coarse and fine glass powders with different grain diameters to replace quartz sand in the UHPC, so as to enhance the fluidity and the compressive strength of the UHPC, and does not need high-temperature curing, but requires standard curing for concrete curing conditions, and the concrete has large shrinkage and is easy to generate shrinkage cracks, the active admixture is used for replacing a cementing material, the shrinkage of UHPC is reduced, the shrinkage cracks generated by the UHPC are reduced, and under the condition of optimizing glass powder, the glass powder is activated to enhance the activity of the glass powder and enable the volcanic ash reaction to be more complete, moreover, the glass powder can be used as well as rubber powder, ceramic powder and the like, different fibers can be adopted for single doping or compound doping, to the concrete maintenance, this patent concrete uses natural maintenance, makes things convenient for actual construction more.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.
The invention also aims to provide the ultra-high performance concrete and the preparation method thereof, and the ultra-high performance concrete has the performance of low shrinkage and no steam curing self-compaction. To achieve these objects and other advantages in accordance with the purpose of the present invention, a low shrinkage, steam cure free, self-compacting C140UHPC and a method for preparing the same are provided.
A preparation method of low-shrinkage steam-curing-free self-compacting C140UHPC is characterized by comprising the following steps: the stirring method comprises the following steps:
step 1: placing the fine quartz sand and the coarse quartz sand in a stirrer, and stirring at a low speed for a certain time to form a uniform mixture;
step 2: placing cement, silica fume, fly ash, active admixture and quartz powder into the mixture obtained in the step (1), and stirring at a low speed for a certain time to uniformly stir the mixture;
and step 3: mixing and stirring the water and the high-efficiency water reducing agent uniformly, adding the mixture into the mixture obtained in the step (2), stirring at a low speed for a certain time, and stirring at a high speed for a certain time until the stirred material is fluidized;
and 4, step 4: weighing a specific amount of fiber, slowly adding the specific amount of fiber into the mixture obtained in the step (3), and continuously stirring at a high speed for a certain time after the addition is finished;
and 5: after the step 4 is finished, slowly pouring the mixed concrete into a mold, pouring and molding the concrete, and maintaining for 24 hours;
step 6: and (5) removing the mould of the formed concrete in the step (5) and naturally curing for 28 days to obtain the low-shrinkage steam-curing-free C140 UHPC.
The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: in step 6, the concrete may be cured by: 1) placing the concrete under natural conditions, covering the test piece with wet linen, and performing high-frequency intermittent watering treatment to keep the linen in a wet state all the time; 2) and placing the test piece in water for curing.
Preferably: the raw materials in the step 1 comprise 212.2kg/m3 of fine quartz sand and 848.7kg/m3 of coarse quartz sand, the particle size of the fine quartz sand is 0.04-0.08 mm, the particle size of the coarse quartz sand is 0.45-0.85 mm, the stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
Preferably: the raw materials in the step 2 comprise 681.7kg/m3 cement, 150.8kg/m3 silica fume, 37.9kg/m3 fly ash and 75.8kg/m3 active admixture, the stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
Preferably: and 2, the active admixture comprises one of glass powder, ceramic powder and the like. The glass powder can not only fill the pores in the slurry structure, but also produce C-S-H gel by volcanic ash reaction, thereby improving the microstructure of the material and enhancing the strength of the material. And the finer the glass frit, the better the activity. Or the rubber powder is adopted, the rubber powder is low in density and easy to deform, and can be extruded by a nearby medium in the stirring and forming processes, so that the rubber powder can generate certain prestress, and after the rubber powder has the prestress, the nearby medium is also pressurized in turn, so that the shrinkage around the rubber powder is limited to a certain extent, and the shrinkage is reduced.
Preferably: the active admixture is preferably glass powder, the glass powder is washed by water and ethanol, dried and then placed in washing liquor, the washing liquor is heated for 1 hour at 80-100 ℃ and naturally cooled, wherein the washing liquor is prepared by mixing 30% of hydrogen peroxide and 98% of sulfuric acid according to the weight ratio of 3: 7, washing the glass sheet with pure secondary distilled water, washing residual washing liquor on the surface, drying the glass sheet with a blower to prepare an activated substrate, and putting the activated substrate into a ball mill to be ground into glass powder with corresponding particle size. Because the active admixture is adopted to ensure that the volcanic ash in the concrete has complete reaction and does not need to be activated by high temperature, the UHPC avoids high-temperature steam curing.
