Effect of nano-silica on rheology and fresh properties of cement pastes and mortars


Amorphous nano-silica (nS) particles (0-2.5 wt%) by cement were incorporated in cement pastes and mortars, and their effect on the fresh state behaviour was analysed. Rheological tests showed that after 75 min from the mixing start, the mortar having 2.5 wt% nS shows insufficient flowability to allow its continuous monitoring in a Viskomat PC viscometer. The influence of nS content was better observed on yield stress when compared with plastic viscosity Values (the first increased about 66.5% while the latter just increased 3.6%). With nS addition, spread, setting time and the moment to reach the maximum temperature decreased 33%, 60% and 51.3%, respectively, when compared with samples without nS. X-ray diffraction showed presence Of Calcium hydroxide after 9 h in the sample with 2.5 wt% nS. The air content increased 79% and apparent density decreased 2.4% when nS was added. (C) 2009 Elsevier Ltd. All rights reserved.



subject category

Construction & Building Technology; Engineering; Materials Science


Senff, L; Labrincha, JA; Ferreira, VM; Hotza, D; Repette, WL

our authors


The authors acknowledge the support of CAPES, Brazil. The authors also thank Weber-Portugal, BASF, H.C. Starck Empowering High Tech Materials and Cimpor, for providing raw materials.

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