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 (using concentrated ammonium nitrate solution as a leachant) coupled with scanning electron microscopy-energy dispersive spectroscopy and differential scanning calorimetry-thermogravimetric 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 were also obtained for totally leached specimens containing nanosilica, as a result of the ability of this admixture to consume portlandite during cement hydration and then reduce the porosity associated with portlandite dissolution during leaching.
Leaching behaviour of cement pastes containing nanosilica / M., Berra; F., Carassiti; Mangialardi, Teresa; Paolini, Antonio Evangelista; Marco, Sebastiani. - In: ADVANCES IN CEMENT RESEARCH. - ISSN 0951-7197. - STAMPA. - 25:6(2013), pp. 352-361. [10.1680/adcr.12.00056]
Leaching behaviour of cement pastes containing nanosilica
MANGIALARDI, Teresa;PAOLINI, Antonio Evangelista;
2013
Abstract
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 (using concentrated ammonium nitrate solution as a leachant) coupled with scanning electron microscopy-energy dispersive spectroscopy and differential scanning calorimetry-thermogravimetric 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 were also obtained for totally leached specimens containing nanosilica, as a result of the ability of this admixture to consume portlandite during cement hydration and then reduce the porosity associated with portlandite dissolution during leaching.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.