Hello everyone, this is RuiGang.
Today, I shared that the steel structure construction site has a situation where the thick-coated fireproof coating falls off.
In this case, most of the bonding strength of the fireproof coating is not enough, and a large piece will fall off.
For thick fire retardant coatings, there are still many particulars on design and construction technology.
Design requirements for thick-coat fire retardant coatings
In the past, it was called "thick-coated fire-retardant coating", but now it is called "non-intumescent fire-retardant coating".
In the design description, if it is an intumescent fireproof coating (thin type), as long as the equivalent thermal resistance value is indicated, the thickness of the coating should not be less than 1.5mm;
For non-intumescent fireproof coatings (thick type), the equivalent thermal resistance, equivalent thermal conductivity and coating thickness should be indicated, the thickness should not be less than 15 mm ("GB14907"), and there is also a standard "GB51249" that should not be less than 10mm.
Used on steel columns, the thick plate of thick-coated fireproof coating is generally 20~50mm, and the improper construction process will easily cause the problem of falling off and cracking.
Construction method of thick-coated fire-retardant coating
In the following cases, the thick-coated fireproof coating should be considered for hanging nets:
l Multiple p
l Multiple paints
Due to the thick coating of the thick-coated fireproof coating, it needs to be coated many times, and the thickness of each coating should not be too thick.
l Check and accept
After the construction is completed, the coating needs to be inspected and accepted to ensure that the coating thickness and surface flatness meet the requirements.。
aints
Due to the thick coating of the thick-coated fireproof coating, it needs to be coated many times, and the thickness of each coating should not be too thick.
l Check and accept
After the construction is completed, the coating needs to be inspected and accepted to ensure that the coating thickness and surface flatness meet the requirements.。
l Beams subjected to shock vibration loads.
l Beams with a coating thickness of 40 mm or more.
l Fire retardant coatings for steel structures with a bond strength of less than or equal to 0.05MP.
l Beams with web heights of more than 1.5m.
When the quality requirements are high, more than 25mm can be considered to hang the net
The construction process of thick fire retardant coatings
l Surface Treatment:
Before construction, it is necessary to remove rust and anti-rust on the surface of steel structural components, and thoroughly remove dust, oil and other debris on the surface of steel components.
l Blend paints：
According to the instructions of the coating, mix the powder and emulsion in a certain proportion and stir evenly to make it a thick and fluid without agglomeration.
Note that the consistency should be determined according to the coating method, so as to facilitate construction, not flowing, and firm bonding.
l Spray or plaster
It is painted by spraying or plastering. When spraying, the spray gun should be perpendicular to the surface of the coated component, the distance should be 40-60cm, the air pressure should be 0.6-0.8MPa, and the diameter of the spray gun mouth should be 6-10mm.
When plastering, the thickness of the coating should be uniform and the surface should be flat and smooth.
l Multiple paints
Due to the thick coating of the thick-coated fireproof coating, it needs to be coated many times, and the thickness of each coating should not be too thick.
l Check and accept
After the construction is completed, the coating needs to be inspected and accepted to ensure that the coating thickness and surface flatness meet the requirements.。
The fire resistance limit is 1-3h, the coating thickness is 10-40mm, and it generally needs to be sprayed 2-5 times.
The first pass to cover the steel surface is sufficient, and the thickness of 5-10mm is sprayed each subsequent pass.