What is the role of unbonded steel strand in prestressed steel strand?

Unbonded steel strands have a wide range of applications. Although they have high material strength and good plasticity, they make a significant contribution to supporting buildings, whether it's subways, bridges, dams, nuclear power plants, or house construction. Prestressed steel strands are indispensable in this field. Prestressed steel strands can be divided into bonded prestressed steel strands and unbonded prestressed steel strands. The difference between bonded and unbonded steel strands lies in whether the steel strand itself comes into contact with the concrete during construction, which is also due to the different production methods. Let's take a look at the role of unbonded steel strands in unbonded steel strands.

The outer surface of the unbonded steel strand is covered with a layer of plastic sheath and grease. In addition to improving the quality of the steel strand itself, it also has an automatic loosening function. Used to isolate the steel strand itself from the concrete appearance. Therefore, it can improve work efficiency and also has a good anti-corrosion effect. Bonded prestressed steel strands do not have this layer of protection. In life, apart from those who need it, we still know more or less about steel strands. Steel strands are products composed of many steel wires, and then during the surface treatment process, we can make the steel strands into products with galvanized layers or aluminum alloy layers according to our needs, that is to say, steel strands can be processed according to our own needs.

Many people may be confused about the selection of unbonded steel strands. So, let's take a look at how to choose steel strands. First, what we need to do is to distinguish the quality of steel strands from their appearance. We can use a small tool, which is a vernier caliper. Use it to measure whether the theoretical dimensions of the product are qualified. Then some manufacturers will do some tricks on the steel bars, such as flattening them. This is a visual trend, so we need to observe from the end of the steel bar to see if it is elliptical, because normally, if we get the steel strand, it should be round. Finally, we also need to judge from the surface of the steel strand. As long as everyone is careful enough, there are no rough spots, no scratches; the manufacturer, batch number, specifications, and other icons are complete.

In the use of ordinary steel strands, rust often occurs. Once the steel strand rusts, it will seriously damage the service life of the entire steel strand, and in turn damage the firmness of the building. Therefore, steel strand manufacturers use galvanizing technology to enhance the corrosion resistance of steel strands. This is the advantage of galvanized steel strands in use.

Unbonded steel strands are made of high-carbon steel wire rods after surface treatment, then cold-drawn into wires, and then stress is eliminated through a stabilization process to extend durability. The wires can have metallic or non-metallic layers. Before the engineering structural components bear the external load, the steel bars in the module are manually pulled to apply pressure, increase stiffness, delay the cracking moment, and increase durability. Prestressed steel strands are more durable than ordinary steel strands, just like tightening the iron hoops before filling the barrel with water, creating reverse compressive stress on the barrel wall. If the applied compressive stress exceeds the tensile stress caused by the water pressure in use, it will not crack or leak. The effect of prestressing on a circular water pool is the same as that of a barrel hoop, and applying prestress to the component before loading the bending component will produce a deformation opposite to the deformation caused by the load action. Before the load requires the component to deform along its direction of action, the opposite deformation of the load needs to be offset first, so that the component can continue to deform along the direction of the load, so prestressing is like adding an extra layer of protection to the component. Therefore, prestressed steel strands are much stronger than ordinary steel strands.