Construction method for preventing cracks and air bubbles of layered thin plastering of wall of super-high industrial plant

Abstract

This invention relates to the field of building construction, specifically to a method for preventing cracking and hollowing in the walls of ultra-high-rise industrial plants using layered thin plastering. Through steps such as base treatment, vertical segmented construction, layered thin plastering, crack resistance enhancement, setting of expansion joints, and differentiated curing, the method can significantly reduce the self-weight of the plaster layer, actively relieve shrinkage stress, and optimize segmentation and curing strategies for ultra-high-rise construction conditions, thereby eradicating hollowing and through cracks, and significantly improving construction efficiency and overall benefits.

Description

Technical Field

[0001] This invention relates to the field of building construction, and specifically to a method for preventing cracking and hollowing of the walls of ultra-high-rise industrial plants by layering thin plaster. Background Technology

[0002] In the plastering construction of high-rise walls (usually referring to walls over 9m), the traditional technique generally adopts a thick plastering method with a total thickness of not less than 25mm, which has the following problems: With its large total thickness and high self-weight load, the plaster layer generates significant vertical stress concentration at the bottom of the wall of a super high-rise building. When the stress exceeds the bonding strength between the mortar and the base layer, it can easily cause large-area hollowing or even detachment.

[0003] Traditional thick plastering is often done in one go or in excessively thick layers. The significant difference in drying rate between the inner and outer layers of mortar leads to the concentration of internal constraint shrinkage stress, causing multiple vertical and horizontal through cracks, which seriously affect the durability of the wall.

[0004] Without effective segmented stress relief measures, it is impossible to eliminate bottom hollows and local cracks caused by the accumulation of construction loads; at the junction of concrete and autoclaved aerated concrete blocks, due to the large difference in the linear expansion coefficient and drying shrinkage rate of the materials, shear stress concentration occurs, which easily leads to the formation of long cracks.

[0005] Meanwhile, the upper part of the walls of super high-rise buildings has high wind speeds and extremely fast moisture evaporation. Conventional uniform maintenance methods cannot guarantee the consistent hydration quality of mortar throughout the entire height, resulting in frequent drying shrinkage cracks and insufficient strength in the upper part.

[0006] Therefore, the inventors conducted further research and developed a construction method for preventing cracking and hollowing of the walls of ultra-high-rise industrial plants by layered thin plastering, which led to this invention. Summary of the Invention

[0007] The purpose of this invention is to provide a construction method for preventing cracking and hollowing of the walls of ultra-high-rise industrial plants by layering thin plaster. This method can significantly reduce the self-weight of the plaster layer, actively relieve shrinkage stress, and optimize the segmentation and maintenance strategies for ultra-high-rise construction conditions, thereby eradicating hollowing and through cracks, and significantly improving construction efficiency and overall benefits.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preventing cracking and hollowing of walls in ultra-high-rise industrial buildings using layered thin plastering includes the following steps: (1) Base treatment: roughen the concrete wall surface to form a rough surface; moisten the aerated block wall surface with water in several times and apply cement-based interface agent; (2) Vertical segmented construction: The wall is divided into multiple construction segments with a height of 3.0m to 3.5m, and construction is carried out sequentially from bottom to top. The interval between construction of adjacent segments is not less than 24 hours. When constructing the upper segment, the completed plaster surface of the lower segment is covered and protected. (3) Layered thin plastering: When constructing each section of the wall, first apply the first layer of base plaster with a thickness of 6mm to 8mm. During construction, compact and knead the mortar to fully fill the micropores of the base layer, and roughen the surface to form a uniform rough surface. After the first layer has initially set, apply the second layer of topcoat plaster with a thickness of 7mm to 9mm, so that the total thickness of the plaster is 15mm. Finally, level and compact the plaster with a screed. (4) Crack resistance enhancement: At the junction of different materials, concrete wall and masonry wall, hot-dip galvanized steel wire mesh is laid, and the overlap width of the steel wire mesh on each side at the junction is not less than 150mm; and reinforcing mesh is added at the four corners of door and window openings and pipeline grooves. (5) Setting of dividing joints: Along the height of the wall, a horizontal dividing joint is preset every 3.0m to 3.5m, with a joint width of 10mm to 15mm, penetrating the plaster layer; before the second layer of plaster is fully set, the dividing strip is embedded. After the joint is cleaned, it is filled with weather-resistant sealant to form a stress relief joint, dividing the large area of ​​plaster layer into several stress relief units with a single area of ​​no more than 20㎡; (6) Differentiated curing: Spray curing shall begin 12 hours after plastering is completed and shall continue for no less than 7 days; for the upper part of the wall, spray no less than 3 times a day to ensure that the plastered surface is always moist.

