Colloidal Stability of Graphene Nanoparticles in Commercial Concrete Admixtures

Concrete is the most widely used construction material in the world, with its production responsible for roughly
8% of global CO₂ emissions. Cement production is responsible for the vast majority of concrete emissions, and
the sector remains one of the hardest to decarbonize due to high process emissions and energy intensity of
manufacturing. Incorporating carbon nanomaterials into cement composites has been shown to allow for lower
cement content and a consequential significant reduction in emissions, additionally enhancing the strength and
reducing the porosity of concrete.

A practical route to deliver these nanomaterials at field-relevant low loadings (0.01-0.1% graphene by weight)
is to pre-load them at high solids into concrete admixtures, which are liquid additives used to modify the
properties of fresh concrete. However, the long-term colloidal stability of graphene nanoparticles in commercial
admixtures over typical industry storage periods of weeks to months remains understudied.

Among several tested commercial superplasticizer admixtures, we found that stable systems exhibited relatively
constant viscosity over time, narrow particle size distributions, higher retained graphene concentrations, and
lower Hegman gauge values. Conversely, admixtures that produced unstable dispersions showed rapid viscosity
drift, broad or bimodal particle size distributions, and visible sedimentation.

Our results highlight the challenges of scaling nanomaterial-enhanced concrete production, where dispersion
stability becomes a key factor in translating laboratory performance to field utility. By establishing rheology,
particle size, and fineness as predictive indicators of stability, this study provides a practical framework for
screening commercial admixtures for long-term nanomaterial dispersion