Title : VALIDATION OF THE HYPOTHESES MADE IN THE DESIGN OF FIRE RESISTANT CONCRETES USING PHYSICOCHEMICAL TECHNIQUES: A CASE STUDY
Authors : E. Menendez(1), L. Vega(2) and C. Andrade(
Publication : 13th – 16th February 2013
Volume :
Pages : 12-Jan
Price : 250
Abstract : To design for the resistance of concrete against fire, some hypotheses for the analysis are used. These hypotheses are based on the use of parametric fire curves. The use of these curves can locate the flux of temperatures inside the concrete that are represented as isotherm curves at different depths from the exposed surface. From these curves, the depth of recovery necessary to maintain the fire resistance during a certain period of time is fixed. One of the simplified methods to evaluate the residual strength of concrete elements exposed to fire is the method of the 500ºC isotherm. According to this method, the residual strength of structural concrete elements is calculated after eliminating the depth of concrete that has been exposed to temperatures higher than 500ºC. The use of different physico-chemical techniques for concrete analysis permits the location of the depth of the isotherm 500. These techniques are mainly X-ray diffraction and simultaneous differential thermal analysis and themogravimetry. The proposed methodology consists of analyzing concrete layers, from the exposed surface to the interior determining the degree of portlandite decomposition. Also, in this work, this methodology is applied to a concrete structure severely damaged by fire, the 106-meter high Windsord building in Madrid, which was exposed for more than 12 hours to a fire in 2006. The experimental results are using to compare the thickness affected by temperatures higher than 500ºC with the recovery thickness used in the analysis to design a concrete that are fire resistant until a certain time, R90, R60, etc. Finally, the consistency between the behavior of the fire-damaged concrete and the theoretical requirements of the regulations is checked.