Influence of added nanosilica and/or silica fume on fresh and hardened properties of mortars and cement pastes

摘要

The rheological characterisation of mortars having low water content is difficult to perform due to internal friction between surface grains and also due to intense agglomeration of particles. In this paper, mortars and cement paste with additions of nanosilica (nS), silica fume (SF) and nS+SF were studied applying a factorial design methodology. Mortars with water/total solids ratios below 16% were characterised in the fresh state by rheological and flow table tests. Thus, all mixtures show suitable workability in both equipments. Compressive strength, setting time, air content, fresh apparent density, hydration temperature and X-ray diffraction were carried out. The optimum amount of nS and SF for each W/B ratio between 0·35 and 0·47 was determined by compressive strength at 28 days. For W/B0·43, nS reaches better performance. In general, nS addition affects the properties more significantly than SF.