Preparation and application of Na2SiO3@EC microcapsules for self-healing alkali-activated slag

• Published in: Construction & building materials Vol. 400; p. 132651
• Main Authors: Yin, Kunpeng, Luo, Zhongtao, Liu, Xiaohai, Pan, Han, Zhi, Tianyi, Feng, Hu, Song, Yatao, Su, Yanfeng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 12.10.2023
• Subjects: Alkali-activated slag; Crack; Image processing; Microcapsule; Self-healing; Self-healing; Alkali-activated slag; Image processing; Microcapsule; Crack
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.132651

•Na2SiO3@EC microcapsule is prepared by solvent evaporation.•Na2SiO3 is released from microcapsule after AAS cracks.•Microcapsules continuously promote repair of AAS mortars.•The secondary hydration reaction is facilitated by microcapsule.•Image processing can visualize and quantify crack changes. Alkali activated slag (AAS) is a promising green building material, but its application has been limited by the high risk of cracking. In this study, the self-healing technology was used in AAS system by introducing self-healing microcapsules. The Na2SiO3@EC microcapsules were designed with sodium silicate (Na2SiO3) as the core material and ethyl cellulose (EC) as the shell material, and the prepared microcapsules were characterized by leaching test and SEM-EDS. The effect of microcapsules on the self-healing of AAS mortars was verified by the post-repair compressive strength test, and the mechanism was discussed based on MIP and hydration heat. The results showed that the core–shell structured Na2SiO3@EC microcapsules were prepared with a core content of 69.42 wt%. The addition of microcapsules could improve workability and mechanical property of AAS mortars. The AAS mortars with Na2SiO3@EC microcapsules had a compressive strength recovery ratio of up to 26.82%. The Na2SiO3 released from microcapsules promoted the secondary hydration of the AAS mortars, and the hydration products refined the pore structure. Image processing methods were effective in visualizing and quantifying the changes in the cracks, and the image results further confirmed the long-term effectiveness of the microcapsules. This study provides guidance on the application of self-healing microcapsules in the AAS system and the visualization of self-healing behavior.