Repair Method for Hollow Areas in Thick Fire-Resistant Coating and Crack-Resistant Mortar Layers on Steel Structure Exterior Walls

Abstract

This invention relates to a composite repair method for hollow areas in a thick fire-retardant coating and crack-resistant mortar layer on a steel structure exterior wall, belonging to the field of fire protection and maintenance construction technology for building steel structures. The structure includes a steel base plate, a corrugated stainless steel wire mesh, a thick fire-retardant coating layer, and a crack-resistant mortar layer. Hollow areas exist only between the fire-retardant coating layer and the crack-resistant mortar layer. The construction steps include: accurately identifying the area of ​​hollow areas; drilling grouting and anchoring integrated holes that penetrate only the crack-resistant mortar layer; high-pressure hole cleaning; low-pressure injection of epoxy resin grout to fill the dense cavities; using galvanized self-tapping screws with washers to penetrate each structural layer and the steel plate for locking and anchoring; finally, sealing the holes and performing curing and acceptance. By restoring interface adhesion through grouting, combined with mechanical anchoring through the steel plate to form a rigid whole, surface layer detachment is effectively prevented. This method has the advantages of strong structural adaptability, convenient construction, and high safety and reliability.

Description

Technical Field

[0001] This invention relates to the field of fire protection and maintenance construction technology for building steel structures, specifically to a composite repair method for hollow areas of thick fire-resistant coating and crack-resistant mortar layer on the exterior walls of steel structures. Background Technology

[0002] In the construction of fire protection systems for steel structural components of building exterior walls, corrugated stainless steel wire mesh is first anchored to the surface of the steel plate of the steel structure base using special anchors. The corrugated stainless steel wire mesh is not laid flat on the steel plate, but rather a structural gap is maintained between it and the steel base. The wire mesh is then securely anchored to the steel plate using anchor bolts. Subsequently, a 25-30mm thick fire-retardant coating layer is sprayed onto the outside of the wire mesh, forming a composite fire-resistant base structure of "steel base + corrugated anchored stainless steel wire mesh + thick fire-retardant coating layer".

[0003] Thanks to the reliable anchoring effect of the corrugated wire mesh, the steel structure base layer and the thick fireproof coating layer are firmly bonded and have strong integrity, eliminating any risk of hollowing, separation, or detachment. To enhance the crack resistance, durability, and overall decorative integrity of the facade, a 20-25mm thick crack-resistant mortar protective layer is uniformly applied to the outside of the thick fireproof coating layer, ultimately forming a complete exterior wall fire protection system.

[0004] During long-term use, due to factors such as interfacial bonding stress, positive and negative wind loads on the external wall, temperature and humidity cycle deformation, and construction interface bonding defects, interface separation, micro-gaps, and local hollow cavities are easily generated between the thick fireproof coating layer and the outer 20-25mm crack-resistant mortar layer. These hollow cavities only exist between the two interfaces and do not involve the structural system between the steel base layer and the fireproof coating layer.

[0005] Existing similar hollow repair techniques have obvious defects: First, the grouting materials lack clear performance parameters, have poor compatibility, and are prone to shrinkage, non-bonding, and secondary delamination; second, there is no dedicated anchoring gasket design, and the screws directly press against the surface layer, which can easily cause local cracking of the crack-resistant mortar and uneven anchoring force; third, it is not clearly adapted to the unique corrugated stainless steel wire mesh structure of this project, resulting in insufficient targeted construction; fourth, single grouting without rigid mechanical anchoring, relying solely on interface bonding, cannot resist the external forces of the external wall, and the crack-resistant mortar layer still has the risk of falling off, failing to meet safety acceptance requirements. Summary of the Invention

[0006] This invention primarily addresses the shortcomings of existing technologies by providing a composite repair method for hollow areas in steel structure exterior walls, combining a thick fire-resistant coating with a crack-resistant mortar layer. This method boasts advantages such as strong structural adaptability, convenient construction, and high safety and reliability. Grouting restores interface adhesion, and mechanical anchoring through steel plates forms a rigid whole, effectively preventing surface layer detachment.