[0009] The vertical compressive stress at the bottom of the wall is proportional to the self-weight of the plaster layer. The traditional 25mm thick mortar generates a large self-weight stress, which can easily cause hollowing at the bottom of the wall of a super high-rise building due to long-term creep or insufficient interfacial adhesion. By limiting the total thickness to 15mm, the self-weight load is reduced by about 40%, which reduces the stress concentration at the bottom from the root.

[0010] Mortar shrinkage due to water loss is the main cause of cracking. If a single 15mm layer is applied, the surface layer shrinks first due to rapid water loss, while the interior shrinks more slowly, creating a constraint that causes the surface layer to be under tension. This solution involves two layers. The first layer is thinner and has a roughened surface, increasing the exposed area and reducing the difference in drying speed between the inside and outside. This significantly reduces shrinkage stress within a single layer. When the second layer is applied, the first layer has already partially shrunk and gained strength. The shrinkage between the two layers is not synchronous, and the stress is released layer by layer, avoiding the through cracks caused by stress superposition in traditional thick plastering.

[0011] Meanwhile, during traditional continuous construction, the wet weight of the newly applied mortar and the vibration load will all be applied to the mortar below that has not yet solidified, resulting in excessive cumulative stress at the bottom.

[0012] The present invention adopts a segmented release mechanism. By setting each segment to 3-3.5 meters and with an interval of ≥24 hours, the lower segment of mortar is given sufficient time for initial setting and strength development. When the bonding force and cohesion of the lower segment of mortar are sufficient to support the construction load of the upper segment, the stress transmission path becomes "upper load - lower hardened structure - wall base", instead of "upper load - lower fluid material - downward accumulation", which fundamentally cuts off the cumulative effect of vertical self-weight stress, thereby avoiding hollowing.

[0013] Hot-dip galvanized steel wire mesh is equivalent to using a steel mesh with a high modulus of elasticity to distribute the concentrated shear strain over a wider transition zone. The wire mesh, through mechanical interlocking with the mortar on both sides, flattens the local stress peaks. When a certain point shows a tendency to crack, the stress is quickly dispersed to the surrounding mortar through the wire mesh, preventing the stress at that point from concentrating to a level sufficient to cause cracking.

[0014] Furthermore, in step (1), the roughening treatment of the concrete wall surface is carried out by high-pressure mechanical spraying with a pressure of 0.8MPa to 1.2MPa. The spraying material is cement paste or interface mortar with a roughening thickness of 2mm and uniform coverage. For the treatment of aerated block wall surface, it is necessary to spray water to moisten it in several times 24 hours in advance, with an interval of no less than 4 hours between each time, to ensure that the wet penetration depth is no less than 15mm. Before construction, there should be no standing water on the surface. Then, the cement-based interface agent is evenly rolled or brushed on.

[0015] Furthermore, in step (3), the roughening treatment after the first layer of base plastering is carried out by using a wooden trowel or a plastic trowel to roughen horizontally or obliquely, with a roughening depth of 1mm to 2mm, to form a rough interface that enhances the mechanical interlocking between layers. The second layer of topcoat plastering is carried out after the first layer has initially set but before it is completely dry.

[0016] The roughening of the first layer surface forms a "mortise and tenon" structure, which directly transmits the shear force of the second layer to the first layer substrate. This mechanical interlocking is more shear-resistant than the pure chemical bonding inside a single layer of mortar.

[0017] Furthermore, in step (4), a 45° oblique reinforcing mesh with a size of 200mm×200mm is added to the four corners of the door and window openings; after backfilling with mortar, a wire mesh is added to the surface of the pipeline groove, with a width of 100mm from the groove edge on each side, and the wire mesh is fixed with cement nails at a spacing of 200mm.

