What is Unbonded Steel Strand?
The popular explanation for unbonded steel strands is to coat a layer of grease and plastic sheath on the steel strands (which can be called bare wires). In the construction of the project, the unbonded steel strand buried in the concrete has grease and sheath on the outside, so that the steel strand is isolated from the concrete and can be loosened freely, and remains unbonded with the concrete. Therefore, it is called an unbonded steel strand.
There are also galvanized unbonded steel strands that can be used for reinforcement projects. That is, the galvanized steel strands are coated with grease and plastic sheath to double guarantee the anti-corrosion effect.
Unbonded steel strands are used more and more widely. It is mainly used for civil construction projects with large static loads, large-span factory buildings, or high-rise buildings. The advantage is that the construction speed is fast, the thickness of the beams and slabs is reduced, the structural performance and the economic effect are increased, that is, the ordinary structure is used to make a 10-floor tall building, but the prestressed unbonded steel strand can cover 11 floors.
For bridge construction and large-span garage prestressing construction, due to the large dynamic load (the vibration of the vehicle driving the beam and slab is greater damage), so the design needs to have bonded steel strands, that is, ordinary steel strands. Due to the construction grouting, the ordinary steel strands are directly bonded to the concrete, resulting in a strong binding force, which enhances safety.