Construction method for reducing the risk of cracking of mass concrete structures

Abstract

The application discloses a construction method for reducing cracking risk of mass concrete structure, and belongs to the field of mass concrete construction.The construction method comprises the following steps: step one, pouring the first layer of concrete in the installed formwork structure; step two, performing chiseling treatment on the layered pouring interface of the first layer of concrete; step three, laying the high-performance slurry storage anti-cracking net structure layer on the layered pouring interface of the first layer of concrete; step four, wetting the layered pouring interface of the first layer of concrete and the surface of the high-performance slurry storage anti-cracking net structure layer with water, and laying the mortar buffer layer in the high-performance slurry storage anti-cracking net structure layer; and step five, pouring the second layer of concrete structure layer on the high-performance slurry storage anti-cracking net structure layer filled with mortar. The construction method can reduce the temperature stress of the mass concrete structure in the cooling process, and reduce the cracking risk of the mass concrete structure.

Description

Technical Field

[0001] This invention relates to the field of large-volume concrete construction, and in particular to a construction method for reducing the risk of cracking in large-volume concrete structures. Background Technology

[0002] In large-scale waterway and water conservancy projects, the pouring of structures such as non-overflow dams, ship locks, flood discharge and sand flushing gates, and power plant buildings requires a large volume of concrete. Therefore, reducing the risk of cracking in large-volume concrete structures has become an important part of quality control for such projects.

[0003] Large-volume concrete structures typically lack steel reinforcement, or have only a small amount of reinforcement on the surface or near openings. Compared to the massive cross-section of the structure, its steel content is extremely low. In reinforced concrete structures, tensile stress is primarily borne by the steel reinforcement, while the concrete only bears compressive stress. However, in large-volume concrete structures, due to the absence of steel reinforcement, tensile stress must be borne by the concrete itself.

[0004] Currently, the domestic and international approach to controlling temperature cracks in large-volume concrete is to release the confining stress of the concrete through layered jointing, thereby reducing the temperature rise due to the heat of hydration. Theoretically, this method can mitigate the cracking risk of large-volume concrete structures to some extent. However, field investigations show that the implementation interval for vertical or horizontal jointing is often limited by various factors such as construction technology, construction materials, and on-site organizational capabilities. Excessively long intervals can increase the confining stress of the old concrete layer on the new concrete layer, thus increasing the risk of structural cracking. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a construction method to reduce the cracking risk of large-volume concrete structures, which can reduce the temperature stress on large-volume concrete structures during the cooling process and reduce the cracking risk of large-volume concrete structures.

[0006] The construction method for reducing the risk of cracking in large-volume concrete structures according to embodiments of the present invention includes the following steps: Step 1: pouring a first layer of concrete in the installed formwork structure and waiting for the first layer of concrete to reach a preset strength; Step 2: roughening the interface of the first layer of concrete pouring; Step 3: laying a high-performance slurry storage and crack-resistant mesh structure layer at the interface of the first layer of concrete pouring, and fixing the high-performance slurry storage and crack-resistant mesh structure on the first layer of concrete with fasteners; Step 4: wetting the interface of the first layer of concrete pouring and the surface of the high-performance slurry storage and crack-resistant mesh structure layer with water, and laying a mortar buffer layer inside the high-performance slurry storage and crack-resistant mesh structure layer; Step 5: pouring a second layer of concrete structure on the high-performance slurry storage and crack-resistant mesh structure layer filled with mortar.

[0007] The construction method for reducing the cracking risk of large-volume concrete structures according to embodiments of the present invention has at least the following beneficial effects: by laying a high-performance grout-storing and crack-resistant mesh structure at the layered pouring interface of the first layer of concrete, the stress concentration phenomenon of the first layer of concrete on the second layer of concrete is dispersed. Buffer mortar is injected into the mesh structure layer to form a mortar buffer layer, so as to ensure that the mortar buffer layer does not leak grout. Moreover, the retarding effect of the mortar buffer layer can significantly reduce the constraint of the first layer of concrete on the second layer of concrete, reduce the cracking risk of the second layer of concrete, thereby optimizing the crack resistance performance of the large-volume concrete structure.

