CN107459308B - High-flow anti-segregation self-compacting concrete - Google Patents
High-flow anti-segregation self-compacting concrete Download PDFInfo
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- CN107459308B CN107459308B CN201710810286.3A CN201710810286A CN107459308B CN 107459308 B CN107459308 B CN 107459308B CN 201710810286 A CN201710810286 A CN 201710810286A CN 107459308 B CN107459308 B CN 107459308B
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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
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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
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
-
- 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 high-flow anti-segregation self-compacting concrete, which comprises the following components: component (cubic dosage kg/m) for carrying out heavy planting: 240-290 parts of cement; 80-110 parts of slag powder; 50-80 parts of fly ash; 860-915 parts of fine aggregate; 870-900 parts of coarse aggregate; 4.2-5.6 of an additive; 170-185 parts of water; the fine aggregate is mixed sand with fineness modulus of machine-made sand and extra-fine sand not less than 2.4; the coarse aggregate is mixed pebbles with the particle size of 5-10 mm and broken stones with the particle size of 10-16 mm according to the mass ratio of 1: 1. When the high-flow-state self-compacting concrete is applied, the high-flow-state self-compacting concrete passes through the narrow gap with dense steel bars without vibration under the action of self weight, keeps good cohesiveness, prevents segregation, and improves engineering quality and construction efficiency.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to high-flow anti-segregation self-compacting concrete without vibration.
Background
Along with the development of social economy and construction technology, the construction forms are more and more abundant, and the complicated special-shaped cast-in-place structure puts higher requirements on concrete materials and construction technology. Concrete materials with high fluidity, cohesiveness and segregation resistance, such as self-compacting concrete, self-leveling concrete, vibration-free concrete and the like, become a new focus. At present, researchers in all countries around the world discuss the design theory and method of self-compacting concrete from different aspects, and form various mix proportion design methods of self-compacting concrete based on different principles or control parameters. Different theoretical bases and different design steps can cause great differences in the values and meanings of all parameters. Under the same condition, different design methods are adopted, and the performance of the designed self-compacting concrete is greatly different.
The acoustic wind tunnel is of an ultra-large special-shaped thin-wall concrete structure, the geometric shape of a tunnel body comprises an octagonal prism, an octagonal frustum, a quadrangular prism, a truncated cone, an irregular space curved surface body and the like, and the cross section of the irregular space curved surface body is converted, the inclined plane of the structure forms an inclination angle of 35-65 degrees, a thin tunnel wall (the wall thickness is 155 mm) and a dense steel bar principle (double-layer bidirectional steel bars phi 12+16mm @150 mm) are adopted during design, steel bars at the combined part of a tunnel body beam, a slab and a column are more dense, the concrete cannot be vibrated during pouring, how to ensure that the concrete at the part is tightly filled, and the concrete is not isolated and does not leak water is guaranteed, and the research on the suitable self-compacting concrete is of great importance in consideration of the special property of the structure of the.
Disclosure of Invention
The invention aims to meet the requirements of workability and vibration-free performance of engineering construction materials and provide high-flow anti-segregation self-compacting concrete. The high-flow anti-segregation self-compacting concrete is applied to large-scale acoustic wind tunnels, vibration-free construction of the concrete is realized in complex structures of thin tunnel walls and dense reinforcing steel bars, segregation and bleeding of the concrete are controlled from the source, and the engineering quality is improved.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
a high flow, segregation resistant, self-compacting concrete, the concrete comprising: the cement, slag powder, fly ash, fine aggregate, coarse aggregate, an additive and water, wherein the weight parts of the components are as follows:
240-290% cement
80-110 parts of slag powder
50-80 parts of fly ash
860 to 915 fine aggregate
Coarse aggregate 870-900
Additive 4.2-5.6
170-185 parts of water;
the fine aggregate is mixed sand of machine-made sand and superfine sand, and the fineness modulus of the mixed sand is not less than 2.4; the coarse aggregate is mixed pebbles with the particle size of 5-10 mm and broken stones with the particle size of 10-16 mm according to the mass ratio of 1: 1.
Furthermore, the fine aggregate is mixed sand formed by mixing machine-made sand and superfine sand according to the mass ratio of 6:4, the mud content is less than 1.2%, and the mud block content is less than 0.2%.
