Single and combined impact of silica fumes with Functionalized multi-walled carbon Nanotubes and nano silica on performance of cement mortars composites

This present work aims to study the impact of single and combined effects of silica fumes (SF) with nano silica (NS) and functionalized multi walled carbon Nanotubes (MWCNTs) on physicomechanical and dynamic properties of cement mortars (CMs). The Portland cement (PC) was partially substituted with different ratios of SF, MWCNTs and NS which, firstly was individually substituted but Secondly, were added together. PC was individually substituted with 2, 4, 6, 8, 10 wt. % of SF then combined with 0.2, 0.4, 0.6, 0.8 and 1.0 wt. % of MWCNTs and 2, 4, 6, 8, 10 wt. % of NS which mixing together. The physicomechanical and dynamic properties such as compressive strength, bending strength, water consistency; both initial and final setting times were measured. The phases of hydration products of some selected samples were additionally investigated by using XRD analyses, the morphology of hardened samples was studied by SEM techniques and TEM showed the particle size of nanoparticles. The results illustrated that, the compressive strength of cement mortars (CM) which containing SF increasing by 27% at 28 days and 11 % for bending strength at early ages comparing to control sample. In combination with functionalized MWCNTS, the compressive and bending strengths increased by 36 and 17 % in case of CMs that containing 0.4 Wt.,% functionalized MWCNTs and 8 Wt.,% SF. additionally, the combination of SF with NS showed increment in compressive strength by 28 % at 8 Wt.,% SF and 8 Wt.,% NS, respectively. SEM-photos showed that CMs containing 0.4 Wt., % functionalized MWCNTs and 8 Wt., % SF had more compacting microstructure than control sample due to bridging effect of MWCNTs and pozzolanic effect of SF.