CN111206792A - Structure for preventing early cracking of concrete long wall, construction method and application - Google Patents
Structure for preventing early cracking of concrete long wall, construction method and application Download PDFInfo
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- CN111206792A CN111206792A CN202010028564.1A CN202010028564A CN111206792A CN 111206792 A CN111206792 A CN 111206792A CN 202010028564 A CN202010028564 A CN 202010028564A CN 111206792 A CN111206792 A CN 111206792A
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
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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
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/62—Insulation or other protection; Elements or use of specified material therefor
- E04B1/66—Sealings
- E04B1/68—Sealings of joints, e.g. expansion joints
-
- 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
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/20—Retarders
- C04B2103/22—Set retarders
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- Architecture (AREA)
- Chemical & Material Sciences (AREA)
- Structural Engineering (AREA)
- Ceramic Engineering (AREA)
- Civil Engineering (AREA)
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- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
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- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention relates to a structure for preventing early cracking of a long concrete wall, a construction method and application, comprising an existing concrete wall, a newly-poured concrete wall and a concrete retarding layer arranged between the existing concrete wall and the newly-poured concrete wall, wherein the setting time of the concrete retarding layer is at least 5 days, the concrete retarding layer reaches the design strength within 28 days after pouring, the shrinkage rate is 0%, the concrete retarding layer comprises 0.5-1% of retarder by weight, and the retarder comprises the following components by weight, 200g/L of gluconic acid, 300g/L of citric acid 200-.
Description
Technical Field
The invention belongs to the field of civil engineering construction, and particularly relates to a structure for preventing early cracking of a concrete long wall, a construction method and application.
Background
The concrete is a mixture formed by a plurality of materials and is a brittle material, and the generation of cracks is difficult to avoid under the action of internal and external forces. A large number of engineering practices show that the cause of the reinforced concrete structure cracks is complex, even a plurality of factors influence each other, the main reason of the concrete cracks is that the concrete deformation is restricted or acted by external force, and the cracks can be generated in the whole process from the concrete pouring to the structure use. Among them, the deformation load is an important factor for causing cracks.
The deformation load refers to temperature shrinkage, dry shrinkage deformation, uneven settlement and the like, and the main reasons for generating cracks of the side wall are dry shrinkage deformation and temperature shrinkage deformation because the side wall is of a concrete thin-wall structure. Wherein the shrinkage deformation of the concrete mainly refers to the volume reduction of the concrete caused by the water loss. The temperature shrinkage deformation is mainly caused by that cement in the concrete releases a large amount of hydration heat in the hardening process of the concrete, and the expansion deformation is caused by the temperature change generated in the structure in the continuous heat dissipation process. The internal temperature rises first and then falls over time, the higher the thickness of the concrete wall, the slower the temperature rises, the slower the fall, and the lower the maximum temperature value.
Investigation and statistics are carried out, wherein the main part of the side wall with cracks in the structure is positioned at the middle lower part and the construction joint; most of cracks in the side wall are vertical, and only a small amount of circumferential and transverse cracks exist. Meanwhile, the fracture can be divided into a surface fracture and a through fracture according to the fracture cracking depth.
Chinese patent application number is CN201611215009.X's patent discloses a cement concrete anti-cracking layer structure, including reserving board and new concreting cement concrete surface course, reserve the board set up in between new concreting cement concrete surface course and the existing building, it is fixed through prefabricated fixed die plate to reserve the board, reserve the board with the height-identity of new concreting cement concrete surface course, reserve the board and be elastic material board, it mainly is extruded polystyrene board or cystosepiment. The installation process is carried out slowly to prevent the elastic material plate from being damaged, the elastic material plate is removed at the later stage, and then the caulking asphalt ointment is poured. In order to prevent different concretes from being deformed differently in dry shrinkage deformation and temperature shrinkage deformation to cause cracking, an elastic reserved plate is arranged between an existing building and a newly poured cement concrete surface layer to separate the existing building from the newly poured cement concrete surface layer, shrinkage constraint is eliminated, deformation cracking is prevented, but the material is not reliably connected with new and old concretes, caulking asphalt factice poured after the caulking factice is removed cannot meet the use requirement, the integral performance of the structure is seriously influenced, and the anti-cracking layer structure is inapplicable to places such as high-rise buildings and the like with high requirements on structural integrity and strength.
