Experimental testing on the residual mechanical properties of ordinary concretes after fire

Concrete is known to have an enhanced behaviour in fire when comparing with bare steel, however there are some chemical and physical transformations in function of temperature that may compromise this performance. The mechanical and thermal properties of concrete at high temperatures and after fire have changes that have been evaluated in a lot of works around the World, however this is still an open field where a lot of research is needed. This paper summarizes the results of an experimental research to assess the residual mechanical properties of ordinary concretes after fire. It was studied the influence of the fire extinguishing methods, the maximum temperature that the concrete was subjected to and the loading level on the residual mechanical properties of calcareous and granite aggregate concretes. The properties studied were the residual compressive, tensile, splitting and flexural strengths and modulus of elasticity. Four levels of temperature; 20ºC, 300ºC, 500ºC and 700ºC; two loading levels (0.3fcd and 0.7fcd) and two cooling processes (cooling in the air and by water jet) were tested. The results showed that the mechanical properties of concretes are affected by the cooling process (fire extinguishing methods) used beyond the high temperatures and loading levels that were subjected to