Effect of polyethylene glycol on chloride binding in mortar

As a widely used chemical admixture, polyethylene glycol (PEG) is often added to concrete as a self-curing or shrinkage-reducing agent. PEG with a low molecular mass can inhibit the corrosion of chloride by increasing the viscosity of the pore solution. The chloride binding capacity of the cement matrix significantly affects the service life of reinforced concrete owing to its high correlation with the concentration of free chloride. However, the influence of PEG on the chloride binding capacity of cement-based materials remains unclear. Through chloride concentration profiles, the assessment of solid phase content based on the TGA/XRD/reference intensity ratio method, and SEM morphology analysis, this study reveals the influence of PEG on chloride binding in mortar. The addition of PEG significantly reduced the chloride binding capacity of the cement matrix. Complexing Ca2+ on the surface of calcium silicate hydrate (C-S-H), to occupy the adsorption sites of chloride, reduces the physical adsorption capacity and the chemical binding ability of the matrix by inhibiting the conversion of ettringite (AFt) to monosulfoaluminate (AFm). Moreover, the addition of PEG spheroidizes C-S-H and reduces its particle size, leading to loose packing of C-S-H in the mortar. Thus, the findings of this study suggest that when PEG is used in cementitious materials, caution and corresponding measures are needed to optimize its impact on durability.