Effect of the addition of nanoparticles of CaCO₃ and different water‐to‐powder ratios on the physicochemical properties of white Portland cement

Abstract

The addition of calcium carbonate nanoparticles (nano-CaCO 3) 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-CaCO 3 , and the following experimental groups were created: G1a (no nano-CaCO 3); G2a (0.5% nano-CaCO 3), G3a (1% nano-CaCO 3), G4a (2% nano-CaCO 3), and G5a (5% nano-CaCO 3). 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-CaCO 3 /0.33 ml); G3b (WPC/0.29 ml); G4b (WPC/nano-CaCO 3 /0.29 ml); G5b (WPC/0.26 ml); and G6b (WPC/nano-CaCO 3 /0.26 ml). The tests were repeated. The data analysis (2-way ANOVA and Tukey test, α = 5%) demonstrated that ST was shorter for samples containing nano-CaCO 3 (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-topowder 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.

Portland Cement: An Overview as a Root Repair Material

“…Carbonates such as sodium carbonate and calcium carbonate are another group of mostly used accelerators, which act as nucleating agents [ 54 ]. Sodium carbonate and sodium bicarbonate decrease the initial and final setting times of Portland cement by enhancing the formation of ettringite and can improve the early age compressive strength of material during the first 7 days, but they can deteriorate it at later ages by replacing the calcium and sodium ions and consequently disintegrating the C-S-H gel structure [ 50 , 55 – 58 ]. Nitrite- and nitrate-based accelerators have shown similar behavior.…”