Mahmood Ammar, Dehn Frank, Thissen Peter
Institute of Functional Interfaces, , Hermann-von-Helmholtz-Platz-1, Karlsruhe 76344, Germany.
Institute of Concrete Structures and Building Materials, Gotthard-Franz-Str. 3, Karlsruhe 76131, Germany.
Langmuir. 2025 Feb 4;41(4):2259-2268. doi: 10.1021/acs.langmuir.4c03811. Epub 2025 Jan 22.
This paper investigates the impact of varying humidity conditions on the carbonation depth in hardened cement paste using a 3-dimensional microscale kinetic Monte Carlo (kMC) approach. The kMC algorithm effectively simulates the carbonation process by capturing the interplay between CO diffusion and relative humidity at the microscale, providing insights into macro trends that align with historical models. The study reveals that the maximum carbonation depth is achieved at relative humidity levels between 55 and 65%, where the balance between water and CO diffusion is optimized. At lower relative humidity levels (<55%), a lower carbonation depth is observed. Conversely, at higher relative humidity levels (>65%), increased water content impedes CO diffusion, resulting in reduced carbonation depth for cement paste. The kMC model demonstrates a parabolic relationship between relative humidity and carbonation depth. Time series analysis shows that Fick's law is consistently followed, with carbonation depth following the relationship x = k√t at constant relative humidity. The kMC also breaks down the event cycle which shows that after an equilibrium (in terms of rate of events) is achieved between CO and HO at a relative humidity of 75%, a shift occurs in the dominance from reactive to transport processes at a relative humidity of 85%. These findings highlight the importance of humidity in influencing carbonation rates on the one hand and demonstrate the effectiveness of the kMC approach in simulating these complex interactions at the microscale on the other hand.
本文采用三维微观动力学蒙特卡洛（kMC）方法，研究了不同湿度条件对硬化水泥浆体碳化深度的影响。kMC算法通过捕捉微观尺度下CO扩散与相对湿度之间的相互作用，有效地模拟了碳化过程，为与历史模型相符的宏观趋势提供了见解。研究表明，在相对湿度为55%至65%之间时，碳化深度达到最大值，此时水与CO扩散之间的平衡得到优化。在较低的相对湿度水平（<55%）下，观察到较低的碳化深度。相反，在较高的相对湿度水平（>65%）下，含水量增加会阻碍CO扩散，导致水泥浆体的碳化深度降低。kMC模型表明相对湿度与碳化深度之间呈抛物线关系。时间序列分析表明，在恒定相对湿度下，碳化深度遵循菲克定律，即x = k√t。kMC还分解了事件循环，结果表明，在相对湿度为75%时，CO与HO之间达到平衡（就事件速率而言）后，在相对湿度为85%时，主导作用从反应过程转变为传输过程。这些发现一方面突出了湿度对碳化速率影响的重要性，另一方面证明了kMC方法在微观尺度上模拟这些复杂相互作用的有效性。
