Seamless construction method for super-long concrete structure

Abstract

The invention provides a seamless construction method for an ultra-long concrete structure. The seamless construction method comprises the following steps that S1, a UEA expanding agent is added into concrete; and S2, an expansion reinforcing band is arranged in the concrete. According to the seamless construction method for the super-long concrete structure, the specific reinforcing area is arranged in the concrete structure through the expansion reinforcing band, the expansion agent is doped, the tensile strength and the expansion rate of the concrete are improved, and therefore the shrinkage stress of the concrete is effectively offset, and structural cracking is prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete construction, and in particular relates to a seamless construction method for an ultra-long concrete structure. Background Art

[0002] As a building form that can accommodate a considerable number of residents, high-rise buildings have become increasingly popular. In the construction industry, ultra-long concrete is one of the main materials used in the construction process of construction projects, and its concrete components are the most important load-bearing components of building structures. The application of pumping concrete technology in construction has led to a gradual increase in the number of temperature shrinkage cracks that are prone to appear in ultra-long concrete structures. Although these cracks are non-structural cracks and generally do not affect the bearing capacity of components and structural safety, they will affect the durability and integrity of the structure. Especially for underground waterproofing projects, the quality of ultra-long concrete construction is crucial to controlling cracks, ensuring the integrity of waterproofing, and ensuring the waterproofing effect. Summary of the invention

[0003] In view of this, the present invention aims to propose a seamless construction method for ultra-long concrete structures to solve the problem of cracking caused by cold shrinkage and dry shrinkage in large-volume ultra-long concrete structures and to control the hazards caused by the tensile stress generated by cold shrinkage and dry shrinkage.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows: A method for seamlessly constructing an ultra-long concrete structure comprises the following steps: S1. Add UEA expansion agent to concrete; S2. Set expansion reinforcement strips in concrete.

[0005] Furthermore, the types of the expansion reinforcement belt include continuous expansion reinforcement belt, base plate intermittent expansion reinforcement belt and post-cast expansion reinforcement belt.

[0006] Furthermore, the setting method of the continuous expansion reinforcement belt is: setting it at the position where the shrinkage stress is concentrated, with a width of 2m~3m, setting up dense-hole wire mesh on both sides of the reinforcement belt, using small expansion concrete on the outside, changing to large expansion concrete when it reaches the reinforcement belt, and changing to small expansion concrete when it reaches the other side of the reinforcement belt; in this way, an ultra-long concrete structure of 100m~150m can be continuously cast without leaving hard knots, and concrete with different expansion properties can be used in different structural parts.

[0007] Furthermore, the construction method of the intermittent expansion reinforcement belt of the base plate is to first pour concrete and leave a step opening to tie two steel meshes, and vertically add rubber water stop strips or steel plates at both ends of the base plate. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the outer wall steel plate. After the concrete reaches sufficient strength, pour the large expansion concrete of the expansion reinforcement belt, followed by the small expansion concrete.

[0008] Furthermore, the construction method of the post-cast expansion reinforcement belt is as follows: when the concrete cannot be constructed continuously, first pour the small expansion concrete on both sides of the reinforcement belt, and leave step joints on the hard ends on both sides; after the concrete reaches sufficient strength, pour the large expansion concrete of the reinforcement belt, and add rubber water stop strips or steel plates vertically at the ends of the casting belt. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the exterior wall steel plate.

[0009] Furthermore, the mix ratio of the concrete is as follows: during construction, the concrete inside the belt needs to be poured simultaneously with the concrete outside the belt, and the amount of expansion agent in the concrete inside the belt is usually 2% to 3% higher than that in the concrete outside the belt.

[0010] Furthermore, when the concrete is poured near the expansion reinforcement zone, care should be taken to ensure that the insertion point of the vibrating rod is at least 30 cm away from the dense mesh quick-close mesh, and over-vibration is not allowed.

[0011] Furthermore, the concrete at the expansion reinforcement zone is transported by a tower crane bucket and a concrete delivery pipe pump. The pouring of the extra-long seamless raft slab concrete at the reinforcement zone is carried out after the pouring of concrete on one side is completed. The wall concrete is poured after the initial setting and before the final setting of the extra-long seamless raft slab concrete at this position. For the expansion zone concrete, the vibrator can be close to the dense mesh quick-closing net, but it must not collide with it.

[0012] Compared with the prior art, the seamless construction method of the ultra-long concrete structure of the present invention has the following advantages: (1) In the seamless construction method for ultra-long concrete structures described in the present invention, the expansion reinforcement belt increases the tensile strength and expansion rate of concrete by setting a specific reinforcement area in the concrete structure and adding an expansion agent, thereby effectively offsetting the shrinkage stress of the concrete and preventing structural cracking.

