Investigation of the effects of graphene and graphene oxide nanoplatelets on the micro- and macro-properties of cementitious materials

• Durability related properties of GNPs- and GONPs-reinforced concrete are investigated.
• Micro-characterization is used to quantify the effects of GNPs and GONPs on the microstructure of cement paste.
• Atomistic modeling qualitatively demonstrates the different mechanisms of GNPs and GONPs on freeze-and-thaw performance.

Recent research results discover that graphene nanoplatelets (GNPs) and graphene oxide nanoplatelets (GONPs) are capable of enhancing the smartness as well as improving the strength of cementitious materials by utilizing their unique mechanical, thermal and electrical properties. Although the graphene-reinforced concrete exhibits promising potentials in these studies, its application to construction practice demands for a deeper understanding of the effects of graphene nano-particles on the durability-related properties of concrete. To meet this need, this study is focused on the strength, corrosion resistance and freeze-and-thaw performance of graphene-reinforced cementitious materials. In this investigation, the mortar specimens reinforced by different types of GNPs and GONPs are tested and then compared with the benchmark samples. To capture the reinforcement mechanisms of graphene, nano-scale characterization is carried out with a focus on the microstructure of the cement paste around the graphene nano-particles. The observed microstructure morphology and modulus profile show that GNPs and GONPs can significantly reshape the microstructure of cement paste. Based on the micro-characterization, atomistic models of the graphene-reinforced C-S-H gels are constructed and the freeze-and-thaw process is simulated. It is found that in addition to the reshaped microstructure, the effects of graphene and graphene oxides on water migration in the nano-pores of cement paste play an important role in the frost resistance of graphene-reinforced concrete.