Preferably: 2, replacing the cementing materials such as cement, quartz powder and the like with high-activity admixtures, wherein the replacement degree is 5 percent, 10 percent and the like, for example, replacing 10 percent of cement with 1000-mesh glass powder; the aggregate can be replaced by high-activity admixture with different particle sizes, for example, 400-mesh ceramsite is used for replacing 10% of fine quartz sand, and the like. The addition of fly ash and active admixture can change the working performance of UHPC, so that the UHPC can achieve the self-compacting effect.
Preferably: the raw materials in the step 3 comprise 189.3kg/m3 of water and 45.5kg/m3 of high-efficiency water reducing agent; the water reducing agent comprises at least one of a polycarboxylic acid water reducing agent, a melamine water reducing agent, a naphthalene water reducing agent and an AE water reducing agent; the low-speed stirring speed is 60-70 r/min, the high-speed stirring speed is 120-1300 r/min, and the stirring time is not less than 5 min.
Preferably: and 4, the raw material composition of the steel fiber is 155.9kg/m3, and the fiber comprises one or more of alkali-resistant glass fiber, carbon fiber, basalt fiber, polyvinyl alcohol fiber, polyacrylonitrile fiber, high-density polyethylene fiber, polyamide or polyimide fiber, polypropylene fiber, aromatic polyamide fiber or metal fiber.
The concrete has the compression strength of 112.5MPa in 7 days, the compression strength of 140MPa in 28 days, the breaking strength of 28.6MPa in 28 days, the tensile strength of 10.9MPa in 28 days, the expansion degree of 211mm and the microstrain of 1769 mu epsilon in the first 7 days. The invention has the following beneficial effects:
the preparation process is simple, and the ultra-high performance concrete with excellent performances in all aspects can be prepared by adopting the conventional process.
The preparation method of the invention adopts batch feeding and multi-step stirring, and the obtained concrete has high compactness, good raw material dispersibility and excellent comprehensive performance. The invention does not need a thermal curing system and achieves the purpose of no steam curing.
And thirdly, the ultra-high performance concrete prepared by the invention has certain fluidity due to the action of the optimal water-cement ratio and the high-efficiency water reducing agent, can be used for pumping the concrete, does not need vibration in the pouring process, naturally compacts the concrete, naturally removes gas in the slurry, and is the concrete with excellent self-compacting property.
And fourthly, replacing different components with active admixtures with different particle sizes, reducing the content of a cementing material in the ultra-high performance concrete, increasing the compactness of the ultra-high performance concrete, and improving the mechanical property, the wear resistance, the fatigue performance and the shrinkage of the ultra-high performance concrete. The exploitation and utilization of natural resources are reduced on the environment, the purposes of energy conservation and emission reduction are achieved, waste glass is recycled, the occupied area of waste stacking is reduced, the consumption of natural materials is reduced, and carbon emission is reduced; in addition, the disposal cost of the waste glass can be saved economically, and the cost of concrete can be reduced; the working performance and strength of the concrete can be technically improved.
And fifthly, mineral admixtures such as fly ash and active admixtures are adopted, the working performance of the concrete mixture is optimized, the compactness and the homogeneity of the concrete are improved, the shrinkage of the concrete is further reduced, the mechanical property and the volume stability of the ultra-high performance concrete are provided, the fly ash is a porous material and has a good water-retaining effect, along with the progress of hydration reaction, the fly ash slowly releases water, the self-maintenance is realized, the surface of micro-particles of the fly ash is smooth, the flowability of the concrete is greatly improved, and the optimized water-cement ratio ensures that the concrete can completely achieve the excellent self-compaction effect.
