Six supplementary cementitious materials (SCMs) were identified to be incorporated in concrete exposed to high-temperature cycling conditions within the thermal energy storage literature. The selected SCMs are bauxite, chamotte, ground granulated blast furnace slag, iron silicate, silica fume, and steel slag. A microstructural characterization was carried out through an optical microscope, X-ray diffraction analysis, and FT-IR. Also, a pozzolanic test was performed to study the reaction of SCMs silico-aluminous components. The formation of calcium silica hydrate was observed in all SCMs pozzolanic test. Steel slag, iron silicate, and ground granulated blast furnace slag required further milling to enhance cement reaction. Moreover, the tensile strength of three fibers (polypropylene, steel, and glass fibers) was tested after exposure to an alkalinity environment at ambient temperature during one and three months. Results show an alkaline environment entails a tensile strength decrease in polypropylene and steel fibers, leading to corrosion in the later ones. Funding This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE and RTI2018-093849-B-C32—MCIU/AEI/FEDER) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018-102431-T). This work is partially supported by ICREA under the ICREA Academia programme. This study was partially funded by AEI—Spanish Ministry of Science, Innovation and Universities (PCI2020-120695-2/AEI/10.13039/501100011033 and PCI2020-120682-2/AEI/10.13039/501100011033 through PCI call). Acknowledgments The authors would like to thank the Catalan Government for the quality accreditation given to their research groups (2017 SGR 1537 and 2017 SGR 118). GREiA and DIOPMA are certified agents TECNIO in the category of technology developers from the Government of Catalonia. The authors also thank the companies that provided the material to make possible this experimental research: Gestión Medioambiental de Neumáticos S.L., Arciresa, EDERSA—Masaveu Industria and Promsa—Megasa.