Izadifar Mohammadreza, Ukrainczyk Neven, Koenders Eduardus
Institute of Construction and Building Materials, Technical University of Darmstadt, Franziska-Braun-Str. 3, 64287 Darmstadt, Germany.
Langmuir. 2024 Sep 17;40(37):19332-19342. doi: 10.1021/acs.langmuir.4c00890. Epub 2024 Sep 5.
This study employs computational chemistry to investigate the detailed mechanisms behind the dissolution of thermally activated clays, which are emerging as promising supplementary cementitious materials (SCM) for enhancing concrete properties and reducing carbon footprint. Specifically, the study employs a first-principles methodology for obtaining activation energies (Δ) involved in the dissolution of metakaolinite (MK) silicate units using NaOH and KOH activators. The investigation includes considerations of hydrolyzing oxo-bridging covalent bonds, van der Waals (vdW) interactions, and the influence of water molecules surrounding alkali cations. The study employs the enhanced dimer method within density functional theory (DFT) to propose four models for determining the activation energies required to break oxo-bridging bonds. The results demonstrate that KOH generally requires lower activation energies than NaOH, particularly when considering vdW interactions. They also highlight the lower activation energy required for commencing the dissolution of silicate units and emphasize the significance of the hydration shell around cations. The proposed methodology contributes to establishing a systematic database of atomistic activation energies, essential for atomistic kinetic Monte Carlo upscaling and mesoscopic forward dissolution rate calculations in clays. This holds relevance in understanding their reactivity within cementitious materials.
本研究采用计算化学方法来探究热活化黏土溶解背后的详细机制，热活化黏土正成为一种有前景的辅助胶凝材料（SCM），可用于改善混凝土性能并减少碳足迹。具体而言，该研究采用第一性原理方法来获取偏高岭土（MK）硅酸盐单元在使用NaOH和KOH活化剂时溶解过程中涉及的活化能（Δ）。研究内容包括对水解氧桥共价键、范德华（vdW）相互作用以及碱金属阳离子周围水分子影响的考量。该研究在密度泛函理论（DFT）框架下采用增强二聚体方法，提出了四种用于确定断裂氧桥键所需活化能的模型。结果表明，KOH通常比NaOH需要更低的活化能，特别是在考虑vdW相互作用时。研究结果还突出了开始溶解硅酸盐单元所需的较低活化能，并强调了阳离子周围水化层的重要性。所提出的方法有助于建立一个原子活化能的系统数据库，这对于黏土中原子动力学蒙特卡洛尺度放大和介观正向溶解速率计算至关重要。这对于理解它们在胶凝材料中的反应活性具有重要意义。
