Concrete block and reinforced protective layer block, is in the masonry structure and frame structure, under the beam, to expand the confined area, reinforced position, to prevent corrosion of steel exposed and the function.
Is a solution to the often used local pressure.
Reinforced concrete cover thickness is related to the bearing capacity and durability of the structure, the function such as fire prevention. Has the following role and influence of reinforced concrete guard-layer:
1, maintenance structure durability of concrete protective layer is too thin to penetrate in the wet gas and water, too thick, easy to produce cracks, these could make the steel corrosion and inflation, so that the destruction of a concrete influence use and security of structure.
2, under external force Protection layer for steel bar anchoring force, takes advantage of the anchoring force between concrete and reinforcing steel bar, the two together, jointly participate in the work. Protective layer too thin or missing, reduce its anchorage force which reduces the structure to withstand the axial force and bending moment.
3, from the calculation formula of flexural bearing capacity of normal section
M a l or less FCBX (h0 x / 2) + fy 'AS' (ho - a s') a (sigma pO 'a fpy) a p' (ho - a p '), you can see that when the gluten protective layer through the thick section effectively reduced height h0, will reduce the cross section flexural bearing capacity. Visible protective layer thickness is how important factor affecting bearing capacity of structure.
4, fire protection layer of concrete has a certain thermal insulation effect, can more easily to soften when you encounter fire reinforced protection, if too thin, protective layer thickness under the environment of high temperature easy craze, cause reinforced in overheating and reduce the strength to destroy the whole structure. Hunan hengyang in 2003 a project is due to the high temperature heat from the burning of fire to soften steel lead to collapse and cause heavy casualties accident.
In the quality inspection of the current work, therefore, more attention paid to the protection layer thickness control, new rules to entities in the process of acceptance testing.