Disclosure of Invention
The invention aims to provide a structure, a construction method and application for preventing early cracking of a concrete long wall, and the structure, the construction method and the application have good cracking prevention effect and are simple to construct.
The invention relates to a structure for preventing early cracking of a long concrete wall, which comprises an existing concrete wall body, a newly-poured concrete wall body and a concrete retarding layer arranged between the existing concrete wall body and the newly-poured concrete wall body, wherein the setting time of the concrete retarding layer is at least 5 days, the concrete retarding layer achieves the design strength within 28 days after pouring, the shrinkage rate is 0%, the concrete retarding layer comprises 0.5-1% of retarder by weight, and the retarder comprises the following components by weight, 200g/L of sucrose 100-.
Preferably, the length of the newly cast concrete wall is more than 30m, and is generally 30-40 m. The early stage is 7-28 days after pouring. The design strength refers to the strength required by construction, and is generally the same as the strength of a newly-poured concrete wall.
Preferably, when the thickness of the newly poured concrete wall is 0.3-1m, the setting time of the concrete retarding layer is 5-10 days, and when the thickness of the newly poured concrete wall is 1-1.5m, the setting time of the concrete retarding layer is 10-15 days.
Preferably, the newly poured concrete wall is perpendicular to the existing concrete wall.
The invention provides a construction method of a structure for preventing a long concrete wall from cracking early, which comprises the following steps of pouring a concrete retarding layer on an existing concrete wall, and then pouring a newly-poured concrete wall on the concrete retarding layer.
The invention provides an application of a concrete retardation layer in preventing early cracking of a concrete long wall, wherein the concrete retardation layer comprises 0.5-1 wt% of a retarder, and the retarder comprises the following components, by weight, 200g/L of sucrose, 300g/L of citric acid, 10-50g/L of sodium tripolyphosphate and 10-50g/L of sodium pyrophosphate.
During construction, when a new concrete wall is poured, a concrete or mortar retarding layer of 5cm to 10cm is firstly poured on the existing concrete wall, then a conventional concrete wall required by design is poured, because the concrete or mortar retarding layer is not condensed in the early hardening and cooling processes of the conventional concrete wall body, the concrete newly poured into the wall body is not restricted by the existing concrete wall body in the condensing and cooling shrinkage processes, when the concrete or mortar retardation layer is solidified, the early temperature shrinkage deformation of the newly poured concrete is basically finished, thereby leading the newly poured concrete wall not to be restricted by the existing concrete in the early hardening process, therefore, cracking caused by early coagulation and temperature drop can not occur, the concrete retardation layer has long retardation time and high structural strength, and after the concrete retardation layer is hardened, the strength can meet the design requirement.
The concrete crack has the beneficial effects that the concrete crack is caused mainly because the large deformation difference exists between the new concrete structure and the old concrete structure, so that when the side plates shrink, the bottom plate can generate large shrinkage constraint on the side plates, and the crack is caused. In order to solve such problems, the current treatment measures mainly include 1 strict control of material properties including cement, coarse aggregate, addition of admixtures such as water-reducing agent and expanding agent to reduce water consumption, cement usage, hydration heat, and the like. And 2, strictly controlling construction procedures, such as strengthening the monitoring of the temperature of the concrete, reasonably pouring and layering, controlling the template structure, the template rigidity and the template removal time, strengthening the early maintenance of the concrete (such as water spraying), and strengthening the toughness of materials (such as adding steel fiber materials into the concrete). In addition to the control of materials and construction process, the prior art also includes the addition of an elastic material layer on the old and new concrete surface, such as extruded polystyrene board and foam board material, but the elastic material layer can cause gaps among materials and has great influence on the properties such as the strength of the final structure.
