Effect of nano-SiO2 and nano-TiO2 addition on the rheological behavior and the hardened properties of cement mortars

This paper reports on the use of nano-SiO2 (nS) and nano-TiO2 (nT) in cement pastes and mortars. Samples with 0-3 wt.% nS, 0-12 wt.% nT and 0.5 water/binder weight ratio were prepared. Rheological and flow table measurements were carried out. In addition, the design of experiments was applied to validate the results found. The temperature of hydration and compressive strength with 28 days was also determined. In general, mortars exhibited noticeable differences in the rheological behavior, but less evident in temperature of hydration and compressive strength. The values of torque, yield stress and plastic viscosity of mortars with nanoadditives increased significantly, reducing the open testing time in rheology tests. Meanwhile, the flow table values reduced. In addition, spread on table and initial yield stress exhibited a power correlation, while the spread on table and plastic viscosity did not show any special relationship. The results of kinetics of hydration followed the same tendency found by rheology, in which samples with higher amounts of nS and nT showed remarkable changes in relation to the samples without nanoadditives. Mechanical properties were not significantly affected by nanoparticles in the range considered in this work. (C) 2011 Elsevier B.V. All rights reserved.