The glass is mainly prepared from quartz sand, soda ash, feldspar, limestone and the like, and comprises the chemical components of SiO2, Na2O, CaO, Al2O3, a small amount of K2O, MgO and the like, and due to the characteristics of the chemical components, the active admixture obtained by grinding and screening the waste glass has the pozzolanic activity, so that the setting time of concrete can be reduced, the strength and the durability of the concrete can be improved, and the fine glass powder adopted by the invention has the particle size of 1000 meshes, is the preferable particle size, and can generate more sufficient pozzolanic reaction and has a coarser particle size.
The invention is based on the theory of maximum bulk density, and the active admixtures with different particle diameters are doped, so that the gaps stacked among the quartz sand are filled, the structure is more compact, the bulk density of the ultra-high performance concrete particles is optimized, the components are fully stacked, and the ultra-high strength of the ultra-high performance concrete is ensured;
eighthly, by optimizing the basic mixing proportion, the ultra-high performance concrete with the shrinkage micro-strain of 1769 mu epsilon in the first 7 days, the compressive strength of 81.5MPa in the 7 days, the compressive strength of 100MPa in the 28 days, the flexural strength of 20.4MPa in the 28 days and the tensile strength of 7.76MPa in the 28 days is prepared. In addition, the material has the advantages of stable performance, strong impact resistance, greenness and low price, can be suitable for various complex loaded structures in road and bridge engineering, such as bridge closure sections, bridge deck pavement, expansion joints, wet joints and the like, and is suitable for wide popularization.
Detailed Description
The present invention will be described in further detail with reference to examples, but is not limited thereto.
A preparation method of low-shrinkage steam-curing-free self-compacting C140UHPC is characterized by comprising the following steps: the stirring method comprises the following steps:
step 1: placing the fine quartz sand and the coarse quartz sand in a stirrer, and stirring at a low speed for a certain time to form a uniform mixture;
step 2: placing cement, silica fume, fly ash, active admixture and quartz powder into the mixture obtained in the step (1), and stirring at a low speed for a certain time to uniformly stir the mixture;
and step 3: mixing and stirring the water and the high-efficiency water reducing agent uniformly, adding the mixture into the mixture obtained in the step (2), stirring at a low speed for a certain time, and stirring at a high speed for a certain time until the stirred material is fluidized;
and 4, step 4: weighing a specific amount of fiber, slowly adding the specific amount of fiber into the mixture obtained in the step (3), and continuously stirring at a high speed for a certain time after the addition is finished;
and 5: after the step 4 is finished, slowly pouring the mixed concrete into a mold, pouring and molding the concrete, and maintaining for 24 hours;
step 6: and (5) removing the mould of the formed concrete in the step (5) and naturally curing for 28 days to obtain the low-shrinkage steam-curing-free C140 UHPC.
The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: in step 6, the concrete may be cured by: 1) placing the concrete under natural conditions, covering the test piece with wet linen, and performing high-frequency intermittent watering treatment to keep the linen in a wet state all the time; 2) and placing the test piece in water for curing.
Preferably: the raw materials in the step 1 comprise 212.2kg/m3 of fine quartz sand and 848.7kg/m3 of coarse quartz sand, the particle size of the fine quartz sand is 0.04-0.08 mm, the particle size of the coarse quartz sand is 0.45-0.85 mm, the stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
Preferably: the raw materials in the step 2 comprise 681.7kg/m3 cement, 150.8kg/m3 silica fume, 37.9kg/m3 fly ash and 75.8kg/m3 active admixture, the stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
Preferably: and 2, the active admixture comprises one of glass powder, ceramic powder and the like. The glass powder can not only fill the pores in the slurry structure, but also produce C-S-H gel by volcanic ash reaction, thereby improving the microstructure of the material and enhancing the strength of the material. And the finer the glass frit, the better the activity. Or the rubber powder is adopted, the rubber powder is low in density and easy to deform, and can be extruded by a nearby medium in the stirring and forming processes, so that the rubber powder can generate certain prestress, and after the rubber powder has the prestress, the nearby medium is also pressurized in turn, so that the shrinkage around the rubber powder is limited to a certain extent, and the shrinkage is reduced.
