Effect of thermal treatment of SiC nanowhiskers on rheological, hydration, mechanical and microstructure properties of Portland cement pastes

Utilization of Thermally Treated SiC Nanowhiskers and Superplasticizer for Cementitious Composite Production

“…Comparing the mixes with SP and a different content of NWs, the 0.50% NW content showed the highest strengths for both NT-NW and 500-NW. This agrees with the results presented in [ 23 ], in which the 0.50% content led to the greatest mechanical performances for NW-cement composites without SP. This suggests that, despite improving the dispersion of NWs and consequently the mechanical performance composite, SP cannot properly disperse the NWs when this nanomaterial is used above the optimum incorporation level.…”

“…This trend was associated with some factors: (i) the particle size of the NWs (much smaller than the cement) reduced the interparticle distance and increased the friction and the probability of collision between the particles, increasing the energy required to flow; (ii) the very high SSA of the NWs (10.64 m 2 /g for NT-NW and 11.51 m 2 /g for 500-NW compared with 0.33 m 2 /g for the cement) increased the surface interactions between the particles and consequently the trend for agglomeration; (iii) part of the mixing water was adsorbed on the surface of the hydrophilic NWs [12], reducing the amount of free water to lubricate the cement grains and increasing the relative particle concentration [30]; (iv) the rod-like shape of the NWs may hinder the relative movement between the grains. Similar results were reported by some authors when studying cementitious mixtures with NWs, CNTs, and carbon nanofibers [23,[31][32][33].…”

“…Azevedo et al [ 22 ] incorporated 0.25–1.00 wt % of raw SiC NWs in cementitious composites, observing increases of 107% and 75% in the flexural strength of the composite, respectively at 7 and 28 days of hydration when compared with plain cement paste. Azevedo et al [ 23 ] investigated the effect of thermal treatment of SiC NWs on the fresh and hardened properties of contentious composites without a superplasticizer. The authors found 28-day compressive and flexural strength improvements respectively of 43% and 50% when 0.50 wt % SiC NWs thermally treated at 500 °C were incorporated in comparison with plain cement paste.…”

Influence of Ultrasonication of Functionalized Carbon Nanotubes on the Rheology, Hydration, and Compressive Strength of Portland Cement Pastes

“…of CNT up to 0.10%. Additionally, the increase in yield stress caused by the incorporation of other nanomaterials has already been reported in the literature [55][56][57]. Mendoza Reales et al [56] observed that incorporating 1% NS in cement paste increased its static τ0 from 30 to 260 Pa. Hou et al [57] observed that the incorporation of 2.25% of colloidal NS increased the yield stress of paste from about 49 to 71 Pa (i.e., by 45%).…”

“…One of the few studies that show the detailed rheological characterization of CNT-reinforced cementitious pastes is that from Andrade Neto et al [53], which also found a progressive increase in yield stress with the increase of CNT up to 0.10%. Additionally, the increase in yield stress caused by the incorporation of other nanomaterials has already been reported in the literature [55][56][57]. Mendoza Reales et al [56] observed that incorporating 1% NS in cement paste increased its static τ 0 from 30 to 260 Pa. Hou et al [57] observed that the incorporation of 2.25% of colloidal NS increased the yield stress of paste from about 49 to 71 Pa (i.e., by 45%).…”