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A platform for research: civil engineering, architecture and urbanism
Effect of chloride ingress on self-healing recovery of smart cementitious composite incorporating crystalline admixture and MgO expansive agent
Abstract In this study, the effect of chloride environment containing various concentrations of chloride ion (Cl−) on self-healing performance of pre-cracked cementitious composite containing crystalline admixture (CA) and MgO expansive agent (MEA) was investigated under wet-dry cycles in chloride solutions. The results revealed that the Cl− changed the mineralogy of self-healing products, and consequently, affected the crack closure ratio and mechanical strength recovery. When self-healing occurred in distilled water, a large amount of ettringite (AFt) were detected, whereas in Cl− solution, monosulfate (AFm) was consumed by Cl− to form Friedel's salt (Fs), and then the Fs was decomposed to Al(OH)3(AH3) due to carbonation. During the multiphase conversion process, hydroxide (OH−) was released into crack solution, therefore the dissolved carbon dioxide (CO2) concentration was increased. The carbonation of the crystals formed in cracks was accelerated with the volume expansion, which achieved rapid crack sealing but contributed little to the mechanical performance recovery.
Highlights Crack closure under wet/dry cycles in chloride solution is higher than the one in distilled water. Element analysis shows that calcium is vital for crack healing either in water or chloride solution. AFm is consumed by chloride ion to form Fs, and Fs were decomposed to AH3 by carbonation. Soluble reactive silica reacts with calcium hydrate to form C-S-H gel to heal concrete cracks. Expansion of magnesium hydroxide facilitates crack self-healing by interconnected network.
Effect of chloride ingress on self-healing recovery of smart cementitious composite incorporating crystalline admixture and MgO expansive agent
Abstract In this study, the effect of chloride environment containing various concentrations of chloride ion (Cl−) on self-healing performance of pre-cracked cementitious composite containing crystalline admixture (CA) and MgO expansive agent (MEA) was investigated under wet-dry cycles in chloride solutions. The results revealed that the Cl− changed the mineralogy of self-healing products, and consequently, affected the crack closure ratio and mechanical strength recovery. When self-healing occurred in distilled water, a large amount of ettringite (AFt) were detected, whereas in Cl− solution, monosulfate (AFm) was consumed by Cl− to form Friedel's salt (Fs), and then the Fs was decomposed to Al(OH)3(AH3) due to carbonation. During the multiphase conversion process, hydroxide (OH−) was released into crack solution, therefore the dissolved carbon dioxide (CO2) concentration was increased. The carbonation of the crystals formed in cracks was accelerated with the volume expansion, which achieved rapid crack sealing but contributed little to the mechanical performance recovery.
Highlights Crack closure under wet/dry cycles in chloride solution is higher than the one in distilled water. Element analysis shows that calcium is vital for crack healing either in water or chloride solution. AFm is consumed by chloride ion to form Fs, and Fs were decomposed to AH3 by carbonation. Soluble reactive silica reacts with calcium hydrate to form C-S-H gel to heal concrete cracks. Expansion of magnesium hydroxide facilitates crack self-healing by interconnected network.
Effect of chloride ingress on self-healing recovery of smart cementitious composite incorporating crystalline admixture and MgO expansive agent
Xue, Caihong (author) / Li, Wengui (author) / Luo, Zhiyu (author) / Wang, Kejin (author) / Castel, Arnaud (author)
2020-10-01
Article (Journal)
Electronic Resource
English
| Springer Verlag | 2019