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The article examines the effect of nanosilica on the leaching behavior of cement pastes Portand tested for ultra-accelerated runoff, combined with a scanning electron microscope analysis and thermal analysis. E ‘was found that the addition of nano-silica improves the chemical resistance of the cement paste through a significant slowing of leaching and subsequent delay of the decrease of the compressive strength of the cement paste leached.
The influence of nanosilica (nanoscale-size particles of amorphous silica) on the leaching behaviour of Portland cement pastes made with a relatively low water/binder ratio (w/b = 0.36) and different nanosilica contents (0-3.8 wt.% of binder) was investigated through the use of an ultra-accelerated leaching test (concentrated ammonium nitrate solution as a leachant) coupled with SEM-EDS and DSC-TGA analyses. The effect of leaching on the physical and mechanical properties of such pastes was assessed and their chemical resistance to leaching was evaluated through a parametric model. It was found that the addition of nanosilica improves the chemical resistance of cement pastes by producing a significant leaching deceleration (up to 69%). As a result, the decay of compressive strength of leached specimens (about 60% reduction) is significantly retarded. Higher residual compressive strengths are also obtained for totally leached specimens containing nanosilica, as a result of the ability of this admixture of consuming portlandite during cement hydration and then reducing the porosity associated with portlandite dissolution during leaching.
Scarica Articolo ISI
31 Dicembre 2012
Sviluppo del Sistema e della Rete Elettrica nazionale (RETE 2012)