[0007] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions: A method for repairing hollow areas in a composite structure of thick fire-retardant coating and crack-resistant mortar layer on steel structure exterior walls includes the following construction components: a steel structure base plate, on the surface of which a corrugated stainless steel wire mesh is pre-installed and securely anchored to the base plate using anchors, with a structural gap maintained between the wire mesh and the base plate, avoiding direct bonding. A 25-30mm thick fire-retardant coating layer is sprayed onto the outer side of the base plate, ensuring a tight bond between the base plate and the coating layer without hollow areas. An outer layer of the fire-retardant coating is a intact 20-25mm thick crack-resistant mortar layer, with interface hollow areas existing between the fire-retardant coating and the mortar layer. The specific construction steps are as follows: Step 1: Accurately identify and mark the area of ​​voids and cavities at the interface between the thick fireproof coating layer and the crack-resistant mortar layer.

[0008] Step 2: Drill grouting holes with a diameter of 8-12mm and a spacing of 300-500mm on the crack-resistant mortar layer. The holes should penetrate only 20-25mm of the crack-resistant mortar layer and reach the bottom of the grouting hole directly to the interface cavity.

[0009] Step 3: High-pressure air is used to purge the hollow cavities at the interface to remove floating dust and impurities.

[0010] Step 4: Use a grouting machine to inject epoxy resin grout at low pressure (0.1-0.3 MPa) to completely fill and compact the voids and cavities at the interface.

[0011] Step 5: In the grouting hole, use galvanized self-tapping screws with round metal washers to pass the self-tapping screws through the metal washers, crack-resistant mortar layer, 25-30mm thick fireproof coating layer, and corrugated stainless steel wire mesh in sequence, completely penetrating the steel structure base plate and locking it in place.

[0012] Step 6: Seal the holes with crack-resistant repair mortar to restore the intact surface layer.

[0013] Step 7: Allow to cure naturally for more than 24 hours, and complete the acceptance of hollow areas, anchoring, and appearance quality.

[0014] Acceptance criteria: Hollow Area Re-inspection: Use a hollow area hammer to thoroughly tap the repaired area. There should be no hollow sound at the interface between the thick fireproof coating layer and the crack-resistant mortar layer, and the area should be dense and complete.

[0015] Anchoring acceptance: All screws should be secure and free from slippage, and the washers should be tightly bonded to the mortar surface, with no pressure cracks or splits in the surface. If necessary, an on-site pull-out test can be conducted to verify whether the pull-out force of a single screw consistently reaches 1.5kN or higher.

[0016] Visual inspection: The surface of the repaired area should be flat and intact, and the sealing joint should be smooth and natural.

[0017] Overall safety acceptance: It was finally confirmed that the entire crack-resistant mortar layer was firmly anchored, with no risk of falling off, and met the acceptance requirements for external wall safety protection and fire protection.

[0018] Preferably, the epoxy resin grouting material described in step 4 has the following performance parameters: viscosity of 30-80 mPa·s at 25℃, 1-3 hours of workable time before curing, bonding strength ≥3.5MPa, compressive strength ≥10MPa, tensile strength ≥2.5MPa after complete curing, and is resistant to aging, temperature changes, and wet-dry cycles, and has good compatibility with fire protection systems.

[0019] Preferably, the corrugated stainless steel wire mesh is a non-adhesive structure, which is directly anchored to the steel plate of the steel structure base layer by anchor bolts. This is the structural basis for ensuring that there are no voids between the steel plate of the steel structure base layer and the thick fireproof coating layer.

[0020] Preferably, the metal washer has an outer diameter of 30mm and a central hole diameter of 8mm, which is matched with a self-tapping screw with an outer diameter of 6mm and a length of 55mm. This is used to increase the surface area of ​​the surface layer, disperse the fastening stress, and prevent the crack-resistant mortar surface layer from cracking.

[0021] Preferably, the grouting hole and the self-tapping screw anchoring hole are in the same integrated hole position, and the hole spacing is uniformly controlled between 300 and 500 mm; after the 6 mm self-tapping screw penetrates the steel plate and is anchored, the single pull-out force reaches 1.5 to 1.8 kN, and it can withstand tensile and shear loads at the same time.