The setting time of the existing concrete is generally about 1 day, in order to reduce the internal temperature of the existing concrete, the existing concrete is generally cooled by adopting a water spraying mode, or a water reducing agent and a retarder are added to reduce the heat release, so that the setting time is prolonged, the setting time is generally within 2-3 days under the condition of adding the retarder, if the concrete is excessively delayed, the construction period and the engineering quality of a wall body can be seriously influenced, and generally, the wall body concrete is required to avoid the occurrence of an overtime delayed setting phenomenon.
The research discovers that the retarder is added into the concrete of the newly-poured concrete wall body, so that the effect of avoiding early cracking is not great. Experiments show that if the delayed coagulation time of the concrete or mortar delayed coagulation layer is increased to be within 3 days, the cracking prevention effect is limited, and if a better effect is obtained, the setting time of the concrete or mortar delayed coagulation layer needs to be prolonged to be finished after the early temperature reduction of newly-cast wall concrete, and the cracking prevention effect is better.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
In the figure, 1 is an existing concrete wall, 2 is a newly poured concrete wall, and 3 is a concrete or mortar retarding layer.
Detailed Description
Example 1
As shown in figure 1, the mortar slow-setting wall comprises an existing concrete wall body 1, a newly-poured concrete wall body 2 and a mortar slow-setting layer 3 arranged between the existing concrete wall body and the newly-poured concrete wall body, wherein the setting time of the mortar slow-setting layer is 6 days, the mortar slow-setting layer reaches the design strength within 28 days after pouring, the shrinkage rate is 0%, the mortar slow-setting layer comprises 0.5% of a retarder by weight, and the retarder comprises the following components by weight, 100g/L of sucrose, 300g/L of citric acid, 50g/L of sodium tripolyphosphate and 10g/L of sodium pyrophosphate. The thickness of the newly-poured concrete wall body is 50 cm.
The construction method comprises the following steps of pouring a 5cm mortar retarding layer on the existing concrete wall body, and then pouring a newly-poured concrete wall body on the mortar retarding layer.
Example 2
The mortar retarder comprises an existing concrete wall body, a newly-poured concrete wall body and a concrete retarder layer arranged between the existing concrete wall body and the newly-poured concrete wall body, wherein the setting time of the mortar retarder layer is 10 days, the concrete retarder layer achieves design strength within 28 days after pouring, the shrinkage rate is 0%, the concrete retarder layer comprises 0.8% of retarder by weight, and the retarder comprises the following components by weight, 200g/L of sucrose, 200g/L of citric acid, 10g/L of sodium tripolyphosphate and 50g/L of sodium pyrophosphate. The thickness of the newly-poured concrete wall body is 1 m.
The construction method comprises the following steps of pouring a concrete retarding layer of 8cm on the existing concrete wall body, and then pouring a newly-poured concrete wall body on the concrete retarding layer.
Comparative example 1
The construction method comprises the steps of pouring the newly-poured concrete wall on the existing concrete wall.
Comparative example 2
The concrete retarder comprises an existing concrete wall body, a newly-poured concrete wall body and a concrete retarding layer arranged between the existing concrete wall body and the newly-poured concrete wall body, wherein the setting time of the concrete retarding layer is 2 days, the concrete retarding layer achieves design strength within 28 days after pouring, the shrinkage rate is 0%, the concrete retarding layer comprises a retarder with the weight percentage of 0.2%, and the retarder comprises the following components in percentage by weight, 50g/L of gluconic acid, 100g/L of citric acid, 5g/L of sodium tripolyphosphate and 10g/L of sodium pyrophosphate. The thickness of the newly-poured concrete wall body is 50 cm.
The construction method comprises the following steps of pouring a concrete retarding layer on the existing concrete wall body, and then pouring a newly-poured concrete wall body on the concrete retarding layer.
The data in table 1 were obtained by analyzing the cracking of the walls of comparative examples 1-2 and inventive walls within 70 days after casting.
TABLE 1 cracking distribution table for the walls of the present invention and comparative examples 1-2
It can be found from table 1 that the concrete or mortar retardation layer with long retardation time is added between the existing concrete wall and the newly poured concrete wall, so that cracks are basically avoided.
