Although many studies considered crystalline admixtures (CA) as the self-healing agent, only limited studies investigated the potential effects of aggressive ions on the self-healing performance of marine structures. Furthermore, there is an increasing trend to use SCMs to improve concrete resilience while lowering carbon footprint. This study investigated the effects of CA and sustainable waste wood biochar (WWB) on the self-healing of cement pastes exposed to simulated seawater or 5 % sodium sulphate solution. Three-point loading was used to initiate the cracks while keeping the cracked samples unseparated. The healing rate was investigated using optical microscopy and binary image processing. The self-healing products characterisation was conducted using Scanned Electron Microscopy equipped with Energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), Thermogravimetric analysis (TG), and Fourier-transform Infrared Spectroscopy (FTIR). Cracks were completely healed after 42 days for CA-based samples when exposing to wet/dry cycles in seawater (SWWD) and sulphate solution (SWD). EDS, XRD and TG results confirmed the formation of calcite as the main healing products, while a small portion of brucite was observed in healing products for SWWD. FTIR spectra further confirmed the formation of C-S-H gel and AFt in healing productions exposed to SWWD and SWD. Although WWB addition did not improve healing performance of WWB-cement composites, it led to a relatively complex cracking path, providing more nucleation sites for the self-healing process.

中文翻译：

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暴露于硫酸盐溶液和模拟海水的结晶外加剂的生物炭-水泥复合材料的自修复


尽管许多研究认为结晶外加剂 （CA） 是自愈剂，但只有有限的研究调查了侵袭性离子对海洋结构自愈性能的潜在影响。此外，使用 SCM 来提高混凝土弹性同时降低碳足迹的趋势越来越明显。本研究调查了 CA 和可持续废木材生物炭 （WWB） 对暴露于模拟海水或 5% 硫酸钠溶液的水泥浆自我修复的影响。使用三点加载来引发裂纹，同时保持裂纹样品不分离。使用光学显微镜和二值图像处理研究愈合率。使用配备能量色散 X 射线光谱 （SEM-EDS）、X 射线衍射 （XRD）、热重分析 （TG） 和傅里叶变换红外光谱 （FTIR） 的扫描电子显微镜进行自修复产物表征。当暴露于海水 （SWWD） 和硫酸盐溶液 （SWD） 中的湿/干循环时，基于 CA 的样品在 42 天后完全愈合。EDS、XRD 和 TG 结果证实方解石的形成是主要的愈合产物，而在 SWWD 的愈合产物中观察到一小部分水镁石。FTIR 光谱进一步证实了暴露于 SWWD 和 SWD 的愈合产物中 C-S-H 凝胶和 AFt 的形成。WWB 的添加虽然没有提高 WWB-水泥复合材料的愈合性能，但它导致了相对复杂的开裂路径，为自修复过程提供了更多的成核位点。