Multi-scale Study of Calcium Leaching in Cement Pastes with Silica Nanoparticles

Abstract

Calcium leaching is a degradation process consisting in the progressive dissolution of the cement paste as a consequence of the migration of the calcium ions to the aggressive solution. Although the most important changes take place at the nano- and micro-scale, their consequences are observed at every length scale. Within this work, a multi-scale approach combining a wide variety of experimen- tal techniques was used to study such phenomenon in cement pastes with silica nanoparticles. The experimental results proved that the pozzolanic reaction in- duced by the nanoparticles resulted in a C-S-H gel more stable chemically and with longer silicate chains. In addition, the reduction of the amount of portlandite gave place to pastes with improved microstructure. As a consequence, the per- formances of such pastes were greatly enhanced both before and during the degra- dation process.