[0018] Furthermore, in step (5), the dividing seam is embedded 2 to 3 hours after the second layer of plastering is completed; the embedding depth of the weather-resistant sealant is not less than 5 mm, and the surface is smoothed into a concave shape.

[0019] When the wall contracts, the deformation is attracted to this pre-designed expansion joint for displacement compensation, the stress is unloaded, and it is filled with highly elastic weather-resistant sealant, which is both waterproof and can adapt to the expansion and contraction of the expansion joint.

[0020] Furthermore, in step (6), the middle and lower parts of the wall are sprayed 2 to 3 times a day.

[0021] The upper part of a super high-rise building experiences high wind speeds, and according to the principle of convection heat transfer, the surface moisture evaporation rate is much higher than that of the lower part. The mortar hydration reaction requires continuous moisture, and excessive water loss will lead to hydration stagnation, surface shrinkage, and cracking. The middle and lower parts are sprayed less frequently than the upper part, which can create a gradient water replenishment and ensure that the mortar hydration reaction takes place in a similar humidity environment throughout the entire height.

[0022] Furthermore, before step (1), there are also steps for quality control of wall construction: before construction, layout design is carried out to ensure that the mortar joints are horizontal and vertical, the upper and lower layers are staggered, the staggered joint length is not less than 1 / 3 of the brick length, and the mortar joint fullness is not less than 90%; after construction, the wall surface is checked with a straightedge, the surface flatness error is not greater than 5mm, and the unqualified parts are chiseled or repaired before plastering.

[0023] By adopting the above solution, the present invention has the following advantages compared with the prior art: 1. Innovative Thin-Layer + Layered Structure System: This invention strictly limits the total plaster thickness to 15mm and creatively divides it into a first base plaster layer (6-8mm) and a second topcoat plaster layer (7-9mm). This structure significantly reduces the self-weight of the plaster layer in principle, thereby reducing the risk of hollowing at the bottom of high-rise walls due to vertical stress concentration. At the same time, the double-layer structure effectively disperses the drying shrinkage stress of the mortar, avoiding the through cracks caused by uneven drying and shrinkage stress concentration due to excessive thickness of a single layer of traditional thick plaster. The roughening treatment on the surface of the first layer forms a rough interface, creating a mechanical interlock between the two layers, which is significantly better than the interlayer bonding force of a single thick plaster.

[0024] 2. Innovation of Vertical Segmented Stress Relief System: For super high-rise walls above 9m, each segment is constructed in sections with a height of 3.0m to 3.5m, and construction is carried out vertically from bottom to top. The construction interval between segments is ≥24 hours. When constructing the upper segment, the completed plaster surface of the lower segment must be covered and protected. This innovative process allows the mortar of the lower segment to bear the load of the upper segment after it has initially set and formed a certain strength. This realizes the segmented release and transfer of the self-weight stress of vertical construction, and completely solves the problem of hollowing caused by stress accumulation at the bottom of the wall that has plagued traditional processes.

[0025] 3. Innovation of Composite Crack-Resistant Network System: This invention constructs a composite crack-resistant system of "interface reinforcement + node reinforcement + stress diversion". By laying hot-dip galvanized steel wire mesh at the junction of two different materials, concrete wall and masonry wall, and specifying an overlap width of ≥150mm, the shear stress caused by the difference in the linear expansion coefficients of the materials is effectively constrained, and the crack driving force is actively dispersed. This network system works in conjunction with the layered plastering structure to block the initiation and propagation of cracks from multiple dimensions.

[0026] 4. Innovative Active Expansion Joint Stress Relief: By pre-setting a horizontal expansion joint with a width of 10-15mm every 3.0m-3.5m along the wall height and filling and sealing it with weather-resistant sealant, a large area of ​​plaster layer is divided into several stress release units (single block ≤20㎡). This design changes passive crack prevention to active guidance, artificially pre-setting a channel for the release of shrinkage stress, transforming the originally disordered and harmful shrinkage deformation into orderly and controllable regular cracking, structurally eliminating the conditions for the generation of through cracks.

