Numerical prediction of the optimal dosage of graphene in cementitious composites

A novel numerical model is developed to determine the optimal graphene dosage for the best mechanical properties by predicting the maximised total surface area of graphene in hardened cement mixes. The model was based on the concept of critical distance, where any adjacent graphene with a spatial distance less than the critical distance was simulated to re-agglomerate. This critical distance, defined as a function of graphene diameter and cement viscous resistance, was extracted from X-ray computed tomography (XCT) measurements of tested samples and used as a model input. To calculate the surface area of graphene re-agglomerates in hardened cement, a stacking factor, defining the sequential stacking of graphene plates determined by SEM micrographs, was introduced. Viscous resistance and flowability of the cement mixes were quantified to establish a functional relationship with the critical distance, while compressive testing was conducted to determine the optimal graphene dosage experimentally. Results revealed a constant ratio of the critical distance to the pristine graphene diameter, which was found to be a function of the flowability of the mix. The numerical model was validated by comparing the predicted optimal graphene dosage, size distribution, and total surface area of graphene against experimental results.