What Is a PC Steel Bar?
A PC (Prestressed Concrete) steel bar is a high-strength steel bar used in pre-stressed concrete to enhance its tensile strength. These bars are pre-tensioned to apply compressive force to concrete, increasing the overall strength of the structure. They are typically stressed to about 80% of their yield point.
In manufacturing, the steel is drawn into wires, heat-treated for required mechanical properties, cut to specified lengths, and subjected to thread rolling. Chemical composition typically focuses on three elements: phosphorus (P), sulfur (S), and copper (Cu).
Uses of PC Steel Bars
PC steel bars are extensively used in construction for various applications including:
- Foundation piles for buildings and power transmission towers
- Concrete poles for communication towers
- Concrete sleepers for railways
- Piles for sewage systems, culverts, and bridges
They come in both fully threaded and end-threaded variants, with the former often used as ground anchors or in temporary construction materials.
Types of PC Steel Bars
There are two main shapes: deformed round steel SBBR and deformed PC bar SBPD, classified into three strength classes (A, B, C). Standard sizes range from φ9.2 mm to φ32 mm for deformed round steel bars and φ7.4 mm to φ13 mm for deformed PC bars. Key mechanical properties include load, tensile strength, elongation, and relaxation values for 0.2% permanent elongation.
PC steel bars are manufactured as rolled bars (stretched and blued), heat-treated bars (quenched and tempered, sometimes drawn before heat treatment), and drawn bars (drawn and blued). Exposure to sudden temperature changes, like fire or welding, can significantly reduce their strength and toughness.