Surface Coating Method for Cement-Based Materials to Improve Chloride Ion Penetration Resistance Using Amine-Based CO2 Solvent

Abstract

The application of coatings on concrete surfaces serves as a protective shield, guarding the structure against chlorides and averting corrosion of the reinforcement, consequently enhancing its durability. This study investigates the resistance of cement mortar samples to chloride ion penetration when coated with an amine-based carbon dioxide (CO2) solvent. Various factors, including monoethanolamine (MEA) concentrations of 1, 10, and 30wt.%; water-to-cement ratios (w/cm) of 0.35, 0.4, and 0.5; coating timings on day 3 and day 27; and pre-conditioning methods such as air drying, are investigated for their impact on the performance of chloride penetration resistance. Specifically, pre-conditioning significantly enhanced the performance of the coatings, especially in samples with a higher w/cm. Coatings applied at an early stage demonstrated superior resistance to chloride ion penetration compared to those applied later in the curing process. Moreover, solutions with higher concentrations of MEA, capturing more CO2, encouraged the resistance against chloride penetration by reducing capillary macropores within the cement mortar samples. Diffusivity analysis of the coated surface layer confirmed the efficacy of the CO2-dissolved MEA solution as a barrier against chloride ion penetration. Optimal performance was possibly observed in the samples produced by a w/cm of 0.4 and their treatment with more than 10% MEA concentrations.