Investigation of the dispersion of reduced graphene oxide in cementitious composites under different mixing strategies

The use of reduced graphene oxide (rGO) to enhance the strength, durability, and electromagnetic properties of cementitious composites has received extensive attention in recent years. However, the agglomeration behavior of rGO in alkaline environment greatly reduces its reinforcement effect on cement-based materials. This study aims to develop a practical and feasible dispersion scheme to facilitate the practical application of rGO in cement systems. To achieve this goal, four different mixing protocols were evaluated, including the typical combination of superplasticizer and ultrasound (Methods 1), and three preparation methods involving direct dry mixing of cement clinker with rGO (Methods 2), dry mixing of sand with rGO (Methods 3), and dry mixing of sand with rGO solution (Methods 4).The mechanical and durability properties of the cement mortar samples were analyzed under different mixing protocols to determine the effects of rGO on the performance of the composite. Furthermore, the microstructure and hydration product of the cementitious composite were investigated using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) to assess the dispersion of rGO in the cement matrix. The test results indicated that the direct dry mixing of sand with rGO (Method 3) was the most effective dispersion scheme among the evaluated mixing protocols. The flexural and compressive strengths of the cement mortar samples produced using Method 3 were increased by 26.01% and 39.8%, respectively, after 28 days as compared to the control samples. This enhancement can be attributed to the shear effect of the sand grains, which effectively reduces the aggregation of rGO in the cement matrix, leading to stronger nucleation effects occurring in the cement hydration. In addition, well-dispersed rGO improves the pore structure of the composite and increases its erosion resistance. The results of this study may provide valuable insights for the large-scale production of rGO-cement composites with enhanced properties and contribute to the development of sustainable and high-performance construction materials.