Browsing Comunicacions a congressos (Enginyeria Industrial i de l’Edificació) by Author "Boquera, Laura"
Now showing 1 - 2 of 2
Results Per Page
- ItemOpen AccessDevelopment of a new concrete for high-temperature thermal energy storage(2022) Cabeza, Luisa F.; Boquera, Laura; Castro Chicot, José Ramón; Pisello, Anna LauraVision: Being a reference group of engineering at an international level, always linked to the University of Lleida. Mission: To propose solutions to the industry in the fields of sustainability, energy engineering and control, through research, technology transfer and training. Objectives: To improve existing knowledge through research and innovation ; To help increase the competitiveness of companies through collaborations, whether for the design of new products or as a technology consultancy.
- ItemOpen AccessSteel slag concrete: thermo-mechanical stability under high-temperature cycles(Universitat de Lleida. Grup de Recerca en Energia i Intel·ligència Artificial (GREiA), 2021) Boquera, Laura; Castro Chicot, José Ramón; Fernández, Ángel G.; Navarro Ezquerra, Antonia; Pisello, Anna Laura; Cabeza, Luisa F.INTRODUCTION: The improvement of the output efficiency in CSP plants is a challenge of major interest. To achieve this objective, an increase of temperature in the heat transfer and the storage media is required to increase power block efficiency. Among the suitable material options, concrete was determined to have attractive properties. Concrete is a heterogeneous material, made of several components that allows to choose the best dosage to obtain the desired properties in the final blender. Worldwide availability of concrete components and their low cost, contribute to implement eco-friendly measures. The environmental impact of the materials is a substantial parameter to take into consideration when selecting concrete components. There are by-products from industries that can be revalorized by including them into concrete mixtures, replacing cement percentage or using them as aggregates. A by-product from the metallurgy industry, known as steel slag or electric arc furnace slag, was previously studied as aggregates in concrete for thermal energy storage. In this paper, the thermal stability under high-temperature cycles, of two cement types with steel slag as the only aggregate in the concrete mixture is compared. As further novelty, the thermal cycles were adapted to heating rates currently used in the operation of a CSP plant. MATERIALS AND METHODS: In the present study two concrete dosages were designed. One using ordinary Portland cement and the other with calcium aluminate cement. In both binders, steel slag was used as aggregate, considering granulometries of 0-12 mm. Physical, thermal and mechanical properties were studied before and after thermal cycles. To study the thermal stability, 10 continuous thermal cycles were carried out. The thermal cycle profile consisted on a first cycle with a low heating rate 1 ºC/min up to 290 ºC followed by an isothermal step of 4 hours. Continuously, temperature increased up to 700 ºC with the same heating rate and maintaining during 4 hours. After, the samples were cooled down to 290 ºC, at a rate below 1 ºC/min. For the next cycles the heating rate was increased to 15 ºC/min, considering the same time for the isothermal steps and the cooling part. RESULTS: The external appearance showed a geometry preservation in all samples. There were no important cracks in the surface, only micro-fissures in the samples after some thermal cycles. There is a strong connection between the aggregates and both types of cement paste, conferring a bonding in the concrete mixture. No spalling signs nor thermal expansion of aggregates was observed. The mass loss was around 4 % in both mixtures after the thermal cycles. The thermal conductivity was reduced 50 % after the 10 thermal cycles. Despite the high compressive strength obtained before any thermal treatment, the compressive strength drastically decreased 80 % after the 10 thermal cycles. CONCLUSIONS: Despite the low thermal conductivity achieved after thermal cycles, a high integrity preservation of the concrete mixtures was observed. The compatibility of steel slag highlight with both cement types conferring a hydraulic bonding to the mixture, appreciating small fissures.