Flexural creep of multi-wall carbon nanotube reinforced cement based composites under high stress level

Different concentrations (0–0.2 wt.%) of multiwall carbon nanotubes (MWCNT) was used to improve the mechanical properties of cementitious composites. The first part of the work showed that adding 0.05 wt.% of MWCNT produced a maximum reinforcement in terms of flexural and compressive strength. The second, the role of MWCNT on mechanical strength improvement was investigated. MWCNTs can absorb water to weaken the cement hydration at the beginning, and then, release water to promote the hydration of cement. The third part focused on using a home-made four-point bending testing device to study the flexural creep behavior under high stress levels (70, 80 and 90% of the flexural strength) and the results are discussed in terms of creep strain and Poisson ratio difference. The data obtained were also compared with the empirical creep models and the creep coefficients obtained were agreement with that from the AASHTO model. Finally, a regression analysis was used to fit the creep compliance of MWCNTs reinforced cementitious composites for the range of conditions studied. The results showed that the creep compliance can be fitted by a power-law for a stress level below 0.85, while a linear function was obtained above.