[0013] (2) The seamless construction method of the super-long concrete structure described in the present invention uses the principle of combining "resistance" and "release" in the expansion reinforcement belt. By using prestressed and shrinkage-compensating concrete, the cracking of the super-long concrete structure is effectively prevented, thereby ensuring the quality of the structural engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 Flow chart of the method for seamless construction of super-long concrete structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0016] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0017] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0018] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0019] A seamless construction method for an ultra-long concrete structure, such as Figure 1 As shown, the following steps are included: S1. Add UEA expansion agent to concrete; S2. Set expansion reinforcement strips in concrete.

[0020] Concrete with UEA expansion agent expands during the hardening process. Under the constraints of steel bars and adjacent positions, the steel bars are tensile and the concrete is compressed. When the tensile stress of the steel bars is balanced with the compressive stress of the concrete, then: Ac.σc=As.Es.ε2. Assume: μ=As / Ac, then σc=μ. Es.ε2; In the formula, σc is the pre-compressive stress of concrete (Mpa), As is the cross-sectional area of ​​steel bars, μ is the reinforcement ratio (%), Ac is the cross-sectional area of ​​concrete, Es is the elastic modulus of steel bars (Mpa), and ε2 is the limited expansion rate of concrete (%). It can be seen from the formula that σc is proportional to ε2, and the limited expansion rate ε2 increases with the increase of the UEA dosage. Therefore, by adjusting the UEA dosage, the concrete can obtain a pre-compressive stress of 0.2~0.7MPa. According to the horizontal normal force σx distribution curve, it is assumed that a larger expansion stress σc is applied where the stress is large, and a smaller expansion stress is applied on both sides to fully compensate for the shrinkage stress of the structure and control the appearance of ordered cracks.

[0021] The key construction technologies of concrete expansion reinforcement strips mainly include setting location, strip width and reinforcement arrangement, concrete mix ratio and construction method. The expansion reinforcement belt should be set at the location where the concrete shrinkage stress is the largest, usually in the middle of the length direction. The belt width is generally 1.5 meters to 2.0 meters, and the specific width can be adjusted according to the project requirements. Dense mesh wire mesh needs to be arranged on both sides of the belt to separate the concrete inside the belt from the concrete outside the belt. The wire mesh is arranged vertically between the upper and lower layers of steel bars, and the two ends are tied to the steel bars to ensure the stability of the belt.

[0022] Inside the belt, a certain proportion of horizontal temperature steel bars need to be added, usually 10% to 15% of the total steel bars, evenly distributed on the upper and lower layers of steel bars. These steel bars are perpendicular to the length of the expansion reinforcement belt, and both ends extend 2 meters outside the belt and are fixed to the steel bars to improve the tensile strength and stability of the belt.

[0023] The mix ratio of concrete is also one of the key technologies. The strength grade of the concrete inside the belt is usually one level higher than that of the concrete outside the belt. An appropriate amount of UEA expansion agent is added to increase the expansion rate of the concrete and reduce the possibility of cracking. The amount of expansion agent in the concrete inside the belt is usually 2% to 3% higher than that of the concrete outside the belt to ensure the compensation shrinkage effect of the belt.

[0024] During construction, the concrete inside the belt needs to be poured at the same time as the concrete outside the belt to ensure the continuity of construction. After pouring, sufficient maintenance is required to ensure the strength and stability of the concrete. In addition, the treatment of construction joints is also very important, and it is necessary to ensure that the concrete inside and outside the belt is tightly combined to avoid water seepage and cracking.

[0025] The layout principles of expansion reinforcement belts are as follows: Expansion reinforcement belts should be arranged at locations with large tensile stress, reinforcement changes, cross-section mutations, and stress concentration locations. When the length of the structure reaches more than 70m, reinforcement belts must be installed regardless of whether they are required in the calculation.

[0026] There are three types of expansion reinforcement belts: (1) Continuous expansion reinforcement belt At the location where the shrinkage stress is concentrated, an expansion reinforcement belt with a width of 2m~3m is set up, and dense wire mesh is set up on both sides of the belt to prevent the concrete on both sides from flowing into the reinforcement belt. During construction, small expansion concrete is used on the outside of the belt, and large expansion concrete is used when it reaches the reinforcement belt. When it reaches the other side of the reinforcement belt, it is changed to small expansion concrete. In this way, an ultra-long concrete structure of 100m~150m can be continuously poured without leaving hard stubble, and concrete with different expansion properties can be used in different structural parts.