[0027] 5. Innovative full-cycle differentiated maintenance process: In response to the special working conditions of high wind speed and rapid water loss in the upper part of the walls of super high-rise buildings, a strategy of focusing on strengthening the moisturizing and maintenance of the upper part of the walls is proposed, with spraying ≥3 times a day and a maintenance period ≥7 days; This process innovatively matches the differentiated drying environment of super high-rise walls at different heights, ensuring that the hydration reaction of the mortar is full and synchronous throughout the entire height range, and completely solving the problems of surface cracking and insufficient strength caused by rapid water loss in the upper part. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] A method for preventing cracking and hollowing of the walls of ultra-high-rise industrial buildings using layered thin plastering includes the following steps: 1. Quality control of wall construction: (1) Before masonry, the layout design should be carried out to ensure that the mortar joints are horizontal and vertical, the upper and lower layers are staggered (the staggered joint length is not less than 1 / 3 of the brick length), and the mortar joint fullness is ≥90%.

[0030] (2) After the masonry is completed, the wall surface is checked with a straightedge to ensure that the surface flatness is ≤5mm. Any unqualified parts are chiseled or repaired before plastering.

[0031] 2. Grassroots processing: (1) Cleaning: Remove floating dust, oil stains, release agent, loose mortar and other attachments from the wall surface. Repair holes and honeycomb-like pits.

[0032] (2) Concrete wall surface: High pressure mechanical spraying (pressure 0.8~1.2MPa) is used for roughening treatment. The spraying material is cement paste or interface mortar. The roughening thickness is about 2mm, and the coverage is uniform to form a rough surface and enhance the adhesion.

[0033] (3) Aerated concrete block wall: Sprinkle water to moisten the surface 24 hours in advance, with an interval of no less than 4 hours between each application, to ensure that the wet penetration depth is ≥15mm. There should be no obvious water accumulation on the surface before construction. Then apply cement-based interface agent (roller or brush), ensuring no missed areas or drips, and proceed to the plastering process immediately after drying.

[0034] 3. Vertical segmented construction: Divide the wall into sections with a height of 3.0m to 3.5m, and construct from bottom to top. The interval between each section construction is ≥24 hours. When constructing the upper section, the completed plaster surface of the lower section must be covered and protected.

[0035] 4. Layered thin plastering: (1) First layer of base coat: The plaster thickness is 7mm. Use a trowel to evenly press the mortar into the base layer, compact and knead it to fully fill the micropores. After the base coat is completed, use a wooden or plastic trowel to roughen the surface horizontally or diagonally to form a uniform rough surface. Do not polish it. The roughening depth is about 1-2mm.

[0036] (2) Second layer of coating: After the first layer has initially set (about 3 hours, depending on the temperature and humidity) and before it is completely dry, the second layer of coating is 8mm thick, with a total thickness of 15mm. Finally, use a scraper to level, compact, and finish.

[0037] 5. Crack resistance enhancement: Hot-dip galvanized steel wire mesh is laid at the junction of concrete and masonry blocks, with an overlap of 150mm on each side, fixed with cement nails at 200mm intervals; 45° diagonal reinforcing mesh with dimensions of 200×200mm is added to the four corners of door and window openings; after backfilling mortar, steel wire mesh is also added to the surface of the pipeline trench, with a width of 100mm from the trench edge on each side.

[0038] 6. Dividing seam settings: (1) A horizontal dividing joint is set every 3.0m to 3.5m along the height of the wall, with a joint width of 10 to 15mm, penetrating the plaster layer, and the dividing strip is embedded 2 to 3 hours after the second layer of plastering is completed (before final setting).

[0039] (2) After cleaning the joint, fill it with weather-resistant sealant with an embedding depth of ≥5mm and smooth the surface to form a concave shape.

[0040] (3) Divide the large-area plaster layer into stress relief units of ≤20㎡, actively guide the orderly generation of drying shrinkage cracks, and protect the large wall surface from irregular through cracks.

[0041] 7. Curing: Start spray curing 12 hours after plastering is completed, and continue curing for ≥7 days; spray the upper part of the wall ≥3 times a day, and the middle and lower parts 2 to 3 times a day, focusing on areas with high wind speed and rapid water loss, and keep the plastered surface moist during this period.

