Abstract The use of ettringite-based materials for thermochemical heat energy storage has attracted researchers' attention in recent years since ettringite has advantages like low material cost and high energy storage density (~500 kWh/m3). However, carbonation, which modifies its structure and reduces the capacity of energy storage, is an important hindrance to real applications. To address this issue, the present study focuses on the carbonation kinetics of three ettringite-based and corresponding meta-ettringite-based materials (dehydrated samples) exposed to different relative humidity (RH) and CO2 concentrations. A mixture of 80 wt% pre-blended Calcium Aluminate Cement/20 wt% OPC (C80P20) proved to be the most resistant against CO2. The hydrated and dehydrated C80P20 grains carbonated slowly at 50% RH and 1 vol% CO2, consuming little ettringite after 28 days. At 90% RH, carbonation was accelerated such that all ettringite and meta-ettringite materials were depleted at 11 days with vaterite and aragonite as the main calcium carbonates. The produced CaSO4 hydrates were found as hemihydrate at 70% RH and gypsum at 90% RH. Finally, the thermal energy storage capacity (TESC) of the material was systematically quantified as essentially decreasing with the carbonation degree of ettringite-based materials.

中文翻译：

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钙矾石和偏钙矾石基材料碳化的比较动力学研究

摘要 由于钙矾石具有材料成本低、储能密度高（~500 kWh/m3）等优点，近年来，钙矾石基材料用于热化学热能储存引起了研究人员的关注。然而，碳化会改变其结构并降低储能能力，是实际应用的重要障碍。为了解决这个问题，本研究侧重于暴露于不同相对湿度 (RH) 和 CO2 浓度下的三种钙矾石基材料和相应的偏钙矾石基材料（脱水样品）的碳化动力学。80 wt% 预混铝酸钙水泥/20 wt% OPC (C80P20) 的混合物被证明对二氧化碳的抵抗力最强。水合和脱水的 C80P20 颗粒在 50% RH 和 1 vol% CO2 下缓慢碳酸化，28 天后消耗很少的钙矾石。在 90% RH 下，碳酸化加速，使得所有钙矾石和偏钙矾石材料在 11 天耗尽，球霰石和文石作为主要的碳酸钙。发现生成的 CaSO4 水合物在 70% RH 下为半水合物，在 90% RH 下为石膏。最后，材料的热能储存容量 (TESC) 被系统地量化为随着钙矾石基材料的碳化程度而基本降低。