CN110105012B - High-performance admixture special for sprayed concrete - Google Patents
High-performance admixture special for sprayed concrete Download PDFInfo
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- CN110105012B CN110105012B CN201910371601.6A CN201910371601A CN110105012B CN 110105012 B CN110105012 B CN 110105012B CN 201910371601 A CN201910371601 A CN 201910371601A CN 110105012 B CN110105012 B CN 110105012B
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- admixture
- component
- shotcrete
- special
- sprayed concrete
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Classifications
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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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00034—Physico-chemical characteristics of the mixtures
- C04B2111/00146—Sprayable or pumpable mixtures
- C04B2111/00155—Sprayable, i.e. concrete-like, materials able to be shaped by spraying instead of by casting, e.g. gunite
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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
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00724—Uses not provided for elsewhere in C04B2111/00 in mining operations, e.g. for backfilling; in making tunnels or galleries
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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
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
Abstract
The invention belongs to the technical field of constructional engineering, and particularly relates to a special admixture for high-performance shotcrete, which comprises two main components, namely an adhesion component and an early-strength component, wherein the mass ratio of the adhesion component to the early-strength component is 60-70: 30-40. Wherein the cohesive component is a mixture of modified latex powder and an ultrafine mineral admixture, the mass ratio of the modified latex powder to the ultrafine mineral admixture is 20-30: 70-80, and the early strength component is high-activity tricalcium aluminate. According to the invention, through the synergistic effect of the cohesive component and the early strength component, the cohesive property and the early strength of the sprayed concrete are effectively improved, so that the rebound rate of the sprayed concrete is reduced, and the compactness is improved. The material provides an effective way for really realizing the high performance of the sprayed concrete.
Description
Technical Field
The invention belongs to the technical field of building engineering materials, and particularly relates to a special admixture for high-performance shotcrete.
Background
The sprayed concrete is an important component of tunnel engineering, and the construction performance and the service state of the sprayed concrete are important factors influencing the construction progress and the later-stage use state of the tunnel engineering. The sprayed concrete can be divided into dry spraying and wet spraying according to different construction processes. Wherein, dry spraying concrete is less adopted at present because of serious dust pollution and great harm to constructors in the construction process. The use of the wet spraying method effectively reduces the dust pollution in the spraying process, the rebound rate of the sprayed concrete is reduced, and the construction efficiency is obviously improved. Therefore, the wet spraying method has become a main construction method for spraying concrete in a tunnel. However, the wet shotcrete construction process still has the outstanding problems of high rebound resilience, insufficient early strength, etc., which significantly reduces the shotcrete construction efficiency and causes deterioration phenomena such as shrinkage cracking. On the other hand, the conventional shotcrete only considers the requirement of the compressive strength index in the design process of the mix proportion, but does not consider the requirement of durability. The design concept also causes the outstanding problems of the strength shrinkage, poor impermeability and the like of the sprayed concrete in engineering practice. However, the primary support shotcrete of the tunnel is an important barrier for protecting the safe and stable service of the tunnel structure and is also a key component for calculating the stress of the tunnel supporting structure, so that the compressive strength index is far insufficient to be considered in the design process of the mix proportion of the shotcrete, and the durability index still needs to be further considered. The invention provides the special admixture for the high-performance shotcrete, which can effectively solve the problem of durability of the shotcrete and enable the shotcrete to have high performance. The special admixture mainly comprises the following functions: (1) the cohesiveness of the sprayed concrete is improved, the rebound rate is reduced, and the one-time spraying thickness is improved; (2) the early strength of the sprayed concrete is improved, the compactness is improved, and the durability of the sprayed concrete is effectively improved.
At present, researchers at home and abroad have made certain progress on the aspects of concrete admixture, durability improvement and the like, but special admixtures comprehensively considering the construction performance and long-term durability of sprayed concrete are still rarely reported. Chinese patent CN102826774A "nano-grade shotcrete modifying admixture" reduces the rebound of shotcrete by using nano-silica and mineral admixtures. However, the main component of the modified admixture is nano-silica, and the nano-silica accounts for 70-95% of the total mass. Because the nano silicon dioxide raw material has higher cost and the improvement effect on the cohesiveness of the concrete is not obvious, the modified admixture in the invention needs to account for 10-15% of the total mass of the sprayed concrete cement. Because the material has higher cost and larger mixing amount, the popularization and the application are limited. Chinese patent CN1262254A 'preparation technology and method of high-activity concrete admixture', Chinese patent CN1792955A 'high-activity concrete admixture', Chinese patent CN101037310A 'high-performance pump concrete containing mineral admixture' and the like all provide special admixtures suitable for concrete under different working conditions. However, relatively few high performance concrete admixtures have been proposed for the specific application and durability requirements of shotcrete.
