▎ 摘　　要

Stable dispersion of graphene oxide (GO) nanosheets in cementitious environments has been remained an acute challenge in cement mortar nanocomposites. In this work, chitosan (CS) biopolymer is grafted onto GO nanosheets to improve their dispersion stability in the cementitious medium and overcome the agglomeration issue. The dispersion behavior of nanosheets is evaluated by visual observation, UV-vis spectroscopy, and zeta potential measurements. It is demonstrated that the amount of CS added to GO grafting reaction mixture controls the stability of nanosheets, and the nanosheets modified by the addition of 5 wt% CS in the grafting reaction mixture (GO-CS5) show the highest stability in the medium. A conceptual model is proposed to interpret the role of CS, as a strong metal chelating agent, on the agglomeration behavior of GO nanosheets. Moreover, the addition of GO-CS5 to cement mortar leads to lower fluidity loss while maintaining mechanical strength compared to the addition of GO due to better dispersion and interfacial interactions of GO-CS5 in cement.