Thermal energy storage (TES) systems play an important role in the management of thermal energy and associated consumption. Furthermore, using TES, combustion of fossil fuels and their associated environmental impacts are avoided. In particular, demand for high temperature energy storage is increasing and research focuses on the development of suitable materials for these applications. A limited number of studies focus on the use of sensible heat storage systems that exploit concrete as a TES under high temperature conditions for concentrating solar power (CSP) plant systems. The main drawback to overcome in concrete TES is the degradation of the concrete after charging and discharging thermal cycles. This study aims to develop a novel concrete formulation designed for high-temperature applications and capable of withstanding thermal cycling. To achieve this, a refractory concrete was conceptualized using calcium aluminate cement (CAC) and refractory aggregates, specifically basalt and chamotte. The formulation also incorporates a heat treatment applied after the cu[[ring period to enhance its performance under extreme thermal conditions. This heat treatment is what allows to transform a CAC concrete, that unites the dispersed material through hydraulic nodes, into a refractory concrete, that unites the dispersed material through its ceramisation. The new concrete formulation was analysed to evaluate its performance before and after 25 thermal cycles. Results show that thermal conductivity and compressive strength after ceramisation have values around 1.7 W/m⋅K and 52 MPa, respectively. It was also observed that the initial thermal treatment was not necessary, because the ceramisation of the concrete can also be achieved during the thermal cycling process if the correct heating and cooling rates are used. The developed new concrete formulation containing refractory aggregates demonstrated excellent thermo-physical and mechanical properties that make it suitable for high-temperature TES applications (temperatures up to 700 ◦C).

This project has received funding from the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement 101036910 (StoRIES). This work was partially funded by the Ministerio de Ciencia e Innovación - Agencia Estatal de Investigación (AEI) (PID2021-123511OB-C31- MCIN/AEI/10.13039/501100011033/FEDER, UE and RED2022-134219-T). This study received funding from the Ministerio de Ciencia e Innovación - Agencia Estatal de Investigación (MCIN/AEI/10.13039/501100011033) through the PCI2020-120695-2 project and the European Union “NextGenerationEU"/PRTR". The authors from University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group (2021 SGR 01615). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme. This work was partially funded by the European Union—NextGenerationEU under Italian Ministry of University and Research (MUR) National Innovation Ecosystem grants ECS00000041— VITALITY—CUP J97G22000170005 and CUP B43C22000470005. The authors thank the PhD school in Energy and Sustainable Development at CIRIAF University of Perugia.