Claims (6)
1. A structure for preventing early cracking of a long concrete wall is characterized by comprising an existing concrete wall body, a newly-poured concrete wall body and a concrete retarding layer arranged between the existing concrete wall body and the newly-poured concrete wall body, wherein the setting time of the concrete retarding layer is at least 5 days, the concrete retarding layer achieves design strength within 28 days after pouring, the shrinkage rate is 0%, the concrete retarding layer comprises a retarder with the weight percentage of 0.5-1%, and the retarder comprises the following components, by weight, 200g/L of sucrose 100-.
2. The structure for preventing the early cracking of the concrete long wall according to claim 1, wherein when the thickness of the newly cast concrete wall is 0.3 to 1m, the setting time of the concrete retarding layer is 5 to 10 days; when the thickness of the newly-poured concrete wall body is 1-1.5m, the setting time of the concrete retarding layer is 10-15 days.
3. A structure for preventing early cracking of a long concrete wall according to claim 1 or 2, wherein the length of the newly cast concrete wall is greater than 30 m.
4. The structure for preventing the early cracking of a long concrete wall according to claim 1 or 2, wherein the newly cast concrete wall is perpendicular to the existing concrete wall.
5. A method of constructing a structure for preventing early cracking of a long concrete wall according to any one of claims 1 to 4, comprising the steps of placing a concrete retarding layer on an existing concrete wall, and then placing a newly placed concrete wall on the concrete retarding layer.
6. The use of a concrete retarding layer for preventing early cracking of a long concrete wall, wherein the concrete retarding layer is used in the structure for preventing early cracking of a long concrete wall according to any one of claims 1 to 4, and the early stage is 7 to 28 days after casting.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010028564.1A CN111206792A (en) | 2020-01-11 | 2020-01-11 | Structure for preventing early cracking of concrete long wall, construction method and application |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010028564.1A CN111206792A (en) | 2020-01-11 | 2020-01-11 | Structure for preventing early cracking of concrete long wall, construction method and application |
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| CN111206792A true CN111206792A (en) | 2020-05-29 |
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| CN202010028564.1A Pending CN111206792A (en) | 2020-01-11 | 2020-01-11 | Structure for preventing early cracking of concrete long wall, construction method and application |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100760904B1 (en) * | 2007-06-01 | 2007-09-21 | 홍사광 | A method of construction for reinforcement of building and fabric thereof |
| CN101280556A (en) * | 2008-05-27 | 2008-10-08 | 中国长江三峡工程开发总公司 | New and old roller compacted concrete joint anticracking technique |
| CN102168407A (en) * | 2011-03-23 | 2011-08-31 | 中交三航局第三工程有限公司 | Method for preventing and controlling cracks of long and big-segment bracket cantilever box girder structure |
| CN102249610A (en) * | 2011-05-12 | 2011-11-23 | 中国葛洲坝集团股份有限公司 | Interface concrete and construction method |
| CN105036695A (en) * | 2015-07-28 | 2015-11-11 | 盐城工学院 | Repairing and protecting layer for reinforced concrete structure body and construction method of repairing and protecting layer |
-
2020
- 2020-01-11 CN CN202010028564.1A patent/CN111206792A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100760904B1 (en) * | 2007-06-01 | 2007-09-21 | 홍사광 | A method of construction for reinforcement of building and fabric thereof |
| CN101280556A (en) * | 2008-05-27 | 2008-10-08 | 中国长江三峡工程开发总公司 | New and old roller compacted concrete joint anticracking technique |
| CN102168407A (en) * | 2011-03-23 | 2011-08-31 | 中交三航局第三工程有限公司 | Method for preventing and controlling cracks of long and big-segment bracket cantilever box girder structure |
| CN102249610A (en) * | 2011-05-12 | 2011-11-23 | 中国葛洲坝集团股份有限公司 | Interface concrete and construction method |
| CN105036695A (en) * | 2015-07-28 | 2015-11-11 | 盐城工学院 | Repairing and protecting layer for reinforced concrete structure body and construction method of repairing and protecting layer |
Non-Patent Citations (1)
| Title |
|---|
| 严捍东: "《新型建筑材料教程》", 31 January 2005, 中国建材工业出版社 * |
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Application publication date: 20200529 |