Thermal conductivity plays an important role in energy storage when the materials are charging and discharging. This paper presents an experimental investigation of the evolution of thermal conductivity up to 600 °C in different concretes. Moreover, the thermal conductivity was measured during thermal fatigue cycles when temperature ranged between 300 and 600 °C, simulating the operation conditions in a storage system of molten salts in a Concentrating Solar Power Plant (CSP). Five concrete compositions were analysed using diverse types of aggregates with different thermal response, covering a wide range of the initial thermal conductivity. The results confirm that the loss of thermal conductivity with temperature during the first heating is mainly due to the free water loss. Moreover, the type of aggregate influences the overall thermal performance of concrete due to its thermal conductivity and the volumetric differences with the cement paste. Siliceous aggregates underwent the highest decrease of thermal conductivity of concrete (+50%) with regard to room temperature. Regarding the cooling phase, thermal conductivity recovers between 20% and 40% depending on the type of aggregate. The outcomes of the present study demonstrate that the assumption of a constant thermal conductivity value in numerical simulations to predict its thermal capacity for energy storage is not appropriate.

当材料进行充电和放电时，热导率在能量存储中起着重要作用。本文介绍了对不同混凝土中高达600°C的导热率演变的实验研究。此外，在温度为300到600℃的热疲劳循环过程中测量了导热系数，模拟了聚光太阳能发电厂（CSP）中熔融盐存储系统中的运行条件。使用具有不同热响应的多种类型的骨料分析了五种混凝土成分，涵盖了广泛的初始热导率。结果证实，第一次加热过程中导热系数随温度的损失主要是由于游离水的损失。此外，骨料的类型因其导热系数和与水泥浆的体积差异而影响混凝土的整体热性能。相对于室温，硅质骨料的混凝土导热系数下降幅度最大（+ 50％）。关于冷却阶段，根据骨料的类型，热导率恢复在20％至40％之间。本研究的结果表明，在数值模拟中采用恒定的热导率值来预测其储能热容量的假设是不合适的。关于冷却阶段，根据骨料的类型，热导率恢复在20％至40％之间。本研究的结果表明，在数值模拟中采用恒定的热导率值来预测其储能热容量的假设是不合适的。关于冷却阶段，根据骨料的类型，热导率恢复在20％至40％之间。本研究的结果表明，在数值模拟中采用恒定的热导率值来预测其储能热容量的假设是不合适的。