Further, the slag powder is S95-grade slag, and the specific surface area is 480 square meters per kg.
Further, the fly ash is first-grade fly ash, the water requirement ratio is 94%, the fineness (the residue of a 0.045mm square-hole sieve) is 7.4%, the ignition loss is 3.1%, the water content is 0.4%, and SO is3The content is 0.79%.
Further, the additive is a polycarboxylate water reducing agent.
Further, the additive is a TF-500 polycarboxylate high-performance water reducing agent, and the water reducing rate is 20.4.
The invention has the beneficial effects that:
1) the concrete is prepared by preferably selecting raw materials such as cement, slag, fly ash and an additive, and through theoretical design, experimental study and simulation application, the workability (fluidity, cohesiveness and water retention) of the concrete is improved, so that the concrete meets the requirements of automatic filling, compaction and vibration-free tamping in the process of casting a complex special-shaped thin-wall structure in situ; meanwhile, the phenomena of segregation and bleeding of concrete are effectively prevented, the risk of concrete quality defects is reduced, and the structural quality of the wind tunnel body is ensured;
2) the invention is different from other concrete in the selection and proportion of coarse aggregate and fine aggregate, and the coarse aggregate adopts mixed stones formed by mixing small cobbles with the particle size of 5-10 mm and 10-16 mm broken stones according to the proportion of 1: 1; the fine aggregate is mixed sand with fineness modulus of machine-made sand and superfine sand not less than 2.4, so that the selected coarse and fine aggregates improve the fluidity of concrete and the clearance passing rate of reinforcing steel bars, and meanwhile, the good aggregate grading can maximally ensure the cohesiveness and the water retention of the concrete, and prevent the occurrence of segregation to the maximum extent from the source of raw materials;
3) the invention selects the high-performance water reducing agent with the water reducing rate of 20.4 percent, slightly increases the using amount of the water reducing agent, reduces the water consumption of concrete, reduces the water-cement ratio, greatly improves the fluidity of the concrete, and simultaneously ensures that the concrete has high durability and high strength performance.
Detailed Description
The high flow, segregation-resistant, self-compacting concrete of the present invention is further described in detail below with reference to specific examples, which are intended to provide a clear understanding of the present invention from the aspects of theoretical design, experimental study and simulation application, but should not be construed as limiting the scope of the present invention.
The workability of concrete is mainly evaluated by the following indexes: slump and slump spread mainly reflect fluidity; the extension time Tj500 mainly reflects the viscosity of the mixture; the retardation rate H2/H1 (H2 represents the height of the concrete at the far end of the rear groove of the L-shaped instrument, and H1 represents the height of the concrete at the near end of the rear groove of the L-shaped instrument) index of the L-shaped instrument test reflects the clearance passing property and the segregation resistance; the test result of the U-shaped instrument can reflect the clearance passing capacity and the filling capacity of the concrete; the J-ring test may reflect the filling and passing ability of the concrete. The workability evaluation index of the self-compacting concrete commonly used in the specification is shown in the following table.
The invention aims at selection and preparation of cement, water-cement ratio, aggregate, sand ratio, cementing material composition (fly ash mixing amount, slag mixing amount, different amounts of limestone powder for replacing fly ash and different limestone powder fineness) and additives (water reducing agent and expanding agent) in concrete, and can greatly influence the property of the final mixture, thereby influencing the construction quality of the concrete. The influence of each parameter on the workability of the concrete is researched by using a single variable method. Through multiple comparison of working tests, the influence of each component parameter is comprehensively considered, and the optimized mixing ratio is determined as follows:
component cubic dosage kg/m for cultivating fruit
240-290% cement
80-110 parts of slag powder
50-80 parts of fly ash
860 to 915 fine aggregate
Coarse aggregate 870-900
Additive 4.2-5.6
170-185% of water
According to the invention, by selecting a low water-cement ratio, using mixed sand of machine-made sand and extra-fine sand as fine aggregate, and using mixed stones formed by mixing small pebbles with the particle size of 5-10 mm and broken stones with the particle size of 10-16 mm according to a mass ratio of 1:1 as coarse aggregate, the fluidity of concrete and the clearance passing rate of reinforcing steel bars are improved; reasonably optimizing the variety and the mixing amount of the slag and the fly ash, and introducing a high-performance water reducing agent to play a certain role in improving the cohesiveness and the water-retaining property of the concrete.
