Research on the construction process of tunnel fire protection coating

0 Introduction:
tunnel is a weak link in the whole road traffic, and its safety or not directly affects the smooth flow of the whole road. Traffic accidents or geological disasters in tunnels affect road traffic for a long time and are difficult to resume, while traffic accidents are most seriously affected by traffic fire accidents. In order to reduce the damage caused by traffic accidents, the tunnel during the construction and maintenance of fire prevention measures
the
. These include the installation of sprinkler systems, the installation of concrete sacrificial layers, the use of fire-resistant fiber concrete, the pasting of tunnel-specific fire protection panels, the spraying of tunnel-specific fire protection coatings, the injection of inorient fiber fire protection materials, and various measures have advantages and disadvantages. Comparing, it is found that spraying fireproof coatings is the most cost-effective fire prevention method. Fire protection coating is mechanically sprayed on the inner wall and vault surface of the tunnel, which protects the heat from fire, which can effectively prevent the strength of reinforced concrete in the tunnel from decreasing at high temperature, avoid the cracking of concrete and the loss of support capacity caused by the destruction of reinforced steel in the lining, etc. In this paper, the construction process of tunnel fire prevention coating is to better play the advantages of tunnel fire prevention coating through construction control and improve its fire resistance and use effect.1 Scope of application
Since the main component of tunnel fire protection coating is aluminumate cement, it can be applied to general civil concrete structure building fire prevention and tunnel fire spraying engineering, performance indicators meet the "concrete structure fire protection coating" standard. Fireproof coating formulations such as Table 1.
Aluminum acid cement and adhesive powder mainly play a bonding role, in the construction process to add a moderate amount of water by stirring evenly, the powder dissolved in the slurry paint, increase the strength of the coating bonding, to ensure that the paint firmly attached to the tunnel wall. The zircon, mica and pearl rock in the coating play a thermal insulation role, hollow glass beads, aluminum hydroxide, magnesium hydroxide, etc. in the coating when the heat absorbs heat melting decomposition, reduce the coating temperature, play a fire-resistant role.
2 Process Principle
Tunnel fire protection coating construction process is generally 3 layers of spaced construction, respectively, the grass-roots (surface bottoming), middle layer construction and surface (surface coating) construction. The single-component coating is mixed with water according to the ratio of 1:0.75, which is suitable for mortar pump spraying. The coating is stirred and set aside for a period of time before being sprayed and constructed by extruded mortar pump, and the coating is maintained after spraying until the design requirements are met.
3 Process and operation requirements
3.1 Construction machinery and materials preparation
3.1.1 construction tools and personnel
a) mortar mixer for tunnel fire prevention paint mixing, generally using horizontal mixers or ordinary vertical concrete mixers, mixing while adding paint and water. To ensure that the stirred paint has sufficient viscosity, water consumption to be moderate, water volume will be too large in the paint part of the material in the spray gap will occur precipitation, over the mortar pump difficulties, easy to damage equipment, paint spraying on the tunnel wall. Too little water consumption, increased paint viscosity, poor mobility, spraying to increase the load of the pump, will also lead to equipment damage.
b) Special spray equipment (extruded mortar pump, air compressor) at the mortar machine feed port to add a filter, the paint in the large particles of material filtered down, so as not to damage the spray equipment, or affect the coating after spraying bonding strength. In tunnel spray construction, small area repair, usually need to roll coating equipment or roll brush.
c) When applying a special plate of mortar to repair a dead end left by spraying in a tunnel or a small defect in construction, it is necessary to use the iron plate to stir the appropriate coating to repair it.
d) cleaning equipment is mainly water spray equipment or brushes, used after construction to clean the spraying tools, keep the construction equipment clean and clean, to avoid coating dry curing attached to the inner wall of the equipment blocking lines, affecting the next construction application.
e) transport vehicles generally use large-scale heavy vehicle transport fire protection coatings.
f) construction personnel need construction skilled workers 8 to 10 people, in terms of construction experience and construction skills can be to ensure the quality of the project, cost savings.
3.1.2 Construction preparation
First clean up the concrete surface of the tunnel dust, oil, etc. , so that the tunnel wall surface is more suitable for bonding with fire protection coatings, and with concrete to repair the tunnel wall surface uneven place, to ensure the smoothness of the tunnel concrete surface. At the same time, the surface is particularly smooth tunnel wall hairing, so that the tunnel fire protection coating is easier to bond. Where water leaks and seepages in the tunnel, water-stopping and filling must be carried out. Sprinkle and moisten the tunnel wall before construction to ensure that the coating is well bonded to the tunnel wall.
3.1.3 Grass-roots construction
water and paint roughly according to the ratio of 0.75:1 (quality ratio) mixed, mixed with a blender, so that the paint into a thick slurry, according to the equipment spray pressure, adjust the ratio of water to paint, to suitable for construction equipment spray construction. Before spraying, use the stirred slurry to make a horizontal strip thickness mark of 2.5 m on the tunnel wall as a reference for the thickness of the coating. Construction is carried out with a sprayer from the waist of the tunnel to the top (bottom to top), approximately 5 mm thick at a time. After the first spray is dry, continue spraying a second time, so that the cycle is reached until the design thickness is reached. Due to the high pressure of equipment spraying during construction, the coating formed by spraying is not smooth enough on the tunnel wall, in order to improve the aesthetics of the coating coating, generally after the last spray, to immediately use the slurry for manual filling to find flat, trim and polish, so that the coating surface is smooth and smooth, and ensure that the coating reaches the design thickness. There are also colored coatings painted on the surface to improve the aesthetics and finish of the tunnel.
3.1.4 Surface construction
in the paint base after basic dry molding (need 3 d) to carry out surface construction, the surface requirements of higher projects, such as municipal engineering, before the surface construction is best in the grass surface scrape a layer to find flat putty, so that the surface flat, surface construction after the tunnel wall clean and bright. Surface coatings generally have a low viscosity and can be constructed using equipment spraying, hand brushing or rolling coating. The brushing process is required to be uniform, smooth and colorless. The boundaries of different colors require straight and clear.
3.1.5 Coating maintenance
When the temperature is above 5 degrees C, natural conservation 28 d is generally required, the maintenance conditions are basically the same as ordinary concrete, if damage to the coating is found in the maintenance process, it should be repaired in a timely manner.4 Conclusion
At present, China has become the world's largest tunnel and underground projects, tunnel structure is the most complex, tunnel construction is the fastest growing country, in view of the tragic lessons of various road fires, tunnel fire safety has caused China's transportation and fire, safety and supervision departments to attach great importance to. The construction process is simple and easy to carry out, can guarantee the construction quality, after the completion of the project can improve the fire prevention capacity of the tunnel, can improve the overall inter-layer structure of the tunnel wall, so that the fire resistance advantages of the tunnel fire protection coating to be given full play to improve the tunnel's driving safety factor, this paper to guide the tunnel fire paint spraying construction has a greater promotion and application value.