Effect of the addition of nanoparticles ofCaCO3and different water-to-powder ratios on the physicochemical properties of white Portland cement

The addition of calcium carbonate nanoparticles (nano-CaCO3) accelerates the hydration of Portland cement improving its mechanical properties. Conversely, nano-CaCO(3)addition leads to reduction in the water required during initial PC hydration. Therefore, the use of a correct water-to-powder ratio is fundamental for manipulating this hydraulic cement. This study evaluated the effect of nano-CaCO(3)addition and different water-to-powder ratios on the physicochemical properties of white Portland cement (WPC). WPC was associated to different concentrations of nano-CaCO3, and the following experimental groups were created: G1a (no nano-CaCO3); G2a (0.5% nano-CaCO3), G3a (1% nano-CaCO3), G4a (2% nano-CaCO3), and G5a (5% nano-CaCO3). The setting-time (ST), compressive strength (CS), dimensional change (DC), solubility (S), and pH were assessed (24 hr and 30 days). Next, WPC + 5% nano-CaCO(3)was manipulated varying the water-to-powder ratio: G1b (WPC/0.33 ml); G2b (WPC/nano-CaCO3/0.33 ml); G3b (WPC/0.29 ml); G4b (WPC/nano-CaCO3/0.29 ml); G5b (WPC/0.26 ml); and G6b (WPC/nano-CaCO3/0.26 ml). The tests were repeated. The data analysis (2-way ANOVA and Tukey test,alpha= 5%) demonstrated that ST was shorter for samples containing nano-CaCO3(p < .05). Reduction in CS was observed for all groups at 30 days, except G5a, G2b, and G6b (p < .05). DC and S had no statistical difference among groups (p > .05) independently of nano-CaCO(3)water-to-powder ratio. After 30 days, there was significant reduction in pH for G3a and G6b (p < .05). The different concentrations of nano-CaCO(3)and water-to-powder ratios affected the physicochemical properties of WPC, especially the setting-time and compressive strength.

Automated summary

The addition of nano-CaCO3 accelerates the hydration of Portland cement and improves its mechanical properties. The correct water-to-powder ratio is essential for manipulating the hydraulic cement. Different concentrations of nano-CaCO3 and water-to-powder ratios affect the physicochemical properties of white Portland cement, especially setting-time and compressive strength.