Architecture：Thermoanalytical Techniques.pdfVIP

1 1 Thermoanalytical Techniques 1.0 INTRODUCTION Thermal analysishas been defined by the International Confedera- tion of Thermal Analysis (ICTA) as a general term which covers a variety of techniques that record the physical and chemical changes occurring in a substance as a function of temperature.[1][2] This term, therefore, encom- passes many classical techniques such as thermogravimetry (TG), evolved gas analysis (EGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC), and the modern techniques, such as thermo- mechanical analysis (TMA) as well as dynamic mechanical analysis (DMA), and dilatometry, just to name a few. The application of thermal analysis to the study of construction materials stems from the fact that they undergo physicochemical changes on heating. 1 2 Chapter 1 - Thermoanalytical Techniques 2.0 CLASSICAL TECHNIQUES Ever since the invention of DSC, there has been much confusion over the difference between DTA and DSC. The exact ICTA definition of DTA is a method that monitors the temperature difference existing between a sample and a reference material as a function of time and/or temperature assuming that both sample and reference are subjected to the same environ- ment at a selected heating or cooling rate.[1][2] The plot of ∆T as a function of temperature is termed a DTA curve and endothermic transitions are plotted downward on the y-axis, while temperature (or time) is plotted on the x-axis. DSC, on the other hand, has been defined as a technique that records the energy (in the form of heat) required to yield a zero temperature difference between a substance and a reference, as a function of either temperature or time at a predetermined heating and/or cooling rate, once again assuming t