Early and middle stages of multicomponent cement hydration under the effect of geothermal water and increased temperatures

Abstract

The study of early and middle stages of hydration in the systems composed of Portland cement Class G (PC) – silica fume (SF) – metakaolin (MK) and PC – SF – blast furnace slag (BFS) was performed by Isothermal calorimetry, Thermogravimetric, X-ray diffraction, and Fourier Transform Infrared analyses in the mid-IR region. The influence of composition, temperature (25, 60, and 80 °C), and hydration media (water and geothermal solution) was investigated. Geothermal solution delayed main hydration, however, considering the times of the calorimetric maxima at 25 °C, it led to the formation of hydration products with more polymerized structures in larger amounts than during the hydration process using water. At higher temperatures, the deceleration effect of the geothermal solution became less evident, nevertheless higher degree of silica polymerization and more hydration products were found in samples that were hydrated in water. Regardless of the hydration temperature, the hydration carried out in geothermal solution became more effective already after 40 h. The effect of fine additives advanced by higher temperatures resulted in accelerated hydration represented by faster depletion of gypsum. The presence of SO4-AFm and CO3-AFm phases was confirmed during the deceleration period of the hydration process using water and geothermal solution, respectively.