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a b s t r a c tIn this study two different types of nano-silica (nS) were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD), but produced through two different processes: fumed powder silica and precipitated silica in colloidal suspension. The influence of nano-silica on SCC was investigated with respect to the properties of concrete in fresh (workability) and hardened state (mechanical properties and durability). Additionally, the densification of the microstructure of the hardened concrete was verified by SEM and EDS analyses. The obtained results demonstrate that nano-silica efficiently used in SCC can improve its mechanical properties and durability. Considering the reactivity of the two applied nano-silicas, the colloidal type showed a higher reactivity at early age, which influenced the final SCC properties.
In this study, three different types of nano-silica were applied in self-compacting concrete (SCC), one produced by the controlled dissolution of the olivine mineral and two having similar particle size distributions (PSD), but produced through two different processes: fumed powder nano-silica and precipitated silica in colloidal suspension. The influence of the nano-silica on SCC was investigated with respect to the properties of the concrete in fresh (workability) and hardened state (durability properties). Additionally, the densification of the microstructure of the hardened concrete was analyzed by SEM and EDS techniques. The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its durability properties. Considering the reactivity of the different nano-silica studied, the colloidal type showed a higher reactivity at early age, which influenced the final SCC properties.
Nano-silica, one of the substances boosting the field of nanomaterials, can be produced by dissolving olivine in acid. The dissolution of olivine is a convenient alternative route to the existing methods of nano-silica production (neutralization of sodium silicate and flame hydrolysis) because the olivine dissolution is a low temperature process making this method cheaper and greener. Furthermore, this process can use waste olivine materials for the production of nano-silica. The produced nano-silica has a specific surface area between 100 and 400 m2/g; a primary particle size between 10 and 25 nm, which is agglomerated in clusters; and an impurity content below 5 wt.%. In addition, olivine nano-silica can be classified as a pozzolanic material with an activity index of 101%. The optimum replacement level of olivine nano-silica in conventional vibrated concrete is around 5% by volume resulting in: 1) a compressive strength increase of 20%; 2) a CO2 emission reduction of 3%. Therefore, the use of the olivine nano-silica in CVC does not only improve the compressive strength but also reduce the CO2 emissions.
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