Effect of graphene nanoplatelets on the behaviour of cementitious compounds: an experimental investigation.

Concrete has an inherent tendency towards brittle behaviour and micro-cracking, which can further degrade the durability in harsh environments. Graphene nanoplatelets (GNPs) have been recognized as highly potential nano-enhancements for improving the mechanical and durability performance of cement-based materials. While there is extensive literature evaluating the impact of GNPs on concrete, it is generally limited to low amounts of graphene, one or two properties assessed, and therefore, the overall impact of varying amounts of GNPs on the material remains unclear. The purpose of this research was to provide a thorough experimental assessment of how GNPs affect the fresh-state, mechanical and long-term durability properties of the concrete. Twenty-five different concretes at five strength levels (M20–M40) were made using GNPs at concentrations ranging from 0 to 20% by weight of cement. The experimental portion of this project included evaluations of fresh-state properties (workability and setting characteristics), mechanical properties (compressive strength, flexural strength, split tensile strength), and durability properties (water absorption, sulfate resistance, and rapid chloride ion permeation). The results show that incorporating GNP into cementitious composite systems significantly enhance their properties and performance. The compressive strength of the GNP containing systems reached around 47Mpa while the flexural strength of the same systems reached 7.3 Mpa. The split tensile strength of these systems showed significant improvement in comparison to control systems. Additionally, the durability of the systems was significantly enhanced with respect to water absorption (reduced from around 4.5 to 1.6%), sulphate expansion (from 12.5% to 3.8%) and chloride permeability (reduced to approximately 650 coulombs) all demonstrating substantial pore refinement and resistance to aggressive ions. The above improvements have been attributed to the nano-filling effect of GNP; nucleation of hydrates during curing; and crack bridging effects caused by the presence of GNP. The collective effects of GNP provide microstructural density through the formation of a well bonded matrix and improved interface. The highest strength and durability were achieved with 20% GNP, however a GNP dosage range of 5–10% GNP was determined to be the optimal balance of performance and workability. These data demonstrate the strong potential of GNP as a means to develop high performance and durable nano engineered concrete systems for the development of advanced structural and infrastructures systems.