| Key points of construction technology for DPS high-speed bridge deck |
The main purpose of setting up a waterproof layer on the bridge deck is to improve the durability and integrity of the bridge, play a role in interlayer waterproofing, impermeability, and adhesion transition, and prevent damage such as displacement, peeling, detachment, and uneven surface of the bridge deck. The water-based aromatic rubber asphalt waterproof coating has high shear resistance and resistance to displacement in the bridge deck waterproof layer, which can effectively strengthen interlayer bonding, improve bridge deck waterproof performance, prevent steel corrosion, and have good economic and social benefits. This article combines the bridge deck waterproof project of Liuqian Expressway to introduce the technical standards, construction requirements, and related technologies in the construction of bridge deck waterproof layer, and summarizes the key points and key technologies of bridge deck waterproof layer construction technology
1、 The importance of bridge deck waterproof layer
Due to the early damage of the asphalt concrete surface layer on the bridge deck being mainly caused by water hazards, the main reason is that the construction of the cement concrete pavement layer and asphalt concrete pavement on the bridge deck were carried out separately by different construction contractors, and the corresponding construction technology requirements were not properly connected due to different responsible parties, resulting in a disconnect in quality control. Due to the non-standard and imperfect construction of the waterproof layer on the bridge deck, the damage and leakage caused by the water on the surface of the road directly affect the bonding between the two. The concave part of the cement concrete surface of the bridge deck is prone to water accumulation during the use of the road, which is difficult to eliminate. At high temperatures, it is easy to cause water vapor, which leads to the detachment of the asphalt concrete surface layer from the cement concrete pavement layer, directly resulting in the detachment of the asphalt surface layer from the bridge deck cement concrete pavement layer without bonding, forming a water containing interlayer. Finally, the local early damage, cracking, and pit formation of the asphalt pavement layer, after the pushing action, form a large surface and overall detachment and damage of the asphalt concrete pavement layer. Making the asphalt concrete surface layer a separate stress layer accelerates the damage of the bridge deck asphalt concrete surface layer.
2、 Research on Waterproof Layer Materials for Bridge Decks
Due to the fact that the waterproof layer of the bridge deck is set between the concrete bridge deck and the asphalt concrete pavement layer, the technical key of this project is not only to ensure sufficient impermeability of the waterproof layer, but also to ensure sufficient bonding strength and shear strength between the waterproof layer and the concrete bridge deck and asphalt concrete pavement layer to meet the needs of fast bridge driving. After analysis, we have preliminarily selected two or three materials as the materials to be promoted by the design institute, namely permanent curing liquid DPS, permanent curing liquid RMO, and polymer asphalt waterproof coating.
（1） Permeable waterproofing agent for concrete surface
1. Gudun Permanent Condensate Product Description: Permeable concrete surface waterproof agent DPS is a rigid crystalline waterproof material with hydrophobicity, hydrophilicity, impermeability, crystallinity and protection, which is formed by adding gel materials for cross chain reaction with silicon polar substances as the base material. It is an inorganic solution with higher specific gravity than water and lower viscosity than water. It has better permeability than water. When sprayed on the concrete surface, it can naturally penetrate into the interior, and promote the release of calcium ions to generate chemical hinge reaction, so as to form fully hydrophobic calcium silicate ion cementitious crystals. Blocking gaps and capillary holes to provide long-term waterproofing on a certain thickness of concrete surface; Prevent the erosion of concrete and internal steel reinforcement by media such as acid, alkali, salt, sulfide, etc. using water as a carrier; Improve the ability of concrete to resist weathering, freeze-thaw, slow down alkali aggregate reaction, and have long-lasting protective ability. It can delay the service life of concrete bridges and construction projects
The advantages of solid shield permanent condensate are:
① Penetrating waterproofing agent can penetrate into the interior of concrete by 20-50mm, forming an integrated structure with the concrete surface, and is an inorganic material with a long-term waterproof life;
② Penetrating waterproofing agents have a wide range of applications and can be applied to various parts and nodes of construction projects;
③ Penetrating waterproofing agents have no special requirements for surface conditions and are suitable for various geometric shapes;
④ Penetrating waterproofing agent is non-toxic, odorless, non flammable, and belongs to environmentally friendly waterproofing materials.
2. Performance and Model of DPS Technology for Solid Shield Permanent Condensation Liquid:
① The technical indicators of the penetrating waterproofing agent have reached JC/Tl018-2006
② The main models are: (1500 DPS type).
