The self-healing, fresh properties, hydration, and other characteristics of the cement paste modified with biochar as a green additive were explored in this work. Evaluation of early-age hydration was conducted using setting time measurement and isothermal calorimetry, and later-age hydration was investigated using thermogravimetric analysis. The mechanical and transport properties were investigated by using compressive strength and electrical resistivity measurements, respectively. The chemical characterization of the healing products was conducted via Fourier transform infrared spectroscopy, scanning electron microscopy equipped with X-ray energy-dispersive spectroscopy, and thermogravimetric analysis. The mechanical strength recovery and crack filling were examined using the three-point bend test and optical microscopy, respectively. The paste with biochar showed an increased setting time and delayed hydration at an early age because of reduced alkali concentrations in the pore solution due to alkali uptake by biochar. However, at later ages, the hydration was improved in the paste with biochar, which is attributed to internal curing. Biochar effectively decreased autogenous shrinkage in the paste, which is attributed to internal curing. Biochar was shown to reduce the electrical resistivity and compressive strength of the cement paste due to higher overall water/cement and macrovoid formation, respectively. The chemical characterization of the healing products showed that they are primarily made up of calcium–silicate–hydrate, calcium carbonate, calcium hydroxide, and ettringite. The content of calcium carbonate was increased in the healing products of the paste with biochar relative to the control paste. The mechanical strength recovery and crack filling were improved in the paste with biochar relative to the control paste, indicating the positive impact of biochar on the self-healing of the paste.

中文翻译：

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生物炭作为绿色添加剂对可持续胶凝材料自修复和性能的影响


本工作探讨了生物炭作为绿色添加剂改性水泥净浆的自修复性、新鲜性、水化性等特性。使用凝固时间测量和等温量热法评估早期水合作用，并使用热重分析研究后期水合作用。分别通过压缩强度和电阻率测量来研究机械和传输性能。通过傅里叶变换红外光谱、配备 X 射线能量色散光谱的扫描电子显微镜和热重分析对治疗产品进行化学表征。分别使用三点弯曲试验和光学显微镜检查机械强度恢复和裂纹填充。由于生物炭吸收碱，孔隙溶液中的碱浓度降低，因此含有生物炭的糊状物在早期表现出凝固时间增加和水合延迟。然而，在后来的岁月里，生物炭糊状物的水合作用得到了改善，这归因于内部固化。生物炭有效地减少了浆料中由于内部固化而产生的自收缩。由于较高的总水/水泥和大孔隙形成，生物炭分别降低了水泥浆的电阻率和抗压强度。治疗产品的化学特性表明，它们主要由硅酸钙水合物、碳酸钙、氢氧化钙和钙矾石组成。相对于对照糊剂，含有生物炭的糊剂的愈合产物中碳酸钙的含量增加。 与对照糊剂相比，含有生物炭的糊剂的机械强度恢复和裂缝填充得到改善，表明生物炭对糊剂的自修复具有积极影响。