Rheological Behavior of Fresh Cement Composites with Graphene Oxide-Coated Silica Fume

Although graphene oxide (GO) can be well dispersed in water, it tends to reagglomerate in an alkaline cement hydration environment, thus seriously degrading the workability and mechanical strength of the mixture. This study proposes a more targeted approach by using GO-coated silica fume (SF) to promote the utilization efficiency of GO in cement composites. Specifically, the surface of pristine SF particles is modified to convert their zeta potential (from - 23 to +3 mV, named MSF), and then a MSF@GO hybrid is prepared via electrostatic adsorption of GO on the surface of the MSF. It is found that adding 5MSF@GO hybrid (5% MSF together with 0.04% GO) can increase the flow diameter of the mixture by similar to 5%; simultaneously, it can greatly reduce yield stress and plastic viscosity by similar to 52% and similar to 26%, respectively, relative to 0.04% by weight GO-modified paste. Additionally, using the MSF@GO hybrid can counteract the delay in the early-age strength of the SF-cement system. These findings suggest that using GO nanoengineered SF surface has great potential to develop high-performance cementitious composites. (c) 2023 American Society of Civil Engineers.