3. Usage: Permeable waterproofing agent is used for waterproofing and seepage prevention of concrete, ceramic tile, clay brick, stone and other materials in construction projects, as well as for waterproofing and seepage prevention of bridge deck, bridge body and pavement concrete. Concrete surface waterproofing agent is a kind of cement building waterproofing agent, which is sprayed on the concrete surface, infiltrates several centimeters inside, reacts with alkali substances inside the concrete, forms water insoluble gel, blocks voids and pores, and forms a dense permanent waterproof layer. As it is an inorganic mixture, it is not affected by water, sunlight, temperature and other external environments, and has a permanent waterproof effect
（2） Polymer modified asphalt waterproof coating (chloroprene latex)
1. Product description: water emulsion neoprene asphalt waterproof coating, also known as neoprene latex asphalt waterproof coating, is composed of cationic neoprene latex and cationic asphalt lotion. The particles of neoprene rubber and petroleum asphalt, with the help of cationic surfactant, are stably dispersed in water to form an emulsion. The appearance of the water emulsion chloroprene rubber asphalt waterproof coating is a dark brown emulsion, which combines the dual characteristics of rubber and asphalt. Compared with similar solvent based coatings, both use chloroprene rubber and petroleum asphalt as the main film-forming substances, so their performance is similar. However, the water emulsion chloroprene rubber asphalt waterproof coating uses water instead of organic solvents, which not only reduces costs, but also has the advantages of low measurement, non-toxic, non flammable, and no environmental pollution during construction. The main product belongs to the cationic water emulsion type. It is used for bridge deck waterproofing, which can prevent steel corrosion caused by concrete bridge deck seepage and improve the service life of bridge beams
2. Characteristics and Technical Performance:
① Has broad temperature adaptability. During asphalt concrete construction operations, it does not dissipate at high temperatures of 140 ℃ to 180 ℃, and does not crack under dynamic loads at low temperatures of 20 ℃ to 30 ℃ The material solidifies into film blocks with good film toughness. Due to the addition of chemical additives to the material, it can form a film in a short period of time, shortening the construction time for bridge deck waterproofing Strong adhesion, with the addition of penetrant and tackifier in the formula, improves the permeability and bonding performance of the coating, and can bond the pavement layer with the bridge deck as a whole; ④ After the construction of the waterproof layer, the shear strength between the bridge deck and the pavement layer reaches 0.5-1. OMpa, the tomb layer cracks by Zmm, and the coating film does not
Cracking; ⑤ Construction operability: Cold construction operations, mechanization, high degree of automation, non-toxic materials, and no environmental pollution; ⑥ The performance indicators of bridge deck waterproof coating comply with both the JC/T975-2005 standard for the building materials industry and the JT/T535-2004 standard for the transportation industry.
3、 Construction of bridge deck waterproof layer
（1） Construction sequence arrangement
Cleaning of the working surface before spraying (after passing the inspection) - spraying the first layer of concrete surface waterproofing agent - spraying the second layer of concrete surface waterproofing agent - cleaning of the working surface before spraying (after passing the inspection) - spraying the first layer of polymer modified asphalt waterproof coating - spraying the second layer of polymer modified asphalt waterproof coating - spraying the third layer of polymer modified asphalt waterproof coating
（2） Construction method
Grassroots treatment: Use milling and planing mechanical equipment to treat the bridge deck, requiring the surface to be free of floating slurry, flat, clean, and free of visible water. Strengthen special areas such as bridge deck drainage outlets and anti-collision wall corners. Spray coating construction: Spray several times in layers, and the coating thickness should meet the standard requirements. Finished product protection: Pedestrians and vehicles are prohibited from walking before practical action
（3） Construction of permeable waterproofing agent on concrete surface
1. Construction preparation and construction methods
① Waterproof agents must be stored in sealed containers, and their quality should meet the technical standards of the product, with indicators that meet the design requirements;
② The concrete bridge deck has undergone milling and planing treatment;
③ Clean the milled bridge deck, first manually treat the local pollution on the bridge deck with a wire brush, then use a hair dryer to clean up the floating ash on the bridge deck. After passing the acceptance of the previous process, seal the bridge deck, and then carry out the construction of permeable waterproofing agent for the bridge deck concrete;
④ Before spraying waterproofing agent, water the concrete tomb layer with clean water to moisten it;
⑤ After the base layer is free of floating water, immediately use a high-pressure airless sprayer to spray the first layer of concrete bridge deck waterproofing agent on the surface of the bridge deck;
⑥ When the waterproofing agent penetrates into the interior of the base layer and there is no obvious wet state on the surface, spray a second coat of waterproofing agent. Spray twice in a row without any omissions;
⑦ After spraying the waterproof agent for the second time, a specially assigned person should be responsible for observing the evaporation of the coating. After 2-3 hours, when the waterproof agent coating is about to dry, it should immediately use a spray to spray clean water for curing. The tomb layer should be kept wet for 24 hours, and the spraying of clean water should not be too much to avoid loss. Make the waterproof agent fully react with calcium ions in the tomb layer to block pores;
