Development of nano-graphene cementitious composites (NGCC)

Abstract

Ordinary Portland cement (OPC) is the main constituent of concrete works as a principal binder for aggregates and intrinsically transmits the brittleness into concrete through the formation of hydration crystals in the cement microstructure. A number of nano cementitious composites were developed in recent years to offset the brittleness with newly discovered nanomaterials and the most prevalent among those is the graphene oxide (GO). The main objective of this PhD research work is to develop nano graphene cementitious composites (NGCC) using low cost, two dimensional (2D) graphene nanoplatelets (GNPs) and one dimensional (1D) graphited carbon nanofibres (GCNFs) with unique conical surface morphology. The GNPs were sourced synthesised in an environmental friendly way via plasma exfoliation whereas, GCNFs were manufactured through catalytic vapour grown method. The project further investigated the effect of these nanomaterials in regulating the distinctive microstructure of cement matrix leading to enhance its mechanical properties. Three different types of high-performance NGCC namely NGCC-Dot, NGCC-Fnt and NGCC-CNF, are developed by activating pristine GNPs (G-Dot), functionalised GNPs (G-Fnt) and graphited nanofibers (G-CNFs) into the cement matrix respectively. It is found through various characterization and experimental techniques that both GNPs and GCNFs regulated the cement microstructure and influenced the mechanical properties of NGCC uniquely. A remarkable increase in the flexural and the tensile strength of newly developed NGCC has been achieved and that could be attributed to the formation of distinctive microstructure regulated by catalytic activation of these nanomaterials. The shape (1D, 2D) and unique morphology of these nanomaterials played a vital role in the mechanism of crystal formation to regulate the cement microstructure. Based on the observations of test results and comprehensive characterization, the possible mechanisms of crystal formation and development of distinctive microstructure of NGCC has been established which has then proceeded to the development of a physical model for NGCC development.