[0022] Preferably, several vent holes are provided above the grouting holes, and the grouting holes and vent holes are distributed in a plum blossom shape.

[0023] The present invention can achieve the following effects: This invention provides a composite repair method for hollow areas in thick fire-resistant coatings and crack-resistant mortar layers on steel structure exterior walls. Compared with existing technologies, it has the advantages of strong structural adaptability, convenient construction, and high safety and reliability. Grouting restores interface adhesion, and mechanical anchoring through steel plates forms a rigid whole, effectively preventing surface layer detachment. It has the following beneficial effects: I. The structure is perfectly adapted to the actual project: The unique structure of setting a 25-30mm thick fireproof coating layer on the base layer and a corrugated stainless steel wire mesh that is not attached to the steel plate but pre-anchored to the steel plate is clearly defined, which accurately matches the on-site working conditions and has strong technical relevance.

[0024] Second, the parameters of the grouting materials are clearly defined and compliant: the core performance indicators of the epoxy resin grouting material are limited, the parameters are quantifiable and detectable, and the requirements for disclosure of technical content in invention patent applications are met.

[0025] III. Optimized gasket specifications for better protection: The use of special metal gaskets with an outer diameter of 30mm and a center hole of 8mm further expands the stress-bearing area, effectively disperses the fastening stress, and completely avoids cracking of the anti-crack mortar surface layer under pressure.

[0026] IV. Clear Anchoring Performance Indicators: It is clearly stated that after a 6mm self-tapping screw penetrates the steel plate for anchoring, the pull-out force can reach 1.5 to 1.8kN. The mechanical performance parameters are complete and the technical solution is rigorous.

[0027] V. One hole serves two purposes, making construction simple and efficient: Grouting and anchoring share the same hole position, with a hole spacing of 300-500mm, reducing the number of holes to be drilled in the intact surface layer, simplifying the process and making on-site management easy.

[0028] VI. Double reinforcement for permanent anti-detachment: The epoxy resin grouting material has no shrinkage and fills the interface cavity, restoring the interface adhesion; the self-tapping screws with washers penetrate the steel plate and lock it in place, forming a rigid whole between each structural layer and the steel base layer, effectively resisting wind loads and temperature deformation, and completely eliminating the risk of detachment. Attached Figure Description

[0029] Figure 1 This is a cross-sectional schematic diagram of the interlayer void defect in the steel structure composite protective structure of the present invention.

[0030] Figure 2 This is a flowchart of the integrated grouting and anchoring repair process of the present invention.

[0031] Figure 3 This is a schematic diagram of the construction of the epoxy resin grouting material of the present invention.

[0032] Figure 4 This is a schematic diagram of the plum blossom-shaped arrangement of the grouting holes and venting holes of the present invention.

[0033] Figure 5 This is a cross-sectional view of the self-tapping screw with washer and hole sealing of the present invention.

[0034] In the diagram: 1. Steel plate for the base layer of steel structure; 2. Corrugated stainless steel wire mesh; 3. Thick fireproof coating layer; 4. Interface void cavity; 5. Crack-resistant mortar layer; 6. Grouting machine; 7. Grouting hole; 8. Epoxy resin grout; 9. Ventilation hole; 10. Self-tapping screw; 11. Metal washer; 12. Crack-resistant repair mortar. Detailed Implementation