[0042] The above are merely specific embodiments of the present invention. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in the present invention are for reference only and are not absolute limitations. Any non-substantial modifications made using the present invention shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A construction method for preventing cracks and hollowing of a layered thin plaster of a wall body of an ultrahigh-rise industrial plant, characterized in that, Includes the following steps: (1) Base treatment: roughen the concrete wall surface to form a rough surface; moisten the aerated block wall surface with water in several times and apply cement-based interface agent; (2) Vertical segmented construction: The wall is divided into multiple construction segments with a height of 3.0m to 3.5m, and construction is carried out sequentially from bottom to top. The interval between construction of adjacent segments is not less than 24 hours. When constructing the upper segment, the completed plaster surface of the lower segment is covered and protected. (3) Layered thin plastering: When constructing each section of the wall, first apply the first layer of base plaster with a thickness of 6mm to 8mm. During construction, compact and knead the mortar to fully fill the micropores of the base layer, and roughen the surface to form a uniform rough surface. After the first layer has initially set, apply the second layer of topcoat plaster with a thickness of 7mm to 9mm, so that the total thickness of the plaster is 15mm. Finally, level and compact the plaster with a screed. (4) Crack resistance enhancement: At the junction of different materials, concrete wall and masonry wall, hot-dip galvanized steel wire mesh is laid, and the overlap width of the steel wire mesh on each side at the junction is not less than 150mm; and reinforcing mesh is added at the four corners of door and window openings and pipeline grooves. (5) Setting of dividing joints: Along the height of the wall, a horizontal dividing joint is preset every 3.0m to 3.5m, with a joint width of 10mm to 15mm, penetrating the plaster layer; before the second layer of plaster is fully set, the dividing strip is embedded. After the joint is cleaned, it is filled with weather-resistant sealant to form a stress relief joint, dividing the large area of ​​plaster layer into several stress relief units with a single area of ​​no more than 20㎡; (6) Differentiated curing: Spray curing shall begin 12 hours after plastering is completed and shall continue for no less than 7 days; for the upper part of the wall, spray no less than 3 times a day to ensure that the plastered surface is always moist.

2. The construction method according to claim 1, characterized in that: In step (1), the roughening treatment of the concrete wall surface is carried out by high-pressure mechanical spraying with a pressure of 0.8MPa to 1.2MPa. The spraying material is cement paste or interface mortar with a roughening thickness of 2mm and uniform coverage. For the treatment of aerated block wall surface, it is necessary to spray water to moisten it in several times 24 hours in advance, with an interval of no less than 4 hours between each time, to ensure that the wet penetration depth is no less than 15mm. Before construction, there should be no standing water on the surface. Then, the cement-based interface agent is evenly rolled or brushed on.

3. The construction method according to claim 1, characterized in that: In step (3), the roughening treatment after the first layer of base plastering is carried out by using a wooden trowel or a plastic trowel to roughen horizontally or diagonally, with a roughening depth of 1mm to 2mm, to form a rough interface that enhances the mechanical interlocking between layers. The second layer of topcoat plastering is carried out after the first layer has initially set but before it is completely dry.

4. The construction method according to claim 1, characterized in that: In step (4), a 45° diagonal reinforcing mesh with a size of 200mm×200mm is added to the four corners of the door and window openings; after backfilling with mortar, a wire mesh is added to the surface of the pipeline groove, with a width of 100mm from the groove edge on each side, and the wire mesh is fixed with cement nails at a spacing of 200mm.

5. The method for constructing anti-cracking and anti-hollowing plastering of the walls of ultra-high-rise industrial plants according to claim 1, characterized in that: In step (5), the dividing seam is embedded 2 to 3 hours after the second layer of plastering is completed; the embedding depth of the weather-resistant sealant is not less than 5 mm, and the surface is smoothed into a concave shape.

6. The method for constructing anti-cracking and anti-hollowing plastering walls of ultra-high-rise industrial plants according to claim 1, characterized in that: In step (6), the middle and lower parts of the wall are sprayed 2 to 3 times a day.

7. The method for constructing anti-cracking and anti-hollowing plastering walls of ultra-high-rise industrial buildings according to claim 1, characterized in that: Before step (1), the following steps are included: layout design before masonry, ensuring that the mortar joints are horizontal and vertical, staggered between upper and lower layers, with the staggered joint length not less than 1 / 3 of the brick length, and the mortar joint fullness not less than 90%; after the masonry is completed, the wall surface is checked with a straightedge, and the surface flatness error is not greater than 5mm. Unqualified parts are chiseled or repaired before plastering.