Disclosure of Invention
The invention aims to provide a special admixture for high-performance shotcrete, which overcomes the defects of poor cohesiveness, high rebound rate, low early strength and the like of the traditional shotcrete.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows.
The problems of high rebound rate, insufficient early strength and the like are solved by increasing the cohesiveness and early strength of the shotcrete, namely the special admixture for the high-performance shotcrete comprises two core components: a cohesive component and an early strength component. The cohesive component is formed by mixing modified latex powder and an ultrafine mineral admixture, and the mass ratio of the modified latex powder to the ultrafine mineral admixture is 60-70: 30-40. Wherein the early strength component consists of tricalcium aluminate with high activity. The cohesive component and the early strength component have synergistic effect, so that the cohesive property of the sprayed concrete can be effectively improved, the rebound rate of the sprayed concrete is reduced, and the durability of the sprayed concrete is effectively improved by improving the early strength.
Specifically, the admixture special for the high-performance shotcrete comprises the following components.
The cohesive component (60-70%) comprises two main components of modified latex powder and a mineral admixture, and the mass ratio of the modified latex powder to the superfine mineral admixture is 20-30: 70-80. The modified latex powder is formed by polymerizing vinyl acetate in the presence of acetic acid, and the polymerization degree is 300-600. The superfine mineral admixture is one of silica fume and superfine slag powder or a mixture of the silica fume and the superfine slag powder in any proportion, and the fineness d50 of the superfine mineral admixture is less than 5 mu m.
The early strength component (30-40%) mainly comprises high-activity tricalcium aluminate powder with fineness d50 less than 15 μm.
The mass ratio of the special admixture to the sprayed concrete cementing material is 5-10: 90-95.
The admixture special for the high-performance shotcrete can effectively reduce the rebound rate of the shotcrete, improve the once-spraying thickness and improve the early strength. Specifically, the special admixture can realize that the rebound rate of the sprayed concrete side wall is less than or equal to 5 percent, the vault is less than or equal to 8 percent, the once spraying thickness is more than or equal to 40cm, and the 1d compressive strength of the jet-forming concrete is more than or equal to 15 MPa.
Detailed Description
In order to better illustrate the features of the present invention, the following description will be given with reference to specific examples, but the present invention is not limited to the examples. The mixing process of the shotcrete containing the modified admixture comprises the following steps: firstly adding the coarse aggregate, the fine aggregate, the cement and the special admixture into a stirrer, stirring for 2 minutes, then adding the water and other additives, stirring for 2 minutes, and taking out of the stirrer.
Comparative example 1
As a comparative example, a test was conducted using shotcrete not doped with the special admixture of the present invention. In the test, the mixing amount of the coagulant is 7 percent of the total mass of the cementing material, and the coagulant is added at a nozzle. And (4) carrying out a test by adopting a wet spraying process, wherein the test section of the test is grade III surrounding rock.
The test raw materials comprise: cement of Jinqi brand P.O.42.5; common river sand with fineness modulus of 2.7; grading broken stone with the particle size of 5-15 mm; the water reducing agent is a polycarboxylic acid water reducing agent produced by Jiangsu company; the accelerator is an alkali-free liquid accelerator.
The formulation of the shotcrete without the special admixture is shown in the table below.
| Ordinary portland cement | Fly ash | Sand | Stone (A. B. C. A. stone | Water (W) | Water reducing agent | Accelerating agent |
| 400 | 80 | 750 | 950 | 195 | 1.0% | 7% |
The initial setting time of the cement with the admixture of the quick-setting agent is 2min35s, and the final setting time is 5min23 s. When no special admixture is added, the rebound rate of the side wall in the concrete spraying process is 11 percent, and the rebound rate of the arch crown is 18 percent. The compressive strength of the sprayed concrete 1d is 8.9MPa by core drilling sampling.
Example 1
The admixture special for the sprayed concrete comprises the following components in parts by weight:
21 parts of modified latex powder; 24.5 parts of silica fume and 24.5 parts of superfine mineral powder; 30 parts of high-activity tricalcium aluminate.
The admixture special for the high-performance sprayed concrete accounts for 5% of the using amount of the cementing material, and the admixture of the quick-setting agent accounts for 7% of the total mass of the cementing material in the test, and is added at a nozzle. The formulation of the shotcrete incorporating the special admixtures is shown in the following table.
| Ordinary portland cement | Special admixture | Fly ash | Sand | Stone (A. B. C. A. stone | Water (I) | Water reducing agent | Accelerating agent |
| 370 | 22.5 | 80 | 750 | 950 | 195 | 1.0% | 7% |
After the special admixture is added, the rebound rate of the side wall is 3 percent and the rebound rate of the vault is 5 percent in the concrete spraying process. The compressive strength of the shotcrete 1d is 18.1MPa by core drilling sampling.
Example 2
The admixture special for the sprayed concrete comprises the following components in parts by weight:
21 parts of modified latex powder; 24.5 parts of silica fume and 24.5 parts of superfine mineral powder; 30 parts of high-activity tricalcium aluminate.
