Influence of inorganic compounds on self-repairing capability and frost resistance of concrete incorporating ion chelating agent

Abstract

Cracks can decrease the durability of concrete structures. The ion chelating agent (ICA) can repair concrete cracks through precipitates formed by chelation crystallization reactions. However, its capacity to repair internal damage in concrete is limited, and the chelation crystallization reaction slows down in cold environments. Some inorganic compounds (magnesium fluosilicate and sodium silicate) can promote precipitation formation within concrete, potentially enhancing its self-repairing capability. This study explores the synergistic effects of ICA and these inorganic compounds on the self-repairing capability and frost resistance of concrete. To achieve this research objective, parameters such as visual crack closure, compressive strength reserved ratio, pore structure change, chloride diffusion coefficient, and the microstructure and composition of the repair products were investigated. Sodium silicate and ICA demonstrated significant improvements in the self-repairing capability and frost resistance of concrete. Concrete containing 0.5 wt% sodium silicate and 0.5 wt% ICA, after 28 d of standard curing, fully repaired surface cracks with a width of 0.49 mm. After 300 freeze-thaw cycles, the chloride diffusion coefficient increase rate and harmful pores proportion in the concrete containing 0.5 wt% sodium silicate and 0.5 wt% ICA were reduced by 51.7 % and 76.6 %, respectively, compared to the control concrete. Following 28 d of curing after freeze-thaw damage, the compressive strength reserved ratio of concrete with 0.5 wt% sodium silicate and 0.5 wt% ICA increased by 38.5 %, while the chloride diffusion coefficient increase rate and the harmful pores proportion decreased by 68.5 % and 84.9 %, respectively, compared to the control concrete. Furthermore, SEM-EDS analyses revealed significant amounts of calcium carbonate and some calcium silicate within the cracks of the concrete containing ICA and sodium silicate, and that the internal damage was primarily repaired by a combination of calcium carbonate and calcium silicate.