Effect of carbon nanotubes on mechanical properties, and hydration process of face slab concrete at early ages

Early-age cracking of face slab concrete (FSC) is a complex problem related to the mechanical properties and hydration process (HP), representing a critical durability concern for concrete face rockfill dam. The excellent physical and chemical properties of Carbon nanotubes (CNTs) enable their potential to mitigate early-age cracking in FSC. This study investigated the potential application of the hydration kinetic model (Krstulovic-Dabic model) on FSC by incorporating CNTs and resulting structural changes in micro- and macro-scales. The mechanical performance of FSC was significantly enhanced by CNTs, particularly at 0.06 wt%, where the 3-day tensile strength reached the 7-day level of the unmodified control. The Krstulovic-Dabic model revealed that while CNTs delayed the early hydration of FSC, their impact on the later ages was clearly turned around. This reversal has been evidenced by a series of experimental analyses (X-ray diffraction, thermogravimetry , and isothermal calorimetry). This study revealed the relationship between the mechanical properties and early-age hydration process of CNTs-modified FSC, thereby offering insights for improving the early-age cracking resistance of FSC. • The application of the hydration kinetic model (K-D model) on FSC was assessed. • CNTs decreased the crystal orientation of CH. • The mechanical performance of FSC was significantly enhanced by incorporating CNTs. • CNTs delayed early hydration of FSC; their impact on later ages was turned around.