Exploring optimal dispersion process parameters for fabrication of graphene-reinforced cement composites

Graphene and its derivatives have been studied as nano-reinforcement in cement-based composites to improve their mechanical, transport and durability characteristics. However, the agglomeration effect due to the strong van der Waals force between graphene sheets makes the uniform dispersion difficult and limit the efficacy of graphene. The goal of this paper is to determine an optimal dispersion process for incorporating graphene nanoplatelets (GNPs) into cement-based composites. Surfactant-assisted sonication was used for the dispersion of graphene sheets. The effects of sonication amplitude, sonication duration, sample volume, surfactant type, and surfactant-to-GNP ratio on the dispersion performance were studied. As for the surfactant type, two polycarboxylate superplasticizers, two ionic surfactants, and one non-ionic surfactant were considered. Taguchi method of experimental design with an orthogonal array of L25 was employed to minimize the number of experiments needed to assess the effects of selected factors on the dispersion process. The average particle size, UV-vis absorbance, residual absorbance after 24 h, and zeta potential were measured through dynamic light scattering and UV-vis spectroscopy tests. Two multi-criteria decision making methods, namely Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) and Principle Component Analysis (PCA) methods, were then employed to determine the optimal values of experimental factors for the dispersion. Finally, graphene-mortar composites were fabricated using two different surfactants and the properties of the developed composites were evaluated. The results indicates a 32% and 52% improvement in compressive strength and volume of permeable voids of graphene-enhanced mortar composites.