Preferably: the active admixture is preferably glass powder, the glass powder is washed by water and ethanol, dried and then placed in washing liquor, the washing liquor is heated for 1 hour at 80-100 ℃ and naturally cooled, wherein the washing liquor is prepared by mixing 30% of hydrogen peroxide and 98% of sulfuric acid according to the weight ratio of 3: 7, washing the glass sheet with pure secondary distilled water, washing residual washing liquor on the surface, drying the glass sheet with a blower to prepare an activated substrate, and putting the activated substrate into a ball mill to be ground into glass powder with corresponding particle size. Because the active admixture is adopted to ensure that the volcanic ash in the concrete has complete reaction and does not need to be activated by high temperature, the UHPC avoids high-temperature steam curing.
Preferably: 2, replacing the cementing materials such as cement, quartz powder and the like with high-activity admixtures, wherein the replacement degree is 5 percent, 10 percent and the like, for example, replacing 10 percent of cement with 1000-mesh glass powder; the aggregate can be replaced by high-activity admixture with different particle sizes, for example, 400-mesh ceramsite is used for replacing 10% of fine quartz sand, and the like. The addition of fly ash and active admixture can change the working performance of UHPC, so that the UHPC can achieve the self-compacting effect.
Preferably: the raw materials in the step 3 comprise 189.3kg/m3 of water and 45.5kg/m3 of high-efficiency water reducing agent; the water reducing agent comprises at least one of a polycarboxylic acid water reducing agent, a melamine water reducing agent, a naphthalene water reducing agent and an AE water reducing agent; the low-speed stirring speed is 60-70 r/min, the high-speed stirring speed is 120-1300 r/min, and the stirring time is not less than 5 min.
Preferably: and 4, the raw material composition of the steel fiber is 155.9kg/m3, and the fiber comprises one or more of alkali-resistant glass fiber, carbon fiber, basalt fiber, polyvinyl alcohol fiber, polyacrylonitrile fiber, high-density polyethylene fiber, polyamide or polyimide fiber, polypropylene fiber, aromatic polyamide fiber or metal fiber.
The concrete has the compression strength of 112.5MPa in 7 days, the compression strength of 140MPa in 28 days, the breaking strength of 28.6MPa in 28 days, the tensile strength of 10.9MPa in 28 days, the expansion degree of 211mm and the microstrain of 1769 mu epsilon in the first 7 days.
Example 1
The low-shrinkage steam-curing-free self-compacting C140UHPC comprises the following components in percentage by weight: 757.5kg/m3 cement; 212.2kg/m3 of fine quartz sand; 848.7kg/m3 of coarse quartz sand; 150.8kg/m3 of quartz powder; silica fume 150.8kg/m 3; 37.9kg/m3 of fly ash; 189.3kg/m3 of water; 45.5kg/m3 of high-efficiency water reducing agent; the steel fiber 155.9kg/m 3.
Pouring quartz sand with two particle sizes into a stirrer, and stirring at a low speed for 5 min; sequentially adding quartz powder, silica fume and fly ash, finally adding cement, and stirring at low speed for 10min to fully stir the materials; uniformly stirring water and a water reducing agent, slowly adding a mixed solution of the water and the water reducing agent after the materials are uniformly stirred, firstly stirring at a low speed for 2min, and then stirring at a high speed for 5min until a stirred substance is fluidized; finally, adding steel fibers, and continuing to stir at high speed for 10 min; and pouring, molding and standing the concrete for 24 hours, then removing the mold, and naturally curing for 28 days.
Example 2
The low-shrinkage steam-curing-free self-compacting C140UHPC comprises the following components in percentage by weight: 681.7kg/m3 cement; 75.8kg/m3 of active admixture; 212.2kg/m3 of fine quartz sand; 848.7kg/m3 of coarse quartz sand; 150.8kg/m3 of quartz powder; silica fume 150.8kg/m 3; 37.9kg/m3 of fly ash; 189.3kg/m3 of water; 45.5kg/m3 of high-efficiency water reducing agent;
pouring quartz sand with two particle sizes into a stirrer, and stirring at a low speed for 5 min; sequentially adding quartz powder, silica fume, fly ash and active admixture, finally adding cement, and stirring at low speed for 10min to fully stir the materials; uniformly stirring water and a water reducing agent, slowly adding a mixed solution of the water and the water reducing agent after the materials are uniformly stirred, firstly stirring at a low speed for 2min, and then stirring at a high speed for 5min until a stirred substance is fluidized; and pouring, molding and standing the concrete for 24 hours, then removing the mold, and naturally curing for 28 days.