[0008] According to some embodiments of the present invention, in step three, the laying area of ​​the high-performance slurry storage and crack-resistant mesh structure layer is not less than 90% of the upper surface of the first layer of concrete.

[0009] According to some embodiments of the present invention, in step three, the height of the high-performance slurry storage and crack-resistant network structure layer is not greater than two-thirds of the maximum nominal particle size of the aggregate.

[0010] According to some embodiments of the present invention, in step three, the high-performance slurry storage and crack-resistant mesh structure layer is a quadrilateral mesh.

[0011] According to some embodiments of the present invention, the grid side length of the high-performance slurry storage and crack-resistant mesh structure layer is not less than four-thirds of the maximum nominal particle size of the aggregate.

[0012] According to some embodiments of the present invention, the material thickness of the high-performance slurry storage and crack-resistant mesh structure layer is 1 mm to 10 mm.

[0013] According to some embodiments of the present invention, in step four, the top elevation of the mortar buffer layer is higher than the top elevation of the high-performance slurry storage and crack-resistant mesh structure layer.

[0014] According to some embodiments of the present invention, in step four, the mortar buffer layer consists of cement, fly ash, sand, water, and retarder.

[0015] According to some embodiments of the present invention, in step five, the second layer of concrete is poured within 7 to 28 days after the first layer of concrete is poured.

[0016] According to some embodiments of the present invention, in step five, after laying a mortar buffer layer in the high-performance slurry storage and crack-resistant mesh structure layer, the second layer of concrete is poured within two hours.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0019] Figure 1 This is a flowchart illustrating the construction method steps for reducing the risk of cracking in large-volume concrete structures according to an embodiment of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram of a high-performance slurry storage and crack-resistant mesh structure layer laid in the middle;

[0021] Figure 3 for Figure 1 Side view of the high-performance slurry storage and crack-resistant mesh structure layer laid in the middle;

[0022] Figure 4 for Figure 1 A schematic diagram of the structure in which the second layer of concrete is poured on a high-performance slurry storage and crack-resistant mesh structure layer.

[0023] Figure 5 The diagram shows the shrinkage strain of the new concrete layer under the following conditions: no material is laid (KB group), a high-performance slurry storage and crack-resistant mesh structure layer is laid (WG group), and the new and old concrete layers are laid with a pouring interval of 7 days and 28 days.

[0024] Figure label:

[0025] The first layer of concrete is 100mm, and the interface for layered pouring is 110mm.

[0026] High-performance slurry storage and crack-resistant mesh structure layer 200, fastener 210;

[0027] 300mm mortar buffer layer;

[0028] The second layer of concrete is 400mm thick. Detailed Implementation

[0029] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0031] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. Any mention of "first" or "second" is for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0032] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0033] refer to Figures 1 to 5 A construction method for reducing the risk of cracking in large-volume concrete structures according to embodiments of the present invention is described.

[0034] like Figure 1 As shown in the figure, the construction method for reducing the risk of cracking in large-volume concrete structures according to an embodiment of the present invention includes:

[0035] Step 1: Pour the first layer of concrete 100 in the installed formwork structure, and wait for the first layer of concrete 100 to reach the preset strength;

[0036] Step 2: Roughen the interface 110 of the first layer of concrete 100.

[0037] Step 3: Lay a high-performance slurry storage and crack-resistant mesh structure layer 200 at the layered pouring interface 110 of the first layer of concrete 100, and fix the high-performance slurry storage and crack-resistant mesh structure on the first layer of concrete 100 by fasteners 210.