The admixture special for the high-performance sprayed concrete accounts for 10% of the cement dosage, and the admixture of the quick-setting agent accounts for 7% of the total mass of the cementing material in the test, and is added at a nozzle. The formulation of the shotcrete incorporating the special admixture is shown in the following table.
| Ordinary portland cement | Special admixture | Fly ash | Sand | Stone (A. B. C. A. stone | Water (I) | Water reducing agent | Accelerating agent |
| 360 | 44 | 80 | 750 | 950 | 195 | 1.0% | 7% |
After the special admixture is added, the rebound rate of the side wall is 1 percent and the rebound rate of the vault is 3 percent in the concrete spraying process. The compressive strength of the sprayed concrete 1d is 20.9MPa by core drilling sampling.
From the above test results, it can be seen that: the admixture special for shotcrete used in examples 1 to 2 had the same components but different amounts. Compared with the comparative example 1, the use of the special admixture can effectively improve the cohesiveness of the shotcrete, so that the rebound rate of side walls and vaults is reduced, and the early-strength component in the special admixture can effectively improve the compressive strength of the shotcrete 1 d. As can be seen from the test results of comparative examples 1 and 2, as the addition amount of the special admixture is increased, the cohesiveness of the shotcrete is increased, the rebound rate is further reduced, and the 1d compressive strength is remarkably improved. According to the test results, the special admixture for the high-performance shotcrete is successfully prepared by using the synergistic effect of the cohesive component and the early strength component, and the use of the admixture can effectively improve the cohesive property of the shotcrete, reduce the rebound rate, improve the early strength and improve the durability of the shotcrete.
Claims (3)
1. The admixture special for the high-performance shotcrete is characterized by comprising two main components, namely an adhesion component and an early strength component, wherein the mass ratio of the adhesion component to the early strength component is 60-70: 30-40, the adhesion component is a mixture of modified latex powder and an ultrafine mineral admixture, the mass ratio of the modified latex powder to the ultrafine mineral admixture is 20-30: 70-80, the early strength component is high-activity tricalcium aluminate, the modified latex powder is formed by polymerizing vinyl acetate in the presence of acetic acid, and the polymerization degree is 300-600.
2. The admixture special for the high-performance shotcrete as claimed in claim 1, wherein the ultra fine mineral admixture is one of silica fume, ultra fine slag powder or a mixture of them in any proportion, and the fineness d50 of the ultra fine mineral admixture is less than 5 μm.
3. The admixture special for the high-performance shotcrete according to claim 1, wherein a mass ratio of the admixture to the shotcrete binding material is 5-10: 90-95.
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| CN201910371601.6A CN110105012B (en) | 2019-05-06 | 2019-05-06 | High-performance admixture special for sprayed concrete |
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| CN201910371601.6A CN110105012B (en) | 2019-05-06 | 2019-05-06 | High-performance admixture special for sprayed concrete |
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| CN110105012A CN110105012A (en) | 2019-08-09 |
| CN110105012B true CN110105012B (en) | 2022-07-22 |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112456851B (en) * | 2020-11-07 | 2022-05-03 | 江苏博拓新型建筑材料股份有限公司 | Water-reducing early strength mineral admixture and preparation method thereof |
| CN114477843B (en) * | 2022-01-27 | 2022-09-09 | 武汉源锦建材科技有限公司 | Heat-resistant admixture for shotcrete and application thereof |
| CN114538820B (en) * | 2022-04-27 | 2022-08-09 | 中国铁道科学研究院集团有限公司铁道建筑研究所 | Sprayed concrete rebound inhibition method based on full flow control |
| CN114804749A (en) * | 2022-04-29 | 2022-07-29 | 中铁三局集团有限公司 | Superfine modified silica micropowder low-resilience high-early-strength wet-spraying concrete and construction method thereof |
| CN114907072A (en) * | 2022-05-24 | 2022-08-16 | 中建八局检测科技有限公司 | Plateau tunnel shotcrete and preparation method thereof |
| CN115073054A (en) * | 2022-07-21 | 2022-09-20 | 北京建筑大学 | High-strength ultrafine additive for shotcrete, preparation method and use method thereof, low-resilience shotcrete and preparation method thereof |
| CN115536300B (en) * | 2022-10-31 | 2023-09-29 | 中铁十一局集团有限公司 | Functional admixture for sprayed concrete and preparation method and application thereof |
| CN115536302B (en) * | 2022-11-07 | 2023-09-12 | 贵州天威建材科技有限责任公司 | Silicon-manganese slag-based super-early-strength sprayed concrete admixture and sprayed concrete |
| CN115849764B (en) * | 2022-11-25 | 2023-10-27 | 四川沃庆新材料科技有限公司 | Sprayed concrete admixture and preparation method and application thereof |
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