(484d) Enhanced Concrete Performance Using Graphene Produced Via a Continuous, Controllable, and Scalable Process

The construction sector accounts for 40% of energy-related carbon emissions [1]. Concrete is the most commonplace construction material within the built environment, with cement, its main component, accounting for up to 8% of greenhouse gas emissions. Graphene is a two-dimensional (2D) material exhibiting high electronic, thermal, and mechanical properties. This material can serve as a concrete additive to not only improve its mechanical and durability performance, but also minimize its environmental impact by reducing the amount of cementitious material needed, thereby lowering carbon emissions. However, adding graphene reduces workability of concrete, and limits its ability to be placed into its mould/formwork. A more uniform graphene dispersion within concrete, and therefore better workable mixes, can be achieved by optimising the lateral size and thickness of graphene particles.

In the present work [2] (see Figure 1), we have developed an in-house turbulent Taylor-Couette (TC) flow system that generates the necessary conditions (strain rates) for effective and highly-controllable graphite exfoliation. We demonstrate our technological process for versatile and tonnage-production capability of pristine Few Layer Graphene (FLG) of required specification in terms of material quality and physical characteristics. The specification of FLG is determined through various characterisation techniques, such as AFM, UV-Vis, and Raman spectroscopy. In parallel, we showcase our novel on-line monitoring system based on optical spectroscopy for real-time measurement and on-the-fly control of the concentration and average number of atomic layers for the 2D material produced. This Industry 4.0 compatible process enables control over the whole value chain ensuring traceability, minimal waste, on-demand materials by design, adherence to ISO standards, and batch-to-batch conformity.

To understand the effect of FLG with different specifications on the fresh and hardened properties of cementitious mixes, we have conducted the following quantitative assessments:

• Isothermal calorimetry to determine the hydration profiles
• Slump flow to understand the rheology
• Compressive and flexural strength tests to investigate the structural performance
• Mercury Intrusion Porosimetry to characterise the porosity
• Scanning electron microscopy to study the surface morphology
• X-ray diffraction to analyse the physical properties
• Thermogravimetric analysis to determine the evolution of the chemical structure
  
  

By varying the exfoliation process conditions, multi-liter batches containing concentrated FLG dispersions with different specifications are produced particularly in terms of FLG concentration, thickness, and lateral size distributions. Different loading concentrations of FLG with best-performing specifications are blended into mortar samples and the above mentioned chemical and mechanical tests are conducted at different curing ages in order to understand the effect of FLG concentrations on the properties of cementitious materials. Quantitative assessment of the cured samples revealed improvements in key concrete performance characteristics, including compressive and flexural strength. These are directly compared with conventional concrete without graphene to determine the structural performance benefits resulting from the graphene additives. With such structural performance improvements in concrete, we showcase the positive environmental impact it has on the reduction of carbon dioxide emissions and of the amounts of precursors used and waste produced, increasing the overall sustainability levels within the construction sector by using 2D materials.

Acknowledgements: This research has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 707340, and support from the EPSRC CDT in Advanced Characterisation of Materials (2018 NPIF grant EP/S515085/1) and UKRI Impact Acceleration Account (EP/X52556X/1).

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