Example 1
The concrete of the invention is provided with a specific C30 concrete mix proportion design (mix proportion numbered SCC) in the cast-in-place concrete acoustic wind tunnel engineering construction, and in order to compare the mix proportion difference between the common concrete and the self-compacting concrete, the mix proportion (mix proportion numbered NC) corresponding to the common concrete is also listed in the following table.
TABLE 2
Cement:
the cement in the raw materials of the SCC and NC concrete is P.O 42.5.5R early strength type common Portland cement produced by the Unioncement company Limited in North China, which contains 6% of gypsum, 6% of limestone powder, 10% of slag, 0.06% of grinding aid, 373-388 square meters per kg of specific surface area, 33.9MPa of compressive strength at 3d and 52.7MPa of compressive strength at 28 d.
Fine aggregate:
and (3) machining sand: the finished product is more regular and can be processed into different sands according to different process requirementsThe sand with regular and large size can better meet daily requirements. The machine-made sand is generally particles having a particle size of 4.75mm or less, but excluding soft rock and weathered rock. The manufactured sand in the embodiment is manufactured sand produced by Skawa Fuling, and the apparent density is 2690kg/m3The content of the stone powder is 7.2 percent (MB = 0.7), the fineness modulus is 2.5, the particle size is 0.30-4.75 mm, and the particle size grading is good.
Ultra-fine sand: the obtained natural river sand with fineness modulus of 0.7-1.5 is tested according to the method specified in the building sand (GB/T14684). The ultrafine sand in the present example had a mud content of 1.2%, a fineness modulus of 0.8, and an average particle size of 0.23 mm.
The SCC concrete is mixed sand formed by mixing Fuling produced machine-made sand and superfine sand according to the mass ratio of 6:4, the fineness modulus is 2.4, the mud content is less than 1.2 percent, and the mud block content is less than 0.2 percent; the NC concrete adopts the natural sand produced in Mianyang, the sand in the area II, the fineness modulus is 2.6, and the mud content is 2.5%.
Coarse aggregate:
the pebbles produced in the embodiment are pebbles produced in Sichuan Mianyang, the particle size is 5-25 mm, the water content is 0.5%, the apparent density is 2680kg/m for high speed cultivation, the stacking density is 1640 kg/m for high speed cultivation, the porosity is 39%, the mud content is 0.4-0.8%, the mud block content is 0.2-0.3%, and the needle piece content is 6%; the broken stone is limestone broken stone with the particle size of 10-16 mm, the water content of 1.5 percent and the apparent density of 2700kg/m3The mud content is 0.2%, the needle sheet content is 5.1%, and the void ratio is 33%.
The SCC concrete is made of mixed stones formed by mixing Mianyang small cobbles with the particle size of 5-10 mm and 10-16 mm broken stones according to the mass ratio of 1: 1; the NC concrete selects macadam with the grain diameter of 5-20 mm for common commercial concrete.
Water reducing agent:
all adopt TF-500 polycarboxylate high-performance water reducing agent, the water reducing rate is 20.4 percent, the bleeding rate is 30.8 percent, the gas content is 2.6 percent, the solid content is 9.6 percent, the pH value is 5.0, and the density is 1.03kg/m3。
Fly ash
All are first-grade fly ash, the fineness (the residue of a 0.045mm square-hole sieve) is 7.4 percent, the ignition loss is 3.1 percent, the water content is 0.4 percent, and the SO3 content is as follows: 0.79 percent.
Slag powder
The slag is produced by Chongqing iron and steel group in S95 grade, and the specific surface area is 480 square meters per kg.
The concrete 28d mixed and stirred in the above-mentioned proportions has the following indexes such as strength, slump expansion and the like.
TABLE 3
As can be seen from the comparison of the above table, the strength of the SCC concrete 28d of the invention is not much different from that of the common concrete, but indexes such as slump and slump expansion and the like all reach excellent levels, which reflects that the concrete of the invention has good fluidity, cohesiveness and water-retaining property. The concrete is simple, convenient and quick to construct in large-three-dimensional special-shaped thin-wall acoustic wind tunnel engineering construction, the concrete with narrow gaps of reinforcing steel bars is high in trafficability, segregation and bleeding phenomena do not occur in pouring, and the flatness of the inner profile of the hole body structure after the formwork is removed, the compactness of the concrete and the strength level of the concrete can meet the requirements of design and use processes.
