Abstract Controlled low-strength materials (CLSMs) with high workability and relatively high thermal conductivity can function as a thermal grout in the heat exchanger of ground source heat pump systems. The degree of saturation of CLSM strongly influences its thermal conductivity and thus affects the heat transfer capacity of the heat exchanger system. This study investigates the degree of saturation–thermal conductivity relationship of steelmaking slag-based CLSM using two sample preparation methods: a modified high-pressure membrane extractor coupled with a thermal needle probe (HP) and air-dried (AD) methods. The effect of grinding steelmaking slag on the mechanical properties and thermal conductivity of CLSM is also evaluated. The engineering properties test results indicate that ground steelmaking slag presents a positive effect on the compressive strength and thermal conductivity of CLSMs owing to the reduction of the inherent porosity and increased specific surface area of the raw steelmaking slag by the grinding. The degree of saturation and thermal conductivity have a linear relationship for both the AD and HP test methods. However, it was found that the AD method overestimates the thermal conductivity owing to the uneven distribution of the water content in the specimen. Finally, predictive equations are proposed to estimate the thermal conductivity of CLSM for the entire range of degree of saturation. Compared to the recently proposed equation, these equations are more appropriate for thermal conductivity estimation of grouting materials based CLSM, especially at low water content.

中文翻译：

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炼钢渣基可控低强度材料在整个饱和度范围内的热导率：地源热泵系统研究

摘要 具有高可加工性和相对高热导率的可控低强度材料 (CLSM) 可作为地源热泵系统热交换器中的热灌浆。CLSM 的饱和度强烈影响其热导率，从而影响换热器系统的传热能力。本研究使用两种样品制备方法研究了炼钢炉渣基 CLSM 的饱和度与热导率的关系：改进的高压膜提取器结合热针探针 (HP) 和风干 (AD) 方法。还评估了研磨炼钢渣对 CLSM 机械性能和热导率的影响。工程性能测试结果表明，磨碎的炼钢渣对 CLSMs 的抗压强度和热导率有积极影响，这是由于研磨降低了炼钢原渣的固有孔隙率和增加了比表面积。饱和度和热导率对于 AD 和 HP 测试方法都具有线性关系。然而，发现由于试样中水含量的不均匀分布，AD方法高估了热导率。最后，提出了预测方程来估计整个饱和度范围内 CLSM 的热导率。与最近提出的方程相比，这些方程更适用于基于 CLSM 的灌浆材料的热导率估计，