Early Hydration of Portland Cement

Abstract: The production of cement is responsible for approximately 7 % of the total CO2 emissions caused by man. To compensate for high energy consumption and CO2 emission, thus making the utilization of concrete more sustainable, several strategies can be used. Regardless of the approach used to construct the ultimate sustainable concrete, tools to evaluate the effects of the efforts are needed. In this work methodologies whereby Fourier Transform Infrared (FTIR) spectroscopy can be made use of, both in situ and ex situ, have been proposed and validated by means of complementary techniques including scanning electron microscopy, Vicat, and isothermal calorimetry. The FTIR techniques were proven to offer powerful tools for monitoring the complex chemical reactions taking place during the first day of Portland cement hydration. Sulfate transformations and interplay between hydration and carbonation are two examples of cement chemistry which has been addressed. The complementarity of isothermal calorimetry and in situ FTIR was demonstrated in particular. Usefulness of the latter for the study of the first stages of cement hydration emerges. The novel approach offers detailed chemical information which allows for the evaluation of additives regarding the nature of their effects on the overall cement performance. In this spirit, the impacts of colloidal nano-silica (CNS), sodium hydroxide and calcium chloride were described. This work hopes to contribute a chemical analytic tool to serve in the quest for sustainability of built environment with regard to energy and materials.