The water-cement ratio is the ratio (weight) of the water consumption of the concrete to all the cementing materials, and the ratio of the water consumption of each cubic meter of the concrete to the use amount of all the cementing materials.
In this example: the water consumption of the self-compacting concrete SCC is 176kg/m, the cementing material is cement, fly ash and slag powder, the sum of the consumption of the cement, the fly ash and the slag powder is 280+70+100=450kg/m, and the water-cement ratio is 176/450= 0.39.
Sand rate: SP = mass of sand S/(amount of sand S + amount of stone G) × 100%, which is the percentage of the mass of sand in the concrete to the total mass of sand and stone. Variations in sand ratio can cause significant changes in the total surface area of the aggregate, thereby having a greater impact on the workability of the concrete mix.
Workability includes fluidity, cohesiveness, and water retention.
The concrete layered segregation is mainly divided into two types: the slurry is separated and appears as bleeding; the aggregates are separated and are in a layered state with more coarse aggregates on the lower surface and more slurry on the upper surface. Both separations tend to occur simultaneously. In the embodiment, the concrete is selected and added with the high-efficiency water reducing agent, the water consumption is less, the segregation phenomenon of slurry is improved from the raw materials, and meanwhile, the mixed coarse aggregate and the mixed aggregate are selected, the grading is good, the wrapping property of the cement is good, and the layering of the aggregate and the slurry is effectively avoided.
Claims (3)
1. A high flow, segregation resistant, self-compacting concrete, comprising the components of: the cement, slag powder, fly ash, fine aggregate, coarse aggregate, an additive and water, wherein the weight parts of the components are as follows:
240-290% cement
80-110 parts of slag powder
50-80 parts of fly ash
860 to 915 fine aggregate
Coarse aggregate 870-900
Additive 4.2-5.6
170-185 parts of water;
the fine aggregate is mixed sand of machine-made sand and superfine sand, and the fineness modulus of the mixed sand is not less than 2.4; the coarse aggregate is mixed pebbles with the particle size of 5-10 mm and broken stones with the particle size of 10-16 mm according to the mass ratio of 1: 1; the fine aggregate is mixed sand formed by mixing machine-made sand and superfine sand according to the mass ratio of 6:4, the mud content is less than 1.2%, and the mud block content is less than 0.2%; the additive is TF-500 polycarboxylate high-performance water reducing agent, and the water reducing rate is 20.4%.
2. The high flow state segregation resistant self-compacting concrete according to claim 1, wherein said slag powder is S95 grade slag with a specific surface area of 480 square meters per kg.
3. The high flow state segregation-resistant self-compacting concrete according to claim 1, wherein the fly ash is first-grade fly ash, the water demand ratio is 94%, the fineness is 7.4%, the loss on ignition is 3.1%, and the water content is 0.4%，SO3The content is 0.79%.
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| CN109942261A (en) * | 2017-12-21 | 2019-06-28 | 兴业县银基混凝土有限公司 | A kind of self-compacting concrete |
| CN109678421B (en) * | 2019-01-07 | 2019-10-29 | 容梦晗 | A kind of concrete composition and preparation method thereof |
| CN110078431A (en) * | 2019-06-03 | 2019-08-02 | 青岛中建富兴商砼有限公司 | Anti- isolation high-strength heat-insulating concrete of one kind and preparation method thereof |
| CN110606705A (en) * | 2019-10-30 | 2019-12-24 | 中国建筑第八工程局有限公司 | High flow state fair-faced concrete |
| CN114890755B (en) * | 2022-06-20 | 2023-04-14 | 保利长大工程有限公司 | High-water-retention anti-segregation high-durability precast beam artificial-vibration-free concrete and preparation method thereof |
| CN115108783A (en) * | 2022-07-06 | 2022-09-27 | 保利长大工程有限公司 | Self-compacting concrete for controlling reinforcing steel bar protection layer and preparation method thereof |
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