[0035] The technical solution of the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0036] Example: Figure 1-5 As shown, a composite repair method for hollow areas in a thick fire-retardant coating and crack-resistant mortar layer on a steel structure exterior wall is described. The construction structure includes: a steel base plate 1; a corrugated stainless steel wire mesh 2 pre-installed on the surface of the steel base plate 1; the corrugated stainless steel wire mesh 2 securely anchored to the steel base plate 1 using anchors; a structural gap is maintained between the corrugated stainless steel wire mesh 2 and the steel base plate 1, and they are not directly bonded. This non-bonded structure, where the corrugated stainless steel wire mesh 2 is directly anchored to the steel base plate 1 using anchor bolts, forms the structural basis for ensuring no hollow areas between the steel base plate 1 and the thick fire-retardant coating layer 3. A 25-30mm thick fire-retardant coating layer 3 is sprayed in layers on the outer side of the steel base plate 1, ensuring a tight bond between the steel base plate 1 and the thick fire-retardant coating layer 3 without hollow areas. The outer layer of the thick fire-retardant coating layer 3 is an intact 20-25mm thick crack-resistant mortar layer 5, and there is an interface hollow cavity 4 between the thick fire-retardant coating layer 3 and the crack-resistant mortar layer 5. The specific construction steps are as follows: Step 1: Accurately identify and mark the area of ​​the interface voids 4 located only between the thick fireproof coating layer 3 and the crack-resistant mortar layer 5.

[0037] Step 2: Drill grouting holes 7 with a diameter of 8-12 mm and a spacing of 300-500 mm on the crack-resistant mortar layer 5. The drilling should penetrate only 20-25 mm of the crack-resistant mortar layer 5, and the bottom of the grouting hole 7 should reach the interface void cavity 4. Several ventilation holes 9 are provided above the grouting holes 7, and the grouting holes 7 and ventilation holes 9 are distributed in a quincunx pattern.

[0038] The drilling depth must be precisely controlled to penetrate only the 20-25mm thick crack-resistant mortar layer 5, ensuring the bottom of the hole reaches the interface cavity 4 between the thick fireproof coating layer 3 and the crack-resistant mortar layer 5. It is absolutely forbidden to drill through the 25-30mm thick fireproof coating layer 3, otherwise it will damage its adhesion to the steel substrate, and may even damage the internal corrugated stainless steel wire mesh 2 and the steel substrate 1.

[0039] Step 3: High-pressure air is used to purge the hollow cavity 4 at the interface to remove floating dust and impurities.

[0040] High-pressure air is used to blow away the hollow cavity 4 of the interface through the integrated hole to thoroughly remove floating dust, powder, loose impurities and moisture from the interface, ensuring that the grouting interface is clean and dry, and ensuring that the subsequent grouting material can fully bond with the base layer on both sides.

[0041] Step 4: Use the grouting machine 6 to inject epoxy resin grout 8 under low pressure, with a grouting pressure of 0.1 to 0.3 MPa, to completely fill and compact the interface voids and cavities 4.

[0042] The performance parameters of epoxy resin grout 8 are as follows: viscosity at 25℃ is 30~80mPa·s, there is a 1-3 hour working time before curing, and after complete curing, the bonding strength is ≥3.5MPa, the compressive strength is ≥10MPa, the tensile strength is ≥2.5MPa, and it is resistant to aging, temperature change, and wet-dry cycles, and has good compatibility with fire protection systems.

[0043] A low-pressure grouting machine 6 is used, with the pressure strictly controlled between 0.1 and 0.3 MPa. Grouting is performed hole by hole, following a bottom-up, top-down, and bottom-to-center sequence. When a uniform, bubble-free grout continuously overflows from adjacent vent holes 9, it indicates that the cavity is completely filled. Grouting is then stopped, and the holes are temporarily sealed. The grout is allowed to cure completely, typically for 3-7 days.

[0044] Step 5: In the grouting hole 7, use galvanized self-tapping screws 10, in conjunction with round metal washers 11, to pass the self-tapping screws 10 through the metal washers 11, the crack-resistant mortar layer 5, the 25-30mm thick fireproof coating layer 3, and the corrugated stainless steel wire mesh 2 in sequence, completely penetrating the steel structure base plate 1 and locking it under force.

[0045] The metal washer 11 has an outer diameter of 30mm and a center hole diameter of 8mm. It is matched with the self-tapping screw 10, which has an outer diameter of 6mm and a length of 55mm. It is used to increase the surface area of ​​the surface layer, disperse the fastening stress, and prevent the crack-resistant mortar surface layer from cracking.

[0046] Grouting hole 7 and self-tapping screw 10 anchoring hole are in the same integrated hole position, with the hole spacing uniformly controlled between 300 and 500 mm. After the 6 mm self-tapping screw penetrates the steel plate and is anchored, the tensile pull-out force of a single screw reaches 1.5 to 1.8 kN, and it can simultaneously withstand tensile and shear loads.

