Regulation of carbon nanotubes on internal humidity of concrete with recycled tire rubber: Mechanism analysis and modeling

Abstract

As an eco-friendly nanocomposite material, carbon nanotubes (CNTs) reinforced rubberized concrete (CNTCRC) has the potential to enhance the shrinkage of concrete at nano-scale. The internal relative humidity (IRH) of concrete is the main driving force of shrinkage, which can effectively control the shrinkage of concrete. This study evaluated the effect of CNTs on the humidity of rubberized concrete through humidity monitoring experiments. Molecular dynamics (MD) techniques were utilized to explore the mechanism of CNTs on humidity regulation. A two-stage model considering the cement hydration and humidity diffusion was established to simulate the humidity of CNTCRC numerically. The MD simulation results indicated that the vacuum layer around CNTs caused by van der Waals forces accelerated the hydration kinetics by activating water molecules. When the CNTs content was 0.1 %, the ultimate degree of cement hydration increased by 8 %, and the humidity diffusion coefficient reduced by 41 %. The humidity model robustly predicted the humidity distribution in CNTCRC under sealed and drying conditions. 0.1 % CNTs is recommended to achieve an optimal balance between mechanical strength and shrinkage performance of rubberized concrete.