Residual Compressive Stress-Strain Relationship for Concrete Subjected to Elevated Temperatures

This study attempts to investigate the post-fire residual stress-strain behaviour of unconfined plain and fibrous concretes under axial compression. The experimental variables of the study were concrete strength levels, volume fractions of flat crimped steel fibres and polypropylene fibres, inclusion of hybrid fibres and temperature of exposure. A total of 147 cylindrical specimens (150 x 450 mm) were cast and tested under this study. The specimens were first exposed to temperatures ranging from room temperature to 800°C and then tested under uni-axial compression after cooling to obtain complete residual stress-strain response. Based on the test data obtained, a simple empirical model is proposed to describe the complete residual stress-strain relationships of plain and fibre reinforced concrete after exposure at elevated temperatures. Important observations have been made in the paper about the influence of temperature on various mechanical properties namely strength, stress-strain curves, compressive toughness and modulus of elasticity of both plain and fibrous concretes.