Residual mechanical properties of calcareous and granite aggregate concretes after fire

The residual mechanical properties of concrete after a fire depend on the high temperatures to which the material was subjected and the nature of the fire extinguishing process used. Knowledge of these properties is of the utmost importance in an evaluation of the residual load-bearing capacity of reinforced concrete elements and their repair after fire. This paper presents the results of an assessment of the residual mechanical properties of ordinary concrete after fire. Concretes comprising granite and calcareous aggregates were studied as they are commonly used around the world in civil engineering construction. The study considered different loading levels (0·3f_cd and 0·7f_cd), different cooling processes (cooling in air and by water jet) and varying maximum temperatures of concrete exposure (20, 300, 500 and 700°C). The mechanical properties of the concretes (residual compressive strength, direct and splitting tensile and flexural strengths and modulus of elasticity) after being subjected to high temperatures were studied. High temperatures and sudden cooling of the concrete showed a negative effect on its residual mechanical properties. This effect was more significant for the residual compressive strength than for the other mechanical properties.