An isothermal heat flow calorimeter for large-volume applications

Design, construction, calibration, and testing of a new isothermal heat flow calorimeter suitable for investigation of large-volume specimens are presented. The measuring vessel has the volume of 1370 cm, and the calorimeter allows for the measurement at surrounding air temperatures of 5-60 °C. A practical application of the device is demonstrated at the determination of specific hydration heat of cement paste and concrete with silicaaggregate size of up to 16 mm, having the same water/ cement ratio. The differences over the whole measuring time period of about 100 h are lower than 2% which indicates a good potential of the calorimeter for the measurement of total hydration heat of composite materials. A reference measurement of hydration heat of cement paste using common isothermal heat flow calorimeter with the measuring vessel of 1 cm shows an agreement within ±7%, which seems acceptable, taking into account the heat transport processes in the far larger specimens. The designed calorimeter may find use in future also in other applications where larger specimens are required, such as the measurement of adsorption heat, solution heat, various reaction heats, and enthalpy of liquid-solid transition in heterogeneous systems with large representative elementary volumes. © Akadémiai Kiadó, Budapest, Hungary 2011.