ASSESSMENT OF MATERIAL PROPERTIES OF CONCRETE GRAVITY DAMS – AN INDIAN CASE STUDY
Differential Thermal Analysis (DTA) are techniques in which the physical property of a substance is measured as a function of temperature when the substance is subjected to a controlled temperature programme. In DTA, the temperature difference between the substance and reference material is measured as a function of temperature. When the substance and reference material are subjected to the same temperature controlled programme the Differential Thermogram is a plot between the temperature difference of substance and reference material on one axis, and temperature or time on the other. The reference material is a known substance which is thermally inactive over the whole temperature range of interest. The DTA thermogram records the difference in temperature (ΔT) in the form of endotherms and exotherms. An endotherm or endothermic peak is a peak where the temperature of the sample falls below that of the reference material, i.e. ΔT is negative, whereas an exotherm or exothermic peak is a peak where the temperature of the sample rises above that of the reference material, i.e. ΔT is positive. The concrete core samples from different locations are tested for DTA analysis, and typical test result are given in Figure 6. Based on the test result of the DTA analysis, it was seen that there was the presence of unreacted calcium hydroxide and silica in all the samples.
Figure 6. Typical DTA curve for concrete sample of dam
Vol XXXII Issue 1
DAM ENGINEERING
15
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