Effect of White-Portland cement containing micro and nano silica on the mechanical and freeze-thaw properties of self compacting mortars

This study concentrated to investigate the influences of white-Portland cement (W-PC) containing silica fume (SF: micro-silica (mu Si) and nano-silica (nSi)) as replacement (2-4 wt%) on mechanical (strength and durability), physical and microstructural behaviors of self-compacting mortars (SCMs) fabricated at 0.48-0.63 w/b ratios. In keeping with these purposes, besides of carrying out the workability (mini-slump flow: M-SF and V-funnel: V-F) experiments of SCMs, the mechanical and microstructural tests implemented were: unconfined compressive strength (UCS), flexural strength (FS), freeze-thaw (F-T) and scanning electron microscope (SEM) analysis. The outcomes displayed that, in comparison with the control, replacing W-PC by SF (particularly nSi) enhanced the UCS and FS, resisted against F-T durability by lowering the strength losses in UCS and FS. The ameliorated microstructure resulting in a reduction in the number and/or a narrowing in the size of micro-cracks and pores contributed to generate a more compact and consolidated SCM structure for the improving of strength and durability due of pore-filling effect and superior pozzolanic characteristics of mu Si and especially nSi, this in turn reduced the permeability of SCM, which has a significant effect on the strength and durability behaviors of the SCM.