State about the Prestressing Steel
For prestressed concrete members, the high-tensile steel, used generally, consists of wires, bars or strands. The high tensile strength of steel is generally achieved by marginally increasing the carbon content in steel in comparison to mild steel. High-tensile steel usually contains 0.6 to 0.85% carbon, 0.7 to 1 % manganese, 0.05% of sulphur and phosphorus. The high carbon steel ingots are hot rolled into rods and cold drawn through a process of dies to reduce the diameter and increase the tensile strength. The durability of wires gets improved due to the cold-drawing operation. The cold-drawn wires are then tempered to improve their properties. Tempering or ageing or stress relieving by heat treatment of wires at 150-420°C improves the tensile strength. These cold-drawn wires are generally available in nominal sizes of 2.5, 3,4,5,7 and 8 mm diameter. #question..