Synergistic effect of ion chelating agent and inorganic compound on pore structure, mechanical and self-healing performance of cement-based materials

Abstract

Abstract Ion chelating agent can effectively improve the self-healing of concrete. In order to further enhance the self-healing ability of cement-based materials, ion chelating agent and inorganic compounds (sodium silicate and sodium bicarbonate) were used together in this paper. Pore size distribution, mechanical and self-healing performance of the mortars with ion chelating agent and inorganic compounds were investigated. The results showed that harmful pores (pore diameter above 0.1 μ m) of the mortar was reduced and mechanical properties was increased by adding ion chelating agent and inorganic compounds, especially mortar mixed with 0.50% ion chelating agent and 0.25% sodium silicate had the least harmful pores and the highest compressive strength and flexural strength. Moreover, the self-healing properties of mortars were significantly improved by combination of ion chelating agent and inorganic compound. Especially for mortar mixed with 0.5% ion chelating agent and 0.5% sodium silicate, the relative water permeability coefficient decreased to 0 after curing for 28 d, and the cracks with width of 0.31 mm and 0.46 mm could be completely closed after curing for 3 d and 28 d respectively. SEM observation showed that the calcium carbonate, ettringite and calcium carbonate were covered by CSH gel in the cracks and interior of the mortar mixed with ion chelating agent and sodium silicate, which proved that the ion chelating agent and sodium silicate had synergistic effect on the self-healing properties of cement-based materials.