Study of the development of hydration of ternary cement pastes using X-ray computed microtomography, XRD-Rietveld method, TG/DTG, DSC, calorimetry and FTIR techniques

This paper analyzes and discusses in depth the development of hydration of ternary cement pastes with silica fume (8%) and nano-silica (3%), with water/binder (w/b) ratios of 0.4 and 0.6 up the age of 28 days. The study was based on parameters obtained from X-ray computed microtomography (mu CT), XRD-Rietveld Method, TG/DTG/DSC analysis, calorimetry and FTIR techniques. As expected, a reduction in porosity and a densification of the microstructure were observed in these cementitious systems modified with mineral additions. This was potentiated by a complex system made up of multidimensional binding particles (from the nanoscale to the microscale - particles of nano-silica, silica fume and Portland cement), which provided an acceleration of hydration and pozzolanic reactions at all ages. As a result, especially from the pozzolanic activities, it was verified a significant reduction in the amount of calcium hydroxide (CH) followed by increasing in the amount of C-S-H. This work showed the role of the mineral additions used in this research (under ternary condition) at early ages for pastes and its effect on the hydration kinetics. Besides that, the effect of water on later ages on pastes studied was presented. Finally, the positive impact on concrete durability properties was discussed in terms of scientific arguments.