[0027] (2) Intermittent expansion reinforcement belt of the bottom plate When the concrete supply or construction force cannot meet the requirements of continuous operation and continuous construction is impossible, the intermittent expansion reinforcement belt method can be used. In order to improve the waterproof effect of the post-cast reinforcement belt of the bottom plate, a step joint is left, that is, the concrete is poured first and the step opening is left (two steel meshes are tied). The hard stubble needs additional waterproofing treatment: rubber water stop strips or steel plates are added vertically at the ends of the bottom plate. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the outer wall steel plate to prevent horizontal water infiltration. The next construction needs to be at least 3 days apart. After the concrete reaches sufficient strength, the large expansion concrete of the expansion reinforcement belt is poured, followed by the small expansion concrete.

[0028] (3) Post-cast expansion reinforcement strip When the concrete cannot be constructed continuously, you can also pour the small expansion concrete on both sides of the reinforcement belt first, and leave step joints on both sides of the hard stubble. After an interval of more than 3 days, pour the large expansion concrete of the reinforcement belt when the concrete reaches sufficient strength. Rubber water stop strips or steel plates are added vertically at the ends of the pouring belt. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the external wall steel plate to prevent water infiltration in the horizontal direction.

[0029] When pouring concrete, be careful to prevent concrete from other parts from entering the expansion post-casting zone to avoid affecting the design effect. The pipe-lubricating mortar before pouring concrete must be discarded, and the waste concrete caused by pipe removal to troubleshoot or other reasons is strictly prohibited from entering the working surface. It is strictly prohibited to scatter concrete in the parts that have not been poured. To avoid the formation of potential cold joints or weak points. Concrete scattered on the working surface, concrete poured out of the pipe removal, pipe-lubricating mortar, etc. should be hoisted out of the working surface.

[0030] When pouring concrete near the expansion reinforcement zone, care should be taken to ensure that the insertion point of the vibrating rod is at least 30 cm away from the dense mesh quick-close net, and excessive vibration is not allowed.

[0031] The concrete at the expansion reinforcement zone is hoisted by a tower crane bucket and a concrete delivery pipe pump. The ultra-long seamless raft concrete at the reinforcement zone is poured after the concrete pouring on one side is completed, and the wall concrete is poured after the initial setting and before the final setting of the ultra-long seamless raft concrete at this part. For the expansion zone concrete, the vibrator can be close to the dense mesh quick-close net, but it must not collide.

[0032] Early plastic cracks and settlement cracks are prone to appear at the coarse steel bars on the surface of the super-long seamless raft slab after vibration and before initial setting. They must be eliminated by controlling the material feeding and secondary vibration to avoid becoming concrete defects, causing stress concentration and affecting the prevention and control effect of temperature shrinkage cracks. After the bottom plate is poured to the elevation, it is repeatedly smoothed and pressed with a polishing machine before final setting to prevent the appearance of shrinkage cracks on the concrete surface.

[0033] Expansive concrete can only exert its expansion efficiency if it is fully wet-cured. It is necessary to improve maintenance awareness, set up full-time maintenance personnel, and establish a strict concrete maintenance system. After the concrete is poured, it should be moisturized for 14 days. After the concrete is leveled, it should be sprinkled with water to moisten it, and then covered tightly with a plastic film, such as a layer of sacks. During the curing period, spray mist water to keep the relative humidity of the environment above 80% to reduce the shrinkage of the concrete. In order to release some shrinkage stress, the construction method of "post-casting expansion reinforcement belt" is adopted in the wall construction, that is, with the expansion reinforcement belt as the boundary, small expansion concrete mixed with 12% UEA is poured in sections. After curing for 28 days, the expansion reinforcement belt is backfilled with large expansion concrete mixed with 15% UEA. The post-cast expansion reinforcement belt can be set according to the traditional post-cast belt.

