Improvement on mechanical and piezoresistivity properties of cementitious binder by using surface oxidized multi-wall carbon nanotubes

Two types of the cementitious binders (MWNT/CB, AMNT/CB) filled with 0.5 wt.% multi-wall carbon nanotube (MWNT), and acid-treatment MWNT (AMNT) were prepared. The surfaces of MWNT and AMNT were firstly characterized with TEM micrograph and FT-IR spectrum before and after acid oxidation. The electrical resistivities (ρ) and the longitudinal strains (ε₁) of two cured nanocomposites under cyclic compressive stress (σ) are real-time collected, in order to investigate their piezoresistivity properties, associated with mechanical behaviors. On one hand, acid treatment can enhance interface bonding between AMNT and cementitious binder decorated with some hydrophilic groups, resulting in some mechanical improvements; on the other hand, it causes better distribution and more network pathway, AMNT/CB has resultantly balanced piezoresistivity property with regular and consistent variation of ρ following the σ, or the ε₁, and fixed stress/strain sensitivity (around 62), compared to that of MWNT/CB.