[0038] Step 4: Wet the layered pouring interface 110 of the first layer of concrete 100 and the surface of the high-performance slurry storage and crack-resistant mesh structure layer 200 with water, and lay a mortar buffer layer 300 inside the high-performance slurry storage and crack-resistant mesh structure layer 200.

[0039] Step 5: Pour the second layer of concrete 400 on the high-performance grout storage and crack-resistant mesh structure layer 200 filled with mortar.

[0040] It should be noted that in step one, taking into account the general construction speed in the project, the time interval for pouring the second layer of concrete is usually set to 7 to 28 days after the first layer of concrete is poured.

[0041] In some specific embodiments of the present invention, in step two, the upper surface of the first layer of concrete 100 is roughened using a chisel, and then the loose concrete debris is cleaned up. Specifically, tools such as electric hammers, hydraulic hammers, cutting machines, or drilling machines are used to remove the laitance on the upper surface of the first layer of concrete 100 down to the exposed large stones. The roughening depth is controlled between 3mm and 10mm, and the roughening rate should not be less than 90% of the upper surface of the old concrete base layer. The specific depth should be adjusted according to design requirements or actual needs. It should be noted that, since construction joints are easily formed at the joint when new and old concrete are combined, affecting the continuity of the concrete structure and being detrimental to the bending and shear resistance of the concrete structure, roughening the first layer of concrete 100 removes the laitance on the concrete surface, allowing the high-performance grout-storing and crack-resistant mesh structure layer 200 and the mortar buffer layer 300 laid on top to bond tightly and firmly with the first layer of concrete 100.

[0042] like Figure 2 and Figure 3 As shown, in some specific embodiments of the present invention, in step three, the high-performance slurry-storage crack-resistant mesh structure layer 200 is laid on the layered pouring interface 110, and the laying area should be no less than 90% of the upper surface of the old concrete base layer. Then, fasteners 210 are used to fix the four corners of the high-performance slurry-storage crack-resistant mesh structure layer 200 to the upper surface of the first layer of concrete 100, so as to ensure that the high-performance slurry-storage crack-resistant mesh structure layer 200 can provide sufficient restraint on the first layer of concrete 100 and the second layer of concrete 400, and under the fixation of the fasteners, it is difficult for it to be displaced under normal stress, thereby reducing the risk of cracking of the large volume of concrete as a whole. It is conceivable that the fasteners can be expansion bolts or steel wire bindings, etc.

[0043] In some specific embodiments of the present invention, in step four, the high-performance slurry storage and crack-resistant mesh structure layer 200 has a height of 5 mm to 50 mm and is not greater than two-thirds of the maximum nominal particle size of the aggregate. The high-performance slurry storage and crack-resistant mesh structure layer 200 is square in shape, with a mesh side length not less than four-thirds of the maximum nominal particle size of the aggregate. The high-performance slurry storage and crack-resistant mesh structure layer 200 has a thickness of 1 mm to 10 mm.

[0044] It should be noted that aggregates used in concrete are typically a mixture of particles with various sizes. To classify and standardize aggregates and determine the size range of concrete aggregates, the maximum nominal particle size (MPD) is used to represent the largest aggregate size. That is, the MPD refers to a standard value for the aggregate particle size, which is the largest particle size that can pass through a sieve. Determining the MPD is crucial for concrete mix design and construction, as it affects the concrete's fluidity, strength, workability, and overall performance characteristics. Depending on specific concrete design requirements and engineering needs, aggregates with different MPDs can be selected to meet specific engineering requirements.

[0045] Therefore, if the height of the high-performance grout-storage crack-resistant mesh structure layer 200 exceeds two-thirds of the maximum nominal aggregate size, it may lead to a large gap between the mesh and the concrete. That is, a deeper mesh will occupy part of the space in the concrete, potentially affecting the concrete's fluidity and workability, resulting in a lower slump, increased construction difficulty, and even inadequate filling. This reduces the bond strength between the mesh and the concrete, affecting the reinforcement effect. Furthermore, a mesh side length of no less than four-thirds of the maximum nominal aggregate size ensures that the aggregate particles are evenly distributed within each mesh, further enhancing the bonding density between the first layer of concrete 100 and the second layer of concrete 400.