[0047] Inside the original grouting hole 7, insert the self-tapping screw 10 through the special washer 11. Use a power tool to screw it in at a uniform speed, with the screw passing through the following sequence: metal washer 11 → crack-resistant mortar layer 5 → thick fireproof coating layer 3 → corrugated stainless steel wire mesh 2 → completely penetrating the steel structure base plate 1. Finally, the screw threads tightly engage and lock with the steel base plate, ensuring all stress is borne by the steel structure base, forming an extremely reliable rigid anchoring system. When tightening, ensure that the washer 11 is evenly and completely adhered to the surface of the crack-resistant mortar layer, without warping.

[0048] Step 6: Use crack-resistant repair mortar 12 to seal the holes and restore the surface layer.

[0049] All construction holes shall be sealed, compacted, smoothed, and finished, and the gasket 11 and screw heads shall be completely and tightly covered. The sealed surface shall be smooth and consistent with the original intact crack-resistant mortar surface, without obvious unevenness or repair marks, and the original appearance of the facade shall be completely preserved.

[0050] Step 7: Allow to cure naturally for more than 24 hours, and complete the acceptance of hollow areas, anchoring, and appearance quality.

[0051] The specific working principle is as follows: The steel base plate is 8mm thick, with a corrugated stainless steel wire mesh surface. It is securely anchored to the steel plate using anchor bolts, but not adhering to the steel plate surface. A 30mm thick fire-retardant coating is sprayed on the outer side, with no voids between the steel base plate and the fire-retardant coating. A 25mm thick crack-resistant mortar layer is then applied to the outer side. The surface layer is intact, with only interface voids or cavities between the fire-retardant coating layer and the crack-resistant mortar layer. These voids are repaired using the method of this invention. 1. Accurately identify and mark the area of ​​interface hollowness. Repair by extending the boundary by 100mm.

[0052] 2. Drill 10mm integrated holes at 400mm intervals, penetrating only the 25mm crack-resistant mortar layer, with the bottom of the hole aligned with the interface cavity.

[0053] 3. High-pressure air is used to purge floating dust and impurities from the interface cavity.

[0054] Fourth, use single-component polyurethane grout with parameters that meet the requirements, and perform low-pressure grouting at 0.2MPa until the grout overflows fully at the orifice and the interface cavity is completely compacted.

[0055] 5. After the grout has cured, use 6mm self-tapping screws with a length of 55mm and a metal washer with an outer diameter of 30mm and a center hole of 8mm to screw into the original hole. The screws penetrate the steel plate and are locked in place. The actual measured tensile strength of a single screw is 1.8kN, which meets the design requirements of 1.0~1.2kN.

[0056] 6. Use crack-resistant repair mortar to seal the holes and level and restore the surface.

[0057] 7. After 24 hours of curing, the interface should be free of hollow areas, screws should be secure, surface should be free of cracks, and the anti-crack mortar layer should be firmly anchored to meet the requirements for safe use.

[0058] In summary, this composite repair method for hollow areas in thick fire-resistant coatings and crack-resistant mortar layers on steel structure exterior walls precisely addresses the interface hollowness problem under specific structural conditions. It cleverly integrates the advantages of both chemical bonding (grouting) and mechanical anchoring (screws) technologies, achieving a synergistic effect. The method clearly defines the performance parameters of key materials and the crucial points for construction process control, resulting in a rigorous and highly operable technical solution. It effectively solves the problems of poor reliability, easy detachment, and significant damage associated with traditional methods, permanently eliminating the risk of detachment and meeting stringent engineering quality acceptance requirements.