[0034] After 2 days of concrete pouring, loosen the formwork by 1-2mm, set a flower pipe on the top of the wall for watering and curing, and continue to water curing for 14 days after removing the formwork. Construction of floor expansion reinforcement belt The floor expansion reinforcement belt is separated by a dense mesh quick-closed net, and the fixing method is the same as the raft slab. During pouring, the method of continuous pouring is adopted. The expansion reinforcement belt is externally made of small expansion concrete mixed with 12% UEA. When pouring to the reinforcement belt, large expansion concrete mixed with 15% UEA is used. When pouring to the other side, it is changed to pouring concrete mixed with 12% UEA. The quality of the project is in accordance with the detailed feasibility construction plan, technical disclosure and strict implementation prepared before construction. The results of temperature control show that the temperature difference between the inside and outside of the concrete does not exceed 25℃, realizing the continuous construction of raft slab concrete pouring, and has achieved the success of ultra-long seamless structure raft slab concrete pouring. The expansion reinforcement belt increases the tensile strength and expansion rate of concrete by setting a specific reinforcement area in the concrete structure and using the addition of expansion agent, thereby effectively offsetting the shrinkage stress of concrete and preventing structural cracking. Compared with the traditional post-casting technology, this method has the following innovations: ‌Preventing structural cracking: The expansion reinforcement belt uses the principle of combining "resistance" and "release" to effectively prevent the cracking of over-long concrete structures through the use of prestressed and shrinkage-compensating concrete, thereby ensuring the quality of structural engineering. ‌Improving construction efficiency: The setting of the expansion reinforcement belt simplifies the construction process, reduces the time for removing the formwork and support, speeds up the construction speed, and reduces the construction cost. ‌Reducing construction costs: The construction method of the expansion reinforcement belt reduces the use of turnover materials and avoids the cost of separately supporting formwork scaffolding and covering and cleaning the post-casting belt, thereby reducing construction costs. In summary, the innovation of the concrete expansion reinforcement belt lies in that it effectively solves the problem of cracking of concrete structures through specific construction technology and material application, improves construction efficiency, and reduces construction costs. It is an innovative construction technology with significant advantages.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for seamless construction of an ultra-long concrete structure, characterized in that: The steps include: S1. Add UEA expansion agent to concrete; S2. Set expansion reinforcement strips in concrete.

2. A seamless construction method for an ultra-long concrete structure according to claim 1, characterized in that: The types of expansion reinforcement strips include continuous expansion reinforcement strips, intermittent expansion reinforcement strips on the bottom plate, and post-cast expansion reinforcement strips.

3. A seamless construction method for an ultra-long concrete structure according to claim 2, characterized in that: The method for setting the continuous expansion reinforcement belt is as follows: it is set at the position where the shrinkage stress is concentrated, with a width of 2m~3m, dense-hole wire mesh is set up on both sides of the reinforcement belt, small expansion concrete is used on the outside, and large expansion concrete is used when it reaches the reinforcement belt, and small expansion concrete is changed to the other side of the reinforcement belt; this cycle is continued, and an ultra-long concrete structure of 100m~150m can be continuously cast without leaving hard knots, and concrete with different expansion properties can be used in different parts.

4. A seamless construction method for an ultra-long concrete structure according to claim 2, characterized in that: The construction method of the intermittent expansion reinforcement belt of the bottom plate is to first pour concrete and leave a step opening to tie two steel meshes, and vertically add rubber water stop strips or steel plates at the two ends of the bottom plate. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the outer wall steel plate. After the concrete reaches sufficient strength, pour the large expansion concrete of the expansion reinforcement belt, followed by the small expansion concrete.

5. The method for seamless construction of an ultra-long concrete structure according to claim 2, characterized in that: Construction method of post-cast expansion reinforcement belt: When concrete cannot be constructed continuously, first pour small expansion concrete on both sides of the reinforcement belt, and leave step joints on both sides of the hard stubble; when the concrete reaches sufficient strength, pour large expansion concrete for the reinforcement belt, and add rubber water stop strips or steel plates vertically at both ends of the pouring belt. The water stop strips or steel plates should extend vertically from the cushion layer to the connection with the exterior wall steel plate.

6. The method for seamless construction of an ultra-long concrete structure according to claim 1, characterized in that: The concrete mix ratio is as follows: During construction, the concrete inside the belt needs to be poured at the same time as the concrete outside the belt, and the amount of expansive agent in the concrete inside the belt is usually 2% to 3% higher than that in the concrete outside the belt.

7. The method for seamless construction of an ultra-long concrete structure according to claim 1, characterized in that: When pouring concrete near the expansion reinforcement zone, care should be taken to ensure that the insertion point of the vibrating rod is at least 30 cm away from the dense mesh quick-close net, and excessive vibration is not allowed.

8. The method for seamless construction of an ultra-long concrete structure according to claim 1, characterized in that: The concrete at the expansion reinforcement zone is transported by tower crane bucket and concrete delivery pipe pump. The pouring of extra-long seamless raft slab concrete at the reinforcement zone is carried out after the pouring of concrete on one side is completed. The wall concrete is poured after the initial setting and before the final setting of the extra-long seamless raft slab concrete in this part. For the expansion zone concrete, the vibrator can be close to the dense mesh quick-closing net, but it must not collide with it.

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