Preliminary Studies of High-Strength Stainless Prestressing Steels

Abstract

This paper presents the preliminary results of a study examining the stress vs. strain behavior, stress relaxation, and corrosion resistance of six candidate high-strength stainless steels (HSSSs) for potential use as corrosion-resistant prestressing reinforcement in concrete structures. Austentic grades 304 and 316; duplex grades 2101, 2205, and 2304; and a precipitation hardened martensitic grade 17-7 were selected for the investigation and cold drawn to diameters of approximately 4 mm (0.16 in). Tensile strengths of 1290 to 1550 MPa (185 to 225 ksi) were achieved in the cold-drawn HSSS wires. 1000-hr stress relaxation of all candidate HSSSs was predicted to be between 6 and 8 % based on the results of short-term relaxation tests conducted at 70% ultimate tensile capacity. Cyclic polarization testing for chloride-induced corrosion resistance determined that in alkaline pore solutions, 2205 and 2304 exhibited low corrosion susceptibility and 304 exhibited moderate corrosion susceptibility at 0.5 M chloride concentrations. When exposed to carbonated pore solutions with 0.5 M chloride, grades 2205 and 2304 exhibited low and moderate corrosion susceptibility, respectively. Duplex grade 2205 exhibited superior corrosion resistance in all cases. Based on these results, optimal HSSSs were identified as duplex grades 2205 and 2304.