Portland cement matrix containing micro and nano-silica

Reference Presenter Authors
04-008 Thiago Melanda Mendes Mendes, T.M.(Universidade Tecnológica Federal do Paraná); Repette, W.L.(Universidade Federal de Santa Catarina); This study aims to evaluate mechanical and rheological properties, as well the microstructure of Portland cement matrix containing nano-silica. Pure clinker and two different Portland cements were tested; the particle size distribution of matrix was modified by the incorporation of 11, 6.2, 3.2, 1.7, 0.85 and 0.42 wt.% of nano-silica. The water demand and the consumption of dispersant were adjusted, and rheological properties were measured by rotational rheometry. Mechanical performance was evaluated by compressive strength. Scanning Electron Microscopy was used to evaluate the microstructure of Portland cement matrix. The high specific surface area of nano-silica leads to an increasing on the water demand and, on the consume of dispersant by the suspensions. An increasing on apparent yield stress and viscosity of Portland cement matrix was verified, as a consequence of the reduction on the inter particle separation (IPS) of these suspensions. Mechanical performance was directly affect by the specific surface area (SSA) of studied Portland cements, and a reduction in mechanical performance was achieved due the increasing on the open porosity, resulting from water demand and agglomeration of nano-particles. According to the content of nano-silica, the microstructure of Portland cement matrix changes from an agglomerate of nano-particles into a porous structured, leading to the better mechanical behavior of the mixtures studied.
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