Elevated Temperature Testing of Thermomechanically Treated Steel Bars

The details of experimental testing of thermomechanically treated reinforcing bars at elevated temperatures are presented in this paper. Rebars of 10-, 12-, 16-, 20-, and 25-mm diameter were used in the testing program. An electrical furnace was used to heat the bars to 100°C–900°C in increments of 100°C. The chemical composition of the rebars complied with bar manufacturing standards. The effect of bar diameter on the mechanical properties was random at ambient temperature, which also followed for the testing at elevated temperatures. These differences were due to the differences in the bar chemical composition. The yield plateau of the 25-mm-diameter bar disappeared on heating at 100°C, whereas this phenomenon occurred at 300°C for the rest of the bars. The rebar ultimate strength up to 300°C was higher compared with the strength at ambient temperature owing to blue-brittleness effects. The reduction coefficients for the proportional and yield strengths and the elastic moduli for all bars were similar at all heating temperatures. Brittle behavior of the bars tested at high temperatures was observed relative to the ambient temperature up to 500°C, which changed to ductile behavior thereafter. The suggested models to predict stress–strain curves for the strain-hardening region provided a reasonable match with the average observed curves for the bars tested at both ambient and elevated temperatures.