Investigation of the dispersion of multi-layer graphene nanoplatelets in cement composites using different superplasticiser treatments

Abstract

The emergence of nanomaterials research over the past decades, allows the construction sector to turn the cement-based structures into fully digitised, cognitive assets with additional functionalities and improved durability and sustainability performance. Multi-layer graphene nanoplatelets (GNPs) is one such nanomaterial that could be used in cementitious structures. However, the homogenous dispersion of commercially available GNPs has been found to be a key challenge in the literature. This study aimed to develop a practical dispersion protocol to promote the use of GNPs in cementitious systems. Four different commonly used superplasticisers were tested, including a lignosulphonate, a naphthalene-based and two polycarboxylates, along with sonication. The GNPs were characterised using Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and X-Ray Diffraction analysis (XRD). The effect of the different superplasticisers on the GNPs dispersion in water was tested with zeta-potential, while UV–Vis spectroscopy was used to examine the effect of the superplasticiser dosage. This was followed by rheology testing that assessed the impact of the superplasticisers on dispersing the GNPs in cement paste. It was found that dispersion of GNPs in water with sonication is not sufficient and a chemical treatment is also needed. The polycarboxylates that work by a steric hindrance mechanism, by physically separating the GNPs and cement particles, were found to be more effective compared to the plasticisers that work by electrostatic repulsion. This research provides a practical dispersion protocol for GNPs in cementitious systems to promote more advanced construction materials.