Effect of structurally different aluminosilicates on early-age hydration of calcium aluminate cement depending on temperature

Abstract

The work is concerned with the effect of two kinds of aluminosilicate addition with zeolitic and non-zeolitic structure on early-age hydration of calcium aluminate cement at different curing temperatures. The hydration kinetics was examined by conductometry and the formed hydrates were recognized by thermal analysis, X-ray diffraction and FTIR spectroscopy. In the conductometric investigations a specific cell was designed to examine the setting and hardening of cement paste by simultaneous monitoring electrical conductivity and internal temperature versus time.It was found that the studied aluminosilicates have a different interaction mechanism in the induction stage and their influence on the kinetics of the hydration process varies with temperature. The non-zeolitic addition, regardless of the curing temperature, acts as an accelerator but the zeolitic, depending on the temperature, acts as a retarder or an accelerator of setting and hardening of calcium aluminate cement. The effect was mainly attributed to the different structure of the aluminosilicates. It was observed that both mineral additions reduce the self-heating and thus can prevent the hydrogarnet formation already during early hydration process. However, the initially formed hydration products depend principally on the temperature than on the used amount of the aluminosilicates.