211 / 2022-06-07 14:01:18

Healing of concrete cracks by in-situ synthesis of ettringite induced by electric field

in-situ synthesize ettringite, crack healing, electric field, concrete

Cracking is inevitable in concrete and can seriously threaten the durability of the structures. This paper proposed electric-induced in-situ synthesis of ettringite as a crack healing strategy for concrete structure. Composite solutions of aluminum sulfate and calcium acetate with four different molar ratios of Ca to Al (1, 3, 5, 7) were used as electrolyte solutions. The effectiveness of healing was evaluated by crack closure ratio, permeability, and coverage ratio of the crack section, while the composition and microstructure of products were also investigated. From the results, when the Ca-Al ratio is 3 or 5, the crack closure time shortened to 1 day, and the permeability coefficient reduced by nearly 4 orders of magnitude compared to the unrepaired specimen after healing for 7 days. Of all the groups, the products penetrated the entire crack, and the coverage ratio of crack section can reach more than 60% when the Ca-Al ratio is 5. Additionally, ettringite was detected as the main phase of products by X-ray diffraction and thermogravimetric analysis (TGA). Needle-shaped ettringite can be observed during the whole healing period through scanning electron microscopy (SEM). In-situ synthesized ettringite crystals evolved from small and short prismatic shapes to long and acicular shapes. These crystals overlapped with each other and formed a dense network structure.