Example 3
The low-shrinkage steam-curing-free self-compacting C140UHPC comprises the following components in percentage by weight: 681.7kg/m3 cement; 75.8kg/m3 of active admixture; 212.2kg/m3 of fine quartz sand; 848.7kg/m3 of coarse quartz sand; 150.8kg/m3 of quartz powder; silica fume 150.8kg/m 3; 37.9kg/m3 of fly ash; 189.3kg/m3 of water; 45.5kg/m3 of high-efficiency water reducing agent; the steel fiber 155.9kg/m 3.
Pouring quartz sand with two particle sizes into a stirrer, and stirring at a low speed for 5 min; sequentially adding quartz powder, silica fume, fly ash and active admixture, finally adding cement, and stirring at low speed for 10min to fully stir the materials; uniformly stirring water and a water reducing agent, slowly adding a mixed solution of the water and the water reducing agent after the materials are uniformly stirred, firstly stirring at a low speed for 2min, and then stirring at a high speed for 5min until a stirred substance is fluidized; finally, adding steel fibers, and continuing to stir at high speed for 10 min; and pouring, molding and standing the concrete for 24 hours, then removing the mold, and naturally curing for 28 days.
The shrinkage strain, compressive strength, flexural strength and tensile strength of the test piece molded according to the above formulation, preparation method and curing system were measured with reference to "reactive powder concrete", standard of test method for fiber concrete "and standard of test method for long-term performance and durability of ordinary concrete", and the test results are shown in tables 1 and 2.
Table 1: measurement results of basic mechanical properties of different proportions
| Numbering | Example 1 | Example 2 | Example 3 |
| 7 day compressive strength (MPa) | 108.6 | 98.1 | 112.5 |
| 28 days compressive strength (MPa) | 130 | 122 | 140 |
| 28 days rupture strength (MPa) | 20.8 | 22.4 | 28.6 |
| 28 days tensile Strength (MPa) | 9.7 | 8.1 | 10.9 |
Table 2: micro strain (mu epsilon) with different proportions
| Numbering | 1 day | 2 days | 3 days | 4 days | 5 days | 6 days | 7 days | 10 days | 13 days | 16 days | 20 days | 24 days | 28 days |
| Example 1 | 555 | 993 | 1311 | 1596 | 1725 | 1831 | 1891 | 1973 | 2029 | 2080 | 2124 | 2170 | 2209 |
| Example 2 | 564 | 1006 | 1335 | 1603 | 1756 | 1845 | 1901 | 1970 | 2032 | 2084 | 2131 | 2180 | 2225 |
| Example 3 | 518 | 926 | 1228 | 1496 | 1628 | 1724 | 1769 | 1819 | 1871 | 1913 | 1961 | 1997 | 2035 |
As shown in the above Table 1 and Table 2, the low shrinkage steam-free self-compacting C140UHPC prepared by the invention has the characteristics of low shrinkage, high compressive strength, high tensile strength and high flexural strength.
Claims (10)
1. A preparation method of low-shrinkage steam-curing-free self-compacting C140UHPC is characterized by comprising the following steps: the stirring method comprises the following steps: step 1: placing the fine quartz sand and the coarse quartz sand in a stirrer, and stirring at a low speed for a certain time to form a uniform mixture; step 2: placing cement, silica fume, fly ash, active admixture and quartz powder into the mixture obtained in the step (1), and stirring at a low speed for a certain time to uniformly stir the mixture; and step 3: mixing and stirring the water and the high-efficiency water reducing agent uniformly, adding the mixture into the mixture obtained in the step (2), stirring at a low speed for a certain time, and stirring at a high speed for a certain time until the stirred material is fluidized; and 4, step 4: weighing a specific amount of fiber, slowly adding the specific amount of fiber into the mixture obtained in the step (3), and continuously stirring at a high speed for a certain time after the addition is finished; and 5: after the step 4 is finished, slowly pouring the mixed concrete into a mold, pouring and molding the concrete, and maintaining for 24 hours; step 6: and (5) removing the mould of the formed concrete in the step (5) and naturally curing for 28 days to obtain the low-shrinkage steam-curing-free C140 UHPC.
2. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: in step 6, the concrete may be cured by: 1) placing the concrete under natural conditions, covering the test piece with wet linen, and performing high-frequency intermittent watering treatment to keep the linen in a wet state all the time; 2) and placing the test piece in water for curing.
3. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: step 1 instituteThe raw materials consist of fine quartz sand 212.2kg/m3848.7kg/m of coarse quartz sand3The granularity of the fine quartz sand particles is 0.04-0.08 mm, the granularity of the coarse quartz sand particles is 0.45-0.85 mm, the stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
4. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: the raw materials in the step 2 consist of 681.7kg/m of cement3150.8kg/m of silica fume337.9kg/m of fly ash375.8kg/m of active admixture3The stirring time is not less than 5min, and the stirring speed is 60-70 r/min.
5. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: 2, the active admixture comprises one of glass powder, ceramic powder and the like, and replaces cement, so that the using amount of a cementing material is reduced, and the shrinkage is reduced; or the rubber powder is adopted, the rubber powder is low in density and easy to deform, and can be extruded by a nearby medium in the stirring and forming processes, so that the rubber powder can generate certain prestress, and after the rubber powder has the prestress, the nearby medium is also pressurized in turn, so that the concrete shrinkage around the rubber powder is limited to a certain extent, and the shrinkage is reduced.
6. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: the active admixture is preferably glass powder, the glass powder is washed by water and ethanol, dried and then placed in washing liquor, the washing liquor is heated for 1 hour at 80-100 ℃ and naturally cooled, wherein the washing liquor is prepared by mixing 30% of hydrogen peroxide and 98% of sulfuric acid according to the weight ratio of 3: 7 volume ratio, washing the glass sheet with pure secondary distilled water, washing residual washing liquid on the surface, drying by a blower to prepare an activated substrate, putting the activated substrate into a ball mill to be ground into glass powder with corresponding grain diameter, and because the volcanic ash in the concrete is completely reacted by adopting the active admixture and the activity is not required to be activated by high temperature, the UHPC is free from high-temperature steam curing.
7. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: step 2, replacing the cementing materials such as cement, quartz powder and the like with high-activity admixtures, wherein the replacement degrees are 5%, 10%, 15% and the like, for example, 10% of cement is replaced by 1000-mesh glass powder; the aggregate can be replaced by high-activity admixture with different particle sizes, for example, 400-mesh ceramsite is used for replacing 10% of fine quartz sand, and the like, the fly ash is added, and the working performance of UHPC can be changed by adding the active admixture, so that the self-compacting effect is achieved.
8. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: the raw material composition in the step 3 is 189.3kg/m of water345.5kg/m of high-efficiency water reducing agent3(ii) a The water reducing agent comprises at least one of a polycarboxylic acid water reducing agent, a melamine water reducing agent, a naphthalene water reducing agent and an AE water reducing agent; the low-speed stirring speed is 60-70 r/min, the high-speed stirring speed is 120-1300 r/min, and the stirring time is not less than 5 min.
9. The process for preparing a low shrinkage, non-autoclaved and self-compacting C140UHPC according to claim 1, wherein: step 4 the raw material composition is 155.9kg/m steel fiber3The fiber comprises one or more of alkali-resistant glass fiber, carbon fiber, basalt fiber, polyvinyl alcohol fiber, polyacrylonitrile fiber, high-density polyethylene fiber, polyamide or polyimide fiber, polypropylene fiber, aromatic polyamide fiber or metal fiber.
10. The low shrinkage, non-autoclaved, self-compacting C140UHPC according to claim 1, wherein: the concrete has the compression strength of 112.5MPa in 7 days, the compression strength of 140MPa in 28 days, the breaking strength of 28.6MPa in 28 days, the tensile strength of 10.9MPa in 28 days, the expansion degree of 211mm and the microstrain of 1769 mu epsilon in the first 7 days.
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