Abstract
For a controlled particle size distribution, nano-silica was added to three different cements. The chemical and mineralogical compositions of the cements were characterized by fluorescence and X-ray diffraction. The granulometric distributions of cements and nano-silicas were obtained by laser granulometry and dynamic lightning scattering. The specific surface area of the raw materials was determined by gas adsorption. The effect of nano-silica and type of cement on rheological behavior was evaluated by rotational rheometry. The mechanical performance was investigated through the compression strength. The microstructural analysis was performed by scanning electron microscopy. The water demand and the consumption of dispersant increases according to the nano-silica content. The reduction in the inter-particle separation, and the agglomeration of nano-silica led to an increase in the viscosity of the suspension. The mechanical performance was directly affected by the specific surface area of the cements. Microstructural analysis showed that nano-silica changed from a layered adsorbed structure, to a porous or agglomerated structure.
Highlights
The use of nano-materials is a current trend, which can contribute to the improvement of the mechanical performance of cement-based materials
The present study evaluates controlled granulometries of nano-silica as an addition to different cements
The dispersant consumption and water demand of the suspensions were directly affected by the incorporation of nano-silica
Summary
The use of nano-materials is a current trend, which can contribute to the improvement of the mechanical performance of cement-based materials. For nano-silica obtained by sol-gel processing from ash of rice husk, Lima et al (2011) presented a gain on the compressive strength of the mixtures formulated with 2.5 and 5 wt %-1, replacing the cement mass, when compared to the reference mixture without the nano-silica. The authors suggested that optimum content of nano-silica, considering the compressive strength, does not depend on size of the particles in these nano-silica suspensions. The authors showed that compressive strength of mixtures varies according to the water/powder ratio and to the specific surface area of nano-silica. Comparing powdered nano-silica of different sizes, Givi, Rashid, Aziz and Salleh (2010) revealed that the optimum content of nano-silica, considering the compressive strength, varies according to the particle size of nano-silica
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