The Effect of Biochar on the Dispersion Stability of Graphene Oxide in Alkaline Cement Solution

Graphene oxide nanosheets have captured researchers’ interest due to unique morphology and remarkable mechanical properties, positioning them as promising supplementary materials for concrete. Nonetheless, a significant challenge of using graphene oxide in cement-based materials is its poor dispersion in alkaline cement solution. This study investigates the effect of using biochar as a dispersive agent for graphene oxide in both water and cement pore solution. In biochar-free samples, graphene oxide is observed to agglomerate immediately in cement pore solution and form palm tree leaf-like clusters, whereas biochar interacts with reactive cations and trap these cations within its microporous structure. This interaction results in the formation of C–S–H gel-like substances on the surface of biochar-cement and hence the concentration of cations near the functional groups of graphene oxide decreases, leading to significantly improved dispersion. In addition, it has been found that incorporating polycarboxylate ether-based superplasticizer further improves the dispersion stability of graphene oxide in cement pore solution. The results of this study could be the starting point for future researchers to use biochar as a dispersive agent for graphene oxide in cementitious composites. Due to the carbon-negative nature of biochar, cementitious composites containing graphene oxide and biochar will possess not only excellent mechanical and durability properties but also offer significant environmental benefits.