[0046] Specifically, the raw material of the high-performance slurry storage and crack-resistant mesh structure layer 200 is basalt fiber or glass fiber. Compared with other high-tech fibers, basalt fiber has the characteristics of high strength and high modulus, as well as high compressive strength and shear strength, and excellent performance in adapting to various environments. It is a pure natural inorganic non-metallic material, as well as a new basic material and high-tech fiber.

[0047] In some specific embodiments of the present invention, in step four, water is sprayed to moisten the upper surface of the first layer of concrete 100 and the surface of the high-performance slurry storage and crack-resistant mesh structure layer 200, so that the surface is not dry and no water is formed. The pre-prepared buffer mortar is slowly injected into the upper surface of the first layer of concrete 100 by means of manual shoveling or feeding by a concrete placing machine, and fills each grid in the high-performance slurry storage and crack-resistant mesh structure layer 200. The filling height of the buffer mortar is controlled to be 0mm to 5mm above the top of the high-performance slurry storage and crack-resistant mesh structure layer 200, so that the buffer mortar can be connected to the first layer of concrete and the second layer of concrete at the same time, thereby ensuring the tightness of the bond between the first layer of concrete and the second layer of concrete.

[0048] Specifically, the components of the buffer mortar are cement, fly ash, sand, water, and retarder. Assuming a total mass of 100%, the composition is: cement 13.07 to 13.58 wt.%, fly ash 8.53 to 9.38 wt.%, sand 67.95 to 69.72 wt.%, water 7.02 to 7.84 wt.%, and retarder 1.03 to 1.45 wt.%.

[0049] like Figure 4 As shown, in some specific embodiments of the present invention, in step five, within 7 to 28 days after the first layer of concrete 100 is poured, a second layer of concrete 400 is poured on top of the high-performance grout-storage crack-resistant mesh structure layer 200 filled with buffer mortar. Specifically, the interval between the pouring time of the second layer of concrete 400 and the spreading time of the buffer mortar should preferably be 0 to 2 hours. That is, the second layer of concrete 400 is poured within 0 to 2 hours after the buffer mortar is spread, 7 to 28 days after the pouring time of the first layer of concrete 100.

[0050] It is conceivable that if a concrete structure requires the pouring of two or more layers of concrete, then steps one through five should be repeated until the concrete pouring is completed, in order to complete the construction of a large-volume concrete structure.

[0051] It should be noted that if the first layer of concrete has not yet reached a certain strength, the weight of the second layer and the construction process may have an adverse effect on the first layer, resulting in a weak bond between the two layers. Therefore, when the second layer of concrete is poured on top of the first layer, the first layer of concrete should have sufficient strength and stability to ensure a good bond between the two layers.

[0052] Furthermore, such as Figure 5 As shown, Figure 5 To investigate the shrinkage and deformation of the new concrete layer with and without the high-performance slurry storage and crack-resistant mesh structure layer 200, and the new concrete layer with and without the old concrete layer under different pouring intervals, the different pouring intervals are 7 days and 28 days.

