High-temperature stability of ambient-cured one-part alkali-activated materials incorporating graphene nanoplatelets for thermal energy storage

This study aims to develop an ambient-cured nano-engineered one-part alkali-activated materials with excellent thermal characteristics using graphene nanoplatelets (GNPs) and ternary precursors. Their compressive strength, thermal properties, microstructure, pore structure were characterised through visual observation, isothermal calorimetry, TGA, XRD, SEM/EDS and X-ray μCT after high temperature exposure to 200–800 °C. The research findings indicated high strength characteristics of the developed AAM (∼80 MPa) at ambient condition, which could further reach to approx. 100 MPa after being heated up to 400 °C. GNPs provided nucleation effects for promoting geopolymerisation and crystallisation. As observed from X-ray CT, a high extent of severe cracks initiated from the core and propagated towards the surface. From SEM/EDS analysis, high Na/Al and Na/Si ratios or low Si/Al and Ca/Si ratios highly correlated to thermal stability. Overall, the research outcomes implied the promising use of the nano-engineered AAMs for thermal energy storage (TES) at 400 °C.