Concrete at high temperatures above 1000/spl deg/C

Abstract

Ordinary concrete samples made from the most common Portland Type I cement as well as some uncommon glossy-looking concrete lumps collected from an actual fire scene have been examined using thermal gravity analysis (TGA), differential thermal analysis (DTA), X-ray diffraction, and scanning electron microscope/energy dispersive X-ray spectrometry (SEM/EDX) with the aid of an unsealed furnace. Changes in crystallography, color, appearance, shape, density, and elemental composition with respect to temperature are carefully examined. Concrete rapidly losses all of its strength when exposed to high temperatures above 900/spl deg/C. As the temperature exceed 1200/spl deg/C, concrete tends to melt and yield numerous lumps or awls, even though each of its components has an extremely high melting point. The atmospheric current and the classes and amounts of the combustible materials at the fire scene as well as the structure of the construction can further influence the distribution of the lumps or awls. It is therefore very important for fire fighters and fire investigators to be aware of these aspects so as to do a safer and better job. A sufficient amount of high molecular-weight organic polymers with the aid of a good air supply is most likely to result in high temperatures exceeding 1200/spl deg/C.<>