⑧ The key to spraying concrete penetrant waterproofing agent is to fully wet the base layer, spray a sufficient amount of waterproofing agent, extend the wetting and curing time, and allow the waterproofing agent to penetrate into the interior of the wet bridge deck;
⑨ The dosage of the sprayed solid shield concrete penetrating permanent liquid waterproofing agent is: the dosage of the first layer of concrete penetrating waterproofing agent sprayed is about 0.2kg/m2, and the dosage of the second layer of concrete penetrating waterproofing agent sprayed is about 0.2kg/m. Ensure that the penetration depth of the concrete penetrating waterproofing agent is not less than 10mm·
2. Precautions for Construction of Shield Permanent Liquid DPS
① Before spraying, the concrete bridge deck must be completely wetted;
② When spraying, be sure to spray carefully and evenly without any omissions;
③ After the first spray coating is completed, it should be allowed to dry naturally. During the drying period, a second spray of concrete penetrant waterproofing agent can be prepared to prepare for the second spray;
④ After the completion of the second homework, clean water spraying and maintenance should be carried out, and the amount of water used during maintenance should not be excessive to avoid washing away the waterproofing agent;
⑤ Construction cannot be carried out on rainy days. After construction, the coating cannot be soaked in rainwater before it dries. Construction is not allowed when the wind is above level five
3. Security protection measures
① The construction site should close off traffic and set up construction safety warning traffic signs;
② Arrange dedicated personnel to conduct safety control on the construction bridge deck and observe the changes in waterproofing agent spraying at any time
（4） Construction of polymer modified asphalt waterproof coating (chloroprene latex)
1. Construction preparation and construction methods
① After 24 hours of spraying the concrete penetrant waterproofing agent, before carrying out large-scale spraying construction, use a hair dryer to clean the floating ash on the surface of the bridge deck;
② The construction of polymer modified asphalt waterproof coating adopts advanced waterproof coating spraying machine, with high atomization degree and uniform spraying surface;
③ When spraying polymer modified asphalt waterproof coating, the coating should be stirred to dilute it, increase its activity, facilitate infiltration into the capillary pores of the coating, and improve the bonding strength and shear strength of the entire waterproof coating. The construction speed should not be too fast, and the coating should be sprayed evenly without bubbles;
④ When spraying the second coat of paint, it can only be carried out after the first coat of paint has dried (usually 12 hours), and at the same time, the working surface of the first coat of paint should be repaired and locally sprayed. When spraying the third coat of paint, it should also be carried out after the second coat of paint has dried (usually 24 hours later). Polymer modified asphalt waterproof coating should strive for uniformity and consistent thickness during spraying construction, and the basic requirements are thin, transparent, even, and firm. There should be no omissions, so that the bridge deck forms a seamless waterproof layer as a whole;
⑤ When spraying waterproof coating, the anti-collision wall of the bridge should be covered and protected by a dedicated person using plywood. The person holding the plywood should move at a constant speed with the progress of the spraying machine to prevent the polymer modified asphalt from spraying onto the anti-collision wall or guardrail and causing pollution;
⑥ After the waterproof coating is sprayed three times, arrange for manual application of the waterproof coating on the upward SCM at the junction of the anti-collision wall and the bridge deck to ensure that the joint leakage is formed by pouring the bridge deck and the anti-collision wall twice. Before application, use transparent tape to stick it evenly along the upward SCM, and after application, tear it off to prevent pollution of the bridge deck. At the same time, check the waterproof coating of the bridge deck and find some uneven or damaged areas
Fang, timely repair;
⑦ The construction is fast and simple, which is conducive to environmental protection. The coating construction adopts water-based cold construction operation and mechanized operation, and there is no harmful gas generated during the construction;
⑧ Before spraying waterproof coating, randomly place some iron pieces on the bridge deck. When spraying the iron pieces, keep them consistent with the normal spraying during construction. After the spraying is completed, it is convenient to use a magnetic energy thickness detector to detect the coating thickness;
⑨ The amount of chloroprene latex asphalt waterproof coating sprayed three times should be controlled between 1.5kg/m2 and 2.0kg/m2 (generally determined according to the test section), ensuring that the coating thickness reaches 0.8-1.2mm after the sprayed coating is dry.
2. Construction precautions
① The construction of polymer modified asphalt waterproof layer can only be carried out after the acceptance of the previous process is qualified;
② Ensure uniform coating during construction (with a certain amount meeting the design specifications and without settling in low-lying areas);
③ Avoid the passage of personnel and vehicles during the construction process;
④ Each layer of paint must be inspected after application;
⑤ When carrying out the next construction process, try to avoid damaging the waterproof layer as much as possible. If there is any damage, it should be promptly repaired;
⑥ Construction cannot be carried out on rainy days, and the coating cannot be soaked in rainwater before it dries after construction. Construction is not allowed in winds above level five;
⑦ During the construction process, it is strictly prohibited to step on the wet waterproof layer indiscriminately. After the waterproof layer is completed, it is necessary to strictly prevent sharp objects, vehicle operation, and other human damage to the waterproof layer before laying the asphalt concrete pavement layer
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