Enhanced properties of cement mortars with multilayer graphene nanoparticles

The present work aims to combine multilayer graphene (MLG) nanoparticles with Ordinary Portland Cement (OPC) mortar specimens, evaluating possible improvements on their mechanical properties and ultimately coming up with an ideal and effective concentration for future applications. Mortars with water/cement ratio of 0.4, MLG dosage varying from 0.015 to 0.033% by weight of cement and sand at a proportion of 3× the weight of cement were prepared. 50 × 100 mm cylindrical specimens were shaped and subjected to compressive and splitting tensile strength tests at the ages of 3, 7 and 28 days. In addition, SEM micrographs and metallographic images were collected and analyzed in order to better characterize the sample's morphology and also in attempt of explaining the MLG influence on cement paste. The optimal tensile strength was achieved with samples designed with MLG dosage of 0.033%, for which the corresponding increases were 100.0, 144.4 and 131.6%, after 3, 7 and 28 days, respectively, compared with samples without MLG. On the other hand, the optimal compressive strength increases were obtained with samples designed with MLG dosage of 0.021%, with improvements of 63.6, 94.1 and 95.7% after 3, 7 and 28 days, respectively, compared with samples without MLG. The addition of MLG is believed to accelerate cement hydration reactions, reduce the pore volume and harden cement properties. An improvement in thermal conductivity is also associated to MLG incorporation, and this favorable heat transfer in OPC-based mortars probably promoted the observed changes in the composite chemical structure and mechanical properties herein analyzed.