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Author(s):	Unterderweide, Klaus; Rigo, Ellen
Title:
Abstract:	Für die Planung von Instandsetzungsmaßnahmen nach einem Brand stellt sich die Frage, welche maximale Temperatur erreicht wurde. Die bisher praktizierten Untersuchungen beschränkten sich auf röntgenographische Messungen oder thermoanalytische Untersuchungen bzw. Porositätsmessungen. Diese Methoden haben den Nachteil, dass die erfahrene Brandtemperatur nicht kontinuierlich nachgewiesen werden kann. Sie decken lediglich enge Temperaturbereiche ab. Im Rahmen der hier vorgestellten Untersuchungen wurde erstmals die Infrarot-Spektroskopie eingesetzt. Der große Vorteil hierbei ist, dass auch nicht-kristalline (amorphe) Anteile erfasst werden können. Es konnte gezeigt werden, dass die Temperatur die Lage der Si-O-Streckschwingungsbande der festigkeitsbestimmenden Calciumsilikathydrat-Phasen (CSH-Phasen) beeinflusst, wobei diese sich irreversibel mit zunehmender Temperatur zu niedrigeren Wellenzahlen verschiebt. Die Verschiebung ist vermutlich auf eine Depolymerisation der kettenförmigen Si-O-Si-Ketten der CSH-Phasen bis hin zum Monosilikat b-C2S zu erklären. A new approach to determine the maximum temperature of fire damaged reinforced concrete building elements. When a fire has damaged a reinforced concrete structure, an engineer has to work out a proper and efficient repair strategy. Because of the effect of the fire on the structural properties of the concrete and the steel, it is important to know the maximum temperature reached. Actually, methods like x-ray diffraction, thermogravimetry and mercury intrusion are used for this investigation. These methods can only determine a few temperature steps and can’t provide a stepless thermometer. From these methods no step-less heat exposure can be drawn. For the first time the FTIR spectroscopy was used to determine the maximum temperature. This method has the advantage that the amorphous structures can be examined. It is shown that the wavenumber of the Si-O-stretching mode is a function of the temperature. The wavenumber decreases with increasing temperature. It should be noted that this correlation is independent from the time the sample is exposed to temperature. The decreases of the wavenumber is probably due to the fact that the Si-O-Si-chains of the CSH phases do depolymerise until monosilicate b-C2S.
Source:	Bauphysik 35 (2013), No. 5
Page/s:	323-327
Language of Publication:	German

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