[0053] Figure 5The data was obtained from the following tests: When the pouring interval reached the preset value, steps one to five were performed on the old layer of concrete. After the new layer of concrete reached the standard for demolding, the formwork was removed, and a support frame was installed on both sides of the length of the new layer of concrete. The dial gauge reading was adjusted to zero, and a dial gauge was installed on each of the two support frames. The two dial gauges were in close contact with the two sides of the new layer of concrete. The start time of the test was recorded. The dial gauge readings were recorded at 3, 7, 14, 20, 28, 36, 44, and 60 days. The readings of the two dial gauges were added together to obtain the shrinkage deformation value of the new layer of concrete. KB-7d and KB-28d represent the shrinkage deformation values ​​of the new concrete layer poured 7 days and 28 days after the old concrete layer was poured, respectively, without the high-performance slurry storage and crack-resistant mesh structure layer. WG-7d and WG-28d represent the shrinkage deformation values ​​of the new concrete layer poured 7 days and 28 days after the old concrete layer was poured, respectively, with the high-performance slurry storage and crack-resistant mesh structure layer installed. Figure 3 The data shows that regardless of whether the pouring interval is set to 7 days or 28 days, WG-7d and WG-28d exhibit greater shrinkage deformation than KB-7d and KB-28d. This phenomenon indicates that the crack control technology of laying a high-performance slurry storage and crack-resistant mesh structure layer in the old concrete layer can better guide the shrinkage deformation of the new concrete layer, release more of the constraint stress of the new concrete foundation, make the new concrete layer less prone to cracking, and significantly reduce the cracking risk of the concrete structure.

[0054] The high-performance slurry-storage crack-resistant mesh structure layer used in the experiment was made of basalt fiber. The mesh structure layer was 3 cm high, with a mesh side length of 10 cm and a thickness of 3 mm. The retarded mortar consisted of cement, fly ash, sand, water, and a retarder. Specifically, cement accounted for 13.38 wt.%, fly ash 8.93 wt.%, sand 68.82 wt.%, water 7.53 wt.%, and the retarder 1.34 wt.

[0055] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A construction method for reducing the risk of cracking in large-volume concrete structures, characterized in that, include: Step 1: Pour the first layer of concrete (100) into the installed formwork structure, and wait for the first layer of concrete (100) to reach the preset strength; Step 2: Roughen the interface (110) of the first layer of concrete (100) during layer pouring; Step 3: Lay a high-performance slurry storage and crack-resistant mesh structure layer (200) on the layered pouring interface (110) of the first layer of concrete (100), and fix the high-performance slurry storage and crack-resistant mesh structure layer (200) on the first layer of concrete (100) by fasteners (210). The height of the high-performance slurry storage and crack-resistant mesh structure layer (200) is not greater than two-thirds of the maximum nominal particle size of the aggregate. Step 4: Wet the layered pouring interface (110) of the first layer of concrete (100) and the surface of the high-performance slurry storage and crack-resistant mesh structure layer (200) with water, and lay a mortar buffer layer (300) in the high-performance slurry storage and crack-resistant mesh structure layer (200). The components of the mortar buffer layer (300) are cement, fly ash, sand, water and retarder. Step 5: Pour the second layer of concrete (400) on the high-performance slurry storage and crack-resistant mesh structure layer (200) filled with mortar.

2. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 1, characterized in that, In step three, the laying area of ​​the high-performance slurry storage and crack-resistant mesh structure layer (200) is not less than 90% of the upper surface of the first layer of concrete (100).

3. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 1, characterized in that, In step three, the high-performance slurry storage and crack-resistant mesh structure layer (200) is a quadrilateral mesh.

4. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 3, characterized in that, The grid side length of the high-performance slurry storage and crack-resistant mesh structure layer (200) is not less than four-thirds of the maximum nominal particle size of the aggregate.

5. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 3, characterized in that, The material thickness of the high-performance slurry storage and crack-resistant mesh structure layer (200) is 1 mm to 10 mm.

6. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 1, characterized in that, In step four, the top elevation of the mortar buffer layer (300) is higher than the top elevation of the high-performance slurry storage and crack-resistant mesh structure layer (200).

7. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 1, characterized in that, In step five, the second layer of concrete (400) is poured within 7 to 28 days after the first layer of concrete (100) is poured.

8. The construction method for reducing the risk of cracking in large-volume concrete structures according to claim 1, characterized in that, In step five, after laying the mortar buffer layer (300) in the high-performance slurry storage and crack-resistant mesh structure layer (200), the second layer of concrete (400) is poured within 1 hour.

Images