MEASURING CASTABLE RHEOLOGY BY EXOTHERMIC PROFILE

As castable placement technology advances, further information is needed to assess the rheological properties. Flowability, set time and strength gain measurements hav e been successfully used to assess rheology, however a growing number of laboratories are supplementing these measurements with an Exothermic Profile measurement of the castable and also the raw materials used to formulate the castable. The heat of hydration of Portland cement and Calcium Aluminate Cement are on the same order at about 500 kJ/kg. Because Calcium Aluminate Cement releases this energy over a much shorter period of time, this reaction is easy to measure, even when the cement contents are low. Certain deflocculated castables also exhibit a heat rise during initial f locculation, well before hydration, marking the end of working time. Because these measurements can be automated with a thermocouple and a PC, the test is easy to set up and run. Creating an exothermic profile on a neat cement paste gives information about the composition and reactivity of that cement and may be useful for QA purposes.This paper will present practical examples of the above-mentioned topics and attempt to explain the reason for the occurrences. Resul ts and discussion concerning the repeatability and reproducibility of these tests will also be presented.