Performance of Portland cement pastes containing nano-silica and different types of silica

This work compares the influence of nano-silica with three different silica-based materials (quartz, ultra fine quartz, and silica fume) on hydration, rheology, porous structure, and compression strength in cement pastes with 2.5% cement replacement. Results of calorimetry showed that the inclusion of the silica fume and of nano-silica resulted in an acceleration of hydration of the pastes. In regard to quartz, no change in comparison to the reference was observed until a median particle size of 0.6 mu m was reached. The use of nano-silica and silica fume was responsible for refinement of the porous structure and for an increase in compressive strength of the paste in comparison to the reference, caused by their role on heterogeneous nucleation and pozzolanic reactivity. On the other hand, quartz and ultrafine quartz did not have a marked effect on these properties. The rheological properties were also found to improve with addition of the different silicas. (C) 2017 Elsevier Ltd. All rights reserved.