[0059] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for repairing hollow areas in a composite repair system of thick fire-resistant coating and crack-resistant mortar layer on the exterior wall of a steel structure, characterized in that... The construction structure includes: a steel base plate (1), on which a corrugated stainless steel wire mesh (2) is pre-installed, and the corrugated stainless steel wire mesh (2) is securely anchored to the steel base plate (1) by anchors. A structural gap is maintained between the corrugated stainless steel wire mesh (2) and the steel base plate (1), and they are not directly bonded. A 25-30mm thick fireproof coating layer (3) is sprayed on the outside of the steel base plate (1) in layers. The steel base plate (1) and the thick fireproof coating layer (3) are tightly bonded without any hollow areas. The outer layer of the thick fireproof coating layer (3) is an intact 20-25mm thick crack-resistant mortar layer (5). There are interface hollow cavities (4) between the thick fireproof coating layer (3) and the crack-resistant mortar layer (5). The specific construction steps are as follows: Step 1: Accurately identify and mark the area of ​​the interface voids (4) located only between the thick fireproof coating layer (3) and the crack-resistant mortar layer (5); Step 2: Drill grouting holes (7) with a diameter of 8-12 mm and a spacing of 300-500 mm on the crack-resistant mortar layer (5). The holes only penetrate the crack-resistant mortar layer (5) with a thickness of 20-25 mm. The bottom of the grouting hole (7) reaches the interface cavity (4). Step 3: High-pressure air is used to purge the hollow cavity at the interface (4) to remove floating dust and impurities; Step 4: Use a grouting machine (6) to perform low-pressure grouting of epoxy resin grout (8) at a grouting pressure of 0.1 to 0.3 MPa to completely fill and compact the interface voids (4); Step 5: In the grouting hole (7), use galvanized self-tapping screws (10) and round metal washers (11) to pass the self-tapping screws (10) through the metal washers (11), crack-resistant mortar layer (5), 25-30mm thick fireproof coating layer (3), and corrugated stainless steel wire mesh (2) in sequence, completely penetrating the steel structure base plate (1) and locking it under force; Step 6: Use crack-resistant repair mortar (12) to seal the holes and restore the intact surface layer; Step 7: Allow to cure naturally for more than 24 hours, and complete the acceptance of hollow areas, anchoring, and appearance quality.

2. The method for repairing hollow areas of thick fireproof coating and crack-resistant mortar layer on steel structure exterior walls according to claim 1, characterized in that, The performance parameters of the epoxy resin grout (8) mentioned in step 4 are: viscosity of 30~80mPa·s at 25℃, 1-3 hours of workable time before curing, bonding strength ≥3.5MPa, compressive strength ≥10MPa, tensile strength ≥2.5MPa after complete curing, and it is resistant to aging, temperature change, and dry-wet cycles, and has good compatibility with fire protection systems.

3. The method for repairing hollow areas of thick fireproof coating and crack-resistant mortar layer on steel structure exterior walls according to claim 1, characterized in that, The wavy stainless steel wire mesh (2) is a non-adhesive structure, which is directly anchored to the steel base plate (1) of the steel structure by anchor bolts. This is the structural basis to ensure that there is no hollow between the steel base plate (1) and the thick fireproof coating layer (3).

4. The method for repairing hollow areas of thick fireproof coating and crack-resistant mortar layer on steel structure exterior walls according to claim 1, characterized in that, The metal gasket (11) has an outer diameter of 30 mm and a central hole diameter of 8 mm. It is matched with a self-tapping screw (10) with an outer diameter of 6 mm and a length of 55 mm. It is used to increase the surface area of ​​the surface layer, disperse the fastening stress, and prevent the crack-resistant mortar surface layer from cracking.

5. The method for repairing hollow areas of thick fireproof coating and crack-resistant mortar layer on steel structure exterior walls according to claim 1, characterized in that, The grouting hole (7) and the anchoring hole of the self-tapping screw (10) are the same integrated hole position, and the hole spacing is uniformly controlled at 300-500mm; after the 6mm self-tapping screw penetrates the steel plate and is anchored, the single pull-out force reaches 1.5-1.8kN, and it can bear tensile and shear loads at the same time.

6. The method for repairing hollow areas of thick fireproof coating and crack-resistant mortar layer on steel structure exterior walls according to claim 1, characterized in that, Several ventilation holes (9) are provided above the grouting hole (7), and the grouting hole (7) and ventilation holes (9) are distributed in a plum blossom shape.

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