Thermo-mechanical stability of concrete containing steel slag as aggregate after high temperature thermal cycles.

• Steel slag as aggregate in concrete for high temperature TES. • Concrete mixtures thermally cycled from 290 to 700 °C. • OPC and CAC with steel slag preserve integrity after thermal cycling. • Concrete with steel slag revealed promising specific heat capacity. • Thermal conductivity and compressive strength need further improvement. Thermal energy storage represents a crucial element to increase solar power dispatchability. Within sensible heat storage in solid media, concrete is considered a low-cost alternative to be further developed and therefore, this has been addressed in this paper. Four concrete dosages were designed, combining each type of considered cement, ordinary Portland and calcium aluminate cement, with each type of considered aggregate, silico-calcareous and a steel slag. Thermo-mechanical properties of concrete were studied before and after 10 thermal cycles from 290 °C to 700 °C. Maximum operating temperature and heating rates were selected accordingly to the targeted application, a concentrating solar power (CSP) tower plant. At macro-level, results show thermal cycle stability of concrete with steel slag aggregate in both cement types. On the contrary, at micro-level, the petrography analysis shows the lack of bonding between steel slag aggregate and the cement paste. In contrast, concrete mixtures containing silico-calcareous aggregates collapse after thermal cycling. [ABSTRACT FROM AUTHOR]