Investigating the Effect of CNTs on Early Age Hydration and Autogenous Shrinkage of Cement Composite

Abstract

In this study, the effect of carbon nanotubes (CNTs) on the physical properties of cement composites was investigated. The mechanism of the change of autogenous shrinkage of CNTs-reinforced cement composites was also examined. In the experiments, ordinary Portland cement (OPC) and fly ash (FA) were used as binders, and 0.0, 0.1, 0.3, and 0.5% multi-walled CNTs (MWCNTs) were added to fabricate pastes. When the hydration heat was measured through isothermal calorimetry, it was found that CNTs accelerated the early age hydration of the pastes and that the hydration rate increased as the CNT content increased. The compressive strength was the highest when the CNT content was 0.1%. As the CNT content increased, the internal relative humidity (IRH) decreased and autogenous shrinkage showed a decreasing tendency. Through the analysis of the correlation between autogenous shrinkage and IRH, it was confirmed that the reduction in autogenous shrinkage due to the addition of CNTs resulted from the decrease in bulk strain.

Effects of Multi-Walled Carbon Nanotube Dosages and Sonication Time on Hydration Heat Evolution in Cementitious Composites

“…The experiment performed by Park and Choi [21] shows that the setting time of a cement composite with CNTs reduced proportionally to the amount of carbon nanotubes added by 2.4% and 3.0% for initial and final setting times, respectively. Therefore, it was concluded that CNTs accelerate the hydration process in the early stages by reducing its induction period; however, the influence in later hydration stages was not significant between different CNT amounts.…”

Reinforcement of Cement Nanocomposites through Optimization of Mixing Ratio between Carbon Nanotube and Polymer Dispersing Agent

“…Research on utilizing CNT as a construction material continues, capitalizing on its beneficial properties [3]. CNTs can act as a filler, effectively bridging the gaps among numerous pores formed during cement hydration [4,5]. In addition, owing to their substantial specific surface area, CNTs actively accelerate cement hydration, thereby contributing to the overall enhancement of the mechanical properties of cement [6].…”