abstract
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.
keywords
NANO-SIO2; PARTICLES; CONCRETE
subject category
Construction & Building Technology; Engineering; Materials Science
authors
Senff, L; Labrincha, JA; Ferreira, VM; Hotza, D; Repette, WL
our authors
João António Labrincha Baptista
Full professor
Victor Miguel Carneiro de Sousa Ferreira
Associate Professoracknowledgements
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.