Ceramics-Silikáty 54 (3) 269-276 (2010)

EFFECT OF TEMPERATURE UPON THE STRENGTH DEVELOPMENT RATE AND UPON THE HYDRATION KINETICS OF CEMENTS

Ľ. Ježo , T. Ifka , B. Cvopa , J. Škundová , V. Kovár , M. T. Palou

The effects of temperatures upon the properties and upon the hydration kinetics of three kinds of cements (Portland cement CEM I, blended cements CEM II/B and CEM III/A) have been undertaken and reported in this work. The rate at which the compressive strength increases depends on the ratio clinker/blast furnace slag and on temperature. Then, a new criterion “Index of temperature strength development” was introduced in order to characterise the rate at which the compressive and flexural strength increase with temperature and with time. Two types of calorimeter were used; the first one to determine the values of hydration heat under isothermal conduction, while the second was used to investigation the influence of temperatures upon the flow of hydration heat and subsequently to calculate the apparent activation energy. The activation energy (E_{CEM I} = 10.24 ±0.36 kJ kmol^-1, E_{CEM II/B} = 11.95 ±0.97 kJ kmol^-1, E_{CEM III/A} = 17.33 ± 0.60 kJ kmol^-1) of different cement was found strongly depending on the replacement ratio of blast furnace slag.

Keywords: Temperature, Strength, Index of temperature strength development, Hydration heat, Activation energy